CN110108091B - Cryogenic liquefaction system with improved hydrogen separation membrane insertion for STAR propane dehydrogenation - Google Patents

Abstract

The invention provides a cryogenic liquefaction system with improved hydrogen separation membrane embedded aiming at a STAR propane dehydrogenation process, and belongs to the technical field of petrochemical industry. The system is from dehydrogenation toStarting from the composition characteristics of the product, a hydrogen membrane separation unit is introduced after a shallow cooling unit, most hydrogen is separated by utilizing the selective permeation of a membrane, and then the hydrogen is further pressurized and liquefied by deep cooling, and propane and propylene are further separated from the rest non-condensable components. By embedding the improved cryogenic liquefaction system in the hydrogen membrane separation unit, the compression load can be obviously reduced while high-concentration hydrogen is obtained, the total compression energy consumption can be reduced by 8-24%, the heat exchange load of the cryogenic unit can be reduced by 80-86%, the purity of the byproduct hydrogen can be improved to 99 mol% from 82 mol%, and the requirements of hydrogen consumption devices such as hydrocracking and the like in a refining enterprise are met. Under the optimal working condition, the 35 ten thousand tons of STAR process can save the compression energy consumption by 1020kW and produce qualified hydrogen 16198Nm³/h。

Description

STAR Propane Dehydrogenation Hydrogen Separation Membrane Embedded Improved Cryogenic Liquefaction System

technical field

The invention relates to an improved cryogenic liquefaction system embedded in a hydrogen separation membrane for a STAR propane dehydrogenation process, belonging to the field of petrochemical industry. In this process, a hydrogen membrane separation unit is embedded between the shallow cooling unit and the cryogenic unit, and most of the hydrogen in the reaction product is removed through the selective permeation of the membrane. Further pressurization and cryogenic liquefaction can reduce the compression energy consumption of cryogenic liquefaction process while obtaining high-concentration hydrogen.

Background technique

Propylene is the basic raw material for three major synthetic materials, plastics, synthetic rubbers and synthetic fibers. In addition, propylene is also widely used in the production of acrylonitrile, isopropanol, acetone and propylene oxide. In 2018, the global propylene production capacity exceeded 140 million tons and the consumption exceeded 100 million tons. In the next 5-10 years, the average annual growth rate of world propylene production capacity and consumption will be about 4-5%. According to the type of raw materials, the main production routes of propylene can be divided into three types: oil head (steam cracking, catalytic cracking), coal head (methanol to olefins), and gas head (propane dehydrogenation). In recent years, with the large-scale exploitation of shale gas resources around the world, the production of propane has continued to increase, and its price has plummeted, which has greatly promoted the development and industrial application of propane dehydrogenation. In 2018, the total capacity of propane dehydrogenation to olefins exceeded 12 million tons, and it was the most important new source of propylene.

Propane dehydrogenation to propylene technology mainly includes Oleflex process of UOP company, Catofin process of Lummus company, STAR process of Wood company and PDH process of Linde company. Compared with other process technologies, the STAR process converts propane to propylene through two steps of steam reforming dehydrogenation and partial oxidative dehydrogenation at higher reaction pressure (0.5MPaG), with relatively smaller reactor volume and higher one-way conversion rate. Especially in the partial oxidative dehydrogenation process, the use of hydrogen partial combustion and dehydrogenation reaction coupling can not only promote the reaction process, but also provide the heat required for the reaction, which has significant advantages.

In addition to the target product propylene, the propane dehydrogenation process also produces a large amount of hydrogen and methane by-products. Benefiting from the combustion consumption of hydrogen during partial oxidative dehydrogenation, the STAR process produces far less non-condensable components than other propane dehydrogenation processes. Even so, the STAR reaction product still contains a lot of non-condensable components. According to a typical STAR plant of 350,000 tons, the total content of non-condensable components (hydrogen, methane, oxygen, nitrogen, carbon monoxide) in the reaction product is as high as 22.18 mol% after removing moisture and carbon dioxide. Subject to the existence of a large number of non-condensable components, the traditional STAR process adopts a cryogenic liquefaction system, which needs to be carried out under the conditions of high pressure and low temperature of 3.20 MPaG and -78 °C. MPaG is pressurized to 3.20 MPaG, and the compression energy consumption is very large; 2) In the cryogenic process, non-condensable components such as methane and nitrogen coexist with hydrogen, and the concentration of by-product crude hydrogen is less than 90mol%, which cannot be directly used for Typical hydrogen consumption processes in refining and chemical enterprises such as hydrocracking and hydrotreating will cause great waste when used as fuel. Taking a typical 350,000-ton STAR propane dehydrogenation process as an example, the dehydrogenation reaction product compression energy consumption is as high as 6400 kW; the by-product hydrogen is purified to more than 99%, assuming a recovery rate of 80%, which can be used for refinery hydrogenation units every year. Provide about 115 million standard square meters of hydrogen.

