Dimethyl sulfoxide recovery device and method

Abstract

The invention relates to the technical field of dimethyl sulfoxide recovery and purification, and discloses a dimethyl sulfoxide recovery device and method. The device comprises a first buffer tank, a first distillation tower, a second buffer tank, a second distillation tower, a third distillation tower, a product recovery unit and an automatic control unit, which are sequentially connected in series along a material flow direction. The product recovery unit comprises a qualified product tank and an unqualified product tank. A pH value automatic control unit arranged in the second buffer tank, a temperature difference automatic control unit arranged in the second distillation tower, and an automatic control unit arranged in a discharge system of the third distillation tower constitute the automatic control unit. The automatic control unit automatically adjusts and detects the distillation system online, stably controls the operation of the distillation device, and ensures that a stable high-purity DMSO product is obtained through the discharge automatic control unit of the product tower. The invention improves the utilization rate of raw materials, reduces safety risks, and ensures the safe, stable and continuous operation of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of dimethyl sulfoxide recovery and purification, and in particular to a dimethyl sulfoxide recovery device and method. Background Art

[0002] Dimethyl sulfoxide (DMSO) is a transparent, colorless, odorless, slightly bitter, highly polar aprotic solvent. It has the characteristics of high polarity, high hygroscopicity, high boiling point, flammability and low toxicity. It can dissolve various polar organic gases, liquids or polymers other than alkanes. It is known as the "universal solvent" and is widely used in many fields such as pesticides, medicines, electronic materials and carbon fibers.

[0003] In the field of carbon fiber, DMSO is a good solvent for polyacrylonitrile-based carbon fiber and plays a vital role in the production process of carbon fiber precursor. A large amount of DMSO is used in the polymerization reaction and coagulation bath drawing process, and the direct discharge of waste liquid containing DMSO will cause environmental pollution and affect the health of animals and plants. In the industrial equipment for carbon fiber production, the recycled dimethyl sulfoxide accounts for more than 90% of the total solvent demand, which directly affects the production cost of carbon fiber; recovering and separating DMSO solvent for recycling can greatly improve the efficiency of raw material use and generate huge economic benefits. At the same time, it also reduces the pollution of waste solvents to the environment and relieves the pressure of environmental protection; therefore, DMSO solvent recovery is an important production unit in the carbon fiber device.

[0004] The dimethyl sulfoxide (DMSO) solvent introduces some impurities during the polymerization process and cannot be directly recycled. It needs to be refined to remove impurities such as organic matter, acrylonitrile polymer, metal ions and water. Due to the decomposition of DMSO at high temperature or under acidic conditions, light component impurities such as dimethyl sulfide and dimethyl sulfide will be produced, which has a strong impact on the quality of the DMSO product recovered. Improper disposal can also cause fire and even cause explosion, and there is a large production safety hazard. According to existing literature reports, in the refining process of DMSO, alkaline inhibitors such as sodium hydroxide and sodium carbonate are added to prevent the decomposition of DMSO, but this method can bring new problems, namely, scaling and crystallization accumulation may occur at the reboiler heat transfer surface, tray, packing layer, etc. of the rectifying tower, which increases the safety and environmental protection risk of separation.

[0005] Strictly controlling the content of salt substances in the material, increasing the safety of the dimethyl sulfoxide recovery system and the stability of the dimethyl sulfoxide recovery quality are key issues in the dimethyl sulfoxide recovery process. Summary of the Invention

[0006] The present invention aims to overcome the problems of insecurity in the prior art dimethyl sulfoxide aqueous solution recovery and refining process and the instability of the quality of the DMSO recovered product, and to provide a dimethyl sulfoxide recovery device and method. The present invention improves the raw material utilization rate, reduces safety risks, and ensures the safe, stable and continuous operation of the system.

[0007] To achieve the above objectives, the present invention provides a dimethyl sulfoxide recovery device, which includes: a first buffer tank, a first distillation tower, a second buffer tank, a second distillation tower, a third distillation tower, a product recovery unit, and an automatic control unit, which are sequentially connected in series along the material flow direction. The product recovery unit includes a qualified product tank and an unqualified product tank. The dimethyl sulfoxide aqueous solution contains organic impurities, metal impurities, dimethyl sulfoxide, and water.

[0008] The first buffer tank sends the dimethyl sulfoxide aqueous solution into the first distillation tower for first distillation, and removes water and some impurities from the top of the tower;

[0009] The second buffer tank is used to fully contact the first concentrated liquid from the first distillation tower with the treatment agent to obtain a first mixed liquid;

[0010] The second distillation tower is used to perform a second distillation on the first mixed liquid, and further remove water and impurities from the top of the tower;

[0011] The third distillation tower is used to perform a third distillation on the second concentrated liquid from the second distillation tower to further remove heavy impurities and water to obtain a dimethyl sulfoxide recovery product;

[0012] The automatic control unit comprises:

[0013] A pH value automatic control unit provided at the outlet of the second buffer tank;

[0014] A temperature difference automatic control unit is provided in the second distillation tower;

[0015] A discharge automatic control unit is provided on the extraction pipeline of the condenser of the third distillation tower, wherein the discharge automatic control unit comprises a signal processor and an automatic regulating three-way valve connected to the product recovery unit;

[0016] The pH value automatic control unit, the temperature difference automatic control unit and the automatic regulating three-way valve are each electrically connected to the signal processor; the pH value automatic control unit includes an online pH meter for collecting the pH value of the material at the outlet of the second buffer tank and providing a pH control variable to the signal processor according to the pH value;

[0017] The temperature difference automatic control unit is used to collect the temperature difference value of the second distillation tower and provide the temperature control variable to the signal processor according to the temperature difference value;

[0018] The signal processor is used to receive the pH control variable from the pH value automatic control unit and the temperature control variable from the temperature difference automatic control unit, compare the two to see whether they meet the requirements, select one of the control variables to execute, and automatically adjust the connection direction of the three-way valve;

[0019] When the signal processor determines that the pH control variable and the temperature control variable both reach the set range, the automatic adjustment three-way valve automatically connects to the qualified product tank; when either the pH value variable or the temperature difference variable cannot meet the set range, the automatic adjustment three-way valve automatically connects to the unqualified product tank.

