United States Environmental Protection Agency Air and Energy Engineering Research Laboratory Research Triangle Park NC 27711 Research and Development EPA/600/S7-87/028 Feb. 1988 &EPA Project Summary Conceptual Designs and Cost Estimates for E-SOX Retrofits to Coal-Fired Utility Power Plants D. F. Becker and J. L. DuBard A conceptual design and cost esti- mate, based on information available at the beginning of 1987, was done for six cases of a retrofit of the E-SOX process to a utility. The annualized cost ranged from $301 to $378 per ton of SO2 removed. The generic cost basis, used for other cost estimates, was used in this study and applied to a 500 MWe utility burning eastern medium sulfur (2.5%) bituminous coal. Capital costs compare very favorably with other retrofit SO2 removal technologies. Sorbent or reagent cost is the largest single component of the costs. This Project Summary was devel- oped by EPA's Air and Energy Engi- neering Research Laboratory. Research Triangle Park. NC, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). Background E-SOx technology has been proposed as a feasible way to lower SO, emissions from power plants upon retrofit to an existing electrostatic precipitator (ESP). In a conceptual study to evaluate various retrofit situations, applicable bases were kept identical with those of a similar study in 1983 on Limestone Injection Multistage Burner (LIMB) systems. The conceptual designsdiscussed here are based on a generic power plant. All subsystems necessary for a complete E- S0« system are included in the costs. Equipment and systems were optimized on a limited basis, because this is not a site-specific study. Thus, costs will vary from those presented here, as specific locations are considered. The study provides a point of reference for compar- ison purposes, and shows where future research and development efforts should be concentrated. Scope and Approach After the LIMB study, plant size was selected as 500 MW, with existing particulate control equipment designed to meet the 1971 New Source Perfor- mance Standards for particulate matter. The process designs were based on lime stoichiometries and approach tempera- tures necessary to achieve 50% sulfur reduction for a typical eastern, medium sulfur (2.5%) bituminous coal. Two process conditions were selected using hydrated lime as a reagent, and one using quicklime. For one of the lime hydrate process conditions, four ESP upgrade conf igurations were evaluated. Six E-SOx cases were investigated: Case /—Hydrated lime reagent, Ca/S = 1.3, approach temperature 4°C, original 218 SCA ESP, retrofit- ted with precharger and large diameter electrodes. Case 2—As Case 1, except no pre- charger, weighted wires instead of large diameter discharge electrodes, and 0.5 m longer collecting plates in each field. Case 3—As Case 1, except original 150 SCA ESP, plate height increased by 0.9 m, and collecting plates ------- in each field increased in length by 0.5 m. Case 4—As Case 3, except no pre- charger, weighted wires instead of large diameter discharge electrodes, and an additional short third active field. Case 5—As Case 1, except a Ca/S ratio of 1.5 and an approach temper- ature of 10°C. Case 6—As Case 1, except pebble quicklime is used as a reagent. The study consisted of the conceptual equipment selection, equipment arran- gement, and capital and first year operating and maintenance cost esti- mates for the E-SOx system and all supporting equipment for the above six cases. Findings The mechanical equipment used as a basis for these designs is predominantly commercial. Lime receiving and storage and slurry preparation are state-of-the- art for many existing scrubbers, both wet and dry. On the other hand, the two-fluid nozzle arrangement, because of its requirement for a relatively flat and fine droplet size distribution (40-50 fim), requires some developmental work. Also some of the chosen ESP modifications, which use advanced technology to achieve the required particulate removal (e.g., the precharger and large-diameter electrodes), require developmental work. Hence, there is more uncertainty in the ESP performance of Cases 1, 3, 5, and 6 than in Cases 2 and 4, which are more conventional ESP upgrades. Because limited laboratory scale process data are available, process uncertainties are associated with reagent stoichiometry, approach temperature, and residence time. Residence time also raises the question of whether adequate spray drying can occur without wetting the ESP. Concerning ESP performance for the E-SOx process, computed ESP collection efficiency and particulate mass emis- sions are tabulated for each case in Table 1. ESP performance was assessed using Southern Research Institute's ESP Mathematical Model. A comparison of Cases 1 and 2 shows that a modest increase in plate length will achieve the same ESP