Structure and reactivity of residual carbon from circulating fluidized bed coal gasification fine ash

Due to the high carbon and ash content of coal gasification fine ash (CGFA) produced by circulating fluidised bed gasifiers, it is mainly dissipated in landfills, resulting in soil and water pollution and energy wastage. The presence of carbon limits the application of CGFA in building materials and ceramics. Large-scale dissipation of CGFA can be achieved if the carbon in CGFA has active oxidation properties and potential as a material for the preparation of carbon. Therefore, exploring the form of carbon present in CGFA is crucial for the resourceful and harmless use of CGFA. Demineralisation of different types of CGFA from a circulating fluidised bed gasifier with a gas production capacity of 40,000 Nm3/h was carried out to obtain demineralised carbon (DC) and to investigate the structure and reactivity of the DC. The d002 and Lc values of the DC increased, the cross-linkage decreased, the main microcrystalline structural parameters of the aromatic carbon network layer with swelling effect increased in the vertical direction, the aromatic carbon and aliphatic hydrocarbon functional groups increased and the oxygen-containing functional groups all tended to decrease to different degrees. Based on the changes of CGFA chemical structure before and after acid treatment, a CGFA chemical structure model was constructed. Through TG experiments and Raman analysis of the samples, the activation energy value of the DC carbon was less than 70 kJ/mol, and the relationship between the carbon structure and combustion reactivity of the Raman characterisation was constructed. The DC had a specific surface area above 350 m2/g and was prepared as activated carbon after KOH and high temperature activation. The activated carbon had a specific surface area of 1636.2211 m2/g, a pore volume of 1.6796 cm3/g and a density of 1 g/cm3. The above indicates that CGFA has the potential to be used as a fuel for combustion, secondary gasification and DC can be used as an adsorbent or a pressed precursors for activated carbon.