Separation and recovery equipment and process for R410A mixed refrigerant based on eutectic solvent

Abstract

The invention belongs to the technical field of separation and recovery, and particularly relates to separation and recovery equipment and process for an R410A mixed refrigerant based on a deep eutectic solvent. The separation and recovery equipment for the R410A mixed refrigerant based on the eutectic solvent comprises an absorption tower, a first flash tank and a second flash tank, the liquid outlet end and the liquid inlet end of the absorption tower are communicated and connected through a circulating pipe; the first flash tank and the second flash tank are arranged on the circulating pipe; a first heat exchanger is arranged on the circulating pipe and between the first flash tank and the second flash tank, and a second heat exchanger is arranged on the circulating pipe and between the second flash tank and the liquid inlet end of the absorption tower; the gas outlet end of the first flash tank is communicated with the gas inlet end of the absorption tower through a communicating pipe; a third heat exchanger is arranged on the communicating pipe. By adopting the equipment and the process provided by the invention, the recovery rates of R32 and R125 in the R410A mixed refrigerant both reach 95% or above.

Description

Technical Field

[0001] The present invention belongs to the field of separation and recovery technology, and in particular relates to a separation and recovery device and process for an R410A mixed refrigerant based on a low eutectic solvent. Background Art

[0002] Hydrofluorocarbons (HFCs) are widely used as refrigerants in air conditioning and refrigeration systems as a replacement for ozone-damaging chlorofluorocarbons (CFCs). While HFCs have no ozone depletion potential (ODP), they have a high global warming potential (GWP), exacerbating climate change by trapping heat in the atmosphere. Consequently, HFCs are being phased out in favor of refrigerants with lower GWPs.

[0003] However, due to the increasing demand for HFCs, the need for efficient separation and recovery of HFCs has become increasingly urgent. R410A mixed refrigerant is an azeotropic mixture consisting of 50wt% R32 (difluoromethane) and 50wt% R125 (pentafluoroethane). R32 can be mixed with hydrofluoroolefins (HFOs) and formulated as a low-global warming potential refrigerant, while R125 has the potential to be used as a raw material for other products. Therefore, the development of efficient separation methods for this azeotropic mixture is necessary, not only to reduce their environmental impact, but also to promote the sustainable use of refrigerants.

[0004] Due to the azeotropic behavior of R32 and R125, traditional gas separation methods (such as cryogenic distillation) are not suitable for the separation of R32 and R125. Absorption separation based on ionic liquids (ILs) is considered a potential alternative. Ionic liquids have significant advantages such as low volatility, high thermal stability and flexible designability, which make them have application potential in selective gas absorption. However, the high cost and complex preparation process of ionic liquids limit their widespread use in practical applications. To address these challenges while maintaining the excellent properties of ILs, deep eutectic solvents (DES) emerged as a new generation of ILs. They were reported by Abbott in 2003 and have been widely studied since then. DES are composed of hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). The melting point of DES is significantly lowered due to the hydrogen bonds between the hydrogen bond acceptors and hydrogen bond donors. Due to their advantages such as simple preparation, low cost and adjustable structure, deep eutectic solvents have been increasingly used in various fields such as organic synthesis, electrochemistry, extraction separation and gas absorption, making them promising and cost-effective candidates for the separation of R32 and R125.

[0005] While prior art has reported some studies using DES for natural gas separation and purification, such as CO / CH4 and CO2 / N2 separations, fewer studies have explored their application in the absorption of hydrofluorocarbons (HFCs). Jovell et al. measured the solubility of R134a in six DESs prepared from [C2mim][Cl] and [HC4F9CO2] / [HC4F9SO3] and correlated them using the soft-SAFT model; they found that a higher acid ratio resulted in greater R134a solubility. Castro et al. measured the solubility of R32, R125, and R134a in six DESs composed of perfluorinated acids and fluorinated ionic liquids and correlated them using the NRTL model. However, most current studies have been limited to experimental measurements of HFC solubility in DESs or correlations with classical activity coefficient models (such as NRTL) or equations of state (such as soft-SAFT). Considering the huge design space of DES, relying solely on experimental screening of DES is costly and cannot guarantee the optimal DES, thus failing to fully realize the potential of DES as an HFC absorbent.

[0006] Furthermore, classical activity coefficient models and equation of state models typically require extensive experimental data to fit the model parameters, which limits their predictive power for novel systems. Molecular simulation can be used to explore the molecular interactions between HFCs and DESs. For example, Abedin et al. used molecular simulation to evaluate mixtures of fluorinated refrigerants with choline chloride-based DESs, revealing strong interactions between chloride anions and refrigerant atoms. However, this method is computationally expensive and unsuitable for large-scale screening of DESs.

[0007] In addition, more importantly, the existing technology is limited to experimental measurement or prediction of the solubility or activity coefficient of refrigerant gas in DES based on thermodynamic models, and cannot be applied in the process. Summary of the Invention

[0008] In response to the above-mentioned deficiencies in the prior art, a separation and recovery device and process for R410A mixed refrigerant based on a low eutectic solvent are provided. By using the device and process of the present invention, the purity of R32 and R125 in the R410A mixed refrigerant can reach above 95%.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] The present invention protects a separation and recovery device for an R410A mixed refrigerant based on a low eutectic solvent, comprising an absorption tower, a first flash tank and a second flash tank.

