xvEPA TVA United States Environmental Protection Agency Industrial Environmental Research Laboratory Research Triangle Park NC 27711 EPA-600/7-80-050 March 1980 Tennessee Valley Authority Office of Power Energy Demonstrations and Technology Muscle Shoals Al 35660 EDT-112 Preliminary Economic Analysis of a Lime Spray Dryer FGD System Interagency Energy/Environment R&D Program Report ------- RESEARCH REPORTING SERIES Research reports of the Office of Research and Development, U.S. Environmental Protection Agency, have been grouped into nine series. These nine broad cate- gories were established to facilitate further development and application of en- vironmental technology. Elimination of traditional grouping was consciously planned to foster technology transfer and a maximum interface in related fields. The nine series are: 1. Environmental Health Effects Research 2. Environmental Protection Technology 3. Ecological Research 4. Environmental Monitoring 5. Socioeconomic Environmental Studies 6. Scientific and Technical Assessment Reports (STAR) 7. Interagency Energy-Environment Research and Development 8. "Special" Reports 9. Miscellaneous Reports This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT RESEARCH AND DEVELOPMENT series. Reports in this series result from the effort funded under the 17-agency Federal Energy/Environment Research and Development Program. These studies relate to EPA's mission to protect the public health and welfare from adverse effects of pollutants associated with energy sys- tems. The goal of the Program is to assure the rapid development of domestic energy supplies in an environmentally-compatible manner by providing the nec- essary environmental data and control technology. Investigations include analy- ses of the transport of energy-related pollutants and their health and ecological effects; assessments of, and development of, control technologies for energy systems; and integrated assessments of a wide range of energy-related environ- mental issues. EPA REVIEW NOTICE This report has been reviewed by the participating Federal Agencies, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Government, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. This document is available to the public through the National Technical Informa- tion Service, Springfield, Virginia 22161. ------- EPA-600/7-80-050 EDT-112 March 1980 Preliminary Economic Analysis of a Lime Spray Dryer FGD System by T.A. Burnett and W.E. O'Brien TVA Office of Power Division of Energy Demonstrations and Technology Muscle Shoals, Alabama 35660 Interagency Agreement No. D9-E721-BI Program Element No. INE827 EPA Project Officer: Theodore G. Brna Industrial Environmental Research Laboratory Office of Environmental Engineering and Technology Research Triangle Park, NC 27711 Prepared for U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Research and Development Washington, DC 20460 ------- DISCLAIMER This report was prepared by the Tennessee Valley Authority and has been reviewed by the Office of Environmental Engineering and Technology, U.S. Environmental Protection Agency, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Tennessee Valley Authority or the U.S. Environ- mental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. ii ------- ABSTRACT A preliminary economic analysis of two flue gas desulfurization (FGD) processes, one dry and one wet, were performed for a new 500-MW power plant burning western coal having 0.7% sulfur, 9.7% ash, and a heating value of 9,700 Btu/lb and meeting current new source performance standards (70% S02 removal and 0.03 Ib/MBtu particulate emission). The generic lime spray dryer process used a baghouse for particulate collection, while the wet limestone slurry process had an electrostatic precipitator (ESP) for particulate control. In addition to the coal noted, the final report will include an economic evaluation for both a low- and a high- sulfur eastern coal. Results of the preliminary analysis show that the capital investment costs for the generic lime spray dryer process for S02 and particulate removal are $132/kW while being $186/kW for the ESP-wet limestone slurry combination. First-year and levelized annual revenue requirements are 6.20 and 8.55 mills/kW, respectively, for the dry FGD process; 8.55 and 11.71 mills/kWh, respectively, for the wet process. Sensitivity analyses indicate (1) delivered raw material costs do not significantly affect the annual revenue requirements for either the wet or dry process, (2) annual revenue requirements for the spray dryer are insensitive to the raw material stoichiometry, and (3) waste disposal for the wet process even with fixation is still more expensive than for the generic lime spray dryer process. iii ------- CONTENTS Abstract iii Figures vii Tables viii Abbreviations and Conversion Factors ix Acknowledgements x Executive Summary xi Introduction 1 Conclusions 4 Recommendations 5 Design and Economic Premises 6 Design Premises 5 Emission Standards 6 Fuel 7 Power Plant Design 8 Power Plant Operation 8 Flue Gas Composition 8 Absorber Design 9 Reheat 10 Raw Materials 10 Waste Disposal 11 Economic Premises 11 Capital Costs H Capital Investment Estimates 14 Annual Revenue Requirements 17 Process Background and Description 19 Generic Lime Spray Dryer Process 19 Process Description 19 Analysis of Processing Subsections 23 Limestone Slurry Process 28 Process Description 28 Analysis of Processing Subsections 31 Economic Evaluation and Comparison 38 Accuracy of Estimates 38 Capital Investment 39 Generic Lime Spray Dryer Process 39 Limestone Slurry Process 41 v ------- Comparison 4^ Annual Revenue Requirements /- Generic Lime Spray Dryer Process 42 Limestone Slurry Process 45 Comparison ^c Sensitivity Analysis 47 Sensitivity to Raw Material Prices ^ Sensitivity to Raw Material Stoichiometry 49 Sensitivity to Waste Disposal Costs 49 References 52 vi ------- FIGURES Number S-l Generic lime spray dryer process. Block flow diagram . . . S-2 Limestone slurry process. Block flow diagram S-3 Sensitivity of the first-year annual revenue require- ments to the delivered cost of the raw material Xxi S-4 Sensitivity of the first-year annual revenue require- ments to the raw material stoichiometry in the absorber . . xxi 1 Generic lime spray dryer process. Flow diagram 20 2 Limestone slurry process. Flow diagram 29 3 Sensitivity of the first-year annual revenue require- ments to the delivered cost of the raw material 48 4 Sensitivity of the first-year annual revenue require- ments to the raw material stoichiometry in the absorber . . 48 vii ------- TABLES Number Page S-l Major Design Premises .. S-2 Base-Case Comparison of Capital Investments and Annual Revenue Requirements .. S-3 Summary of the Total Capital Investments .. S-4 Summary of First-Year Annual Revenue Requirements . 1 Contract Awards for Spray Dryer-Based FGD Systems ^ 2 Coal Composition and Flow Rate 3 Fly Ash Analysis 4 Base-Case Flue Gas Composition and Flow Rate 5 Design Conditions for Absorber System Calculations .... 1n 6 Levelized Annual Capital Charges for Regulated Utility Financing ., 7 Cost Indexes and Projections 8 Projected 1984 Unit Costs for Raw Materials, Labor, and Utilities 9 Generic Lime Spray Dryer Process Material Balance 2i 10 Generic Lime Spray Dryer Process Base-Case Equipment List, Description, and Cost 2, 11 Limestone Slurry Process Material Balance »_ 12 Limestone Slurry Process Base-Case Equipment List, Description, and Cost _? 13 Generic Lime Spray Dryer Process Total Capital Investment . 40 14 Limestone Slurry Process Total Capital Investment 42 15 Base-Case Total Direct Investments and Total Capital Investments ,, 16 Summary of the Total Capital Investments /- 17 Generic Lime Spray Dryer Process Annual Revenue Require- ments 44 18 Limestone Slurry Process Annual Revenue Requirements ... //: 19 Base-Case Total First-Year and Levelized Annual Revenue Requirements 20 Summary of the Total First-Year Revenue Requirements ... /7 21 Comparison of Total Capital Investment and First-Year Unit Revenue Requirements for the Generic Lime Spray Dryer Process at Various Raw Material Stoichiometries viii ------- ABBREVIATIONS AND CONVERSION FACTORS ABBREVIATIONS o aftj actual cubic feet kg Btu British thermal unit k& °C degrees Celsius kW dia diameter kWh ESP electrostatic precipitator lb °F degrees Fahrenheit k FD forced draft M FGD flue gas desulfurization min ft feet mol ft/sec feet per second MW g gram ppm gal gallon sft3 gpm gallons per minute sec gr grain vol hr hour wt ID induced draft yr in. inch kilogram kiloliter kilowatt kilowatthour pound thousand (kilo) million (mega) minute mole megawatt (electrical) parts per million (volume) standard cubic feet second volume weight year CONVERSION FACTORS To convert from English units acres British thermal units degrees Fahrenheit minus 32 feet square feet cubic feet cubic feet per minute gallons (U.S.) gallons per minute grains per cubic foot horsepower inches pounds (mass) pounds per cubic foot pounds (force) per square inch miles standard cubic feet per minute (60°F) tons (short)3 To metric units hectares kilocalories degrees Celsius centimeters square meters cubic meters cubic meters per second liters liters per second grams per cubic meter kilowatts centimeters kilograms kilograms per cubic meter Pascals (Newton per square meter) meters normal cubic meters per hour (0°C) metric tons Multiply by 0.405 0.252 0.5556 30.48 0.0929 0.02832 0.000472 3.785 0.06308 2.288 0.746 2.54 0.4536 16.02 6895 1609 1.6077 0.9072 a. All tons, including tons of sulfur, are expressed in short tons. ix ------- ACKNOWLEDGEMENTS Partial, support for this study was provided by the Department of Energy by means of pass-through funds to the Environmental Protection Agency. ------- PRELIMINARY ECONOMIC ANALYSIS OF A LIME SPRAY DRYER FGD SYSTEM EXECUTIVE SUMMARY Dry-scrubbing flue gas desulfurization (FGD) technology using a concentrated solution or suspension of a reactive absorbent in a spray dryer is a recent development in electric utility FGD. It is receiving extensive attention, at the present time, and contracts have been awarded for nine commercial installations. Much of this interest is due to some potentially significant technical advantages over conventional wet FGD technology—the process design is relatively simple; stack gas reheat may be substantially reduced or eliminated, and the product is a dry waste rather than a wet sludge. These dry scrubbers have one significant disadvantage—the use of an expensive (relative to limestone) alkali absorbent, either lime or soda ash. The raw material cost penalty for using lime or soda ash must be offset by savings in capital charges and maintenance costs for spray dryer systems to be economically competitive with the wet limestone systems. Minimizing these raw material costs is one of the reasons that the first commercial utility applications of these systems are on boilers fired with lignite and subbituminous coals. Both of these types of coals are normally low in sulfur and, therefore, the amount of expensive alkali raw material to be consumed in the FGD system is minimized. (In fact, the average fuel sulfur level at the utility boilers currently under contract is less than 1.0%.) These fuels also produce a highly alkaline ash which, if recycled through the spray dryer, can further reduce makeup raw material requirements. Although capital investments and revenue requirements for these processes have been estimated by various process vendors and compared with a conventional wet limestone slurry process, no independent economic comparisons based on comparable design and economic premises have been published. The purpose of this economic evaluation is to compare the costs of the spray dryer FGD technology with those of the limestone slurry process based on the technical and economic premises developed jointly by the Environmental Protection Agency (EPA) and the Tennessee Valley Authority (TVA). In addition to the base-case evaluations, sensitivity analyses of raw material costs and stoichiometries on the annual revenue requirements were performed. The capital investment and annual revenue requirements xi ------- for the limestone slurry process with sludge fixation by the IU Conversion Systems, Incorporated (IUCS) process and landfill disposal were determined for comparison with the costs of pond disposal. DESIGN AND ECONOMIC PREMISES Design Premises Table S-l lists the major design premises for this study. The base-case power plant is a new, 500-MW coal-fired power unit located in the Great Plains - Rocky Mountain region. The fuel is a subbituminous coal with a heating value of 9,700 Btu/lb and containing 0.7% sulfur (dry basis), 9.7% ash, and 16% moisture. The boiler heat rate is 9,500 Btu/kWh. TABLE S-l. MAJOR DESIGN PREMISES Item Premise Power plant Operating schedule Fuel Base year FGD waste disposal S02 removal- efficiency Particulate removal efficiency SOo absorber redundancy New, Great Plains - Rocky Mountain region, 500-MW coal-fired boiler, 9,500 Btu/kWh heat rate 130,400 hr, 30-yr life, 5,500-hr first- year operation Subbituminous coal; 9,700 Btu/lb, 0.7% sulfur, 9.7% ash, 16% moisture Capital investment: mid-1982 Revenue requirements: 1984 Limestone: clay-lined pond Generic lime spray dryer: landfill 70% 99.8% (0.03 Ib of particulates/MBtu heat input) 33% (3 operating trains, 1 spare) The FGD unit includes all the equipment necessary to meet the recent (June 1979) new source performance standards (NSPS) for both particulate matter (0.03 Ib/MBtu heat input) and S02 (overall 70% removal for low-sulfur coals). The overall design for the generic lime spray dryer system is based on vendor information, while the design of the limestone slurry process is based on in-house data and previous evaluations by TVA. xii ------- Economic Premises The project is assumed to begin in mid-1980 with a 3-yr construction period ending in mid-1983. The midpoint of construction costs, and therefore the basis for the capital investment costs, is mid-1982. The revenue requirements are based on 1984 costs. Delivered costs for raw materials are projected based on mid-1979 prices in the Great Plains - Rocky Mountain region. Labor rates for 1984 for this region are assumed to be equivalent to those for a midwestern location and are projected from current midwestern labor costs. Capital investment estimate is made up of direct investment, indirect investment, and