WO2016127707A1 - 一种连续制备高堆积密度甲硫氨酸结晶的方法 - Google Patents

一种连续制备高堆积密度甲硫氨酸结晶的方法 Download PDF

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Publication number
WO2016127707A1
WO2016127707A1 PCT/CN2015/098368 CN2015098368W WO2016127707A1 WO 2016127707 A1 WO2016127707 A1 WO 2016127707A1 CN 2015098368 W CN2015098368 W CN 2015098368W WO 2016127707 A1 WO2016127707 A1 WO 2016127707A1
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Prior art keywords
methionine
crystallizer
bulk density
crystals
crystallization
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PCT/CN2015/098368
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English (en)
French (fr)
Inventor
陈志荣
王志轩
陈聪
王正江
王存超
李寅
张志香
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Shandong Nhu Amino Acid Co ltd
Zhejiang University ZJU
Zhejiang NHU Co Ltd
Original Assignee
Shandong Nhu Amino Acid Co ltd
Zhejiang University ZJU
Zhejiang NHU Co Ltd
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Priority to BR112017017246-1A priority Critical patent/BR112017017246B1/pt
Priority to JP2017552207A priority patent/JP6423109B2/ja
Priority to US15/549,833 priority patent/US10293273B2/en
Priority to MYPI2017001156A priority patent/MY183295A/en
Priority to SG11201705530VA priority patent/SG11201705530VA/en
Priority to CA2974447A priority patent/CA2974447A1/en
Priority to AU2015382630A priority patent/AU2015382630B2/en
Priority to RU2017121649A priority patent/RU2678585C2/ru
Application filed by Shandong Nhu Amino Acid Co ltd, Zhejiang University ZJU, Zhejiang NHU Co Ltd filed Critical Shandong Nhu Amino Acid Co ltd
Priority to EP15881855.9A priority patent/EP3246310B1/en
Priority to MX2017010418A priority patent/MX372561B/es
Priority to KR1020177022736A priority patent/KR101975189B1/ko
Publication of WO2016127707A1 publication Critical patent/WO2016127707A1/zh
Anticipated expiration legal-status Critical
Priority to ZA2017/05902A priority patent/ZA201705902B/en
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0036—Crystallisation on to a bed of product crystals; Seeding
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C323/00—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups
    • C07C323/50—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and carboxyl groups bound to the same carbon skeleton
    • C07C323/51—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and carboxyl groups bound to the same carbon skeleton having the sulfur atoms of the thio groups bound to acyclic carbon atoms of the carbon skeleton
    • C07C323/57—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and carboxyl groups bound to the same carbon skeleton having the sulfur atoms of the thio groups bound to acyclic carbon atoms of the carbon skeleton the carbon skeleton being further substituted by nitrogen atoms, not being part of nitro or nitroso groups
    • C07C323/58—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and carboxyl groups bound to the same carbon skeleton having the sulfur atoms of the thio groups bound to acyclic carbon atoms of the carbon skeleton the carbon skeleton being further substituted by nitrogen atoms, not being part of nitro or nitroso groups with amino groups bound to the carbon skeleton
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0004—Crystallisation cooling by heat exchange
    • B01D9/0013—Crystallisation cooling by heat exchange by indirect heat exchange
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B01D9/0027—Evaporation of components of the mixture to be separated by means of conveying fluid, e.g. spray-crystallisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/005—Selection of auxiliary, e.g. for control of crystallisation nuclei, of crystal growth, of adherence to walls; Arrangements for introduction thereof
    • B01D9/0054—Use of anti-solvent
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C319/00—Preparation of thiols, sulfides, hydropolysulfides or polysulfides
    • C07C319/26—Separation; Purification; Stabilisation; Use of additives
    • C07C319/28—Separation; Purification
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D2009/0086—Processes or apparatus therefor

Definitions

  • the invention belongs to the technical field of chemical production.
  • the present invention relates to a process for continuously preparing high bulk density methionine crystals, mainly involving a novel methionine crystallization process and an improved crystallization apparatus.
  • Methionine is one of the essential amino acids for animal growth. It is also the only sulfur-containing amino acid and is an important feed additive. Methionine products are available in both solid and liquid forms. Currently, the world's leading methionine market is solid methionine.
  • methionine is mainly synthesized by chemical methods. According to the raw material route, there are mainly malonic ester method, acrolein method, amino lactone method and the like. At present, the main manufacturers of methionine in the world such as Adisseo, Caoda, Sumitomo and Degussa mainly use the acrolein method. The method uses acrolein and methyl mercaptan as raw materials to produce methylthiopropionaldehyde, methylthiopropane. The aldehyde is then subjected to condensation, hydrolysis, and acidification to produce methionine, but different manufacturers have different hydrolysis and acidification crystallization routes.
