Dimethyl sulfoxide recovered from dimethyl sulfoxide mother liquor and preparation process thereof

Abstract

The invention relates to the technical field of chemical engineering and separation, and discloses a technology for recovering dimethyl sulfoxide from dimethyl sulfoxide mother liquor and preparing the dimethyl sulfoxide from the dimethyl sulfoxide mother liquor, and the technology comprises the following steps that firstly, the dimethyl sulfoxide mother liquor containing impurities such as water and alcohol ethers is subjected to multi-dimensional diagnosis, and the content of key components of the dimethyl sulfoxide mother liquor is obtained; based on a diagnosis result, an optimal process path in high-water-content purification, organic impurity purification or composite extraction cooperation is adaptively selected for separation and purification. According to the invention, the tower top waste heat of the DMSO rectification unit is used for preheating the mother liquor before extraction, so that an efficient energy coupling closed loop is constructed; and a multi-layer material closed-loop network is established by recycling tower kettle raffinate of the extraction agent recovery tower, removing impurities from a middle-section side line and utilizing material flows among different process paths to perform solvent synergistic regeneration. According to the invention, high-efficiency, low-consumption and high-purity recovery of DMSO mother liquor from different sources is realized, the adaptability and economical efficiency of the process are remarkably improved, and long-period stable operation of the system is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical engineering and separation technology, and particularly relates to a dimethyl sulfoxide mother liquor recovery dimethyl sulfoxide and a preparation process thereof. BACKGROUND

[0002] Dimethyl sulfoxide (DMSO) is an extremely important aprotic polar solvent. Due to its excellent solubility and unique chemical properties, it is known as "universal solvent" and plays an indispensable role in many modern industrial fields such as medicine, pesticide, electronics, and polymer materials. In these industrial production processes, a large amount of DMSO mother liquor with complex components is inevitably produced. From the perspective of economy and environmental protection, efficient and low-cost recovery of the mother liquor to realize the recycling of dimethyl sulfoxide resources is not only the key link for enterprises to reduce costs and increase efficiency, but also meets the strategic requirements of current green chemical industry and sustainable development, and has important practical significance.

[0003] At present, the technical route commonly used in the industry for the recovery of DMSO mother liquor mainly relies on rectification, which separates DMSO from water and organic impurities by using the difference in boiling points. In some cases, in order to deal with complex impurity systems, pretreatment methods such as extraction are used to remove non-target components first, and then the regenerated DMSO is obtained by subsequent rectification. These methods achieve the recovery of DMSO to some extent, but with the increasing refinement of production and the increasingly strict environmental protection requirements, the existing technology has exposed many inherent defects in practical application.

[0004] A core challenge is that DMSO mother liquor in industrial production comes from various sources, and its components vary greatly. For example, the water content may vary from a few percent to more than 80 percent, and the types and contents of organic impurities also vary greatly. The traditional recovery process often uses a fixed set of parameters and processes. This "one-size-fits-all" processing mode makes it difficult to adapt to different characteristics of the incoming material, resulting in serious constraints on the overall processing efficiency and economy. Especially when the mother liquor has a high water content, since DMSO and water can form stable hydrogen-bonded compounds, direct rectification not only requires a large amount of energy, but high-temperature operation may also cause a small amount of DMSO decomposition, affecting product quality. In addition, when the mother liquor contains complex organic impurities with similar boiling points to DMSO or can form azeotropes, a single rectification or extraction method often cannot achieve complete separation, which not only results in low recovery rate of DMSO and large solvent loss, but more seriously, some impurities will accumulate in the recycled extraction agent, gradually reducing the efficiency of the solvent, eventually forcing the entire solvent system to be replaced at a high cost, significantly increasing operating costs and lacking long-term stability. SUMMARY

[0005] The application aims to provide a dimethyl sulfoxide mother liquor recovery dimethyl sulfoxide and its preparation process, aiming to solve the technical problems of low overall processing efficiency, high energy consumption, large solvent loss and poor long-term running stability caused by the inability of the existing dimethyl sulfoxide recovery process to adapt to the large fluctuations in raw material components.

[0006] The first aspect of the application provides a precursor composition for preparing high-purity dimethyl sulfoxide.

[0007] The precursor composition is a key intermediate state before entering the final rectification purification unit after preliminary extraction and separation of impurities in the preparation process described in the application. The composition creates favorable conditions for subsequent efficient and low-energy consumption to obtain high-purity dimethyl sulfoxide products by precise component composition.

[0008] Specifically, the precursor composition is composed of the following components in mass fraction:

[0009] Dimethyl sulfoxide: 50-70 parts;

[0010] Water: 30-50 parts;

[0011] And an extractant selected from aromatic hydrocarbon solvents and ether solvents: 0.1-1.0 parts.

[0012] In a preferred embodiment, the aromatic hydrocarbon solvent is xylene, and the ether solvent is methyl tert-butyl ether. In this precursor composition, the ratio of the target product dimethyl sulfoxide to water is adjusted to a range suitable for rectification separation, and only trace amounts of extractant are contained, and the material system is relatively pure, greatly reducing the load and separation difficulty of the subsequent rectification process.

[0013] The second aspect of the application provides a dimethyl sulfoxide mother liquor recovery dimethyl sulfoxide preparation process.

[0014] The preparation process builds an intelligent, low-carbon, and cyclic recovery system by introducing multi-dimensional diagnostic decision-making, energy integration coupling, material closed-loop circulation, and cross-path collaborative regeneration.

