Gas-liquid separation and purification system and method based on liquid organic dehydrogenation process

Abstract

The invention provides a gas-liquid separation and purification system and method based on a liquid organic dehydrogenation process. A methylcyclohexane dehydrogenation product is separated into a gas-phase dehydrogenation product and a liquid-phase dehydrogenation product through a first gas-liquid separator; the absorption tower receives the gas-phase dehydrogenation product and absorbs and removes organic matter components in the gas-phase dehydrogenation product with the help of an absorbent, and crude hydrogen is obtained; the molecular sieve filter receives the crude hydrogen and filters and purifies the crude hydrogen to obtain high-purity hydrogen; the solvent regeneration tower is used for analyzing and regenerating 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 matter 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 to complete regeneration and reuse of the absorbent. Through the combination of the absorption tower and the regeneration solvent tower, the problem of separation of hydrogen and aromatic organic matters can be solved, the load of a pure working section is reduced, the material service life of an absorption working section is effectively prolonged, and deep purification of hydrogen and efficient recovery of organic matters are realized.

Description

TECHNICAL FIELD

[0001] The present 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 a liquid organic dehydrogenation process. BACKGROUND

[0002] Under the background of global energy transformation and carbon neutralization, hydrogen energy as a clean and efficient secondary energy carrier faces a storage and transportation bottleneck in large-scale application. Organic liquid hydrogen storage (Liquid Organic Hydrogen Carriers Technology, LOHC) technology is particularly suitable for large-scale, long-distance storage and transportation of hydrogen and international trade due to its high hydrogen storage density, good safety and reversibility. In this technology system, methylcyclohexane (Methylcyclohexane, MCH) is considered to have great development prospects as a liquid hydrogen carrier because of its moderate theoretical hydrogen storage capacity (6.22wt%), stable physicochemical properties, mature commercial hydrogenation process, and reversibility of the Methylcyclohexane-Toluene-Hydrogen (Methylcyclohexane-Toluene-Hydrogen, MTH) cycle. The core is an efficient dehydrogenation process: stable storage of MCH is dehydrogenated under the action of a catalyst to release hydrogen and regenerate toluene, realizing the recycling of the carrier. This process usually includes MCH preheating and vaporization, catalytic dehydrogenation reaction, reaction product condensation and cooling, and gas-liquid separation.

[0003] The dehydrogenation reaction product is a complex mixture containing hydrogen, unreacted MCH, target product toluene, and by-products such as biphenyl and other light aromatic hydrocarbons. Efficient separation of high-purity hydrogen and maximum recovery of organic matter (especially toluene) are key to achieving closed-loop economic operation of the MTH system. Current mainstream separation and purification technology routes include: condensation separation + adsorption purification, cryogenic + adsorption purification, cryogenic + membrane separation, cryogenic + Pressure Swing Adsorption (PSA), etc.

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

[0005] To solve the problems in the background art, the application provides a gas-liquid separation and purification system and method based on a liquid organic dehydrogenation process. The system comprises: a first gas-liquid separator, which is used to separate methylcyclohexane dehydrogenation products into gaseous dehydrogenation products and liquid dehydrogenation products; an absorption tower, which is in communication with the first gas-liquid separator, and is used to receive the gaseous dehydrogenation products and remove organic components in the gaseous dehydrogenation products by means of an absorbent to obtain crude hydrogen gas; a molecular sieve filter, which is in communication with the absorption tower, and is used to receive the crude hydrogen gas, filter and purify the crude hydrogen gas, and obtain high-purity hydrogen gas; and a solvent regeneration tower, which is in communication with the absorption tower, and is used to perform resolution and regeneration treatment on liquid mixed components discharged from the absorption tower, so that the absorbent in the liquid mixed components is enriched at the bottom of the tower, the organic components are enriched at the top of the tower, and the absorbent enriched at the bottom is returned to the absorption tower to complete the regeneration and reuse of the absorbent. By means of the combination of the absorption tower and the regeneration solvent tower, the problem of separation of hydrogen gas and aromatic organic components can be solved, the load of the purification section is reduced, the material life of the absorption section is effectively prolonged, and deep purification of hydrogen gas and efficient recovery of organic components are realized.

[0006] The specific application contents are as follows: In a first aspect, the application provides a gas-liquid separation and purification system based on a liquid organic dehydrogenation process, which comprises: a first gas-liquid separator, which is used to separate methylcyclohexane dehydrogenation products into gaseous dehydrogenation products and liquid dehydrogenation products; an absorption tower, which is in communication with the first gas-liquid separator, and is used to receive the gaseous dehydrogenation products and remove organic components in the gaseous dehydrogenation products by means of an absorbent to obtain crude hydrogen gas; a molecular sieve filter, which is in communication with the absorption tower, and is used to receive the crude hydrogen gas, filter and purify the crude hydrogen gas, and obtain high-purity hydrogen gas; a solvent regeneration tower, which is in communication with the absorption tower, and is used to perform resolution and regeneration treatment on liquid mixed components discharged from the absorption tower, so that the absorbent in the liquid mixed components is enriched at the bottom of the tower, the organic components are enriched at the top of the tower, and the absorbent enriched at the bottom is returned to the absorption tower to complete the regeneration and reuse of the absorbent.

[0007] Optionally, the number of trays in the absorption tower is 8-15.

[0008] Optionally, the absorption tower is provided with an interstage cooling device, which comprises 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 in communication with the absorption tower; The inter-stage pump pumps the heated absorbent in the absorption tower to an inter-stage cooler, and returns to the absorption tower after being cooled to continue participating in the absorption of the organic component in the gas phase dehydrogenation product.

[0009] Optionally, the inter-stage pump is connected to the absorption tower through a first connecting port, and the inter-stage cooler is connected to the absorption tower through a second connecting port. The first connecting port is located in the middle section of the absorption tower, and the second connecting port is located on the side of the first connecting port away from the top of the absorption tower.

[0010] Optionally, the number of trays in the solvent regenerator is 8-15.

[0011] Optionally, a waste heat exchanger is further included, which is arranged between the solvent regenerator and the absorption tower, and is used to receive the liquid phase mixture component discharged from the absorption tower and the regenerated absorbent discharged from the solvent regenerator, and perform heat exchange treatment to raise the temperature of the liquid phase mixture component to a first preset interval and lower the temperature of the regenerated absorbent to a second preset interval.

[0012] Optionally, a second gas-liquid separator is further included, which is arranged between the waste heat exchanger and the solvent regenerator, and is provided with a first connecting pipeline and a second connecting pipeline between the second gas-liquid separator and the solvent regenerator. The second gas-liquid separator is used to perform gas-liquid separation treatment on the heated liquid phase mixture component discharged from the waste heat exchanger, so that the liquid phase mixture component is separated into a liquid phase mixture and a gas phase mixture. The gas phase mixture enters the solvent regenerator through the first connecting pipeline, and the liquid phase mixture enters the solvent regenerator through the second connecting pipeline.

[0013] Optionally, the first connecting pipeline and the solvent regenerator are connected through a third connecting port, and the second connecting pipeline and the solvent regenerator are connected through a fourth connecting port. The third connecting port is located on the side of the solvent regenerator close to the top, and the fourth connecting port is located on the side of the third connecting port away from the top of the solvent regenerator.

[0014] Optionally, a compressor is further included, which is arranged between the first gas-liquid separator and the absorption tower, and is used to pressurize the gas phase dehydrogenation product and send it into the absorption tower.

