KR102319305B1 - Process for continuous recovering (meth)acrylic acid and apparatus for the process - Google Patents

Abstract

The present invention relates to a method for recovering (meth)acrylic acid and an apparatus used for the recovery method. In the method for recovering (meth)acrylic acid according to the present invention, an aqueous solution of (meth)acrylic acid having a different concentration is discharged from the absorption tower, respectively, so that an aqueous solution having an acrylic acid concentration can be obtained from the lower portion of the absorption tower, and a high (meth)acrylic acid recovery rate It enables the stable recovery of (meth)acrylic acid and operation of the process, which can secure

Description

Method and apparatus for recovery of (meth)acrylic acid

The present invention relates to a method and apparatus for recovering (meth)acrylic acid.

(Meth)acrylic acid is generally prepared by a gas phase oxidation reaction of a compound such as propane, propylene, or (meth)acrolein in the presence of a catalyst. For example, in the presence of an appropriate catalyst in the reactor, propane, propylene, etc. are converted to (meth)acrylic acid via (meth)acrolein by a gas phase oxidation reaction, and (meth)acrylic acid, unreacted propane or propylene, ( A mixed gas containing meth) acrolein, an inert gas, carbon dioxide, water vapor, and various organic by-products (acetic acid, low-boiling by-product, high-boiling by-product, etc.) by the above reaction is obtained.

The (meth)acrylic acid-containing mixed gas is brought into contact with an absorption solvent in a (meth)acrylic acid absorption tower to be recovered as a (meth)acrylic acid aqueous solution. And, the (meth) acrylic acid is degassed insoluble gas is recycled through the synthesis reaction of (meth) acrylic acid, a part is incinerated and converted into harmless gas and discharged. And, the (meth)acrylic acid aqueous solution is extracted, distilled and purified to obtain (meth)acrylic acid.

On the other hand, in order to improve the recovery efficiency of such (meth)acrylic acid, various methods for controlling process conditions or process order have been proposed. Among them, as a method for separating water and acetic acid from the (meth)acrylic acid aqueous solution obtained in the (meth)acrylic acid absorption tower, a method of azeotropic distillation using a hydrophobic solvent in a distillation column is known. As another method, a method of reducing energy consumption by supplying an aqueous (meth)acrylic acid solution to the extraction column and using a hydrophobic solvent to obtain a (meth)acrylic acid extract with a reduced water content and a raffinate solution and distilling the extract is known. have.

However, in the known method for the recovery of (meth)acrylic acid, the absorption tower discharges a single stream of aqueous solution to the bottom, and when it is desired to increase the concentration of the discharged (meth)acrylic acid aqueous solution, the separation efficiency of the absorption tower decreases If the concentration of the (meth)acrylic acid aqueous solution discharged to increase separation efficiency is maintained low, there is a limit in that the purification (or distillation) load in the subsequent purification (or distillation) process cannot but increase.

An object of the present invention is to provide a method for recovering (meth)acrylic acid that can ensure a high (meth)acrylic acid recovery rate and more improved operating stability.

Another object of the present invention is to provide an apparatus usable for the recovery of the (meth)acrylic acid.

The present invention is

(meth) acrylic acid, an organic by-product, and a mixed gas containing water vapor in contact with water in a (meth) acrylic acid absorption tower to prepare a (meth) acrylic acid aqueous solution;

discharging (meth)acrylic acid aqueous solution of a first concentration from the side of the (meth)acrylic acid absorption tower; and

At the bottom of the (meth) acrylic acid absorption tower, comprising the step of discharging a (meth) acrylic acid aqueous solution of a second concentration;

The first concentration, the concentration of (meth) acrylic acid is lower than the second concentration,

A method for recovering (meth)acrylic acid is provided.

In addition, the present invention,

a mixed gas inlet to which a mixed gas including (meth)acrylic acid, organic by-products, and water vapor is supplied;

A first concentration discharge unit for discharging a (meth)acrylic acid aqueous solution of a first concentration; and

a second concentration discharge unit for discharging a second concentration of (meth)acrylic acid aqueous solution;

The first concentration discharge part is located on the side,

The second concentration discharge unit provides a (meth)acrylic acid absorption tower located at the bottom.

The method and apparatus for recovering (meth)acrylic acid according to the present invention, by discharging aqueous solutions of (meth)acrylic acid of different concentrations from the absorption tower, respectively, ensure a high recovery rate of (meth)acrylic acid and stable (meth)acrylic acid It enables recovery and operation of the process.

