Method and system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid

Abstract

The invention provides a method and a system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, the method and the system utilize the self weight of the waste liquid to enter a chromatographic device, then the waste liquid is mixed with steam condensate generated by the system, and neopentyl glycol in the waste liquid is dissolved in the steam condensate under the pressure of-80 to-95 kPa and the temperature of 85-95 DEG C; meanwhile, ester substances such as neopentyl glycol formate in the waste liquid are hydrolyzed to form formic acid, neopentyl glycol, carbon dioxide, nitrogen and the like. Formic acid and neopentyl glycol are dissolved in steam condensate at the same time to form a water-phase material, and the rest liquid component is an oil-phase material. After the water-phase material is treated by the light component removal tower, the dissolved neopentyl glycol is obtained, and the aim of recovering the neopentyl glycol is achieved. In addition, the system and the method can recover neopentyl glycol in the waste liquid, so that the production cost is reduced, and the production benefit is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of waste liquid recovery and relates to a method and a system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid. Background Art

[0002] Neopentyl glycol is a white crystalline solid with hygroscopicity. It is mainly used in the production of unsaturated resins, oil-free alkyd resins, polyurethane foams and plasticizers for elastomers, surfactants, etc. It has a wide range of applications.

[0003] The crude neopentyl glycol produced in the production process of neopentyl glycol is removed by a light removal tower and a heavy removal tower to obtain a neopentyl glycol aqueous solution. However, when the crude neopentyl glycol is removed from wastewater by a light removal tower, ester substances such as neopentyl glycol formate will be produced, affecting the purity and acid value of the product. When the crude neopentyl glycol treated by the light removal tower is removed by a heavy removal tower to remove the produced ester substances, part of the neopentyl glycol will be removed at the same time, resulting in a waste of resources. The waste liquid produced by the heavy removal tower is usually sold directly, but some neopentyl glycol and neopentyl glycol formate are still present in the waste liquid, resulting in a waste of resources. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, so as to solve the problem of waste of existing neopentyl glycol synthesis waste liquid resources.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present application provides a method for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, comprising: the neopentyl glycol synthesis waste liquid is dehydrated through an evaporator and then transported together with steam condensate to a chromatograph for hydrolysis to obtain an aqueous phase material and an oil phase material containing neopentyl glycol, wherein the steam condensate is a condensate produced by heating the chromatograph with steam.

[0006] Preferably, the temperature of the steam condensate is 85-95°C.

[0007] Preferably, the flow rate of the steam condensate to the dehydrated neopentyl glycol synthesis waste liquid is 3-4:1.

[0008] Preferably, the steam condensate is water.

[0009] Preferably, the pressure of the chromatograph is -80 to -95 kPa.

[0010] In a second aspect, the present application provides a system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, comprising: a deweighting tower, an evaporator and a chromatograph connected in sequence, the chromatograph is also connected to a water phase pump and an oil phase pump, respectively, the oil phase pump is connected to an oil phase recovery tank; a steam heating coil is arranged on the outside of the chromatograph, the steam heating coil is connected to a steam pipeline and a condensate pipe, respectively, and the condensate pipe is connected to the chromatograph.

[0011] Preferably, a waste liquid flow meter is provided on the pipeline between the evaporator and the chromatograph, and a condensate flow meter is provided on the condensate pipe.

[0012] Preferably, a vent pipe is further provided on the top of the chromatograph, and the vent pipe is respectively connected to the nitrogen pipeline and the gas phase pipeline.

[0013] Preferably, the chromatograph is also connected to a condensate replenisher pipe, and the condensate replenisher pipe is provided with a replenisher flowmeter and a replenisher valve.

[0014] Preferably, a circulating pump is further provided between the bottom of the deweighting tower and the top of the evaporator.

[0015] The present invention has the following beneficial effects: (1) The present application utilizes the waste liquid's own weight to enter the chromatograph, and then mixes with the steam condensate generated by the system itself. At a pressure of -80~-95kPa and a temperature of 85-95°C, the neopentyl glycol in the waste liquid dissolves in the steam condensate; at the same time, ester substances such as neopentyl glycol formate in the waste liquid are hydrolyzed to form formic acid, neopentyl glycol, carbon dioxide, nitrogen, etc. Formic acid and neopentyl glycol are simultaneously dissolved in the steam condensate to form an aqueous phase material, and the remaining liquid components are oil phase materials. After the aqueous phase material is treated in a light removal tower, dissolved neopentyl glycol is obtained, thereby achieving the purpose of recovering neopentyl glycol.

