Method for recycling methionine hydroxy analogues in ammonium sulfate by-product

Abstract

The present invention relates to the field of chemical technology, and in particular to a method for recycling methionine hydroxy analogs in ammonium sulfate byproducts. The ammonium sulfate byproduct produced in the methionine preparation process is reacted with calcium oxide or calcium hydroxide at a reaction temperature of 50°C to 95°C for 60 to 120 minutes. The resulting reaction solution is deaminated and filtered to obtain a methionine hydroxy analog calcium salt aqueous solution, which is then concentrated, crystallized, filtered, and dried to obtain a methionine hydroxy analog calcium salt compound; the ammonium sulfate byproduct contains methionine hydroxy analogs. The present invention simultaneously converts valuable methionine hydroxy analogs in ammonium sulfate into beneficial methionine hydroxy analog calcium salts, truly achieving complete separation of methionine hydroxy analogs from ammonium sulfate, converting divalent anions into gypsum, and recovering ammonia into ammonia water or liquid ammonia, thereby improving raw material utilization and generating almost no waste.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and in particular to a method for recycling methionine hydroxy analogues in ammonium sulfate byproducts. Background Art

[0002] As we all know, methionine production processes are divided into chemical synthesis and fermentation. Chemical synthesis generally produces D,L-methionine, while fermentation produces L-methionine. Chemical synthesis is currently the predominant method for methionine production. Current literature reports simplistically and roughly summarize chemical methionine synthesis as the cyanohydrin method and the hydantoin method. The cyanohydrin method produces methionine hydroxy analogs (also known as liquid methionine), while the hydantoin method produces D,L-methionine. However, this description is overly general and inaccurate, and is likely to lead to misunderstandings. From an analysis of chemical synthesis methionine production processes, most solid methionine production processes involve the cyanohydrin (methionine intermediate 2-hydroxy-4-methylthiobutyronitrile) synthesis process. The major differences lie in the synthesis method of 5-(β-methylthioethyl)-hydantoin, the 5-(β-methylthioethyl)-hydantoin hydrolysis agent, and the final byproducts. Therefore, based on the characteristics of methionine production and after a long period of research on methionine production processes, in order to facilitate the identification of current methionine production processes at home and abroad, we mainly divide the chemical synthesis methionine production processes into the following production processes:

[0003] (1) Cyanohydrin method, i.e., hydrolysis of cyanohydrin with sulfuric acid to produce methionine hydroxy analogues and ammonium sulfate as a by-product. Companies using this process include Adisseo, Novus, Sumitomo, and Wabon Bio;

[0004] (2) Sodium cyanide-sodium hydantoin process (also known as traditional Rhone-Poulenc production process), which uses sodium cyanide, ammonium carbonate, and methylthiopropionaldehyde as raw materials to prepare a sodium carbonate aqueous solution of 5-(β-methylthioethyl)-hydantoin. Sodium hydroxide hydrolyzes the 5-(β-methylthioethyl)-hydantoin-sodium carbonate aqueous solution to obtain a saponified solution, which is neutralized with sulfuric acid to obtain methionine, with sodium sulfate as a by-product. Companies that use this process include Ningxia Ziguang Tianhua Methionine and Russia Volga;

[0005] (3) Cyanohydrin-sodium hydantoin process (also known as improved Rhone-Poulenc production process), which uses cyanohydrin (2-hydroxy-4-methylthiobutyronitrile) and ammonium carbonate aqueous solution as raw materials to react with two components to prepare 5-(β-methylthioethyl)-hydantoin aqueous solution, hydrolyzes 5-(β-methylthioethyl)-hydantoin with sodium hydroxide to obtain saponified solution, which is neutralized with sulfuric acid to obtain methionine and produce sodium sulfate as a by-product. Companies using this process include Adisseo and Ningxia Ziguang Tianhua Methionine (partial technical transformation);

[0006] (4) Cyanohydrin-potassium hydantoin process, i.e., a two-component reaction using cyanohydrin (2-hydroxy-4-methylthiobutyronitrile) and ammonium carbonate aqueous solution as raw materials to prepare 5-(β-methylthioethyl)-hydantoin aqueous solution, potassium carbonate or potassium hydroxide hydrolyzes 5-(β-methylthioethyl)-hydantoin to obtain a saponified solution, which is acidified and neutralized with carbon dioxide to obtain methionine, and the potassium bicarbonate aqueous solution containing methionine is regenerated by decarbonization (carbon dioxide) and then recycled to the alkali for hydrolysis of 5-(β-methylthioethyl)-hydantoin aqueous solution, without producing inorganic salts as by-products. Companies that use this process include Evonik, Sumitomo and Shandong Xinhecheng Amino Acids.

