NUREG/CR-2658

PNL-4174

RZ

Characteristics of

Combustion Products:

"A Review of the Literature

Manuscript Completed: January 1983

Date Published: July 1983

Prepared by

M. K. W. Chan, J. Mishima

Pacific'Northwest Laboratory

Richland, WA 99352

Prepared for

Division of Risk Analysis

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, D.C. 20555

NRC FIN B2287, B2407

ABSTRACT

To determine the effects of fires in nuclear fuel cycle facilities,

Pacific Northwest Laboratory (PNL) has surveyed the literature to gather data

on the characteristics of combustion products. This report discusses the theories of the origin of combustion with an emphasis on the behavior of the combustible materials commonly found in nuclear fuel cycle facilities. Data that

can be used to calculate particulate generation rate, size, distribution, and

concentration are included. Examples are given to illustrate the application

of this data to quantitatively predict both the mass and heat generated from

fires. As the final result of this review, information gaps are identified

that should be filled for fire accident analyses in fuel cycle facilities.

iii

CONTENTS

ABSTRACT ..... .... . . . . . . . . . . . . . .. . . . .. . . . iii.. 

NOMENCLATURE ................... ....... ...... ... ................ xi

EXECUTIVE SUMMARY ................................ ..... ...... xv

1.0 INTRODUCTION..................................................... 1.1

2.0 THE STUDY OF FIRE AND COMBUSTION PRODUCTS ........................ 2.1

2.1 FIRE AND COMBUSTION PROCESSES ............................... 2.3

2.1.1 Pyrolysis ............................................ 2.4

2.1.2 Combustion ........................................... 2.6

2.1.3 Flammability Characteristics ......................... 2.7

2.1.4 Energy in the Combustion Process ..................... 2.8

2.1.5 Enclosure Fires ........................ r .............. 2.11

2.1.6 Mass and Heat Generation in the Combustion

Process .... ............................ 2.13

2.2 MECHANISMS OF SOOT FORMATION ................................ 2.16

2.2.1 Carbon Formation by Charged Bodies..... .............. 2.17

2.2.2 Polymerization and Dehydrogenation via Acetylene ..... 2.17

2.2.3 Polymerization via Aromatics and Polycyclics ......... 2.18

2.2.4 Condensation and Graphitization ...................... 2.18

2.2.5 Nucleation .... e .......... ..................... ...... 2.19

2.3 BEHAVIOR OF AIRBORNE MATERIALS .............................. 2.19

2.3.1 Coalescence ........ . ................................. 2.21

2.3.2 Settling ............................................. 2.22

2.3.3 Summary ............................................... 2.24

2.4 FACTORS THAT INFLUENCE THE GENERATION OF SMOKE .............. 2.24

2.4.1 Chemical Factors ..................................... 2.25

2.4.2 Physical Factors ..................................... 2.26

2.5 METHODS OF EXPERIMENTAL FIRE STUDY .......................... 2.33

2.5.1 The Study of Combustion Products in Flames ........... 2.35

2.5.2 The Study of Combustion Products in Smokes ........... 2.36

3.0 CHARACTERISTICS OF FIRE-GENERATED PRODUCTS ....................... 3.1

3.1 PRODUCTS IN FLAMES .......................................... 3.4

3.1.1 Products in Diffusion Flames ......................... 3.11

3.1.2 Summary ................................................ 3.18

v
3.2 PRODUCTS IN SMOKE .............................. 3.20

3.2.1 Percentage of Smoke Particulates Airborne, Mass Loss

Rates, and Product Generation Rates .................. 3.20

3.2.2 Particle Size and Particle Size Distribution ......... 3.26

3.2.3 Chemical Composition of Airborne Particles ........... 3.26

3.2.4 Particulate Concentration ............................ 3.28

3.2.5 Summary .............................................. 3.32

3.3 ENERGY RELEASE RATE ............... .................... 3.34

3.4 RATE EQUATIONS OF COMBUSTION PROCESSES.......... ....... 3.37

3.4.1 Mass Loss Rate ....................................... 3.7

3.4.2 Heat Release Rate .................................... 3.9

3.4.3 Product Generation Rate .............................. 3.40

4.0 DISCUSSION ..................................................... 4.1

4.1 THE STUDY OF COMBUSTION PRODUCTS ............................ 4.1

4.2 APPLICATION*OF THE DATA ..................................... 4.1

4.3 IDENTIFICATION OF INFORMATION GAPS .......................... 4.3

5.0 REFERENCES ..................................................... 5.1

APPENDIX--COLLECTION OF LITERATURE DATA ................... I ........... A.1

vi
FIGURES

2.1 Actual and Convective Heats of Combustion of Red Oak as

Functions of Time ..................... ...................... 2.15

2.2 Summary of Possible Mechanisms of Soot Formation

via Acetylene ..... ............................... 2.18

2.3 Summary of Proposed Mechanisms of Soot Formation ................. 2.20

2.4 Effect of Coagulation on Growth of Droplets...................... 2.22

2.5 Effect of Surface Coatings on Smoke Buildup for Plywood

in Nonflaming Exposure ..................... 2.26

2.6 Smoke Accumulation Curves for Smoldering Samples of

Various Materials................... o ....... ................. 2.27

2.7 Smoke Accumulation Curves for Active Flaming Combustion

of Samples of Various Materials....... . ......... o ............ 2.28

2.8 Effect of Layer Thickness on Maximum Specific Optical Density.... 2.29

2.9 Effect of Sample Orientation on Specific Optical Density.. ....... 2.30

2.10 Effect of Material Density of Maximum Specific Optical

Density.................. ................. .................. 2.31

/

2.11 Smoke Production of Hardboard Within a Heated Furnace ............ 2.32

2.12 Effect of Energy Flux on Dm of Douglas Fir....................... 2.33

2.13 Weight Loss for Wood and PVC Samples Burned Under Nonflaming

Conditions at Different Environmental Temperatures............... 2.34

2.14 Weight Loss for Wood and PVC Samples Burned Under Flaming

Conditions at Different Environmental Temperatures ............... 2.34

2.15 Smoke Buildup for Fiberboard Burned Under Nonflaming Combustion

in Reduced Oxygen Atmospheres ........ ................... 2.35

2.16 General Analytical Scheme for Chemical Analysis of Smokes........ 2.39

3.1 Schematic Representation of Combustion Products Study

in Flame ............................................. 3.3

3.2 Schematic Representation of Combustion Products Study

in Smoke ............... .............. ............... .......... 3.4

vii
3.3 Concentration Profiles in a Flat Acetylene-Oxygen Flame at a

Pressure of 20 mm Hg and a Flow Velocity of the Unburned Gas

of 50 cm/sec ..................................................... 3.6

3.4 Profiles of Signal Intensities Relative to Argon for Major

Stable Species in an Acetylene-Oxygen Flame Near the Sooting Limit ............................................................ 3.7-

3.5a Concentration Profiles of the Gaseous Compounds 02, H2 , CO,

C02 and CH4 Along the Flame for Different CH4 :0 2 Feed Ratios ..... 3.9

3.5b Concentration Profiles of the Gaseous Compounds C2H 2 , C2 C4,

C2 H6 , C4 H4 and C6 H6 Along the Flame for Different CH2 :0 2

Feed Ratios ........................................ .............. 3.10

3.6a Influence of Atomizing Air Pressure on Axial Profile of Soot

Mass Loading at Cold Gas Velocity of 0.96 m/sec .................. 3.13

3.6b Influence of Atomizing Air Pressure on Axial Profile of Soot

Mass Loading at Cold Gas Velocity of 2.67 m/sec .................. 3.13

3.7 Schematic of Apparatus for Monochromatic Transmission

Measurements ............... .................................... 3.17

3.8 Approximate Size Distributions, N(rI Versus Particle Radius r

as Determined from Multiwavelengt Aonochromatic Transmission

Experiments ...................................................... 3.19

3.9 Effect of the Ventilation Air Temperature on the Particulate

Volume Fraction for Flaming Combustion of Hydraulic Fluid

Exposed to a Radiant Flux of 5 W/cm2 ............. . ....... 3.33

3.10 Factory Mutual Combustibility Apparatus ......................... 3.35

3.11 Chamber for High Pressure Spray Flammability Tests ............... 3.36

viii
TABLES

2.1 Physical Properties of Commercial Plastics .............. 2.2

2.2 Characteristics and Behavior of Fuel Materials................ 2.3

2.3 Flammability Characteristics ................................. 2.8

2.4 Heats of Combustion......... ......... . ........ ......... . 2.9

2.5 Mean Bond Energies.............................................. 2.10

2.6 The Minimum Time for Particulates and Droplet Settling in a

Flow-Through Combustion Chamber. .... .................. 2.23

2.7 Factors That Affect the Characteristics of Combustion Products 2.25

2.8 Test Devices for Studying Smoke................................ 2.38

3.1 Information Available in the Literature for the Fuel Materials

of Interest Found in Fuel Cycle Facilities..................... 3.2

3.2 Mole Fraction of Major Stable Species Expected in the Burned

Gas of a C2 H2 -0 2 Premixed Flame ..... ............ ......... ...... 3.7

3.3 Additional Species Near the End of the Reaction Zone in a

C2 H2 -0 2 Flame................ ................................ 3.8

3.4 Carbon Particle Diameters of C2 H2 -0 2 in a Premixed Flame

Under Various Experimental Conditions....... ............. 3.11

3.5 Carbon Particle Diameters in Turbulent Diffusion Flames

Calculated by Utilizing the Modified Eddy-Dissipation Model .... 3.12

3.6a Arithmetic Mean Particle Diameter (A) of Spherical Kerosene

Particles at Cold Gas Velocity of 0.96 m/sec................... 3.14

3.6b Arithmetic Mean Particle Diameter (A) of Spherical Kerosene

Particles at Cold Gas Velocity of 2.67 m/sec ................... 3.14

3.7 Polycyclic Aromatic Hydrocarbons in the Combustion Products of

Kerosene................................ 3.15

3.8 Soot Volume Fractions and Size Distributions in Experimental

Fl ames ....... ...................... 3.16

3.9a Percentage of Smoke Particles Generated from Various Fuel

Materials ................... _......... ....... o ..... 3.22

ix
3.9b Experimental Methods and References ............................ 3.23

3.10 Mass Loss Rates for Combustible Materials ....................... 3.24

3.11 Product Generation Rates for Various Materials .................. 3.25

3.12 Particle Size and Particle Size Distribution of Fuel

Materials..................................... 3.27

3.13 Composition of PVC Samples ............ ................... 3.28

3.14 Amounts of PCAHs Found in Smoke Particles Generated from

PVC Under Simulated Fire Conditions ............................. 3.29

3.15 Major PCAH Species Found in Particulate Smoke of

Hydraulic Fluid............ ................. 3.30

3.1.6 Mass Loss Data for Hydraulic Fluid and PVC ...................... 3.30

3.17a Major Volatile Components from Hydraulic Fluid .................. 3.31

3.17b Major Volatile Components from PVC .............................. 3.32

3.18 Sample Weight Loss and Smoke Concentration Data for Hydraulic

Fluid ........................................................... 3.33

3.19 Energy Release Rates for Various Combustible Materials .......... 3.34

3.20 Results of Heat Output Tests on Various Types of Hydraulic

Fluid ....................................... 3.38

3.21 Combustion Efficiency ................................. 3.41

x
NOMENCLATURE

d particulate diameter

do initial particulate diameter

Dvs mean particle diameter

Fj product generation efficiency

Fv soot volume fraction

mass generation rate of product j 3

6" product generation rate of species j for pyrolysis Pi

b" bj product generaticn rate for species of j for combustion

Ha actual heat of combustion

Hi heat of combustion

Ht heat of complete combustion

I laser intensity

Io initial intensity

k Cunningham correction factor

k yield of product j expected from stoichiometry

K rate constant which depends on thermal and kinetic properties of

fluid

L .pathlength or mean beam length

L heat required to generate a unit mass of the fuel vapors

M02 mass fraction of oxygen

Me soot refractive index

A ýmass loss rate

Mp total particulate mass

M" mass loss rate of pyrolysis

p

xi
A.- mass loss rate of combustion b

No total particle concentration

3

Np particle number concentration per cm

(N p)o initial particle concentration

N(r) particle size distribution

Pp particle density

q e "external heat flow

qfc flame convective heat flux

"", qfr flame radiative heat flux

qf' total flame heat flux

fs

q" net heat flux received by the fuel material per unit fuel surface

area

q r surface reradiation heat loss rate rr

Qa'" heat release rate

a

radiative heat release rate

r

61. convective heat release rate

c

Qext mean extinction efficiency

rmax most probable particle radius

t time in seconds

T extinction coefficient

V test chamber volume

Tt terminal settling velocity

Xa ratio of actual to complete heat of combustion (combustion efficiency)

Xc convective fraction of heat of complete combustion

Xr radiative fraction of heat of complete combustion

Yj yield of product j

xii
0equivalence ratio

volume fraction

Ocorr corrected volume fraction

Omeas measured volume fraction

xiii

EXECUTIVE SUMMARY

The objective of this state-of-the-art literature review on characteristics of combustion products is to identify useful information (mass generation

rates of smoke particles, particulate size and distribution, particulate concentration, energy generation rates, etc.) on the combustible materials that

are commonly found in fuel cycle facilities (polymethylmethacrylate, polystyrene, polyvinyl chloride, elastomers, cellulosic materials, and organic

fluids). This information will be used in analysis of the radiological consequences of fires inside the facilities. At the same time, the complex phenomena of fire, combustion and heat generation are briefly introduced to provide the readers some basic understanding in interpreting and utilizing the

collected data.

The characteristics of fire generated products and energy releases are a

strong function of three main variables--temperature, oxygen availability in an

enclosure, and chemical compositions of fuel materials. The mechanism of soot

formation, which is responsible for the particulate size, concentration, and

radiation in the fire enclosure, is still a mystery. Many different mechanisms

have been proposed. Among them, soot formation, involving processes of dehydrogenation and aggregation via acetylene, polyacetylenes and polycyclic aromatic hydrocarbons (PCAHs), is the most promistng route. The study of combustion products found in the flame zones is the basic process in understanding

soot formation. Besides the principal combustion product gases (CO, C02 , H2 ,

and H2 0), small amounts of acetylene, polyacetylene, carbon particles and several PCAHs were detected in the premixed and diffusion flames of acetylene.

Yet, more quantitative data are needed for verification.

The majority of characteristics and energy data of combustion products are

found in the fire studies by A. Tewarson et al. of Factory Mutual Research and

B. T. Zinn et al. of Georgia Institute of Technology. All these available data

were obtained by conducting experiments in a small-scale combustion apparatus.

The appendix is a data bank (collection of raw data) with some of the selected

characteristics tabulated in Section 3.0. These data are believed to be the

best information available in the literature today. Using this selective

information in Section 3.0, examples are provided to demonstrate the application of the data.

There is a lack of combustion product data in the literature for cellulosic materials, elastomers, kerosene and for "typical mixtures" (representing

fractions) of combustible materials found inside fuel cycle facilities. The

effects of radioactive particles on fire-generated particles, and vice versa,

are yet unknown. The uncertainty of the utilization of the small-scale data to

predict the outcome of a facility fire has been a concern for large-scale accident analysis.

xv
I
1.0 INTRODUCTION

One of the potentially destructive accidents to a nuclear facility is

fire. Radioactive materials which can be released as aerosols during a fire

accident impose a potential risk to the public. Both radioactive particulate

material and fire-generated particulate material that remain airborne through

the ventilation system can cause filter clogging, which can destroy the filter

element. A whole new path of the release of radioactive material to the atmosphere results if filter paths are destroyed or plugged. Fire can initiate

other possible accidental events inside a nuclear facility, ranging from simple

spills of radioactive powder to major accidents like explosions or criticalities. All these accidents would cause airborne releases of radioactive materials within the facility.

Since the generation of particulate material from a fire is inevitable, it

is important to understand the characteristics of fire-generated products. By

knowing these particulate characteristics and their interaction with airborne

radioactive particles, an estimate of radioactive material release can provide

the information necessary for safety analysis reports and environmental impact

statements.

In this report, state-of-the-art combustion products studies are first

reviewed with emphasis on the phenonema of fire and combustion resulting in

both mass and energy generation, the behavior of airborne materials, and the

various factors that influence the generation of smoke. Next the data available on the characteristics of combustion products and energy releases are discussed and tabulated. With the application of engineering approximations and

necessary modifications to the existing data, this information will allow us to

analyze fires in fuel cycle facilities. This review will be updated as additional information becomes available.

This report is divided into two parts for discussion:

" Qualitative Assessment (Section 2.0) introduces fire and combustion processes, identifies and discusses the possible mechanisms and the energy

involved in combustion product formation and behavior of airborne material; discusses the effect of certain parameters on the characteristics of

combustion products; and identifies the methods of experimental fire

study.

" Quantitative Assessment (Section 3.0) presents and discusses quantitatively the characteristics of products generated by burning various materials such as those found in the most recent combustion studies. Products

in both flames and smoke are discussed. Energy release rate in combustion

is also considered.

Background information on fire and combustion (Section 2.0) is given

before the more detailed discussion on the characteristics of combustion products (Section 3.0). A reader who has an understanding of the recent fire literature may want to refer directly to Section 3.0.

1.1

2.0. THE STUDY OF FIRE AND COMBUSTION PRODUCTS

Fires in buildings generate toxic gases and a complex mixture of solid and

liquid particles. These unwanted products are commonly known as smoke. For

better understanding of the smoke problems, both physical and chemical properties of these smoke particles are being examined by many researchers. Studies

have shown that the particles that make up smoke can be detrimental to safety

and health. The purpose of this report is to present available information

gathered from a state-of-the-art literature review on characteristics of combustion products, which will implement our further study on fires in fuel cycle

facilities which possibly cause the release of radioactive materials to the

environment.

The properties of smoke particles are normally studied by simulating fires

in both small- and large-scale chambers equipped with measuring devices. Materials used in these experiments are those which are commonly found and used in

homes and for building materials; i.e., wood, polyvinyl chloride (PVC), polymethylmethacrylate (PMMA), polystyrene (PS), etc. A few studies have also been

conducted by collecting smoke samples during real fires (Burgess, Treitmar and

Gold 1979; Long 1972), using prototype sampler systems which were installed in

a firefighter's turnout coat. These studies only identified the chemical components of combustion products found in the flame zone and in smoke.

This review will focus on combustion product characterization by burning

combustible materials found in nuclear facilities. These combustible materials

can be identified as follows:

" PMMA (viewing windows of gloveboxes)

* PS (ion exchange resin)

" PVC (wrapping/covers)

" elastomers (i.e., rubber and other plastics used as seals/gaskets)

* cellulose

" cellulosic materials (i.e., paper and rags for cleaning)

" organic fluids (i.e., kerosene as liquid-liquid extraction solvent and

hydraulic fluids as lubricants).

Table 2.1 shows some of the physical properties of the three commercial

plastics, and Table 2.2 shows some characteristics and behavior of materials

which can be found in fuel cycle facilities. Both physicochemical and

combustion/pyrolysis properties of some of the combustible materials listed

above are tabulated in Section 3.0.

At this point it is desirable to define the terminology of combustion

products common to investigators in the field. When combustible gases or

vapors burn in air, smoke as well as heat is released into the air as particles

during the processes of pyrolysis and combustion (Saito 1974). Smoke is an

aggregation of submicron solid and liquid particles (such as the carbonaceous

particles soot, ash, droplet or tar, spotted fragments, and other condensed

matter) formed due to poor mixing of fuels with air (Murty 1978). In an actual

2.1
TABLE 2.1. Physical Properties of Commercial Plastics(a)

Property PMMA PS PVC

Decomposition tem- 170-300 300-400 200-300

perature range,°C

Ignition temp.,°C

Flash ignition 280-300 345-360 391

Self ignition 450-462 488-496 454

Limiting 02 0.173 0.181 0.45-0.49

N02/(N02 + NN2 )

Surface flammability 0.6-1.6 0.5-2.5 Self-extinguishing

(burning rate),

in./min

Specific heat, 0.35 0.32 0.20-0.28

cal/g-°C

Thermal conductivity 4.0-6.0 1.9-3.3 3.0-7.0

(10-4 cal/sec-cm2 ), ,C/cm

(a) Hilado 1969.

fire, the possible constituents of combustion products generated can be categorized as gases, vapors and particulate material. Some components of these

products are:

" gases

- carbon monoxide (CO), carbon dioxide (C02 )

- oxides of nitrogen (NOx)

- oxygen (02)

- other (e.g., HCl, HCN, H2 , C6 H6 , etc.)

" vapors

- water (present and generated by combustion)

- condensible (inorganic and organic)

" particulate material - soot

- mineral ash - condensed vapor - other (e.g., PCAHs)

2.2
TABLE 2.2. Characteristics and Behavior of Fuel Materials

Material

PMMA (a)

(C5H80)n

pS(a)

(C8H8)n

PVC(a)

(C2 H3Cl)n

Elastomer(b)

Cellulosl

material k)

Characteristics

Easy to ignite and softens as it burns.

Easy to ignite. Softens and bubbl es as it burns, and

generates some black smoke and airborne carbon. The

principal combustion products are C02 and CO.

Difficult to ignite and evolves white smoke. Held horizontally, it is self-extinguishing. The major products

of pyrolysis and combustion are C02 , CO, and HCl. It

softens as it burns.

Possesses a high degree of elasticity. Natural rubber

illustrates the structural requirements of an

elastomer--long, flexible chains, weak intermolecular

force, and occasional cross-linking.

Easy to ignite. Not noticeably affected by 02.

More volatiles, less char because heating rate is

higher. Typical combustion products of volatiles are

C02, CO, H2 0, N2 .

Boyd 1977.

(a) Hilado 1969.

(b) Morrison and

Due to the complex phenomena of combustion, no single study has been able

to thoroughly and quantitatively describe the properties of these products initially found in the flames which diffuse away as smoke and gases. The literature we reviewed showed that most investigators quantitatively emphasized the

materials generated in the flames or identified and measured the characteristics of airborne materials found in smoke away from the flames. In order to

master these transient properties, the mechanisms of'product formation and the

behavior of airborne particles must be known.

2.1 FIRE AND COMBUSTION PROCESSES

In a classical sense, the processes of pyrolysis (volatilization) and combustion define fire. These two processes do not necessarily coexist in a

simple combustion process (e.g., burning of methane gas), but burning requires

the presence of oxygen, and combustible volatiles evolve during the pyrolysis

of solid and liquid fuels exposed to a high-temperature environment. In order

to characterize a burning object, the study of flammability characteristics

becomes important.

2.3
Fire inside a fuel cycle facility is quite different from other enclosure

fires, such as residential and non-nuclear industrial fires, because of differences in 1) the types and amounts of combustible materials and 2) the distribution and the flow pattern of air (or oxygen). (The ventilation system inside a

nuclear facility is designed differently than most other industries' systems.)

In a fire, heat and mass (smoke and other toxic gases) are generated.

These two variables are dependent on each other. The laws of physics and chemistry predict that, as more heat is formed in a combustion process, more C02

and H2 0 are formed due to the completeness of combustion; while when less heat

is formed, more of other products (i.e., byproducts of incomplete combustion

such as soot, CO and organic vapors) are found. Therefore both mass and heat

generation in a fire must be considered together when analyzing the accident.

The concepts mentioned above are necessary in understanding fire and combustion processes. More detailed information is discussed in the following

sections.

2.1.1 Pyrolysis

In most chemistry texts, pyrolysis is defined as chemical decomposition by

the action of heat. The role of oxygen in pyrolysis was subject to controversy

in the late 1960s. In the model derived from Fenimore and Jones' (1966) smoke

measurement experiments, oxygen from the surrounding atmosphere was assumed to

be completely consumed in the flame zone so that polymer degradation occurred

by pyrolysis in the absence of 02. This has been called a thermal degradation

model. In another model, referred to as oxidative or thermo-oxidative degradation, Burge and Tipper (1969) postulate that oxygen may play a role in pyrolysis at the polymer surface. They performed a test similar to those by Fenimore

and Jones except that they burned the polymeric materials at a subatmospheric

pressure of 50 mm Hg in an oxygen-argon mixture with 20 02. Cheng, Ryand and

Baer (1969) have presented their data from a similar experiment to support the

possibility of oxidative degradation under certain conditions. Their conclusion is that it is probable, depending on the material and the combustion condition, that thermal degradation and/or oxidative degradation may be important

to polymer combustion.

Condensed fuels found in fires can be viewed as suppliers of gaseous -

fuels. Thus, from this viewpoint, pyrolysis of the condensed fuel via the

chemical breakdown of the fuel constituents under the influence of heat plays a

central role in the phenomenon of fire.

Condensed fuels found in a fuel cycle facility are in solid and liquid

form. Among the solid fuels, polymeric materials like PMMA, PVC and other

plastics are viewing glass for gloveboxes and bagging materials; PS is found in

ion exchange resin; natural and synthetic rubber is found in surgeons' gloves

and gasketing material on the gloveboxes; and cellulosic materials are found in

rags, papers and cardboards. Among the liquid fuels, kerosene, hydraulic

fluids and other high-boiling organic fluids are often found in the nuclear

facility. On a molecular scale, the mechanisms by which the gaseous fuel is

liberated are different for the solid and liquid fuels.

2.4
.2.1.1.1 Solid Fuels

Some solids are distilled when subjected to heat, while some are melted to

a liquid form before the generation of combustible gases. The former is usually called a sublimation process, where the Volatile gases emitted in the

interior of the solid seep out of the solid before reacting with air. Cellulosic materials usually behave this way when exposed to heat. As suggested by

Murty (1978), the study of pyrolyzing this type of solid consequently involves

two steps: first, to find the rate of evolution of volatiles in the interior

of the solid as a function of the external surface heat flux condition; and

second, to find the flame stand-off distance and surface heat flux in the gas

phase as a function of quantity and quality of the volatiles transpiring from

the surface. When subjected to heat, other solids are melted to a liquid form

before the generation of combustible gases. This involves two processes--

decomposition of solid to liquid phase and vaporization of liquid to gaseous

phase. Generation of volatiles via these processes usually requires more

energy than sublimation. Polymeric materials like plastic and elastomers usually behave this way.

The complexity of the breakdown schemes of most solid fuels is so great

that appreciable uncertainties always remain in a description of their pyrolysis mechanisms. Nonetheless, information on heat of decomposition

(i.e., amount of heat required to decompose a unit mass of material), heat of

vaporization (also called gasification or sublimation), and heat of depolymerization for simple chemical compounds is often obtainable in physics and chemistry textbooks (e.g., Hilado 1969; Morrison and Boyd 1977). For most of the

combustible materials found in a fuel cycle facility, Tewarson et al. (1980b)

have been able to provide information on heat required to generate a unit mass

of vapor by measuring the steady-state mass loss rate in pyrolysis in their

Factory Mutual combustion test chamber in a nitrogen environment.

(See Table 3.10 of Section 3.2.1. For other fuel materials refer to

Tables A.1.1 and A.1.3 of Appendix A.1 and Tables A.7.2 and A.7.3 of

Appendix A.7.)

2.1.1.2 Liquid Fuels

In a conventional sense, pyrolysis is unimportant in the condensed phase

for liquid-fueled fires. Usually temperatures within the liquid phase are too

low for a significant amount of chemical breakdown to occur during a typical

fire. This may not be true, however, for high-boiling liquids or for the

higher-boiling residues that remain toward the end of a fire in liquid-fuel

mixtures.