According to the composition of a typical STAR propane dehydrogenation product, shown in Table 1, hydrogen is the predominant non-condensable component. The introduction of more efficient hydrogen separation technology, coupled with the traditional liquefaction process, is expected to greatly improve the high-pressure and low-temperature liquefaction conditions, reduce compression power consumption through staged pressurization/condensation, and by-produce high-concentration hydrogen to increase product value. Pressure swing adsorption and membrane separation are two separation technologies that do not depend on the phase equilibrium relationship of the separation object, and both have been widely used in hydrogen separation and purification. Compared with pressure swing adsorption, hydrogen membrane separation can concentrate carbon three (propane, propylene) and other condensed objects on the high-pressure retentate side, which is conducive to subsequent pressure boosting and condensation liquefaction, and is more suitable for combining with the STAR propane dehydrogenation process. . To sum up, the present invention will embed a hydrogen membrane separation unit after the shallow cooling unit in the STAR propane dehydrogenation process, remove most of the hydrogen in the reaction product through selective permeation, and then further pressurize and cryogenically liquefy, and Obtain high-concentration hydrogen while reducing the compression energy consumption of cryogenic liquefaction process.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an improved cryogenic liquefaction system embedded in a hydrogen separation membrane for the STAR propane dehydrogenation process. This process introduces a hydrogen membrane separation unit after the shallow cooling unit in the STAR propane dehydrogenation process, and uses the selective permeation of the membrane to separate most of the hydrogen in the reaction product, and then further pressurizes and cryogenic liquefaction, from the remaining non-condensing group. Further separation of carbon three (propane and propylene) in the fraction.

Technical scheme of the present invention:

An improved cryogenic liquefaction system embedded in the hydrogen separation membrane for the STAR propane dehydrogenation process, the propane dehydrogenation reaction product S1 cooled to normal temperature is pressurized by the first compressor 1 and then enters the first cooler 2 to reduce the temperature to normal temperature, and then enter the decarburization/dehydration system 13, at the same time, the decarburization absorbent S2 also enters the decarburization/dehydration system 13; in the decarburization/dehydration system 13, five streams of material output are generated, and the decarburization absorbent is rich in liquid S3 and condensed water S4 are sent to the outside world, the first light hydrocarbon condensate S5 is sent to the deethanizer, the dehydration cycle gas S6 is returned to the inlet of the first compressor 1, and the decarburized and dehydrated propane dehydrogenation reaction product S7 is sent to the first heat exchanger 6;

The propane dehydrogenation reaction product S7 after decarburization and dehydration passes through the first heat exchanger 6, the second cooler 4 and the third cooler 7 in order to cool down, and then enters the first gas-liquid separation tank 9, and the second is extracted at the bottom of the tank. Light hydrocarbon condensate S8, the first non-condensable gas S9 is produced at the top of the tank;

The first non-condensable gas S9 is heated through the second heat exchanger 14 and the heater 15 in turn, then enters the hydrogen membrane separation unit 16, and obtains the membrane separation permeate S18 of hydrogen concentration on the low pressure side, and the hydrogen concentration reaches more than 99 mol%, Membrane separation retentate S19 with most of the hydrogen removed on the high pressure side is obtained, and the hydrogen concentration is lower than 25 mol% under suitable operating pressure;

The membrane separation retentate gas S19 is reduced to normal temperature by the fourth cooler 8, and then enters the second compressor 3, and after the secondary pressurization, enters the second heat exchanger 14 for pre-cooling, and then enters the fifth cooler 17 for further cooling, and then Entering the second gas-liquid separation tank 11, the third light hydrocarbon condensate S11 is produced at the bottom of the tank, and the second non-condensable gas S12 is produced at the top of the tank; the second non-condensable gas S12 is combined with the top gas S14 of the deethanizer to enter The cold box 10 is further cryogenically cooled, and then enters the third gas-liquid separation tank 18, where the fourth light hydrocarbon condensate S15 is produced at the bottom of the tank, and the third non-condensable gas S16 is produced at the top of the tank;