[0015] Specifically, the preparation process includes the following steps:

[0016] Step S1 Multi-dimensional diagnosis: This step dynamically matches the optimal processing path for the entire process system through accurate quantitative analysis of the raw material mother liquor. First, the water content, total alcohol ether organic impurity content, and specific key impurity content in the dimethyl sulfoxide mother liquor to be treated are determined. Then, according to the preset criterion model, the subsequent process path and the corresponding extractant are selected. In a specific embodiment, the preset criterion includes:

[0017] When the water content is not less than 75% and the content of specific key impurities is less than 0.8%, it is a high-water-content and low-complexity system. The system determines to select non-polar xylene as the extractant to break the strong polar system of DMSO and water with the highest efficiency and realize separation from a large amount of water.

[0018] When the water content is not more than 30% and the content of total alcohol ether organic impurities is not less than 10%, it is a high-organic-impurity system. The system determines to select medium-polar methyl tert-butyl ether as the extractant to utilize its excellent solubility to alcohol and ether impurities to extract and separate them from the DMSO water system.

[0019] When the components of the mother liquor are between the above two cases, or the content of specific key impurities is not less than 0.8%, it is a complex complex system, and a single extractant is difficult to consider. The system determines to use sequential extraction strategy: first, a small amount of xylene is used for pretreatment to selectively remove part of the strong hydrophobic or key impurities; then methyl tert-butyl ether is used for main extraction to separate the remaining alcohol and ether impurities.

[0020] Step S2 extraction separation: this step is the core unit of the preliminary separation of impurities and target product. First, the waste heat generated in step S3 is used to preheat the mother liquor to 40-60°C through heat exchange. The technical mechanism of this is that appropriately increasing the temperature can reduce the liquid viscosity and increase the molecular kinetic energy, thereby significantly improving the mass transfer efficiency of the subsequent extraction process. Then, the preheated mother liquor is contacted with the extractant selected in step S1 in a countercurrent extraction column, and the volume ratio of the extractant to the mother liquor is 1:1 to 5:1. Finally, a dimethyl sulfoxide-rich raffinate phase and an impurity-loaded extract phase are obtained.

[0021] Step S3 rectification purification: this step is a refining unit to obtain the final product, and is also a "heat source" unit for energy cascade utilization of the system. The raffinate phase obtained in step S2 is subjected to vacuum rectification. The technical mechanism of vacuum is that the boiling point of DMSO is significantly reduced, so that distillation can be carried out at a more moderate temperature, effectively avoiding the thermal decomposition of DMSO at high temperature, ensuring product quality, and reducing heating energy consumption. High-purity dimethyl sulfoxide product is obtained from the column bottom, and the heat of the high-temperature steam distilled from the column top is led to the preheating unit of step S2, realizing closed-loop circulation of system internal energy.

[0022] Step S4 extractant recovery and circulation: this step is the key to process economy. Through efficient recovery and fine management of the extractant, the main material circulation of the system is formed. First, the extract phase generated in step S2 is subjected to atmospheric rectification to recover the extractant. This step includes two innovative material circulation designs:

[0023] Firstly, part of the residual liquid in the tower kettle is returned to the extraction unit in step S2. The technical mechanism is that the stream of residual liquid, although enriched with high-boiling-point impurities, still contains a certain amount of extractant and has part of the extraction capacity. Using it to preliminarily wash the raw material mother liquor can effectively reduce the input amount of fresh extractant.

[0024] Secondly, side-drawing is performed at a position 1 / 3 to 1 / 2 of the theoretical plate number from the top of the recovery tower. The technical mechanism is that, according to the distillation theory, the medium-boiling-point impurities with boiling points between the extractant and the high-boiling-point impurities form a concentration peak in this area. Through side-drawing, these impurities can be continuously and directionally discharged from the system, avoiding their infinite accumulation in the circulating solvent, thereby prolonging the overall service life of the extractant.

[0025] Step S5 cross-path coordinated regeneration: this step is a deep innovation of the present application, which is used to solve the problem of accumulation of specific impurities that cannot be removed by conventional circulation, and constitutes a material auxiliary circulation of the system. When the concentration of hydrophilic impurities in the methyl tert-butyl ether extractant used in circulation accumulates to more than 1.5-2.5% of the preset threshold, the regeneration program is started. The technical mechanism is that, by using the principle of liquid-liquid distribution balance, the "dirty" methyl tert-butyl ether is mixed and washed with the high-water-content mother liquor to be introduced into another process path at a volume ratio of 1:8 to 1:3. Since the solubility of hydrophilic impurities in the water phase is much greater than that in the methyl tert-butyl ether phase, they will preferentially transfer from the methyl tert-butyl ether phase to the water phase with a large amount of water, thereby purifying and regenerating the methyl tert-butyl ether. This "waste treatment with waste" design ingeniously utilizes the characteristics of different material streams in the system, without the need for additional chemical agents or complex purification equipment, to achieve deep regeneration of the solvent.

[0026] In summary, the present application includes at least one of the following beneficial technical effects:

[0027] 1. The present application can accurately identify the key component characteristics of the raw material mother liquor by setting a multi-dimensional diagnosis step, and adaptively match the most optimized process path accordingly. This ensures that the system can always operate under the most efficient and most targeted conditions, regardless of the complex feedstock containing high water content, high organic impurities or special impurities, thereby completely solving the poor universality and poor treatment effect of traditional fixed processes when dealing with fluctuating raw materials.