Pyrolysis of liquid fuels involves the transition from liquid to gas

(vaporization). Liquid fuels can be classified into two types: those that are

easily vaporized and those that are not, depending on their chemical and physical properties. After they have vaporized, as in solid fuel, the volatile

vapors can burn with air.

2.5
2.1.2 Combustion

Combustion itself is a very complex phenomenon. Generally, it may involve

both mass and heat transfer processes (i.e., diffusion of oxygen and combustion

products), thermodynamics, aerodynamics, and kinetics of several simultaneous

and/or competing chemical reactions (i.e., series of oxidation reactions, thermal decomposition of fuel).

Fundamentally, combustion requires three important elements: 1) fuels,

2) oxygen and 3) external energy. (External energy refers here to ignition

sources or a high-temperature environment where combustible vapors can be selfignited in the presence of oxygen.) Without any one of these elements, combustion would not exist.

Combustion is known as the mechanism by which hydrocarbon volatiles

(pyrolyzates) oxidize at the high temperatures encountered in a flame. 'Three

main zones are typically identified in order of occurrence in premixed flames

(i.e., flames generated by combustion of a specified ratio' of air and gaseous

fuel in a mixture): a nonluminous zone, a main reaction zone and a glowing

burned gases' zone. In a nonluminous zone, complex fuel molecules are thermally unstable at combustion temperatures. As these fuel molecules enter the

reaction zone their internal energy increases rapidly due to collisions with

other very energetic, high-temperature molecules. Bond rupture occurs so that

chemical potential energy is transformed into thermal and mechanical energy. A

fuel containing energy-rich bonds such as carbon-carbon, carbon-hydrogen and

hydrogen-hydrogen is a common source of chemical potential energy. Besides

formation of energy in the reaction zone, the mechanism of cracking or dissociation of fuel molecules produces simpler monatomic or diatomic species that

react to form gaseous combustion products (i.e., C02 , CO, H2 0, and H2 ). In

addition to these predominant products of combustion, trace amounts of other

species such as NOx and particulate materials may form in the reaction zone of

the flame. The glowing burned gases' zone contains the newly formed particulate materials, which are responsible for the color of the flame.

Beside flaming combustion, there are other types of combustion processes

such as char oxidation and oxygen depletion of solid fuel interior cavities

known as deep-seated fires (Krause et al. 1980). These processes require less

oxygen (ranging from 3 to 9%) and are most often found in burning of charcoal

or in the dying period of a solid-fuel fire.

The quantification of combustion (i.e., stoichiometry) is the most useful

type of technical analysis of any physical or chemical phenomenon in the study

of combustion. A stoichiometric mixture is one in which the proper ratio of

fuel to oxygen is theoretically correct, causing complete oxidation in a

chemical reaction. For example, to have stoichiometric combustion of one mole

of methane, two moles of oxygen are required. The reaction yields one mole of

C02 and two moles of water:

CH4 + 202 + C02 + 2H2 0 (2.1)

2.6
(Assume that the dissociation of C02 and H20 to CO, 02, OH" and H2 is not

accounted for by the above reaction.)

In a fire, there are usually situations when combustible mixtures contain

excess oxidant ("lean" mixtures) or excess fuels ("rich" mixtures). The relative proportions of C02 , CO, H2 0, H2 and particulate materials that are produced depend upon the degree of richness or leanness and the temperature and

pressure conditions in a fire. Equivalence ratios (0) (fuel-air or air-fuel)

are the most common ways of quantitatively expressing the richness or leanness

of a mixture. This topic will be covered in more depth in Section 3.0.

For the most part, the combustion process utilizes stationary flames

rather than propagating or explosion flames such as found, e.g., in the operation of internal combustion engines (Boisdron and Brock 1972). There are two

types of stationary flames--premixed flames and diffusion flames. As discussed

by Long (1972), no flame may be characterized as being either purely premixed

or purely diffusional. For example, rich, premixed bunsen-type flames depend

on the outer diffusion flame zone for stability, while diffusion flames depend

on a premixing region near the burner rim for stability. Murty (1978) has provided definitions for the two kinds of flames:

e Premixed Flame--a result of the rapid exothermic combustion reaction of

the combustion mixture formed by premixing a fuel with an oxidant (i.e.,

02) in the proper proportions. Such a well-mixed combustion is said to be

kinetically controlled.

* Diffusion Flame--a result of an exothermic combustion reaction due to the

diffusion of oxidant into the fuel zone caused by temperature and gaseous

concentration gradients established in space. Such a poorly-mixed combustion is said to be diffusion-controlled.

In the case of a fire, diffusion flames predominate as a result of the combustion processes of a fire.

2.1.3 Flammability Characteristics

It is important that fire researchers be able to describe the behavior of

a material when it is exposed to fire. Flammability characteristics are the

properties used to define such behavior. For example, to determine surface

flammability of a test specimen, rate of burning (or mass loss rate) must be

considered; to obtain the heat contribution from a particular combustible, the

heat of combustion value is needed; and to characterize the fire gases, measurements of concentrations of decomposition and gaseous combustion products

are desired. Table 2.3 is a list of flammability characteristics and some

factors for measuring them.

Some of the characteristics found in the above table, e.g., heat and mass

generation from combustion processes, are discussed in more detail in

Section 2.1.6.

2.7
TABLE 2.3. Flammability Characteristics

Characteristics Some Measures of the Characteristic

Ease of ignition

Surface flammability

0

0

0

0

S

0

0

0

0

S

0

0

0

Decomposition temperature

Flash-ignition temperature

Self-ignition temperature

Limiting oxygen concentration

Rate of burning

Flame spread rating

Extent of burning

Heat of combustion

Fuel equivalent

Fuel distribution rating

Maximum smoke density

Total smoke production

Maximum observation rate

Heat contribution

Smoke production

Fire gases e Concentration of decomposition and combustion

gaseous products

Fire endurance

S

Hour ratings of resistance

Penetration time

2.1.4 Energy in the Combustion Process

In the process of combustion, products are formed and heat is liberated

(exothermic reaction). The amount of thermal energy released depends on the

completeness of combustion, which in turn depends on burning conditions and the

types of fuel material. The amount of energy released in combustion is dependent upon the availability of oxygen. Thus, heat release is an indication of

oxygen consumption (Krause et al. 1980).

In general, the quantity of heat evolved can be defined as heat of combustion when one mole of a hydrocarbon is burned completely to form C02 and H2 0.

The values of heat of combustion for many substances at standard temperature

and pressure (STP) can be found in many physics and chemistry textbooks. With

the known mechanism of formation of particular species from combustion, the

quantity of heat evolved can then be calculated and corrected to actual

temperature and pressure of the burning environment. Table 2.4 is a list of

heat-of-combustion data (i.e., kJ/g of fuel consumed). Heat of combustion can

also be obtained by an approach which enables one to estimate the energy from

bond strength (based on bonds broken and formed). This approach gives a good

approximation when heat of combustion data for materials are not readily found

in handbooks. Table 2.5 is a list of energy data for bonds between various

atoms.

2.8
TABLE 2.4. Heats of Combustion(e)

Heat of

KJ/ g

Combustion

Fuel KJ/g 02

Organic Liquids and Gases

Formul a

Methane

Ethane

n-Butane

n-Octane

Polyethylene

Acetylene

Ethylene

Benzene

1-Butanol

n-Butyraldehyde

Butryric acid

n-Butylamine

1-Butanethoil

Ethyl chloride

Ethyl bromide

Synthetic Polymers

CH4

C2 H6

C4 Hjo

C8 H1 8

(- C2H4

C2 H2

C2 H4

C6 H6

C4 H1 00

C4 H80

C4 H8 02

C4 H1 iN

C4 Hj 0 S

C2 H5 Cl

C2 H5 Br

-50.01

-47.48

-45.72

-44.42

-43.28

-48.22

-47.16

-40.14

-33.13

-31.92

-22.79

-37.96

-32.77

-19.01

-11.93

-12.54

-12.75

-12.78

-12.69

-12.65

-15.69

-13.78

-13.06

-12.79

-13.08

-12.55

-12.85

-12.32

-12.78

-12.50

Polyethylene

Polypropylene

Polyi sobutyl ene

Polybutadiene

Polystyrene

Polyvinyl chloride

Polyvinylidene chloride

Polyvinylidene fluoride

Polymethyl methacrylate

Polyacrylonitrile

Polyoxymethyl ene

Polyethylene terephthalate

Polycarbonate

Cell-ulose triacetate

Nylon -6,6

Isobutene polysulfone

(- C2 H4 -)n

(- C3 H6 - n

( C4 H8 -)n

( C4 H6 -)n

(- C8H 8 -)n

(- C2 H3 CI -)n

(- C2 H2 C]2 In

(- C2 H2 F2 -)n

(- C5 H8 02 -)n

(- C3 H3 N )n

(- CH2 0 )n

(- C10H8 04 -)

(- C1 6 H1 4 0 3 I'n

(- C12 H1 6 0 8 -)n

( - C6 H11NO -)n

(- C4H 8 02 S )n

-43.28

-43.31

-43.71

-42.75

-39.85

-16.43

-8.99

-13.32

-24.89

-30.80

-15.46

-22.00

-29.72

-17.62

-29.58

-20.12

-12.65

-12.66

-12.77

-13.14

-12.97

-12.84

-13.61

-13.32

-12.98

-13.61

-14.50

-13.21

-13.12

-13.23

-12.67

-12.59

(a) Huggett 1978.

2.9
TABLE 2.5.

Bond

C-C cCý_

C=C

C-H

C- 0

C=O

C-N

C --N

C-Cl

C-Br

C-I

C-F

C-S

0-0

0=0

N--N

N- N

H-H

Mean Bond Energies, kcal/mole(a)

Energy

83

147

194

98

84

172

70

213

78

66

57

116

62

33

119

38

225

104

Bond

O-H

0- N

N--H

P-P

S-S

Cl-Cl

Br-Br

I -I

F-F

H-Cl

H-Br

H--I

H- F

H-P

H -S

P-Cl

P-Br

S-Cl

Energy

110

150

93

51

50

58

46

36

37

103

88

72

135

76

81

76

65

60

(a) Abstracted from Pauling (1964) and Weast (1981).

In an actual fire inside a compartment, turbulent diffusion flames are

important. Oxygen is supplied to reaction zones by turbulent mixing of flammable gas and air prior to ignition. As time goes on, the quantity of oxygen may

not be sufficient to maintain "clean" combustion due to the earlier consumption

in a confined compartment. Incomplete combustion then dominates. Total heat

release at that point can no longer be estimated from the heat-of-combustion

calculation.

Thus, besides the mechanisms of products formation, determining the total

heat liberated in an actual fire is an additional complexity to the study of

combustion (Sections 2.1.5 and 3.3).

Huggett (1978) has developed a new technique, oxygen consumption calorimetry, which measures the rate of heat release from a fire. He concluded that

the heat release from a fire involving conventional organic fuels is 13.1 kJ/g

of oxygen consumed, with an accuracy of ±5% or better (see Table 2.4). Using

the oxygen consumption calorimetry method, Huggett also showed that incomplete

combustion and variation in fuel have only a minor effect on the rate of energy

release in a fire. Thus an accurate rate of heat release in a fire can be

determined-from three simple measurements: 1) the flow of air into the fire

system, and the concentration of oxygen in 2) the inlet and 3) the exhaust

streams.

2.10
Once the products of combustion become airborne, heat can be liberated or

consumed by chemical reactions between combustion products and species generated earlier. These reactions. may be ekothermic or endothermic, depending on

the nature of reactants and products in the presence of available energy. New

particulate species may be formed while others disappear, but the energy example, the formation of nitrogen oxides (NOx) via fixation of atmospheric nitrogen, is an endothermic reaction.

2.1.5 Enclosure Fires

Currently, in the field of fire science, strong emphasis is being placed

on the study of enclosure fires. Ignition, fire spread, and fully developed

fire inside an enclosure are the most important fire characteristics that are

being studied. Among these phenomena, the aspects of both mass and energy

generation in various stages of a fire are also considered in understanding the

fire hazard.

Flame radiation, the size of combustion zones and flame length, air

entrainment, mixing and other physicochemical processes governing the behavior

of these fires are not well understood (McCaffrey 1979). Today, many basic

research programs on modeling of fire flows (Alpert et al. 1981; Zukoski et al.

1981; and Alvares et al. 1980) involve the prediction of flow and heat transfer

patterns produced by pool fires, crib fires, wall fires and ceiling fires.

Much progress has been made in experimentally verifying their models.

Fire in a fuel cycle fabrication facility (or other nuclear facility)

represents a special kind of enclosure fire. The amount and the types of combustible materials (i.e., viewing windows of gloveboxes) found in these enclosures are unique for the handling of radioactive materials. The noncombustible

walls and ceiling are made of concrete and steel. The ventilation system is

different, too; it draws fresh air into the enclosure or room through the ceiling ventilator, while the room air is drawn out close to the floor. The dynamics of air flow play an important role in characterizing the results of a fire

in a nuclear facility. The enclosure itself is kept at slightly lower than

atmospheric pressure, but this negative pressure will not significantly affect

the chemistry and physics of the combustion process. As the fire grows, however, pressure in the enclosure increases. This becomes important in characterizing the flow of the fire-generated material. The increase of pressure

will also suppress or enhance various chemical and physical reactions in the

flame zones and their vicinities.

In a typical enclosure fire (e.g., a fire inside a fuel processing room of

a nuclear facility with an ignition source on a piece of processing equipment),

the amount of combustible materials and the availability of oxygen are the most

important parameters which control the severity of the fire. To help illustrate the combustion process, the progress of a fire in an enclosure will be

followed. Let us assume the room initially contains various equipment made of

metal and plastic materials that are arbitrarily distributed throughout the

room. The wall and ceiling are also constructed of combustible materials.

2.11
(Although this is not the case for nuclear facilities, this assumption is made

to illustrate a "fully-involved" fire.) The room has a ventilation system

where air is continuously drawn in and out through the ventilation system.

The fire starts out on some equipment in a small area in the middle of the

room. In the early stages of the fire, oxygen in the flaming vicinity is continuously consumed. An oxygen concentration gradient develops and more oxygen

is drawn into the fire region by means of molecular and turbulent diffusion.

Both heat-and smoke are generated as combustion products. At this point,

flames may not reach the ceiling, although there is convective heat transfer to

the ceiling since heated air and smoke rise., The smoke cloud above the burning

equipment represents the buoyant heat plume, and this heat and smoke will

1pool'' in the upper portion of the room as times goes on.

As the fire grows and the diffusion flame becomes larger, both heat conduction and flame radiation (mainly due to the luminous part of the flame where

soot particles are generated and oxided) become significant parts of heat

transfer. The neighboring equipment begins to smolder as the temperature of

the environment rises by various heat transport processes (convective and~radiative heat transfer), generating various kinds of combustible vapors, and the

quantity of these vapors depends on material properties and fire conditions.

The temperature of an ordinary enclosure fire ranges fronm-200 to 1000'C, with a

heat flux up to -10 W/cm2 .

Both pyrolysis and combustion of materials are occurring. There may be

multiple ignitions in the vicinity of the original ignition source but if a

fire is to become serious, the actual number of burning objects in the lower

portion of the room is not as important as the conditions in the zone of hot

gases filling the upper portion of the room. At this stage of fire growth, the

instant the flames impinge against the ceiling constitutes one of the most

important events since combustible gases from pyrolysis and incomplete combustion, or the ceiling itself, can ignite and contribute to the burning in the

room. These flames add to the heated zone at the ceiling and reinforce the

radiation process which is bathing the entire room. One of the most important

consequences of this radiation contribution is that other combustible materials

in the process of pyrolysis are ignited. For example, cleaning paper and rags

on the rack and eventually other equipment in the room start burning.

As more heat and combustible gases generated from pyrolysis build Up in

the room and there is increased air flow *into the room by the pumpi-ng act-ion of

the fire plume, there is a point in time known as flashover when all the combustible material in the room ignites and begins to contribute to the fire..

From that moment on, the fire in such a room is considered "fully involved." A

steady-state fire condition may be achieved with consumption of oxygen and

generation of combustion products at some fixed state. The duration of steadystate combustion depends mainly on the chemical and physical properties and the

amount of combustib'le materials that remain. Due to the complexity of the combustion process, the steady state may only exist for an extremely short period

of time after the fire growth is exceeded. It is very difficult to pinpoint

2.12
this moment and attempt mathematically to predict the fire process. Although

steady-state combustion can be described mathematically it is not meaningful

for an actual fire.

Although the ventilation system inside the nuclear facility is designed

differently than most other enclosures (i.e., houses or industrial buildings),

no significant differences in burning are expected initially because in the

ventilated fire stage, the amount and the nature of the combustible materials

control the progression of the fire. Both combustion products and unburnt

vapors and hot gases are generated. The average mass density of these gases is

much less than that of the surrounding atmosphere. This makes the gases buoyant and they accelerate upward, creating a pressure change which tends to draw

fresh air into the fire. The rate of production and the temperature of hot

gases from a fire depend strongly on the rate of air entrainment in the fire

plume (Zukoski et al. 1981). As the gas layer builds up from the ceiling

(i.e., ceiling layer or hot gas layer), the ceiling inlet air carries some of

these gases, during mixing, back to a cooler area (i.e., cool layer or lower

layer of an enclosure). Thus the air supplied to the flame may contain portions of combustion products and unburnt vapor or gases from the hot layer.

The fraction of hot gases entrained depends on their density. These hot gases

will not escape the room until they reach the outlet ventilators near the

floor. There is a possibility that they may never reach the exit ventilators,

not because the fire ceases, but because the increase in pressure inside the

enclosure can cause backflow of the ventilated air inlet from the ceiling. As

more burnt and unburnt gases are entrained,,the fire becomes "oxygen controlled" (i.e., when oxygen concentration is insufficient to maintain

combustion).

Thus depending on the availability of oxygen and the size of the enclosure, the fire inside a nuclear facility can be a very smoky ("dirty") fire.

One would anticipate that the characteristics of the combustion products and

the amount of energy release can be quite different depending on the orientation of the ventilation system. The ventilated air flow rates into and out of

the room also play an important role in the characterization of combustion

products.

Many enclosure fire studies have been concerned with more sophisticated

problems of combustion phenomena that can affect the characteristics of combustion products. Most of these problems have not been resolved, however, and the

understanding of the radiative and turbulent aspects of a fire is limited.

Thus entrainment models (e.g., by Zukoski et al. 1981) and many other physicochemical processes (e.g., flame radiation, chemical reactions, etc.) governing

the behavior of a fire will not be discussed in this review.

2.1.6 Mass and Heat Generation in the Combustion Process

Both mass and energy generation in a fire do not operate independently of

each other. The amount of fire-generated products and the heat generation rate

depend on the chemical and physical characteristics of the combustible materials and the availability of oxygen under various fire conditions. In the

2.13
studies of physicochemical and combustion/pyrolysis properties of polymeric

materials and heat release rate in fires, Tewarson et al. (1980a,b) relate the

heat generation rate as a function of mass generation rate. The details of

this information and the mass-energy relationship are summarized in

Section 3.3. The mass generation rate of some chemical species can also be

estimated by knowing the fraction of the species found in the exhaust gases.

(See also Section 3.2.1 and Tables 3.10, 3.11 and 3.19 for the tabulation of

some experimental mass and energy generation data from combustion of the materials of interest.)

Consider a fire of a glovebox in a fuel cycle facility as a typical enclosure fire. Initially, energy is given off as the result of combustion. The

amount of energy generated is the function of:

" the mass and chemical composition of fuel vapors (pyrolysates) evolved

from the glovebox materials during the pyrolysis reaction

" the amount of oxygen present and the diffusion efficiency of oxygen to the

flame front

" the efficiency of the chemical processes to convert fuel vapors to various

products of complete and incomplete combustion.

If all the generated vapors react (are burned) to yield combustion products,

total heat release can be obtained simply from the heat-of-complete-combustion

table (Table 2.4) by summing the heat contributions of individual materials of

the glovebox. These values are based on the following assumed products of combustion: C02 , H2 0 (vapor), HF, HCl, Br2 , S02, and N2 .

In the case of an actual fire, however, the fuel vapors do not completely

burn; thus actual energy released is only a fraction of the total energy

resulting from complete combustion. The ratio of actual to complete heat of

combustion is normally defined as combustion efficiency Xa of the fuel. (Section 3.3 discusses energy release rates, and a list of Xa for the materials of

interest is found in Table 3.21.)

According to Tewarson et al. (1980a), a portion of the actual energy generated heats the gases (convective heat energy), while the remainder is flameradiative heat energy. Therefore, actual heat of combustion is the sum of convective and radiative heats of combustion. It follows that the combustion

efficiency X is the sum of the convective and radiative fractions of heat of

Complete comgustion (X and Xr, respectively). The values of X and X for

various combustible materials can be found in Tables A.1.2 and U.1.4 of Appendix A.1 and Table A.2.1 of Appendix A.2.

Radiation from soot particles, C02, and water vapor (flame radiation) is

the primary heat transfer mode in large-scale fires that induce fuel

gasification/pyrolysis. The flux of this radiation depends on the above species concentration, flame temperature and geometry. Again, this shows that

energy generation, especially the radiative fraction, is strongly dependent on

the type and amount of material generated in large fires.

2.14
The chemical composition of fuel vapors and products can change significantly in various stages of a fire and thus actual, convective and radiative

heat releases will also change. Tewarson et al. (1980a) presented the data of

actual and convective heats of combustion of red oak as functions of time for

two external heat flux values for piloted and auto-ignition (see Figure 2.1).

The heats of combustion vary with time, external heat flux and the mode of

ignition.

The unburned fuel vapor from the flaming glovebox is entrained with the

burned gases and air to the ceiling layer via the fire plume. According to

Pagni and Shih (1976), all the unburned vapors which enter the upper layer are

called excess pyrolysate. As this gas flows from the glovebox, it spreads the

fire throughout the structure by burning whenever it reaches ambient oxygen at

sufficiently high temperature. Additional amounts of excess pyrolysate may be

contributed from combustible material which is smoldering or decomposing due to

heat given off by burning objects in the vicinity. This phenomena is believed

to be responsible for the rapid involvement of the entire structure observed in

full-scale fire tests.

15.0

- 10.0

I--

0

C-,

5.0

0

0 500 1000

TIME, sec

FIGURE 2.1. Actual and Convective Heats of Combustion of Red Oak

as Functions of Time

2.15
The above example shows that neither mass nor heat generation should be

considered independently when analyzing fires in nuclear fuel cycle facilities.

2.2 MECHANISMS OF SOOT FORMATION

The generation of soot particles in flames is not only responsible for the

radiant energy in a fire and the amount of these particulate materials airborne, but also their rate of growth, which can affect the rate of filter plugging in nuclear facilities. Particles deposited continuously onto the filter

can eventually lead to plugging and breakage of filter elements due to the high

pressure that can result from the restrictive flow of burnt gases (from the

fire) to the atmosphere. The behavior of airborne particulate materials and

how it affects their growth are discussed in Section 2.3. Section 3.2.1 is a

collection of experimental data on particulate generation rate for the materials of interest.

This section covers the state-of-the-art studies on soot formation in

flames. In the literature, the study of the mechanisms of soot formation is

usually divided into two tasks:

" Chemical Task--which deals with the formation of soot precursors

from fuel and looks into the possible initiation of the nucleation

process. The kinetics of these chemical reactions are of prime

concern.

" Physical Task--which deals with the limitation on the growth of

freshly formed carbon particles to a certain size. In other words,

this part of the study concentrates on the behavior of the airborne

materials as discussed in Section 2.3.

Many recent articles were found in which the authors describe their

attempts to collect data for elucidation of the mechanisms of combustion product formation. These investigators have studied only the flame zones of both

premixed and diffusion flames. No exact mechanisms have been identified that

may be combined with some of the well-defined behavior of airborne materials to

enable a better understanding of combustion phenomena.

The formation of organic matter (soot and hydrocarbons) in premixed flames

has been' a mystery for many years, and studies of this area are still continuing. The polycyclic aromatic hydrocarbons (PCAHs) found with soot collected

from premixed flames have been considered as end products of side reactions of

other reactive cyclic intermediates, and not themselves intermediates in the

process of soot formation (D'Alessio et al. 1974). This belief was questioned

by those who observed that the PCAH compounds are intermediate in the formation

of the large polybenzenoid radials which constitute soot. D'Alessio's study

concluded that there are two distinct groups of PCAHs: the "unreactive" PCAHs,

which are byproducts of soot formation; and the "reactive" PCAHs, which account

for the formation of only a small fraction of the soot observed in both premixed high and low pressure flame.

2.16
For diffusion flames, there is even more uncertainty about the mechanisms

of soot formation (Boisdron and Brock 1972). In diffusion flames of organic

compounds it is generally believed that soot formation depends on pyrolysis,

which at the same time is attended by polymerization rather than degralatiorrv.

There is some evidence that soot particles are formed by two possible prf sese

within the pyrolytic zones of diffusion flames, one involving nucleation of

solid carbonaceous materials from reaction of the intermediate pyrolysis and

the other involving free radical polymerization of the products of pyrolysis to

yield long chain polymers which may subsequently condense and appear finally as

"soot droplets."

The following models, which describe the chemical aspects of soot formation, were briefly discussed by McHale and Skolnik (1979) and Chien and.Seader

(1975).

2.2.1 Carbon Formation by Charged Bodies (ionic nucleation)

This model, which was proposed by Howard in 1969, is based on the belief

that a neutral precursor acquires a charge. Howard believed that the charged

precursors do not agglomerate until the particles are large enough to overcome

their electrostatic repulsion between crystallites. Howard predicted that the

size necessary for agglomeration under normal flame conditions is 20 to 30 A,

which is in agreement with experimental values. Chains will then be formed

after particle growth ceases due to the insufficient kinetic energy to overcome

electrostatic repulsion. However, this model became unreliable after the study

by Wersborg et al. in 1971 to 1973, who claimed that the approach of the model

is weak due to its simplicity and the fact that most particles in a flame are

not charged.

2.2.2 Polymerization and Dehydrogenation via Acetylene

It was initially proposed by Porter (1953) that carbon or soot particles

are formed by two simultaneous chemical reactions--polymerization and dehydrogenation. First of all, fuel material is decomposed by heat; then acetylene

and its intermediates (i.e., free radicals, ions, etc.) are found. The process

of polymerization, which yields polyacetylenes, is followed by dehydrogenation,

which yields soot particles. The polymerization process is thought to involve

acetylene with a series of reactions with free radicals to give a distribution

of polyacetylenes and then free radicals, according to the following scheme

(Boisdron and Brock 1972; Bonne, Homann and Wagner 1965):

PA-- PA-- PA--

+ +

C2H + C2 2. C4 H (+H2 ) + C2 H2 - C6 H (+H2) + C2 H2 - C H (+H2 )---

C4 H2 (+H) C6 H2 (+H) C8 H2 (+H)

C23+ C2 H2 - C4H 3 (+H2 ) + C2 H2 ---- C6 H3 (+H2 ) + C2H2- C8H3(+H2)-

P + +

PA --- PA ---- PA -.--

2.17
where PA = polyacetylenes. Polyacetylenes up to C1 2 H2 were detected in the

study by Bonne, Homann and Wagner (1965). For the overall view of soot formation via acetylene, Williams and Smith (1970) presented a scheme (Figure 2.2)

which involved many possible routes.

C2 H2

. H_ C2 RADICALS

POLYACETYLENES IONS

~1 (POLYMERIZATION)

NUCLEI

I (POLYACETYLENES)

POLYMERIC AROMATICS AND •CARBON PARTICLES AND

POLYMER-LIKE MATERIALS POLYMERIC SOLIDS • SOOT

(AGGLOMERATION, FURTHER REACTIONS, ETC.)

