Chemical looping combustion

Abstract

Chemical looping combustion (CLC) and looping cycles in general represent an important new class of technologies, which can be deployed for direct combustion as well as be used in gasification applications. In this type of system, a solid carrier is used to bring oxygen to the fuel gas, so that it can be subsequently released as a pure CO2 stream suitable for use, or, more likely, for sequestration. The solid is then regenerated in a reactor using air, so that the technology effectively achieves oxygen separation from air without the use of a cryogenic process or membrane technology. In a sense, cycles using liquids, such as amine scrubbing, could also be regarded as a type of looping cycle, the key being that the carrier must be regenerated and reutilized for as long as possible. However, this chapter will restrict itself to considering the uses of solid carriers only and, more specifically, those in which oxygen is transported and not CO2 as is the case for calcium looping. Particular focuses of this chapter will be on the use of this technology for H2 production and gasification applications, as well as its use with solid fuels. Another issue that will be discussed is high-pressure cycles, which are ultimately necessary if such systems are to be integrated into high-efficiency electrical energy cycles.