Studies on gas-solid-solid circulating fluidized-bed reactors

In the gas-solid-solid circulating fluidized-bed reactor (GSSCFR),a packed bed and a fluidized bed are interconnected. Large catalyst particles are fi xed in a packed bed, in which the catalytic reaction takes place. Powder, o ften used as adsorbent or heat carrier, is circulated between the two beds to enhance the efficiency of mass and heat transfer. The hydrodynamic behav iors of gas-powder flow through the packed bed, such as the mass flow rates , the powder hold-up and the pressure gradient along the packed bed are stu died under different operating conditions. The catalytic oxidation-dehydrog enation of butene (C4H8) to butadiene (C4H6) in the GSSCFR las an example i s described. The experimental results show that the C4H8 conversion and the C4H6 yield are increased by 10-20% and 10-15%, respectively, and the H2O/C 4H8 molar flux ratio in the feed is reduced from 16: 1 to 8: 1 when compare d with those existing in industrial adiabatic packed-bed reactors. Finally, a hydrodynamic model is established. It further testifies that the GSSCFR can effectively combine the chemical reaction with heat transfer by using t he powder as a heat carrier. (C) 1999 Elsevier Science Ltd. All rights rese rved.