KR20050055386A - Apparatus and method for concentration of acrylamide solution - Google Patents

Abstract

The present invention relates to an apparatus and a method for concentrating an aqueous acrylamide solution produced by hydration of acrylonitrile using a metal catalyst or microorganism. More specifically, the present invention relates to a concentrating device for acrylamide aqueous solution including a concentrating tower, a heating evaporator, a gas-liquid separator, and a product cooling device, and a method for concentrating an acrylamide aqueous solution, wherein the concentrating device is used.

According to the present invention, it is possible to prepare a high quality acrylamide aqueous solution of stable high quality without the occurrence of polymerization by preventing the inside of the condenser that is heated and evaporated to prevent drying of the polymerized product, and to always saturate oxygen in the acrylamide aqueous solution. .

Description

Apparatus and Method for Concentration of Acrylamide Solution

Field of invention

The present invention relates to an apparatus and method for concentrating an aqueous acrylamide solution produced by the hydration of acrylonitrile using a metal catalyst or microorganism. More specifically, the present invention relates to a useful apparatus and method for obtaining a high concentration of acrylamide by a concentration method of removing water at atmospheric pressure and high temperature by injecting only air without adding another polymerization agent to prevent polymerization.

Background of the Invention

Acrylamide is a monomer of polyacrylamide that is used for a variety of applications such as strength enhancers, flocculants, precipitants, soil modifiers and petroleum recovering agents, and is supplied to the market in powder or 30-50% aqueous solution. Instead of the conventional sulfuric acid method in the manufacturing method of such acrylamide, the manufacturing method by the hydration reaction of acrylonitrile using a metal copper type catalyst or a microorganism was developed recently.

When the acrylonitrile concentration in the reaction solution is increased by acrylonitrile hydration reaction, the acrylonitrile hydration reaction rate is lowered. Therefore, the acrylonitrile concentration is generally used at a concentration of 30% or less. As a result, the concentration of acrylamide produced is low, so that a concentration process is required to obtain acrylamide as a high concentration or powder product for useful use as a raw material of the polymer. However, since the polymerization of acrylamide during the concentration is easy to occur and the water-soluble polymer is included in the product, it is a cause of quality deterioration. Therefore, various methods have been proposed for the prevention of polymerization during the concentration process.

Generally known polymerization inhibitors of acrylamide include alkylamines, benzoquinones, methoxyphenols, thioureas, cupric ions, cupric ions and manganese ions. They have a problem of delaying polymerization because the vapor pressure is low in the form of liquid or solid and remains in the concentrate even after concentration.

In Japanese Patent Application Laid-Open No. 48-62713, acrylonitrile has a function of controlling the polymerization of acrylamide. Thus, an acrylonitrile-acrylamide-water three-component solution is prepared, and then vacuum distillation is carried out in a short time using a centrifugal thin film evaporator. The method of concentrating by means of the present invention was proposed, and Japanese Patent Office 55-27048 reduced the copper ions to a monovalent state, and when acrylonitrile was discharged in a non-oxidizing atmosphere, the polymerization was effective in the range of 50 to 200 ° C. This is described. However, in order to obtain a high quality product of acrylamide as a raw material of the polymer, the content of acrylonitrile needs to be 0.1% or less, and when copper ions are added, there is a disadvantage that a process of concentration and removal must be added.

In the acrylamide-water two-component system, copper ions are not added, and a method of concentrating under low pressure and low pressure while injecting oxygen into the polymerization inhibitor is used. At this time, since the action of initiating polymerization when the amount of oxygen injected is small, Japanese Patent Application Laid-Open No. 54-106420 proposes a method of adding at least 4 moles of nitrogen monoxide per mole of oxygen injected into each device. However, its use on a commercial scale is practically inadequate in that nitrogen monoxide is expensive and harmful.

Japanese Special Office 55-27898 supplies dilute acrylamide aqueous solution to a concentrator consisting of an oxygen gas absorber, a heating device, and a reduced pressure evaporator, and circulates 10 to 500 times the concentrated acrylamide aqueous solution in the concentrator. While the oxygen was dissolved in the aqueous solution in the oxygen gas absorber and heated to 20 to 60 ° C in the heating device, the temperature difference between the feed liquid and the discharge liquid to the evaporator was kept in the range of 1 to 20 ° C, and the water was A method of evaporating off has been proposed.

In the various conventional thickening methods listed above, the apparatuses used were centrifugal thin-film evaporators, forced circulation evaporators, ascending thin-film evaporators, falling film-type evaporators, and the like. The aqueous acrylamide solution attached to the inner gas phase base wall or the acrylamide aqueous solution attached due to the occurrence of drift at the bottom of the concentrator having the highest concentration of acrylamide was likely to proceed to the polymer. In order to solve this problem, Japanese Patent Laid-Open No. Hei 9-278727 proposed a method of concentrating at a pressure of 130 to 250 mmHg while introducing oxygen-containing gas using a device made of copper.

