A gas-liquid separation and purification system and method based on a liquid organic dehydrogenation process

Abstract

The application provides a gas-liquid separation and purification system and method based on a liquid organic dehydrogenation process, which separates methylcyclohexane dehydrogenation products into gaseous dehydrogenation products and liquid dehydrogenation products through a first gas-liquid separator; an absorption tower receives the gaseous dehydrogenation products and removes organic components in the gaseous dehydrogenation products by means of an absorbent to obtain crude hydrogen; a molecular sieve filter receives the crude hydrogen, and high-purity hydrogen is obtained after filtration and purification; a solvent regenerator performs resolution and regeneration treatment on the liquid phase mixed components discharged from the absorption tower, so that the absorbent in the liquid phase mixed components is enriched at the bottom of the tower, the organic components are enriched at the top of the tower, the absorbent enriched at the bottom of the tower is returned to the absorption tower, and the regeneration and reuse of the absorbent are completed. The combination of the absorption tower and the regenerator can solve the separation problem of hydrogen and aromatic organic matter, reduce the load of the purification section, effectively prolong the service life of the material in the absorption section, and realize deep purification of hydrogen and efficient recovery of organic matter.

Description

Technical Field

[0001] This application relates to the technical field of organic liquid hydrogen storage, and in particular to a gas-liquid separation and purification system and method based on liquid organic dehydrogenation process. Background Technology

[0002] Against the backdrop of a global push for energy transition and carbon neutrality, hydrogen energy, as a clean and efficient secondary energy carrier, faces storage and transportation bottlenecks for large-scale application. Liquid Organic Hydrogen Carriers Technology (LOHC) is particularly suitable for large-scale, long-distance hydrogen storage, transportation, and international trade due to its high hydrogen storage density, good safety, and reversibility. Within this technology system, methylcyclohexane (MCH) is widely recognized as a promising liquid hydrogen carrier due to its moderate theoretical hydrogen storage capacity (6.22 wt%), stable physicochemical properties, mature and commercially viable hydrogenation process, and the reversibility of the methylcyclohexane-toluene-hydrogen (MTH) cycle. Its core lies in an efficient dehydrogenation process: stable MCH undergoes a dehydrogenation reaction under the action of a catalyst, releasing hydrogen and regenerating it into toluene, thus achieving the recycling of the carrier. This process typically includes steps such as MCH preheating and vaporization, catalytic dehydrogenation reaction, condensation and cooling of reaction products, and gas-liquid separation.

[0003] The dehydrogenation reaction products are a complex mixture containing hydrogen, unreacted MCH, the target product toluene, and byproducts (such as light aromatic hydrocarbons like biphenyl). Efficient separation of high-purity hydrogen and maximal recovery of organic matter (especially toluene) are key to achieving closed-loop economic operation of the MTH system. Currently, mainstream separation and purification technologies include: condensation separation + adsorption purification, cryogenic + adsorption purification, cryogenic + membrane separation, and cryogenic + pressure swing adsorption (PSA).

[0004] Although existing processes have been applied in small-scale or specific scenarios, when it comes to large-scale industrial applications, there are problems such as difficulty in achieving both hydrogen recovery rate and purity, inability to meet the stringent standards for hydrogen used in fuel cells, and high energy consumption. Summary of the Invention

[0005] To address the problems existing in the background technology, this application provides a gas-liquid separation and purification system and method based on a liquid organic dehydrogenation process. The system includes: a first gas-liquid separator, used to separate the methylcyclohexane dehydrogenation product into a gas-phase dehydrogenation product and a liquid-phase dehydrogenation product; an absorption tower, connected to the first gas-liquid separator, used to receive the gas-phase dehydrogenation product and absorb and remove the organic components in the gas-phase dehydrogenation product with the aid of an absorbent to obtain crude hydrogen; a molecular sieve filter, connected to the absorption tower, used to receive the crude hydrogen and perform filtration and purification to obtain high-purity hydrogen; and a solvent regeneration tower, connected to the absorption tower, used to perform analytical regeneration treatment on the liquid-phase mixed components discharged from the absorption tower, so that the absorbent in the liquid-phase mixed components is enriched at the bottom of the tower, and the organic components are enriched at the top of the tower, and the absorbent enriched at the bottom of the tower is returned to the absorption tower, completing the regeneration and reuse of the absorbent. By combining an absorption tower and a regeneration solvent tower, the problem of separating hydrogen and aromatic organic compounds can be solved, the load on the purification section can be reduced, the material life of the absorption section can be effectively extended, and deep purification of hydrogen and efficient recovery of organic compounds can be achieved.

[0006] The specific details of the invention are as follows:

[0007] In a first aspect, this application provides a gas-liquid separation and purification system based on a liquid organic dehydrogenation process, the system comprising:

[0008] A first gas-liquid separator is used to separate the methylcyclohexane dehydrogenation product into a gas phase dehydrogenation product and a liquid phase dehydrogenation product.

[0009] An absorption tower is connected to the first gas-liquid separator. The absorption tower is used to receive the gas-phase dehydrogenation product and absorb and remove the organic components in the gas-phase dehydrogenation product with the help of an absorbent to obtain crude hydrogen.

[0010] A molecular sieve filter is connected to the absorption tower. The molecular sieve filter is used to receive the crude hydrogen gas, filter and purify it to obtain high-purity hydrogen gas.

[0011] A solvent regeneration tower is connected to the absorption tower. The solvent regeneration tower is used to perform analytical regeneration treatment on the liquid phase mixture discharged from the absorption tower, so that the absorbent in the liquid phase mixture is enriched at the bottom of the tower and the organic components are enriched at the top of the tower. The absorbent enriched at the bottom of the tower is returned to the absorption tower, thus completing the regeneration and reuse of the absorbent.

[0012] Optionally, the number of trays in the absorption tower is set to 8 to 15.

[0013] Optionally, an interstage cooling device is provided around the absorption tower, the interstage cooling device including an interstage pump and an interstage cooler; the interstage cooler is connected to the interstage pump, and the interstage pump and the interstage cooler are respectively connected to the absorption tower;

[0014] The interstage pump pumps the heated absorbent from the absorption tower to the interstage cooler for cooling, and then returns it to the absorption tower to continue to absorb and remove organic components from the gas-phase dehydrogenation products.

[0015] Optionally, the interstage pump is connected to the absorption tower via a first connection port, and the interstage cooler is connected to the absorption tower via a second connection port;

[0016] The first connection port is located in the middle section of the absorption tower, and the second connection port is located on the side of the first connection port away from the top of the absorption tower.

[0017] Optionally, the number of trays in the solvent regeneration tower is set to 8 to 15.

[0018] Optionally, it also includes a waste heat exchanger, which is disposed between the solvent regeneration tower and the absorption tower, for receiving the liquid phase mixture discharged from the absorption tower and the regenerated absorbent discharged from the solvent regeneration tower, and performing heat exchange treatment to raise the temperature of the liquid phase mixture to a first preset range and lower the temperature of the regenerated absorbent to a second preset range.

[0019] Optionally, it also includes a second gas-liquid separator, which is disposed between the waste heat exchanger and the solvent regeneration tower, and a first connecting pipe and a second connecting pipe are provided between the second gas-liquid separator and the solvent regeneration tower;

[0020] The second gas-liquid separator is used to perform gas-liquid separation treatment on the heated liquid-phase mixture discharged from the waste heat exchanger, so that the liquid-phase mixture is separated into a liquid-phase mixture and a gas-phase mixture. The gas-phase mixture enters the solvent regeneration tower through the first connecting pipeline, and the liquid-phase mixture enters the solvent regeneration tower through the second connecting pipeline.

[0021] Optionally, the first connecting pipe is connected to the solvent regeneration tower through a third connecting port, and the second connecting pipe is connected to the solvent regeneration tower through a fourth connecting port. The third connecting port is located on the side of the solvent regeneration tower near the top of the tower, and the fourth connecting port is located on the side of the third connecting port away from the top of the solvent regeneration tower.

[0022] Optionally, the system also includes a compressor, which is disposed between the first gas-liquid separator and the absorption tower. The compressor is used to pressurize the gas-phase dehydrogenation product before sending it into the absorption tower.

