Pretreatment system for desalting salt-containing alcohol-water mixture

Abstract

The utility model provides a pretreatment system for desalting a salt-containing alcohol-water mixture, which comprises a coarse separation tower and a dehydrating tower, a bottom extraction port of the coarse separation tower is connected with an extraction port of the dehydrating tower, and an extraction port at the bottom of the dehydrating 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 utility model relates to the technical field of chemical process equipment, specifically relates to a kind of pretreatment system for salt-containing alcohol water mixture desalination. BACKGROUND

[0002] Polyhydric alcohol refers to the alcohol containing two and more hydroxyl groups, general formula is C n H 2n+2-x (OH) x (x≥2), its boiling point is higher than that of monohydric alcohol with same carbon atom number, water solubility increases with the increase of hydroxyl number, and acetaldehyde condensation method is the main process method for preparing polyhydric alcohol. Due to the addition of inorganic salt (such as NaOH, KOH solution), inorganic acid (such as sulfuric acid, hydrochloric acid solution) in the condensation reaction process, the byproduct fusel alcohol, light and heavy component impurities, inorganic salt (Na2SO4, K2SO4) etc. are accompanied in the product polyhydric alcohol, the above products are dissolved in water, and are in homogeneous miscible state, if only distillation column is used for separation, the inorganic salt dissolved in water is precipitated at the same time at the column bottom, and the crystal is precipitated at the column bottom, which blocks the tower filler, etc., so that the reaction cannot be continuously operated. If only the crystallizer is used to evaporate water to remove salt, the condensed water evaporated will carry polyhydric alcohol product, resulting in product loss and wastewater COD exceeding standard. SUMMARY

[0003] Therefore, the utility model provides a kind of pretreatment system for salt-containing alcohol water mixture desalination, solve the technical problem that inorganic salt dissolved in water is precipitated at the same time at the column bottom only by using distillation column in prior art to separate, easy to block tower, only use crystallizer to evaporate water to remove salt, the condensed water evaporated will carry polyhydric alcohol product, and wastewater COD exceeds standard.

[0004] The utility model provides a kind of pretreatment system for salt-containing alcohol water mixture desalination, including: coarse separation tower;Dehydration tower, the bottom sampling outlet of the coarse separation tower is connected with the sampling inlet of the dehydration tower, and the bottom sampling outlet of the dehydration tower is connected with coarse salt-containing mixture pipeline and salt-containing pipeline;Phase separation tank, the top sampling outlet of the dehydration tower is connected with the sampling inlet of the phase separation tank, and the sampling outlet of the phase separation tank is connected with water reuse pipeline and reflux pipeline;Wherein, fusel alcohol and part of water are sampled out at the top of the coarse separation tower, and solid inorganic salt crystal is precipitated at the bottom of the coarse separation tower;The dehydration tower is used to desalination treatment to the solid inorganic salt crystal precipitated from the coarse separation tower, and the salt-containing alcohol mixture is desalination treated by the coarse separation tower and the dehydration tower.

[0005] In a possible implementation manner, the coarse separation tower includes: a first distillation column;First crystallizer, the first distillation column is installed at the top of the first crystallizer, and the first distillation column is fixedly connected with the first crystallizer.

[0006] In a possible implementation, the coarse separation tower further comprises: a first feed inlet, which is arranged on the side of the bottom of the first rectifying tower; and a second feed inlet, which is arranged in the middle of the first rectifying tower; wherein the first feed inlet and the second feed inlet are both internally extended structures.

[0007] In a possible implementation, the dehydration tower comprises: a second rectifying tower; and a second crystallizer, wherein the second rectifying tower is arranged on the top of the second crystallizer, and the second rectifying tower is fixedly connected with the second crystallizer; the bottom of the first crystallizer and the bottom of the second crystallizer are both conical structures, and the inclination angles of the first crystallizer and the second crystallizer are greater than the angle of repose.