[0028] 2. The present application uses the high-temperature steam discharged from the high-energy consumption unit to preheat the cold mother liquor entering the low-energy consumption unit through an energy coupling system. This design realizes the cascade utilization of waste heat within the system, greatly reduces the dependence on external fresh steam and other primary energy sources, and directly reduces the production utility cost.

[0029] 3.The application maximizes the utilization of materials and significantly saves solvent costs through multi-level material closed-loop design. The residue from the bottom of the extractant recovery column is reused at the front end of the extraction, and the material flow between different process paths is used for cross-collaborative regeneration, which successfully converts the original waste material flow into valuable resource flow. These designs greatly reduce the amount of fresh extractant and the amount of waste liquid to be treated, achieving the ultimate utilization of resources.

[0030] 4.The application can efficiently and directionally discharge the medium-boiling impurities that are easily enriched in the conventional rectification by innovatively setting a side-line discharge port on the extractant recovery column. This fundamentally avoids the performance degradation of the circulating solvent due to pollution, solves the problem of product purity fluctuation caused by impurity accumulation, and significantly improves the operation reliability of the entire system.

[0031] 5.The application realizes the unity of economic benefits and environmental benefits by constructing a highly integrated resource recycling system. Through internal energy cascade utilization and multi-path material closed-loop and collaborative regeneration, the application not only performs well in reducing operating costs, but also reduces the generation of waste heat and waste liquid from the source. It upgrades a traditional separation and recovery process into a low-carbon and green circular economy example, which has significant social benefits and promotional value. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The figure is a schematic diagram of the method of the application. DETAILED DESCRIPTION

[0033] The following will be combined with the Figure 1 The application will be further described in detail.

[0034] The application provides a dimethyl sulfoxide mother liquor recovery dimethyl sulfoxide and a preparation process thereof.

[0035] Example 1

[0036] This embodiment shows a preparation process for recovering dimethyl sulfoxide by using a composite extraction collaborative path.

[0037] 1. Step S1: Multi-dimensional diagnosis of mother liquor and dynamic selection of process path Take 1000 kg of dimethyl sulfoxide mother liquor to be treated, and analyze and determine that the composition is: water content is 55%, total alcohol ether organic impurity content is 8%, and specific key impurity A content is 1.0%. According to the preset criterion, the component meets the triggering condition of process path III, and the system selects to use the composite extraction collaborative path.

[0038] 2. Step S2: Energy coupling preheating and multi-stage countercurrent extraction The 1000 kg mother liquor is pumped into heat exchanger E1 and preheated to 50°C by exchanging heat with 105°C steam from the overhead of DMSO rectification column T1 in subsequent step S3. The preheated mother liquor is fed into the extraction system, and first undergoes pretreatment extraction: 60 kg of xylene is added, and after mixing and extraction, the phases are separated. The main liquid phase after separation is pumped into a multi-stage countercurrent extraction column, and countercurrent extraction is performed with 2800 kg of methyl tert-butyl ether (MTBE) at 50°C. After separation, the raffinate phase and the extract phase are obtained.

[0039] 3. Step S3: Dimethyl sulfoxide (DMSO) rectification purification The raffinate phase obtained in step S2 is pumped into DMSO rectification column T1. The column is operated at an absolute vacuum pressure of 12 kPa, with the column bottom temperature controlled at 120°C and the reflux ratio set at 2.8. High-purity DMSO product is continuously withdrawn from the column bottom.

[0040] 4. Step S4: Extractant recovery and recycling The two extract phases produced in step S2 are fed into respective recovery columns T2 and T3. Impurities with medium boiling points are continuously discharged from the side draw at the middle section of the recovery columns. The pure extractants recovered from the column tops are recycled for use. At the same time, a portion of the residual liquid discharged from the column bottoms is taken out, with a flow rate equivalent to 10% of the fresh extractant make-up amount, and after cooling, it is pumped back to the first few stages of the extraction column for material coupling and recycling.

[0041] 5. Step S5: Cross-path collaborative regeneration When the concentration of hydrophilic impurities in the MTBE recycling system is monitored to reach 2.0%, a "dirty" MTBE stream is introduced from the recycling system, mixed with another batch of high-water-content mother liquor at a volume ratio of 1:5, and allowed to separate into layers. The separated upper layer of purified MTBE is returned to its recycling system.

[0042] Example 2

[0043] This example demonstrates a preparation process for recovering dimethyl sulfoxide using a high-water-content purification path.

[0044] 1. Step S1: Multi-dimensional diagnosis of mother liquor and dynamic selection of process path Take 1000 kg of dimethyl sulfoxide mother liquor to be processed, and analyze and determine its composition: water content is 75%, total alcohol and ether organic impurity content is 2%, and specific key impurity A content is 0.7%. According to the preset criteria, the composition meets the triggering conditions of process path I, and the system selects xylene as the main extractant.

[0045] 2. Step S2: Energy coupling preheating and multi-stage countercurrent extraction The 1000 kg mother liquor is pumped into heat exchanger E1 and heat exchanged with 95°C high-temperature steam discharged from the top of DMSO rectification column T1 in subsequent step S3 to preheat the mother liquor to 40°C. The preheated mother liquor is pumped into a multi-stage countercurrent extraction column and countercurrently extracted with 1000 kg dimethylbenzene at 40°C. After separation, the raffinate phase and the extract phase are obtained.

