Rate atmospheric distillation unit

Since cracking stocks generally do not have to meet the color specifications that lube distillates do, higher flash zone temperatures (up to 8(X)°F) can be tolerated. Fuel units are normally designed to distill material boiling up to 1100°F (at atmospheric pressure) from the feed, and some units have distilled beyond 12(X)°F at low feed rates. 

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. 

It consisted of a single-pass, five-plate, water-cooled condenser capable of independent flow and temperature control. Heat was supplied to the evaporator reservoir, so that it could be operated at selected temperature levels. The rotating assembly, consisting of a shaft with spacers capable of accepting six disks 12 inches in diameter, of varying thickness and composition, was equipped with a variable speed drive. With the arrangement shown, approximately 2 sq. feet of disk-condenser surface area was available for mass transfer. Tests were performed on this unit at atmospheric pressure, using city water (125 p.p.m. of dissolved solids) as feed, to determine the effect on distillation rate of (1) reservoir tem-... 

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