[0020] Preferably, the temperature difference automatic control unit includes a lower temperature control point arranged at the bottom of the second distillation tower and an upper temperature control point arranged at 1 to 6 theoretical plates away from the lower temperature control point, and a calculation unit for calculating the difference between the lower temperature control point and the upper temperature control point; preferably, the upper temperature control point is arranged at 2 to 5 theoretical plates away from the lower temperature control point, and more preferably, the upper temperature control point is arranged at 3 to 4 theoretical plates away from the lower temperature control point.

[0021] Preferably, the outlet of the unqualified product tank is connected to the inlet of the second buffer tank, so as to send the unqualified dimethyl sulfoxide recovery product into the second buffer tank to be mixed with the first concentrated liquid and the treatment agent and then continue to be recovered.

[0022] Preferably, the top of the second distillation tower is connected to a first buffer tank for recovering part of the dimethyl sulfoxide distilled from the top of the second distillation tower to the first buffer tank.

[0023] A second aspect of the present invention provides a method for recovering dimethyl sulfoxide, which is implemented by the recovery device of the present invention and at least comprises the following steps:

[0024] 1) a dimethyl sulfoxide aqueous solution passes through a first buffer tank and enters a first distillation tower for first distillation to obtain a first concentrated solution, and the first concentrated solution is sent to a second buffer tank; the dimethyl sulfoxide aqueous solution contains organic impurities, metallic impurities, dimethyl sulfoxide, and water;

[0025] 2) mixing the treatment agent introduced through the treatment agent supply line with the first concentrated liquid described in step 1) in a second buffer tank to obtain a first mixed liquid, and adjusting and collecting a pH value signal of the first mixed liquid at the outlet of the second buffer tank using a pH value automatic control unit, and sending the pH value signal to the signal processor;

[0026] 3) feeding the first mixed liquid described in step 2) into a second distillation tower for second distillation to obtain a second concentrated liquid and a second light fraction, and collecting a temperature difference signal of the second distillation tower through a temperature difference automatic control unit, and sending the temperature difference signal to the signal processor;

[0027] 4) feeding the second concentrated liquid described in step 3) into a third distillation tower for third distillation to obtain a dimethyl sulfoxide recovery product;

[0028] 5) if the signal processor determines that the pH value in step 2) reaches the pH setting range and the temperature difference value in step 3) reaches the temperature difference setting range, then the three-way valve of the discharge automatic control unit provided on the extraction pipeline of the condenser of the third distillation tower is controlled to connect to the qualified product tank, otherwise, the three-way valve is controlled to connect to the unqualified product tank;

[0029] Optionally, the dimethyl sulfoxide recovered product in the unqualified product tank in step 5) is sent to the second buffer tank in step 1) to be mixed with the first concentrated liquid and the treatment agent and then further recovered.

[0030] Preferably, in step 5), the pH setting range is 7-12, preferably 8-11, more preferably 8-10, and the temperature difference setting range is 0-10°C, preferably 1-8°C, more preferably 1-5°C.

[0031] Preferably, in step 2), the treatment agent is selected from at least one of aqueous ammonia, aqueous sodium hydroxide solution, aqueous sodium carbonate solution, aqueous potassium hydroxide solution, aqueous potassium carbonate solution and aqueous calcium hydroxide solution; preferably, the treatment agent is at least one of aqueous ammonia and aqueous sodium carbonate solution, and more preferably, the concentration of aqueous ammonia and / or aqueous sodium carbonate solution is 0.2 to 20 wt % respectively.

[0032] Preferably, in the dimethyl sulfoxide aqueous solution in step 1), the dimethyl sulfoxide content is ≤85wt%, preferably 5-80wt%, more preferably the water content in the dimethyl sulfoxide aqueous solution is ≥10wt%, further preferably 20-95wt%.

[0033] Preferably, the conditions of the first distillation in step 1) include: pressure of 5-25 kPa, preferably 5-15 kPa, bottom temperature of 85-120° C., preferably 90-110° C.; and reflux ratio of 0.1-1, preferably 0.1-0.5.

[0034] Preferably, the content of dimethyl sulfoxide in the first concentrated solution is 85-95 wt%, preferably 90-95 wt%.

[0035] Preferably, the conditions of the second distillation include: top pressure of 1-10 kPa, preferably 3-6 kPa; bottom temperature of 90-120°C, preferably 95-110°C; top temperature range of 30-50°C, and reflux ratio of 0.25-3, preferably 0.25-1.

[0036] Preferably, the content of dimethyl sulfoxide in the second concentrated solution is 97-99.5 wt %, preferably 98.5-99.5 wt %.

[0037] Preferably, the second light fraction is mixed with the dimethyl sulfoxide aqueous solution in step 1) in the first buffer tank and then enters the first distillation tower to continue the subsequent reaction. Preferably, the dimethyl sulfoxide content in the second light fraction is 1-30 wt%.