[0015] In a second aspect, the application provides a gas-liquid separation and purification method based on a liquid organic dehydrogenation process, which is suitable for the above-mentioned system and includes the following steps: S1, the methylcyclohexane dehydrogenation product is introduced into a first gas-liquid separator for condensation treatment, so that the methylcyclohexane dehydrogenation product is separated into a gaseous dehydrogenation product and a liquid dehydrogenation product; S2, the gaseous dehydrogenation product is introduced into an absorption tower from the bottom, and an absorbent is introduced into the absorption tower from the top, so that the gaseous dehydrogenation product is in countercurrent contact with the absorbent, and the organic component in the gaseous dehydrogenation product is absorbed by the absorbent to form a liquid phase mixed component, and the remaining gaseous phase is a crude hydrogen gas; S3, the liquid phase mixed component discharged from the absorption tower is introduced into a solvent regeneration tower for resolution and regeneration treatment, so that the absorbent in the liquid phase mixed component is enriched at the bottom, and the organic component is enriched at the top, and the absorbent enriched at the bottom is returned to the absorption tower to complete the regeneration and reuse of the absorbent; S4, the crude hydrogen gas is introduced into a molecular sieve filter for filtration and purification to obtain high-purity hydrogen gas.

[0016] Optionally, the absorbent is sulfolane and / or N-methyl pyrrolidone.

[0017] Optionally, step S2 further comprises: The heated absorbent in the absorption tower is pumped out to an inter-stage cooler by means of an inter-stage pump, and after being cooled, is returned to the absorption tower to continue participating in the absorption of the organic component in the gaseous dehydrogenation product.

[0018] Optionally, in step S2, the pressure in the absorption tower is 0.3-2 MPa, and the temperature is 20-60℃.

[0019] Optionally, in step S3, the temperature at the top of the solvent regeneration tower is 65-80℃, and the temperature at the bottom is 160-175℃.

[0020] Compared with the prior art, the present application has the following advantages: The gas-liquid separation and purification system based on the liquid organic dehydrogenation process provided by the present application separates the methylcyclohexane dehydrogenation product into a gaseous dehydrogenation product and a liquid dehydrogenation product through a first gas-liquid separator; an absorption tower, which is in communication with the first gas-liquid separator, is used to receive the gaseous dehydrogenation product and remove the organic component in the gaseous dehydrogenation product by means of an absorbent to obtain a crude hydrogen gas; a molecular sieve filter, which is in communication with the absorption tower, is used to receive the crude hydrogen gas for filtration and purification to obtain high-purity hydrogen gas; and a solvent regeneration tower, which is in communication with the absorption tower, is used to perform resolution and regeneration treatment on the liquid phase mixed component discharged from the absorption tower, so that the absorbent in the liquid phase mixed component is enriched at the bottom, and the organic component is enriched at the top, and the absorbent enriched at the bottom is returned to the absorption tower to complete the regeneration and reuse of the absorbent.

[0021] By the absorption tower-solvent regeneration tower combination, the energy consumption of the absorption process and the resolution process is extremely low, and the energy consumption is reduced by more than 40% compared with the traditional cryogenic separation system; the solvent regeneration tower is communicated with the absorption tower, and the regeneration and reuse of the absorbent are completed, and compared with the traditional primary gas-liquid separation and gas-liquid separation + cryogenic separation + molecular sieve system, the toluene recovery rate is increased from 96~98.85% to more than 99.9%, which greatly reduces the raw material loss rate. By the absorption tower, almost all the organic matters can be absorbed, and the hydrogen purity is increased from 99% in the traditional cryogenic + molecular sieve system to more than 99.95%, and only a molecular sieve filter is needed to set up, and the hydrogen purity can reach more than 99.99%, meeting the fuel cell grade hydrogen supply (purity ≥ 99.97%).

[0022] In addition, since the absorption tower almost absorbs all the organic matters, the molecular sieve filter only needs to filter and purify a small part or almost no organic matter, and thus the molecular sieve filter can have a service life of more than 40 months, compared with the traditional process which needs to be regenerated and replaced with molecular sieve every 3~6 months, which is more environmentally friendly.

[0023] In summary, the system provided by the application can balance the hydrogen recovery rate and purity, meet the strict standards of fuel cell hydrogen, and has low energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 The structure schematic diagram of the gas-liquid separation and purification system based on the liquid organic dehydrogenation process provided by the embodiments of the application is shown; Figure 2 The partial enlarged view of the absorption tower in the gas-liquid separation and purification system provided by the embodiments of the application is shown; Figure 3 The partial enlarged view of the solvent regeneration tower in the gas-liquid separation and purification system provided by the embodiments of the application is shown; Figure 4 The flow chart of the gas-liquid separation and purification method based on the liquid organic dehydrogenation process provided by the embodiments of the application is shown; Figure 5 The gas-liquid separation and purification system structure diagram of methylcyclohexane dehydrogenation provided by the comparative example of the application is shown.

[0026] Reference signs: 1- first gas-liquid separator, 2- absorption column, 3- solvent regeneration column, 31- overhead condenser, 32- bottom reboiler, 4- molecular sieve filter, 5- interstage cooling device, 51- interstage pump, 52- interstage cooler, 53- first connecting port, 54- second connecting port, 6- waste heat exchanger, 7- second gas-liquid separator, 71- first connecting pipeline, 72- second connecting pipeline, 73- third connecting port, 74- fourth connecting port, 8- compressor, 9- first condenser, 10- second condenser, 11- first mixer, 12- second mixer, 13- third connecting pipeline; 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 DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and in no way limits the present application and its application or uses. Based on the embodiments in the present application, any person skilled in the art, under the inspiration of the present application or by combining the present application with other prior art features, obtains any product same or similar to the present application, falls within the protection scope of the present application. In addition, all other embodiments obtained by the ordinary skilled in the art without carrying out creative labor, fall within the protection scope of the present application.

[0028] The specific experimental steps or conditions not mentioned in the embodiments can be carried out according to the conventional experimental steps or conditions described in the prior art in the field. The reagents and other instruments used, if not specified by the manufacturer, are all conventional reagent products that can be obtained by purchase. In addition, the drawings are only schematic illustrations of the embodiments of the present application, and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and thus repeated description thereof will be omitted. Some block diagrams shown in the drawings are functional entities, which do not necessarily correspond to physically or logically independent entities.

[0029] The techniques, methods, and equipment known to those skilled in the relevant art can not be discussed in detail, but under appropriate circumstances, the techniques, methods, and equipment should be considered as part of the present application.

[0030] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0031] The organic liquid dehydrogenation reaction product is a complex mixture containing hydrogen (65-75 mol%), unreacted MCH, target product toluene, and byproducts such as light aromatic hydrocarbons (e.g., biphenyl). Efficient separation of high-purity hydrogen and maximum recovery of organic matter (especially toluene) are key to achieving closed-loop economic operation of the MTH system. Current mainstream separation and purification technology routes include: Condensation separation + adsorption purification: The basic scheme is that the reaction product is condensed and gas-liquid separated once to recover most of the liquid organic matter, and 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 for small devices, but the organic matter recovery rate is low and the material loss is large.

[0032] Deep cooling + adsorption purification: To improve the recovery rate, most large-scale chemical processes add a deep cooling section (-10°C to -20°C) after preliminary pressurization to condense and separate most of the organic matter in the gas phase using low temperature (efficiency 98-99%), and the separated gas phase hydrogen is then refined by molecular sieve. This scheme significantly improves the recovery rate.

[0033] Deep cooling + membrane separation: Patent CN118286822A reports an attempt to combine deep cooling pretreatment and membrane separation technology to purify hydrogen, with the expectation of reducing energy consumption or improving efficiency.

[0034] Deep cooling + PSA: Patent CN218810346U reports that its hydrogen production system uses pressure swing adsorption (PSA) to obtain high-purity hydrogen, which can be combined with deep cooling for large-scale devices. PSA is characterized by its high product purity (which can meet the standard for hydrogen used in fuel cells).

[0035] Although existing processes have been applied in small-scale or specific scenarios, there are significant bottlenecks and defects when it comes to large-scale industrial applications, especially in the pursuit of high recovery rate, high purity, low energy consumption, and operational reliability: Inherent defects of condensation separation and "dew point drift" problem: The traditional condensation process has the phenomenon of "dew point drift" of organic matter under high hydrogen (incondensable gas) partial pressure, resulting in a much higher actual condensation temperature than the theoretical value and a continuous decrease. To achieve a high organic matter recovery rate (e.g., toluene > 99.8%), the required condensation temperature is extremely low (often <-60°C), which is extremely difficult to achieve in large-scale industrial devices, with high energy consumption and investment, and strict cold preservation requirements.

