Modelling and simulation of fluidized-bed boilers and gasifiers for carbonaceous solids
SUMMARY A comprehensive computer simulation program that can deal with a wide range of different operating conditions in fluidized bed combustion and gasification has been developed. It includes the possibility of simulating operations with various types of coal, charcoal or wood and can predict the behaviour of a real unit by giving several important performance parameters, such as: (a) Emulsion and bubble gas composition profiles throughout the bed height. The components included are: CO2 , CO, 02, N 2 , H2 0, H2 , CH4 , SO2 , NO, C2 H 6 , H2 S, NH3 and Tar. (b) Gas phase composition throughout the freeboard height. (c) Solid compositions of the coal (or any other carbonaceous material), limestone and inert in the bed and throughout the freeboard. The considered components are: C, H, 0, N, S, ash, volatiles, moisture in the coal, CaCO3, CaO, CaSO4 , moisture in the limestone, Si0 2 , and moisture in the inert. (d) Temperature profiles of all phases throughout the bed and the freeboard. (e) Solid particle size distributions in the bed and in the freeboard sections. The considered effects are: elutriation, entrainment, attrition and recycling in all the three possible types of solid phases present; (f) Heat transfered to water/steam inside the tubes, steam production and tube surface temperatures in the case of boiler simulation.