FIGURE 2.2. Summary of Possible Mechanisms of Soot Formation

via Acetylene

2.2.3 Polymerization via Aromatics and Polycyclics

Rummel and Veh (1941) believed that prior to carbon formation, aromatics

and polycyclic hydrocarbons are formed in the combustion of hydrocarbon fuels.

In a study by Gaydon and Wolfhard (1970), experimental evidence revealed that

it is unlikely aromatics and polycyclics are intermediates in soot formation;

Palmer and Cullis (1965) proposed that highly unsaturated aliphatics may serve

as soot precursors.

2.2.4 Condensation and Graphitization

Condensation occurs when the partial pressure of the vapor pressure

becomes higher than the saturated Vapor pressure. These condensing vapors form

liquid droplets which then graphitize. Parker and Wolfhard (1953) suggest that

the formation of soot obeys this mechanism, and it is currently believed to be

one of the more promising explanations. They also believed that this mechanism

may account, at least partially, for the type of liquidaerosol or smoke that

2.18
results when polymers are pyrolyzed in a nonflaming combustion mode. Chien and

Seader (1975) suggested that this mechanism of soot formation is most likely

found in diffusion flames, where the residence time is relatively long in the

pre-carbon zone. Since graphitization is a process which requires high temperatures and long time periods to occur, the residence time of the particles in a

premixed flame is sufficient to form large graphite layers (Bonne, Homann and

Wagner 1965). This was also confirmed by x-ray investigation of the soot

collected.

2.2.5 Nucleation

There are two principal mechanisms in nucleation (Boisdron and Brock

1972): chemical and physical. Formation of soot particles in combustion processes is an example of chemical nucleation. The second mechanism involves

growth from supersaturated vapor and classifies further as either homogeneous

or heterogeneous physical nucleation. The study of soot particle. formation

began in 1959, when Tenser pointed out that nucleation may occur in flaming

combustion systems. In 1965, Palmer and Cullins concluded in their study that

polyunsaturated hydrocarbon compounds are responsible for the initiation of the

nucleation process, which was strongly supported by the work of Bonne, Homann

and Wagner in the same year. For example, in an acetylene-oxygen flame at low

pressure, Bonne and his associates were able to identify and trace the concentrations of the species C2 H2 , C4H2, C6 H2 , C8 H2 , and CIOH2 throughout the entire

flame zone. Bittner (1978) collected and illustrated a summary of mechanisms

proposed over the years in Figure 2.3.

The figure summarizes all the possible mechanisms of soot formation via

various identified intermediate species. Since soot particles contain much

lower ratios of H/C than fuel molecules do, soot formation must involve processes of dehydrogenation (moving left to right in Figure 2.3) and aggregation

(moving top to bottom). Two extreme routes, the C2 route and the saturated

polymer route, are believed to occur at 3000 and 700 0K, respectively. In the

temperature range of 1200 to 2200 0 K, the possible mechanisms which are represented by the central portion of Figure 2.3 are most likely to occur in soot

formation. The role of PCAHs, which were thought to be stable byproducts, is

illustrated in the center of the figure. Polycyclic aromatic hydrocarbons have

also been proposed as intermediates of soot formation because they have sufficiently low vapor pressures to physically condense to liquid droplets, which

then form soot.

Based on the complexity and the uncertainty of product formation in

flames, more quantitative data on this phenomenon are necessary to solve this

mystery.

2.3 BEHAVIOR OF AIRBORNE MATERIALS

Now that we have discussed the formation of soot and other possible chemical species in flames, there are questions to be answered concerning the behavior of those airborne particles as they leave the flame zone. For example, the

change in particles as a function of time with various forces has been a main

2.19
DEHYDROGENATION ; %

POLYMERIZATION N CODNSTO \\ CONDENSATION

AND \ I

DERYDROGENATION POLYACETYLENES

PCAH SURFACE

<STABLELE GROWTHBY

IPCAH DECOMPOSITION

BYPRODUCTS DEHYDROGENATION

PHYSICAL AND

CONDENSATION POLYMER I ZAT ION

I POLYMERIZATION

SATURATED OR LIQUID DROPLETS CARBON PARTICLES

UNSATURATED - CONTAINING - WITH GRAPHITEPOLYMERS POLYCYCLIC COMPOUNDS LIKE STRUCTURE

FIGURE 2.3. Summary of Proposed Mechanisms of Soot Formation

concern in fire study. In fact, the study of these particle characteristics is

necessary for fire safety and environmental concerns. Changes through time in

the conditions of the airborne materials can occur by the following mechanisms

(Chien and Seader 1975):

" shear

" evaporation

" condensation

" coalescence (agglomeration)

" settling

" diffusion.

Measurements have been made on the characteristics of airborne materials

(i.e., soot and smoke) utilizing laws of optical scattering phenomena

(Bouguer's law and Mie theory, etc.), which assume stable smoke suspension.

Therefore, the influence of the above mechanism on particle suspension stability can strongly affect the accuracy of the measurements. This is especially

significant for the unstable particles of smoke in the vicinity of the flame

zone, where the magnitude of external forces (i.e., thermal energy, concentration gradient, etc.) is still great.

2.20
Theories describing the particulate behavior for most of these mechanisms

are currently available (Chien and Seader 1975). In particular, theories for

the phenomena of particle settling and agglomeration have gained the most

attention in combustion product study.

2.3.1 Coalescence(a)

Coalescence of airborne particles occurs when they collide with one

another and larger particles are formed as a result. The mechanisms and forces

causing the collisions are thermal, electrical, magnetic, hydrodynamic, gravitational, etc. Some of these mechanisms may act concurrently, generally in the

presence of thermal effect.

For thermal coalescence, particles airborne into the atmosphere above the

flame have a tendency to merge together because of Brownian motion or diffusion. The rate of decrease of particulate concentration by these "sticky" collisions is governed by a decay rate equation:

dNP2

S-KN 2 (2.3) dt Kp

where N = particulate concentration/cm3

t.= time, sec

K = a rate constant.

The above equation can then be integrated to express particulate concentration as a function of time:

1 1 + Kt (2.4)

p po0

where (N )0 is the initial particle concentration. Experimental values for K

ranged fRom 5 x 10-9 cm3 /sec for typical particulate clouds to

4*x 10-10 cm3/sec for very fine material (Corrin 1974). Equation (2.4) can be

further reduced to relate the particulate growth in transit. By using

Bouguer's law for monochromatic light as applied to smoke of uniform particulate size and concentration (based on single scattering phenomena) with Equation (2.4), Chien and Seader came up with the following equation:

(a) The words "agglomeration and "coagulation," frequently found in combustion

literature to describe the behavior of particles, are usually used

synonymously (Burgess, Treitmar and Gold 1979). In this report the term IIcoalescence" will be used in their place.

2.21
[d 3+ 6K Mp t 1/3

d = pp V I (2.5)

where do and d are initial and time-dependent particulate diameters, respectively, M is the total particulate mass, pp is the particulate density, and V

is the te~t chamber volume.

Assuming a particulate density p of 1.3 g/cm3 , Chien and Seader show a

plot of particulate diameter as a function of time for two different initial

particulate diameters of 0.05 and 0.5 jim [Equation (2.5)] using the standard

volume of a flow-through combustion chamber (Figure 2.4). Notice that total

mass concentrations of 0.5 to 2.5 jg/cm3 are used as parameters in the plot.

Figure 2.4 also shows that the initial particulate size is a significant factor

only during the first few minutes. Very small particles coalesce rapidly at

first.

2.3.2 Settling

Gravitational force causes interacting particles to fall as their accumulated mass overcomes the buoyancy and drag forces that originally suspended the

particles. For spherical solid particles, settling theory has been well developed and Stoke's law applied. The law relates the terminal settling velocity

with other parameters as follows (Chien and Seader 1974):

2.5

2.0 DROPLET MASS CONCENTRATION =2.5pggcum3

W 1.5

M 1g.m DROPLET MASS CONCENTRATION - 0.5 

~1.0

a..

0x

0 10 20 30 40 50

TIME, min

FIGURE 2.4. Effect of Coalescence on Growth of Droplets

2.22
2

g d (p - p)k

V - p (2.6)

t 0 . 18 2

where Vt = terminal settling velocity

g = acceleration due to gravity

d = particulate diameter

p = density of the gas stream

k = Cunningham correction factor

p = gas viscosity.

Equation (2.6) contains the Cunningham correction factor k, which is

appropriate when the particle size reaches the mean-free path of the fluid molecules. The correction is directly proportional to temperature and inversely

proportional to particle size. When droplets form by condensation and then

fall through a still gas, one can also utilize Stoke's law to evaluate their

terminal settling velocities, provided that the droplets remain essentially

spherical and behave like solid particles. Notice that Equation (2.6) applies

only to particles smaller than about 10 pm dia.

To predict the particulate and droplet settling in a flow-through combustion chamber under fire-test conditions, Chien and Seader calculated the corrected terminal settling velocity with corresponding k value as a function of

particle diameter. Their results are tabulated in Table 2.6 (with air temperature at 70'F and pressure 1.0 atm).

TABLE 2.6. The Minimum Time for Particulates and Droplet

Settling in a Flow-Through Combustion Chamber

Droplet Corrected Terminal Cunningham Minimum Time to

Particulate Settling Velocity, Correction Settle at Bottom

Diameter,pm ft/min Factor, k of Chamber, min

0.1 0.000221 2.88 6500

0.25 0.000806 1.682 1800

0.5 0.00254 1.325 600

1.0 0.00890 1.160 150

2.5. 0.0512 1.064 30

The last column in Table 2.6 represents the time required for the corresponding particle sizes to settle 1.5 ft, the height of the chamber. These

calculated values indicate that the extent of droplet and particle settling

during the first 10 min of a combustion test would be almost negligible.

2.23
2.3.3 Summary

The behavior of airborne materials from a combustion process may affect

the stability of suspended smoke particles, which in turn determines the accuracy of measurements of smoke properties. Two important conclusions can be

drawn from the literature for two possible mechanisms of particulate behavior:

1. Coalescence. Particle size increases rapidly during the first few minutes

after a particle is formed, as shown in Figure 2.4. After 20 min the size

becomes fairly constant, especially for low particulate mass density.

This implies that by knowing how fast the particles travel, more accurate

measurements can be made at a known distance (where particles become

stable) from the initial particle source. Although this known distance

might be quite far in comparison to the size of the test chamber, unless

the particles are moving extremely slowly, which is not the case in a

fire, one can use Equation (2.5) to predict the particle diameters as a

function of time, provided that the other factors in the equation are

known.

2. Settling. Based on the values in Table 2.6, the settling of the combustion-generated particulates (usually <1 um dia) would be negligible during

the first 10 min of the test.

2.4 FACTORS THAT INFLUENCE THE GENERATION OF SMOKE

Extensive studies have considered the effects of various chemical and

physical factors on the generation of combustion products. Chien and Seader

(1974) have presented a list of factors (Table 2.7) such as light transmission;

airborne mass loss; and particulate mass and size, shape, and phase state which

affect smoke characteristics.

Both experimental and theoretical studies contribute valuable information

on how certain factors affect the generation of combustion products. Tsuchiya

and Lier (1975) made a theoretical study of the chemical composition of the

surrounding environment of building fires. By assuming complete mixing of all

components in the system, the reaching of equilibrium both chemically and thermally by all reactions, and uniform gas temperatures and composition, they

relate the following parameters: 1) nature of fuel, 2) adequacy of oxygen supply, 3) temperature, 4) quantity of each combustion product, and 5) quantity of

combustion heat. Of these five groups of variables, if any three are fixed,

the remaining two may be determined by solving the simultaneous equations of

material conservation, heat conservation, and chemical equilibrium. 'Some of

the general conclusions made by Tsuchiya and Leir have been proven experimentally. For example, the quantity of CO produced from carbon-containing materials increases with increasing temperature.

King (1975) stated that factors which can govern a material's tendency to

smoke and produce CO include material composition, density, weight, thickness,

external surface characteristics, geometry heat flux, air flow, oxygen availability and pressure. He concluded that combustion can change from a flaming

2.24
TABLE 2.7. Factors That Affect the Characteristics ,of Combustion Products

Chemical Factors Physical Factors

Fuel types Exposed surface area

Fire retardants Sample thickness, weight and density

Surface coatings Orientation

Functional groups Enclosure volume

Heat flux

Oxygen availability

Ventilation

Space temperature

Char formation

Coagulation, settling

Diffusion

Polydi spersion

to a smoldering mode as the oxygen concentration is depleted. Many other

investigators provided similar information, and they claimed that the quantity

and nature of combustion products generated from flaming and nonflaming combustion processes are determined mainly by the chemical and physical nature of

materials, the temperature, and the oxygen supply.

2.4.1 Chemical Factors

Types of materials and the fire retardants and surface coatings found on

them are some of the more important chemical factors considered in many combustion or fire studies. These factors can drastically change the characteristics

of combustion products. The chemistry of these changes can easily be determined by differential thermal analysis, thermogravimetry and time-of-flight

mass spectrometry (Hilado 1969).

Gross, Loftus and Robertson (1969) have studied how surface coatings can

alter the smoke production of an exterior-grade plywood 1/4-in. thick under

nonflaming conditions. The results are plotted in terms of specific optical

density and transmittance versus time (shown in Figure 2.5).

Gross' study also presented the smoke accumulation curves for both smoldering and flaming specimens of various materials (shown in Figures 2.6 and

2.7). They summarized that the maximum smoke accumulation values for the

flaming tests were always less than those for the smoldering tests, except for

PS and PVC (noncellulosic materials), which have rapid rates of smoke production under flaming conditions.

Seader and Einhorn's studies (1976) generally agreed with the above study

by Gross, Loftus and Robertson. They showed that some materials, particularly

rubber, exhibit large values of smoke accumulation, while glass fiber insulation, chlorinated PVC, asbestos fiber insulation, polytetrafluorethylene, and

polyvinylbutynol have low values of smoke accumulation for both nonflaming and

flaming conditions.

2.25
300

WALL '.US --- TED 1

PAPER UNCOATED

2

VINYL

200 FILM z

LUa

01

"-- ~VARNISH • 1002 ]o -r 20

CLOTH 50

ALKYD PAINT

o 1 100

0 4 8 12 16 20

TIME, min

FIGURE 2.5. Effect of Surface Coatings on Smoke Buildup

for Plywood in Nonflaming Exposure

In general, fire retardants are thought to increase smoke density or opacity (Seader and Einhorn 1976). However, if materials tend to melt and drip as

they burn, this may alter the effect of fire retardants. The complexity of

additive interactions for various materials of building construction, interior

design, etc., will continue to be the main concern for fire-retardant

treatments.

2.4.2 Physical Factors

In general, some of the well-known physical factors which influence the

generation of smoke during small-scale fire experiments are sample weight (density) and thickness, its orientation and exposed surface area, heat flux, oxygen availability and ventilation, space (ambient) temperature, pressure, and,

particulate coalescence. Parameters that specifically affect particle size

and/or particle statistics include relative humidity and rate of smoke generation (Welker and Wagner 1977; Gross, Loftus and Robertson 1969). Some of the

important physical factors are examined below.

2.4.2.1 The Material Itself

Three physical factors influencing smoke generation which are commonly

found in combustion product studies are material thickness, material density

and horizontal or vertical orientation. Seader and Einhorn have collected the

2.26
400 CELLULOSE ACETATE

BUTYRAT• POLYSTR•

V300 WOOD

POLYVINYL CHLORIDE

20-FIBE BOARD WOOL RUG

ACRYLIC

100

0 300 600 900 1200 1500 1800 2100 2400

TINM. sec

FIGURE 2.6. Smoke Accumulation Curves for Smoldering

Samples of Various Materials

results from several combustion studies that show how these physical factors

have affected smoke production (Figures 2.8, 2.9, and 2.10). As shown in

Figure 2.8, for thin materials or layers of the same material, the specific

optical (smoke) density is almost directly proportional to the:thickness.

According to Seader and Einhorn, when a certain critical thickness is exceeded,

the specific optical density remains essentially constant with increasing

thickness. This critical thickness varies and may depend on several other factors including sample density, thermal conductivity, and tendency to form a

char layer; for nonfoamed plastics, the critical thickness may be as small as

0.25 in. In Figure 2.9, adapted from Zinn and Cassanova's work (1976), smoke

forms faster for horizontal materials than for vertical materials. They stated

that this is true for both thermoplastic and nonthermoplastic materials. In

Figure 2.10, the relationship between the maximum specific optical density of

rigid-urethane foam and foam density is fairly linear. Figure 2.10 also illustrates that a thinner rigid-urethane foam produces less smoke under the nonflaming mode of the fire test, while for the same thickness, the foam produces

more smoke in a nonflaming mode than in a flaming mode of combustion.

2.27
700

POLY STYRENE

600

POLYV I NYL CHLOR I DE

500

400

~300

200-

WOOL R G

RED OAK

100PLYWOOD 10ACRYLIC .- • " F IBE RBOAR D

01

0 300 600 900 1200

TIME, sec

FIGURE 2.7. Smoke Accumulation Curves for Active Flaming

Combustion of Samples of Various Materials

2.28
1000

-J

<• •800 00

U

u 600 ABS LAYERS (NBS SRM 1007),

J00

tu. _ýu FLAMING

E

D- 2

w

< 400

2 z/

U1 U• 200 -- •SRM 1I006) NONFLAMING,

0

0 0.03 0.06 0.09

THICKNESS (INCH)

FIGURE 2.8. Effect of Layer Thickness on Maximum Specific

Optical Density

2.4.2.2 Temperature

Temperature is a major factor that will predetermine the existence of combustion. According to Hilado (1970), the temperature of burned gas is much

higher than the ignition temperature, and the difference between these two provides the driving force for maintaining combustion. The fire is extinguished

when the difference is too small to support combustion. In an actual fire, a

material is subjected to a broad range of irradiance levels, from pre-ignition

to flashover.

From the burning of hardboard (batch operation) in a small-scale smoke

chamber (where smoke is confined to the chamber during testing), Gross, Loftus

and Robertson (1969) observed that smoke accumulation from pyrolytic decomposition was low at temperatures below 300°C, and peak smoking occurred when the

temperature was approximately 380'C (see Figure 2.11). At higher temperatures,

self-ignition with flaming combustion occurred, reducing smoke accumulation

drastically. At very high temperatures the smoke accumulation again increased.

2.29
60

50• 

- -V ERTICAL

>: 40

IZ

z

J.< 30

U

I0

Y

u 20

U HARDWOOD, 0.40cm THICKNESS,

(L FLAMING In

10

0.

0 100 200 300 400 500 600 700 800

TIME, sec

FIGURE 2.9. Effect of Sample Orientation on Specific Optical Density

This could be caused by flaming combustion, which enhances smoke generation due

to depleted oxygen and high temperatures inside the closed chamber. A similar

relationship would be expected as a function of irradiance level on a single

exposed surface of cellulosic materials.

Seader and Einhorn found that temperature affects smoke accumulation in

the same way (Figure 2.12), except that the effect is in terms of increasing

energy flux with Douglas fir as test specimens.

Figure 2.12 illustrates that a heat flux of 2.5 W/cm2 , used in the standard nonflaming test, is insufficient to ignite most materials. Therefore, in

many standard flaming experiments, the radiant heat flux is supplemented with

propane-air pilot flames. Heat fluxes in actual fires can attain levels of at

least 10 W/cm2 , and the temperatures found in ordinary building fires range

from 500 to 1300'K (Tsuchiya and Leir 1973)..

2.30
600

E

O. 500 - NF = NONFLAMING MODE

>:0. S-INCH THICK

(RIGID-URETHANE Z FOAM (NF)

w 400

_j0

U

Lt- 300

U RIGID-URETHANE

U

W 200 CL

1000

RIGID-URETHANE FOAM (F)

0

0 2 4 6 8 10 12 14 16 18

FOAM DENSITY, lb/ft 3

FIGURE 2.10. Effect of Material Density on Maximum Specific Optical

Densi ty

In an actual fire the combustion of a given material will usually occur in

the temperature environment produced by the combustion of neighboring materials. This is especially true in a room in which flashover has occurred

(Powell et al. 1979). This aspect of elevated temperature environment has been

thoroughly examined (Bankston et al . 1978) for both flaming and nonflaming combustion by burning many plastic and cellulosic materials in small-scale

flow-through chambers(smoke flows out of chamber during test). The collected

data indicate that in flaming tests of both-PVC and wood, higher environmental

temperatures generally result in greater optical densities and larger smoke

particles, while in nonflaming tests of wood higher temperatures result in

lower smoke densities and smaller smoke particles. Bankston's results do not

agree with Figure 2.11 for nonflaming tests, probably because different types

of chambers and experimental conditions were used in the two studies.

Powell et al. (1979) also studied the effect of elevated temperatures upon

the rates of sample weight loss for Douglas fir and rigid PVC under both nonflaming and flaming conditions (Figures 2.13 and 2.14). Under nonflaming conditions, the rates change drastically for both materials as temperature is

raised, while the rates are only slightly affected in flaming tests.

2.31
S0.6

0.4

0

0.2 /

0 200 400 600 80 1000 1200

FURNACE TEMPERATURE, °C

FIGURE 2.11. Smoke Production of Hardboard Within a Heated Furnace

2.4.2.3 Quantity of Available Oxygen

The presence of oxygen is necessary for burning. The partial oxygen pressure at the time of the fire in a compartment can strongly affect the smoking

and burning rate. Saito (1974) and Gross, Loftus and Robertson (1969) showed

that changes in the oxygen concentration of the ambient atmosphere surrounding

the specimen significantly influence smoke production (Figure 2.15).

The rate of smoke produced in nonflaming combustion increases with oxygen

concentration for cellulosic materials. Gross, Loftus and Robertson also discovered that the rate of smoke production depends upon the spacing between the

sample and the front face of the furnace in a combustion chamber. They believe

that with adequate space between sample and furnace face, free convection of

air passes over the sample during pyrolysis and causes continuous smoke

generation.

For flaming conditions King (1975) studied the effects of normal (initial

21% 02 concentration) and oxygen-lean (initial 15% 02 concentration) atmospheres on the rates of smoke and CO production from burning PVC, red oak, ABS

and PS. They found that small changes in 02 concentration had very little

effect on the rate of smoke production. They also indicated that the rates of

CO production increase with decreasing atmospheric oxygen concentrations.

Figure A.1.2 of Appendix A.1 also illustrates this effect.

2.32
_r

E , o0 00

FLAM I NG REG ION C,---• 8I

9do

>:, 800

WI

4NONFLAM I NG REG ION

S 200

0

0 1 2 3 4, 5 6 7 8

ENERGY FLUX, W/cm2

FIGURE 2.12. Effect of Energy Flux on Dm of Douglas Fir

To study changes in burning smoke production rates for different types and

sizes of openings, Saito (1974) used the empirical formula

RB = 5.5 AHI/2 (2.7)

where

R = burning rate

R = area of the opening

H = height of the opening

AHI/ 2 = ventilation parameter.

His results did not correlate well with the above equation so Saito concluded

that smoke generation rate is inversely related to burning rate.

2.5 METHODS OF EXPERIMENTAL FIRE STUDY

Experimental studies of combustion products have been broken down into two

categories: products in flames and smoke. The studies concentrated in the

flame zone help identify possible chemical species-as a function of flame

height and width in time. From this, possible mechanistic formulations of carbon particles (soot) are proposed. There is also interest in the chemical and

2.33
100

90

80

70

• 60

;c 50

-j

30

20

10

0

5 10 15 20 25

TIME, mrin

FIGURE 2.13.

100

90

so

70

60

so

40

I30

20

10

0

FIGURE 2.14.

Weight Loss for Wood and PVC Samples Burned Under Nonflaming Conditions at Different Environmental Temperatures

5 10

TIME. wIn

is 2e

Weight Loss for Wood and PVC Samples Burned Under Flaming

Conditions at Different Environmental Temperatures

2.34
z

uJ

,-J0 300

U

0

U

U_

U200

In

84 0 12 16 20

TIME, min.

FIGURE 2.15. Smoke Buildup for Fiberboard Burned Under Nonflaming

Combustion in Reduced Oxygen Atmospheres

physical properties as well. as the opacity of smoke evolved from the fire.

This knowledge of smoke characteristics provides information for assessing

safety during a fire.

2.5.1 The Study of Combustion Products in Flames

The methods of generating a flame are different with respect to the fuel

materials being used. For gaseous fuel, a bunsen burner may be used to produce

a premixed flame; a diffusion flame can be obtained by using a special burner

constructed with two concentric tubes with fuel flowing from the inner tube and

air (or 02) from the outer tube. For liquid fuel, the fuel material may be

vaporized and mixed with air (or 02) to give a premixed flame, while a diffusion flame is normally obtained by igniting a small pool of liquid fuel in a

pan of a specific size with the presence of air (or 02). For solid fuel,

diffusion flames of various materials are usually studied by burning a small

2.35
sample with another flame source or by wetting a sample with liquid fuel and

burning it until the solid sample can sustain its own flame.

In general, samples are drawn directly from the flame with probes for

analysis. After the samples are drawn from the flame, chemical composition can

be identified with a gas chromatograph and/or a gas chromatograph/mass spectrometer. Optical methods (scattering and extinction) are often used to measure

particle numbers and mass concentrations. Particle size measurements can be

made by diffusion-broadening spectroscopy or electron micrography.

In the 1970s more advanced equipment such as electrical aerosol analyzers

(EAAs) and condensation nuclei counters (CNCs) were developed to measure the

particulate sizes and distributions. These devices are commonly used to study

smoke characteristics by in-situ measurements.

2.5.2 The Study of Combustion Products in Smokes

Many researchers have studied thermal degradation and characteristics of

combustion products found in smoke produced by burning of both natural and synthetic materials used in building structures and interior furnishings. It has

been a concern that simulating fire in small-scale enclosures may not produce

results similar to those one would get in a real structural fire. With the

assistance of two Boston fire companies, Burgese, Treitman and Gold (1979)

studied toxic gases produced in an actual fire. They used a prototype sampling

system which was designed into a firefighter's turnout coat. No comparison of

the results has yet been made with data obtained from other fire studies in

small chambers.

Most of the published studies of smoke characteristics have been performed

by simulating flaming and/or nonflaming tests in small-scale combustion chambers. (For example, a National Bureau of Standards chamber, sometimes modified

for specific types of smoke studies, is a well-known standard apparatus.) The

fire conditions simulated in the small-scale tests may not be severe enough to

adequately gauge the behavior of the test materials in real fires. Today many

scientists are designing and generating their fire experiments under conditions

which closely resemble the actual fire scenario in a room or entire structure.

In recent years, the study of smoke evolved during combustion in fire has

gained attention from scientists and engineers, who have developed a number of

smoke test methods to measure certain physical characteristics. Seader and

Einhorn (1976) have tabulated a list of the more widely known devices

(Table 2.8).

Opacity of the smoke is determined by continuous measurement of the amount

of light transmitted through smoke particles generated from a combustion

source. A photocell is commonly used, parallel to the light source, to collect

the transmitting light. Portions of the nontransmissible light source are

either scattered or absorbed by smoke particles present. According to Gross,

Loftus and Robertson (1969), optical density is the single measurement most

2.36
characteristic of a "quantity of smoke" with regard to opacity. Therefore, a

fundamental law by Bouguer, based on percent light transmittance, is an appropriate measure of opacity:

Optical density= loglo (F/Fo) (2.8)

where F = transmitted light or flux

Fo= incident light or flux.

