Abstract
Gasification is considered a clean and effective way to convert low quality biomass to higher value gas and solve various waste utilization problems as well. However, only 80% of biomass is converted through thermal processes. The remaining part is char, which requires more time for conversion and in that case reduces the efficiency of gasifier. Seeking to optimize the process of gasification, this work focuses on the intensification of residual char gasification in a gasifier. For this purpose, three different types of char prepared from wood, sewage sludge and tire were examined under different conditions in a lab-scale gasification setup. Results showed that the air flux increase from 0.11 kg/(m2s) to 0.32 kg/(m2s) intensified the gasification process and the gasification rate increased from 0.8 to 2.61 g/min with the decrease of duration of wood char gasification by 72%. An additional introduction of pyrolysis gas into the char gasifier led to decreased bed temperatures, but the gasification rate increased from 0.8 to 1.25 g/min and from 2.61 g/min to 2.83 g/min, respectively, for the wood char and the sewage sludge char. Moreover, the use of pyrolysis gas coupled with air as the gasifying agent enhanced the composition of produced gas from char, and the CO2 concentration decreased by 1.68 vol% while the H2 concentration increased by 2.8 vol%.
Highlights
Gasification is considered a clean and effective way to convert low quality biomass to higher value gas and solve various waste utilization problems as well
A different method of residual char usage was proposed by Van de Steene et al [21], which focused on wood char gasification in a continuous downdraft fixed bed reactor
The first set of char gasification experiments were performed at different air fluxes using wood, sewage sludge and tires char to analyze char gasification under a supply of air
Summary
Gasification is considered a clean and effective way to convert low quality biomass to higher value gas and solve various waste utilization problems as well. A different method of residual char usage was proposed by Van de Steene et al [21], which focused on wood char gasification in a continuous downdraft fixed bed reactor. Char gasification is mainly performed in the twostage gasifier or even in a separate one Though, another option related to thermal conversion of char is to intensify the char gasification in the remaining gasifier, in which case the gasifier efficiency increases, remaining energy from unconverted char is recovered and syngas composition is enhanced. A char gasification unit was designed based on the reduction zone in the downdraft gasifier setup and three different types of char prepared from wood, sewage sludge and tire were examined supplying different air flux of air. To investigate syngas effect on char gasification and enhancement on syngas composition, the pyrolysis gas was produced on site and supplied to the char gasification unit
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