## METHODOLOGY, ASSUMPTIONS, AND REFERENCES PRELIMINARY NOx CONTROLS COST ESTIMATES FOR INDUSTRIAL BOILERS

By Sikander Khan Environmental Engineer, U.S. EPA

OCTOBER-NOVEMBER 2003Preliminary NOx Controls Cost Estimates

2 

### PRELIMINARY COST ESTIMATES FOR NOx CONTROLS INDUSTRIAL BOILERS

1.0 METHODOLOGY

The cost estimates covered in this report were developed as part of the investigations conducted for the proposed Interstate Air Quality Rule (IAQR) for industrial boilers. These costs are preliminary and are being reviewed further by the EPA.

The costs were developed for three boiler sizes, with heat inputs of 100, 250, and 1,000 MMBtu/hr. The following NOx control technologies were included in these estimates for coal-, natural gas-, and oil-fired boilers (except as noted below):

Low-NOx burner (LNB) Overfire air (OFA) Gas recirculation (GR) (only for gas- and oil-fired boilers) SCR SNCR

It is to be noted that the purpose of this evaluation was to develop cost information for a large range of industrial boiler sizes and associated NOx control technologies. The decision on the use of this information in the proposed IAQR will be made as part of the Rule itself.

The methodology can be divided into two major activities: 1) Developing design basis for each NOx control system and determining its operating impacts on the boiler performance and 2) determining capital and operating costs associated with retrofitting the NOx control system. These two activities, along with the associated assumptions and references, are described below.

2.0 DESIGN BASIS AND PERFORMANCE IMPACTS

Combustion and boiler efficiency calculations were performed using standard procedures (1,2) , for the three boiler sizes of 100, 250, and 1,000 MMBtu/hr. Tables 1 and 2 summarize the key data determined from these calculations for the three boilers firing coal, oil, and gas. In addition, the average uncontrolled, baseline NOx levels for these boilers were established as follows (see Attachments 1 and 2):

1. Coal-fired boilers (bituminous and sub-bituminous coals): 0.72 lb/MMBtu 2. Gas-fired boilers: 0.25 lb/MMBtu 3. Oil-fired boilers: 0.22 lb/MMBtu

The above NOx levels are mainly based on the ICI database. Based on a further clarification provided by ICF (3) , the NOx levels provided in Attachment 1 for oil firing doPreliminary NOx Controls Cost Estimates

3 not represent the maximum levels reported in the ICI database. Therefore, the costs were calculated for two additional baseline NOx levels of 0.36 and 0.5 lb/MMBtu. ICF indicated that these costs would be applied selectively to the oil-fired boilers with the reported baseline levels around these two high values.

The above information was used to determine the NOx reduction levels and the boiler performance impacts, as described below separately for each type of control technology:

2.1 LNB, OFA, and GR

The NOx reduction levels achievable with LNB, OFA, and GR technologies for different fuels are summarized in Table 3, along with the supporting references. The following assumptions and criteria were used to establish the impacts of these technologies on the plant performance:

1. With the use of OFA on coal firing, the unburned carbon level at the boiler outlet increases by 50 percent. This increase in the unburned carbon level reduces the boiler efficiency and results in an increased coal consumption and auxiliary power consumption associated with the draft fans.

2. The GR systems for the gas- and oil-fired boilers are designed for a recirculation rate of 20 percent. For full-load operation, a gas recirculation rate of 15 percent is used to estimate the fan power consumption requirement.

3. LNB and OFA do not result in a change in the gas- and oil-fired boiler efficiencies. In general, the gas recirculation does not have a substantial impact on the heat transfer within the boiler and the original steam temperatures can be maintained. It is recognized that some boiler would require modification of the heating surfaces for these temperatures.

The plant performance impacts associated with the use of LNB, OFA, and GR are summarized in Table 4. These impacts were used for the estimation of operating resulting from the use of these technologies.

2.2 SCR

The SCR technology is considered applicable to all three fuel (coal, gas, and oil) applications. A conservative NOx reduction effectiveness of 80 percent was selected for this estimating effort. The following assumptions and criteria were used to establish the SCR design parameters and the impacts on the plant performance:

1. The methodology described in Attachment 5 was used to estimate the catalyst volumes for various boiler applications. The space velocities (1/hr) used were 3,750 for coal, 16,800 for gas, and 11,800 for oil. The ammonia slip levels used were 5 ppm for coal and oil and 10 ppm for gas.Preliminary NOx Controls Cost Estimates

4 2. The reagent was assumed to be anhydrous ammonia with electrical heating for vaporization.