The fourth light hydrocarbon condensate S15 passes through the cold box 10 to recover the low temperature cooling capacity, and then is combined with the second light hydrocarbon condensate S8 and the third light hydrocarbon condensate S11, and then enters the first heat exchanger 6 to recover the medium and low temperature cooling capacity, and finally sends it to the first heat exchanger 6. To the deethanizer; the third non-condensable gas S16 recovers the low-temperature cooling capacity through the cold box 10, and then enters the turbo refrigerator 12, and then enters the cold box 10 to recover the low-temperature cooling capacity after expansion and cooling; the third non-condensable gas S16 is fully After the cold energy is recovered, it is called the tail gas S17 of the propane dehydrogenation process.

The beneficial effects of the present invention are as follows: a hydrogen membrane separation unit is embedded between the shallow cooling unit and the cryogenic unit, most of the hydrogen in the reaction product is removed through the selective permeation of the membrane, and the condensable components such as propane and propylene are subjected to non-phase separation. It becomes concentrated, greatly reduces the gas flow, and then further pressurizes and cryogenic liquefaction, which can significantly reduce the compression energy consumption of the cryogenic liquefaction process while obtaining high-concentration hydrogen. Taking a typical 350,000-ton STAR propane dehydrogenation process as an example, the reaction product enters the hydrogen membrane separation unit after shallow cooling at 2.30MPaG and -24°C, and the membrane separation retentate gas is carried out at 3.20MPaG and -78°C. In cryogenic liquefaction, the total compression energy consumption is reduced by 16.1%, the purity of hydrogen is increased from 82.8 mol% to 99.0 mol%, and the recovery rate is over 85%. Considering the energy saving and hydrogen production, the improved cryogenic liquefaction system embedded in the hydrogen separation membrane has significant economic advantages.

Description of drawings

Figure 1 is a cryogenic liquefaction system in a typical STAR propane dehydrogenation process.

Figure 2 is a modified cryogenic liquefaction system embedded in a hydrogen separation membrane for the STAR propane dehydrogenation process.

In the figure: 1 first compressor; 2 first cooler; 3 second compressor; 4 second cooler; 5 decarburization/dehydration system; 6 first heat exchanger; 7 third cooler; 8 fourth cooler; 9 first gas-liquid separation tank; 10 cold box; 11 second gas-liquid separation tank; 12 turbo refrigerator; 13 decarburization/dehydration system; 14 second heat exchanger; 15 heater; 16 hydrogen membrane Separation unit; 17 fifth cooler; 18 third gas-liquid separation tank; S1 cooled propane dehydrogenation reaction product; S2 decarburization absorbent; S3 decarburization absorbent rich liquid; S4 condensate water; S5 first light hydrocarbon condensate liquid; S6 dehydration recycle gas; S7 propane dehydrogenation reaction product after decarburization and dehydration; S8 second light hydrocarbon condensate; S9 first non-condensable gas; S10 deethanizer overhead gas; S11 third light hydrocarbon condensate; S12 second non-condensable gas; S13 propane dehydrogenation process tail gas; S14 deethanizer overhead gas; S15 fourth light hydrocarbon condensate; S16 third non-condensable gas; S17 propane dehydrogenation process tail gas; S18 membrane separation permeate gas; The S19 membrane separates the retentate.

Detailed ways

The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

Example 1

Embodiment 1 For the propane dehydrogenation reaction product of a typical 350,000-ton STAR process of a certain enterprise, a traditional cryogenic liquefaction system is used for processing, and the corresponding technical scheme is described as follows:

