V

Reference

NBS

Pub!* - cations

NAT'L INST. OF STAND & TECH R.I.C.

A 111 DM SlATTfl

NBSIR 78-1494

Test Procedures for the

Determination of the Gross Calorific

Value of Refuse and RefuseDerived-Fuels by Oxygen Bomb

Calorimetry

Summary of the 1 977 Fiscal year

Results

D. R. Kirklin, D. J. Mitchell, J. Cohen, E. S. Domalski, and S. Abramowitz

Chemical Thermodynamics Division

and the

Thermal Processes Division

National Bureau of Standards

Washington, D C. 20234

December 1978

Prepared for: U.S. Department of Energy

Office of the Assistant Secretary

Conservation and Solar Applications

Division of Building Community Systems

Urban Waste Technology Branch

Washington, D.C. 20545

and

U.S. Environmental Protection Agency

Municipal Environmental Research Laboratory

Solid and Hazardous Waste Research Division

. Cincinnati, OH 45268

100

.056

78-1494

NBSIR 78-1494

TEST PROCEDURES FOR THE

DETERMINATION OF THE GROSS CALORIFIC

VALUE OF REFUSE AND REFUSEDERIVED-FUELS BY OXYGEN BOMB

CALORIMETRY

SUMMARY OF THE 1977 FISCAL YEAR

RESULTS

WsWonaT Bureau of Standards APR 17 1Q7S

D. R. Kirklin, D. J. Mitchell, J. Cohen, E. S. Domalski, and S. Abramowitz

Chemical Thermodynamics Division

and the

Thermal Processes Division

National Bureau of Standards

Washington, D C. 20234

December 1978

Prepared for U.S. Department of Energy

Office of the Assistant Secretary

Conservation and Solar Applications

Division of Building and Community Systems

Urban Waste Technology Branch

Washington, D.C. 20545

and

U.S. Environmental Protection Agency

Municipal Environmental Research Laboratory

Solid and Hazardous Waste Research Division

Cincinnati, OH 45268

IU &S LaC(JLAj!X£(11\ Cx^j .

1

, ftJ J.\ r ' o

' J

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Or. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

/ V

V '4^'^
...

„ v ^ V . ••

^ - , ;> ;

:

' ; ,

• : , •'•' • :

•

' • "

•; -i

' '-‘A . A

: v V ; A

i \ .:

' -A '%, 'V,, : -i v

... •- .... -

:

.

'

-

'

V ,

'

.'-a
Table of Contents

Abstract 1

Introduction 2

Experimental

Materials 6

Equipment and Its Purpose 8

Methods 8

Results and Discussion 13

Calorimetric Results 13

Analytical Results 15

Conclusions 17

References 19

ii
?

; r

1

' <

r - 1

, :> . " ! i i

• 't

• ~ : •

' vi? ;

• ; . .. •.

• • • • -

:

'

•

. r

' « i
List of Tables

Table I 20

Benzoic Acid Calibration Results

Table II 21

Calorific Values (MJ kg ) for Teledyne National RDF

Table III J 22

Calorific Values (MJ kg"1

) for ECO-FUEL II RDF

T

Table IV 23

RDF Analyses (as determined basis)

Table V

Emission Spectrochemical Analysis of Teledyne 24

National RDF Residue

iii
List of Figures

Figure Legends 25

Figure 1

Schematic diagram of a bomb calorimeter 26

Figure 2 27

Time- temperature curve for a bomb calorimeter

Figure 3 28

Moisture loss of an RDF sample with time

Figure 4 29

Moisture gain of an RDF sample with time

iv
TEST PROCEDURES FOR THE DETERMINATION OF THE GROSS CALORIFIC VALUE OF

REFUSE AND REFUSE-DERIVED-FUELS BY OXYGEN BOMB CALORIMETRY

SUMMARY OF THE 1977 FISCAL YEAR RESULTS

D. R. Kirklin, D. J. Mitchell, J. Cohen, E. S. Domalski and S. Abramowitz

National Bureau of Standards

Washington, DC 20234

ABSTRACT

Gross calorific values have been determined for refuse-derived-fuels

(RDF) from two manufacturers. Teledyne National and Combustion Equipment

Associates. Test procedures used are modifications of those used for coal

1 2 and coke ’

. The calorific values (moisture- and ash-free basis) obtained

for Teledyne National RDF ranged from 24.51 to 25.20 MJ kg ^ (10539 to

10835 Btu lb "*") with a standard deviation of 0.8 percent. The calorific

values (moisture- and ash-free basis) of Combustion Equipment Associates

ECO-FUEL II RDF ranged from 21.93 to 22.16 MJ kg" 1 (9427 to 9528 Btu lb

_1

)

with a standard deviation of 0.4 percent. Results of 23 laboratory samples

are presented at various stages of sample preparation which were derived

from single field samples from each of the two sources. Calorimetric

results based on an equilibrated laboratory sample are presented along with

some semi-quantitative spectrochemical results. The results indicate that

the techniques of oxygen bomb calorimetry can be successfully applied to a

non-homogeneous refuse stream after considerable processing to prepare a

"homogeneous" refuse-derived-fuel (RDF)

