The effects of three kinds of red mud from alumina plant on limestone’s sulfation kinetics were investigated by thermogravimetric analysis method. Red mud can effectively improve the desulfurization performance of limestone in the whole temperature range. Red mud has little effect on the rate constant of the surface reaction (k), but it can significantly improve the effective diffusivity of reactant in the product layer (Ds). The enhancement of sulfation is more pronounced once the product layer has been formed and consequently the promoting effect becomes greater once the sulfation reaction becomes diffusion controlled.

Subscript textThe kinetic model for simulating the mechanism of the promoted effect of methanol on the NOxOUT process has been established and it mainly includes the optimal sub-mechanisms respectively for the NOxOUT process and the chemical reaction of methanol. The oxygen concentration does not obviously influence the maximum NO reduction efficiency in the range of 1-6 %, but the temperature window is overall shifted to lower temperature zone with oxygen concentration increased. Meanwhile, the mole ratio of urea to nitric oxide by a factor of 2 should be maintained between 1.5 and 2 from both the efficiency and running cost view. Also, ample residence time of 300/T-400/T s must be guaranteed for the reduction occurring thoroughly. Methanol does not compromise the maximum NO reduction efficiency and broadens the temperature window towards low temperature zone. The promoted mechanism of methanol on the NOxOUT process is the abundant OH formation through the methanol regenerative reaction of CH2OH/CH3O+H2O=CH3OH+OH and methanol should be maintained at 50-100 ppm for an obvious promoted effect. During the co-injection of methanol and urea, the “ammonia slip” is depressed, especially at 1173 K where the promoted effect on NO reduction is obvious, but emission of nitrous oxide is also markedly increased at this temperature.