[0008] In a possible implementation, the dehydration tower further comprises: a third feed inlet, which is arranged on the side of the bottom of the second rectifying tower; and a fourth feed inlet, which is arranged in the middle of the second rectifying tower; wherein the third feed inlet and the fourth feed inlet are both internally extended structures.

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

[0010] In a possible implementation, the pretreatment system further comprises: a first solid-liquid separator, wherein the sampling outlet at the bottom of the coarse separation tower is connected with the sampling inlet of the first solid-liquid separator, and the sampling outlet of the first solid-liquid separator is connected with the third feed inlet and the fourth feed inlet of the dehydration tower; and a second solid-liquid separator, wherein the sampling outlet at the bottom of the dehydration tower is connected with the second solid-liquid separator, and the second solid-liquid separator samples a coarse salt-containing mixture and salt.

[0011] In a possible implementation, the pretreatment system further comprises: a first heater, which is connected outside the first crystallizer; and a second heater, which is connected outside the second crystallizer; wherein the first heater and the second heater are any one of a plate heat exchanger, a vertical tube-shell heat exchanger, a horizontal tube-shell heat exchanger, a spiral plate heat exchanger, a coiled tube heat exchanger or a jacketed tube heat exchanger.

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

[0013] In a possible implementation, the crude separation tower and the dehydration tower are made of austenitic stainless steel.

[0014] The pretreatment system for desalting a salt-containing alcohol-water mixture comprises a crude separation tower, a dehydration tower, a crude separation tower bottom sampling outlet connected with a dehydration tower sampling inlet, a dehydration tower bottom sampling outlet connected with a crude salt-containing mixture pipeline and a salt-containing pipeline, a phase separation tank, a dehydration tower top sampling outlet connected with a phase separation tank sampling inlet, and a phase separation tank sampling outlet connected with a water recycling pipeline and a reflux pipeline. The crude separation tower separates out solid inorganic salt crystals, and the dehydration tower desalts the solid inorganic salt crystals separated out by the crude separation tower, so that the salt-containing alcohol mixture is desalted by the crude separation tower and the dehydration tower. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Fig. 1 is a structural schematic diagram of a pretreatment system according to an embodiment of the present application;

[0016] Figure 2 Fig. 2 is a structural schematic diagram of a crude separation tower of a pretreatment system according to an embodiment of the present application;

[0017] Figure 3 Fig. 3 is a structural schematic diagram of a dehydration tower of a pretreatment system according to an embodiment of the present application.

[0018] KEY

[0019] 1, crude separation tower; 11, first rectifying tower; 111, first feeding port; 112, second feeding port; 12, first crystallizer;

[0020] 2, dehydration tower; 21, second rectifying tower; 211, third feeding port; 212, fourth feeding port; 22, second crystallizer;

[0021] 3, phase separation tank;

[0022] 4, first solid-liquid separator;

[0023] 5, second solid-liquid separator;

[0024] 6, first heater;

[0025] 7, second heater. DETAILED DESCRIPTION

[0026] In the description of the utility model, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, top, bottom, etc.) in the utility model embodiments are only used to explain the relative position relationship, movement condition, etc. between components in a certain specific posture (as shown in the drawings), if the specific posture changes, then the directional indication also changes accordingly. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. 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 can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device.

[0027] In addition, the reference to "embodiments" in this document means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the utility model. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] The technical solutions in the embodiments of the utility model will be described clearly and completely in the following with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only a part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the utility model.

[0029] Alcohols containing two or more hydroxyl groups are called polyols, and low polyols are viscous liquids with much higher boiling points than monohydric alcohols with the same number of carbon atoms. With the increase of the number of hydroxyl groups, water solubility increases, and the more widely used polyols include 1,4-cyclohexane dimethyl alcohol, 1,6-hexanediol, 1,3-butanediol, etc.

