A numerical model for understanding the behaviour of coals in an entrained-flow gasifier

Experimental data from gasification of the same coals in a 5 MWth entrained flow gasifier were used to validate the performance of the model. Model calculations of the impact of oxygen-carbon stoichiometry on char conversion, cold gas efficiency (CGE) and product gas composition, using laboratory-scale measurements as inputs, are consistent with measurements at pilot-scale. The model results show that maximum CGEs for the higher reactivity coals with relatively high volatile matter are achieved within a narrow range of O:C ratios between 1.05-1.13, whilst the least reactive coal with high fixed carbon achieves its maximum CGE value at a higher O:C ratios of 1.36. Importantly, the model is able to reflect the significant differences in gasification behaviour of the four coals, which is consistent with lab-scale and larger-scale investigations. This work demonstrates the relevance of bench-scale gasification data in the assessment and interpretation of coal gasification behaviour under complex high pressure and high temperature conditions using appropriate mechanisms and sub-models.