Andover Technology Partners Page 1 February 2 6 , 2010

To: Ravi Srivastava , Elineth Torres , Keith Barnett

C c: Clint Burklin

Fm: Jim Staudt

Re: Wet Scrubber Cost Algorithms

Industry comme nted that both the gas flowrate and the capital cost estimating approach

that w ere described in my March 10 memo and used in ISIS underestimated kiln gas flowrates and kiln capital cost. In response to questions raised by industry, I am revisiting the gas flowrate estimating approach and capital cost estimates for wet

scrubbers.

Background

The flowrate calculation in my original Technical memo issued last spring is based upon

the kiln exhaust gas flow rate information provided in Table 3.1.1 on page 247 of “Innovations in Portland Cement Manufacturing” published by the Portland Cement

Associatio n, 2004, which was used to develop Table 1 of the memo I prepared on NOx,

SO 2 and CO 2 emissions last spring.

Data from Table 3.1.1 that included specific fuel consumption and kiln exit gas flowrate

was converted from metric to English units for Table 1 of my March 10 memo, and the resulting flowrates were used to estimate the gas flowrate of kilns for the purpose of estimating the cost of wet scrubbers.

Evaluation of Data Industry comments suggested that the data in Table 3.1.1 of “Innovations in Portland

Cement Manufact uring” underestimate actual flowrates experienced in practical cement

kilns that would need to be treated with a scrubber

. Data submitted by industry (National

Cement and the PCA ), and d ata provided to me by Mr. Keith Barnett of US EPA showed

that the sta ck gas flow rates did, in fact, generally exceed the flowrates (expressed in

terms of scf/ton clinker) that were on Table 1 of my original memo. Where this data provided oxygen concentrations, they were generally much higher than what would be expected if the gas were from the kiln alone. This indicates that there are other sources of gas flow that dilute the kiln exhaust and increase the total flowrate beyond what is expected at the kiln exit

. Therefore, while the data in my original memo may have

accur ately represented the kiln gas flow, it did not capture all of the gas that would likely

be treated if a wet scrubber were installed. Data provided by Keith Barnett included data from 57 kilns including kilns of all major types. The data included informa tion on whether or not there was an alkali bypass or an in

- line raw mill. In estimating dscf per short ton of feed or dscf per short ton of clinker (assuming 1.65 tons of feed per ton of clinker) there was a relatively wide scatter from kiln to kiln, but regardless of kiln type 

# Andover Technology PartnersAndover Technology Partners Page 2 the rates were generally in the same range

. Table 1 below shows the results of an analysis of this data. With regard to use of alkali bypass or in

- line raw mill, there was no consistent pattern (either above or below the average o r median).

Recognizing that the data showed a fairly wide scatter in reported flowrate s , it is not possible to arrive at a single value that will be precisely accurate for each kiln; however my goal was to arrive at a number that would likely be represe ntative for many facilities and for any individual facility the error would b e minimized

. Based upon the data in Table 1, and because the ISIS data is represented in the form of clinker output, I

recommend using a gas flowrate equal to 100,000 dscf/ton of clinker, resulting in:

D SCFM = 100000 * TPDCLINKER/ (24*60) = 69 * TPDCLINKER E.1

TPDCLINKER = TPY CLINKER/(365*0.90) = 3.04E

- 3 * TPY CLINKER E.2

Where

DSCFM is the stack flowrate of the kiln in dscfm TPDCLINKER is the capacity of the kiln in short tons per day TPYCLINKER is the capacity of the kiln in short tons per year

Equations E.1 and E.2 should be used in lieu of equations E.28 and E.29 of my original

memo. I recommend that th e s e equation s be used for all kiln types because there doesn’t seem to be enough difference between kiln type, e xcept possibly for a slight difference for preheater kilns, to warrant different numbers.

