阅读说明：本技术 纯化甲硫氨酸的制造方法 (Method for producing purified methionine ) 是由 山城直也 守本玲 佐藤庆孝 于 2018-12-25 设计创作，主要内容包括：本发明的目的在于提供能够实现洗涤效率的提高的纯化甲硫氨酸的制造方法。该制造方法为由粗制甲硫氨酸的浆料制造纯化甲硫氨酸的方法,其包括下述工序：工序(1),使用连续式过滤机对粗制甲硫氨酸的浆料进行固液分离；工序(2),向粗制滤饼喷吹粗洗水来洗涤该粗制滤饼,所述粗制滤饼是通过对上述粗制甲硫氨酸的浆料进行固液分离而得到的；以及工序(3),将准纯化滤饼与精洗水混合来洗涤该准纯化滤饼,所述准纯化滤饼是通过向上述粗制滤饼喷吹粗洗水来洗涤该粗制滤饼而得到的。(The purpose of the present invention is to provide a method for producing purified methionine, which can improve the washing efficiency. The process for producing purified methionine from a slurry of crude methionine comprises the steps of: a step (1) of subjecting a slurry of crude methionine to solid-liquid separation using a continuous filter; a step (2) of washing the crude cake obtained by solid-liquid separation of the slurry of crude methionine by blowing crude washing water to the crude cake; and a step (3) of washing the quasi-purified cake obtained by washing the crude cake by blowing crude washing water to the crude cake, by mixing the quasi-purified cake with the fine washing water.)

1. A process for producing purified methionine from a slurry of crude methionine, comprising the steps of:

a step of subjecting the slurry of crude methionine to solid-liquid separation using a continuous filter;

a step of washing a crude cake obtained by subjecting the slurry of crude methionine to solid-liquid separation by blowing crude washing water to the crude cake; and

and a step of washing the quasi-purified filter cake obtained by washing the crude filter cake by blowing crude washing water to the crude filter cake, by mixing the quasi-purified filter cake with the fine washing water.

2. The method according to claim 1, wherein the water content of the quasi-purified filter cake is 20 mass% or more and 40 mass% or less.

Technical Field

The present invention relates to a process for producing purified methionine.

Background

As a method for producing methionine, for example, the following methods are known. The method comprises the following steps: a liquid containing methionine salt (hereinafter, sometimes referred to as "hydrolysis reaction liquid") was obtained by hydrolyzing 5- (2-methylthioethyl) hydantoin (hereinafter, sometimes referred to as "methionine hydantoin"), and a slurry of methionine (hereinafter, sometimes referred to as "slurry") was obtained by introducing carbon dioxide into the hydrolysis reaction liquid to precipitate methionine.

In this production method, a methionine powder as a product can be obtained by washing a cake (cake) of methionine obtained by solid-liquid separation of a slurry and then drying the cake.

A cake of methionine obtained by solid-liquid separation of the slurry (hereinafter, sometimes referred to as a crude cake) contains impurities such as potassium. Therefore, in order to obtain high-quality methionine having a low content of the impurities (hereinafter, sometimes referred to as purified methionine), various studies have been made on a method for washing a crude cake (for example, see patent document 1).

In patent document 1, after solid-liquid separation of a slurry is performed using a batch-type centrifugal filter, washing of a crude cake is attempted by blowing washing water to the crude cake using a sprayer in the centrifugal filter.

Disclosure of Invention

Problems to be solved by the invention

In order to improve the productivity of methionine, the inventors of the present application studied replacing the batch filter used in the solid-liquid separation of the slurry with the continuous filter. In this study, a continuous filter was used to separate a slurry into a solid and a liquid to obtain a crude cake, and the crude cake was washed with a sprayer in the filter.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing purified methionine, which can improve the impurity removal rate per unit amount of washing water, that is, the washing efficiency of methionine, when a continuous filter is used.

Means for solving the problems

The present inventors have intensively studied about the fact that impurities contained in a crude cake are not easily removed when a continuous filter is used, and as a result, they have found that impurities taken into methionine crystal grains and impurities other than the impurities are mixed in the impurities contained in the crude cake, and have found the following findings: the latter impurity can be easily removed by the spray-based washing, but the former impurity is not easily removed, and in order to remove the impurity, it is necessary to contact the crystal grains of methionine with washing water for a certain period of time, thereby completing the present invention. That is, the process for producing purified methionine according to the present invention is a process for producing purified methionine from a slurry of crude methionine, comprising the steps of:

a step (1) of subjecting a slurry of crude methionine to solid-liquid separation using a continuous filter;

a step (2) of washing the crude cake obtained by solid-liquid separation of the slurry of crude methionine by blowing crude washing water to the crude cake; and

and (3) washing the quasi-purified cake obtained by washing the crude cake by blowing crude washing water to the crude cake, by mixing the quasi-purified cake with the fine washing water.

