MULTICYCLE STUDY ON CHEMICAL-LOOPING COMBUSTION OF METHANE WITH CASO4 OXYGEN CARRIER IN A FIXED BED REACTOR

摘要

IntroductionChemical-looping combustion (CLC) has been proposed as a new technology that can be used to control the greenhouse gas emission with less energy loss[1]. A number of metal oxides have been extensively investigated as potential oxygen carriers in CLC of methane or natural gas in many research centers such as Tokyo Institute of Technology[2,3], Chalmers University of Technology[4-6], CSIC[7,8], and Korea Institute of Energy Research[9,10]. However, these oxygen carriers also have some significant disadvantages for application in the CLC system, for example, high cost of these metal materials, the heavy carbon deposition problem, and potential heavy-metal pollution to the environment. Alstom Power Inc. Have started investigation on the feasibility of CaSO4 based oxygen carrier in CLC system[11], but they still have not published key data yet. CANMET has also explored the use of CaSO4 as oxygen carrier in CLC[12]. As a novel oxygen carrier, CaSO4 has many advantages. It is much more environmentally sound as a nonmetal oxide. CaSO4 is cheaper due to vast gypsum resources all over the world. Compared with metal oxides,[13] CaSO4 has a relatively higher oxygen capacity. A CLC system using two interconnected fluidized bed reactors is proposed for direct use of coal and other solid fuels such as biomass, solid wastes and cokes[14]. It is mainly composed of a bubbling fluidized bed, a fluidized bed, and a cyclone.