[0030] Currently, in the preparation method of 1,3-butanediol, the acetaldehyde condensation method is mainstream. Its production process is as follows: acetaldehyde is condensed in alkaline aqueous solution to generate 3-hydroxybutyraldehyde, the reaction solution is neutralized after adding acid, and 1,3-butanediol is generated by hydrogenation. If inorganic alkali (such as NaOH, KOH aqueous solution) is used in the condensation reaction, and inorganic acid (such as sulfuric acid, hydrochloric acid aqueous solution) is used for neutralization, although the raw material cost is lower, inorganic salt (Na2SO4, K2SO4) will be generated. The inorganic salt is dissolved in water, and the product 1,3-butanediol and the by-produced fusel alcohol, light and heavy component impurities are also dissolved in water, resulting in the above-mentioned multi-component homogeneous phase being mixed, which cannot be separated by simple liquid-liquid phase separation. And the boiling point of 1,3-butanediol is higher than that of water, and it does not azeotrope with water, so the target product 1,3-butanediol cannot be obtained from the top of the column before the water is evaporated.

[0031] If only a rectifying column is used for separation, the inorganic salt dissolved in water will be precipitated as crystals in the column at the same time as water is separated from the top of the column, and the crystals will quickly clog the rectifying column packing, the column bottom and the reboiler, so that continuous operation is not possible. If only a crystallizer is used to evaporate water to remove salt, the condensed water evaporated will entrain 1,3-butanediol product, resulting in product loss and the COD of the discharged wastewater exceeding the standard. In addition, the crystallizer is operated continuously, and only one crystallizer is equivalent to one theoretical plate, so the fusel alcohol cannot be completely removed from the 1,3-butanediol product. Furthermore, 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 result in the operation temperature of the evaporation crystallization being too high and the residence time of the crystallization operation being too long. The product 1,3-butanediol is heat sensitive, and it is easy to deteriorate if the residence time at high temperature is too long. In addition, the suspension of 1,3-butanediol without water and salt crystals will cool down after being discharged from the crystallizer, and when the temperature is reduced to below 20℃, the viscosity of the suspension will increase to more than 200cp, which is too high for centrifugal or filtration separation of solids.

[0032] Therefore, the utility model provides a kind of for the pretreatment system for the desalination of salt-containing alcohol water mixture, Figure 1 As shown in the structure schematic diagram of the pretreatment system provided by an embodiment of the utility model, as Figure 1 As shown, the pretreatment system comprises: coarse separation column 1, dehydration column 2, the bottom sampling outlet of coarse separation column 1 is connected with the sampling inlet of dehydration column 2, the sampling outlet at the bottom of dehydration column 2 is connected with coarse salt-containing mixture pipeline and salt-containing pipeline;Phase separation tank 3, the sampling outlet at the top of dehydration column 2 is connected with the sampling inlet of phase separation tank 3, and the sampling outlet of phase separation tank 3 is connected with water recycling pipeline and reflux pipeline, wherein the fusel alcohol and part of water are sampled from the top of coarse separation column 1, and the solid inorganic salt crystals are precipitated from the bottom of coarse separation column 1;Dehydration column 2 is used to desalt the solid inorganic salt crystals precipitated from coarse separation column 1, and the salt-containing alcohol mixture is desalted by coarse separation column 1 and dehydration column 2.

[0033] Specifically, the reaction product contains product polyol compound, byproduct fusel, water, inorganic salt, light component impurity and heavy component impurity, the polyol compound is preferably dihydric alcohol with carbon atom number of 3-8 and hydroxyl number of 2-4, preferably, the polyol compound is 1,3-butanediol. The present application removes water, salt and fusel component through the pretreatment system of the coarse separation tower 1 and the dehydration tower 2, avoids equipment blockage, reduces separation energy consumption and reduces operation strength.