[0023] Secondly, this application provides a gas-liquid separation and purification method based on a liquid organic dehydrogenation process. The method is applicable to the aforementioned system and includes the following steps:

[0024] S1. The methylcyclohexane dehydrogenation product is passed into the first gas-liquid separator for condensation treatment, so that the methylcyclohexane dehydrogenation product is separated into gas phase dehydrogenation product and liquid phase dehydrogenation product.

[0025] S2. The gaseous dehydrogenation product is fed into the absorption tower from the bottom of the tower, and the absorbent is fed into the absorption tower from the top of the tower, so that the gaseous dehydrogenation product and the absorbent are in countercurrent contact. The organic components in the gaseous dehydrogenation product are absorbed by the absorbent to form a liquid phase mixed component, and the remaining gas phase is crude hydrogen.

[0026] S3. The liquid phase mixture discharged from the absorption tower is passed into the solvent regeneration tower to perform desorption and regeneration treatment on the liquid phase mixture, so that the absorbent in the liquid phase mixture is enriched at the bottom of the tower and the organic components are enriched at the top of the tower. The absorbent enriched at the bottom of the tower is returned to the absorption tower to complete the regeneration and reuse of the absorbent.

[0027] S4. The crude hydrogen gas is passed through a molecular sieve filter for filtration and purification to obtain high-purity hydrogen gas.

[0028] Optionally, the absorbent is sulfolane and / or N-methylpyrrolidone.

[0029] Optionally, step S2 further includes:

[0030] The heated absorbent in the absorption tower is pumped out to the interstage cooler by an interstage pump, cooled down, and then returned to the absorption tower to continue participating in the absorption of organic components in the gas-phase dehydrogenation products.

[0031] Optionally, in step S2, the pressure in the absorption tower is 0.3MPa~2MPa, and the temperature is 20℃~60℃.

[0032] Optionally, in step S3, the temperature at the top of the solvent regeneration tower is 65℃~80℃, and the temperature at the bottom of the tower is 160℃~175℃.

[0033] Compared with the prior art, this application has the following advantages:

[0034] The gas-liquid separation and purification system based on liquid organic dehydrogenation technology provided in this application separates the dehydrogenation product of methylcyclohexane into gas-phase dehydrogenation product and liquid-phase dehydrogenation product through a first gas-liquid separator; an absorption tower, connected to the first gas-liquid separator, is used to receive the gas-phase dehydrogenation product and absorb and remove the organic components in the gas-phase dehydrogenation product with the help of an absorbent to obtain crude hydrogen; a molecular sieve filter, connected to the absorption tower, is used to receive the crude hydrogen and filter and purify it to obtain high-purity hydrogen; a solvent regeneration tower, connected to the absorption tower, performs analytical regeneration treatment on the liquid-phase mixed components discharged from the absorption tower, so that the absorbent in the liquid-phase mixed components is enriched at the bottom of the tower and the organic components are enriched at the top of the tower, and the absorbent enriched at the bottom of the tower is returned to the absorption tower, thus completing the regeneration and reuse of the absorbent.

[0035] By combining an absorption tower and a solvent regeneration tower, the energy consumption of both the absorption and desorption processes is extremely low, reducing energy consumption by more than 40% compared to traditional cryogenic separation systems. The solvent regeneration tower is connected to the absorption tower, completing the regeneration and reuse of the absorbent. Compared to traditional single-stage gas-liquid separation and gas-liquid separation + cryogenic separation + molecular sieve systems, the toluene recovery rate is increased from 96-98.85% to over 99.9%, significantly reducing raw material loss. The absorption tower can absorb almost all organic matter, increasing hydrogen purity from 99% in traditional cryogenic + molecular sieve systems to over 99.95%. Only one molecular sieve filter is needed to achieve hydrogen purity of over 99.99%, meeting the requirements for fuel cell-grade hydrogen supply (purity ≥99.97%).

[0036] Furthermore, since the absorption tower absorbs almost all organic matter, the molecular sieve filter only needs to filter and purify a very small portion or almost none of the organic matter. As a result, the molecular sieve filter can achieve a service life of more than 40 months. Compared with the traditional process that requires frequent regeneration and replacement of molecular sieves every 3 to 6 months, it is more environmentally friendly and user-friendly.

[0037] In summary, the system provided in this application can balance hydrogen recovery rate and purity, meet the stringent standards for hydrogen used in fuel cells, and has low energy consumption. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic diagram of the gas-liquid separation and purification system based on liquid organic dehydrogenation process provided in this application embodiment is shown.

[0040] Figure 2 A partially enlarged view of the absorption tower in the gas-liquid separation and purification system provided in the embodiments of this application is shown;

[0041] Figure 3 A partially enlarged view of the solvent regeneration tower in the gas-liquid separation and purification system provided in the embodiments of this application is shown;

[0042] Figure 4 A flowchart of a gas-liquid separation and purification method based on liquid organic dehydrogenation process provided in an embodiment of this application is shown.

[0043] Figure 5 A structural diagram of the gas-liquid separation and purification system for methylcyclohexane dehydrogenation provided in this application is shown.

[0044] Figure label:

[0045] 1-First gas-liquid separator, 2-Absorption tower, 3-Solvent regeneration tower, 31-Top condenser, 32-Bottom reboiler, 4-Molecular sieve filter, 5-Interstage cooling device, 51-Interstage pump, 52-Interstage cooler, 53-First connection port, 54-Second connection port, 6-Waste heat exchanger, 7-Second gas-liquid separator, 71-First connecting pipe, 72-Second connecting pipe, 73-Third connection port, 74-Fourth connection port, 8-Compressor, 9-First condenser, 10-Second condenser, 11-First mixer, 12-Second mixer, 13-Third connecting pipe;

[0046] 101 - Third condenser, 102 - First stage gas-liquid separator, 104 - Fourth condenser, 105 - Second stage gas-liquid separator, 106 - First stage molecular sieve filter, 107 - Second stage molecular sieve filter, 108 - Third mixer. Detailed Implementation

[0047] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. Based on the embodiments of this application, any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the protection scope of this application. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this application.

[0048] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of this application and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0049] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of this application specification.

[0050] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0051] Organic liquid dehydrogenation reaction products are complex mixtures containing hydrogen (65-75 mol%), unreacted MCH, the target product toluene, and byproducts (such as biphenyl and other light aromatics). Efficient separation of high-purity hydrogen and maximal recovery of organic matter (especially toluene) are key to achieving closed-loop economic operation of MTH systems. Currently, mainstream separation and purification technologies include:

[0052] Condensation separation + adsorption purification: The basic scheme involves condensing and separating the reaction products once to recover most of the organic matter in the liquid phase. However, a small amount of organic matter (3-5%) is still entrained in the gas phase (mainly hydrogen), which needs to be removed by subsequent molecular sieve adsorption. This scheme is simple to implement with small-scale equipment, but the organic matter recovery rate is low and the material loss is large.

[0053] Cryogenic purification combined with adsorption: To improve recovery rates, most large-scale processes add a cryogenic stage (-10℃ to -20℃) after initial pressurization. This utilizes the low temperature to condense and separate most of the organic matter in the gas phase (efficiency 98-99%). The separated gaseous hydrogen is then purified by molecular sieves. This approach significantly improves recovery rates.

[0054] Cryogenic + Membrane Separation: Patent CN118286822A reports an attempt to combine cryogenic pretreatment with membrane separation technology to purify hydrogen, with the aim of reducing energy consumption or improving efficiency.

[0055] Cryogenic + PSA: Patent CN218810346U reports that its hydrogen production system uses pressure swing adsorption (PSA) to obtain high-purity hydrogen, which can be combined with cryogenic technology for large-scale installations. PSA is characterized by its high product purity (meeting hydrogen standards for fuel cells).

[0056] While existing processes have been applied in small-scale or specific scenarios, they exhibit significant bottlenecks and shortcomings when applied to large-scale industrial applications, especially when pursuing goals such as high recovery rates, high purity, low energy consumption, and operational reliability.

[0057] The inherent defects of condensation separation and the "dew point drift" problem: Under high hydrogen (non-condensable gas) partial pressure, traditional condensation processes cause organic matter to exhibit "dew point drift," resulting in actual condensation temperatures that are much higher than theoretical values ​​and continue to decrease. To achieve high organic matter recovery rates (e.g., toluene > 99.8%), extremely low condensation temperatures are required (often < -60℃). This makes deep cryogenics extremely difficult to achieve in large-scale industrial plants, resulting in huge energy consumption and investment, and stringent cold preservation requirements.