Another way of quantifying the particle density in smoke is by continuously filtering the smoke through a known area of filter paper (Gross, Loftus

and Robertson 1969); the resultant spot is classified according to its degree

of blackness, commonly referred to as "smoke shade."

In the United States the most widely accepted flow-through and batch

devices for determining smoke opacity are the Steiner Tunnel (ASTM E-84 test)

and the NBS-AMINCO Smoke Density Chamber, respectively (Seader and Einhorn

1976). By filtering the smoke particles, accumulated particulate mass is also

determined. In some tests, however, the sample weight is monitored continuously; thus the rate of material airborne can be determined.

A strategy has been developed at the Flammability Research Center, University of Utah for the chemical analysis of combustion products from natural and

synthetic materials (Seader and Einhorn 1976). A schematic illustration of the

scheme is presented in Figure 2.16.

2.37
TABLE 2.8. Test Devices for Studying Smoke

Designation

ASTM E-84 Steiner

tunnel test

ASTM E-286 8-ft tunnel

test

ASTM D-2843 smoke test

(Rohm and Haas XP-2

Smoke-Density Chamber)

ASTM E-162 radiant

panel test

NBS-AMINCO smokedensity chamber

Monsanto chamber

(based on ASTM D-757

Test)

NBS-LRL smoke-density

chamber

FRS fire propagation

furnace

Michigan chemical

oxygen index/smoke

densitometer (Modified

ASTM D-2863 Test)

Wayne State chamber

Modified TGA apparatus

Ohio State combustibility apparatus

Japanese Building

Research Institute and

NRC of Canada apparatus

Japanese Industrial

Standard A-1321 smoke

chamber

Arapahoe smoke chamber

SRI mass burning rate

apparatus

Georgia Tech Combustion

Products test chamber

Type of

Operation

FT

Optical

Opacity

X

Usual Measurements

Particulate Mass or Concentration

(gravimetric)

Particulate

Properties

FT X

B X

FT X

B X

X

FT X

B, FT X

B X

FT X

FT

FT X

FT X

FT X

B X

FT

F T

FT X

X

X

X

X

X

(a) B = Batch operation (smoke confined to chamber during test)

FT = Flow-through operation (smoke flows out of chamber during test).

2.38
FIGURE 2.16. General Analytical Scheme for Chemical Analysis

of Smokes

2.39

3.0 CHARACTERIZATION OF FIRE-GENERATED PRODUCTS

Our objective is to be able to characterize the energy output, the combustion products and the airborne radioactive materials generated as a function of

time and conditions in the event of a fire accident inside a fuel cycle

facility. In particular, the characteristics that we are most interested in

are as follows:

" percentage of initial combustibles that becomes airborne

" particle size distribution and particulate concentration

* chemical composition of airborne materials

" energy input to the combustion gases.

The airborne combustion products (gases, vapors, and particulates)

entrained with extraneous particulate materials (i.e., radionuclides, ambient

dust, etc.) present a potential hazard to the environment if they escape the

building. The materials which are most available as combustible fuels in a

facility fire are:

" polymethylmethacrylate (PMMA)

" polyvinyl chloride (PVC)

" elastomers (i.e., rubber and other commercial samples or plastics

such as polyethylene and polypropylene)

" cellulose

" cellulosic materials (i.e., papers and rags)

" organic fluids (i.e., kerosene, acetone, alcohol, hydraulic fluids

and other high-boiling organic liquids).

Data from the literature on these combustibles were collected to be used

as input to gas dynamics and material transport codes which predict the combustion product histories of the facility atmosphere under various fire conditions. Some of the airborne particulate characteristics will be used to

evaluate the engineering safety system (i.e., filters) of the facility.

Finally, a-method will be developed to calculate and predict the fire energy

and combustion product generation.

Because the combustion process is very complex it is rather difficult to

describe for an enclosure fire. Nonetheless, it is important to predict and

evaluate the hazards presented by a fire. Currently, several fire modeling

techniques are in the process of development and refinement. These techniques

function at different technical levels and fire scales (Tewarson 1980b). Data

inputs to these fire models include enclosure geometry, availability of oxygen,

heat of combustion, smoke generation, etc. Therefore, various physical/

chemical and combustion/pyrolysis properties of materials (i.e., plastics,

3.1
celluosic materials and organic fluids) are being determined in many fire

research organizations. For example, Tewarson and other researchers at Factory

Mutual Research Corporation (1976, 1980, 1980a and 1980b) are heavily involved

in studying materials properties in their small-scale test apparatus. Some of

the information they can provide are mass loss rate in pyrolysis and combustion

of various materials, heat release rate based on the concepts of convective and

radiative heat transfer, and product generation rate of various chemical

species (i.e., CO, C02 , gaseous hydrocarbons and soot).

B. T. Zinn et al. of Georgia Institute of Technology (1978, 1980) have

been characterizing airborne materials in their Combustion Products test

chamber over the past few years. Their objective is to define the percentage

of the original material becoming airborne, particle size and distribution,

chemical composition, and quantity of airborne material in terms of volume

concentration.

Table 3.1 shows the data available from the literature reviewed, and the

characteristics of combustion products of various materials of interest are

tabulated in Sections 3.1 and 3.2. These data were obtained from small

combustion-test apparatuses under a limited set of approximate fire conditions.

TABLE 3.1. Information Available in the Literature for the Fuel.

of Interest Found in Fuel Cycle Facilities

Fuel Materials

PMMA

Percentage of

Original Material

Airborne or Mass

Generation Rate

X(P)(F,NF)

X(P)(F,NF)

X(P)(F,NF)

Particle Size

and

Distribution

Chemical

Composition

X(P)(F,NF) NX

X(P)(F,NF) NX

X(P)(F,NF) X(P)(F,NF)

PS

Airborne

Material

Concentration

X(P)

X(P)

X(P)

X*(P)

NX

NX

X(F)

X(F)

Material s

Energy Release

from

Combustion

X(F)

PVC

Elastomers (i.e.,

rubber and plastics)

Cellulosic materials

(i.e., paper and rags)

Cellulose

Organic liquids -

Kerosene

Hydraulic fluids

X*(P)(F,NF) X*(P)(F,NF) NX

NX

X(P)

NX

X(P)

X(PS)

X(P)

NX

NX

X*(F)

NX

X(F)

NX

X(PV)

X(P)

X(P,V)

X(P)

X(P)

NX

NX

X = information available in literature

NX = information not available in literature

F = flaming combustion

NF = nonflaming combustion (pyrolysis)

V = vapor (in pyrolysis) only

P = particulate only

PS = particle size only

X* = information available for some plastics only

3.2
Two areas of combustion products study are found in the literature--

characterization of combustion products in flame and in smoke. Figures 3.1 and

3.2 show the general trends of how combustion products in flame and smoke

(respectively) have been studied. In general, materials are divided into three

classes--gaseous, liquid and solid combustibles--and analysis is made of size,

chemistry, mass quantity and energy of the airborne materials generated from

combustion. Both flaming and nonflaming combustion (pyrolysis) are usually

examined for each material being tested. In flaming combustion, two types of

flames, premixed and diffusion, are usually considered. Diffusion flames are

dominant in enclosure fires because this type of flame is diffusion controlled,

which is characteristic of uncontrolled fires. The reason that many

researchers study the combustion products of flames is to better understand the

formation process of soot particles and to be able to elucidate the mechanisms

of soot formation.

FIGURE 3.1. Schematic Representation of Combustion Products

Study in Flame

3.3
FIGURE 3.2. Schematic Representation of Combustion Products

Study in Smoke

3.1 PRODUCTS IN FLAMES

The characteristics of combustion products found in the flame zones are

not necessarily the same as those found in their vicinity, even for the simple

combustion process of burning a candle. This is due to the complex behavior of

particles, which are impacted by various forces as they leave the flame zone.

Determining the degree of change of these characteristics is more uncertain in

an accidental fire. It is important to identify data on the principal species

found in both premixed and diffusion flames because these species may serve as

nuclei which promote particle growth or possible further chemical reaction

after they escape from the -flame zone. Unfortunately, the literature has very

limited data on characteristics of combustion products in flames. Most of the

data were obtained from both premixed and diffusion flames by burning combustible gases and liquids. Very few solid fuels were tested. In all hydrocarbon

flames studied, carbon (soot) formation was observed.

Since data on the fuel materials that we are interested in are not available in the literature of premixed flames studies, data on other fuel materials

will be presented to compare with data from materials of interest found in diffusion flame studies. The ideal combustible used for the premixed flame

studies is acetylene (C2 H2 ) because its flame is very stable (Bonne, Homann and

Wagner 1965; Bittner 1978; Chippet and Gray 1978; Driscoll et al. 1978).

3.4
Flames with various C2H2:02 ratios and gas velocities were studied at both lowand high-pressure environments (ranging from 20 mm Hg to 760 mm Hg). Lowpressure premixed flames were used to study the kinetic relationships between

soot, PCAHs and other hydrocarbon species that may be important in soot nucleation or surface growth.

In all flames three different zones (Bonne, Homann and Wagner 1965;

D'Alessio et al. 1974; Bittner 1978) can be distinguished based on their

appearance: 1) a nonluminous (dark) zone directly above the burner (found in

all premixed flame studies); 2) the blue-green main reaction zone, where the

volatiles generated from the fuel are oxidized; and 3) the reaction zone, which

is followed by the upwards-extended region of the yellow- to orange-flowing

burned gases, a criterion for the onset of carbon formation. Two zones, the

reaction zone and the burned gases' region, were the main areas for sampling.

In 1965, Bonne, Homann and Wagner used both aromatic and aliphatic hydrocarbon

mixtures with oxygen for fuel materials in their premixed flame study at low

(20 mm Hg) pressure.

A similar study was conducted in 1978 at the same pressure by Bittner,

using acetylene-oxygen mixtures only. The experimental conditions a e the same

in both studies: a C2H2:02 ratio of 0.95 (or the equivalence ratio, a) 0 =

2.4) with an unburned gas velocity of 50 cm/sec. (Note: 5 mole % argon was

added to the unburned gas for measurement purposes in Bittner's study.) The

concentration profile measurements of major stable species in the burned gas

region agree well with Bonne et al.'s study. Figure 3.3 illustrates their

similar results in a C2 H2 -02 flame.

As can be seen in Figures 3.3 and 3.4, oxygen is completely consumed by

about 13 mm (end of reaction zone) above the burner. At this point CO and H2

have nearly reached their final values. Carbon dioxide and H2 mole-fractions

peak near 10 mm, and decrease slightly into the burned gas region. All values

become constant >30 mm. Thus, based on these studies, the mole fractions of

the major stable species found in the burned gas region of the premixed C2H2-02

flames are tabulated in Table 3.2.

Besides the major oxidation products, species that can be detected in the

burned gas region are polyacetylenes and soot particles. Each represents a

very small fraction of the total burned gas, about 10-3 mole. According to

investigators (Bonne, Homann and Wagner 1965; Bittner 1978), the concentrations,

of the polyacetylenes are greatest early in the reaction zone and reach a

constant final value in the burned gas. Before the end of the reaction zone,

polyacetylene hydrocarbons up to a mass of 146 (unsaturated hydrocarbons

(a) Equivalence ratio, 0, is defined as the actual fuel-air ratio divided by

the stoichiometric fuel-air ratio (F/A):

(F/A) If 0 > 1, mixture is rich.

= actual If 0 = 1, mixture is stoichiometric.

(F/A)stoichiometric If o < 0 < 1, mixture is lean.

3.5
0.4

0.3-

U_ 0.2

H2

0.1H Z

lOC 2

0 10 20 30 40 50 60

HEIGHT ABOVE BURNER, mm

FIGURE 3.3. Concentration Profiles in a Flat Acetylene-Oxygen

Flame (C2H2:02 = 0.95, or 0 = 2.4) at a Pressure

of 20 mm Hg and a Flow Velocity of the Unburned

Gas of 50 cm/sec (reprinted with permission from

Bonne, Homann and Wagner, Copyright 1965, Tbe

Combustion Institute, all rights reserved)

containing more C-atoms than the fuel molecules) are identified but the concentrations of these intermediate products become immeasurably small at the end of

the reaction zone, where oxygen is also completely consumed.

Bittner (1978) has also considered the variation of gas produced from rich

C2H2-02 mixtures at different equivalence ratios. At 0 = 2.0, the features of

the flame core are essentially the same but with lower CO, H2, acetylene and

polyacetylene concentrations, which might be expected. At 0 = 1.5, no acetylenes or polyacetylenes were detectable in the burned gas, while at 0 > 2.4 the

concentrations of both acetylenes and polyacetylenes were increased. In addition to the species observed in the flame at 0 = 2.4, several high-molecularweight aromatic hydrocarbons were observed. Their masses, molecular formulas,

and possible structures are listed in Table 3.3. The quantities of these particles were not measurable. They are believed to serve as surface growth precursors because they were airborne with the burned gas.

In 1974, D'Alessio et al. measured the concentrations of major stable

gases of a methane-02 flame at 1 atm with an unburned gas velocity of

7.4 cm/sec. Figures 3.5a and 3.5b show the major stable chemical species found

as a function of distance from the tip of the burner.

As can be seen from Figure 3.5, the concentrations of both H2 and CO are

similar in a CH4 -0 2 flame. This is quite different from the C2H2-02 flame,

where at a similar 0 the concentration of CO is almost three times as much as

the concentration of H2 (see Figures 3.3 and 3.4). This might be explained by

3.6
20

0e

0:

&-

_j

(D

1A

15

10

5

1 2 3 4

HEIGHT ABOVE BURNER, cm

FIGURE 3.4. Profiles-of Signal Intensities Relative to Argon

for Major Stable Species in-an Acetylene-Oxygen

Flame Near the Sooting Limit (0 = 2.4, P = 20.torr,

V : 50 cm/sec, 5 mole % argon, X = mole fraction)

(Bittner 1978)

TABLE 3.2. Mole Fraction of Major Stable Species Expected

in the Burned Gas of a C2 H2 -0 2 Premixed Flame

= 2.4, P =: 20 mm Hg, gas velocity = 50 cm/sec)

Species

CO

H2

H2 0

Co2

C2H2

Mole Fraction, X

Bonne et a]. Bittner

0.62 0.56

0.16

0.075

0.06

0.05

0.21

0.075

0.061

0.055,

Average Mile

Fraction, Ave

0.59

0.19

0.075

0.06

0.05

3.7
TABLE 3.3. Additional Species Near

Zone in a C2 H2 -0 2 Flame

Vo = 50 cm/sec)

MOLECULAR POSSIBLE

MASS FORMULA SPECIES

the End of the Reaction

(= 3.0, P = 20 torr,

STRUCTURE

CH 3

@

92 C/h8

102 CH6

104 C8H8

118 CgH10

128 C10H8

130 C10H10

TOLUENE

PHENYLACETYLENE

STYRENE

METHYL STYRENE

NAPHTHALENE

PHENYL BUTADIENE

DIHYDRONA PHTHALENE

METHYL NAPHTHALENE

C- CH

HC = CH2 @

HC = CH2

c3

H

CH

C CH

H 2

CH3

142 C11H10

146 C12H2 HEXACETYLENE

HC E C(-C =C-4 C1 CCH

the fact that acetylene contains more carbon and less hydrogen than methane.

The concentration of C02 found in a CH4 -0 2 flame is quite comparable with that

found in a C2 H2 -0 2 flame. Oxygen was used up in the oxidation reaction at

-7 mm above the burner, fairly low in comparison to the 13 mm found with C2 H2 .

Figure 3.5b shows other possible hydrocarbon intermediates which have substantially higher concentrations than those found in the C2 H2 -0 2 flame.

Thus, based on the available data, one can predict and identify the possible major components of the burned gas found in premixed flames of hydrocarbon fuel, but often the quantities of these major species are impossible to

estimate by generalizing from the available information (i.e., C2 H2 -0 2 and

CH4 -0 2 flames). Therefore, in order to determine the amount of each major

3.8
-J 20 0

0 12

Z, mm

FIGURE 3.5a. Concentration

and CH4 Along

C-H4 :02

CH4 :02

CH4 :02

Profiles of the Gaseous Compounds 02, H2 , CO, C02

the Flame for Different CH4:0 2 Feed Ratios

= 0.9, • = 1.8

- 1.0, : 2.0

= 1.3, @ = 2.5

3.9
6

0J0 3

Cz

5

0

5 10

Z, mm

FIGURE 3.5b. Concentration Profiles of

C2 H6 , C4 H2 , C4 H4 and C6 H6

CH4:02 Feed Ratios

CH4 :0 2 = 0.9,

CH4 :0 2 1.0,

CH4:02= 1.3,

the Gaseous Compounds C2 H2 , C2 H4 ,

Along the Flame for Different

= 1.8 = 2.0

=2.5

3.10
component in the burned gas of a certain fuel at various conditions, one must

conduct the experiment of interest.

Particle diameters of carbon were also measured in studies of C2 H2 -0 2 premixed flames. Table 3.4 shows the particle diameters measured by various

investigations with methods indicated. These studies show that at low pressure, mean particle diameter slightly increases as equivalence ratio increases,

with the mean diameter ranging from 0.016 to 0.018 pm. At a higher pressure

(1 atm), the particle diameter is considerably larger (0.2 pm) and varies

little as a result of equivalence ratio changes from 2.5 to 5.0. Diffusion

broadening spectroscopy and electron micrography were used to measure particle

diameters and their results show reasonable agreement.

3.1.1 Products in Diffusion Flames

It is quite interesting to compare the carbon particle diameters from a

sample withdrawn from a diffusion C2 H2 flame with those from a premixed flame.

Magnussen et al. (1978) have studied the effects of turbulent structure on soot

formation and combustion in C2 H2 diffusion flames. Utilizing the eddydissipation model modified with the influence of structural changes in the flow

due to variation of the Reynolds number (Re), the particle diameter is calculated (Table 3.5).

In this study the fuel C2 H2 was introduced upward into stagnant air

through a convergent nozzle with an exit diameter of 3 mm. The combustion air

was entrained from the surrounding air into the flame by turbulent diffusion.

Surrounding air temperature and pressure were approximately 20OC and 1 atm.

Magnussen et al. observed that the comp'utational particle diameters were of

about the same magnitude as those observed experimentally in flames.

By comparing these results with those in Table 3.4, one can see that the

carbon particles found in turbulent diffusion flames are an order of magnitude

smaller than the particles found in premixed flames at the same pressure.

Again, these data are for illustration only. In an actual fire inside a fuel

TABLE 3.4. Carbon Particle Diameters of C2 H2 -0 2 in a Premixed

Flame Under Various Experimental Conditions

Height Above

Experimental Conditions Burner Where

P, V Samples Were Particle

Reference mm Hg cm/sec • Withdrawn, mm Diameter, um Method of Measurement

Bonne et al. 20 50 3 dm = 0.016

(1965) Electron Micrography

20 50 4 -- dm = 0.018

Driscoll 760 20 2.5-5.0 30 0.25 Diffusion Broadening

et al. Spectroscopy-

(1978) 760 20 2.5-5.0 30 0.20 Electron Micrography

3.11
TABLE 3.5. Carbon Particle Diameters in Turbulent

Diffusion Flames Calculated by Utilizing

the Modified Eddy-Dissipation Model

Gas Velocity, Particle

Re m/sec Diameter, Um

40000 121.0 0.00204

50000 151.3 0.01785

52500 216.6 0.01324

55000 166.4 0.01686

55000 165.2 0.01424

55000 164.0 0.01180

56500 233.7 0.01195

cycle facility, C2 H2 is not likely to be present. Even though it may be

present, its unburned gas velocity is not likely to be >100 m/sec.

3.1.1.1 Kerosene

Information on particulate diameter, mass loading of soot particles and

identified PCAHs from turbulent diffusion flames of kerosene is available in

the study by Prado et al. (1978). Three atomizing air pressures were studied:

184 kPa (12 psig), 205 kPa (15 psig) and 239 kPa (20 psig). For determining

mass loading of soot particles, two cold gas velocities were used: 0.96 m/sec

and 2.67 m/sec, with an equivalence ratio of 1 and total air flow at a constant

value of 56.7 kg/hr (15.75 g/sec). Figures 3.6a and 3.6b (Prado et al. 1978)

show the mass loading of soot under these conditions.

Both figures show that there can be two distinct chemical processes in the

flame: soot can form to maximum loading, and then can disappear through combustion. Figure 3.6a shows one exception: the profile at 184 kPa exhibits a

plateau rather than a peak. Other experiments (Bittner 1978) also showed that

as equivalence ratios increased, so did the amount of soot formed. Therefore,

based on this information, considerable amounts of soot particles will survive

and become part of the product gases at low atomizing-air pressure, high equivalence ratios, and low 02 concentrations in surrounding air. The 02 in air

can oxidize the available carbon particles and reduce the amount of soot escaping through the flame zone.

Particle size was analyzed by electron microscopy at a magnification of

81,OOOX, which was increased to 200,OOOX. Two types of carbonaceous material

were observed. Close to the nozzle, in the zone of soot formation, the

particles looked like agglomerates of partially coalesced spherical units. The

individual spherical units in this material were very poorly defined and it was

not possible to measure their size. Farther from the nozzle, the material had

3..12
250

MV

E

UIVr%

E

Vi

"in

E

LA

t

0. -J

200

150

I0O

10

50

0

0 10 20 30 40 50 60 70

DISTANCE FROM NOZZLE, cm

0 10 20 30 40 50

DISTANCE FROM NOZZLE, cm

FIGURE 3.6a. Influence of Atomizing

Air Pressure on Axial

Profile of Soot Mass

Loading at Cold Gas

Velocity of 0.96 m/sec

[Kerosene:air fuel

equivalence ratio =

1.0; atomizing air

pressure = (o) 184 kPa

(12 psig), (o) 205 kPa

(15 psig), and (A)

239 kPa (20 psig)]

FIGURE 3.6b. Influence of Atomizing

Air Pressure on Axial

Profile of Soot Mass

Loading at Cold Gas

Velocity of 2.67 m/sec

[Kerosene:air fuel

equivalence ratio =

1.0; atomizing air

pressure = (o) 184 kPa

(12 psig), (o) 205 kPa

(15 psig), and (A)

239 kPa (20 psig)]

the classical appearance of necklace-like units of spherical particles. The

sizes of these well-defined units are reported in Tables 3.6a and 3.6b (Bittner

1978).

From Tables -3.6a and 3.6b, Bittner drew these conclusions:

* Changes in the atomizing air pressure., even when drastically

changing the total amount of soot emitted, do not affect the

particle size (Table 3.6a).

3.13
TABLE 3.6a. Arithmetic Mean Particle Diameter' (A) of Spherical

Kerosene Particles at Cold tas Velocity of 0.96 m/sec

(mean fuel equivalence ratio = 1.0)

Distance

from

Nozzle, cm

6

10

53 (exhaust)

Arithmetic Mean Particle Diameter, A

Atomizer Atomizer Atomizer

Air Pressure, Air Pressure, Air Pressure,

184 kPa 205 kPa 239 kPa

191 (a) (a)

211 220 254

249 298 (a)

(a) Poorly defined carbonaceous material.

TABLE 3.6b. Arithmetic Mean Particle Diameter (A) of Spherical

Kerosene Particles at Cold Gas Velocity of 2.67 m/sec

[atomizer air pressure = 184 kPa (12 psig), distance

from nozzle = 20 cm]

Mean Fuel

Equivalence Ratio

0.8

0.9

1.0

1.2

Arithmetic

Mean Particle

Diameter, A

(a)

146

145

139

(a) Poorly defined carbonaceous material.

0 Increasing the equivalence ratio by increasing cold gas velocity

results in a higher temperature through the reduction of heat loss

per unit energy input. An increase in temperature results in a

decrease in the size of particles through an increase in the number

of particles formed per unit volume, all other parameters being

constant.

From gas chromatographic-mass spectrometric (GC-MS) analysis of the

methylene chloride extracts of the sootsamples, and subsequent peak area

integration of the chromatographic peaks, Magnussen et al. (1978) have determined the detailed quantitative and qualitative composition of the PCAHs formed

within the flame. Quantitative values for the identified PCAHs ranging from

3.14
two- to seven-ring structures at two points along the burner axis (atomizing

air pressure of 184 kPa) are reported for kerosene in Table 3.7. Some additional conclusions can be drawn:

" There is an enrichment of heavier PCAHs as the samples are

collected at greater distances from the burner nozzle.

" There is a reduction of PCAHs containing methyl and phenyl groups,

which are expected to disappear as they move further downstream in

the burned gas.

TABLE 3.7. Polycyclic Aromatic Hydrocarbons in the Combustion

Products of Kerosene

Mass Loading, mg/S m3

Major PCAHs Identified

(particulate in burned gas)

Naphtalene

Acenaphthyl ene

Acenapthene

Fluorene

Phenanthrene/anthracene

4H-Cyclopentha (def)phenanthrene

Fl uoranthene

Benzacenaphthyl ene

Pyrene

Methyl fl uoranthrene/methyl pyrene

Benzo(ghi)fluoranthene

Cycl openta (cd)pyrene

Benzofl uoranthene

Benzo (e)pyrene/benzo (a)pyrene

Perylene

Indeno(1,2,3-cd )pyrene

Benzo(ghi)perylene/anthanthrene

Coronene

TOTALS

20 cm

from Nozzle

0.8

18.0

0.8

0.3

2.1

1.2

4.5

2.1

1.6

0.5

3.7

17.0

1.3

1.2

0.8

0.8

5.4

2.6

78.0

4U cm

from Nozzle

1.9

19.0

0.6

0.2

1.3

0.6

3.2

1.2

9.2

0.3

2.2

16.0

1.1

0.8

1.2

0.7

5.4

3.9

67.0

3.15
3.1.1.2 Plastics and Flammable Liquids

In a diffusion flame study by Pagni and Bard (1978), soot volume fractions

in flames have been measured in situ for solid (i.e., PS and PMMA were

included), cellular (foam) and liquid hydrocarbon fuels. Approximate detailed

size distributions of carbon particles in flames were also determined using a

multiwavelength laser transmission technique. The most probable particle size

was obtained based on the extinction coefficient ratio derived from the Mie

scattering theory. This information is shown in Table 3.8.

TABLE 3.8. Soot Volume Fractions and Size Distributions

in Experimental Flames

N O0 x i0-9 ,,

rmax, m cm 3 f x 106

Solids

PS, 0.021 27 4.6

(C8 H8 )n

Polypropylene, 0.005 155 0.36

(C3 H8 )n

PMMA, 0.018 2.9 0.31

(C5 H8 02)n

Polyoxymethyl ene, 0.22

(CH20)n

Foams

PS (GM-48), 0.061 1.1 4.7

(C8 H8 )n

Polyurethane (mattress), 0.014 16 0.80

(C3 . 2H5 . 30No.23)n

Polyurenthane (GM-21), -0.80

(C3 . 4H6 . 1 0No 16)n

Liquids

Iso Octane, C8 H18 0.023 2.7 0.62

Acetone, C3 H6 0 --- 0.18

Alcohol, C2H6 0 --- 0.11

3.16
Figure 3.7 shows an apparatus schematic for the multiwavelength transmission experiments. It consists of two lasers, a calculator which serves as a

timer, a narrow band pass filter, and a movie camera. The initial dimensions

of the fuel material were as follows:

Solid -- Thin disk 1-cm high and 7.5-cm dia (flame height -8 cm),.

Foam -- Rectangular parallelepiped 15 cm x 7 cm x 10 cm (flame

height -8 cm).

Liquid -- Dish 1-cm high and 10-cm dia (flame height -18 cm).