3. The pressure drop through the SCR reactor and additional ductwork was assumed to be 6 in. wt.

4. Catalyst replacement requirement was based on a very conservative assumption of 1/3 rd of the catalyst being replaced every year. There is substantial industry information available that the average catalyst life span, especially with catalyst management schemes, is substantially more than the 3 years assumed for these estimates (see Attachment 6).

The above assumptions were used to determine the impacts of the use of SCR on plant performance, which are summarized in Table 5.

2.3 SNCR

The cost estimates have been developed for SNCR systems for all three fuel applications. However, it is recognized that SNCR technology may not, in general, be effective for small, shop-assembled gas- and oil-fired boilers (the physical constraints associated with such boilers may not permit proper location of the SNCR reagent injection nozzles).

The SNCR system design and boiler performance impacts have been estimated, based on the methodology provided in an EPRI report (4) . Additional assumptions and criteria used are as follows:

1. A NOx reduction effectiveness of 40 percent was used for all boiler cases. Attachment 7 lists information on many SNCR installations, especially for the smaller boiler sizes, which supports the 40 percent effectiveness level selected for this study.

2. The reagent was assumed to be urea.

3. Because of the injection of water within the boiler, as part of the SNCR process, there will be a reduction in boiler efficiency. This reduction will result in increased fuel consumption and ash generation, as applicable (4)

. Table 6 summarizes the plant performance impacts resulting from the use of SNCR.

3.0 CAPITAL AND LEVELIZED COSTS

The capital costs ($/MMBtu/hr) for the application of the NOx control technologies for various boiler sizes included in this evaluation were based on recent industry data (5) and Attachments 3 and 5. In general, these costs were identified for one boiler size and then scaling factors were used to project these costs for other boiler sizes. The costs are based on 1999 dollars.Preliminary NOx Controls Cost Estimates

5 The levelized costs ($/ton of NOx removed) were calculated using the estimates of the capital costs and increased consumable rates associated with each technology, as shown in Tables 4 through 7. The economic factors used in these calculations (5-9) were as follows:

Anhydrous ammonia, $/ton 260 Urea, $/gal 0.95 Water, $/gal 0.0006 Bituminous coal, $/MMBtu 1.45 Sub-bituminous coal, $/MMBtu 1.20 Oil, $/MMBtu 3.5 Gas, $/MMBtu 5.0 Power, mills/kwh 25.0 Solid waste disposal, $/ton 12 Operator cost, $/hr 30 SCR catalyst, $/cu. ft. 396 Useful life, years 30 Carrying charges, % 12.00 Levelization factor 1.0 Maintenance cost (% of capital cost) 1.5

A US Department of Commerce, Bureau of Economic Analysis (10) , price index was used to adjust cost basis from one year to another. The levelized costs for various technology retrofits are presented in Table 8.

3.1 Sensitivity Cases

Two sensitivity cases were evaluated to see the effect of changes in the study assumptions on the technology costs: 1) increased cost of power from 25 mills/kwh to 50 mills/kwh and 2) an increase of 25 percent in the SCR capital cost. Only a few retrofit options were evaluated to see the impact of these changes – the impact on other options will be similar. Table 9 presents the results. A comparison of Table 9 and corresponding values in Table 8 shows that:

1. Increase in the cost of power has virtually no impact on the LNB/OFA option, since the increase in power consumption for this option is quite small.

2. Increase in the cost of power has a relatively small impact on the SCR option. This impact ranges from approximately 0.8 to 6.8 percent of the total cost in $/ton of NOx removed.