[0058] Economic and engineering issues of cryogenic processes: Cryogenic (especially ultra-low temperature cryogenic) requires high equipment investment in large-scale installations, consumes huge amounts of energy to maintain low-temperature operation, has complex system insulation design, and has poor overall economic efficiency.

[0059] Limitations of membrane separation technology: In large-scale applications, membrane separation (such as CN118286822A) is prone to "concentration polarization" due to uneven gas distribution, accelerating membrane aging and failure. More importantly, there is an irreconcilable contradiction between its hydrogen recovery rate (70%-85%) and product purity (95%-99%): pursuing high purity requires multiple stages in series, which further reduces the recovery rate; improving the recovery rate sacrifices purity, making it difficult to simultaneously meet the stringent standards for hydrogen used in fuel cells (purity ≥99.97%, CO ≤0.2ppm).

[0060] Energy consumption and reliability risks of PSA technology: Although PSA can produce high-purity hydrogen, its combined energy consumption with cryogenic processes (such as cryogenic + PSA) is superimposed. Cryogenic processes consume enormous amounts of energy to maintain low temperatures, and the frequent, second-level pressure switching of PSA also consumes significant amounts of energy. The combination of the two results in high overall power consumption, and the reliability risk of the complex control system increases sharply under high load and large-scale operation, leading to increased maintenance costs.

[0061] Adsorbent consumption and maintenance issues: When molecular sieve adsorbents undertake the final purification task, especially when the front-end separation is incomplete (high organic content), they are prone to saturation and deactivation, requiring frequent regeneration or replacement, which increases operating costs and operational complexity.

[0062] In summary, the aforementioned problems ultimately lead to existing large-scale processes generally facing core pain points such as insufficient toluene recovery rate (<98%), serious material waste, frequent molecular sieve replacement, unstable or unacceptable hydrogen product purity, excessively high overall energy consumption, and challenges in system complexity and reliability. These issues severely restrict the economic feasibility and industrialization of MCH dehydrogenation technology in large-scale hydrogen energy storage and transportation scenarios.

[0063] In view of the problems existing in related technologies, such as unstable or unacceptable purity of hydrogen products, excessively high overall energy consumption, and frequent replacement of molecular sieves, this application provides a gas-liquid separation and purification system based on liquid organic dehydrogenation technology. Figure 1 A schematic diagram of the gas-liquid separation and purification system based on liquid organic dehydrogenation technology provided in this application embodiment is shown; as follows: Figure 1 As shown, the system includes:

[0064] First gas-liquid separator 1, the first gas-liquid separator 1 is used to separate the methylcyclohexane dehydrogenation product into gas phase dehydrogenation product and liquid phase dehydrogenation product;

[0065] Absorption tower 2 is connected to the first gas-liquid separator 1. Absorption tower 2 is used to receive the gas phase dehydrogenation product and absorb and remove the organic components in the gas phase dehydrogenation product with the help of an absorbent to obtain crude hydrogen.

[0066] Molecular sieve filter 4 is connected to the absorption tower 2. The molecular sieve filter 4 is used to receive the crude hydrogen gas, filter and purify it to obtain high-purity hydrogen gas.

[0067] Solvent regeneration tower 3 is connected to the absorption tower 2. The solvent regeneration tower 3 is used to perform analytical regeneration treatment on the liquid phase mixture discharged from the absorption tower 2, so that the absorbent in the liquid phase mixture is enriched at the bottom of the tower and the organic components are enriched at the top of the tower. The absorbent enriched at the bottom of the tower is returned to the absorption tower, thus completing the regeneration and reuse of the absorbent.

[0068] It should be noted that the first condenser 9 is connected to the first gas-liquid separator 1. The first condenser 9 is used to cool the methylcyclohexane dehydrogenation product, reduce the temperature of the methylcyclohexane dehydrogenation product, and cause the heavy components that were originally in the gas phase to condense into the liquid phase due to the decrease in saturated vapor pressure, thereby reducing their entrainment in the gas phase and improving the purity and recovery rate of the liquid phase product after gas-liquid separation.

[0069] Before entering the first gas-liquid separator 1, the methylcyclohexane dehydrogenation product is first cooled in the first condenser 9, and then passed into the first gas-liquid separator 1 for gas-liquid separation.

[0070] It should be noted that the absorption tower 2 is used to receive the gas-phase dehydrogenation products. Specifically, the gas-phase dehydrogenation products are preferably introduced into the absorption tower 2 from the bottom. The fresh absorbent enters the absorption tower 2 from the top along the third connecting pipe 13, and then the gas-phase dehydrogenation products entering from the bottom and the absorbent entering from the top are absorbed in a countercurrent contact in the absorption tower 2.

[0071] In this embodiment of the invention, only one molecular sieve filter 4 is needed to meet the requirements of hydrogen supply at the fuel cell level, and a small molecular sieve filter can meet the usage requirements. Compared with the traditional separation system, the amount of molecular sieve used in the molecular sieve filter 4 of this application is reduced by about 90%.

[0072] It should also be noted that the second mixer 12 is connected to the first gas-liquid separator 1 and is used to receive and recover the liquid phase dehydrogenation products separated by the first gas-liquid separator 1.

[0073] It should also be noted that the first mixer 11 is connected to the absorption tower 2 and the third connecting pipe 13, and is used to mix the absorbent regenerated in the solvent regeneration tower 3 with the added / fresh absorbent entering the absorption tower along the third connecting pipe 13.

[0074] In specific implementation, the methylcyclohexane dehydrogenation product is first condensed in the first condenser 9 to 20℃~25℃, and then the condensed methylcyclohexane dehydrogenation product is passed into the first gas-liquid separator 1 for gas-liquid separation to obtain gas-phase dehydrogenation product and liquid-phase dehydrogenation product. The liquid-phase dehydrogenation product is used as a hydrogen storage carrier and recovered by the second mixer 12. The gas-phase dehydrogenation product is passed from the bottom of the absorption tower 2 into the absorption tower and comes into countercurrent contact with the absorbent that is introduced from the top of the tower along the third connecting pipe 13. The absorbent removes the organic components in the gas-phase dehydrogenation product. The absorption process removes organic matter to obtain crude hydrogen gas with a purity of over 99.95%. The crude hydrogen gas is then passed through a molecular sieve filter 4 for filtration and purification to obtain high-purity hydrogen gas with a purity of over 99.99%. The liquid-phase mixture containing the absorbed organic matter is discharged from the bottom of the tower and passed into a solvent regeneration tower 3 for desorption and regeneration treatment. This process enriches the absorbent in the liquid-phase mixture at the bottom of the tower and enriches the organic matter at the top of the tower. The absorbent enriched at the bottom of the tower is then returned to the absorption tower 2 via the first mixer 11, completing the regeneration and reuse of the absorbent.

[0075] In this embodiment, the absorption tower-solvent regeneration tower combination results in extremely low energy consumption during both the absorption and desorption processes, reducing energy consumption by over 40% compared to traditional cryogenic separation systems. The solvent regeneration tower is connected to the absorption tower, enabling the regeneration and reuse of the absorbent. Compared to traditional single-stage gas-liquid separation and gas-liquid separation + cryogenic separation + molecular sieve systems, the toluene recovery rate is increased from 96-98.85% to over 99.9%, significantly reducing raw material loss. The absorption tower can absorb almost all organic matter, increasing hydrogen purity from 99% in traditional cryogenic + molecular sieve systems to over 99.95%. Only one molecular sieve filter is needed to achieve hydrogen purity of over 99.99%, meeting fuel cell-grade hydrogen supply requirements (purity ≥99.97%). Furthermore, since the absorption tower absorbs almost all organic matter, the molecular sieve filter only needs to filter and purify a very small portion or almost none of the organic matter, allowing the molecular sieve filter to have a lifespan of over 40 months. This is more environmentally friendly and efficient than the traditional process that requires frequent regeneration and replacement of the molecular sieve every 3-6 months.

[0076] In some embodiments, the number of trays in the absorption tower 2 is set to 8 to 15.

