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HWF NOTES©


Gossman Consulting, Inc.                     June, 1993
THE CLEAN AIR ACT AND CEMENT KILN NOX EMISSIONS

Ron Gossman

All cement kilns that burn or plan to burn waste derived fuels are now under firm EPA control under the Boiler and Industrial Furnace regulation, 40CFR 266. So what is next? Well, it seems that the EPA is out to make life miserable for all cement kilns, not just those that burn waste derived fuels. The office of Air and Radiation, Office of Air Quality Planning and Standards released a February, 1993 DRAFT report on Alternative Control Techniques Document - Control of NOx Emissions from Cement Manufacturing. The following is quoted from Chapter 1 of that document.

"Congress, in the Clean Air Act Amendments of 1990 (CAAA), amended Title I of the Clean Air Act (CAA) to address ozone non-attainment areas. A new subpart 2 was added to Part D of Section 103. Section 183(c) of the new Subpart 2 provides that:

[w]ithin three years after the date of the enactment of the [CAAA], the administrator shall issue technical documents which identify alternate controls for all categories of stationary sources of...oxides of nitrogen which emit, or have the potential to emit 25 tons per year or more of such air pollutant.

This alternative control technique (ACT) document provides technical information for use by state and local agencies to develop and implement regulatory programs to control (NOx) emissions from cement kilns."

WHO IS AFFECTED? The EPA stated that cement kilns are a stationary source that emit more than 25 tons of NOx per year. The document went into a great deal of detail describing various cement kilns, processes and variations thereto. In the end, they were categorized into four types: long wet kiln, long dry kiln, preheater kiln, and precalciner kiln.

WHAT IS THE ALLEGED PROBLEM? This may be a facetious question since there is no doubt that a cement kiln does emit a great deal of NOx. However, the EPA presents "conclusive" data, which could cause a flammable response by state and local officials as goaded by radical environmentalists, without any reasonable justification.

First, the EPA presented data from a 1982 Portland Cement Association survey of NOx emissions from 24 different kilns. The average results for the long wet kiln was 4.97 lb/ton of clinker. For the long preheater kiln, the average was 2.98. For the precalciner kiln, the average was 3.86.

Second, the EPA combined data from a German report published in 1987 with data from 18 kilns in several other countries. (This later data is from a secondary source.) The average results for the long wet kiln was 4.07 lb/ton of clinker. For the preheater kiln, the average was 3.13. For the precalciner kiln, the average was 3.77.

Third, the EPA presented data collected by the Portland Cement Association and utilized in the revision of the AP-42 Air Pollution Emission Factors published in September, 1991. This data concluded that the long wet kiln average was 8.2 lb/ton of clinker. The long dry kiln average was 5.7. The preheater kiln average was 5.5, and the precalciner kiln was 4.8.

Fourth, during the preparation of this document, the EPA conducted their own survey. They said there were 48 kilns with data, but from the table one could count at least 53. There were possibly 61, since some locations listed multiple kilns but only one emission number. Some of the data points, could be identified as having been included in the previously cited study. The results of this survey concluded that the long wet kiln emission average was 9.7 lb/ton of clinker. The long dry kiln average was 8.6. The preheater kiln average was 5.9. Finally, the precalciner average was 3.4. It was these final survey results which were used in the balance of the document for performance and cost results. The results of the four different data packages are shown in Table 1.

PROPOSED SOLUTIONS. The document explored various techniques and process controls which can/may reduce NOx emissions. The process controls were covered in fair detail, but for the well run facility it is every day business as usual with not much of an improvement in emissions to be expected. The EPA proposed three different methods of NOx control through the use of technology.

The first was the use of a "low NOx burner" to facilitate staged combustion. The EPA referred to claims that such a burner can reduce emissions "by up to 30%". Later, they stated that the low NOx burner can achieve 20-30% emission reduction. The EPA then used 25% in their cost effectiveness calculations.

The second control technology proposed was "selective catalytic reduction" (SCR). This uses ammonia in the presence of a catalyst as a post combustion control of emissions. The EPA cited extensive use in Japan to achieve 90% emission reduction from fossil fuel-fired boilers. They also stated that the technology has been used for gas turbines and internal combustion engines in the United States. Because of fouling the catalyst in cement plants, the SCR would need to be installed after the particulate collection equipment and would thus require flue gas reheating. The EPA alleged that the SCR technology could achieve 80-90% emission reduction. They then used 80% in their cost effectiveness calculations.