1
TEST PROCEDURES FOR THE DETERMINATION OF THE GROSS CALORIFIC VALUE OF

REFUSE AND REFUSE-DERIVED-FUELS BY OXYGEN BOMB CALORIMETRY

SUMMARY OF THE 1977 FISCAL YEAR RESULTS

D. R. Kirklin, D. J. Mitchell, J. Cohen, E. S. Domalski and S. Abramowitz

National Bureau of Standards

Washington, DC 20234

Introduction

The economic and population growth of the U.S.A. has brought about an

ever-increasing problem which manifests itself through the generation of

residential and commercial solid waste at an enormous rate. Our industrial,

commercial, and domestic activities have made the disposal of solid waste a

problem of primary concern. Landfilling and incineration are the most

common methods of solid waste disposal. The disposal of solid waste in or

on the land is wasteful in terms of land management and the incineration

process generates large quantities of wasted energy. Moreover, landfilling

and incineration can present a danger to our health and to our environment.

However, useful materials can be recovered from solid waste. Paper products, metals, glass, rags, rubber and plastics can account for 50 to 80

percent of solid waste that could be available for salvage and recovery.

Solid waste also represents a potential source of fuel that can be converted

into energy. In addition, resource recovery from solid waste is accompanied

by conservation of our natural resources. Therefore, increased interest in

resource recovery from solid waste has been quite evident in recent years.

2
The recovery and utilization of energy from solid waste has been the

subject of much interest since much concern is being expressed about our

fuel shortages. Solid waste is a potential source of fuel which can be

utilized in power plant boilers to generate steam for energy purposes.

Therefore, much systems development is centered around the conversion of

solid waste to energy. Before solid waste can be effectively utilized in

power plant boilers much testing is necessary. The areas of solid waste

analysis, ash analysis, stack emission testing, corrosion testing, and

boiler performance must be examined thoroughly.

The American Society of Mechanical Engineers (ASME) Committee for Performance Test Code 33-Large Incinerators (PTC-33) has indicated that a need

exists to find a more accurate test procedure for the determination of

calorific values of refuse and refuse-derived-fuels (RDF) which will more

accurately represent a corresponding large array of collected raw refuse.

If an improved calorific value test procedure is available to the ASME PTC33 Committee, it can offer a better mechanism to public works administrators

and private owners by which they can evaluate whether or not their large incinerators and refuse-fired boilers are in compliance with contract performance

specifications with greater accuracy and higher confidence than is currently

available. The E-38 Committee on Resource Recovery of the American Society

of Testing Materials (ASTM) is interested in establishing standard test

methods to evaluate refuse-derived-fuels (RDF) as an article of commerce. A

laboratory procedure giving reproducible results will better equip commercial laboratories to certify accurately the energy content of RDF

of various compositions. As an article of commerce, RDF can be bought and

3
sold as a regulated low-sulfur fuel to supplement other fossil fuels. The

U.S. Department of Energy (DoE) and the U.S. Environmental Protection Agency

(EPA) are collaborating in resource recovery programs to facilitate the

development of various waste-to-energy technologies. The need for information on the calorific values of waste streams has been acknowledged by

incinerator operators and designers for many years.

The quantity of energy liberated per unit mass of refuse burned (gross

calorific value of refuse) can be directly obtained from a bomb calorimetric

experiment. The techniques of bomb calorimetry have been documented and are

well characterized 1 ’ 2

. Bomb calorimetry is used extensively in the determination of the calorific value of various fossil fuels 3

. Therefore, it

would be extremely advantageous to be able to determine accurately the

calorific values of refuse and RDF by bomb calorimetric methods.

However, municipal refuse is far from being an easily characterized

homogeneous fuel. Its makeup can vary widely depending upon many geographical, seasonal, and weather-related factors. This variability will effect

both a refuse stream' s potential as a fuel source and its impact as a contributor to environmental pollution.

The objectives of this research program are three-fold:

1. Development of test procedures to determine the gross calorific

value of refuse and RDF by bomb calorimetric methods.

4
2 . Evaluation of sample characteristics by analyzing for moisture,

ash, carbon, hydrogen, nitrogen, sulfur and chlorine.

3. Evaluation of the homogeneity and sample preparation requirements

for bomb calorimetric experiments utilizing two bomb calorimeters

which have capabilities for handling samples that differ by an

order of magnitude in mass (i.e. 2.5 g and 25 g)

The small bomb calorimetric sample from a non-homogeneous refuse stream

is a subject of considerable interest. A 20 kg (44 pound) (or larger) field

sample of refuse/RDF must undergo a great deal of processing to obtain

homogeneous bomb calorimetric samples. A conventional bomb calorimeter is

capable of handling refuse/RDF samples of 2-3 grams in size. Therefore,

development of a larger bomb calorimeter that would be capable of handling

refuse/RDF samples of 20-30 grams in size is included in this research

program in order to examine the effect of different types of samples (based

upon degree of sample preparation) on the calorific determination of a

conventional (2.5 g sample) and larger (25 g sample) bomb calorimeter.

At the outset of this research program, it was decided that the initial

samples selected for characterization and calorific value determination

would be RDF rather than raw refuse itself. RDF is more homogeneous,

characterizable, and generally, easier to handle. Initial work on RDF would

provide better insight into problems which would be encountered in handling

less processed RDF and raw refuse.