[0036] Economic and engineering problems of deep cooling process: Deep cooling (especially ultra-low temperature deep cooling) has high equipment investment in large-scale devices, huge energy consumption for maintaining low temperature operation, complex system cold preservation design, and poor overall economic efficiency.

[0037] Limitations of membrane separation technology: Membrane separation (such as CN118286822A) is prone to "concentration polarization" due to uneven gas distribution in large-scale applications, accelerating membrane aging and failure. More importantly, there is a difficult trade-off between hydrogen recovery rate (70%-85%) and product purity (95%-99%): pursuing high purity requires multiple stages in series, resulting in further reduction of recovery rate; improving recovery rate sacrifices purity, making it difficult to meet the stringent standards of hydrogen for fuel cells (purity ≥ 99.97%, CO ≤ 0.2 ppm).

[0038] Energy consumption and reliability risk of PSA technology: Although PSA can produce high-purity hydrogen, the process combined with cryogenic (such as cryogenic + PSA) has the problem of superimposed energy consumption. Cryogenic maintenance consumes a lot of energy, and frequent second-level pressure switching in PSA also consumes a lot of energy. The combination of the two makes the overall power consumption high, and the reliability risk of the complex control system increases dramatically under high load and large-scale operation, increasing maintenance costs.

[0039] Adsorbent consumption and maintenance problems: Molecular sieve adsorbent, which is responsible for the final refining task, especially when the front-end separation is not complete (high organic content), is prone to saturation and deactivation, requiring frequent regeneration or replacement, increasing operating costs and operational complexity.

[0040] In summary, the above problems ultimately lead to the core pain points of existing large-scale processes, such as insufficient toluene recovery rate (<98%), serious material waste, frequent molecular sieve replacement, unstable or difficult-to-meet hydrogen product purity, and high overall energy consumption, as well as system complexity and reliability challenges, which severely restrict the economic feasibility and industrialization of MCH dehydrogenation technology in large-scale hydrogen energy storage and transportation scenarios.

[0041] In view of the problems of unstable or difficult-to-meet hydrogen product purity, high overall energy consumption, and frequent molecular sieve replacement in related technologies, the present application provides a gas-liquid separation and purification system based on a liquid organic dehydrogenation process, Figure 1 The structure of the gas-liquid separation and purification system based on the liquid organic dehydrogenation process provided by the embodiments of the present application is shown in the structure diagram. As shown in Figure 1 The system comprises: A first gas-liquid separator 1 for separating methylcyclohexane dehydrogenation products into gas-phase dehydrogenation products and liquid-phase dehydrogenation products; An absorption tower 2 in communication with the first gas-liquid separator 1, the absorption tower 2 is used to receive the gas-phase dehydrogenation products and remove the organic components in the gas-phase dehydrogenation products by means of an absorbent, to obtain crude hydrogen gas; A molecular sieve filter 4 in communication with the absorption tower 2, the molecular sieve filter 4 is used to receive the crude hydrogen gas, filter and purify it, and obtain high-purity hydrogen gas; The solvent regeneration tower 3 is communicated with the absorption tower 2, and is used for performing desorption and regeneration treatment on the liquid-phase mixed components discharged from the absorption tower 2, so that the absorbent in the liquid-phase mixed components is enriched at the bottom of the tower, the organic component is enriched at the top of the tower, and the absorbent enriched at the bottom is returned to the absorption tower, thereby completing the regeneration and recycling of the absorbent.

[0042] It should be noted that the first condenser 9 is communicated with the first gas-liquid separator 1, and is used for cooling the methylcyclohexane dehydrogenation product, reducing the temperature of the methylcyclohexane dehydrogenation product, and condensing the heavy components originally in the gas phase into the liquid phase due to the decrease of the saturated vapor pressure, thereby reducing the entrainment amount of the heavy components in the gas phase, and improving the purity and recovery rate of the liquid-phase product after gas-liquid separation.

[0043] That is, before entering the first gas-liquid separator 1, the methylcyclohexane dehydrogenation product is cooled in the first condenser 9, and then enters the first gas-liquid separator 1 for gas-liquid separation.

[0044] It should be noted that the absorption tower 2 is used for receiving the gas-phase dehydrogenation product, and specifically, the gas-phase dehydrogenation product is preferably introduced into the absorption tower from the bottom of the absorption tower 2. The fresh absorbent is introduced into the absorption tower 2 from the top along the third connecting pipeline 13, and the gas-phase dehydrogenation product entering from the bottom and the absorbent entering from the top are countercurrently contacted and absorbed in the absorption tower 2.

[0045] In the embodiment of the present application, only one molecular sieve filter 4 is required to meet the requirements of fuel cell level hydrogen supply, and a small molecular sieve filter can meet the use requirements. Compared with the traditional separation system, the amount of molecular sieve in the molecular sieve filter 4 of the present application is reduced by about 90%.

[0046] It should be further noted that the second mixer 12 is communicated with the first gas-liquid separator 1, and is used for receiving and recycling the liquid-phase dehydrogenation product separated from the first gas-liquid separator 1.

[0047] It should be further noted that the first mixer 11 is communicated with the absorption tower 2 and the third connecting pipeline 13, and is used for mixing the regenerated absorbent in the solvent regeneration tower 3 and the additional / fresh absorbent entering the absorption tower along the third connecting pipeline 13.

[0048] In actual implementation, the methylcyclohexane dehydrogenation product is first introduced into the first condenser 9 to be condensed to 20-25 DEG C, and then the condensed methylcyclohexane dehydrogenation product is introduced into the first gas-liquid separator 1 to be gas-liquid separated to obtain a gas-phase dehydrogenation product and a liquid-phase dehydrogenation product, the liquid-phase dehydrogenation product is recycled as a hydrogen storage carrier through the second mixer 12; the gas-phase dehydrogenation product is introduced from the bottom of the absorption tower 2 into the absorption tower to be countercurrently contacted with the absorbent introduced from the top along the third connecting pipeline 13, the absorbent absorbs and removes the organic component in the gas-phase dehydrogenation product to obtain crude hydrogen gas, the purity of the crude hydrogen gas is more than 99.95%; the crude hydrogen gas is introduced into the molecular sieve filter 4 to be filtered and purified to obtain high-purity hydrogen gas, the purity of the high-purity hydrogen gas is more than 99.99%; the liquid-phase mixed component in which the organic matter is absorbed is discharged from the bottom and introduced into the solvent regenerator 3 to be resolved and regenerated, so that the absorbent in the liquid-phase mixed component is enriched at the bottom and the organic component is enriched at the top, and the absorbent enriched at the bottom is returned to the absorption tower 2 through the first mixer 11 to complete the regeneration and reuse of the absorbent.

[0049] In the embodiment, through the absorption tower-solvent regenerator combination, the energy consumption of the absorption process and the resolution process is extremely low, and the energy consumption is reduced by more than 40% compared with the traditional cryogenic separation system; the solvent regenerator is communicated with the absorption tower to complete the regeneration and reuse of the absorbent, compared with the traditional one-step gas-liquid separation and gas-liquid separation + cryogenic separation + molecular sieve system, the toluene recovery rate is increased from 96-98.85% to more than 99.9%, and the raw material loss rate is greatly reduced. Through the absorption tower, almost all the organic matter can be absorbed, the hydrogen purity is increased from 99% in the traditional cryogenic + molecular sieve system to more than 99.95%, and only a molecular sieve filter needs to be set in the subsequent process, and the hydrogen purity can reach more than 99.99% to meet the fuel cell level hydrogen supply (purity ≥ 99.97%). In addition, since the absorption tower almost absorbs all the organic matter, the molecular sieve filter only needs to filter and purify a small part or almost no organic matter, and thus the molecular sieve filter can have a service life of more than 40 months, compared with the traditional process which needs to be frequently regenerated and replaced with molecular sieve every 3-6 months, and is more environmentally friendly.