The equation for the calculation of soot volume fraction in flames (fv)

was based on the Mie scattering theory, and its final form is:

3

f = 18.62 N r

v o max

(3.1)

where

rmax = most probable particle radius

No = total particle concentration

RECEIVER

FLAME

FILTER

FUEL

MOVIE

CAMERA

TIMER

LASER

FIGURE 3.7. Schematic of Apparatus for Monochromatic

Transmission Measurements

3.17
and

xn (I/I )

N 0 (3.2)

Lr T

max

where

I = laser intensity

10 = initial intensity

T' = extinction coefficient

L = pathlength or mean beam length.

Table 3.8 shows that PS flames are an order of magnitude "sootier" (f

5 x 10-6) than all the other fuels. Although both solid and foam PS have the

same fv' the latter has particles much larger (-0.06 pm) than any other fuel

(-0.02 um) considered. Pagni and Bard (1978) agreed that the ranking of the f.

results is consistent with observed flame luminosity and smokiness, and with

data in the literature. Good agreement exists between experimental mass

pyrolyzing rates and rates calculated from a radiation model for fv of solid PS

and PMMA, derived independently from infrared flame transmittance and radiance

data. Using the parameters in Table 3.8 in the following equation (Pagni and

Bard 1978),

N(r) = No(27 r 3 /2 rmax exp(-3r/r max),

most probable particle size distribution Nfrý versus particle radius is plotted

in Figure 3.8 for the fuel materials consi e ed.

3.1.2 Summary

The study of combustion products in flames has been reviewed and the characteristics of these products as detailed in the literature are recorded.

Since information on the fuels of interest is currently unavailable, to gain

perspective we presented the characteristics of burning an acetylene and oxygen

mixture. The acetylene flame was chosen because it was found to be very sooty

and stable and so served as an ideal combustible for soot formation study.

Besides the principal burned gases (CO, C02 , H2 , H2 0, C2 H2 ), small amounts

of acetylene, polyacetylene, carbon particles and several PCAHs were detected

in the burned gas region of the flame at higher equivalence ratios. At a low

equivalence ratio (0 < 1.5) no acetylene or polyacetylenes were detectable, but

the concentration of species increases with increasing equivalence ratio. The

soot mole fraction has a fairly constant value of -2.5 x 10-3 in the burned gas

region under the following conditions: C2 H2 -0 2 = 1.4; P = 20 mm Hg; flow velocity = 50 cm/sec. The particle diameter is ~0.02 um at low pressure and an

3.18
le2

E

=L

I--

0

ti

0 0.02 0.04. 0.06 0.08

PARTICLE RADIUS r, pm

0.10 0.12 0.14

FIGURE 3.8. Approximate Size Distributions Njrý Versus

Particle Radius r as Determined frm Multiwavelength Monochromatic Transmission

Experiments

order of magnitude larger at higher pressure. In a C2 H2 diffusion flame, the

particle diameters are between 0.01 and 0.02 im.

Some characteristics of combustion products in diffusion flames are available for fuel materials such as kerosene, PS, PMMA, acetone and alcohol. In a

pressurized kerosene diffusion flame, the amount of soot formed depends

strongly on atomizing air pressure, high equivalence ratio and cold gas velocity. At an atomizing air pressure of 184 kPa (12 psig), an equivalence ratio

3.19
of 1.0 and a cold gas velocity of 0.96 m/sec, the mass loading of soot is about

103 mg/S m3 in the burned gas zone of the flame. As the cold gas velocity

increases to 2.67 m/sec, the soot mass 'loading is as low as zero (see Figure 3.6a). The particle diameter found in kerosene flame ranges from 0.015 pm

to 0.03 pm under conditions listed in Tables 3.6a and b. The mass loading of

total PCAHs found within the flame was 70 mg/S m3 at a distance of 40 cm from

the burner nozzle. Qualitative compositional information on these hydrocarbons

is listed in Table 3.7. There is a possibility that these small species will

serve as surface growth precursors as they travel with the burned gases.

Various solids and liquids in buoyant diffusion flames were studied. The

characteristics of particle diameter, particle concentration and volume fraction are available for PMMA, PS, acetone and alcohol. For the solid fuels the

initial fuel geometry was a thin disk 1 cm high and 7.5 cm dia. Table 3.8 contains information on fuel characteristics, and the parameters in the table were

used to determine most probable particle size distribution (Figure 3.8).

3.2 PRODUCTS IN SMOKE

Numerous studies of the properties of the combustion products generated by

fires in buildings have been made at the Georgia Institute of Technology (GIT).

In their studies, samples of polymers and hydraulic fluid were burned under

controlled conditions to obtain measurements on smoke particle size distribution, total smoke particulate mass generated, particulate size and the chemical

properties of smoke particulate products. The ventilated Combustion Products

test chamber (CPTC) being used at GIT can simulate a wide variety of environmental conditions that may be encountered in actual fire situations. Information on smoke particulate generation is also presented in the study by Seader

and Einhorn (1975).

From steady state heat balance at the surface, Tewarson et al. (1978,

1980) derive equations for mass loss rate in combustion and pyrolysis. Product

generation rates for some chemical species are also considered. These data are

available for limited combustible materials at present.

The information on smoke products introduced above is tabulated and

presented in the Sections 3.2.1 through 3.2.4.

3.2.1 Percentage of Smoke Particulates Airborne, Mass Loss Rates,

and Product Generation Rates

The percentages of particulate materials found in smoke were measured for

the following combustible fuels (Chien and Seader 1975; Bashston et al. 1978;

Zinn et al. 1978, 1980):

" wood--red oak, white oak, Douglas fir, and redwood

" polymers--PMMA, PVC, PS, polypropylene, and polyethylene

" hydraulic liquids.

3.20
The information obtained is tabulated as follows:

* percent of initial material converted to smoke particulates

" percent of sample weight loss that became smoke particulates

* percent of initial material that became char residue.

These data are summarized in Table 3.9a, and the corresponding experimental methods and conditions and their influences are given in Table 3.9b.

Notice that for the nonflaming mode with a heat flux of 5 W/cm and air temperature of 25 0C, the time required for total sample weight loss ranges from 10 to

25 min. (For other combustible materials, see also Table A.3.1 of

Appendix A.3, Tables A.4.1, to A.4.4 and A.4.6 to A.4.11 of Appendix A.4,

Tables A.5.1 to A.5.3 of Appendix A.5, and Tables A.6.2 and A.6.4 of

Appendix A.6). None of these materials left any appreciable amount of char

residue, with the PVC taking the longest time to lose 99% of its original

weight (24 min in the nonflaming mode). (The weight losses of these materials

as a function of time can be found in Figures A.5.1, A.5.5 and A.5.7 of

Appendix A.5 and Figure A.6.1 of Appendix A.6). To obtain the particulate

mass, filters were used to collect the smoke.

Based on surface heat balance, Tewarson et al. derived two equations for

mass loss rate--one for pyrolysis and another for smoke generation. The mass

loss rate of a fuel depends on the magnitude of net heat flux the fuel receives

in a fire and the heat required to generate a unit mass of the fuel vapors

(Tewarson 1980b). The equations are expressed as follows:

Mass loss rate in pyrolysis: (Mr)

=p (4 - qrr) L, (3.4)

Mass loss rate in combustion: (Ms)

Aq"6"+ " rr)/L (3.5)

where qfs is the total flame heat flux to the fuel surface and equal to the

summation of flame convective heat flux-q"c and flame radiative heat flux

qf,. Value q" is the surface reradiation energy and L is the heat required to

generate a unit mass of vapors. Both L and q*r are functions of material properties only and are- independent of fire conditions (Tewarson 1980b).

The mass loss rates for various combustible materials are tabulated in

Table 3.10. Those in the flaming combustion mode are higher than the mass loss

rates in pyrolysis because of the additional energy from heat convection and

radiation due to the flame at the combustible's surface. It is also true that

both external heat flux and availability of 02 increase the mass loss rate in

combustion foe all materials except PS and oak, which are char-forming materials whose combustion efficiency Xa is smaller than for the nonaromatic

polymers.

3.21
TABLE 3.9a. Percentage of Smoke Particles

Various Fuel Materials

Generated from

Flaming

or Nonflaming

Combustion

F

Initial

Material Converted to Smoke

Particulates,%

0.2-0.4

Sample Weight Loss to

Become Smoke

Particulates,%

Initial Material To

Become Char

Residue,%

0.2-1

Fuel Material

Woods (a)

Remarks

The range of % refers to the

range of wood samples (i.e.,

red oak, white oak, Douglas

fir, redwood). All the

smoke particulates evolved

fron a known weight of material were collected by a

filter and weighed at nor- mal atmospheric composition.

Douglas flr(b) NF

F

3-17

2.6-1

22-33

20-30 Heat flun of 3.2-

6.2 W/cm . Air flow rate of

142-425 z/min, and normal

atmospheric composition.

20-30 Heat flux of 2.5-5 W/cm2 . Air flow rate of 280-

425 i/min, and normal

atmospheric composition.

20-30 Heat flux of 6.2 W/cm2 , and

atmospheric compositions of

80% N2, 10% 02, 10% C02 ; and

80% N2 , 5% 02, 10% C02,

5% CO.

0 See Table 3.9b, (a).

-0 Heat flux of 5 W/cm 2

, air

flow rate 425 £/min, at room

temperature and normal

atmospheric composition.

7.9 See Table 3.9b, (a).

-0 See Table 3.9b, (c).

-0 See Table 3.9b, (c).

0.2 See Table 3.9b, (a).

-0 See Table 3.9b, (c).

PMMA(c) F

F, NF

0.6

<1

PVC F 10.2

PS

Polyethylene

Polypropylene

Polypropylene

NF

F

F

NF

F

F

F

NF

F

NF

F

2.5

9.3

3.2

8.4

8.3 0.05 See Table 3.9b, (a).

21.0

1.2

1.8

12.1

1.8

12.1

-0 See Table 3.9b, (c).

-0 See Table 3.9b, (c).

-0

-0

-0

See Table 3.9b, (c).

Hydraulic

fluid _

2.8 0 (10 min) ý Type (2190 TEP, MIL-2-17331A)

The given value is inaccurate

because the lower stages of

Cascade impactor became

clogged by large soot

particles.

Radiant thermal fluxes of 3.5, 5, 7.5 W/cm2 correspond to surface temperatures (nonflaming) of 240, 340 and

470'C, respectively. (a),(b),(c),(d) are explained further in Table 3.9b.

3.22
TABLE 3.9b. Experimental"Methbods-and References (from Table 3.9a)

Fuel Material

(a) Wood

.Apparatus, Initial and Environmental Conditions

Apparatus:

Conditions:

(b) Douglas fir Apparatus:

Modified ASTM D-757 globar

flammability testing chamber

(flow-through chamber)

Initial sample wt. = 0.5 g

Air flow, rate = 8.1 cm/sec

Heat flux = 3.8 W/cm2

Environmental conditions =

normal

Ventilated Combustion Products

chamber (CPTC)

Initial sample wt. = not given

Initial sample volume = 75 mm x

75 mm x 6.4 mm

Exposed surface area 56.25 Cm2

Air.flow rate = 142 to 425 £/min

Heat flux ranges from 2.5 to

6.2 W/cm2

Normal or atmospheric compositions of

-- 80% N2 , 5%,02, 10% C02, 5% CO

-- 80%_ N2 , 10% 02, 10% CO2

Reference

Chien and

Seader

(1975)

Bankston

et al.

(1978)

Conditions:

Environmental

Conditions:

(c) PMMA

(and other

polymers)

(d) Hydraulic

fluid

Same apparatus and range of conditions in (b)

above except the initial sample volume = 75 mm x

75 mm x 3.2 mm, and sample wt..= 15-209. The

exposed surface area 56.25 cm2 .

Zi nn

et al.

(1978)

Apparatus:

Conditions:

CPTC

Initial sample wt. = 20 g (in

shallow circular aluminum dish

7.6 cm dia and 1 cm deep)

Exposed surface area = 45 cm2

Air flow rate = 425 t/m at 25°C

Heat flux = 5 W/cm2

Zinn

et al.

(1980)

3.23
TABLE 3.10. Mass Loss Rates for Combustible Materials

Combustible (kW/m2)

PN4A 0

3 . (,m /seE)/10 3

1.4 0.183-

0.531

21-56

L

1.63

(kWg 2 )

11

(9/m sec)

0

(9/m 4ec)

6-28

3 1 (a)_ 6 0 (b) N(b) 0.233 29-45 1.63 11 25-30 30-60

PVC 0 21 0 17-18

Granular PS

Polypropylene

0

2.0 0.671-

0.874

1.4 0.233-

0.524

1.4 0.196-

0.507

63-65 2.4.7

39-35 1.70

23-66 2.03

14

18

0 15-12.5

0 0 3-24

52(a)

3 1 (a)_71

0.8.6 0.233 58 2.03 18 17 45

Oak (a) 1.4 0.233 16.7 1.7(c 16 9-10 18-11 5.5(d)

(a) Data taken from Tewarson's

(b) Natural air flow.

(c) For ii 46 kW/m2.

(d) For < 46k 46 km- W/r

previous studies.

Utilizing the expressions for mass loss rate, Tewarson (1980b) derived two

additional equations relating product generation rate as the function of mass

loss rate:

Product generation rate for pyrolysis (G~j):

G". = (Yj/L)(q" - q") = Y. M

pi * e rr j p (3.6)

Product generation rate for combustion (Gbj):

Gj (Yj/L)(qe + qf - rr) Y M (3.7)

where YV is the ratio of mass generation rate of a product j to mass loss rate

of. the Laterial, which is available for C02 , CO, total gaseous hydrocarbons

expressed as HC, and the mixture of soot and low vapor pressure liquids

expressed as S. Table 3.11 presents all the data that enable calculation of

j and 4 for various materials.

3.24
TABLE 3.11. Product Generation Rates for Various Materials

Generation Rate, g/m2 - sec

Combustible

PM*¶A

YC02- YCO

2.2 0.311-

<O.On0

1.9(b) 0.007

PVC 0.46 0.04-

0.03

Polystryene 2.2 0.07-

0.01

Polypropylene 2.7 0.2

. YHC

<0.001

0.001

0.003-

0.001

0.02-

0.001

0.007-

0.001

0.03

<0.001

YS

0.023

0" a)

0

Al (a)

6-28

G Pco 2

0 0 0

0.01-

0.03

-- 12-30 30-60 23-57 0.08-

0.21

_4S GbC

0 13.2-

62

-- 57-115

0.09-

0.07

0.20

0.07

0 17-18 0 0 0 0 7.8-

8.3

0 15-12.5 0 0 0 0 33-

27.5

0 3-24 0 0 0 0 8.1-

65

•(co

0.3-

<0.03

0.2-

0.4

0.7-

0.5

1.05-

0.13

0.6-

4.8

2.25

0.04-

0.06

•bHC

(0.03

0.03-

0.06

0.05-

0.02

0.3-

0.01

0.02

1.35

<0.02

0.65

1.3

3-2.5

0.21-

1.68

0.27-

0.17

1. 9 (b)

Oak 1.3

0.05

0.002-

0.005

-- 17 45

0.015 9-10 18-11

32.5

11.7-13

0.85

0.02-

0.05

0.51

<0.009

-- 86

0.14- 23.4-

0.15 14.3

(a) Obtained from Table 3.10.

(b) With external heat flux, qe"
3.2.2 Particle Size and Particle Size Distribution

Ranges of particulate mass median diameter (MMD) and particle size distribution (standard deviation) for cellulose and various polymers are t bulated

in Table 3.12 with both normal and high ventilation air temperatures.(aj All

these data were obtained from B. T. Zinn et al. of the Georgia Institute of

Technology (Bankston et al. 1978; Zinn et al. 1978, 1980). Notice that in

flaming combustion in both normal and highly ventilated conditions, MMD and

particle size distribution data are unavailable forsthe polymers (except PMMA)

because the large, sooty particles produced during flaming combustion tends to

rapidly clog up the Cascade impactor plates used. For PMMA the quantities of

smoke particulates collected were too small for reliable size distribution measurements. Only mean particle diameter is measured in these conditions by

in-situ optical techniques.

3.2.3 Chemical Composition of Airborne Particles

Various polymers and a combustible hydraulic fluid were tested for the

presence of PCAHs and other hydrocarbons in airborne particulates (away from

the flames) by Zinn et al. Among the polymers tested, the only samples yielding significant amounts of PCAHs were the PVC samples; Some of the suspected

classes of non-PCAH compounds that can be found in smoke particles generated

from polymers include aldehydes and ketones, acids, bases, phenols, aliphates,

aromatics, esters, ethers and chlorinated compounds. The chemical analysis

schemes were developed for these studies (Zinn et al. 1978, 1980). The most

recent apparatus has been developed by GIT to identify the major volatile

species generated by pyrolysis.

3.2.3.1 PCAHs in Smoke Particles Generated from PVC

The PCAHs found in PVC particles are shown in Table 3.14 (Zinn et al.

1978). The PVC samples were tested individually and their various compositions

are tabulated in Table 3.13. The particles analyzed were generated by exposing

the sample to.a heat source inside the Georgia Tech CPTC and sampling the combustion products at 30 x/min through a triple-thickness glass-fiber filter.

This represented -20 of the total gas flow through the CPTC. The collected

particulate smoke from nonflaming PVC combustion weighed about 20 mg, and with

flaming PVC combustion, 27 mg. During flaming combustion, a propane flame was

used to induce combustion. A blank run on the propane flame only showed no

detectable concentration of PCAHs.

3.2.3.2 PCAHs in Smoke Particles Generated from Hydraulic Fluids

Under the thermal flux of 5 W/cm and ventilating air flow of 425 x/min,

smoke particles were collected to identify PCAHs in the sample. The initial

(a) For detailed tabulation, see the appendix (Tabl-es A.4.1 to A.4.4, A.4.7 to

A.4.12, A.5.1 to A.5.3, A.6.1 to A.6.3; Figures A.4.1 to A.4.6, A.5.2 to

A.5.4, A.5.6, A.5.8 to A.5.12, A.6.1 to A.6.2).

3.26
TABLE 3.12. Particle Size and Particle Size Distribution of Fuel Materials

Fuel

Material

Douglas fir

PMMA

PS

Mass Median

Diameter

MMD. pm

0.5-0.9

0.4

1.0

Standard

Deviation. ,

1.8-2.0

2.4

2.0

0.7

2.6

1.9

1.9

Volume Surface

Mean Particle

Dia at Maximum

Optical Density

Drs. pm

0.75-0.8

0.5-0.45

0.9

0.75-0.55

0.5-1.2

0.6

1.2

1.2-1.3

1.4

1.3

1.3-1.25

1.1

1.3

1.3-1.35

1.6

1.2

1.0

1.2

1.1-1..15

1.23

Heat Flux,

-F or NF W/cm2

NF 3.2-6.2

F 2.5-5

NF 6.2

(aJ

Polyethylene 1.5

2.05

Air Flow

Rate,

I/mi n

142-425

283-425

Environmental Conditions

Normal temp. (25*C) and composition

Normal temp. (25°C) and composition

Normal temp.; composition of 80% N2.

5-10% 02, 10% CO2 , 5% CO

Air temp. of 25-200*c. normal composition

1.75

1.8

1.45

NF 5 425

F 5 425-283

NF 5 425

F 5 425

F 5 425

NF 5 425

F 5 425

F 5 425

NF 5 425

F 5 425

F 5 425

NF 5 425

F 5 425

F 5 425

NF 5 425

F 5 425

F 5 425

NF 5 425

Air temp. of

Normal temp.

Normal temp.

Air temp. of

Normal temp.

Normal temp.

Air temp. of

Normal temp.

Normal temp.

Air temp. of

Normal temp.

Normal temp.

Air temp. of

Normal temp.

Normal temp.

Air temp. of

Normal temp.

25-200%C. normal composition

(25°C) and composition

(25°C) and composition

25-200%; normal composition

(25°C) and composition

(25°C) and composition

25-200°C; normal composition

(25%C) and composition

(25°C) and composition

25-200*C; normal composition

(25°C) and composition

(25%C) and composition

25-200'C; normal composition

(25%C) and composition

(25%C) and composition

25-200%C; normal composition

(25%C) and composition

Polypropylene

PVC 1.4

Hydraulic

fluid

1.33-1.31 5 425 Al' temp. of 25-300%C; normal composition

(a) F . Flaming combustion.

NF = Nonflaming combustion.
TABLE 3.13. Composition of PVC Samples, g

Plastici'zer Plasticizer

PVC Lead 6-10 Di-Isodecyl

Sample Resin Stabilizer Phthalate Phthalate CaC0 3 A.2O_3 z•O SbO 3 Lubricants

1 100 5 ............

2 100 5 4b ....... 1.5

3 100 5 45 -- 50 .. 1.5

4 100 5 45 .... 50 - 1.5

5 100 5 45 ...... 5 1.5

b 100 5 45 - 50 - 5 1.5

7 100 5 45 .... 50 5 0.5

8 100 7.4 - 30 .... 2 0.4

sample mass was 20 g. The amount of particulate smoke collected on the filter

was 145 mg. This filtrated sample contained 20 mg of extractable organics,

2 mg of PCAHs and 18 mg of aliphatics. Table 3.15 shows the major PCAH species

found in the smoke of burning hydraulic fluid. (For other materials, see

Tables A.6.4 and A.6.5 of Appendix A.6.)

3.2.3.3 Volatile Compounds

Volatile species that may be generated during the process of pyrolysis

often interact with airborne particles. Two types of behavior can be revealed

during the interaction--volatile deposition onto and release from the particulate surface. A special apparatus has been developed at GIT to identify these

volatiles. The results for hydraulic fluid and PVC are shown in Tables 3.16

and 3.17a and b. The results for polymer materials are under investigation at

GIT and are unavailable at this time.

3.2.4 Particulate Concentration

Particulate concentrations in terms of mass per unit volume are not currently available in the literature for the materials of interest, but they can

be estimated from mass loss data in a known chamber volume. Published data on

volume fraction (volume concentration) were found for hydraulic fluid. Again,

this information was determined by Zinn et al. (1980) in flaming tests on the

hydraulic fluid. The Mie theory was used to calculate the soot refractive

index me = 1.57 to 0.56i. Zinn observed that optical density ratios measured

for the soot particles produced by the burning of hydraulic fluid were about

20% lower than the theoretical values for spherical particles.

3.28
TABLE 3.14. Amounts of PCAHs Found in Smoke Particles Generated from PVC Under

Simulated Fire Conditions, jig of PCAH/g Pure Resin

Peak

No.

Mol ec. Tr Weight

PVC-1 PVC-I

PVC-O PVC-I PVC-2 PVC-3 PVC-4 PVC-5 . 3.5 7.5 NF F NF TF NFTF N NF~F NF F NF F TF N Name of PCAH

1 3.0 128 Naphthalene

2

3

4

5

4.6

4.9

6.4

6.7

142

142

156

1S6

1-Methylnaphthalene .. ..

2-Methylnaphthalene .. ..

2-Ethyinaphthalene .. ..

2,6-Dimethylnaphthalene .. ..

1,6-Dimethylnaphthalene

r.3

6 7.1 154 Diphenyl .. .. .. .. .. .. .. .. .. .. .. ..

7 7.5 156 2,3-Dlmethylnaphthalene .. .. .. .. .. .. .. .. .. .. .. ..

1.5-Dimethylnaphthalene

8 .11.4 168 Dlhydrofluorene (?)

9 12.3 165 Fluorene 13.1 -- 3.6 -- 5.5 -- 21.6 -- 16.1 -- 36.0 --

10 10.4 178 Phenanthrene 25.2 22.5 29.1 3.6 35.7 -- 40.3 -- 36.7 -- 41.6 2.3

Anthracene

11 21.4 192 1-Methylphenanthrene 21.1 19.1 19.1 3.5 19.1 -- 20.3 -- 18.0 -- 20.3 --

2-Methylanthracene

12 22.4 192 9-Methylanthracene 16.5 11.3 15.5 3.6 9.6 1.6 30.7 -- 12.9 -- 17.3 --

13 .23.9 206 9,10-Dimethylanthracene 16.7 14.3 15.6 4.7 13.1 2.0 13.1 -- 10.7 -- 18.0 --

14 25.9 202 Fluoranthene 10.5 12.3 10.5 0 6.5 2.1 8.5 1.5 6.5 -- 9.8.

15 27.2 202 Pyrene 7.6 19.3 11.6 6.1 6.7 8.4 9.2 2.7 7.6 -" 11.5 --

16 28.8 216 1,2-Benzofluorene 31.3 9.3 35.3 4.5 17.3 5.3 25.6 2.0 20.9 -- 24.5 2.9

17 29.3 216 2,3-Benzofluorene 21.9 8.4 32.8 5.9 16.8 2.4 19.3 2.0 19.3 -- 22.8 2.9

18-21 30.8-34.6 230 Methylbenzofluorene (?)

22 35.5 228 Chrvsene. 1.2-Benzo- 8.7 24.4 16.0 10.5 12.7 10.5 6.1 4.4 16.7 2.3 14.3 3.6

-- 19.3

6.9 40.0

9.5 28.7

11.3 24.3

26.0 23.9

3.9 13.2

8.4 13.1

15.3 40.0

23.1 29.3

36.5 22.1

4.7 4.7

3.3 3.3

anthracene Triphylene

23 37.5-39.0 256 Dimethyl (MW 228) (?)

24 39.4 256 7.12-Dlmethylbenzo(a)-

anthracene

25 45.7 252 Benzo(a)pyrene,

Benzo(e)pyrene

26 47.7 252 Perylene

Total PCAH

3.5 -- 3.5 -- 3.5 -- . 3.5 -- 3.5 -- 3.5 --

3.2 3.2 5.3 2.4 4.4 4.4 3.2 3.2 4.4 0 3.2 -

3.3 3.3 7.3 2.4 4.5 2.4 2.0 2.4 3.3 0 2.0 --

182.6 149.4 205.2 47.1 155.4 39.1 203.4 18.2 176.6 2.3 224.8 11.7

5.3

154.2

5.3

275.2

ta) Heat flux = 5 W.
TABLE'3.15. Major PCAH Species Found in Particulate

Smoke of Hydraulic Fluid

PCAH Percent

Anthracene/phenanthrene 1

Fl uoranthene 29

Pyrene 45

1,2, Benzothorene, etc. 6

2,13 Benzothoranthene, etc. 12

2,4 Benzo(a)pyrene 0.7

TABLE 3.16.

Sample

Hydraulic Fluid

PVC

Mass Loss

Sample

Mass, mg

22.22

10.33

Data for Hydraulic Fluid and PVC

Ash Particulate Vapor

Mass, mg Mass, mg Mass, mg

0.29 0.67 21.26

2.77 0.31 7.25

Thus it appears that the soot particles produced in flaming tests of the

hydraulic fluid are nonspherical. The equation used to calculate the volume

fraction is:

27 (3.8)

where

Dvs

Io

I

Qext

m

L

= volume fraction

= mean particle diameter

= incident light intensity

= light intensity transmitted through smoke

= mean extinction efficiency

= refractive index

=.optical path length.

3.30
TABLE 3.17a. Major Volatile Components

from Hydraulic Fluid

Concentration,(a)

Compound mg/m 3

CO 600

Air

CO2

Propene

H20

Acetal dehyde

Butene

Acrolein

Propionaldehyde

Acetone

1,3 Heptadiene

Methacrolein

5-Heptan-2-one

Cycl oheptane

Benzene

10000

700

7000

2000

2000

200

800

2000

ý400

300

800

1000

800

(a) Calculated on the basis of a

20-gal sample burning into a

25,000-ft 3 space. The data are

for the vapor phase. Values for

compounds adsorbed onto particles

range from 1 to 4% of values shown.