[0011] The liquid outlet end of the absorption tower and its liquid inlet end are connected through a circulation pipe. The absorption tower is used for countercurrent contact between the R410A mixed refrigerant and the low eutectic solvent; the first flash tank and the second flash tank are arranged on the circulation pipe, and the first flash tank is connected to the liquid outlet end of the absorption tower.

[0012] A first heat exchanger is provided on the circulation pipe between the first flash tank and the second flash tank, and a second heat exchanger is provided on the circulation pipe between the second flash tank and the liquid inlet end of the absorption tower; a pump body is also provided on the circulation pipe between the second heat exchanger and the second flash tank.

[0013] The gas outlet end of the first flash tank is connected to the gas inlet end of the absorption tower through a connecting pipe, and a third heat exchanger is provided on the connecting pipe.

[0014] Preferably, the absorption tower is a plate tower comprising six plates, and the parameters in the absorption tower are: absorption is carried out at an absorption temperature of 273.15K to 323.15K and an absorption pressure of 1 bar to 10 bar.

[0015] Preferably, the pressure in the first flash tank is 1 bar to 2 bar, and the temperature is 298.15 to 313.15K.

[0016] Preferably, the pressure in the second flash tank is 0.1 bar to 0.6 bar, and the temperature is 298.15K to 313.15K.

[0017] Preferably, a deep eutectic solvent is delivered to the liquid inlet end of the absorption tower, and an R410A mixed refrigerant is delivered to the gas inlet end of the absorption tower, and the mass ratio of the deep eutectic solvent to the R410A mixed refrigerant is 5 to 30:1.

[0018] Preferably, the deep eutectic solvent is screened according to the following steps:

[0019] Selection of potential hydrogen bond acceptors and hydrogen bond donors suitable for absorption separation of R410A mixed refrigerant.

[0020] COSMO-RS was used as a thermodynamic property prediction model to calculate the infinite dilution activity coefficients of difluoromethane and pentafluoroethane in candidate hydrogen bond acceptor-hydrogen bond donor combinations, respectively. Based on the infinite dilution activity coefficients, the absorption capacity and separation selectivity of the candidate hydrogen bond acceptor-hydrogen bond donor combinations for difluoromethane and pentafluoroethane were calculated, and hydrogen bond acceptor-hydrogen bond donor combinations with better difluoromethane absorption capacity and difluoromethane / pentafluoroethane separation selectivity were screened out.

[0021] The COSMO-RS model was used to calculate the melting points of the optimal hydrogen bond acceptor-hydrogen bond donor combinations and to screen the hydrogen bond acceptor-hydrogen bond donor combinations that can be used as R410A mixed refrigerants.

[0022] According to the screened hydrogen bond acceptor-hydrogen bond donor combinations, deep eutectic solvents with different molar ratios are prepared.

[0023] Preferably, the hydrogen bond acceptor is selected from quaternary ammonium salts, quaternary phosphonium salts or metal salts; and the hydrogen bond donor is selected from carboxylic acids, alcohols, amides or phenols.

[0024] Preferably, the better hydrogen bond acceptor-hydrogen bond donor combination satisfies the following requirements: difluoromethane absorption capacity and difluoromethane / pentafluoroethane separation selectivity are ranked in the top 50% among all candidate hydrogen bond acceptor-hydrogen bond donor combinations.

[0025] Preferably, the screening condition for the hydrogen bond acceptor-hydrogen bond donor combination that can be used as R410A mixed refrigerant is that the melting point is lower than 298.15K.

[0026] Preferably, the molar ratio of hydrogen bond acceptor to hydrogen bond donor is 0.3 to 2:1. After screening, [N 1,1,3,2, The DES consisting of OH]Br and 4-oxopentanoic acid (1:1, 2:1) or oxalic acid (1:3) exhibited high separation efficiency while balancing solvent consumption and operating costs.

[0027] Preferably, the preparation conditions of the deep eutectic solvent are: stirring at 60° C. to 120° C. for 1 h to 4 h.

[0028] The present invention also protects a separation and recovery process of R410A mixed refrigerant based on a deep eutectic solvent, using a separation and recovery device for R410A mixed refrigerant based on a deep eutectic solvent, comprising the following steps:

[0029] The R410A mixed refrigerant and the deep eutectic solvent are simultaneously conveyed into the absorption tower, the R410A mixed refrigerant and the deep eutectic solvent are in countercurrent contact, and pentafluoroethane is obtained at the gas outlet end of the absorption tower top, and the difluoromethane-rich deep eutectic solvent is obtained at the liquid outlet end of the absorption tower bottom.

[0030] The difluoromethane-rich low eutectic solvent is transported to the first flash tank via a circulation pipe. The first flash tank desorbs part of the mixed gas to obtain pentafluoroethane and concentrated difluoromethane-rich low eutectic solvent. The pentafluoroethane is refluxed into the absorption tower via a connecting pipe and exchanges heat with the third heat exchanger during the reflux process.

[0031] The concentrated difluoromethane-rich deep eutectic solvent is transported to the second flash tank via a circulation pipe and exchanges heat with the first heat exchanger during the transportation process. The second flash tank fully desorbs the difluoromethane and obtains high-purity difluoromethane at the gas outlet end at the top of the second flash tank. The high-purity deep eutectic solvent is recovered at the liquid outlet end at the bottom of the second flash tank.

