The behaviour of bed material during fluidized bed gasification: The effects of mineral matter interactions

Abstract

In the British Coal Topping cycle coal is partially gasified in a pressurized fluidized bed gasifier to give a char and ash. A study of eight UK coals has shown that under these conditions each coal produced an ash which has a much finer size distribution than the parent coal. Changes in ash composition with size fraction have been related to the mineral matter in each coal. Each ash showed a decrease in SiO 2 and Al 2O 3 with decreasing size and an increase in Fe 2O 3 content. Fine pyrite particles have been observed to coat the surfaces of many of the larger clay particles. In instances where agglomeration between clay particles had occurred bonds of either FeSO or an iron aluminosilicate glass were observed. Part washing one of the coals preferentially removed quartz, kaolinite and illite, thus enriching the remaining mineral matter in pyrite. The run-of-mine coal, although with a higher ash content, would be expected to show a lower propensity towards the formation of agglomerates.