[0077] It should be noted that, Figure 2 A partially enlarged view of the absorption tower in the gas-liquid separation and purification system provided in this application embodiment is shown; as follows: Figure 2 As shown, the number of trays in absorption tower 2 is set to 8 to 15. For example, the number of trays in absorption tower 2 can be set to one or any two of the following: 8, 9, 10, 11, 12, 13, 14, and 15.

[0078] In this embodiment, the tray is the core unit for gas-liquid two-phase contact within the absorption tower 2. The gaseous dehydrogenation product rises from the bottom of the tower and passes through the openings or channels on the tray; the liquid absorbent flows down from the top of the tower, forming a liquid layer on the tray. Each tray provides one contact opportunity for the gas and liquid phases, allowing the organic matter in the gaseous dehydrogenation product to be transferred to the liquid absorbent through mass transfer processes such as dissolution and diffusion. By setting the number of trays in the absorption tower 2 to 8-15, sufficient contact frequency and mass transfer between the gas and liquid phases are ensured, improving the absorption rate of the absorbent while reducing cost and energy consumption.

[0079] In some implementations, such as Figure 1 and 2 As shown, an interstage cooling device 5 is provided around the absorption tower 2. The interstage cooling device 5 includes an interstage pump 51 and an interstage cooler 52. The interstage cooler 52 is connected to the interstage pump 51, and the interstage pump 51 and the interstage cooler 52 are respectively connected to the absorption tower 2.

[0080] The interstage pump 51 pumps the heated absorbent in the absorption tower 2 to the interstage cooler 52 for cooling, and then returns it to the absorption tower 2 to continue to absorb and remove organic components from the gas phase dehydrogenation products.

[0081] It should be noted that the inlet of the interstage pump 51 is connected to the absorption tower 2, the outlet of the interstage pump 51 is connected to the inlet of the interstage cooler 52, and the outlet of the interstage cooler 52 is connected to the absorption tower 2, thus forming a closed loop.

[0082] It should be noted that the interstage pump 51 can be a magnetically driven centrifugal pump, a variable frequency screw pump, etc., suitable for conveying the volatile absorbent (such as sulfolane) in this application. The interstage cooler 52 can be a detachable shell-and-tube cooler, a plate cooler, etc., suitable for the low viscosity, clean absorbent (such as N-methylpyrrolidone) in this application, ensuring a stable heat transfer coefficient.

[0083] In practice, the absorbent in the absorption tower 2 absorbs the organic matter in the gas-phase dehydrogenation products, and the temperature of the absorbent rises. At this time, the heated absorbent is introduced from the absorption tower 2 into the inlet of the interstage pump 51, circulates in the pump, and flows from the outlet of the interstage pump 51 to the inlet of the interstage cooler 52 for cooling. The cooled absorbent is then returned to the absorption tower 2 from the outlet of the interstage cooler 52.

[0084] In this embodiment, the absorption process in absorption tower 2 is an exothermic reaction. As absorption proceeds, the temperature inside the tower gradually increases, and this temperature increase significantly reduces the solubility of the absorbent for organic matter. Therefore, the heated absorbent in absorption tower 2 is pumped out to interstage cooler 52 by interstage pump 51 to achieve "circulation" of the absorbent. Interstage cooler 52 can remove the heat generated during the absorption process and return the cooled absorbent to absorption tower 2 to continue participating in the absorption and removal of organic components from the gaseous dehydrogenation products, thus maintaining the low-temperature absorption environment in absorption tower 2.

[0085] In some implementations, such as Figure 2 As shown, the interstage pump 51 is connected to the absorption tower 2 through the first connection port 53, and the interstage cooler 52 is connected to the absorption tower 2 through the second connection port 54; the first connection port 53 is located in the middle section of the absorption tower 2, and the second connection port 54 is located on the side of the first connection port 53 away from the top of the absorption tower 2.

[0086] It should be noted that the first connection port 53 is located in the middle section of the absorption tower 2, and the second connection port 54 is located on the side of the first connection port 53 away from the top of the absorption tower 2. For example, if the number of trays in the absorption tower is 8, then the first connection port 53 is located on the 3rd to 5th trays of the absorption tower, such as the 4th tray, and the second connection port 54 is located on the 4th to 6th trays of the absorption tower, such as the 5th tray (the second connection port 54 is located below the first connection port 53, that is, closer to the bottom of the tower).

[0087] It should be noted that a built-in liquid level sensor is installed at the first connection port 53, which is linked to the frequency conversion system of the interstage pump 51. When the liquid level in the middle section of the absorber tower 2 changes due to feed fluctuations (such as a sudden increase in the concentration of gas-phase dehydrogenation products leading to accelerated absorbent consumption), the liquid intake of the interstage pump 51 is adjusted in real time to avoid the liquid layer on the tray becoming too thin due to excessive liquid intake (affecting mass transfer) or the cooling load becoming insufficient due to insufficient liquid intake (temperature control failure).

[0088] It should be noted that a "liquid seal baffle" is installed at the connection between the first connection port 53, the second connection port 54 and the absorption tower 2. The baffle is formed by the liquid column pressure of the return liquid itself to prevent the rising gas phase in the absorption tower 2 from entering the return liquid pipeline through the first connection port 53 and the second connection port 54.

[0089] In this embodiment, the gaseous dehydrogenation products in the absorption tower 2 flow from bottom to top, and the absorbent is sprayed from top to bottom. The gas and liquid phases contact each other in opposite directions in the tray of the absorption tower 2, forming an organic matter concentration gradient of "high at the bottom and low at the top". The first connection port 53 is located in the middle section of the absorption tower 2, and the second connection port 54 is located on the side of the first connection port 53 away from the top of the absorption tower 2. The middle section absorbent, which has "increased temperature and decreased absorption capacity", can be extracted and cooled by the interstage cooling device 5 and then sent back into the absorption tower 2 to specifically restore the absorption capacity of the absorbent, fill the gap of "middle section absorption efficiency decay", avoid the mass transfer bottleneck caused by overheating of the absorbent, and achieve a balance between energy consumption and stability.

[0090] In some embodiments, the number of trays in the solvent regeneration tower 3 is set to 8 to 15.

[0091] It should be noted that solvent regeneration tower 3 can be a plate tower or a packed tower.

[0092] It should be noted that, Figure 3 A partially enlarged view of the solvent regeneration tower in the gas-liquid separation and purification system provided in this application embodiment is shown; as follows: Figure 3 As shown, the number of trays in the solvent regeneration tower 3 is set to 8 to 15. For example, the number of trays in the solvent regeneration tower 3 can be set to one or any two of the following: 8, 9, 10, 11, 12, 13, 14, and 15.

[0093] It should be noted that the top of solvent regeneration tower 3 is connected to the top condenser 31, which is used to condense the gaseous mixture escaping from the top of solvent regeneration tower 3, allowing the condensed liquid to reflux back to the top of the tower. The bottom of solvent regeneration tower 3 is connected to the bottom reboiler 32, which is used to heat the rich solvent (absorbent for absorbing organic matter) at the bottom of the tower, effectively heating the feed to the solvent regeneration tower and reducing the heat load on the solvent regeneration tower. The loss rate of the absorbent at the bottom of the tower after separation is less than 0.02%.

[0094] It should also be noted that after the gas mixture is condensed in the overhead condenser 31, a mixture of non-condensable gas and organic toluene will be produced. If the non-condensable gas accumulates at the top of the column, it will cause the pressure inside the column to rise, disrupting the gas-liquid balance inside the column. In this case, the non-condensable gas can be extracted to remove excess gas in a timely manner and control the column pressure within the design range.

[0095] It should also be noted that the second mixer 12 is connected to the top condenser 31 and is used to receive the organic components of the hydrogen storage carrier discharged from the top of the solvent regeneration tower 3. In specific implementation, the generated organic toluene mixture is fed into the second mixer 12, which receives the organic toluene mixture discharged from the top of the solvent regeneration tower 3 for subsequent recovery. Through the recovery of the organic toluene mixture, the toluene recovery rate is increased from 96% in the traditional gas-liquid separation system to over 99.9%, and compared with the cryogenic separation process, the toluene recovery rate is increased from 98.9% to over 99.9%.

