Distillation continuous catalyst regeneration

The process consists of a reactor section, continuous catalyst regeneration unit (CCR), and product recovery section. Stacked radial-flow reactors are used to minimize pressure drop and to facilitate catalyst recirculation to and from the CCR. The reactor feed consists solely of LPG plus the recycle of unconverted feed components no hydrogen is recycled. The liquid product contains about 92 wt% benzene, toluene, and xylenes (BTX) (Figure 6-7), with a balance of Cg aromatics and a low nonaromatic content. Therefore, the product could be used directly for the recovery of benzene by fractional distillation (without the extraction step needed in catalytic reforming). 

The moving-bed catalytic cracking process is similar to the FCC process. The catalyst is in the form of pellets that are moved continuously to the top of the unit by conveyor or pneumatic lift tubes to a storage hopper, then flow downward by gravity through the reactor, and finally to a regenerator. The regenerator and hopper are isolated from the reactor by steam seals. The cracked product is separated into recycled gas, oil, clarified oil, distillate, naphtha, and wet gas. 

In this case, it is the fluid medium, the fuel oil preheated to its evaporation point, that undergoes the value-adding conversion. Its long hydrocarbon chains are quickly cracked when encountering the catalyst particles in the fluid mix. The fluid is sent to a reactor. Cyclones at the top of the reactor separate the gaseous hydrocarbon fluid from the spent catalyst and transport it into a distillation unit. The solid catalyst particles are collected at the bottom of the reactor and sent to a regenerator, from where they are fed back into the catalytic riser in a continuous process. 

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