[0046] 3. Step S3: Distillation purification of dimethyl sulfoxide (DMSO) The raffinate phase obtained in step S2 is pumped into DMSO rectification column T1. The column is operated at an absolute vacuum pressure of 5 kPa, the column bottom temperature is controlled at 100°C, and the reflux ratio is set at 1.5. High-purity DMSO product is continuously collected from the column bottom.

[0047] 4. Step S4: Extractant recovery and circulation The extract phase produced in step S2 is sent to dimethylbenzene recovery column T2 for rectification recovery. A portion of the residual liquid discharged from the column bottom is taken out, which is equivalent to 5% of the fresh dimethylbenzene make-up amount, and pumped back to the extraction column after cooling for material coupling circulation.

[0048] Example 3 This example shows a preparation process for recovering dimethyl sulfoxide using an organic impurity purification path.

[0049] 1. Step S1: Multi-dimensional diagnosis of mother liquor and dynamic selection of process path Take 1000 kg of dimethyl sulfoxide mother liquor to be treated, and analyze and determine its composition: water content is 30%, total alcohol and ether organic impurity content is 10%, and specific key impurity A content is 0.5%. According to the preset criterion, the composition meets the triggering condition of process path II, and the system selects methyl tert-butyl ether (MTBE) as the main extractant.

[0050] 2. Step S2: Energy coupling preheating and multi-stage countercurrent extraction The 1000 kg mother liquor is pumped into heat exchanger E1 and heat exchanged with 95°C high-temperature steam discharged from the top of DMSO rectification column T1 in subsequent step S3 to preheat the mother liquor to 40°C. The preheated mother liquor is pumped into a multi-stage countercurrent extraction column and countercurrently extracted with 1000 kg dimethylbenzene at 40°C. After separation, the raffinate phase and the extract phase are obtained.

[0051] 3. Step S3: Distillation purification of dimethyl sulfoxide (DMSO) The raffinate phase obtained in step S2 is pumped into DMSO rectification column T1. The column is operated at an absolute vacuum pressure of 5 kPa, the column bottom temperature is controlled at 100°C, and the reflux ratio is set at 1.5. High-purity DMSO product is continuously collected from the column bottom.

[0052] 4. Step S4: Extractant recovery and recycling The extract phase generated in step S2 is sent to MTBE recovery column T3 for rectification recovery. A portion of the column bottom discharge is taken out, which flow rate is equivalent to 15% of the fresh MTBE make-up amount, and after cooling, it is pumped back to the extraction column for material coupling circulation.

[0053] 5. Step S5: Cross-path synergistic regeneration When the concentration of hydrophilic impurities in the MTBE circulation system is monitored to reach 2.5%, a stream of "dirty" MTBE is drawn from the circulation system, mixed with another batch of high-water-content mother liquor in a volume ratio of 1:3, and allowed to stand and separate. The separated upper layer of purified MTBE is returned to its circulation system.

[0054] Comparative Example 1: Compared with Example 1, the difference is that in step S1, multi-dimensional diagnosis is not performed, but process path II is directly selected, that is, only methyl tert-butyl ether (MTBE) is used for extraction, and xylene is not used for pretreatment. The remaining steps are the same as Example 1.

[0055] Comparative Example 2: Compared with Example 1, the difference is that in step S2, the mother liquor is not preheated by the overhead vapor from step S3, but an independent external steam source is used to heat the mother liquor to 50°C. The remaining steps are the same as Example 1.

[0056] Comparative Example 3: Compared with Example 1, the difference is that in step S4, the column bottom residue of extractant recovery columns T2 and T3 is all treated as waste liquid, and part of it is not returned to the extraction unit for material coupling circulation. The remaining steps are the same as Example 1.

[0057] Comparative Example 4: Compared with Example 1, the difference is that in step S4, the extractant recovery columns T2 and T3 are not provided with a side draw port for directional discharge of medium-boiling impurities. The remaining steps are the same as Example 1.

[0058] Comparative Example 5: Compared with Example 1, the difference is that the cross-path synergistic regeneration step of step S5 is omitted. When the concentration of hydrophilic impurities in the MTBE circulation system is monitored to exceed the standard, the part of "dirty" MTBE is treated as waste liquid, and an equal amount of fresh MTBE is supplemented to maintain the system operation. The remaining steps are the same as Example 1.

[0059] Test Example 1: Verification of multi-dimensional diagnosis and composite extraction synergy

[0060] Experimental steps

[0061] 1. Raw material preparation: Take the same source and same batch of dimethyl sulfoxide mother liquor, which has the same composition as described in Example 1. Divide the mother liquor into two equal parts, which are used for testing in the schemes of Example 1 and Comparative Example 1, respectively.

[0062] 2. Process execution:

[0063] Example 1 group: One of the mother liquor was treated according to the composite extraction synergistic path described in Example 1. That is, first using xylene for pretreatment extraction, after separation, using methyl tert-butyl ether for main extraction.

[0064] Comparative Example 1 group: Another mother liquor was treated according to the single extractant path described in Comparative Example 1. That is, directly using methyl tert-butyl ether for extraction, omitting the xylene pretreatment step.

[0065] 3. Sample collection: After both processes entered the stable running state, timing started. After 5 hours of continuous operation, every 1 hour, 50 mL of sample was taken from the outlet of the final product of each process. The samples of Example 1 group were labeled as E1-1, E1-2, E1-3, E1-4, E1-5, respectively. The samples of Comparative Example 1 group were labeled as C1-1, C1-2, C1-3, C1-4, C1-5, respectively.