[0032] The high-purity deep eutectic solvent is transported to the absorption tower via a circulation pipe, and heat is exchanged with the second heat exchanger during the transportation process, and the high-purity deep eutectic solvent is reused.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention provides a separation and recovery device for an R410A mixed refrigerant based on a deep eutectic solvent, comprising an absorption tower, a first flash tank, and a second flash tank. In the absorption tower, the R410A mixed refrigerant is countercurrently contacted with the deep eutectic solvent to separate and obtain high-purity pentafluoroethane. The first flash tank and the second flash tank are then used to further separate to obtain high-purity difluoromethane and high-purity deep eutectic solvent. This device not only achieves the separation of high-purity difluoromethane and high-purity pentafluoroethane, but also achieves the reuse of the high-purity deep eutectic solvent. The purity of difluoromethane and pentafluoroethane is above 95%, and the purity of the deep eutectic solvent is above 99%.

[0035] 2. The present invention proposes a systematic DES screening method for separating azeotropic R410A mixed refrigerants. First, the experimental solubilities of R32 and R125 in DES were collected from the literature, and the experimental solubility data were evaluated and linearly calibrated to improve the predictive ability of the COSMO-RS model. Then, COSMO-RS was used to screen 1152 candidate hydrogen bond acceptor-hydrogen bond donor combinations based on their absorption capacity and infinite dilution separation selectivity (including a wide selection of 77 HBAs and 120 HBDs with different molar ratios). Solid-liquid phase equilibrium calculations were then performed to determine the room temperature low eutectic solvent. Furthermore, the low eutectic solvent was further evaluated for its separation performance through process simulation in Aspen Plus. Finally, quantum chemical calculations were performed to clarify the intermolecular interactions between DES and R410A mixed refrigerants. The results showed that [N 1,1,3,2, The DES composed of OH]Br and 4-oxopentanoic acid or oxalic acid showed excellent absorption potential and separation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Comparison of the calculated solubility values obtained using COSMO-RS and the experimental solubility; (a) shows the solubility of R32 in DES, and (b) shows the solubility of R125 in DES.

[0037] Figure 2 To predict HBA and HBD using COSMO-RS and value.

[0038] Figure 3 (a) is the COSMO-RS prediction of HBA:HBD molar ratio of 1:2. (b) The figure shows the COSMO-RS prediction of HBA:HBD molar ratio of 1:2. value.

[0039] Figure 4 R32 and σ-profile values of four representative HBDs.

[0040] Figure 5 1152 DES predicted for COSMO-RS and value.

[0041] Figure 6 is the SLE predicted by COSMO-RS; (a) is [N 1,1,3,2, OH]Br and 4-oxopentanoic acid, (b) Figure [N 1,2,2, C2OC1][BF4] and 4-oxopentanoic acid, (c) Figure [N 1,1,3,2, OH]Br and oxalic acid.

[0042] Figure 7 Schematic diagram of the absorption separation principle based on DES for separating R32 and R125 according to the present invention.

[0043] Figure 8 Figures (a) to (f) show the effects of DES mass flow rate and absorption tower operating pressure on the purity of R125 in DES1 to DES6.

[0044] Figure 9 In the figure, (a) shows the influence of the pressure of the first flash tank and the second flash tank on the R32 recovery rate; (b) shows the influence of the pressure of the first flash tank and the second flash tank on the R32 purity.

[0045] Figure 10 The diagram shows the quantum chemical calculation results of different DES-R32 / DES-R125 systems.

[0046] Figure 11 Schematic diagram of the separation and recovery equipment for R410A mixed refrigerant based on low eutectic solvent. DETAILED DESCRIPTION

[0047] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0048] The process of separation and recovery equipment of R410A mixed refrigerant based on deep eutectic solvent, such as Figure 7 and Figure 11 As shown, the goal of the separation process is to achieve a mass purity of R125 and R32 of more than 95%.

[0049] Example 1

[0050] The separation and recovery process of R410A mixed refrigerant based on a deep eutectic solvent includes the following steps:

[0051] An R410A mixed refrigerant and a deep eutectic solvent are simultaneously conveyed into an absorption tower 1, where the R410A mixed refrigerant and the deep eutectic solvent are in countercurrent contact. Pentafluoroethane is obtained at the gas outlet of the top of the absorption tower 1, and a difluoromethane-rich deep eutectic solvent is obtained at the liquid outlet of the bottom of the absorption tower 1. The absorption tower 1 is provided with six trays and operates at a temperature of 298.5 K and an absorption pressure of 4.5 bar. The R410A mixed refrigerant is introduced at a flow rate of 1000 kg / h, and the deep eutectic solvent DES3 is introduced at a flow rate of 8600 kg / h.

[0052] The difluoromethane-rich deep eutectic solvent is transported to the first flash tank 2 via the circulation pipe 7. The first flash tank 2 desorbs part of the mixed gas to obtain pentafluoroethane and concentrated difluoromethane-rich deep eutectic solvent. The pentafluoroethane is refluxed into the absorption tower 1 via the connecting pipe 8 and exchanges heat with the third heat exchanger 6 during the reflux process. The pressure in the first flash tank 2 is 1.6 bar and the temperature is 25°C.

[0053] The concentrated difluoromethane-rich deep eutectic solvent is transported to the second flash tank 3 via the circulation pipe 7 and exchanges heat with the first heat exchanger 4 during the transportation process. The second flash tank 3 fully desorbs the difluoromethane, and high-purity difluoromethane is obtained at the gas outlet end at the top of the second flash tank 3. The high-purity deep eutectic solvent is recovered at the liquid outlet end at the bottom of the second flash tank 3. The pressure in the second flash tank 3 is 0.1 bar and the temperature is 55°C.