other capital charges. The direct investment is based on equipment lists and other installation costs (such as piping, electrical, instrumentation, etc.) are factored from the equipment costs. Indirect investment (engineering design and supervision, construction expense, etc.) is estimated based on the direct investment. Other capital costs (allowance for startup and modification, interest during construction, etc.) are estimated from the total direct and indirect investment. These preliminary capital investment estimates are normally considered to have a -20% to +40% range of accuracy (i.e., in an actual application of the generic lime spray dryer process for this 500-MW boiler the capital investment could range from 20% less to 40% more than the projected $132.3/kW) Two types of annual revenue requirements are projected—first year and levelized. Both are based on 5,500 hours of operation per year at full load (about a 63% capacity factor) and both use a levelized capital charge. Levelized annual revenue requirements differ from first-year annual revenue requirements in that they take into consideration the time value of money over the life of the FGD unit and are calculated using a 10% discount factor, 6% inflation factor, and a 30-yr economic life. PROCESS BACKGROUND AND DESCRIPTION Generic Lime Spray Dryer Process The generic lime spray dryer process (Figure S-l) contains only two major equipment items, a spray dryer and a baghouse. Most of the flue gas from the boiler passes untreated to the spray dryer where it contacts an atomized slurry of lime and recycled waste. The sulfur oxides are absorbed and react with the lime, and fly ash alkali if present, to form calcium sulfite and calcium sulfate. The slurry concentration is adjusted so that the water injected into the spray dryer is insufficient to saturate the flue gas and the resulting waste material leaves as dry particulate matter entrained in the flue gas. xiii ------- STACK PARTIAL BYPASS X H- BOILER MATERIAL HANDLING AND FEED PREPARATION 4 '\ ^ SOo jT fc P ARTICULATE ^ ABSORPTION ^ REMOVAL „ W ^ _ ^^ WASTE STORAGE 1 ^ GAS ~ HANDLING ^ WASTE DISPOSAL Figure S-l. Generic lime spray dryer process. Block flow diagram. ------- The remaining flue gas from the boiler (22% of the total gas rate) bypasses the spray dryers and enters the flue gas ducts downstream of the spray dryers but before entering the baghouse. The system is designed such that the overall SOo removal will meet the recently promulgated (June 1979) NSPS (i.e., 70% removal for coal containing 0.7% sulfur). The calcium-based particulate matter formed in the spray dryer and the fly ash from the boiler are removed in the baghouse, which is designed to meet the NSPS for particulate matter (0.03 Ib/MBtu). Part of the waste material from the baghouse (both fly ash and calcium-based salts) is temporarily stored in a hopper before trucking to the landfill. The remainder is reslurried and recycled to the spray dryer. The only other area is the lime preparation area where lime is stored, slaked, and pumped to the spray dryers. Surge capacity for both the dry lime and the lime slurry is included. Limestone Slurry Process The limestone slurry process (Figure S-2) is also a relatively simple process containing only two major equipment items, a high-efficiency electrostatic precipitator (ESP) and a venturi/spray tower wet scrubber. Although ESP's are not normally considered a part of the limestone slurry process, they have been included in this limestone slurry process so that it can be compared with the generic lime spray dryer process. Flue gas from the boiler passes through the ESP for fly ash removal to meet the NSPS. (The fly ash from the ESP is trucked to the disposal pond.) The flue gas from the ESP is divided into two streams. Most (72%) of the flue gas enters the S02 scrubbers where 90% of the entering S02 is absorbed to achieve the overall 70% SC>2 removal required by the NSPS for the 0.7% sulfur coal. The remaining flue gas bypasses the scrubbers and enters the flue gas ducts after the scrubber, providing sufficient heat to make reheating unnecessary. Part of the recirculating slurry in the absorption section is bled off and pumped to the disposal pond. The wet calcium sulfite-sulfate salts settle out as a 40% (by weight) sludge, and the supernate is recycled for reuse in the process. The major remaining processing area is the limestone preparation area where the makeup limestone is stored, crushed, milled, and slurried before being added to the recirculating slurry. Surge capacity for both dry limestone and the limestone slurry is included. ECONOMIC EVALUATION AND COMPARISON Preliminary estimates of capital investment, first-year revenue requirements, and levelized annual revenue requirements were prepared for both the generic lime spray dryer process and the limestone slurry process based on the design and economic premises. These results are shown in Table S-2. xv ------- PARTIAL BYPASS " , BOILER PARTICULATE REMOVAL GAS HANDLING STACK t ABSORPTION I WASTE DISPOSAL MATERIAL HANDLING AND FEED PREPARATION Figure S-2. Limestone slurry process. Block flow diagram. ------- TABLE S-2. BASE-CASE COMPARISON OF CAPITAL INVESTMENTS AND ANNUAL REVENUE REQUIREMENTS Generic lime spray dryer process Capital investment (1982 $) M$ $/kW Total first-year revenue require- ments (1984 $) M$ mills/kWh Levelized annual revenue require- ments (1984 $) M$ mills/kWh 66.2 132.3 17.04 6.20 23.52 8.55 Limestone slurry process 93.2 186.4 23.50 8.55 32.19 11.71 The capital investment for the generic lime spray dryer process is $66.2M ($132.3/kW) in mid-1982 dollars. The total direct investment portion of the capital investment, which includes equipment costs and installation expenses, accounts for $32.5M. The major processing areas, in terms of investment required, are particulate matter removal ($11.1M), gas handling ($7.2M), and S02 absorption ($7.2M). These areas alone account for 78% of the direct investment. The indirect investments (engineering design and supervision, architect and engineering contractor, etc.) are about $18.2M; the other capital charges (allowance for startup and modifications, interest during construction, etc.) make up the remaining $15.5M. The capital investment for the limestone slurry process is $93.2M ($186.4/kW) in mid-1982 dollars. The total direct investment portion of the capital investment accounts for $45.7M. The major processing areas in this total direct investment are S02 absorption ($13.7M), particulate matter removal ($12.4M), and gas handling ($9.9M). These three areas account for about 79% of the direct investment. The indirect investments and the other capital charges account for $25.5M and $21.9M of the capital investment respectively. The first-year and the levelized annual revenue requirements for the generic lime spray dryer process are $17.OM (6.20 mills/kWh) and $23.5M (8.55 mills/kWh) respectively. The major component of these revenue requirements is the levelized capital charges of $9.7M. Other important annual costs are maintenance ($1.9M), overheads ($1.8M), elec- tricity ($1.5M), and lime ($1.0M). xvii ------- The first-year and the levelized annual revenue requirements for the limestone slurry process are $23.5M (8.55 mills/kWh) and $32.2M (11.71 mills/kWh) respectively. Again, the major component of these revenue requirements is the levelized capital charges of $13.7M. Other major annual costs are maintenance ($3.5M), overheads ($3.0M), and electricity ($1.8M). Comparisons In terms of both capital investment and first-year annual revenue requirements, the base-case generic lime spray dryer process is sub- stantially lower in cost than the base-case limestone slurry process as shown in Table S-2. The capital investment for the generic lime spray dryer process is about 29% lower, and the first-year annual revenue requirements are about 28% lower, than those for the limestone slurry process. If these total capital investments are broken down into individual investment areas as shown in Table S-3, the reasons for the higher cost of the limestone slurry process are apparent. With the exception of the material handling area and particulate matter handling and recycle area (which the limestone slurry process does not have), the area investments for the limestone slurry process are higher than those for the generic lime spray dryer process. In fact the differences in only three areas, the SC>2 absorption, disposal area preparation, and gas-handling areas, account for a $12.8M difference in direct investment, or about $26.OM in total capital investment when the other capital charges are adjusted to reflect the higher direct investment. TABLE S-3. SUMMARY OF THE TOTAL CAPITAL INVESTMENTS Investment area Material handling Feed preparation Gas handling S02 absorption Particulate removal Particulate handling and recycle Solids disposal Disposal area preparation Land All other capital costs Total capital investment Total cost Generic lime spray dryer process 2,443 599 7,190 7,173 11,133 1,425 379 321 515 34,993 66,171 , k$ Limestone slurry process 919 1,071 9,924 13,734 12,395 - 1,453 3,793 910 48,910 93,109 Basis: TVA design and economic premises. xviii ------- The lower investment costs for the generic lime spray dryer process in these three areas are primarily due to the use of the spray dryer absorber. The design of the generic lime spray dryer process precludes the need for mist eliminators and the large recirculating slurry pumps which are used in the SC^ absorption area of the limestone slurry process. The higher land and disposal area preparation costs (i.e., pond construction) for the limestone slurry process are due to the nature of the settled sludge in the pond (i.e., the sludge in the pond is only 40% solids) in contrast to the dry waste going to the landfill in the generic lime spray dryer process. The first-year annual revenue requirements are broken down into various annual costs in Table S-4. Major cost differences between the processes are costs for raw materials, maintenance, and levelized capital charges. The higher raw material cost for the generic lime spray dryer process is due to the consumption of expensive lime ($102/ton) rather than limestone ($8.50/ton). Maintenance costs for the limestone slurry process are substantially higher because of the need to recirculate large amounts of limestone slurry through the process equipment. Levelized capital charges are higher for the limestone slurry process because of the higher total capital investment required. TABLE S-4. SUMMARY OF FIRST-YEAR ANNUAL REVENUE REQUIREMENTS Raw materials Operating labor and supervision Electricity Maintenance Levelized capital charges Other annual costs Total first-year revenue requirements Total cost, $ Generic lime spray dryer process 1,026,900 948,800 1,485,600 1,939,400 9,727,100 1,912,600 Limestone slurry process 133,900 1,321,600 1,764,300 3,464,700 13,698,800 3,120,500 17,040,400 23,503,800 SENSITIVITY ANALYSIS Sensitivity to Raw Material Cost The generic lime spray dryer process is more sensitive to changes in the delivered price of the raw material than the limestone slurry process. Because of the low-sulfur coal used and the low S02 removal requirement, however, cost changes from the base case do not significantly xix ------- change the economic results, as shown in Figure S-3. The generic lime spray dryer process has lower first-year annual revenue requirements regardless of the raw material prices selected. The limestone slurry process, because of the low unit cost of limestone as well as the low-sulfur level in the coal and the low SO? removal requirement, is essentially insensitive to the delivered price of limestone. Sensitivity to Raw Material Stoichiometry Since the design Stoichiometry for the limestone slurry process is based on the results from actual low-sulfur coal applications, only the base-case Stoichiometry for the limestone slurry process was evaluated. The generic lime spray dryer process, however, represents technology which has not been demonstrated on a commercial scale and hence may change as this technology is developed further. Therefore, a range of raw material stoichiometries from 1.00 (-18.0%) to 1.46 (+19.7%) was evaluated. The results of this sensitivity analysis are not significantly different from those previously discussed for the sensitivity to raw material prices (i.e., regardless of what reasonable raw material Stoichio- metry is used for the generic lime spray dryer process, the generic lime spray dryer process has a lower first-year annual revenue requirement than the base-case limestone slurry process) as shown in Figure S-4. Sensitivity to Waste Disposal Costs Since some power plant locations do not have sufficient land available for ponding of the limestone slurry process waste, the relative economics for a limestone slurry process with an alternative disposal method, the IUCS fixation process, were also evaluated. The limestone slurry process up to the point at which the purge stream leaves the scrubbers is identical for both cases. For the base-case limestone slurry process, the scrubbing waste is simply pumped to the pond and the supernate is returned to the process. For the limestone slurry - IUCS fixation process, the waste is pumped to a thickener and filter for dewatering, mixed with lime and fly ash, and allowed to set up before being hauled by truck to an onsite landfill for disposal. The total capital investment for this combination limestone slurry - IUCS pro.cess is $91.4M ($183/kW) in 1982 dollars or nearly $2.0M less than the base-case limestone slurry process with ponding. This decrease in capital investment is due to the substantially lower disposal area preparation costs and land requirements for the IUCS alternative. The first-year and the levelized annual revenue requirements for the limestone slurry - IUCS fixation process are $24.98M (9.08 mills/kWh) and $35.20M (12.80 mills/kWh) respectively. These costs are about 6% higher than those for the base case (i.e., with ponding) primarily because of the higher labor costs and related higher overhead costs. xx ------- LIMESTONE COST, S/TON X X M- 10.0 § 9.0 1/5 rf cn 2 8'° W a. D 8' Q£ g 7.0 Z UJ w ^ 6.0 i >« H w 2 fc 5.0 4.0 5.00 8.50 12.00 1 1 1 ~ Limestone slurry process "— ~~" - — Generic 1 iine spray dryer process i i i 10.0 g 9.0 en * g 8.0 M 1 M K P£ p 7-0 u S a: 5 6.0 f H t/3 fc 5.0 4.0 n 1 1 1 I 1 Limestone