[0038] Preferably, the conditions of the third distillation include: pressure of 1-8 kPa, preferably 3-6 kPa; bottom temperature of 90-120° C., preferably 95-110° C.; and reflux ratio of 0.25-5, preferably 0.5-3.

[0039] Preferably, in the dimethyl sulfoxide recovered product from the qualified product tank in step 5), the dimethyl sulfoxide content is 99.85-99.99 wt %, preferably 99.9-99.99 wt %.

[0040] Preferably, the water content in the recovered dimethyl sulfoxide product is ≤500 ppm.

[0041] The present invention mainly focuses on distillation, and accurately controls the process conditions of distillation through an automatic control unit, effectively avoiding the decomposition of DMSO, alleviating the accumulation of treatment agents such as inorganic bases / salts in the tower bottom, reducing the risk of explosion, and improving the safety of the DMSO refining process; the present invention has the advantage of being simple in process flow, being able to stably obtain high-purity DMSO products, and meeting the recovery requirements of high-end DMSO products.

[0042] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The figure is an overall schematic diagram of a dimethyl sulfoxide recovery device according to one embodiment of the present invention.

[0044] Description of Reference Numerals

[0045] 1. Dimethyl sulfoxide aqueous solution 2. First buffer tank 3. First light fraction

[0046] T1, first distillation tower 4, first concentrated liquid T2, second distillation tower

[0047] 5. Treatment agent 6. Second buffer tank 7. First mixed liquid

[0048] 9. Second light fraction 10. Second concentrated liquid T3. Third distillation tower

[0049] 11. Third light fraction 12. Heavy fraction 13. Qualified product tank

[0050] 14. Unqualified product tank 15. Treatment agent pump 16. pH value automatic control unit

[0051] 17. Temperature difference automatic control unit 18. Discharging automatic control unit 19. Automatic control system DETAILED DESCRIPTION

[0052] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0053] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0054] In the present invention, unless otherwise specified, directional words such as "up, down, left, right" generally refer to the up, down, left, and right shown in the reference drawings; "inside and outside" refer to the inside and outside relative to the outline of each component itself. In the present invention, unless otherwise specified, the "bottom" of a container refers to the position 90-100% from top to bottom of the container; the "top" of a container refers to the position 0-10% from top to bottom of the container; the "upper part" of a container refers to the position 0-30% from top to bottom of the container; and the "middle part" of a container refers to the position 30-70% from top to bottom of the container.

[0055] like Figure 1 As shown, one aspect of the present invention provides a dimethyl sulfoxide recovery device, which includes: a first buffer tank 2, a first distillation tower T1, a second buffer tank 6, a second distillation tower T2, a third distillation tower T3, a product recovery unit and an automatic control unit 19, which are sequentially connected in series along the material flow direction. The product recovery unit includes: a qualified product tank 13 and an unqualified product tank 14; the dimethyl sulfoxide aqueous solution 1 contains organic impurities, metal impurities, dimethyl sulfoxide and water; the first buffer tank 2 feeds the dimethyl sulfoxide aqueous solution 1 into the first distillation tower T1 for first distillation, and removes water and some impurities from the top of the tower;

[0056] The second buffer tank 6 is used to fully contact the first concentrated liquid from the first distillation tower T1 with the treatment agent 5 to obtain a first mixed liquid 7;

[0057] The second distillation tower T2 is used to perform a second distillation on the first mixed liquid, and further remove water and impurities from the top of the tower;

[0058] The third distillation tower T3 is used to perform a third distillation on the second concentrated liquid 10 from the second distillation tower T2 to further remove the heavy component 12 impurities and water to obtain a dimethyl sulfoxide recovery product;

[0059] The automatic control unit 19 includes:

[0060] A pH value automatic control unit 16 is provided at the outlet of the second buffer tank 6;

[0061] A temperature difference automatic control unit 17 is provided in the second distillation tower T2;

[0062] A discharge automatic control unit 18 is provided on the extraction pipeline of the condenser of the third distillation tower T3, and the discharge automatic control unit 18 includes a signal processor and an automatic regulating three-way valve connected to the product recovery unit;

[0063] The pH value automatic control unit 16, the temperature difference automatic control unit 17 and the automatic regulating three-way valve are each electrically connected to the signal processor;

[0064] The pH value automatic control unit 16 includes an online pH meter for collecting the pH value of the material at the outlet of the second buffer tank 6 and providing a pH control variable to the signal processor according to the pH value;

[0065] The temperature difference automatic control unit 17 is used to collect the temperature difference value of the second distillation tower T2 and provide the temperature control variable to the signal processor according to the temperature difference value;

[0066] The signal processor is used to receive the pH control variable from the pH value automatic control unit 16 and the temperature control variable from the temperature difference automatic control unit 17, compare whether both meet the requirements, select one of the control variables to execute, and automatically adjust the connection direction of the three-way valve;

[0067] When the signal processor determines that the pH control variable and the temperature control variable both reach the set range, the automatic adjustment three-way valve automatically connects to the qualified product tank; when either the pH value variable or the temperature difference variable cannot meet the set range, the automatic adjustment three-way valve automatically connects to the unqualified product tank.

[0068] According to an embodiment of the present invention, the inlet of the first distillation tower T1 is connected to the outlet of the first buffer tank 2 .

[0069] According to an embodiment of the present invention, the inlet of the second buffer tank 6 is connected to the outlet of the bottom of the first distillation tower T1 and the supply pipeline of the treatment agent 5.

[0070] According to an embodiment of the present invention, the inlet of the second distillation tower T2 is connected to the outlet of the second buffer tank 2 .

