Development of an advanced calcium-based sorbent for desulfurizing hot coal gas

Modern coal power plants that employ an IGCC system provide an efficient me ans for power generation. However, toxic and extremely corrosive sulfurous gases produced in a coal gasifier need to be removed from the hot gas prior to combustion in gas turbines. Due to stringent environmental laws, a rege nerable sorbent that can remove the unwanted gases at high temperature (e.g . 1170 K) is preferred. In this work, composite sorbents consisting of a li mestone core and a cement shell were prepared by pelletizing the powdered m aterials. In some cases limestone was also incorporated in the shell. The s orbents were characterized by measuring their crushing strength and their a dsorption capacity when exposed to H2S gas at high temperature. Several dif ferent hydraulic cements were tested including Type I, Type III, and Type I V Portland cements and CA-14 calcium aluminate cement. Other factors invest igated included the shell thickness, concentration of limestone in the shel l, and pelletization time. The results showed that formulations containing high concentrations of limestone in the shell had higher absorption capacit ies but at the expense of pellet strength. Longer pelletization times impro ved pellet strength. The best overall results were achieved when CA-14 ceme nt was incorporated in the shell. While a foundation was laid for sorbents based on the core-in-shell pellet concept, further development is essential and is underway. (C) 2001 Elsevier Science Ltd. All rights reserved.