[0050] In some embodiments, the number of trays in the absorption tower 2 is set to 8-15.

[0051] It should be noted that, Figure 2 A partial enlarged view of the absorption tower in the gas-liquid separation and purification system provided by the embodiment of the application is shown. Figure 2 As shown in the figure, the number of trays in the absorption tower 2 is set to 8-15, and for example, the number of trays in the absorption tower 2 can be set to one of 8, 9, 10, 11, 12, 13, 14, 15 or a range value of any two thereof.

[0052] In this embodiment, the tray is the core unit of the gas-liquid two-phase contact in the absorption tower 2, the gas phase dehydrogenation product rises from the bottom, passes through the openings or channels on the tray; the liquid phase absorbent flows down from the top, and forms a liquid layer on the tray. Each tray can provide one contact opportunity for the gas-liquid two-phase, through the mass transfer process such as dissolution and diffusion, so that the organic matter in the gas phase dehydrogenation product is transferred to the liquid phase absorbent. By setting the number of trays in the absorption tower 2 to 8-15, the contact times and mass transfer of the gas-liquid two-phase are ensured, the absorption rate of the absorbent is improved, and the cost and energy consumption are reduced.

[0053] In some embodiments, as shown in Figure 1 and 2 The absorption tower 2 is provided with an inter-stage cooling device 5, the inter-stage cooling device 5 includes an inter-stage pump 51 and an inter-stage cooler 52; the inter-stage cooler 52 is connected to the inter-stage pump 51, and the inter-stage pump 51 and the inter-stage cooler 52 are respectively communicated with the absorption tower 2; The inter-stage pump 51 pumps the heated absorbent in the absorption tower 2 to the inter-stage cooler 52, and returns to the absorption tower 2 after cooling to continue participating in the absorption of the organic components in the gas phase dehydrogenation product.

[0054] It should be noted that the inlet of the inter-stage pump 51 is communicated with the absorption tower 2, the outlet of the inter-stage pump 51 is communicated with the inlet of the inter-stage cooler 52, and the outlet of the inter-stage cooler 52 is communicated with the absorption tower 2, so as to form a closed loop.

[0055] It should be noted that the inter-stage pump 51 can be a magnetic drive centrifugal pump, a variable frequency screw pump, etc., which can be suitable for conveying the absorbent (such as sulfolane) with volatility in the present application. The inter-stage cooler 52 can be a detachable shell and tube cooler, a plate cooler, etc., which is suitable for the low viscosity and clean absorbent (such as N-methyl pyrrolidone) in the present application, and ensures the stability of the heat transfer coefficient.

[0056] In specific implementation, the absorbent in the absorption tower 2 absorbs the organic matter in the gas phase dehydrogenation product, and the temperature of the absorbent is increased. At this time, the absorbent with increased temperature is introduced from the absorption tower 2 to the inlet of the inter-stage pump 51, circulated in the pump, and flows from the outlet of the inter-stage pump 51 to the inlet of the inter-stage cooler 52 for cooling. The cooled absorbent returns to the absorption tower 2 from the outlet of the inter-stage cooler 52.

[0057] In this embodiment, the absorption process in absorption tower 2 is an exothermic reaction. As absorption proceeds, the temperature within the tower gradually increases. This temperature increase significantly reduces the absorbent's solubility in organic matter. Therefore, the heated absorbent in absorption tower 2 is pumped out to interstage cooler 52 via interstage pump 51, achieving a "circulating flow" of the absorbent. Interstage cooler 52 removes the heat generated during the absorption process and returns the cooled absorbent to absorption tower 2 to continue absorbing and removing organic components from the gas-phase dehydrogenation product, maintaining a low-temperature absorption environment in absorption tower 2.

[0058] In some embodiments, as Figure 2 As shown, the interstage pump 51 is connected to the absorption tower 2 through a first connection port 53, and the interstage cooler 52 is connected to the absorption tower 2 through a 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.

[0059] It should be noted that the first connecting port 53 is located in the middle section of the absorption tower 2, and the second connecting port 54 is located on the side of the first connecting port 53 away from the top of the absorption tower 2. For example, if the number of tower plates in the absorption tower is 8, the first connecting port 53 is located at the 3rd to 5th tower plates of the absorption tower, such as the 4th tower plate, and the second connecting port 54 is located at the 4th to 6th tower plates of the absorption tower, such as the 5th tower plate (the second connecting port 54 is located below the first connecting port 53, that is, closer to the bottom of the tower).

[0060] It should be noted that a built-in liquid level sensor is installed at the first connection port 53 and is linked to the frequency conversion system of the interstage pump 51. When the liquid layer height in the middle section of the absorption tower 2 changes due to feed fluctuations (for example, a sudden increase in the concentration of gas-phase dehydrogenation products leads to accelerated absorbent consumption), the liquid withdrawal rate of the interstage pump 51 is adjusted in real time to avoid excessive liquid withdrawal resulting in too thin a liquid layer on the tray (impacting mass transfer) or insufficient liquid withdrawal resulting in insufficient cooling load (temperature control failure).

[0061] It should be noted that a "liquid seal baffle" is provided at the connection between the first connecting port 53, the second connecting port 54 and the absorption tower 2, which uses the liquid column pressure of the return liquid itself to form a seal to prevent the rising gas phase in the absorption tower 2 from entering the return liquid pipeline from the first connecting port 53, the second connecting port 54.

[0062] In this embodiment, the gaseous dehydrogenation product in the absorption tower 2 flows from bottom to top, the absorbent is sprayed from top to bottom, the gas-liquid two phases are countercurrently contacted in the tower plate of the absorption tower 2, and a “low at the top and high at the bottom” organic concentration gradient is formed. The first connecting port 53 is located in the middle section of the absorption tower 2, and the second connecting port 54 is located on the side of the first connecting port 53 away from the tower top of the absorption tower 2. The middle section absorbent with “temperature rise and absorption capacity decrease” can be extracted, cooled by the inter-stage cooling device 5, and then sent back to the absorption tower 2 to restore the absorption capacity of the absorbent and fill the gap of “middle section absorption efficiency decay”, avoid the mass transfer bottleneck caused by overheating of the absorbent, and balance the energy consumption and stability.

[0063] In some embodiments, the number of tower plates in the solvent regenerator 3 is 8-15.

[0064] It should be noted that the solvent regenerator 3 can be a plate column or a packed column.

[0065] It should be noted that, Figure 3 A partial enlarged view of the solvent regenerator in the gas-liquid separation and purification system provided by the embodiment of the application is shown. As shown in Figure 3 The number of tower plates in the solvent regenerator 3 is 8-15. For example, the number of tower plates in the solvent regenerator 3 can be one of 8, 9, 10, 11, 12, 13, 14, 15 or a range value of any two of them.

[0066] It should be noted that the top of the solvent regenerator 3 is communicated with the overhead condenser 31, and the overhead condenser 31 is used to condense the gaseous mixture escaping from the top of the solvent regenerator 3, so that the condensed liquid returns to the top. The bottom of the solvent regenerator 3 is communicated with the bottom reboiler 32, and the bottom reboiler 32 is used to heat the rich solvent (absorbent absorbing organic matter) at the bottom, effectively heat the solvent regenerator feed, and reduce the heat load of the solvent regenerator. The loss rate of the absorbent at the bottom after separation is less than 0.02%.

[0067] It should also be noted that after the gaseous mixture is condensed in the overhead condenser 31, non-condensable gas and organic toluene mixture will be produced. If the non-condensable gas accumulates at the top of the tower, the pressure in the tower will increase, which will destroy the gas-liquid balance in the tower. At this time, the non-condensable gas can be extracted and the excess gas can be discharged in time to control the tower pressure within the design range.