5
Refuse/RDF has five forms: (1) as-received refuse with the "white

goods" removed ("white goods" are large items such as refrigerators, stoves,

sinks, etc.); (2) shredded refuse of 2.5 to 7.5 cm (1 to 3 inch) particle

size; (3) shredded refuse with most of the "heavy fraction" removed ("heavy

fraction" is the non- combustibles such as glass, ceramics, metals, etc.);

(4) refuse pellets; (5) refuse powder. Forms #3, #4, and #5 are more common

forms of RDF. The sample preparation required to prepare a bomb calorimetric sample from any of the five refuse/RDF forms is such that the bomb

calorimetric sample is definitely an RDF. In fact, the preparation of a

homogeneous sample for a calorific determination (regardless of the technique to be utilized) is the processing of an RDF of some degree. Therefore,

the initial testing performed in this research project started with forms #4

and #5

.

Experimental

Materials

1. Benzoic Acid . Standard Reference Material 39i was obtained from

the NBS standard samples storeroom. The sample has a certified energy of

combustion of 26434 + 3 J*g

1

at standard bomb conditions. All samples were

drawn from the same bottle. Previous tests with benzoic acid, SRM 39i, have

shown no significant differences in portions drawn from various sampling

areas of the bottle.

2. Oxygen . Ultra High Purity (UHP) grade of oxygen was supplied by

Matheson Gas Products. This oxygen is specified to contain combustible

impurities not exceeding 0.002 percent and total impurities of less than

0.05 percent.

6
3. Teledyne National RDF . In late February 1977, a 20-kg (44 pound)

sample of extruded RDF pellets was received from Teledyne National. The

field sample was from the Baltimore County Resource Recovery Plant located

in Cockeysville, MD. The collection of extruded pellets was contained in a

cardboard box enclosed in a plastic sheet. The box of RDF pellets remained

approximately one month in the laboratory. Thereafter, the cardboard box

was taped shut with duct tape and moved to a refrigerator/freezer unit to

obtain a more controllable environment.

The Teledyne National pellets are cylindrical in shape having a diameter

of 2.5 cm (1 inch) and are broken-off lengths of about 2.5 to 7.5 cm (1 to

3 inches) . The extruded pellets were broken up in an arbor press or put

through a grinder and run through a micromill to yield a 10 mesh powder.

The RDF was homogenized in a vee blender to provide an analysis sample.

About 2.5 grams of the 10 mesh powder was placed into a pellet press (diameter, 1.59 cm or 0.625 inch) and pellets were fabricated for the bomb

calorimetric experiments under approximately 10,000 lbs of force.

4. Combustion Equipment Associates RDF . In May 1977, NBS received

shipment of a 20-kg (44 pound) field sample of ECO-FUEL II RDF fuel from the

Combustion Equipment Associates. The field sample was contained in a plastic

bag which was twisted and taped shut. The plastic bag was enclosed in a

cardboard box. The ECO-FUEL II RDF was approximately minus 425 ym (minus

40 mesh) particle size. The sample was placed in a controlled environment

ref rigerator/freezer unit.

7
Equipment and Its Purpose

1. FAMCO Arbor Press . This press was necessary to fracture the

extruded pellets of Teledyne National into fibrous pieces at the front end

of the sample preparation.

2. Quaker City Mill, Model 4, Grinder . A grinder similar to a

'"sausage grinder" was necessary to break up the fibrous pieces of RDF.

3. Wylie Micro-Mill . This mill with a 1.27 cm (1/2 inch) diameter

input throat produced a 2 mm (10 mesh) RDF sample after treatment with the

larger Model 4 grinder.

4. Vee Blender . The vee blender was necessary to blend the 2 mm (10

mesh) RDF to obtain a homogeneous analysis sample of RDF.

5. Sample Pellet Press . The combustion samples were pressed into a

pellet under approximately 10,000 lbs of force.

6. Isoperibol Oxygen Bomb Calorimeter . This is an isothermal-jacket

calorimeter. The calorimeter reaction vessel is submerged in a water bath

which is controlled to +0.003 K. This prevents thermal leakage from the

laboratory surroundings.

7. Quartz Oscillator Thermometer . This uses the frequency of oscillation of a temperature sensitive quartz crystal to determine the calorimeter temperature. The NBS standard frequency of 100 kHz was utilized.

Methods

1. Sample Requirements . It is necessary that a reproducible family

of analysis samples be prepared from a gross field sample of refuse or

refuse-derived-fuel (RDF). The analysis sample must be representative of

the field sample and unaffected by the laboratory techniques utilized to

8
produce these analysis samples. In order to obtain precise calorimetric

results, the analysis samples must be homogeneous. If it is assumed that

the grinding and blending of the sample produces a homogeneous product, then

the only constituent that must be measured and maintained is the moisture

content. Therefore, the analysis samples were equilibrated in a constant

humidity container maintained at the average relative humidity of the bomb

calorimetric laboratory. The temperature and relative humidity of the

laboratory are maintained at 295 K and 45 percent, respectively.

2 . Typical Sample Preparation

a. Type I Samples . A random sample of extruded Teledyne National

pellets (the laboratory sample) was removed from the field sample of RDF.