[0007] Among the aforementioned methionine production processes, only the production process for methionine hydroxy analogues is essentially the same across all companies, employing the cyanohydrin process. The biggest difference lies in the methods used to separate and purify methionine hydroxy analogues from ammonium sulfate. Some utilize phase separation, concentration, and filter press to obtain the methionine hydroxy analogue product, while others utilize organic solvent extraction. Regardless of the method, ammonium sulfate containing methionine hydroxy analogues is inevitably produced. Failure to separate the methionine hydroxy analogues from the ammonium sulfate not only wastes the valuable methionine hydroxy analogues but also generates a significant amount of odor during the drying, transportation, and use of the ammonium sulfate, limiting its subsequent use.

[0008] The typical treatment method involves dissolving ammonium sulfate containing methionine hydroxy analogs in water (or washing with a saturated ammonium sulfate solution). During the ammonium sulfate concentration and crystallization process, due to the relatively low solubility of methionine hydroxy analogs in saturated ammonium sulfate solutions (the content of methionine hydroxy analogs in saturated ammonium sulfate solutions is 2% to 3%), the methionine hydroxy analogs float on the surface of the saturated ammonium sulfate solution, forming a phase separation. However, this repeated operation (especially concentration) and repeated heating of the methionine hydroxy analogs lead to decomposition, producing large amounts of foul-smelling gases that pollute the environment, resulting in large amounts of exhaust gas that need to be incinerated, high fuel consumption, and high energy consumption. Furthermore, this method of separating methionine hydroxy analogs from ammonium sulfate is incomplete, with the resulting byproduct ammonium sulfate containing approximately 0.8% to 2.0% of methionine hydroxy analogs, resulting in high energy consumption and environmental costs. There have also been reports of using electrodialysis and continuous chromatography to separate methionine hydroxy analogs from ammonium sulfate, but these have not yet been commercialized.

[0009] Methionine hydroxy analog calcium salt, also known as hydroxymethionine calcium, or MHA-Ca, is a calcium salt containing 84% 2-hydroxy-4-methylthiobutyric acid and is primarily used as a feed additive. Methionine hydroxy analogs have been used in the livestock industry since the 1950s and have proven themselves as an excellent methionine source for the feed, livestock, and pet manufacturers. MHA-Ca is a solid, granular product containing 100% monomer, making it a cost-effective methionine source. Besides being a methionine source, it offers several additional performance advantages, providing an optimal source of methionine and high-quality calcium for animals, particularly in ruminant, laying hen, and aquaculture feeds. Therefore, MHA-Ca is ideal for use in premixes, concentrates, and farm-mixed feeds, offering the same benefits and bioavailability as DL-methionine. Currently, the main production methods of methionine hydroxy analog calcium salt include solvent method and dry mixing method. The solvent method uses water as the reaction medium, and the methionine hydroxy analog aqueous solution reacts with calcium hydroxide, crystallizes, filters, and dries to obtain methionine hydroxy analog calcium salt; the dry mixing method is to directly mix commercial-grade methionine hydroxy analog with a mass percentage of 88% with calcium hydroxide or calcium oxide powder, and then dry, crush, and sieve to obtain methionine hydroxy analog calcium salt. The product quality of methionine hydroxy analogues produced by the two methods can meet the requirements of national standards, but the product appearance (color, fluidity) is different. The methionine hydroxy analogue calcium salt produced by the solvent method is generally superior to the dry mixing method in quality. The methionine hydroxy analogue calcium salt produced by the dissolution method has a light color (off-white or even white), good fluidity, a low methionine odor, is not easy to agglomerate, has a high methionine hydroxy analogue content, few impurities, and a uniform product color. The methionine hydroxy analogue calcium salt produced by the dry mixing method is a light brown powdery solid with poor fluidity, a strong methionine odor, is easy to agglomerate, has a methionine hydroxy analogue content that just meets the national standard requirements (84%), has a high impurity content, and has an uneven product color. Although the production process of methionine hydroxy analogue calcium salt using commercial-grade methionine hydroxy analogue is simple, its cost is mainly controlled by the market price of methionine hydroxy analogue, resulting in a high production cost.

