Petroleum and Its Products
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Fluid catalytic cracking Warren Letzsch∗
Crude oil comprises hundreds of molecules that boil over a wide temperature range. The lighter products can be separated directly by distillation into LPG, gasoline, naphtha, kerosene, and diesel fuels. Heavier products (BP > 650◦ F/344◦ C) include vacuum gas oils and resids. Thermal and catalytic cracking processes in petroleum refining reduce the molecular weight of these heavier constituents and produce more valuable lighter products such as LPG, gasoline and diesel fuels. Catalytic cracking was first commercialized in 1936 by Eugene Houdry. This fixed bed process was a major improvement over the thermal cracking processes it replaced due to the improved yield distribution and superior product properties. Multiple vessels were utilized that alternated between cracking, stripping, regeneration, and purge cycles. This configuration was quickly replaced by a moving bed reactor and a separate regenerator or kiln that first used a bucket lift to move the pelleted catalyst followed later by a pneumatic air lift system. The last of these units was built around 1960. Standard Oil of New Jersey developed their own cracking process rather than pay the large royalty being asked at the time. They commercialized the fluid catalytic cracking (FCC) process in three years, starting in 1939 and culminating in 1942 with the startup of PCLA#1 at their Baton Rouge, Louisiana refinery. The inherent superiority of the fluid process to transfer both heat and catalyst ultimately made it the catalytic cracking process of choice. Many different designs of fluid catalytic crackers have been introduced over the years. Table 6.1 is a list of the various FCCU configurations and the approximate year of their commercial introduction. Fluid catalytic cracking has evolved considerably over the more than 60 years since its inception. As seen in Figure 6.1 these changes have encompassed all aspects of *Senior Refining Consultant, Stone & Webster Inc—A Shaw Group Company.
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CHAPTER 6 Table 6.1. Evolution of fluid catalytic crackers Commercial fluid catalytic crackers 1942 1943 1945 1947 1951 1952 1953 1955 1956 1958 1961 1962 1967 1971 1972 1972 1973 1973 1981 1982 1985 1990 1991 1993 1996 2002
Model I upflow Model II downflow Sinclair design Model II side by side Kellogg orthoflow A Exxon Model IV Kellogg orthoflow B Shell two stage reactor UOP straight riser (SBS) Exxon riser cracker HOC cracker (Phillips) Kellogg orthoflow C Texaco design Gulf FCC process Exxon flexicracker Amoco ultracracking UOP high efficiency design Kellogg orthoflow F Total petroleum resid cracker Ashland/UOP RCC unit IFP R2R Kellogg/Mobil HOC Deep catalytic cracking (RIPP and S&W) Exxon flexicracker III MSCC UOP/Coastal Catalytic pyrolysis process
the process as it has adapted to meet ever-changing demands and to accommodate new technologies. The initial units (1940s) were tall, had dense bed reactors and were made of carbon steel. Dilute phase catalyst coolers and regenerator steam coils were employed to limit the rege
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