Andover Technology Partners Page 1 March 10

, 200 9

To: Ravi Srivastava , Samudra Vijay, Elineth Torres

Fm: Jim Staudt

Re: NOx , SO 2 and CO 2 emissions from Cement Kilns (Emissions Memo)

– revised from

comments

In this effort I am developing NOx, SO 2 , and CO 2 emissions estimating algorithms as

well as cost alg orithms for control technologies used in cement kilns. This memo will

focus primarily on algorithms to assess emissions, gas flowrates, and heat inputs to

cement kilns , which will be useful in helping assess control strategies for cement kilns.

Terms use d in the algorithms are shown in a table in the appendices of this memo.

Kiln Energy Intensity

Gas treatment technologies generally have capital costs that tend to be related to the gas

volume being treated because this parameter impacts the sizing of th e hardware. Burners

have costs related to thermal input

. As a result, it is necessary to relate the kiln type and

kiln capacity (in short tons or metric ton ne s clinker per unit of time 1 ) to the heat input

and /or the gas flow. Fortunately, there is publis hed data to help develop these relations.

This approach also has the benefit of permitting us to relate many more things to heat

input, such as NOx, SO 2 , and CO 2 emissions. Heat input is also related to clinker

production, depending upon the kiln type. So, algorithms can be produced that are

related to clinker capacity, but also take advantage of the relationships with heat input.

Fortunately, the Portland Cement Association (PCA) has published data on the heat input

to various kilns by type of kiln an d by size. The data is expressed in heat input per unit

of clinker and wet gas flow per unit of clinker , and is summarized in Table 1

.

Table 1. Specific Kiln Fuel Consumption and Total Exit Gas Flows for Various Kiln Types

Kiln Type Specific Fuel Consu mption (SFC) Exit Gas Flowrate (EGF W ) Kcal/kg MMBtu/sh.ton

Low High Avg. Low High Avg. Nm3/kg SCF/sh.ton

wet 1,300 1,650 1,475 4.679 5.939 5.309 3.4 108,990

long dry 1,100 1,300 1,200 3.959 4.679 4.319 1.8 57,701

preheater 750 900 825 2.699 3.239 2 .969 1.5 48,084

precalciner 720 850 785 2.591 3.059 2.825 1.4 44,878

Metric units from “Innovations in Portland Cement Manufacturing ”, Portland Cement

Association, 200 4 , p 247, and converted to English units for this memo

The primary fuel being burned in kilns is coal. However, the kilns have been trending

toward using other fuels, particularly alternative fuels, such as coke, waste tires, and

1 Clinker capacity is normally expressed in metric ton ne s (tonnes) or in short tons (tons) per hour. 

# Andover Technology PartnersAndover Technology Partners Page 2 other waste , especially oily wastes . Table 2 shows different fuels and available heat at

700 0 C for a kiln. 2 Bear in mind that the heat values of Table 2 are representative and

there is significant variation among fuels and the manners in which plants measure and

report this data

. Figure 1 shows the temperature of the material and the gas as it passes

though the kiln. As shown in Figure 1, 700 0 C is where preheating of feed material ends

and where calcination begins

. 2 A cement kiln is a counter

- current heat exchanger, so is

important to keep in min d that the gas flow is from left to right (initially increasing but

then steadily decreasing temp) and the material is passing from right to left (steadily

increasing temp and then temp drop) as it transforms from raw material to clinker.

Table 2 Comparis on of “Available Heat” at 700 C of Different Fuels

Hansen, E., "Changing Process Priorities when Firing Alternate Fuels", 2003 IEEE PCA meeting

Hansen, E., "Changing Process Priorities when Firing Alternate Fuels", 2003 IEEE PCA meeting

2 Hansen, E., "Changing Process Priorities when Firing Alternate Fuels", 2003 IEEE PCA

meetingAndover Technology Partners Page 3 The most impor tant fuels are Coal, Petroleum Coke, Tires/Tire Derived Fuel (TDF) and

Heavy Fuel Oil (HFO). Other fuels are not as widely used or are difficult to characterize

in general. Liquid hazardous waste may be oily waste with significant moisture content

(thus a low heating value) that would produce similar CO 2 per Btu of heat input as heavy

fuel oil, but with a higher moisture content . In order to relate the gas flowrate to heat

input for coal, calculations were made. The combustion calculations in the

Consta nts_CC worksheet of CUECost 3 were used in order to estimate the CO 2 and

moisture generation from bituminous coal combustion (shown as Logan, WV BIT) , PRB

coal combustion (Rosemont PRB) , heavy oil combustion, tire derived fuel combustion

and petroleum coke combustion, which are the most important fuels for cement kilns.

The results are shown in Table 3 and the detailed calculations from CUECost’s

Constants_CC worksheet are shown in the appendices. As with the fuel available heat

data, the data in this tab le should be regarded as representative, and there will be some

variation even within fuel types

.

Table 3 . Approximate CO 2 and H 2 O quantity from combustion of fuels

Variable Name Flue Gas Tires Petroleum

Coke Heavy

Fuel Oil Rosemont

PRB Logan,

WV BIT Met hane

LBMCO2MMBTU lbmoles CO 2 /MMBtu 4.26 4.83 3.85 4.25 4.53 2.39

LBCO2MMBTU lb CO 2 /MMBtu 187.44 212.56 169.32 186.83 199.52 105.02

LBMH2OMMBTU lbmoles/MMBtu 2.76 2.76 2.23 3.23 4.14 2.77

LB H2O MMBTU lbs/MMBtu 49.71 49.73 40.26 58.21 74.64 49.92

. CO 2 f rom Fuel Combustion

It is possible at this point to relate the CO 2 production from fuel combustion and gas flow

to fuel heat input

.

