Jean-Xavier Morin

Chemical Looping Combustion of Refinery Fuel Gas with CO 2 Capture

Chemical looping combustion (CLC) is a relatively new technology, which integrates air separation into the combustion process and produces a separate CO 2 /H 2 O flue gas stream for CO 2 capture. The basic process principle of a circulating fluidized bed (CFB) boiler is to perform solid fuel combustion in a high inventory fluidized bed where the solid fuel and the sorbent are recycled many times. The low temperature, long fuel residence time and high combustion efficiency inherent in the process result in low emissions and the ability to burn any solid fuel. For conventional applications of coal fired power plants without CO 2 capture, circulating fluidized bed (CFB) technology is demonstrated an unparalleled ability to achieve low SO 2 and low NO x emissions without the need for back-end equipment, such as selective catalytic reduction system. This is possible due to low combustion temperatures and the staging of air.

An ALSTOM Vision of Future CFB Technology Based Power Plant Concepts

ALSTOM is actively working to develop circulating fluidized bed (CFB) based technologies to continue to reduce costs and mitigate CO2 . Advanced ALSTOM concepts include “the oxygen-fired CFB,” which uses pure oxygen plus recirculated flue gas (mainly CO2 ) as a combustion medium, resulting in a flue gas stream with a high CO2 concentration. Consequently, CO2 can be separated from the flue gas stream relatively easily. As such, this technology is geared toward CO2 mitigation. Another advancement, “the circulating moving bed (CMBTM )” system, uses a novel heat exchanger design that heats the energy cycle working fluid to the high temperature levels required for advanced power generation systems. The CMBTM combustion system is also an enabling technology for hydrogen production and CO2 capture from combustion systems utilizing innovative chemical looping gasification and syngas decarbonization. Chemical looping is another development path towards CO2 mitigation. In ALSTOM’s processes, oxygen (from air) is transported by a solid oxygen carrier for combustion or gasification of the fuel. CO2 is captured in a separate chemical loop in the gasification process. The process can be used to produce nearly pure CO2 and steam for a Rankine cycle; or synthesis gas or hydrogen with CO2 capture for IGCC’s, fuel cells, or industrial use. This paper will discuss ALSTOM’s latest work and the technical and economic implications of these advanced CFB-based systems. These advanced power generation units can be built from proven fluid bed design features and systems and the same processes supporting current-state technology enable rational development of future-state power generation and CO2 capture.Copyright