1 is a conceptual diagram of an apparatus for recovering (meth)acrylic acid according to an embodiment of the present invention.
2 is a conceptual diagram of a conventional (meth)acrylic acid recovery device.

(meth)acrylic acid recovery method of the present invention,

(meth) acrylic acid, an organic by-product, and a mixed gas containing water vapor in contact with water in a (meth) acrylic acid absorption tower to prepare a (meth) acrylic acid aqueous solution;

discharging (meth)acrylic acid aqueous solution of a first concentration from the side of the (meth)acrylic acid absorption tower; and

At the bottom of the (meth) acrylic acid absorption tower, comprising the step of discharging a (meth) acrylic acid aqueous solution of a second concentration;

The first concentration is maintained at a lower concentration of (meth)acrylic acid than the second concentration.

In addition, the (meth)acrylic acid absorption tower of the present invention,

a mixed gas inlet to which a mixed gas including (meth)acrylic acid, organic by-products, and water vapor is supplied;

A first concentration discharge unit for discharging a (meth)acrylic acid aqueous solution of a first concentration; and

a second concentration discharge unit for discharging a second concentration of (meth)acrylic acid aqueous solution;

The first concentration discharge part is located on the side,

The second concentration discharge unit is located at the bottom.

In the present invention, terms such as first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from other components.

In addition, the terminology used herein is only used to describe exemplary embodiments, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as "comprise", "comprising" or "have" are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features or It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, elements, or combinations thereof.

Also in the present invention, when it is said that each layer or element is formed "on" or "over" each layer or element, it means that each layer or element is formed directly on each layer or element, or other It means that a layer or element may additionally be formed between each layer, on the object, on the substrate.

Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In this specification, first, the term '(meth)acrylic acid' is used to collectively refer to acrylic acid, methacrylic acid, or a mixture thereof.

In addition, the 'mixed gas containing (meth)acrylic acid' refers to a mixed gas that may be generated when (meth)acrylic acid is produced by a gas phase oxidation reaction. That is, according to one embodiment of the present invention, at least one compound ('raw material compound') selected from the group consisting of propane, propylene, butane, i-butylene, t-butylene and (meth) acrolein is used as a catalyst. The (meth)acrylic acid-containing mixed gas can be obtained by a method of gas-phase oxidation reaction under At this time, the (meth)acrylic acid-containing mixed gas includes (meth)acrylic acid, unreacted raw material compound, (meth)acrolein, inert gas, carbon monoxide, carbon dioxide, water vapor and various organic by-products (acetic acid, low-boiling by-product, high-boiling by-product, etc.) may be included. Here, 'light ends' or 'high boiling point by-products' (heavies) are a kind of by-product that can be generated in the production and recovery process of the desired (meth)acrylic acid, and have a molecular weight higher than (meth)acrylic acid. Small or large compounds are collectively referred to.

In addition, 'feed' refers to a liquid mixture containing a solute to be extracted, and a solute having solubility in an extraction solvent and other ingredients not soluble in an inert material. ) may be a mixture of Here, when the extraction solvent is added to the feed, the solute is dissolved from the feed to the extraction solvent by mass transfer. Accordingly, the extraction solvent in which a significant amount of the solute is dissolved forms an extract, and the feed that has lost a significant amount of the solute forms a raffinate.

And, '(meth)acrylic acid aqueous solution' is a feed containing (meth)acrylic acid, and may be obtained by, for example, contacting the (meth)acrylic acid-containing mixed gas with water or water vapor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily practice the present invention.

However, the present invention may be implemented in various different forms and is not limited to the implementation examples described herein.

(meth)acrylic acid recovery method of the present invention, (meth)acrylic acid, an organic by-product and a mixed gas containing water vapor in contact with water in a (meth)acrylic acid absorption tower to prepare a (meth)acrylic acid aqueous solution; discharging (meth)acrylic acid aqueous solution of a first concentration from the side of the (meth)acrylic acid absorption tower; and discharging (meth)acrylic acid aqueous solution of a second concentration from the lowermost part of the (meth)acrylic acid absorption tower; The first concentration is maintained at a lower concentration of (meth)acrylic acid than the second concentration.

