RU2091116C1 - Method of rectification separation of multicomponent mixtures - Google Patents

Abstract

FIELD: rectification processes. SUBSTANCE: initial mixture is fed into column wherein countercurrent liquid-gas interaction takes place on contact grades for stripping low-boiling components. Liquid flowing down from lower part of column is heated in evaporator and ascending vapors are condensed in dephlegmator. Upper and lower rectification products are withdrawn. According to invention, initial mixture, prior to be fed into column, recycles between charging stock tank and dephlegmator functioning as cooling liquid. EFFECT: enhanced efficiency of process. 1 dwg

Description

 The invention relates to the gas, gas processing and petrochemical industries, in particular to an improved method for processing liquid and gaseous multicomponent mixtures, to the hardware design of heat and mass transfer processes in a gas-liquid system.

 A known method of separating a multicomponent mixture (Promotional brochure "Export Model" A "CR ARNOLD, INTERESTS, Houston, Texas), in which the initial mixture is pumped through heat exchangers, where it is subsequently heated, is fed to the evaporator. Vapors from the evaporator enter the distillation column passing from below to the top, where the low-boiling fraction vapors are separated, which are removed from the top of the column to condensation, and then the low-boiling liquid fraction enters reflux tanks. la.

 The disadvantage of this method is the low quality of the upper separation product of the low boiling fraction due to the lack of irrigation in the column.

 Closest to the invention in technical essence is a method for separating a multicomponent mixture in a modular installation for oil and gas processing (article by V. A. Okorokov, L. M. Velinsky "Modular installations for the processing of oil and gas condensate into motor fuel." Chemical and petroleum engineering, 1995, N 12.), in which the method of separation of a multicomponent liquid mixture according to ed. St. N 1456174).

 Hydrocarbon raw materials in the form of a heated hydrocarbon condensate are fed into the furnace, where it is overheated above the boiling point, and then sent in the vapor state to the column to separate the gasoline fraction from the top of the column, for which the vapor is condensed in an air cooling apparatus, and then fed to a container, from which part the gasoline fraction is taken in the form of a finished product, and the rest is returned in the form of reflux (irrigation) to the column.

 The disadvantage of this method is the high capital and energy costs, especially for low-power installations, since column irrigation requires reflex capacity, irrigation feed pumps and the heat of the vapor from the top of the column is not utilized.

 The aim of the invention is to reduce capital and energy costs.

 The goal is achieved in that in a method for separating multicomponent mixtures by rectification, which includes supplying the initial mixture to the column, countercurrent contacting of the liquid and gas at the contact steps for stripping low-boiling components, heating the liquid flowing from the bottom of the column in the evaporator, condensation of rising vapors in the reflux condenser and selection of the upper and lower distillation products, the initial mixture is recycled between the raw material tank and the reflux condenser as a coolant before being fed to the column, heated in phlegmator, selected and served in a column or evaporator as a raw material.

 In comparison with the known technical solutions, the proposed method, in which raw materials are recycled between the raw material tank and the reflux condenser, are heated in the reflux condenser using raw materials as a coolant, are selected and fed to the column or evaporator, it allows the heat of the top of the column to be used for heating raw materials, utilizing the heat of the top of the column. Using the proposed method eliminated the reflux capacity and reflux pump used to supply reflux to the column, which allowed to reduce capital and energy costs when separating mixtures.

 The applicant does not know from the existing level of technology a method for separating multicomponent mixtures of rectification paths in which a reduction in capital and energy costs would be achieved in a similar way.

 The drawing shows a diagram of a method for separating a multicomponent mixture by distillation.

The method is implemented as follows:
Raw materials in the form of a multicomponent liquid mixture from the tank 1 through line 2 are pumped 3 to the annulus 4 of the reflux condenser installed in the upper part of the column 5, where they are heated by the steam flow exiting the column supplied to the reflux condenser through line 6.

 After the reflux condenser, the heated stream of the initial mixture is fed through line 7 to the evaporator 8, in which it is heated to a temperature corresponding to the evaporation temperature of the low-boiling fraction.

 The excess flow of the initial mixture from the reflux condenser 4 through line 9 is returned through the air cooling apparatus 10 to the raw material tank 1.