[0071] According to an embodiment of the present invention, the inlet of the third distillation tower T3 is connected to the bottom outlet of the second distillation tower T2.

[0072] Each part can be added with various pipelines or valves and components that may be needed in the industry as needed. The present invention has no special requirements for this. For example, the present invention Figure 1 The CWS on the top pipeline of the distillation tower shown is a cooling water supply pipe, and the CWR is a cooling water return pipe. For ease of understanding, the dimethyl sulfoxide aqueous solution flowing out of the first buffer tank is defined as 1A.

[0073] This device automatically adjusts and detects the recovery system online through an automatic control unit, stably controls the vapor-liquid load of the distillation, and ensures that a stable high-purity DMSO product is obtained through the discharge automatic control unit of the product tower.

[0074] The present invention mainly focuses on distillation, and accurately controls the process conditions of distillation through an automatic control unit, effectively avoiding the decomposition of DMSO, alleviating the accumulation of treatment agents such as inorganic alkali / salts in the tower bottom, reducing the risk of explosion, and improving the safety and raw material utilization rate of the DMSO refining process; the present invention has a simple process flow, and the automatic control unit automatically adjusts and detects the recovery system online, so that high-purity DMSO products can be stably obtained, meeting the recovery requirements of high-end DMSO products.

[0075] According to a preferred embodiment of the present invention, the temperature difference automatic control unit 17 includes a lower temperature control point arranged at the bottom of the second distillation tower T2 and an upper temperature control point arranged at 1 to 6 theoretical plates away from the lower temperature control point, and a calculation unit for calculating the difference between the lower temperature control point and the upper temperature control point. Preferably, the upper temperature control point is arranged at 2 to 5 theoretical plates away from the lower temperature control point, and more preferably, the upper temperature control point is arranged at 3 to 4 theoretical plates away from the lower temperature control point.

[0076] According to a preferred embodiment of the present invention, the pH value automatic control unit includes an online pH meter, an alkaline solution pump and a signal transmitter arranged at the outlet of the second buffer tank.

[0077] According to a preferred embodiment of the present invention, a treatment agent pump 15 is provided on the treatment agent 5 supply pipeline, and preferably, a pH signal is linked to the treatment agent pump 15 for control.

[0078] According to a preferred embodiment of the present invention, the outlet of the unqualified product tank 14 is connected to the inlet of the second buffer tank 6, so as to send the unqualified dimethyl sulfoxide recovery product into the second buffer tank 6 to be mixed with the first concentrated liquid and the treatment agent 5 and then continue the subsequent reaction.

[0079] According to a preferred embodiment of the present invention, the top of the second distillation tower T2 is connected to the first buffer tank 2 for recovering part of the dimethyl sulfoxide distilled from the top of the second distillation tower T2 into the first buffer tank 2.

[0080] The dimethyl sulfoxide recovery method of the present invention is implemented by the recovery device of the present invention and comprises at least the following steps:

[0081] 1) The dimethyl sulfoxide aqueous solution passes through the first buffer tank 2 and enters the first distillation tower T1 for first distillation to obtain a first concentrated liquid, which is then sent to the second buffer tank 6;

[0082] 2) the treatment agent 5 introduced through the treatment agent 5 supply pipeline is mixed with the first concentrated solution described in step 1) in the second buffer tank 6 to obtain a first mixed solution 7, and the pH value signal of the first mixed solution at the outlet of the second buffer tank 6 is adjusted and collected by the pH value automatic control unit 16, and the pH value signal is sent to the signal processor; the dimethyl sulfoxide aqueous solution 1 contains organic impurities, metallic impurities, dimethyl sulfoxide and water;

[0083] 3) feeding the first mixed liquid described in step 2) into a second distillation tower T2 for second distillation to obtain a second concentrated liquid 10 and a second light fraction 9, and collecting a temperature difference signal of the second distillation tower T2 through a temperature difference automatic control unit 17, and sending the temperature difference signal to the signal processor;

[0084] 4) sending the second concentrated liquid described in step 3) into the third distillation tower T3 for third distillation to obtain a dimethyl sulfoxide recovery product;

[0085] 5) If the signal processor determines that the pH value in step 2) reaches the pH setting range and the temperature difference value in step 3 reaches the temperature difference setting range, the three-way valve of the discharge automatic control unit 18 provided on the extraction pipeline of the condenser of the third distillation tower T3 is controlled to connect the qualified product tank 13, otherwise, the unqualified product tank 14 is connected;

[0086] Optionally, the dimethyl sulfoxide recovered product in the unqualified product tank 13 in step 5) is sent to the second buffer tank 6 in step 1 and mixed with the first concentrated liquid and the treatment agent 5 to continue recovery.

[0087] In the present invention, unless otherwise specified, the dimethyl sulfoxide content in the dimethyl sulfoxide aqueous solution 1 and the first concentrated solution is determined independently by using a refractometer and an external standard method; the water content in the dimethyl sulfoxide aqueous solution 1 and the first concentrated solution is determined independently by using a subtraction method, and the influence of organic trace impurities is ignored.

[0088] The present invention mainly focuses on distillation, and accurately controls the process conditions of distillation through an automatic control unit, effectively avoiding the decomposition of DMSO, alleviating the accumulation of treatment agents such as inorganic bases / salts in the tower bottom, reducing the risk of explosion, and improving the safety of the DMSO refining process. The process flow of the present invention is simple, and a high-purity DMSO product can be stably obtained, meeting the demand for high-end DMSO products.

[0089] According to a preferred embodiment of the present invention, in step 5), the pH setting range is 7-12, preferably 8-11, more preferably 8-10, and the temperature difference setting range is 0-10°C, preferably 1-8°C, more preferably 1-5°C.

