JP2008143812A

JP2008143812A - Method for producing aqueous solution of acrylamide

Info

Publication number: JP2008143812A
Application number: JP2006330806A
Authority: JP
Inventors: Yuichi Someya; 雄市染矢; Hitoshi Tachibana; 均立花; Saburo Takenouchi; 三郎竹之内
Original assignee: Dianitrix Co Ltd
Current assignee: Dianitrix Co Ltd
Priority date: 2006-12-07
Filing date: 2006-12-07
Publication date: 2008-06-26
Anticipated expiration: 2026-12-07
Also published as: JP5048314B2

Abstract

<P>PROBLEM TO BE SOLVED: To control an acrylamide concentration in an obtained aqueous solution of acrylamide in a specific range. <P>SOLUTION: In the method for producing an aqueous solution of acrylamide, having a reaction process of acrylonitrile, a concentration process, a purification process and a product storage part, a first concentration meter is arranged at the concentrate storage part of the concentration process, a second concentration meter is arranged between the purification process and the product storage part, a third concentration meter is arranged at the product storage part, the measured data of the second concentration meter or their changes control the concentration condition of the concentration part of the concentration process and the measured data of the first concentration meter and the third concentration meter or their changes regulate the control condition of the concentration condition of the concentration part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

この発明は、濃度を一定範囲内に保ったアクリルアミド水溶液の製造方法に関する。 The present invention relates to a method for producing an aqueous acrylamide solution having a concentration kept within a certain range.

アクリルアミドは、金属銅触媒を用い、水の存在下でアクリロニトリルを水和反応することにより製造され、水溶液として得られる。そして、水溶液として、又は粉末状にして、市場に供給される。 Acrylamide is produced by hydrating acrylonitrile in the presence of water using a copper metal catalyst, and is obtained as an aqueous solution. And it is supplied to the market as an aqueous solution or in powder form.

この水和反応においては、副反応の生成を抑制するため、原料のアクリロニトリル濃度が低く抑えられ、また、原料のアクリロニトリルの転化率をあまり上げすぎないようにされている。このため、上記水和反応後、得られたアクリルアミド水溶液の濃度を出荷の濃度に調整するための濃縮工程や、未反応原料及び触媒を除去するための精製工程が必要となる。 In this hydration reaction, in order to suppress the formation of side reactions, the concentration of the raw material acrylonitrile is kept low, and the conversion rate of the raw material acrylonitrile is not excessively increased. For this reason, after the said hydration reaction, the concentration process for adjusting the density | concentration of the obtained acrylamide aqueous solution to the density | concentration of a shipment, and the refinement | purification process for removing an unreacted raw material and a catalyst are needed.

上記の濃縮工程において、温度をかけると、アクリルアミドの重合が生じるおそれがあるため、減圧蒸留法によって水を除去することが知られている（特許文献１等参照）。さらに、濃縮時のアクリルアミドの重合抑制をより確実に行うため、装置の一部を銅製とし、酸素含有ガスを導入することが知られている（特許文献１参照）。 In the above concentration step, when temperature is applied, acrylamide polymerization may occur, and it is known to remove water by a vacuum distillation method (see Patent Document 1, etc.). Furthermore, in order to more reliably suppress polymerization of acrylamide during concentration, it is known that a part of the apparatus is made of copper and an oxygen-containing gas is introduced (see Patent Document 1).

特開平０９−２７８７２７８号公報JP 09-2787278 A

ところで、アクリルアミド水溶液を出荷する場合、その濃度を所定範囲内にする必要がある。しかし、各原料、触媒、水和反応条件、濃縮工程や精製工程の条件等の微妙な変化によって、製品として得られるアクリルアミド水溶液中の濃度が変化することがある。濃度が変化すると、ポリアクリルアミド製造の際に濃度の微調整が必要となり、また、濃度が高い場合、そのままで重合すると重合熱の増大によって温度が高くなりすぎる可能性があり、安全性上の問題や品質の問題が生じる場合がある。 By the way, when shipping an acrylamide aqueous solution, the concentration needs to be within a predetermined range. However, the concentration in the acrylamide aqueous solution obtained as a product may change due to subtle changes in the raw materials, catalysts, hydration reaction conditions, conditions of the concentration process and purification process, and the like. If the concentration changes, fine adjustment of the concentration is required during the production of polyacrylamide, and if the concentration is high, if the polymerization is performed as it is, the temperature may become too high due to an increase in polymerization heat, which is a safety problem. And quality problems may occur.

そこで、この発明は、得られるアクリルアミド水溶液中のアクリルアミド濃度を、所定範囲におさめることを目的とする。 Accordingly, an object of the present invention is to keep the acrylamide concentration in the obtained acrylamide aqueous solution within a predetermined range.

この発明は、アクリロニトリルを、触媒の存在下で、水和してアクリルアミドを生成する反応工程、この反応工程で得られた生成液であるアクリルアミド水溶液を濃縮する濃縮工程、この濃縮工程で得られた濃縮液から、未反応のアクリロニトリル及び触媒を除去する精製工程、及び上記精製工程で精製された精製液を貯留する製品貯留部を有するアクリルアミド水溶液の製造方法であって、上記濃縮工程は、上記反応工程で生成された生成液を、濃縮する濃縮部と、この濃縮部で濃縮された濃縮液を貯留する濃縮液貯留部とを有し、上記濃縮液貯留部には、上記濃縮液の濃度を計測する第１濃度計と、上記濃縮液の一部を上記濃縮部に戻す濃縮液戻し部とが設けられ、上記の精製工程と製品貯留部との間に第２濃度計が設けられ、上記製品貯留部には、上記精製液の撹拌機構と第３濃度計が設けられ、上記第２濃度計の計測データ又はその変化により、上記濃縮部の濃縮条件を制御し、上記の第１濃度計及び第３濃度計の計測データ又はその変化により、上記濃縮部の濃縮条件の制御条件を調整することにより、上記課題を解決したのである。 The present invention is a reaction step in which acrylonitrile is hydrated in the presence of a catalyst to produce acrylamide, a concentration step in which an aqueous acrylamide solution that is a product obtained in this reaction step is concentrated, and the concentration step obtained. A purification process for removing unreacted acrylonitrile and catalyst from the concentrate, and a method for producing an acrylamide aqueous solution having a product reservoir for storing the purified liquid purified in the purification process, wherein the concentration process comprises the reaction A concentration unit for concentrating the product solution generated in the step; and a concentrate storage unit for storing the concentrate concentrated in the concentration unit, wherein the concentration of the concentrate is set in the concentrate storage unit. A first concentration meter to be measured, and a concentrate return unit for returning a part of the concentrate to the concentration unit, and a second concentration meter is provided between the purification step and the product storage unit, Product The distillation unit is provided with a stirring mechanism of the purified liquid and a third concentration meter, and controls the concentration conditions of the concentration unit according to measurement data of the second concentration meter or a change thereof, and the first concentration meter and The above problem has been solved by adjusting the control condition of the concentration condition of the concentration unit based on the measurement data of the third densitometer or its change.