CO2FUEL (in Short ton s) = (LBCO2MMBTU/2000) * SFC * MCLINKER E.1

Where MCLINKER is the amount of clinker that is produced in short tons and

LBCO2MMBTU is determined by the weighted average (weighted by heat input) of the

L BCO2MMBTU for the fuels used, and CO2FUEL is the amount of CO 2 released by the

fuel during combustion . To arrive at the amount of CO 2 from fuel combustion from a

kiln for the year, substitute tons per year of clinker produced by the kiln (TPY) for

MCLINKER.

3 US EPA’s Coa l Utility Environmental Cost model, available at:

http://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryID=63456Andover Technology Partners Page 4 CO 2 from Limestone Calcination and the effect of Substitute Materials

Limestone is the predominant so urce of calcium for the clinker . Assuming limesto ne as

pure calcium carbonate (CaCO 3 ) , c hemistry dictates that it will produce 0.44 tons of CO 2

f

or every ton of pure calcium carbonate calcined to CaO

. Of cou rse, actual mined

limestone is not pure CaCO 3

. If substitute materials that do not require calci nation , such

as steelmaking slag or fly ash

, are used in lieu of limestone as a feed material , this will

reduce the CO 2 from producing the clinker in proportion to the amount of substitute

materials added.

The approximate weight percent of CaO in clinker i s 65 %, 4 and 56% of CaCO 3 is CaO.

Assuming that CaCO 3 is the primary source of calcium, which is usually the case, it

therefore takes about 1. 16 ton s of CaCO 3 to provide the CaO for 1 ton of clinker

. O ther

sources of calcium may offer some advantages. Ac cording to Reference 5 , 172 pounds of

steelmaking slag provides about the same amount of calcium as 200 pounds or more of

limestone, but without the release of roughly 88 pounds of CO 2 that is released upon

calcination of the 200 pounds of limestone (44% o f CaCO 3 is released as CO 2 during

calcination )

. Using this ratio, roug hly 1 ton of steelmaking slag will prov ide enough

calcium for one ton of clinker and will replace the 1. 16 ton s of CaCO 3 that, when

calcined, releases about 0.51 tons of CO 2

.

From che mistry,

CO2CLINKER = 0.44 * MLIMESTONE * PURLIMESTONE E.2

Where MLIMESTONE and MCLINKER are in the same mass units and PURLIMESTONE is

the fraction of limestone used in that kiln that is CaCO 3

.

Now, when limestone is the only source of calcium and 1. 16 to n s of CaCO 3 provide the

CaO for one to n of clinker

, from Equation E.2 it is apparent that

.

CO2CLINKER (in Short ton s)

= 0.5 1 * MCLINKER * PURLIMESTONE (in short tons) E. 3

And, this can be modified to address substitutes for limestone as follows:

CO2CLINKE R (in Short ton s)

= 0.51 * MCLINKER * PURLIMESTONE * (1

– CASUB) E. 4

Where

CASUB is the fraction of clinker calcium sourced from materials that do not need

to be calcined , such as steelmaking slag or fly ash from power plants . So, if 80 %

of the calcium i s sourced from limestone and the remainder of the calcium i s from

a material that does not need to be calci ned, then CASUB is equal to 0.20

.

Now, if the alternative source of calcium is steelmaking slag of similar composition as in

Reference 5 (172 pounds of slag provides as much calcium as 200 pounds of limestone)

, then

4 “ Innovations in Portland Cement Manufacturing”, Portland Cement Association, 2004, p 260

, 5 J. Staudt, “ Steelmaking Slag as Recovered Mineral Components (RMC) in Portland Cement Production ”,

prepared for the National Slag Association, December 12, 2007Andover Technology Partners Page 5 MCLINKER = MLIMESTONE * PURLIMESTONE /1. 16 + MSLAG E. 5

Where MSLAG , MLIMESTONE and MCLINKER are in the same units (ie, short tons)

.

Kilns may be limited by th e amount of feed materials that they can process , in other cases

it may be by the gas volume or heat input

. It depends upon the particular kiln. In the

case where material handling limits the kiln output, MLIMESTONE + MSLAG are

effectively limited and de termine the capacity of the kiln . As a result, and because slag is

more efficient than limestone at providing the calcium for clinker, the use of slag also

increases the amount of clinker that can be produced from a kiln

. Assuming that the

rated capacity of the kiln is based upon the use of limestone, then

CAPACITYHR *1.16 / PURLIMESTONE

= MAX (MLIMESTONEHR)

=MAX(MLIMESTONEHR +MSLAGHR) E. 6

is a limitation of the kiln, or in other words the total limestone and slag injection cannot

exceed the clinker capa city of the kiln times 1. 16

Where CAPACITYHR is the rated capacity in clinker production per hour based

on only limestone , MLIMESTONEHR is the limestone per hour and MSLAGHR

is the slag per hour

Equation E.5 can be represented on an hourly basis as:

MCLIN KER HR = MLIMESTONE HR * PURLIMESTONE /1. 16 + MSLAG HR E.7

Using equations E.6 and E.7, it can be shown that at full capacity :

MCLINKERHR

= (CAPACITYHR*1. 16 /PURLIMESTONE

– MSLAGHR)/1. 16 +MSLAGHR E.8

Or

MCLINKERHR = CAPACITY HR /PURLIMESTONE + 0.13 8 * MSLAGHR E. 9

These will apply for any period of time so long that you are consistent with the time

(such as capacity or clinker or slag mass per hour, per day, year, e tc.) and with units (ie.,

all in short tons ).