[0090] According to a preferred embodiment of the present invention, the treatment agent 5 in step 2 is selected from at least one of ammonia water, sodium hydroxide aqueous solution, sodium carbonate aqueous solution, potassium hydroxide aqueous solution, potassium carbonate aqueous solution and calcium hydroxide aqueous solution. Preferably, the treatment agent 5 is at least one of ammonia water and sodium carbonate aqueous solution, and more preferably, the concentration of ammonia water and / or sodium carbonate aqueous solution is 0.2 to 20 wt % respectively.

[0091] According to a preferred embodiment of the present invention, in the dimethyl sulfoxide aqueous solution 1 of step 1, the dimethyl sulfoxide content is ≤85wt%, preferably 5-80wt%, more preferably the water content in the dimethyl sulfoxide aqueous solution 1 is ≥10wt%, further preferably 20-95wt%.

[0092] According to a preferred embodiment of the present invention, the conditions of the first distillation in step 1 include: pressure of 5-25 kPa, preferably 5-15 kPa; bottom temperature of 85-120°C, preferably 90-110°C; reflux ratio of 0.1-1, preferably 0.1-0.5.

[0093] According to a preferred embodiment of the present invention, the content of dimethyl sulfoxide in the first concentrated solution is 85-95 wt%, preferably 90-95 wt%.

[0094] According to a preferred embodiment of the present invention, the conditions of the second distillation include: top pressure of 1-10 kPa, preferably 3-6 kPa; bottom temperature of 90-120°C, preferably 95-110°C; top temperature range of 30-50°C; reflux ratio of 0.25-3, preferably 0.25-1.

[0095] According to a preferred embodiment of the present invention, the content of dimethyl sulfoxide in the second concentrated solution is 97-99.5 wt %, preferably 98.5-99.5 wt %.

[0096] According to a preferred embodiment of the present invention, the second light fraction is mixed with the dimethyl sulfoxide aqueous solution in step 1 in the first buffer tank 2 and then enters the first distillation tower T1 for subsequent recovery. Preferably, the dimethyl sulfoxide content in the second light fraction is 1 to 30 wt%.

[0097] According to a preferred embodiment of the present invention, the conditions of the third distillation include: pressure of 1-8 kPa, preferably 3-6 kPa; bottom temperature of 90-120°C, preferably 95-110°C; reflux ratio of 0.25-5, preferably 0.5-3.

[0098] According to a preferred embodiment of the present invention, the dimethyl sulfoxide content in the dimethyl sulfoxide recovered product in the qualified product tank 13 in step 5 is 99.85-99.99wt%, preferably 99.9-99.99wt%.

[0099] According to a preferred embodiment of the present invention, preferably, the water content in the dimethyl sulfoxide recovered product is ≤500 ppm.

[0100] The present invention will be described in detail below through examples, but the scope of protection claimed in the present invention is not limited to the scope described in the examples.

[0101] In the Examples and Comparative Examples, organic impurities and metallic impurities in the dimethyl sulfoxide aqueous solution were negligible;

[0102] The dimethyl sulfoxide content in the dimethyl sulfoxide aqueous solution and the first concentrated solution is determined independently by using a refractometer and an external standard method, and the water content in the dimethyl sulfoxide aqueous solution and the first concentrated solution is determined independently by using a subtraction method;

[0103] The dimethyl sulfoxide content in the second concentrated liquid and the dimethyl sulfoxide recovery product is determined with reference to GB / T21395-2008; the water content in the dimethyl sulfoxide recovery product is determined using a moisture meter.

[0104] The following examples adopt Figure 1 The recovery device and process shown are as follows:

[0105] like Figure 1As shown, a preferred dimethyl sulfoxide recovery device provided by the present invention includes a first buffer tank 2, which is connected to a first distillation tower T1 through a pipeline. The first distillation tower T1 is used to perform a first distillation on a dimethyl sulfoxide aqueous solution 1, and a first concentrated liquid 4 is obtained at the bottom of the tower, and a first light fraction 3 is obtained at the top of the tower; the bottom of the first distillation tower T1 is connected to a second buffer tank 6 through a pipeline, and the first concentrated liquid 4 enters the second buffer tank 6 and is fully contacted with a treatment agent 5 to obtain a first mixed liquid 7; the outlet of the second buffer tank 6 is provided with a pH meter for monitoring the pH value of the first mixed liquid 7; the outlet of the second buffer tank 6 is connected to the middle inlet of the second distillation tower T2 via a pipeline, for subjecting the first mixed liquid 7 to a second distillation, obtaining a second concentrated liquid 10 in the bottom of the tower and a second light fraction 9 at the top of the tower; the bottom of the second distillation tower T2 is connected to the inlet of the third distillation tower T3, and the bottom of the second distillation tower T2 is connected to the middle of the third distillation tower T3, for subjecting the second concentrated liquid 10 to a third light fraction 11 at the top of the tower;

[0106] The device further comprises a pH value automatic control unit 16 provided in the second buffer tank, a temperature difference automatic control unit 17 provided in the second distillation tower, and an automatic control unit 18 provided in the discharge system of the third distillation tower. These three units constitute an automatic control unit 19.

[0107] The pH value automatic control unit includes an online pH meter and an alkali solution pump located at the outlet of the second buffer tank. The pH signal is interlocked with the treatment agent pump 15 and transmitted to the signal processor described below. The temperature difference automatic control unit mainly includes an upper temperature control point and a lower temperature control point. The lower temperature control point of the second distillation tower is located at the bottom of the tower. The number of theoretical plates between the upper and lower temperature control points is approximately 3 to 5 theoretical plates, and more preferably 4 plates. The temperature difference is automatically interlocked with the heat source, and the temperature difference signal is transmitted to the signal processor described below. The automatic discharge adjustment unit includes a signal processor and an automatic adjustment three-way valve.

