KR20060083867A - Liquid-liquid extracting method - Google Patents

Abstract

Provides a method for carrying out a large flow of liquid liquor extraction by a wide range of operation, an efficient and simple method, especially in the case of extracting useful components from wastewater exceeding 50 t / hr generated from a device for producing high purity terephthalic acid. .

After mixing the extractant for extracting the desired components from the wastewater and the wastewater by flowing the mixture through a pipe having a structure for mixing them, supplying the mixed liquid to the vessel while decelerating using gravity, and standing still to separate the liquid liquid. Liquid liquid extraction method.

Stationary Separator, Static Mixer, Wastewater, Extractant

Description

Liquid extraction method {LIQUID-LIQUID EXTRACTING METHOD}

1 is an explanatory diagram showing an aspect of the present invention.

* Description of the symbols for the main parts of the drawings *

1: terephthalic acid plant

2: static mixer

3: political separator

4: static mixer

5: political separator

6: pump

7: pump

8: flow regulator

9: flow regulator

10: flow controller

11: flow regulator

S1: Terephthalic Acid Plant Wastewater Discharge Furnace

S2: Wastewater 1st Stage Static Mixer Supply Furnace

S3: Paraxylene Supply Furnace

S4: Paraxylene first stage static mixer flow controller supply passage

S5: Paraxylene 1st Stage Static Mixer Supply Furnace

S6: 1st stage static separator supply path

S7: first stage static separator to para xylene exit

S8: first stage stationary separator, para-xylene conveying path

S9: first stage static separator wastewater outlet

S10: Paraxylene 2nd Stage Static Mixer Flow Controller Supply Path

S11: Paraxylene 2nd Stage Static Mixer Supply Furnace

S12: 2nd stationary separator supply path

S13: to the second stage stationary separator, para-xylene exit

S14: second stage stationary separator, para-xylene conveying path

S15: 2nd stationary separator wastewater outlet

This invention relates to the method of liquid-liquid extraction of the target component, for example from wastewater of large flow volume exceeding 50 t / hr.

Since the usefulness in wastewater is low in recovery efficiency when the concentration is low, it is usually treated by the activated sludge method. For example, the wastewater generated from the apparatus for producing high purity terephthalic acid contains a large amount of paratoluic acid, which is a reaction intermediate, but is usually treated by an activated sludge process because of its low concentration.

However, in the treatment by the activated sludge method, not only valuables are lost but also a lot of energy such as electricity is consumed for operation. It may also be the cause of odor. As the size of the wastewater increases due to the increase in size, such as an apparatus for producing terephthalic acid, it is necessary to remove and recover useful materials from the wastewater from the viewpoint of economical efficiency as well as the global environment.

As a method of recovering useful substances in wastewater, for example, Japanese Patent No. 289927 discloses a method for extracting paratoluic acid contained in wastewater generated from an apparatus for producing terephthalic acid with paraxylene. Since this method uses paraxylene, which is a raw material of terephthalic acid, as an extractant, it is an excellent method because it does not require a regeneration step of the extractant. However, in the conventional extraction apparatus, the apparatus cost is high and the economy is inferior.

(Patent Document 1) Japanese Patent No. 289927

Methods of extracting useful materials from wastewater are well known. For example, Chapters 11 to 5 of the revised edition of the Chemical Engineering Manual (Chemical Engineering Society) provide various methods.

However, for example, the mixer settler extractor described in chapter 11.5.1 of the above handbook is complicated and expensive in the case of multi-stage extraction. For this reason, in the case of multiple stages, a tower extraction device is used. For example, the countercurrent differential extraction tower described in Section 11.5.2 of the above handbook has a simple structure, which causes drift. As a result, it is difficult to increase the size and is rarely adopted industrially. In order to prevent this, pulsating or the like can suppress drift, but the structure becomes complicated and expensive. In addition, although the structure of the comparative semi-stage extraction tower described in chapter 11.5.3 of the above handbook is simple in structure, the operation range is narrow and there is no flexibility in operation. In order to improve this, although the stirring type | mold stage extraction tower etc. which were described in the chapter 11.5.4 of the said manual are proposed, the apparatus becomes complicated and expensive. In this way, the tower extractor is complicated and expensive to avoid drift and take a wider operating range.

If there is an efficient and inexpensive extraction device, not only can the lean wastewater contained in the waste water or the like be recovered, but also the purification of the waste water can be carried out and the water can be recycled.

