Pretreatment system for desalting salt-containing alcohol-water mixture

Abstract

The invention provides a pretreatment system for desalting a salt-containing alcohol-water mixture. The pretreatment system comprises a coarse separation tower and a dehydration tower, a bottom extraction port of the coarse separation tower is connected with an extraction port of the dehydration tower, and an extraction port at the bottom of the dehydration tower is connected with a coarse salt-containing mixture pipeline and a salt-containing pipeline; an extraction port at the top of the dehydrating tower is connected with an extraction port of the phase-splitting tank, an extraction port of the phase-splitting tank is connected with a water recycling pipeline and a return pipeline, and water, salt and fusel components are continuously separated and removed through the pretreatment system of the coarse separation tower and the dehydrating tower, so that equipment blockage is avoided, the separation energy consumption is reduced, and the operation intensity is reduced. The coarse separation tower and the dehydration tower have rectification and crystallization coupling effects, the purpose of separating water, salt and a target product can be achieved at the same time, the simplest process flow is achieved, the number of equipment is reduced, the occupied area is small, and the cost is further saved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical process equipment, and in particular to a pretreatment system for desalting a salt-containing alcohol-water mixture. Background Art

[0002] Polyols refer to alcohols containing two or more hydroxyl groups, with the general formula C n H 2n+2-x (OH) x (x≥2), its boiling point is higher than that of monohydric alcohol with the same number of carbon atoms, and its water solubility increases with the number of hydroxyl groups. The acetaldehyde condensation method is the main process for preparing polyols. Due to the addition of inorganic salts (such as NaOH, KOH aqueous solution) and inorganic acids (such as sulfuric acid, hydrochloric acid aqueous solution) during the condensation reaction, the resulting polyol products are accompanied by by-products such as fusel alcohols, light and heavy component impurities, and inorganic salts (Na2SO4, K2SO4). The above products are all soluble in water and are in a homogeneous miscible state. If only a distillation tower is used for separation, while the water is separated at the top of the tower, the inorganic salts dissolved in the water will simultaneously precipitate crystals at the bottom of the tower, clogging the tower packing, etc., resulting in the inability to operate the reaction continuously. If only a crystallizer is used to evaporate water for desalination, the evaporated condensed water will carry the polyol product, resulting in product loss and excessive COD in the discharged wastewater. Summary of the invention

[0003] In view of this, the present invention provides a pretreatment system for desalting salt-containing alcohol-water mixtures, which solves the technical problems in the prior art that only a distillation tower is used to separate inorganic salts dissolved in water and crystals are precipitated at the bottom of the tower at the same time, which is easy to clog the tower; and only a crystallizer is used to evaporate water for desalination, the evaporated condensed water will carry polyol products, and the COD of the discharged wastewater will exceed the standard.

[0004] The present invention provides a pretreatment system for desalting a salt-containing alcohol-water mixture, comprising: a coarse fractionation tower; a dehydration tower, wherein a bottom extraction port of the coarse fractionation tower is connected to an extraction port of the dehydration tower, and the bottom extraction port of the dehydration tower is connected to a crude salt-containing mixture pipeline and a salt-containing pipeline; a phase separation tank, wherein a top extraction port of the dehydration tower is connected to an extraction port of the phase separation tank, and the extraction port of the phase separation tank is connected to a water recycling pipeline and a reflux pipeline; wherein fusel alcohol and part of water are extracted from the top of the coarse fractionation tower, and solid inorganic salt crystals are precipitated from the bottom of the coarse fractionation tower; the dehydration tower is used for desalting the solid inorganic salt crystals precipitated from the coarse fractionation tower, and the salt-containing alcohol mixture is desalted through the coarse fractionation tower and the dehydration tower.

[0005] In a possible implementation, the coarse fraction tower includes: a first distillation tower; and a first crystallizer, wherein the first distillation tower is installed on the top of the first crystallizer, and the first distillation tower is fixedly connected to the first crystallizer.

[0006] In a possible implementation, the coarse fractionation tower further includes: a first feed inlet, which is opened on the side of the bottom side of the first distillation tower; a second feed inlet; the second feed inlet is opened in the middle of the first distillation tower; wherein the first feed inlet and the second feed inlet are both inwardly extending structures.