[0054] The high-purity deep eutectic solvent is transported to the absorption tower 1 via the circulation pipe 7 and exchanges heat with the second heat exchanger 5 during the transportation process, and the high-purity deep eutectic solvent is reused.

[0055] Example 2

[0056] The separation and recovery process of the R410A mixed refrigerant based on the deep eutectic solvent is the same as the preparation steps of Example 1, except that DES3 is replaced by DES4, and the deep eutectic solvent DES4 is introduced at a flow rate of 9000 kg / h.

[0057] Example 3

[0058] The separation and recovery process of the R410A mixed refrigerant based on the deep eutectic solvent is the same as the preparation steps of Example 1, except that DES3 is replaced with DES6, the deep eutectic solvent DES6 is introduced at a flow rate of 7500 kg / h, and the pressure in the first flash tank 2 is controlled to be 1.1 bar.

[0059] Example 4

[0060] The separation and recovery process of R410A mixed refrigerant based on a deep eutectic solvent includes the following steps:

[0061] An R410A mixed refrigerant and a deep eutectic solvent are simultaneously conveyed into an absorption tower 1, where the R410A mixed refrigerant and the deep eutectic solvent are in countercurrent contact. Pentafluoroethane is obtained at a gas outlet at the top of the absorption tower 1, and a difluoromethane-rich deep eutectic solvent is obtained at a liquid outlet at the bottom of the absorption tower 1. The absorption tower 1 is provided with six trays and operates at a temperature of 273.15 K and an absorption pressure of 10 bar. The R410A mixed refrigerant is introduced at a flow rate of 1000 kg / h, and the deep eutectic solvent DES3 is introduced at a flow rate of 8600 kg / h.

[0062] The difluoromethane-rich deep eutectic solvent is transported to the first flash tank 2 via the circulation pipe 7. The first flash tank 2 desorbs part of the mixed gas to obtain pentafluoroethane and concentrated difluoromethane-rich deep eutectic solvent. The pentafluoroethane is refluxed into the absorption tower 1 via the connecting pipe 8 and exchanges heat with the third heat exchanger 6 during the reflux process. The pressure in the first flash tank 2 is 1 bar and the temperature is 313.15K.

[0063] The concentrated difluoromethane-rich deep eutectic solvent is transported to the second flash tank 3 via the circulation pipe 7 and exchanges heat with the first heat exchanger 4 during the transportation process. The second flash tank 3 fully desorbs the difluoromethane, and high-purity difluoromethane is obtained at the gas outlet end at the top of the second flash tank 3. The high-purity deep eutectic solvent is recovered at the liquid outlet end at the bottom of the second flash tank 3. The pressure in the second flash tank 3 is 0.4 bar and the temperature is 303.15K.

[0064] The high-purity deep eutectic solvent is transported to the absorption tower 1 via the circulation pipe 7 and exchanges heat with the second heat exchanger 5 during the transportation process, and the high-purity deep eutectic solvent is reused.

[0065] Example 5

[0066] The separation and recovery process of R410A mixed refrigerant based on a deep eutectic solvent includes the following steps:

[0067] An R410A mixed refrigerant and a deep eutectic solvent are simultaneously conveyed into an absorption tower 1, where the R410A mixed refrigerant and the deep eutectic solvent are in countercurrent contact. Pentafluoroethane is obtained at the gas outlet of the top of the absorption tower 1, and a difluoromethane-rich deep eutectic solvent is obtained at the liquid outlet of the bottom of the absorption tower 1. The absorption tower 1 is provided with six trays and operates at a temperature of 323.15 K and an absorption pressure of 1 bar. The R410A mixed refrigerant is introduced at a flow rate of 1000 kg / h, and the deep eutectic solvent DES3 is introduced at a flow rate of 8600 kg / h.

[0068] The difluoromethane-rich deep eutectic solvent is transported to the first flash tank 2 via the circulation pipe 7. The first flash tank 2 desorbs part of the mixed gas to obtain pentafluoroethane and concentrated difluoromethane-rich deep eutectic solvent. The pentafluoroethane is refluxed into the absorption tower 1 via the connecting pipe 8 and exchanges heat with the third heat exchanger 6 during the reflux process. The pressure in the first flash tank 2 is 2 bar and the temperature is 298.15K.

[0069] The concentrated difluoromethane-rich deep eutectic solvent is transported to the second flash tank 3 via the circulation pipe 7 and exchanges heat with the first heat exchanger 4 during the transportation process. The second flash tank 3 fully desorbs the difluoromethane, and high-purity difluoromethane is obtained at the gas outlet end at the top of the second flash tank 3. The high-purity deep eutectic solvent is recovered at the liquid outlet end at the bottom of the second flash tank 3. The pressure in the second flash tank 3 is 0.6 bar and the temperature is 298.15K.

[0070] The high-purity deep eutectic solvent is transported to the absorption tower 1 via the circulation pipe 7 and exchanges heat with the second heat exchanger 5 during the transportation process, and the high-purity deep eutectic solvent is reused.