[0108] An online pH meter collects the pH value of the material at the outlet of the second buffer tank and provides a pH control variable to the signal processor based on the pH value; a temperature difference controller collects the temperature difference value of the second distillation tower and provides a temperature control variable to the following signal processor based on the temperature difference value; the signal processor receives the pH control variable from the pH controller and the temperature control variable from the thermometer, compares the two to see whether they meet the requirements, selects one of the control variables to execute, and automatically adjusts the connection direction of the three-way valve.

[0109] When the signal processor determines that the pH value variable and the temperature difference variable both reach the set range, the automatic adjustment three-way valve automatically connects to the qualified product tank; when either the pH value variable or the temperature difference variable cannot meet the set range, the automatic adjustment three-way valve automatically connects to the unqualified product tank.

[0110] Example 1

[0111] A raw material dimethyl sulfoxide aqueous solution with a dimethyl sulfoxide content of 50wt% enters a first distillation tower T1 and is subjected to a first distillation at a pressure of 15kPa and a bottom temperature of 105°C; a reflux ratio of 0.5 is used to obtain a first concentrated liquid and a first light fraction 3; 1wt% diluted ammonia water is fully mixed with the first concentrated liquid in a second buffer tank 6 to obtain a first mixed liquid 7, with a pH setting range of 8-10; the first mixed liquid enters a second distillation tower T2 and is subjected to a second distillation at a pressure of 9kPa, a bottom temperature of 120°C, and a reflux ratio of 1; the temperature difference setting range of the second distillation tower T2 does not exceed 8°C, and a second concentrated liquid with a water content of 789ppm is obtained in the bottom of the tower. The second concentrated liquid is added to a third distillation tower T3 and subjected to a third distillation and purification at a pressure of 5kPa, a bottom temperature of 105°C, and a reflux ratio of 2, to obtain a dimethyl sulfoxide recovery product at the top of the tower. Gas chromatography analysis showed that the recovered product obtained from the qualified dimethyl sulfoxide product tank had a dimethyl sulfoxide content of 99.83 wt % and a water content of 893 ppm.

[0112] Example 2

[0113] A raw material dimethyl sulfoxide aqueous solution with a dimethyl sulfoxide content of 50wt% enters a first distillation tower T1 and is distilled at a pressure of 20kPa and a bottom temperature of 112°C; a reflux ratio of 0.2 is used to obtain a first concentrated liquid and a first light fraction 3; a 2wt% Na2CO3 aqueous solution is fully mixed with the first concentrated liquid in a second buffer tank 6 to obtain a first mixed liquid 7, with a pH setting range of 9-11; the first mixed liquid enters a second distillation tower T2 and is distilled at a pressure of 8kPa, a bottom temperature of 118°C, and a reflux ratio of 2; the temperature difference setting value range of the second distillation tower T2 does not exceed 3°C, and a second concentrated liquid with a water content of 450ppm is obtained in the bottom of the tower. The second concentrated liquid is added to a third distillation tower and subjected to a third distillation purification at a pressure of 6kPa, a bottom temperature of 108°C, and a reflux ratio of 2, and a dimethyl sulfoxide recovery product is obtained at the top of the tower. Gas chromatography analysis showed that the recovered product obtained from the qualified dimethyl sulfoxide product tank had a dimethyl sulfoxide content of 99.89 wt % and a water content of 518 ppm.

[0114] Example 3

[0115] A raw material dimethyl sulfoxide aqueous solution with a dimethyl sulfoxide content of 50wt% enters the first distillation tower T1, and is distilled at a pressure of 20kPa and a bottom temperature of 112°C; a reflux ratio of 0.2 is used to obtain a first concentrated liquid and a first light fraction 3; 1wt% ammonia water and 10wt% Na2CO3 aqueous solution are configured into a treating agent in a 1:1 ratio, and the treating agent is fully mixed with the first concentrated liquid in a second buffer tank 6 to obtain a first mixed liquid 7, with a pH setting range of 9-10; the first mixed liquid enters the second distillation tower T2, and is subjected to a second distillation at a pressure of 8kPa, a bottom temperature of 118°C, and a reflux ratio of 2; the temperature difference setting value range of the second distillation tower T2 does not exceed 1°C, and a second concentrated liquid with a water content of 270ppm is obtained in the bottom of the tower. The second concentrated liquid is added to the third distillation tower, and a third distillation purification is carried out at a pressure of 5kPa, a bottom temperature of 105°C, and a reflux ratio of 2, and a dimethyl sulfoxide recovery product is obtained at the top of the tower. Gas chromatography analysis showed that the recovered product obtained from the qualified dimethyl sulfoxide product tank had a dimethyl sulfoxide content of 99.88 wt % and a water content of 587 ppm.