[0066] 4. Sample analysis: All 10 samples collected were analyzed under the same analysis conditions using high performance liquid chromatography (HPLC). The mass percentage concentration of the specific key impurity A in each sample was quantitatively determined and recorded by standard curve method.

[0067] Experimental data

[0068] Table 1 Comparison of residual content of key impurity A in final products of Example 1 and Comparative Example 1

[0069] Sample No. Key impurity A residual content (w / w, %) E1-1 0.0052 E1-2 0.0048 E1-3 0.0055 E1-4 0.0051 E1-5 0.0049 C1-1 0.153 C1-2 0.148 C1-3 0.155 C1-4 0.161 C1-5 0.15

[0070] Experimental summary

[0071] As can be seen from the experimental data in Table 1, the residual content of key impurity A in the product obtained by the preparation process of Example 1 is significantly lower than that obtained by the process of Comparative Example 1. The impurity content of the former is stably at an extremely low level of about 0.005%, while that of the latter is as high as about 0.15%, with a nearly 30-fold difference in impurity removal effect. This result clearly proves the advancement of the technical solution described in the present application.

[0072] The results deeply reveal the technical mechanism of the multi-dimensional diagnosis and composite extraction synergistic path of the present application. In Comparative Example 1, although the single methyl tert-butyl ether (MTBE) extractant has a good removal effect on conventional alcohol and ether impurities, it has a low extraction distribution coefficient and insufficient mass transfer driving force as a medium-polar solvent for some specific key impurities A which are strongly hydrophobic or have special interaction with the DMSO / water system. Therefore, the impurities will penetrate the extraction unit in large quantities, eventually remaining in the product, resulting in substandard product purity.

[0073] The technical solution of the present application first identifies that the presence of the key impurity A poses a major threat to product quality through preset diagnostic criteria, and therefore enables the composite extraction path. The small amount of non-polar xylene introduced in the first step precisely targets and efficiently captures this strongly hydrophobic key impurity A, selectively removing it from the main liquid phase using the "like dissolves like" principle. After this pretreatment step, the liquid phase entering the main extraction unit is basically free of key impurity A, and the subsequent MTBE extraction can focus on removing the remaining alcohol and ether impurities, achieving functional complementation and synergistic effect between different extractants. Therefore, the present application is not simply a step-by-step addition, but establishes an intelligent technical system of "diagnosis-decision-execution", which can adaptively build the most efficient separation scheme according to the complexity of the raw material, thereby effectively solving the "short board effect" of single extractant when facing complex material systems, and ensuring that the final product can meet extremely high purity standards.

[0074] Test Example 2: Verification of System Energy Integration Coupling Benefits

[0075] Experimental steps

[0076] 1. System setup and configuration:

[0077] Example 1 group: Build a complete preparation process system. The overhead vapor outlet of the DMSO rectification column T1 is connected to the heat medium inlet of the heat exchanger E1 for preheating the mother liquor; the outlet of E1 is connected to the condensing system.

[0078] Comparative Example 2 group: Build a preparation process system that is identical to Example 1 group except for the heat recovery part. The heat medium inlet of the heat exchanger E1 is connected to an independent external steam supply source equipped with a precision mass flow meter. The overhead vapor outlet of the DMSO rectification column T1 is directly connected to an independent condensing cooling system.

[0079] 2. Process operation and data recording:

[0080] The same feedstock mother liquor with same component, flow rate and initial temperature was fed into two sets of system and the process was started. The extraction temperature, rectification pressure, reflux ratio and all the core process parameters of the two sets of system were kept consistent. After the process entered the stable running state, the timing was started and the continuous running was carried out for 8 hours. During this period:

[0081] For the example 1 group, only the total energy consumed by the rectification column T1 column heater was recorded.

[0082] For the comparative example 2 group, the total energy consumed by the rectification column T1 column heater and the cumulative consumption of the external steam supply were recorded at the same time, and the total energy consumption was obtained by adding the two. The cumulative total energy consumption was recorded every 2 hours.

[0083] Experimental data

[0084] Table 2 Comparison of total energy consumption of example 1 and comparative example 2 when processing the same amount of mother liquor

[0085] Run time (h) Total energy consumption (MJ) for Example 1 Total energy consumption (MJ) for Comparative Example 2 2 205 267 4 412 535 6 608 793 8 815 1061

[0086] Experimental summary

[0087] According to the experimental data in table 2, after 8 hours of continuous stable running, the total energy consumption of the example 1 scheme is 815 MJ, while the total energy consumption of the comparative example 2 scheme is as high as 1061 MJ. The results clearly show that compared with the traditional decentralized energy supply scheme, the technical scheme of the present application can significantly reduce the overall energy consumption of the process, with an energy saving rate of more than 23%.

[0088] This significant difference is due to the fundamental difference in the design of the energy flow of the system. In the scheme of comparative example 2, each unit operation is regarded as an independent "energy island", and the heat required for preheating the mother liquor must be provided by external primary energy, while the large amount of latent heat carried by the high-temperature steam discharged from the top of the rectification column is directly discharged into the cooling medium, causing serious waste of energy. This is a typical and inefficient linear "input-use-waste" energy utilization mode.