この発明によると、濃縮液貯留部に第１濃度計が、精製工程と製品貯留部との間に第２濃度計が、及び製品貯留部に第３濃度計が設けられる。第２濃度計の測定で、精製液のアクリルアミド濃度が低いと測定されると、濃縮部での濃縮条件を変更して濃縮度を上昇させる。これにより、アクリルアミド濃度を上昇させることができる。一方、アクリルアミド濃度が高いと測定されると、濃縮部での濃縮条件を変更して濃縮度を低下させる。これにより、アクリルアミド濃度を低下させることができる。
また、第１濃度計や第３濃度計によって計測されるデータ及びその変化を見ることにより、濃縮度の変更の速度を速めたり、緩和させたりすることで、得られる製品であるアクリルアミド水溶液の濃度が、第２濃度計による調整で、大きくぶれるのを抑制することができる。
これらにより、アクリルアミド水溶液の濃度を精度よく管理することが可能となる。 According to the present invention, the first concentration meter is provided in the concentrate storage part, the second concentration meter is provided between the purification step and the product storage part, and the third concentration meter is provided in the product storage part. If it is measured by the second densitometer that the purified solution has a low acrylamide concentration, the concentration is increased by changing the concentration conditions in the concentration section. Thereby, an acrylamide density | concentration can be raised. On the other hand, when it is measured that the acrylamide concentration is high, the concentration condition in the concentration part is changed to reduce the concentration. Thereby, an acrylamide density | concentration can be reduced.
In addition, by observing the data measured by the first densitometer and the third densitometer and their changes, the concentration of the acrylamide aqueous solution, which is the product obtained, can be increased or decreased by accelerating or mitigating the concentration change rate. However, the adjustment by the second densitometer can suppress a large shake.
As a result, the concentration of the acrylamide aqueous solution can be accurately controlled.

以下、この発明の実施形態について詳細に説明する。
この発明にかかるアクリルアミド水溶液の製造方法は、図１に示すように、反応工程（ａ）、濃縮工程（ｂ）、精製工程（ｃ）、及び製品貯留部（ｄ）の各工程を有する方法である。以下、それぞれの工程について説明する。 Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the method for producing an aqueous acrylamide solution according to the present invention comprises a reaction step (a), a concentration step (b), a purification step (c), and a product reservoir (d). is there. Hereinafter, each process will be described.

（反応工程（ａ））
反応工程（ａ）は、図１に示すように、アクリロニトリル（ＡＮ）、銅触媒等の触媒、及び水を反応槽１１に導入し、このアクリロニトリルを触媒の存在下で水和し、生成液であるアクリルアミドを生成する工程である。 (Reaction step (a))
In the reaction step (a), as shown in FIG. 1, acrylonitrile (AN), a catalyst such as a copper catalyst, and water are introduced into a reaction vessel 11, and this acrylonitrile is hydrated in the presence of the catalyst. This is a process for producing a certain acrylamide.

このときの反応温度は、通常５０〜２００℃、好ましくは７０〜１５０℃である。反応圧力は、通常、常圧〜２ＭＰａ、好ましくは常圧〜０．６ＭＰａである。また、触媒寿命を永続させるために反応系は酸素不在下にしてもよい。原料となる水及びアクリロニトリルは反応器に連続的に供給され、反応器中で所定時間滞留して、未反応原料を含む反応液として連続的に抜き出される。反応器は１段の他、２〜５段程度の複数の反応器を用いた多段反応としてもよい。 The reaction temperature at this time is 50-200 degreeC normally, Preferably it is 70-150 degreeC. The reaction pressure is usually normal pressure to 2 MPa, preferably normal pressure to 0.6 MPa. Further, the reaction system may be in the absence of oxygen in order to perpetuate the catalyst life. Water and acrylonitrile as raw materials are continuously supplied to the reactor, stay in the reactor for a predetermined time, and are continuously extracted as a reaction liquid containing unreacted raw materials. The reactor may be a single stage or a multistage reaction using a plurality of reactors of about 2 to 5 stages.

反応時の反応器中のアクリロニトリル濃度は特に制限はなく、原料アクリロニトリルと水の供給割合や、反応転換率、反応を多段で行う場合は何段目の反応器か等によって変わりうるが、アクリロニトリル濃度が低すぎると反応速度の低下を招くことがあるので、反応器の出口での反応液の液相成分中のアクリロニトリル濃度として、通常１重量％以上、好ましくは３重量％以上、更に好ましくは４〜８重量％である。水の使用量はアクリロニトリルの化学量論量以上であればよいが、アクリロニトリルの水に対する溶解度が余り大きくなく均一液相反応を行うことが難しいので、通常、アクリロニトリルの化学量論量の数倍から数十倍用いられる。また、場合によっては、メタノール、エタノール等のアルコール類を併用することもできる。生成するアクリルアミドは重合性に富んでいるので反応を行うにあたってはハイドロキノン、ｔ−ブチルカテコール等の重合禁止剤を使用してもよい。 The acrylonitrile concentration in the reactor during the reaction is not particularly limited, and may vary depending on the supply ratio of the raw material acrylonitrile and water, the reaction conversion rate, the stage of the reactor when the reaction is performed in multiple stages, etc., but the acrylonitrile concentration Is too low, the reaction rate may be lowered. Therefore, the acrylonitrile concentration in the liquid phase component of the reaction liquid at the outlet of the reactor is usually 1% by weight or more, preferably 3% by weight or more, more preferably 4%. ~ 8% by weight. The amount of water used may be more than the stoichiometric amount of acrylonitrile, but the solubility of acrylonitrile in water is not so large and it is difficult to carry out a homogeneous liquid phase reaction, so usually from several times the stoichiometric amount of acrylonitrile. Used several tens of times. In some cases, alcohols such as methanol and ethanol can be used in combination. Since the acrylamide to be produced is rich in polymerizability, a polymerization inhibitor such as hydroquinone or t-butylcatechol may be used for the reaction.

