Modeling of Drying Stage in a Bubbling Fluidized Bed Coal Gasifier

Coal is one of the world's main sources of power, providing a quarter of primary energy and more than 40% of electricity. Clean coal technology using gasification is a promising alternative to meet the global energy demand. In gasification, coal is converted to synthesis gas, a mixture of carbon monoxide and hydrogen, which is further converted to liquid fuels via Fischer-Tropsch synthesis. A typical Fischer-Tropsch synthesis accepts the synthesis gas at definite hydrogen to carbon monoxide ratio. Coal gasifiers consist of two stages namely, drying zone and gasification / reaction zone. Coal enters reaction zone after getting dried in the drying zone. Moisture level varies from 2-8% for medium and high-grade coals, and is the key for a) Temperature of the reaction zone b) Efficiency of the gasifier c) Hydrogen to carbon monoxide ratio of synthesis gas. Drying stage of a bubbling fluidized bed gasifier using hot air is modeled and simulated for 2 kg/hr of coal feed for various parameters including, initial moisture content, particle diameter, air superficial velocity, relative humidity and feed air temperature. The effect of above parameters on entry temperature of reaction zone and final moisture content in air are investigated.