[0034] Figure 2 As shown in the structure schematic view of the coarse separation tower of the pretreatment system provided by the embodiment of the present application, the coarse separation tower 1 comprises: Figure 2 As shown, the coarse separation tower 1 comprises: a first rectifying tower 11; a first crystallizer 12, the first rectifying tower 11 is installed at the top of the first crystallizer 12, and the first rectifying tower 11 is fixedly connected with the first crystallizer 12; wherein the first rectifying tower 11 is one or both of a packed tower or a plate tower; and the first crystallizer 12 is one of an FC type crystallizer, a DT type crystallizer or a DTB type crystallizer.

[0035] Specifically, the first rectifying tower 11 is installed on the first crystallizer 12, the upper part is the first rectifying tower 11, and the lower tower kettle is the first crystallizer 12; the first rectifying tower 11 and the first crystallizer 12 can be connected by using a flange, or the first rectifying tower 11 and the first crystallizer 12 can be welded together, so that they have the functions of rectification and crystallization at the same time; the use of the flange can meet the requirements of equipment strength, rigidity, stability and sealing performance, and also take into account the convenience and adjustability of installation; the tower internals can be installed between each tower section through the equipment flange, and the internal distribution can be adjusted by the reaction process, so that better reaction intervals and crystallization effects are achieved.

[0036] The present application combines the structures of the rectifying tower and the crystallizer together, so that the dehydration and salt precipitation operations can be completed in the same equipment and can be continuously performed, the precipitated inorganic salt does not cause equipment blockage, the equipment can be continuously and stably operated, or can be switched to intermittent operation at any time, the processing capacity is large and flexible; through the coupling of rectification and crystallization, water, salt, fusel and reaction product polyol can be separated at the same time, the alcohol aqueous solution discharged from the tower top is avoided from entraining the polyol product, and the product loss amount is reduced. The number of equipment is reduced, the land occupation is small, and the cost is saved.

[0037] In a possible implementation, the coarse dividing tower 1 further comprises: a first feed inlet 111, the first feed inlet 111 is arranged on the side of the bottom of the first rectifying tower 11; a second feed inlet 112, the second feed inlet 112 is arranged in the middle of the first rectifying tower 11; and the first feed inlet 111 and the second feed inlet 112 are both in an inner extension structure. Specifically, the multiple feed inlet positions can meet the desalination and dehydration process of different feed ratios. The feed inlet in the inner extension structure is convenient for liquid distribution, and further realizes mass transfer separation. According to different requirements of the feed composition of the separated material and the fusel alcohol content of the outlet, the feed position of the dehydration tower 2 can be located in the middle position of the upper rectifying tower of each device or can be fed from the bottom of each device, a crystallizer or a heating circulating pipeline. If the feed is from the middle of the rectifying tower, the feed inlet below is preferably a through-flow tray.

[0038] Figure 3 As shown in the structure schematic diagram of the dehydration tower of the pretreatment system provided by the embodiment of the utility model, as shown in the structure schematic diagram of the dehydration tower of the pretreatment system provided by the embodiment of the utility model, Figure 3 As shown, the dehydration tower 2 comprises: a second rectifying tower 21; and a second crystallizer 22, the second rectifying tower 21 is installed on the top of the second crystallizer 22, and the second rectifying tower 21 and the second crystallizer 22 are connected through flanges; wherein the second rectifying tower 21 is one or a combination of a packed tower and a plate tower; and the second crystallizer 22 is an FC type crystallizer.

[0039] Similarly, the second rectifying tower 21 is installed on the top of the second crystallizer 22, and the second rectifying tower 21 and the second crystallizer 22 can be intercepted by using flanges or can be welded together, so that they have the functions of rectification and crystallization at the same time. The use of flanges can meet the requirements of equipment strength, rigidity, stability and sealing performance, and can also consider the convenience and adjustability of installation. The tower internals can be installed between each tower section through the equipment flanges, and the internal distribution can be adjusted according to the reaction process, so that better reaction intervals and crystallization effects are achieved.

