Refinery catalytic cracking units

Pocock, A., Economies of Power Recovery from Flue Gases of an Oil Refinery Catalytic Cracking Unit, Paper from Thermofluids Conference, Dec. 1-3, 1976, Hobart, Australia. 

National Emission Standards for Hazardous Air Pollutants for Primary Copper Smelting National Emission Standards for Hazardous Air Pollutants for Secondary Aluminum Production National Emission Standards for Hazardous Air Pollutants for Primary Lead Smelting National Emission Standards for Hazardous Air Pollutants for Petroleum Refineries Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units... 

Pollutants for Petroleum Refineries Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units... 

Refinery Catalytic cracking unit columns A supplier error caused the unit to be purged with a containing 93% oxygen. Several explosions and fires resulted. Always test purge gas before use. 

For many waste water strippers used in refinery services, rapid rates of reboiler fouling are experienced, not due to corrosion, but as a consequence of heavy hydrocarbon sludge, that settles out in the bottom of the sour water stripper feed tank. In particular, slurry oil that is produced in a refinery catalytic cracking unit can accumulate in the stripper s feed tank. This slurry oil, being denser than water, settles out in the tank and eventually is drawn into the suction of the sour water stripper feed pump. The heavy hydrocarbon phase then accumulates in the stripper s reboiler, and with time and temperature fouls the reboiler s tubes. 

The process of fluid catalytic cracking (FCC) is the central process in a modem, gasoline-oriented refinery. In U.S. refineries, the amount of feed processed by fluid catalytic cracking units (FCCU) is equivalent to 35% of the total cmde oil processed in the United States (1). As of January 1991, installed FCCU capacity in the United States was 8.6 x ICf m /d (5.4 x 10 barrels/d). 

In support of the power recovery expander market for fluid catalytic cracking units in refineries, some turboexpander manufacturers have an ongoing program to improve the solid particle erosion characteristics of the machine. Improved erosion characteristics will result in longer blade life, less downtime, and consequently greater profits for the users. 

While this unit is considerably cheaper, it also has certain disadvantages. For example, changes or upsets in any one unit may be felt throughout the refinery because of the changes in fractionator operation. However, the considerable cost saving possible with the combination type unit has permitted many small refineries to finance a catalytic cracking unit when they could not afford a conventional model. 

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. 

Ethylene is a constituent of refinery gases, especially those produced from catalytic cracking units. The main source for ethylene is the steam cracking of hydrocarbons (Chapter 3). Table 2-2 shows the world ethylene production by source until the year 2000. U.S. production of ethylene was approximately 51 billion lbs in 1997. ... 

Sulfur is removed from a number of refinery process off-gas streams (sour gas) to meet the sulfur oxide emissions limits of the Clean Air Act and to recover salable elemental sulfur. Process off-gas streams, or sour gas, from the coker, catalytic cracking unit, hydrotreating units, and hydroprocessing units can contain high concentrations of hydrogen sulfide mixed with light refinery fuel gases. 

Catalytic cracking units are one of the largest sources of sour and phenolic wastewaters in a refinery. Pollutants from catalytic cracking generally come from the steam strippers and overhead accumulators on fractionators, used to recover and separate the various hydrocarbon fractions produced in the catalytic reactors. 

In Western Europe it is expected that new isomerization capacity may exceed alkylation installations since naphtha availability generally exceeds demand. By selecting isomerization over alkylation the octane number of the gasoline pool may be increased without increasing the volume. Moreover, olefinic charge stock avails for alkylation are considerably smaller in Europe since there are fewer catalytic cracking units per refinery than in the United States and Canada. It is predicted that C5, and to a lesser extent C5/C6 isomerization, will prevail over alkylation in Western Europe until more catalytic cracking units are installed and/or a shift in the demand for naphtha over fuel oil is experienced. 

Table I shows the products from a well-designed gas-recovery unit in a typical refinery having a catalytic-cracking unit and a thermal-cracking unit. Where only the propane propylene is charged to the polymerization unit a depropanizer is added to separate the Cs and lighter from the C and heavier, shown in the last column of the table.

In 2002, a French court found the president of Total guilty of manslaughter in the death of six operators from the fluid catalytic cracking unit explosion at the La Mede refinery. He was sentenced to 18 months in prison (suspended) and fined 4,500 ( 4,000) (CCPS, 2008a). 

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