[0007] In a possible implementation, the dehydration tower includes: a second distillation tower; a second crystallizer, wherein the second distillation tower is installed on the top of the second crystallizer, and the second distillation tower is fixedly connected to the second crystallizer; the bottoms of the first crystallizer and the second crystallizer are both conical structures, and the inclination angles of the first crystallizer and the second crystallizer are greater than the repose angle.

[0008] In a possible implementation, the dehydration tower also includes: a third feed inlet, which is opened on the side of the bottom side of the second distillation tower; and a fourth feed inlet, which is opened in the middle of the second distillation tower; wherein the third feed inlet and the fourth feed inlet are both inwardly extending structures.

[0009] In one possible implementation, the first distillation tower is either a packed tower or a plate tower; the first crystallizer is one of a FC crystallizer, a DT crystallizer or a DTB crystallizer; and / or the second distillation tower is either a packed tower or a plate tower; the second crystallizer is a FC crystallizer.

[0010] In a possible implementation, the pretreatment system also includes: a first solid-liquid separator, the bottom outlet of the crude separation tower is connected to the outlet of the first solid-liquid separator, and the outlet of the first solid-liquid separator is connected to the third feed inlet and the fourth feed inlet of the dehydration tower; a second solid-liquid separator, the bottom outlet of the dehydration tower is connected to the second solid-liquid separator, and the second solid-liquid separator extracts a crude salt-containing mixture and salt.

[0011] In a possible implementation, the pretreatment system also includes: a first heater, which is connected to the outside of the first crystallizer; a second heater, which is connected to the outside of the second crystallizer; wherein the first heater and the second heater are one of a plate heat exchanger, a vertical shell and tube heat exchanger, a horizontal shell and tube heat exchanger, a spiral plate heat exchanger, a coil heat exchanger or a shell and tube heat exchanger.

[0012] In a possible implementation, the diameter of the coarse fractionation tower is 350-400 mm; the diameter of the dehydration tower is 300-350 mm.

[0013] In a possible implementation, the tower bodies of the coarse fractionation tower and the dehydration tower are made of austenitic stainless steel.

[0014] The present invention provides a pretreatment system for desalting a salt-containing alcohol-water mixture, the pretreatment system comprising: a coarse fractionation tower, a dehydration tower, the bottom extraction port of the coarse fractionation tower is connected to the extraction port of the dehydration tower, the extraction port at the bottom of the dehydration tower is connected to a coarse salt-containing mixture pipeline and a salt-containing pipeline; a phase separation tank, the extraction port at the top of the dehydration tower is connected to the extraction port of the phase separation tank, the extraction port of the phase separation tank is connected to a water reuse pipeline and a reflux pipeline, wherein fusel alcohol and part of water are extracted from the top of the coarse fractionation tower, and solid inorganic salt crystals are precipitated from the bottom of the coarse fractionation tower; the dehydration tower is used to desalt the solid inorganic salt crystals precipitated from the coarse fractionation tower, and the salt-containing alcohol mixture is desalted by the coarse fractionation tower and the dehydration tower. The present invention continuously separates and removes water, salt and fusel alcohol components through the coarse fractionation tower and the dehydration tower pretreatment system, avoids equipment blockage, reduces separation energy consumption, and reduces operation intensity. The crude fractionation tower and dehydration tower have the coupling effect of distillation and crystallization, which can simultaneously achieve the purpose of separating water, salt and target products, realize the simplest process, reduce the number of equipment, occupy a small area, and further save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 FIG. 1 is a schematic diagram of the structure of a pretreatment system provided by an embodiment of the present invention;

[0016] Figure 2 The figure is a schematic structural diagram of a coarse fractionation tower of a pretreatment system provided in one embodiment of the present invention;

[0017] Figure 3 Shown is a schematic structural diagram of a dehydration tower of a pretreatment system provided in one embodiment of the present invention.

[0018] Description of reference numerals:

[0019] 1. coarse fraction tower; 11. first distillation tower; 111. first feed inlet; 112. second feed inlet; 12. first crystallizer;

[0020] 2. Dehydration tower; 21. Second distillation tower; 211. Third feed inlet; 212. Fourth feed inlet; 22. Second crystallizer;

[0021] 3. Phase separation tank;

[0022] 4. The first solid-liquid separator;

[0023] 5. Second solid-liquid separator;

[0024] 6. The first heater;

[0025] 7. Second heater. DETAILED DESCRIPTION

[0026] In the description of the present invention, the meaning of "multiple" is at least two, for example, two, three, etc., unless otherwise clearly and specifically limited. In the embodiment of the present invention, all directional indications (such as up, down, left, right, front, back, top, bottom ...) are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0027] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Alcohols containing more than two hydroxyl groups are called polyols. Low-order polyols are viscous liquids with a much higher boiling point than monohydric alcohols with the same number of carbon atoms. As the number of hydroxyl groups increases, the water solubility increases. The most widely used polyols include 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,3-butanediol, etc.