The propane dehydrogenation reaction product S1 cooled to normal temperature is pressurized to 1.40 MPaG by the first compressor 1 and then enters the first cooler 2, and then is further pressurized to 3.20 MPaG by the second compressor 3 and then enters the second cooler 4. Reduce the temperature of the material to normal temperature, and then enter the decarburization/dehydration system 5. At the same time, the decarburization absorbent S2 also enters the decarburization/dehydration system 5; in the decarburization/dehydration system 5, five streams of material output are generated, and the decarburization The absorbent rich liquid S3 and condensed water S4 are sent to the outside world, the first light hydrocarbon condensate S5 is sent to the deethanizer, the dehydration cycle gas S6 is returned to the inlet of the first compressor 1, and the decarburized and dehydrated propane dehydrogenation reaction product S7 , sent to the first heat exchanger 6;

The propane dehydrogenation reaction product S7 after decarburization and dehydration passes through the first heat exchanger 6, the third cooler 7 and the fourth cooler 8 to cool down, and then enters the first gas-liquid separation tank 9, and the second Light hydrocarbon condensate S8, the first non-condensable gas S9 is produced at the top of the tank; the first non-condensable gas S9 and the deethanizer overhead gas S10 are combined into the cold box 10 for further deep cooling, and then enter the second gas-liquid separation tank 11 , the third light hydrocarbon condensate S11 is produced at the bottom of the tank, and the second non-condensable gas S12 is produced at the top of the tank;

The third light hydrocarbon condensate S11 passes through the cold box 10 to recover the low temperature cooling capacity, and then joins with the second light hydrocarbon condensate S8 and enters the first heat exchanger 6 to recover the medium and low temperature cooling capacity, and finally sends it to the deethanizer; The non-condensable gas S12 recovers the low-temperature cooling capacity through the cold box 10, and then enters the turbine refrigerator 12. After expansion and cooling, it enters the cold box 10 again to recover the low-temperature cooling capacity; the second non-condensable gas S12 fully recovers the cooling capacity and is called propane Dehydrogenation process tail gas S13.

In this example, the power consumption of the first compressor 1 and the second compressor 3 is the most important utility consumption, with a total installed power of 6350 kW. The cold box 10 is the most critical cold exchange equipment, in which the light hydrocarbon condensation amount reaches 5782 kg/h. The concentration of by-product hydrogen is only 82.82 mol%, which cannot be directly used in hydrogen-consuming units such as hydrocracking in refining and chemical enterprises.

Example 2

Embodiment 2 For the propane dehydrogenation reaction product of a typical 350,000-ton STAR process of a certain enterprise, the hydrogen separation membrane provided by the present invention is used to inline the improved cryogenic liquefaction system for processing, and the specific technical scheme is as follows:

As shown in Fig. 2, the propane dehydrogenation reaction product S1 cooled to normal temperature is pressurized to 1.90MPaG by the first compressor 1 and then enters the first cooler 2, the temperature is lowered to normal temperature, and then enters the decarburization/dehydration system 13, At the same time, the decarburization absorbent S2 also enters the decarburization/dehydration system 13; five material outputs are generated in the decarburization/dehydration system 13, and the decarburization absorbent rich liquid S3 and condensed water S4 are sent to the outside world, and the first light The hydrocarbon condensate S5 is sent to the deethanizer, the dehydration cycle gas S6 is returned to the inlet of the first compressor 1, and the decarburized and dehydrated propane dehydrogenation reaction product S7 is sent to the first heat exchanger 6;

The propane dehydrogenation reaction product S7 after decarburization and dehydration passes through the first heat exchanger 6, the second cooler 4 and the third cooler 7 in order to cool down, and then enters the first gas-liquid separation tank 9, and the second is extracted at the bottom of the tank. The light hydrocarbon condensate S8, the first non-condensable gas S9 is produced at the top of the tank; the first non-condensable gas S9 passes through the second heat exchanger 14 and the heater 15 to be heated up in sequence, and then enters the hydrogen membrane separation unit 16, and is on the low-pressure side. The membrane separation permeate gas S18 with hydrogen concentration is obtained, and the hydrogen concentration reaches more than 99 mol%, and the membrane separation retentate gas S19 is obtained from which most of the hydrogen is removed on the high pressure side, and the hydrogen concentration is lower than 35 mol%;