3. Increase in the capital cost of SCR results in an increase of approximately 13 to 19 percent in the total cost in $/ton of NOx removed. It is to be noted that, with a 25 percent increase in capital cost, the levelized cost remains around $2000 per ton of NOx removed for boilers 250 MMBtu/hr and larger, with a capacity factor of 50 percent or higher.Preliminary NOx Controls Cost Estimates

6 5.0 REFERENCES

1. “Steam Its Generation and Use,” Babcock and Wilcox, 40 th Edition

2. “Power Test Code – Steam Generating Units,” ASME PTC 4.1, 1991

3. “Personal Call from S. Khan of EPA to B. Galef of ICF,” 9/29/03

4. “SNCR Feasibility and Economic Evaluation Guidelines for Fossil-Fired Utility Boilers,” EPRI TR-103885, May 1994

5. “Status Report on NOx Controls for Gas Turbines/Cement Kilns/Industrial Boilers/Internal Combustion Engines, Technologies & Cost Effectiveness,” NESCAUM, December 2000

6. “Coal Utility Environmental Cost (CUECost) Workbook User’s Manual, Version 1.0,” EPA-600/R-99-056 (NTIS PB99-151938), June 1999

7. “EPA Modeling Application Using The Integrated Planning Model,”, http://www.epa.gov/airmarkets/epa-ipm/index.html
8. “Annual Energy Review 2000,” DOE, http://www.eia.doe.gov/aer/aerpdf.html
9. “Electric Power Monthly September 2003,” DOE, http://www.eia.doe.gov/cneaf/electricity/epm/epm.pdf
10. “Implicit Price Deflator,” Table 7.3. Quantity and Price Indexes, http://www.bea.doc.gov/bea/dn/nipaweb/TableViewFixed.aspPreliminary NOx Controls Cost Estimates

7 TABLE 1 COMBUSTION CALCULATIONS- COAL-FIRED BOILERS

Bituminous Coal Sub-Bituminous Coal Parameter Boiler –100 MMBtu/hr Boiler –250 MMBtu/hr Boiler – 1000 MMBtu/hr Boiler –100 MMBtu/hr Boiler –250 MMBtu/hr Boiler – 1000 MMBtu/hr Fuel carbon, wt. % 67.94 67.94 67.94 42.22 42.22 42.22 Fuel ash, wt. % 12.71 12.71 12.71 7.41 7.41 7.41 Fuel sulfur, wt. % 3.43 3.43 3.43 0.73 0.73 0.73 Fuel heating value, Btu/lb 11922 11922 11922 7090 7090 7090

Steam flow, lb/hr 86455 205750 822978 81680 194500 777500 Steam temp., F 460 600 600 460 600 600 Unburned carbon, % 0.5 0.5 0.5 0.5 0.5 0.5 Stack gas temp., F 330 330 330 280 280 280 Boiler efficiency, % 87.798 88.028 88.098 82.981 83.211 83.281 Fuel use, lb/hr 8424 21005 83955 14160 35324 141086 Flue gas temp. at boiler outlet, F 685 685 685 650 650 650

Flue gas from combustion, lb/hr 99,500 248,130 991,730 104,810 261,200 1.101,660

TABLE 2 COMBUSTION CALCULATIONS- GAS- & OIL-RED BOILERS

Natural Gas Oil Parameter Boiler –100 MMBtu/hr Boiler –250 MMBtu/hr Boiler – 1000 MMBtu/hr Boiler –100 MMBtu/hr Boiler –250 MMBtu/hr Boiler – 1000 MMBtu/hr Fuel ash, wt. % NA NA NA 0.06 0.06 0.06 Fuel sulfur, wt. % NA NA NA 0.99 0.99 0.99 Fuel heating value, Btu/lb 22548 22548 22548 18268 18268 18268

Steam flow, lb/hr 79580 189900 797410 81930 196190 824460 Steam temp., F 460 600 600 460 600 600 Stack gas temp., F 480 480 250 480 480 345 Boiler efficiency, % 81.131 81.361 85.439 83.554 84.081 88.338 Fuel use, lb/hr 4437 11091 44349 5475 13685 54740 Flue gas temp. at boiler outlet, F 650 650 650 650 650 650

Flue gas from combustion, lb/hr 78,840 197,080 788,060 93,422 233,530 934,100Preliminary NOx Controls Cost Estimates

8 TABLE 3 NOx REDUCITON CAPABILITIES OF VARIOUS TECHNOLOGIES

NOx Level At Boiler Outlet, lb/MMBtu Boiler Fuel LNB LNB/OFA LNB/OFA/GR Bituminous coal (1) 0.45 0.35 NA Sub-bituminous coal (1) 0.35 0.25 NA Natural gas (2) See note 0.1 0.05 Oil (0.36 lb/MMBtu) (3) NA NA 0.25 Oil (0.5 lb/MMBtu) (2) See note 0.35 0.25

Notes

1. The NOx levels achievable for bituminous and sub-bituminous coals are based on information provided in Attachments 3 and 4, which takes into account the limitations caused by the relatively smaller sizes of the industrial boilers compared to the utility boilers. Also, gas recirculation technology is not considered applicable to coal-fired boilers.