[0030] At present, the acetaldehyde condensation method is the mainstream in the preparation method of 1,3-butanediol. Its production process is as follows: acetaldehyde undergoes a condensation reaction in an alkaline aqueous solution to generate 3-hydroxybutyraldehyde, and after adding acid to neutralize the reaction liquid, it is hydrogenated to generate 1,3-butanediol. If an inorganic base (such as NaOH, KOH aqueous solution) is used in the condensation reaction, and an inorganic acid (such as sulfuric acid, hydrochloric acid aqueous solution) is used for neutralization, although the raw material cost is low, inorganic salts (Na2SO4, K2SO4) will be generated. The inorganic salts are soluble in water, and the product 1,3-butanediol and the by-product fusel alcohols, light and heavy component impurities are also soluble in water, resulting in the above-mentioned multi-components being homogeneously miscible and unable to be separated by simple liquid-liquid phase separation. In addition, the boiling point of 1,3-butanediol is greater than that of water, and it does not azeotropize with water, so that the target product 1,3-butanediol cannot be obtained from the top of the tower before the water evaporates.

[0031] If only a distillation tower is used for separation, while water is separated from the top of the tower, the inorganic salts dissolved in the water will also precipitate crystals in the tower kettle in proportion. The crystals will quickly block the distillation tower packing, the tower kettle and the reboiler, and continuous operation is impossible. If only a crystallizer is used to evaporate water for desalination, the evaporated condensed water will carry 1,3-butanediol products, resulting in product losses and excessive COD of discharged wastewater. In addition, the crystallizer is operated continuously, and one crystallizer is only equivalent to one theoretical plate, and fusel alcohol cannot be completely removed from the 1,3-butanediol product. In addition, when a large amount of water is evaporated and the water content in the remaining 1,3-butanediol aqueous solution is low, the boiling point of 1,3-butanediol will increase, which will cause the operating temperature of evaporation crystallization to be too high, the residence time of the crystallization operation to be long, and the product 1,3-butanediol is heat-sensitive and easy to deteriorate if it stays too long at high temperature. The suspension of 1,3-butanediol and salt crystals that does not contain water will cool down after leaving the crystallizer. When it drops below 20°C, the viscosity of the suspension will increase sharply to more than 200cp. Too high a viscosity is not conducive to centrifugal or filtration separation of solids.

[0032] Therefore, the present invention provides a pretreatment system for desalination of saline alcohol-water mixture, Figure 1 FIG. 1 is a schematic diagram of the structure of a preprocessing system provided by an embodiment of the present invention. Figure 1 As shown, the pretreatment system includes: a coarse fractionation tower 1, a dehydration tower 2, the bottom extraction port of the coarse fractionation tower 1 is connected to the extraction port of the dehydration tower 2, the extraction port at the bottom of the dehydration tower 2 is connected to the coarse salt mixture pipeline and the salt pipeline; a phase separation tank 3, the extraction port at the top of the dehydration tower 2 is connected to the extraction port of the phase separation tank 3, the extraction port of the phase separation tank 3 is connected to the water reuse pipeline and the reflux pipeline, wherein, the top of the coarse fractionation tower 1 extracts fusel alcohol and part of water, and the bottom of the coarse fractionation tower 1 precipitates solid inorganic salt crystals; the dehydration tower 2 is used to desalinate the solid inorganic salt crystals precipitated from the coarse fractionation tower 1, and the salt-containing alcohol mixture is desalted by the coarse fractionation tower 1 and the dehydration tower 2.

[0033] Specifically, the reaction product of the present invention contains a product polyol compound, a by-product fusel alcohol, water, inorganic salt, light component impurities, and heavy component impurities. The polyol compound is preferably a diol having 3-8 carbon atoms and 2-4 hydroxyl groups. Preferably, the polyol compound is 1,3-butanediol. The present invention continuously separates and removes water, salts, and fusel alcohol components through a pretreatment system of a crude fractionation tower 1 and a dehydration tower 2, thereby avoiding equipment blockage, reducing separation energy consumption, and reducing operation intensity.