  • Adisseu is hydrolyzed with NaOH to produce sodium methionate, which is acidified by sulfuric acid to obtain methionine, and by-product sodium sulfate;
  • Caoda is hydrolyzed with calcium hydroxide, acidified by hydrochloric acid to obtain methionine, and vice versa. Produces sodium chloride and calcium carbonate.
  • the above-mentioned hydrolysis and acidification crystallization route causes the crystal to be powdery due to the large amount of by-products and the presence of impurities therein, which is inconvenient to separate, and is easy to generate dust during drying, packaging, and use.
  • Degussa's hydrolysis and acidification crystallization routes are more advantageous.
  • the process uses condensation of hydrocyanic acid with methylthiopropanal to prepare methylthioethylhydantoin, which is then hydrolyzed with potassium carbonate and acidified by carbon dioxide to obtain methionine.
  • By-product carbon dioxide and potassium hydrogencarbonate can be recycled. This greatly reduces the amount of solid waste discharged and is a clean production route.
  • the acidification crystallization process has been the focus of research. point. Due to the acidification of gaseous carbon dioxide, the methionine suspension in the acidification process has a very serious foaming phenomenon, resulting in excessive crystal nuclei in the subsequent crystallization process, and the crystal particles are very fine, and in general, often scaly crystals. Such scaly crystals are extremely fragile, resulting in very poor solid-liquid separation. Severe foaming often leads to interruptions in the production process, making production impossible.
  • Patent Document 1 discloses a methionine crystallization process as an early patent. The process is carried out by hydrolyzing 5-( ⁇ -methylmercaptoethyl)hydantoin in the presence of potassium carbonate, followed by neutralization and crystallization by introducing carbon dioxide into the hydrolyzate, and the precipitated methionine is precipitated. Separation, the concentrated filtrate can be applied to the hydrolysis of 5-( ⁇ -methylmercaptoethyl)hydantoin.
  • neutralization and crystallization of the crystals are severe, and the resulting methionine crystals are scaly and have a low bulk density. If recrystallization is used to improve the methionine crystal form, additional equipment and energy consumption are required, which is not an economical method.
  • Patent Document 2 employs a method of adding a defoaming agent to an aqueous solution of an alkali metal salt of methionine at a concentration of 1000 to 10,000 ppm.
  • the methionine thus obtained is a porous spherical crystal, and the particle diameter is mostly in the range of 100 to 200 ⁇ m, and the deposit and the mother liquid remain in the micropores.
  • more water is needed for washing, which increases energy consumption and reduces the economics of the process.
  • Patent Document 3 also uses an additive (gluten, polyvinyl alcohol, methyl cellulose, etc.) to control the foaming phenomenon.
  • the literature indicates that a portion of the methionine dissolved in the mother liquor during the hydrolysis will form a methionine polymer which will have an effect on the crystalline crystal form precipitated during crystallization and recrystallization.
  • the content of the polymer is controlled by decomposing the methionine polymer by heating the hydrolyzate at 160-200 ° C for 1-5 hours. Under the methionine crystallization method, the obtained crystals were in the form of granules or slabs having a bulk density of 625 kg/m 3 .
  • heating the hydrolyzate although the methionine polymer is hydrolyzed, the obtained crystal grain bulk density is still not high. And heating the hydrolyzate for a long time increases energy consumption and reduces the production capacity of the production device.
  • Patent Document 4 proposes to obtain methionine crystals by a semi-batch crystallization method using a crystallization tank with a draft tube.
  • the process is to firstly use 15-40% aqueous methionine solution together with a coagulant (sorbitan laurate, polyvinyl alcohol or hydroxypropyl methylcellulose) for batch neutralization and crystallization for 20-40 minutes.
  • the long crystals were then added to the remaining 60-85% aqueous solution of methionine to continuously neutralize the crystals for 40-90 min for long crystals.
  • the bulk density of the methionine crystals obtained under the conditions described in the literature was 550 kg/m 3 , which was still not high.
  • Patent Document 5 proposes that the amount of the by-product methionine polymer in the hydrolyzate can be reduced by the first reactor without agitation hydrolysis and the second reactor continuing to heat, using polyvinyl alcohol as a flocculant and simultaneously crystallization.
  • the mother liquor jacket is used for recycling in the hydrolyzate to obtain a crystal of methionine having a high bulk density.
  • Neutralization crystallization was carried out at a crystallization temperature of 10 to 30 ° C and a carbon dioxide pressure of 0.1 to 1 MPa to obtain a methionine crystal having a bulk density of 703 kg/m 3 .
