Cat cracker feed

Hydrofining usually involves only minor molecular changes of the feed with hydrogen consumption in the range of about 100 to 1,000 cu.ft./bbl. Typical applications include desulfurization of a wide range of feeds (naphtha, light and heavy distillates, and certain residua) and occasional pretreatment of cat cracker feeds. 

Medium and heavy vacuum fraction as cat cracker feed (400-585°C)... 

The residual hydrotreated shale oil was mixed with regular refinery cat cracker feed at a rate of 3%, with no detectable shifts in yields or other adverse consequences. Similarly, the gasoline range cut had no detectable effects on hydrocracker operations at 1.5% of feed. 

Residual Fuel. The residual fuel produced by both the pilot and refinery meets all government specifications for low sulfur, high pour point 6 fuel oil. The residual fuels are in fact very "clean" as shown in Table VIII by the high hydrogen and low sulfur, metals, carbon and asphaltenes content. This stock is better utilized as cat cracker feed than residual fuel, since higher value gasoline and kerosene fuel can be easily produced via catalytic processing. 

Primary Name Fuel oil. No. 4 Common Synonyms Caswell No. 2 333AB Cat cracker feed stock EINECS 270-673-5 EPA Pesticide Chemical Code 063514 Fuel oil No. 4 Diesel fuel No. 4. 

The gas oil feed for the conventional cat cracker comes primarily from the atmospheric column, the vacuum tower, and the delayed coker. In addition, a number of refiners blend some atmospheric or vacuum resid into the feedstocks to be processed in the FCC unit. 

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. 

The teed to the cat cracker in a typical refinery is a blend of gas oils from such operating units as the crude, vacuum, solvent deasphalting, and coker. Some refiners purchase outside FCC feedstocks to keep the FCC feed rate maximized. Other refiners process atmospheric or vacuum residue in their cat crackers. In recent years, the trend has been toward heavier gas oils and residue. Residue is most commonly defined as the fraction of feed that boils above 1,050°F (565 C). Each FCC feed stream has different distillation characteristics. 

One area of cat cracking not fully understood is the proper determination of carbon residue of the feed and how it affects the unit s coke make. Carbon residue is defined as the carbonaceous residue formed after thermal destruction of a sample. Cat crackers are generally limited in coke burn capacity, therefore, the inclusion of residue in the feed produces more coke and forces a reduction in FCC throughput. Conventional gas oil feeds generally have a carbon residue less than 0,5 wt for feeds containing resid, the number can be as high as 15 wt lf. 

For many years, cat cracker operators have used additive compounds for enhancing cat cracker performance. The main benefits of these additives (catalyst and feed additives) are to alter the FCC yields and reduce the amount of pollutants emitted from the regenerator. The additives discussed in this section are CO promoter, SO reduction, ZSM-5, and antimony. 

The calculation of heat balance around the reactor is illustrated in Example 5-6. As shown, the unknown is the heat of reaction. It is calculated as the net heat from the heat balance divided by the feed flow in weight units. This approach to determining the heat of reaction is acceptable for unit monitoring. However, in designing a new cat cracker, a correlation is needed to calculate the heat of reaction. The heat of reaction is needed to specify other operating parameters, such... 

In a cat cracker, a portion of the feed, mostly from secondary cracking and polymerization reactions, is deposited on the catalyst as coke. Coke formation is a necessary byproduct of the FCC operation the heat released from burning coke in the regenerator supplies the heat for the reaction. 

Cracking large hydrocarbons usually results in olefins, molecules with double bonds. Thats why the refinery cat crackers and thermal crackers are sources of ethylene and propylene. But the largest source is olefin plants where ethylene and propylene are the primary products of cracking one or more of the following ethane, propane, butane, naphtha, or gas oil. The choice of feedstock depends both on the olefins plant design and the market price of the feeds. 

A number of refiners have processed residue containing feedstocks in commercial FCC units. Feeds with as much as 5.1%w RCR ( 6.5%w CCR) and 85 ppm Ni + V have been processed in Phillips Borger Refinery.(4) Ashland has processed feedstocks of up to 7.1%w RCR ( 8.5%w CCR) and 85 ppm Ni + V in their RCC (Reduced Crude Conversion) process.(5,6) A commercial scale ART (Asphalt Residual Treating) unit has processed residues containing levels of contaminants as high as 13.5%w RCR and 300 ppm Ni + V (7,8). However, in typical day-to-day operation of residue cat crackers, feedstock quality is not as extreme as those illustrated above. 

Application To produce propylene and ethylene from low-value, light hydrocarbon streams from ethylene plants and refineries with feeds in the carbon number range of C4 to C8, such as steam cracker C4/C5 olefins, cat-cracker naphthas, or coker gasolines. 

Alkylation tests were conducted in the pilot plant with a cat cracker mixed olefin feed. As the water In HF was increased from 0.25 to about 2.8 percent, the alkylate composition changed dramatically. These changes are summarized In Table III detailed alkylate compositions are given In Table VIII. 

Some normal butane is also produced from butylenes but this is estimated at only 4-6%. The higher octane isobutylene alkylate and a claimed yield increase must be contrasted with normal paraffin production from olefins and a higher isobutane requirement. The typical mixed 03 = 704= feed can be made to produce a high octane alkylate with either acid catalyst by the optimization of other variables. The highest alkylate octane numbers reported are produced with sulfuric acid catalyst, alkylating with a typical cat cracker butylene olefin. 

With the old amorphous catalyst, the cat cracker was getting about 16 gallons of gasoline from each barrel of feed. But with the new zeolite catalyst, the same cracker squeezed out another 8 gallons of gasoline from the same barrel of feed. That s a fifty percent increase in gasoline yield — an almost unbelievable result. 

Cat. cracker (fluid) Cost based on fresh feed 35,000 14,000,000 400 ... 

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