So, in theory, if slag w ere used as the only source of calcium up to the limit of the kiln’s

material handling capacity where

MSLAGHR=CAPACITYHR*1.16/PURLIMESTONE

,

the kiln o utput could be increased by 16 %. But, material handling is usually not the

limiting factor. O ther factors limit the use of slag, ofte n the composition of the slag

relative to the desired mineral content of the clinker . Since it is necessary to have the

correct mineral composition for the clinker, the slag composition relative to the desired

clinker composition is often the limiting fact or . N ormally the slag addition rate can be

roughly between 5% and 10% of the original clinker capacity, which typically increases

kiln output roughly by the amount of slag added

. 6 So, the ability to increase kiln output

while using slag will actually var y for each kiln based upon the particulars of its design

6 NOX Control Technologies for the Cement Industry, FINAL REPORT

, EPA Contract No. 68

- D98

- 026

, Work Assignm ent No. 2

- 28, EC/R Project No. ISD

- 228, September 19, 2000Andover Technology Partners Page 6 and the composition of the slag that is available

. But, it is fair to say that substitution of

limestone with slag or another source of calcium that does not require calcining (such as

power plant f ly ash if it is high in free lime ) wil l increase capa city of the kiln, and this is

a major reason why kiln operator s frequently add slag or fly ash when these materials are

available

.

Other effects of substitute materials

S teelmaking slag is closer in chem ical composition to the clinker than limestone, which

reduces the amount of thermal energy necessary to produce an equivalent amount of

clinker. Therefore, this will reduce fuel consumption. This will be examined later when

evaluating energy saving effec ts. Moreover, substitution of limestone with slag will

reduce NOx emissions as well.

Total CO 2

Total CO 2 emissions are the sum of the CO 2 generated from fuel combustion and the CO 2 generated from calcination, and is represented by:

CO2TOTAL = CO2FUEL + CO 2CLINKER E.1 0

From equa tions E.1 and E.4, equation E.10 can be shown to be:

CO2TOTAL (in short tons) =

MCLINKER*[(LBCO2MMBTU/2000)* SFC + 0.5 1 *PURLIMESTONE *(1

– CASUB)] E.11

Where MCLINKER is in short tons

. To arrive at the total CO 2 per year, substitute the

tons per year of clinker (TPY) for MCLINKER.Andover Technology Partners Page 7 Uncontrolled NOx Emissions from Cement Kilns

NOx emissions from cement kilns result from oxidation of fuel nitrogen (fuel NOx),

oxidation of nitrogen in the combustion air (thermal NOx), and oxidation of nitrogen in

the feed materials (feed NOx). Feed materials sometimes have significant levels of

ammonia, which can also tend to reduce the NOx produced during combustion.

Therefore, there is some variability in NOx emissions for kilns of similar type d epending

upon a range of factors. However, as will be shown, some trends can be found.

The uncontrolled NOx emission s from cement kilns were shown in the 1994 ACT , AP

- 42

per Reference 7 and a 2000 EPA NOx Report as reported in Reference 8

, and these are

shown in Table 4.

Table 4. NO

x Emissions (pounds per ton clinker [lb/t]) by Kiln Type

EPA 1994 ACT AP

- 42 2000 EPA NOx Report

Kiln Type Range Average/

Percent Higher

than PH/PC Kiln percent Higher

than PH/PC Kiln Average Range

Wet 3.6

– 19.5 9.7 /155 7.4 /76 6.2 1.9

- 13.4

Long Dry 6.1

– 10.5 8.6 /126 6.0 /43 4.5 2.5

- 7.1

Preheater 2.5

– 11.7 5.9 /55 4.8 /14 1.7 0.4

- 3.7

PH/PC 0.9

– 7.0 3.8 /

---- 4.2 /

---- 2.9 1.1

- 5.6

Alternative Control Techniques Document Update

- NOx Emissions from New Cement Kilns, EPA

- 453/R

- 07

- 006, November 2007

Portland Cement Association, “Summary of Control Techniques for Nitrogen Oxides”, PCA R&D SN3049, 2008

NOX Control Technologies for the Cement Industry, FINAL REPORT

, EPA Contract No. 68

- D98

- 026

, Work Assignmen t No. 2

- 28,

EC/R Project No. ISD

- 228, September 19, 2000

It is possible to estimate the average NOx emission in lb/MMBtu of various kiln types

using the data of Table 4 and Table 1 by divid ing the NOx generation per ton of cli nker

by the heat input per to n of clinker for each kiln type . According to the average va lues

from the 1994 ACT shown in Table 4 , the NOx emissions range from a low of 0.85

lb/MMBtu (for precalciner kilns) to a high of 1.38 lb/MMBtu for Long Wet and Long

Dry kilns. Using the AP

- 42 e stimates, NOx emissions are over a narrower band around 1

lb/MMBtu

– ranging from a low of 0.95 lb/MMBtu for a precalciner to a high of 1.05

lb/MMBtu for a Wet process kiln , and the EPA 2000 numbers suggest lower values

. Table 5 shows the results of these calculations. An interesting result of these estimates is

that

– except for the estimates made with the EPA 2000 data

- the emissions rates for

cement kil ns appears to be roughly in the range of 1 lb/MMBtu to 1.5 lb/MMBtu for all

kiln types, and that , f or uncontrolled kilns, the emissions rate in lb/ ton of clinker is

