FCC Economics

The cat cracker s operational philosophy is dictated by refinery-economics. Economics of a refinery are divided into internal and external economics. 

Internal economics largely depends on the cost of raw crude and the FCC unit s yields. The cost of crude can outweigh the benefit from the cat cracker yields. Refiners who operate their units by a kind of intuition may drive for more throughput, but this may not be the most profitable approach. 

External economics are factors that are generally forced upon the refineries. Refiners prefer not to have their operations dictated by external economics. However, they may have to meet particular requirements such as those for reformulated gasoline. 

Because of the high cost of new units and the importance of the FCC on refinery profitability, improvements should be made to the existing units to maximize their performance. These performance indices are  

Product selectivity simply means producing more liquid products and less coke and gas. Depending on the unit s objectives and constraints, below are some of the steps that directionally improve product selectivity  

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FCC economics makes the refinery a viable entity. Over the years, refineries without cat crackers have been shut down because they were not profitable. 

This chapter discusses the factors affecting yields and qualities of FCC product streams. The section on FCC economics describes several options that can be used to maximize FCC performance and the refinery s profit margin. 

The ethylene feedstock used in most plants is of high purity and contains 200—2000 ppm of ethane as the only significant impurity. Ethane is inert in the reactor and is rejected from the plant in the vent gas for use as fuel. Dilute gas streams, such as treated fluid-catalytic cracking (FCC) off-gas from refineries with ethylene concentrations as low as 10%, have also been used as the ethylene feedstock. The refinery FCC off-gas, which is otherwise used as fuel, can be an attractive source of ethylene even with the added costs of the treatments needed to remove undesirable impurities such as acetylene and higher olefins. Its use for ethylbenzene production, however, is limited by the quantity available. Only large refineries are capable of deUvering sufficient FCC off-gas to support an ethylbenzene—styrene plant of an economical scale. 

C. A. Cabrera, C. L. Hebner, and S. P. Davis, "Improve Refinery Economics via Enhanced ECC Operations," presented at Katalistiks 8thMnnual FCC Symposium, Budapest, Hungary, June 1987. 

Interest in the application of turboexpanders turbine to FCC unit is very high, and deservedly so. The power recovery turboexpander offers practical improvement in FCC unit operating economics. Modern designs that encompass the entire system have fully overcome problems and concerns that may have existed decades ago. Expander metallurgy is available to vastly reduce erosion rates experienced when... 

Most refineries produce sufficient gas oil to meet the cat crackers demand. However, in those refineries in which the gas oil produced does not meet the cat cracker capacity, it may be economical to supplement feed by purchasing FCC feedstocks or blending some residue. The refinery-produced gas oil and any supplemental FCC feedstocks are generally combined and sent to a surge drum, which provides a steady flow of feed to the charge pumps. This drum can also separate any water or vapor that may be in the feedstocks. 

Long straight-chain paraffins are important to the economics of an FCC unit. They crack easily to gasoline and LPG, with minima] production of slurry and fuel gas. 

The fluidization characteristics of an FCC catalyst largely depend on the unit s mechanical configuration. The percentage of less than 40 microns in the circulating inventory is a function of cyclone efficiency. In units with good catalyst circulation, it may be economical to minim the fraction of less than 40-micron particles. This is because after a few cycles, most of the 0-40 microns will escape the unit via the cyclones. 

The most economical cyanide control method in a rehnery appears to be upstream control using polysulhdes. Sodium and ammonium polysulhde (APS) have been used to inhibit cyanide-induced corrosion in FCC and coker fractionation systems [63]. The polysulhde combines with cyanide, forming thiocyanate according to the reaction... 

In 1973, the Arab oil embargo and the sudden escalation in crude oil prices (Figures 1,2) and availability placed refiners under great economic pressures to process more abundant, less expensive, metals-contaminated crude oils and residuum feedstocks. The need for metals-resistant FCC became apparent, and work on understanding metal-catalyst interactions became an area of intense research in industrial laboratories and in the academic community. 

Inferior feeds influence FCC operations and product distribution negatively, resulting in the sharp drop of economic benefits. Refineries are seeking technological... 

The FCC unit can be easily converted to MIP-CGP operation mode with minimal revamping costs. Today, more than 20 FCC units operating in MIP-CGP mode have been put into operation in China, resulting in great economic and social benefits. 

Alkylation processes usually combine isobutane with an alkene or with mixed alkene streams (C3-C5 olefins from FCC units). The best octane ratings are attained when isobutane is alkylated with butylenes. Alkylation of higher-molecular-weight hydrocarbons (>C5) is less economic because of increased probability of side reactions. Phillips developed a technology that combines its triolefin process (metathesis of propylene to produce ethylene and 2-butenes) with alkylation since 2-butenes yield better alkylate than propylene.290 Since ethylene cannot be readily used in protic acid-catalyzed alkylations, a process employing AICI3 promoted by water was also developed.291... 

There are several uranium ore-bodies in the world that cannot be leached economically with sulfuric acid because of the high limestone content of the ore. Such ore-bodies are generally leached with an alkaline solution of sodium carbonate and bicarbonate. Carbonate also forms anionic complexes with the uranyl ion the predominant species being UC fCC 4- — and may therefore also be treated with anion-exchange resins. 

For these and other reasons, only a few papers have been devoted to the modeling of FCC risers. The great economic importance of the FCC process, the competition between companies, and the high cost of good research on FCC have given rise to a lot of confidentiality in this field, and thus many studies do not appear in the open literature. 

Direct Synthesis the crystallization is done in the presence of organic templates (2) such as TBAOH, crown ethers,. ..These syntheses unfortunately suffer from two economic drawbacks, i.e. the long synthesis times (between 3 to 8 days) compared to the classical synthesis (typically 16 hours) and the use of costly, sometimes toxic, and not always recyclable organic molecules Hydrothermal Treatment a post-synthesis treatment widely practiced in the industry because it also modifies the texture (creation of desired mesoporosity) of the zeolite. Such a treatment also takes place in the regenerator of every FCC unit... 

Arbel et al. (1997) give a detailed account of this procedure applied to a fluidized catalytic cracker unit control is possible when only one of the four dominant variables is under feedback control. The effectiveness of the partial control scheme is limited in satisfying the economic objectives when only one dominant variable is in closed-loop control. Superior reactor performance is achieved when all four dominant variables in the reactor are used. However, this requires manipulated variables that were not part of older FCC designs. The new manipulators have been added on modern units to make... 

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