Multistage continuous crystallization method of short rod-like methionine crystals

Abstract

The invention provides a multistage continuous crystallization method of short rod-like methionine crystals. The method includes: connecting a plurality of crystallizers in series; under the action ofa circulating device, dissolving a methionine raw material at 80-130DEG C; letting the dissolved feed solution enter a first stage crystallization kettle, and controlling the kettle temperature at 60-80DEG C; enabling the slurry to enter a second stage crystallization kettle, and controlling the kettle temperature at 40-60DEG C; enabling the slurry to enter a third stage crystallization kettle, and controlling the kettle temperature at 25-40DEG C; letting the slurry enter a fourth stage crystallization kettle, and controlling the kettle temperature at 15-25DEG C; letting the final slurry flowout of the crystallization kettle and enter a solid-liquid separation system, discharging the separated solid out of the system, and returning part of the mother liquor into a dissolution kettle forfurther circulation, with the circulation volume being 20-60% of the mother liquor volume. The stage number of the crystallization kettles is supposed to be optimized according to the actual situation, and the general ideal situation is 2-4 stages. The prepared methionine crystals have short rod-like crystal habit, the crystal size is uniform, the bulk density is high, the fluidity is good, the quality is stable, the operation is simple, and the production efficiency is high, therefore the method is suitable for large-scale industrial production.

Description

technical field [0001] The invention belongs to the field of industrial production technology of amino acids, and relates to a multistage continuous crystallization method of short rod-shaped methionine crystals. Background technique [0002] Methionine is the only sulfur-containing amino acid among the eight essential amino acids. It is one of the important components of protein in the human body and animals. It is widely used in the fields of medicine, food, feed and cosmetics, among which feed additives are the main application Huge amount. [0003] The global demand for methionine has reached 1.3 million tons per year and is increasing at a rate of 6% per year. China’s demand in 2015 also exceeded 160,000 tons. Imports, and high-quality methionine with high bulk density and good fluidity still mainly rely on imports. [0004] The production process of methionine mainly includes biological enzyme resolution method, microbial fermentation method and chemical synthesis me...

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Problems solved by technology

[0005] At present, the refining and separation method of methionine mainly focuses on the separation and purification of methionine and inorganic salts. Patent CN104926701A discloses a process for the purification of methionine. This method uses macroporous adsorption resin to undergo adsorption and desorption processes to achieve the separation of methionine and by-product salts The purpose; patent CN104693082A discloses a method for the separation and purification of methionine by continuous chromatography, which uses the difference between the adsorption and desorption of methionine and sodium sulfate mother liquor to chromatographic materials to achieve the purpose of desalination, but these methods generally have high material use costs and high efficiency. Low and difficult to meet the needs of industrial production of large quantities of methionine

[0006] Multi-stage evaporation and concentration of methionine aqueous solution to crystallize and purify methionine is a commonly used method for the purification and separation of methionine in the industry. It is easy to operate and can be industrialized on a large scale. Subsequent granulation process, resulting in high production costs. In addition, long-term high-temperature concentration leads to thermal decomposition of methionine, resulting in dimethyl disulfide or methyl mercaptan with a foul smell

[0007] Patent CN103804252A discloses a methionine crystallization and separation system and a process for crystallization and separation of methionine. The process mainly uses the solubility difference between methionine and sodium sulfate to carry out fractional crystallization, that is, first cooling and crystallizing to precipitate a low-solubility dense-phase methionine product. The phase is evaporated and concentrated to produce sodium sulfate as a by-product to achieve the purpose of desalting and purifying methionine. However, this method has the following disadvantages: first, high-concentration sodium sulfate will become an impurity that will significantly affect the crystallization process and efficiency of methionine, and it is easy to produce secondary nucleation. Impurities Adsorption and storage lead to problems such as low product purity, poor crystal morphology, uneven particle size distribution, low bulk density, and low separation efficiency; secondly, limited by the solubility of methionine, dilute phase solutions mainly composed of sodium sulfate still have a certain content methionine, high-temperature evaporation and concentration to prepare sodium sulfate will cause methionine to decompose, affect the quality of by-product sodium sulfate and reduce the overall methionine yield

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