[0040] In a possible implementation, the dehydration tower 2 further comprises: a third feed inlet 211, the third feed inlet 211 is arranged on the side of the bottom of the second rectifying tower 21; and a fourth feed inlet 212, the fourth feed inlet 212 is arranged in the middle of the second rectifying tower 21, wherein the third feed inlet 211 and the fourth feed inlet 212 are both in an inner extension structure,

[0041] Similarly, multiple feed inlet positions can be used to meet the desalination and dehydration process of different feed ratios. The inner extension structure of the feed inlet facilitates liquid distribution, further realizes mass transfer and separation. According to different requirements of the feed composition of the separated material and the hydrol alcohol content of the discharge, the feed position of the dehydration tower 2 can be located at the middle position of the upper rectifying tower of each device, or can be fed from the bottom of the crystallizer or the heating circulating pipeline of each device. If the feed is from the middle of the rectifying tower, the perforated tray is preferred below the feed inlet. The perforated tray has a large opening of 20-30 mm, and the structure is simple without internal parts such as downcomer and overflow weir. The micron-millimeter level salt crystallization is difficult to block such a large opening, and the filler or other tray types are easy to be blocked.

[0042] In a possible implementation, the bottoms of the first crystallizer 12 and the second crystallizer 22 are both conical structures. The conical structure makes the crystallization not easy 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 angle of repose. The inclination angle refers to the angle between the inclined surface of the crystallizer and the Y-axis of the plane coordinate system. The angle of repose 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 angle of repose, and the inner wall is polished, there is no material in the crystallizer, preventing the crystallization from being blocked.

[0044] In a possible implementation, a pressure gauge and a thermometer are further arranged on the rough separation tower 1 and the dehydration tower 2. 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, a sampling outlet at the bottom of the rough separation tower 1 is connected to a sampling inlet of the first solid-liquid separator 4, and a sampling outlet of the first solid-liquid separator 4 is connected to a third feed inlet 211 and a fourth feed inlet 212 of the dehydration tower 2; and a second solid-liquid separator 5, a sampling 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 samples a coarse salt-containing mixture and salt. Specifically, the first solid-liquid separator 4 is used for solid-liquid separation of inorganic salt crystallization of the solid sampled from the first crystallizer 12, and the second solid-liquid separator 5 is used for solid-liquid separation of the coarse salt-containing mixture and the salt sampled from the second crystallizer 22.

[0046] In a possible implementation, the pre-treatment system further comprises: a first heater 6 connected outside the first crystallizer 12; and a second heater 7 connected outside the second crystallizer 22; wherein the first heater 6 and the second heater 7 are one of a plate heat exchanger, a vertical tube-shell heat exchanger, a horizontal tube-shell heat exchanger, a spiral plate heat exchanger, a coil heat exchanger or a jacketed tube heat exchanger. The heater matched with the crystallizer is external, and is located below the liquid level in the crystallizer. The static liquid level presses the heated solution in the heat exchanger, so that the solution does not vaporize in the heat exchanger, but vaporizes in the crystallizer to precipitate crystals, thereby preventing the heating surface from being scaled. The heat exchange tube in the heater maintains a high flow rate to prevent the heat exchange tube from being scaled.

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

[0048] In a possible implementation, the tower body material of the coarse division tower 1 and the dewatering tower 2 is austenitic stainless steel, which has better corrosion resistance, and the inner surface roughness can be further guaranteed, thereby better satisfying the anti-blocking performance.

[0049] The working process of the pre-treatment system is as follows:

[0050] The separated components include product polyols, byproduct fusel, water, inorganic salts, light component impurities and heavy component impurities. The mixture is pumped to the coarse division tower 1, the fusel and part of the water are separated out from the first gas sampling outlet 113 at the top of the first rectifying tower 11 through rectification of the packing in the upper first rectifying tower 11. The first rectifying tower 11 obtains a mixture of products, water, inorganic salts and light and heavy component impurities. Since the first crystallizer 12 installed at the bottom of the first rectifying tower 11 is a conical structure, the precipitated crystals will not cause blockage. The crystals are sampled from the sampling outlet at the bottom of the first crystallizer 12 and then sent to the dewatering tower 2. The crystal grains can be used as the crystal seeds of the dewatering tower 2. A slurry inlet and a crystallization slurry outlet are further arranged at 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 crystallization particles are small, and the temperature is higher. After flashing out the solvent, the crystals grow in the first crystallizer 12 and then fall down and are sampled from the sampling outlet at the bottom of the first crystallizer 12.

