Toxic substances from coal combustion -- A comprehensive assessment
The Clean Air Act Amendments of 1990 identify a number of hazardous air pollutants (HAPs) as candidates for regulation. Should regulations be imposed on HAP emissions from coal-fired power plants, a sound understanding of the fundamental principles controlling the formation and partitioning of toxic species during coal combustion will be needed. With support from the Federal Energy Technology Center (FETC), the Electric Power Research Institute, and VTT (Finland), Physical Sciences Inc. (PSI) has teamed with researchers from USGS, MIT, the University of Arizona (UA), the University of Kentucky (UK), the University of Connecticut (UC), the University of Utah (UU) and the University of North Dakota Energy and Environmental Research Center (EERC) to develop a broadly applicable emissions model useful to regulators and utility planners. The new Toxics Partitioning Engineering Model (ToPEM) will be applicable to all combustion conditions including new fuels and coal blends, low-NOx combustion systems, and new power generation plants. Development of ToPEM will be based on PSI's existing Engineering Model for Ash Formation (EMAF). This report covers the reporting period from 1 July 1999 to 30 September 1999. During this period the MIT INAA procedures were revised to improve the quality of the analytical results. Two steps have been taken to reduce the analytical errors. A new nitric acid leaching procedure, modified from ASTM procedure D2492, section 7.3.1 for determination of pyritic sulfur, was developed by USGS and validated. To date, analytical results have been returned for all but the last complete round of the four-step leaching procedure. USGS analysts in Denver have halted development of the cold vapor atomic fluorescence technique for mercury analysis procedure in favor of a new direct analyzer for Hg that the USGS is in the process of acquiring. Since early June, emphasis at USGS has been placed on microanalysis of clay minerals in project coals in preparation for use of the Stanford/USGS SHRIMP RG Ion Microprobe during August 1999. The SHRIMP-RG data confirm that Cr is present at concentrations of about 20 to 120 ppm, just below the electron microprobe detection limits (100 to 200 ppm), as suspected from Phase 1 microprobe work and previous studies of clay mineral separates. The University of Utah has started trial runs on the drop tube furnace to ensure that the gas analysis system is working properly and that the flow pattern within the furnace is laminar and direct. A third set of ASTM samples will be prepared at the University of Utah for the Phase 1 and Phase 2 coals. This time the INAA counting time will be optimized for the elements in which the authors are interested, guided by the results from the first two samples. The iodated charcoal which was used by MIT for vapor phase Hg collection was tested to see whether it collected other vapor phase metals. A second set of tests were performed at PSI using the entrained flow reactor (EFR). The University of Arizona's pilot-scale downflow laboratory combustion furnace was used to test the partitioning of toxic metals in the baseline experiments for the Phase 2 North Dakota lignite and the Pittsburgh seam bituminous coal at baghouse inlet sampling conditions. In addition, baseline data were collected on combustion of the Phase 1 Kentucky Elkhorn/Hazard bituminous coal. Emphasis at the University of Kentucky was placed on (1) collection of new Hg XAFS data for various sorbents, and (2) on collection of XAFS and other data for arsenic, sulfur, chromium and selenium in two baseline ash samples from the University of Arizona combustion unit. A preliminary interpretation of the mercury data is given in this report. Revision was made to the matrix for the initial experiments on mercury-ash interactions to be conducted at EERC. The overall goal of this effort is to collect data which will allow one to model the interactions of mercury and fly ash (specifically, adsorption of Hg{sup 0} and Hg{sup +2} and oxidation of Hg{sup 0}) in the air heater and particulate control device of a coal-fired power plant. The simple mass balance model for emissions of mercury from coal-fired power plants was revised to further test the current understanding of mercury transformations in flue gas. Improvements were made to the model for major element vaporization. The method for predicting vaporization of major elements predicts the total amount vaporized within a factor of two.
- Research Organization:
- Federal Energy Technology Center Morgantown (FETC-MGN), Morgantown, WV (United States); Federal Energy Technology Center Pittsburgh (FETC-PGH), Pittsburgh, PA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC22-95PC95101
- OSTI ID:
- 757425
- Report Number(s):
- DE-AC22-95PC95101-15; TRN: AH200019%%167
- Resource Relation:
- Other Information: PBD: 1 Nov 1999
- Country of Publication:
- United States
- Language:
- English
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