[0071] In the embodiment of the present invention, the screening method of the deep eutectic solvent is:

[0072] COSMO-RS (Realistic Solvent-Like Conductor Screening Model) is a method based on quantum chemical calculations and statistical thermodynamics that can be used to predict the thermodynamic properties of liquids and their mixed systems. The method generally includes two key steps: (1) quantum chemical calculations of the compounds involved; (2) application of statistical thermodynamic methods to analyze the intermolecular interactions and predict the thermodynamic properties of the mixed system. COSMO-RS prediction requires screening the charge density distribution (i.e., σ-profile), which is derived from standard quantum chemical calculations. The σ-profile of each molecule only needs to be calculated once and saved to a COSMO file for future use. Currently, the COSMO database contains a large number of COSMO files for common solvents, cations, and anions, which can quickly and efficiently predict various thermodynamic properties of different systems.

[0073] COSMO-RS can calculate the solubility of a gas through an iterative process by adjusting the mole fraction x j , so that the calculated partial pressure p j When x is equal to the given reference pressure p, j It is the solubility of gas in solvent. j Calculated by formula (1):

[0074]

[0075] Among them, γ j represents the activity coefficient, Represents the vapor pressure of a pure compound; in COSMO-RS, accurate gas phase energies are usually obtained through quantum chemical calculations, and then the vapor pressure is estimated using the COSMOtherm tool. These energy files are usually stored in COSMO files for subsequent calculations. In system S, the activity coefficient γ at a specific composition j Calculate by formula (2):

[0076]

[0077] Activity coefficient at infinite dilution Calculate by formula (3):

[0078]

[0079] in, Represents component j in system S with composition x j The activity coefficient under the conditions, The representative composition is x j The chemical potential of component j in system S is represents the chemical potential of pure component j, R represents the gas constant, and T represents the temperature. represents the infinite dilution activity coefficient of component j in system S, represents the chemical potential of component j under infinite dilution conditions in system S.

[0080] The gas phase is assumed to be an ideal gas by changing x in each iteration step. j To calculate γ j , and then calculate p according to formula (1) j .

[0081] To evaluate the absorption capacity and separation potential of DES, the absorption capacity at infinite dilution was calculated by COSMO-RS. and separation selectivity As shown in formula (4) and formula (5):

[0082]

[0083] in, and represent the infinite dilution activity coefficients of R32 and R125 in DES, respectively.

[0084] COSMO-RS was also used to predict the solid-liquid equilibrium (SLE) of each HBA:HBD binary combination to find the required DES for absorption at room temperature. The SLE calculation of the binary combination is expressed by formula (6):

[0085]

[0086] Among them, T m,i and ΔH fus,i represent the melting point and enthalpy of fusion of the pure components, respectively.

[0087] In this paper, all COSMO-RS calculations were performed using the COSMOthermX (version 2024) software package at the TZVP level with the parameters BP_TZVP_24.ctd. In addition, Gaussian 09 (version E.01) was used to optimize the geometry of each compound, and intermolecular interaction energies were calculated at the B3LYP / 6-31+G(d,p) level of theory, combined with DFT-D3 (BJ) dispersion correction.

[0088] 2. Evaluation and calibration of COSMO-RS:

[0089] Before applying COSMO-RS to screen DES for separation of R410A mixed refrigerants, it is necessary to evaluate its prediction accuracy by comparing with experimental data. To achieve this goal, 290 data points of solubility of hydrofluorocarbons in deep eutectic solvents were collected from the open literature (156 for R32 and 134 for R125) and compared with the COSMO-RS prediction results at different temperatures and pressures, such as Figure 1 As shown in the figure, the calculated solubility of R32 and R125 in DES has a good linear relationship with the experimental results, and the determination coefficient (R 2 ) reached 0.97 and 0.96, respectively. In other words, COSMO-RS can effectively capture the solubility trend of R32 / R125 in DES from a qualitative perspective, and thus can perform preliminary screening of DES. However, due to systematic bias, COSMO-RS underestimates the solubility of R32 in DES and overestimates the solubility of R125 in DES. In order to quantify these biases, the average relative deviation (ARD) was calculated using formula (7). The results show that the ARD values of R32-DES and R125-DES are 0.2138 and 0.3568, respectively, which indicates that the quantitative prediction performance of COSMO-RS still has a lot of room for improvement.

[0090]

[0091] In order to reduce the influence of COSMO-RS error, R32 and R125 are linearly calibrated, as shown in equations (8) and (9), respectively:

[0092] x R32,calib =(x R32,COSMO +0.0103) / 0.8691 (8)

[0093] x R125,calib =(x R125,COSMO -0.0187) / 1.1189 (9)

[0094] Among them, x R32,calib and x R125,calib represent the linearly calibrated R32 and R125 solubilities, respectively, and x R32,COSMO and x R125,COSMO Respectively represent the solubility of R32 and R125 originally predicted by COSMO-RS. Figure 1 As shown in Figures 1(a) and 1(b), linear calibration significantly reduces the ARD of COSMO-RS. The ARD of R32-DES decreases from 0.2138 to 0.1697, and the ARD of R125-DES decreases from 0.3568 to 0.1470. These results demonstrate that the quantitative accuracy of COSMO-RS is significantly improved after linear calibration.