[0051] The material from the coarse separation column to the first dehydration column 2 contains polyols, water, inorganic salts, light component impurities, heavy component impurities, part of the inorganic salts are in solid crystalline state, and part of the inorganic salts are dissolved in solution. The azeotrope is added to the dehydration column 2, and the remaining water is vaporized and removed by using the principle of azeotropic distillation, and the inorganic salts dissolved in water are also completely precipitated. The through-flow tray below the inlet of the second rectifying column 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 continuously performed.

[0052] The inorganic salt crystalline solid and the liquid phase crude product obtained from the dehydration column 2 are separated from the solid salt by centrifugation or filtration in the second solid-liquid separator 5, to complete the desalting and primary separation process. The crude polyol liquid obtained by desalting does not contain inorganic salts, and can be sent to subsequent other processes for further refining to obtain the final high-purity product, and will not block the subsequent equipment. The water and the azeotrope are distilled from the top of the second rectifying column 21, condensed and separated in the phase separation tank 3, the azeotrope is recycled, and the water is returned to the reaction system for recycling.

[0053] Example 1

[0054] The liquid phase component obtained from the pilot hydrogenation reactor is pumped to the coarse separation column 1. The theoretical plate number of the first rectifying column 11 is 3-20, and the reflux ratio is 0.5-2. The T1 can be operated under vacuum, normal pressure or positive pressure, preferably -80-200 kPaG. The operating temperature at the top of the first rectifying column 11 is 40-130°C, and the operating temperature at the bottom is 75-140°C. The feed is introduced from the bottom inlet of the first crystallizer 12 or the heating circulation pipeline. The feed flow rate is 110-130 L / h. Through the action of rectification and crystallization, water and fusel alcohol are removed from the top, and 1,3-butanediol, salt and other impurities are removed from the bottom. The liquid at the bottom of the coarse separation column 1 is filtered and sent to the dehydration column 2. The theoretical plate number of the second rectifying column 21 is 3-20. It can be operated under vacuum, normal pressure or positive pressure, preferably -80-200 kPaG. The operating temperature at the top is 40-130°C, and the operating temperature at the bottom is 75-140°C. The azeotropic distillation operation is carried out by feeding from the bottom inlet of the second crystallizer 22 or the heating circulation pipeline in the middle of the column. Fusel alcohol, water and azeotrope are distilled together from the top. The azeotrope and water are separated, and the azeotrope is completely returned. Through the second crystallizer 22, the inorganic salt is precipitated as a solid. The target product 1,3-butanediol and the inorganic salt crystalline are separated by a centrifuge or a filter, to complete the desalting and purification. In this reaction process, the rectifying column and the crystallizer do not appear to be blocked, and the process operation of removing the inorganic salt from the polyol solution can be realized. The double columns are made of stainless steel, and no intergranular corrosion, pitting corrosion and other corrosion phenomena occur during the operation of the device. The equipment is connected by using the type of equipment flange bolt and nut fastener, which meets the equipment sealing requirements and does not leak. The pretreatment system can meet the simplest process route, mechanical strength and sealing performance, and can realize continuous and stable operation of the process.