slurry process _ _ B Generic lime spray dryer process — _ i i i i i 75.00 102.00 125.00 LIME COST (DELIVERED), $/TON Figure S-3. Sensitivity of the first-year annual revenue requirements to the delivered cost of the raw material. RAW MATERIAL STOICHIOMETRY, MOL ALKALI/MOL S02 ABSORBED Figure S-4. Sensitivity of the first-year annual revenue requirements to the raw material stoichiometry in the absorber. ------- CONCLUSIONS AND RECOMMENDATIONS Conclusions For a new, 500-MW power unit burning a 0.7% sulfur subbituminous coal, the generic lime spray dryer process has a lower total capital investment and lower annual revenue requirements than a comparable limestone slurry process. These differences in capital investment and annual revenue requirements are larger than the uncertainty surrounding the comparability of preliminary economic estimates of this type (+10%). Therefore, for the assumed design and economic premises the generic lime spray dryer process appears to have a significant economic advantage over a conventional limestone slurry process. For these design and economic premises, the generic lime spray dryer process maintains its economic advantage over the limestone slurry process for all ranges of raw material costs and raw material stoichio- metries studied. The generic lime spray dryer process also has an economic advantage over a combined limestone slurry - IUCS process for fixation and landfill instead of ponding waste disposal. Recommendations Since only a single base-case application of the generic lime spray dryer process has been considered in this study, a definitive economic analysis of this process is suggested as the logical next step. Not only would the accuracy of the capital investment and annual revenue requirements for the base case be increased, but several case variations (power unit size, sulfur level in the coal, S02 removal efficiency, for example) could be evaluated. Other areas which require additional study (and which will be evaluated in the final report for this project) include: « Generic soda ash spray dryer process for a low-sulfur subbituminous coal application. o Generic lime spray dryer process for a low-sulfur eastern coal application. o Generic lime spray dryer process for a high-sulfur eastern coal application. xxii ------- PRELIMINARY ECONOMIC ANALYSIS OF A LIME SPRAY DRYER FGD SYSTEM INTRODUCTION One of the recent developments in flue gas desulfurization (FGD), the so-called dry scrubbing technology using a concentrated solution or suspension (depending on whether the alkali material is sodium- or calcium-based) of a reactive absorbent in a spray dryer, is currently receiving a considerable amount of attention. Much of this interest is due to some potentially significant technical advantages over conventional wet FGD technology (primarily lime or limestone slurry scrubbing). In particular, the process design is relatively simple and a dry waste, rather than a wet sludge, is produced. Nine contracts have been awarded for these dry scrubbers (listed in Table 1), six for commercial utility boilers and three for industrial boilers. With the exception of one utility boiler application which uses a sodium-based system, the systems under contract use lime-based spray dryer technology. Of the six utility boiler applications, three are lignite-fired boilers and three are fired with subbituminous coal. All six of these boiler fuels are relatively low in sulfur (<1%) and have a highly alkaline fly ash. Two of the three industrial boiler applications, on the other hand, involve eastern bituminous coals which have higher sulfur levels and relatively low alkalinity in the fly ash. These dry scrubbers have one significant disadvantage—the use of an expensive (relative to limestone) alkali absorbent, either lime or soda ash. As long as the savings in capital charges and maintenance costs for the spray dryer systems are higher than the raw material cost penalty for lime or soda ash, the spray dryer systems will remain econom- ically competitive with the wet limestone systems. This is one of the reasons that the first commercial applications are on utility boilers fired with lignite and subbituminous coals. Since both of these types of coals are normally low in sulfur, the amount of sulfur to be removed, and hence the consumption of expensive alkali raw material in the FGD system, is minimized. (In fact, the average sulfur levels in the fuels at the utility boilers currently under contract are all less than 1.0% sulfur.) ------- TABLE 1. CONTRACT AWARDS FOR SPRAY DRYER-BASED FGD SYSTEMS Installation Utility Boiler Coyote Unit 1 Antelope Valley Unit 1 Laramie River Unit 3 Stanton Unit 2 Springerville Unit 1 Springerville Unit 2 Rawhide Unit 1 Industrial Boiler Strathmore Paper Co. Celanese University of Minnesota Size, gross MW 410 440 575 63 350 350 250 14e 22e 83e Fuel type (% S) Lignite (0.78) Lignite (0.68) Subbituminous Lignite (0.77) Subbituminous Subbituminous Subbituminous Bituminous (2. Bituminous (1. Subbituminous (0.54) (0.69) (0.69) (0.29) 0-2.5) 0-2.0) (0.6-0. S02 Alkali raw Startup removal, % material date 50 62 85 73 61 61 70 75 70-80 7) 70 Soda ash Lime Lime Lime Lime Lime Lime Lime Lime Lime 4/81 4/82 4/81 9/82 2/85 9/86 12/83 7/79 1/80 9/81 Vendor RI/WF3 Joy/Niro B&WC R-Cd Joy/Niro Joy/Niro Joy/Niro Mikropul RI/WF Carborundum a. Rockwell International/Wheelabrator-Frye. b. Western Precipitation Division of Joy Manufacturing c. Babcock and Wilcox. d. Research-Cottrell. e. Based on 2,900 aft /MW. Company /Niro Atomizer, Inc. ------- Another advantage for the spray dryer processes associated with these western coals is the relatively high alkalinity of the fly ash from these coals. Not only does this alkalinity react with sulfur in the boiler and thus reduce the amount of sulfur removal required in the FGD system, but the alkalinity in the fly ash also removes sulfur oxides (SOX) from the flue gas in the spray dryer (if recycled) and thereby decreases the consumption of makeup alkali raw material. Thus, in order to reflect the current utility market for these spray dryer systems, the fuel chosen for this study is a low-sulfur subbituminous coal containing a highly alkaline ash. Although capital investments and revenue requirements for these dry scrubbing processes have been estimated by various process vendors and compared with a conventional wet limestone slurry process, no independent economic comparisons have been published. The purpose of this study is to make an economic comparison of a generic lime spray dryer process with a conventional wet limestone slurry process using the same design and economic premises. In addition to these base-case evaluations, a sensitivity analysis is included in which the annual revenue requirements are calculated for various raw material costs and stoichiometries. The capital investment and annual revenue requirements for an alternate limestone slurry process with sludge fixation and landfill disposal are also included. ------- CONCLUSIONS For a new, 500-MW power unit burning a 0.7% sulfur subbituminous coal, the generic lime spray dryer process has a lower total capital investment and lower annual revenue requirements than a comparable limestone slurry process. These differences in capital investment and annual revenue requirements are larger than the uncertainty surrounding the comparability of preliminary economic estimates of this type (+10%). Therefore, for the assumed design and economic premises the generic lime spray dryer process appears to have a significant economic advantage over a conventional limestone slurry process. For these design and economic premises, the generic lime spray dryer process maintains its economic advantage over the limestone slurry process for all ranges of raw material costs and raw material stoichio- metries studied. The generic lime spray dryer process also has an economic advantage over a combined limestone slurry - IUCS process for fixation and landfill instead of ponding waste disposal. ------- RECOMMENDATIONS Since only a single base-case application of the generic lime spray dryer process has been considered in this study, a definitive economic analysis of this process is suggested as the logical next step. Not only would the accuracy of the capital investment and annual revenue requirements for the base case be increased, but several case variations (power unit size, sulfur level in the coal, S02 removal efficiency, for example) could be evaluated. Other areas which require additional study (and which will be evaluated in the final report for this project) include: • Generic soda ash spray dryer process for a low-sulfur subbituminous coal application. • Generic lime spray dryer process for a low-sulfur eastern coal application. • Generic lime spray dryer process for a high-sulfur eastern coal application. ------- DESIGN AND ECONOMIC PREMISES This study compares the economics of two FGD systems on an equitable basis using conditions that are as representative as possible of projected industry conditions and that provide a clearly definable breakdown of costs into significant and useful divisions. The premises used in this study have been developed by the Tennessee Valley Authority (TVA), the U.S. Environmental Protection Agency (EPA), and others during similar economic evaluations made since 1967. Criteria of the premises are designed to establish efficiencies, process flow rates, and other operating and design conditions. The economic premises are designed to represent the many factors affecting costs. DESIGN PREMISES The utility plant design and operation is based on Federal Energy Regulatory Commission (FERC) historical data (1) and TVA experience. The conditions used are representative of a typical modern boiler for which FGD systems would most likely be considered. An Upper Great Plains and Rocky Mountain location typical of Wyoming, Colorado, Nebraska, and North and South Dakota is used because the concentration of both low- sulfur subbituminous coal supplies and power plants in this area make it representative of the segment of the power industry most attracted to the spray dryer FGD technology* Although the FGD design is assumed to be proven, in keeping with current industry practice a redundant absorber train is provided to maintain acceptable boiler availability. In the integration of the absorber system with the boiler systems, provision for turndown and maintenance are limited to provision of a common plenum between the systems with dampers to allow individual trains to be shut down. Emission Standards New source performance standards (NSPS) established by EPA (2) specify a maximum emission, based on heat input, of 0.03 Ib/MBtu for particulate matter, 1.2 Ib/MBtu for S02, and 0.5 Ib/MBtu for NOX. In addition to meeting this maximum emission limit of 1.2 Ib/MBtu for SO?, the NSPS also require that new plants must reduce the uncontrolled SO? emissions from 70% to 90%, depending on the uncontrolled S02 emission level. For the low-sulfur subbituminous coal chosen in this study, this percentage S07 reduction is 70%. In addition it is assumed that the ------- boiler is designed to meet the 0.5 Ib/MBtu NOX standard and that the FGD system includes all the process equipment needed to meet both the 0.03 Ib/MBtu particulate matter standard and the 70% S02 removal standard. Fuel The coal premises are composites of many samples representing major western coal production areas. The subbituminous coal is assumed to have a heating value of 9,700 Btu/lb and an ash content of 9.7% (both as fired) and a sulfur content of 0.7% (dry basis). The composition and flow rates for the base-case conditions are shown in Table 2. Although fly ash compositions are not normally of great significance in specifying a limestone FGD system, if the fly ash contains appreciable alkalinity it can have a significant effect on the economics of dry FGD systems which consume an expensive alkali raw material. Because of the high alkalinity of many western coals, a typical alkaline fly ash with the composition shown in Table 3 is used. TABLE 2. COAL COMPOSITION AND FLOW RATE Coal component C H 0 N S Cl Ash H20 Wt % as fired 57.00 3.90 11.50 1.20 0.59 0.10 9.70 16.00 Ib/hr 279,100 19,100 56,310 5,876 2,889 A90 47,500 78,350 Basis: 500-MW new coal-fired unit, 9,500 Btu/kWh, 9,700 Btu/lb heating value, 0.7% sulfur in coal, dry basis. ------- TABLE 3. FLY ASH ANALYSIS Fly ash component Wt Si02 A120 Fe203 CaO MgO Na-,0 K20 Ti02 S03 Other Total 32.2 17.4 6.0 20.0 4.7 1.7 0.5 1.0 15.3 1.2 100.0 Power Plant Design A single horizontal opposed, balanced-draft boiler for a 500-MW net electrical output is used. This net output does not include the power requirements for the FGD system. In contrast to some previous FGD studies by TVA, particulate matter removal and disposal have been included as part of the FGD unit rather than as part of the boiler because of the nature of the dry sorbent processes, which collect fly ash and sulfur salts simultaneously. Power Plant Operation An operating life of 30 years and a total operating lifetime of 130,500 hours are used. For this study a boiler capacity factor of 62.8% (equivalent to full load for 5,500 hr/yr) and a boiler heat rate of 9,500 Btu/kWh are used. Flue Gas Composition Flue gas compositions are the result of boiler design, fuel, and a variety of operating conditions. Combustion and emission conditions used to determine flue gas composition are based on balanced-draft boiler design and average values for the sulfur content of coal. Flue gas compositions are based on combustion of pulverized coal using a total air rate equivalent to 139% of the stoichiometric requirement. This includes 20% excess air to the boiler and 19% air inleakage in the boiler air heater. These values reflect TVA operating experience with horizontal, frontal-fired, coal-burning units. It is assumed that 80% of the ash present in coal is emitted as fly ash and 85% of the sulfur in coal is emitted as SOX. Three percent of the SOX emitted is assumed to be SO^ and the remainder S02. The base-case flue gas composition and flow rates calculated for these conditions are shown in Table 4. 