（濃縮工程（ｂ））
上記の反応工程（ａ）で得られる生成液は、濃縮工程（ｂ）に送られ、濃縮される。これにより、アクリルアミド水溶液中のアクリルアミド濃度が、最終製品としたときに好ましい濃度範囲内になるように調整される。 (Concentration step (b))
The product liquid obtained in the reaction step (a) is sent to the concentration step (b) and concentrated. Thus, the acrylamide concentration in the acrylamide aqueous solution is adjusted so as to be within a preferable concentration range when the final product is obtained.

この濃縮工程（ｂ）は、図１に示すように、上記の反応工程（ａ）で生成されたアクリルアミド水溶液を濃縮する濃縮部（ｂ１）と、この濃縮部で濃縮された濃縮液を貯留する濃縮液貯留部（ｂ２）とを有する。 In this concentration step (b), as shown in FIG. 1, a concentration unit (b1) for concentrating the acrylamide aqueous solution produced in the reaction step (a) and a concentrated solution concentrated in this concentration unit are stored. A concentrated liquid reservoir (b2).

この濃縮部（ｂ１）は、濃縮缶２１より構成され、この濃縮缶２１内に、上記反応工程（ａ）、及び濃縮液貯留部（ｂ２）より送られてきたアクリルアミド水溶液を導入し、減圧蒸留することによって、水を除去し、アクリルアミド水溶液を濃縮する。 This concentration part (b1) is comprised from the concentration can 21, The acrylamide aqueous solution sent from the said reaction process (a) and the concentrate storage part (b2) is introduce | transduced in this concentration can 21, and it carries out vacuum distillation To remove the water and concentrate the aqueous acrylamide solution.

このときの濃縮条件は、圧力が３０〜６０Ｔｏｒｒ、好ましくは４０〜５０Ｔｏｒｒ、温度が２５〜６０℃、好ましくは３５〜４５℃の範囲内で行われるが、この濃縮条件のより細かい調整は、後述するように、複数設けられる濃度計の計測データによって制御され、最終製品としてのアクリアルアミド水溶液が、好ましい濃度範囲内になるように調整される。 The concentration conditions at this time are 30 to 60 Torr, preferably 40 to 50 Torr, and a temperature of 25 to 60 ° C., preferably 35 to 45 ° C. The finer adjustment of the concentration conditions will be described later. As described above, it is controlled by the measurement data of a plurality of densitometers, and the aqueous acrylamide solution as the final product is adjusted to be within a preferable concentration range.

上記の濃縮部（ｂ１）で濃縮された濃縮液は、ほぼ常圧の濃縮液貯留部（ｂ２）の濃縮液貯留タンク２２に送られる。この濃縮液貯留部（ｂ２）での圧力をほぼ常圧とする方法としては、例えば、減圧状態にある濃縮缶２１の濃縮液を濃縮液貯留タンク２２内に送るための配管の出口部分を、濃縮液貯留タンク２２内に貯留された濃縮液の中に挿入する方法があげられる。 The concentrated solution concentrated in the concentration unit (b1) is sent to the concentrated solution storage tank 22 of the concentrated solution storage unit (b2) at almost normal pressure. As a method of setting the pressure in the concentrated liquid storage part (b2) to a substantially normal pressure, for example, an outlet part of a pipe for sending the concentrated liquid in the concentrated can 21 in a reduced pressure state into the concentrated liquid storage tank 22, There is a method of inserting into the concentrated liquid stored in the concentrated liquid storage tank 22.

この濃縮液貯留部（ｂ２）には、循環配管からなる濃縮液循環部２３が設けられ、濃縮液貯留タンク２２内の濃縮液が、この濃縮液貯留タンク２２及び濃縮液循環部２３内を循環し、濃縮液が均一に保持される。この循環配管には、上記濃縮液の濃度を計測する第１濃度計２４が設けられる。この第１濃度計２４によって、濃縮液貯留タンク２２内の濃縮液のアクリルアミド濃度が測定される。 The concentrated liquid storage section (b2) is provided with a concentrated liquid circulation section 23 comprising a circulation pipe, and the concentrated liquid in the concentrated liquid storage tank 22 circulates in the concentrated liquid storage tank 22 and the concentrated liquid circulation section 23. Thus, the concentrated solution is kept uniform. The circulation pipe is provided with a first concentration meter 24 for measuring the concentration of the concentrated liquid. The first concentration meter 24 measures the acrylamide concentration of the concentrate in the concentrate storage tank 22.

上記の濃縮液貯留タンク２２中の濃縮液は、次工程である精製工程（ｃ）に送られるが、この濃縮液の一部は、濃度を調整するため、濃縮液戻し部２６を介して、上記濃縮部（ｂ１）に戻される。この濃縮液は、上記した反応工程（ａ）で得られた生成液と共に濃縮缶２１に送られるので、実質上、希釈されることとなり、濃縮缶２１で、再度、濃縮されることとなる。 The concentrated liquid in the concentrated liquid storage tank 22 is sent to the next purification step (c), and a part of this concentrated liquid is adjusted via the concentrated liquid return unit 26 to adjust the concentration. It returns to the said concentration part (b1). Since this concentrated liquid is sent to the concentration can 21 together with the product liquid obtained in the reaction step (a) described above, it is substantially diluted and is concentrated again in the concentration can 21.

上記濃縮液戻し部２６には、熱交換器２５が設けられる。この熱交換器２５には、冷媒体又は熱媒体のいずれかの熱交換媒体が流され、上記濃縮液戻し部２６を流れる、上記の生成液及び濃縮液の混合液（以下、「濃縮対象液」と称する。）が冷却又は加温され、上記濃縮液の一部は、上記濃縮部（ｂ１）における圧力での沸点となる温度付近に調整される。このような温度とされた濃縮液は、例えば、濃縮缶２１内にフラッシュ（雰霧）されることにより、水とアクリロニトリルとが吸引され、外部に出される。 The concentrate return unit 26 is provided with a heat exchanger 25. A heat exchange medium, either a refrigerant body or a heat medium, is flowed through the heat exchanger 25, and the mixed liquid of the product liquid and the concentrated liquid (hereinafter, “concentration target liquid” flowing through the concentrated liquid returning unit 26. Is cooled or warmed, and a part of the concentrated liquid is adjusted to a temperature near the boiling point at the pressure in the concentrated part (b1). The concentrated liquid having such a temperature is, for example, flushed (misted) into the concentration can 21, whereby water and acrylonitrile are sucked and discharged to the outside.