[0010] Based on the above-mentioned prior art, it is of great significance to study how to solve the problem of separating methionine hydroxy analogues from ammonium sulfate and recovering methionine hydroxy analogues entrained in ammonium sulfate. Summary of the Invention

[0011] In view of this, the purpose of the present invention is to provide a method for recycling methionine hydroxy analogues in ammonium sulfate by-products, while converting valuable methionine hydroxy analogues in ammonium sulfate into beneficial methionine hydroxy analogue calcium salts, truly achieving complete separation of methionine hydroxy analogues from ammonium sulfate, while divalent anions are converted into gypsum, and ammonia is recovered and converted into ammonia water or liquid ammonia, thereby improving the utilization rate of raw materials and almost no waste is generated.

[0012] The present invention solves the above technical problems through the following technical means:

[0013] The invention provides a method for recycling methionine hydroxy analogues in ammonium sulfate by-products. The method comprises the following steps: reacting the ammonium sulfate by-product produced in a methionine preparation process with calcium oxide or calcium hydroxide at a reaction temperature of 50° C. to 95° C. for 60 to 120 minutes; deaminating and filtering the obtained reaction solution to obtain a methionine hydroxy analogue calcium salt aqueous solution; concentrating, crystallizing, filtering, and drying the solution to obtain a methionine hydroxy analogue calcium salt compound; and

[0014] In some embodiments, the ammonium sulfate by-product is ammonium sulfate solid obtained after oil phase concentration and filter pressing or aqueous ammonium sulfate aqueous solution in the aqueous phase.

[0015] In some embodiments, the ammonium sulfate byproduct needs to be diluted with water before reacting with calcium oxide or calcium hydroxide to a solution having an ammonium sulfate content of 25% to 40% and a methionine hydroxy analogue content of 1.0% to 8.0%.

[0016] In some embodiments, the mass percentage of the calcium oxide is ≥87%, wherein the magnesium oxide content is ≤4%, the silicon dioxide content is ≤4%, the aluminum oxide content is ≤0.9%, the sulfur trioxide is ≤0.7%, and the ferric oxide is ≤0.3%. The calcium hydroxide is obtained by filtering the calcium oxide hydrated slurry through a 20-40 mesh sieve.

[0017] In some embodiments, the molar ratio of calcium ions of the calcium oxide or calcium hydroxide to sulfate is 1:1, and the molar ratio of calcium ions of the calcium oxide or calcium hydroxide to methionine hydroxy analogue is 0.50-0.55:1.0.

[0018] In some embodiments, the endpoint pH of the reaction between the ammonium sulfate by-product produced in the methionine preparation process and calcium oxide or calcium hydroxide is controlled at 7.0 to 7.5.

[0019] In some embodiments, the deamination end point is when the ammonia content is less than 30 ppm.

[0020] In some embodiments, an organic polymer flocculant is added to the reaction solution after deamination, and the mixture is stirred at a temperature of 60° C. to 80° C. for 15 to 30 minutes and then filtered.

[0021] In some embodiments, the organic polymer flocculant is anionic polyacrylamide, the concentration of the organic polymer flocculant is 0.1% to 0.2%, and the amount of the organic polymer flocculant added is 1 to 10 ppm of the reaction solution.

[0022] In some embodiments, the content of the methionine hydroxy analog calcium salt compound is ≥96%, and the structural formula of the methionine hydroxy analog calcium salt compound is as follows:

[0023]

[0024] The present invention has the following beneficial effects:

[0025] (1) The present invention uses calcium oxide or calcium hydroxide to hydrolyze and neutralize ammonium sulfate containing methionine hydroxy analogues, which can not only effectively convert methionine hydroxy analogue monomers, dimers and trimers into methionine hydroxy analogue calcium salt products, but also can convert ammonium sulfate into volatile ammonia gas and calcium sulfate precipitates that are easy to separate and remove. The water-soluble methionine hydroxy analogue calcium salt is simple to separate and purify from the generated calcium sulfate and residual calcium hydroxide. After the hydrolysis is completed, the precipitate can be removed by simple filtration, thereby avoiding the accumulation of divalent anion impurities sulfate in the methionine hydroxy analogue calcium salt aqueous solution and preventing the discharge of salt-containing wastewater, thereby truly achieving an environmentally friendly and clean production process.