[0095] 3. Screening of DES for separation of R32 and R125:

[0096] 3.1 Pre-screening of HBA and HBD:

[0097] The initial HBA and HBD candidate components included 77 HBAs and 120 HBDs. To reduce the computational cost, the list of HBAs and HBDs was pre-screened. The absorption capacity of each HBA and HBD was calculated using COSMO-RS. and selectivity The results are as follows Figure 2 As shown, HBA has a higher Some HBDs showed a larger This result emphasizes the importance of combining HBA and HBD to form a DES to enhance the separation performance of R32 / R125. and Therefore, only the candidate components that ranked in the top 50% in these two criteria were selected. and The lower limits of α and β were 2.1551 / 1.0714 for HBA and 0.6564 / 2.0407 for HBD, respectively. Therefore, after screening, 9 HBAs and 32 HBDs were retained.

[0098] 3.2 Based on and EDS Screening:

[0099] In order to screen for better DES for separation of R32 / R125, the effect of different HBA:HBD molar ratios on the absorption separation effect was studied, and the molar ratios of the two were selected from 1:3, 1:2, 1:1 and 2:1. In this way, 9 HBAs and 32 HBDs were randomly combined to generate 1152 DES candidates. The absorption separation potential of different DES candidates was calculated using COSMO-RS. and Conduct an assessment. Figure 3 (a) and Figure 3 (b) shows the HBA:HBD molar ratio of 1:2 and from Figure 3 As shown in (a), the change of HBD (y axis) The effect of HBD on In this study, four representative HBDs, HBD6 (4-oxopentanoic acid), HBD12 (1,2-benzenediol), HBD14 (4-methoxyphenol) and HBD31 (xylose), were selected. The values are arranged in the following order: HBD6>HBD31>HBD14>HBD12, and this trend can be explained by the σ-profile obtained by COSMO-RS. Figure 4 As shown in the figure, the σ-profile of R32 shows obvious peaks in both the nonpolar region and the HBA region, indicating that R32 has the potential to interact with compounds with σ-profile distributions in the nonpolar and HBD regions. From the σ-profiles of the four HBDs, it can be seen that they show obvious peaks in both the nonpolar and HBD regions, and the order of peak intensity is the same as their σ-profiles, i.e. HBD6>HBD31>HBD14>HBD12. Figure 3 As shown in (b), in the combination of HBA and HBD with a molar ratio of 1:2, the changes in HBA and HBD can affect Similar changes were observed in other HBA and HBD combinations, namely when the molar ratios were 1:3, 1:1, and 2:1.

[0100] Figure 5 Shows different HBA:HBD molar ratios and With the increase of HBD molar ratio, gradually decreases, and shows a corresponding increase. This trend can be Figure 2 The results can be explained by the fact that HBA mainly affects HBD main impact Overall, the majority of DES candidates are concentrated in the lower left quadrant, indicating relatively poor absorption and separation capabilities. To screen for DESs with high absorption and separation potential, DESs located in the upper right quadrant were prioritized. Consequently, the 28 DESs roughly form a quasi-Pareto front, representing their thermodynamically optimal performance among the 1,152 DES candidates. In other words, from a thermodynamic perspective, these 28 DES candidates are superior to all other candidates.

[0101] 3.3 DES screening based on SLE:

[0102] Not all of the 28 DES candidates screened above can be used as room temperature solvents for the absorption and separation of R410A. To solve this problem, COSMO-RS further predicted the SLE, melting temperature (T m ) below 298.15K were set as potential room temperature DES. Before this evaluation, the melting points and melting enthalpies of pure components were collected from the NIST database. Due to the lack of melting point and melting enthalpy data for mannose acid and malic acid, the SLE of DES combinations containing these substances could not be evaluated. Therefore, 4 of the 28 DES were discarded. After the SLE calculation, 6 of the remaining 24 DES met the melting point restriction, as determined by [N 1,1,3,2, OH]Br or [N 1,2,2, C2OC1][BF4] as HBA is paired with 4-oxopentanoic acid or oxalic acid as HBD in different molar ratios. The corresponding SLE phase diagram is shown in the figure below. Figure 6 shown.

[0103] 4. Process simulation for separation of R32 and R125:

[0104] Aspen Plus was used to simulate the continuous separation process of R410A mixed refrigerant, using the RadFrac block, equilibrium level model and NRTL thermodynamic method. The components of R32 and R125 were directly retrieved from the Aspen database, which does not contain DES. Therefore, the molecular weight (MW), density (ρ) and normal boiling point (T) of DES were input. b ), defining DES as a virtual component.

[0105] To obtain the NRTL model parameters, COSMO-RS was used to predict the solubility of R32 and R125 in different DES at different pressures and temperatures. The solubility data were calibrated using equations (8) and (9), and the quasi-experimental solubility data were obtained to fit the NRTL model parameters.

[0106] Since the separation performance is mainly affected by the operating pressure P and the DES mass flow rate Sol in the absorption tower, sensitivity analysis is then performed to study their effects on the DES absorption performance. Figure 8 The sensitivity analysis results are shown in the figure, as shown in the figure, satisfying w R125 The operating area for ≥95% separation tasks is located in the red upper right quadrant.

[0107] Higher P and Sol values improve the purity of R125, but this increases costs. Therefore, a trade-off should be made between P and Sol. A moderate operating pressure of 4.5 bar is selected for all DESs. The DES mass flow rates for DES1 to DES6 are 8400 kg / h, 8300 kg / h, 8600 kg / h, 9000 kg / h, 9400 kg / h, and 7500 kg / h, respectively.