According to the previously disclosed methods, the (meth)acrylic acid aqueous solution is discharged as a single stream from the bottom of the absorption tower, supplied to the extraction tower, using a hydrophobic solvent, to obtain a (meth)acrylic acid extract, and distilling the extract (meth)acrylic acid is recovered.

However, the present inventors, in the course of research on the existing (meth)acrylic acid recovery method, in order to increase the purification efficiency of (meth)acrylic acid, to increase the concentration of the discharged (meth)acrylic acid aqueous solution, the absorption tower Separation efficiency is lowered, and when the concentration of the discharged (meth)acrylic acid aqueous solution is kept low in order to increase the separation efficiency, there is a problem in that the purification (or distillation) load is inevitably increased in the subsequent purification (or distillation) process. was confirmed.

Accordingly, as a result of continuous research by the present inventors, streams having different concentration values are discharged separately from the side and bottom of the absorption tower, and through a separate process, for example, a low concentration (meth)acrylic acid aqueous solution is extracted in the extraction process In a method of introducing a high-concentration (meth)acrylic acid aqueous solution to the distillation process, it was confirmed that the separation efficiency can be increased while increasing the energy efficiency of the process, and the present invention has been completed.

First, in the method for recovering (meth)acrylic acid according to the embodiment, a mixed gas including (meth)acrylic acid generated by the synthesis reaction of (meth)acrylic acid, an organic by-product, and water vapor is used in a (meth)acrylic acid absorption tower and contacting with water to obtain an aqueous (meth)acrylic acid solution. In the present specification, the absorption process means a process for obtaining an aqueous (meth)acrylic acid solution as described above in the absorption tower.

More specifically, the synthesis reaction of (meth)acrylic acid may be carried out by oxidizing one or more compounds selected from the group consisting of propane, propylene, butane, isobutylene, and (meth)acrolein under a gas phase catalyst. have.

In this case, the gas phase oxidation reaction may be carried out under a gas phase oxidation reactor having a conventional structure and reaction conditions. A conventional catalyst in the gas phase oxidation reaction may also be used, for example, the catalyst disclosed in Korean Patent Registration Nos. 0349602 and 037818 may be used.

The (meth)acrylic acid-containing mixed gas generated by the gas phase oxidation reaction includes, in addition to (meth)acrylic acid as the target product, unreacted raw material compounds, intermediate (meth)acrolein, inert gas, carbon dioxide, water vapor, and various organic by-products (acetic acid) , low-boiling by-products, high-boiling by-products, etc.) may be included.

This (meth) acrylic acid aqueous solution can be obtained in the form of an aqueous solution in which (meth) acrylic acid is dissolved by supplying a mixed gas containing (meth) acrylic acid to the (meth) acrylic acid absorption tower, and contacting it with water as an absorption solvent. .

Here, the type of the (meth)acrylic acid absorption tower may be determined in consideration of the contact efficiency of the mixed gas and the absorption solvent, for example, a packed column type absorption tower, a multistage tray type. type) absorption tower. The packed column type absorption tower may have a filler such as a lashing ring, a pall ring, a saddle, a gauze, and a structured packing type applied therein. have.

And, in consideration of the efficiency of the absorption process, the mixed gas may be supplied to the lower portion of the absorption tower, and the absorption solvent including water may be supplied to the upper portion of the absorption tower.

The absorption solvent may include water such as tap water and deionized water, and may include circulating process water introduced from another process (eg, an aqueous phase recycled from an extraction process and/or a distillation process). In addition, the absorption solvent may contain a trace amount of organic by-products (eg, acetic acid) introduced from other processes. However, in consideration of the absorption efficiency of (meth)acrylic acid, it is preferable that the absorption solvent supplied to the absorption tower (in particular, the circulation process water) contains 15 wt% or less of organic by-products.

On the other hand, in the (meth)acrylic acid absorption tower, an internal pressure of about 1 to about 1.5 bar or about 1 to about 1.3 bar, and about 50 to about It may be operated under an internal temperature of 100°C or about 50 to about 80°C.

On the other hand, the (meth)acrylic acid aqueous solution, made through the absorption process, increases in concentration as the absorption of (meth)acrylic acid increases toward the bottom inside the absorption tower. In general, at the bottom of the absorption tower, about 50 to about 80% by weight are formed.

According to an example of the present invention, at this time, a relatively low concentration, first concentration aqueous solution of (meth)acrylic acid is discharged to the side of the (meth)acrylic acid absorption tower, and a second relatively high concentration solution is discharged to the bottom. A (meth)acrylic acid aqueous solution of concentration is discharged.