This production method is characterized in that coarse washing water is blown to a crude cake obtained by solid-liquid separation of a slurry using a continuous filter to wash the cake, and then the cake is mixed with fine washing water to wash the cake. In this production method, impurities present on the surface of methionine crystal grains are removed by washing the crude cake by blowing crude washing water thereto, and impurities present in the methionine crystal grains are removed by washing the quasi-purified cake by mixing with fine washing water. In this production method, a method of washing the cake by spraying washing water (hereinafter, sometimes referred to as spray washing) and a method of washing the cake by mixing the cake with washing water (hereinafter, sometimes referred to as reslurry washing) are performed in combination, whereby impurities contained in the crude cake can be removed with a smaller amount of washing water than in a method of washing only by either spray washing or reslurry washing. In this production method, the efficiency of washing methionine can be improved when a continuous filter is used.

ADVANTAGEOUS EFFECTS OF INVENTION

As is clear from the above description, the production method of the present invention can improve the efficiency of washing methionine when a continuous filter is used. The method can obtain high-quality purified methionine with low impurity content with small amount of washing water even in the case of using a continuous filter.

Detailed Description

The present invention will be described in detail below based on preferred embodiments. In the present specification, the details of the conventionally known parts other than those necessary for explaining the present invention are omitted.

[ Process for producing purified methionine ]

The production method of the present invention is a method for producing purified methionine from a slurry of crude methionine, and comprises a separation step, a coarse wash water spray-blowing step, and a fine wash water mixing step.

As a method for producing a slurry of crude methionine, for example, a method in which a crystallization step is performed after a hydrolysis step described below can be cited.

[ hydrolysis step ]

In the hydrolysis step, methionine hydantoin is hydrolyzed in the presence of a basic compound such as potassium hydroxide, sodium hydroxide, potassium carbonate, or potassium hydrogencarbonate. Thus, a methionine salt-containing liquid (hereinafter, sometimes referred to as a hydrolysis reaction liquid) was obtained. In the hydrolysis step, the pressure is set within the range of about 0.5 to 1.0 MPaG. The temperature is set within the range of 150-200 ℃. In addition, as a method for producing methionine hydantoin as a raw material, for example, a method of reacting 3-methylthiopropanal cyanohydrin with carbon dioxide and ammonia in water is given.

[ crystallization Process ]

In the crystallization step, carbon dioxide is introduced into the hydrolysis reaction liquid obtained in the hydrolysis step. Thus, methionine is precipitated, and methionine slurry in which methionine crystal grains are dispersed can be obtained. In the crystallization step, the crystallization temperature is usually 0 to 50 ℃, preferably 10 to 30 ℃. The crystallization time is usually 30 minutes to 24 hours based on the time until carbon dioxide is saturated in the reaction solution and methionine is sufficiently precipitated.

In the present invention, the slurry of methionine obtained by introducing carbon dioxide into the hydrolysis reaction liquid is the slurry of crude methionine. The concentration of methionine in the crude methionine slurry is usually in the range of 5 to 30 mass% in terms of solid content concentration. The slurry of crude methionine contains basic compounds such as potassium hydroxide used for hydrolysis, methionine dimer, glycine and alanine generated by decomposition of methionine, and other impurities.

[ separation Process ]

In the separation step, the slurry of the crude methionine obtained in the crystallization step is subjected to solid-liquid separation to obtain a cake of the crude methionine as a solid component (i.e., a crude cake) and a mother liquor as a liquid component. In this production method, a continuous filter (hereinafter, simply referred to as a filter in some cases) is used to separate solid from liquid in the slurry of crude methionine.

In the present invention, the filter is not particularly limited as long as it is a continuous filter as described below. As the continuous filter, a pressure type filter or the like can be exemplified.

In the separation step, a slurry of crude methionine is continuously supplied from the reaction tank in which the crystallization step is performed to the filter. In this filter, solid-liquid separation is continuously performed, and a crude cake in the form of a plate is continuously formed. The thickness of the plate-like crude cake is set within the range of 15 to 100 mm. In this separation step, various conditions for solid-liquid separation are appropriately set so that the water content of the crude cake becomes substantially 40 mass% or less.

