Circulating bed absorption for flue gas desulfurization: A fundamental study

The Tennessee Valley Authority (TVA) has been interested in the circulating bed absorption (CBA) technology for the control of sulfur dioxide (SO{sub 2}) emissions from coal-fired power plants. This technology incorporates a semi-dry, lime-based flue gas desulfurization (FGD) process that offers some potentially significant advantages over conventional spray dryer and wet scrubbing FGD systems. In a project co-funded by the TVA and the Center for Applied Energy Research (CAER), a pilot-scale fluid bed reactor was modified to simulate a generic CBA process. The objective of the CAER test program was to evaluate the influence of basic operating parameters such as calcium-to-sulfur ratio (Ca/S), inlet flue gas temperature, flyash loading, fuel chloride, gas residence time and approach to saturation temperature on the overall sulfur capture and sorbent utilization in the CBA process. The overall sulfur capture varied between 45 and 99.5% depending on the specific test conditions. An increased fuel chloride level enhanced the sulfur capture in the system. Fly ash also enhanced sulfur capture and was postulated to assist in CBA reactor particle agglomeration. The reactor SO{sub 2} capture efficiency decreased with increasing inlet SO{sub 2} concentration and a constant Ca/S ratio.