Capturing CO2 from large-scale power generation combustion systems such as fluidized bed combustors (FBCs) may become important in a CO2-constrained world. Using previous experience in capturing pollutants such as SO2 in these systems, we discuss a range of options that incorporate capture of CO2 with CaO in FBC systems. Natural limestones emerge from this study as suitable high-temperature sorbents for these systems because of their low price and availability. This is despite their limited performance as regenerable sorbents. We have found a range of process options that allow the sorbent utilization to maintain a given level of CO2 separation efficiency, appropriate operating conditions, and sufficiently high power generation efficiencies. A set of reference case examples has been chosen to discuss the critical scientific and technical issues of sorbent performance and reactor design for these novel CO2 capture concepts.

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The traditional trend towards the development and use of power plants with ever increasing efficiencies is now being coupled to the use of a wider range of fuels and technologies designed to minimise CO 2 emissions. Alternative solid fuels such as biomass and waste products, which can be classified as CO 2 neutral, are being used alone or cofired with fossil fuels. The cofiring of biomass and coal is currently the most efficient and effective method for using biomass to generate power. CO 2 capture technologies include systems for either precombustion or postcombustion CO 2 removal. Gasification of fuels (using either oxygen or steam as the oxidant) produces a gas that can be conditioned to enable precombustion CO 2 removal. Post-combustion CO 2 capture can be carried out using either solid or aqueous sorbent processes. Oxy firing of fuels is a technology that would enable more efficient post-combustion CO 2 capture. The various combinations of new fuels, novel technologies and higher temperature component operating conditions are producing challenging operating environments for components. Deposition, erosion and corrosion issues for hot gas path components in these advanced power generating systems, which are potentially life limiting, are reviewed. Reduction in heat transfer owing to high rates of deposition can significantly reduce heat transfer and increase the need for component cleaning. Depending on the system, component parts can include various heat exchangers, gas cleaning systems and gas turbines.

The requirements to supply increasing quantities of electricity and simultaneously to reduce the environmental impact of its production are currently major issues for the power generation industry. Routes to meeting these challenges include the development and use of power plants with ever increasing efficiencies coupled with the use of both a wider range of fuels and technologies designed to minimise CO2 emissions. For fireside hot gas path components, issues of concern include deposition, erosion and corrosion in novel operating environments and increased operating temperatures. The novel operating environments will be produced both by the use of new fuel mixes and by the development of more complex gas pathways (e.g. in various oxyfired or gasification systems). Higher rates of deposition could significantly reduce heat transfer and increase the need for component cleaning. However, degradation of component surfaces has the potential to be life limiting, and so such effects need to be minimised. Materials and operational issues related to these objectives are reviewed.

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An integrated appraisal of five technology scenarios for the co-combustion of biosolids in the UK energy and waste management policy context is presented. Co-combustion scenarios with coal, municipal solid waste, wood, and for cement manufacture were subject to thermodynamic and materials flow modeling and evaluated by 19 stakeholder representatives. All scenarios provided a net energy gain (0.58-5.0 kWh/kg dry solids), having accounted for the energy required for transportation and sludge drying. Cocombustion within the power generation and industrial (e.g., cement) sectors is most readily implemented but provides poor water utility control, and it suffers from poor public perception. Co-combustion with wastes or biomass appears more sustainable but requires greater investment and presents significant risks to water utilities. Incongruities within current energy and waste management policy are discussed and conclusions for improved understanding are drawn.