An ALSTOM Vision of Future CFB Technology Based Power Plant Concepts

Abstract

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.

Kinetic Model for Parallel Reactions of CaSO4 with CO in Chemical-Looping Combustion

“…Recently CaSO 4 is becoming an attractive oxygen carrier for the commercial application of CLC because of its easy availability and low price. Previous investigations − have been performed on CLC of gaseous and solid fuels with the CaSO 4 oxygen carrier and many promising results have been obtained. Although the potential sulfur release partially resulted in a decline in the reactivity of the CaSO 4 oxygen carrier during the cyclic use, the CaSO 4 oxygen carrier had high reduction reactivity and stability in a long-time reduction−oxidation test by using the gaseous fuels in a laboratory fixed/fluidized bed reactor. − Thus, the CaSO 4 oxygen carrier may be a low-cost alternative oxygen carrier with high oxygen capacity even though the sulfur release problem exists.…”

Overview of Solid Fuels Combustion Technologies

“…Additionally, the high costs associated with both cryogenic-type ASU, or oxygen transport membrane type oxygen supply systems, are avoided. The trade-off is a more complex boiler process [30,32,86].…”

Flue gas desulfurization under simulated oxyfiring fluidized bed combustion conditions: The influence of limestone attrition and fragmentation

“…Carbon dioxide partial pressures in the reaction zone under oxyfiring conditions are much larger than those establishing under air-blown combustion conditions. Although most of the research activity in oxyfiring has concentrated on pulverized coal boilers, recently the application of this technology to circulating fluidized bed (CFB) coal boilers has been addressed (Jukkola et al, 2005;Czakiert et al, 2006;Saastamoinen et al, 2006;Jia et al, 2007;Eriksson et al, 2008). CFBs appear to be particularly suited for oxyfiring conditions because of the fuel flexibility and better temperature control (which allows to reduce the amount of recycled flue gas).…”