United States Environmental Protection Agency National Risk Management Research Laboratory Cincinnati, OH 45268 Research and Development EPA/600/SR-01/087 January 2002 Cost of Catalytic Reduction (SCR) Application for NO Control on Coal-fired Boifers Wojciech Jozewicz The report provides a methodology for estimating budgetary costs associ- ated with retrofit applications of selec- tive catalytic reduction (SCR) technology on coal-fired boilers. SCR is a post- combustion nitrogen oxides (NOX) con- trol technology capable of providing NOX reductions >90%. With SCR, NOX reduc- tions are achieved by injecting ammo- nia into the flue gas, which then passes through layers of catalyst in a reactor. The ammonia and NOX react on the sur- face of the catalyst, forming nitrogen and water. In the U.S., SCR has been applied mainly to electrical utility boil- ers firing coal and natural gas and tang- ing in capacity from 25 to 800 MW. The costing methodology presented in the report is applicable to SCR retro- fits on coal-fired boilers tanging in ca- pacity from 100 to about 850 MW and with design efficiencies of 80-95% NOX removal. The cost equations and vari- ables used in the methodology are based on information obtained from SCR system suppliers and reflect ex- perience gained from >200 SCR appli- cations. Note, however, that the budgetary cost estimates for typical SCR applications that this methodology provides cannot replace the detailed site-specific engineering cost studies or cost quotations that are developed by SCR system suppliers. This Project Summary was developed by the National Risk Management Re- search Laboratory's Air Pollution Pre- vention and Control Division, Research Triangle Park, NC, to announce key find- ings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). Background Selective catalytic reduction (SCR) is a postcombustion nitrogen oxides (NOX) control technology capable of providing NOX reductions >90%. With SCR, NOX reductions are achieved by injecting am- monia into the flue gas, which then passes through layers of catalyst in a reactor. The ammonia and NOX react on the sur- face of the catalyst, forming molecular nitrogen (N2) and water. In the U.S., SCR has been applied mainly to electric utility boilers firing coal and natural gas. The report provides algorithms for esti- mating costs and performance of generic SCR retrofit applications on coal-fired boilers. Specifically, the algorithms are applicable to SCR systems with design efficiencies of 80-95% NOX removal that can operate on coal-fired boilers ranging in size from approximately 100 to 850 MW. The cost equations and variables are based on industrial experience gained from >200 SCR applications. Note that the algorithms presented in this work are not meant to replace the detailed engi- neering studies or cost quotations that are developed by system suppliers, nor should these algorithms be used to de- termine detailed site-specific costs for ret- rofit SCR applications. The Costing Algorithms SCR budgetary costing algorithms for capital as well as fixed and variable op- erating and maintenance (O&M) costs (in January 2000 dollars) are given below. ------- The capital cost, D ($/kW), of an SCR retrofit application is estimated using Equation (1): D = 75 {300,000 Z/A}035 (1) where: Z = [(B/1.5)° °5(C/100)°4] and D = capital cost ($/kW) 75 = capital cost ($/kW) associated with a typical SCR retrofit on a 300,000 kW coal-fired unit 300,000 = reference to a 300,000 kW baseline unit (basis for the economy- of-scale adjustment in the equation) B = NOX (lb/106 Btu) at the inlet of the SCR reactor; range of approximately 0.15-2.5 lb/106 Btu 0.05 = exponent for inlet NOX concentra- tion C = NOX removal efficiency (%); range of 80-95% 0.4 = exponent for NOX removal efficiency A = plant capacity (kW); range of approxi- mately 100,000-850,000 kW 0.35 = exponent for an economy-of-scale adjustment factor (scaled from a 300,000 kW unit) The complexity of an SCR system design is dependent on the plant layout. For ex- ample, a relatively constrained plant lay- out may involve a more difficult SCR system design compared to a relatively uncon- strained layout and, therefore, may require more ductwork and air heater modifica- tions. In contrast, a relatively uncon- strained layout may not need air heater modifications and more than the typical amount of ductwork. To account for vary- ing levels of design complexity, a degree of difficulty is associated with an SCR retrofit application. In this context, the av- erage degree of difficulty is assigned to a retrofit where the SCR installation is rela- tively simple (i.e., the facility has adequate space for the