8 ------- TABLE 4. BASE-CASE FLUE GAS COMPOSITION AND FLOW RATE Flue gas component Volume, % Ib/hr N2 °2 co2 so2 so3 NOX (as NO) HC1 H20 Ash 73.09 5.39 12.24 0.04 - 0.03 0.01 9.20 - 3,887,000 327,200 1,023,000 4,760 184 1,590 504 314,600 38,000 Total 100.00 5,597,000 Basis: 500-MW new coal-fired unit, 9,500 Btu/lb heating value, 0.7% sulfur, dry basis, 1,754,000 aft^/min at 300°F. Absorber Design Absorber design criteria are based on TVA operating experience, general power industry practice, and information from process and equip- ment vendors. The generic lime spray dryer process is based on vendor information. The limestone process is based on TVA experience at the Shawnee EPA Alkali Test Demonstration Facility, extensive power industry experience with these processes, and vendor information. Both the generic lime spray dryer and the limestone slurry processes are fed from a common plenum located downstream of the boiler air heaters. Both of these FGD processes consist of four parallel trains of absorbers of which three are operating and one is a spare. In addition, since only 70% S02 removal is required to meet the NSPS, part of the flue gas in both processes is bypassed around the absorbers for reheat purposes. The remaining flue gas passes through the absorbers where, depending on the process, the S02 removal is 80% to 90%. As the flue gas leaves the absorber, the hot bypassed flue gas is mixed with the scrubbed flue gas to obtain a 175 F recombined flue gas. The generic lime spray dryer process feeds a single baghouse. Since the flue gas from these spray dryers is not saturated and does not contain entrained liquid, mist eliminators are not required. Induced- draft (ID) fans located between the baghouse and the stack are provided to compensate for the assumed total pressure drop of 12 inches H20 for the generic lime spray dryer process. ------- The limestone slurry process is provided with high efficiency (99.8%) electrostatic precipitators (ESP) for particulate matter removal, venturi scrubber presaturators before the absorber, and chevron-type mist eliminators after the spray towers. The mist eliminators reduce the moisture content of the scrubbed gas to 0.1%. This reduces the reheating load, decreases deposition and corrosion in downstream equipment, and reduces particulate matter emission. A 16-inch 1^0 pressure drop is assumed for the limestone slurry process, and in contrast to the generic lime spray dryer process which uses ID fans, a forced-draft (FD) fan is included between the boiler plenum and each venturi scrubber to compensate for this pressure drop. Operating conditions for the absorbers are shown in Table 5. These conditions are used for both the base-case and case variation studies. Cost scaling factors based on gas and product rates are used to calculate values at conditions other than the base case. TABLE 5. DESIGN CONDITIONS FOR ABSORBER SYSTEM CALCULATIONS Operating conditions Generic lime spray dryer Limestone Presaturator Type Liquid 3 Liquid/gas, gal/kaft Pressure drop, in. H20 Absorber Type Slurry solids, % „ Liquid/gas, gal/kaft Pressure drop, in. 1^0 Liquid in exit gas, % Slurry added, % solids Effluent, % solids Total pressure drop, in. 1^0 None Spray dryer 22.5 0.3 2 0.0 22.5 100 12 Venturi Scrubber 20 9 liquid Spray tower 15 40 2 0.1 60 15 16 Reheat Flue gas reheat to 175 F for both processes is provided by bypassing part of the incoming flue gas around the absorbers. Raw Materials The raw materials used for each process are listed below. Limestone is crushed and wet ground as part of the scrubbing operation. The lime is not processed before use. 10 ------- Generic lime spray Property Limestone process dryer process Size as received Ground size Analysis „ Bulk density, Ib/ft 0 - 1-3/4 in. 10% to pass 200 mesh 90% CaC03 95 3/4 90% 55 - 1-1/4 in. CaO Waste Disposal The disposal area is located one mile from the plant site. An earthen-diked, clay-lined pond, designed to minimize the sum of land and construction costs, is used for the limestone slurry process. Pond evaporation is assumed equal to rainfall. The limestone process waste is assumed to settle to a 40% solids sludge. An area-fill type landfill is used for the generic lime spray dryer process. The landfill size is based on a waste bulk density of 50 Ib/ft-* and a 30-ft fill depth. Provisions for normal site maintenance of the pond and for normal landfill operations, including covering the waste and contouring to control runoff are included. No costs are provided for monitoring or post-operation maintenance. ECONOMIC PREMISES The economic premises are divided into capital costs for construction of the FGD system and annual revenue requirements for its operation. The premises are based on regulated utility economics using the design premises as a costing basis. The estimates use cost information obtained from engineering-contracting, processing, and equipment companies; raw material suppliers; and published cost indexes. Spray dryer costs were obtained by scaling vendor-supplied information. Raw material costs are based on those prevailing in the Upper Great Plains - Rocky Mountain region. Labor costs are assumed equivalent to those in the Midwest. Capital Costs The capital structure for the electric utility company is assumed to be: Common stock 35% Preferred stock 15% Long-term debt 50% 11 ------- The cost of capital is assumed to be: Common stock 11.4% Preferred stock 10,0% Long-terra debt 9.0% Weighted cost of capital (based on capital costs above) 10.0% The discount rate is 10%, the same as the weighted cost of capital. For other economic factors needed in financial calculations, the following values are assumed: Investment tax credit 10% Federal and State income tax 50% Property tax and insurance 2.5% Annual inflation rate 6% The levelized annual capital charge approach used in these premises is similar to that used by the Electric Power Research Institute (EPRI) (3). Depreciation— A 30-yr economic life and a 30-yr tax life are assumed for the utility plant. Salvage value is less than 10% and is equal to removal costs. The annual sinking fund factor for a 30-yr economic life and 10.0% weighted cost of capital is: Sinking fund factor = Q + wcc)n - f = °-61% (1) where: n = economic life (in years) WCC = weighted cost of capital (as a decimal fraction) The use of the sinking fund factor does not indicate that regulated utilities commonly use sinking fund depreciation. The sinking fund factor is used since it is equivalent to straight-line depreciation levelized for the economic life of the facility using the weighted cost of capital. An annual interim replacement allowance of 0.56% is also included as an adjustment to the depreciation account to ensure that the initial investment will be recovered within the actual rather than the forecasted life of the facility. Since power plant retirements occur at different ages, an average service life is estimated. Many different retirement dispersion patterns occur. The type S-l Iowa State Retirement Dispersion pattern is used (4). This S-l pattern is symmetrical with respect to the average-life axis and the retirements are represented to occur at a low rate over many years. The interim replacement allowance does not cover replacement of individual items of equipment since these are covered by the maintenance charge. 12 ------- The sum of the years digits method of accelerated depreciation is used for tax purposes. On a levelized basis (using flow- through accounting) this results in a credit in the fixed charge rate as follows: Accelerated tax depreciation = - -, - + \\ (WCC) where: CRF = Capital recovery factor (weighted cost of capital plus sinking fund factor) for the economic life (as a decimal fraction) CRF = Capital recovery factor for the tax life (as a decimal fraction) nT = Tax life (in years) TTR Levelized accelerated depreciation credit = (ATD - SLD) x — 1 IK where: ATD = Accelerated tax depreciation (as a decimal fraction) SLD = Straight-line depreciation (as a decimal fraction) ITR = Income tax rate (as a decimal fraction) For a 50% tax rate, 30-yr tax life, 30-yr book life, 10.0% weighted cost of capital, and 0.61% sinking fund factor, the annual levelized accelerated depreciation credit is 1.36% using flow-through accounting. Investment Tax Credit — The levelized investment tax credit is calculated as follows : (CRF ) (Investment tax credit rate) Levelized investment tax credit = n + wee1) f - TTRl - where CRF , WCC, and ITR are the same factors previously defined in equations (1) and (2). Using a 10.0% weighted cost of capital, 0.61% sinking fund factor, 10% investment tax credit rate, 50% income tax rate, the levelized investment tax credit is 1.92% annually. Income Tax — The levelized income tax is calculated as follows: , . j • „ r™^ , x-rr, OT^I ri Debt Ratio x Debt CostT r ITR -\ Levelized income tax = 1CRFB + AIR- SLD ] [1 -- ^j - J 4 _ ITRJ (4) where: AIR = Allowance for interim replacement 13 ------- Using a 10.61% capital recovery factor (weighted cost of capital plus sinking fund factor), 0.56% allowance for interim replacements, 3.3% straight-line depreciation, 50% debt ratio, 9.0% debt cost, and a 50% income tax rate, the levelized income tax rate is 4.31%. Annual Capital Charge— The levelized annual capital charges for a publicly owned electric utility, as shown in Table 6, are 14.7% of the total investment. The annual capital charge includes charges for the capital recovery factor, interim replacements, insurance, and property taxes, State and Federal income taxes, and credits for investment credits and accelerated deprecia- tion. TABLE 6. LEVELIZED ANNUAL CAPITAL CHARGES FOR REGULATED UTILITY FINANCING Capital charge, % Capital recovery factor 10.61 Interim replacements 0.56 Insurance and property taxes 2.50 Levelized income tax 4.31 Investment credit (1.92) Accelerated depreciation (1.36) Total 14.70 The annual capital charge is applied to the total capital investment. It is recognized that land and working capital (except spare parts) are not depreciable and that provisions must be made at the end of the economic life of the facility to recover their capital value. In addition, investment credit and accelerated depreciation credit cannot be taken for land and working capital (except spare parts). The cumulative effect of these factors makes an insignificant change in the annual capital charge rate and is therefore ignored. Capital Investment Estimates Capital investment estimates for this study are based on an Upper Great Plains and Rocky Mountain location and represent projects beginning in 1981 and ending in 1983. Capital cash flows for a standard project are assumed to be 25% the first year, 50% the second year, and 25% the third year of the project life. Capital costs for fixed assets are projected to mid-1982, which represents the approximate midpoint of the 14 ------- construction expenditure schedule. The estimates in this study are based on a process description, flowsheet, material balance, and equipment list. These preliminary-level estimates are considered to have a -20% to +40% range of accuracy. The total fixed capital investment consists of direct capital costs for equipment, building, utilities, service facilities, raw material and byproduct storage, waste disposal facilities, engineering design and supervision, construction expense, contractor fees, and contingency. The total capital investment consists of the total fixed capital invest- ment plus allowances for startup and modifications, royalties, the cost of funds during construction, plus the cost of land and working capital. Direct Capital Investment Process— Direct capital costs cover process equipment, piping, insulation, transport lines, foundations, structures, electrical equipment, instru- mentation, raw material and byproduct storage, site preparation and excavation, buildings, roads and railroads, trucks, and earthmoving equipment. Direct investment costs are prepared using the average annual Chemical Engineering (5) cost indexes and projections as shown in Table 7. TABLE 7. COST INDEXES AND PROJECTIONS Year Plant Material Labor 1978 218.8 240.6 185.9 1979a 240.2 262.5 209.7 1980 259. 286. 226. a 4 1 5 1981 278. 309. 244. a 9 0 6 1982a 299.8 333.7 264.2 1983 322. 360. 285. a 3 4 3 1984 344. 385. 305. a 9 6 3 a. TVA projections. b. Same as index in Chemical Engineering (5) for "Equip imei it, c. machinery, supports." Same as index in Chemical Engineering (5) for "Construction labor." The overtime premium for 7% overtime is included in the construction labor. Appropriate amounts for sales tax and for freight are included in the process capital costs. Direct Capital Investment - Utilities, Services and Miscellaneous— Necessary electrical substations and conduit and steam, process water, fire and service water, instrument air, chilled water, inert gas, and compressed air distribution facilities are included in the utilities investment. These facilities are costed as increments to the facilities already required by the power plant. Service facilities such as maintenance 15 ------- shops, stores, communications, security, offices, and road and railroad facilities are estimated on the basis of process requirements. Services, non-power plant utilities, and miscellaneous costs will normally be in the range of 4% to 8% of the total process capital depending on the type of process. A 6% rate is used in this evaluation for both processes. Indirect Capital Investment— Indirect capital investment covers engineering design and supervision, architect and engineering contractor costs, construction costs, contractor fees, and contingency. Construction facilities (which include costs for mobile equipment, temporary lighting, construction roads, raw water supply, construction safety and sanitary facilities) and other similar expenses incurred during construction are considered as part of construc- tion expenses and are charged to indirect capital investment. Listed below are the indirect costs used: % of direct investment Engineering design and supervision 7 Architect and engineering contractor 2 Construction expense 16 Contractor fees 5 Total 30 A contingency of 20% is included because projects normally have a higher likelihood of exceeding rather than underrunning the capital estimate. While actual projects could properly have both project and process con- tingencies of varying amounts, depending on the type and developmental maturity of the process, comparability among processes could be skewed by the use of different contingencies in the same study. Other Capital Charges— Startup and modification allowances are estimated at 8% to 12% of the total fixed investment depending upon the complexities of the process being studied. For these processes a midpoint value of 10% of the total fixed investment was assumed. Cost of funds during construction is 15.6% of the total fixed investment for each process. This factor is equivalent to the 10% weighted cost of capital with 25% of the construction expenditures of the first year, 50% the second year, and 25% the third year of the project construction schedule. Expenditures are assumed uniform over each year. Startup costs are assumed to occur late enough in the project schedule that there are no charges for the use of money used to pay startup costs. 