Release of sulfur dioxide and nitric oxide and characteristic of coal combustion under the effect of calcium based organic compounds

The influences of calcium based organic compounds of calcium propionate (CP), the product of the modified calcium hydroxide by propionic acid (named as MCP) and the product of the modified calcium hydroxide and magnesium oxide by propionic acid (named as MCMP) on the release of sulfur dioxide (SO2) and nitric oxide (NO) and on the characteristic of coal combustion have been studied. With the addition of CP, MCP or MCMP, SO2 release is greatly reduced, both the momentary value and the total conversion value of fuel-S to SO2, especially when temperature is above 1273 K where the traditional inorganic calcium compound is little reactive. Below 1100 K, the fuel-N to NO conversion is heightened if the calcium based organic compound is added and this mainly ascribes to the promoted effect of the alkaline-earth metal. As temperature is increased, the depressed effect, which is generated by the organic component, gradually becomes prevalent and the fuel-N to NO conversion is subsequently reduced. Meanwhile, for an acceptable SO2 and NO reduction efficiency, the calcium based organic compound should be added following the determined mole ratio of calcium to sulfur (Ca/S) between 1.5 and 2. The coal combustion course is promoted to lower temperature zone under the effect of CP, MCP or MCMP and the difference of the promoted effect between Ca/S = 1 and 2 is not obvious. Finally, kinetic parameters are calculated using the Coats–Redfern method and the reaction model of f(α) = (1 − α)1.5 properly describes coal combustion course. And the activation energy is strongly reduced with the addition of CP, MCP or MCMP.