[0068] It should be noted that the second mixer 12 is in communication with the overhead condenser 31, and is configured to receive the hydrogen storage carrier organic component discharged from the top of the solvent regeneration tower 3. In a specific implementation, the generated organic toluene mixture is introduced into the second mixer 12, and the second mixer 12 receives the organic toluene mixture discharged from the top of the solvent regeneration tower 3 for subsequent recovery. By recovering the organic toluene mixture, the recovery rate of toluene is increased from 96% in a conventional gas-liquid separation system to more than 99.9%, and compared with the deep cooling method, the recovery rate of toluene is increased from 98.9% to more than 99.9%.

[0069] In this embodiment, the solvent regeneration tower 3 is configured to recover the absorption capacity of the absorbent (i.e., convert the absorbent into lean solvent) by heating and desorbing the solute (e.g., organic matter) in the rich solvent (absorbent containing organic matter) from the absorbent. The tray is a key place for realizing gas-liquid mass transfer. The rich solvent enters from the upper part of the tower and flows downward along the tray. The steam generated by heating (e.g., water vapor generated by the bottom reboiler 32) rises from the bottom of the tower and fully contacts the rich solvent on each layer of the tray. Each tray is equivalent to a small "separation unit". The solute is continuously transferred from the absorbent to the gas phase. The number of trays in the solvent regeneration tower 3 is set to 8-15, which can realize "deep regeneration of absorbent, efficient purification of product, and reasonable control of energy consumption".

[0070] In some embodiments, as shown in Figure 1 The waste heat exchanger 6 is arranged between the solvent regeneration tower 3 and the absorption tower 2, and is configured to receive the liquid phase mixture component discharged from the absorption tower 2 and the regenerated absorbent discharged from the solvent regeneration tower 3, and perform heat exchange treatment to raise the temperature of the liquid phase mixture component to a first preset interval and lower the temperature of the regenerated absorbent to a second preset interval.

[0071] It should be noted that the temperature of the first preset interval is 150-165°C. For example, the temperature of the first preset interval can be one of 150°C, 152°C, 155°C, 157°C, 160°C, 164°C, 165°C, or a range value of any two thereof.

[0072] It should be noted that the temperature of the second preset interval is 60-90°C. For example, the temperature of the second preset interval can be one of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or a range value of any two thereof.

[0073] It should be noted that, as shown in Figure 1As shown, the system can further include a second condenser 10 disposed between the waste heat exchanger 6 and the absorption tower 2, for condensing the regenerated absorbent after heat exchange in the waste heat exchanger 6, so that the temperature of the regenerated absorbent after heat exchange is reduced to a third preset interval. The temperature of the third preset interval is 20-30°C. For example, the temperature of the third preset interval can be one of 20°C, 22°C, 25°C, 27°C, 29°C, 30°C or a range value of any two thereof.

[0074] In this embodiment, the waste heat exchanger 6 reuses the heat that would otherwise be wasted by "heating the low-temperature stream with the high-temperature stream", reduces the heat exchange loss with the outside, makes the energy circulation of the entire absorption-regeneration system more efficient, realizes two-way optimization of the absorbent temperature through waste heat recovery, reduces the energy consumption of the solvent regeneration tower 3, improves the process stability of the absorption tower 2 and the solvent regeneration tower 3, conforms to the principle of "energy cascade utilization" in the process, and ultimately improves the economy and environmental protection of the entire system.

[0075] In some embodiments, as shown in Figure 1 and 3 As shown, the system can further include a second gas-liquid separator 7 disposed between the waste heat exchanger 6 and the solvent regeneration tower 3, and a first connecting pipeline 71 and a second connecting pipeline 72 are disposed between the second gas-liquid separator 7 and the solvent regeneration tower 3. The second gas-liquid separator 7 is used for gas-liquid separation treatment of the liquid-phase mixed components discharged from the waste heat exchanger 6 after temperature rise, so that the liquid-phase mixed components are 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 pipeline 71, and the liquid-phase mixture enters the solvent regeneration tower 3 through the second connecting pipeline 72.

[0076] It should be noted that the first connecting pipeline 71 is provided with a flow regulating valve installed thereon, which is used to adjust the feed amount of the gas-phase mixture according to the upper pressure in the solvent regeneration tower 3, so as to avoid sudden rise of the tower pressure caused by fluctuation of the gas amount. The second connecting pipeline 72 is provided with a liquid level control valve which is opened when the liquid level reaches a set value, so as to avoid emptying or overflowing of the liquid phase into the gas phase area.

[0077] In this embodiment, the second gas-liquid separator 7 is disposed between the waste heat exchanger 6 and the solvent regeneration tower 3, and is used for gas-liquid separation treatment of the liquid-phase mixed components discharged from the waste heat exchanger 6 after temperature rise, so that the liquid-phase mixed components are separated into a liquid-phase mixture and a gas-phase mixture. The liquid-phase mixture and the gas-phase mixture are separated and enter the solvent regeneration tower 3, which effectively slows down the impact of the gas phase on the tower internals under high vacuum, makes the pressure and temperature gradient in the tower more gentle, and avoids the risk of "tower impact" and "liquid leakage" caused by mixed flow.

[0078] In some embodiments, as shown in FIG. 1, the first connecting pipeline 71 and the solvent regenerator 3 are connected through a third connecting port 73, and the second connecting pipeline 72 and the solvent regenerator 3 are connected through a fourth connecting port 74. The third connecting port 73 is located on the side of the solvent regenerator 3 close to 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 regenerator 3. Figure 3

[0079] It should be noted that the third connecting port 73 is located on the side of the solvent regenerator 3 close to the top of the tower (i.e. the middle upper part), and the fourth connecting port 74 is located on the side of the third connecting port 73 away from the top of the solvent regenerator 3 (the fourth connecting port 74 is located below the third connecting port 73, i.e. closer to the bottom of the tower). For example, if the number of trays in the solvent regenerator 3 is 8, the third connecting port 73 is located above the 5th tray of the solvent regenerator 3 (the gas phase mixture enters the upper packing), and the fourth connecting port 74 is located on the 5th tray of the solvent regenerator 3 (the liquid phase mixture directly enters the distributor).

[0080] In this embodiment, the third connecting port 73 (gas phase mixture pipeline outlet) is located on the side of the solvent regenerator 3 close to the top of the tower, and the fourth connecting port 74 (liquid phase mixture pipeline outlet) is located on the side of the third connecting port 73 away from the top of the solvent regenerator 3. The third connecting port 73 and the fourth connecting port 74 form an ordered flow field in the tower, in which the light components are purified upwards and the heavy components are resolved downwards. This layout matches the separation requirements of each space in the tower, improves the overall processing capacity of the solvent regenerator 3, and reduces the solvent circulation amount due to the optimized mass transfer efficiency, thereby further reducing the system energy consumption.

[0081] In some embodiments, as shown in FIG. 1, the system further comprises a compressor 8, which is arranged 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. Figure 1

[0082] In this embodiment, the absorption tower 2 is at a high pressure and low temperature, which is beneficial to the absorption process. Therefore, the compressor 8 is arranged between the first gas-liquid separator 1 and the absorption tower 2. By pressurizing the gas phase dehydrogenation product to increase the partial pressure of the organic matter, the mass transfer efficiency in the absorption tower 2 is optimized, the absorption driving force is enhanced, the operating pressure requirement of the absorption tower 2 is met, the stable operation of the absorption process is ensured, and the separation effect and economy of the overall system are improved.