[0026] (2) The present invention uses calcium oxide or calcium hydroxide to hydrolyze and neutralize ammonium sulfate containing methionine hydroxy analogues. The recovery and reuse rate of methionine hydroxy analogues is as high as 99%. The purity of the obtained methionine hydroxy analogue calcium salt product is ≥96%, which meets the national quality requirements. In addition, the ammonium sulfate is converted into high-value ammonia gas, which can be recycled to produce ammonia water or liquid ammonia, and the sulfate ion is converted into high-quality gypsum. The product content is ≥97.0%, avoiding the generation of waste residue.

[0027] (3) The present invention uses calcium oxide or calcium hydroxide to hydrolyze and neutralize ammonium sulfate containing methionine hydroxy analogues, converting both methionine hydroxy analogues and ammonium sulfate, which are both easily soluble in water, into water-soluble methionine hydroxy analogue calcium salt, water-insoluble calcium sulfate and volatile ammonia, thereby achieving the purpose of separation by simple means such as steam stripping and filtration, indirectly increasing the yield of methionine hydroxy analogues, reducing the discharge volume of ammonium sulfate mother liquor, reducing or avoiding the generation of ammonium sulfate by-products, saving energy consumption, and not generating saline wastewater, thereby having good environmental and economic benefits.

[0028] (4) Compared with the traditional methionine hydroxy analogue calcium salt production process, the present invention comprehensively utilizes ammonium sulfate containing methionine hydroxy analogue, has low production cost, and fully recovers the hydrolyzing agent calcium ions. It not only increases the recovery rate of methionine hydroxy analogues in ammonium sulfate, but also the methionine hydroxy analogues entrained in ammonium sulfate are comprehensively utilized, converting waste into high-value methionine hydroxy analogue calcium salt, high-quality gypsum and high-value ammonia water or liquid ammonia products. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 is a schematic diagram of the production process of methionine hydroxy analogues according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic flow chart of a method for recycling methionine hydroxy analogs in an ammonium sulfate by-product of the present invention;

[0031] Figure 3 The present invention is a method for recycling methionine hydroxy analogs in ammonium sulfate by-products involving a chemical reaction;

[0032] Figure 4 This is the composition of the ammonium sulfate by-product in the embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All raw materials, equipment, or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0035] This application is to recycle the methionine hydroxy analogue in the ammonium sulfate by-product produced in the methionine preparation process. The method of obtaining the ammonium sulfate by-product is described in detail in the following sections. Figure 1 2-Hydroxy-4-methylthiobutyronitrile and sulfuric acid are subjected to hydration and hydrolysis reactions to obtain a methionine hydroxy analogue, ammonium bisulfate, and an ammonium sulfate mixture. Ammonia is added to the mixture to neutralize the ammonium bisulfate in the mixture to obtain a heterogeneous mixed aqueous solution containing a methionine hydroxy analogue and ammonium sulfate. Phase separation is performed at 50° C. to 65° C., and an upper oil phase is 60% to 75% of a methionine hydroxy analogue, containing a small amount of ammonium sulfate (10% to 15%) and water (15% to 25%). The lower layer is an ammonium sulfate aqueous solution, wherein the ammonium sulfate content is 15% to 45%, contains a small amount of methionine hydroxy analogue (1.5% to 10.0%), and the remainder is water. The oil phase is concentrated and dehydrated to a water content of less than 2%, and then the precipitated ammonium sulfate is filtered to obtain an ammonium sulfate content of 80% to 95% by weight, a methionine hydroxy analogue of 5% to 19%, and a water content of 0.1% to 1.0%. The filtrate is a high-concentration methionine hydroxy analogue with a content of ≥97%. The filtrate is diluted with water to 88% to obtain a commercial-grade methionine hydroxy analogue product, wherein the content of 2-hydroxy-4-methylthiobutyric acid is ≥65%, the content of dimer is ≤20%, and the content of trimer is ≤3%.

[0036] Please refer to Figure 2 The recycling method of methionine hydroxy analogues of the present application is to produce ammonium sulfate by-product containing methionine hydroxy analogues in the methionine preparation process (the composition of which can be found in Figure 4 ) reacts with calcium oxide or calcium hydroxide at a reaction temperature of 50°C to 95°C for 60 to 120 minutes, deaminates the resulting reaction solution, filters it, and obtains a methionine hydroxy analog calcium salt aqueous solution, which is then concentrated, crystallized, filtered, and dried to obtain a methionine hydroxy analog calcium salt compound. The chemical reactions involved in the above-mentioned methionine hydroxy analog recycling method are as follows: Figure 3 shown.