Specifically, the first concentration may be about 40% by weight or less, preferably, about 30% by weight or less, or about 5 to about 30% by weight, and the second concentration is about 60% by weight or more, Preferably, it may be at least about 70% by weight, or from about 70 to about 95% by weight. However, the present invention is not necessarily limited to the above range, and may be determined differently depending on the operating conditions of the process, such as the temperature and pressure inside the absorption tower, and the concentration of (meth)acrylic acid to be finally obtained.

And, the non-condensable gas from which (meth)acrylic acid is degassed is discharged to the upper end of the absorption tower.

At this time, the side of the (meth)acrylic acid absorption tower is about 40 to the lower side from the top when the top of the (meth)acrylic acid absorption tower is set to 0, and the bottom is 100 It may mean a side portion at any one point corresponding to about 99, preferably at any one point corresponding to about 50 to about 90.

In the recovery method of (meth)acrylic acid of one embodiment, the first concentration (meth)acrylic acid aqueous solution discharged from the side is removed from water through a separate extraction process, etc., and then the second concentration (meth)acrylic acid aqueous solution discharged from the bottom. It can be purified by a method such as distillation with

On the other hand, at least a portion of the non-condensable gas discharged to the upper portion of the (meth) acrylic acid absorption tower may be supplied to a process of recovering organic by-products (especially acetic acid) contained in the non-condensable gas again, and the remainder is supplied to a waste gas incinerator and can be discarded. That is, according to one embodiment of the invention, by contacting the non-condensable gas with an absorption solvent, a process of recovering acetic acid contained in the non-condensable gas may be performed.

The step of contacting the non-condensable gas with the absorption solvent may be performed in an acetic acid absorption tower. At this time, for effective acetic acid absorption, the acetic acid absorption tower may be operated under a pressure condition of about 1 to about 1.5 bar, preferably a pressure condition of about 1 to about 1.3 bar, and about 50 to about 100° C., preferably It may be controlled to proceed at a temperature condition of about 50 to about 80 °C. In addition, specific operating conditions of the acetic acid absorption tower may be in accordance with Korean Patent Application Laid-Open No. 2009-0041355.

At this time, an absorption solvent (process water) for absorbing acetic acid is supplied to the upper portion of the acetic acid absorption tower, and an aqueous solution containing acetic acid may be discharged to the lower portion of the acetic acid absorption tower. And, the aqueous solution containing acetic acid may be supplied to the upper portion of the (meth)acrylic acid absorption tower and used as an absorption solvent. In addition, the non-condensable gas from which the acetic acid is degassed may be recycled and reused in the synthesis reaction process of (meth)acrylic acid.

As described above, when the (meth)acrylic acid aqueous solution having a relatively low concentration is directly discharged from the side of the absorption tower, since a relatively large amount of water is discharged therewith, the amount of water discharged to the lower portion of the absorption tower is inevitably reduced and , thus, it is possible to discharge a high concentration (meth)acrylic acid aqueous solution to the lower part of the absorption tower.

In general, in an absorption tower discharging only a single stream, if the concentration of (meth)acrylic acid discharged to the lower portion of the absorption tower is increased, the absorption efficiency of the absorption tower is reduced, and in the non-condensable gas discharged to the upper portion of the absorption tower, The content of (meth)acrylic acid is increased, resulting in a loss of (meth)acrylic acid.

However, as in the present invention, when a relatively low concentration of (meth)acrylic acid aqueous solution is directly discharged from the side of the absorption tower, it has little effect on the absorption efficiency of the absorption tower, and is discharged to the bottom of the absorption tower ( The efficiency of meth)acrylic acid can be increased, and a separately discharged low-concentration (meth)acrylic acid aqueous solution can also be easily recovered through an extraction process or the like.

According to one embodiment of the invention, the (meth) acrylic acid aqueous solution of the first concentration discharged to the side, compared to the (meth) acrylic acid aqueous solution of the second concentration discharged to the bottom, about 10% by weight to about 50% by weight Preferably, the amount of water in the aqueous solution of (meth)acrylic acid of the first concentration discharged to the side is about 10% by weight to about 70% by weight, based on the total amount of water discharged from the (meth)acrylic acid absorption tower. It may be desirable to discharge in a weight percent, or in a proportion from about 30 weight percent to about 70 weight percent.