[0034] Figure 2 FIG. 1 is a schematic diagram of the structure of a coarse fractionation tower of a pretreatment system provided in one embodiment of the present invention; Figure 2 As shown, the crude fraction tower 1 includes: a first distillation tower 11; a first crystallizer 12, wherein the first distillation tower 11 is installed on the top of the first crystallizer 12, and the first distillation tower 11 is fixedly connected to the first crystallizer 12; wherein the first distillation tower 11 is one or both of a packed tower and a plate tower; and the first crystallizer 12 is one of a FC type crystallizer, a DT type crystallizer or a DTB type crystallizer.

[0035] Specifically, the first distillation tower 11 is installed on the first crystallizer 12, the upper part is the first distillation tower 11, and the lower tower kettle is the first crystallizer 12. The first distillation tower 11 and the first crystallizer 12 can be connected by using flanges, or the first distillation tower 11 and the first crystallizer 12 can be welded together so that they have both distillation and crystallization functions. The flange connection can meet the strength, rigidity, stability, and sealing of the equipment while taking into account the convenience and adjustability of installation. The tower internals can be installed separately in each tower section through the equipment flange, and the distribution of the internals can be adjusted according to the reaction process to achieve a better reaction interval and crystallization effect.

[0036] The present invention combines the structure of a distillation tower and a crystallizer together, so that the dehydration and salt precipitation operations can be completed in the same device and can be carried out continuously, so that the precipitated inorganic salts will not cause equipment blockage, the equipment can be operated continuously and smoothly, and can also be switched to intermittent operation at any time, with a large and flexible processing capacity; through the coupling of distillation and crystallization, water, salt, fusel alcohol and the reaction product polyol can be separated at the same time, and the alcohol aqueous solution discharged from the top of the tower is prevented from entraining the polyol product, thereby reducing the amount of product loss. The number of equipment is reduced, the area is small, and the cost is saved.

[0037] In a possible implementation, the coarse fraction tower 1 also includes: a first feed inlet 111, the first collection inlet 111 is opened on the side of the bottom side of the first distillation tower 11; a second feed inlet 112; the second collection inlet 112 is opened in the middle of the first distillation tower 11; wherein the first feed inlet 111 and the second feed inlet 112 are both inwardly extending structures. Specifically, multiple feed inlet positions are adopted to meet the desalination and dehydration processes with different feed ratios. The feed inlet adopts an inwardly extending structure to facilitate liquid distribution and further realize mass transfer separation. According to the different requirements of the feed composition of the separated material and the content of the fusel alcohol in the discharged material, the feed position of the dehydration tower 2 can be located in the middle of the upper distillation tower of each device, or it can be fed from the bottom crystallizer or heating circulation pipeline of each device. If feeding from the middle of the distillation tower, a flow-through tray is preferably provided below the feed inlet.

[0038] Figure 3 FIG. 1 is a schematic diagram of the structure of a dehydration tower of a pretreatment system provided by an embodiment of the present invention. Figure 3 As shown, the dehydration tower 2 includes: a second distillation tower 21; a second crystallizer 22, the second distillation tower 21 is installed on the top of the second crystallizer 22, and the second distillation tower 21 is connected to the second crystallizer 22 through a flange; wherein the second distillation tower 21 is a packed tower or a plate tower or a combination of the two; the second crystallizer 22 is a FC type crystallizer.

[0039] Similarly, the second distillation tower 21 is installed on the top of the second crystallizer 22. The second distillation tower 21 and the second crystallizer 22 can be intercepted by using flanges, or the second distillation tower 21 and the second crystallizer 22 can be welded together so that they have both distillation and crystallization functions. The use of flange connection can meet the strength, rigidity, stability and sealing of the equipment while taking into account the convenience and adjustability of installation. The tower internals can be installed separately in each tower section through the equipment flange, and the distribution of the internals can be adjusted according to the reaction process to achieve a better reaction range and crystallization effect.

[0040] In a possible implementation, the dehydration tower 2 further includes: a third feed port 211, which is opened on the side of the bottom side of the second distillation tower 21; a fourth feed port 212, which is opened in the middle of the second distillation tower 21, wherein the third feed port 211 and the fourth feed port 212 are both inwardly extending structures.

