RU2621349C1 - Method for separation of isophetic-pentan-isohexan-hexane fraction, reducing the share of recycle flows in the system - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a process for separating iso-pentane, isohexane, hexane fraction, reducing the proportion of the recycle stream in the system is to allocate the commodity isomerate from the feed stream by sequentially passing the last column stabilization, deisopentanization column and deisohexanization column. The method is characterized in that the withdrawal of the side stream from column deizopentanization is performed in the stripping section; heating the stripping section of the column a residue using heat stabilization.

EFFECT: installation of the stripping section allows to improve the quality of fractionation by stripping off light isopentane components and to reduce the amount of recycle stream.

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Description

The invention relates to the field of secondary processing of petroleum products and can be used in the refining industry, in particular in the isomerization process.

It is known that isomerization is currently considered the most efficient way to produce pure high-octane gasoline components (A. Shakun. Russian Isomalk-2 isomerization technology is the best technological solution for the production of EURO-4 and EURO-5 gasolines / A.N. Shakun , E.V. Demidova // Oil, Gas, Innovations. - 2010. - No. 9. - P. 44-46). The octane number of the isomerizate is determined by the depth of isomerization of the feedstock, which largely depends on the separation scheme of the reaction products and the degree of recirculation of unconverted normal paraffin hydrocarbons (Ivanchina E.D., Kirgina M.V., Chekantsev N.V., Dolganov I.M., Sharova ES Methods of optimization and organization of energy and resource-saving chemical and technological systems of oil refining industries. Textbook. - Tomsk: TPU Publishing House, 2013. - 159 p.).

Isolation of normal hydrocarbons from isomerization products requires additional installation of deisopentanization and deisohexanization columns. Technological schemes of isomerization are complicated, which accordingly entails an increase in energy consumption for the separation of isomerization products. A known method for the separation of the isopentane-pentane-hexane fraction in the isomerization process, based on four simple distillation columns for fractionation of the feedstock - NK-70 ° C fraction of straight-run gasoline and reaction products with the separation of butane, isopentane, pentane, isohexane and hexane, returns pentane to the reactor as a recycle, separation and stabilization of reaction products in the processing unit of the isomerizate from the separator and two distillation columns with the return of the isomerizate after mixing with the feedstock in the first fractionator separation unit (YM Zhorov Isomerization of hydrocarbons Chemistry and Technology -.. M .: Chemistry, 1983, 304 pp.).

The disadvantages of this method are:

- the need to use a large number of fractionation equipment (six distillation columns, condensers, refrigerators and boilers, a separator), which leads to significant capital costs for the implementation of the separation method and increase the cost of the final separation products;

- hexane of the feedstock obtained in the fourth distillation column of the separation unit of the feedstock is not subjected to isomerization, which reduces the yield of the valuable final product of isohexane in the process, since pentane and hexane are measured together in the isomerization reactor.

The closest in technical essence is the method of separation of the isopentane-pentane-hexane fraction in the isomerization process, in which the ballast product contained in the raw material is distilled from the first distillation column for preparing raw materials, the residue from the bottom of the distillation column is sent to convert pentanes and hexanes to isomers in a reactor isomerization; isomerization products are sent to the second stabilization distillation column, from which butane is removed from the top of the column, and isomerizate containing reaction isomers obtained during the reaction, which are sent to the separation of the third distillation column of deisopentanization, from which isopentane, pentane recycle is removed and hexane fraction, pentane recycling is returned to the isomerization reactor. Isopentane contained in the feed is removed as the ballast product from the top of the first distillation column, the reaction isopentane is removed from the top of the third distillation column of deisopentanization, a mixture of isohexane and normal hexane is removed from the bottom of the distillation column, which is fed to the additional fourth distillation column the isohexane fraction is removed by distillate, and a hexane recycling which is sent for re-conversion isomerization reactor, and the remainder - boiling components (. A method for separating isopentane-pentane-hexane fraction Patent №2478601 RU, appl 23.01.2012, published 04.10.2013..).

The disadvantage of this method is a significant amount of isopentane in the recycle fraction, which is ballast; a large number of recycle streams in the lateral overhead output and, as a result, fuzzy separation.

The objective of the invention is the development of resource and energy-saving fractionation technology at the installations of the oil refining complex, which consists in improving the quality of separation between normal components and isocomponents, as well as reducing the consumption of recycle streams.

The problem is solved in that in the method for the separation of the isopentane-pentane-isohexane-hexane fraction, which consists in separating the commodity isomerizate from the feed stream by sequentially passing the stabilization column, the deisopentanization column and the deisohexanization column, and differs from the prototype in that the lateral output the overhead from the deisopentanization column is carried out in the stripping section; to heat the stripping section, the heat of the remainder of the stabilization column is used. The analysis of the results of calculating the actual operation of the deisopentanization column was carried out, which showed that the separation of n-pentane and isopentane in the column is not efficient enough, since the content of low-octane components (normal hydrocarbons) in the recycle streams is not high enough and the content of isocomponents is large, which leads to to suboptimal operation of the isomerization unit as a whole.

The figure shows a schematic diagram of the separation of isomerization products at the installation.

The figure indicates:

1 - stabilization column; 2 - column deisopentanization; 3 - column deisohexanization; 4 - stripping section; I - products of isomerization reactions; II - reflux; III - stable isomerizate; IV - isopentane fraction; V is the fraction of n-pentane; VI - depentanized isomerizate; VII — isohexane fraction; VIII - fraction of n-hexane; IX — bottoms product of the deisohexanization column; X - recycling (fraction of n-pentane and n-hexane)

In this regard, it was proposed to organize the withdrawal of the lateral overhead of the deisopentanizer column through an additional stripping section. To create a resource-energy-saving technology, it was proposed to use the following heat supply options:

- due to the feed of the bottoms product of the deisopentanization column as a coolant into the boiler of the stripping section;

- due to the supply of cubic product of the stabilization column as a coolant in the boiler of the stripping section.

In the UniSim Design software package, mathematical models of the deisopentanization column for both of these options were created.

As calculations of the actual operation of the installation showed, the deisohexanization column works quite efficiently, providing the necessary degree of separation between n-hexane and its high-octane isomers. In this regard, a change in the n-hexane recovery system is not required in this case.

Since, according to the task, the proposed options for improving the existing technology for the separation of isomerizate should be resource-energy-saving, the main principle in organizing the operation of the new stripping column could not be the use of additional energy resources. In order to increase the degree of heat recovery at the installation, the use of internal high-temperature process flows was considered as heat carriers to the stripping section.

The installation of the stripping section will improve the quality of fractionation due to the stripping of light isopentane components and reduce the amount of recycle stream.

Claims (1)

The method of separation of isopentane-pentane-isohexane-hexane fraction, which reduces the proportion of recycle streams in the system, which consists in isolating the commodity isomerizate from the feed stream by sequentially passing the stabilization column, the deisopentanization column and the deisohexanization column, characterized in that the side stream is removed from the deisopane column to the stripping section; to heat the stripping section, the heat of the remainder of the stabilization column is used.

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