The laboratory sample was weighed, milled, ground to 2 mm (10 mesh) and

blended thoroughly. The Teledyne National sample and Combustion Equipment

Associates sample (ECO-FUEL II) are, at this stage, similar in physical

form. Teledyne National laboratory samples are 2 mm (10 mesh) while ECOFUEL II field samples were received as 425-250' ym (40-60 mesh) and were not

usually ground further. A series of samples may now be pressed into pellets

for combustion and analysis purposes. A pellet at this stage will be

described as a Type I sample. Type I pellets are equilibrated in a constant

humidity atmosphere, weighed, and then dried to constant weight at 105 °C in

a drying oven to form Type II pellets. The dried pellets are reweighed and

the volatile content (assumed moisture) of Type I pellets can be computed.

9
b. Type II Samples . Pellets which have been dried in an oven at

105° C are weighed and placed in a controlled constant humidity atmosphere

(45 percent R.H.) for about 48 hours. The samples are then reweighed, and

from the weight gain, the moisture content of the sample is calculated.

Samples treated in this manner to determine moisture content are known as

Type II samples.

c. Type III Samples . If the ground and blended RDF was split and

blended several times before being pressed into pellets, then the RDF

laboratory sample pellets are called Type III. Weighing and drying steps

were performed in the same manner as for Type II samples.

In all cases. Type I, II, and III samples are equilibrated in a

constant humidity (equal to the average relative humidity of the laboratory) atmosphere for approximately two days.

3. Typical Calorimetric Experiment . Bomb calorimetric techniques

are well characterized and are described in detail elsewhere, but a brief

description of the method which was employed in this work follows. Figure

1 shows a typical isothermally-jacketed calorimeter system 1

* 2

. In the

thermochemical investigations, the heat evolved by a measured amount of RDF

burned is compared with the heat evolved by a measured amount of a selected

standard reaction, using a fixed calorimeter system with a substantially

constant temperature rise. The standard reaction is the combustion of

benzoic acid under standard bomb conditions producing a temperature rise of

three degrees (K) . The energy equivalent of the calorimeter is determined

from the amount of energy produced by the standard reaction and its accompanying side reactions and the corrected temperature rise. The observed temperature rise must be corrected for stirring energy and thermal leakage from

the surroundings.

10
Multiplication of the energy equivalent of the calorimeter by the

corrected temperature rise in the RDF experiment gives the total energy

produced in the RDF combustion experiment. This total energy is then

corrected for the various side reactions and divided by the mass of RDF to

produce the gross calorific value of RDF. In a typical RDF experiment, an

equilibrated RDF pellet is weighed in a weighed platinum crucible. The

crucible and sample are supported inside an oxygen bomb. The sample is in

contact with a 2 cm length of 0.076 mm (.003 in) wire. The bomb also

contains 1 cm of H^O to dissolve the gaseous products of combustion and

maintain an atmosphere that is saturated with water. The sealed bomb is

then charged with 3.10 MPa (30.62 atm) of high-purity oxygen. The bomb is

lowered into a weighed calorimeter and the covered calorimeter is submerged

in the constant temperature water bath. The calorimeter system is then

heated to slightly below 25 °C. Figure 2 shows a time-temperature curve

for a typical bomb calorimetric experiment. The temperature is measured

during the period before the sample is ignited (line ab in Figure 2),

during the reaction period immediately after the sample is ignited (line be

in Figure 2), and during the period after the reaction is complete (line eh

in Figure 2). The difference between a point in the after-period and a

point in the fore-period gives the observed temperature rise. The slope of

the fore- and after-periods allow one to calculate the portion of the

temperature rise due to stirring energy and thermal leakage. The submerged

calorimeter must be stirred at a constant rate to obtain a uniform and

meaningful temperature vs. time curve. A preliminary experiment was performed to determine the amount of RDF sample necessary to produce a three

degree (K) rise in the calorimeter since our comparison reaction (benzoic

acid combustion) produces a three degree (K) rise in the calorimeter.
4. Typical Analytical Procedure . The combustion samples were weighed

three times. Immediately after the pelleted laboratory samples were prepared, they were weighed to get an initial sample mass. The samples were

then placed in a drying oven until they reached a constant mass. The dried

samples were equilibrated in a constant humidity atmosphere until they

again reached a constant mass. This data permitted a calculation of moisture

content at various stages of the sample history.

After the calorimetric measurements were completed, the gaseous products

were analyzed for carbon dioxide by passing the dried gaseous products

through weighed absorption tubes containing successive layers of ascarite,

magnesium perchlorate, and phosophorous pentoxide, each separated by a

layer of asbestos fibers. The total amount of acid (nitric and sulfuric)

was determined by titration of a portion of the bomb washings with a standard alkaline solution with the aid of a pH meter. A known amount of

silver nitrate was added to a second portion of the bomb washings and the

solution was titrated with ammonium thiocyanate to determine soluble chloride.

Sulfur was precipitated as barium sulfate from the remainder of the bomb

washings and the precipitate was weighed in order to determine the amount

of sulfur.

The RDF residue remaining in the platinum crucible was weighed and

elemental analysis performed using emission spectroscopy. The spectrochemical analysis were also performed on the processed (10 mesh) RDF samples.

