Chloroacetic acid purification system

Abstract

The utility model discloses a chloroacetic acid purification system which comprises a packed tower, a deacidification kettle, a washing tower and a vacuum pump, a top liquid inlet of the packed tower is connected with a chloroacetic acid reaction liquid pipeline, the bottom of the packed tower is provided with a liquid-phase material outlet and a gas-phase material inlet, and the top of the packed tower is provided with a gas-phase material outlet. A bottom liquid-phase material outlet of the packed tower is connected with a top inlet of the deacidification kettle, a jacket is arranged on the outer side of the deacidification kettle and provided with a steam inlet and a steam condensate outlet, a top gas-phase material outlet of the deacidification kettle is connected with a bottom gas-phase material inlet of the packed tower, and a bottom discharge port of the deacidification kettle is connected with a glycine production line. And the deacidification kettle is communicated with a vacuum pump. Compared with a traditional chloroacetic acid purification method, the consumption of the catalyst can be further reduced, the process is short, the energy consumption is low, and when the purified chloroacetic acid is used for glycine synthesis, the purified chloroacetic acid is not obviously different from the chloroacetic acid purified by the traditional method.

Description

Technical Field

[0001] The utility model relates to the technical field of glycine production, in particular to a chloroacetic acid purification system. Background Art

[0002] my country is currently a major consumer of industrial-grade glycine, and the vast majority of glycine is produced using the chloroacetic acid ammonolysis method. Even most food-grade glycine is synthesized and purified using this method. The quality of chloroacetic acid significantly impacts glycine production, primarily because it contains excessive impurities. This increases the amount of impurities in the reaction mixture used for glycine synthesis, hindering crystallization and reducing yield. It also increases the consumption of other materials and energy used in glycine production.

[0003] Chloroacetic acid is generally obtained by chlorination of acetic acid. Acetic acid directly reacts with chlorine under the action of a catalyst. In addition to most of the chloroacetic acid, the chloroacetic acid reaction solution also contains a small amount of acetic acid, dichloroacetic acid, hydrogen chloride, acetyl chloride, etc. The purification method of chloroacetic acid currently adopted in industry is relatively long. Generally, the chlorination reaction solution is reacted with a small amount of water to destroy the active ingredients such as acetyl chloride therein, and then the dichloroacetic acid therein is reduced by catalytic hydrogenation. Finally, low-boiling-point substances such as acetic acid and hydrogen chloride are removed by rectification to obtain chloroacetic acid. This method has a long process flow, high energy consumption, and is also related to dangerous hydrogenation reduction reaction. During hydrogenation reduction, part of the chloroacetic acid is also reduced to acetic acid, which in disguised form causes the production of more by-product hydrochloric acid with extremely low economic value. In addition, the active ingredients such as acetyl chloride themselves are also catalysts for chlorination reaction, but are not effectively recovered, and the price of the catalyst is relatively high.

[0004] Therefore, the economic benefits of traditional purification methods are not significant. Utility Model Content

[0005] The utility model aims to provide a purification system for chloroacetic acid. Compared with traditional purification methods, the system can further reduce the consumption of catalysts, and the process is short and energy-saving. When the purified chloroacetic acid is used for glycine synthesis, there is no significant difference from the chloroacetic acid purified by traditional methods.

[0006] In order to achieve the above-mentioned purpose of the invention, the technical solution of the present utility model is as follows:

[0007] A chloroacetic acid purification system comprises a packed tower, a deacidification kettle, a washing tower and a vacuum pump. The top liquid inlet of the packed tower is connected to a chloroacetic acid reaction liquid pipeline, the bottom of the packed tower is provided with a liquid material outlet and a gaseous material inlet, the top of the packed tower is provided with a gaseous material outlet, the liquid material outlet at the bottom of the packed tower is connected to the top inlet of the deacidification kettle, a jacket is provided on the outer side of the deacidification kettle, the jacket is provided with a steam inlet and a steam condensate outlet, the gaseous material outlet at the top of the deacidification kettle is connected to the gaseous material inlet at the bottom of the packed tower, the bottom discharge port of the deacidification kettle is connected to a glycine production line, the washing tower is connected to the packed tower, and the vacuum pump is respectively connected to the washing tower, the packed tower and the deacidification kettle.

[0008] The deacidification kettle is provided with a distributor, and the chloroacetic acid material flows into the deacidification kettle with the distributor through the packing tower. Under the action of centrifugal force, the chloroacetic acid reaction liquid is evenly distributed on the inner wall of the deacidification kettle. Under the action of gravity, the material flows along the inner wall of the deacidification kettle to form a thin liquid film. The entire deacidification kettle is under negative pressure, achieving the effect of thin film evaporation.

