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Title: Performance degradation and recovery of YSZ membrane under sulphuric acid thermal decomposition
Author: He, Guanghu
ISNI:       0000 0004 2744 148X
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2013
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The effect of sulphur dioxide (SO2) present in the cathode feed stream on the performance of a 8 mole% yttria-stabilized zirconia/platinum (8YSZ/Pt) cell was studied. SO2 concentration of 30% in oxygen (5ml/min) and helium (30ml/min) was exposed to the cell applying an external dc voltage of 1.5V at 850˚C. Experiments showed that the cell performance had a sharp degradation (type I degradation) followed by a gradual degradation (type II degradation) inferred from current and oxygen permeate flux changes. Type II degradation may be related to formation of sulphide on cathode of membrane cell during the SO2 exposure period. Strong but short dc voltage pulses could reduce significantly membrane performance degradation impacting upon both charge transfer and mass transfer properties. In this work, the optimum voltage pulse for achieving the most stable membrane performance in SO2 exposure time was 10V, 0.08s length. High pulse frequency was helpful for achieving a high and stable membrane performance SO2 exposure tests lasting up to 2 hours. An oxygen separation process based on a YSZ tubular membrane was constructed and initial proof of concept experiments performed. Performance degradation by sulphur poisoning and recovery by voltage pulse of YSZ tubular membrane were also observed with this system. However, the oxygen permeation flux of the YSZ tubular membrane was lower than that of YSZ planar membrane, which may be related to YSZ thickness and the gas flow pattern. Initial experiments to integrate the membrane system into the thermal decomposition of H2SO4 to produce SO2 and O2 were carried out in a quartz tube reactor filled with an alumina supported Pt catalyst. A promising and feasible method of monitoring oxygen in-situ to determine acid conversion was proposed. Future work should concentrate on improvement of YSZ tubular membrane configuration and deeper integration of membrane operation and acid decomposition.
Supervisor: Allen, R. W. K. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available