As described previously, the slurry of crude methionine contains impurities. Therefore, the crude cake obtained by the solid-liquid separation also contains impurities.

In the present invention, impurities derived from basic compounds used in the hydrolysis step, such as potassium hydroxide, sodium hydroxide, potassium carbonate, and potassium hydrogencarbonate, are contained in the crude cake. Therefore, depending on the type of the basic compound used, the impurities derived from the basic compound vary. For example, in the case of using a basic potassium compound containing potassium carbonate, potassium hydrogencarbonate, and potassium hydroxide as the basic compound, the impurity concentration is represented by a potassium concentration. The impurity concentration of the crude cake in this case is usually in the range of 0.5 to 8 mass%. The potassium concentration is expressed as a ratio of the mass of potassium to the mass of the crude cake after drying. In the present invention, the mass of potassium is obtained in the following manner: the amount of potassium ions measured by ion chromatography was converted into the mass of potassium. The analysis conditions for determining the amount of potassium ions are as follows.

(conditions for ion chromatography analysis)

Column: dionex IonPac CS12A

Column size: an inner diameter of 4mm and a length of 250mm

Eluent: 18mmol/L methanesulfonic acid

[ procedure of coarse Water spray-blowing ]

In the coarse washing water spraying step, washing water is sprayed to the coarse filter cake obtained in the separation step, and the coarse filter cake is washed. In the present invention, the washing water used for washing the crude cake is crude washing water. In this production method, the rough washing water spraying step is carried out in the filter used in the separation step or in a device different from the filter. From the viewpoint of production efficiency, it is preferable to perform the rough washing water blowing step in the filter used in the separation step. In this production method, in the filter, coarse washing water is blown to a continuously formed plate-like coarse filter cake to wash the coarse filter cake. Thereby, a part of the impurities contained in the crude filter cake is washed away. Thus, the crude filter cake after washing contains less impurities than the amount of impurities before washing. In the present invention, the crude cake after washing, in which the amount of impurities is reduced by washing with the crude washing water, is referred to as a purified cake. In the rough washing water spraying and blowing step, the temperature of the rough washing water is usually set to an appropriate temperature within the range of 5 to 35 ℃.

In this production method, a sprayer is used to spray the crude cake with the crude washing water. In this production method, the sprayer for spraying the coarse washing water onto the coarse cake is not particularly limited as long as the spraying amount of the coarse washing water can be adjusted and the coarse washing water can be sprayed onto the entire coarse cake without omission.

In the coarse washing water spraying step, the mass of the coarse washing water sprayed onto the crude cake is preferably 100g or more, and preferably 300g or less, based on 100g of the mass of the crude cake after drying, from the viewpoint of efficiently removing impurities. The mass of the crude washing water is more preferably 150g or more, and still more preferably 250g or less, based on 100g of the dried mass of the crude cake.

In this production method, water may be used as the crude washing water, and an aqueous solution of methionine may be used as the crude washing water. The crude washing water is preferably an aqueous solution of methionine, from the viewpoint of preventing the methionine constituting the crude cake from dissolving in the crude washing water and improving the yield of methionine in the product. In this case, the concentration of methionine in the crude washing water is preferably 1.0 mass% or more, more preferably 2.0 mass% or more. Since the saturation solubility of methionine in water at normal temperature and pressure was 3.0 mass%, the upper limit of the concentration of methionine in the crude washing water was 3.0 mass%. That is, the concentration of methionine in the crude washing water was 3.0 mass% or less. In the present invention, the concentration of methionine can be measured by liquid chromatography.

The water used in the crude washing water is not particularly limited. Examples of the water include distilled water, pure water, ion-exchanged water, condensed water of steam, and industrial water.

The water content of the quasi-purified cake obtained by performing the coarse wash water spraying step in the continuous filter is usually 20 mass% or more and 40 mass% or less. In the purification of methionine, the production method of the present invention is applied when the water content of the quasi-purified cake is within the above range, whereby the efficiency of washing methionine can be improved.