[0041] Similarly, multiple feed port positions can meet the desalting and dehydration processes with different feed ratios. The feed port adopts an inward extension structure to facilitate liquid distribution and further realize mass transfer separation. According to the different requirements of the feed composition of the separated material and the content of the fusel alcohol in the discharged material, the feed position of the dehydration tower 2 can be located in the middle of the upper distillation tower of each device, or it can be fed from the crystallizer or heating circulation pipeline at the bottom of each device. If the feed is fed from the middle of the distillation tower, the flow-through tray is preferably below the feed port. The opening of the flow-through tray is large, 20 to 30 mm, and the structure is simple. There are no internal parts such as downcomers and overflow weirs. It is difficult for salt crystals of micrometer to millimeter level to block such a large opening, and the filler or other tray types are easily blocked.

[0042] In a possible implementation, the bottoms of the first crystallizer 12 and the second crystallizer 22 are both conical structures, and the conical structure makes it difficult for crystals to be blocked in the first crystallizer 12 and the second crystallizer 22.

[0043] The inclination angle of the first crystallizer 12 and the second crystallizer 22 is greater than the repose angle. The inclination angle refers to the angle between the inclined surface of the crystallizer and the Y-axis of the plane coordinate system. The repose angle refers to the critical state of whether an object on the inclined surface slides down or not. Since the inclination angle of the crystallizer is greater than the repose angle and the inner wall is polished, no material is stored in the crystallizer to prevent crystal blockage.

[0044] In a possible implementation, a pressure gauge and a thermometer are also provided on the coarse fractionation tower 1 and the dehydration tower 2, and the pressure gauge and the thermometer can effectively monitor the reaction process.

[0045] In a possible implementation, the pretreatment system further includes: a first solid-liquid separator 4, the bottom outlet of the coarse fractionation tower 1 is connected to the outlet of the first solid-liquid separator 4, the outlet of the first solid-liquid separator 4 is connected to the third feed inlet 211 and the fourth feed inlet 212 of the dehydration tower 2; a second solid-liquid separator 5, the outlet at the bottom of the dehydration tower 2 is connected to the second solid-liquid separator 5, and the second solid-liquid separator 5 extracts a crude salt-containing mixture and salt. Specifically, the first solid-liquid separator 4 is used to perform solid-liquid separation on the solid inorganic salt crystals extracted from the first crystallizer 12, and the second solid-liquid separator 5 is used to perform solid-liquid separation on the crude salt-containing mixture and salt extracted from the second crystallizer 22.

[0046] In a possible implementation, the pretreatment system further includes: a first heater 6, which is connected to the outside of the first crystallizer 12; a second heater 7, which is connected to the outside of the second crystallizer 22; wherein the first heater 6 and the second heater 7 are both plate heat exchangers, vertical shell and tube heat exchangers, horizontal shell and tube heat exchangers, spiral plate heat exchangers, coil heat exchangers or shell and tube heat exchangers. The heater matched with the crystallizer is externally placed, and its position is lower than the liquid level in the crystallizer. The heated solution in the heat exchanger is pressed by the static liquid level, so that the solution does not vaporize inside the heater, but vaporizes when it rises to the crystallizer, precipitates crystals, and prevents scaling of the heating surface; a high flow rate is maintained in the heat exchange tube of the heater to prevent scaling of the heat exchange tube.

[0047] In a possible implementation, the diameter of the coarse fractionation tower 1 is 350-400 mm, and the diameter of the dehydration tower 2 is 300-350 mm; preferably, the diameter of the coarse fractionation tower 1 is 400 mm, and the diameter of the dehydration tower 2 is 350 mm.

[0048] In a possible implementation, the tower bodies of the coarse fractionation tower 1 and the dehydration tower 2 are made of austenitic stainless steel. Austenitic stainless steel has better corrosion resistance, and the inner surface roughness can be further guaranteed, thereby better meeting the anti-clogging performance.