7 Alternat ive Control Techniques Document Update

- NOx Emissions from New Cement Kilns, EPA

453/R

- 07

- 006, November 2007

8 Portland Cement Association, “Summary of Control Techniques for Nitrogen Ox ides”, PCA R&D

SN3049 , 2008Andover Technology Partners Page 8 primarily a function of the heat demand of the kiln per ton of clinker. These results are

consistent with information from Hansen (e

- mail June 20, 2008) that states that

uncontrolled NOx em issions (all process types, wet, long dry, preheater and precalciner

with the exception of low NOx calciners or those equipped with staged combustion) are

in the range of 1.0 to 1.3 lb/MMBtu . Therefore, this is a reasonable range to use for

baseline, unco ntrolled NOx emissions from cement kiln s, with the lower part of the range

perhaps being newer precalciner kilns and the higher end of the range long kilns. Since a

precalciner kiln burns a significant part of the fuel in the calciner at a lower temperatu re

where negligible thermal NOx is formed, it is reasonable that the NOx in lb/MMBtu

might be somewhat less for a precalciner than for other kilns. Also, precalciner and

perhaps preheater kilns, having a separate temperature zone for preheat with high

int eraction between gas and solids, might benefit more from ammonia that sometimes is

released from feed materials and can reduce NOx through selective non

- catalytic

reduction (SNCR) reactions. Finally, wet kilns often burn a significant amount of waste

fuel, which can impact NOx emissions

– sometimes positively and sometimes negatively.

Table 5. Estimated Uncontrolled NOx Emission s for Cement Kilns in lb/MMBtu

Estimated from Average D ata in Tables 1 and 4.

1994 ACT AP

- 42 2000 EPA

Wet 1.52 1.16 0.97

Long Dry 1.52 1.06 0.79

Preheater 1.35 1.10 0.39

PH/PC 0.94 1.04 0.72

For cement kilns with additional controls, such as fuel staging, emission will be less. The

cost and performance of these controls will be discussed later in this document. To

deter mine the uncontrolled NOx level for a cement kiln, the following equation would be

used.

MCLINKERHR * SFC * NOXMMBTU = LBNOXHR (lbs of NOx per hour)

, or

TPY * SFC * NOXMMBTU = LBNOXYR (lbs of NOx per year) E.12

Where MCLINKERHR is equal to the ton s of clinker produced per hour and

NOXMMBTU may be in the range of 1 to 1.3 lb/MMBtu, depending upon the kiln type

and other characteristics

. TPY is equal to the tons of clinker per year. In the following

section, the effects of kiln age and capacity will be examined.

Impact of Kiln Age and Capacity on NOx Emissions

The 2002 National Emissions Inventory (2002 NEI) reflects the estimates of emiss ions as

submitted by states. Because it has kiln

- specific emissions data, it enables us to relate the

emissions to the specific kilns, which enables us to examine factors that may impact

emissions. 2002 NE I data provided i n the Cap+Trade worksheet was plotted by kiln

type, by capacity and by year installed to determine the impact of these parameters onAndover Technology Partners Page 9 NOx emissions in lb/ton of clinker and lb/MMBtu of heat input

. The NEI data is

provided by states as their estimates of emissions from sources. So, t here is some

variability in the methods used to develop this data that makes it somewhat less reliable

than, for instan ce, power plant continuous emission monitoring system (CEMS) data

under the Title I V program. Nevertheless, this data is examined on the following pages

since it is the best data currently available for all kilns

. An important aspect of this data

is that it represents emissions from kilns with whatever controls that they have installed.

So, newer kilns, which are more likely to have combustion controls, are more likely to

have lower NOx emissions. Some older kilns have installed NOx controls due to loca l

requirements. Some of these kilns have post combustion controls as well, which will

affect the values shown. The information regarding the NOx control equipment is not

available for each kiln. Therefore, it is not possibl e to discern the effect of NOx control

equipment from this data. The averages and medians are shown in Table 6 by kiln type.

These dif fer from the previous estimates. While the trends are generally consistent with

what i s expected, the estimated value in lb/MMBtu for wet kilns is highe r than the other

estimates . The average result showing a higher NOx in lb/ ton of clinker for wet versus

dry kilns is unexpected. However, as will be shown, there is a lot of scatter in the data

that can throw the averages off such that they are not repre sentative. Because there are

no negative emission rates, the distribution of emissions values tends to behave more like

a log

- normal distribution than a normal distribution, with high values being far higher

than the mode (or most frequent level) than low values. As a result, the m edian values

are less affected by these high outliers than mean values , and that is why median values

are also shown. Median values are therefore probably more reliable than the averages in

estimating the behavior of the popula tion as a whole.

Table 6. Averages /Medians of NOx emissions from NEI data in Cap+Trade

workbook

PC PH D ry Wet

NOx, lb/ton clinker (average) 3.69 7.06 8.86 8.40

NOx, lb/MMBtu (average) 1.08 1.78 1.85 2.07

NOx, lb/ton clinker (median) 3.37 4.68 7.19 7. 71

NOx, lb/MMBtu (median) 0.99 1.27 1.38 1.99

In the following pages the NOx emissions reported in the NEI data will be presented for

each kiln type as a function of kiln date of operation and kiln capacity.Andover Technology Partners Page 10 Wet Kilns

As shown in Figures 4a and 4b a nd 4c

, there is no apparent correlation between NOx

emissions from wet kilns and either kiln age or kiln capacity.