[0055] The above merely describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A pretreatment system for desalination of a salt-containing alcohol-water mixture, characterized in that, It comprises: a rough separation tower (1); a dehydration tower (2), a tower bottom sampling outlet of the rough separation tower (1) is connected with a sampling inlet of the dehydration tower (2), a tower bottom sampling outlet of the dehydration tower (2) is connected with a crude salt-containing mixture pipeline and a salt-containing pipeline; a phase separation tank (3), a tower top sampling outlet of the dehydration tower (2) is connected with a sampling inlet of the phase separation tank (3), a sampling outlet of the phase separation tank (3) is connected with a water recycling pipeline and a reflux pipeline; wherein, the rough separation tower (1) separates out fusel alcohol and part of water at the tower top, and separates out solid inorganic salt crystals at the tower bottom; the dehydration tower (2) is used for desalination treatment of the solid inorganic salt crystals separated out by the rough separation tower (1), and the salt-containing alcohol mixture is desalination treated through the rough separation tower (1) and the dehydration tower (2).

2. The pretreatment system of claim 1, wherein, The rough separation tower (1) comprises: a first rectifying tower (11); a first crystallizer (12), the first rectifying tower (11) is installed at the top of the first crystallizer (12), and the first rectifying tower (11) is fixedly connected with the first crystallizer (12).

3. The pretreatment system of claim 2, wherein, The rough separation tower (1) further comprises: a first feed inlet (111), the first feed inlet (111) is arranged on the side surface of the bottom side of the first rectifying tower (11); a second feed inlet (112), the second feed inlet (112) is arranged in the middle of the first rectifying tower (11); wherein, the first feed inlet (111) and the second feed inlet (112) are both inner extension structures.

4. The pretreatment system of claim 2, wherein The dehydration tower (2) comprises: a second rectifying tower (21); a second crystallizer (22), the second rectifying tower (21) is installed at the top of the second crystallizer (22), and the second rectifying tower (21) is fixedly connected with the second crystallizer (22); the bottom of the first crystallizer (12) and the bottom of 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 angle of repose.

5. The pretreatment system of claim 4, wherein, The dehydration tower (2) further comprises: a third feed inlet (211), the third feed inlet (211) is arranged on the side surface of the bottom side of the second rectifying tower (21); a fourth feed inlet (212), the fourth feed inlet (212) is arranged in the middle of the second rectifying tower (21); wherein, the third feed inlet (211) and the fourth feed inlet (212) are both inner extension structures.

6. The pretreatment system of claim 4, wherein The first rectifying tower (11) is any one of a packed tower or a plate tower; the first crystallizer (12) is one of an FC type crystallizer, a DT type crystallizer or a DTB type crystallizer; and / or The second rectifying tower (21) is any one of a packed tower or a plate tower; the second crystallizer (22) is an FC type crystallizer.

7. The pretreatment system of claim 5, wherein, The pretreatment system further comprises: a first solid-liquid separator (4), a tower bottom sampling outlet of the rough separation tower (1) is connected with a sampling inlet of the first solid-liquid separator (4), a sampling outlet of the first solid-liquid separator (4) is connected with the third feed inlet (211) and the fourth feed inlet (212) of the dehydration tower (2); A second solid-liquid separator (5) is connected to the outlet of the dehydration tower (2), and the second solid-liquid separator (5) discharges a coarse salt-containing mixture and salt.

8. The pretreatment system of claim 4, wherein, The pretreatment system further comprises a first heater (6) connected outside the first crystallizer (12) and a second heater (7) connected outside the second crystallizer (22).

9. The pretreatment system of claim 8, wherein, The first heater (6) and the second heater (7) are one of a plate heat exchanger, a vertical tube-shell heat exchanger, a horizontal tube-shell heat exchanger, a spiral plate heat exchanger, a coil heat exchanger or a jacketed tube heat exchanger.

10. The pretreatment system of any one of claims 1-9, wherein, The diameter of the coarse separation tower (1) is 350-400 mm, and the diameter of the dehydration tower (2) is 300-350 mm.

11. The pretreatment system of any one of claims 1 to 9, wherein, The tower body materials of the coarse separation tower (1) and the dehydration tower (2) are austenitic stainless steel.

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