Regenerators fluid catalytic cracking

CATALYSTS - REGENERATION - FLUID CATALYTIC CRACKING UNITS] (Vol5)... 

The MTO process employs a turbulent fluid-bed reactor system and typical conversions exceed 99.9%. The coked catalyst is continuously withdrawn from the reactor and burned in a regenerator. Coke yield and catalyst circulation are an order of magnitude lower than in fluid catalytic cracking (FCC). The MTO process was first scaled up in a 0.64 m /d (4 bbl/d) pilot plant and a successfiil 15.9 m /d (100 bbl/d) demonstration plant was operated in Germany with U.S. and German government support. 

The most dominant catalytic process in the United States is the fluid catalytic cracking process. In this process, partially vaporized medium-cut petroleum fractions called gas oils are brought in contact with a hot, moving, freshly regenerated catalyst stream for a short period of time at process conditions noted above. Spent catalyst moves continuously into a regenerator where deposited coke on the catalyst is burnt off. The hot, freshly regenerated catalyst moves back to the reactor to contact the hot gas oil (see Catalysts, regeneration). 

A. P. Kreuding, "Power Recovery Techniques as AppHed to Fluid Catalytic Cracking Unit Regenerator Flue Gas," presented at 79thFEChE... 

Catalytic Pyrolysis. This should not be confused with fluid catalytic cracking, which is used in petroleum refining (see Catalysts, regeneration). Catalytic pyrolysis is aimed at producing primarily ethylene. There are many patents and research articles covering the last 20 years (84—89). Catalytic research until 1988 has been summarized (86). Almost all catalysts produce higher amounts of CO and CO2 than normally obtained with conventional pyrolysis. This indicates that the water gas reaction is also very active with these catalysts, and usually this leads to some deterioration of the olefin yield. Significant amounts of coke have been found in these catalysts, and thus there is a further reduction in olefin yield with on-stream time. Most of these catalysts are based on low surface area alumina catalysts (86). A notable exception is the catalyst developed in the former USSR (89). This catalyst primarily contains vanadium as the active material on pumice (89), and is claimed to produce low levels of carbon oxides. 

Fluid catalytic cracking units present formidable emission control problems. Contaminants are present in both reactor product gas and regenerator flue gas. The reactor product contains hydrogen sulfide, ammonia, and cyanides, plus combined sulfur and nitrogen in the liquid products. Hydrogen sulfide, ammonia and cyanides are handled as part of the overall refinery waste water cleanup. The combined sulfur and nitrogen may be removed by hydrotreating. 

Fluid catalytic cracking is one of the most important conversion processes in a petroleum refinery. The process incorporates most phases of chemical engineering fundamentals, such as fluidization, heat/mass transfer, and distillation. The heart of the process is the reactor-regenerator, where most of the innovations have occurred since 1942. 

Chen Junwu, Cao Hanchang, and Liu Taiji, Catalyst Regeneration in Fluid Catalytic Cracking Volume 21... 

The alkylation unit in a petroleum refinery is situated downstream of the fluid catalytic cracking (FCC) units. The C4 cut from the FCC unit contains linear butenes, isobutylene, n-butane, and isobutane. In some refineries, isobutylene is converted with methanol into MTBE. A typical modern refinery flow scheme showing the position of the alkylation together with an acid regeneration unit is displayed in Fig. 1. 

The fluid catalytic cracking (FCC) is a very dynamic nnit that is typically the major conversion process in a refinery. Proper modeling and nnderstanding of unit capabilities represents a tremendons opportunity to improve the overall nnit operation and minimize unit emissions. The combustion chemistry in the FCC regenerator that produces environmental pollntants is extremely complex as nnmerons interactions and reactions occnr between the various chemical species. 

Indicated in Fig. 2 is a representative fluid catalytic cracking unit, comprising ( )a reactor (2) a regenerator (3) the main fractionator (4) an air blower or compressor (3) a spent-catalyst stripper (6) catalyst recovery equipment, including cyclones internal in the reactor and regenerator and slurry settler, and possibly an electrostatic precipitator and (7) a gas-recovery unit. The catalyst used is essentially u specially prepared composite of silica and alumina. 

Shell fluid catalytic cracking a two-stage fluid catalytic cracking process in which the catalyst is regenerated. 

UOP fluid catalytic cracking a fluid process of using a reactor-over-regenerator design. 

Fluid catalytic cracking (FCC) of heavy oil fractions is a well-known process in oil refineries. Numerous books (e.g., 1—3) and publications about the different aspects of this subject are available. This chapter is concerned with the modeling of the transfer line or riser reactor of an FCC unit (FCCU) or of a pilot plant. The riser reactor in FCCUs is a vertical pipe about 1 m in diameter and 10-30 m in height. The hot catalyst coming from the regenerator at about 710 ° C first comes in contact with steam and is fluidized. Then, at a height of some meters above, the catalyst is mixed with the preheated feedstock at about 300 ° C. 

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