However, in order to minimize the possibility of polymerization by heat, it may be a very advantageous method to concentrate at low temperature under reduced pressure, but it is impossible to supply excess oxygen in order to keep the device under reduced pressure, and sufficient oxygen is dissolved in the acrylamide aqueous solution. Even if it is, since degassing of oxygen proceeds rapidly when it reaches the boiling point for evaporation of water is not effective in preventing polymerization. In addition, acrylamide attached to the gas phase part of the apparatus with splash is often produced in the base wall, and moreover, since it is made under reduced pressure, the amount of the acrylamide aqueous solution adhering to the base wall of the gas phase part in the apparatus is further increased. The resulting polymer is desorbed in the form of an elastic gel or popcorn, which is difficult to remove, and when incorporated into the acrylamide concentrate, reduces the stability of the product and causes polymerization of the entire apparatus.

In this regard, as known from Japanese Patent Application Laid-Open No. 48-62717, the method of concentrating by injecting air under atmospheric pressure has significant advantages. The pressure reducing device is omitted by heating the acrylamide to a temperature lower than the boiling point while concentrating air well under normal pressure and absorbing moisture in the air, thus simplifying the device and making it easier to operate. It can increase the solubility of the has the advantage of having more stability in terms of preventing polymerization.

However, the concentration method shown in the examples of Japanese Patent Application Laid-Open No. 48-62717 also shows a limitation that it does not completely solve the possibility of producing a polymer in the apparatus. Injecting acrylamide aqueous solution and air into the lower part of the double tube concentrator, the ratio of air injected during concentration is very large compared with the theoretical value, which increases the risk of acrylamide splashing and the gas-liquid separator is dried to attach acrylamide polymer. It did not solve the possibility.

Japanese Unexamined Patent Publication No. 5-78293 discloses a concentrator that can be concentrated under the same conditions. That is, in a concentrator composed of a heater and a gas-liquid separator, an aqueous acrylamide solution is flowed along the pipe wall and the oxygen-containing gas coexists and is heated. To remove moisture by containing water in an oxygen-containing gas at atmospheric pressure. However, the aqueous acrylamide solution flows along the wall of the pipe to easily form a drift and contact with the oxygen-containing gas only at the interface, which is insufficient to dissolve oxygen, thereby preventing the formation and adhesion of polymers in the device.

Therefore, the present inventors can obtain a stable, high-quality acrylamide aqueous solution that is stable without polymerization by concentrating with oxygen being always saturated in the acrylamide aqueous solution without drying all parts in the apparatus during the whole process of heating and evaporation. It confirmed and completed this invention.

As a result, the main object of the present invention is to provide a concentrating device and a method for obtaining a stable high quality high concentration acrylamide aqueous solution without causing polymerization to always saturate oxygen in the acrylamide aqueous solution.

In order to achieve the above object, the present invention, the acrylamide aqueous solution and air is introduced into the bottom of the concentration tower (6) which is heated and evaporated at the same time; A gas-liquid separator 7 for separating water-containing air and acrylamide products; A product cooling device 9 for immediately cooling the separated high concentration acrylamide aqueous solution; In the concentrator of acrylamide aqueous solution including a condenser (8) for cooling the air containing water, the concentration tower (6) has a plurality of in order to facilitate the mixing of acrylamide and air and to prevent the acrylamide aqueous solution from stagnating Sus 316 tube (5), characterized in that the air disperser (4) is installed at the bottom of the concentration tower (6) in order to ensure that the injected air is well distributed in the tube (5) It provides a concentrator of acrylamide aqueous solution.

The present invention also provides a method for concentrating an acrylamide aqueous solution, wherein the acrylamide aqueous solution prepared by the catalytic hydration reaction of acrylonitrile is heated and evaporated under atmospheric pressure to be concentrated.

In the present invention, the water and acrylamide aqueous solution is introduced into the lower portion of the concentration tower of the concentrating device to absorb and remove moisture in the acrylamide into the air.

In the concentration method of the present invention, the temperature of the aqueous solution in the concentration tower is maintained at 74-82 ° C., the temperature of the gas-liquid separator is maintained at 82-88 ° C., and the air is injected to maintain the humidity of the gas-liquid separator 80-90. It may be characterized by maintaining in%, it is characterized by cooling the product immediately below room temperature after concentration.