Fig ure 4a. NOx emissions (lb/ton

clinker) versus year on line for wet

kilns

Fig ure 4b. NOx emissions (lb/ton

clinker) versus capacity for wet kilns

Figure 4b. NOx emissions

(lb/MMBtu) versus capacity for wet

kilnsAndover Technology Partners Page 11 Long Dry Kilns

In the case of long dry kilns, there is at best a very weak correlation between NOx

emissions and year on line or capacity , as shown in Figures 5a, 5b and 5c . However, any

trend appears too weak to be of great use in characterizing kiln NOx rate with any

accuracy.

Figure 5a. NO x emissions (lb/ton

clinker) versus year on line for long dry

kilns

Fig ure 5b. NOx e missions (lb/ton

clinker) versus capacity for long dry

kilns

Figure 5c. NOx emissions (lb/MMBtu

clinker) versus capacity for long dry

kilnsAndover Technology Partners Page 12 Preheater Kilns

In the case of preheater kilns, there appears to be a significant correlation bet ween NOx

emissions and year on line or capacity , as shown in Figures 6a, 6b and 6c

. The

correlation appears slightly stronger when using kiln capacity

. Kiln capacity and year on

line are related since newer kilns tend to be larger. Larger or newer kilns tend to have

lower emissions. This may be explained by better efficiency and more controls.

Figure 6 a. NOx emissions (lb/ton

clinker) versus year on line for

preheater kilns

Figure 6 b. NO x emissions (lb/ton

clinker) versus capacity for

preheater kilns

Figure 6c. NOx emissions

(lb/MMBtu) versus capacity for

preheater kilnsAndover Technology Partners Page 13 Precalciner Kilns

As shown in Figure 7a, 7b and 7c, i n the case of precalciner kilns there appears to be a

very slight correlation between NOx emissio ns and year on line or capacity, albeit much

weaker than that for preheater kilns. The correlation appears slightly stronger when using

kiln capacity. Kiln capacity and year on line are related since newer kilns are usually

larger. Hence, newer and larg er kilns tend to have lower emissi ons; but the data does not

support that in every case, as demonstrated by the scatter.

Figure 7 a. NOx emissions (lb/ton clinker)

versus year on line for precalciner kilns

Figure 7 b. NOx emissions (lb/ton clinker)

versus capacity for precalciner kilns

Figure 7c. NOx emissions (lb/MMBtu) versus

capacity for precalciner kilnsAndover Technology Partners Page 14 Uncontrolled SO 2 Emissions From Cement Kilns

SO 2 emissions from cement kilns are the product of sulfur in the fuel as we ll as sulfur in

the feed materials. Ideally, the SO 2 will be well captured to form gypsum by the free

CaO that is released in the kiln

. In addition to reducing undesir able SO 2 emissions

, conversion to sulfates can be beneficial for the product. Gypsum i s used in finished

cement, and gypsum produced on site may reduce the amount of gypsum that must be

purchased. Synthetic gypsum from wet FGD systems may be used in place of natural

, purchased gypsum if of adequate quality. Therefore, SO 2 capture has both environmental

as well as economic benefits for cement manufacturing.

However, the processes in a kiln that affect conversion of sulfur in the fuel and

conversion of the sulfur in the feed materials to sulfates are many. Sulfur in the fuel will

oxidize t o SO 2 during pyroprocessing and a significant amount is likely to be captured in

the form of sulfates as the gas passes through the calcination zone. Preheater and

Precalciner kilns tend to be very effective at capturing fuel

- generated SO 2 , while long dry

and wet kilns are less effective.

Local oxygen concentrations in the kiln play a significant role. Kiln operators attempt to

maintain an oxidizing environment throughout the kiln because this is beneficial to both

calcination and clinker reactions. Red uced sulfur comp ounds, which can form in oxygen

depleted environments, are undesirable in the product while sulfates are desirable in the

product

. However, kiln operators also minimize excess air to keep efficiency high and

NOx low . As a result of the lo w excess air , lo cal reducing zones may result. Sulfates in

processed materials may be reduced to SO 2 or to reduced sulfur compounds in reducing

zones

.

Alternatively, other sulfur forms in the feed may be released and oxidize to form SO 2

. Changing the fo rm of sulfur in the feed material will therefore affect the SO 2 emissions.

Because sulfur in the feed materials may be released prior to calcining reactions, for most

kiln types the SO 2 released from feed materials is not as readily captured as SO 2 from

fu el sulfur. For example, if the sulfur in the feed materials is of a form that readily

releases SO 2 upon heating, much of the SO 2 from this source will be emitted unless there

is an SO 2 control device to treat the exhaust gas. Table 7 shows emissions dat a from a

2001 Portland Cement Survey. The results show a great deal of variation. The

consolidated results also don’t examine the impacts of kiln feed materials, just kiln type.

