NONISOTHERMAL FLUIDIZED-BED REACTOR MODEL FOR CHAR GASIFICATION, TAKING INTO ACCOUNT BUBBLE-GROWTH

A two-phase model taking into account the non-isothermal character of coal gasification as well as bubble growth in the bed is presented. Numerical computations have been carried out to analyse the effects of the operating (process and hydrodynamic) variables on the performance of a reactor for steam-oxygen char gasification and to choose conditions to ensure proper fluidized-bed behaviour without disturbances resulting from the formation of slugs. The computations reveal that the model enables one to predict correctly the char feed rate (or the bed height) giving undisturbed operation of the bed. It is shown that two zones can be distinguished in the reactor: a high-temperature zone (near the distributor), where a sudden drop in temperature is observed, and a zone of almost uniform temperature distribution. The conclusions are in good agreement with data in the literature.