[0009] The gaseous material outlet of the packed tower is connected to the bottom of the scrubbing tower, the top of the scrubbing tower is connected to a glacial acetic acid pipeline, and the bottom of the scrubbing tower is connected to a chloroacetic acid preparation raw material tank. Chloroacetic acid, acetic acid, and acetyl chloride in the gas phase are liquefied, and some hydrogen chloride dissolves in the acetic acid, forming an anhydrous acetic acid solution containing a small amount of chloroacetic acid, acetyl chloride, and hydrogen chloride. This solution can be directly used in the synthesis of chloroacetic acid.

[0010] The bottom of the washing tower is also connected to the top of the washing tower through a delivery pump. The glacial acetic acid absorbed by the washing tower, including chloroacetic acid, acetic acid and acetyl chloride, is delivered to the top of the washing tower through the delivery pump, thereby realizing the recycling of the glacial acetic acid.

[0011] The top of the washing tower is connected to a vacuum pump, which is connected to a packing tower through the washing tower, and is further connected to a deacidification kettle through the packing tower. The vacuum pump provides a negative pressure environment for the washing tower, the packing tower, and the deacidification kettle. The vacuum pump is a water-jet vacuum unit, which sucks out hydrogen chloride gas that is not easily dissolved by glacial acetic acid in the washing tower, dissolves it in water to form dilute hydrochloric acid, and sends the dilute hydrochloric acid to a chlorinated tail gas treatment system for further treatment.

[0012] The bottom discharge port of the deacidification kettle is provided with a U-shaped liquid seal to ensure that the lower liquid pipe is also full of liquid under negative pressure conditions to prevent air from entering and destroying the negative pressure environment;

[0013] The height between the bottom of the U-shaped liquid seal and the lower liquid outlet of the deacidification kettle is not less than 7.5m to ensure continuous discharge under negative pressure.

[0014] Beneficial effects of the utility model:

[0015] 1. In the utility model, the mode of chloroacetic acid reaction solution is adopted to heat under reduced pressure, the impurity with boiling point lower than chloroacetic acid in the reaction solution is vaporized, then the material vaporized is absorbed by low-temperature anhydrous acetic acid, the acetic acid after the absorption can be directly used as the raw material of chloroacetic acid production, the scheme not only reclaims acetic acid, but also can directly recycle to catalyst-acetyl chloride, can reduce the consumption of chlorination reaction catalyst, because the value of catalyst is much higher than acetic acid, so the scheme can produce obvious economic benefit. And the traditional chloroacetic acid purification method, because acetyl chloride meets water reaction, can not recycle the acetyl chloride dissolved in the chloroacetic acid reaction.

[0016] 2. In the present invention, chloroacetic acid, after low-boiling-point substances have been removed, is prepared into an aqueous solution. The solution does not contain hydrogen chloride. When used to synthesize glycine, the amount of ammonium chloride produced is significantly reduced compared to when synthesizing glycine using untreated chloroacetic acid, thereby reducing the energy consumption required for the subsequent separation of ammonium chloride and glycine. The amount of ammonium chloride produced when using treated chloroacetic acid for glycine synthesis is comparable to that produced when synthesizing glycine using chloroacetic acid obtained using conventional purification methods.

[0017] 3. In the present invention, dangerous hydrogenation reduction reaction is no longer involved, thus reducing the risk level of the entire system.

[0018] 4. In the present invention, chloroacetic acid can be obtained as a raw material that meets the production needs of glycine by only one step of reduced pressure and heating, which greatly simplifies the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the purification system of chloroacetic acid of the present invention.

[0020] Among them, 1. Packing tower; 2. Deacidification kettle; 3. Reaction liquid pipeline; 4. Jacket; 5. Distributor; 6. Washing tower; 7. Vacuum pump; 8. U-shaped liquid seal. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

[0022] Research has found that the boiling points of acetic acid, hydrogen chloride, and acetyl chloride are all lower than those of chloroacetic acid. These impurities can be removed through vacuum distillation or flash distillation. The remaining dichloroacetic acid has little negative impact on the chloroacetic acid-glycine synthesis reaction, so further separation is unnecessary. Furthermore, substances like acetic acid have low heats of vaporization, making distillation energy-efficient. Even the sensible heat of the chlorination reaction liquid is sufficient to maintain the heat required to vaporize the small amount of acetic acid in the reaction liquid.