（精製工程（ｃ））
この精製工程（ｃ）は、上記濃縮工程（ｂ）で得られた濃縮液から、未反応のアクリロニトリル及び触媒を除去する工程である。この精製工程（ｃ）は、未反応のアクリロニトリルを除去する放散塔３１と、反応工程（ａ）から付随してきた触媒を除去する脱触媒塔３２からなる。 (Purification step (c))
This purification step (c) is a step of removing unreacted acrylonitrile and catalyst from the concentrate obtained in the concentration step (b). This purification step (c) comprises a stripping tower 31 for removing unreacted acrylonitrile and a decatalyzing tower 32 for removing the catalyst accompanying the reaction step (a).

上記放散塔３１では、塔の上段部から上記濃縮液が投入され、底部から抜き出される。一方、塔の下段部から空気が送り込まれ、塔頂部から抜き出される。そして、塔内部で両者は向流し、その際、アクリロニトリルが空気と共に、上方に移動する。そして、アクリロニトリルは、空気と共に、塔頂部より外部に出される。このアクリロニトリルは、回収された後、反応工程（ａ）の原料アクリロニトリルの一部として使用される。 In the stripping tower 31, the concentrated liquid is introduced from the upper stage of the tower and is extracted from the bottom. On the other hand, air is fed from the lower stage of the tower and extracted from the top of the tower. Then, both counter flow inside the tower, and at that time, acrylonitrile moves upward together with air. And acrylonitrile is taken out outside from the tower top part with air. After the acrylonitrile is recovered, it is used as a part of the raw material acrylonitrile in the reaction step (a).

アクリロニトリルを除去した濃縮液は、続いて、脱触媒塔３２に送られる。この脱触媒塔３２には、イオン交換樹脂が充填されており、ここで触媒成分が除去される。 Subsequently, the concentrated liquid from which acrylonitrile has been removed is sent to the decatalyzing tower 32. The decatalyzing tower 32 is filled with an ion exchange resin, where the catalyst component is removed.

この放散塔３１及び脱触媒塔３２を通過することにより、精製された精製液は、製品貯留部（ｄ）に送られる。そして、この精製工程（ｃ）と製品貯留部（ｄ）との間には、第２濃度計３３が設けられる。この第２濃度計３３により、上記精製液のアクリルアミド濃度が測定され、所定の濃度範囲にあるか否かが判断される。 The purified liquid purified by passing through the stripping tower 31 and the decatalyzing tower 32 is sent to the product storage section (d). A second densitometer 33 is provided between the refining step (c) and the product reservoir (d). The second densitometer 33 measures the acrylamide concentration of the purified solution, and determines whether it is within a predetermined concentration range.

（製品貯留部（ｄ））
この製品貯留部（ｄ）は、上記の精製工程（ｃ）で精製された精製液を貯留する部である。この製品貯留部（ｄ）には、上記精製液の撹拌機構を有する。この撹拌機構としては、種々の機構があるが、例えば、下記の２つの撹拌機構があげられる。 (Product storage part (d))
This product storage part (d) is a part which stores the refinement | purification liquid refine | purified by said refinement | purification process (c). This product reservoir (d) has a stirring mechanism for the purified liquid. There are various mechanisms as the stirring mechanism, and examples thereof include the following two stirring mechanisms.

１つ目の撹拌機構としては、図１に示すように、並列に配された複数の製品貯留タンク４１ａ、この複数の製品貯留タンクを並列に配されるように連結した配管からなる製品循環部４２、及びこの製品循環部に設けられた循環ポンプ４３から構成される。精製工程（ｃ）からの精製液は、受け入れライン４６を経由して製品貯留タンク４１ａに送られる。そして、製品貯留タンク４１ａ内の精製液が、この製品貯留タンク４１ａ及び製品循環部４２内を、循環ポンプ４３によって循環し、結果として、精製液が撹拌されることとなり、精製液が均一に保持される。 As shown in FIG. 1, the first agitation mechanism includes a plurality of product storage tanks 41a arranged in parallel, and a product circulation section composed of a pipe connecting the plurality of product storage tanks arranged in parallel. 42 and a circulation pump 43 provided in the product circulation section. The purified liquid from the purification step (c) is sent to the product storage tank 41a via the receiving line 46. Then, the purified liquid in the product storage tank 41a is circulated in the product storage tank 41a and the product circulation part 42 by the circulation pump 43. As a result, the purified liquid is agitated and the purified liquid is kept uniform. Is done.

上記の製品貯留タンク４１ａは複数設けられるが、上記の循環による撹拌は、それぞれの製品貯留タンク４１ａ毎に、それぞれ別個に行ってもよく、複数の製品貯留タンク４１ａ内の精製液をまとめて行ってもよい。別個に行った場合、それぞれの製品貯留タンク４１ａ毎の精製液のアクリルアミド濃度は異なる状態となる場合が生じ、一方、複数の製品貯留タンク４１ａ内の精製液をまとめて行った場合は、それらの製品貯留タンク４１ａ内の精製液のアクリルアミド濃度は、同一となる。 A plurality of the product storage tanks 41a are provided. The agitation by the circulation may be performed separately for each product storage tank 41a, and the purified liquid in the plurality of product storage tanks 41a is collectively performed. May be. When it is performed separately, the acrylamide concentration of the purified liquid for each product storage tank 41a may be different. On the other hand, when the purified liquids in the plurality of product storage tanks 41a are collected together, The acrylamide concentration of the purified liquid in the product storage tank 41a is the same.

上記製品循環部４２には、第３濃度計４４が設けられる。これにより、この製品循環部４２を通る精製液のアクリルアミド濃度が測定される。そして、循環・撹拌を、個々の製品貯留タンク４１ａ毎に行う場合は、上記の第３濃度計４４により、循環・撹拌されている製品貯留タンク４１ａ中の精製液のアクリルアミド濃度を測定することができる。また、循環・撹拌を、複数の製品貯留タンク４１ａ内の精製液をまとめて行う場合は、それらのまとめた精製液のアクリルアミド濃度を測定することができる。 The product circulation unit 42 is provided with a third concentration meter 44. Thereby, the acrylamide concentration of the purified liquid passing through the product circulation part 42 is measured. When the circulation / stirring is performed for each product storage tank 41a, the third concentration meter 44 can measure the acrylamide concentration of the purified liquid in the product storage tank 41a being circulated / stirred. it can. Moreover, when circulating and stirring are collectively performed for the purified solutions in the plurality of product storage tanks 41a, the acrylamide concentration of the combined purified solutions can be measured.

次に、２つめの撹拌機構としては、図２に示すように、製品貯留タンク４１ｂ及びこの製品貯留タンク内の精製液を撹拌する撹拌装置４５から構成される。この場合は、製品貯留タンク４１ｂ内の精製液は、撹拌装置４５によって撹拌される。 Next, as shown in FIG. 2, the second stirring mechanism includes a product storage tank 41b and a stirring device 45 for stirring the purified liquid in the product storage tank. In this case, the purified liquid in the product storage tank 41 b is stirred by the stirring device 45.

