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In the near future biomass gasification is likely to play an important role in energy production and conversion. Its application has great potential in the context of climate change mitigation, increasing efficiency and energy security. Atmospheric circulating fluidised bed (CFB) technology was selected for the current study. An original computer simulation model of a CFB biomass gasifier was developed using ASPEN Plus (Advanced System for Process ENgineering Plus). It is based on Gibbs free energy minimisation and the restricted equilibrium method was used to calibrate it against experimental data. This was achieved by specifying the temperature approach for the gasification reactions. The model predicts syn-gas composition, heating values and conversion efficiency in good agreement with published experimental data. Operating parameters such as equivalence ratio (ER), temperature, and air preheating were varied over a wide range. They were found to have great influence on syn-gas composition, heating value, and conversion efficiency. The results indicate an ER and temperature range over which hydrogen (H2) and carbon monoxide (CO) production is maximised, which is desirable as it ensures a high heating value and cold gas efficiency (CGE). Gas heating value was found to decrease with increasing ER. Air preheating increases H2 and CO production, which in turn increases gas heating value and gasifier CGE. The effectiveness of air preheating decreases with increasing ER. A critical air temperature exists after which additional preheating has little influence, this temperature is high for low ERs and low for high ERs.
Doherty, W., Reynolds, A., Kennedy, D.: Simulation of a Circulating Fluidised Bed Biomass Gasifier Using ASPEN Plus – A Performance Analysis, in A. Ziebik, Z. Kolenda, and W. Stanek (eds). Proc. 21st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, 1241-1248. Krakow, Poland, 2008.