16 ------- For both processes, royalty fees of 0.5% of the direct investment are charged. Land cost is assumed to be $5,000 per acre. Working capital is the total amount of money invested in raw materials, supplies, finished and semifinished products, accounts receivable, and monies on deposit for payment of operating expenses such as salaries, wages, raw materials, purchases, taxes, and accounts payable. For these premises, working capital is defined as the equivalent cost of 1 month's raw material, 1.5 months' conversion cost, and 1.5 months' plant and administrative overhead costs. In addition, it includes an amount equal to 3% of the total direct investment to cover spare parts, accounts receivable, and monies on deposit to pay taxes and accounts payable. Annual Revenue Requirements Annual revenue requirements use 1984 costs and are based on 5,500 hours of operation per year at full load. Annual revenue requirements are divided into direct costs and indirect costs. Both first-year and levelized annual revenue requirements are determined. Levelized annual revenue requirements are based on a 10% discount factor and a 6% inflation rate over the 30-yr life of the power unit. Direct costs consist of raw materials, labor, utilities, maintenance, and analytical costs. Indirect costs consist of levelized annual capital charges and overheads. Direct Costs— Projected raw material, labor, and utility costs are listed in Table 8. Unit costs for steam and electricity are based on the assumption that the required energy is purchased from another source. Unit costs ($/kW, mills/kWh) are calculated on the basis of net power output of the boiler excluding the electricity consumed by the pollution control systems. Actually, electrical use by the pollution control equipment after the ESP will result in a derating of the utility plant for either a new or a retrofitted unit. To minimize iterative calculations, the pollution control equipment is charged with purchased electricity instead of derating the utility plant. Maintenance costs are estimated as a percentage of the direct investment, based on unit size and process complexity. For the limestone slurry process, non-pond maintenance is 8% and pond maintenance is 3%. For the generic lime spray dryer process, maintenance is 6%. Indirect Costs— The levelized annual capital charges consist of a sinking fund factor, an allowance for interim replacement, property taxes, insurance, weighted cost of capital, income tax, credits for accelerated depreciation, and investment credit. The levelized annual capital charge for a regulated utility, as was shown in Table 6, is 14.7%. 17 ------- TABLE 8. PROJECTED 1984 UNIT COSTS FOR RAW MATERIALS, LABOR, AND UTILITIES $/unit Raw materials Limestone Lime Labor Operating labor Analyses Mobile equipment Utilities Q Process water Electricity 8.50/ton 102.00/ton 15.00/man-hr 21.00/man-hr 21.00/man-hr 0.14/kgal 0.037/kWh a. Varies according to process-dependent water requirements. Plant and administrative overhead is 60% of conversion costs less utilities. The plant and administrative overheads include plant services such as safety, cafeteria, medical, plant protection, janitor, purchasing personnel, general engineering (excluding maintenance), interplant communications and transportation, recreational facilities, and the expenses connected with management activities. Fringe benefits such as retirement, vacation, dental and medical plans are included in the base wage rates. 18 ------- PROCESS BACKGROUND AND DESCRIPTION GENERIC LIME SPRAY DRYER PROCESS The generic lime spray dryer process (Figure I and Table 9) is a relatively simple processing system requiring few items of process equipment. Makeup lime is slurried, atomized into the flue gas stream, and the resulting waste material is collected along with the fly ash in the baghouse. The concentration of the lime slurry is adjusted so that the amount of water injected into the flue gas stream does not saturate the flue gas. Mist eliminators (a frequent source of operating problems) are not required. In addition, since the flue gas stream is unsaturated, the waste material is collected as dry particulate matter. In this particular application (primarily due to both the relatively low S02 removal required and the highly alkaline nature of the fly ash), most of the collected waste material is reslurried and recycled through the spray dryer. This recycling of waste material increases the lime utilization in the process and thereby reduces the consumption of this costly alkali raw material. The waste that is not recycled is trucked to a landfill for disposal. Flue gas bypass around the spray dryer is used in this application because it is more economical to treat part of the flue gas at a higher S02 removal efficiency than to remove 70% of the S02 from all of the flue gas. By using flue gas bypass and having hot (-300 F) flue gas available for reheat, the spray dryer can be operated so that the treated flue gas more closely approaches the flue gas saturation temper- ature. As the flue gas approaches saturation temperature, the alkali droplets retain their moisture longer and increase the liquid-phase residence time for S02 absorption. This results in a better raw material utilization (as well as a higher S02 removal efficiency) in the spray dryer. Although there is an additional capital investment for the flue gas bypass ductwork, this is offset by both the lower capital investment for the spray dryers and the lower annual cost for lime. Process Description Flue gas from the boiler air heater enters the three operating trains (the fourth is a spare) of the FGD system through a common plenum. Most of the flue gas (78%) from the plenum passes directly into the top of the spray dryers. The rest of the flue gas bypasses the spray dryers for reheat purposes. The spray dryer contains an atomizing system 19 ------- N3 o Figure 1. Generic lime spray dryer process. Flow diagram. ------- TABLE 9. GENERIC LIME SPRAY DRYER PROCESS MATERIAL BALANCE 1 2 t .', ', (( / fi ") 1° Stream No. Total stream. Ib/hr sft^min at 60°F Temperature, °F Pressure, psisi Rpm Specific gravity pH Undisaolved solids. Z 1 489,700 2 Combustion air 5,119,000 1,131,066 80 3 Combustion air 4,419,000 976,466 535 4 Gas to econom zer 4,897,000 1,045,000 890 5 Gas to air neater 4,897,000 1,045,000 705 Stream No, Description 1 1 '. '} / 8 9 10 Total stream, Ib/hr sft3/min at 6Qf>F Temperature, °F Pressure , psig gpm Specific gravity PH Undissolved solids, % 11 Waste to recycle parttculate silo 55,450 12 Makeup water to recycle slurry tank 83,150 166 13 Recycle slurry to spray dryer 138,600 iO 14 Makeup lime to slaker 3,661 15 Makeup water to slaker 11,350 23 Stream No. 1 i '} it / H 4 10 Description iQtal sueam. Ib/hr sftVmtn at 6Q°F Temperature, °F Pressure , psig Kpm Spt'cific gravity PH Undissolved solids, % 16 Grit to landfill 366 17 Lime slurry to spray dryer 14,650 22.5 18 Dilution water to spray drver 19,890 60 40 a. Includcs air inleukage Into the 21 ------- designed to spray the lime slurry and a waste recycle slurry perpen- dicularly to the gas flow in the spray dryer. (The lime slurry and the waste recycle slurry are combined into a single stream and atomized in the spray dryer.) The SOX and HC1 in the flue gas react readily with the lime slurry by the following reactions: Ca(OH)2 + S02 -> CaS03 4- H20f (5) Ca(OH)2 + SCL -> CaSO^ + H20t (6) Ca(OH) + 2HC1 -> CaCl + 2HOt (7) In addition to these primary reactions, the following secondary reaction also occurs: CaS03 + 1/202 -*• CaS04 (8) The water content of the feedstreams is controlled so that all of the water fed to the spray dryer evaporates and the mixed calcium salts and fly ash leave the spray dryer as dry particulate matter entrained in the flue gas. Since the flue gas is not saturated and contains no liquid carryover, mist eliminators are not required. The particulate matter- laden flue gas from thp. bottom of the spray dryer is mixed with the 300°F flue gas which bypassed the spray dryer and is passed to the baghouse. The baghouse not only removes the fly ash and the calcium- based particulate matter from the flue gas, but it also significantly increases the contact time between the calcium-based particulate matter and the SC>2-containing flue gas. This increased contact time leads to the additional conversion of both SOX by reactions (5) and (6) and CaSO-j by reaction (3) . The flue gas from the baghouse passes through an ID fan and is vented to the stack. The flue gas enters the stack at about 175 F and, therefore, additional reheat is not required. The fabric bags in the baghouse are cleaned periodically. The particulate matter drops into hoppers at the bottom of the baghouse. Pneumatic conveyors move the particulate matter to either the recycle storage silos or the waste storage bins. Waste solids from the silo are reslurried with makeup water and recycled through the spray dryer. The waste storage bin is emptied into trucks for transport to a landfill. Bulk shipments of pebble lime are received by rail and sent to the storage silo. The lime is periodically moved to intermediate storage bins from which process requirements are removed. The pebble lime from the bins is slaked with makeup water and pumped as a 22.5% slurry to the lime slurry tank. This makeup slurry is pumped to the spray dryer as needed. 22 ------- Analysis of Processing Subsections To facilitate cost determinations and comparisons, the lime process is divided into seven processing sections and the processing equipment is assigned to the appropriate section. The equipment list, giving the description and cost of each equipment item by section, is shown in Table 10. These costs do not include the investment required for founda- tions, structures, electrical components, piping, instruments and controls, etc. Each of these processing sections is described in more detail below. Material Handling— This and the following section, feed preparation, compose the raw material receiving and preparation section. The material handling section includes all of the equipment to receive lime by rail and to maintain a supply of lime to the weigh feeders. It includes a lime storage silo with a 30-day capacity and two lime feed bins each having a 12-hr capacity. Feed Preparation— The feed preparation sections include the equipment necessary to convert the makeup lime into slurry for S02 absorption. Two trains of lime preparation equipment (feeders, slakers, tanks, and agitators) are used. Each train is sized to handle 50% of the full load capacity. A slurry feed tank with a 4-hr capacity is provided. Gas Handling— Included in this area is an inlet plenum interconnecting the flue gas ducts which feed the scrubber trains. It also includes the bypass ducting around the spray dryers. Four ID fans are provided between the baghouse and the stack to compensate for the pressure drop through the FGD system. S02 Absorption— Four spray dryers are provided (three operating and one spare); each is sized to handle one-third of the total flue gas volume. Particulate Removal— A single baghouse containing 28 compartments and the associated equipment is provided. Particulate Handling and Recycle— A single train of equipment to store, reslurry, and recycle the waste material is provided. Two particulate storage bins are included to provide a 24-hr capacity for waste material to be landfilled. Waste Disposal— This section contains no processing equipment. It includes trucks to transport the waste absorbent to the landfill and earthmoving equipment 23 ------- TABLE 10. GENERIC LIME SPRAY DRYER PROCESS BASE-CASE EQUIPMENT LIST, DESCRIPTION, AND COST Area 1 — Material Handling Item No. Description Total material cost, 1982 $ Total labor cost, 1982 $ 1. Conveyor, lime 1 unloading (enclosed) 2. Elevator, storage 1 silo 3. Silo, lime storage Vibrators 4. Conveyor, live lime feed 5. Elevator, live lime feed 6. Bin, lime feed Belt, 24 in. x 1,500 ft 390,000 242,800 long, 30 hp, 100 tons/hr, 200 ft/min Continuous bucket, 16 in. 33,600 3,300 x 8 in. x 11-3/4 in., 75 ft lift, 15 hp, 100 tons/hr, 160 ft/min 40 ft dia x 50 ft straight 65,200 194,300 side, 62,800 ft3, 60° slope, carbon steel Bin activator, 10 ft dia 14,000 1,300 Belt, 14 in. x 100 ft 23,800 7,600 long, 2 hp, 16 tons/hr, 100 ft/min Continuous bucket, 8 in. 49,300 4,000 x 5-1/2 in. x 7-3/4 in., 35 ft lift, 2 hp, 16 tons/ hr, 150 ft/min 11 ft dia x 12 ft straight 10,600 28,200 side, 1,140 ft3> 60° slope, w/cover, carbon steel 7. Dust collecting system Subtotal Bag filter, polypropylene bag, 2,200 ft3/min, 7-1/2 hp (1/2 cost in feed prepa- ration area) 3,900 600 590,400 482,100 (continued) 24 ------- TABLE 10 (continued) Area 2 — Feed Preparation 1. 2. 3. 