2. It is recognized that some of the smaller boilers (especially the shop-built boilers) may not have space to add OFA. The NOx reduction capability is conservatively selected for the gas- and oil-fired boilers, so that the boilers, which cannot be retrofitted with OFA, would still, on an average, be able to achieve the NOx level listed for the LNB/OFA.

3. For oil firing with the baseline emission of 0.36 lb/MMBtu, the LNB and LNB/OFA technologies may not provide significant NOx reduction.Preliminary NOx Controls Cost Estimates

9 TABLE 4 BOILER PERFORMANCE IMPACTS OF LNB, OFA, AND GR

Technology Boiler Size MMBtu/hr Reduction in Boiler Efficiency % Increased Auxiliary

Power

kW Increased Fuel Use

lb/hr Increased Ash Generation lb/hr 100 0.23 0.5 19 20

250 0.23 1.0 48 51 LNB/OFA on bituminous coal

1000 0.23 4.5 193 204

100 0.23 0.5 33 20

250 0.23 1.0 81 51LNB/OFA on subbituminous coal

1000 0.23 4.5 325 203

100 NA 18 NA NA

250 NA 45 NA NA LNB/OFA/GR on
gas

1000 NA 159 NA NA

100 NA 21 NA NA

250 NA 52 NA NA LNB/OFA/GR on oil

1000 NA 197 NA NAPreliminary NOx Controls Cost Estimates

10 TABLE 5 BOILER PERFORMANCE IMPACTS OF SCR

Fuel Boiler Size MMBtu/hr Anhydrous Ammonia Use lb/hr Increased Auxiliary

Power

kW Catalyst Replacement Ft 3 /yr

100 20 72 138

250 49 184 345 Coal

1000 195 691 1380

100 9 65 21

250 21 140 58 Gas

1000 83 425 247

100 15 67 39

250 38 144 97 Oil, 0.5 lb/MMBtu Inlet NOx

1000 150 538 387

100 11 62 42

250 27 131 102 Oil, 0.36 lb/MMBtu Inlet NOx

1000 109 488 406Preliminary NOx Controls Cost Estimates

11 TABLE 6 BOILER PERFORMANCE IMPACTS OF SNCR

Technology Boiler Size MMBtu/hr Reduction in Boiler Efficiency % Urea Use gph Water Use
gpm Increased Fuel Use

lb/hr (1) Increased Auxiliary

Power

kW Increased Ash Generation lb/hr 100 0.48 13 3 40 3 5

250 0.48 34 7 100 6 13 Coal

1000 0.48 134 29 399 26 52

100 0.18 5 1 169 0.4 NA

250 0.18 13 3 423 3 NA Gas

1000 0.18 52 11 1776 10 NA

100 0.37 10 2 19 1 0.14

250 0.35 26 6 48 5 0.34 Oil, 0.5 lb/MMBtu Inlet NOx

1000 0.35 103 22 202 19 1.43

100 0.27 7 2 14 1 0.1

250 0.26 19 4 35 5 0.25 Oil, 0.36 lb/MMBtu Inlet NOx

1000 0.25 74 16 145 14 1.1

Notes

1. The fuel use is expressed in lb/hr for coal and oil and scf/hr for gas.Preliminary NOx Controls Cost Estimates

12 TABLE 7 CAPITAL COSTS FOR NOx CONTROL TECHNOLOGY APPLICATIONS

Capital Costs, NOx Control Retrofits $/MMBtu/hr Technology Fuel

Boiler Size 100 MMBtu/hr Boiler Size 250 MMBtu/hr Boiler Size 1000 MMBtu/hr LNB Coal (bit. and sub-bit.) 5097 3872 2554

