State-of-the-art review of fluidized bed stripper internals

Fluidized bed strippers play a significant role in fluid catalytic cracking (FCC) and fluid coking hydrocarbon processing operations. In the FCC process, the catalyst particles retained by the reactor cyclones contain substantial product hydrocarbon vapors. Failure to remove these vapors from the catalyst results in the loss of valuable products and undesirably high temperatures in the regenerator. In FCC applications, entrained and adsorbed hydrocarbon vapors are typically removed from the catalyst in a fluidized bed stripper using steam. In a fluid coker stripper, steam is propelled upwards to remove entrained and adsorbed hydrocarbons from the coke particles downflowing from the fluid coker reactor, thereby minimizing the carry-under of valuable hydrocarbon product. For both applications, several different proprietary and standard baffles have been used in these fluidized bed strippers. The most prevalent types of baffles are disk and donut trays, grating trays, horizontal sheds, and structured packings. This review summarizes studies available in the open literature on fluidized bed strippers as applied to the FCC and fluid coker unit operations. Overall, fluid catalytic cracking strippers, in particular disk and donut strippers, have received the most attention due to their much wider industrial usage. In past studies, experimental efforts have been dedicated to stripping efficiencies of various internals as a function of solids mass flux and stripping gas velocity, as well as stripper flooding and other flow dynamics issues. Typical commercial stripper operating problems have been pointed out, and methods to diagnose the problems have been identified. Fundamental theories on mass transfer in strippers are lacking.