[0096] In this embodiment, the solvent regeneration tower 3 uses heating and desorption to remove the solute (such as organic matter) from the rich solvent (the absorbent that absorbs organic matter) from the absorbent, restoring the absorbent's absorption capacity (i.e., converting it into a lean solvent). The trays are the key locations for achieving gas-liquid mass transfer. The rich solvent enters from the top of the tower and flows downwards along the trays; the steam generated by heating (such as the water vapor generated by the reboiler 32 at the bottom of the tower) rises from the bottom of the tower and comes into full contact with the rich solvent on each tray. Each tray is equivalent to a small "separation unit," where the solute continuously transfers from the absorbent to the gas phase. The number of trays in the solvent regeneration tower 3 is set to 8-15, which can achieve "deep regeneration of the absorbent, efficient purification of the product, and reasonable control of energy consumption."

[0097] In some implementations, such as Figure 1 As shown, it also includes a waste heat exchanger 6, which is disposed between the solvent regeneration tower 3 and the absorption tower 2. It is used to receive the liquid phase mixture discharged from the absorption tower 2 and the regenerated absorbent discharged from the solvent regeneration tower 3, and to perform heat exchange treatment to raise the temperature of the liquid phase mixture to a first preset range and lower the temperature of the regenerated absorbent to a second preset range.

[0098] It should be noted that the temperature of the first preset range is 150℃~165℃. For example, the temperature of the first preset range can be one or any two of the following: 150℃, 152℃, 155℃, 157℃, 160℃, 164℃, and 165℃.

[0099] It should be noted that the temperature of the second preset range is 60℃~90℃. For example, the temperature of the second preset range can be one or any two of 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, and 90℃.

[0100] It should also be noted that, such as Figure 1 As shown, the system may further include a second condenser 10, which is disposed between the waste heat exchanger 6 and the absorption tower 2. The second condenser 10 is used to condense the regenerated absorbent after heat exchange in the waste heat exchanger 6, thereby reducing the temperature of the regenerated absorbent to a third preset range. The temperature of the third preset range is 20℃~30℃. For example, the temperature of the third preset range can be one or any two of 20℃, 22℃, 25℃, 27℃, 29℃, and 30℃.

[0101] In this embodiment, the waste heat exchanger 6 reuses heat that would otherwise be wasted by heating the low-temperature material with high-temperature material, reducing heat exchange losses between the system and the outside world, making the energy cycle of the entire absorption-regeneration system more efficient. By recovering waste heat, the temperature of the absorbent is optimized in both directions, which reduces the energy consumption of the solvent regeneration tower 3 and improves the process stability of the absorption tower 2 and the solvent regeneration tower 3. This conforms to the principle of "energy cascade utilization" in the process, and ultimately improves the economy and environmental protection of the entire system.

[0102] In some implementations, such as Figure 1 and 3 As shown, it also includes a second gas-liquid separator 7, which is disposed between the waste heat exchanger 6 and the solvent regeneration tower 3. A first connecting pipe 71 and a second connecting pipe 72 are provided between the second gas-liquid separator 7 and the solvent regeneration tower 3.

[0103] The second gas-liquid separator 7 is used to perform gas-liquid separation treatment on the heated liquid phase mixture discharged from the waste heat exchanger 6, so that the liquid phase mixture is separated into a liquid phase mixture and a gas phase mixture. The gas phase mixture enters the solvent regeneration tower 3 through the first connecting pipe 71, and the liquid phase mixture enters the solvent regeneration tower 3 through the second connecting pipe 72.

[0104] It should be noted that the first connecting pipe 71 is equipped with a flow regulating valve, which is installed on the first connecting pipe 71 and is used to regulate the feed rate of the gas phase mixture according to the pressure in the upper part of the solvent regeneration tower 3, so as to avoid the pressure inside the tower from sudden increase due to gas flow fluctuations. The second connecting pipe 72 is equipped with a liquid level control valve, which is used to open when the liquid level reaches the set value to prevent the liquid phase from emptying or overflowing into the gas phase zone.

[0105] In this embodiment, the second gas-liquid separator 7 is located between the waste heat exchanger 6 and the solvent regeneration tower 3. It is used to perform gas-liquid separation treatment on the heated liquid phase mixture discharged from the waste heat exchanger 6, so that the liquid phase mixture is separated into a liquid phase mixture and a gas phase mixture. The liquid phase mixture and the gas phase mixture enter the solvent regeneration tower 3 in separate phases, which effectively reduces the impact of the gas phase on the tower internals under high vacuum, makes the pressure and temperature gradient inside the tower more gradual, and avoids the risk of "tower rush" and "liquid leakage" caused by mixed flow.

[0106] In some implementations, such as Figure 3 As shown, the first connecting pipe 71 is connected to the solvent regeneration tower 3 through the third connecting port 73, and the second connecting pipe 72 is connected to the solvent regeneration tower 3 through the fourth connecting port 74. The third connecting port 73 is located on the side of the solvent regeneration tower 3 near the top of the tower, and the fourth connecting port 74 is located on the side of the third connecting port 73 away from the top of the solvent regeneration tower 3.

[0107] It should be noted that the third connection port 73 is located on the side of the solvent regeneration tower 3 near the top (i.e., the upper middle part), and the fourth connection port 74 is located on the side of the third connection port 73 away from the top of the solvent regeneration tower 3 (the fourth connection port 74 is located below the third connection port 73, i.e., closer to the bottom of the tower). For example, if the solvent regeneration tower 3 has 8 trays, then the third connection port 73 is located above the 5th tray of the solvent regeneration tower 3 (where the gas phase mixture enters the upper packing), and the fourth connection port 74 is located on the 5th tray of the solvent regeneration tower 3 (where the liquid phase mixture directly enters the distributor).

[0108] In this embodiment, the third connection port 73 (gas phase mixture pipeline outlet) is located on the side of the solvent regeneration tower 3 near the top of the tower, and the fourth connection port 74 (liquid phase mixture pipeline outlet) is located on the side of the third connection port 73 away from the top of the solvent regeneration tower 3. The third connection port 73 and the fourth connection port 74 enable the gas phase mixture and the liquid phase mixture to form an orderly flow field in the tower where "light components rise for purification and heavy components descend for desorption". This layout allows each section of space in the tower to match the separation requirements of the corresponding phase, thereby improving the overall processing capacity of the solvent regeneration tower 3. Furthermore, due to the optimized mass transfer efficiency, the solvent circulation volume can be reduced, further reducing the system energy consumption.

[0109] In some implementations, such as Figure 1As shown, it also includes a compressor 8, which is disposed between the first gas-liquid separator 1 and the absorption tower 2. The compressor 8 is used to pressurize the gas-phase dehydrogenation product and then send it into the absorption tower 2.

[0110] In this embodiment, the high pressure and low temperature of the absorption tower 2 are conducive to the absorption process. Therefore, the compressor 8 is set between the first gas-liquid separator 1 and the absorption tower 2. By increasing the pressure, the partial pressure of organic matter in the gas phase dehydrogenation products is increased, the mass transfer efficiency in the absorption tower 2 is optimized, the absorption driving force is enhanced, and the operating pressure requirements of the absorption tower 2 are matched to ensure the stable operation of the absorption process and improve the separation effect and economy of the overall system.

[0111] Secondly, this application provides a gas-liquid separation and purification method based on a liquid organic dehydrogenation process, which is applicable to the aforementioned system. Figure 4 A flowchart of a gas-liquid separation and purification method based on a liquid organic dehydrogenation process provided in this application is shown; as follows: Figure 4 As shown, the method includes the following steps:

[0112] S1. The methylcyclohexane dehydrogenation product is passed into the first gas-liquid separator 1 for condensation treatment, so that the methylcyclohexane dehydrogenation product is separated into gas phase dehydrogenation product and liquid phase dehydrogenation product.

[0113] S2. The gaseous dehydrogenation product is introduced into the absorption tower 2 from the bottom of the tower, and the absorbent is introduced into the absorption tower 2 from the top of the tower, so that the gaseous dehydrogenation product and the absorbent are in countercurrent contact. The organic components in the gaseous dehydrogenation product are absorbed by the absorbent to form a liquid phase mixed component, and the remaining gas phase is crude hydrogen.