The results, presented in Figure 3.9 and Table 3.18, were corrected to the

standard flow rate (425 x/min) with the following equation:

0 1 0 Vt

)corr meas V 25 meas 925 L9T+ 2731 (3.9)

where Vt is the volumetric flow rate at temperature T and V2 5 is at 25°C.

3.31
TABLE 3.17b. Major Volatile Components from PVC

Concentration,(b)

Compound (a) mg/m 3

CO 3

Air

CO2 53

H20 32

1,3 Butadiene 3

Acetone 3

3-Chl oro-2-methyl propene 3

1,4 Dichlorobutane 1

Benzene 9

Acetic acid 1

Toluene 2

(a) HCl was identified separately using a

nonchromatographic method.

(b) Calculated on the basis of a 3-ft length of

cable burning into a 25,000-ft 3 space. The

data are for the vapor phase. Values for

compounds adsorbed onto particles range from

1 to 4% of the values shown.

3.2.5 Summary

Studies of combustion products found in smoke have been reviewed and data

on the characteristics of these materials, collected under simulated fire conditions, are tabulated.

Table 3.9a presents the percentages of smoke particles becoming airborne

for most of the materials of interest (except cellulosic materials and

kerosene); the corresponding experimental methods and approximate fire conditions are given in Table 3.9b. Tables 3.10 and 3.11 show mass loss rates and

product generation rates, respectively, for many polymeric materials as a

function of external heat flux and 02 availability. Particle size and distribution can be found in Table 3.12 in terms of mass mean diameter, volume surface mean particle diameter and standard deviation. (The particle size and

distribution were also measured under approximate fire conditions.) Chemical

analysis for particulate materials collected from burning hydraulic fluid and

various compositions of PVC samples are shown in Tables 3.14 through 3.18.

There is little information on particulate concentration for the materials of

3.32
/1

- ii

E

0

C, 0

LUJ

-. J

0

25C

l00%

4 --- 1009C

0 2 - 4 6 8 10 12 14 16

TIME, min

FIGURE 3.9. Effect of the Ventilation Air Temperature

Volume Fraction for Flaming Combustion of

Exposed to a Radiant Flux of 5 W/cm2

on the Particulate

Hydraulic Fluid

TABLE 3.18. Sample Weight Loss and Smoke

for Hydraulic Fluid

Mode

Nonfl ami ng (b)

Flaming

Flaming

Flaming

Ventilation Air

Temperature, 'C

25

25

100

300

Concentration Data

Peak Volume(a)

Fraction, ppm

0.83

4.54

4.11

5.58

(a) Based on mR = 1.50 - O.Oi for nonflaming

combustion and mR = 1.57 - 0.56i for

flaming combustion at a standard flow rate

of 425 i/min.

(b) During the initial nonflaming phase,

spontaneous ignition occurred 5.9 min after

initiation of exposure.

3.33
interest in terms of mass concentration as a function of time. Nonetheless,

from the available mass loss data in a known chamber volume, mass density as a

function of time can be estimated.

3.3 ENERGY RELEASE RATE

The expression for energy release rate (Tewarson 1980b) is:

a = X a(Ht (H /L)(qe e + q• qfs -rr)•" (3.10)

where q"s is equal to the sum of flame convective and radiative heat flux to

the surface, respectively:

• $0 • II qfs= fc +qfr (3.11)

Table 3.19 presents energy release rates (using Equation 3.10) for the

fuel materials we have been considering. Energy release rate is a function of

external heat flux qe, volumetric flow rate of air into the apparatus and

R e M a

TABLE 3.19. Energy Release Rates for Various Combustible Materials

Combustible

PMMA

kW7m2

0

m3/secX1O3 42

H LX

j ~kW/Mr2 Xa k W/,ýM2 kWIM2

1.4 0.183- 25.2 1.63

0.531

3 1(a)_ 6 0 (b) N(b) 0.233 25.2 1.63

Pvc

Granular PS

Polypropylene

0

0

0

52(a)

2.0 0.671- 16.4 2.47

0.874

1.4 0.233- 39.2 1.70

0.524

1.4 0.196- 43.3 2.03

0.507

0.86 0.233 43.3 2.03

11 0.99- 21-56 150-680

0.98

11 0.86 29-45 650-1250

21 0.35 63-65 95-100

14 0.68- 39-35 390-320

0.67

18 0.99- 23-66 100-930

0.91

18 0.63 58 1250

16 0.68 16-7 220-140

0.71

Oak (a) 1.4 0.233 17.7 1. 7(c) 5.5(d)

(a) Data taken from Tewarson's

(b) Natural air. flow.

(c) For < 46 kW/m 2 .

(d) For qe > 46 kW/m 2 .

previous studies.

3.34
mass fraction of 02. Note that Ht and L are material properties and are

expected to be independent of fire environment, while Qa depends on both material properties and fire environment. Figure 3.10 shows the Factory Mutual

small-scale apparatus that Tewarson has been using to obtain the data for the

calculation of energy release rates.

TO

EXHAUST

BLOWER

. 0. 30m TO

PHOTO

aO.'

~~TRONICSOURCE . TO ELECTRON I C' SUE

K MA NOMETER

TO TEMPERATURE AND

-PRODUCT SAMPLING

INSTRUMENTS

STEEL- 11m

DUCT

(0. lOm di

EXHAU ST

COLLECTION CONE

-(ALUM I NUM FOI L)

0.25m

0.41m

QUARTZ TUBE

(0.17m dia)-

HIANT HEATERS

MOVABLE

-WATER COOLED

SHIELD

ANALYZER

FLOOR OR N2

FIGURE 3.10. Factory Mutual Combustibility Apparatus

3.35
According to Tewarson, q4 and qýr are accurate to about.±30 and ±20%,

respectively. Therefore, the calculation of energy release rates with this

equation could have an uncertainty of 50%. Based on the data shown in

Table 3.19, the energy release rate of the given combustibles increases with

increasing availability of 02 and presence of external heat flux q". This is

true for all the materials considered except PS, which has a lower heat release

rate at a higher fraction of 02 concentration. Tewarson (1980b) stated that

this is due to the char-forming nature of PS. Also, With the high-charring

behavior, the mass loading rate of PS is suppressed.

In the study of high-pressure spray flammability, Roberts and Brooks

(1981) determined the heat output of various types of hydraulic fluids. The

experiments were performed in a ventilated test chamber with two axial fans

mounted near the floor. The chamber, housed in a laboratory, was constructed

from 0.8 mm sheet steel and was 12 ft long x 8 ft wide x 8 ft high with a door

at one end and a Perspex window on the other. Figure 3.11 is a cutaway drawing

of the chamber, showing the position of the equipment.

A metering pump capable of delivering up to 0.5 £/min of fluid against a

back pressure of 6.9 MPa (1000 lb/in. 2 ) was used to disperse the fluid. A

FIGURE 3.11. Chamber for High Pressure Spray Flammability Tests

3.36
premixed propane/air flame was used to ignite the hydraulic fluid spray and to

stabilize the flame throughout the test. The equipped instrumentation is capable of measuring pressure and temperature of the spray, thermal radiation of

the flame, oxygen concentration from the stack, and temperature rise of the

exhaust gases.

The results in average values are summarized in Table 3.20. For more

detailed tabulation, refer to Table A.7.1 of Appendix A.7. The calorific

values of each fluid were determined in a standard high-pressure oxygen bomb.

The comparison of energy outputs from various hydraulic fluids can be made

directly from the table. A comparison between the sets of data obtained for

mineral oil and water-in-oil emulsion is of interest, since the latter consists

of about 60% mineral oil, 40% water, with traces of anti-corrosion and stabilizing additives.

3.4 RATE EQUATIONS OF COMBUSTION PROCESSES

Tewarson et al. (1978, 1980) of Factory Mutual Research Corporation has

derived the following three rate equations which describe the amount of material loss, heat release and product generation in a fire as a function of material properties and fire conditions.

3.4.1 Mass Loss Rate (M")

The mass loss rate of various combustible materials depends on the available net heat flux received by the material in a fire and the heat requirement

to generate a unit mass of combustible vapors (Tewarson 1980a):

(3.12)

n

where

= mass loss rate of the material

" = net heat flux received by the fuel material per unit fuel

qn surface area

L = heat required to generate a unit mass of the fuel vapors.

Mass loss rates for the two phenomena, pyrolysis and combustion, are

defined as follows (Tewarson 1980b):

* mass loss' rate in pyrolysis (MI)

b - qrr)/L (3.13)

3.37
TABLE 3.20. Results of Heat Output Tests on Various Types of "Hydraulic Fluid

Fluid Type

Mineral oil

Water-in-oil

emulsion

Phosphate

ester

Water-glycol

Average Fluid

Temperature, *C

48

Average Spraying

Rate, g1sec

3.7

Average

Calorific Total Heat

Value Output, kJ/g

00

48

46

40

4.2

5.2

4.9

44.9

25.7

30.8

14.7

27.8

17.9

19.4

5.3

Combustion

Efficiency,%

62

70

63

36

26

45

13

8.5

6.7

2.7

Radiative

Contribution,%

43

Average Air

Consumption,

kg/kg of fluid

14.1
where

(qe - q" ) = the net heat flux

e rr

°" qe = external heat flux

= surface reradiation loss.

rr

e mass loss rate in combustion (Mg)

b (qe + qfs qrr)/L (3.14)

where q f - qrris the net heat flux, and the total flame heat flux

qfS is included in the net heat transfer because of the flaming combustion. Value qjs is the summation of flame convective heat flux q"c and

radiative heat flux q0r"

(Equations 3.13 and 3.14 are the final forms which were used in

Section 3.2.1 for calculation of mass loss rate in pyrolysis and combustion.)

3.4.2 Heat Release Rate (Q•)

To be able to describe the rate of fire growth and the size of the fire,

heat release rate must be considered. The measurement of heat release rates in

fires can be expressed as follows (Tewarson 1980a):

Q H M" (3.15)

where

Hi= the heat of combustion

Al= mass loss rate in combustion b

= the heat release rate.

When all the fuel vapors burn completely, Hi of Equation (3.15) is defined as

heat of complete combustion of the fuel Ht (original discussion of Ht can be

found in Section 2.1.4). In an actual fire, where both material pyrolysis and

combustion often coexist and oxygen is not always available, fuel vapors

generated from pyrolysis do not often burn completely. Therefore, Hi is

defined as the actual heat of combustion of fuel Ha, and Q" is the actual heat

release rate. Thus Equation (3.15) can be rewritten as a

= Ha A" (3.16)

3.39
Furthermore, the ratio of actual to complete heat of combustion (Ha/Ht) is

defined as combustion efficiency of the fuel Xa. Therefore,

X aH Mb (3.17)

or from Equation (3.14) and Equation (3.17), the heat release rate is written

as

X (H /L) ( +" " q ") (3.18) Qa aHt e fs rr

(Equation 3.18 is the final expression which was used in Section 3.3 for the

calculation of energy release rates.)

Notice that Qa depends on the material properties and fire environment

(Tewarson 1980b); i.e., thermal environment qe and qfs, availability of oxygen,

Xa, and material Xa, Ht/L, and qr"e

Heat release rate (Tewarson 1980b) deals with a) the combustion efficiency

of combustible materials, b) the ratio of heat of complete combustion to heat

required to generate a unit mass of vapors and c) the net heat flux absorbed by

the surface. Tewarson studied the dependency of heat release rate on thermal

and over- or underventilated fire environment and various materials. He found

that the combustion efficiency for an overventilated fire environment becomes

approximately constant for each generic type of material tested. The combustion efficiency X. may be classified as shown in Table 3.21. According to

Tewarson, combustion efficiency can decrease if:

" the ratio of carbon relative to H,O, etc., in the vapors decreases

" the gas-phase reactions are quenched or retarded by lack of available

oxygen, chemical retardants in the materials, or decrease in temperature

* soot-forming reactions are preferred in the gas phase (i.e., PS).

3.4.3 Product Generation Rate G'!

The combustion product (i.e., C02 , CO, H2 0, smoke, and low volatile hydrocarbons) generation rate is equal to the fractional yield of the product times

the mass loss rate, according to Tewarson (1080b). This is expressed as:

' Y." (3.19)

j,

3.40
TABLE 3.21. Combustion Efficiency, Xa

Non-aromatic polymers(a)

PMMA High (0.81 < Xa < 0.97)

Polypropylene

Aromatic compounds(b)

Red oak Medium (0.51 < Xa < 0.7)

PS

Chlorinated compound

PVC Low (Xa 0.35)

(a) non-charring materials.

(b) charring materials.

where

j = combustion product

= is the mass generation rate of product j-per unit surface area j

Mi" = the mass loss rate by pyrolysis or combustion

Yj = the yield of product j, which can be expressed as the

multiple of the yield of product j expected from stoichiometry

kj, and the product generation efficiency fj:

Y= fj kj (3.20)

Thus product generation rate for pyrolysis of certain species can be

written as

G" = fk/L) (qe "" ) (3.21)

pj e rr

Product generation rate for combustion is (using Equation 3.14)

Gb = f (k./L) (qeI + "I" = " (3.22)

bj j3 e fs rr

Notice that, like Qa Gi' depends on both material properties and fire conditions. (Equations 3.31 and 3.22 are the final expressions that were

used in Section 3.2.1 for the calculation of product generation rates.)

3.41
S
4.0 DISCUSSION

The discussion below is followed by examples that illustrate the use of

the available data. Information gaps are then identified based on this literature review.

4.1 THE STUDY OF COMBUSTION PRODUCTS

The combustion products generated have been the main subject in fire

research due to their threat to public health and safety in the event of an

enclosure fire. Today, the characteristics of fire-generated products are

examined by conducting laboratory tests. During the past few years, smallscale fire tests of all types have come under considerable criticism because of

the growing evidence that they are not good predictors of actual fire performance and because the quoting of small-scale test data can be misleading to

fire-safety regulatory officials and the public. Still, large-scale tests are

costly and time-consuming, and a philosophy is needed on the relevant roles of

both large- and small-scale tests. According to Punderson (1981), there seems

to be a developing consensus as follows:

" The best test methods for judging acceptability of materials and for public fire-safety standards are based on full-scale, end-use simulations

related to realistic fire scenarios. (Note that an end-use simulation

generally requires that the test specimen be in the form of an end-use

product rather than a small specimen of material.)

" Small-scale tests are essential for guidance of research programs that are

developing new materials and products.

At the present time, only small-scale test data are readily available for

various sets of approximate fire conditions. Unfortunately, a real fire is not

a set of time and temperature conditions; nonetheless, the combination of the

discrete small-scale data, under different sets of fire conditions, can be used

carefully, based on the current stage of combustion technology, to approximate

the outcome of the combustion process in a well-defined fire scenario of

interest.

4.2 APPLICATION OF THE DATA

The characteristic data of fire-generated products (mass and energy) measured by Factory Mutual Research and GIT are the best available today for fire

accident analysis inside a nuclear fuel cycle facility. The data are limited

to combustible materials normally found in fuel cycle facilities. In this section examples are given to demonstrate general usage of the data collected in

Tables 3.9, 3.10, 3.11, 3.12, and 3.19.

Major fire consequences such as elevated room temperature and pressure

resulting from the generation of heat, smoke particles, toxic gases and

unburned vapors are the important parameters for enclosure fire analysis. Both

4.1
temperature and pressure gradients govern the dynamics of fluid motion and the

thermodynamics of gas interaction, as well as particle behavior. To estimate

these parameters, fire source terms such as the rates of mass and energy generation in the fire, and the particulate characteristics are necessary.

Mass loss rate (sometime referred as generation or burning rate) of a fuel

depends strongly on the chemical and physical properties of the material

itself, its surface area, heat fluxes from the external source such as burning

objects nearby, and the availability of oxygen (see Sections 2.4 and 3.2 for

details). Table 3.10 may be used to estimate mass loss rates for materials of

interest. For example, assuming 1000 g of a PMMA slab burning in an overventilated room with no external heat source, a steady state mass loss rate (flowing

combustion) of 28 g/sec can be used, provided that the slab has a constant

burning surface area of 1 M2 . If the burning conditions do not change significantly, the time required to consume 1000 g (at 1000 g/28 g/sec) is approximately 35 sec.

From Table 3.11, the generation rates of gases, smoke, and hydrocarbons

(in the form of unburnt vapor) can be obtained for the flaming combustion of

PMMA. For example, under the above burning conditions, the steady state generation rate for C02 is 62 g/sec; for CO and hydrocarbons, less than 0.03 g/sec

each; and for smoke, 0.65 g/sec. During the PMMA fire, particles with a volume

diameter of 1.2 .im at maximum optical density (from Table 3.12) can be

generated.

Energy generation rate is a strong function of mass loss rate. The actual

energy generated from a burning episode is composed of convective and radiative

fractions. The convective fraction of energy is responsible for the heating of

the combustion gases. Actual energy generation rates can be obtained from

Table 3.19, while the convective and radiative fractions can be calculated

using Table A.1.2 in the appendix. For example, assuming the same PMMA slab is

burning, the steady state energy generation rate is 680 kW. From Table A.1.2

the convective fraction is 0.64/0.94 (defined as Xc/X ) under a normal air conditions in a room, while the radiative fraction is-0.30/0.94 (defined as

Xr/Xa). Therefore the steady state convective energy release rate is

680 kW(0.64/0.94) = 217 kW

and the steady state radiative energy release rate is

680 kW(O.30/0.94) = 463 kW.

The above examples are applicable for a specific fire condition. Since

fire is a dynamic process, a set of discrete mass and energy rates under different fire conditions are rquired to realistically predict the outcome of an

enclosure fire. It must be further understood that the data are mainly for

overventilated fire and independent burning of material. Smoldering combustion, which is responsible for the increased generation rate of flammable

vapor, is the characteristic of underventilated fires.

4.2
Besides the characteristics found in the examples above, additional information that may be obtained in Section 3.0 (and the appendix) includes:

* product generation rates of CO, C02 , and total gas hydrocarbon (Figures

A.1.3 to A.1.5)

e product generation efficiencies (Tables A.1.2 and A.1.4)

e actual heat release rates (Figures A.I.1 and A.1.6)

* heat required to generate a unit mass of vapor (Table A.1.1 and A.1.5)

* convective and radiative heat release rates per unit surface area of the

material [Equation (3.17) of Section 3.4 with replacement of Xa by Xc and

Xr, respectively]

" combustion efficiency (Tables A.1.2 and A.1.4)

" convective and radiative fractions of heat of complete combustion

(Table A.2.6)

" surface reradiation loss (Tables A.1.2 and A.1.4)

* flame height (see Tewarson 1980b)

* excess pyrolysate (see Tewarson 1980b).

4.3 IDENTIFICATION OF INFORMATION GAPS

The numerous assumptions required to arrive at an estimate of the characteristics of airborne combustion products for the examples indicate the lack of

usable data for certain materials of interest in this study. Data on the

energy release rate (derived from the mass loss rate and combustion efficiency), fraction of mass loss rates generated as particles, size distribution

of the airborne particulate materials, and chemical composition of the airborne

materials are estimated by conducting laboratory-scale fire experiments. This

available information must be used carefully in a postulated fire scenario

inside a real-scale enclosure. There are, in fact, some information gaps which

must be filled in order to predict and describe the characteristics of airborne

materials in a nuclear facility fire. The gaps are identified below:

" lack of combustion product data for cellulosic materials (i.e., paper and

rags)

e lack of combustion product data for elastomers (i.e., both synthetic and

natural rubber materials used in glovebox and surgeons' gloves)

" lack of some combustion data for organic fluids that are possibly found as

working fluids in fuel processing (i.e., kerosene--as fuel for heating

requirements of some process equipment). The information found for kerosene is solely for jet spray combustion.

4.3
* lack of combustion data for mixtures of the combustible materials of

interest

" lack of information on how radioactive particles have influenced the characteristics of the airborne combustion products, and vice versa.

" lack of information on a "scaling factor" which can be used to approximately convert the data obtained from small-scale combustion experiments

to an actual fire

* Lack of energy information on significantly reduced oxygen levels that

would cover underventilated burn modes.

4.4
5.0 REFERENCES

Alpert et al. 1981. Modeling of Ceiling Fire Spread and Thermal Radiation.

Factory Mutual Research, Norwood, Massachusetts.

Alvares et al. 1980. Fire Protection Countermeasures for Containment Ventilation Systems. UCID-1878, Lawrence Livermore National Laboratory,

Livermore, California.

Bankston, C. P. et al. 1978. Review of Smoke Particulate Properties Data for

Natural and Synthetic Materials. NBS-GCR-78-147, Georgia Institute of Technology, Atlanta, Georgia.

Bittner, J. D. 1978. "Formation of Soot and Polycyclic Aromatic Hydrocarbons

in Combustion Systems." In Combustion Research on the Characterization of

Particulate Organic Matter from Flames, eds. R. A. Hites and J. B. Howard,

pp. 21-40. PB-291 314, National Technical Information Service, Springfield,

Virginia.

Boisdron, Y. and J. R. Brock. 1972. "Particle Growth Processes and Initial

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Applications, and Implications to Inhalation Toxicity, pp. 129-'150. Charles

C. Thomas, pub., Springfield, Illinois.

Bonne, U., K. H. Homann, and H. G. Wagner. 1965. "Carbon Formation in Premixed Flames." In Tenth Symposium (International) on Combustion, pp. 503-

512. The Combustion Institute, Pittsburgh, Pennsylvania.

Burge, S. J. and C. F. H. Tipper. 1969. "The Burning of Polymers." Combustion and Flame 13:495-505.

Burgess, W. A., R. D. Treitmar and A. Gold. 1979. Air Contaminants in Structural Fires--Final Report. PB299017, Harvard School of Public Health,

Cambridge, Massachusetts.

Cheng, J., N. W. Ryan and A. D. Baer. 1969. "Oxidative Decomposition of PBAA

Polymers at High Heating Rates." In Twelfth Symposium (International) on

Combustion, pp. 525-532. The Combustion Institute, Pittsburgh, Pennsylvania.

Chien, W. P. and J. D. Seader. 1975. Smoke Measurement in a Modified NBS

Smoke Density Chamber. FRC/UU-44 (UTEC 75-055), Flammability Resources

Center, University of Utah, Salt Lake City, Utah.

Chippet, S. and W. A. Gray. 1978. "The Size and Optical Properties of Soot

Particles." Combustion and Flame 31:149-159.

Currin, Myron L. 1974. Physics of Smoke Formation. Colorado State University, Fort Collins, Colorado.

5.1
D'Alessio, A. et al. 1974. "Soot Formation in Methane-Oxygen Flames." In

Fifteenth Symposium (International) on Combustion, pp. 1427-1438. The Combustion Institute, Pittsburgh, Pennsylvania.

Driscoll, J. F. et al. 1978. "Submicron Particle Size Measurements in an

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Edwards, J. B. 1974. Combustion-Formation and Emission of Trace Species.

Ann Arbor Science Publishers, Michigan.

Emmons, Howard W. 1980. The Growth of Fire Science. Harvard University,

Cambridge, Massachusetts.

Fenimore, C. P. and G. W. Jones. 1966. "Modes of Inhibiting Polymer Flammability." Combustion and Flame 10:245-301.

Gaydon, A. G. and H. G. Wolfhard. 1970. I Flames--Their Structure, Radiation

and Temperature. Chapman and Hall, London.

Gross, D., J. J. Loftus and A. F. Robertson. 1969. "Method for Measuring

Smoke from Burning Materials." In ASTM Special Technical Publication 422.

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Huggett, Clayton. 1978. "Oxygen Consumption Calorimetry." Paper presented at

the 1978 Fall Technical Meeting of the Eastern Section of Center for Fire

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Institute, Miami, Florida, November 29-December 1.

King, T. V. 1979. Smoke and Carbon Monoxide Formation from Materials Tested

in the Smoke Chamber. NBSIR 75-901, Center for Fire Research, National

Bureau of Standards, Washington, D.C.

Krause, F. R. et al. 1980. LWR Fire Protection Design Verification by Thermodynamic Simulation. SAND80-1020, Sandia National Laboratory, Albuquerque,

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Kunngi, M. and H. Tinno. 1974. "Determination of Size and Concentration of

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Long, R. 1972. Studies on Polycyclic Aromatic Hydrocarbon in Flames.

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5.2
McCaffrey, Bernard J. 1979. Purely Buoyant Diffusion Flames:. Some Experimental Results. Center for Fire Research, National Bureau of Standards,

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McHale, E. T. and E. G. Skolnik. 1979. Final Technical Report--Chemistry of

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Pagni, P. J. and B. Bard. 1978. "Particulate Volume Fractions in Diffusion

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Palmer, H. B. and C. F. Cullis. 1965. "The Formation of Carbon from Gas."

In Chemistry and Physics of Carbon, ed. P. L. Walker, Jr., Marcel Dekker,

Inc., New York.

Parker, W. G. and H. G. Wolfhard. 1953. "Some Characteristics of Flames

Supported by NO and NO2 ." In Fourth Symposium (International) on Combustion,

pp. 420-428. The Combustion Institute, Pittsburgh, Pennsylvania.

Pauling, L. ed. 1964. College Chemistrx. 3rd ed., p. 315, W. H. Freeman and

Company, San Francisco, California.

Pourprix, M. et al. 1978. "Size Distribution of Combustion Aerosols."

Gosselachaft Fur Aerosol Forchung (GAF):76-78.

Powell, E. A. et al. 1979. "The Effects of Environmental Temperature Upon

the Physical Characteristics of the Smoke Produced by Burning Wood and PVC

Samples." Fire and Materials 3(1):12-15.

Prado, G. P. et al. 1978. "Soot and Hydrocarbon Formation in a Turbulent

Diffusion Flame." In Combustion Research on Characterization of Particulate

Organic Matter from Flames, ed. R. A. Hites and J. B. Howard, pp. 6-18. PB291 314, National Technical Information Service, Springfield, Virginia.

Punderson, J. 0. 1981. "A Closer Look at Cause and Effect in Fire

Fatalities--The Role of Toxic Fumes." Fire and Materials 5(1):41-46.

Roberts, A. F. and F. R. Brooks. 1981. Hydraulic Fluids: An Approach to

High Pressure Spray Flammability Testing Based on Measurement of Output.

Explosion and Flame Laboratory, Harper Hill, Buxton, Derbyshire, England.

Rummel, K. and P. 0. Veh. 1941. Arch Eisenhutten Wesen 14:489.

5.3
Saito, F. 1974. "Smoke Generation from Building Materials." In Fifteenth

Symposium (International) on Combustion, pp. 1383-1393. The Combustion

Institute, Pittsburgh, Pennsylvania.

Seader, J. D. and I. N. Einhorn. 1976. Some Physical, Chemical,

Toxicological, and Physiological Aspects of Fire Smokes. Flammability

Research Center, University of Utah, Salt Lake City, Utah.

Tesner, P. A. 1959. "Formation of Dispersed Carbon by Thermal Decomposition

of Hydrocarbons." In Seventh Symposium (International) on Combustion,

pp. 546-553. The Combustion Institute, Pittsburgh, Pennsylvania.

Tewarson, A. 1980a. "Heat Release Rate in Fires." Fire and Materials

4(4):185-191.

Tewarson, A. 1980b. Physico-Chemical and Combustion/Pyrolysis Properties of

Polymeric Materials--Technical Report. PMRC J. I. OEON 6,RC, National Bureau

of Standards, Washington, D.C.

Tewarson, A. and R. F. Pion. 1976. "Flammability of Plastics - I. Burning

Intensity." Combustion and Flame 26:85-103.