このとき、第３濃度計４４は、製品貯留タンク４１ｂ中に配することにより、撹拌後の精製液の濃度を的確に測定することができる。 At this time, the third concentration meter 44 can accurately measure the concentration of the purified liquid after stirring by being disposed in the product storage tank 41b.

（精製液のアクリルアミド濃度の調整）
上記精製液たるアクリルアミド水溶液のアクリルアミド濃度は、所定範囲、例えば、５０．０〜５１．０重量％の１％程度の狭い範囲内、好ましくは５０．０〜５０．３重量％の０．３％程度の狭い範囲内におさめるのが好ましい。この濃度範囲が広すぎたり、また、この濃度範囲から逸脱したりすると、出荷先の使用者側での濃度調整が必要となり、手間が生じる。 (Adjustment of acrylamide concentration in purified solution)
The acrylamide concentration of the purified acrylamide aqueous solution is within a predetermined range, for example, a narrow range of about 1% of 50.0 to 51.0% by weight, preferably 50.0 to 50.3% by weight of 0.3%. It is preferable to keep it within a narrow range. If this density range is too wide or deviates from this density range, it is necessary to adjust the density on the user side of the shipping destination, resulting in trouble.

上記の製造方法の中で、精製液のアクリルアミド濃度に根本的な影響を与えるのは、濃縮工程（ｂ）の濃縮部（ｂ１）の濃縮条件である。この濃縮条件は、上記したように、温度及び圧力とで決まる。ただ、圧力の変動は、より大きな濃縮度の変化を生じさせるため、濃縮度を細かく変更したい場合は、温度を制御する方が好ましい。この発明においては、この濃縮部（ｂ１）の温度条件を制御することにより、精製液のアクリルアミド濃度を狭い所定範囲内におさめるのである。 In the above production method, it is the concentration condition of the concentration part (b1) in the concentration step (b) that fundamentally affects the acrylamide concentration of the purified solution. As described above, this concentration condition is determined by temperature and pressure. However, since fluctuations in pressure cause a greater change in concentration, it is preferable to control the temperature when it is desired to finely change the concentration. In the present invention, the acrylamide concentration of the purified solution is controlled within a narrow predetermined range by controlling the temperature condition of the concentration section (b1).

なお、この濃縮部（ｂ１）におけるアクリルアミド濃度は、目的の濃度の０．２〜１．０重量％、好ましくは０．３〜０．６重量％低めになるように調製することが好ましい。後の精製工程（ｃ）で原料のアクリロニトリルを留去する際、若干の水も同伴して留去されるため、精製工程（ｃ）終了後において、上記した範囲程度、アクリルアミド濃度が上昇してしまうためである。 In addition, it is preferable to prepare so that the acrylamide density | concentration in this concentration part (b1) may be 0.2 to 1.0 weight% of the target density | concentration, Preferably it becomes 0.3 to 0.6 weight% lower. When the raw material acrylonitrile is distilled off in the subsequent purification step (c), some water is also distilled off, so that after the purification step (c), the acrylamide concentration is increased by about the above-mentioned range. It is because it ends.

上記濃縮部（ｂ１）に導入されるアクリルアミド水溶液は、上記のとおり、反応工程（ａ）からの生成液と、濃縮液貯留部（ｂ２）からの濃縮液の混合液である濃縮対象液であるが、これの温度は、熱交換器２５の制御次第で調整することができる。このため、この熱交換器２５を制御することにより、濃縮部（ｂ１）の濃縮条件の１つである温度を制御することができる。 As described above, the acrylamide aqueous solution introduced into the concentration part (b1) is a liquid to be concentrated which is a mixed liquid of the product liquid from the reaction step (a) and the concentrated liquid from the concentrated liquid storage part (b2). However, the temperature of this can be adjusted depending on the control of the heat exchanger 25. For this reason, by controlling this heat exchanger 25, the temperature which is one of the concentration conditions of the concentration part (b1) can be controlled.

この熱交換器２５を制御する方法としては、熱交換器２５を流れる熱交換媒体の温度を制御する方法と、熱交換媒体の流速を変化させる方法が挙げられる。以下においては、熱交換媒体の温度を制御する方法を記載するが、熱交換媒体の流速を変化させる方法を用いても、同様に行うことができる。 Examples of the method for controlling the heat exchanger 25 include a method for controlling the temperature of the heat exchange medium flowing through the heat exchanger 25 and a method for changing the flow rate of the heat exchange medium. In the following, a method for controlling the temperature of the heat exchange medium will be described, but the method can be similarly performed by using a method for changing the flow rate of the heat exchange medium.

この熱交換器２５を制御するための判断基準として、主に上記第２濃度計３３の計測データを用い、これに、上記の第１濃度計２４及び第３濃度計４４の計測データやそのデータの変化を併用する。次に、この判断基準と、熱交換器２５の制御方法である熱交換媒体の温度制御方法について説明する。 As a criterion for controlling the heat exchanger 25, measurement data of the second densitometer 33 is mainly used, and measurement data of the first densitometer 24 and the third densitometer 44 and data thereof are used. In combination with changes. Next, a description will be given of this determination criterion and a heat exchange medium temperature control method which is a control method of the heat exchanger 25.

まず、第２濃度計３３で、精製工程（ｃ）から製品貯留部（ｄ）に送られる精製液のアクリルアミド濃度を測定する。その測定データが、上記したような目的の濃度範囲より高い場合は、熱交換器２５に流す熱交換媒体の温度を少し下げる。すると、濃縮部（ｂ１）の濃縮缶２１中の濃縮対象液の温度は低くなっていく。このため、濃縮缶２１の減圧濃縮において、水の留去量が減少し、この濃縮部（ｂ１）から濃縮液貯留部（ｂ２）に送られる濃縮液のアクリルアミド濃度を低下させることができる。 First, the second densitometer 33 measures the acrylamide concentration of the purified solution sent from the purification step (c) to the product reservoir (d). When the measurement data is higher than the target concentration range as described above, the temperature of the heat exchange medium flowing through the heat exchanger 25 is slightly lowered. Then, the temperature of the concentration target liquid in the concentration can 21 of the concentration part (b1) becomes lower. For this reason, in vacuum concentration of the concentration can 21, the amount of distilled water decreases, and the concentration of acrylamide in the concentrated liquid sent from the concentrated part (b1) to the concentrated liquid storage part (b2) can be lowered.