[0116] Example 4

[0117] A raw material dimethyl sulfoxide aqueous solution containing 50 wt% dimethyl sulfoxide content enters a first distillation tower T1 and undergoes a first distillation at a pressure of 15 kPa and a bottom temperature of 105°C; a reflux ratio of 0.5 to obtain a first concentrated solution and a first light fraction 3; 1 wt% diluted ammonia water is thoroughly mixed with the first concentrated solution in a second buffer tank 6 to obtain a first mixed solution 7 with a pH setting range of 6.5-7.9; the first mixed solution enters a second distillation tower T2 and undergoes a second distillation at a pressure of 9 kPa, a bottom temperature of 120°C, and a reflux ratio of 1; the temperature difference setting range of the second distillation tower T2 does not exceed 8°C, and a second concentrated solution with a water content of 1850 ppm is obtained in the bottom of the tower. The second concentrated solution is added to a third distillation tower T3 and subjected to a third distillation and purification at a pressure of 5 kPa, a bottom temperature of 105°C, and a reflux ratio of 2, to obtain a dimethyl sulfoxide recovery product at the top of the tower. Gas chromatography analysis showed that the recovered product obtained from the qualified dimethyl sulfoxide product tank had a dimethyl sulfoxide content of 98.60 wt % and a water content of 5320 ppm.

[0118] Example 5

[0119] A raw material dimethyl sulfoxide aqueous solution with a dimethyl sulfoxide content of 50wt% enters a first distillation tower T1 and is subjected to a first distillation at a pressure of 15kPa and a bottom temperature of 105°C; a reflux ratio of 0.5 is used to obtain a first concentrated liquid and a first light fraction 3; 1wt% diluted ammonia water is fully mixed with the first concentrated liquid in a second buffer tank 6 to obtain a first mixed liquid 7, with a pH setting range of 8-10; the first mixed liquid enters a second distillation tower T2 and is subjected to a second distillation at a pressure of 9kPa, a bottom temperature of 120°C, and a reflux ratio of 1; the temperature difference of the second distillation tower T2 is set at 11°C, and a second concentrated liquid with a water content of 0.6% is obtained in the bottom of the tower. The second concentrated liquid is added to a third distillation tower T3 and subjected to a third distillation and purification at a pressure of 5kPa, a bottom temperature of 105°C, and a reflux ratio of 2, to obtain a dimethyl sulfoxide recovery product at the top of the tower. Gas chromatography analysis showed that the recovered product obtained from the qualified dimethyl sulfoxide product tank had a dimethyl sulfoxide content of 97.34 wt % and a water content of 2.5 %.

[0120] Comparative Example 1

[0121] A raw material dimethyl sulfoxide aqueous solution with a dimethyl sulfoxide content of 50wt% enters the first distillation tower T1, and is subjected to a first distillation under a pressure of 15kPa and a bottom temperature of 105°C; a reflux ratio of 0.5 to obtain a first concentrated solution and a first light fraction 3; 1wt% diluted ammonia water is fully mixed with the first concentrated solution in a second buffer tank 6 to obtain a first mixed solution 7, where there is no pH automatic control unit; the first mixed solution enters the second distillation tower T2, and is subjected to a second distillation under a pressure of 9kPa, a bottom temperature of 120°C, and a reflux ratio of 1; the second distillation tower T2 has no temperature difference control unit, and other process conditions are the same as in Example 1. The dimethyl sulfoxide recovery product is obtained at the top of the third distillation tower. Gas chromatography analysis shows that the dimethyl sulfoxide moisture and organic impurity content in the dimethyl sulfoxide recovery product fluctuate, the product quality is unstable, and the batch difference is large.

[0122] By comparison, it is shown that the present invention has the advantage of being able to stably obtain high-purity DMSO products.

[0123] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention may be subjected to various simple modifications, including combining the specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A dimethyl sulfoxide recovery device, characterized in that, The device includes: A first buffer tank (2), a first distillation tower (T1), a second buffer tank (6), a second distillation tower (T2), a third distillation tower (T3), a product recovery unit and an automatic control unit (19) are sequentially connected in series along the material flow direction, wherein the product recovery unit comprises: a qualified product tank (13) and a unqualified product tank (14); a dimethyl sulfoxide aqueous solution (1) contains organic impurities, metal impurities, dimethyl sulfoxide and water; The first buffer tank (2) feeds the dimethyl sulfoxide aqueous solution (1) into the first distillation tower (T1) for first distillation, and removes water and some impurities at the top of the tower; The second buffer tank (6) is used to fully contact the first concentrated liquid (4) from the first distillation tower (T1) with the treatment agent (5) to obtain a first mixed liquid (7); The second distillation tower (T2) is used to perform a second distillation on the first mixed liquid, and further remove water and impurities from the top of the tower; The third distillation tower (T3) is used to perform a third distillation on the second concentrated liquid (10) from the second distillation tower (T2), further removing the heavy component (12) impurities and water to obtain a dimethyl sulfoxide recovery product; The automatic control unit (19) comprises: a pH value automatic control unit (16) provided at the outlet of the second buffer tank (6); A temperature difference automatic control unit (17) provided in the second distillation tower (T2); A discharge automatic control unit (18) is provided on the extraction pipeline of the condenser of the third distillation tower (T3), wherein the discharge automatic control unit (18) comprises a signal processor and an automatic regulating three-way valve connected to the product recovery unit; The pH value automatic control unit (16), the temperature difference automatic control unit (17) and the automatic regulating three-way valve are each electrically connected to the signal processor; The pH value automatic control unit (16) includes an online pH meter for collecting the pH value of the material at the outlet of the second buffer tank (6) and providing a pH control variable to the signal processor according to the pH value; The temperature difference automatic control unit (17) is used to collect the temperature difference value of the second distillation tower (T2) and provide the temperature control variable to the signal processor according to the temperature difference value; The signal processor is used to receive the pH control variable from the pH value automatic control unit (16) and the temperature control variable from the temperature difference automatic control unit (17), and select one of the control variables to execute by comparing whether the two meet the requirements, thereby automatically adjusting the connection direction of the three-way valve; When the signal processor determines that both the pH control variable and the temperature control variable have reached the set range, the three-way valve is automatically adjusted to connect to the qualified product tank; when either the pH value variable or the temperature difference variable fails to meet the set range, the three-way valve is automatically adjusted to connect to the unqualified product tank; The temperature difference automatic control unit (17) comprises a lower temperature control point arranged at the bottom of the second distillation tower (T2), an upper temperature control point arranged at a distance of 1 to 6 theoretical plates from the lower temperature control point, and a calculation unit for calculating the difference between the lower temperature control point and the upper temperature control point; The outlet of the unqualified product tank (14) is connected to the inlet of the second buffer tank (6), and is used to send the unqualified dimethyl sulfoxide recovery product into the second buffer tank (6) to be mixed with the first concentrated liquid (4) and the treatment agent (5) and then continue to be recovered.