performance improvement as the installation of novel electrodes. With low-resistivity fly ash and reasonable plate area after an E-SO, retrofit (SCA of 173 ft2/1000 acfm [571 m2/1000 m3/ min] prior to ESP modifications), the precharger offers little performance advantage. It quickly charges the dust particles that otherwise would be charged within 0.6 or 0.9 m of travel along a conventional gas passage. The large-diameter discharge electrodes, on the other hand, pffer a performance advantage due to the increased intere- lectrode electric field. In Cases 3 and 4, with a much lower plate area after an E-SO, retrofit (SCA of 118 ft2/1000 acfm [391 mVlOOO mVmin] prior to ESP modifications), a substantial rebuild of the ESP is required to limit particulate emissions to 0.1 lb/108 Btu (0.04342 kg/ GJ). Table 2 summarizes the capital and operating and maintenance (O&M) costs for the six E-SO, cases. The capital costs compare very favorably with other retrofit S02 removal technologies. This is attrib- uted to the maximum use of existing equipment and minimal new equipment requirements. First year O&M costs are largely influenced by lime consumption and delivered cost. As a way to compare overall costs of the systems. Table 3 presents total first year costs on an annualized basis, as well as costs per ton of SOz removed. The costs per ton of S02 removed indicate that E-SOxtechnology, if it can be suc- cessfully commercialized, should com- pete very favorably with other retrofit SOz removal technologies. In summary, the following conclusions can be drawn: • The mechanical system design for the most part utilizes commercially avail- able equipment. The only items that pose developmental problems are the two-fluid nozzle spray system, the ESP precharger, and the ESP large diame- ter electrodes. • From an operating point of view, the greatest concern is adequate spray drying in the (gutted) first field of the ESP to minimize tenacious deposits in subsequent ESP fields. • ESP performance on this type of particulate needs to be verified. In particular, the mass loadings and size distribution of the particulate at the end of the spray section, the ESP electrical properties (secondary vol- tages and currents), and gas distribu- tion device requirements need to be established. • The capability of a vacuum type fly ash handling system to continuously remove hopper material needs to be demonstrated. Additional equipment requirements(for example a delumper to prevent oversize material) need to be defined. • Retrofit capital costs will be very site specific, particularly if conventional ESP modifications (taller plates or an outlet field) are required. • The largest single component affect- ing the operating cost is reagent consumption. Therefore, process stoichiometry is critical to cost. Also, pebble lime shows a distinct economic advantage over lime hydrate. • Future research efforts should be concentrated on optimizing the pro- cess parameters, in particular, slurry droplet size, Ca/S ratio, approach temperature, and residence time requirements. • Because of the performance advan- tages indicated by the precharger and large diameter electrodes, these technologies should be further dem- onstrated at an appropriate equipment scale. ------- Table 1. Precipitator Performance Case No. SCA. ff/IOOOacfm* Outlet Emissions, lt>/10eBtu>> Co/lection Efficiency, % 1 173 0.08 99.59 2 201 0.08 99.56 3 163 0.08 99.57 4 148 0.07 99.62 5 171 0.08 99.57 6 172 0.08 99.58 *1 ftV/000 acfm = 3.32 m*/m3/min "1 /b/W6Btu = 0.4342 kg/GJ Table 2. Cost Summary (January 1987 Dollars) First Year Operating and Capital Cost Case No. 1 2 3 4 5 6 stooo 19.100 23,700 22,700 19,400 19.100 15.900 $/kW 38 47 45 39 38 32 Maintenance Cost SlOOO/yr 6,800 6,980 6.940 6.890 7,480 6.070 Mills/kWh 2.39 2.45 2.44 2.42 2.62 2.13 Table 3. First Year Annual/zed Costs (January 1987 $1000/yr) Case No. Annual/zed Capital Cost First Year O&M Cost Total First Year Annual/zed Cost $/ton SOi Removed 1 3.440 6.800 10.240 345 2 4.260 6,980 11.240 378 3 4.090 6.940 11.030 371 4 3.500 6.890 10.390 350 5 3.440 7,480 10,920 368 6 2.870 6,070 8,940 301 D. Becker is with Gilbert/Commonwealth, Inc., Reading, PA 19603; and J. DuBard is with Southern Research Institute, Birmingham, AL 35255. Samuel L. Rakes is the EPA Project Officer (see below}. The complete report, entitled "Conceptual Designs and Cost Estimates for E- SO, Retrofits to Coal-Fired Utility Power Plants," fOrder No. PB 88-143 995/ AS; Cost: $14.95, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, V'A 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 U.S.OFFICIAL MM 'V 3 &TE / fir. ;jooi z / , -. ; _ / , £i METERi ooi z f\ 7 -. ; _ u ,L 9 ^ i — Official Business Penalty for Private Use $300 EPA/600/S7-87/028 0000329 PS U S 68V1R PROTECTION AGENCY R66IOH 5 LIBRARt 230 S OfftRBORH STRSIT CMICA60 IL «0€04 ------- |