Development and Validation of a Gasification Model Including Non-equilibrium Methane Production

In this work, a gasification model for biomass conversion to syngas was developed and validated building upon an equilibrium model developed by Rodrigues et al. [1]. The model development and validation were guided by data from entrained flow gasification experiments performed at SINTEF Energy Research [2] with three different types of feedstocks. The main limitation of the original gasification model was that, as an equilibrium model, it did not predict any formation of CH₄ at the experimental temperatures. CH₄ production was modelled by introducing a pyrolysis step before the actual gasification, occurring at a fixed temperature, ΔT, below the gasification temperature. The selection of a proper ΔT is an important tuning step for the model and is dependent on the feedstock. Using ΔT = 350°C showed a good improvement compared to the original equilibrium model, reducing the mean absolute percentage error (MAPE) from 42.4% and 35.4% to 28.4% and 26.1% for the first two feedstocks. For the last feedstock, used for validation, ΔT = 350°C overpredicted the CH₄ drastically due to the higher carbon and hydrogen and lower oxygen concentration in the feedstock. Reducing ΔT to 100°C predicted the CH₄ concentration much better. With this adjustment the MAPE improved from 46.4% for the original model to 27.7% for the extended model. This shows that the approach developed allows including CH₄ production, leading to an overall increase in the accuracy of the simulations while retaining the advantages of an equilibrium model.