逆に、上記測定データが、目的の濃度範囲より低い場合は、熱交換器２５に流す熱交換媒体の温度を少し上げる。すると、濃縮部（ｂ１）の濃縮缶２１中の濃縮対象液の温度は高くなっていく。このため、濃縮缶２１の減圧濃縮において、水の留去量が増大し、この濃縮部（ｂ１）から濃縮液貯留部（ｂ２）に送られる濃縮液のアクリルアミド濃度を増大させることができる。 On the other hand, when the measurement data is lower than the target concentration range, the temperature of the heat exchange medium flowing through the heat exchanger 25 is slightly increased. Then, the temperature of the concentration target liquid in the concentration can 21 of the concentration part (b1) becomes higher. For this reason, in the vacuum concentration of the concentration can 21, the amount of distilled water is increased, and the acrylamide concentration of the concentrate sent from the concentration section (b 1) to the concentrate storage section (b 2) can be increased.

上記の方法で得られる精製液のアクリルアミド濃度を修正することができるが、上記第２濃度計３３だけで制御していくと、得られる精製液のアクリルアミド濃度が経時的に波打つおそれがあり、１点に収束させるのが困難となる場合がある。これを防止するために、第１濃度計２４及び第３濃度計４４が用いられる。 The acrylamide concentration of the purified solution obtained by the above method can be corrected. However, if the concentration is controlled only by the second densitometer 33, the acrylamide concentration of the obtained purified solution may undulate over time. It may be difficult to converge to a point. In order to prevent this, the first densitometer 24 and the third densitometer 44 are used.

上記第１濃度計２４は、濃縮工程（ｂ）の濃縮液貯留部（ｂ２）における濃縮液のアクリルアミド濃度を測定し、また、上記第３濃度計４４は、製品貯留部（ｄ）の精製液のアクリルアミド濃度を測定する。 The first concentration meter 24 measures the acrylamide concentration of the concentrate in the concentrate storage part (b2) of the concentration step (b), and the third concentration meter 44 is a purified solution in the product storage part (d). Measure the acrylamide concentration.

まず、第２濃度計３３と第１濃度計２４との関係について記載する。
第２濃度計３３の測定データが目的の濃度範囲より高い場合、上記したように、熱交換器２５での熱交換媒体の温度を少し下げることにより、得られる濃縮液のアクリルアミド濃度を低下させるが、第１濃度計２４での測定データが目的の濃度範囲内にある場合や、第１濃度計２４での測定データが目的の濃度範囲より高くても、第１濃度計２４での測定データの変化が下降方向（濃度が低くなる方向）の場合、第２濃度計３３の測定データが目的の濃度範囲内になるのは間近であるといえる。この場合、濃縮部（ｂ１）での濃縮条件の制御条件、すなわち、熱交換器２５での熱交換媒体の温度の下げ幅を小さくすることにより、第２濃度計３３を流れる精製液のアクリルアミド濃度の変化を調整し、目的の濃度範囲内に、波打つことなく、おさめることができる。 First, the relationship between the second densitometer 33 and the first densitometer 24 will be described.
When the measurement data of the second densitometer 33 is higher than the target concentration range, as described above, the acrylamide concentration of the resulting concentrate is lowered by slightly lowering the temperature of the heat exchange medium in the heat exchanger 25. When the measurement data in the first concentration meter 24 is within the target concentration range, or even if the measurement data in the first concentration meter 24 is higher than the target concentration range, the measurement data in the first concentration meter 24 When the change is in the descending direction (direction in which the density decreases), it can be said that the measurement data of the second densitometer 33 is close to being within the target density range. In this case, the acrylamide concentration of the purified liquid flowing through the second densitometer 33 is reduced by reducing the control condition of the concentration condition in the concentration section (b1), that is, the decrease in the temperature of the heat exchange medium in the heat exchanger 25. It is possible to adjust the change of the light intensity within the target concentration range without undulation.

また、第２濃度計３３の測定データが目的の濃度範囲より低い場合、上記したように、熱交換器２５での熱交換媒体の温度を少し上げることにより、得られる濃縮液のアクリルアミド濃度を上昇させるが、第１濃度計２４での測定データが目的の濃度範囲内にある場合や、第１濃度計２４での測定データが目的の濃度範囲より低くても、第１濃度計２４での測定データの変化が上昇方向（濃度が高くなる方向）の場合、第２濃度計３３の測定データが目的の濃度範囲内になるのは間近であるといえる。この場合、濃縮部（ｂ１）での濃縮条件の制御条件、すなわち、熱交換器２５での熱交換媒体の温度の上げ幅を小さくすることにより、第２濃度計３３を流れる精製液のアクリルアミド濃度の変化を調整し、目的の濃度範囲内に、波打つことなく、おさめることができる。 Further, when the measurement data of the second densitometer 33 is lower than the target concentration range, as described above, the temperature of the heat exchange medium in the heat exchanger 25 is slightly increased to increase the acrylamide concentration of the obtained concentrated liquid. However, even if the measurement data with the first densitometer 24 is within the target concentration range, or even if the measurement data with the first densitometer 24 is lower than the target concentration range, the measurement with the first densitometer 24 is performed. When the data change is in the increasing direction (in which the density increases), it can be said that the measurement data of the second densitometer 33 is close to being within the target density range. In this case, the acrylamide concentration of the purified liquid flowing through the second concentration meter 33 is reduced by reducing the control condition of the concentration condition in the concentration section (b1), that is, the increase in the temperature of the heat exchange medium in the heat exchanger 25. The change can be adjusted and kept within the desired concentration range without undulation.