[0083] In a second aspect, the present application provides a gas-liquid separation and purification method based on a liquid organic dehydrogenation process. The method is suitable for the system described above. Figure 4 ​​A flow chart of the gas-liquid separation and purification method based on the liquid organic dehydrogenation process is shown in the embodiments of the present application; as shown in Figure 4 The method comprises the following steps: S1, the methylcyclohexane dehydrogenation product is introduced into the first gas-liquid separator 1 for condensation treatment, so that the methylcyclohexane dehydrogenation product is separated into a gaseous dehydrogenation product and a liquid dehydrogenation product; S2, the gaseous dehydrogenation product is introduced from the bottom of the tower into the absorption tower 2, and the absorbent is introduced from the top of the tower into the absorption tower 2, so that the gaseous dehydrogenation product is in countercurrent contact with the absorbent, and the organic component in the gaseous dehydrogenation product is absorbed by the absorbent to form a liquid phase mixture component, and the remaining gaseous phase is a crude hydrogen gas; S3, the liquid phase mixture component discharged from the absorption tower 2 is introduced into the solvent regeneration tower 3 for desorption and regeneration treatment, so that the absorbent in the liquid phase mixture component is enriched at the bottom and the organic component is enriched at the top, and the absorbent enriched at the bottom is returned to the absorption tower 2, completing the regeneration and reuse of the absorbent; S4, the crude hydrogen gas is introduced into the molecular sieve filter 4 for filtration and purification to obtain high-purity hydrogen gas.

[0084] It should be noted that the purity of the crude hydrogen gas is above 99.95%, and the purity of the high-purity hydrogen gas is above 99.99%.

[0085] It should be further noted that the gas-liquid molar ratio of the gaseous dehydrogenation product to the absorbent in the absorption tower 2 is 3:1 to 6:1, and for example, the molar ratio can be one of 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 6:1 or a range value of any two thereof. The gas-liquid molar ratio is maintained at 3:1 to 6:1, which can ensure that the organic matter in the gaseous dehydrogenation product is "excessive but not overloaded" - avoiding the unsaturation of dissolution of the absorbent due to excessive amount (waste of absorbent capacity), and ensuring that most of the organic matter can be captured by the absorbent, so that the absorption rate is stable at 90% to 95%. At the same time, the above-mentioned molar ratio can reduce the circulation amount of the absorbent, thereby reducing the system energy consumption and providing stable feed conditions for subsequent processes.

[0086] In this embodiment, the overall process flow has high efficiency and low energy consumption, the toluene recovery rate reaches 99.9%, the hydrogen product purity reaches above 99.99% (reaching the fuel cell use standard of 99.97%), and the molecular sieve usage in the hydrogen secondary purification section can be effectively reduced and the service life can be effectively prolonged. The high raw material recovery rate and the low loss rate in the solvent circulation process do not require regeneration, which is particularly suitable for large-scale engineering use, and is an ideal LOHC dehydrogenation gas-liquid separation and purification method.

[0087] In some embodiments, the absorbent is sulfolane and / or N-methyl pyrrolidone.

[0088] It should be noted that both sulfolane and N-methyl pyrrolidone belong to "polar aprotic solvents", and their molecular structure (containing strong polar groups such as sulfone group, amide group) makes them have excellent solubility for unsaturated hydrocarbons (such as olefins, aromatic hydrocarbons). The boiling point of sulfolane is as high as 285℃, and the boiling point of N-methyl pyrrolidone is 202℃, which can withstand temperature changes in the absorption-regeneration cycle.

[0089] It should be noted that the fresh absorbent enters the absorption tower 2 along the third connecting pipeline 13, and the absorbent in the solvent regenerator 3 is cooled by the waste heat exchanger 6 and then enters the absorption tower 2 again for absorption, realizing the recycling of the absorbent. Therefore, the absorbent entering the absorption tower along the third connecting pipeline 13 is only used as a supplement to supplement the small amount of absorbent lost periodically, and the process cost and energy consumption are reduced.

[0090] In this embodiment, the absorbent is sulfolane and / or N-methyl pyrrolidone, which has the combined advantages of "high selectivity of dissolution, strong stability, and good mass transfer", and can efficiently absorb the organic matter in the gas phase dehydrogenation product, and can adapt to the absorption-regeneration cycle process, and can balance the technical performance and economic environmental protection.

[0091] In some embodiments, step S2 further comprises: The heated absorbent in the absorption tower 2 is pumped out to the inter-stage cooler 52 by the inter-stage pump 51, cooled, and then returned to the absorption tower 2 to continue participating in the absorption of the organic components in the gas phase dehydrogenation product.

[0092] In this embodiment, the absorption process in the absorption tower 2 is an exothermic reaction, and as the absorption proceeds, the temperature in the tower will gradually rise, and the temperature rise will significantly reduce the solubility of the absorbent to the organic matter. Therefore, the heated absorbent in the absorption tower 2 is pumped out to the inter-stage cooler 52 by the inter-stage pump 51 to realize the "circulating flow" of the absorbent, and the inter-stage cooler 52 can remove the heat generated during the absorption process, and the cooled absorbent is returned to the absorption tower 2 to continue participating in the absorption of the organic components in the gas phase dehydrogenation product, thereby maintaining a low-temperature absorption environment in the absorption tower 2.

[0093] In some embodiments, in step S2, the pressure in the absorption tower 2 is 0.3MPa~2MPa, and the temperature is 20℃~60℃.

[0094] It should be noted that the pressure in the absorption tower is 0.3MPa~2MPa, and for example, the pressure in the absorption tower can be one of 0.3MPa, 0.4MPa, 0.5MPa, 0.7MPa, 0.9MPa, 1.0MPa, 1.5MPa, 1.8MPa, 2MPa or a range value of any two of them.

[0095] It should be noted that the temperature in the absorption tower is 20-60°C, and for example, the temperature in the absorption tower can be one of 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or a range value of any two of them.

[0096] In this embodiment, by controlling the pressure in the absorption tower to be 0.3-2 MPa, the absorption driving force is improved, and the mass transfer efficiency is optimized; the temperature is 20-60°C, the solubility and mass transfer kinetics are balanced, the activity of the absorbent is ensured, and high pressure and low temperature are beneficial to the high absorption rate of the absorbent in the absorption tower. The synergistic regulation of the two is the core guarantee for efficient, stable and economic absorption.

[0097] In some embodiments, in step S3, the temperature at the top of the solvent regeneration tower 3 is 65-80°C, and the temperature at the bottom is 160-175°C.

[0098] It should be noted that the temperature at the top of the solvent regeneration tower 3 is 65-80°C, and for example, the temperature at the top of the solvent regeneration tower can be one of 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C or a range value of any two of them.

[0099] It should be noted that the temperature at the bottom is 160-175°C, and for example, the temperature at the bottom can be one of 160°C, 162°C, 165°C, 168°C, 170°C, 173°C, 175°C or a range value of any two of them.

[0100] It should also be noted that the absolute pressure of the solvent regeneration tower 3 is 1-30 kPa, and for example, the absolute pressure of the solvent regeneration tower 3 can be one of 1 kPa, 5 kPa, 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa or a range value of any two of them. The solvent regeneration tower 3 is a high-vacuum tower, which can effectively reduce the energy consumption of engineering operation, and the relative volatility of the absorbent and the absorbed organic matter is large, so that the absorbent can be recovered and regenerated with fewer trays, effectively reducing the fixed equipment investment.

[0101] In this embodiment, by controlling the temperature of the solvent regenerator overhead to be 65-80℃, it is beneficial to recover light components, control energy consumption and emissions; the temperature at the bottom of the tower is 160-175℃, which realizes the desorption of the driving absorbent and regeneration. The temperature gradient (high temperature→low temperature) from the bottom to the top of the solvent regenerator forms a mass transfer environment of "stepwise desorption-purification", the high-temperature zone at the bottom of the tower: most of the absorbent is desorbed, and the absorbent completes the main regeneration here; the low-temperature zone at the top of the tower: through condensation reflux, the absorbent is recovered and the target component is finally purified. This gradient design not only ensures the regeneration efficiency of the absorbent, but also avoids the loss of the absorbent or the decrease of the product purity caused by the too high temperature at the top of the tower, while reducing the overall energy consumption (without the need to heat the whole tower to the temperature at the bottom of the tower).

[0102] In order to enable those skilled in the art to more clearly understand the present application, the gas-liquid separation and purification system and method based on the liquid organic dehydrogenation process described in the present application will be described in detail through the following examples.