[0049] The working process of the pretreatment system of the present invention is:

[0050] The components to be separated include product polyols, byproduct fusel alcohols, water, inorganic salts, light component impurities, and heavy component impurities. The mixture is pumped to the coarse fraction tower 1, and fusel alcohols and part of the water are separated from the first gas extraction port 113 at the top of the first distillation tower 11 after being rectified by the packing of the upper first distillation tower 11. The first distillation tower 11 obtains a mixture of product, water, inorganic salts, and light and heavy component impurities. Since the first crystallizer 12 installed at the bottom of the first distillation tower 11 is a conical structure, the precipitated crystals will not cause blockage. After being extracted from the extraction port at the bottom of the first crystallizer 12, they are sent to the dehydration tower 2. The crystal grains can be used as seeds for the dehydration tower 2. A slurry inlet and a crystal slurry outlet are also provided on one side of the bottom of the first crystallizer 12. The slurry heated by the first heater 6 enters the first crystallizer 12 from the slurry inlet. The crystal particles are smaller and have a higher temperature. They rise to the surface. After the solvent is flashed out, the crystals grow in the first crystallizer 12 and then fall down. They are extracted from the extraction port at the bottom of the first crystallizer 12.

[0051] The material from the coarse fractionation tower to the dehydration tower 2 contains polyols, water, inorganic salts, light component impurities, and heavy component impurities. The inorganic salt part is in a solid crystalline state, and part of the inorganic salt is dissolved in the solution. An azeotropic agent is added to the dehydration tower 2, and the remaining water is vaporized and removed by the azeotropic distillation principle. At the same time, all the inorganic salts dissolved in water will be precipitated. The flow-through tower plate below the feed port of the second distillation tower 21 and the second crystallizer 22 prevent the inorganic salts from causing equipment blockage, so that the dehydration and salt precipitation operations can be completed in the same equipment and can be carried out continuously.

[0052] The inorganic salt crystal solid and the crude liquid product obtained in the dehydration tower 2 are centrifuged or filtered to remove the solid salt in the second solid-liquid separator 5 to complete the desalination and initial separation process. The crude polyol liquid free of inorganic salt obtained by desalination can be sent to other subsequent processes for further refining to obtain the final high-purity product, and will no longer block the subsequent equipment. Water and entrainer are evaporated from the top of the second distillation tower 21, and after condensation, they are allowed to stand in the phase separation tank 3 for phase separation, the entrainer is recycled, and the water is returned to the reaction system for recycling.

[0053] Example 1

[0054] The liquid components obtained from the pilot hydrogenation reactor are pumped to the coarse fraction tower 1. The theoretical plate number of the first distillation tower 11 is 3 to 20, and the reflux ratio is 0.5 to 2. T1 can be operated under vacuum, normal pressure, and positive pressure, preferably -80 to 200 kPaG. The top operating temperature of the first distillation tower 11 is 40 to 130 ° C, and the bottom operating temperature is 75 to 140 ° C. Feed from the bottom feed port of the first crystallizer 12 or the heating circulation pipeline, and the feed flow rate is 110 to 130 L / h. Through distillation and crystallization, water and fusel alcohol are discharged from the top, and 1,3-butanediol, salt and other impurities are discharged from the bottom of the tower. The bottom liquid of the coarse fraction tower 1 is sent to the dehydration tower 2 after filtration. The theoretical plate number of the second distillation tower 21 is 3 to 20. It can be operated under vacuum, normal pressure, and positive pressure, preferably -80 to 200 kPaG, the top operating temperature is 40 to 130 ° C, and the bottom operating temperature is 75 to 140 ° C. Feed the material from the bottom feed port of the second crystallizer 22 or the middle of the tower on the heating circulation pipeline to perform azeotropic distillation operation. Fusel alcohol, water and entrainer are discharged from the top distillation together. The entrainer and water phase, the entrainer all reflux. Through the second crystallizer 22, the inorganic salt is precipitated as a solid. The target product 1,3-butanediol and the inorganic salt crystal pass through a centrifuge or filter to achieve the desalination and purification goal. During this reaction, the distillation tower and the crystallizer are not blocked, and the process operation of removing the inorganic salt from the polyol solution can be achieved. The double towers are made of stainless steel, and no corrosion phenomena such as intergranular corrosion and pitting corrosion occur during the operation of the device. The equipment is connected using equipment flange bolts and nuts fasteners to meet the equipment sealing requirements and no leakage occurs. The pretreatment system can meet the simplest process route, mechanical strength and sealing, and can achieve continuous and smooth operation of the process.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pretreatment system for desalination of a salty alcohol-water mixture, characterized in that: include: Coarse fraction tower (1); A dehydration tower (2), wherein the bottom outlet of the crude fraction tower (1) is connected to the outlet of the dehydration tower (2), and the bottom outlet of the dehydration tower (2) is connected to a crude salt mixture pipeline and a salt pipeline; A phase separation tank (3), wherein the top extraction port of the dehydration tower (2) is connected to the extraction port of the phase separation tank (3), and the extraction port of the phase separation tank (3) is connected to a water recycling pipeline and a reflux pipeline; The crude fraction tower (1) extracts fusel alcohol and part of water from the top, and solid inorganic salt crystals are precipitated from the bottom of the crude fraction tower (1); the dehydration tower (2) is used to desalinate the solid inorganic salt crystals precipitated from the crude fraction tower (1), and the salt-containing alcohol mixture is desalted through the crude fraction tower (1) and the dehydration tower (2).