Table 7. 2001 Emissions Data from Portland Cement Association 2001 Survey

Kiln type Number of

plants in

database Number of

tests in

database SO 2 emission rates, Kilograms SO 2 per metric ton clinker

(pounds SO 2 per ton clinker)

Minimum Maximum Average

Wet 11 20 <0.01 (<0.01) 16.32 (32.63) 2.90 (5.80)

Long dry 9 27 0.01 (0.02) 9.09 (18.17) 1.43 (2.85)

Preheater 11 30 <0.01 (<0.01) 3.27 (6.54) 0.70 (1.39)

Calciner 7 24 <0.00 (<0.00) 4.42 (8.83) 0.96 (1.92)

F. M. Miller, G. L. Young, and M. von Seebach , Formation and Techniques for C ontrol of

Sulfur Dioxide and Other Sulfur Compounds in Portland Cement Kiln Systems, PCA R&D Serial No. 2460Andover Technology Partners Page 15 In order to examine the effects of kiln type, fuel and raw materials on SO 2 emissions,

average SO 2 emissions in lb/ton clinker were estimated from 2002 National Emissions

Inventory data in the Cap+Trade workbook for each market (except for Maine, which

was separated from New York) by kiln type. Location has a major role in determining

the fuel and limestone used. Limestone (or an alternate source o f calcium) is typically

sourced from quarries that are close to the kiln since limestone is heavy and expensive to

transport and the kiln uses a lot of it. Coal is also sourced from what is available in that

market. Other feed materials may be from other locations and are less plant

- specific. As

shown on Figure 8, preheater and precalciner kilns generally, but not always, have the

lowest SO 2 emission rate. Wet and long dry kilns generally have the highest SO 2 emissions rates. However, even within kiln t ypes there is substantial variation in SO 2 emissions when comparing different locations. Locations are markets in the Cap+Trade

workbook, except for Maine, which was separated because that kiln (which has since

been converted to a precalciner kiln) was kn own to be scrubbed at the time . Atlanta,

Birmingham, Detroit, Minneapolis, Kansas City, and New York have very high SO 2 emissions compared to other locations, such as Dallas, Denver, Florida, Los Angeles

Maine, Phoenix, Pittsburgh, Salt Lake City, San Fra ncisco and Seattle. Table 8 shows the

average emissions level for each kiln type for each market, and the color indicates

whether or not the emissions rate is above or below the average. Since several locations

show that their emissions are consistently ab ove or below the average for all or nearly all

kiln types, location definitely has a significant role in SO 2 emissions from cement kilns.

Figure 8. Average SO 2 emissions (in lbs/ton clinker) by kiln type and locationAndover Technology Partners Page 16 Kiln age and capacity were also examined in order to determine if capacity or age has a

significant impact on SO 2 emissions within kiln types. The results of this analysis are

shown on the following pages

.

Table 8. Average SO 2 Emission fo r each kiln type in each market (lbs/ton clinker)

(red is above the average and green is below the average for that kiln type)

PC PH Dry Wet

Atlanta 1.76 2.73 11.42 11.92

Baltimore/Philadelphia 3.14 4.79 7.53 6.31

Birmingham 0.33 0.61 0.00 13.99

Chicago 5.58 4.47 5.88 9.50

Cincinnati 0.19 4.93 12.53 0.00

Dallas 2.12 0.00 3.45 7.26

Denver 0.32 0.27 1.07 4.24

Detroit 5.23 0.00 18.10 17.69

Florida 0.45 0.02 0.00 0.00

Kansas City 3.81 5.88 14.88 8.61

Los Angeles 0.43 2.18 0.27 0.00

Minneapolis 13.37 0.00 8.15 0.00

Maine 0.00 0.00 0.00 1.67

New York/Boston 0.00 0.30 0.00 20.06

Phoenix 0.87 0.07 5.69 0.00

Pittsburgh 0.00 0.00 5.17 3.29

Salt Lake City 0.13 0.00 0.00 0.77

San Antonio 0.84 0.58 0.51 8.98

San Francisco 0.78 0.05 1 .51 0.00

Seattle 0.53 0.00 0.00 3.80

St. Louis 2.18 0.00 1.42 7.02

Average of above 2.34 2.07 6.51 8.34

Average for all in kiln

type 1.75 2.03 7.14 8.27

Figure 9 and Table 9 show the median SO 2 emissions (in lb/ton clinker). There is a slight

difference from what is shown in Figure 8 and Table 8. But, the trends overall are

similar. Median values tend to be less impacted by outliers than averages

. So, in most

(but not all) cases the median values are lower because they are less impacted by v ery

high values . So, median is more represent ative than the average for the majority of kilns,

but will not be representative for kilns with unusually high values.Andover Technology Partners Page 17 Figure 9

. Median SO 2 emissions (in lbs/ton clinker) by kiln type and locationAndover Technology Partners Page 18 Table 9. Median SO 2 Emission for each kiln type in each market (lbs/ton clinker)

. (red is above the average and green is below the average for that kiln type

PC PH Dry Wet

Atlanta 0.95 2.73 11.42 12.25

Baltimore/Philadelphia 3.14 3.95 7.31 7.49

Birmingham 0.09 0.61 0.00 13.99

Chicago 5.58 5.77 5.88 9.50

Cincinnati 0.19 5.04 12.53 0.00

Dallas 2.94 0.00 3.45 7.59

Denver 0.32 0.10 1.07 4.24

Detroit 5.23 0.00 5.31 18.00

Florida 0.45 0.02 0.00 0.00

Kansas City 1. 25 5.88 24.85 8.61

Los Angeles 0.17 2.18 0.11 0.00

Minneapolis 13.37 0.00 8.15 0.00

Maine 0.00 0.00 0.00 1.67

New York/Boston 0.00 0.30 0.00 11.98

Phoenix 1.30 0.07 8.51 0.00

Pittsburgh 0.00 0.00 5.41 3.95

Salt Lake City 0.13 0.00 0.00 0.70

San Antonio 0.75 0.61 0.51 8.98

San Francisco 0.49 0.05 1.51 0.00

Seattle 0.53 0.00 0.00 3.80

St. Louis 2.18 0.00 1.51 7.02

Median of above 0.85 0.61 5.41 7.59

Median of all in kiln

type 0.88 0.63 2.13 7.43Andover Technology Partners Page 19 Effects of year on line and capacity were also examined in the same way as for NOx

emissions. Figures 10a and 10 b show that there are no trends between SO 2 emissions and

year on line or capacity for wet kilns. This is consistent with the previous result that

suggests that other conditions, such as fuel and feed materials, have a larger impact.