The membrane separation retentate gas S19 is lowered to normal temperature through the fourth cooler 8, and then enters the second compressor 3, is pressurized to 3.20 MPaG for the second time, enters the second heat exchanger 14 for pre-cooling, and then enters the fifth cooler 17 for further cooling , and then enter the second gas-liquid separation tank 11, the third light hydrocarbon condensate S11 is produced at the bottom of the tank, and the second non-condensable gas S12 is produced at the top of the tank; the second non-condensable gas S12 and the deethanizer overhead gas S14 Plying into the cold box 10 for further deep cooling, and then into the third gas-liquid separation tank 18, the fourth light hydrocarbon condensate S15 is produced at the bottom of the tank, and the third non-condensable gas S16 is produced at the top of the tank;

The fourth light hydrocarbon condensate S15 passes through the cold box 10 to recover the low temperature cooling capacity, and then is combined with the second light hydrocarbon condensate S8 and the third light hydrocarbon condensate S11, and then enters the first heat exchanger 6 to recover the medium and low temperature cooling capacity, and finally sends it to the first heat exchanger 6. To the deethanizer; the third non-condensable gas S16 recovers the low-temperature cooling capacity through the cold box 10, and then enters the turbo refrigerator 12, and then enters the cold box 10 to recover the low-temperature cooling capacity after expansion and cooling; the third non-condensable gas S16 is fully After the cold energy is recovered, it is called the tail gas S17 of the propane dehydrogenation process.

In this implementation case, the power consumption of the first compressor 1 and the second compressor 3 is the most important public utility consumption, and the total installed power is 4820 kW, which saves 24% compared to the traditional cryogenic liquefaction system in Example 1. . The cold box 10 is the most critical cold exchange equipment, in which the light hydrocarbon condensation capacity is 1115 kg/h. Compared with the traditional cryogenic liquefaction system in Example 1, the load is reduced by 80.7%. The concentration of hydrogen produced by membrane separation reaches 99.0mol%, which meets the needs of hydrogen-consuming units such as hydrocracking in refining and chemical enterprises. The hydrogen recovery rate reaches 83.7%, and the hydrogen output is 15159 Nm ³ /h.

Example 3

Embodiment 3 For the propane dehydrogenation reaction product of a typical 350,000-ton STAR process of a certain enterprise, the hydrogen separation membrane provided by the present invention is used to process the improved cryogenic liquefaction system, and the specific technical scheme is as follows:

As shown in Figure 2, the propane dehydrogenation reaction product S1 cooled to normal temperature is pressurized to 2.30MPaG by the first compressor 1 and then enters the first cooler 2, the temperature is lowered to normal temperature, and then enters the decarburization/dehydration system 13, At the same time, the decarburization absorbent S2 also enters the decarburization/dehydration system 13; five material outputs are generated in the decarburization/dehydration system 13, and the decarburization absorbent rich liquid S3 and condensed water S4 are sent to the outside world, and the first light The hydrocarbon condensate S5 is sent to the deethanizer, the dehydration cycle gas S6 is returned to the inlet of the first compressor 1, and the decarburized and dehydrated propane dehydrogenation reaction product S7 is sent to the first heat exchanger 6;

The propane dehydrogenation reaction product S7 after decarburization and dehydration passes through the first heat exchanger 6, the second cooler 4 and the third cooler 7 in order to cool down, and then enters the first gas-liquid separation tank 9, and the second is extracted at the bottom of the tank. The light hydrocarbon condensate S8, the first non-condensable gas S9 is produced at the top of the tank; the first non-condensable gas S9 passes through the second heat exchanger 14 and the heater 15 to be heated up in sequence, and then enters the hydrogen membrane separation unit 16, and is on the low-pressure side. The membrane separation permeate gas S18 with hydrogen concentration is obtained, and the hydrogen concentration reaches more than 99 mol%, and the membrane separation retentate gas S19 is obtained from which most of the hydrogen is removed on the high pressure side, and the hydrogen concentration is lower than 25 mol%;

The membrane separation retentate gas S19 is reduced to normal temperature through the fourth cooler 8, and then enters the second compressor 3, and after the secondary pressurization to 3.20 MPaG, enters the second heat exchanger 14 for precooling, and then enters the fifth cooler 17 for further Cool down, then enter the second gas-liquid separation tank 11, produce the third light hydrocarbon condensate S11 at the bottom of the tank, and produce the second non-condensable gas S12 at the top of the tank; the second non-condensable gas S12 and the top gas of the deethanizer S14 is combined into the cold box 10 for further cryogenic cooling, and then enters the third gas-liquid separation tank 18, where the fourth light hydrocarbon condensate S15 is produced at the bottom of the tank, and the third non-condensable gas S16 is produced at the top of the tank;