That is, in the process of removing water from an acrylamide synthesis reaction solution to which no other polymerization inhibitor is added and concentrating it into a high concentration of acrylamide aqueous solution, the apparatus used includes at least a heating evaporator, a gas-liquid separator, and a product cooling device. And a concentration apparatus including an air disperser at an introduction portion so as to introduce an amount of air capable of saturating an amount of moisture to be concentrated to a predetermined concentration, so that it can be well dispersed and sufficiently contacted with an aqueous acrylamide solution. It is characterized in that it is made at normal pressure and high temperature. The acrylamide aqueous solution sufficiently in contact with the air in the concentrator is stabilized by maintaining the temperature of about 6 to 8 ° C lower than that of the vapor and the vapor, which is heated while rising inside the condenser tube. By maintaining the humidity of more than% it is possible to solve the problem that all parts in the concentrator is dried. In addition, since only the minimum amount of air saturating air containing the outflow of water is used, it is possible to solve the problem of polymerization due to entrainment caused by excessive air injection.

EMBODIMENT OF THE INVENTION Hereinafter, the detail of this invention is demonstrated according to attached drawing.

1 shows a concentrator used in the present invention. High temperature acrylamide is more likely to occur in polymerization, so once it is passed through a heating device, it is limited to its installation so as not to pass through contaminated valves, pumps, etc., and is composed of only a minimum device. That is, a high concentration acrylamide aqueous solution separated from a concentration tower 6 in which acrylamide aqueous solution and air are introduced to simultaneously heat and evaporate, and a gas-liquid separator 7 separating water-containing air and acrylamide products It consists of a product cooling device 9 for immediate cooling and a condenser 8 for cooling the air containing moisture.

Acrylamide aqueous solution 1 and air 3 are injected at the bottom of the concentration column 6. The concentration tower 6 is composed of 22 sus 316 tubes 5 having a relatively small inner diameter of 1 inch and a length of 1 m in order to facilitate mixing of acrylamide and air and to prevent stagnant aqueous acrylamide solution. An air disperser 4 is installed at the bottom of the concentrating tower so that the injected air is well dispersed in all tubes of the concentrating tower. The dispersed air bubbles here are sufficiently brought into contact with the acrylamide aqueous solution and then heated together with the acrylamide aqueous solution while rising inside the tube.

The acrylamide aqueous solution and the water containing water passed through the concentrator are introduced into the gas-liquid separator (7) so that the water-containing air is separated into the condensate (12) and the air (13) through the condenser (8) and the acrylamide concentrate Flows out to the bottom. At this time, the gas-liquid separator is in the form of a cyclone such that the humid air introduced therein wets the wall while turning inside the gas-liquid separator 7.

The hot concentrated liquid flowing out to the bottom of the gas-liquid separator is cooled by flowing through the product cooling device 9 connected to the bottom of the gas-liquid separator. The cooled concentrate is transferred to the product tank 11 below about 1.5m so that no differential pressure in the gas-liquid separator is generated and the possibility of polymerization by temperature is prevented, thereby increasing stability.

In operating conditions, the process takes place under normal pressure and the evaporation temperature is such that the heat source of the concentrator is controlled by measuring the temperature of the gas-liquid separator. The air injection was calculated from the amount of water that can be saturated at each temperature, ie the saturated humidity. Air, which has a lower specific heat than aqueous acrylamide solution, is heated rapidly while passing through the concentrator. That is, the temperature of the aqueous solution in the concentrator is 74 ~ 82 ℃ while the temperature of the air containing water in the gas-liquid separator is in the range of 82 ~ 88 ℃ increased by 6 ~ 8 ℃.

In addition, since the air passing through the concentrator is in good contact with the acrylamide aqueous solution and contains water close to the saturated humidity, the humidity in the gas-liquid separator is maintained at 80 to 90%, resulting in the drying of the gas-liquid separator. I never do that. The concentration of acrylamide contained in the effluent obtained by cooling the water-containing air was 0.1% or less, and hardly entrained droplets were generated. The acrylamide concentrate separated in the gas-liquid separator is passed to the product tank while being cooled to room temperature through the product cooling apparatus, so that it is possible to produce a stable and high quality acrylamide containing no polymer.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are merely for the purpose of helping the understanding of the present invention, but the present invention is not limited thereto.

In the following examples, the formation of the polymer in the concentration process was determined by visually observing the white insoluble matter when 10 ml of the concentrated product dissolved in 100 ml of methanol, and the production of the polymer after concentration was confirmed by dismantling the device. It was.

Example 1

Aqueous acrylamide 41% solution prepared by the catalytic hydration of acrylonitrile and air at room temperature were injected into the lower part of the concentrator 6 at 56 kg / hr and 21 kg / hr, respectively, and 12 kg / hr of water was discharged together with the air. 43 kg / hr of 52% acrylamide concentrate was obtained. At this time, a high temperature steam was injected into the jacket of the heating evaporator as a heat source so that the temperature of the water-containing air, which is heated in the concentrator and introduced into the gas-liquid separator 7, was maintained at 82 ° C.