[0016] (2) The system and method can recover neopentyl glycol from waste liquid, reduce production costs, and increase production benefits. 1.15 tons of neopentyl glycol can be recovered every day, and the annual benefit can be increased by 3.79 million yuan / 8,000 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid provided in an embodiment of the present application; Symbols represent: 1-deweighting tower, 2-evaporator, 3-chromatograph, 4-water phase pump, 5-oil phase pump, 6-oil phase recovery tank, 7-steam heating coil, 8-steam pipeline, 9-condensate pipe, 10-waste liquid flowmeter, 11-condensate flowmeter, 12-vent pipe, 13-nitrogen pipeline, 14-gas phase pipeline, 15-condensate replenishing liquid pipe, 16-replenishing liquid flowmeter, 17-replenishing liquid valve, 18-circulation pump. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.

[0019] Example 1 The present application embodiment provides a method for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, the method comprising: During the synthesis of neopentyl glycol, a large amount of waste liquid is produced in the deweighting tower. The main components and contents of the waste liquid are 22-25% neopentyl glycol, 35-37% neopentyl glycol formate, 40-43% neopentyl glycol hydroxypivalate, etc. After the waste liquid passes through the evaporator to remove most of the water, it is discharged into the chromatograph by its own gravity. At the same time, the steam condensate with a temperature of 85-95°C is also discharged into the chromatograph and mixed with the waste liquid. In the process of mixing the waste liquid and the steam condensate, the neopentyl glycol in the waste liquid dissolves in the steam condensate at a pressure of -80~-95kPa and a temperature of 85-95°C; at the same time, ester substances such as neopentyl glycol formate in the waste liquid are hydrolyzed to form formic acid, neopentyl glycol, carbon dioxide, nitrogen, etc. Formic acid and neopentyl glycol are dissolved in the steam condensate at the same time to form water phase materials, and the remaining liquid components are oil phase materials.

[0020] In the embodiment of the present application, the steam condensate is water, and the flow rate of the steam condensate to the dehydrated neopentyl glycol synthetic waste liquid is 3-4:1. When the flow rate of the steam condensate to the dehydrated neopentyl glycol synthetic waste liquid is 3:1 or 4:1, the content of the remaining neopentyl glycol in the oil phase material no longer changes significantly. Among them, when the flow rate of the steam condensate to the dehydrated neopentyl glycol synthetic waste liquid is 3:1, the content of the remaining neopentyl glycol in the oil phase material is about 7.31%; when the flow rate of the steam condensate to the dehydrated neopentyl glycol synthetic waste liquid is 4:1, the content of the remaining neopentyl glycol in the oil phase material is about 6.79%.

[0021] Example 2 The present application embodiment provides a system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, the system comprising a deweighting tower 1, an evaporator 2 and a chromatograph 3 connected in sequence, as shown in the attached Figure 1 shown.

[0022] Specifically, the deweighting tower 1 is a device for removing heavy components from waste liquid, and the waste liquid after the heavy components are removed is discharged into the evaporator 2 through the circulation pump 18 to remove most of the water. The waste liquid treated by the evaporator 2 is discharged into the chromatograph 3, and at the same time, the steam condensate generated in the system is also discharged into the chromatograph 3, wherein the steam condensate is condensed by the steam heating coil 7 heating the chromatograph 3.

[0023] In the chromatograph 3, the waste liquid is mixed with the steam condensate, and the neopentyl glycol in the waste liquid is dissolved in the steam condensate; at the same time, the ester substances such as neopentyl glycol formate in the waste liquid are hydrolyzed to form formic acid, neopentyl glycol, carbon dioxide, nitrogen, etc. Formic acid and neopentyl glycol are dissolved in the steam condensate at the same time to form water phase materials, and gas phase components such as carbon dioxide and nitrogen are discharged from the chromatograph 3, and the remaining liquid components are oil phase materials.

[0024] The chromatograph 3 is also connected to the water phase pump 4 and the oil phase pump 5, respectively, and the oil phase pump 5 is connected to the oil phase recovery tank 6. The water phase material separated by the chromatograph 3 is transported to the light removal tower by the water phase pump 4 to remove the contained water and formic acid and recover the dissolved neopentyl glycol. The oil phase material separated by the chromatograph 3 is transported to the oil phase recovery tank 6 by the oil phase pump 5 and then sold out.

[0025] In order to facilitate the smooth discharge of the waste liquid in the evaporator 2 into the chromatograph 3, the pressure in the deweighting tower 1 and the chromatograph 3 is kept consistent, so that the waste liquid is discharged into the chromatograph 3 under its own gravity, which prolongs the retention time of the steam condensate and the waste liquid in the chromatograph 3 and increases the hydrolysis time of the ester substances. Among them, the pressure in the deweighting tower 1 and the chromatograph 3 is -80~-95kPa.