[0108] For the first flash tank (P1) and the second flash tank 2 (P2), the temperature was kept constant at 298.15K and 328.15K, and the operating pressure was further optimized. However, for DES2, in order to meet the separation target, the temperature of the first flash tank was adjusted to 318.15K. Taking DES1 as an example, the effects of P1 and P2 on the R32 recovery rate and R32 product purity are shown as follows: Figure 9 (a) and Figure 9 (b) Increasing P1 can improve the R32 recovery rate, but will reduce the purity of the R32 product. Conversely, increasing P2 will lead to a decrease in both the R32 recovery rate and the R32 product quality. To ensure that the R32 purity reaches above 95wt% while having a high recovery rate, P1 and P2 are ultimately set to 1.3bar and 0.1bar, respectively. Similar trends are observed for other DES, and their optimal P1 and P2 values are determined accordingly. A summary of the simulation results is shown in Table 1.

[0109] Table 1 Process simulation results based on different DES

[0110] DES DES6 DES5 DES4 DES3 DES2 DES1 DES usage (kg / h) 7500 9400 9000 8600 8300 8400 Absorption pressure (bar) 4.5 4.5 4.5 4.5 4.5 4.5 R125 purity 0.9527 0.9561 0.9510 0.9535 0.9578 0.9548 First flash tank pressure (bar) 1.1 1.4 1.6 1.6 1.2 1.3 First flash tank temperature (℃) 25 25 25 25 45 25 Second flash tank pressure (bar) 0.1 0.1 0.1 0.1 0.1 0.1 Second flash tank temperature (℃) 55 55 55 55 55 55 Energy consumption of the first flash tank (kW) 44.94 44.16 46.18 46.03 15.70 46.15 Energy consumption of the second flash tank (kW) 72.78 89.41 96.53 97.26 37.69 101.61 R32 purity 0.9573 0.9529 0.9501 0.9527 0.9515 0.9503 R32 recovery rate 0.7828 0.7730 0.8146 0.8152 0.3739 0.7294 Pump energy (kW) 1.93 2.64 2.30 2.25 2.21 2.24 Total energy (kW) 119.66 136.21 145.03 145.55 55.61 150.01

[0111] As shown in Table 1, the performance of DES is ranked as follows based on energy, solvent consumption, and R32 recovery: DES6 > DES3 > DES4 > DES5 > DES1 > DES2. Therefore, DES3, DES4, and DES6 are identified as the three optimal DES for R32 / R125 separation.

[0112] 5. Quantum chemical calculations

[0113] To study the microscopic mechanism of the absorption behavior of R32 and R125 in three different DESs at the molecular level, the interaction energy between the R410A mixed refrigerant gas and DES was analyzed based on the results of quantum chemical calculations. The interaction energy between DES and R32 or R125 was determined using equation (10).

[0114] ΔE = E A+B - E A - E B (10)

[0115] where E A+B , E A and E B represent the energies of A and B, single A, and single B, respectively.

[0116] As Figure 10 shown, the interaction energy of DES-R32 follows the following rule:

[0117] DES4-R32 > DES3-R32 > DES6-R32, which is consistent with the value predicted by COSMO-RS. In addition, the closest interatomic interaction distances are arranged in the following order: DES4-R32 < DES3-R32 < DES6-R32, which indicates that DES4-R32 has a stronger interaction compared to DES3-R32 and DES6-R32, consistent with the calculated interaction energy. For the DES-R125 system, the interaction energies are arranged in the following order: DES4-R125 > DES3-R125 > DES6-R125, which is consistent with the DES-R32 system. Similarly, the closest interatomic interaction distances follow the trend of DES4-R125 < DES3-R125 < DES6-R125, further indicating that DES4 has a stronger interaction with R125. In addition, the interaction energy of DES-R32 is higher than that of DES-R125, which indicates that DES has a stronger affinity for R32. Therefore, DES is more inclined to absorb R32 rather than R125, enabling the selective separation of the two gases.

[0118] In summary, the present invention provides a systematic solvent multi-scale screening method for screening DES to selectively separate R32 and R125 from R410A mixed refrigerant. In order to ensure reliable preliminary screening, 290 solubility data points of hydrofluorocarbons in low eutectic solvents were first collected from the public literature, and 156 solubility data points (R32) and 134 solubility data points (R125) were used for linear calibration to evaluate and enhance the prediction accuracy of COSMO-RS. The present invention also conducted preliminary screening of 77 HBs and 120 HBDs, eliminated components with poor absorption separation potential, retained 9 HBAs and 32 HBDs, and from these DES combinations, 1152 DES candidates with different molar ratios were evaluated based on their absorption capacity and selectivity, and finally 28 DES with application potential were identified. SLE calculations further narrowed the selection range to six room temperature DES, which were then simulated and evaluated using AspenPlus. The results showed that [N 1,1,3,2, The DES, consisting of [OH]Br with 4-oxopentanoic acid (1:1, 2:1) or oxalic acid (1:3), exhibited high separation efficiency while balancing solvent consumption and operating costs. Furthermore, quantum chemical calculations confirmed the strong interaction between DES and R32, validating their preferential absorption behavior relative to R125.

[0119] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. The above-described embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of protection thereof is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention, and the scope of protection of the present invention shall be subject to the claims.