[0089] The technical scheme provided by the present application embodies the systematic energy integration and cascade utilization idea. The steam at the top of the rectifying tower is no longer regarded as waste heat, but is identified as an "internal secondary energy" having utilization value. By constructing a heat exchange loop, the otherwise discarded heat is accurately delivered and used to preheat the cold material entering the system, forming an efficient internal energy closed loop. This design cleverly couples a step requiring energy consumption with a step generating waste heat, and the technical mechanism lies in realizing the circulation of energy within the system and the cascade utilization of grade, thereby minimizing the dependence on external primary energy without affecting any process effect. This not only directly reduces the operating cost of production, but also embodies the advanced design concept of green and low carbon, and is an important part of the core innovation of the present application.

[0090] Test Example 3: Verification of the Coupling Circulation Benefit of the Tower Residual Liquid Material

[0091] Experimental Steps

[0092] 1. System configuration and calibration:

[0093] Example 1 group: Build a complete preparation process system. Configure a flow divider at the outlet of the tower bottoms of the extractant recovery towers T2 and T3, one way to the waste liquid storage tank, and the other way through a precision metering pump connected to the feed inlet of the first few stages of the extraction tower.

[0094] Comparative Example 3 group: Build a preparation process system that is identical to Example 1 group except for the reuse of tower residual liquid. The outlet of the tower bottoms of the recovery towers T2 and T3 is directly connected to the waste liquid storage tank.

[0095] High-precision mass flow meters are configured for the two systems to monitor and record the total mass of fresh extractant supplied to the system in real time.

[0096] 2. Long-term operation and data collection:

[0097] The same component and flow rate of raw material mother liquor are introduced into the two systems, and the process is started to reach a stable running state. Start timing and perform continuous operation test for 100 hours. During this period, the total amount of circulating solvent in the two processes is maintained constant by the automatic control system, and any reduction in solvent amount due to process loss is automatically supplemented by fresh extractant. Every 25 hours, the total mass of fresh extractant accumulated in the two systems is read and recorded from the mass flow meter.

[0098] Experimental Data

[0099] Table 3 Comparison of total fresh extractant supplement amount in long-term operation between Example 1 and Comparative Example 3

[0100]

[0101] Experiment summary

[0102] The data in Table 3 clearly shows that the scheme of Example 1 only needs to supplement 6.9 kg of fresh extractant during the continuous operation cycle of up to 100 hours, while the scheme of Comparative Example 3 consumes as high as 41.5 kg, which is 6 times more than the former. This result powerfully proves the great advantages of the technical scheme of the present application in saving solvent and reducing operation cost.

[0103] Behind this significant difference is the fundamental difference in the value recognition of the materials in the system. Comparative Example 3 adopts the traditional linear processing mode, directly regarding the residue in the bottom of the extractant recovery column as useless waste liquid and discarding it. The defect of its technical mechanism lies in that, although the residue is rich in high-boiling impurities, its main component is still the extractant itself, and a large amount of solvent value contained therein is discarded together with the impurities, causing direct and great material loss and increasing the burden of subsequent waste liquid treatment.

[0104] The technical scheme of the present application successfully transforms this "waste liquid stream" into a "resource stream" through ingenious material coupling design. Its technical mechanism lies in the deep understanding that the column residue still retains considerable "residual extraction capacity". By quantitatively and controllably returning it to the front end of the extraction unit for preliminary washing of the initial raw material mother liquor, it is equivalent to using a "poor solvent" to pre-shoulder a part of the extraction load of impurities. This not only fully squeezes the residual value of this part of solvent, but also directly reduces the demand for high-purity "rich solvent" by the rear-end main extraction unit. This design is a key embodiment of the material closed-loop circulation idea of the present application, which turns a material loss point into a gain node that improves the overall material utilization rate of the system, thereby achieving double improvement of economic benefit and environmental benefit.

[0105] Test Example 4: Verification of impurity directional enrichment and side-line discharge function

[0106] Experimental steps

[0107] 1. System configuration and preparation:

[0108] Example 1 group: build a complete preparation process system. Ensure that the middle and upper sections of the MTBE recovery column T3 have been correctly installed and the side-line discharge port is opened, which is connected to an impurity collection tank through a control valve.

[0109] Comparative Example 4 group: build a preparation process system which is exactly the same as Example 1 group except for the side-line discharge port. The MTBE recovery column T3 is a standard rectifying column without any side-line discharge function.

[0110] Both systems used the same batch of clean MTBE as the initial circulating extractant.

[0111] 2. Long-term operation and sample collection:

[0112] The feedstock mother liquor with the same composition and flow rate was fed into both systems, and the process was started. After the process entered a stable operation state, the timer was started, and a 100-hour continuous operation test was performed. At the beginning of the operation time and at the 25th, 50th, 75th, and 100th hours, the following sampling operations were performed:

[0113] The sample was taken from the MTBE storage tank of the main circulation pipeline and labeled as the circulating solvent sample.

[0114] The sample was taken from the outlet of the final product and labeled as the DMSO product sample.

[0115] 3. Sample analysis:

[0116] Gas chromatography was used to analyze all collected samples.

[0117] For the circulating solvent sample, the mass percentage concentration of a representative medium-boiling impurity was quantitatively determined.

[0118] For the DMSO product sample, the total purity was determined.