[0026] In addition, before entering the chromatograph 3, the temperature of the steam condensate will decrease during the pipeline transportation process, resulting in the inability to dissolve neopentyl glycol and hydrolyze ester substances. Therefore, in order to prevent the temperature of the steam condensate from decreasing when entering the chromatograph 3, a steam heating coil 7 is arranged outside the chromatograph 3, so that the steam heating coil 7 can be used to keep the chromatograph 3 warm, thereby increasing the dissolution rate of neopentyl glycol and the hydrolysis rate of ester substances. In addition, according to experimental results, the waste liquid discharged from the bottom of the deweighting tower will become more viscous when it is lower than 70°C, which is not conducive to transportation. Therefore, the arrangement of the steam heating coil 7 can also facilitate the operation of the waste liquid in the chromatograph 3.

[0027] In order to heat the chromatograph 3 by the steam heating coil 7, the two ends of the steam heating coil 7 are respectively connected to the steam pipeline 8 and the condensate pipe 9, and the condensate pipe 9 is connected to the chromatograph 3. The steam pipeline 8 is introduced with high-temperature steam having a pressure of 0.4 MPa and a temperature of 145-155°C, and the steam heating coil 7 is heated by the high-temperature steam, thereby keeping the chromatograph 3 warm. After the high-temperature steam heats the steam heating coil 7, it is condensed into a steam condensate at 85-95°C, which is discharged into the chromatograph 3 through the condensate pipe 9 to dissolve the neopentyl glycol and hydrolyze the ester substances.

[0028] In order to control the flow rate of steam condensate and waste liquid into the chromatograph 3, a waste liquid flowmeter 10 is provided on the pipeline between the evaporator 2 and the chromatograph 3, and a condensate flowmeter 11 is provided on the condensate pipe 9. When the content of the steam condensate condensed by the steam heating coil 7 is low, it is necessary to replenish the steam condensate for the chromatograph 3. Based on this, the chromatograph 3 is also connected to the condensate replenishing liquid pipe 15, and the condensate replenishing liquid pipe 15 is provided with a replenishing liquid flowmeter 16 and a replenishing liquid valve 17, so as to control the delivery and flow control of the replenishing steam condensate.

[0029] In normal production process, chromatograph 3 is set to negative pressure operation, so that waste liquid can be discharged smoothly. Chromatograph 3 is also provided with vent pipe 12 at the top, vent pipe 12 is connected with nitrogen pipeline 13 and gas phase pipeline 14 respectively. Vent pipe 12 is connected with gas phase pipeline 14, gas generated inside chromatograph 3 can be discharged, and overpressure inside chromatograph 3 is prevented, which plays a role of safety protection. When the internal pressure of chromatograph 3 is low, nitrogen is filled into chromatograph 3 through nitrogen pipeline 13 to reach a predetermined pressure. In the embodiment of the present application, control valves are respectively provided on nitrogen pipeline 13 and gas phase pipeline 14 to control exhaust and nitrogen intake respectively.

[0030] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, 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 method for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, characterized in that: include: The neopentyl glycol synthesis waste liquid is dehydrated in an evaporator and transported to a chromatograph together with a steam condensate for hydrolysis to obtain a water phase material and an oil phase material containing neopentyl glycol. The steam condensate is a condensate generated by heating the chromatograph with steam.

2. The method for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 1, characterized in that: The temperature of the steam condensate is 85-95°C.

3. The method for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 1, characterized in that: The flow rate of the steam condensate to the dehydrated neopentyl glycol synthesis waste liquid is 3-4:

1.

4. The method for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 1, characterized in that: The steam condensate is water.

5. The method for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 1, characterized in that: The pressure of the chromatograph is -80~-95kPa.

6. A system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid, characterized in that: include: A deweighting tower (1), an evaporator (2) and a chromatograph (3) are sequentially connected, the chromatograph (3) is also respectively connected to a water phase pump (4) and an oil phase pump (5), the oil phase pump (5) is connected to an oil phase recovery tank (6); a steam heating coil (7) is arranged outside the chromatograph (3), the steam heating coil (7) is respectively connected to a steam pipeline (8) and a condensate pipe (9), the condensate pipe (9) is connected to the chromatograph (3).

7. The system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 6, characterized in that: A waste liquid flow meter (10) is provided on the pipeline between the evaporator (2) and the chromatograph (3), and a condensate flow meter (11) is provided on the condensate pipe (9).

8. The system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 6, characterized in that: A vent pipe (12) is also provided on the top of the chromatograph (3), and the vent pipe (12) is connected to a nitrogen pipeline (13) and a gas phase pipeline (14) respectively.

9. The system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 6, characterized in that: The chromatograph (3) is also connected to a condensate replenisher pipe (15), and the condensate replenisher pipe (15) is provided with a replenisher flow meter (16) and a replenisher valve (17).

10. The system for recovering neopentyl glycol from neopentyl glycol synthesis waste liquid according to claim 6, characterized in that: A circulating pump (18) is also provided between the bottom of the deweighting tower (1) and the top of the evaporator (2).

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