[0103] Example 1 An annual output of 20,000 tons of hydrogen methylcyclohexane dehydrogenation device is calculated, and the gas-liquid separation process of methylcyclohexane dehydrogenation is simulated by using the system of the present application.

[0104] (1) Absorption section: The methylcyclohexane dehydrogenation product is composed of 74mol% hydrogen and 26mol% toluene-methylcyclohexane mixture, the dehydrogenation product is 40,000kg / h, the temperature is 76℃, and the pressure is 0.15MPaG. The methylcyclohexane dehydrogenation product is condensed to 20℃ after the reaction in the reactor is completed, and then introduced into the first condenser 9. The condensed methylcyclohexane dehydrogenation product is introduced into the first gas-liquid separator 1 for gas-liquid separation, and the gas phase dehydrogenation product and the liquid phase dehydrogenation product are obtained. The liquid phase dehydrogenation product is recycled as a hydrogen storage carrier through the second mixer 12, and the recycling amount is about 36,372.2kg / h.

[0105] The gas phase dehydrogenation product (composition: 1189kg organic matter and 2438.5kg hydrogen) from the top of the first gas-liquid separator 1 is pressurized to 0.3MPaG by the compressor 8, and the pressurized gas phase dehydrogenation product is introduced into the absorption tower 2 from the bottom of the absorption tower 2. Fresh absorbent (25℃ cyclobutane sulfone mixture) 30,000kg / h is introduced into the absorption tower along the third connecting pipeline 13, and the number of plates of the absorption tower is 10. The absorbent enters the absorption tower 2 from the first plate (the top of the absorption tower), and the gas phase dehydrogenation product enters the absorption tower from the bottom of the absorption tower 2, and the two are countercurrently contacted, so that the absorbent in the absorption tower 2 absorbs the organic matter in the gas phase dehydrogenation product. The tower pressure of the absorption tower 2 is controlled at 0.3MPaG, the temperature of the absorbent is controlled at 15-30℃, and the molar ratio of the gas phase dehydrogenation product to the absorbent is 3:1.

[0106] The absorption process will cause the absorption effect to decrease due to heat release, so an interstage pump 51 is arranged at the fourth tray of the absorption tower 2, the interstage pump 51 draws 15000 kg / h of absorbent at a temperature of 35.6°C from a first connecting port 53, and after being cooled to 25°C by an external cooling heat exchanger, the absorbent is returned to the fifth tray of the absorption tower 2 from a second connecting port 54, thereby enhancing the absorption effect.

[0107] (2) Hydrogen purification section: The absorbed gaseous dehydrogenation product is discharged from the top of the absorption tower 2 as crude hydrogen gas, about 2440.2 kg / h. The purity of the crude hydrogen gas reaches more than 99.95%, and the crude hydrogen gas is further filtered and purified by a small molecular sieve filter 4 to obtain high-purity hydrogen gas, the purity of the high-purity hydrogen gas is more than 99.99%, which can be directly used as standard hydrogen for fuel cells.

[0108] (3) Regeneration and recovery section: The liquid phase mixture component (consisting of 4wt% toluene and methylcyclohexane and other organic substances and 96wt% sulfolane absorbent) 31187.6 kg / h is discharged from the bottom of the absorption tower 2, at this time the temperature of the liquid phase mixture component discharged from the bottom of the absorption tower 2 is 81.2°C, and after being heated to 164.7°C by heat utilization and solvent regeneration tower bottom stream heat exchange, the heated liquid phase mixture component enters the second gas-liquid separator 7 for gas-liquid separation to obtain a gas phase mixture and a liquid phase mixture, the gas phase mixture enters the solvent regeneration tower 3 from the third connecting port 73, i.e. above the fifth tray, through the first connecting pipeline 71, and the liquid phase mixture enters the solvent regeneration tower 3 from the fourth connecting port 74, i.e. the fifth tray, through the second connecting pipeline 72. The absolute pressure of the solvent regeneration tower 3 is 15kPa, the solvent regeneration tower 3 has a total of 10 trays, the temperature at the top of the solvent regeneration tower 3 is 80°C, and the temperature at the bottom is 165°C. The liquid phase recovered at the top of the tower is 1183.8 kg / h, which is a hydrogen storage material with a toluene and methylcyclohexane content of >99.4%. The bottom is 29999.92 kg / h of absorbent. The top of the solvent regeneration tower 3 is provided with a tower top condenser 31, and the condensed liquid is returned to the solvent regeneration tower 3. The hydrogen and non-condensable gas system is extracted to ensure the pressure balance of the regeneration tower 3 system, and can also enhance the system operation stability. The bottom of the solvent regeneration tower 3 is provided with a tower bottom reboiler 32, the absorbent is discharged from the tower bottom reboiler 32, cooled to 85°C by a waste heat exchanger 6, and then cooled to 25°C by a second condenser 10 before being returned to the absorption tower 2 for reabsorption. Fresh absorbent is only supplemented as a supplement absorbent and is supplemented periodically.

[0109] The toluene and methylcyclohexane mixture recovery rate of the scheme of the present application reaches more than 99.9%, and the energy consumption of the absorption process and the desorption process is extremely low (about 5000kw). The hydrogen purity is improved from 96-99% in the traditional separation method to more than 99.99%, which meets the hydrogen supply requirements of fuel cells (purity ≥99.97%).

[0110] Example 2 Example 2 differs from Example 1 in that: (1) the absorbent in the absorption section is adjusted to N-methyl pyrrolidone, and other steps are the same as in Example 1.

[0111] Example 3 Example 3 differs from Example 1 in that: (1) the inter-stage pump 51, the first connecting port 53, the second connecting port 54, and the inter-stage cooler 52 in the absorption section are removed, and other steps are the same as in Example 1.

[0112] Example 4 Example 4 differs from Example 1 in that: (3) the second gas-liquid separator 7, the first connecting pipeline 71, the third connecting port 73, the second connecting pipeline 72, and the fourth connecting port 74 in the regeneration and recovery section are removed, and other steps are the same as in Example 1.

[0113] Example 5 Example 5 differs from Example 1 in that: (3) the waste heat exchanger 6 and the second condenser 10 in the regeneration and recovery section are removed, and other steps are the same as in Example 1.

[0114] Example 6 Example 6 differs from Example 1 in that: (1) the pressure and temperature of the absorption tower in the absorption section are adjusted to 1 MPa and 40℃, respectively, and other steps are the same as in Example 1.

[0115] Example 7 Example 7 differs from Example 1 in that: (3) the top temperature and the bottom temperature of the solvent regeneration tower 3 in the regeneration and recovery section are adjusted to 65℃ and 175℃, respectively, and other steps are the same as in Example 1.

[0116] Example 8 Example 8 differs from Example 1 in that: (3) the number of trays of the solvent regeneration tower 3 in the regeneration and recovery section is adjusted to 12, and other steps are the same as in Example 1.

[0117] Example 9 Example 9 differs from Example 1 in that: (1) the number of trays of the absorption tower 2 in the absorption section is adjusted to 15, and other steps are the same as in Example 1.

[0118] The system of embodiments 2-9 and the scheme, the recovery rate of the toluylmethylcyclohexane mixture reaches more than 99.9%, and the energy consumption of the absorption process and the resolution process is extremely low (about 5000kw). The hydrogen purity is improved from 96-99% in the traditional separation method to more than 99.99%, meeting the hydrogen supply (purity ≥ 99.97%) of the fuel cell.

[0119] Comparative example 1 The gas-liquid separation process of the traditional methylcyclohexane dehydrogenation product is as follows: Using a methylcyclohexane dehydrogenation device with an annual output of 20,000 tons of hydrogen, Figure 5 The structure diagram of the gas-liquid separation and purification system of methylcyclohexane dehydrogenation provided by the comparative example of the present application is shown in FIG. 1. Figure 5 As shown in FIG. 1, the system of the comparative example is used to simulate the gas-liquid separation process of methylcyclohexane dehydrogenation.

