燃煤固硫及催化燃烧一体化添加剂的催化作用机理研究

An integrated additive that has catalysis and sulfur retention functions was investigated by thermogravimetry analysis. In the TG experiments of catalytic sulfation reaction, 4.1‰ of SO2 was introduced into the system at the appointed temperature. Results show that in the presence of Fe2O3, the sulfation efficiency of CaO is 12%～58% higher than that of pure CaO at the temperature range of 650 ℃~1 000 ℃. TG curves can be divided into two ranges according to the slope, which indicates there are two different mechanisms for the sulfation reaction of CaO. In the TG study of catalytic coal combustion reaction in the airflow, results show that the mass-loss rate of coal sample doped with integrated additive increases in the main combustion interval. The ignition temperature t1 and burnout temperature t2 shift to low temperature region. The shape of DTG curve of sample doped with additive becomes sharp. Furthermore, the kinetic parameters of coal combustion reaction and CaO sulfation reaction with and without additives were calculated according to the nonisothermal combustion model and grain model respectively. Results show that catalytic promoter Fe2O3 in additive exhibits high catalytic performances both for sulfur retention of CaO and coal combustion. The promotion of coal combustion rate attributes to the increasing of active site of carbon surface by ion exchange between carbon and adding metal, thus the adsorption rate of oxygen is accelerated while the active energy and pro-exponent coefficient are decreased. The catalytic promoter Fe2O3 in the additive catalyzes the reaction of SO2 to SO3 in the chemical reaction control region and accelerates the sulfation reaction rate of CaO in the diffusion control region. Fe2O3 alleviates the aggregation of CaSO4 and weakens the pore closure in the CaO sulfation reaction.