[0119] Experimental data

[0120] Table 4 Comparison of circulating solvent quality and product purity stability in Example 1 and Comparative Example 4

[0121]

[0122] Experimental summary

[0123] The experimental data in Table 4 reveals the significant difference in long-term operation stability between the two technical solutions. When using the scheme of Example 1, the concentration of impurity B in the circulating MTBE solvent is always maintained at a very low level of 0.09% or less within a 100-hour operation period, showing excellent stability, and the purity of the final DMSO product is also constant at 99.97% or more. In sharp contrast, in the scheme of Comparative Example 4, the concentration of impurity B increases sharply over time, reaching more than 30 times the initial concentration, directly leading to the continuous deterioration of the purity of the final product, falling below 99.5%.

[0124] This result profoundly reflects the inherent defects of conventional recovery process in dealing with materials containing medium-boiling impurities. The technical mechanism lies in that, in the standard rectification process, the impurities with boiling points between light components and heavy components are difficult to completely vaporize from the top of the column, nor can they be effectively enriched and settled at the bottom of the column. Therefore, they are continuously "trapped" and accumulated in a certain area of the rectification column. In the scheme of Comparative Example 4, due to the lack of effective discharge channels, the concentration of these impurities inevitably continues to rise in the entire solvent circulation loop, thereby reducing the purity and extraction efficiency of the circulating solvent, and finally penetrating into the raffinate phase, polluting the final product.

[0125] The technical scheme of the present application precisely solves this technical problem by providing a side discharge port in the extractant recovery column. The technical mechanism is based on a deep understanding and application of the mass transfer and heat transfer theory of rectification process, and the discharge port is accurately set at the theoretical plate position where these medium-boiling impurities are naturally enriched. By continuously or intermittently leading out a small stream of material from this "concentration peak" area, these accumulated impurities can be directed and efficiently "removed" from the system. This fine design is equivalent to installing a "detoxification" valve for the circulation system, which ensures that the circulating solvent can be maintained in a high-purity and high-activity state for a long time, thereby ensuring the long-term stable operation of the entire process and the continuous high quality of the final product. It is one of the key innovations of the present application to realize long-period, high-efficiency and stable production.

[0126] Test Example 5: Verification of the cross-path synergistic regeneration benefit of the extractant

[0127] Experimental steps

[0128] 1. Preparation and sampling of contaminated solvent:

[0129] By continuously running the process of Example 1 and artificially reducing the amount of side-line impurity removal, the accumulation of hydrophilic impurities in the circulating MTBE solvent is accelerated. When the online analytical instrument shows that the concentration of impurity C in the circulating MTBE reaches 2.51%, stop running and take out 200L of the "contaminated MTBE" from the system. After mixing thoroughly, divide it into two equal parts, each of 100.5L, and use them for the subsequent two schemes.

[0130] 2. Regeneration / replacement operation:

[0131] Example 1 group: Take one of the 100.5L contaminated MTBE and mix it with another process path to be processed, high-water mother liquor with a water content of 80%, according to a volume ratio of 1:5. Mix the two in a mixing and clarifying tank with stirring for 15 minutes, then stand for 30 minutes to completely separate the phases. Separate the upper MTBE phase as "purified MTBE".

[0132] Comparative Example 5 Group: Another 100.5 L of contaminated MTBE was discharged into the designated organic waste liquid collection tank. Then, an equal volume of fresh MTBE with purity of 99.9% or above was supplemented into the system.

[0133] 3. Analysis and Measurement:

[0134] The residual concentration of impurity C in the "purified MTBE" obtained from Example 1 Group was analyzed by gas chromatography.

[0135] By the measurement device, the volume of fresh MTBE supplemented into the system and the volume of organic waste liquid discharged into the waste liquid collection tank in Comparative Example 5 Group were accurately recorded.

[0136] Experimental Data

[0137] Table 5 Comparison of resource consumption and waste liquid generation between Example 1 and Comparative Example 5 in treating the same degree of contaminated solvent

[0138] Test item Example 1 protocol Comparative Example 5 protocol Volume of contaminated MTBE to be treated (L) 100.5 100.5 Initial concentration of hydrophilic impurity C (w / w, %) 2.51 2.51 Concentration of impurity C in MTBE after purification (w / w, %) 0.06 Not applicable Fresh MTBE make-up (L) 0 100.5 Additional amount of organic waste liquid to be treated (L) 0 100.5

[0139] Experimental Summary

[0140] The experimental data in Table 5 directly shows the huge difference in economic and environmental benefits between the two schemes. To solve the problem of the same degree of solvent contamination, the Example 1 scheme does not consume any fresh solvent and does not generate any additional organic waste liquid. However, the traditional scheme of Comparative Example 5 pays a high price of "one contaminated, one newly purchased, and one discarded", that is, it consumes an equal amount of fresh solvent as the contaminated solvent and generates an equal amount of high-concentration organic waste liquid to be treated.

[0141] The fundamental reason for this result lies in the unique cross-pathway collaborative regeneration technology of the present application. Its technical mechanism lies in the ingenious use of the basic physical and chemical principles of liquid-liquid distribution equilibrium. The solubility of hydrophilic impurity C in the aqueous phase is much greater than its solubility in the organic phase. When the organic phase containing a small amount of impurity C is in contact with a high-water mother liquor with a volume several times that of the organic phase, a strong mass transfer driving force will be formed, driving the impurity C molecules to spontaneously and efficiently migrate from the organic phase to the aqueous phase until a new phase equilibrium is reached. Since the aqueous phase has a large volume, most of the impurities are eventually "captured" in the aqueous phase, thus deeply purifying the organic phase.