SCR system). Equation (1) assumes this average degree of difficulty. The fixed O&M cost, E ($/yr), is as- sumed to be 0.66% of the capital cost and is estimated using Equation (2): E = D«A«C (2)D where: D E = fixed O&M cost ($/yr)D D = capital cost ($/kW) from Equation (1)D A = plant capacity (kW); range of approxi-D mately 100,000-850,000 kW C = a constant; 0.0066 yr1 The variable O&M cost, F ($/yr), is esti- mated using Equation (3): F = G {225«[0.37B«H«(C/100)« (8760/2000)]«1.005«1.05 + 0.025. D.A.Z+ 1.45.A} (3) where: F = variable O&M cost ($/yr) G = annual capacity factor (expressed as a fraction) B = inlet NOX (lb/106 Btu); range of 0.15- 2.5 lb/106 Btu H = heat input (106Btu/hr) C = NOX removal efficiency (%); range of 80-95% D = capital cost ($/kW) A = plant capacity (kW); range of approxi- mately 100,000-850,000 kW Validation of the Costing Algorithms The costing methodology presented above was derived from information pro- vided by SCR system suppliers and is deemed valid for typical coal-fired SCR retrofit applications for NOX removal effi- ciencies in the range of 80-95%. Note, however, that this methodology is in- tended and valid for developing budget- ary cost estimates and assumes typical installations. Therefore, the methodology should not be expected to account for reported costs of each site-specific SCR retrofit application. In a 1998 study conducted for North- east States for Coordinated Air Use Man- agement (NESCAUM) and Mid-Atlantic Regional Air Management Association (MARAMA), the capital cost for SCR ret- rofit on dry-bottom wall- and tangentially fired boilers to achieve 85% NOV reduc- tion was estimated to be 70-90 $/kW. Simi- larly, the study estimated that the capital cost of SCR retrofits to achieve 90% NOX reduction from wet-bottom boilers would also be 70-90 $/kW. Note that these esti- mates were based on 330 MW units. In comparison, the costing methodology re- sults in an estimate of approximately 70 $/kW for similar units. Recent literature reflects a range of 55- 140 $/kW as being typical of site-specific retrofit SCR capital costs for all types of utility boilers. By comparison, the costing methodology estimates a capital cost of approximately 50-110 $/kW to achieve 85-95% NOX removal efficiency. The NESCAUM/MARAMA report esti- mated a combined fixed and variable O&M cost of reducing NOX by 70-80% for a 330 MW dry-bottom boiler at approxi- mately $1.1 million/yr and approximately $2.8 million/yr for a similar-sized wet-bot- tom boiler. The costing methodology esti- mates the combined fixed and variable O&M costs for all boiler types to be about $1.0 to 1.7 million/yr for 85% NOX re- moval. In another economic analysis of SCR retrofits on 300 and 500 MW boilers to reduce NOX by 80-85%, combined O&M costs were estimated to be $1.6-3.2 million/yr. Based on the above comparisons, the capital and O&M cost estimates derived from applying this methodology are deemed reasonably accurate and fall well within the ranges reported elsewhere. Actual cost reported from site-specific SCR retrofit applications, as well as indi- vidual facility engineering studies, would more accurately reflect the circumstances of individual facilities. As a result, it is also reasonable to expect that reported actual costs may not always conform to budgetary cost estimates that have been designed around typical installations. While the methodology has been shown to consistently estimate costs that fit well with other reported actual and estimated costs, occasionally it can be expected that there will be data with higher or lower costs. ------- Wojciech Jozewicz is with ARCADIS Geraghty & Miller, Inc., Research Triangle Park, NC 27709. Ravi K. Srivastava is the EPA Project Officer (see below). The complete report, entitled "Cost of Selective Catalytic Reduction (SCR) Appli- cation for NOX Control on Coal-Fired Boilers," will be available at http:// www.epa.gov/ORD/NRMRLyPubs/600R01087/600R01087all.pdf. It will also be available from NTIS (Order No. PB2002-100499; Cost: $23.00, subject to change) at the following address: National Technical Information ServiceO 5285 Port Royal RoadD Springfield, VA 22161-0001D Telephone: (703) 605-60000 (800) 553-6847 (U.S. only) The EPA Project Officer can be contacted at: Air Pollution Prevention and Control Division National Risk Management Research Laboratory U. S. Environmental Protection Agency Research Triangle Park, NC 27711-0001 United StatesD Environmental Protection Agency D CenterforEnvironmental Research InformationD Cincinnati, OH 45268D PRESORTED STANDARDD POSTAGES FEES PAIDD EPAD PERMIT No. G-35D Official Business Penalty for Private Use $300 EPA/600/SR-01/087 ------- |