 The vapor stream from the evaporator 8 is fed via line 11 to the distillation section 12 of column 5 for mass transfer with reflux (condensed liquid), which is fed through line 13 to the upper contact stage for irrigation. As a result of the interaction, the liquid product is enriched with high-boiling components, and the vapors are low-boiling.

 The low-boiling fraction steam stream leaving the distillation section is fed through line 6 to the tube space of the reflux condenser 4, where it is passed from top to bottom, cooled, condensed and collected in a liquid collector 14, separated from the distillation section 12 by a blank plate 15.

 From the liquid collector 14, part of the liquid is returned to the column through line 13 as irrigation (reflux), and the balance amount of the low-boiling fraction is withdrawn via line 16 to the collection tank of the finished product.

 The part of the feed stream that does not evaporate in the column (high boiling fraction) is taken to an intermediate tank via line 17.

According to the proposed method, the feedstock in the form of a liquid enters from the raw material tank 1 in an amount of 2135 kg / h into the annular space of the reflux condenser 4 with a pressure of 0.7 atm. huts and a temperature of 20 ^o C and has the following composition mol. d. nC ₅ 0.18952; C _6, 0.09372; C ₇ 0.19968; C ₈ 0.22558; C ₉ 0.07688; C ₁₀ - 0.0491; Fr 190 ^o C 0,03555; Fr. 210 ^° C. 0.03217; Fr 230 ^o C - 0,02739; Fr. 250 ^° C. 0.02739; Fr. 270 ^° C 0.01952; Fr 290 ^o C - 0.01235; Fr 310 ^o C 0,00458; Fr. 345 ^° C. 0.00675.

In the reflux condenser 4, the feed stream is heated to 100 ^° C. by the steam stream leaving column 5 coming through line 6 and sent through line 7 to evaporator 8 in an amount of 625 kg / h. The evaporator is heated to a temperature of 183 ^o C, corresponding to the evaporation temperature of the low boiling fraction. The excess of the initial mixture (1510 kg / h) from the reflux condenser 4 is returned through the air cooling apparatus 10 to the raw material tank 1.

The vapor stream from the evaporator 8 with a temperature of 183 ^o CC at a pressure of 0.5 ATM. huts sent to the refection section of the column 5 from bottom to top for contact on the mass transfer stages 12 with reflux supplied to the upper stage of the mass transfer sections for irrigation. As a result of the interaction, the liquid product is enriched with high boiling components, and the vapors are low boiling.

The steam stream of the upper product leaving the mass transfer section in an amount of 716 kg / h with a temperature of 124 ^o C is sent to the tube space of the reflux condenser 4, where it is condensed, passed from top to bottom, cooled to a temperature of 45 ^o C and collected in a liquid collector 14, separated from mass transfer section blank plate 15.

From the liquid collector 14, part of the liquid stream is returned to the distillation column as reflux for irrigation through line 13 in the amount of 326 kg / h, and the balance amount of 390 kg / h of low boiling fraction having the following composition in mole. d. nC ₅ 0.25457; C ₆ - 0.12387; C ₇ 0.25697; C ₈ 0.27499; C ₉ 0.01721; C ₁₀ 0.01210; FR 190 ^o 0,00029, divert along line 16 to the collection tank of the finished product.

At the same time, the part of the feed stream (high boiling fraction) not evaporating in the evaporator 8 in the amount of 236 kg / h, having the following composition in mol. d. nC ₅ 0.01019; C ₆ 0.01120; C ₇ 0.04508; C ₈ 0.099368; C ₉ 0.06604; C ₁₀ 0.15047; Fr. 190 ^o C - 0.13327; Fr. 210 ^° C. 0.12130; Fr. 230 ^° C. 0.10328; Fr. 250 ^o C - 0.10328; Fr. 270 ^° C. 0.07361; Fr. 290 ^° C. 0.04657; Fr. 310 ^o C - 0.01727; FR 345 ^o C 0,02477, taken along line 17 to the intermediate tank.

Claims (1)

 A method for separating multicomponent mixtures by distillation, including supplying the initial mixture to the column, countercurrent contacting of the liquid and gas at the contact steps for stripping low boiling components, heating the liquid flowing from the bottom of the column in the evaporator, condensation of rising vapors in the reflux condenser and selection of the upper and lower rectification products characterized in that the initial mixture is recycled between the feed tank and the reflux condenser as coolant before being fed into the column, heated to reflux torre, selected and served in a column or evaporator as a raw material.