Sulfur capture by fly ash in air and oxy-fuel pulverised fuel combustion

摘要

Ash produced during oxy-fuel combustion is expected to differ to ash produced during air combustion due to the higher CO_2 and SO_2 atmosphere in which it is generated. For a quantitative understanding of the sulfation behaviour of fly ash in oxy-fuel combustion with flue gas recycling, fly ash from three commercial Australian sub-bituminous coals were tested and decomposed under an inert atmosphere. Thermal evolved gas analysis was completed for ash produced in both air and oxy-fuel with full flue gas recycling combustion environments. Pure salts were also tested under the same conditions to allow identification of the species in the ash which capture sulphur, along with thermodynamic modelling using Fact-sage 6.3. The sulfur evolved during the decomposition of the air and oxy-fuel fly ash was compared with the total sulphur in the ash, determined by the Eschka method in order to close the sulfur mass balance. Both total sulfur captured by the ash and the sulfur evolved during decomposition were higher for oxy-fuel fly ash than their air counterparts. Correlations of capture with ash chemistry are presented.