[0037] The structural formula of the methionine hydroxy analog calcium salt compound of the present application is as follows:

[0038]

[0039] Example 1

[0040] 1000.0 g of ammonium sulfate solid containing a methionine hydroxy analogue, wherein the methionine hydroxy analogue content is 15.0%, the ammonium sulfate content is 84.0%, and the moisture content is 1.0%, is then added with 1100.0 g of water, and the mixture is heated to 60° C. for complete dissolution to obtain an ammonium sulfate aqueous solution containing a methionine hydroxy analogue, wherein the ammonium sulfate content is 40.0% and the methionine hydroxy analogue content is 7.14%.

[0041] 442.97 grams of calcium oxide powder with a mass percentage of 87% was added to the ammonium sulfate aqueous solution obtained above, wherein the molar ratio of calcium ion to sulfate was 1:1, and the molar ratio of calcium ion to methionine hydroxy analogue was 0.525:1. The reaction temperature was 85°C, and the reaction was kept warm for 90 minutes. After the reaction, deamination was carried out at 85°C, and ammonia was recovered to prepare ammonia water or liquid ammonia. The residual ammonia content in the mixed solution after deamination was 25ppm, and 2300.0 grams of a mixed solution containing a large amount of white precipitate was obtained. The pH of the mixed solution was 7.5. 23.0 grams of anionic polyacrylamide aqueous solution with a concentration of 0.1% was added to the mixed solution, and stirred at 60°C for 15 minutes. The emulsion suspended in the mixed solution precipitated in large quantities, and then the precipitate was filtered at 60°C and washed with a small amount of water. The solid matter was dried to obtain 1128.40 grams of gypsum with a content of 97%. The washing water and the filtrate were combined to obtain The reaction mixture was concentrated to a methionine hydroxy analog aqueous solution containing 1058.0 g of methionine hydroxy analog calcium salt, wherein the methionine hydroxy analog calcium salt content was 15.99%. The solution was then cooled to 25°C for crystallization. The precipitated white crystals were filtered and dried to obtain 165.69 g of methionine hydroxy analog calcium salt product, with a content of 97%. The filtrate had a mass of 130.13 g, wherein the methionine hydroxy analog calcium salt content was 6.50%. The filtrate was recycled to the next batch of methionine hydroxy analog calcium salt aqueous solution concentration step. Throughout the entire process, the recovery rate of methionine hydroxy analog in ammonium sulfate reached 99%.

[0042] Example 2

[0043] 1000.0 g of ammonium sulfate solid containing a methionine hydroxy analogue, wherein the methionine hydroxy analogue content is 5.0%, the ammonium sulfate content is 94.9%, and the moisture content is 0.1%, is then added 3796.0 g of water, and the mixture is heated to 60° C. for complete dissolution to obtain an ammonium sulfate aqueous solution containing a methionine hydroxy analogue, wherein the ammonium sulfate content is 25.0% and the methionine hydroxy analogue content is 1.04%.

[0044] 473.50 g of calcium oxide powder with a mass percentage of 87% was added to the ammonium sulfate aqueous solution obtained above, wherein the molar ratio of calcium ion to sulfate was 1:1, and the molar ratio of calcium ion to methionine hydroxy analog was 0.5:1. The reaction temperature was 85°C, and the reaction was kept warm for 90 minutes. After the reaction, deamination was carried out at 85°C, and ammonia was recovered to prepare ammonia water or liquid ammonia. The residual ammonia content in the deaminated mixed solution was 20 ppm, and 5000.0 g of a mixed solution containing a large amount of white precipitate was obtained. The pH of the mixed solution was 7.2. 5.0 g of an anionic polyacrylamide aqueous solution with a concentration of 0.1% was added to the mixed solution, and stirred at 60°C for 15 minutes. The emulsion suspended in the mixed solution precipitated in large quantities. The precipitate was then filtered at 60°C and washed with a small amount of water. The solid matter was dried to obtain 1274.82 g of gypsum with a content of 97%. The washing water and the filtrate were combined. 3800.0 g of a methionine hydroxy analogue aqueous solution containing 1.48% calcium salt of methionine hydroxy analogue was obtained. The solution was concentrated to a 50% calcium salt of methionine hydroxy analogue, then cooled to 25°C for crystallization. The precipitated white crystals were filtered and dried to obtain 55.08 g of a calcium salt of methionine hydroxy analogue product with a calcium salt content of 97%. The filtrate weighed 43.26 g, containing 6.50% calcium salt of methionine hydroxy analogue. The filtrate was recycled to the next batch of calcium salt of methionine hydroxy analogue aqueous solution. Throughout the entire process, the recovery rate of methionine hydroxy analogue in ammonium sulfate reached 99%.