次に、第２濃度計３３と第３濃度計４４との関係について記載する。
第２濃度計３３の測定データが目的の濃度範囲より高い場合、上記したように、熱交換器２５での熱交換媒体の温度を下げることにより、得られる濃縮液のアクリルアミド濃度を低下させるが、第３濃度計４４での測定データが目的の濃度範囲より低い場合は、熱交換器２５での熱交換媒体の温度を保持するか、温度の下げ幅を小さくすることにより、濃度が高めの精製液を製品貯留部（ｄ）に送ることができる。そして、製品貯留部（ｄ）での精製液のアクリルアミド濃度が所定範囲に入った場合、又は、所定範囲内に入りつつある場合は、第３濃度計４４による制御を解除する。これにより、製品貯留部（ｄ）での精製液のアクリルアミド濃度を所定範囲におさめることができる。なお、第２濃度計３３の測定データが目的の濃度範囲より高く、かつ、第３濃度計４４での測定データが目的の濃度範囲より高い場合は、製品貯留部（ｄ）での精製液のアクリルアミド濃度を下げる必要があるので、第２濃度計３３の測定データが目的の濃度範囲より高い場合に行う上記制御を行うのがよい。 Next, the relationship between the second densitometer 33 and the third densitometer 44 will be described.
When the measurement data of the second densitometer 33 is higher than the target concentration range, as described above, by reducing the temperature of the heat exchange medium in the heat exchanger 25, the acrylamide concentration of the resulting concentrated liquid is reduced. When the measurement data obtained by the third densitometer 44 is lower than the target concentration range, the temperature of the heat exchange medium in the heat exchanger 25 is maintained, or the temperature decrease is reduced, so that the concentration is increased. The liquid can be sent to the product reservoir (d). Then, when the acrylamide concentration of the purified liquid in the product reservoir (d) falls within a predetermined range, or when entering the predetermined range, the control by the third concentration meter 44 is released. Thereby, the acrylamide density | concentration of the refinement | purification liquid in a product storage part (d) can be settled in a predetermined range. When the measurement data of the second concentration meter 33 is higher than the target concentration range and the measurement data of the third concentration meter 44 is higher than the target concentration range, the purified solution in the product reservoir (d) Since it is necessary to lower the acrylamide concentration, it is preferable to perform the above control when the measurement data of the second densitometer 33 is higher than the target concentration range.

また、第２濃度計３３の測定データが目的の濃度範囲より低い場合、上記したように、熱交換器２５での熱交換媒体の温度を上げることにより、得られる濃縮液のアクリルアミド濃度を上昇させるが、第３濃度計４４での測定データが目的の濃度範囲より高い場合は、熱交換器２５での熱交換媒体の温度を保持するか、温度の上げ幅を小さくすることにより、濃度が低めの精製液を製品貯留部（ｄ）に送ることができる。そして、製品貯留部（ｄ）での精製液のアクリルアミド濃度が所定範囲に入った場合、又は、所定範囲内に入りつつある場合は、第３濃度計４４による制御を解除する。これにより、製品貯留部（ｄ）での精製液のアクリルアミド濃度を所定範囲におさめることができる。なお、第２濃度計３３の測定データが目的の濃度範囲より低く、かつ、第３濃度計４４での測定データが目的の濃度範囲より低い場合は、製品貯留部（ｄ）での精製液のアクリルアミド濃度を上げる必要があるので、第２濃度計３３の測定データが目的の濃度範囲より低い場合に行う上記制御を行うのがよい。 Further, when the measurement data of the second concentration meter 33 is lower than the target concentration range, as described above, the acrylamide concentration of the obtained concentrated liquid is increased by increasing the temperature of the heat exchange medium in the heat exchanger 25. However, when the measurement data obtained by the third densitometer 44 is higher than the target concentration range, the concentration of the heat exchange medium in the heat exchanger 25 is maintained or the increase in temperature is reduced to reduce the concentration. The purified liquid can be sent to the product reservoir (d). Then, when the acrylamide concentration of the purified liquid in the product reservoir (d) falls within a predetermined range, or when entering the predetermined range, the control by the third concentration meter 44 is released. Thereby, the acrylamide density | concentration of the refinement | purification liquid in a product storage part (d) can be settled in a predetermined range. When the measurement data of the second concentration meter 33 is lower than the target concentration range and the measurement data of the third concentration meter 44 is lower than the target concentration range, the purified liquid in the product reservoir (d) Since it is necessary to increase the acrylamide concentration, it is preferable to perform the control described above when the measurement data of the second densitometer 33 is lower than the target concentration range.

なお、第１濃度計２４による熱交換器２５の熱交換媒体の温度の微調整と、第３濃度計４４による熱交換器２５の熱交換媒体の温度の微調整が相反する場合、製品貯留タンク４１ａ，４１ｂ中の精製液の濃度調整を優先する観点から、第３濃度計４４による熱交換器２５の熱交換媒体の温度の微調整を優先させるのが好ましい。 When the fine adjustment of the temperature of the heat exchange medium of the heat exchanger 25 by the first concentration meter 24 and the fine adjustment of the temperature of the heat exchange medium of the heat exchanger 25 by the third concentration meter 44 are contradictory, the product storage tank From the viewpoint of giving priority to concentration adjustment of the purified solution in 41a and 41b, it is preferable to give priority to fine adjustment of the temperature of the heat exchange medium of the heat exchanger 25 by the third concentration meter 44.

なお、上記製品貯留部（ｄ）が複数の製品貯留タンク４１ａを用い、各製品貯留タンク４１ａを個別に循環・撹拌する場合において、それぞれのタンクのアクリルアミド濃度が異なる場合、これらを適宜組み合わせて循環・撹拌することにより、アクリルアミド濃度を目的の濃度範囲内におさめることができるときは、この適宜組み合わせる方法を採用することができる。 In the case where the product storage section (d) uses a plurality of product storage tanks 41a and circulates and agitates each product storage tank 41a individually, if the acrylamide concentration in each tank is different, the product storage section (d) circulates by appropriately combining them. When the acrylamide concentration can be kept within the target concentration range by stirring, this method of appropriate combination can be employed.

また、上記製品貯留部（ｄ）におけるアクリルアミド濃度が高い場合は、ここに水を加え、濃度を目的の濃度範囲内にしてもよい。 Moreover, when the acrylamide concentration in the said product storage part (d) is high, water may be added here and a density | concentration may be in the target concentration range.

上記の方法を採用することにより、精製液のアクリルアミド濃度が経時的に波打つのを防止でき、安定的に狭い範囲の濃度のアクリルアミド水溶液を得ることができる。 By employing the above method, it is possible to prevent the acrylamide concentration of the purified solution from undulating with time, and to stably obtain an acrylamide aqueous solution having a narrow range of concentrations.