4. Item Feeder, lime bin discharge Feeder, slaker Slaker Tank, slaker No. Description 2 Vibrating, 3-1/2 hp, carbon steel 2 Screw, 12 in. dia x 12 ft long, 1 hp, 2 tons/hr 2 5 hp slaker, 1 hp classifier, 1.0 ton/hr 2 6 ft dia x 8 ft high, 1,700 Total material cost, 1982 $ 8,400 6,600 72,500 5,400 Total labor cost, 1982 $ 800 400 23,900 7,500 product gal, open top, four 6 in. baffles, agitator supports, carbon steel, neoprene lined 5. Agitator, slaker product tank 6. Pump, slaker product tank 7. Tank, slurry feed 2 turbines, 24 in. dia, 3 hp, neoprene coated Centrifugal, 40 gpm, 50 ft head, 1-1/2 hp, carbon steel, neoprene lined (2 operating, 1 spare) 10 ft dia x 12 ft high, 7,100 gal, open top, four 10 in. baffles, agitator supports, carbon steel, neoprene lined 15,800 1,800 5,300 2,300 6,500 9,500 8. Agitator, slurry feed tank 9. Pump, slurry feed tank 10. Dust collecting system Subtotal 40 in. dia, 7-1/2 hp, neoprene coated Centrifugal, 40 gpm, 200 ft head, 5 hp, carbon steel, neoprene lined (3 operating, 5 spare) Bag filter, polypropylene bag, 2,200 ft3/min, 7-1/2 hp, (1/2 cost in material handling area) 15,300 40,000 3,900 1,300 6,000 600 179,700 54,100 (continued) 25 ------- TABLE 10 (continued) Area 3—-Gas Handling Item No. Description Total material cost, 1982 $ 1. Fan Induced draft, 382,000 aft3/min, 12 in. static head, 875 rpm, 1,250 hp, fluid drive, double width, double inlet (4 operating) Subtotal 3 rotary atomizers, carbon steel, (3 operating, 1 spare) Subtotal Total labor cost, 1982 $ 1,583.600 99.600 1.583.600 99,600 Area 4 — S0? Absorption Item No. Description 1. Spray dryer 4 48 ft dia x 54 ft high, with Total material cost, 1982 $ 4,324,000 Total labor cost, 1982 $ 548.000 4,324.000 548,000 Area 5—Particulate Removal Item No. Description Total Total material labor cost, cost, 1982 $ 1982 $ 1. Baghouse 1 Subtotal Automatic fabric filter, 28 compart- 8,262,000^ 2,871.100 ments, 2.5 air-to-cloth ratio 8.262.000 2.871.100 (continued) 26 ------- TABLE 10 (continued) Area 6 — Particulate Handling Item No. and Recycle Description Total material cost, 1982 $ Total labor cost, 1982 $ 1. Conveyor, particu- 1 Pneumatic, pressure-vacuum, late feed to bin 250 hp 2. Bin, particulate storage 2 24 ft dia x 25 ft straight side, 11,300 ft3, 60° slope, w/cover, carbon steel 243,100 75,600 43,600 131,400 3. Vibrator 2 Silo, particulate 2 recycle Bin activator, 10 ft dia 25 ft dia x 30 ft straight side, 14,700 ft3f 60° slope, w/cover, carbon steel 18,600 2,500 51,200 149,700 4. Feeder, particu- late 5. Feeder, recycle slurry tank 6. Tank, recycle slurry Vibrating, 3-1/2 hp, carbon steel Screw, 12 in. dia x 12 ft long, 5 hp, 50 tons/hr 21 ft dia x 23 ft high, 55,400 gal, open top, four 21 in. baffles, agitator supports, carbon steel, neo- prene lined 8,400 800 30,800 4,500 25,700 38,700 7. Agitator, recycle slurry tank 8. Pump, recycle slurry feed Subtotal 84 in. dia, 30 hp, neoprene coated Centrifugal, 80 gpm, 200 ft head, 10 hp, carbon steel, neoprene lined (3 operating, 5 spare) 42,100 65.400 2,600 7,600 528.900 413.400 Basis: Most equipment cost estimates are based on informal vendor quotes and TVA information. The only exception is the cost for the spray dryers which is based on information supplied by the vendor. These costs represent equipment costs only. Costs for piping, elec- trical equipment, instruments, foundations, and other installation costs are not included. The differences in area costs between the equipment list and the capital summary sheets are due to these installa- tion costs. 27 ------- to distribute the waste evenly throughout the landfill. Therefore, these costs are not shown in the equipment list, but rather they are listed as a direct investment component of the capital investment. LIMESTONE SLURRY PROCESS The limestone slurry process (Figure 2 and Table 11) is also a relatively simple processing system requiring few items of process equipment. Although not usually considered as part of the FGD system, a high-efficiency (99.8%) ESP has been included in the limestone slurry process upstream of the FGD system. This change in the typical economic analysis of the limestone slurry process (i.e., including the cost of the ESP's) is necessary to provide comparability with the generic lime spray dryer process. Another significant design change for the limestone slurry process is the inclusion of partial flue gas bypass around the scrubber. Since only 70% SC>2 removal is required in this low-sulfur coal application, it was considered more economical to design the FGD system for 90% S02 removal and treat only enough flue gas to meet the required S02 reduction. Under these conditions sufficient heat is available from the bypassed gas to eliminate the need for additional reheat. Otherwise the limestone slurry process is of conventional design. The makeup limestone is ground, slurried, and added as needed to maintain a 15% solids slurry recirculating through the scrubber. A purge stream is bled off the absorber loop and is pumped to the disposal pond. The pond supernate is recycled and reused in the process. The fly ash from the ESP is trucked to and disposed of in the pond. Process Description The flue gas from the boiler air heater passes through both the high-efficiency ESP and the power plant ID fans before entering a common plenum. This common plenum distributes the gas to four trains of FD booster fans and absorbers. (Three of these scrubber trains are operating and one is a spare.) These FD booster fans are provided downstream of the plenum to compensate for the pressure drop in the FGD system. Approximately 28% of the 300°F flue gas from the booster fan bypasses the venturi/spray tower absorbers and enters the ducts downstream from the absorbers for reheat purposes. The remaining flue gas enters a venturi absorber where the flue gas, in contact with recirculated limestone slurry, is adiabatically cooled and saturated. This cooled flue gas enters the spray tower absorbers and passes countercurrently to the recirculating 15% solids limestone slurry which absorbs the SOX. The absorbers are equipped with chevron-type mist eliminators. Absorber outlet gas is heated from 130°F to 175 F before entering the stack by mixing with the bypassed flue gas. 28 ------- BOILER to VO ," ELECTROSTATIC 'ECONOMIZER! PRECIPITATOR FD FAN COAL POND SUPERNATE RETURN TO WASTE DISPOSAL POND Figure 2. Limestone slurry process. Flow diagram. ------- TABLE 11. LIMESTONE SLURRY PROCESS MATERIAL BALANCE Description I I \ '. 6 7 H 9 |0 Total stream, Ib/hr «fr3/mln at 60<>F Temperature. °F pressure. osiff Soecific Rravltv oH Undissolved solids, 7. 1 Coal to boiler 489,700 2 Combustion air to air heater 5, 119,000 1,131,000 80 3 Combustion air to boiler 4 ^4 11,000 976,400 535 4 Gas to economizer 4,897,000 1,045,000 896 5 Gas Co air heater 4,897,000 1.045.000 7S5 L k ') ft / H 9 Iff Description /rain at 60OF Pressure, psift pom Specific ftravity uH Undissolved solids, X 6 Gas to ESP ] ,700.000 7 863.200 8 Gas from 922.300 9 Gas to stack 1.259.000 10 to venturi 20.930 15 1 ; i 4 '> ; H 9 10 §tream No. Description Total stream, Ib/hr sft'/min at 60OF Temperature, QV Pressure, psla uH Undisaolved solids. £ 11 Makeup water to scrubber 170,100 340 12 Reclrculated slurry to absorber 23,050,000 130 41.860 15 13 Slurry to pond 48,810 89 15 14 Pond supernace to reclrcutatlon tank 26,690 53 15 limestone to weigh belts 5,728 | s fl / 8 4 IU J t ream No. Description Total stream, Ib/hr sftVnln at 60op prflflfl.Mrp- psig sB6Cific gravity oH Unrflosnlved solids. % 16 Pond supernate to wee ball mill 3,820 8 17 Mills product tank feed 9,546 12 60 18 Makeup slurry to recirculat ion tank 9,546 12 60 30 ------- A bleedstream from the recirculation tank is fed to the pond feed tank from which it is pumped to the onsite pond. The solids in the slurry settle to form a sludge containing approximately 40% solids. The pond supernate is recycled to the wet ball mills and the absorber recir- culation tank. Makeup limestone is received by rail and stored in a pile onsite. The limestone is removed from the pile and fed first to gyratory crushers and then to ball mills where it is wet ground to 70% minus 200 mesh. The effluent from the ball mill is stored as a 60% solids slurry, first in the ball mill product tank and then in the slurry feed tank. This makeup limestone slurry is pumped to the absorber recirculation tank where it is combined with scrubber effluent slurry and recycle pond water to maintain a 15% solids content in the recirculating slurry. Analysis of Processing Subsections To facilitate cost determinations and comparisons, the limestone slurry process is divided into six processing sections and the processing equipment is assigned to the appropriate section. The equipment list, giving the description and cost of each equipment item by section, is shown in Table 12. These costs do not include the investment required for foundations, structures, electrical components, piping, instruments, and controls, etc. Each of these processing sections is described below. Material Handling— This area includes all of the facilities needed for receiving the raw limestone, areas for a storage stockpile sufficient for 30 days at normal operating conditions, and an in-process limestone storage for 24 hours. Feed Preparation— A single train of gyratory crushers and wet ball mills to convert the raw limestone to a 70% minus 200 mesh, 60% solids slurry is included in this area. It also contains a product storage tank with capacity equal to an 8-hr supply of makeup slurry. Particulate Removal— Four high-efficiency ESP units (99.8% removal) are included in this area. These ESP's are sized for a low-sulfur, western coal application. Gas Handling— Included in this area is one inlet flue gas plenum interconnecting the four flue gas ducts which feed the absorbers and four FD fans. Also included are the FD fans and the bypass ducting around the absorbers. Each of these FD fans is sized to handle one-third of the total flue gas volume and to compensate for the pressure drop in the FGD system. 31 ------- TABLE 12. LIMESTONE SLURRY PROCESS BASE-CASE EQUIPMENT LIST, DESCRIPTION, AND COST Area 1 — Materials Handling 1. 2. 3. 4. Item Mobile equipment Hopper, reclaim Feeder, live limestone storage Pump , tunnel sump No. 1 1 1 2 Description Bucket tractor 7 ft x 4-1/4 ft x 2 ft deep, carbon steel Vibrating pan, 3.5 hp Vertical, 60 gpm, 70 ft head, Total material cost, 1982 $ 60,800 700 15,400 4,300 Total labor cost , 1982 $ — 1,300 2,700 1,100 5. Conveyor, live limestone feed 6. Conveyor, live limestone feed (incline) 7. Elevator, live limestone feed 8. Bin, crusher 1 feed 9. Dust collecting 1 system Subtotal 5 hp,carbon steel, neoprene lined (1 operating, 1 spare) Belt, 30 in. wide x 100 ft long, 2 hp, 100 tons/hr, 60 ft/min Belt, 30 in. wide x 190 ft long, 40 hp, 35 ft lift, 100 tons/hr, 60 ft/min Continuous bucket, 12 in. x 8 in. x 11-3/4 in., 75 hp, 90 ft lift, 100 tons/hr, 160 ft/min 13 ft dia x 21 ft high, w/ cover, carbon steel Bag filter, polypropylene bag, 2,200 aft3/min, 7-1/2 hp, automatic shaker system 34,300 102,800 6,900 6,700 6,300 48,000 20,300 2,400 14,500 18,100 279,900 66.700 (continued) 32 ------- TABLE 12 (continued) Area 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 2 — Feed Preparation Item No. Feeder , crusher 1 Crusher 1 Ball mill 1 Tank, mills 1 product Agitator, mills 1 product tank Pump, mills 2 product tank Tank, slurry 1 feed Agitator, slurry 1 feed tank Pump, slurry 6 feed tank Dust collecting 1 system Subtotal Total material cost, Description 1982 $ Weigh belt, 18 in. wide x 14 23,100 ft long, 2 hp, 3.0 tons/hr Gyratory, 0 x 1-1/2 to 3/4 in., 67,700 75 hp, 3.0 tons/hr Wet, open system, 100 hp, 174,400 3.0 tons/hr 10 ft dia x 10 ft high, 5,500 6,200 gal, open top, four 10 in. baffles, agitator supports, carbon steel, flakeglass lined 36 in. dia, 10 hp, neoprene 10,500 coated Centrifugal, 12 gpm, 60 ft 6,200 head, 1 hp, carbon steel, neoprene lined (1 operating, 1 spare) 11 ft dia x 11 ft high, 7,500 4,300 gal, open top, four 11 in. baffles, agitator supports, carbon steel, flakeglass lined 44 in. dia, 15 hp, neoprene 11,000 coated Centrifugal, 4 gpm, 60 ft 17,700 head, 1/4 hp, carbon steel, neoprene lined (3 operating, 3 spare) Bag filter, polypropylene 6,700 bag, 2,200 aft3/min, 7-1/2 hp, automatic shaker system 328,200 (continued) 33 Total labor cost, 1982 $ 1,800 7,600 17,800 11,000 500 1,400 10,500 900 4,300 18,100 73,900 ------- TABLE 12 (continued) Area 3—Particulate Removal Item No. Description Total Total material labor cost, cost, 1982 $ 1982 $ 1. ESP 4 99.8% removal efficiency SCA = 700 2. Conveyor, flyash 1 Pneumatic, pressure-vacuum, to particulate 75 hp bin 3. Bin, particulate 2 25 ft dia x 27 ft high, w/cover, carbon steel 8,020,000 4,010,000 109,800 69,300 39,000 108,600 4. Vibrator Subtotal 2 Bin activator, 10 ft dia 28,000 2,600 Area 4 — Gas Handling Item No. Description 1. Fans 4 Forced draft, 421,000 Total material cost, 1982 $ 2,276,200 Total labor cost, 1982 $ 147,500 890 rpm, 2,250 hp, fluid drive, double width, double inlet (3 operating, 1 spare) Subtotal 2.276.200 147.500 Area 5 — SO? Absorption Item No. 1. Venturi absorber 4 Description L/G = 20, pressure drop = 9 in. H20 (3 operating, 1 spare) (continued) 34 Total material cost, 1982 $ 632,900 Total cost, labor 1982 $ 86,000 ------- TABLE 12 (continued) Area 5 (continued) Item No. Description Total Total material labor cost, cost, 1982 $ 1982 $ 2. Tank, venturi hold 3. Agitator, venturi hold tank 4. Pumps, venturi recycle 5. S02 absorber 6. Tank, recircula- tion 7. Agitator, recir- culation tank 8. Pump, slurry recirculation 12 15-1/2 ft dia x 31-1/2 ft high, 44,500 gal, open top, four 15-1/2 in. wide baffles, agitator supports, carbon steel, flakeglass lined (3 operating, 1 spare) 62 in. dia, 40 hp, neoprene coated (3 operating, 1 spare) Centrifugal, 7,000 gpm, 100 ft head, 350 hp, carbon steel, neoprene lined (3 operating, 5 spare) Spray tower, 34 ft long x 17 ft wide x 40 ft high, 1/4 in. carbon steel, neoprene lining; FRP spray headers, 316 stain- less steel chevron vane entrain- ment separator and nozzles (3 operating, 1 spare) 31-1/2 ft dia x 31-1/2 ft high, 184,200 gal, open top, four 31-1/2 in. wide baffles, agi- tator supports, carbon steel, flakeglass lined (3 operating, 1 spare) 124 in. dia, 60 hp, neoprene coated (3 operating, 1 spare) Centrifugal, 7,000 gpm, 100 ft head, 350 hp, carbon steel, neoprene lined (6 operating, 6 spare) 63,700 156,300 96,900 32,700 421,000 37,000 3,485,000 401,200 158,400 354,500 293,300 99,100 631,500 55,600 (continued) 35 ------- TABLE 12 (continued) Area 5 (continued) 9. 10. Item No . Pump , makeup 2 water Soot blowers 44 Subtotal Description Centrifugal, 2,620 gpm, 200 ft head, 250 hp, carbon steel (1 operating, 1 spare) Air, retractable Total material cost, 1982 $ 25,600 377,100 6,185,400 Area 6 — Solids Disposal 1. 2. 3. 4. Item No. Tank, pond 1 feed Agitator, pond 1 feed tank Pumps , pond feed 4 Pumps , pond 2 return Subtotal Description 15-1/2 ft dia x 31-1/2 ft high 44,500 gal, open top, agitator supports, four 15-1/2 in. baffles, carbon steel, flake- glass lined 2 turbines, 52 in. dia, 40 hp, neoprene coated Centrifugal, 89 gpm, 130 ft head, 3 hp, carbon steel, neoprene lined (2 operating, 2 spare) Centrifugal, 127 gpm, 200 ft head, 10 hp , carbon steel, neoprene lined (1 operating, 1 spare) Total material cost, 1982 $ 15,900 21,700 18,200 6,200 62,000 Total labor cost, 1982 $ 2,700 318,700 1,543,800 Total labor cost, 1982 $ 39,100 1,800 3,900 700 45,500 Basis: Most equipment cost estimates are based on informal vendor quotes and TVA information. These costs represent equipment costs only. Costs for piping, elec- trical equipment, instruments, foundations, and other installation costs are not included. The differences in area costs between the equipment list and the capital summary sheets are due to these installation costs. 