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Title: Engineering scale-up and environmental effects of the calcium looping cycle for post-combustion carbon dioxide capture
Author: Cotton, A.
Awarding Body: Cranfield University
Current Institution: Cranfield University
Date of Award: 2013
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This thesis has addressed several gaps in the knowledge with regards to the calcium looping cycle for carbon dioxide capture, including identification of engineering challenges associated with the scale-up of the technology to pilot scale and beyond; assessment of changes in sorbent morphology during the pilot scale capture process; and partitioning of elemental impurities in the limestone between the solid and gaseous phase during the carbon dioxide capture process. Hydrodynamic investigations identified the optimum superficial velocities required for the reactor in order to optimise solids entrainment and flux, and to minimise gas bypassing. Estimations made in determining how particle attrition would affect minimum fluidisation velocity confirmed a decrease of approximately 0.09m/s for every 5 % reduction in particle size. Amendments made to the exhaust diameter and position, and the loop seals, improved the pressure balance of the system thus enhancing solids transfer. Reactor and process modifications, including modification of carbonator temperature, and maintenance of temperature above 420°C in standpipes resulted in improved carbon dioxide capture %. Increasing bed inventory had a positive effect of carbon dioxide capture % due to an increased Ca looping ratio. Steam addition also benefitted the carbonation process, due to improved sorbent morphology and therefore carbon dioxide diffusion into the sorbent. Sulfur dioxide was considered to have a detrimental effect on carbon dioxide capture due to pore pluggage, although burner- derived steam had a positive effect in maintaining capture %. Gaseous elemental emissions from the process were low for all elements, but concentrations of elements in the solid sorbent phase were influenced by bed inventory, implying that filtering systems may be required in industry for the large masses of sorbent required. Concentrations of elements in the sorbent were identified to be below levels typical of cement, with the exception of Ni, implying that there is potential for spent sorbent to be used in the cement industry with adequate mitigation measures in place.
Supervisor: Oakey, John; Patchigolla, Kumar Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Carbon Capture ; Limestone ; Elements ; Cement