Table 1. Stack flowrates of cement kilns

dscf/short

ton feed ds cf/short

ton clinker Stack Temp

- deg F number
of kilns

All Kilns Average 62,586 103,266 351 57

Median 59,112 97,534 330
Dry Average 64,074 105,722 379 15

Median 60,171 99,283 375

Preheater Average 62,513 97,669 438 10

Median 49,104 79,119 398

Precalciner Average 61,182 100,951 266 18

Median 56,214 92,752 259

Wet Average 63,249 104,361 363 14

Median 65,457 108,004 347
Analysis of data that was provided by Mr. Keith Barnett, US EPA, 2/24/10

Wet Scrubber Capital Costs

My March mem o provided a means to estimate capital costs that related capital cost to flowrate. This was developed based upon information in a PCA article (SP129) by Gerald Young in 2002 entitled “Review of SO 2 (HCl) Scrubbers” as well as other data cited in the memo, including a PSD analysis from Florida Rock industries

. The PCA article discussed use of a scrubber at an Essroc cement kiln and provided cost

information. Also cited in my earlier memo was the cost of the Lehigh Cement MasonAndover Technology Partners Page 3 City, IA plant, which appeared at the time to be much more costly (in $/scfm) than o ther data. Because it was much higher and because it was also part of a facility expansion, it raised some doubt about whether the cost information was comparable.

It is important to note that, unlike power plants, there are very few cement kilns that have actually installed, no less retr ofit, wet scrubbers. And, the cement companies are not under an obligation similar to that of an electric utility which must publicly release

information to a utility commission on project cost once executed . As a res ult, the data

on actual cement kiln wet scrubber projects is very limited and it is necessary to rely on industry estimates, which may be biased. Industry provided the estimates shown in Table 2 along with estimated SCFM and $/SCFM using equation E.1. If equation E. 1 is used to

estimate the gas flowrate of the 1.2 million tpy Mason City scrubber at about $28

million 1 , then 250,000 scfm results, and the cost is roughly $113/scfm

.

Table 2. Capital Cost Estimates Provided by PCA.

TPY Capital Cost E st

. SCFM est. $/scfm

Wet 1,300,000 $44,000,000 272,688 $161

Dry 537,201 $24,200,000 112,683 $215
Precalciner (Existing) 784,799 $24,000,000 164,619 $146
Precalciner (Proposed) 1,600,000 $19,000,000 335,616 $57

Source: PCA comments to NESHAP, Appendix 2, page 500 of 513

The PCA paper “Review of SO 2 (HCl) Scrubbers” mentioned that a scrubber cost of about $30

- $60 per scfm (2 002 dollars). However, it is necessary to add a device to remove chlorides in many cases because chlorides cannot be readmitted to the kiln in the

manner sulfates and sulfites could. The chloride removal equipment would add roughly another $30

- $60/scfm to the cost according to the PCA paper . I did not include the

chloride removal in my prior memo because of the focus on SO 2

. Nevertheless, if the

mid

- point of $45/scf is used for both the scrubber and the chloride removal for a total of $90/scf and this is escalated to 2007 d ollars using the CEPCI, then this results in $120/scfm (or $107/scfm if in 2005 dollars) , which is slightly abo ve the estimated cost for Mason City and slightly below the estimated cost of the existing precalciner kiln

shown in Table 2 above. It is my opinion that the industry is far more likely to install

scrubbers on newer kilns than older ones. This means that they are more likely to install them on precalciner and preheater kilns than on wet or long dry kilns. So, I suggest that we focus on the cost numbers above for precalciner kilns. As for the proposed kiln, this cost may be low because it is both larger and because it does not have the added cost

associated with a retrofit.

Therefore, I suggest that we use $120/scfm (or $107/scfm if using 2005 dollars ) as the capital cost for a wet scrubber. So, the following equation should be used for capital

cost:

1 Bahner, Icenhour, Lany, Barnett, Summary of Environmental and Cost Impacts of Proposed Revisions to Portland Cement New Source Performance Standards (40CFR Part 60, subpart F), Docket Number EPA

HQ

- OAR

- 2007

- 0877Andover Technology Partners Page 4 CC (2007$ ) = 120 * DSCFM E.3a CC (2005$) = 107 * DSCFM E.3b

Since, DSCFM is directly proportional to the kiln size, you could alternatively make capital cost directly related to kiln size using equations E.1 and E.2. Equations E.3a and

E.3b should be used in lieu of equation E.30 of my original memo on the capital cost of

scrubbers.

