Mechanism of SO_2 removal in O_2/CO_2 combustion
O_2/CO_2 combustion is one of the processes to remove S O_2 from pulverized-coal fired boiler.In this paper, SO_2 emission and remova l in O_2/CO_2 combustion were investigated in a fixed bed reactor and a drop t ube reactor. The results indicated that the amount of SO_2 emission was much l ess than conventional air combustion due to the presence of both homogeneous des ulphurization and heterogeneous desulphurization in O_2/CO_2 combustion.Experi mental study also suggested that the change of flue gas composition led to the d ifference of sulphur oxidation degree and the sulphur in coal could be released in different speciations and SO_2 is only one of them.In O_2/CO_2 atmosphere, the desulphurization agent in coal itself showed different desulphurization beh aviour comparing with that in air combustion; the desulphurization agent had an optimized microstructure which was beneficial not only for the improvement of th e desulphurization efficiency but also for the adsorption of sulphur in the bott om ash.The kinetics calculation results also verified the above mechanism.