Utilization of AFBC waste by-product as a FGD sorbent for circulating dry scrubbing

The Tennessee Valley Authority (TVA) is currently interested in finding applications for the spent bed sorbent by-product generated at their 160 MW AFBC facility. Calcium utilization in this by-product is relatively low, having an available alkalinity from 20 to 40 wt%, as Ca(OH){sub 2}, thus, creating a potential disposal problem. It is possible that this byproduct material could be used as a supplemental sorbent in the Gas Suspension Absorption (GSA) reactor located at the TVA`s Center for Emissions Research in Paducah, Kentucky. GSA technology is a semi-dry, lime based, FGD process that utilizes a circulating bed arrangement for contacting sorbent with SO{sub 2}-laden flue gas under coolside conditions. A pilot-scale fluid bed reactor was modified to simulate a generic circulating dry scrubber (CDS) process similar to the GSA technology.The purpose of this program was to investigate the feasibility of using AFBC waste in conjunction with hydrated lime as a sorbent for the CDS process. An AFBC by-product from the 160 MW plant was pulverized to liberate CaO and slaked along with a fresh lime feedstock. CDS sulfur capture was evaluated with and without chloride addition to the sorbent slurry. Control tests using lime-only feeds were also conducted. In general, themore » sulfur capture reactivity of the sorbent which included slaked lime/AFBC material was found to be equivalent to or greater than that containing only fresh lime. With a nominal Ca/S ratio of 1.3 (1.0 with fresh lime, 0.3 slaked by-product), the reactor sulfur capture varied between 65 and 90% depending on the specific test conditions. An effective fuel chloride of 0.2 wt% was found to enhance the sulfur capture by as much as 8 to 12%.« less