Yinghui Liu

The Study of Calcium Sulfate Decomposition by Experiments Under O2/CO2 Atmosphere

Sulphur emission and the effect on ash properties and boiler- tube corrosion in oxy-fuel combustion have received increasing attention in the recent years. Early investigation about calcium- based desulphurization in oxy-fuel, addressed the advantage to reduce the SO2 emission. This paper, the decomposition of calcium sulphate was characterized by thermogravimetric analyzer. The results showed that the decomposition inhibited by increasing O2 concentration and SO2 concentration resulted from recycled flue gas. And CO2 concentration had the negative effect, which can be solved by changing O2 concentration through appropriately adjusting recycled flue gas ratio. The kinetics mechanism of calcium sulfate-decomposition in oxy-fuel combustion was further analyzed. Compared with conventional atmosphere, the reaction activation energy was heightened in oxy-fuel conditions, and the difference increased with rising temperature. So it can further confirm the advantage of calcium utilization rate under high temperature in oxy-fuel condition.

Oxy-fuel heat transfer characteristics and impacts on boiler design

Abstract: An outline of the basis of radiative transfer which dominates furnace heat transfer for coal-fired oxy-fuel furnaces is presented and illustrated by comparisons of the significance of the radiating species influencing heat transfer, and also differences between air-fired and oxy-fuel fired furnaces. Heat balances and heat transfer for three different oxy-fuel furnaces of 1.2 MWt, 30 and 420 MWe are given by a simple well-stirred reactor model and also comprehensive computational fluid dynamics models. It is concluded that oxy-fuel combustion can be operated at the same heat transfer rate as air-firing, but results in operational changes – lower volumetric gas flow rate, lower adiabatic flame temperature and lower flue exit gas temperature – associated with the higher gas emissivity of oxy-fuel firing and different heat capacity of the flue gas.