In the first concentration (meth)acrylic acid aqueous solution and the second concentration (meth)acrylic acid aqueous solution, the non-condensable gas discharged to the upper part has the same discharge ratio as above, and the relative amount of water discharged maintains the above range and the process proceeds It is possible to minimize the amount of (meth)acrylic acid lost through.

In addition, when the relative amount of water discharged to the side and the bottom satisfies the above range, the process load is reduced in the subsequent extraction or distillation process for obtaining (meth)acrylic acid with high purity from the (meth)acrylic acid aqueous solution. Specifically, for example, when the amount of water contained in the side, that is, the first concentration (meth)acrylic acid aqueous solution is relatively larger, the extraction organic solvent required in the extraction process for extracting (meth)acrylic acid therefrom In this case, the use of an azeotropic solvent added to the distillation process is relatively reduced, so that the process load in the distillation process is reduced to increase energy efficiency, while the purification efficiency in the distillation process is reduced. decreased, resulting in an increase in the loss of acrylic acid. Conversely, when the amount of water contained in the side, that is, the first concentration (meth)acrylic acid aqueous solution is relatively small, the amount of the extraction solvent required in the extraction process for extracting (meth)acrylic acid therefrom is reduced, In this case, the amount of the azeotropic solvent additionally added in the distillation process is increased, and the acrylic acid purification efficiency in the distillation process is increased, so that the loss of acrylic acid can be reduced, but since the amount of water removed from the extraction column is reduced, Advantageous effects of the present invention described above, that is, a disadvantage in that the increase in energy efficiency is reduced may occur.

On the other hand, (meth)acrylic acid can be extracted by contacting the first concentration (meth)acrylic acid aqueous solution discharged to the side of the absorption tower with an extraction solvent containing a hydrophobic organic solvent in the (meth)acrylic acid extraction tower. As such, through the method of contacting the (meth)acrylic acid aqueous solution with the extraction solvent in the extraction column, most of the water contained in the (meth)acrylic acid aqueous solution can be removed. Accordingly, the processing burden of the distillation process, which is a subsequent process, can be reduced, and thus the energy efficiency of the entire process can be improved.

On the other hand, the extraction solvent supplied to the extraction column includes a hydrophobic organic solvent, and may include organic by-products. Specifically, the extraction solvent is benzene (benzene), toluene (toluene), xylene (xylene), n-heptane (n-heptane), cycloheptane (cycloheptane), cycloheptene (cycloheptene), 1-heptene (1- heptene), ethyl-benzene, methyl-cyclohexane, n-butyl acetate, isobutyl acetate, isobutyl acrylate, n-propyl acetate, isopropyl acetate, methyl isobutyl ketone, 2-methyl-1-heptene, 6-methyl- 1-heptene (6-methyl-1-heptene), 4-methyl-1-heptene (4-methyl-1-heptene), 2-ethyl-1-hexene (2-ethyl-1-hexene), ethylcyclopentane (ethylcyclopentane), 2-methyl-1-hexene (2-methyl-1-hexene), 2,3-dimethylpentane (2,3-dimethylpentane), 5-methyl-1-hexene (5-methyl-1-hexene) ), and one or more hydrophobic organic solvents selected from the group consisting of isopropyl-butyl-ether.

And, if the extraction column is a conventional extraction column according to a liquid-liquid contact method, it may be used without particular limitation.

In addition, the method for recovering (meth)acrylic acid may further include distilling the extracted extract and a second concentration (meth)acrylic acid aqueous solution to obtain (meth)acrylic acid.

Then, the feed is brought into contact with the azeotropic solvent introduced from the upper portion, and is heated to an appropriate temperature while distillation by evaporation and condensation is performed.

At this time, in order to efficiently separate (meth)acrylic acid contained in the feed from the remaining components (eg, water, acetic acid, extraction solvent, etc.), the distillation is preferably performed in an azeotropic distillation method.

The solvent applied to the azeotropic distillation method is preferably a hydrophobic azeotropic solvent that can form an azeotrope with water and acetic acid and does not form an azeotrope with (meth)acrylic acid.

