Hydrogen production from biomass for use in solid oxide fuel cells

• Main Author: Sattar, Anwar
• Published: University of Birmingham 2015
• Subjects: 660; TP Chemical technology
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675778

This thesis presents an investigation into the use of four biochars (wood, rapeseed, miscanthus and sewage sludge) to generate a hydrogen-rich syngas that can be utilised in solid oxide fuel cells. Experimental investigations are split into three sections; (i) biochar characterisation, (ii) biochar gasification and (iii) the use of syngas in a single, microtubular solid oxide fuel cell. Characterisation revealed that wood biochar had the highest carbon content at 71.58%, sewage sludge had the lowest at 30% and rapeseed had the highest mineral content. The effects of temperature on gasification were investigated over a temperature range of 650 - 850°C at a steam flow of 172 g min\(^-\)\(^1\) kg\(^-\)\(^1\) biochar and effects of steam flow at 850°C over a steam flow range of 54 - 277 g min\(^-\)\(^1\) kg\(^-\)\(^1\) biochar. Results revealed the transient behaviour of the process as well as the effects of temperature and steam flow. Dry gas yield increases with both temperature and steam flow, with wood biochar giving maximum values of 2.58 m\(^3\) kg\(^-\)\(^1\) at 850°C and 277 g min\(^-\)\(^1\) kg\(^-\)\(^1\) biochar. Hydrogen content decreases at high temperatures and peak hydrogen content, 58.7%, was achieved at 750°C from the rapeseed biochar. Syngas from wood and rapeseed biochars was collected and used in a microtubular solid oxide fuel cell. Gas from rapeseed had a negative effect on the fuel cell performance, leading to a 28% decrease in the performance over the 30 minutes of potentiostatic operation of 0.7 V. Gas from wood biochar was more suitable and was used in the solid oxide fuel cell for approximately 500 minutes, giving an initial electrical efficiency of 16.8% at 0.7 V.