Residuum cracked

In addition, thermally cracked residua will also contain two other fractions the carbenes and the carboids (Figure 6-6) These fractions are also defined by solubility and are precursors to coke (Speight, 1999). Both fractions are, by definition, insoluble in benzene (or toluene) but the carbenes are soluble in carbon disulfide (or pyridine) whereas the carboids are insoluble in carbon disulfide (or pyridine). Only traces of these materials occur in conventional petroleum and heavy oil. Any such quantities are not sufficient to alter the character of the asphaltenes if the benzene-treatment of the feedstock is omitted. On the other hand, feedstocks that have received some thermal treatment (such as visbroken feedstocks and cracked residua) may have considerable quantities of these materials present as they are also considered to be precursors to coke. 

Coking is a thermal process for the continuous conversion of heavy, low-grade oils into lighter products. The feedstock can be reduced crude, straight-run residua, or cracked residua, and the products are gases, naphtha, fuel oil, gas... 

Cracked residua residua that have been subjected to temperatures above 350°C (660°F) during the distillation process. 

Heavy fuel oils usually contain cracked residua, reduced crude, or cracking coil heavy product that is mixed (cut back) to a specified viscosity with cracked gas oils and fractionator bottoms. For some industrial purposes in which flames or flue gases contact the product (ceramics, glass, heat treating, and open-hearth furnaces) fuel oils must be blended to contain... 

Nature of the feed stock to the unit. Adding 10 to 15% cracked residuum to a reduced crude feed increased the lump yield 10 to 15% at constant temperature and constant soaking time. 

The Cherry-P process is a process for the conversion of heavy cmde oil or residuum into distillate and a cracked residuum (Ueda, 1976, 1978). 

The ET-II process is a thermal cracking process for the production of distillates and cracked residuum for use as a metallurgical coke and is designed to accommodate feedstocks such as heavy oils, atmospheric residua, and vacuum residua (Kuwahara, 1987). The distillate (referred to in the process as cracked oil) is suitable as a feedstock to hydrocracker and fluid catalytic cracking. The basic technology of the ET-II process is derived from that of the original Eureka process. 

ET-II process a thermal cracking process for the production of distillates and cracked residuum for use in the production of metallurgical coke of this Earth and not extraterrestrial ... 

Gas oil above 500°F, vegetable oil Liquid naphtha above 500°F, quenching oils Topped crude (below 25°API), fuel oil Cracked residuum, coke-oven gas, illuminating gas... 

O. Exchanger tubes are usuidly steel for oil-to-oil or admiralty for oil-to-water, but 5 to 7 per cent chromium tubes are used for cracked residuum. 

The flashing and cutback of cracked residuum is highly advantageous because it produces a lower gravity residuum, and by Fig. 19-1 a greater yield of gasoline. 

Fig. 19-18. Adiabatic vaporization curve of one 14 API cracked residuum, and the construction curves used in computing the amounts of vaporization.

Cracking imposes an additional penalty in a vacuum unit in that it forms gas which cannot be condensed at the low pressures employed. This gas must be vented by compressing it to atmospheric pressure. This is accomplished by means of steam jet ejectors. Ideally, it would be possible to operate a vacuum pipe still without ejectors, with the overhead vapors composed only of steam. In practice, however, leakage of air into the system and the minor cracking which occurs make it necessary to provide a means of removing non-condensibles from the system. In addition to the distillation of atmospheric residuum, the lube vacuum pipe still is also used for rerunning of off specification lube distillates. 

Solvent Deasphalting This is the solvent extraction of virgin residuum to remove asphaltenes or other tarry constituents. The deasphalted oil may be further processed into lubricating oils and greases, or used as cat cracking feed. 

Figure 2 shows a simplified flow plan for a typical conversion type refinery. The atmospheric P/S residuum can be fed to a vacuum pipestill. The vacuum tower enables the refiner to cut deeper into the crude, at the same time avoiding high temperatures (above about 750 °F) which cause thermal cracking with resultant deposition of coke and tarry residues in the equipment. 

---