Specifically, the hydrophobic azeotrope solvent is benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptane, cycloheptene, 1-heptene (1). -heptene), ethyl-benzene, methyl-cyclohexane, n-butyl acetate, isobutyl acetate, isobutyl acrylate , n-propyl acetate, isopropyl acetate, methyl isobutyl ketone, 2-methyl-1-heptene, 6-methyl -1-heptene (6-methyl-1-heptene), 4-methyl-1-heptene (4-methyl-1-heptene), 2-ethyl-1-hexene (2-ethyl-1-hexene), ethylcyclo Pentane (ethylcyclopentane), 2-methyl-1-hexene (2-methyl-1-hexene), 2,3-dimethylpentane (2,3-dimethylpentane), 5-methyl-1-hexene (5-methyl-1- hexene) and isopropyl-butyl-ether (isopropyl-butyl-ether) may be at least one solvent selected from the group consisting of.

And, in consideration of production efficiency and the like according to the process, the hydrophobic azeotropic solvent is preferably the same as the extraction solvent of the extraction process.

On the other hand, in such a method for recovering (meth)acrylic acid, each of the above-described steps may be organically performed. And, in addition to the above-described steps, processes that can be conventionally performed before, after, or at the same time of each step may be further included and operated.

On the other hand, according to another aspect of the present invention, (meth) acrylic acid, an organic by-product, and a mixed gas inlet to which a mixed gas containing water vapor is supplied; A first concentration discharge unit for discharging a (meth)acrylic acid aqueous solution of a first concentration; and a second concentration discharge unit for discharging an aqueous (meth)acrylic acid solution of a second concentration; The first concentration discharge unit is located on the side, and the second concentration discharge unit is located at the bottom, (meth)acrylic acid absorption tower is provided.

1 is a conceptual diagram of an apparatus for recovering (meth)acrylic acid according to an embodiment of the present invention.

2 is a conceptual diagram of a conventional (meth)acrylic acid recovery device.

Referring to FIG. 1 , the (meth)acrylic acid absorption tower 100 of the present invention includes a mixed gas inlet 110 to which a mixed gas including (meth)acrylic acid, an organic by-product, and water vapor is supplied; A first concentration discharge unit 120 for discharging a (meth)acrylic acid aqueous solution of a first concentration; and a second concentration discharge unit 130 for discharging a (meth)acrylic acid aqueous solution of a second concentration; The first concentration discharge unit is located at the side, and the second concentration discharge unit is located at the bottom.

The (meth)acrylic acid absorption tower 100 may be a packed column type absorption tower or a multistage tray type, and the packed column type absorption tower has a lashing ring therein. ring), pall ring (pall ring), saddle (saddle), gauze (gauze), a filler such as structured packing (structured packing) may be applied.

In particular, in the absorption tower of (meth)acrylic acid of the embodiment, the first concentration discharge unit 120 is located at a point corresponding to about 40 to about 99% from the top of the absorption tower 100 downward. can do.

In addition, the apparatus for recovering (meth)acrylic acid according to the present invention, although not separately shown in the drawings, may have a conventional configuration in the art to which the present invention pertains.

Hereinafter, through specific examples of the invention, the operation and effect of the invention will be described in more detail. However, these embodiments are merely presented as an example of the invention, and the scope of the invention is not defined thereby.

< Example >

Example One

A (meth)acrylic acid absorption tower was prepared with an absorption section at the top, a cooling section at the bottom, and a heat exchanger for cooling the lower condensate and re-introducing it into the absorption tower.

The absorption section had an inner diameter of 70.6 cm and consisted of 35 stages with a sieve tray including down-comers at intervals of 7 cm.

The cooling section located just below the absorption section had an inner diameter of 100 cm, an aperture ratio of 17%, and a Hole ID of 3 mm, and consisted of 4 stages with dual flow trays spaced 10 cm apart.

The liquid condensed in the lower part of the absorption tower was cooled while passing through an indirect heat exchanger, and the uppermost temperature of the absorption tower was kept constant by re-injecting it to the top of the cooling section of the absorption tower (the top of the dual flow tray).

Mixed gas containing acrylic acid, 100L / min N ₂ heated to a high temperature of 800 ℃, acrylic acid, acetic acid, water containing 60.9% by weight, 1.85% by weight, 37.25% by weight, respectively, 46.2g / min aqueous solution By contacting, a dilution gas at 165° C. was prepared, and this was introduced from the bottom of the absorption tower.

At the top of the absorption tower, acrylic acid and acetic acid of 1.66 and 8.2 wt%, respectively, of absorbed water were added at 18.23 g/min.