Operating costs of wet scrubbers

The PCA comments to the NESHAP show total annual costs that in two of the four cases

are ov er half of the capital cost, in one case are about a third of the capital cost and in another case are over one fourth of the capital cost. Since PCA did not outline the assumptions regarding capital recovery or SO 2 content, both of which are important factors in estimating annual costs, it is not possib le to fully evaluate these costs. However, in two of the four cases several million dollars a year are claimed to be necessary for natural gas , presumably to reheat the gas. My opinion is that this natural gas should not be necessary. Wet scrubbers don’t require r eheating of the gas because normally a new chimney is installed with a wet scrubber that is capable of handling the

moisture

- laden exhaust gas

– at least that has been the experience with hundreds of wet scrubbers used in the power industry

. In the past the exhaust from the wet scrubbers was reheated. However, this was before companies realized that it was far better to install a

new stack that could handle the wet gas than use so much natural gas

.

Alternatively, it m ay be possible that these facilities are also including RTO’s for VOC control and they have mistakenly included natural gas in the scrubber cost. But, in any

event, natu ral gas is not needed for a wet scrubber.

Therefore, it is my opinion that the variable and fixed operating cost equations s hould be maintained as they were, except as follows:

**•** Because the gas flowrate calculations have changed, the water usage should change as well. Since the estimated SCFM have roughly doubled from the previous memo, the estimate of water usage should increase from 30 gallons per ton of clinker to 60 gallons per ton of clinker and cost increased to about $0.025 per ton of clinker.

**•** For equation E.33 of my previous memo that is used to estimate the fan power usage, substitute 100,000 for EGFW and also substitute 0.90 for 0.85 (90% capacity factor) , making it Shaft kW= (TPY CLINKER /(8760*0.90)) * 100,000 * 5.8 (10) - 5

=7.36E

- 4 * TPY CLINK ER E.33

**•** Because chlorides cannot be readmitted to the kiln, there is a wast e stream
associated with this . The size of this stream would largely be determined by the

chloride levels in the fee d materials and fuel. I do not have typical data for

chloride s or what is involved in disposing of them (chlorides were not with in the scope of my analysis) ; but, the people working on the NESHAP might have thatAndover Technology Partners Page 5 information. The cost to l andfill dry, inert material, such as coal ash, will vary by location, but from my recollection is on average about $10/ton. I do n ot know

what form the chlorides would be in or i f landfill would be appropriate or if there

is a beneficial use for them.

Summary

Upon review of reported data I determined that the information used to estimate kiln exhaust gas flow underestimates stack gas flow. This is because of other equipment that exists at the cement plant that dilutes the kiln exhaust, increasing total volume flow. A means of estimating the total stack flow was developed from actual plant data and provided.

Until there are some m ore scrubbers built and data more available, there will be some uncertainty in the capital cost of scrubbers. Nevertheless, a cost estimating equation was developed and this is consistent with much of the data that is available; however, some

data suggests higher costs and some much lower costs.

Based upon my revi ew of operating cost estimates and the aforementioned changes to gas flowrate estimates, I recommended changes to some of the operating cost equations

. Finally, I have come to learn that th e industry generally assumes a capacity factor of 90% when relating daily or hourly capacity to annual capacity rather than 85%, which is what I assumed when I wrote my original memo. This w ill have a small effect on a number of the equations developed i n the original memo

. T he effect will, in general

, result in slightly more conservative results (higher costs or flows). I will take a look at the memo and let you know what equations might need to be changed.Andover Technology Partners Page 6 Appendix List of Terms

Term Definition

DSCFM

TPDCLINKER

TPYCLINKER is the stack flowrate of the kiln in dscfm is the capacity of the kiln in short tons per day is the capacity of the kiln in short tons per year