Hydrocracking unit

Typical feedstock composition, yields and product properties for a hydrocracking unit (to be continued). 

Solvents are recovered from the oil stream through distillation and steam stripping in a fractionator. The stream extracted from the solvent contains high concentrations of hydrogen sulfide, aromatics, naphthenes and other hydrocarbons, and is often fed to the hydrocracking unit. 

Naphthas obtained from cracking units generally contain variable amounts of olefins, higher ratios of aromatics, and branched paraffins. Due to presence of unsaturated compounds, they are less stable than straight-mn naphthas. On the other hand, the absence of olefins increases the stability of naphthas produced by hydrocracking units. In refining operations, however, it is customary to blend one type of naphtha with another to obtain a required product or feedstock. 

Kerosine, a distillate fraction heavier than naphtha, is normally a product from distilling crude oils under atmospheric pressures. It may also he obtained as a product from thermal and catalytic cracking or hydrocracking units. Kerosines from cracking units are usually less stable than those produced from atmospheric distillation and hydrocracking units due to presence of variable amounts of olefinic constituents. 

Gas oil is a heavier petroleum fraction than kerosine. It can be obtained from the atmospheric distillation of crude oils (atmospheric gas oil, AGO), from vacuum distillation of topped crudes (vacuum gas oil, VGO), or from cracking and hydrocracking units. 

A major use of gas oil is as a fuel for diesel engines. Another important use is as a feedstock to cracking and hydrocracking units. Gases produced from these units are suitable sources for light olefins and LPG. Liquefied petroleum gas LPG may be used as a fuel, as a feedstock to... 

MM. Internal decarburization/fissuring of piping in a hydrocracker unit after 235,000 hours of service. 

Failure of hydrocracker unit reactor due to localized overheating... 

New Brunswick, Canada Process Facility—A fire originated in the feed heater of a hydrocracker and resulted in one fatality and significant damage to a Hydrocracking Unit. 

The hydrocracking unit is typically used to produce reformer feedstock, jet fuel plus gasoline, and distillate blend components. Feedstock consists of cycle oil, coker distillates, and gas oils. 

TABLE 2-4. Effect of Process Variables on Hydrocracking Unit Operation... 

Fig. 2. Aerial view of small portion of a Texas petroleum refinery, showing the hydrocracking unit just left of center of view...

The sulfur oxidation is carried out at pressure higher than 8 atm and below 180 °C, with a proprietary supported-Mo oxide-based catalyst, for example, an alpha alumina-supported MgMo04 catalyst, operating at 110 °C and 17 atm [59c]. All the products produced by oxidation side reactions and by hydroperoxide reduction are separated from the gas oil stream together with the sulfones. This operation may result in diesel yield loss therefore, the valorization or upgrade of this oxidized stream affects the process economics. This stream can be blended into the heating oil pool or treated in a hydrocracking unit to recover valuable products. 

Feeds. Properties of two hydrofined test feeds are given in Table I. The California gas oil blend was used in tests simulating a hydrocracking unit producing both naphthas and jet fuel, the Mid-Continent blend in tests representing a unit producing naphtha as the major product. 

The Demex process is a solvent extraction demetallizing process that separates high metal vacuum residuum into demetallized oil of relatively low metal content and asphaltene of high metal content (Table 8-5) (Houde, 1997). The asphaltene and condensed aromatic contents of the demetallized oil are very low. The demetallized oil is a desirable feedstock for fixed-bed hydrodesulfurization and, in cases where the metals and carbon residues are sufficiently low, is a desirable feedstock for fluid catalytic cracking and hydrocracking units. 

Table IV. Properties of Oil Entering Catalytic Hydrocracking Unit...

Catalyst performance is determinedby activity, selectivity andstability. Whereas activity is indispensable, selectivity is often of prime importance (e.g. lube base oil yield in catalytic dewaxing), particularly if an improved selectivity can break a bottleneck in a unit (e.g. by lower gas makes which break up the gas train bottleneck a in a hydrocracking unit). Catalyst life is determined both by the start of run activity and deactivation rate. With high activity catalysts in low severity duty (e.g. naphtha hydrotreating), catalyst life can be very long (e.g. 5-10 years), and in some cases the... 

As a result, MWP sorted from municipal solid wastes can be processed in a refinery, which has a dechlorination unit installed prior to the hydrocracking unit. Even though commercial catalysts showed satisfactory performance at high temperatures, neutral catalysts based on activated carbon can also be utilized for this purpose. 

---