From the top of the absorption tower, using a pump in the 27th sieve tray, a first concentration of acrylic acid aqueous solution of 5.26g/min was discharged. In the first concentration aqueous solution of acrylic acid, the concentrations of acrylic acid and acetic acid were 19.15% by weight and 3.92% by weight, respectively.

The second concentration aqueous solution of acrylic acid was discharged through the lower part of the absorber so that the temperature of the upper end of the absorption tower was kept constant at 64° C. and the level of the lower liquid level of the absorption tower was kept constant.

After operating the absorption tower for about 10 hours, the discharge flow rate of the absorption tower lower liquid, that is, the flow rate of the second concentration aqueous acrylic acid solution was 36.98 g/min, and the concentrations of acrylic acid and acetic acid were 72.37% by weight and 2.49% by weight, respectively. .

The non-condensable gas discharged to the upper part of the absorption tower was discharged at 147.30 g/min, the concentration of acrylic acid in the exhaust gas was 0.39 wt%, and _{the ratio of H 2} O/N ₂ was 16.4:100, and the The temperature of the two-concentration aqueous acrylic acid solution was 75.3° C., and the top and bottom pressures of the absorption tower were 117 mbar and 165 mbar, respectively.

The operating conditions and results are summarized in Table 1 below.

Example 2

From the top of the absorption tower, using a pump on the 27th sieve tray, the same procedure as in Example 1 was performed except that 6.89 g/min of the first concentration aqueous acrylic acid solution was discharged.

The operating conditions and results are summarized in Table 1 below.

Example 3

From the top of the absorption tower, using a pump on the 27th sieve tray, the same procedure as in Example 1 was performed, except that an aqueous acrylic acid solution having a first concentration of 8.79 g/min was discharged.

The operating conditions and results are summarized in Table 1 below.

Example 4

From the top of the absorption tower, using a pump on the 27th sieve tray, the same procedure as in Example 1 was performed, except that 10.74 g/min of an aqueous acrylic acid solution having a first concentration was discharged.

The operating conditions and results are summarized in Table 1 below.

Example 5

From the top of the absorption tower, using a pump in the 27th sieve tray, the same procedure as in Example 1 was performed, except that an aqueous solution of acrylic acid having a first concentration of 12.59 g/min was discharged.

The operating conditions and results are summarized in Table 1 below.

Example 6

From the top of the absorption tower, using a pump in the 8th sieve tray, the same procedure as in Example 1 was performed, except that an aqueous acrylic acid solution having a first concentration of 7.61 g/min was discharged.

The operating conditions and results are summarized in Table 1 below.

Example 7

From the top of the absorption tower, using a pump in the 16th sieve tray, the same procedure as in Example 1 was performed, except that 7.95 g/min of an aqueous acrylic acid solution having a first concentration was discharged.

The operating conditions and results are summarized in Table 1 below.

Example 8

From the top of the absorption tower, using a pump on the 23rd sieve tray, the same procedure as in Example 1 was performed, except that an aqueous solution of acrylic acid having a first concentration of 8.39 g/min was discharged.

The operating conditions and results are summarized in Table 1 below.

Example 9

From the top of the absorption tower, using a pump in the 35th sieve tray, the same procedure as in Example 1 was performed, except that an aqueous acrylic acid solution having a first concentration of 13.04 g/min was discharged.

The operating conditions and results are summarized in Table 1 below.

comparative example One

The same procedure as in Example 1 was carried out, except that only a single stream of second concentration acrylic acid was discharged to the bottom without side discharge.

The operating conditions and results are summarized in Table 1 below.

1st concentration acrylic acid aqueous solution 2nd concentration acrylic acid aqueous solution Top exhaust non-condensable gas flux
(g/min) acrylic acid
density
(weight%) acetic acid
density
(weight%) flux
(g/min) acrylic acid
density
(weight%) acetic acid
density
(weight%) flux
(g/min) acrylic acid
density
(weight%) H ₂ O/N ₂
(%) Example 1 5.26 19.15 3.92 36.98 72.37 2.49 147.30 0.39 16.4 Example 2 6.89 20.07 3.84 35.30 75.15 2.44 147.23 0.4 16.4 Example 3 8.79 21.66 3.84 33.49 77.65 2.38 147.22 0.41 16.4 Example 4 10.74 23.25 3.82 31.58 80.62 2.31 147.15 0.4 16.4 Example 5 12.59 26.42 3.87 29.52 83.3 2.19 147.29 0.41 16.5 Example 6 7.61 9.63 5.07 34.55 77.0 2.31 147.29 0.61 16.4 Example 7 7.95 13.09 4.38 34.05 77.73 2.33 147.42 0.49 16.4 Example 8 8.39 17.75 4.01 33.37 79.13 2.35 147.60 0.43 16.45 Example 9 13.04 47.62 3.18 28.98 73.75 2.42 147.28 0.41 16.4 Comparative Example 1 - - - 42.05 66.68 2.68 147.41 0.40 16.4