Figure 10 a. SO 2 emissions (lb/ton clinker) versus year on line for wet kilns

Figure 10b

. SO 2 emissions (lb/ton clinker) versus capacity for wet kilnsAndover Technology Partners Page 20 Figures 11a and 11 b show that there are no trends between SO 2 emissions and year on

line or capacity for dry kilns either. This is consistent with the previous result that

suggests that other conditions, such as fuel and feed m aterials, have a larger impact.

Figure 11 a. SO 2 emissions (lb/ton clinker) versus year on line for dry kilns

Figure 1b

. SO 2 emissions (lb/ton clinker) versus capacity for dry kilnsAndover Technology Partners Page 21 Figures 12 a and 12 b show that there are no strong trends between SO 2 emissions and year

on line or capacity for preheater kilns

– at least for lower capacities. This is consistent

with the previous result s that suggest that other conditions, such as fuel and feed

m aterials, can have a large impact

. However, at larger capacities and for newer units, the

SO 2 emissions tend to be consistently low , as demonstrated by the red line . So, it appears

that the larger or newer units may have better inherent SO 2 capture than the smaller and

older ones.

Figure 12 a. SO 2 emissions (lb/ton clinker) versus year on line for preheater kilns

Figure 12b

. SO 2 emissions (lb/ton clinker) versus capacity for preheater kilnsAndover Technology Partners Page 22 F igures 13a and 13 b show that there are no strong trends between SO 2 emissions and year

on line or capacity for precalciner kilns at lower capacities. This is consistent with the

previous results that suggest that other conditions, such as fuel and feed ma terials, can

have a large impact. However, at larger capacities and for newer units, the SO 2 emissions

are consistently low , as shown by the red line . So, it the larger or newer units appear to

have better inherent SO 2 capture than the smaller and older ones.

Figure 13 a. SO 2 emissions (lb/ton clinker) versus year on line for precalciner kilns

Figure 13b

. SO 2 emissions (lb/ton clinker) versus capacity for precalciner kilnsAndover Technology Partners Page 23 Summary of Emissions

It is acknowledged that the data available for estimating emissions rates, particularly for

NOx and SO 2 , has some uncertainties. However, reasonable estimating methods, as

described in this memo, are possible at this time. And, as more information beco mes

available, the estimating methods described in this memo will be refined and improved

upon. The following conclusions have been reached regarding CO 2 , NOx and SO 2

emissions from kilns.

**•** CO 2 emissions from a kiln can be estimated from heat input and fu el

characteristics and from clinker production and the amount of clinker calcium

sourced from limestone versus other sources that do not require calcining.

Algorithms are provided in this memo to permit these calculations.

**•** Average uncontrolled NOx emissio ns may be in the range of abo ut 1

- 2 lb/MMBtu

for all kiln types

, and a narrower range for most dry process kilns (1

- 1.3

lb/MMBtu)

, and kilns with controls will likely have lower NOx than in this range

.

**•** For long kilns (wet and dry) there is no observed impa ct from kiln age or kiln size

on NOx emissions (lb/ton clinker basis and lb/MMBtu basis ).

**•** For preheater and precalciner kilns, trends were observed that show ed lower NOx

emissions (lb/ton clinker basis and lb/MMBtu basis ) for larger and newer kilns

**•** SO 2 emi ssions are impacted by location and by kiln type , with wet kilns generally

having the highest emissions and preheater kilns the lowest

.

**•** SO 2 emissions from long kilns (wet or dry) are not impacted by kiln size or age

.

**•** SO 2 emissions from preheater and precal ciner kilns do not appear to be impacted

by size or age for smaller or older kilns. However newer and larger kilns appear

to have consistently low SO 2 emissions.

For estimating NOx emissions, the median NOx levels in lb/MMBtu in Table 10 are

recommended for the model

. Earlier discussion cited the variability within kiln types that

is not captured in Table 10. Of course, as better data is available in the future, the

emissions assumptions for the model will be improved.

Table 10 . Median NOx emission ( lb/MMBtu)

PC PH D ry Wet

NOx, lb/MMBtu (median) 0.99 1.27 1.38 1.99

For SO 2 emissions, I recommend using the median SO 2 emissions by kiln type and region

shown in Table 9. However, for each data point in Table 9 that represents median

emissions within a market and kiln type, there may be very few numbers behind it . So,

there may be a question of statistical relevance . However, since the values in Table 9 are

being used only to characterize the specific kilns of that type within those markets rather

th an used to represent a broader population of kilns, this approach should provide

reasonable results. Of course, as better data is available in the future, the emissions

assumptions for the model will be improved.Andover Technology Partners Page 24 

### Appendices

1 Typical properties of delaye d petroleum coke

2. Ultimate Analysis values for Heavy No. 6 Fuel Oil‚ lb/lb fuel

3. Tire Derived Fuel Analysis

4. Combustion Calculations from CUECost

5. List of TermsAndover Technology Partners Page 25 Appendix 1. Typical properties of delayed petroleum coke

(Ultimate Analysi s as Received, Weight %)