12
Results and Discussion

The primary objective of this study is to evaluate test procedures for

the determination of calorific values of refuse and refuse-derived-fuels by

bomb calorimetric methods. Tables I, II and III present results of combustion experiments. When using refuse or refuse-derived-fuels (RDF) as a

substitute fuel, it is meaningful to analyze for the amount of moisture,

ash, pollutant species, and corrosive species. These data can be found in

Table IV. In addition, an elemental analysis would help to characterize

the non- combustible portion of refuse and RDF. These analytical results

are presented in table V.

Calorimetric Results

Table 1 presents a summary of the results of five calibration experiments. The calibration of the calorimeter was performed with the

calorimetric standard, benzoic acid (SRM 39i) , which has an energy of

combustion of 26434 + 3 J g

^ at 25 °C and standard bomb conditions. Table

I contains the amount of heat supplied to the calorimeter from the benzoic

acid combustion (Q ) , the electrical ignition energy (q-ign) , the formaDxi tion of nitric acid (q-HNO^), the Washburn correction to standard states

(q-wc) , and the correction to make the final temperature 28 °C (q-T

corr) . The total energy supplied to the calorimeter and the corrected

temperature rise are necessary to calculate the energy equivalent of the

calorimeter. The energy equivalent is adjusted for the masses of the

sample, the crucible and the water contained inside the bomb. The energy

equivalent of the calorimeter (E

g ^) was found to be 14554.75 J K ^ at 301

K. The energy equivalent of the standard calorimeter (Egi ) was adjusted

for the heat capacities of the initial contents of the bomb to obtain the

13
energy equivalent of the actual calorimeter (E • A heat capacity of 1 J

g

^ K^ was assumed for RDF since it is primarily cellulose. [a-cellulose

,

the chief constituent of paper pulp, has a heat capacity of 1.16 J g

^ K

^

at 298 K.

]

The calorific data on RDF from Teledyne National and Combustion Equipment Associates are presented in tables II and III, respectively.

The calorific values are presented in three sets (as determined,

moisture-free, and moisture- and ash-free). The moisture content was

determined as described in the section on Methods under part 2b for Type II

samples prior to each calorimetric run. For Type I samples, a separate

moisture determination was carried out on samples from the same batch. The

calculation of the calorific values on a moisture-free (MF) basis was

performed using the above moisture data. The residue found in the combustion bomb after a calorimetric experiment was used to represent the ash

content of the RDF sample and was employed to compute the calorific values

on a moisture- and ash-free (MAF) basis.

Three types of experimental data are presented based upon the treatment

of the RDF samples. Type I samples received the minimum preparation necessary

to prepare pellets for our combustion experiment. The Teledyne National RDF

was received as extruded pellets and thus had to be ground and then pressed

into pellets. ECO-FUEL II from Combustion Equipment Associates needed only

to be pressed into a pellet. Type II and Type III samples were oven dried

14
at 105 °C until a constant mass was obtained and then allowed to equilibrate

with ambient room temperature and relative humidity. The temperature and

relative humidity of the bomb calorimetry laboratory are maintained at 295 K

and 45 percent, respectively. The drying and equilibration periods lasted

for approxiamtely 48 hours each. The respective processes were allowed to

continue undisturbed for approximately 40 hours with the sample masses

periodically monitored during the last 8 hours. No attempt was made to

determine the minimum time necessary for drying and equilibration. In

addition. Type III samples were subjected to several splitting steps as

explained in the experimental procedures (part 2c)

The moisture- and ash-free (MAF) statistical results are included in

the Tables for Teledyne National and ECO-FUEL II RDF. The statistical

considerations for Type I Teledyne National RDF are not meaningful since

only one preliminary experiments of Type I was performed.

Analytical Results

Table IV presents the results of laboratory analyses performed as part

of the calorimetric determinations. The major constituent of refuse is

cellulose (C,Hir.O c ) which is 44.45 percent carbon (C) by mass and our

measured carbon percentages are around 45 percent. The elements sulfur (S)

and chlorine (Cl) are important due to their pollutant and corrosive properties. The sulfur content of the two RDF’s studied was less than 1

percent (by mass). This is very good since fuel oils and coals often

contain greater than 1 percent sulfur. Although the soluble chlorine results

are also less than 1 percent, only small quantities of HC1 are necessary to

cause extensive corrosive damages to power generating equipment.

15
The moisture and ash content greatly affect the calorific value of

these fuels. Ash also presents a slagging problem in boiler operation since

it must be removed from the boilers. Both RDF's tested had approximately 12

percent residue. However, the most variable property is the moisture

content. The deliquescent nature of RDF causes moisture content to vary

with ambient conditions. In order to obtain reproducible data based upon

moisture content, samples were equilibrated in a controlled 45 percent

relative humidity atmosphere. Figures 3 and 4 are typical examples of the

variability of sample mass (due to moisture content) with time during the

equilibration period. Figure 3 represents a Type I sample of as-received

RDF the loses moisture while equlibrating with ambient conditions (22 °C; 45

percent relative humidity) . Figure 4 is typical of a Type II or III sample

which has previously been dried and therefore picks up moisture during the

equilibration period. After equilibration both Teledyne and ECO-FUEL II RDF

had a moisture content of about 3.8 percent as shown in Table IV.