However, the method of extracting paratoluic acid contained in the wastewater generated from the apparatus for producing terephthalic acid with paraxylene disclosed in Japanese Patent No. 289927 (Patent Document 1) does not have an inexpensive extraction device and is carried out commercially. It is difficult.

Accordingly, the present invention provides a method for carrying out a large flow rate of liquid liquor extraction in a wide operating range, in an efficient and simple manner, in particular from wastewater exceeding 50 t / hr generated from an apparatus for producing industrially important high purity terephthalic acid. It is an object of the present invention to provide a suitable method for extracting.

The present invention is made by mixing and standing still as in the conventional extraction operation, but provides an extraction method suitable for treating a large flow rate of wastewater.

That is, according to the present invention, the extractant for extracting the desired components from the wastewater and the wastewater is mixed by flowing them through a pipe having a structure in which they are mixed, and then the mixed liquid is supplied to the vessel while decelerating using gravity, Iii) separating the liquid solution. It is preferable to supply the said mixed liquid from the lower part of a container, decelerating using gravity.

In addition, the present invention is characterized in that the mixed liquid is fed from a lower part of the container, left to stand, and then separated by separating the liquid from the bottom of the container by mixing the extractant for extracting the desired components from the waste water and the waste water by flowing them through a pipe having a structure for mixing them. It relates to a liquid liquid extraction method.

As the piping, a static mixer is suitable. Moreover, it is preferable to arrange | position the said piping in an up-down direction, and when a hard liquid is a dispersed phase, a flow is made from top to bottom, and when a heavy liquid is a dispersed phase, it is preferable to flow up from a bottom. Do. Herein, the hard liquid means that the density is small in the liquid to be mixed, and is usually an organic liquid, and the heavy liquid means that the density is large in the liquid to be mixed, and is usually water.

As a method of slowing the inflow rate of the mixed liquid, a method of supplying the lower portion of the container by using gravity to decelerate is preferable because it does not disturb the flow in the stationary separation. As a deceleration method by gravity, gravity may be put in the direction which opposes gravity from the lower part of a container, may be supplied toward a container bottom surface, inverted from the container bottom surface, and may be decelerated using gravity. Either way, it is desirable to confirm that the inflow rate is decelerated in a short time without accompanying turbulence in the vessel by computer analysis of the flow state.

In another aspect, the present invention is a liquid liquid extraction method, characterized in that the container is under pressure and the waste water and the extractant are drawn out by using the pressure of the container, or the liquid level control device and pressure control device between the gas phase and the liquid state when the container is full It provides a liquid solution extraction method characterized in that it is not provided.

It is preferable to remove the wastewater and the extractant after the stationary separation, respectively, by adjusting the flow rate cascade-controlled based on the amount of the wastewater flowing into the vessel or the amount of the extractant.

Moreover, this invention is provided with the partition board which the said container has the height of 10 to 70% of a container height, and removes the heavy liquid (water phase) which liquid-liquid separated from the lower part on the opposite side to the side which supplied the said mixed liquid, A liquid liquid extraction method is provided, wherein the hard liquid (organic phase) separated from the liquid liquid is removed from an upper portion on the side opposite to the side to which the mixed liquid is supplied.

It is also possible to combine the liquid-liquid extraction method in two or more stages, and to perform multistage extraction. In addition, wastewater from a terephthalic acid plant may be used as the wastewater.

The present invention is, for example, after flowing a mixture (raw material to be solvent extraction, specifically waste water) and the extractant in a pipe having a structure in which the flow is mixed, and then, the water is full and pressurized By supplying the lower part of the stationary separator and extracting the extract and the extractant using the pressure of the stationary separator under pressure based on the flow rate of the extract or extractant, a liquid liquid extraction method suitable for treating a large flow rate can be provided.

The mixing of the extract and the extractant is not economical because a stirrer is used in a conventional mixer settler extractor, but in the case of a multistage, a fairly expensive stirring apparatus and a stirring vessel are required. In addition, the columnar shape without a mechanical stirring device is inadequately mixed, resulting in poor extraction efficiency. In the present invention, by using a pipe having a structure in which the flows are mixed, the mixing is efficiently completed by a simple device.