[0023] Example 1

[0024] This embodiment provides a chloroacetic acid purification system, comprising a packed tower 1, a deacidification kettle 2, a washing tower 6, and a vacuum pump 7. The top liquid inlet of the packed tower 1 is connected to the chloroacetic acid reaction liquid pipeline 3. The bottom of the packed tower 1 is provided with a liquid material outlet and a gaseous material inlet. The top of the packed tower 1 is provided with a gaseous material outlet. The liquid material outlet at the bottom of the packed tower 1 is connected to the top inlet of the deacidification kettle 2. The outer side of the deacidification kettle 2 is provided with a jacket 4. The jacket 4 is provided with a steam inlet and a steam condensate outlet. The gaseous material outlet at the top of the deacidification kettle 2 is connected to the gaseous material inlet at the bottom of the packed tower 1. The bottom discharge port of the deacidification kettle 2 is connected to the glycine production line. The washing tower 6 is connected to the packed tower 1. The vacuum pump 7 is respectively connected to the washing tower 6, the packed tower 1, and the deacidification kettle 2.

[0025] In the present embodiment, pyrochloroacetic acid reaction solution is fed in the packed tower 1 continuously, chloroacetic acid forms liquid film on filler, the heat that the reaction solution itself carries is carried out, vaporizes part low-boiling-point substance, and the chloroacetic acid material flows into the depickling still 2 through packed tower 1 again, and the low-boiling-point substance-hydrogen chloride, Acetyl Chloride, acetic acid that have not been vaporized in the chloroacetic acid material are distilled under negative pressure in the depickling still 2, thereby vaporize quickly.The gaseous phase material vaporized from the depickling still 2 enters packed tower 1 again, and with the liquid material mass transfer and heat transfer flowing down from the cat head, extracts the chloroacetic acid (being equivalent to the stripping section of rectifying operation) in the depickling still 2 vaporized materials, thereby under the prerequisite that guarantees that low-boiling-point substance is removed thoroughly, reduces the chloroacetic acid vaporization amount as much as possible.Low-boiling-point substance flows out from packed tower 1 top with gaseous phase state, carries out subsequent treatment.

[0026] In this embodiment, the pressure of the deacidification reactor 2 is controlled at -90 to -85 kPa by a vacuum pump 7. The chloroacetic acid reaction solution at a temperature of 100°C enters the packed tower 1 from the top of the packed tower 1. The discharge temperature of the deacidification reactor 2 is maintained at 100°C by controlling the amount of heating steam. When the chloroacetic acid reaction solution is directly added to water to prepare a 75% concentration of chloroacetic acid aqueous solution, the hydrogen chloride content in the aqueous solution is 2%, the acetic acid content is an average of 0.8%, and the dichloroacetic acid content is 3.5%. However, when the chloroacetic acid reaction solution is treated to remove low-boiling-point substances and then prepared into a 75% concentration of chloroacetic acid aqueous solution, the hydrogen chloride content in the aqueous solution is reduced to 0%, the acetic acid content is reduced to 0.4%, and the dichloroacetic acid content is 3.6%.

[0027] In the aqueous solution prepared after removing low-boiling-point substances from chloroacetic acid in the present embodiment, the content of dichloroacetic acid slightly increased. The main reason is that, when removing low-boiling-point substances, a small amount of chloroacetic acid was vaporized, and the relative ratio of dichloroacetic acid to chloroacetic acid in the reaction solution slightly increased. However, after calculation, the chloroacetic acid after removing low-boiling-point substances was subjected to an aminating reaction to synthesize glycine under the same conditions, which could generate approximately 6.5% less ammonium chloride, significantly reducing the energy consumption of subsequent separation of ammonium chloride and glycine, and improving the yield of glycine.

[0028] Example 2

[0029] The difference between this embodiment and embodiment 1 is that, in this embodiment, a distributor 5 is provided in the deacidification kettle 2, and the rest of the structure is the same as that of embodiment 1.

[0030] In this embodiment, the chloroacetic acid material flows into the deacidification kettle 2 with a distributor 5 through the packed tower 1. Under the action of centrifugal force, the chloroacetic acid reaction liquid is evenly distributed on the inner wall of the deacidification kettle 2. Under the action of gravity, the material flows along the inner wall of the deacidification kettle 2 to form a thin liquid film. The entire deacidification kettle 2 is under negative pressure, achieving the effect of thin film evaporation.

[0031] Example 3

[0032] This embodiment differs from Example 1 in that the gaseous material outlet of packed tower 1 is connected to the bottom of scrubbing tower 6, the top of scrubbing tower 6 is connected to a glacial acetic acid pipeline, and the bottom of scrubbing tower 6 is connected to a chloroacetic acid preparation raw material tank. The bottom of scrubbing tower 6 is also connected to the top of scrubbing tower 6 via a delivery pump. The remaining structure is the same as that of Example 1.

[0033] In this embodiment, the chloroacetic acid, acetic acid, and acetyl chloride in the gas phase are liquefied, and some hydrogen chloride dissolves in the acetic acid, forming an anhydrous acetic acid solution containing a small amount of chloroacetic acid, acetyl chloride, and hydrogen chloride. This solution can be directly used in the synthesis of chloroacetic acid. The bottom of the scrubber 6 is connected to the top of the scrubber 6 via a transfer pump. The glacial acetic acid absorbed by the chloroacetic acid, acetic acid, and acetyl chloride in the scrubber 6 is transported to the top of the scrubber 6 via the transfer pump, thereby recycling the glacial acetic acid.

[0034] Example 4

[0035] The difference between this embodiment and embodiment 1 is that, in this embodiment, the top of the washing tower 6 is connected to the vacuum pump 7, the vacuum pump 7 is connected to the packing tower 1 through the washing tower 6, and the vacuum pump 7 is connected to the deacidification kettle 2 through the packing tower 1. The rest of the structure is the same as that of embodiment 1.

[0036] In this embodiment, the vacuum pump 7 is a water-jet vacuum unit, which is connected to the deacidification kettle 2 through the washing tower 6 and the packing tower 1. The vacuum pump 7 provides a negative pressure environment for the washing tower 6, the packing tower 1 and the deacidification kettle 2. The vacuum pump 7 sucks out the hydrogen chloride gas in the washing tower 6 that is not easily dissolved by glacial acetic acid and dissolves it in water to form dilute hydrochloric acid, and then sends the dilute hydrochloric acid to the chlorinated tail gas treatment system for further treatment.

[0037] Example 5

[0038] Compared with Example 1, the present embodiment is different in that, in the present embodiment, a U-shaped liquid seal 8 is provided at the bottom discharge port of the deacidification kettle 2, and the height of the bottom of the U-shaped liquid seal 8 from the lower liquid port of the deacidification kettle 2 is not less than 7.5m. The rest of the structure is the same as that of Example 1.

[0039] In this embodiment, the U-shaped liquid seal 8 ensures that the lower liquid pipe is also in a full liquid state under negative pressure conditions to prevent air from entering and destroying the negative pressure environment; the bottom of the U-shaped liquid seal 8 is at least 7.5m above the lower liquid outlet of the deacidification kettle 2 to ensure continuous discharge under negative pressure conditions.

[0040] It is understood that the present invention is described by way of certain embodiments, and those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Furthermore, under the guidance of the present invention, these features and embodiments may be modified to suit specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A purification system for chloroacetic acid, characterized in that: The invention comprises a packing tower (1), a deacidification kettle (2), a washing tower (6) and a vacuum pump (7), wherein the top liquid inlet of the packing tower (1) is connected to a chloroacetic acid reaction liquid pipeline (3), the bottom of the packing tower (1) is provided with a liquid material outlet and a gaseous material inlet, the top of the packing tower (1) is provided with a gaseous material outlet, the liquid material outlet at the bottom of the packing tower (1) is connected to the top inlet of the deacidification kettle (2), a jacket (4) is provided on the outside of the deacidification kettle (2), a steam inlet and a steam condensate outlet are provided on the jacket (4), the gaseous material outlet at the top of the deacidification kettle (2) is connected to the gaseous material inlet at the bottom of the packing tower (1), the bottom discharge port of the deacidification kettle (2) is connected to a glycine production line, the washing tower (6) is connected to the packing tower (1), and the vacuum pump (7) is respectively connected to the washing tower (6), the packing tower (1) and the deacidification kettle (2).

2. The chloroacetic acid purification system according to claim 1, wherein: A distributor (5) is provided in the deacidification kettle (2).

3. The purification system of chloroacetic acid according to claim 1, wherein: The gas phase material outlet of the packed tower (1) is connected to the bottom of the washing tower (6), the top of the washing tower (6) is connected to the glacial acetic acid pipeline, and the bottom of the washing tower (6) is connected to the chloroacetic acid preparation raw material tank.

4. The purification system of chloroacetic acid according to claim 3, wherein: The bottom of the washing tower (6) is also connected to the top of the washing tower (6) via a delivery pump.

5. The purification system of chloroacetic acid according to claim 3, characterized in that: The top of the washing tower (6) is connected to a vacuum pump (7), the vacuum pump (7) is connected to the packing tower (1) through the washing tower (6), and the vacuum pump (7) is connected to the deacidification kettle (2) through the packing tower (1).

6. The purification system of chloroacetic acid according to claim 1, characterized in that: The bottom discharge port of the deacidification kettle (2) is provided with a U-shaped liquid seal (8).

7. The purification system of chloroacetic acid according to claim 6, characterized in that: The height between the bottom of the U-shaped liquid seal (8) and the lower liquid outlet of the deacidification kettle (2) is not less than 7.5m.

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