Spectrochemical analysis was performed on Teledyne National RDF. X-ray

fluorescence spectra were recorded to identify the major elemental constituents for both RDF samples. Significant amounts of Si, Ca, Fe, Zn, Ti,

Sr and Pb were observed. Spectra of unprocessed RDF and the combustion

residue of RDF were nearly identical with respect to the elements present.

Emission spectrochemical studies were performed to give a semi-quantitative

analysis of the elements. The semi-quantitative results obtained for the

combustion residue of RDF are presented in Table V. The elements are listed

in order of decreasing abundance. The approximate percentages are enclosed

in parenthesis immediately following the elemental symbol.

16
Conclusions

Our results on a limited number of samples have demonstrated that RDF

samples can be processed for bomb calorimetric experiments to produce

results with a precision (standard deviation of a measurement) approximately

equal to or better than one percent. The calorific values determined for

three types of sample preparation for the same RDF show no significant

differences. Due to the arbitrary selection of the RDF field samples, the

precision of the data obtain is a more important result, however, in no way

do we suggest that the experimental results presented are typical of the

average stream of the RDF’s tested. For Teledyne National samples, the

calorific values slightly increased with increased sample processing but

opposite trends were observed for ECO-FUEL II samples. Moreover, the

percent deviation (for moisture- and ash-free RDF) based on all three types

of samples was 0.8% for Teledyne National RDF and 0.4% for ECO-FUEL II RDF.

Percent deviations between any two sample preparation types for either

Teledyne National or ECO-FUEL II ranged from 0.2 percent ECO-FUEL II to 0.9

percent, respectively.

Our standard deviations of a measurement are much less than one would

initially expect for something initially as non-homogeneous as refuse or

RDF. This was achieved by using the amount of combustion residue of each

experiment to calculate a MAF calorific value rather than an average ash

value determined by conventional ASTM procedures. For some RDF samples the

ash values are not constant. Non-combustibles must "stick" to RDF particles

and are therefore not uniformly distributed throughout the RDF samples.

Therefore, a more precise ash-free heating value can be calculated using the

amount of ash contained in each combustion sample.

17
Coals of various ranks have typical moisture- and ash-free (MAF) gross

heating values^ ranging from 34.89 to 25.59 MJ kg ^ (15000 to 11000 Btu

lb ^). Our MAF-RDF results ranged from 25.20 to 21.93 MJ kg ^ (10835 to

9427 Btu lb "*). Our results are based upon two 20-kg (44 pound) field

samples of RDF. It is not possible to evaluate without additional testing

whether our results are typical of the RDF's produced by either manufacturer.

However, the RDF's calorific value makes it definitely a viable competitor

of some low rank coals. Also bituminous coals typically demand a greater

degree of fineness than low rank coals to achieve complete carbon burnout^.

The necessary degree of fineness for RDF's may even be less (i.e. larger

particles) than that for the low rank coals.

All fuels contain mineral matter that goes through varying stages of

decomposition and recomposition in the combustion process. It eventually

becomes either bottom ash or flyash. Coal may have ash contents of the

order of 5 to 30 percent compared to the 12 percent values we experienced

with RDF. However, ash fusibility data is necessary to properly evaluate

the ash problem concerning refuse/RDF.

The degree of fineness required for refuse/RDF in order to obtain

reproducible calorific results has not been determined. Our preliminary

results were based upon a starting material of processed RDF. We have built

a larger than conventional bomb calorimeter that can handle a 20-30 gram

sample of refuse/RDF. Concurrent testing of refuse/RDF samples in both our

conventional size and larger size calorimeters should answer this question.

18
References

1. E. J. Prosen, Experimental Thermochemistry , Chapter 6, F. D. Rossini,

editor, Interscience Publishers, New York, 1956.

2. R. S. Jessup, NBS Monograph 7, 1960, Precise Measurement of Heat of

Combustion with a Bomb Calorimeter, (U.S. Government Printing Office,

Washington, DC 20420).

3. American Society of Testing and Materials, 1977 Annual Book of ASTM

Standards , (Standards D240, D2382, D2015, and D3286), Philadelphia, PA

1977.

4. ibid, 1977 Annual Book of ASTM Standards , (Standards D388), Philadelphia,

PA 1977.

5. H. E. Burbach, D. A. Harris, R. P. Hensel, 0. Martinez and G. W.

Thimot, Power 121 , 41 (1977).