[0114] S3. The liquid phase mixture discharged from the absorption tower 2 is passed into the solvent regeneration tower 3 to perform analysis and regeneration treatment on the liquid phase mixture, so that the absorbent in the liquid phase mixture is enriched at the bottom of the tower and the organic components are enriched at the top of the tower. The absorbent enriched at the bottom of the tower is returned to the absorption tower 2 to complete the regeneration and reuse of the absorbent.

[0115] S4. The crude hydrogen gas is passed through molecular sieve filter 4 for filtration and purification to obtain high-purity hydrogen gas.

[0116] It should be noted that the purity of crude hydrogen is above 99.95%, while the purity of high-purity hydrogen is above 99.99%.

[0117] It should also be noted that the gas-liquid molar ratio of the gas-phase dehydrogenation product to the absorbent in absorber tower 2 is 3:1 to 6:1. For example, the molar ratio can be any one of 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 6:1, or any combination thereof. Maintaining the gas-liquid molar ratio at 3:1 to 6:1 ensures that the organic matter in the gas-phase dehydrogenation product is "excessive but not overloaded"—avoiding both unsaturated dissolution of the absorbent due to excess (wasting absorbent capacity) and ensuring that most of the organic matter can be captured by the absorbent, keeping the absorption rate stable at 90% to 95%. Simultaneously, the above molar ratio controls the absorbent circulation rate, reducing system energy consumption and providing stable feed conditions for subsequent processes.

[0118] In this embodiment, the overall process flow is highly efficient and energy-saving, achieving a toluene recovery rate of 99.9% and a hydrogen product purity of over 99.99% (meeting the fuel cell standard of 99.97%). Furthermore, it effectively reduces the amount of molecular sieve used in the secondary hydrogen purification stage and extends its lifespan. The high raw material recovery rate, low solvent recycling rate, and lack of regeneration requirements make it particularly suitable for large-scale engineering applications, making it an ideal LOHC dehydrogenation gas-liquid separation and purification method.

[0119] In some embodiments, the absorbent is sulfolane and / or N-methylpyrrolidone.

[0120] It should be noted that both sulfolane and N-methylpyrrolidone are "polar aprotic solvents," and their molecular structures (containing strongly polar groups such as sulfone and amide groups) give them excellent solubility for unsaturated hydrocarbons (such as alkenes and aromatics). Sulfolane has a high boiling point of 285℃, while N-methylpyrrolidone has a boiling point of 202℃, and both are resistant to temperature changes during absorption-regeneration cycles.

[0121] It should be noted that the fresh absorbent enters the absorption tower 2 along the third connecting pipe 13, while the absorbent in the solvent regeneration tower 3 is cooled by the waste heat exchanger 6 and then pumped back into the absorption tower 2 for absorption, thus realizing the recycling of the absorbent. Therefore, the absorbent entering the absorption tower along the third connecting pipe 13 is only used as a supplementary absorbent to replenish the very small amount of absorbent that has been lost, thereby reducing process costs and energy consumption.

[0122] In this embodiment, the absorbent is sulfolane and / or N-methylpyrrolidone. Through the combined advantages of "high selective solubility, strong stability and excellent mass transfer", it can not only efficiently absorb organic matter in gas phase dehydrogenation products, but also adapt to the absorption-regeneration cycle process, taking into account both technical performance and economic and environmental protection.

[0123] In some implementations, step S2 further includes:

[0124] The heated absorbent in the absorption tower 2 is pumped out to the interstage cooler 52 by the interstage pump 51, cooled down, and then returned to the absorption tower 2 to continue to participate in the absorption of organic components in the gas phase dehydrogenation products.

[0125] In this embodiment, the absorption process in absorption tower 2 is an exothermic reaction. As absorption proceeds, the temperature inside the tower gradually increases, and this temperature increase significantly reduces the solubility of the absorbent for organic matter. Therefore, the heated absorbent in absorption tower 2 is pumped out to interstage cooler 52 by interstage pump 51 to achieve "circulation" of the absorbent. Interstage cooler 52 can remove the heat generated during the absorption process and return the cooled absorbent to absorption tower 2 to continue participating in the absorption and removal of organic components from the gaseous dehydrogenation products, thus maintaining the low-temperature absorption environment in absorption tower 2.

[0126] In some embodiments, in step S2, the pressure in the absorption tower 2 is 0.3 MPa to 2 MPa, and the temperature is 20°C to 60°C.

[0127] It should be noted that the pressure in the absorption tower is 0.3MPa to 2MPa. For example, the pressure in the absorption tower can be one or any two of the following: 0.3MPa, 0.4MPa, 0.5MPa, 0.7MPa, 0.9MPa, 1.0MPa, 1.5MPa, 1.8MPa, and 2MPa.

[0128] It should be noted that the temperature in the absorption tower is 20℃~60℃. For example, the temperature in the absorption tower can be one or any two of the following: 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, and 60℃.

[0129] In this embodiment, by controlling the pressure in the absorption tower to 0.3MPa~2MPa, the absorption driving force is enhanced and the mass transfer efficiency is optimized; the temperature is 20℃~60℃ to balance the solubility and mass transfer kinetics and ensure the activity of the absorbent. High pressure and low temperature are conducive to the high absorption rate of organic matter by the absorbent in the absorption tower. The synergistic regulation of the two is the core guarantee for achieving efficient, stable and economical absorption.

[0130] In some embodiments, in step S3, the temperature at the top of the solvent regeneration tower 3 is 65°C to 80°C, and the temperature at the bottom of the tower is 160°C to 175°C.

[0131] It should be noted that the temperature at the top of solvent regeneration tower 3 is 65℃~80℃. For example, the temperature at the top of solvent regeneration tower can be one or any two of the following: 65℃, 68℃, 70℃, 72℃, 75℃, 78℃, and 80℃.

[0132] It should be noted that the temperature at the bottom of the tower is 160℃~175℃. For example, the temperature at the bottom of the tower can be one or any two of the following values: 160℃, 162℃, 165℃, 168℃, 170℃, 173℃, and 175℃.

[0133] It should also be noted that the absolute pressure of solvent regeneration tower 3 is 1 kPa to 30 kPa. For example, the absolute pressure of solvent regeneration tower 3 can be one or any two of the following: 1 kPa, 5 kPa, 10 kPa, 15 kPa, 20 kPa, 25 kPa, and 30 kPa. Solvent regeneration tower 3 is a high-vacuum tower, which can effectively reduce the energy consumption of engineering operation. Moreover, the relative volatility of the absorbent and the absorbed organic matter is relatively high, so the absorbent recovery and regeneration can be completed with fewer trays, effectively reducing the initial investment in fixed equipment.

[0134] In this embodiment, controlling the temperature at the top of the solvent regeneration tower to 65℃~80℃ facilitates the recovery of light components and controls energy consumption and emissions; the temperature at the bottom of the tower is 160℃~175℃, enabling the desorption of the absorbent and achieving regeneration. The temperature gradient (high temperature → low temperature) from bottom to top within the solvent regeneration tower creates a "stepwise desorption-purification" mass transfer environment. In the high-temperature zone at the bottom of the tower, most of the absorbent is desorbed, and the absorbent completes its main regeneration here; in the low-temperature zone at the top of the tower, absorbent recovery and final purification of the target components are achieved through condensation and reflux. This gradient design ensures the regeneration efficiency of the absorbent, avoids absorbent loss or product purity reduction due to excessively high top temperatures, and reduces overall energy consumption (without needing to heat the entire tower to the bottom temperature).

[0135] To enable those skilled in the art to better understand this application, the following embodiments will be used to provide a detailed description of a gas-liquid separation and purification system and method based on liquid organic dehydrogenation technology.

[0136] Example 1

[0137] The calculations were performed using a methylcyclohexane dehydrogenation unit with an annual hydrogen production capacity of 20,000 tons, and the gas-liquid separation process of methylcyclohexane dehydrogenation was simulated using the system of this application.

