Experimental and Engineering Support for the CAFB (Chemically Active Fluid-Bed) Demonstration: Residue Disposal/Utilization

摘要

The report gives results of an investigation of the disposal and utilization of spent sulfur sorbent from the Chemically Active Fluid-bed (CAFB) process. Lignite ash with a minimum of 10% CaO can be used as a replacement for sand or medium aggregate or as a partial replacement for light aggregate in cement block manufacturing with higher strengths (14.68 to 26.82 MPa) than standard mixes, 4.62 to 5.62 MPa at 28 day cure tests. This indicates that the cement content of the mix may be reduced when CAFB residue is used. Disposal tests indicate that pH, calcium, and sulfate in the leachate are primary environmental concerns. Some lignites and coal may produce levels of trace materials (e.g., selenium, iron, and manganese) that exceed regulations. Any appreciable sulfide in the spent sorbent must be converted to sulfate before disposal. Fine particle size, possibly as small as -44 micrometers, appears necessary for complete conversion of the calcium sulfide to calcium sulfate in completely sulfided sorbent. Cementitious compounds may be formed under CAFB operating conditions, thus aiding disposal and reducing leachates from the spent sorbent.