2. The pretreatment system according to claim 1, characterized in that: The crude fraction tower (1) comprises: a first distillation tower (11); A first crystallizer (12), wherein the first distillation tower (11) is installed on the top of the first crystallizer (12), and the first distillation tower (11) is fixedly connected to the first crystallizer (12).

3. The pretreatment system according to claim 2, characterized in that: The coarse fraction tower (1) further comprises: A first feed inlet (111), wherein the first feed inlet (111) is opened on a side surface of a bottom side of the first distillation tower (11); A second feed inlet (112); the second feed inlet (112) is opened in the middle of the first distillation tower (11); Wherein, the first feed port (111) and the second feed port (112) are both inwardly extending structures.

4. The pretreatment system according to claim 2, characterized in that: The dehydration tower (2) comprises: a second distillation tower (21); A second crystallizer (22), wherein the second distillation tower (21) is installed on the top of the second crystallizer (22), and the second distillation tower (21) is fixedly connected to the second crystallizer (22); The bottoms of the first crystallizer (12) and the second crystallizer (22) are both conical structures, and the inclination angles of the first crystallizer (12) and the second crystallizer (22) are greater than the repose angle.

5. The pretreatment system according to claim 4, characterized in that: The dehydration tower (2) further comprises: A third feed inlet (211), the third feed inlet (211) being opened on a side surface at one side of the bottom of the second distillation tower (21); a fourth feed inlet (212), the fourth feed inlet (212) being opened in the middle of the second distillation tower (21); Wherein, the third feed port (211) and the fourth feed port (212) are both inwardly extending structures.

6. The pretreatment system according to claim 4, characterized in that: The first distillation tower (11) is any one of a packed tower or a plate tower; the first crystallizer (12) is one of an FC crystallizer, a DT crystallizer or a DTB crystallizer; and / or The second distillation tower (21) is a packed tower or a plate tower; the second crystallizer (22) is a FC type crystallizer.

7. The pretreatment system according to claim 5, characterized in that: The pre-processing system also includes: A first solid-liquid separator (4), wherein the bottom outlet of the coarse fractionation tower (1) is connected to the outlet of the first solid-liquid separator (4), and the outlet of the first solid-liquid separator (4) is connected to the third feed inlet (211) and the fourth feed inlet (212) of the dehydration tower (2); A second solid-liquid separator (5), wherein the extraction port at the bottom of the dehydration tower (2) is connected to the second solid-liquid separator (5), and the second solid-liquid separator (5) extracts a crude salt-containing mixture and salt.

8. The pretreatment system according to claim 4, characterized in that: The pretreatment system further comprises: a first heater (6), the first heater (6) being connected to the outside of the first crystallizer (12); a second heater (7), the second heater (7) being connected to the outside of the second crystallizer (22); Preferably, the first heater (6) and the second heater (7) are one of a plate heat exchanger, a vertical shell and tube heat exchanger, a horizontal shell and tube heat exchanger, a spiral plate heat exchanger, a coil heat exchanger or a shell and tube heat exchanger.

9. The pretreatment system according to any one of claims 1 to 8, characterized in that: The diameter of the coarse fractionation tower (1) is 350-400 mm; the diameter of the dehydration tower (2) is 300-350 mm.

10. The pretreatment system according to any one of claims 1 to 8, characterized in that: The tower bodies of the coarse fractionation tower (1) and the dehydration tower (2) are made of austenitic stainless steel.

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