Hydrocracking high-pressure

In the two-stage operation, the feed is hydrodesulfurized in the first reactor with partial hydrocracking. Reactor effluent goes to a high-pressure separator to separate the hydrogen-rich gas, which is recycled and mixed with the fresh feed. The liquid portion from the separator is fractionated, and the bottoms of the fractionator are sent to the second stage reactor. 

Hydrocracking a catalytic high-pressure high-temperature process for the conversion of petroleum feedstocks in the presence of fresh and recycled hydrogen carbon-carbon bonds are cleaved in addition to the removal of het-eroatomic species. 

Figure 24.1 is a sketch of a centrifugal pump, driven by a three-phase motor, with a turbine helper. This particular pump was charging a light gas oil stream to a high-pressure hydrocracker. The pump was operating quite close to its design conditions of... 

Hydrocracking (Figure 4-10) is a thermal process (>350°C, >660°F) in which hydrogenation accompanies cracking. Relatively high pressure (100-2000 psi)... 

The wide ranges of temperature and pressure employed for the hydrodesulfurization process virtually dictate that many other reactions will proceed concurrently with the desulfurization reaction. Thus, the isomerization of paraffins and naphthenes may occur and hydrocracking will increase as the temperature and pressure increase. Furthermore, at the higher temperatures (but low pressures) naphthenes may dehydrogenate to aromatics and paraffins dehydrocyclize to naphthenes, while at lower temperature (high pressures) some of the aromatics may be hydrogenated. 

The hydrocracker simulator was also converted to subroutine form for inclusion in the nonlinear programming model of the Toledo process complex. The subroutine was considerably simplified, however, to save computer time and memory. The major differences are (1) the fractionation section is represented by correlations instead of by a multi-stage separation model, (2) high pressure flash calculations use fixed equilibrium K-values instead of re-evaluating them as a function of composition, and (3) the beds in each reactor are treated as one isothermal bed, eliminating the need for heat balance equations. 

Many processes of gas absorption with chemical reaction are set up at high pressures, result of technical and/or economical requirements. That is, for example, processes of hydrocracking and hydrorefining of heavy oils and processes of oxydation of liquid effluents. However, if many chemical systems are found to determine the mass transfer parameters in an industrial reactor at atmospheric pressure by using the chemical method, they become scarce at elevated pressures. Several physical and chemical methods have been proposed chemical methods present some severe drawbacks, since one has to replace the gas-liquid system of interest by another one, presenting different physical properties (specially a different coalescence behaviour). 

The flash of 27-multicomponent mixtures in the high pressure hydrocracking separator were calculated in this paper. To those polar components, special treatment were used. The properties M, Tc, Pc of petroleum fractions were calculated by Riazi and Daubeit [11](1980) correlations, and co was calculated by Lee and Keslefs correlation. A group of typical results... 

Hydrocracking Distillates heavier than diesel are catalytically cracked at high pressure in the presence of hydrogen to produce either gasoline or diesel and lighter products. Generally, the objective is to produce diesel and lighter products such as two-carbon... 

For materials selection, hydrocrackers are treated the same as hydrodesulfurizers, particularly in the first stage. From a materials standpoint, the demarcation between low-pressure units (hydrodesulfurizers) and high-pressure units (usually hydrocrackers) is 650 psia (4,480 kPa). 

In some later work at UOP it was shown that in isomerization and hydrocracking of normal decane the reaction of hydrocracking could be virtually stopped if one operates at very high pressures (up to 1500 atmospheres), however, as the pressure is increased, it is the isomerization reaction which is stopped last. These results reinforce the sequential carbonium ion mechanism, wherein each transformation can be reversed by excessive hydrogen pressure. 

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