Cocurrent gas-solid downflow fluidized bed (downer) reactors: (III). Gas and solid mixing

The axial gas and solids dispersions in the downer are much smaller than that in riser, while the radial gas-solid mixing is comparable between the two, making downer reactor a far better candidate for short contact time reactions where the intermediates are the desired product. Available measurement techniques and reported experimental results of gas and solid mixing are summarized, and analysis is provided for the mixing mechanism in the downer reactor. The different mixing phenomena in risers and downers are also compared.