Moving-bed catalytic cracking process

THERMOFOR PROCESS. A moving-bed catalytic cracking process in which petroleum vapor is passed up through a reactor countercurrent to a flow of small beads or catalyst. The deactivated catalyst then passes through a regenerator and is recirculated. 

Figure 7-14 Thermofor moving bed catalytic cracking process.

Houdriflow catalytic cracking a continuous moving-bed catalytic cracking process employing an integrated single vessel for the reactor and regenerator kiln. 

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. 

Socony-Vacuum utilized Thermofor kilns to bum off coke deposited on Fuller s earth during the filtration of lube oils (57). They adapted one of these kilns to introduce the first moving bed catalytic cracking process. The first semi-commercial 500 BPD (barrel per day) Thermofor Catalytic Cracking (TCC) unit went on stream in the Paulsboro refinery in 1941. It utilized bucket elevators to transport catalyst from the reactor to the regenerator. In 1943, Socony-Vacuum installed a 10,000 BPD TCC unit (52) at a subsidiary refinery. 

Fig. 21-7. Feed preparation for moving-bed catalytic cracking processes.

Moving-bed catalytic cracking a cracking process in which the catalyst is continuously cycled between the reactor and the regenerator. 

Figure 19. Moving bed catalytic crackers (A) Thermoform moving bed process (B) Houdry catalytic cracking process.

The Houdry fixed-bed cyclic units were soon displaced in the 1940s by the superior Fluid Catalytic Cracking process pioneered by Warren K. Lewis of MIT and Eger Murphree and his team of engineers at Standard Oil of Newjersey (now Exxon). Murphree and his team demonstrated that hundreds of tons of fine catalyst could be continuously moved like a fluid between the cracking reactor and a separate vessel for... 

The first cracking catalysts were acid-leached montmorillonite clays. The acid leach was to remove various metal impurities, principally iron, copper, and nickel, that could exert adverse effects on the cracking performance of a catalyst. The catalysts were first used in fixed- and moving-bed reactor systems in the form of shaped pellets. Later, with the development of the fluid catalytic cracking process, clay catalysts were made in the form of a ground, sized powder. Clay catalysts are relatively inexpensive and have been used extensively for many years. 

The cracking reaction in all catalytic cracking processes is affected by the following factors (2) catalyst type and inherent activity charge stock characteristics and midboiling point space rate, usually measured in terms of liquid oil volume per volume of catalyst per hour ratio of catalyst to oil, the amount of catalyst in the reaction zone per unit of oil reacted, which in the fixed-bed process becomes the ratio of reciprocal space rate to time on stream, and in the moving-bed process is the ratio of catalyst rate to oil rate temperature and oil partial pressure. 

The fluid-bed process differs from the fixed-bed and moving-bed processes, insofar as the powdered catalyst is circulated essentially as a fluid with the feedstock. The several fluid catalytic cracking processes in use differ primarily in mechanical design. Side-by-side reactor-regenerator construction along with unitary vessel construction (the reactor either above or below the regenerator) are the two main mechanical variations. 

Inherent drawbacks of fixed-bed catalytic cracking were overcome by the development of moving-bed processes in which the cracking and regeneration reactions are carried out in separate vessels and the catalyst is continuously circulated from one vessel to the other (51). Moving-bed processes have the following advantages ... 

These fluidized beds have proved very useful in chemical technology when one wishes to move a granular solid through a series of processing steps in a continuous fashion. Their most dramatic application is in fluidized-bed catalytic cracking, which is a standard petroleurn refining operation, but Zenz and Othmer [12] list dozens of other applications. This brief treatment only shows how they are formed more on their properties and uses can be found elsewhere [2, Chap. 1 12 13]. 

Moving-bed Thermofor cracking with bucket elevators, and the Thermofor Catalytic cracking (T.C.C.) and Houdriflow air-lift processes are examples. 

Catalytic cracking is a process that is currently performed exclusively over fluidized catalyst beds. The fluid catalytic cracking (FCC) process was introduced in 1942 and at that time replaced the conventional moving bed processes. These early processes were based on acid-treated clays as acidic catalysts. The replacement of the amorphous aluminosilicate catalysts by Faujasite-type zeolites in the early-1960s is regarded as a major improvement in FCC performance. The new acidic catalysts had a remarkable activity and produced substantially higher yields than the old ones. 

Fluidized catalytic processes, in which the finely powdered catalyst is handled as a fluid, have largely replaced the fixed-bed and moving-bed processes, which use a beaded or pelleted catalyst. A schematic flow diagram of fluid catalytic cracking (FCC) is shown in Fig. 4. 

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