The fourth light hydrocarbon condensate S15 passes through the cold box 10 to recover the low temperature cooling capacity, and then is combined with the second light hydrocarbon condensate S8 and the third light hydrocarbon condensate S11, and then enters the first heat exchanger 6 to recover the medium and low temperature cooling capacity, and finally sends it to the first heat exchanger 6. To the deethanizer; the third non-condensable gas S16 recovers the low-temperature cooling capacity through the cold box 10, and then enters the turbo refrigerator 12, and then enters the cold box 10 to recover the low-temperature cooling capacity after expansion and cooling; the third non-condensable gas S16 is fully After the cold energy is recovered, it is called the tail gas S17 of the propane dehydrogenation process.

In this implementation case, the power consumption of the first compressor 1 and the second compressor 3 is the most important public utility consumption, and the total installed power is 5330 kW, which saves 16% compared to the traditional cryogenic liquefaction system in Example 1. . The cold box (15) is the most critical cold exchange equipment, in which the light hydrocarbon condensation capacity is 799 kg/h. Compared with the traditional cryogenic liquefaction system in Example 1, the load is reduced by 86.2%. The concentration of hydrogen produced by membrane separation reaches 99.0 mol%, which meets the needs of hydrogen-consuming units such as hydrocracking in refining and chemical enterprises. The hydrogen recovery rate reaches 86.0%, and the hydrogen output is 16198 Nm ³ /h.

Example 4

Embodiment 4 For the propane dehydrogenation reaction product of a typical 350,000-ton STAR process of a certain enterprise, the hydrogen separation membrane provided by the present invention is used to process the improved cryogenic liquefaction system, and the specific technical scheme is as follows:

As shown in Figure 2, the propane dehydrogenation reaction product S1 cooled to normal temperature is pressurized to 2.70MPaG by the first compressor 1 and then enters the first cooler 2, the temperature is lowered to normal temperature, and then enters the decarburization/dehydration system 13, At the same time, the decarburization absorbent S2 also enters the decarburization/dehydration system 13; five material outputs are generated in the decarburization/dehydration system 13, and the decarburization absorbent rich liquid S3 and condensed water S4 are sent to the outside world, and the first light The hydrocarbon condensate S5 is sent to the deethanizer, the dehydration cycle gas S6 is returned to the inlet of the first compressor 1, and the decarburized and dehydrated propane dehydrogenation reaction product S7 is sent to the first heat exchanger 6;

The propane dehydrogenation reaction product S7 after decarburization and dehydration passes through the first heat exchanger 6, the second cooler 4 and the third cooler 7 in order to cool down, and then enters the first gas-liquid separation tank 9, and the second is extracted at the bottom of the tank. The light hydrocarbon condensate S8, the first non-condensable gas S9 is produced at the top of the tank; the first non-condensable gas S9 passes through the second heat exchanger 14 and the heater 15 to be heated up in sequence, and then enters the hydrogen membrane separation unit 16, and is on the low-pressure side. The membrane separation permeate gas S18 with hydrogen concentration is obtained, and the hydrogen concentration reaches more than 99 mol%, and the membrane separation retentate gas S19 with most of the hydrogen removed at the high pressure side is obtained, and the hydrogen concentration is lower than 22 mol%;

The membrane separation retentate gas S19 is reduced to normal temperature through the fourth cooler 8, and then enters the second compressor 3, and after the secondary pressurization to 3.20 MPaG, enters the second heat exchanger 14 for precooling, and then enters the fifth cooler 17 for further Cool down, then enter the second gas-liquid separation tank 11, produce the third light hydrocarbon condensate S11 at the bottom of the tank, and produce the second non-condensable gas S12 at the top of the tank; the second non-condensable gas S12 and the top gas of the deethanizer S14 is combined into the cold box 10 for further cryogenic cooling, and then enters the third gas-liquid separation tank 18, where the fourth light hydrocarbon condensate S15 is produced at the bottom of the tank, and the third non-condensable gas S16 is produced at the top of the tank;

The fourth light hydrocarbon condensate S15 passes through the cold box 10 to recover the low temperature cooling capacity, and then is combined with the second light hydrocarbon condensate S8 and the third light hydrocarbon condensate S11, and then enters the first heat exchanger 6 to recover the medium and low temperature cooling capacity, and finally sends it to the first heat exchanger 6. To the deethanizer; the third non-condensable gas S16 recovers the low-temperature cooling capacity through the cold box 10, and then enters the turbo refrigerator 12, and then enters the cold box 10 to recover the low-temperature cooling capacity after expansion and cooling; the third non-condensable gas S16 is fully After the cold energy is recovered, it is called the tail gas S17 of the propane dehydrogenation process.