[0142] The invention is ingenious in that it does not introduce any new chemical reagent or additional processing unit to achieve this process. It creatively couples the "to-be-purified solvent stream" of one process path in the system with the "to-be-processed raw material stream" of another process path. After impurity C is transferred to the high-water-content mother liquor, it will be treated together with the mother liquor as it enters its own purification process, thus not adding any new burden to the system. This "waste treatment with waste" design is a manifestation of highly integrated, resource internalization utilization system engineering thinking. It turns a difficult solvent regeneration problem into an internal material allocation process with no cost and no new pollution, thus overturning the traditional linear processing mode of "pollution-waste-replacement", which is the core innovation of the invention in building a circular economy system.

[0143] The preparation process of recovering dimethyl sulfoxide from a dimethyl sulfoxide mother liquor described below can be mutually corresponding with the above-described dimethyl sulfoxide mother liquor recovering dimethyl sulfoxide.

[0144] The specific steps are as follows:

[0145] S1. Multidimensional diagnosis: measure the water content, total alcohol ether organic impurity content and specific key impurity content in the dimethyl sulfoxide mother liquor to be treated, and select the subsequent process path and the corresponding extractant according to the preset criteria;

[0146] S2. Extraction separation: after preheating the mother liquor using the heat generated by step S3, countercurrent extraction is performed using the extractant selected in step S1 to obtain a raffinate phase rich in dimethyl sulfoxide and an extract phase loaded with impurities;

[0147] S3. Distillation purification: the raffinate phase is subjected to vacuum distillation, and dimethyl sulfoxide product is obtained at the bottom of the column. The heat of the overhead vapor is used for preheating in step S2;

[0148] S4. Extractant recovery and circulation: the extract phase is subjected to distillation to recover the extractant; part of the residue at the bottom of the recovery column is returned to the extraction unit of step S2; and side-draw is performed at the middle section of the recovery column to enrich and discharge impurities;

[0149] S5. Cross-path collaborative regeneration: part of the extractant recycled in step S4 is mixed and washed with a high-water-content mother liquor to achieve purification and regeneration of the extractant.

[0150] Although embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for recovering dimethyl sulfoxide from a dimethyl sulfoxide mother liquor, characterized by, Comprise: dimethyl sulfoxide: 50-70 parts; water: 30-50 parts; and an extractant selected from aromatic hydrocarbon solvents and ether solvents: 0.1-1.0 parts.

2. A process for recovery of dimethylsulfoxide from dimethylsulfoxide mother liquor as claimed in claim 1 wherein, The aromatic hydrocarbon solvent is xylene, and the ether solvent is methyl tert-butyl ether.

3. A preparation process for recovering dimethyl sulfoxide from the mother liquor of dimethyl sulfoxide as described in claim 1, characterized in that, Comprise the following steps: S1. Multidimensional diagnosis: determine the water content, total alcohol ether organic impurity content and specific key impurity content in the dimethyl sulfoxide mother liquor to be treated, and select the subsequent process path and the corresponding extractant according to the preset criterion; S2. Extractive separation: after preheating the mother liquor using the heat generated in step S3, countercurrent extraction is performed using the extractant selected in step S1 to obtain a dimethyl sulfoxide-rich raffinate phase and an impurity-loaded extract phase; S3. Purification by rectification: the raffinate phase is subjected to vacuum rectification, and dimethyl sulfoxide product is obtained from the column bottom, and the heat of the overhead vapor is used for preheating in step S2; S4. Extractant recovery and recycling: the extract phase is subjected to rectification to recover the extractant; part of the residue from the column bottom is returned to the extraction unit in step S2; and side-draw is performed at the middle section of the recovery column to enrich and discharge impurities; S5. Cross-path collaborative regeneration: part of the extractant recycled in step S4 is mixed with a high-water mother liquor to achieve purification and regeneration of the extractant.

4. The manufacturing process of claim 3, wherein, The preset criterion in step S1 comprises: when the water content is not less than 75% and the specific key impurity content is less than 0.8%, xylene is selected as the extractant; when the water content is not more than 30% and the total alcohol ether organic impurity content is not less than 10%, methyl tert-butyl ether is selected as the extractant; when the water content is between 30% and 75% or the specific key impurity content is not less than 0.8%, xylene is first used for pretreatment extraction, and then methyl tert-butyl ether is used for main extraction.

5. The manufacturing process of claim 3, wherein, The preheating temperature in step S2 is 40-60°C; the volume ratio of the extractant to the mother liquor is 1:1 to 5:

1.

6. The manufacturing process of claim 3, wherein, The absolute pressure of the vacuum rectification in step S3 is 5-20 kPa, and the column bottom temperature is 10-140°C.

7. The manufacturing process of claim 3, wherein, The amount of column bottom residue returned to the extraction unit in step S4 is 5-15% of the fresh extractant supplement amount.

8. The manufacturing process of claim 3, wherein, The side-draw position in step S4 is set at 1 / 3 to 1 / 2 of the theoretical tray number from the top of the recovery column.

9. The manufacturing process of claim 3, wherein, The collaborative regeneration in step S5 is triggered when the hydrophilic impurity concentration in the recycled extractant exceeds 1.5-2.5%.

10. The manufacturing process of claim 3, wherein, The mixing volume ratio of the part of the extractant to the high-water mother liquor in step S5 is 1:8 to 1:3.

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