CO2 Capture by Electrothermal Swing Adsorption with Activated Carbon Fibre-phenolic Resin Composite

Hui An (2010). CO2 Capture by Electrothermal Swing Adsorption with Activated Carbon Fibre-phenolic Resin Composite PhD Thesis, School of Mechanical and Mining Engineering, The University of Queensland.

       
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Author Hui An
Thesis Title CO2 Capture by Electrothermal Swing Adsorption with Activated Carbon Fibre-phenolic Resin Composite
School, Centre or Institute School of Mechanical and Mining Engineering
Institution The University of Queensland
Publication date 2010-01
Thesis type PhD Thesis
Total pages 225
Total black and white pages 225
Subjects 09 Engineering
Abstract/Summary Fossil fuel-fired power stations are large sources of CO2. CO2 capture from power station flue gas (i.e. post-combustion CO2 capture) has been recognised as an important strategy for reducing CO2 emissions. Currently, one of the major concerns regarding CO2 capture is its significant cost. The solution is to improve the efficiency of current capture technologies and develop new cost-effective and environmentally friendly technologies. Therefore, this work presents the investigation of a novel CO2 capture technique, electrothermal swing adsorption, which is promising to reduce CO2 capture cost. The objectives of this thesis are to evaluate the possibility of utilising activated carbon fibre-phenolic resin composite as the adsorbent and to investigate and optimise operating conditions of electrothermal swing adsorption in order to reduce energy penalty for CO2 capture. Activated carbon fibre materials have been widely investigated for volatile organic compounds removal. Only a few studies have been conducted for the purpose of CO2 capture. Therefore, it is of great interest to examine the relationship between fabrication conditions and CO2 adsorption capacity of activated carbon fibre-phenolic resin composite. It is found that activated carbon derived from phenolic resin also has the ability to capture CO2. Conventionally, phenolic resin has a small proportion when mixed with carbon fibres to produce a composite and is supposed to play the role of binding material only. This implies that by carefully choosing carbon fibre and phenolic resin, adsorption performance of the composite can be improved. Traditionally, N2 isotherm at -196˚C has been widely employed to analyse the micro-structure of microporous materials. However, analysis by this thesis shows that CO2 isotherm at 0˚C under sub-atmospheric pressure is more appropriate for the characterisation of activated carbon fibre-phenolic resin composites for CO2 adsorption at low relative pressures. Micropore volume by CO2 isotherm, which measures the volume of smaller micropores in the microporosity range, has been identified as a single design parameter for the development of activated carbon fibre-phenolic resin composite. This will greatly facilitate the future improvement of the composite for CO2 capture at low relative pressures. Activated carbon fibre-phenolic resin composite demonstrates better CO2 adsorption capacity than some sorbents, for example, granular activated carbon. Apart from this, another advantage is its ability to be shaped into any forms. In this work, it takes a honeycomb monolithic form, which enables the composite to have good attrition properties and low pressure drops and to be used in dust environments such as flue gas from coal fired power plants. The structure of honeycomb monolithic materials has been studied in catalysis systems. Very little effort has been made to explore the influence of monolithic structure on CO2 adsorption performance of the composite. A theoretical model has thus been developed in order to study this influence. It has been found that two structural parameters void fraction and channel wall thickness are useful in designing the honeycomb monolithic structure of activated carbon fibre-phenolic resin composite. Consequently, the analysis results obtained by the model provide guidance in determining the optimal structure of the composite for CO2 capture. By adopting the optimal structure, CO2 adsorption performance of the composite can be greatly enhanced. The regeneration of the saturated adsorbent is conducted by passing through electricity. A few studies have been undertaken to study the effect of operating conditions on volatile organic compounds capture by electrothermal swing adsorption. Very rare studies have been conducted on the effect of operating conditions on CO2 capture. Efforts have thus been made to systematically investigate and optimise operating conditions of electrothermal swing adsorption system to make it more energy efficient and competitive. Towards this goal, experimental results performed by this thesis have shown that energy input by electricity rather than current intensity has more significant influence on desorption performance of the composite. This decisively confirms the effect of electricity in electrothermal swing adsorption. In addition, the preheating step, which has been reported beneficial in volatile organic compounds capture by electrothermal swing adsorption, proves to be unnecessary under certain circumstances in CO2 desorption by electrothermal effect. A theoretical model has also been built to predict desorption performance of the composite under various conditions and utilised to gain more insights into the influence of operating conditions. Current level has been found to have a direct impact on desorption performance. This has not been reported before. The results of this thesis show that activated carbon fibre-phenolic resin exhibits good CO2 adsorption performance and demonstrates its suitability to be used as the adsorbent in ESA. Additionally, the effects of operating conditions of desorption by electrothermal effect have been investigated and energy efficiency of electrothermal swing adsorption system can be improved by optimising its operating conditions.
Keyword CO2 capture, adsorbent, honeycomb monolithic structure, electrothermal swing adsorption

 
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Created: Wed, 10 Nov 2010, 02:26:04 EST by Mr Hui An on behalf of Library - Information Access Service