[0138] (1) Absorption section:

[0139] The methylcyclohexane dehydrogenation product consists of a mixture of 74 mol% hydrogen and 26 mol% toluene-methylcyclohexane. The dehydrogenation rate is 40,000 kg / h, the temperature is 76℃, and the pressure is 0.15 MPaG. After the reaction in the reactor, the methylcyclohexane dehydrogenation product enters the first condenser 9 and is condensed to 20℃. The condensed methylcyclohexane dehydrogenation product is then passed into the first gas-liquid separator 1 for gas-liquid separation to obtain gas-phase and liquid-phase dehydrogenation products. The liquid-phase dehydrogenation product is recovered as a hydrogen storage carrier via the second mixer 12, with a recovery rate of approximately 36,372.2 kg / h.

[0140] The gas-phase dehydrogenation product (composed of 1189 kg of organic matter and 2438.5 kg of hydrogen) enters the compressor 8 from the top of the first gas-liquid separator 1 and is pressurized to 0.3 MPaG. The pressurized gas-phase dehydrogenation product then enters the absorption tower 2 from the bottom. Fresh absorbent (a mixture of sulfolane at 25°C) at a rate of 30,000 kg / h enters the absorption tower along the third connecting pipe 13. The absorption tower has 10 trays. The absorbent enters the absorption tower 2 from the first tray (top of the absorption tower), while the gas-phase dehydrogenation product enters from the bottom of the absorption tower 2. The two enter in countercurrent contact, allowing the absorbent in the absorption tower 2 to absorb the organic matter in the gas-phase dehydrogenation product. The pressure in the absorption tower 2 is controlled at 0.3 MPaG, the absorbent temperature is controlled at 15~30°C, and the molar ratio of the gas-phase dehydrogenation product to the absorbent is 3:1.

[0141] The absorption process releases heat, which reduces the absorption efficiency. Therefore, an interstage pump 51 is installed at the fourth tray of the absorption tower 2. The interstage pump 51 draws 15,000 kg / h of absorbent at a temperature of 35.6°C from the first connection port 53. After passing through the interstage cooler 52 and the external cooling heat exchanger to 25°C, it returns to the fifth tray of the absorption tower 2 from the second connection port 54 to enhance the absorption efficiency.

[0142] (2) Hydrogen purification section:

[0143] The absorbed gaseous dehydrogenation products are discharged as crude hydrogen from the top of absorption tower 2, at a rate of approximately 2440.2 kg / h. The purity of the crude hydrogen reaches over 99.95%. The crude hydrogen is further filtered and purified by a small molecular sieve filter 4 to obtain high-purity hydrogen with a purity of over 99.99%, which can be directly used as standard hydrogen for fuel cells.

[0144] (3) Recycling and recovery section:

[0145] The liquid phase mixture at the bottom of absorber 2 (composed of 4 wt% toluene and methylcyclohexane, etc., and 96 wt% sulfolane absorbent) at a rate of 31187.6 kg / h is discharged from absorber 2. At this point, the temperature of the liquid phase mixture discharged from the bottom of absorber 2 is 81.2℃. After heat utilization and heat exchange with the bottom stream of the solvent regeneration tower, it is heated to 164.7℃. The heated liquid phase mixture then enters the second gas-liquid separator 7 for gas-liquid separation, obtaining a gas mixture and a liquid mixture. The gas mixture enters the solvent regeneration tower 3 via the first connecting pipe 71 from the third connecting port 73 (above the fifth tray), and the liquid mixture enters the solvent regeneration tower 3 via the second connecting pipe 72 from the fourth connecting port 74 (the fifth tray). The absolute pressure of solvent regeneration tower 3 is 15 kPa. Solvent regeneration tower 3 has 10 trays. The temperature at the top of solvent regeneration tower 3 is 80℃, and the temperature at the bottom is 165℃. The top liquid phase recovery of the tower is 1183.8 kg / h, containing hydrogen storage material with toluene and methylcyclohexane content >99.4%. The bottom of the tower contains 29999.92 kg / h of absorbent. The solvent regeneration tower 3 is equipped with a top condenser 31; the condensed liquid is returned to the solvent regeneration tower 3, and the non-condensable hydrogen system is extracted to ensure the pressure balance of the regeneration tower 3 system and enhance system operational stability. The bottom of the solvent regeneration tower 3 is equipped with a bottom reboiler 32; the absorbent discharged from the bottom reboiler 32 is cooled to 85°C after heat exchange in the waste heat exchanger 6, and then cooled again to 25°C in the second condenser 10 before returning to the absorption tower 2 for reabsorption. Fresh absorbent is only used as a supplementary absorbent and is replenished periodically.

[0146] The proposed solution achieves a toluene-methylcyclohexane mixture recovery rate of over 99.9%, with extremely low energy consumption (approximately 5000 kW) in both the absorption and desorption processes. Hydrogen purity is increased from 96-99% in traditional separation methods to over 99.99%, meeting the hydrogen supply requirements for fuel cells (purity ≥ 99.97%).

[0147] Example 2

[0148] The difference between Example 2 and Example 1 is as follows:

[0149] The absorbent in the absorption section (1) is changed to N-methylpyrrolidone, and the other steps are the same as in Example 1.

[0150] Example 3

[0151] The difference between Example 3 and Example 1 is as follows:

[0152] Remove the interstage pump 51, first connection port 53, second connection port 54, and interstage cooler 52 from the absorption section (1), and the other steps are the same as in Example 1.

[0153] Example 4

[0154] The difference between Example 4 and Example 1 is as follows:

[0155] Remove the second gas-liquid separator 7, the first connecting pipe 71, the third connecting port 73, the second connecting pipe 72, and the fourth connecting port 74 in the (3) regeneration and recycling section. The other steps are the same as in Example 1.

[0156] Example 5

[0157] The difference between Example 5 and Example 1 is as follows:

[0158] Remove the waste heat exchanger 6 and the second condenser 10 in the (3) regeneration and recovery section, and the other steps are the same as in Example 1.

[0159] Example 6

[0160] The difference between Example 6 and Example 1 is:

[0161] The pressure and temperature of the absorption tower in the absorption section (1) are adjusted to 1 MPa and 40 °C respectively. Other steps are the same as in Example 1.

[0162] Example 7

[0163] The difference between Example 7 and Example 1 is as follows:

[0164] The top and bottom temperatures of the solvent regeneration tower 3 in the (3) regeneration and recovery section are adjusted to 65°C and 175°C, respectively. Other steps are the same as in Example 1.

[0165] Example 8

[0166] The difference between Example 8 and Example 1 is:

[0167] The number of trays in solvent regeneration tower 3 in the (3) regeneration and recovery section is adjusted to 12, and the other steps are the same as in Example 1.

[0168] Example 9

[0169] The difference between Example 9 and Example 1 is as follows:

[0170] The number of trays in the absorption tower 2 in the absorption section (1) is adjusted to 15, and the other steps are the same as in Example 1.

[0171] In the systems and schemes of Examples 2-9, the recovery rate of the toluene-methylcyclohexane mixture reaches over 99.9%, and the energy consumption of the absorption and desorption processes is extremely low (approximately 5000 kW). The hydrogen purity is increased from 96-99% in traditional separation methods to over 99.99%, meeting the hydrogen supply requirements of fuel cells (purity ≥ 99.97%).

[0172] Comparative Example 1

[0173] The traditional gas-liquid separation process for the dehydrogenation products of methylcyclohexane is as follows:

[0174] Calculations were performed using a methylcyclohexane dehydrogenation unit with an annual hydrogen production capacity of 20,000 tons. Figure 5 A structural diagram of the gas-liquid separation and purification system for methylcyclohexane dehydrogenation provided in this application is shown, as follows: Figure 5 As shown, a comparative system was used to simulate the gas-liquid separation process of methylcyclohexane dehydrogenation.

[0175] The methylcyclohexane dehydrogenation product, composed of a mixture of 74 mol% hydrogen and 26 mol% toluene-methylcyclohexane, has a dehydrogenation rate of 40,000 kg / h at a temperature of 76°C and a pressure of 0.15 MPaG. After the reactor reaction, the dehydrogenation product enters the third condenser 101 and is condensed to 20°C. The condensed dehydrogenation product is then passed into the first-stage gas-liquid separator 102 for the first gas-liquid separation, obtaining liquid-phase and gas-phase dehydrogenation products. The separated liquid-phase dehydrogenation product is then recovered via the third mixer 108 as a hydrogen storage carrier, with a recovery rate of approximately 36,297.8 kg / h.