[0045] Example 3

[0046] 1000.0 g of ammonium sulfate solid containing a methionine hydroxy analogue, wherein the methionine hydroxy analogue content is 15.0%, the ammonium sulfate content is 84.0%, and the moisture content is 1.0%, is then added with 1100.0 g of water, and the mixture is heated to 60° C. for complete dissolution to obtain an ammonium sulfate aqueous solution containing a methionine hydroxy analogue, wherein the ammonium sulfate content is 40.0% and the methionine hydroxy analogue content is 7.14%.

[0047] To the ammonium sulfate aqueous solution obtained above was added 442.97 g of calcium oxide powder having a mass percentage of 87%, wherein the molar ratio of calcium ions to sulfate was 1:1, and the molar ratio of calcium ions to methionine hydroxy analogue was 0.525:1. The reaction temperature was 85° C. and the reaction was kept warm for 90 min. After the reaction was completed, deamination treatment was carried out at 85° C., and the ammonia was recovered to prepare ammonia water or liquid ammonia. The residual ammonia content in the deaminated mixed solution was 25 ppm, and 2300.0 g of a mixed solution containing a large amount of white precipitate was obtained. The pH of the mixed solution was 7.5. 23.0 g of a 0.1% anionic polyacrylamide aqueous solution was added to the mixed solution, and the mixture was stirred at 60° C. for 15 minutes. A large amount of emulsion suspended in the mixed solution precipitated. The precipitate was then filtered at 60° C. and washed with a small amount of water. The solid was dried to obtain 1128.40 g of gypsum with a content of 97%. The washing water and the filtrate were combined to obtain 1058.0 g of a methionine hydroxy analog aqueous solution, wherein the content of methionine hydroxy analog calcium salt was 15.99%. The solution was flash evaporated to a completely solid state and dried to obtain 176.22 g of a methionine hydroxy analog calcium salt product with a content of 96%. In the entire process, the recovery rate of methionine hydroxy analog in ammonium sulfate reached 99%.

[0048] Example 4

[0049] 1000.0 g of ammonium sulfate solid containing a methionine hydroxy analogue, wherein the methionine hydroxy analogue content is 15.0%, the ammonium sulfate content is 84.0%, and the moisture content is 1.0%, is then added with 1100.0 g of water, and the mixture is heated to 60° C. for complete dissolution to obtain an ammonium sulfate aqueous solution containing a methionine hydroxy analogue, wherein the ammonium sulfate content is 40.0% and the methionine hydroxy analogue content is 7.14%.

[0050] To the ammonium sulfate aqueous solution obtained above was added 532.90 g of calcium hydroxide powder having a mass percentage of 96%, wherein the molar ratio of calcium ions to sulfate was 1:1, and the molar ratio of calcium ions to methionine hydroxy analogue was 0.55:1. The reaction temperature was 85° C. and the reaction was kept warm for 90 min. After the reaction was completed, deamination treatment was carried out at 85° C., and ammonia was recovered to prepare ammonia water or liquid ammonia. The residual ammonia content in the deaminated mixed solution was 25 ppm, and 2300.0 g of a mixed solution containing a large amount of white precipitate was obtained. The pH of the mixed solution was 7.5. 5.0 g of a 0.2% anionic polyacrylamide aqueous solution was added to the mixed solution, and the mixture was stirred at 75° C. for 15 minutes. A large amount of emulsion suspended in the mixed solution precipitated. The precipitate was then filtered at 75° C. and washed with a small amount of water. The solid was dried to obtain 1120.40 g of gypsum with a content of 98%. The washing water and the filtrate were combined to obtain 1058.0 g of a methionine hydroxy analog aqueous solution, wherein the content of methionine hydroxy analog calcium salt was 15.99%. The solution was flash evaporated to a completely solid state and dried to obtain 176.22 g of a methionine hydroxy analog calcium salt product with a content of 96%. In the entire process, the recovery rate of methionine hydroxy analog in ammonium sulfate reached 99%.