[ Fine washing Water mixing Process ]

In the fine washing water mixing step, the quasi-purified filter cake obtained in the coarse washing water spraying step is further washed with washing water. In the present invention, the washing water used for washing the quasi-purified filter cake is the fine washing water. In the fine washing water mixing step, the quasi-purified cake discharged from the filter is thrown into the drum of the stirring apparatus together with the fine washing water. After the charging, the stirring blade in the drum is rotated to stir and mix the purified cake and the washing water. By performing reslurrying washing in this manner, the crystal grains of methionine constituting the quasi-purified filter cake can be brought into contact with the fine washing water for a certain period of time, and impurities remaining in the quasi-purified filter cake (in detail, impurities present in the crystal grains of methionine constituting the quasi-purified filter cake) are removed. This makes it possible to obtain a clean methionine slurry, i.e., a purified methionine slurry. In the fine washing water mixing step, the fine washing water may be introduced into the drum after the fine purification cake is introduced, the fine purification cake may be introduced into the drum after the fine washing water is introduced, or the fine purification cake and the fine washing water may be introduced simultaneously. The temperature of the washing water is usually set to a suitable value within the range of 5 to 35 ℃.

In this production method, the stirring apparatus is not particularly limited as long as the quasi-purified cake and the fine washing water can be sufficiently stirred and mixed in the stirring apparatus.

In the fine washing water mixing step, the mass of the fine washing water to be fed into the drum together with the quasi-purified cake is preferably 100g or more, and preferably 300g or less, with respect to 100g of the mass of the quasi-purified cake after drying, from the viewpoint of effectively removing impurities. The mass of the washing water is more preferably 150g or more, and still more preferably 250g or less, based on 100g of the mass of the quasi-purified cake after drying.

In this production method, water may be used as the washing water, and an aqueous solution of methionine may be used as the washing water. From the viewpoint of preventing the methionine from dissolving in the finishing water and improving the yield of methionine in the product, an aqueous methionine solution is preferred as the finishing water.

In this case, the concentration of methionine in the fine washing water is preferably 1.0 mass% or more, and more preferably 2.0 mass% or more. Since the saturation solubility of methionine in water at normal temperature and pressure was 3.0 mass%, the upper limit of the concentration of methionine in the fine washing water was 3.0 mass%. That is, the concentration of methionine in the fine washing water was 3.0 mass% or less.

The water used in the fine washing water is not particularly limited. Examples of the water include distilled water, pure water, ion-exchanged water, condensed water of steam, and industrial water.

In the fine washing water mixing step, the time for mixing and stirring the quasi-purified cake and the fine washing water (hereinafter, referred to as "stirring time") is appropriately determined in consideration of the influence on the production cost and the effective removal of impurities. Usually, the stirring time is set in the range of 3 minutes to 30 minutes.

In this production method, the slurry of purified methionine obtained in the fine washing water mixing step is usually subjected to solid-liquid separation using a conventionally known solid-liquid separator. Thus, a cake of purified methionine (hereinafter, also referred to as a purified cake) was obtained. That is, the production method further includes a step of performing solid-liquid separation of the slurry of purified methionine (hereinafter, also referred to as a second separation step). The concentration of methionine in the slurry of purified methionine is usually about 20 to 45 mass% in terms of solid content concentration.

In this production method, the purified cake obtained in the second separation step is usually fed into a conventionally known dryer. In the dryer, the purified filter cake is dried. Thus, a high-quality powdery methionine from which water is removed and the impurity content is reduced, that is, a purified methionine is obtained. The production method further includes a step of drying the purified cake obtained by solid-liquid separation of the slurry of purified methionine (hereinafter, also referred to as a drying step).

In this production method, the drying method of the purified cake is not particularly limited as long as the water is sufficiently removed in the drying step to obtain the purified methionine. In this production method, the drying step is constituted by the same contents as those of the drying step in the conventionally known production method. In the production method, the drying temperature is usually 50 to 150 ℃, preferably 100 to 140 ℃. The drying time is usually 10 minutes to 24 hours, preferably 30 minutes to 2 hours. The state where water is sufficiently removed means a state where the water content of the purified methionine is 5 mass% or less.

As described above, the production method is a method for producing purified methionine from a slurry of crude methionine, and includes a separation step, a coarse washing water spray-blowing step, a fine washing water mixing step, a second separation step, and a drying step. Specifically, in this production method, in the separation step, a crude cake is continuously formed from a slurry of crude methionine. In the coarse wash water sparging procedure, the coarse filter cake is washed. The quasi-purified cake obtained by the washing is further washed by mixing with the washing water in the washing water mixing step, to obtain a slurry of purified methionine. In the second separation step, the slurry of purified methionine is subjected to solid-liquid separation to obtain a purified cake. Then, in a drying process, the purified filter cake is dried to obtain purified methionine.

As is clear from the above description, the production method of the present invention can improve the efficiency of washing methionine when a continuous filter is used. In this production method, even when a continuous filter is used, a high-quality purified methionine having a low impurity content can be obtained with a small amount of washing water.