World Energy Council Website http://217.206.197.194:8190/wec

geis/publications/default/tech_papers/17th_congress/1_2_26. asp

Constituent Average Range

Carbon 79.74 75.0

- 86.0

Hydrogen 3.31 3.0

- 3.6

Nitrogen 1.61 1.3

- 1.9

Sulfur 4.47 3.4

- 5.3

Ash 0.27 0.0

- 0.6

Oxygen 0.00 0.0

- 0.1

Moisture 10.60 5.5

- 15.0

HHV, MJ/kg 31.3 29.3

- 33.7

Ash Properties, ppm Average Range

Vanadium <2,000 500

- 2,000

Nickel 336 250

- 450

Iron 84 50

- 250

Volatile Matter, % 10 8

- 16

Appendix 2. Ultimate Analysis values for Heavy No. 6 Fuel Oil‚ lb/lb fuel

Natural R esources Canada website:

http://www.oee.nrcan.gc.ca/industrial/technical

- info/tools/boilers/heavy

- fuel.cfm?attr=24

Carbon (C) 0.874

Hydrogen (H

2 ) 0.101

Nitrogen (N

2 ) 0.003

Oxygen (O

2 ) neg ligible

Sulphur (S) 0.020

Ash 0.001

Higher heating value (HHV) 18‚250 Btu/lbAndover Technology Partners Page 26 Appendix 3. Tire Derived Fuel Analysis

Representative Analysis of TDF Produced By WRI

(Source: TDF Produced From Scrap Tires with 96+% Wire Removed)

Description %By Wt (As

Received) %By Wt (Dry Basis)

Proximate Analysis

Moisture 0.62

----

Ash 4.78 4.81

Volatile Matter 66.64 67.06

Fixed Carbon 27.96 28.13

Total 100.00 100.00

Ultimate Analysis

Moisture 0.62

----

Ash 4.78 4.81

Carbon 83.87 84.39

Hydro gen 7.09 7.13

Nitrogen 0.24 0.24

Sulfur 1.23 1.24

Oxygen (by difference) 2.17 2.19

Total 100.00 100.00

Heat Value BTU/lb kJ/kg

HHV 16,250 37,798

HV Ave 15,500 36,053

TDF Combustion

Characteristics **°** F **°** C

Tires ignite (flash point) 550

- 650 288

- 343

Carbon begins to burn 842 450

Carbon completely burnt 1202 650

© 1986 Waste Recovery, Inc.

84% OF A TIRE,S WEIGHT IS FROM RUBBER COMPOUNDS. REMAINDER

IS BEAD AND BELT WIRE PLUS CARCASS AND CHAFE R FABRIC

From North Carolina Department of Environment and Natural Resources, Division of

Pollution Prevention and Environmental Assistance.

http://www.p2pays.org/ref/11/10504/html/usa /tdfdata.htmAndover Technology Partners Page 27 Appendix 4. Combustion Calculations from CUECostAndover Technology Partners Page 28 Appendix 5. List of Terms

Term Definition

CAPACITYHR

CASUB

CC

CO2FUEL

CO2CLINKER

COSTKWH

COSTNH3LB

COSTNH3YR

DLI

DSCFM

EGFW

FC

FF i

H

LBCO2MMBTU

LBMCO2MMBTU

LBH20MMBTU

LBMH20MMBTU

LBNOXHR

LBSO2CLINKER

LNB

LWS

MAT

MCLINKER

MCLINKERHR

MKF

MLIMESTONE

MLIMESTONEHR

MSLAG

MSLAGHR

NOXMMBTU

PEC

PURLIMESTONE

Q

SCC

SCR

SFC

SCFH

SNCR

TDFPC

TPY

VC Clinker capacity of the kiln in tons per hour

Calcium Substitution Fraction

– fraction of total c alcium from material that

does not need to be calcined

Capital Cost

Fuel CO 2 in pounds that is released from fuel combustion

CO 2 produced by calcination during clinker production

Cost of Power in $/KWhr

Cost of ammonia in $ per pound

Cost of ammonia in $ p er year

Dry Lime Injection

Dry standard cubic feet per minute

Exhaust Gas Flowrate (wet) in standard cubic feet per short ton of clinker

Fixed Cost

Fuel Fraction of i th component of fuel on a Btu basis

Burner heat duty in MM Btu/hr

Pounds (mass) of CO2 pe r MMBtu of fuel input

Pound moles of CO2 per MMBtu of fuel input

Pounds (mass) of H2O per MMBtu of fuel

Pound moles of H2O per MMBtu of fuel

Pounds (mass) of NOx per hour

Lbs of SO 2 per ton of clinker

Low NOx Burner

Limestone Wet Scrubber

Mixing Air Techno logy

Mass of clinker in tons

Mass rate of clinker in tons per hour

Mid Kiln Firing

Mass of limestone, tons

Mass rate of limestone, tons/hr

Mass of slag, tons

Mass rate of slag, tons/hr

NOx lb/MMBtu for the kiln

Purchased Equipment Cost

Purity of the limest one at CaCO 3 Flow in actual cubic meters per hour

Staged Combustion Calciner

Selective Catalytic Reduction

Specific Fuel Consumption in MMBtu per ton of clinker

Standard Cubic Feet per Hour of gas

Selective Non

- Catalytic Reduction

Tire Derived Fuel Precalc iner

Tons per Year of clinker

Variable Cost