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.

ALSTOM is developing and testing a new and more efficient coal combustion technology, including a new type of steam generator known as a “circulating moving bed (CMBTM) combustion system combustor.” The CMBTM combustion system technology involves a novel method of solid fuel combustion and heat transfer. In this design, a heat exchanger will heat the energy cycle working fluid, steam or air, to the high temperature levels required for advanced power generation systems. This will produce a step change in both performance and capital costs relative to today’s pulverized coal and fluid bed boiler designs. In addition to high temperature Rankine cycles, the CMBTM combustion system is an enabling technology for hydrogen production and CO2 capture from combustion systems utilizing innovative chemical looping airblown gasification and syngas decarbonization. ALSTOM’s 3MWth Multi-Use Combustion Test Facility has been modified to allow operation in CMBTM combustion system mode. This paper summarizes the results of this program, which includes performance results from pilot plant testing. Participants include the U.S. DOE, ALSTOM, the University of Massachusetts, and the Massachusetts Institute of Technology. The total program cost is $2,485,468 with the DOE’s National Energy Technology Laboratory (NETL) providing 60% of the funding under Cooperative Agreement No. DE-FC26-01NT41223.

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Circulating Moving Bed (CMB) combustion technology has its roots in traditional circulating fluidized bed technology and involves a novel method of solid fuel combustion and heat transfer. CMB technology represents a step change in improved performance and cost relative to conventional PC and FBC boilers. The CMB heat exchanger will preheat the energy cycle working fluid, steam or air, to the high temperature levels required in systems for advanced power generation. Unique features of the CMB are the reduction of the heat transfer surfaces by about 60% as a result of the enhanced heat transfer rates, flexibility of operation, and about 30% lower cost over existing technology.The objective of this project is to continue development of the CMB technology with a series of proof of concept tests. The tests will be conducted at a scale that will provide the design data for scale up to a demonstration plant. These objectives will be met by conducting a series of experiments in ALSTOM Power's Multi-use Test Facility (MTF). The MTF will be modified to operate under CMB conditions of commercial interest. The experiments will cover the technical issues discussed above and will also show the integration of all of the subsystems operating at commercially significant temperatures. The range of temperatures to be tested will demonstrate the operation of the falling solids heat transfer and bed operation needed for the demonstration plant. The tests will not attempt to show the operation of the integrated CMB with falling solids and gas over the entire expected temperature range at one time. Modifying the MTF for this would not be cost effective. However, at the end of this project all technical concepts used in the CMB will have been investigated and planning will start for the demonstration plant .v

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