[0176] The gaseous dehydrogenation products (composed of 1263.5 kg of organic matter and 2438.5 kg of hydrogen) enter the compressor 8 from the top of the first-stage gas-liquid separator 102 and are pressurized to 0.3 MPaG. After being condensed by the fourth condenser 104, they are fed into the second-stage gas-liquid separator 105 for cryogenic separation. The cold medium is an industrial refrigerant, providing a cold source of -20℃. The separated liquid phase of 1156.9 kg / h is discharged from the bottom of the second-stage gas-liquid separator 105, and the hydrogen gas phase of 2515.1 kg / h is at a temperature of -20℃.

[0177] The hydrogen gas phase passes through the first-stage molecular sieve filter 106 and then the second-stage molecular sieve filter 107. After the two-stage molecular sieve filters adsorb organic matter, the purity of the hydrogen reaches more than 99.97%.

[0178] Simulation results indicate that the overall energy consumption per hour is approximately 7500 kW (the actual energy consumption may be higher due to the cryogenic process). The calculated recovery rates for toluene and methylcyclohexane are approximately 99%. The hydrogen adsorption process utilizes a large quantity of the first-stage molecular sieve filter 106 and the second-stage molecular sieve filter 107, and the adsorbed organic matter is difficult to recover.

[0179] This process consumes a lot of energy, requires large investments in large-scale cryogenic plants, is difficult to maintain, and involves frequent replacements of the first and second stage molecular sieve filters. Ultimately, using hydrogen as a product for sale or downstream use is not economically viable.

[0180] Based on an annual hydrogen production of 20,000 tons, compared with the various embodiments and comparative examples, the systems and processes in the embodiments can increase toluene recovery by more than 3,000 tons per year compared with traditional processes, saving more than 20 million yuan in costs per item; energy consumption is reduced by more than 30% compared with cryogenic processes, saving about 16 million kWh of electricity per year; the molecular sieve replacement cycle is increased tenfold, as conventionally adsorbed organic matter is difficult to recover and process, and the replacement frequency increases from six months to four to six years; the replacement cycle is greatly reduced, enabling stable and continuous large-scale industrial production.

[0181] This application combines an absorption section, a regeneration and recovery section, and a hydrogen purification section, overcoming the limitations of dew point drift. The absorption section and the regeneration and recovery section allow the absorbent to operate continuously throughout the entire process, achieving an organic liquid recovery rate of over 99.9% with minimal absorbent loss. The economic benefits of the examples and comparative examples are significantly different. The high recovery rate of raw materials and high-purity hydrogen (over 99.99%) significantly improve the potential for large-scale plant applications compared to traditional processes. Therefore, the system and method of this application are well-suited for large-scale plants.

[0182] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0183] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to this application.

[0184] The above provides a detailed description of a gas-liquid separation and purification system and method based on liquid organic dehydrogenation technology provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A gas-liquid separation and purification system based on a liquid organic dehydrogenation process, characterized in that, include: A first gas-liquid separator is used to separate the methylcyclohexane dehydrogenation product into a gas phase dehydrogenation product and a liquid phase dehydrogenation product. An absorption tower, connected to the first gas-liquid separator, is used to receive the gas-phase dehydrogenation products and remove organic components from the products using an absorbent to obtain crude hydrogen. An interstage cooling device is provided around the absorption tower, comprising an interstage pump and an interstage cooler. The interstage cooler is connected to the interstage pump, and both the interstage pump and the interstage cooler are connected to the absorption tower. The interstage pump pumps the heated absorbent in the absorption tower to the interstage cooler for cooling, and then returns it to the absorption tower to continue to participate in the absorption and removal of organic components in the gas phase dehydrogenation products. A molecular sieve filter, connected to the absorption tower, is used to receive the crude hydrogen gas, filter and purify it to obtain high-purity hydrogen gas with a purity ≥ 99.99%; the number of molecular sieve filters is one. A solvent regeneration tower is connected to the absorption tower. The solvent regeneration tower is used to perform analytical regeneration treatment on the liquid phase mixture discharged from the absorption tower, so that the absorbent in the liquid phase mixture is enriched at the bottom of the tower and the organic components are enriched at the top of the tower. The absorbent enriched at the bottom of the tower is returned to the absorption tower to complete the regeneration and reuse of the absorbent. The system also includes a waste heat exchanger, which is disposed between the solvent regeneration tower and the absorption tower. The waste heat exchanger is used to receive the liquid phase mixture discharged from the absorption tower and the regenerated absorbent discharged from the solvent regeneration tower, and to perform heat exchange treatment to raise the temperature of the liquid phase mixture to a first preset range and lower the temperature of the regenerated absorbent to a second preset range. The system further includes a second gas-liquid separator, which is disposed between the waste heat exchanger and the solvent regeneration tower. A first connecting pipe and a second connecting pipe are provided between the second gas-liquid separator and the solvent regeneration tower. The second gas-liquid separator is used to perform gas-liquid separation treatment on the heated liquid-phase mixture discharged from the waste heat exchanger, so that the liquid-phase mixture is separated into a liquid-phase mixture and a gas-phase mixture. The gas-phase mixture enters the solvent regeneration tower through the first connecting pipeline, and the liquid-phase mixture enters the solvent regeneration tower through the second connecting pipeline. The first connecting pipe is connected to the solvent regeneration tower through a third connecting port, and the second connecting pipe is connected to the solvent regeneration tower through a fourth connecting port. The third connecting port is located on the side of the solvent regeneration tower near the top of the tower, and the fourth connecting port is located on the side of the third connecting port away from the top of the solvent regeneration tower.

2. The system according to claim 1, characterized in that, The number of trays in the absorption tower is set to 8 to 15.

3. The system according to claim 1, characterized in that, The interstage pump is connected to the absorption tower through a first connection port, and the interstage cooler is connected to the absorption tower through a second connection port; The first connection port is located in the middle section of the absorption tower, and the second connection port is located on the side of the first connection port away from the top of the absorption tower.

4. The system according to claim 1, characterized in that, The number of trays in the solvent regeneration tower is set to 8 to 15.

5. The system according to claim 1, characterized in that, It also includes a compressor, which is located between the first gas-liquid separator and the absorption tower. The compressor is used to pressurize the gas-phase dehydrogenation products and then send them into the absorption tower.

6. A gas-liquid separation and purification method based on a liquid organic dehydrogenation process, the method being applicable to the system described in any one of claims 1-5, characterized in that, The method includes the following steps: S1. The methylcyclohexane dehydrogenation product is passed into the first gas-liquid separator for condensation treatment, so that the methylcyclohexane dehydrogenation product is separated into gas phase dehydrogenation product and liquid phase dehydrogenation product. S2. The gaseous dehydrogenation product is fed into the absorption tower from the bottom of the tower, and the absorbent is fed into the absorption tower from the top of the tower, so that the gaseous dehydrogenation product and the absorbent are in countercurrent contact. The organic components in the gaseous dehydrogenation product are absorbed by the absorbent to form a liquid phase mixed component, and the remaining gas phase is crude hydrogen. S3. The liquid phase mixture discharged from the absorption tower is passed into the solvent regeneration tower to perform desorption and regeneration treatment on the liquid phase mixture, so that the absorbent in the liquid phase mixture is enriched at the bottom of the tower and the organic components are enriched at the top of the tower. The absorbent enriched at the bottom of the tower is returned to the absorption tower to complete the regeneration and reuse of the absorbent. S4. The crude hydrogen gas is passed through a molecular sieve filter for filtration and purification to obtain high-purity hydrogen gas.

7. The method according to claim 6, characterized in that, The absorbent is sulfolane and / or N-methylpyrrolidone.

8. The method according to claim 6, characterized in that, Step S2 also includes: The heated absorbent in the absorption tower is pumped out to the interstage cooler by an interstage pump, cooled down, and then returned to the absorption tower to continue participating in the absorption of organic components in the gas-phase dehydrogenation products.

9. The method according to claim 6, characterized in that, In step S2, the pressure in the absorption tower is 0.3MPa~2MPa and the temperature is 20℃~60℃.

10. The method according to claim 6, characterized in that, In step S3, the temperature at the top of the solvent regeneration tower is 65℃~80℃, and the temperature at the bottom of the tower is 160℃~175℃.

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