The third control technology proposed was "selective non-catalytic reduction" (SNCR). This used ammonia or urea by injection into the kiln in the temperature zone of 1,600F to 2,000F. The EPA cited one experiment on a preheater/precalciner kiln which averaged 40% reduction. They also went on to say that they did not know if SNCR is commercially practical, but they did allege 60-80% emission reduction and then used 75% in their cost effectiveness calculations.

WHAT DOES IT COST? The EPA determined that there are currently three installations of low NOx burners in cement kilns in the United States. These apparently came from Procedair Industries. Using adjusted cost information, the EPA estimated capital costs to be between $149,999 and $215,000. The variance was determined to be a linear function based upon heat duty in MM BTU/hr. This varied depending upon kiln type, previously discussed, and capacity. The heat duty considered was from 113 MM BTU/hr to 300 MM BTU/hr at the burner. Table 2 is a summary of costs considering only lower capacity kilns of the four kiln types. 240,000 tons clinker/yr, 200,000 tons clinker/yr, 320,000 tons clinker/yr, and 800,000 tons clinker/yr respectively. For these four kiln types and capacities, the annual costs as shown in Table 2 varied from $38,000 to 45,000.

There are no SCR systems in cement plants in the United States today. Therefore, the EPA scaled costs based upon costs quoted for application on glass furnace exhaust gases. The capital costs varied from $1,330,000 for the small dry kiln to $3,330,000 for a large precalciner kiln. The annual operating cost varied from $927,000 to $2,190,000.

There are no SNCR systems in cement plants in the United States today. EPA obtained costs from Nalco Fueltech. The capital costs varied from $708,000 to $1,050,000. The annual costs varied from $461,000 to $665,000.

Oh say, can you see, which way this EPA technical guidance to state and local agencies is going? The burner technology is available. It is cheap, but it does not provide much improvement. The SCR technology is very expensive, but its improvement in emissions isn't as good as the data would indicate. The SNCR technology is just right. Capital costs under $1,000,000 and operating costs about $500,000. But, it may not be commercially practical. One experiment showed 40% emission reduction, but it really should be 75% by EPA edict.

The EPA then used all of the numbers it generated, (good, bad, or indifferent), to determine cost effectiveness in dollars per ton of NOX removed from the emissions. The only problem is, some how they conveniently reduced the SNCR annual costs by varying amounts from seven to ten thousand dollars. These costs per ton are shown in Table 3. Unfortunately, the EPA neglected to figure the cost per ton of clinker which is readily available and has also been included in Table 3.

Is this another case of driving an entire industry out of existence by regulating through the back door? Consider commenting on this draft report. The future if the U.S. cement industry could depend on it.

Table 1

Lbs of NOx Per Ton of Clinker



Kiln Type
Data Package
#1 #2 #3 #4

Long Wet Kiln

4.97

4.07

8.2

9.7

Long Dry Kiln

5.70

no data

5.7

8.6

Preheater Kiln

2.98

3.13

5.5

5.9

Precalciner Kiln

3.86

3.77

4.8

3.4

Table 2

Technology Costs

NOX Reduction

Technology

Burner SCR SNCR
Kiln Type Capitol Annual Capitol Annual Capitol Annual
Long Wet Kiln $172,000 $43,000 $1,720,000 $1,330,000 $718,000 $549,000
Long Dry Kiln $149,000 $38,000 $1,330,000 $927,000 $708,000 $461,000
Preheater Kiln $162,000 $41,000 $1,620,000 $1,180,000 $728,000 $492,000
Precalciner Kiln $179,000 $45,000 $2,610,000 $2,190,000 $1,010,000 $665,000

Table 3

Cost Effectiveness

NOX Reduction Technology Burner SCR SNCR
Kiln Type Emission Reduction

cost/ton

Cement Increase

cost/ton

Emission Reduction

cost/ton

Cement Increase

cost/ton

Emission Reduction

cost/ton

Cement Increase

cost/ton

Long Wet Kiln

$150 $0.18 $1,430 $5.54 $620 $2.25

Long Dry Kiln

$180 $0.19 $1,340 $4.64 $710 $2.25

Preheater Kiln

$180 $0.13 $1,570 $3.69 $730 $1.51

Precalciner Kiln

$130 $0.06 $2,010 $2.74 $680 $0.81