As the piping having a structure in which the flows are mixed, for example, there is a stationary mixer called a static mixer. It is known to perform an extraction operation using a static mixer. In the case of performing multistage extraction, a pump is required at each stage due to the pressure loss in the static mixer. According to the present invention, the stationary separator is pressurized to solve the problem that the pump is required at each stage by removing the liquid using a pressure instead of a pump. Moreover, this invention solves the subject that the pressure regulating device for pressurization is added by making the stationary separator full.

In the case of a stationary separator having a conventional interface and a gas phase, two liquid level adjusting devices are required. Moreover, in order to adjust the liquid level, the residence time of the stationary separator is greater than the time required for the original liquid liquid separation. Longer In the present invention, the liquid level control device at the interface between the two liquids is made unnecessary by removing the supplied flow rate of the extract or extractant based on the flow rate. Further, the present invention is characterized in that the liquid level control device at the gas-liquid interface is unnecessary by allowing the stationary separator to become full.

This eliminates the need for liquid level control, and according to the present invention, it is also possible to provide a stationary separator for only the time required for the original liquid liquid separation, not the residence time required for liquid level control. In order to adjust the liquid level, the residence time of the liquid usually more than 10 minutes is required. If the liquid level control is unnecessary by using the present invention, for example, in case of paraxylene and water system which are easy to separate the liquid liquid, the size of the stationary separator can reduce the flow since it can be separated within 1 minute without the flow. Just time.

Specifically, this is achieved by cascade controlling the flow rate and the flow rate from the vessel. For example, when the extractant is paraxylene and the extract is wastewater, a value equal to the flow rate of the supplied paraxylene may be removed by cascade control as the amount of paraxylene taken out from the stationary separator, and the wastewater may be removed so that the container becomes full. Since the wastewater is a heavy liquid, when the seal operation of raising the pipe to be removed to a position higher than the container can be carried out so that the container becomes full.

In the case of controlling the flow rate of waste water, the same value as the flow rate of the supplied waste water is taken out by cascade control as the amount of waste water discharged from the stationary separator, and paraxylene can be taken out so that the container becomes full when it is overflowed from the top of the container. have. Since the flow rate into and out flow rate are not the same, it is necessary to make fine adjustments so that the wastewater does not enter the paraxylene and the paraxylene into the wastewater, but once adjusted, it can be stably removed later without mixing.

The present invention is characterized by minimizing the stationary separator by supplying the mixed liquid from the bottom of the stationary separator to reduce the feed rate using gravity. Furthermore, a filling may be placed inside the supply pipe to slow down the feed rate, but for larger equipment, pipes with sufficient diameter may be used and / or supplied in multiple numbers to increase the cross sectional area of the supply pipe. It is also possible to use a means such as lowering the feed rate by taking a means such as.

In addition, the present invention is characterized by maximizing the separation path time by completely reversing the direction of the heavy liquid flow by supplying a partition plate between the supply port and the outlet of the heavy liquid by supplying from the bottom of the stationary separator. It is preferable that the height of a partition plate is 10 to 70% of a container height. As described above, the supply of the mixed liquid from the lower part can use not only gravity but also inertial force, so that the flow rate of the heavy liquid is higher than that of the hard liquid, and is particularly useful when the flow rate of the heavy liquid dominates the separation. In addition, the hard liquid in this invention means that the density is small in the liquid to mix, and is normally an organic liquid, and a heavy liquid means the density in a liquid to be mixed and is usually water.

In the present invention, since the mixing is carried out by a pipe having a simple structure as described above, and a stationary separator having no special structure is used, it is possible to perform a stable extraction operation in a wide operating range. The lower limit of the operating range is that the mixing in the piping is insufficient because the flow rate drops, but the piping is arranged in the vertical direction, preferably vertical, so that when the hard liquid is a dispersed phase, the flow flows from the top to the bottom and the heavy liquid is dispersed. In the case of a phase, the operation range can be widened by moving from the bottom up. The upper limit of the operating range depends on the separation capability of the stationary separator, but the time to drop the flow rate in the stationary separator rather than the time of liquid separation in the stationary separator is the first limit, so that the diameter of the pipe supplied to the stationary separator is thickened. It is possible to widen the operation range by simple means, for example, and / or supplying a plurality of pieces. In addition, an operation range means the flow range of hard liquid and heavy liquid, and an upper limit and a lower limit of an operation range mean each maximum flow volume and minimum flow volume.

The present invention can be applied to, for example, wastewater treatment in the production of terephthalic acid. An example is described below.

