United States Environmental Protection Agency Industrial Environmental Researc Laboratory Research Triangle Park NC 2771 vvEPA Research and Development EPA-600/S7-82-045 September 1 982 Project Summary Combustion of Oil Shale in Fluidized-Bed Combustors- An Overview Douglas R. Roeck Oil shale can be combusted (alone or as a supplement to coal) and function as an SO2 sorbent in atmospheric fluidized-bed combustion (AFBC). Spent shale from retorting processes may also provide for SO2 sorption and some residual fuel value in AFBC. Commercial applications of direct combustion of oil shale in AFBC are limited, and known to exist only in Estonia (Soviet Union), China, and Southern Germany. Combustion of shale and coal/shale mixtures in AFBCs in the U.S. has been investi- gated on a pilot and laboratory scale. Technical concerns include calcination heat loss, optimal shale sizing, and combustion efficiency. Direct com- bustion of Western U.S. shale in a pilot AFBC resulted in NO* emissions as high as 3 lb/1O6 Btu, although for coal/shale mixtures NOX emissions were below 0.6 lb/106 Btu. Because of its calcium carbonate content, shale can act as an effective SOa sorbent in AFBC, and has resulted in SOa reduction efficiencies of greater than 85% in tests with coal/shale mixtures. A preliminary economic analysis indicates that substituting oil shale for limestone in an AFBC may have significant cost advantages where shale (or spent shale) is available at costs that are competitive with conventional sorbents. This Project Summary was devel- oped by EPA's Industrial Environ- mental 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). Introduction The U.S. has vast oil shale resources that may be commercially developed during the 1980s. Production estimates for the emerging oil shale industry range as high as 3 million bbl/day by the year 2000, although 0.5 million bbl/day may be a more realistic estimate. A single full-scale commercial plant producing 50,000 bbl/day would use 60,000 ton/day of high-grade shale containing 35 gal./ton and would produce 51,000 ton/day of spent shale. AFB combusters could potentially be used to burn virgin oil shale or oil shale fines to produce steam or electricity. Virgin or spent shale could be used in coal/shale mixtures to provide heat and capture potential SOa emissions. The technoeconomic feasibility of using oil shale to provide some heating value and control SOa emissions from coal com- bustion appears to be promising In the U.S., research and pilot scale experiments have been conducted by the U.S. Department of Energy and several private AFBC manufacturers. DOE has conducted tests on oil shale from Colorado, Israel, and Morocco at its research facility in Morgantown, VW. Private research has been conducted by the Babcock and Wilcox (B&W) Re- search and Development Division, by Foster Wheeler Company, and by numerous companies involved in the ------- Table 2. Comparison of Direct Operating Costs for a 250,000 Ib/hr FBC Boiler Burning Coal with Limestone and Oil Shale Sorbents Cost data /S/WOO Ib steam) Test description Base case Case No. J (B&W Test No. Til Case No. 2* (ANL Test No. 171 Case No. 3" (ANL Test No 20) Coal Feed Sulfur rate % Ib/hr 35 34,012 3.6 26,377 3.0 21,632 2.0 28,950 HHV Btu/lb 10,430 12,300 12,183 12,183 Sorbent Sorbent SO, Snlirl rnal Feed Ca/S reduc- waste at at at at at at rote HHV molar tion rate $35/ S5/ $10/ S20/ $25/ $30/ Type Ib/hr Btu/lb ratio % Ib/hr ton ton ton ton ton ton Limestone 12.256 — 3.0 85 13,484 2.38 — 0.2 049 0.61 0.74 Virgin 30.557 1.0OO 2.4 84 31,257 1 85 0.31 shale 061 1.22 — 1.83 Virgin 30.285 3,020 3.1 87.5 23,168 1.51 0.30 shale 0.61 1.21 — 1.82 Spent 5.790 400 1.2 95.9 8,546 203 0.06 shale 0. 12 0.23 — 0.35 Solid waste removal at S6/ ton 0 16 0.16 016 0.16 038 0.38 0.38 0.38 0.28 0.28 0.28 0.28 0 10 0.10 0.10 0.10 Total direct operating cost* 3.92 4.16 4.28 4.41 3.67 3.97 4.58 5.19 3.22 3.53 4.13 4.74 3.32 3.38 3.49 3.61 'Not shown in this table are other components of the total direct operating cost: electricity, oil, and labor. "Tests at ANL were by thermogravimetric analysis on the costs of conventional sorbents as well as other costs related to transporting the raw or spent shale to an industrial or utility-coal-burning facility. For a retorting facility, generating its own power in a fluidized-bed, coal-burning power plant, the concept should be both technically feasible and cost competi- tive with limestone for achieving any required SC"2 reduction. Since oil shale combustion tests to date have been conducted in fluidized bed reactors 18 in. in diameter or less, further testing in larger scale equipment is warranted before firm conclusions can be drawn concerning the prospects of scaling up to commercial application. The preliminary economic analysis indicates that costs for operating an FBC unit using oil shale as an SO2 sorbent are competitive with similarly sized FBCs using conventional limestone sorbent. While direct operating costs were -25 to +21% and total annualized costs -15 to +13%, compared to the coal/limestone base case, these costs are highly dependent on the cost of the shale. Given that the test data used for this cost comparison were developed from FBC units 18 in. in diameter or less, such an assessment should be repeated using test data resulting from larger scale equipment if and when such data become available. Metric Conversion Readers more familiar with metric units are asked to use the following factors to convert certain non-metric units used in this summary. Non-metric Multiplied by Yields metric bbl Btu °F ft gal. in. Ib ton 159 1055 5/9f°F-32) 0.3 3.79 2.54 0.45 8897 I J °C m I cm kg Nt ------- 6.0 5.0 to .1 § t 0) 4.0 3.0 2.0 — — ,- - Spent Shale 10 15 20 Sorbent Cost, $/ton 25 30 Figure 2. Direct operating cost as a function of sorbent cost for various coal- sorbent systems. Douglas R. Roeck is with CCA/Technology Division, Bedford, MA 01730. John O. Mill/ken is the EPA Project Officer (see below). The complete report, entitled "Combustion of Oil Shale in Fluidized-Bed Com- bustors—An Overview," (Order No. PB 82-249 889; Cost: $9.00. subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, MA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Industrial Environmental Research Laboratory U.S. Environmental Protection Agency Research Triangle Park. NC 27711 •&U. S. GOVERNMENT PRINTING OFFICE: I982/559-092/0502 ------- ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Postage and Fees Paid Environmental Protection Agency EPA 335 Official Business Penalty for Private Use $300 PS 0000329 U S ENVIR PROTECTION AGENCY REGION 5 LIBRARY 230 S DEARBORN STREET CHICAGO IL 60604 ------- |