[0120] The methylcyclohexane dehydrogenation product is composed of 74 mol% hydrogen and 26 mol% toluene-methylcyclohexane mixture, the dehydrogenation product is 40,000 kg / h, the temperature is 76℃, the pressure is 0.15 MPaG, and the dehydrogenation product is condensed to 20℃ after the reaction in the reactor is completed. The condensed dehydrogenation product is introduced into the first-stage gas-liquid separator 102 for the first gas-liquid separation, and the liquid-phase dehydrogenation product and the gas-phase dehydrogenation product are obtained. The separated liquid-phase dehydrogenation product is recycled as a hydrogen storage carrier through the third mixer 108, and the recycling amount is about 36,297.8 kg / h.

[0121] The gas-phase dehydrogenation product (composition: 1,263.5 kg of organic matter and 2,438.5 kg of hydrogen) from the top of the first-stage gas-liquid separator 102 is pressurized to 0.3 MPaG by the compressor 8, condensed by the fourth condenser 104, and introduced into the second-stage gas-liquid separator 105 for deep cooling separation. The cold medium uses an industrial refrigerant to provide a cold source of -20℃, and the separated liquid phase 1,156.9 kg / h is discharged from the bottom of the second-stage gas-liquid separator 105, and the hydrogen gas phase is 2,515.1 kg / h at a temperature of -20℃.

[0122] The hydrogen gas phase is filtered 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 the organic matter, the purity of the hydrogen gas reaches more than 99.97%.

[0123] The simulation results show that the overall energy consumption is about 7,500 kw per hour (due to the deep cooling process, the actual energy consumption may be larger). The recovery rate of toluene and methylcyclohexane is about 99%. The amount of hydrogen adsorbed by the first-stage molecular sieve filter 106 and the second-stage molecular sieve filter 107 is large, and the adsorbed organic matter is difficult to recover.

[0124] The process has large energy consumption, large investment in large-scale device, difficult cold preservation, and high replacement frequency of the first and second molecular sieve filters. The final hydrogen gas is not economically suitable for sale or downstream use.

[0125] According to the production of 20,000 tons of hydrogen per year, compared with the examples and comparative examples, the system and process in the examples can increase more than 3,000 tons per year compared with the traditional process of toluene recovery, and can save more than 20 million yuan in single cost; the energy consumption is reduced by more than 30% compared with the deep cooling process, and about 16 million degrees of electricity are saved per year; the molecular sieve replacement cycle is increased by ten times, and the organic matter after conventional adsorption is difficult to recover and process, and the replacement frequency is increased from half a year to 4-6 years; the replacement cycle is greatly reduced, and large-scale industrial production can be stably and continuously carried out.

[0126] The present application combines the absorption section + regeneration and recovery section + hydrogen purification section, breaks through the constraint of dew point drift, and the absorption section + regeneration and recovery section can realize continuous absorption of the absorbent in the whole process, the organic liquid recovery rate reaches more than 99.9%, and the absorbent loss is very small. The economic benefits of the examples and comparative examples are obviously compared, the high recovery rate of raw materials and high-purity hydrogen (more than 99.99%), and the application potential of the traditional process in large-scale devices is obviously improved, so the system and method of the present application are suitable for large-scale devices.

[0127] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms is not necessarily for the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification.

[0128] For method embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the order of the described actions, because according to the present application, certain steps can be performed in other order or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily necessary for the present application.

[0129] The above describes in detail the gas-liquid separation and purification system and method based on the liquid organic dehydrogenation process provided by the present application. The principles and implementation manners of the present application are described by using specific examples. The above description of the examples is only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed. In conclusion, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A gas-liquid separation and purification system based on liquid organic dehydrogenation process, characterized in that: include: a first gas-liquid separator, the first gas-liquid separator being 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, configured to receive the gas-phase dehydrogenation product and absorb and remove organic components in the gas-phase dehydrogenation product by means of an absorbent to obtain crude hydrogen; a molecular sieve filter, connected to the absorption tower, for receiving the crude hydrogen and filtering and purifying it to obtain high-purity hydrogen; The solvent regeneration tower is connected to the absorption tower and is used to perform analytical regeneration treatment on the liquid mixed components discharged from the absorption tower, so that the absorbent in the liquid 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 to complete the regeneration and reuse of the absorbent.

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

3. The system according to claim 1, wherein: An interstage cooling device is provided on the periphery of the absorption tower, and the interstage cooling device includes 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 communicated with the absorption tower; The interstage pump pumps the heated absorbent in the absorption tower to the interstage cooler, cools the absorbent, and then returns it to the absorption tower to continue absorbing and removing the organic components in the gas phase dehydrogenation product.

4. The system according to claim 3, 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 connecting port is located in the middle section of the absorption tower, and the second connecting port is located on a side of the first connecting port away from the top of the absorption tower.

5. The system according to claim 1, wherein: The number of trays in the solvent regeneration tower is set to 8 to 15.

6. The system according to claim 1, wherein: It also includes a waste heat exchanger, which is arranged between the solvent regeneration tower and the absorption tower, and is used to receive the liquid mixed components discharged from the absorption tower and the regenerated absorbent discharged from the solvent regeneration tower, and perform heat exchange treatment to increase the temperature of the liquid mixed components to a first preset range and reduce the temperature of the regenerated absorbent to a second preset range.

7. The system according to claim 6, characterized in that The system further includes a second gas-liquid separator, the second gas-liquid separator being disposed between the waste heat exchanger and the solvent regeneration tower, and a first connecting pipeline and a second connecting pipeline being disposed between the second gas-liquid separator and the solvent regeneration tower; The second gas-liquid separator is used to perform gas-liquid separation on the heated liquid mixed components discharged from the waste heat exchanger, so that the liquid mixed components are separated into a liquid mixture and a gas mixture. The gas mixture enters the solvent regeneration tower through the first connecting pipeline, and the liquid mixture enters the solvent regeneration tower through the second connecting pipeline.

8. The system according to claim 7, characterized in that 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 close to 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.

9. The system according to claim 1, wherein: The system further comprises a compressor, which is arranged between the first gas-liquid separator and the absorption tower. The compressor is used to pressurize the gas-phase dehydrogenation product and then send it into the absorption tower.

10. A gas-liquid separation and purification method based on a liquid organic dehydrogenation process, the method being applicable to the system according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1, passing the methylcyclohexane dehydrogenation product into a first gas-liquid separator for condensation treatment, so that the methylcyclohexane dehydrogenation product is separated into a gas phase dehydrogenation product and a liquid phase dehydrogenation product; S2, passing the gas-phase dehydrogenation product into an absorption tower from the bottom of the tower, and passing an absorbent into the absorption tower from the top of the tower, so that the gas-phase dehydrogenation product and the absorbent are in countercurrent contact, and the organic components in the gas-phase dehydrogenation product are absorbed by the absorbent to form a liquid phase mixed component, and the remaining gas phase is crude hydrogen; S3, passing the liquid mixed components discharged from the absorption tower into a solvent regeneration tower, performing analytical regeneration treatment on the liquid mixed components, so that the absorbent in the liquid mixed components is enriched at the bottom of the tower, and the organic component is enriched at the top of the tower, and 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. Passing the crude hydrogen into a molecular sieve filter for filtration and purification to obtain high-purity hydrogen.

11. The method according to claim 10, characterized in that The absorbent is sulfolane and / or N-methylpyrrolidone.

12. The method according to claim 10, characterized in that Step S2 also includes: The heated absorbent in the absorption tower is pumped out to the interstage cooler by means of an interstage pump, and after cooling, is returned to the absorption tower to continue to absorb the organic components in the gas phase dehydrogenation product.

13. The method according to claim 10, characterized in that In step S2, the pressure in the absorption tower is 0.3 MPa~2 MPa, and the temperature is 20°C~60°C.

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

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