In a solvent of acetic acid, paraxylene was oxidized with air at a reaction pressure of 0.4 to 5 MPa-G and a reaction temperature of 160 to 260 ° C, using a cobalt compound, a manganese compound, and a bromine compound as a catalyst to form crude terephthalic acid. Manufacture. The main impurities in this crude terephthalic acid are 500 to 5000 ppm by weight of 4-carboxybenzaldehyde as an intermediate of oxidation and 100 to 1000 ppm by weight of paratoluic acid.

The crude terephthalic acid thus obtained is dissolved in water by raising the temperature to 225 ° C or higher, preferably 250 to 310 ° C under a pressure of 5 MPa-G or higher, preferably 7 to 9 MPa-G. At this time, it adjusts so that terephthalic acid concentration in water may be 10-40 weight%, Preferably it is 20-35 weight%.

Subsequently, in contact with a catalyst such as palladium in the presence of hydrogen to reduce the oxidation intermediate 4-carboxybenzaldehyde, which is a major impurity in the crude terephthalic acid, to paratoluic acid which is easy to remove by crystallization, After crystallization by reduced pressure in multiple stages, preferably in three to seven stages, solid-liquid separation is carried out to obtain high purity terephthalic acid.

Paraxylene is boosted to 0.15 MPa-G or more, preferably 0.3 to 1.0 MPa-G as a wastewater generated in the manufacturing process of such high purity terephthalic acid, and is mixed by flowing it in a static mixer. The mixing ratio is 5 to 70 parts by weight, preferably 10 to 40 parts by weight of paraxylene with respect to 100 parts by weight of waste water. The number of times of inversion in the static mixer is 2 or more times and 30 times or less, Preferably it is 5 times or more and 15 times or less.

Then, the mixed liquid from the static mixer is supplied from one lower portion partitioned by a partition plate of a stationary separator having a partition plate at the center under a pressure of 0.1 MPa-G or more, preferably 0.25 to 9.95 MPa-G. And wastewater. The separated paraxylene is removed from the other upper part of the stationary separator by the flow rate adjustment in the same amount as that of the supplied paraxylene, and the wastewater is removed from the lower part. The drained wastewater is again mixed with paraxylene by a static mixer, and under the pressure of 0.05 MPa-G or more, preferably 0.2 to 9.9 MPa-G, one lower portion partitioned by a partition plate of a stationary separator having a partition plate at the center thereof. Separation of paraxylene and wastewater by feeding from

In this way, the wastewater from which impurities are extracted twice by paraxylene is removed by steam stripping to remove and recover paraxylene in the mixed and dissolved portions, and then reused as water for purifying crude terephthalic acid. Depending on the type of wastewater, it may not be possible to remove impurities which adversely affect the quality of the high purity terephthalic acid, which is a product, only by extracting with paraxylene. In this case, since these impurities are very small, they are removed by activated carbon, membrane separation or the like, and then reused as water for purifying crude terephthalic acid. In addition, paraxylene taken out from the top of the separator is used as a raw material for producing crude terephthalic acid.

EXAMPLE

Although the Example of this invention is described below, this invention is not limited to the following Example.

Example 1

1 is an explanatory diagram showing one embodiment of the present invention. The wastewater from the terephthalic acid plant 1 flowed through the wastewater discharge path S1 and was boosted to 0.6 MPa-G by the pump 6, and mixed with paraxylene from the supply path S5 and the static mixer 2. The paraxylene from the supply passage S5 flows through the supply passage S3 and is boosted to 0.7 MPa-G by the pump 7, and then flows to 1 part by weight with respect to 4 parts by weight of the wastewater by the flow regulator 10. Adjusted. The static mixer 2 is a product of Noritake Co., Limited. The number of elements for reversing the flow is 12 and the residence time is 15 seconds.

The liquid mixed in the static mixer 2 flowed through the supply path S6, and was supplied from the lower part of the stationary separator 3. The paraxylene after liquid-liquid separation flowed out through the exit S7, flow-controlled by the flow regulator 8, was taken out, was sent to the terephthalic acid plant 1 from the conveyance path S8, and was used as a raw material of terephthalic acid. The flow regulator 8 was cascade-controlled so that it might become the same as the flow volume of the flow regulator 10. The pressure of the stationary separator 3 was 0.55 MPa-G, and the residence time was 3 minutes.