以下に実施例を用いて本発明を更に具体的に説明する。
図１に示す装置を用いてアクリルアミド（以下、「ＡＡＭ」と称する。）の水溶液を製造した。
通常、目標濃度を５０．１０％とし、通常は安定的に操業するが、気温、流量等の微細変動による濃度の微少変化（０．０５％程度）を第１〜第３濃度計を用いてコントロールし、最終的なＡＡＭの濃度を５０．０〜５０．５％の範囲内におさめるようにした。
まず、反応工程（ａ）では、触媒として銅触媒を用い、原料アクリロニトリル（ＡＮ）と水とを水和反応させ、濃縮缶２１を４０ｔｏｒｒに減圧し、ＡＡＭを製造した。
次に、濃縮工程（ｂ）では、第１濃度計２４による測定濃度が４９．９〜５０．０％となるように熱交換器２５の温度を調節して循環運転を行い、この濃度範囲に入った時点でＡＡＭを精製工程（ｃ）に送り出した。
精製工程（ｃ）では、放散塔３１に空気（ａｉｒ）を吹き込むことにより未反応のＡＮを除去した。未反応ＡＮが除去された分、水溶液中のＡＡＭの濃度が僅かに濃くなる。次いで残存する触媒を脱触媒塔３２で吸着除去した。
精製工程（ｃ）を経たＡＡＭ水溶液の濃度を、第２濃度計３３で確認（５０．０〜５０．１％程度となる）しつつ、ＡＡＭ水溶液を製品貯留部（ｄ）に送り出した。製品貯留部（ｄ）の循環部には第３濃度計４４が設けられており、貯留されたＡＡＭ水溶液の濃度を監視した。
上記の流れが安定した段階で、外乱を生じさせた。具体的には、精製工程（ｃ）へのＡＡＭ送り出し量を増加させた。この外乱により、第２濃度計３３での測定濃度が５０％以下（４９．９７％）となったので熱交換器の温度設定を２℃上げた。これにより第１濃度計２４の値が０．１％上がり、５０．０７％の濃度のＡＡＭが送り出された。６０分後、第２濃度計の濃度が０．１％上昇し５０．０７％濃度のＡＡＭを確認した。循環されている製品貯留部（ｄ）のＡＡＭは、濃度５０．１％で安定しており、５０．１％のＡＡＭ水溶液を６０ｍ^３得た。 Hereinafter, the present invention will be described more specifically with reference to examples.
An aqueous solution of acrylamide (hereinafter referred to as “AAM”) was produced using the apparatus shown in FIG.
Normally, the target concentration is set to 50.10%, and it is normally operated stably. However, a slight change (about 0.05%) due to minute fluctuations such as temperature and flow rate is used with the first to third densitometers. The final AAM concentration was controlled within the range of 50.0-50.5%.
First, in the reaction step (a), a copper catalyst was used as a catalyst, the raw material acrylonitrile (AN) and water were subjected to a hydration reaction, and the concentration can 21 was decompressed to 40 torr to produce AAM.
Next, in the concentration step (b), the temperature of the heat exchanger 25 is adjusted so that the concentration measured by the first densitometer 24 is 49.9 to 50.0%, and the circulation operation is performed. Once entered, AAM was sent to the purification step (c).
In the purification step (c), unreacted AN was removed by blowing air into the stripping tower 31. Since the unreacted AN is removed, the concentration of AAM in the aqueous solution is slightly increased. Next, the remaining catalyst was removed by adsorption in the decatalyzing tower 32.
While confirming the concentration of the AAM aqueous solution after the purification step (c) with the second densitometer 33 (about 50.0 to 50.1%), the AAM aqueous solution was sent out to the product reservoir (d). A third concentration meter 44 is provided in the circulation part of the product storage part (d), and the concentration of the stored AAM aqueous solution is monitored.
Disturbances were generated when the above flow stabilized. Specifically, the amount of AAM delivered to the purification step (c) was increased. Due to this disturbance, the concentration measured by the second densitometer 33 became 50% or less (49.97%), so the temperature setting of the heat exchanger was raised by 2 ° C. As a result, the value of the first densitometer 24 increased by 0.1%, and AAM having a concentration of 50.07% was sent out. After 60 minutes, the concentration of the second densitometer increased by 0.1%, and AAM having a concentration of 50.07% was confirmed. The AAM in the product reservoir (d) being circulated was stable at a concentration of 50.1%, and 60 m ³ of a 50.1% AAM aqueous solution was obtained.

この発明にかかるアクリルアミド水溶液の製造方法を行うプロセスの例をしめすプロセス図Process diagram showing an example of a process for carrying out the method for producing an acrylamide aqueous solution according to the present invention 製品貯留部（ｄ）の他の例を示すプロセス図Process diagram showing another example of product reservoir (d)

Explanation of symbols

１１反応槽
２１濃縮缶
２２濃縮液貯留タンク
２３濃縮液循環部
２４第１濃度計
２５熱交換器
２６濃縮液戻し部
３１放散塔
３２脱触媒塔
３３第２濃度計
４１ａ，４１ｂ製品貯留タンク
４２製品循環部
４３循環ポンプ
４４第３濃度計
４５撹拌装置
４６受け入れライン DESCRIPTION OF SYMBOLS 11 Reaction tank 21 Concentration can 22 Concentrated liquid storage tank 23 Concentrated liquid circulation part 24 1st concentration meter 25 Heat exchanger 26 Concentrated liquid return part 31 Stripping tower 32 Decatalyzing tower 33 2nd concentration meter 41a, 41b Product storage tank 42 Product Circulation unit 43 Circulation pump 44 Third concentration meter 45 Stirrer 46 Receiving line

Claims

A reaction step in which acrylonitrile is hydrated to form acrylamide in the presence of a catalyst;
A concentration step of concentrating the acrylamide aqueous solution, which is the product obtained in this reaction step,
A purification step for removing unreacted acrylonitrile and catalyst from the concentrate obtained in this concentration step;
And the manufacturing method of the acrylamide aqueous solution which has the product storage part which stores the refinement | purification liquid refine | purified by the said refinement | purification process,
The concentration step includes a concentration unit that concentrates the product liquid generated in the reaction step, and a concentrate storage unit that stores the concentrated solution concentrated in the concentration unit,
The concentrated liquid storage part is provided with a first concentration meter that measures the concentration of the concentrated liquid, and a concentrated liquid return part that returns a part of the concentrated liquid to the concentrated part,
A second densitometer is provided between the refining process and the product reservoir,
The product reservoir is provided with a stirring mechanism for the purified liquid and a third concentration meter,
The concentration condition of the concentration unit is controlled by the measurement data of the second densitometer or the change thereof, and the concentration condition of the concentration unit is controlled by the measurement data of the first densitometer and the third densitometer or the change thereof. The manufacturing method of the acrylamide aqueous solution characterized by adjusting conditions.

The stirring mechanism of the product storage unit includes a product storage tank and a stirring device for stirring the purified liquid in the product storage tank, or a plurality of product storage tanks arranged in parallel, and the plurality of product storage tanks in parallel. The method for producing an aqueous acrylamide solution according to claim 1, comprising a product circulation part connected so as to be disposed, and a circulation pump provided in the product circulation part.

The acrylamide according to claim 1 or 2, wherein the concentrating condition of the concentrating part is controlled by a heat exchanger provided in a condensate returning part that sends a part of the concentrated liquid to the concentrating part. A method for producing an aqueous solution.