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Carbon Capture from Solid Fuels

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Complimentary tea coffee and biscuits will be served

Abstract

Our continued reliance on fossil fuels and need to reduce our carbon output has led to renewed research into means of capturing carbon dioxide from solid fuels. This seminar will look at three aspects of this process. The first step is the pre-combustion gasification of the solid fuel with CO2 , where understanding of the structure and composition of the fuel is required for enhanced reactivity. Secondly, the gasified fuel is reacted using the chemical looping process, which uses “oxygen carriers” such as iron oxide to produce highly concentrated streams of carbon dioxide and hydrogen during their reduction and oxidation processes. Finally, calcium looping involves the use of solid sorbents based on calcium oxide to absorb CO2 from post-combustion flue gas and to release it at a pure stream at higher temperature.

Speakers

  • Marco Saucedo PhD student, Dept. Chemical Engineering & Biotechnology, University of Cambridge
  • Wen Liu PhD student, Dept. Chemical Engineering & Biotechnology, University of Cambridge
  • Saquib Sultan PhD student, Dept. Chemical Engineering & Biotechnology, University of Cambridge

Speakers’ Abstracts

Marco Saucedo, “The Gasification of Solid Fuels and its Relevance to Chemical-Looping Combustion”

Understanding gasification of fossil and renewable fuels is crucial to the design and development of processes for chemical-looping combustion used for generation of electricity whilst capturing their carbon content as a pure stream of carbon dioxide suitable for sequestration, thus mitigating the effects of climate change. The gasification of various solid fuels with CO2 in a fluidised bed has been investigated. The reactivities of the fuels are compared and discussed with reference to their structure and composition. In addition, a detailed study of the kinetics of a lignite char was carried out showing the effect of inhibition by CO of the char-CO2 reaction. The high gasification rate of the lignite char in CO2 makes it attractive as a fuel for chemical-looping combustion.

Wen Liu, “Production of Very Pure Hydrogen and Simultaneous Carbon Capture”

Hydrogen of very high purity can be produced from coal using the concept of chemical looping. Iron oxide particles, acting as an “oxygen carrier”, are subjected to repeated reduction and oxidation reactions, to produce a highly concentrated stream of carbon dioxide during the reduction process, and a stream of pure hydrogen when the lower iron oxide is oxidised by steam above 600 degrees C. The product hydrogen is immediately suitable for use in PEM fuel cells, whereas the highly concentrated carbon dioxide effluent gas could save the cost of post-combustion separation, prior to carbon storage. The overall process is exothermic and therefore high-grade steam is produced for electricity generation.

Saquib Sultan, “Calcium Looping for the Capture of CO2 ”

Solid sorbents, based on calcium oxide, have the ability to absorb CO2 from post-combustion effluent streams (the carbonation step) and to release the absorbed gas at a higher temperature (calcination), ready for sequestration. Natural CaO-containing sorbents, such as limestone, have been found to lose their ability to capture CO2 with repeated use. Therefore, synthetic sorbents have been investigated in order to improve the durability of these sorbents. It has been found that the addition of inert components to the sorbent aid this higher durability.

This talk is part of the Sustainability in the Built Environment (GreenBRIDGE) series.

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