The wastewater after liquid-liquid separation flowed from the lower part of the stationary separator 3 to the outlet path S9, and mixed with paraxylene from the supply path S11 in the static mixer 4. The outlet path S9 raises the pipe position higher than the stationary separator 3 so that the stationary separator 3 becomes full. The paraxylene from the supply passage S11 flows through the supply passage S3 and is boosted to 0.7 MPa-G by the pump 7, and then flows to 1 part by weight with respect to 4 parts by weight of the wastewater by the flow regulator 11. Adjusted. The static mixer 4 is a product of Noritake Co., Limited, the number of elements for reversing the flow is 12, and the residence time is 15 seconds.

The liquid mixed in the static mixer 4 flowed through the supply path S12, and was supplied from the bottom of the stationary separator 5. The para-xylene after liquid-liquid separation flowed out through the outlet path S13, flow-controlled by the flow regulator 9, was taken out, was sent to the terephthalic acid plant 1 from the conveyance path S14, and was used as a raw material of terephthalic acid. The flow regulator 9 was cascade-controlled so as to be equal to the flow rate of the flow regulator 11. The pressure of the stationary separator 5 was 0.5 MPa-G, and the residence time was 3 minutes.

The wastewater drained from the outlet passage (S15) at the bottom of the stationary separator (5) is stripped and recovered by removing the remaining paraxylene by steam stripping, and then removing the impurities that could not be removed by the paraxylene with the RO membrane, and then terephthalic acid plant (1). ) Was reused as water to purify crude terephthalic acid. The outlet path S15 raises the pipe position higher than the stationary separator 5 so that the stationary separator 5 is full.

As mentioned above, 90 weight% of paratoluic acid contained in the wastewater of the terephthalic-acid plant 1 was collect | recovered by the extremely small apparatus of the total residence time of 6 minutes and 30 second, without using a special stirring apparatus or a packing material.

The present invention provides a method for carrying out a large flow of liquid liquid extraction in a wide range of operation, efficient and simple method.

In the present invention, when the flow rate is high, but the concentration is low, the economical efficiency of recovery is low and the wastewater is discarded as wastewater, for example, when the useful components are extracted from wastewater exceeding 50 t / hr generated from a device for producing high-purity terephthalic acid for reuse of the wastewater. It provides a particularly useful method.

Claims (11)

After mixing the extractant for extracting the desired components from the wastewater and the wastewater by flowing the mixture through a pipe having a structure for mixing them, supplying the mixed liquid to the vessel while using gravity to decelerate, and allowing the liquid to stand to separate the liquid liquid. Liquid liquid extraction method. The method of claim 1, The liquid solution extraction method characterized in that for supplying the mixed liquid from the lower portion of the container while decelerating using gravity. After extracting the wastewater and the extractant for extracting the desired components from the wastewater by flowing them through a pipe having a structure in which they are mixed, the mixed liquid is supplied from the lower part of the container, and the liquid liquid is extracted. Way. The method according to any one of claims 1 to 3, The liquid solution extraction method characterized in that the pipe is a static mixer. The method according to any one of claims 1 to 4, The pipe is arranged in the vertical direction, the flow of liquid from the top down when the hard liquid is dispersed phase, the flow of liquid from the bottom up when the heavy liquid is dispersed phase. The method according to any one of claims 1 to 5, The container is under pressure, and the liquid solution extraction method characterized in that the waste water and the extractant are taken out using the pressure of the container. The method according to any one of claims 1 to 6, The liquid solution extraction method characterized in that the container is in full water and does not have a liquid level control device and a pressure control device between the gas phase and the liquid phase. The method according to any one of claims 1 to 7, And extracting the wastewater and the extractant after the stationary separation, respectively, by adjusting the flow rate controlled by the cascade based on the amount of the wastewater flowing into the vessel or the amount of the extractant. The method according to any one of claims 1 to 8, The container is provided with a partition plate having a height of 10 to 70% of the height of the container, and the liquid liquid separated from the lower side on the side opposite to the side to which the mixed liquid is supplied is taken out, and the liquid liquid from the upper side opposite to the side to which the mixed liquid is supplied. A liquid solution extraction method, characterized in that the separated liquid solution is removed. The liquid liquid extraction method characterized by multiple-stage extraction combining the liquid liquid extraction method in any one of Claims 1-9. The method according to any one of claims 1 to 10, And said wastewater is wastewater from a terephthalic acid plant.

Images