Tewarson, A. et al. 1980. The Influence of Oxygen Concentration on Fuel

Parameters. Factory Mutual Research Corporation, Norwood, Massachusetts.

Tsuchiya, Y. and G. W. Leir. 1975. "Equilibrium Composition of Fire

Atmospheres." J. of Fire ard Flammability 6:5-16.

Wagner, H. G. 1978. "Soot Formation in Combustion." In Seventeenth Symposium

(International) on Combustion, pp. 3-18. The Combustion Institute,

Pittsburgh, Pennsylvania.

Weast, Robert C., ed. 1981. CRC Handbook of Chemistry and Physics. 62nd ed.

CRC Press, Cleveland, Ohio.

Williams, A. and D. B. Smith. 1970. Chem. Rev. 69:267.

Zinn, B. T. and R. A. Cassanova. 1976. "Properties of Combustion Products

from Building Fires." Paper presented at the Annual Conference on Fire

Research of National Fire Prevention and Control Administration, July 14-16,

U.S. Dept. of Commerce, The Johns Hopkins University, Laurel, Maryland.

Zinn, B. T. et al. 1978. Investigation of the Properties of the Combustion

Products Generated by Building Fires--Final Report of National Bureau of

Standards. School of Aerospace Engineering, Georgia Institute of Technology,

Atlanta, Georgia.

Zinn, B. T. et al. 1980. The Smoke Hazards Resulting from the Burning of

Shipboard Materials Used b' the U.S. Navy. NRL 8414, Georgia Institute of

Technology, Atlanta, Georgia.

5.4
Zukoski et al. 1981. Entrainment in Fire Plumes. California Institute of

Technology, Pasadena, California.

5.5

APPENDIX A

COLLECTION OF LITERATURE DATA

COLLECTION OF LITERATURE DATA

This appendix contains copies of data collected from the literature on

the characteristics of combustion products. (Much of the tabulated material

from Section 3.0 is derived from here.) Each section (Appendix A.1 through

A.7) is a collection of tables and figures from one source. At the beginning

of each section, this source is identified and the tables and figures are

listed. A list of nomenclature is also provided if necessary.

A.1
APPENDIX A.1

LITERATURE

Tewarson, A. 1980. :Physico-Chemical and Combustion/Pyrolysis Properties of

Polymeric Materials--Technical Report. PMRC J.I. OEON 6.RC. National

Bureau of Standards, Washington, D.C.

TABLES

A.1.1 Physicochemical Properties of Nonaromatic Materials

A.1.2 Combustion Properties of Nonaromatic Materials

A.1.3 Physicochemical Properties of Polystyrenes

A.1.4 Combustion Properties of Polystyrenes

FIGURES

A.1.1 Actual Heat Release Rate as a Function of Heat Released in the Complete Combustion of Material Vapors, q" + + qfs qrr n e +qs -qrr

A.1.2 Ratio of Yields of CO and C02 for Heptane as a Function of

Oxygen-to-Fuel Stoichiometric Fraction (0) (0 > 1 for overventilated

environment, 0 < 1 for underventilated environment)

A.1.3 Experimental Mass Generation Rate of CO; as a Function of Rate

Expected from Stoichiometry, qn - qe f -q r

A.1.4 Experimentally Measured Mass Generation Rate of CO as a Function of

Rate oil il l! i Expected from Stoichiometry, q = +q fs - qrr

A.1.5 Experimentally Measured Mass Generation Rate of Soot and Low Vapor

Pressure Liquids as a Function of Mass Loss Rate of the Material,

qn ý1= - q1, e + +fs q11 -- rr1

A.1.6 Actual Heat Release Rate Calculated from CO and C02 as a Function of

Actual Heat-Release Rate Calculated from 02 Depletion

NOMENCLATURE

q' Net heat flux per unit surface area of the material, kW/m 2

n

External heat flux per unit surface area of the material, kW/m 2

Te

qfs' Total flame heat flux per unit surface area of the material, kW/m2

A.2
qr, Surface reradiation heat flux per unit surface area of the material

Ht Heat of complete combustion, kJ/g

L Heat required to generate a unit mass of vapor,.kJ/g

A• Actual heat release rate per unit surface area of the material, kW/m 2

YCO Mass fractional yield of CO

YCO2 Mass fractional yield of CO2 2

tog Gen ration rate of product C02'per unit surface area of the material, CO2 g/mp-sec

kCO 2 Yield of.-CO2 expected from stoichiometry

'" Generation rate of soot per unit surface area of the material, g/m 2 -sec S.

Ts Material surface temperature

•a Volumetric flow rate of air into the apparatus, m3/sec

m02 Mass fraction of oxygen

02

XA Combustion efficiency

XC Convective fraction of heat of complete combustion

XR Radiative fraction of heat of complete combustion

YHC Mass fractional yield of hydrocarbon

Flame convective heat flux per unit surface area of the material

Flame radiative heat flux per unit surface area of the material

a Light obscuration parameter, m2 /g

A.3
TABLE A.1.1. Physicochemical Properties of Nonaromatic Materials(a)

Sample

Oak

Polyoxymethylene (POM)

PMMA

Polypropylene (PP)

PVC

(a) For qe 4 46 kW/m 2 . e 2

(b) For ý" > 46 kW/m2.

e

Chemi cal

Formul a

CH1.6*000.71No.o0

Stoichiometric

Air/Fuel Ratio

5.8

CH20

CH1 ' 6 0 00 . 4 0

CH2

CH1 . 5Cl0.50

4.6

8.2

15

5.5

H

17.7

15.4

25.2

43.3

16.4

L,

kJ/g

1.7(a)

5. 5 (b)

2.43

1.63

2.03

2.47

qrr'2

kW/m

16 730

13

11

18

21

690

660

750

780
TABLE A.1.2. Combustion Properties of Nonaromatic Materials

I• (a (m3/sec)

Sample kW/m 2 x10 3 _mC- _4- ICO2

Oak 31 1.4 0.233 0.68 0.49 0.19 1.2

37 1.4 0.233 0.63 0.43 0.20 1.2

42 1.4 0.233 0.64 0.43 0.21 1.2

46 1.4 0.233 0.72 0.45 0.27 1.2

52 1.4 0.233 0.77 0.49 0.28 1.4

60 1.4 0.233 0.74 0.43 0.31 1.3

71 1.4 0.233 0.71 0.37 0.34 1.4

R1,1

0.002. < 0.001 --- 0.135 11

0.004 <0.001 0.017 0.108 

8

0.003 < 0.001 0.013 0.095 

8

0.003 < 0.001 0.013 0.081 

7

0.006 < 0.001 0.104 

9

0.004 < 0.001 0.018 0.137 

8

0.005 X 0.001 0--- .128 

7

z,

POM 0 1.4 0.233 0.93 0.76 0.17

0.303 0.93 0.77 0.16

0.404 0.93 0.76 0.17

0.445 0.93 0.65 0.28

0.521 0.96 0.70 0.26

39 0.86 0.233 0.82 0.53 0.29

52 0.86 0.233 0.71 0.45 0.25

PIMA 0 1.4 0.183 0.99 0.76 0.23

0.195 0.98 0.74 0.24

0.207 0.98 0.70 0.28

0.233 0.94 0.64 Or30

0.318 0.95 0.54 0.41

0.404 0.96 0.48 0.48

0.491 0.97 0.49 0.48

0.531 0.98 0.45 0.53

0 Oýaj 0.233

31 N a 0.233 0.86 0.57 0.29

46 N(a) 0.233 0.86 0.49 0.37

46 1 4 0.233 0.82 0.51 0.31

60 Nta) 0.233 0.86 0.49 0.37

1.4

1.4

1.4

1.4

1.4

1.2

1.0

2.2

2.2

2.1

2.1

2.1

2.2

2.2

2.2

1.9

1.9

1.8

1.9

( 0.001 < 0.001 < 0.001 --- ( 0.001 < 0.001 < 0.001 --- < 0.001 < 0.001 < 0.001 ---

< 0.001 < 0.001 < 0.001 ---

< 0.001 < 0.001 ( 0.001 --- 0.001 < 0.001 < 0.001 --- 0.001 < 0.001 < 0.001 ---

0.011 < 0.001 --- 0 .0 1 1 < 0 . 0 0 1 . . .

...

0 . 0 1 2 < 0 

. 0 0 1 ..

.... 0.011 < 0.001 0.021 0.225

< 0.001 < 0.001 0.023 0.111

< 0.001 < 0.001 0.024 0.055

< 0.001 < 0.001 0.020 0.029 < 0.001 < 0.001 0.012

0.008 < 0.001

0.007 0.001

0.007 < 0.001 --

0.006 ( 0.001 ---

0.232

0.282

0.247

0.257

25

28

37

33

38

118

17

16

17

15

13

12

13

128342

20

15

17

15

12

20

18

132

26

24

26

10/r, 5

1056286

12

127

17477

15

26

38

43

44

21

32

28

433

14

14

23

37

41

44

53

56

37

37

39

PP 0 1.4 0.196 0.99 0.82 0.16 0.208 .0.92 0.63 0.29

0.233 0.86 0.58 0.28

0.266 0.86 0.53 0.33

0.310 0.88 0.46 0.42

0.370 0.88 0.47 0.41

0.427 0.91 0.46 0.45

0.507 0.91 0.43 0.48

52 0.86 0.233 0.63 0.41 0.22

3.1 0.021 0.007 ... ...

2.9 0.032 0.002 

- --- 2.7 0.034 0.001 0.083 ---

2.7 0.023 0.001 0.090 --- 2.8 0.021 ( 0.001 0.064 0.390

2.8 0.014 < 0.001 0.070 0.437

2.9 0.012 < 0.001 --- 0.265

2.9 0.014 < 0.001 ---

1.9 0.054 0.03 --- 0.429

0.46 0.039 0.003 0.091 0.656

0.47 0.034 0.002 0.093 0.489

0.46 0.029 0.001 0.074 0.398

PVC 0 2.0 0.671 0.35 0.17 0.18

0.757 0.35 0.19 0.16

0.874 0.35 0.20 0.14

(a) Natural air flow.
TABLE A.1.3. Physicochemical Properties of Polystyrenes

Somnpleka)

GM-47

GM-49/FR

GM-51

GM-53

Granular polystyrene

Liquid styrene

DensiV.y

kg/mr

16

16

34

29

1,051

Stoi chi omet ri c

Air/Fuel Ratio,

Chemical Formula g/g

CHI.01 13

CH1 0500.004 13

CH1.0100,021 13

CH1 . 0 50 0 . 0 1 2 13

CH 13

CH 13

H

38.1

38.2

35.6

37.6

39.2

40.5

L,

kJ/g

3.00

3.10

2.50

2.25

1.70

0.64

• II,

rr'

kW/m 2

10

13

12

13

14

2

650

690

680

690

700

420

(a) GM-sample designation by the National Bureau of Standards, Center for Fire Research,

Washington, D.C.
TABLE A.1.4. Combustion Properties of Polystyrenes

Rigid Foam Sample

GM.47(a)

"ille

kW/m 2

0

;a (m3/sec)

x10 3

2.0

--. 2 f

0.371

0.501

0.564

0.631

40 0.86 0.233

GM-49/FR(a)

GM-51(a)

GM-53(a)

Granular polystyrene

0 2.0 0.422

0.503

0.555

0.615

0 2.0

0 2.0

0.445

0.498

0.568

0.619

0.445

0.498

0.565

0.628

0.62

0.57

0.55

0.60

0.59

0.55

0.54

0.54

0.57

0.53

0.54

0.51

0.54

0.51

0.52

0.48

0.51

0.68

0.67

0.68

0.68

0.66

0.64

0.67

0.13

0.11

0.10

0.14

0.14

0.11

0.091

0.082

0.11

0.12

0.13

0.11

0.15

0.13

0.13

0.10

0.090

0.40

0.34

0.35

0.34

0.32

0.22

0.21

_-4_

0.49

0.46

0.45

0.46

0.45

0.45

0.45

0.46

0.45

0.41

0.41

0.40

0.39

0.38

0.39

0.38

0.42

0.28

0.33

0.33

0.34

0.34

0.42

0.46

1.8

1.8

1.8

1.9

1.7

1.8

1.7

1.8

1.7

1.7

1.6

1.7

2.2

2.2

2.2

2.3

2.2

2.2

2.3

1.7

iC2

2.1

1.9

1.8

2.0

1.6

- IC0-

0.031

0.023

0.014

0.012

0.052

0.033

0.024

0.021

0.014

0.032

0.033

0.031

0.024

0.031

0.030

0.030

0.033

0.071

0.053

0.032

0.032

0.022

0.024

0.010

0.003

0.001

0.008

0.005

0.004

0.002

0.002

0.002

0.004

0.004

0.003

0.003

0.02

0.01

0.005

0.002

0.003

0.001

(a)

-Y RG--

0.002

0.008

0.007

0.004

0.006

0.27

0.31

0.36

0.37

0.37 0.33

0.37

0.38

0.27

0.27

0.26

0.21

0.30

0.25

0.29

0.24

0.15

0.21

0.20

M2g

1.08

0.951

0.572

0.793

1.32

0.681

0.762

0.771

0.543

0.731

0.724

0.632

0.560

0.811

0.732

0.660

1.10

0.73

0.63

1.1

1.0

6

6

6

10

6

9

9

16

8

9

9

8

11

8

10

14

12

11

15

6

8

9

14

1

kW/m 2

30

30

29

23

54

3836

41

40

41

29

34

18

31

30

28

32

27

41

37

23

32

28

20

0 1.4 0.233

0.264

0.313ja)

0.334 a )

0.375 ýa

0.420ta)

0.5 2 4 (a)

Liquid styrene 0 0.86 0.233 0.50 0.18 0.32 0.062 0.0041 0.33 0.783 6 13

(a) Extensive deposition of

forming materials.

flame soot on the surface; mass loss rate suppressed; combustion similar to the combustion for char-
1000

t'. E

2g

- '< 500

0

0 1000 2000

* II2

qn (HT/L), kW/m2

FIGURE A.1.1. Actual Heat Release Rate as a Function of Heat Released

in the Complete Combustion of Material Vapors, qn = e+

qfs - rr

A.8
HEPTANE

0

100

10

x

0

U

0

U

0. 1

AIR FLOW

2 /sec

1.4 

*

0

0

1.9 0

2.3 A

n o2

0. 170

O. 209

0.230

0.250

0.270

0.209

0.209

0.230

0

0

O (.

%ot

0

0

0

, I I . . 1.1 m | • • . I I I I a I I I

0.1 1.0 10

FIGURE A.1.2. Ratio of Yields of CO and CO for Heptane as a Function

of Oxygen-to-Fuel Stoichiomefric Fraction (0) (o > 1

for overventilated environment, < I for underventilated

environment)

A.9
100

E

5O 0

0

50 100 150 200

, (K 'o 2 /L). gim sec

FIGURE A.1.3. Experimental Mass -Generation Rate of CO2 as a Function

of Rate Expected from Stoichiometry, qn'"-- qe + qf' - qrr

A. 1O
5.0

4.0

3.0

U

4)

U)

E

Cu

0a

2.0

1.0

0

0 50

qn(kco/L), g/m 2sec

100

FIGURE A.1.4. Experimentally Measured Mass Generation Rate of CO as a

Function of Rate Expected from Stoichiometry, q" = + I - n e

A. 11
25

20

E

60

15

10

5

0

0 100 200 300 400 500

So ,kW/m 2

n

Experimentally Measured Mass Generation Rate of Soot and

Low Vapor Pressure Liquids as a Function of Mass Loss

Rate of the Material, qng = + -e " -rr

n~ e qf r

600

FIGURE A.1.5.

A.12
0

A

-0

V)

_-A

RED OAK

PMMA (GRANULAR)

PP (GRANULAR)

POM (GRANULAR)

PS (GRANULAR)

PE (FOAM)

PU (FOAM)

* ANILINE

A METHANOL

* BENZENE

V ACETONE

HEPTANE

I

1000

E

3:

r~i

0

U

a

z.

0

U

U.

0

z

0

9-

w

z

LU

0

=-K

*0

dv.

500

I, I I I I I i .1 i i I I m i 0

0 500

Q' FROM OXYGEN DEPLETION, kWim2

1000

FIGURE A.1.6. Actual Heat Release Rate Calculated from CO and

Function of Actual Heat Release Rate Calculated

Depletion

C02 as a

from 02

A.13
APPENDIX A.2

LITERATURE SOURCE

Tewarson, A. 1980. 4(4):185-191. "Heat Release Rate in .Fires." Fire and Materials

TABLES

A.2.1

A.2.2

Components of Heat-of Combustion

HT/L Values for Fuels

NOMENCLATURE

See Appendix A.1.

A. 14
TABLE A.2.1.

Fuel

Rigid polyethylene foam

Rigid polyurethane foam

PMMA

Flexible polyurethane foam

Red oak

Cellulose

PVC

Components of Heat of Combustion

Heat of Combustion, kJ g-I

Complete Actual Convective Radiative

40.84 22.83 18.79 4.04

26.02 11.84 3.85 7.99

25.20 17.89 10.33 7.56

26.64 14.41 4.46 9.95

17.78 12.69 6.65 6.04

16.48 11.80 5.78 6.02

16.44 5.89 2.43 3.46

A.15
TABLE A.2.2. HT/L Values for Fuels

Fuel (a) H T/L(b)

Red oak (solid) 2.96

Cellulose (filter paper) 4.64

Rigid PI foam (43) 5.14

Rigid PI foam (41) 6.04

POM (granular) 6.37

Rigid PU foam (37) 6.54

Flexible PU foam (I-A) 6.63

PVC (granular) 6.66

PE/48% Cl (granular) 6.72

Rigid PU foam (31) 8.05

Rigid PU foam (29) 8.37

PE/36% Cl (granular) 8.91

Flexible PU foam (23) 10.02

Flexible PU foam (27) 12.26

Nylon (granular) 13.10

Flexible PU foam (21) 13.34

Epoxy/FR/glass fiber (solid) 13.38

PE/25% Cl (granular) 14.90

Rigid PE foam (1) 15.15

PMMA (granular) 15.46

Rigid PE foam (2) 15.65

Methanol (liquid) 16.50

Flexible PU foam (25) 20.03

Rigid PS foam (47) 20.51

PP (granular) 21.37

Rigid PE foam (3) 22.82

PS (granular) 23.04

PE (granular) 24.84

Rigid PS foam (51) 26.79

Rigid PE foam (4) 27.23

A. 16
TABLE A.2.2. (contd)

Fuel (a) HT./L (b)

Rigid PS foam (53) 30.02

Rigid PS foam (49) 30.30

Aniline (liquid) 44.69

Acetone (liquid) 47.48

Styrene (liquid) 63.30

Benzene (liquid) 80.60

Heptane (liquid) 92.83

(a) Numbers in parentheses are PRC sample

numbers.

(b) HIT measured in an oxygen bomb calorimeter and corrected for water as a

vapor for fuels for which data are

not available; L is obtained by measuring the mass loss rate of the fuel

in pyrolysis in N2 environment as a

function of external heat flux for

fuels for which data are not available.

'A.17
APPENDIX A.3

LITERATURE SOURCE

Seader, J. P. and I. N. Einhorn. 1976. Some Physical, Chemical,

Toxicological, and Physiological Aspects of Fire Smokes. Flammability

Research Center, University of Utah, Salt Lake City, Utah.

TABLE

A.3.1 Smoke Particulates Generated from Several Woods and Polymers

A.18
TABLE A.3.1. Smoke Particulates Generated from Several Woods

and Polymers

Material

Red oak

White oak

Black walnut

Marine plywood (Douglas fir)

Redwood

PMMA

Nylon 6/6

Polyethylene terephthalate

Polyethylene

PVC

Polyisoprene

PS

% Converted to

Smoke

Residue Particulate

0.2 0.2

0.7 0.2

1.0 0.3

1.0 0.4

0.2 0.4

0 0.6

2.5 5.5

9.8 5.8

0.05 8.3

7.9 10.2

0 19.4

0.2 21.0

A. 19
APPENDIX A.4

LITERATURE SOURCE

Bankston, C. P. et al'. 1978. Review of Smoke Particulate Properties Data for

Natural and Synthetic Materials. NBS-GCR-78-147, Georgia Institute of Technology, Atlanta, Georgia.

TABLES

A.4.1 Wood Smoke Properties at different radiant heating rates--Nonflaming

Conditions'

A.4.2 Wood Smoke Properties Compared for Flaming and Nonflaming Conditions

A.4.3 Wood Smoke Properties in Different Atmospheric Compositions--

Nonflaming Conditions

A.4.4 Wood Smoke Properties at Different Environmental Temperatures--

Nonflaming Conditions

A.4.5 Wood Smoke Properties at Different Environmental Temperatures--Flaming

Conditions

A.4.6 Composition (in PHR) of PVC Samples

A.4.7 Effect of Sample Composition on PVC Smoke Properties--Nonflaming Conditions

A.4.8 Rigid PVC Smoke Properties at Different Radiant Heating Rates--

Nonflaming Conditions

A.4.9 Rigid PVC Smoke Properties Compared for Flaming and Nonflaming Conditions

A.4.10 Rigid PVC Smoke Properties in Different Atmospheric Compositions--

Nonflaming Conditions

A.4.11 Rigid PVC Smoke Properties at Different Environmental Temperatures--

Nonflaming Conditions

A.4.12 Rigid PVC Smoke Properties at Different Environmental Temperatures--

Flaming Conditions

FIGURES

A.4.1 Particle Size Distributions for Wood Smoke Generated Under Nonflaming

Conditions

A.20
A.4.2 Particle Size Distributions for Wood Smoke Generated Under Flaming and

Nonflaming Conditions

A.4.3 Smoke Particle Size Distribution for PVC Compositions 1 Through 4

Generated Under Nonflaming Conditions

A.4.4 Smoke Partidle Size Distributions for PVC Compositions 5 Through 7

Generated Under Nonflaming Conditions

A.4.5 Particle Size Distributions for Rigid PVC Smoke Generated Under Nonflaming Conditions

A.4.6 Particle Size Distributions for Rigid PVC Smoke Generated Under

Flaming and Nonflaming Conditions

NOMENCLATURE

r Fraction of sample weight loss converted to smoke particulates

ODmax Maximum optical density per meter at 0.458 m (blue) and 0.633 m (red)

D32 Volume-surface mean particle diameter at maximum optical density

F Flaming

NF Nonflaming

A.21
TABLE A.4.1. Wood Smoke Properties at Different

Nonflaming Conditions

Radiant Heating Rates--

r

0.031

DMMD-__•

0.5

. OD

(BIuj),

m

NM

OD

(Rev),

m

NM

a, JIm

Douglas fir 1.86 NM

Nonflaming (3.2 W/cm2 )

Air (142 /min)

Douglas fir 2

Nonflaming (5 W/cm2)

Air (425 z/min)

Douglas fir

Nonflaming (6.2 W/cm2 )

Air (425 k/min)

Douglas fir

Nonflaming (5 W/cm2 )(a)

Air (425 x/min)

0.154

0.165

0.108

0.82

0.90

1.80

1.98

1.96

1.83

1.57

2.48

3.87

1.07 0.75

2.04 0.80

3.46 0.77

(a) Horizontal sample mount

NM = Not measured

TABLE A.4.2. Wood Smoke Properties Compared for

Conditions

Flaming and Nonflaming

. MMD2,- m

OD

(Bluj),

C, .Jm m

Douglas fir 2.37 0.61

Flaming (2.5 W/cm2 )

Air (283 £/min)

Douglas fir

Flaming (5 W/cm2 )

Air (425 Y./min)

Douglas fir 2

Nonflaming (5 W/cm2)

Air (425 _/min)

NM = Not measured

NG = Negligible values

0.025

<0.01

0.43

NM

OD

(Req),

m

0.32

NG

0.52

NM NG 0.47

0.154 0.82 1.98 1.57 1.07 0.75

A. 22
TABLE A.4.3. Wood Smoke

Nonflaming

Properties in Different Atmospheric Compositions--

Conditions

r

0.165

D-MMD pm

0.90

OD

(Blu7),

m

2.48

OD

(ReV),

m

2.04

a, pm

Douglas fir 1.96 0.80

Nonflaming (6.2 W/cm2 )

Air (425 x/min)

Douglas fir

Nonflaming (6.2

80% N2 , 10% 02,

0.221 1.05 1.93 1.95 2.09 1.00

W/cm2 )

10% C02

Douglas fir

Nonflaming

80% N C5% C02, 5%, CO

0.237 0.92 2.28 1.48 1.18 0.75

(6.2 W/cm2)

02, 10%

TABLE A.4.4. Wood Smoke Properties at

Temperatures--Nonflaming

Different Environment

Conditions

OD

(Blue), m-1

1.57

OD

(Red), m1.07

.5pm

Douglas fir 0.75

Nonflaming (5 W/cm2 )

Air (25°C, 425 x/min)

Douglas fir 2

Nonflaming (5 W/cm2)

Air (100'C, 425 x/min)

Douglas fir 2

Nonflaming (5 W/cm2)

Ai,r (200 0C, 425 x/min)

0.97

0.96

0.86

0.74

0.74

0.54

A.23
TABLE A.4.5. Wood Smoke Properties at Different Environmental

Temperatures--Flaming Conditions

OD

(Blue), m-1

NM

OD

(Red), m 1

NM

-32' pm

Douglas fir 0.47

Flaming (5

Air (25°C,

W/cm2 )

425 x/min)

Douglas fir 2

Flaming (5 W/cm2 )

Air (100°Cj 425 x/min)

Douglas fir 2

Flaming (5 W/cm2 )

Air (200 0C, 283 x/min)

Douglas fir 2

Flaming (5 W/cm2)

Air (300 0C, 283 X/min)

NM = Not measured

NM NM

0.13

0.24

0.09

0.19

0.89

1.08

1.20

TABLE A.4.6. Composition (in PHR) of PVC Samples

Sample

1

2

3

4

PVC

Resin

100

100

100

100

Lead

Stabilizer

5

5

5

5

Plasticizer

(6-10)

(Phthalate)

Al 0

CaCO3 A 206

Lubri -

Sb203 cants

45

45

45

45

45

50

1.5

1.5

5 1.5

5 1.5

5 0.5

5

6

7

100

100

5

5

50,

50

Rigid, commercially available

composition unknown.

"standard-impact" formulation;

A.24
TABLE A,4.7. Ef

Noi

PVC-I

Nonflaming (5 W/cm2 )

Air (425 t/min)

PVC-2

Nonflaming (5 W/cm2 )

Air (425 x/min)

PVC-3

Nonflaming (5 W/cm2 )

Air (425 i/min)

PVC-4 2

Nonflaming (5 W/cm2)

Air (425 x/min)

PVC-5

Nonflaming (5 W/cm2 )

Air (425 i/min)

PVC-6

Nonflaming (5 W/cm2)

Air (425 x/min)

PVC-7

Nonflaming (5 W/cm2)

Air (425 x/min)

NM = Not measured.

fect of Sample Compositi

nflaming Conditions

on on PVC Smoke Properties--

r

0.093

D MMDI pm

1.40

OD

(Blu¶),

m

2.08

OD

(Req),

m

2.24

a, pm

1.45

D a-1-32pm

0.99

0.123

0.085

0.125

0.095

0.079

0.070

1.49

1.14

1.37

1.15

0.91

1.20

1.61

1.78

1.61

1.83

1.85

1.86

3.30

NM

4.54

NM

2.19

1.49

3.55 1.05

NM NM

4.99 1.10

NM NM

1.92 0.80

1.42 0.84

A.25
TABLE A.4.8. Rigid PVC Smoke Properties at Different Radiant

Nonflaming Conditions

Heating Rates--

r

0.012

_DMMD' pm

0.42

OD

(Bluj),

m

NM

OD

(ReV)

m

NM

a, Pm

1.90

D32- Pm

PVC-7 NM

Nonflaming (3.2 W/cm2 )

Air (142 t/min)

PVC-7 2 0.030

Nonflaming (5 W/cm2)

Air (425 x/min)

PVC-7 2 0.072

Nonflaming (6.2 W/cm2)

Air (425 t/min)

PVC-7 0.070

Nonflaming (5 W/cm2 )(a)

Air (425 x/min)

(a) Horizontal sample mount.

