Fluidized bed reactors catalytic cracking

The search continues for better and more economical processes for the production of ethylene. Those processes include catalytic thermal cracking, methanol to ethylene, oxidative coupling of methane, advanced cracking technology, adiabatic cracking reactor, fluidized bed cracking, membrane reactor, oxydehy-drogenation, ethanol to ethylene, propylene disproportionation, and coal to ethylene. Much work is still needed before any such process can compete with current processes. 

Buyan, Frank M., and Ross, Mark S. Fluid catalytic cracking reactor multi-feed nozzle system, USP 4650566 (1987) Campbell, H. W., and Hurn, E. J. Circulating Fluidized Bed Combustion on Stream at California Portland Cement Company, Coal Technology (Houston), 8th (3-4), p. 19 (1985). 

Figure 1.9 Industrial reactors (a) ammonia reactor and (b) fluidized-bed catalytic cracking reactor.

Description The DCC process overcame the limitations of conventional fluid catalytic cracking (FCC) processes. The propylene yield of DCC is 3-5 times that of conventional FCC processes. The processing scheme of DCC is similar to that of a conventional FCC unit consisting of reaction-regeneration, fractionation and gas concentration sections. The feedstock, dispersed with steam, is fed to the system and contacted with the hot regenerated catalyst either in a riser-plus fluidized dense-bed reactor (for DCC-I) or in a riser reactor (for DCC-II). The feed is catalytically cracked. Reactor effluent proceeds to the fractionation and gas concentration sections for stream separation and further recovery. The coke-deposited catalyst is stripped with steam and transferred to a regenerator where air is introduced and coke on the catalyst is removed by combustion. The hot regenerated catalyst is returned to the reactor at a controlled circulation rate to achieve the heat balance for the system. 

A major application of fluidized bed technology is to be found in the catalytic-cracking reactor, or Cat Cracker , which lies at the heart of the petroleum refining process. Here, the catalyst particles (which promote the breakdown of the large crude petroleum molecules into the smaller constituents of gasoline, diesel, fuel oil, etc.) are fluidized by the vaporized crude oil. An unwanted by-product of the reactions is carbon, which deposits on the particle surfaces, thereby blocking their catalytic action. The properties of the fluidized state are further exploited to overcome this problem. The catalyst is reactivated continuously by circulating it to another bed, where it is fluidized with air in which the carbon burns... 

Fluidized-bed catalytic cracking units (FCCUs) are the most common catalytic cracking units. In the fluidized-bed process, oil and oil vapor preheated to 500 to SOOT is contacted with hot catalyst at about 1,300°F either in the reactor itself or in the feed line (called the riser) to the reactor. The catalyst is in a fine, granular form which, when mixed with the vapor, has many of the properties of a fluid. The fluidized catalyst and the reacted hydrocarbon vapor separate mechanically in the reactor and any oil remaining on the catalyst is removed by steam stripping. 

Fluid bed reactors became important to the petroleum industry with the development of fluid catalytic cracking (FCC) early in the Second World War. Today FCC is still widely used. The following section surveys the various fluid bed processes and examines the benefits of fluidization. The basic theories of fluidization phenomena are also reviewed. 

Fluidized bed reactors were first employed on a large scale for the catalytic cracking of petroleum fractions, but in recent years they have been employed for an increasingly large variety of reactions, both catalytic and non-catalytic. The catalytic reactions include the partial oxidation of naphthalene to phthalic anhydride and the formation of acrylonitrile from propylene, ammonia, and air. The noncatalytic applications include the roasting of ores and Tie fluorination of uranium oxide. 

Orthoflow A fluidized-bed catalytic cracking process in which the reactor and regenerator are combined in a single vessel. Designed by the MW Kellogg Company and widely used in the 1950s. First operated in 1951 by the British American Oil Company at Edmonton, Alberta. By 1994, more than 120 units had been built. 

The fluidized-bed reactor was originally developed for catalytic cracking in petroleum... 

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