The pressure was kept at atmospheric pressure and the temperature of the acrylamide solution in the concentrator was 74 and 77 ° C. at the bottom and top, respectively, and the temperature difference between the gas-liquid was 5 ° C. As a result of calculating the ratio of air and water present in the gas-liquid separator, the humidity was 89.2%, and the temperature of the product transferred to the product tank through the product cooler after concentration was 35 ° C. After 10 days of continuous operation and dismantling of the apparatus, no methanol insoluble components of the polymer and concentrated product in the apparatus were produced.

Comparative Example 1

The rest of the apparatus was concentrated in the same manner as in Example 1 using the apparatus as shown in FIG. 1 except that the product cooling apparatus was not installed at the bottom of the gas-liquid separator. After six hours of concentrated operation, a large amount of polymer was produced in the product piping and the product tank.

Example 2

The amount of air to be injected was reduced to 13 kg / hr and concentrated in the same manner as in Example 1 except that the temperature of the gas-liquid separator 7 was maintained at 88 ° C. The temperature of the acrylamide solution was 79 and 82 ° C. at the bottom and top, respectively, and the temperature difference between the gas-liquid was 6 ° C., and the humidity was 82.8% when the ratio of air and moisture present in the gas-liquid separator was calculated. It operated for 10 days and obtained the same result as Example 1.

Comparative Example 2

Except that the type of concentrator in which the acrylamide aqueous solution and air are contacted and heated is not a multi-tubular type but a 20 cm diameter packed column filled with 5/8 inch sus 304 polling, Concentrated in the same manner as in Example 1. At this time, the temperature of the bottom and top of the packed column was 55 and 80 ℃, respectively, and the temperature difference between the gas-liquid was small as 2 ℃. After 52 hours of concentrating, the concentrated product was dissolved in methanol and found to be insoluble. The deconcentrator was dismantled and inspected to produce a polymer inside the packed column and under the gas-liquid separator.

Comparative Example 3

The aqueous acrylamide solution prepared in the same manner as in Example 1 was concentrated using a forced thin film flow type evaporator. 40 kg / hr of acrylamide aqueous solution was injected at the top of the evaporator and 1.5 kg / hr of air was injected at the bottom. As a result of heating by steam at 90 ° C. and depressurizing the pressure in the apparatus to 100 mmHg, a large amount of polymer was formed in the bottom of the apparatus and the pipe after 30 minutes.

Having described the specific part of the present invention in detail, it is obvious to those skilled in the art that such a specific description is only a preferred embodiment, thereby not limiting the scope of the present invention. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

The present invention relates to a simple and stable concentrating device and method when the diluted acrylamide aqueous solution is concentrated to a predetermined concentration, the equipment cost is reduced, and the operation method is easy. In addition, it is possible to solve all the conventional problems such as the temperature decrease of the acrylamide aqueous solution during concentration, increase in the amount of dissolved oxygen due to good contact with air, and wet all sections in the device, such as adhesion of polymer due to some drying in the device.

1 shows a concentrator of acrylamide aqueous solution according to the present invention.

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

1: aqueous acrylamide solution 2: pump

3: air 4: disperser

5: tube 6: concentration tower

7: gas-liquid separator 8: condenser

9: Product chiller 10: Condensate container

11: product tank 12: condensate

13: air

Claims (5)

A concentration tower 6 in which acrylamide aqueous solution and air are introduced to the bottom to simultaneously heat and evaporate; A gas-liquid separator 7 for separating water-containing air and acrylamide products; A product cooling device 9 for immediately cooling the separated high concentration acrylamide aqueous solution; In the concentrator of acrylamide aqueous solution including a condenser (8) for cooling the air containing water, the concentration tower (6) has a plurality of in order to facilitate the mixing of acrylamide and air and to prevent the acrylamide aqueous solution from stagnating Sus 316 tube (5), characterized in that the air disperser (4) is installed at the bottom of the concentration tower (6) in order to ensure that the injected air is well distributed in the tube (5) Concentrator of acrylamide aqueous solution. A method for concentrating an acrylamide aqueous solution prepared by catalytic hydration of acrylonitrile by heating and evaporating under atmospheric pressure, wherein the concentrating device of claim 1 is used. The method for concentrating an acrylamide aqueous solution according to claim 2, wherein air and acrylamide aqueous solution are introduced into the lower part of the concentrating device 6 to absorb and remove water in the acrylamide. The temperature of the aqueous solution in the concentration column is maintained at 74 ~ 82 ℃, the temperature of the gas-liquid separator is maintained at 82 ~ 88 ℃, air is injected to the humidity of the gas-liquid separator is 80 ~ 90 A method of concentrating an acrylamide aqueous solution, which is characterized by maintaining at%. The method for concentrating an acrylamide aqueous solution according to claim 4, wherein the product is cooled to room temperature immediately after concentration.