MODELING OF A FLUIDIZED-BED COAL CARBONIZER

A computer model has been developed, based on data currently available in the literature, to simulate air-blown pyrolysis of coal in a carbonizer. A calcium-based sorbent (limestone or dolomite) can also be fed simultaneously with coal to the carbonizer to capture in-situ sulfur released into the gas. In addition to capturing the sulfur, the sorbent also influences the product yields by cracking some tar to gases and soot. Empirical correlations have been derived for the yields (tar, gas, and char) obtained from the carbonization of bituminous coals as well as lignites. These correlations have been incorporated into the computer model; the model predicts the char, soot, tar, spent sorbent, air feed, and product gas flow rates and their compositions, and sulfur capture. This model has been used to predict the carbonizer performance for two feedstocks, Pittsburgh No. 8 bituminous coal and Texas lignite, at pressures of 14 and 10 atm. Also, the effects of feedstock moisture content and operating temperature on the carbonizer performance have been studied for each feedstock and pressure. A coal-water slurry feed has also been considered for the bituminous coal.