2. The recovery device according to claim 1, wherein: The upper temperature control point is set at a distance of 2-5 theoretical plates from the lower temperature control point.

3. The recovery device according to claim 2, wherein: The upper temperature control point is set at a distance of 3 to 4 theoretical plates from the lower temperature control point.

4. The recovery device according to claim 1, wherein: The top of the second distillation tower (T2) is connected to the first buffer tank (2) for recovering part of the dimethyl sulfoxide distilled out along with water from the top of the second distillation tower (T2) into the first buffer tank (2).

5. A dimethyl sulfoxide recovery method, characterized in that, The method is implemented by the recovery device according to any one of claims 1 to 4, and comprises at least the following steps: 1) A dimethyl sulfoxide aqueous solution (1) passes through a first buffer tank (2) into a first distillation tower (T1) for first distillation to obtain a first concentrated liquid (4), and the first concentrated liquid is sent to a second buffer tank (6); the dimethyl sulfoxide aqueous solution contains organic impurities, metal impurities, dimethyl sulfoxide and water; 2) the treatment agent (5) introduced through the treatment agent (5) supply pipeline is mixed with the first concentrated liquid described in step 1) in the second buffer tank (6) to obtain a first mixed liquid (7), and the pH value signal of the first mixed liquid at the outlet of the second buffer tank (6) is adjusted and collected by the pH value automatic control unit (16), and the pH value signal is sent to the signal processor; 3) sending the first mixed liquid (7) described in step 2) into a second distillation tower (T2) for second distillation to obtain a second concentrated liquid (10) and a second light fraction (9), and collecting a temperature difference signal of the second distillation tower (T2) through a temperature difference automatic control unit (17), and sending the temperature difference signal to the signal processor; 4) sending the second concentrated liquid described in step 3) into a third distillation tower (T3) for third distillation to obtain a dimethyl sulfoxide recovery product; 5) if the signal processor determines that the pH value in step 2) reaches the pH setting range and the temperature difference value in step 3) reaches the temperature difference setting range, the three-way valve of the discharge automatic control unit (18) provided on the extraction pipeline of the condenser of the third distillation tower (T3) is controlled to connect the qualified product tank (13), otherwise, the unqualified product tank (14) is connected; The dimethyl sulfoxide recovered product in the unqualified product tank (14) in step 5) is sent to the second buffer tank (6) in step 1) to be mixed with the first concentrated liquid and the treatment agent (5) and then further recovered.

6. The method according to claim 5, wherein: Step 5) The pH setting range is 7-12, and the temperature difference setting range is 0-10°C.

7. The method according to claim 5, wherein: In step 2), the treatment agent (5) is selected from at least one of aqueous ammonia, aqueous sodium hydroxide solution, aqueous sodium carbonate solution, aqueous potassium hydroxide solution, aqueous potassium carbonate solution and aqueous calcium hydroxide solution.

8. The method according to claim 7, wherein: The treatment agent (5) is at least one of aqueous ammonia and aqueous sodium carbonate solution.

9. The method according to claim 8, wherein The concentration of the ammonia water and / or the sodium carbonate aqueous solution is 0.2 to 20 wt %.

10. The method according to claim 5, wherein In the dimethyl sulfoxide aqueous solution (1) of step 1), the dimethyl sulfoxide content is ≤85wt%.

11. The method according to claim 10, wherein: The water content in the dimethyl sulfoxide aqueous solution (1) is ≥10 wt%.

12. The method according to claim 5 or 10, wherein: Step 1) The conditions of the first distillation include: pressure of 5-25 kPa; bottom temperature of 85-120° C.; reflux ratio of 0.1-1; and / or The content of dimethyl sulfoxide in the first concentrated solution is 85-95 wt %.

13. The method according to claim 5, wherein: The conditions of the second distillation include: a tower top pressure of 1-10 kPa; a tower bottom temperature of 90-120° C.; a tower top temperature range of 30-50° C.; a reflux ratio of 0.25-3; and / or The content of dimethyl sulfoxide in the second concentrated solution is 97-99.5 wt %; and / or The second light fraction (9) is mixed with the dimethyl sulfoxide aqueous solution (1) in step 1) in the first buffer tank (2) and then enters the first distillation tower (T1) for subsequent recovery.

14. The method according to claim 13, wherein The content of dimethyl sulfoxide in the second light fraction is 1 to 30 wt %.

15. The method according to claim 5, wherein: The conditions of the third distillation include: pressure of 1-8 kPa; bottom temperature of 90-120° C.; reflux ratio of 0.25-5; and / or Step 5) The dimethyl sulfoxide content in the recovered product from the qualified product tank (13) is 99.85-99.99 wt%.

16. The method according to claim 15, wherein The water content in the dimethyl sulfoxide recovered product is ≤500ppm.

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