Referring to Table 1, when a stream having a relatively low concentration of acrylic acid is separately discharged through the side of the absorption tower as in an example of the present invention, the concentration of acrylic acid discharged to the bottom is reduced to about 10 without lowering the separation efficiency. It can be clearly seen that it can be increased by more than a percentage point.

In addition, when the position of the side of the absorption tower for discharging the first concentration of acrylic acid aqueous solution is moved from the top to the bottom, it can be confirmed that the amount of acrylic acid lost by being contained in the non-condensable gas discharged from the top of the absorption tower can be reduced. , Specifically, when the first concentration aqueous acrylic acid solution is discharged at about 40 to 99% from the top to the bottom, the concentration of acrylic acid contained in the top discharged non-condensable gas is maintained at about 0.45% or less, so that there is no separate side discharge It can be confirmed that the level can be maintained almost equal to that of the comparative example.

100: (meth)acrylic acid absorption tower
110: the supplied mixed gas inlet
120: first concentration discharge unit
130: second concentration discharge unit

Claims (9)

(meth) acrylic acid, an organic by-product and a mixed gas containing water vapor in contact with water in a (meth) acrylic acid absorption tower to prepare a (meth) acrylic acid aqueous solution;
discharging (meth)acrylic acid aqueous solution of a first concentration from the side of the (meth)acrylic acid absorption tower; and
At the bottom of the (meth) acrylic acid absorption tower, comprising the step of discharging a (meth) acrylic acid aqueous solution of a second concentration;
The first concentration, the concentration of (meth) acrylic acid is lower than the second concentration,
The amount of water in the (meth)acrylic acid aqueous solution of the first concentration discharged to the side is discharged in a ratio of 10% to 70% by weight, based on the total amount of water discharged from the (meth)acrylic acid absorption tower,
A method for recovering (meth)acrylic acid.
According to claim 1,
The (meth)acrylic acid aqueous solution discharged to the first concentration is discharged at any one point corresponding to a height of 40 to 99% from the top of the (meth)acrylic acid absorption tower downwards, (meth)acrylic acid recovery method.
According to claim 1,
The step of making the (meth) acrylic acid aqueous solution is carried out under a pressure of 1 to 1.5 bar and a temperature of 50 to 100 ° C., a (meth) acrylic acid recovery method.
According to claim 1,
The (meth)acrylic acid aqueous solution of the first concentration, (meth)acrylic acid recovery method comprising 40% by weight or less of (meth)acrylic acid.
According to claim 1,
The second concentration of (meth)acrylic acid aqueous solution, (meth)acrylic acid recovery method comprising 60% by weight or more of (meth)acrylic acid.
According to claim 1,
The (meth)acrylic acid aqueous solution of the first concentration discharged to the side is discharged in a ratio of 10% to 50% by weight, compared to the aqueous solution of (meth)acrylic acid of the second concentration discharged to the lowermost portion, (meth)acrylic acid recovery method.
delete a mixed gas inlet to which a mixed gas including (meth)acrylic acid, organic by-products, and water vapor is supplied;
A first concentration discharge unit for discharging a (meth)acrylic acid aqueous solution of a first concentration; and
a second concentration discharge unit for discharging a second concentration of (meth)acrylic acid aqueous solution;
The first concentration discharge part is located on the side,
The second concentration discharge part is located at the bottom,
The amount of water in the (meth)acrylic acid aqueous solution of the first concentration discharged to the side is discharged in a ratio of 10 wt% to 70 wt%, based on the total amount of water discharged from the (meth)acrylic acid absorption tower,
(meth)acrylic acid absorption tower.
9. The method of claim 8,
The first concentration discharge unit is located at any one point corresponding to a height of 40 to 99% downward from the top of the (meth)acrylic acid absorption tower, (meth)acrylic acid absorption tower.

Images