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Title: Investigations of the combination of carbon capture and storage via the calcium looping cycle with biomass combustion
Author: Yao, Joseph Genbin
ISNI:       0000 0004 7228 9034
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Bio-energy with carbon capture and storage (BECCS) refers to a group of technologies with the potential to achieve negative CO2 emissions. One example of this is in situ capture of CO2 from biomass combustion using the calcium looping cycle. Calcium looping is a CO2 capture technology whereby a CaO-based sorbent is cycled between two vessels: the carbonator (where CO2 is captured) and calciner (where CaO is regenerated). Since biomass can combust around the operating temperature (650°C) of the carbonator, it is possible to capture the CO2 generated from combustion with the CaO-based sorbent in a single vessel. However, low-temperature combustion of biomass can result in incomplete combustion and tar formation. Raising the temperature of the combustor/carbonator is one solution; however, high temperatures are not thermodynamically favourable for carbonation (at atmospheric pressures). This thesis examines the combination of calcium looping and biomass combustion in a bench-scale 3 kWe pressurised fluidised-bed reactor. It is split into three main parts. The first part is an experimental study of the effects of pressure and temperature on the degree of CO2 capture and tar yield from the in situ capture process. The second part presents the kinetics of carbonation with and without the other combustion product, steam when subject to mild pressurisation (1.5-5 bara). The experimental data were well represented by simple Langmuir adsorption models. The final part of this thesis models the experimental carbonation kinetics data with full reactor models (a two-phase model and a simpler CSTR model) written in MATLAB®. These models were found to work quite well with self-consistent parameters. The purpose of developing the dynamic models for the carbonation process was to create the foundation for a more complex model which can be used to simulate and test the in situ capture process beyond the limited regime considered in the experiments.
Supervisor: Fennell, Paul ; Maitland, Geoffrey Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral