KR20170079853A

KR20170079853A - Method of separation and purification acetic acid from waste water containing acetic acid by using cooling crystallizer

Info

Publication number: KR20170079853A
Application number: KR1020150190861A
Authority: KR
Inventors: 이우진; 김광주; 김영한
Original assignee: 주식회사 한화
Priority date: 2015-12-31
Filing date: 2015-12-31
Publication date: 2017-07-10

Abstract

The present invention relates to a method for separating and purifying acetic acid from wastewater containing acetic acid, and more particularly, to a method for separating and purifying high concentration and high purity acetic acid from acetic acid wastewater by using a film-type cooling crystallizer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and purifying acetic acid in acetic acid wastewater using a film-type cooling crystallizer,

Generally, wastewater containing acetic acid is produced by an acetic acid manufacturing plant and HMX (High Molecular Weight RDX, Cyclotrimethylene-tetranitramine), terephthalic acid, dimethyl terephthalate, isophthalic acid, It is produced in large quantities in many petrochemical plants producing cellulose acetate, ester, acetic anhydride and the like.

Generally, the recovery of acetic acid from acetic acid wastewater is accomplished through azeotropic distillation, liquid - liquid extraction and adsorption. The most commonly used method for economic reasons is azeotropic distillation. However, since acetic acid and water constitute an azeotropic mixture, much energy is required for their separation. In addition, it is difficult to separate more than 95% of acetic acid. In order to separate acetic acid with high purity, the number of distillation tower needs to be increased. In addition, as the concentration of acetic acid increases toward the lower part of the distillation separation tower, corrosiveness of the solution becomes strong, which causes corrosion of the equipment. Therefore, the separation efficiency is low, and energy consumption, facility investment cost, and maintenance cost are large.

The adsorption method using activated carbon is known to effectively remove organic matter from wastewater. However, if the activated carbon is saturated with organic matter, it will lose its ability to remove further, so it is necessary to replace the activated carbon. Therefore, a large amount of activated carbon is required for the adsorption method, and since there is no economical regeneration technology of activated carbon, a large amount of solid waste is generated and it is difficult to commercialize it in a large scale facility.

Wastewater containing high concentrations of acetic acid is produced in large quantities in the production of chemical substances, for example HMX (High Molecular Weight RDX (Cyclotrimethylenetrinitramine)). In the case of acetic acid, there is no economical and effective separation and purification process due to high wastewater treatment cost.

In addition, since the recent rapid industrialization has caused problems due to environmental pollution, an effective method for reusing and recycling organic compounds for solving the problems is required.

Korean Patent Publication No. 10-2007-0006217

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art,

It is an object of the present invention to provide an efficient method for separating and purifying high purity and high concentration acetic acid from acetic acid wastewater by forming acetic acid crystals by controlling the cooling rate of wastewater by using a film-type tubular cooling crystallizer and partially melting the crystals.

In addition, since the high-temperature condition is not required in the separation and purification process of acetic acid, it is possible to reduce the cost of wastewater treatment and energy consumption, to avoid the use of additional solvent, to reuse acetic acid which is an organic compound, And a method for separating and purifying acetic acid from wastewater.

In order to solve the above problem,

One) Acetic acid wastewater is supplied to a membrane-type tubular cooling crystallizer, and acetic acid crystal seeds are supplied to the acetic acid wastewater at a cooling rate of 0.1 to 1 K / min from -6 to 16 캜 To form acetic acid crystals; And

2) heating the acetic acid crystal to a temperature range of -6 to 20 ° C at a heating rate of 0.1 to 5 K / min or to maintain the temperature within the above-mentioned temperature range to partially melt and recover the remaining acetic acid crystals; The present invention also provides a method for separating and purifying acetic acid from acetic acid wastewater.

By using the method for separating and purifying acetic acid of the present invention, it is possible to separate and purify high purity acetic acid of about 98% or more from wastewater. The process is simple and energy consumption is 50% of the distillation and evaporation process.

In addition, by providing a method of separating and purifying acetic acid from wastewater, it is possible to provide an environmentally friendly and economical method in that organic compounds can be recovered and reused.

1 is a flowchart schematically showing a process of separating acetic acid from HMX wastewater.
FIG. 2 is a schematic view showing an apparatus configuration of a film-type tubular cooling crystallizer. FIG.

Conventional processing and purification processes of acetic acid wastewater generated in various processes such as the production process of HMX (High Molecular Weight RDX (Cyclotrimethylenetrinitramine)) are complicated in process complexity, slow process, secondary environmental pollution, Energy consumption and so on. In order to solve such a problem, the inventor of the present invention has found that, in order to solve this problem, acetic acid crystals are formed in a crystallizer by controlling a crystal growth rate using a constant cooling rate, and the crystals are partially melted under a constant heating condition to improve the purity of acetic acid crystals, The acetic acid of high purity can be separated and purified, and the present invention has been completed.

Particularly, while a purification method using a conventional cooling crystallizer has a main purpose of recovering and recycling water from wastewater, the present invention aims at recovering acetic acid, which is an organic compound, in wastewater at a high concentration and a high purity, , Providing more useful effects in terms of environmental and productive aspects.

Hereinafter, the present invention will be described in more detail.

According to the present invention,

1) Acetic acid wastewater is supplied to a film-type tubular cooling crystallizer, and acetic acid crystal seed is added to the acetic acid wastewater at a cooling rate of -6 to 16 ° C at a temperature of -6 to 16 ° C at a cooling rate of 0.1 to 1 K / min To form acetic acid crystals; And

2) heating the acetic acid crystal to a temperature range of -6 to 20 ° C at a heating rate of 0.1 to 5 K / min or to maintain the temperature within the above-mentioned temperature range to partially melt and recover the remaining acetic acid crystals; The present invention relates to a method for separating and purifying acetic acid in acetic acid wastewater.

In step 1), the acetic acid wastewater may be acetic acid wastewater containing more than 60% of acetic acid, which is generated during the production of HMX (High Molecular Weight RDX (Cyclotrimethylenetrinitramine)). The acetic acid wastewater may be one or more selected from 2,4,6-trinitrotoluene, methyldinitrophenol, methyldinitrobenzene and dinitroaniline, And the like. When acetic acid is separated from the wastewater containing the refractory compound, it is difficult to separate and purify the organic mixture because of the similar nature of the organic mixture. However, the separation and purification method of the present invention can solve this problem.

The acetic acid crystal seed preferably uses acetic acid having a purity of 98% or more, which is suitable for inducing a high concentration of acetic acid crystals. The seed is preferably used in an amount of 0.5 to 5 parts by weight, more preferably 0.7 to 3 parts by weight, based on 100 parts by weight of acetic acid wastewater. When the amount of the seed is less than 0.5 parts by weight based on the above-mentioned criteria, there is a problem that crystal formation is difficult. When the amount of the seed is more than 5 parts by weight, the efficiency is lowered.

In the step 1), seed crystals are formed on the inner wall of the crystallizer after the wastewater is supplied to the slurry-type tubular cooling crystallizer, and a seeding process is performed by supplying seeds down to just below the freezing point, thereby inducing a seeding process .

In the step 1), the wastewater is supplied to the crystallizer, and then the cooling rate is adjusted using a temperature controller to regulate supersaturation of the wastewater to produce acetic acid crystals. At this time, the cooling rate is 0.1 to 1 K / min. The cooling temperature range is preferably -6 to 16 ° C, more preferably 0 to 13 ° C.

In the step of forming the acetic acid crystal, the cooling rate is a very important factor for determining nucleation of the acetic acid crystal and the growth rate of the crystal, and the degree of impurity inclusion of the acetic acid crystal varies greatly depending on the cooling rate. In a condition where the cooling rate is excessively high, a large amount of concentrated wastewater can be deeply contained in crystals due to a rapid crystal growth rate, and a large amount of very fine particulate crystals can be generated. On the other hand, under the condition that the cooling rate is excessively low, it is effective to obtain pure acetic acid crystals, but productivity is low, which may be economically undesirable. Therefore, it is preferable to adjust the cooling rate within the above range.

In step 2), acetic acid at a high concentration is recovered from the acetic acid crystals formed by using a cooling crystallizer through partial melting. High purity acetic acid crystals are formed inside the dura, and acetic acid crystals formed outside the dura may contain wastewater. By partially melting the crystals outside the epidermis, the wastewater contained in the acetic acid crystals is separated and removed. That is, it is possible to separate the acetic acid crystal into high purity acetic acid and residual concentrated wastewater through the partial melting. In this case, the heating temperature and the velocity condition are important.

The remaining concentrated wastewater includes water, refractory compounds and the like, and may partially contain non-separated acetic acid. The melting is carried out by partially heating the acetic acid crystal in the crystallizer at a rate of 0.1 to 5 K / min in a temperature range of -6 to 20 ° C to partially melt the crystal and to separate and recover the remaining concentrated wastewater from the crystal.

In the step 2), the partial melting of the acetic acid crystals proceeds, and the remaining concentrated wastewater can be repeatedly subjected to the crystal formation step of the step 1) and the acetic acid recovery step of the partial melting of the step 2). By repeating these steps, it is possible to separate and purify acetic acid with higher yield and higher purity.

The melting temperature is in the range of -6 to 20 ° C, more preferably 0 to 16 ° C. When the melting temperature is lower than -6 ° C, melting is not caused. When the melting point is higher than 20 ° C, The yield may be lowered.

Fig. 2 is a schematic view showing an apparatus schematic of a film-type tubular cooling crystallizer as an example.

The film-type tubular cooling crystallizer disclosed in the present invention includes a jacketed film-type tubular crystallizer 20 and an outer circulator 10 for cooling or heating the jacket to adjust the temperature of the jacket. A temperature controller 40 for controlling the temperature of the crystallizer, and a vacuum device 30 at the bottom of the crystallizer for effective removal of the concentrated wastewater. The center temperature of the wastewater to be purified can be measured with a K-type thermometer.

The circulator is filled with a refrigerant to control the temperature. The refrigerant circulates in the crystallizer and regulates the temperature of the wastewater fed into the crystallizer, thereby allowing the crystal to grow on the cooling surface of the crystallizer. The refrigerant is not particularly limited, but is preferably a mixture of water and ethylene glycol, more preferably a mixture of water and ethylene glycol in a volume ratio of 1: 1 to 1: 3, more preferably a volume ratio of 1: 1 Can be used.

Circulating the refrigerant in the crystallizer to maintain a constant temperature, In order to precisely control the temperature cooling rate of the circulator in the range of 0.1 to 1 K / min, a differential integral temperature controller (PID controller) can be installed in the thermostat and the temperature of the crystallizer can be precisely controlled by the temperature programming method.

Further, the film-type tubular cooling crystallizer of the present invention may further include a vacuum device at the lower part of the crystallizer for efficient separation of the concentrate upon melting.

In general, the epidermal crystallizer can be classified into tubular, rod-like, and plate-like types depending on the type thereof. The plate-type crystallizer has a low efficiency and is not only disadvantageous to continuous process work but also has a problem that it is difficult to precisely control and maintain temperature, which is essential for organic matter separation such as acetic acid. Because of this, the purity of the separation material is low and it is not suitable for separation and purification of high purity substance. On the other hand, in the case of a film-type tubular cooling crystallizer, such a problem can be solved, which is preferable.

The tube-type cooling crystallizer is a device designed to precisely control the temperature outside the cylindrical tubular cooling crystallizer, and to distinguish between opening and closing of the upper and lower parts. Such a film-type tubular crystallizer for cooling crystallization is performed by an indirect cooling method comprising a double jacket tubular crystallizer in which a refrigerant is circulated and a circulator capable of controlling the temperature for cooling or heating the jacket.

Accordingly, the present invention can separate and purify acetic acid having high purity and high purity from acetic acid wastewater.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples illustrate the present invention and the present invention is not limited by the following examples, and various modifications and changes may be made. The scope of the present invention will be determined by the technical idea of the following claims.

< Example >

In the following Examples 1 to 4, acetic acid having a purity of 98% was used as a seed and a mixed solution of water: ethylene glycol = 1: 1 (v / v) was used as a refrigerant used in the crystallizer.

Example One.

Acetic acid was separated and purified from acetic acid wastewater according to the conditions shown in Table 1 below.

85% HMX acetic acid wastewater (100 parts by weight) was supplied to a durable tubular cooling crystallizer and cooled from 20 占 폚 to 4 占 폚. At this time, the cooling rate was maintained at 0.1 K / min, acetic acid crystals (1 part by weight) having 98% purity seed were used, and the seeding point was adjusted between -2 and 15 ° C. Acetic acid crystals were generated from 85% HMX wastewater and partially melted by heating at a temperature range of -6 to 20 占 폚 (heating rate of 1 K / min). 40 ml of the liquid from the mother liquor was melted by separating the whole 400 ml over 10 times in total. The purity of the acetic acid obtained after the crystallization operation was the highest at the seeding temperature of 0 ° C. From the results of Table 1, it was confirmed that 99% or more of pure acetic acid can be obtained at a sweating fraction of 80% or more.

division HMX waste concentration (%) Cooling speed (K / min) seeding point (占 폚) Partial melting (%) The purity (%) of the obtained acetic acid Example 1 85% 0.1 -2 10 94.5 20 96 30 97 40 97.5 50 98 60 98 70 98.5 80 99 90 99.9 100 99.8 0 10 96 20 97 30 98 40 99 50 99.8 60 99.8 70 99.9 80 99.9 90 99.9 100 99.9 One 10 94 20 96 30 97 40 98.5 50 99 60 99.8 70 99.9 80 99.9 90 99.9 100 99.9 2 10 95 20 96.5 30 97 40 97.5 50 98 60 98 70 99 80 99.9 90 99.9 100 99.9 10 10 97 20 98 30 98.5 40 99 50 99.5 60 99.7 70 99.8 80 99.9 90 99.9 100 99.9 15 10 96 20 96.5 30 98 40 98.5 50 99 60 99.3 70 99.7 80 99.9 90 99.9 100 99.9

As can be seen from the results of Table 1, it can be seen that the concentrated solution from the wastewater is effectively discharged or discharged to the mother liquor according to the seeding point in the HMX acetic acid (85%) wastewater. Also, it can be seen that the purity of acetic acid generally increases as the partial melting ratio increases.

More specifically, it was confirmed that the purity increase rate of acetic acid in Example 1 was the best when the seeding point was 0 ° C.

Example 2.

Acetic acid was separated and purified from acetic acid wastewater according to the conditions shown in Table 2 below.

95% < RTI ID = 0.0 > HMX < / RTI > acetic acid wastewater was fed to a durable tubular cooled crystallizer and cooled to 25 占 폚 at 0 占 폚. At this time, the cooling rate was maintained at 0.1 K / min, seeded 98% pure acetic acid crystals (1 part by weight) were used, and the seeding point was adjusted between 2 and 12 ° C. Acetic acid crystals were generated from 85% HMX wastewater and partially melted by heating at a temperature range of -6 to 20 占 폚 (heating rate of 1 K / min). 40 ml of the liquid from the mother liquor was melted by separating the whole 400 ml over 10 times in total. The purity of acetic acid obtained after the crystallization operation was the highest at the seeding temperature of 2 ° C. From the results of Table 2, it was confirmed that acetic acid having a purity of 99% or more was obtained at a sweating fraction of 80% or more.

division HMX waste concentration (%) Cooling rate
(K / min) seeding point (占 폚) Partial melting (%) The purity (%) of the obtained acetic acid Example 2 95 0.1 2 10 97.2 20 97.5 30 98.2 40 98.5 50 98.7 60 98.5 70 99 80 99.2 90 99.7 100 99.9 4 10 97 20 97.3 30 98 40 98.5 50 98.7 60 99 70 99.2 80 99.3 90 99.5 100 99.8 6 10 96.8 20 97.4 30 97.7 40 98.3 50 98.8 60 99.1 70 99.2 80 99.3 90 99.3 100 99.4 8 10 96 20 96.4 30 97 40 97.8 50 98.4 60 98.7 70 98.9 80 99.3 90 99.4 100 99.5 10 10 96 20 96.5 30 97.2 40 98 50 98.5 60 98.7 70 99 80 99.3 90 99.5 100 99.7 12 10 96.8 20 97.2 30 98 40 98.3 50 98.6 60 99 70 99.2 80 99.4 90 99.5 100 99.6

As shown in Table 2 above, the emission effect of the mother liquor can be confirmed according to the seeding time in the HMX acetic acid (85%) wastewater. More specifically, it was confirmed that acetic acid with the highest purity was obtained when the seeding time was 2 ° C in Example 2.

Example 3.

Acetic acid was separated and purified from acetic acid wastewater according to the conditions shown in Table 3 below.

85% < RTI ID = 0.0 > HMX < / RTI > acetic acid wastewater was fed to a durable tubular cooled crystallizer and cooled from 25 占 to 0 占 폚. At this time, cooling rate was maintained at 0.1 K / min or 1 K / min to confirm the influence on the cooling rate. Seed 98% pure acetic acid crystals (1 part by weight) were used, Lt; / RTI > Acetic acid crystals were generated from 85% HMX wastewater and partially melted by heating at a temperature range of -6 to 20 占 폚 (heating rate of 1 K / min). 40 ml of the liquid from the mother liquor was melted by separating the whole 400 ml over 10 times in total.

As can be seen in Table 3 below, when the cooling rate was 0.1 K / min, acetic acid with a purity higher than 1 K / min was obtained. From the results of Table 3, it was confirmed that the purity of acetic acid obtained after the crystallization operation was completed was found to be acetic acid having a purity of 99% or more at a swelling fraction of 60% or more.

division HMX waste concentration (%) Cooling rate
(K / min) seeding point (占 폚) Partial melting
(%) The purity (%) of the obtained acetic acid Example 3 85 0.1 15 10 95.8 20 96.2 30 97.3 40 99 50 99.3 60 99.5 70 99.8 80 99.9 90 99.9 100 99.9 One 10 96.3 20 96.7 30 98.1 40 98.3 50 98.6 60 99 70 99.5 80 99.8 90 99.9 100 99.9

Example 4.

Acetic acid was separated and purified from acetic acid wastewater according to the conditions shown in Table 4 below.

As can be seen in Table 4 below, the purest acetic acid could be recovered at a cooling rate of 0.1 K / min. From the results of Table 4, it was confirmed that the purity of acetic acid obtained after the crystallization operation was completed was found to be acetic acid having a purity of 99% or more at a sweating fraction of 90% or more.

division HMX waste concentration (%) Cooling rate
(K / min) seeding point (占 폚) Partial melting
(%) The purity (%) of the obtained acetic acid Example 4 95 0.1 15 10 97.3 20 97.7 30 98.6 40 99 50 99.3 60 99.4 70 99.5 80 99.5 90 99.6 100 99.7 One 10 97.2 20 97.4 30 98.3 40 98.7 50 99 60 99.1 70 99.2 80 99.2 90 99.3 100 99.4 3 10 95.7 20 96 30 96.5 40 97 50 97.5 60 97.7 70 97.8 80 98 90 99.3 100 99.5 5 10 96 20 96.7 30 97 40 97.2 50 97.5 60 98.2 70 99 80 99.8 90 99.4 100 99.6

As can be seen from the results of Tables 1 to 4, by using the separation and purification method of acetic acid of the present invention, it is possible to recover 98% or more of high purity acetic acid in wastewater containing acetic acid. This method can solve the problem of excessive energy consumption, high cost, and secondary environmental pollution of existing adsorption method, distillation method, and the like, and is easy to apply to mass production. In addition, since it is intended to separate and purify the acetic acid which is an organic compound, collect it, and reuse it, it is advantageous in economic and environmental aspects.

10: Circulator
20: Epidermal Tubular Crystallizer
30: Vacuum device
40: thermostat
50: sampling beaker

Claims

1) Acetic acid wastewater is supplied to a film-type tubular cooling crystallizer, and acetic acid crystal seed is added to the acetic acid wastewater at a cooling rate of -6 to 16 ° C at a temperature of -6 to 16 ° C at a cooling rate of 0.1 to 1 K / min To form acetic acid crystals; And
2) heating the acetic acid crystal to a temperature range of -6 to 20 ° C at a heating rate of 0.1 to 5 K / min or to maintain the temperature within the above-mentioned temperature range to partially melt and recover the remaining acetic acid crystals; Wherein the acetic acid is separated and purified from acetic acid wastewater.

The method according to claim 1,
Wherein the seed is acetic acid having a purity of 98% or more.

The method according to claim 1,
Wherein the seed is used in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of acetic acid wastewater.

The method according to claim 1,
Wherein the residual acetic acid crystals have a purity of 98% or more.

The method according to claim 1,
Wherein the film-type tubular cooling crystallizer is composed of a double-jacketed tubular cooling crystallizer and a circulator, and is performed by an indirect cooling method.

The method according to claim 1,
Wherein the acetic acid wastewater is wastewater containing 60% or more of acetic acid generated in the process of manufacturing a high molecular weight RDX (HMX).

The method according to claim 1,
In the step 1), seed crystals are formed on the inner wall of the crystallizer after the wastewater is supplied to the membrane-type cooling crystallizer, and seeding process is induced by supplying seeds that have been lowered to just below the freezing point Wherein the acetic acid is separated and purified from acetic acid wastewater.

The method according to claim 1,
Wherein the acetic acid wastewater comprises at least one decomposable compound selected from 2,4,6-trinitrotoluene, methyl dinitrophenol, methyl dinitrobenzene and dinitroaniline. .

The method according to claim 1,
Wherein the acetic acid crystals are formed by cooling a mixed solution of water and ethylene glycol in a volume ratio of 1: 1 to 1: 3 as a refrigerant of the film-type tubular cooling crystallizer, by indirect cooling method. Separation purification method.