[0051] Example 5

[0052] 1000.0 g of an ammonium sulfate aqueous solution containing a methionine hydroxy analogue, wherein the methionine hydroxy analogue content is 6.0%, the ammonium sulfate content is 30.0%, and the moisture content is 64%, 160.45 g of calcium oxide powder with a mass percentage of 87% is added, wherein the molar ratio of calcium ions to sulfate groups is 1:1, and the molar ratio of calcium ions to methionine hydroxy analogues is 0.55:1. The reaction temperature is 80° C. and the reaction is kept warm for 120 minutes. After the reaction is completed, deamination treatment is carried out at 80° C., and ammonia is recovered to prepare ammonia water or liquid ammonia. The residual ammonia content in the mixed solution after deammoniation is 28 ppm, and 1050.0 g of a mixed solution containing a large amount of white precipitate is obtained. The pH of the mixed solution is 7.5. 5.0 g of a 0.2% anionic polyacrylamide aqueous solution is added to the mixed solution, and the mixture is stirred at 60° C. for 15 minutes. A large amount of emulsion suspended in the mixed solution is precipitated. The precipitated precipitate is then filtered at 60° C. and washed with a small amount of water. The solid is dried to obtain 403.0 g of gypsum with a content of 97%. The washing water and the filtrate are combined to obtain 650.0 g of a methionine hydroxy analog aqueous solution, wherein the content of methionine hydroxy analog calcium salt is 10.41%. The solution is flash evaporated to a completely solid state and dried to obtain 70.51 g of a methionine hydroxy analog calcium salt product with a content of 96%. In the entire process, the recovery rate of methionine hydroxy analog in ammonium sulfate reaches 99%.

[0053] Example 6

[0054] 1000.0 g of an ammonium sulfate aqueous solution containing a methionine hydroxy analogue, wherein the methionine hydroxy analogue content is 10.0%, the ammonium sulfate content is 15.0%, and the water content is 65%, is added to a calcium hydroxide emulsion filtered after being slurried by calcium oxide (the emulsion is prepared as follows: 96.75 g of calcium oxide with a mass percentage of 87%, a magnesium oxide content of 3.5%, a silicon dioxide content of 2.5%, an aluminum oxide content of 0.8%, and a sulfate radical (calculated as sulfur trioxide) content of 0.1%. The amount is 0.6%, the content of ferric oxide is 0.25%, 200 grams of water is added and stirred thoroughly, and then filtered through a 40-mesh sieve to obtain an emulsion of 294.86 grams of calcium hydroxide emulsion), wherein the molar ratio of calcium ion to sulfate is 1:1, the molar ratio of calcium ion to methionine hydroxy analogue is 0.55:1, the reaction temperature is 95°C, the reaction is kept warm for 60 minutes, and after the reaction is completed, deamination treatment is carried out at 95°C, and the ammonia is recovered to prepare ammonia water or liquid ammonia. The residual ammonia content in the deaminated mixed solution is 20 ppm, and 1250.0 g of a mixed solution containing a large amount of white precipitate is obtained. The pH of the mixed solution is 7.2. 2.0 g of a 0.2% anionic polyacrylamide aqueous solution is added to the mixed solution, and the mixture is stirred at 65° C. for 30 minutes. A large amount of emulsion suspended in the mixed solution is precipitated. The precipitated precipitate is then filtered at 65° C. and washed with a small amount of water. The solid is dried to obtain 201.50 g of gypsum with a content of 97%. The washing water and the filtrate are combined to obtain 1100.0 g of a methionine hydroxy analog aqueous solution, wherein the content of methionine hydroxy analog calcium salt is 10.25%. The solution is flash evaporated to a completely solid state and dried to obtain 116.24 g of a methionine hydroxy analog calcium salt product with a content of 97%. In the entire process, the recovery rate of methionine hydroxy analog in ammonium sulfate reaches 99%.