19
Table I. Benzoic Acid Calibration Results

Expt. No. 1046 1047 1048 1049 1050

AU“ ba (301 10/J-g'1 26410.68 26410.68 26410.68 26410.68 26410.68

V8 1.635791 1.632017 1.650145 1.639178 1.640040

VJ 43202.35 43102.68 4.3581.45 43291.81 43314.57

q (ign) /

J

1.08 1.72 0.94 1.19 1.01

q(HN0

3

)/J 6.80 5.90 5.77 5.20 5.30

q (wc) / j 37.13 34.59 34.96 34.85 34.80

q-T^corr/J .02 .04 -.02 .03 .02

Q-Total/J 43247.38 43144.93 43623.10 43333.08 43355.70

AT (corr) /K 2.969681 2.963055 2.995277 2.976097 2.977749

E

cal

/J ’ K

'1 14562.97 14560.96 14563.96 14560.37 14559.89

C (contents-0. )

/

v 2

6.87 6.87 6.89 6.88 6.88

J*K

-1

E . / J • K

_ 1

si

14556.10 14554.09 14557.07 14553.49 14553.01

E . (mean)/J*K ^ si 14554.75

sd/J-K

-1

1.72 (0. 012%)

sdm/J*K ^ 0.78 (0. 0053%)

20
Table II. Calorific Values/ (MJ kg 1

) a for Teledyne National RDF

Sample Sample Q (T AD

b

) Q (T MF

C

) Q (T f , MAFd

) Statistics

Type Number V 1 v t v f (MAF)

(preliminary run)

Type I 1045 20.02 21.14 24.23

(8608) (9087) (10417)

Type II 1052 21.09 21.94 24.95 24.82

(9068) (9434) (10726) (10672) mean

1053 20.74 21.58 24.51 24.51-25.01

(8918) (9278) (10539) (10539-10752) range

1054 20.55 21.38 25.01 0.27 (1.1%)

(8835) (9191) (10752) (116.53) (1 . 1%) std . de

Type III 1056 20.86 21.71 24.78

(8969) (9332) (10656)

1057 21.12 21.97 25.06

(9809) (9445) (10776)

1058 21.02 21.87 25.06 25.06

(9037) (9402) (10776) (10773) mean

1059 21.24 22.10 25.20 24.79-25.20

(9131) (9499) (10835) (10656-10835) range

1060 21.11 21.96 25.12 0.13 (0.5%)

(9075) (9442) (10799) (55.60) (0.5%) std. dev

1061 21.17 21.02 25.09

(9101) (9468) (10788)

1062 21.08 21.94 25.08

(9065) (9431) (10781)

Types

V > 24.99

(10743) mean

II and III

24.51-25.20

(10539-10835) range

combined 0.20 (0.8%)

(86.21) (0.8%) std. dev

aMJ kg'

1 = 429.9226 Btu lb

^AD = As determined.

was used to calculate the Btu lb values presented

c H MF = Moisture-free MAF = Moisture- and

in parenthesis.

Ash-free

21
Table III. Calorific Values/ (MJ kg

_1

) a for ECO-FUEL II RDF

Sample

Type

Sample

Number

Q

v

(T

f

, ADb

) Q (T,, MFC

) 0 v f

* V

(T

f

, MAFd

) Statistics

(MAF)

Type I 1051 18.53

(7966)

19.44

(8360)

22.14

(9519)

22.15

(9521) mean

1073

18.58 19.50 22.14 22.14-22.16

(7989) (8382) (9517) (9517-9528) range

1074

18.59 19.50 22.16 0.01 (0.06%)

(7992) (8385) (9527) (5.73) (0.06%) std . dev.

Type II. 1063 18.63

(8011)

19.38

(8331)

22.02

(9487)

22.10

(9501) mean

1064

18.74 19.49 22.15 22.02-22.15

(8057) (8379) (9523) (9487-9523) range

1065

18.66 19.40 22.08 0.05 (0.2%)

(8021) (8341) (9493) (19.32) (0.2%) std. dev.

Type III 1066 18.63

(8011)

19.38

(8331)

21.93

(9427)

1067

18.67 19.37 21.95 21.95

(8088) (8328) (9437) (9438) mean

1068 18.62 19.36 21.95 21.93-22.00

(8003) (8323) (9437) (9427-9457) range

1069 18.64 19.38 22.00 0.02 (0.1%)

(8013) (8333) (9457) (10.07) (0.1%) std. dev.

1071

18.62 19.37 21.95

(8007) (8327) (9439)

1072 18.64 19.38 21.94

» (8014) (8334) (9432)

Types I,

22.04

(9475) mean

II and III

21.93-22.16

(9427-9528) range

combined 0.09 (0.4%)

(40.17) (0.4%)std. dev.

l l MJ kg" 1 = 429.9226 Btu lb ^ was used to calculate the Btu lb

b values presented in parenthesis.

'AD = As determined. C MF = Moisture free. dMAF = Moisture- and Ash-free.

