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Title: Design and operation of a novel carbon/air fuel cell
Author: Kaewpet, Prattana
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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A liquid tin anode-indirect carbon air fuel cell (LTA-ICFC) is a type of high-temperature solid oxide fuel cell that allows to electrochemically convert carbonaceous fuels directly to electrical energy with a high theoretical efficiency. A LTA-ICFC, where the electrochemical reactions taking place in an electrochemical reactor are decoupled from the combustion process, offers a number of advantages over a direct carbon air fuel cell. The concept of Indirect carbon-air fuel cell is desirable because: (1) its theoretical thermodynamic efficiency is ~100.3% which is nearly independent of temperature: (2) the reaction product CO2 is generated and exhausted in the 'ex-cell' combustion reactor as a pure substance. This allows simpler recovery, capture, or sequestration of CO2 without the need for further complex separation processes, that would cost and consume energy: (3) a wide choice of carbonaceous fuels can be used: (4) trace elements in the fuels do not poison the electrolyte materials: and (5) the operating temperatures of the two separated reactors can be individually controlled enabling optimisation of different process rates and efficiencies and minimising voltage losses. A number of LTA-ICFCs have been designed, constructed, operated and characterised to identify salient parameters necessary in the scale-up and commercialisation of this type of fuel cell. A high-density alumina ceramic was used as the liquid tin anode container which allowed extensive operation for more than 1,750 hours. A closed-end tubular 10 mol-%YSZ electrolyte with the thickness of 1.57 mm was compatible with the liquid tin and was continuously operated for more than 360 hours. The maximum power density of the fuel cell acquired at 800 °C was 1.3 due to the relatively thick electrolyte. The effect of cathode fabrication methods, preparation conditions of the high temperature composite cathodes (LSM-YSZ and LSM), on their characteristics and function, have been studied. Suitable composite cathodes and current collectors were prepared and characterised using a four-point probe measurement, scanning electron microscopy, and image analysis software (ImageJ). 1D modelling of electrochemical processes and electrochemical characterisation using Electrochemical Impedance Spectroscopy of the operating LTA-ICFC demonstrated the feasibility of the concept of an LTA-ICFC. A key observation was the formation of a tin oxide layer on the electrolyte due to the low dissolution rate of the formed oxide in the bulk of the liquid metal.
Supervisor: Hellgardt, Klaus Sponsor: Government of Thailand
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available