Hydrocracking Process Flow

Figure 16.4 Process flow diagrams for major hydrocracker designs.

Figure 2. Simplified hydrocracking two-stage process flow diagram...

As described earlier, the most common form of hydrocracking process is a two-stage operation. " " This flow scheme has been very popular in the many refineries where it is necessary to maximize the yield of transportation fuels and has the flexibility to produce gasoline, naphtha, jet fuel, or diesel fuel to meet seasonal swings in product demand. 

The mild hydrocracking process uses operating conditions similar to those of a VGO desulfurizer to convert VGO to yield significant lighter products. Consequently, the flow scheme for a mild hydrocracking unit is virtually identical to that of a VGO desulfurizer. 

This example comes from the main fractionation tower in a hydrocracking process, which is operated to make naphtha, kerosene, and diesel products. The bottom product is called unconverted oil, part of which is recycled back to reaction for further conversion and the rest sold as fuel oil to the market. Table 13.3 shows the material balance for the fractionator indicated by expected yields versus the actual yields, as well as the flow rates for feed and products measured online. 

A modem petroleum refinery may have four or more hydrotreating units. Strictly speaking, hydrotreaters are not conversion imits because the breaking of carbon-to-carbon bonds is minimal. However, it is convenient to discuss hydrotreating together with hydrocracking and mild hydrocracking because they employ similar catalysts and process flow schemes. 

The HPC is a mild trickle flow hydrocracking process using a Shell proprietary catalyst and operating at typically 30-50 bar total pressure and at a temperature of about 300-350°C. The plant lay-out is very similar to that of a conventional gas oil hydrotreater. The HPC stage performs actually four functions ... 

A typical flow diagram for hydrocracking is shown in Fig. 15.17. Process flow is similar to hydrotreating in that feed is pumped to operating pressure, mixed with a hydrogen-... 

MAK fining A petroleum refining process which combines MAK hydrocracking with a cold-flow improvement process. Developed by Nippon Ketjen and first licensed in 1998. 

Fixed- or packed-bed reactors refer to two-phase systems in which the reacting fluid flows through a tube filled with stationary catalyst particles or pellets (Smith, 1981). As in the case of ion-exchange and adsorption processes, fixed bed is the most frequently used operation for catalysis (Froment and Bischoff, 1990 Schmidt, 2005). Some examples in the chemical industry are steam reforming, the synthesis of sulfuric acid, ammonia, and methanol, and petroleum refining processes such as catalytic reforming, isomerization, and hydrocracking (Froment and Bischoff, 1990). 

A flow diagram for a proposed shale oil refinery is shown in Figure 5. An FCC unit is used as the primary cracking process. This refinery produces high-octane gasoline and diesel fuel. Jet fuel also could be produced by severely hydrogenating a kerosene cut (10) from the whole-oil hydrotreater or by using a hydrocracker in place of the FCC. The... 

Although SRC-II was basically a thermal liquefaction process, it was most successful using bituminous coals with a high native pyrite content. Iron sulfides are well known to have catalytic properties for coal liquefaction. Recycling part of the ash-minerals-containing bottoms had two beneficial effects (1) it increased the pyrite concentration in the reactor feed, and (2) it increased the residence time for heavy components, thus giving them more time to hydrocrack to distillate products. A block flow diagram of the SRC-II process is shown in Fig. 19.19. 

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