[0055] Example 7

[0056] 1000.0 g of an ammonium sulfate aqueous solution containing a methionine hydroxy analogue, wherein the methionine hydroxy analogue content is 2.0%, the ammonium sulfate content is 45.0%, and the water content is 53%, and 223.73 g of calcium oxide powder with a mass percentage of 87% is added, wherein the molar ratio of calcium ions to sulfate groups is 1:1, and the molar ratio of calcium ions to methionine hydroxy analogues is 0.5:1. The reaction temperature is 60° C., and the reaction is kept warm for 120 minutes. After the reaction is completed, deamination treatment is carried out at 60° C., and ammonia is recovered to prepare ammonia water or liquid ammonia. The residual ammonia content in the deaminated mixed solution is 20 ppm, and 1100.0 g of a mixed solution containing a large amount of white precipitate is obtained. The pH of the mixed solution is 7.0. 2.0 g of a 0.2% anionic polyacrylamide aqueous solution is added to the mixed solution, and the mixture is stirred at 75° C. for 30 minutes. A large amount of emulsion suspended in the mixed solution is precipitated. The precipitated precipitate is then filtered at 75° C. and washed with a small amount of water. The solid is dried to obtain 604.50 g of gypsum with a content of 97%. The washing water and the filtrate are combined to obtain 600.0 g of a methionine hydroxy analog aqueous solution, wherein the content of methionine hydroxy analog calcium salt is 3.76%. The solution is flash evaporated to a completely solid state and dried to obtain 23.5 g of a methionine hydroxy analog calcium salt product with a content of 96%. In the entire process, the recovery rate of methionine hydroxy analog in ammonium sulfate reaches 99%.

[0057] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that the technical solutions of the present invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and such modifications or equivalents shall be encompassed by the claims of the present invention. Any techniques, shapes, and structures not described in detail herein are well known.

Claims

1. A method for recycling methionine hydroxy analogues in ammonium sulfate by-products, characterized in that: The ammonium sulfate by-product produced in the methionine preparation process is reacted with calcium oxide or calcium hydroxide at a reaction temperature of 50° C. to 95° C. for 60 to 120 minutes, the resulting reaction solution is deaminated and filtered to obtain a methionine hydroxy analog calcium salt aqueous solution, which is then concentrated, crystallized, filtered, and dried to obtain a methionine hydroxy analog calcium salt compound; The ammonium sulfate by-product contains methionine hydroxy analogues; before reacting with calcium oxide or calcium hydroxide, the ammonium sulfate by-product needs to be diluted with water to a solution containing 25% to 40% ammonium sulfate and 1.0% to 8.0% methionine hydroxy analogues.

2. The method for recycling methionine hydroxy analogues in an ammonium sulfate by-product according to claim 1, characterized in that: The ammonium sulfate by-product is ammonium sulfate solid obtained after oil phase concentration and filter pressing or aqueous ammonium sulfate aqueous solution in the water phase.

3. The method for recycling methionine hydroxy analogues in an ammonium sulfate by-product according to claim 1, characterized in that: The mass percentage of the calcium oxide is ≥87%, wherein the magnesium oxide content is ≤4%, the silicon dioxide content is ≤4%, the aluminum oxide content is ≤0.9%, the sulfur trioxide is ≤0.7%, and the ferric oxide is ≤0.3%. The calcium hydroxide is obtained by filtering calcium oxide into a hydrated slurry through a 20-40 mesh sieve.

4. The method for recycling methionine hydroxy analogues in an ammonium sulfate by-product according to any one of claims 1 to 3, characterized in that: The molar ratio of calcium ions of the calcium oxide or calcium hydroxide to sulfate is 1:1, and the molar ratio of calcium ions of the calcium oxide or calcium hydroxide to methionine hydroxy analogue is 0.50-0.55:1.

0.

5. The method for recycling methionine hydroxy analogues in an ammonium sulfate by-product according to any one of claims 1 to 3, characterized in that: The pH at the end point of the reaction between the ammonium sulfate by-product produced in the methionine preparation process and calcium oxide or calcium hydroxide is controlled at 7.0-7.

5.

6. The method for recycling methionine hydroxy analogues in an ammonium sulfate by-product according to claim 1, characterized in that: The deamination end point is when the ammonia content is lower than 30 ppm.

7. The method for recycling methionine hydroxy analogues in ammonium sulfate by-product according to claim 1, characterized in that: An organic polymer flocculant is added to the reaction solution after deamination, stirred at a temperature of 60° C. to 80° C. for 15 to 30 minutes, and then filtered.

8. The method for recycling methionine hydroxy analogues in ammonium sulfate by-product according to claim 7, characterized in that: The organic polymer flocculant is anionic polyacrylamide, the concentration of the organic polymer flocculant is 0.1% to 0.2%, and the amount of the organic polymer flocculant added is 1 to 10 ppm of the reaction solution.

9. The method for recycling methionine hydroxy analogues in ammonium sulfate by-product according to claim 1, characterized in that: The content of the methionine hydroxy analog calcium salt compound is ≥96%, and the structural formula of the methionine hydroxy analog calcium salt compound is as follows: 。

Images