22
Table IV. RDF Analyses (as determined basis)

A. Teledyne National, RDF

Exp t . No . %C % Moisture % Residue % Sulfur

1045 5.26 12.08 —

1052 3.74 11.57 0.10

1053 4.15 11.50 0.10

1054 3.75 13.95 0.10

1056 45.94 3.89 11.94 0.12

1057 3.82 11.87 —

1058 3.85 12.25 0.12

1059 3.88 11.84 0.12

1060 3.83 12.08 0.11

1061 3.96 11.76 0.12

1062 45.99 3.93 12.04 0.12

Mean 45.97 3.88 12.08 0.11

Std. Dev. 0.04 0.113 0.66 0.01

% Std. Dev. 0.08 3.04% 5.46 8 . 66

B. Combustion Equipment Associates, ECO- FUEL II RDF

1051 4.69 11.60 0.474

1073 4.69 11.32 .476

1074 4.69 11.36 .502

1063 4.00 11.43 .522

1064 3.68 11.72 .514

1065 44.35 4.10 11.55 .494

1066 3.88 11.67 .488

1067 3.82 11.19 .486

1068 3.85 11.30 .496

1069 3.55 11.36 .493

1071 3.79 11.43 .479

1072 3.86 11.20 .480

Mean 3.84 11.43 0.492

Std. Dev. — 0.16 0.17 0.015

%Std . Dev. 4.20 1.53 3.03

23

%Chlorine

0.23

0.21

0.25

0.20

0.17

0.18

0.21

0.03

14.57

.326

.317

.334

.369

.331

.345

.368

.341

.381

.352

.352

.352

0.347

0.019

5.46
Table V. Emission Spectrochemical Analysis of Teledyne National RDF Residue

% >_ 1 1 > l; > .i .1 > % > .01 .01 > % _> .

Si (50) Mn (.5) Li (.05) Ag (.002)

Ca (15) Ba (.2) Cu (.04) Be (.001)

Na (10) Sr (.2) Cd (.02)

A1 ( 5) Cr (.1) Ni (.02)

Fe ( 2) Pb (.1) V (.02)

Zn ( 2) Sn (.1) Zr (.02)

K ( 2) B (.01)

Mg ( 1) Mo (.01)

Ti ( 1) Rb (.01)

24
FIGURE LEGENDS

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Schematic diagram of a bomb calorimeter.

A water bath jacket, B water bath, C submarine vessel, D

calorimeter vessel, E temperature sensor, F air space, G bomb,

H calorimeter heater, I direction of water flow, J water in

calorimeter vessel, K thermoregulator, L calorimeter stirrer,

M bath stirrer, N bath heater.

Time-temperature curve for a bomb calorimeter experiment.

t^ initial time of an experiment, t^ time at which main reaction

period begins, commenced by ignition of sample, t x , mid-time

determined graphically to calculate the cooling correction,

t e time at which main reaction period ends, tf final

temperature of an experiment, 0^ initial temperature of an experiment, 0f final temperature of an experiment 0j jacket

temperature (i.e.) temperature of water bath), 0oo convergence

temperature (i.e., temperature which the calorimeter would

attain in an infinite time if 0. and the rate of stirring remain

constant

.

Moisture loss of an RDF sample with time.

Moisture loss exhibited by a Type I sample.

Moisture gain of an RDF smaple with time.

Moisture gain exhibited by a Type II or Type III sample.

25
FIGURE 1

26
FIGURE 2

27
2.474

FIGURE 3

CM CM

6/ SSVW

28

TIME /

hour
FIGURE 4
NBS-114A (REV. 9-78)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 78-1494

4. TITLE AND SUBTITLE

Test Procedures for the Determination of the Gross Calorific

Value of Refuse and Refuse-Derived-Fuels by Oxygen Bomb Calori

metry. Summary of the 1977 FY Results

5. Publication Date December 1978

v. . oiwuKmg uigaiiiMiton

7. AUTHOR(S)

D. R. Kirklin, D. J. Mitchell, J. Cohen, E. S. Domalski and

S . Abr amowi t z

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

WN .NV.,s

IsLi

11. Contract/Grant No. 5433405 (DOE)

5433406 (EPA)

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State, ZIP)

U.S. Department of Energy, UrlSan Waste Techn. Branch,

20 Mass. Ave., N.W., Washington, DC 20545

U.S. Environmental Protection Agency, Solid and Hazardous

Waste Res. Div. , 26 W. St. Clair St. Cincinnati. OH 45268

13. Type of Report & Period Covered Interim

1 Apr 1977-30 Sept 1977

^

15. SUPPLEMENTARY NOTES

Funding shared equally by sponsors.

L_l Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or

literature survey, mention it here.) Gross calorific values have been determined for refuse-derived-fuels (RDF) from

two manufacturers, Teledyne National and Combustion Equipment Associates. Test procedures used are modifications of those used for coal and coke^-*^ The calorific values

(moisture- and ash-free basis) obtained for Teledyne National RDF ranged from 24.51 to

25.20 MJ kg 1 (10539 to 10835 Btu lb 1) with a standard deviation of 0.8 percent. The

calorific values (moisture- and ash-free basis) of Combustion Equipment Associates

ECO-FUEL II RDF ranged from 21.93 to 22.16 MJ kg ^ (9427 to 9528 Btu lb

-

-*-) with a standard deviation of 0.4 percent. Results of 23 laboratory samples are presented at

various stages of sample preparation which were derived from single field samples from

each of the two sources. Calorimetric results based on an equilibrated laboratory

sample are presented along with some semi-quantitative spectrochemical results. The

results indicate that the techniques of oxygen bomb calorimetry can be successfully

applied to a non-homogeneous refuse stream after considerable processing to prepare a "homogeneous" refuse-derived-fuel (RDF)

.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons) Bomb calorimetry ; gross calorific values; refuse-derived-fuels;

sample characterization; test procedures.

18. AVAILABILITY Unlimited

Q] For Official Distribution. Do Not Release to NTIS

i Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

\X Order From National Technical Information Service (NTIS), Springfield, V A. 22161

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF

PRINTED PAGES

34

22. Price

$4. 00

USCOMM-DC