NM = Not measured.

0.85

0.73

1.20

1.79

2.00

1.86

0.55

1.17

1.49

0.30 0.62

0.95 0.73

1.42 0.84

TABLE A.4.9. Rigid PVC Smoke Properties Compared for Flaming

Conditions

and Nonflaming

r M-ýHI'p

. OD

(BIlu),

JIm m

2.22 0.95

OD

(ReV),

m

0.56

D32,p-m

PVC-7 0.58

Flaming (2.5 W/cm2 )

Air (425 x/min)

0.012 0.41

PVC-7

Flaming

80% N2,

(2.5 W/cm2 )

10% C02, 10% 02

0.012

0.072

0.44

0.73

2.02

2.00

1.39

1.17

0.68 0.33

PVC-7 0.95 0.73

Nonflaming (6.2 W/cm2 )

Air (425 x/min)

A.26
TABLE A.4.10. Ri

Coi

PVC-7

Nonflaming (6.2 W/cm2 )

Air (425 i/min)

gid PVC Smoke Properties in Different Atmospheric

mpositions--Nonfloaming Conditions

r

0.072

0.076

DDMMD' pm

0.73

0.70

0, pm

2.00

1.94

OD

(Bluj),

m

1.17

1.61

OD

(Re0.

0.95

P-32,pm

0.73

PVC-7

Nonflaming (6.2

80% N2, 10% 02,

1.16 0.67

W/cm2)

10% CO2

PVC-7

Nonflaming

80% N2 , 5%

5% CO

0.064 0.77 2.04 1.14 0.85 0.70

(6.2 W/cm2 )

02, 10% C02,

TABLE A.4.11. Rigid PVC Smoke Properties at Different Environmental

Temperatures--Nonflaming Conditions

OD

(Blue), m-1

0.55

OD

(Red), m-1

PVC-7 0.30 0.62

Nonflaming (5 W/cm2 ) Air (25 0C, 425 x/min)

PVC-7

Nonflaming (5 W/cm2 )

Air (100 0C, 425 x/min)

PVC-7

Nonflaming (5 W/cm2 )

Air (200 0C, 425 x/min)

PVC-7

Nonflaming (5 W/cm2 )

Air (300%, 425 x/min)

0.42

0.45

0.66

0.34

0.32

0.37

1.01

1.11

0.90

A.27
TABLE A.4.12. Rigid PVC Smoke Properties at Different

Temperatures--Flaming Conditions

Environmental

OD

(Blue), m-1

2.04

OD

(Red), m-1

1.53

D32,- Lm

PVC-7 0.73

Flaming (5 W/cm2 )

Air (25°C, 425 X/min)

PVC-7 2

Flaming (5 W/cm2)

Air (100 0C, 425 x/min)

PVC-7 2

Flaming (5 W/cm2)

Air (2000C, 425 x/min)

PVC-7 2

Flaming (5 W/cm2)

Air (3000C, 425 x/min)

PVC-7

Flaming(a)

Air (400 0C, 425 t/min)

(a) No radiant heating.

1.78

2.07

2.69

2.93

1.45

1.67

2.11

2.29

0.76

0.95

1.20

1.22

A. 28
WOOD NONFLAMING 03

V

99 --

I

90

///

/

Lu

ILU

-J

-J

/

/

A

iI

tI

50 I-

-,/

/

/

10

/

.-0O--

-0--.

--O5 W/cm2-_ AIR

6.2 W/cm - AIR

5 W/cm2 - AIR(a)

2_ 3.2 W/cm2- AIR

6.2 W/cm

2

80% N2 , 10%02' 10% CO2

I 1- i , I l I

(a) HORIZONTAL MOUNTING I- I I i L lI

I L

0.3 1.0

PARTICLE DIAMETER,

Particle Size Distributions

Under Nonflaming .Conditions,

3.0 10.0

fom

for Wood Smoke Generated FIGURE.A.4.1.

A.29
99

7

0

90

0

wU

N

(A

Z

L--

-J

-J

(A

4-

50

WOOD IN AIR

NONFLAMING- 5 W/cm 2

10

1

I-0-

.-..-- FLAMING- 2.5 W/cm2

0.3 1.0 3.0

PARTICLE DIAMETER, jim

10.0

FIGURE A.4.2. Particle Size Distributions for Wood

Flaming and Nonflaming Conditions

Smoke Generated Under

A. 30
99

90

PVC NONFLAMING- 5 W/cm2 AIR

7 / /

/

0

LU

Z

LU

-j

50

,

/

/

/

10 -

-0o--

-0--l

COMPOSITION

COMPOSITION

COMPOSITION

COMPOSIT ION

1

2

3

4

I/I

I I I I I I I I I I I I I I I 1

0.3 1.0 3.0 10.0

FIGURE A.4.3.

PARTICLE DIAMETER, .im

Smoke Particle Size Distributions for PVC Compositions 1

Through 4 Generated Under Nonflaming Conditions

A.31
PVC NONFLAMING- 5 W/cm2 AIR 4

/

/

/

/ 99

90

/

/

/

(A

z

LU

(A

d:

50

04

/

- COMPOSITION 5

-"--"COMPOSITION 6

10 -- &,-- COMPOSITION 7

I I I I I I I I I I I I I I I I

0.3 1.0 3.0 10.0

PARTICLE DIAMETER,, rm

FIGURE A.4.4. Smoke Particle Size Distributions forPVC Compositions 5

Through 7 Generated Under Nonflaming Conditions

A.32
RIGID PVC NONFLAMING

99 L90

/

LIP1

(A

-J

Ui

W)

dP

/

0'9

/

-0- 5 W/cm2 -AIR

- 6.2 W/cm -AIR

---- 6.2 W/cm 2-80°N2 10% 02' 10% CO 2

3.2 W/cm -AIR

50

0

10 II I I I I I I I I I . I I I I I 1

0.3 1.0 3.0 10.0

PARTICLE DIAMETER, jm

FIGURE A.4.5. Particle Size Distributions for Rigid PVC Smoke Generated

Under Nonflaming Conditions

A.33
/

99K

4A

0

0-

90

50

/

/

/

/

0 0/

/ e0

V/

/

/

-. 4-- FLAMING- 2.5 W/cm2- AIR

-0--FLAMING- 2.5 W/cm - 80% N2 ,

10% 02. 10% CO 2

-l-- NONFLAMING- 6.2 W/cm2- AIR

/

/

/

/

/

/

/

/

10 k

I I I I I I I i i. I I I I I I

1

0.3 1.0 3.0 10.0

FIGURE A.4.6.

PARTICLE DIAMETER, jm

Particle Size Distribution for Rigid PVC Smoke Generated

Under Flaming and Nonflaming Conditions

A. 34
APPENDIX A.5

LITERATURE SOURCE

Zinn, B. T. et al. 1978. Investigation of the Properties of the Combustion

Products Generated by Building Fires--Final Report of National Bureau of

Standards. School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia.

TABLES

A.5.1 Smoke Property Data Under Nonflaming Conditions at 5 W/cm2 and 25°C

(Materials--PS, PVC, Polypropylene, Polyethylene, and PMMA)

A.5.2 Smoke Property Data in Room Temperature Air at 5 W/cm2

A.5.3 Smoke Property Data Under Flaming Conditions at 5 W/cm2

FIGURES

A.5.1 Sample Weight Loss in Nonflaming Combustion in Room Temperature Air

for Polystyrene, PVC, Polyethylene, and PMMA

A.5.2 Smoke Particle Size Distributions for Five Substrate Polymers Generated Under Low Temperature, Nonflaming Conditions

A.5.3 Smoke Mean Particle Size for Five Substrate Polymers in Nonflaming

Combustion in Room Temperature Ventilation Air

A.5.4 Effect of Ventilation Gas Temperature Upon Mean Particle Diameter for

a PVC Sample in Nonflaming Combustion at 5 W/cm2

A.5.5 Sample Weight Loss in Flaming Combustion in room Temperature Air for

Polystyrene, Polypropylene, Polyethylene, and PMMA

A.5.6 Smoke Mean Particle Diameter for Five Substrate Polymers in Flaming

Combustion in Room Temperature Ventilation Air

A.5.7 Effect of Ventilation Gas Temperature Upon Sample Weight Loss for

Polyethylene and Polystyrene Under Flaming Conditions

A.5.8 Effect of Ventilation Gas Temperature Upon Smoke Mean Particle

Diameter for Flaming Polystyrene at 5 W/cm2

A.5.9 Effect of Ventilation Gas Temp rature Upon Smoke Mean Particle diameter for Flaming PVC at 5 W/cm

A.35
A.5.10 Effect of Ventilation Gas Temperature Upn

eter for Flaming Polypropylene at 5 W/cm

A.5.11 Effect of Ventilation Gas Temperature U on

eter for Flaming Polyethylene at 5 W/cm.

A.5.12 Effect of Ventilation Gas Tempepature Upon

eter for Flaming PMMA at 5 W/cm

Smoke Mean Particle DiamSmoke Mean Particle DiamSmoke Mean Particle DiamNOMENCLATURE

r Fraction of sample weight loss converted to smoke particulates

DMMD Mass median diameter

ODMAX Maximum optical density per meter at 458 nm (blue) and 633 nm (red)

D32 Volume-surface mean particle diameter at maximum optical density

F Flaming

NF Nonflaming

'A. 36
TABLE A.5.1. Smoke Property Data Under Nonflaming Conditions at 5 W/cm2

and 25*C

Material

PS

PVC

Polypropylene

Polyethylene

PMMA

r

0.084

0.093

0.121

NA

<0.01

DMMD,

pm

2.60

1.40

2.05

1.50

0.68

0, pm

1.84

1.45

1.77

1.73

1.87

_DMAX~

0.58 0.63

2.08 2.24

2.12 2.08

1. 4 1 (a) 1 . 5 1 (a)

0.07 0.05

1~321 pmT

1.42

0.98

1.55

1. 0 6 (a)

0.58

Time to

Peak OD,

mm n

11.3

13.5

6.4

9.9

10.7

(a) Measured during nonflaming phase, spontaneous ignition occurred 10 min

after initiation of exposure.

TABLE A.5.2.

Material

PS

PVC

Polypropylene

Polyethylene

PMMA

Smoke Property Data in Room Temperature Air

Type of

Combustion

F

NF

F

NF

F

NF

F

NF

F

NF

•ODA

r _ 11lue DMAX,, Red

0.032 11.29 8.84

0.084 0.58 0.63

0.025 2.55 2.02

0.093 2.08 2.24

0.018 3.34 2.53

0.121 2.12 2.08

0.012 2.70 2.05 --- 1.41 1.51

<0.01 1.43 1.05

<0.01 0.07 0.05

232' Um

1.30

1.42

1.06

0.98

1.21

1.55

1.26

1.06

1.17

0.58

at 5 W/cm 2

Time to

Peak OD,

mi n

5.1

11.3

5.7

13.5

4.5

6.4

6.9

9.9

5.3

10.7

A.37
TABLE A.5.3.

Material

PS

Smoke Property Data Under Flaming Conditions at 5 W/cm2

Temperature, OC

25

200

r

0.032

OCMAxW___

Blue ed

11.29 8.84

12.21 9.99

2D32' pm

1.30

1.35

Ti me to

Peak OD,

mi n

5.1

3.7

PVC

Polypropyl ene

Polyethylene

PMMA

25

200

25

200

25

200

25

200

0.025 2.55 2.02 1.06

3.45 2.64 1.14

0.018 3.34 2.53 1.21 --- 4.46 3.57 1.33

0.012 2.70 2.05 1.26 --- 4.07 3.22 1.33

<0.01 1.43 1.05 1.17

--- 1.60 1.30 1.29

5.7

5.7

4.5

3.9

6.9

5.1

5.3

3.6

A. 38
100

80

I-

,,J

z

60

40

:1:'

'•0

20

0

0 2 4 6 8 10 12 14 16 18 20

TIME, MIN.

FIGURE A.5.1. Sample Weight Loss in

for Polystyrene, PVC,

Nonflaming Combustion in Room Temperature Air

Polyethylene, and PMMA
NONFLAMING, 5 W/cm 2 AT 25°C

99

90

ID 0

/

13 PVC

E3

/ o~vC 0

wU

#A

z

I-

(A

U)

-J

AL

/

A PMMA /

./

50 A

I..

I...

I..

1*** -4:. / POLYPROPYLENEA

/

A /

/

/A

/

/

10

1

0e

-p

0.3 1.0 3.0

PARTICLE DIAMETER, jim

10.0

FIGURE A.5.2. Smoke Particle Size Distributions for Five Substrate

Polymers Generated Under Low Temperature, Nonflaming

Conditions

A.40
2.0

NONFLAMING, 5 W/cm2 AT 250 C

PS

PVC

POLYPROPYLENE

.......................... POLYETHYLENE

E 1.5 J :. _.."

< S

%

0.520 10 25

U I .

0.

0 5 10 15 20 25

TIME, MIN.

FIGURE A,5.3. Smoke Mean Particle Size for Five Substrate Polymers in Nonflaming

Combustion in Room Temperature Ventilation Air

30
1.5

E

=L

LU

-J.U

(LU

1.0

0.5

PVC NONFLAMING, 5 W/cm 2

I I I I 0

0 5 10 15 20 25

TIME, min

FIGURE A.5.4. Effect of Ventilation Gas Temperature Upon Mean Particle Diameter for

a PVC Sample in Nonflaming Combustion at 5 W/cm2
100

80

Io 60

,IZ=

40

0 2 4 6 8 10 12 14

TIME, MIN.

FIGURE A.5.5. .Sample Weight Loss in Flaming Combustion in Room Temperature

Air for Polystyrene, Polypropylene, Polyethylene, and PMMA

A. 43
E

u

N

(A

w

(-3

.-

tuw

<U

.4:

1.4

1.2

1.0

0.8

0.6

0.4

- I

I

I 

\ ,.

- I - PS

----- \

POLYPROPYLENE

......... POLYETHYLENE

l-- PMMA

II- I_ II

0.2

0

0 2 54 6 8

.TIME, MIN

10 12 14 16 18

FIGURE A. 5.6. Smoke Mean Particle Diameter for Five Substrate Polymers.

in Flaming Combustion in Room Temperature Ventilation Air

A.44
100

80

I-2:

U

uJ

N1

60

40

U't

20

0

0 2 4 6 8 10 12 14

TIME, MIN.

FIGURE A.5.7. Effect of Ventilation Gas Temperature Upon Sample Weight Loss for

Polyethylene and Polystyrene Under Flaming Conditions
E

;14

-j~

U

LU

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

0 2 4 6 8 10 12 11 16

TIME, MIN.

FIGURE A.5.8. Effect of Ventilation Gas Temperature Upon Smoke Me n

Particle Diameter for Flaming Polystyrene at 5 W/cm

A. 46
1.4

1.2

200°C

E

(n

w

Lu

1.0

0.8

0.6

2 5C

I

I

I

I

I

I

0.4

0.2

PVC COMPOSITION 1,

FLAMING, 5 W/cm2

I IIIIII

0

0 2 4 6 8

TIME, MIN.

10 12 14 16

FIGURE A.5.9. Effect of Ventilation Gas Temperature Upon imoke Mean

Particle Diameter for Flaming PVC at 5 W/cm

A. 47.
1.4

1.2

E

U.j

CL

-J

u

0.

1.0

0.8

0.6

0.4

00

0.2

0

0 2 4 6 8 10 12 14 16 18

FIGURE A.5.10.

TIME, MIN.

Effect of Ventilation Gas Temperature Upon Smoke Mean Particle Diameter

for Flaming Polypropylene at 5 W/cm'
LU

-j

w

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

0 2

FIGURE A.5.11.

4 6 8 10 12 14 16

TIME. MIN.

Effect of Ventilation Gas Temperature Upon Smoke Mea{

.Particle Diameter for Flaming Polyethylene at 5 W/cm

A.49
1.4

1.2

E

-J

CL

Lu

1.0

0.8

0.6

0.4

(710•

0.2

0

0 1 2 3 4 5 6 7 8 9 10

TIME, MIN.

FIGURE A45.12. Effect of Ventilation

for Flaming PMMA at 5

Gas •emperature Upon Smoke Mean Particle Diameter

W/cml
APPENDIX A.6

LITERATURE SOURCE

Zinn, B. T. et al. 1980. The Smoke Hazards Resulting from the Burning of

Shipboard Materials Used by the U.S. Navy. NRL Report 8414, Georgia Institute of Technology, Atlanta, Georgia.

TABLES

A.6.1 Smoke Property Data for Hydraulic Fluid

A.6.2 Sample Weight Loss and Smoke Concentration Data for Hydraulic Fluid

A.6.3 Mass Loss Data

A.6.4 Particulate Combustion Products of the Tested Materials

A.6.5 Major PCAH Species Found in Particulate Smoke of the Samples

FIGURES

A.6.1 Effect of the Ventilation Air Temperature on the Sample Weight Loss

for Fl ming Combustion of Hydraulic Fluid Exposed to a Radiant Flux of

5 W/cm•

A.6.2 Effect of the Ventilation Air Temperature on the Smoke Mean Particle

Size for Flaming Combustion 'of Hydraulic Fluid Exposed to a Radiant

Flux of 5 W/cm

NOMENCLATURE

See Appendix A.4

A.51
TABLE A.6.1. Smoke Property Data for Hydraulic Fluid

Ventilation, Air

Mode Temperature, 0C

Nonflaming(b) 25

Time to

OD A _- Peak OD,

r B1 ue ea - 2,(a) Pm min

1.23 1.27 1.23 5.9

Flaming

Flaming

Flaming

25 0.028 7.18 5.49

100

300

6.73 5.10

9.41 7.02

1.33

1.31

1.31

6.9

6.5

3.7

(a) Averages for data points near the time of maximum optical density.

(b) During the initial nonflaming phase; spontaneous ignition occurred 5.9 min

after initiation of exposure.

TABLE A.6.2. Sample Weight Loss and Smoke Concentration Data for

Hydraulic Fluid

Ventilation Air

Mode Temperature, 'C

Nonflaming(b) 25

Peak Mass

Loss §ate,

mg/cm sec

0.14

5.6

9.8

11.1

Peak Total

Volume ParticujaIe

Fraction,(a) Volume

ppm cm

0.83 0.32

r

"25-

1.00

0.72

0.74

Flaming

Flaming

Flaming

25

100

300

4.54

4.11

5.58

3.61

2.60

2.68

(a) Based on mR = 1.50 - O.Oi for nonflaming combustion and mR 1.57 - 0.56i

for flaming combustion at a standard flow rate of 425 x/min.

(b) During the initial nonflaming phase; spontaneous ignition occurred 5.9 min

after initiation of exposure.

TABLE A.6.3. Mass Loss Data

Sample Type

Wall insulation material

Cable jacket

Hydraulic fluid

Sample

Mass, mg

27.34.

10.33

22.22

Ash Particulate

Mass, mg Mass, mg

15.71 0.41

Vapor

Mass, mg

11.22

7.25

21.26

2.77

0.29

0.31

0.67

A.52
TABLE A.6.4. Particulate Combustion Products of the Tested Materials

. Test

Wall insulation

material:

nonflaming

flaming

Cable jacket,

flaming

Hydraulic fluid,

flaming

Sample

Mass, 9

7.50

7.60

Particulate

Smoke, mg

35

41

Extractable

Organics,

mg

34

11.5

PCAHs, mg

0.5

1.5

Aliphatic

and Others,

mg

33.5

10

16.4 128

145

17.5

20

2.5 15

20 2 18

TABLE A.6.5. Major Polynuclear-Aromatic-Hydrocarbon

Particulate Smoke of the Samples

Species Found in

Sample

Wall insulation

Cable jacket

Hydraulic fluid

Major PCAH Identified

Anthracene/phenanthrene (178)(a)

Pyrne (202)

Anthracer.e (178)

Fluoranthene (202)

Pyrene (202)

1,2 Benzotheorene or methyl pyrene (216)

2,13 Benzothoranthene (226)

Chrysene, benzoanthracene triphenylene (228)

2,4 Benzo(a)pyrene (252)

Anthracene/phenanthrene

Fluoranthene

Pyrene

1,2 Benzothorene, etc.

2,13 Benzothoranthene, etc.

2, 4 Benzo(a)pyrene

0.5

27

44

4

8

16

0.3

1

29

45

6

12

0.7

(a) Molecular weight.

A.53
100

80 C

II

I I

300CC

60

I-- ~100°C

I

O~P 40

II

20

II

0 -

0 2 54 6 8

TIME, MIN.

FIGURE A.6.1. Effect of Ventilation Air Temperature on the Sample

Weight Loss for Flaming Combustion of HydEaulic

Fluid Exposed to a Radiant Flux of 5 W/cm

10

A.54
I-

-J

U

0(

z

wi

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

c"1 Znf

0 2 4 6 8 10 12 14 16 18 20

TIME, MIN.

FIGURE A.6.2. Effect of the Ventilation Air Temperature on the Smoke Mean Particle

Size for Flamipg Combustion of Hydraulic Fluid Exposed to a Radiant

Flux.of 5 W/cm
APPENDIX A.7

LITERATURE SOURCE

Roberts, A. F. and F. R. Brookes. 1981. Hydraulic Fluids: An Approach to

High Pressure Spray Flammability Testing Based on Measurement of Heat

-utput. Explosion and Flame Laboratory, Harper Hill, Buxton, Derbyshire,

United Kingdom.

TABLES

A.7.1 Results of Heat Output Tests on Hydraulic Fluids

A.712 Comparison of Calorific Values and Heat Output of Hydraulic Fluids

A.7.3 Summary of Table A.7.1 Data for Fluid Temperature of 40°C

A.56
TABLE A.7.1. Results of Heat Output Tests on Hydraulic Fluids

Fluid Type

Mineral oil

Fluid

Temperature, °C

30

35

40

40

40

50

65

Spraying

Rate,

g sec"

3.6

3.7

3.6

4.0

4.0

3.3 3.5

Total

Heat Outqut,

23.9

25.2

25.4

30.5

31.5

26.9

32.9

Radiative

Contribution,

34

37

39

44

46

36

44

Air

Consumption,

kg/kg of Fluid

13.6

13.4

13.5

14.7

14..2

14.8

14.8

Water-in-oil

emulsion

z,

Phosphate ester

Water--glycol A

Water--glycol B(a)

(a) The heat output for

30

30

40

60

65

65

35

40

40

40

50

55

60

40

4.5

4.6

4.4

4.0

3.7

3.8

5.8

5.8

5.8

5.2

5.3

4.3

4.3

4.9

18.7

18.9

16.3

17.2

18.5

17.8

19.8

19.5

18.9

18.7

18.0

20.6

20.0

5.3

33

32

26

26

25

23

47

40

42

52

44

49

46

13

7.8

9.3

8.5

6.0

8.0

8.8

7.8

6.5

6.0

7.6

7.8

7.9

6.6

2.7

this fluid was too low for accurate measurement.
TABLE A.7.2. Comparison of Calorific Values and Heat Output of Hydraulic

Fluids

Fluid Type

Mineral oil

Water-in-oil emulsion

Phosphate ester

Water-glycol

Calorific Valu¶

(gross), U g44.9

25.7

30.8

14.7

Total Heat

Output from

Table A.7.1, kJ g-1

27.8

17.9

19.4

5.3

Ratio,

B/A

0.62

0.70

0.63

0.36

TABLE A.7.3. Summary of Table A.7.1 Data for Fluid Temperature of 400C

Mineral oil(a)

Water-in-oil emulsion

Phosphate ester(a)

Water-glycol

Heat

Outpuj,

kJ g29.1

16.3

19.0

5.3

Radiative

Contribution,

43

26

45

13

Air

Consumption,

kg/kg of Fluid

14.1

8.5

6.7

2.7

(a) Averages of three values.

A. 58
NUREG/CR-2658

PNL-4174

RZ

DISTRIBUTION

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Copies

OFFSITE

W. F. Pasedag

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Regulation

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Accident Evaluation Branch

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U.S. Nuclear Regulatory Commission

Washington, DC 20555

F. R. Krause

Los Alamos Scientific Laboratory

Los Alamos, NM 87545

H. W. Godbee

Oak Ridge National Laboratory

Oak Ridge, TN 37830

ONSITE

Pacific Northwest Laboratory

M. Y. Ballinger

M.K.W. Chan (20)

C. E. Elderkin

J. J. Fuquay

J. A. Glissmeyer

R. L. Hadlock

S. E. King

J. Mishima (5)

P. C. Owczarski

G. N. Slinn

S. L. Sutter

.R. K. Woodruff

Publishing Coordination (2)

Technical Information (VG) (5)

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Research

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Distr-1

NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER - A2ipw58 bY DOC) 11,8.1 NUREG/CR-2658

BIBLIOGRAPHIC DATA SHEET PNL-4174

4. TITLE AND SUBTITLE IAdd Volune No., if fear oroprime) 2. blancik)

Characteristics of Combustion Products: A Review 3. RECIPIENT'S ACCESSION NO.

of the Literature

7. AUTHOR (S) M. K. W. Chan s. DATE REPORT COMPLETED

J Mishima January 1983

9. PERFORMING ORGANIZATION NAME AND MAILING ADDRESS (ncludse Zip Code) DATE REPORT ISSUED

MONTH YEAR

Pacific Northwest Laboratory July 1983

Richland, Washington 99352 6. (Los", wsk)

8. (Les"e blank)

12. SPONSORING ORGANIZATION NAME AND MAILING ADDRESS (Include Zip Code) 10. PROJECT/TASK/WORK UNIT NO.

Division of Risk Analysis

Office of Nuclear Regulatory Research 11 FINNO.

U.S. Nuclear Regulatory Commission B2287 and B2407

Washington, D.C. 20555

13. TYPE OF REPORT PERIOD COVERED (Inclusive d*&$J

15. SUPPLEMENTARY NOTESP (Lve n)

16. ABSTRACT 0200 words o less)

To determine the effects of fires in nuclear fuel cycle facilities, Pacific Northwest Laboratory (PNL) has surveyed the literature to gather data on the characteristics of combustion products, This report discusses the theories of the origin

of combustion with an emphasis on the behavior of the combustible materials commonly found in nuclear fuel cycle facilities. Data that can be used to calculate particulate generation rate, size, distribution, and concentration are included. Examples

are given to illustrate the application of this data to quantitatively predict both

the mass and heat generated from fires. As the final result of this review, information gaps are identified that should be filled for fire accident analyses in fuel

cycle facilities.

17. KEY WORDS AND DOCUMENT ANALYSIS 17a. DESCRIPTORS

17b. IDENTIFIERS;OPEN-ENDED TERMS

18. AVAILABILITY STATEMENT 19. SECURITY CLASS (Th,s reporr) 21. NO. OF PAGES

Unclassified

Unl imi ted 20. SECURI T Y iLASS (Th.oaP 22. PRICE uncm assl T1eo s

NRC FORM 335 f1l-811