In this implementation case, the power consumption of the first compressor 1 and the second compressor 12 is the most important public utility consumption, and the total installed power is 6230kW, which saves 8% compared to the traditional cryogenic liquefaction system in Example 1. The cold box (15) is the most critical cold exchange equipment, in which the light hydrocarbon condensation capacity is 799 kg/h. Compared with the traditional cryogenic liquefaction system in Example 1, the load is reduced by 86.2%. The hydrogen concentration produced by membrane separation reaches 99.0mol%, which meets the needs of hydrogen-consuming units such as hydrocracking in refining and chemical enterprises. The hydrogen recovery rate reaches 87.2%, and the hydrogen output is 16356 Nm ³ /h.

Claims (1)

1. A cryogenic liquefaction system with improved hydrogen separation membrane intercalation for STAR propane dehydrogenation process is characterized in that,

the propane dehydrogenation reaction product (S1) cooled to the normal temperature enters a first cooler (2) after being pressurized by a first compressor (1), the temperature is reduced to the normal temperature, and then the propane dehydrogenation reaction product enters a decarburization/dehydration system (13), and meanwhile, a decarburization absorbent (S2) also enters the decarburization/dehydration system (13); five streams of materials are output in a decarburization/dehydration system (13), a decarburization absorbent rich liquid (S3) and condensed water (S4) are sent out, a first light hydrocarbon condensate liquid (S5) is sent to a deethanizer, dehydrated cycle gas (S6) returns to an inlet of a first compressor (1), and a propane dehydrogenation reaction product (S7) after decarburization and dehydration is sent to a first heat exchanger (6);

the decarbonized and dehydrated propane dehydrogenation reaction product (S7) sequentially passes through a first heat exchanger (6), a second cooler (4) and a third cooler (7) to be cooled, then enters a first gas-liquid separation tank (9), a second light hydrocarbon condensate (S8) is produced at the bottom of the tank, and a first non-condensable gas (S9) is produced at the top of the tank;

the first non-condensable gas (S9) sequentially passes through a second heat exchanger (14) and a heater (15) to be heated, then enters a hydrogen membrane separation unit (16), membrane separation permeation gas with concentrated hydrogen is obtained at a low-pressure side (S18), the hydrogen concentration reaches over 99 mol%, membrane separation permeation residual gas with most of hydrogen removed is obtained at a high-pressure side (S19), and the hydrogen concentration is lower than 25 mol% under proper operating pressure;

the membrane separation residual gas (S19) is cooled to normal temperature by a fourth cooler (8), then enters a second compressor (3), enters a second heat exchanger (14) for precooling after secondary pressurization, then enters a fifth cooler (17) for further cooling, then enters a second gas-liquid separation tank (11), third light hydrocarbon condensate (S11) is produced at the bottom of the tank, and second non-condensable gas (S12) is produced at the top of the tank; the second non-condensable gas (S12) and deethanizer overhead gas (S14) are combined and enter a cooling box (10) for further deep cooling, then enter a third gas-liquid separation tank (18), fourth light hydrocarbon condensate (S15) is produced at the bottom of the tank, and third non-condensable gas (S16) is produced at the top of the tank;

the fourth light hydrocarbon condensate (S15) is subjected to low-temperature cold recovery by a cold box (10), then is combined with the second light hydrocarbon condensate (S8) and the third light hydrocarbon condensate (S11), enters a first heat exchanger (6) to recover medium-low-temperature cold, and finally is sent to a deethanizer; the third non-condensable gas (S16) passes through the cold box (10) to recover low-temperature cold energy, then enters the turbine refrigerating machine (12), and enters the cold box (10) again to recover the low-temperature cold energy after expansion and temperature reduction; the third noncondensable gas (S16) is called as tail gas of the propane dehydrogenation process (S17) after cold energy is fully recovered.

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