Claims

1. A separation and recovery device for R410A mixed refrigerant based on a deep eutectic solvent, characterized in that: include: Absorption tower (1), first flash tank (2) and second flash tank (3); The liquid outlet end of the absorption tower (1) is connected to the liquid inlet end thereof via a circulation pipe (7), and the absorption tower (1) is used for countercurrent contact between the R410A mixed refrigerant and the deep eutectic solvent; The first flash tank (2) and the second flash tank (3) are arranged on the circulation pipe (7), and the first flash tank (2) is connected to the liquid outlet end of the absorption tower (1); A first heat exchanger (4) is provided on the circulation pipe (7) between the first flash tank (2) and the second flash tank (3); a second heat exchanger (5) is provided on the circulation pipe (7) between the second flash tank (3) and the liquid inlet end of the absorption tower (1); a pump body (9) is also provided on the circulation pipe (7) between the second heat exchanger (5) and the second flash tank (3); The gas outlet end of the first flash tank (2) is connected to the gas inlet end of the absorption tower (1) via a connecting pipe (8), and a third heat exchanger (6) is provided on the connecting pipe (8).

2. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 1, characterized in that: The absorption tower (1) is a plate tower comprising six plates. The internal parameters of the absorption tower (1) are as follows: absorption is performed at an absorption temperature of 273.15K to 323.15K and an absorption pressure of 1 bar to 10 bar.

3. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 1, characterized in that: The pressure in the first flash tank (2) is 1 bar to 2 bar, and the temperature is 298.15 to 313.15 K.

4. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 1, characterized in that: The pressure in the second flash tank (3) is 0.1 bar to 0.6 bar, and the temperature is 298.15K to 313.15K.

5. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 1, characterized in that: A low eutectic solvent is delivered to the liquid inlet of the absorption tower (1), and an R410A mixed refrigerant is delivered to the gas inlet of the absorption tower (1), wherein the mass ratio of the low eutectic solvent to the R410A mixed refrigerant is 5 to 30:

1.

6. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 5, characterized in that: Deep eutectic solvents are screened according to the following steps: Select potential hydrogen bond acceptors and hydrogen bond donors suitable for absorption separation of R410A mixed refrigerant; Using COSMO-RS as a thermodynamic model, the infinite dilution activity coefficients of difluoromethane and pentafluoroethane in candidate hydrogen bond acceptor-hydrogen bond donor combinations were calculated. Based on the infinite dilution activity coefficients, the absorption capacity and separation selectivity of the candidate hydrogen bond acceptor-hydrogen bond donor combinations for difluoromethane and pentafluoroethane were calculated, and hydrogen bond acceptor-hydrogen bond donor combinations with better difluoromethane absorption capacity and difluoromethane / pentafluoroethane separation selectivity were screened out. The COSMO-RS model was used to calculate the melting points of optimal hydrogen bond acceptor-hydrogen bond donor combinations and screen for hydrogen bond acceptor-hydrogen bond donor combinations that can be used as R410A mixed refrigerants. According to the screened hydrogen bond acceptor-hydrogen bond donor combinations, deep eutectic solvents with different molar ratios are prepared.

7. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 6, characterized in that: The hydrogen bond acceptor is selected from quaternary ammonium salts, quaternary phosphonium salts or metal salts; the hydrogen bond donor is selected from carboxylic acids, alcohols, amides or phenols.

8. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 6, characterized in that: The optimal hydrogen bond acceptor-hydrogen bond donor combination satisfies the following requirements: difluoromethane absorption capacity and difluoromethane / pentafluoroethane separation selectivity are ranked in the top 50% among all candidate hydrogen bond acceptor-hydrogen bond donor combinations.

9. The separation and recovery equipment for R410A mixed refrigerant based on a deep eutectic solvent according to claim 6, characterized in that: A hydrogen bond acceptor-hydrogen bond donor combination that can be used as R410A mixed refrigerant has a melting point screening condition of less than 298.15K.

10. A separation and recovery process for R410A mixed refrigerant based on a deep eutectic solvent, characterized in that: The separation and recovery equipment for the R410A mixed refrigerant based on the deep eutectic solvent according to any one of claims 1 to 9 is characterized in that it comprises the following steps: The R410A mixed refrigerant and the deep eutectic solvent are simultaneously conveyed into the absorption tower (1), the R410A mixed refrigerant and the deep eutectic solvent are in countercurrent contact, and pentafluoroethane is obtained at the gas outlet end of the top of the absorption tower (1), and the difluoromethane-rich deep eutectic solvent is obtained at the liquid outlet end of the bottom of the absorption tower (1); The difluoromethane-rich deep eutectic solvent is transported to the first flash tank (2) via the circulation pipe (7); the first flash tank (2) desorbs part of the mixed gas to obtain pentafluoroethane and concentrated difluoromethane-rich deep eutectic solvent; the pentafluoroethane is refluxed into the absorption tower (1) via the connecting pipe (8) and exchanges heat with the third heat exchanger (6) during the reflux process; The concentrated difluoromethane-rich deep eutectic solvent is transported to the second flash tank (3) via the circulation pipe (7), and heat is exchanged with the first heat exchanger (4) during the transportation process. The second flash tank (3) fully desorbs the difluoromethane, and high-purity difluoromethane is obtained at the gas outlet end of the tank top of the second flash tank (3). The high-purity deep eutectic solvent is recovered at the liquid outlet end of the tank bottom of the second flash tank (3); The high-purity deep eutectic solvent is transported to the absorption tower (1) via the circulation pipe (7), and exchanges heat with the second heat exchanger (5) during the transportation process, and the high-purity deep eutectic solvent is reused.

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