CATALYTIC SULFUR RELEASES DURING COAL COMBUSTION

摘要

He catalytic effects of doping agents on the coal sulfur release as well as the coal combustion behavior were investigated by thermogravimetry. All experiments were carried out in a flowing air atmosphere at a heating rate of 20 or 30 ℃ /min up to 1000℃ . The doping agents employed were NaCl, CaCl_2, FeCl_3, FeCl_2 and Fe_2O_3. The results show that the addition of the agents in coal reduces the coal sulfur release. CaCl_2 is the most effective one among the agents used. The doping agents work with different mechanisms. The catalysis of NaCl, CaCl_2 and Fe_2O_3 promotes the reactions between SO_2 and the minerals in coal, and enhances the sulfur retention capacity of coal ash and then decreases SO_2 concentration in flue gas. They have weak effect on the combustion behavior of the coal. FeCl_3 and FeCl_2 have strong effects on coal combustion behavior. They accelerated the combustion rate in the region between 300 ℃ and 580 ℃ and improved the ignition of the char subsequently formed, as far as increase SO_2 concentration in flue gas at the temperature region, while they reduces total sulfur release. The reduction of total sulfur release by FeCl_3 and FeCl_2 mainly results from the catalysis of Fe_2O_3 created by them at high temperature.