36 ------- SiOo Absorption— Four trains (three operating, one spare) of venturi/spray tower absorbers with mist eliminators, recirculation tanks, and recirculating pumps are included. Each absorber train is sized to handle one-third of the total flue gas volume. Solids Disposal— Included are one pond feed tank with agitator, pond feed and pond return pumps, and mobile equipment (trucks) to move the fly ash from the ESP to the sludge pond. 37 ------- ECONOMIC EVALUATION AND COMPARISON Based on the power plant, process design, economic premises, and the specific process equipment for each process described in the previous sections, preliminary capital investment, first-year revenue requirements, and levelized annual revenue requirements were prepared for the economic evaluation and comparison of the generic lime spray dryer process and a conventional limestone slurry process. Both first-year and levelized annual revenue requirements are cal- culated. First-year annual revenue requirements are useful for comparing the relative cost differences between processes for their first year of operation, and they are an indicator of the magnitude of the annual revenue requirements. However, these first-year annual revenue require- ments do not represent the actual cost of operating the plant since they do not consider either the time-value of money or the inflationary pressures over the life of the plant. In order to reflect these costs, a levelizing factor (1.886) is applied to the first-year annual revenue requirements to give a levelized annual revenue requirement. This levelizing factor is based on a 10% discount factor and a 6% inflation rate over the 30-yr life of the power unit. Sensitivity analyses have also been performed to evaluate the effects of varying the raw material price and stoichiometry for the generic lime spray dryer process. An alternate case involving sludge fixation for the limestone slurry process has also been included. Even though the generic lime spray dryer process, as described and costed, was assumed to be proven technology, the current status of development does not fully justify this assumption since none of the lime spray dryer processes have been operated on a commercial, coal- fired boiler. However, for TVA cost estimation purposes each system is assumed to be proven technology. ACCURACY OF ESTIMATES The accuracy associated with these preliminary cost estimates, i.e., -20%, +40%, is defined as the relationship between the estimated costs and what the actual installed costs for the process might be. The accuracy assigned to a cost estimate is empirical and not related to variabilities in a statistical sense, but rather, it depends on both the amount and the quality of the technical data available. Accuracy ranges reflect the numerous uncertainties surrounding estimates made using simplifying assumptions. For example, in a preliminary-level estimate 38 ------- in which only a flowsheet, material balance, and an equipment list are available—and all other indirect investments are factored—the uncertainty surrounding the investment is much greater than a definitive-level estimate where quantities and costs for piping, electrical equipment, instruments, etc., are calculated rather than factored. Therefore when estimating the preliminary-level capital investment for a particular process for a particular installation the uncertainty surrounding the costs would be -20%, +40%. However, when comparing the preliminary-level costs for two competing process technologies, many of the same simplifying assumptions are made for each of the processes and therefore the comparability is much greater than the accuracy of the estimates. When directly comparing two similar level estimates, the uncertainty ranges associated with the compared costs are estimated at only llO%. CAPITAL INVESTMENT Generic Lime Spray Dryer Process The total capital investment for the generic lime spray dryer process is $66.2M ($132/kW) in mid-1982 dollars. This total cost can be broken down into the various investment cost categories as shown in Table 13. The total direct investment, which includes processing equip- ment, piping, etc., accounts for about 49% of the total capital investment. The indirect investments such as engineering design and supervision, architect and engineering contractor, construction expense, contractor fees, and project contingency make up about 28% of the total capital investment. The various other capital charges (allowance for startup and modifications, interest during construction, royalties, land, and working capital) make up the remaining 23%. The total direct investment for the generic lime spray dryer process can be further subdivided into the various processing areas. The major investment areas are the particulate matter removal, gas handling, and S02 absorption areas. These areas account for most (78%) of the total direct investment. Major indirect investments are project contingency at $8.4M and the construction expense at $5.2M. Engineering design and supervision, con- tractor fees, and architect and engineering contractor expense contribute significantly less at $2.3M, $1.6M, and $0.7M respectively. Other capital charges, including allowance for startup and modifi- cations, interest during construction, royalties, land, and working capital, account for $15.5M of the total capital investment. The allow- ance for startup and modifications and interest during construction contributed most to the other capital charges. Land and royalties were relatively insignificant at $0.5M and $0.2M. 39 ------- TABLE 13. GENERIC LIME SPRAY DRYER PROCESS TOTAL CAPITAL INVESTMENT (500-MW new coal-fired power unit, 0.7% S in coal; 70% S02 removal; onsite solids disposal) Investment, k$ Direct Investment Material handling 2,443 Feed preparation 599 Gas handling 7,190 S02 absorption 7,173 Particulate removal 11,133 Particulate handling and recycle 1,425 Solids disposal 379 Total process capital 30,342 Services, utilities, and miscellaneous 1,821 Total direct investment excluding disposal field preparation 32,163 Disposal field preparation 321 Total direct investment 32,484 Indirect Investment Engineering design and supervision Architect and engineering contractor Construction expense Contractor fees Contingency Total fixed investment 50,675 Other Capital Charges Allowance for startup and modifications Interest during construction Royalties Land Working capital Total capital investment Dollars of total capital per kW of generation capacity Basis Upper Midwest plant location represents project beginning mid-1980, ending mid-1983. Average cost basis for scaling, mid-1982. Minimum in-process storage, redundant scrubber train, and pumps are spared. Disposal area located one mile from power plant. FGD process investment begins at boiler air heater exit. Boiler plenum and stack excluded. Only nominal construction overtime included. 40 ------- Limestone Slurry Process The total capital investment for the base-case application of the limestone slurry process (a combined particulate-limestone FGD system) is $93.2M ($186/kW) in mid-1982 dollars, as shown in Table 14. The direct investment for the limestone slurry process can be further subdivided into the various processing areas. SC>2 absorption, particulate matter removal, and gas handling account for nearly 79% of the total direct investment. The waste disposal pond construction represents about 8% of the total direct investment. The major indirect investments are project contingency ($11.9M), construction expense ($7.3M), contractor fees ($2.3M), and engineering design and supervision ($3.2M). Architect and engineering contractor costs are significantly less ($0.9M). The remaining $22.OM of the total capital investment is other capital charges. The allowance for startup and modifications and interest during construction together contribute nearly 20% of the total capital investment and make up 83% of the other capital charges. Royalties, land, and working capital are $0.2M, $0.9M, and $2.6M respectively. Comparison The total direct investment and the total capital investment for the two FGD systems are shown in Table 15. The generic lime spray dryer process is substantially (29%) less capital intensive than a limestone slurry process. TABLE 15. BASE-CASE TOTAL DIRECT INVESTMENTS AND TOTAL CAPITAL INVESTMENTS Total direct Total capital investment investment Process Generic lime spray dryer Limestone slurry M$ 32.5 45.7 $/kW 65.0 91.3 M$ 66.3 93.2 $/kW 132.6 186.4 The major investment differences between the generic lime spray dryer process and the limestone slurry process are in the S02 absorption, particulate matter removal, solids disposal equipment, and the waste disposal area preparation as shown in Table 16. With the exception of the investment for the material handling and feed preparation areas, the limestone slurry costs are higher than the costs for the corresponding areas in the generic lime spray dryer process. The lower costs for the generic lime spray dryer process in the other areas are due primarily to the use of the spray dryer. The spray dryer technology eliminates the 41 ------- TABLE 14. LIMESTONE SLURRY PROCESS TOTAL CAPITAL INVESTMENT (500-MW new coal-fired power unit, 0.7% S in coal; 70% S02 removal; onsite solids disposal) Investment, k$ Direct Investment Material handling 919 Feed preparation 1,071 Particulate removal 12,395 Gas handling 9,924 SO absorption 13,734 Solids disposal 1,453 Total process capital 39,496 Services, utilities, and miscellaneous 2,370 Total direct investment excluding pond construction 41,866 Pond construction 3,793 Total direct investment 45,659 Indirect Investment Engineering design and supervision 3,]96 Architect and engineering contractor 913 Construction expense 7,305 Contractor fees 2,283 Contingency 11,871 Total fixed investment 71,227 Other Capital Charges Allowance for startup and modifications 7,123 Interest during construction 11,111 Royalties 228 Land 910 Working capital 2,590 Total capital investment 93,189 Dollars of total capital per kW of generation capacity 186.38 Basis Upper Midwest plant location represents project beginning mid-1980, ending mid-1983. Average cost basis for scaling, mid-1982. Minimum in-process storage, redundant scrubber train, pumps are spared. Disposal pond located one mile from power plant. FGD process investment begins at boiler air heater exit. Boiler plenum and stack excluded. Only nominal construction overtime included. A 2 ------- need for slurry recirculating tanks and pumps and mist eliminators in the S02 absorption area and the thickeners and filtration equipment in the solids disposal area. The higher land and disposal area preparation costs for the limestone process are due to both the type of disposal (pond versus landfill) and the nature of the settled sludge in the pond (i.e., the sludge in the pond is only 40% solids as compared to a dry product going to the landfill in the generic lime spray dryer process). TABLE 16. SUMMARY OF THE TOTAL CAPITAL INVESTMENTS Investment area Material handling Feed preparation Gas handling S02 absorption Particulate removal Particulate handling and recycle Solids disposal Disposal area preparation Land All other capital costs Total capital investment Total cost, Generic lime spray dryer process 2,443 599 7,190 7,173 11,133 1,425 379 321 515 34,993 66,171 , k$ Limestone slurry process 919 1,071 9,924 13,734 12,395 - 1,453 3,793 910 48,910 93,189 Basis: TVA design and economic premises. ANNUAL REVENUE REQUIREMENTS Generic Lime Spray Dryer Process The first-year annual revenue requirements for the generic lime spray dryer process as applied to the previously described base case are $17.04M in 1984 dollars as shown in Table 17. This corresponds to a first-year unit revenue requirement of 6.20 mills/kWh. Equivalent levelized annual revenue requirements for the generic lime spray dryer process are $23.52M, or 8.55 mills/kWh. Annual direct costs (including raw material and conversion costs) are $5.52M or slightly more than 32% of the total first-year annual revenue requirements. Indirect costs, primarily capital charges but also including overhead costs, account for the remaining 68%. The major direct costs are maintenance ($1.9M), electricity ($1.5M) and lime ($1.0M). Together these three items account for 26% of the first-year annual revenue requirements. The other major annual costs are the levelized capital charges of $9.7M and overheads of $1.8M or 57.1% and 10.5% of the total first-year annual revenue requirements respectively. ------- TABLE 17. GENERIC LIME SPRAY DRYER PROCESS ANNUAL REVENUE REQUIREMENTS (500-MW new coal-fired power unit, 0.7% S in coal; 70% S02 removal; onsite solids disposal) Annual quantity Unit cost, $ Total annual cost, $ Direct Costs - First-Year Raw materials Lime Total raw materials cost Conversion costs Operating labor and supervision FGD Solids disposal Utilities Process water Electricity Maintenance Labor and material Analyses Waste disposal operation Total conversion costs Total direct costs 10,068 tons 25,400 man-hr 27,040 man-hr 74,440 kgal 40,151,000 kWh 4,160 man-hr 122,500 tons 102.00/ton 15.00/man-hr 21.00/man-hr 0.14/kgal 0.037/kWh 21.00/man-hr 0.15/ton 1,026.900 1,026,900 381,000 567,800 10,400 1,485,600 1,939,400 87,400 18,400 4,490,000 5,516,900 Indirect Costs - First-Year Overheads Plant and administrative (60% of conversion costs less utilities) Total first-year operating and maintenance costs Levelized capital charges (14.7% of total capital investment) Total first-year annual revenue requirements Levelized first-year operating and maintenance costs (1.886 first-year 0 and M) Levelized annual revenue requirements M$ Mills/kWh First-year annual revenue requirements 17.04 6.20 Levelized annual revenue requirements 23.52 8.55 1,796,400 7,313,300 9.727.100 17,040,400 11.792.900 23,520,000 Basis Upper Midwest plant location, 1984 revenue requirements. Remaining life of power plant, 30 years. Power unit on-stream time, 5,500 hr/yr. Coal burned, 1,347,000 tons/yr, 9,500 Btu/kWh. Total direct investment, $32,484,000; total fixed investment, $50,675,000; and total capital investment, $66,171,000. 