LNB/OFA Coal (bit. and sub-bit.) 7281 5531 3649

LNB/OFA Gas 2554 1940 1280

LNB/OFA/GR Gas 3991 3031 2000

LNB/OFA Oil 2554 1940 1280

LNB/OFA/GR Oil 3991 3031 2000

SCR Coal 14562 11062 7298

SCR Gas 8009 6084 4014

SCR Oil 11067 8407 5547

SNCR Coal 5266 4000 2639

SNCR Gas 4212 3200 2111

SNCR Oil 4081 3100 2045

Notes

1. The cost for each technology was established based on recent industry data (5) and Attachment 3.

2. A scaling factor of 0.3 was used to project costs for different boiler sizes.Preliminary NOx Controls Cost Estimates

13 TABLE 8 NOx Technology Retrofit Costs COAL-, GAS- & OIL-FIRED INDUSTRIAL BOILERS

Fuel Technology N Ox Reductio n % Capacity Factor % $/Ton of Pollutant

1000 MMBtu/hr 250 MMBtu/hr 100 MMBtu/hr

Coal LNB, sub-bituminous 51 14 1520 2304 3033 50 426 645 849 83 256 389 512

Coal LNB/OFA, sub-bituminous 65 14 1727 2608 3428 50 496 743 972 83 306 454 593

Coal LNB/OFA, bituminous 51 14 2197 3317 4358 50 634 947 1239 83 392 581 757

Coal SCR 80 14 4481 5924 7262 50 1359 1766 2141 83 876 1123 1349

Coal SNCR 40 14 2962 4015 4970 50 1510 1814 2073 83 1285 1473 1625

Gas LNB/OFA 60 5 5260 7973 10521 50 526 797 1052 94 280 424 559

Gas LNB/OFA/GR 80 5 6204 9415 12374 50 656 981 1278 94 368 543 700

Gas SCR 80 5 14815 21095 26859 50 1670 2330 2933 94 986 1354 1689

Gas SNCR 40 5 14,165 20,870 27,105 50 2,452 3,116 3,735 94 1,842 2,193 2,521

Oil LNB/OFA (0.5 lb/MMBtu 30 10 2630 3986 5260 inlet NOx) 50 526 797 1052 86 306 464 612

Oil LNB/OFA/GR (0.5 lb/MMBtu 50 10 2505 3790 4973 inlet NOx) 50 533 791 1028 86 326 477 615

Oil LNB/OFA/GR (0.36 lb/MMBtu 30 10 5694 8613 11303 inlet NOx) 50 1210 1798 2337 86 741 1085 1399

Oil SCR (0.36 lb/MMBtu inlet NOx) 80 5 14,601 20,113 25,838 50 1,622 2,178 2,767 86 1,017 1,343 1,694

Oil SCR (0.5 lb/MMBtu inlet NOx) 80 5 10,458 14,443 18,544 50 1,191 1,595 2,014 86 760 997 1,245

Oil SNCR (0.5 lb/MMBtu inlet 40 10 4271 5892 7399 NOx) 50 1749 2070 2367 86 1485 1670 1840

Oil SNCR (0.36 lb/MMBtu inlet 40 10 5497 7753 9842 NOx) 50 1995 2444 2853 86 1628 1889 2123Preliminary NOx Controls Cost Estimates

14 TABLE 9 COST SENSITIVIY EVALUATIONS – NOx TECHNOLOGIES

$/ton of NOx Fuel Technology Sensitivity Parameter (1) NOx Reduction % Capacity Factor

% 1000 MMBtu/hr 250 MMBtu/hr 100 MMBtu/hr Coal LNB/OFA, bituminous Increased power cost 51 14 50 83 2198 635 393 3318 948 582 4359 1240 758

Coal SCR Increased power cost 80 14 50 83 4541 1418 936 5988 1830 1187 7325 2203 1412

Coal SCR Increased capital cost 80 14 50 83 5179 1554 994 6981 2062 1301 8653 2531 1584

NOTES

1. Two sensitivity parameters were evaluation: 1) increased power cost from 25 mills/kwh to 50 mills/kwh and 2) an increase of 25 percent in the SCR capital cost.