Oxy-fuel combustion technology for coal-fired power generation

Oxy-fuel combustion of solid fuels

CO2 capture and separation technologies for end-of-pipe applications – A review

Oxy-fuel combustion of pulverized coal: Characterization, fundamentals, stabilization and CFD modeling

A review of the technologies for coal-based power generation closest to commercial application involving carbon capture is presented. Carbon capture and storage (CCS) developments are primarily adaptations of conventional combustion systems, with additional unit operations such as bulk oxygen supply, CO2 capture by sorbents, CO2 compression, and storage. They use pulverized coal combustion in entrained flow—the dominant current technology for coal-based power, or gasification in entrained flow, although similar concepts apply to other solid–gas contacting systems such as fluidized beds. Currently, the technologies have similar generation efficiencies and are associated with efficiency penalties and electricity cost increases due to operations required for carbon capture. The R&D challenges identified for the combustion scientist and engineer, with current understanding being detailed, are those of design, optimisation and operational aspects of new combustion and gasification plant, controlling the gas quality required by CCS related units and associated emission compliance, and gas separations. Fundamental research needs include fuel reactions at pressure, and in O2/CO2 atmospheres, as few studies have been made in this area. Laboratory results interpreted and then included in CFD models of combustion operations are necessary. Also identified, but not detailed, are combustion issues in gas turbines for IGCC and IGCC-CCS. Fundamental studies should be a component of pilot-plant and demonstrations at practical scale being planned. Concepts for new designs of combustion equipment are also necessary for the next generation of technologies. The challenges involved with the design and operation of these integrated systems, while supplying electricity on demand, are considerable.

Combustion processes for carbon capture

As part of CO2 abatement strategies for climate change, we are investigating coal combusion behaviour in various O2/CO2 mixtures and in air. The goal is to simulate conditions of coal combustion with flue gas recirculation in order to maximize the CO2 concentration in the flue gas prior to its recovery. A western Canadian sub-bituminous coal and a U.S. eastern bituminous coal were investigated. Thermal input was set at 0.21 MW with a flue gas oxygen concentration of 5 vol%. Experiments were done using various O2/CO2 mixtures and air. The oxygen concentration ranged from 21% to 42%. Up to 95% CO2 concentrations were achieved in the flue gas. This paper describes experimental results in terms of flame temperatures and pollutant emissions (NOx', SO2 and CO).

Coal combustion in O2/CO2 mixtures compared with air

Three sub-bituminous and two bituminous coals from Western Canada were used to study the evolution of H2S, COS and SO2 during the pyrolysis and gasification processes in a fixed bed reactor. For all types of coals, most of H2S and SO2 were released during the devolatilization stage. COS was formed only during the gasification stage in the presence of CO2. The mineral matter of coal may have played a role during the gasification stage. Some observations made during this latter stage in CO2 and/or steam were interpreted in terms of the equilibrium effects.



Cinq charbons provenant de l'ouest canadien, trois subbitumineux et deux bitumineux, ont servi a etudier la production de H2S, de COS et de SO2 lors d'experiences de pyrolyse et de gazeification dans un reacteur de type lit fixe. Pour tous Ies echantillons, la production de H2S et de SO2 se deroulait majoritairement lors de l'etape de devolatilisation. La production de COS n'a ete observee qu'en presence de CO2 lors des experiences de gazeification. Le contenu mineral des charbons a pu jouer un rǒle lors de l'etape de gazeification. Lors de ces experiences en presence de CO2 et/ou de vapeur d'eau, certains resultats ont ete interpretes en fonction des effets d'equilibres chimiques.

Allan D. Palmer

Papers

Coal combustion in O2/CO2 mixtures compared with air

Distribution of volatile sulphur containing products during fixed bed pyrolysis and gasification of coals