44 ------- Limestone Slurry Process The first-year annual revenue requirements for the limestone slurry process are $23.50 as shown in Table 18. This corresponds to a first- year unit revenue requirement of 8.55 mills/kWh. Equivalent levelized annual revenue requirements are $32.19M or 11.71 mills/kWh. Annual direct costs for raw materials, labor, utilities, and main- tenance are $6.8M, or only 29% of the first-year revenue requirements. Indirect costs, primarily for capital charges but also including over- head costs, account for the remaining 71%. Raw material costs for the limestone slurry process are about $0.1M. The conversion costs are nearly $5.9M, with the major costs being maintenance and electricity at $3.5M and $1.8M respectively. As would be expected, the levelized capital charge at $13.7M was the major annual expense, representing 58% of the total first-year annual revenue requirements. Comparison The first-year and the levelized annual revenue requirements for each of the FGD processes are shown in Table 19. The generic lime spray dryer process is approximately 27% lower in cost (6.20 mills/kWh versus 8.55 mills/kWh) than the limestone slurry process in terms of both first-year costs and levelized annual revenue requirements. TABLE 19. BASE-CASE TOTAL FIRST-YEAR AND LEVELIZED ANNUAL REVENUE REQUIREMENTS Total first-year Levelized annual revenue requirements Process Generic lime spray dryer Limestone slurry M$ 17.04 23.50 Mills/kWh 6.20 8.55 M$ 23.52 32.19 Mills/kWh 8.55 11.71 Table 20 compares the various component costs of the first-year revenue requirements for each process. The major cost difference between the processes is the cost for capital charges, maintenance, raw materials, and overheads (primarily because of the differences in main- tenance costs). The $0.7M difference in raw material costs between the limestone slurry process and generic lime spray dryer process (limestone is much cheaper than lime) is essentially cancelled by the higher capital charges of the limestone slurry process. Utility costs (electricity and process water) are about the same for both processes although electrical costs are slightly higher for the limestone slurry process. 45 ------- TABLE 18. LIMESTONE SLURRY PROCESS ANNUAL REVENUE REQUIREMENTS (500-MW new coal-fired power unit, 0.7% S in coal; 70% S02 removal; onsite solids disposal) Direct Costs - First-Year Raw materials Limestone Total raw materials cost Conversion costs Operating labor and supervision FGD Solids disposal Utilities Process water Electricity Maintenance Labor and material Analyses Waste disposal operation Total conversion costs Total direct costs Annual quantity 15,800 tons 61,900 man-hr 18,720 man-hr 99,670 kgal 47,683,000 kWh 6,240 man-hr 104,500 tons Unit cost, $ 8.50/ton 15.00/man-hr 21.00/man-hr 0.14/kgal 0.03 7 /kWh 21.00/man-hr 0.15/ton Total annual cost, $ 133.900 133,900 928,500 393,100 14,000 1,764,300 3,464,700 131,000 15,700 6,711,300 6,845,200 Indirect Costs - First-Year Overheads Plant and administrative (60% of conversion costs less utilities) Total first-year operating and maintenance costs Levelized capital charges (14.7% of total capital investment) Total first-year annual revenue requirements Levelized first-year operating and maintenance costs (1.886 first-year 0 and M) Levelized annual revenue requirements 2,959,800 9,805,000 13.698.800 23,503,800 18.492.200 32,191,000 M$ Mills/kWh First-year annual revenue requirements 23.50 8.55 Levelized annual revenue requirements 32.19 11.71 Basis Upper Midwest plant location, 1984 revenue requirements. Remaining life of power plant, 30 years. Power unit on-stream time, 5,500 hr/yr. Coal burned, 1,347,000 tons/yr, 9,500 Btu/kWh. Total direct investment, $45,659,000; total fixed investment, $71,227,000; and total capital investment, $93,189,000. ------- TABLE 20. SUMMARY OF THE TOTAL FIRST-YEAR REVENUE REQUIREMENTS Raw materials Operating labor and supervision Electricity Maintenance Levelized capital charges Overheads Other annual costs Total first-year revenue requirements Total cost, $ Generic lime spray dryer process 1,026,900 948,800 1,485,600 1,939,400 9,727,100 1,796,400 116,200 17,040,400 Limestone slurry process 133,900 1,321,600 1,764,300 3,464,700 13,698,800 2,959,800 160,700 23,503,800 The higher maintenance charge for the limestone process is due to both the larger number of equipment items needed and the problems associated with handling and recirculating a corrosive and erosive scrubbing slurry. SENSITIVITY ANALYSIS Sensitivity to Raw Material Prices The sensitivity of the first-year annual revenue requirements for the generic lime spray dryer process and the limestone slurry process to the delivered raw material cost was calculated. The results of this sensitivity analysis are shown in Figure 3. Although the generic lime spray dryer process is more sensitive than the limestone slurry process to changes in the delivered price of the raw material, the low-sulfur nature of the coal and the low S02 removal requirement preclude changes from the base-case costs from significantly changing the economic results. The generic lime spray dryer process has lower first-year annual revenue requirements regard- less of the raw material prices selected. For example, a 25% increase (or decrease) in the delivered cost of lime results in only a 1.3% increase (or decrease) in the first-year annual revenue requirements for the generic lime spray dryer process. This is still 26.5% less than the first-year annual revenue requirements for the base-case limestone slurry process. 47 ------- .c- oo 10.0 g 9.0 - 7.0 6.0 5.0 LIMESTONE COST, 5/TON 5.00 8.50 12.00 \ Y Limestone slurry process Generic lime spray dryer process I I 75.00 102.00 125.00 LIME COST (DELIVERED), $/TON Figure 3. Sensitivity of the first-year annual revenue requirements to the delivered cost of the raw material. 10.0 9.0 8.0 5- 6-0 5.0 4.0 _L Limestone slurry process Generic lime spray dryer process _L _L _L 0.8 1.0 1.1 1.2 1.3 1.4 1.5 RAW MATERIAL STOICHIOMETRY, MOL ALKALI/MOL S02 ABSORBED Figure 4. Sensitivity of the first-year annual revenue requirements to the raw material stoichiometry in the absorber. ------- The limestone slurry process, due to the low unit cost of limestone as well as the lower sulfur level in the coal and the lower SC>2 removal requirements, is essentially insensitive to the delivered price of limestone. Sensitivity to Raw Material Stoichiometry Since the generic lime spray dryer process technology has only been demonstrated on a pilot-plant scale, the assumed Stoichiometry in the spray dryer could change as the technology is developed further. In addition, the alkalinity in the fly ash from low-sulfur coals may vary between coals. The required lime Stoichiometry for coals with the same sulfur content could change, depending on the fly ash alkalinity of coal being burned. Therefore, a sensitivity analysis showing the changes in total first-year revenue requirements as the raw material Stoichiometry in the spray dryer is changed has been included. Table 21 lists both the base-case and the alternative stoichio- metries used in the sensitivity analysis. The raw material stoichio- metries given are in mols of alkali per mol of S0~ absorbed. The range of stoichiometries shown for the generic lime spray dryer process is 1.00 (-18.0%) to 1.46 (+19.7%). The capital investments for each processing area are adjusted by using area scale factors and the ratio of raw material flow rates through each area. Processing areas that are sized independently of the raw material rates (gas handling and S02 absorption) are the same for each of the alternative stoichiometries. Many of the processing areas that are dependent on the raw material flow rate contribute only minor amounts to the capital investment. For example, a 19.7% increase in raw material flow rate increases the capital investment only about 2%. The annual revenue requirements for the generic lime spray dryer process are somewhat more sensitive to the raw material Stoichiometry than the raw material cost. For example, a 19.7% increase in the raw material Stoichiometry results in a 3.1% increase in first-year revenue requirements. However, from these results (as shown in Figure 4) it is apparent that Stoichiometry changes over a wide range will have little effect on the capital investment and annual revenue requirement relation- ships of the two processes. Sensitivity to Waste Disposal Costs An alternate limestone slurry process in which the waste sludge is dewatered and fixed before disposal in a landfill is included for com- parison purposes. For this alternate process, the front end of the limestone slurry process (through the venturi/spray tower absorbers) is identical to the base-case limestone slurry process. The major difference is that the absorber slurry bleed is treated using a process similar to the IU Conversion Systems, Inc. (IUCS) fixation process. In this process 49 ------- TABLE 21. COMPARISON OF TOTAL CAPITAL INVESTMENT AND FIRST-YEAR UNIT REVENUE REQUIREMENTS FOR THE GENERIC LIME SPRAY DRYER PROCESS AT VARIOUS RAW MATERIAL STOICHIOMETRIES Total Raw material stoichiometry Process Generic lime spray dryer Limestone slurry Variation Low Base High Base Value* 1.00 1.22 1.46 1.12 % change^ -18.0 19.7 - capital $/kW 129.9 132.3 135.0 186.4 investment % change^ -1.8 2.0 - First-year unit revenue requirements Mills/kWh 6.02 6.20 6.39 8.55 % change^ -2.9 3.1 - a. Raw material stoichiometry is defined as mols of alkali per mol of S02 absorbed. b. Change is calculated relative to the base-case value. ------- the mixed sulfite-sulfate sludge, rather than being pumped to a pond for disposal, is dewatered, using a thickener and a filter, to 60% solids, mixed with dry fly ash and lime, and trucked to an onsite landfill for disposal. The capital investment for this process was estimated from the base-case limestone slurry process capital investment by deleting the disposal area preparation (pond construction) and sludge transportation charges and including the investment required for the IUCS process equipment and the landfill preparation. The total capital investment for the limestone slurry-IUCS process is $91.4M (vs. $93.2M for the base-case limestone slurry process). The lower capital investment for the limestone slurry-IUCS process is the result of the much lower land- fill preparation costs ($0.23M for the landfill vs. $3.79M for the pond), which overcome the costs ($2.66M) for the additional equipment (thickeners and filters). The first-year and the levelized annual revenue requirements for the limestone slurry-IUCS process are $24.98M (9.08 mills/kWb.) and $35.20M (12.80 mills/kWh) respectively. These costs are about 6% higher than those for the base case (i.e., with ponding). Although the levelized capital charges are lower ($0.2M) for the limestone slurry-IUCS process, this savings is completely offset by the higher labor costs ($0.88M) and the higher overheads ($0.62M). 51 ------- REFERENCES 1. Machine Readable Data Format of FERC FORM 67 Data, 1969-1973, Applied Data Research, 1976. 2. New Stationary Sources Performance Standards; Electric Utility Steam Generating Units. Fed. Regist., 44(113):33,580-33,624, June 11, 1979, 3. Technical Assessment Guide, EPRI PS-866-SR, Electric Power Research Institute, Palo Alto, California, June 1978. 4. Jeynes, P. H. Profitability and Economic Choice, 1st Ed., The Iowa State University Press, Ames, Iowa, 1968. 5. Economic Indicators, Chemical Engineering, Vols. 83, 84, 85, and 86, 1976, 1977, 1978, and 1979. 52 ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) , REPORT NO. EPA-600/7-80-050 J3. RECIPIENT'S ACCESSION NO. TITLE ANDSUBTITLE Preliminary Economic Analysis of a Lime Spray Dryer FGD System IB. REPORT DATE March 1980 6. PERFORMING ORGANIZATION CODE 7 AUTHOR(S) T.A. Burnett and W.E. O'Brien |8. PERFORMING ORGANIZATION REPORT NO. EDT-112 'PERFORMING ORGANIZATION NAME AND ADDRESS Tennessee Valley Authority Office of Power Division of Energy Demonstrations and Technology Muscle ShoalSi Alabama 35660 10. PROGRAM ELEMENT NO. INE827 11. CONTRACT/GRANT NO. Inter agency Agreement EPA-IAG-D9-E721-BI 2. SPONSORING AGENCY NAME AND ADDRESS EPA, Office of Research and Development Industrial Environmental Research Laboratory Research Triangle Park, NC 27711 A T Pr A TYPE OF REPORT A.NB-P.ERLO eliminary; VERED 14. SPONSORING AGENCY CODE EPA/600/13 -^SUPPLEMENTARY NOTES IERL-RTP project officer is 919/541-2683. Theodore G. Brna, Mail Drop 61, 16. ABSTRACT rep0r(. gives results of a preliminary economic analysis of two flue gas desulfurization (FGD) processes (one dry and one wet) for a new 500-MW power plant burning Western coal having 0. 7% sulfur , 9. 7% ash, and a heating value of 9700 Btu/lb and meeting current new source performance standards (70% SO2 removal and 0.03 Ib/MBtu particulate emission). The generic lime spray-dryer process used a baghouse for particulate collection, while the wet limestone slurry process had an electrostatic precipitator (ESP) for particulate control. (In addition to the coal noted, the final report will include an economic evaluation for both low- and high-sulfur Eastern coals.) The analysis shows capital investment costs of Sl32/kW for the lime process for SO2 and particulate removal, and #186/kW for the limestone process. First year and levelized annual revenue requirements are 6. 20 and 8. 55 mills /kW, respectively, for the lime process; and 8.55 and 11.71 mills /kW, respectively, for' the limestone process. Sensitivity analyses indicate that: (1) delivered raw material costs do not significantly affect the annual revenue requirements for either process- (2) annual revenue requirements for the spray dryer are insensitive to the raw mat- erial stoichiometry; and (3) waste disposal for the wet process, even with fixation, is more expensive than for the dry process. 7. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS COSATl Field/Group Pollution Calcium Carbonates Economic Analysis Spray Drying Analyzing Coal Desulfurization Combustion Flue Gases Calcium Oxides Pollution Control Stationary Sources 13B 05C 13H 14B 21D 07A,07D 21B 07B 18. DISTRIBUHON STATEMENT Release to Public 19. SECURITY CLASS (ThisReport! Unclassified 21. NO. OF PAGES 75 20. SECURITY CLASS (Thispage) Unclassified 22. PRICE EPA Form 2220-1 (9-73) 53 ------- |