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 fixed in a packed bed, in which the catalytic reaction takes place. Powder, often used as adsorbent or heat carrier, is circulated between the two beds to enhance the efficiency of mass and heat transfer. The hydrodynamic behaviors 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 studied under different operating conditions. The catalytic oxidation-dehydrogenation of butene (C4H8) to butadiene (C4H6) in the GSSCFR las an example is 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/C4H8 molar flux ratio in the feed is reduced from 16: 1 to 8: 1 when compared 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 the powder as a heat carrier. (C) 1999 Elsevier Science Ltd. All rights reserved.