  • the obtained crystal bulk density is increased by only 5% compared with the comparative example, and the equipment and energy consumption required for the two heat treatments are increased.
  • Patent Document 6 a crude methionine is recrystallized by a vacuum crystallization method to increase the bulk density of crystals.
  • the process is to dissolve the crude methionine with the solvent and the additive at 100 ° C, and then send it to the vacuum crystallization kettle, the temperature is controlled by the degree of vacuum, the first-order crystallization temperature is controlled by 60-70 ° C, and the secondary crystallization temperature is controlled by 30- At 50 ° C, a methionine crystal having a bulk density of 640 kg/m 3 was finally obtained.
  • the recrystallization step requires reheating, cooling, and cooling of the crude methionine, accompanied by a large amount of liquid circulation, thereby increasing energy consumption and reducing the economics of the process.
  • Patent JP 10306071 proposes a method for crystallizing methionine to eliminate foam in the coexistence of gluten when an aqueous potassium salt solution of methionine is neutralized with an acid; in the Japanese Patent Publication No. 43-22285, it is a methylthioamide.
  • the methionine salt solution is neutralized and crystallized in a solution to which an anionic and nonionic surfactant is added to eliminate foam.
  • the method of neutralizing crystallization of a potassium salt aqueous solution of methionine in a coexistence of polyvinyl alcohol for neutralization and crystallization to eliminate foam is disclosed in JP2921097.
  • the blistering phenomenon during crystallization is an important factor affecting the result of neutralization crystallization.
  • most of the prior art uses an additive such as an antifoaming agent and a flocculating agent in the crystallization process, and some of these additives adhere to the surface of the crystal.
  • the methionine product is taken out, and the other part is left in the mother liquor for recycling with the mother liquor.
  • the circulation of the additive will change the proportion of the additive in the mother liquor, or it may become an unknown substance due to thermal deterioration, thereby neutralizing the crystallization process.
  • Patent Document 1 Special Gong Zhao 54-9174
  • Patent Document 2 DE19547236
  • Patent Document 3 CN1589259
  • Patent Document 4 CN1274717
  • Patent Document 5 CN101602701
  • Patent Document 6 WO2013139562
  • the invention aims to solve the problems that the various methionine crystal production methods in the prior art are easy to generate bubbles, the bulk density is not high, and the crystallization process is affected when the additive is used, by using a gas phase neutralization section.
  • the DTB neutralizes the crystallizer, and the liquid phase neutralization process which is prone to foaming is transferred to the gas phase, thereby fundamentally solving the foaming problem of the neutralization process.
  • the formation of crystal nuclei can be effectively controlled, and a high bulk density methionine product can be obtained.
  • One aspect of the present invention is a method for continuously preparing a high bulk density methionine crystal, which comprises the following steps:
  • the outer circulation material is initially a saturated methionine solution.
  • the high bulk density methionine crystal has a bulk density of at least 800 kg/m3 or more.
  • the 5-( ⁇ -methylmercaptoethyl)hydantoin is first reacted with a potassium carbonate solution to obtain a hydrolyzate containing potassium methionine, and then pre-cooled with the same temperature from the neutralizing crystallizer. Mix to form a mixture.
  • the formation process of the crystal comprises: the neutralization liquid enters the crystallization zone, is mixed with the material in the crystallization zone by stirring in the crystallizer, and is formed on the fine crystal formed in the system. Long, a crystal having a large particle size is formed, and a new crystal nucleus can be formed due to the supersaturation state of the methionine solution.
  • the fine crystal and part of the methionine solution enter the outer circulation pipeline, and are cooled and cooled together, and the circulation is performed; the outer circulation material is used for crystallization in the panning leg.
  • the panning is carried out, and it is partially used for mixing with a hydrolyzate containing potassium methionine.
  • the DTB neutralization zone with a gas phase neutralization section has a gas phase space at the upper portion, a liquid distributor and a gas distributor are provided, and the liquid is used as a dispersed phase for gas-liquid neutralization of carbon dioxide gas as a continuous phase. reaction.
  • the volume ratio of the potassium methionine-containing reaction solution (hydrolyzate) and the external circulation solution entering the DTB in the gas phase neutralization section and the outer circulation line of the crystallizer is 1:5-50, preferably 1:10- 30;
  • the mixed material is lowered by the cooler temperature by 0.5-5 ° C, preferably by 1-3 ° C, and stabilized at 20-40 ° C after circulating cooling.
  • the volume ratio of the outer circulation solution to the crystal slurry discharge amount into the DTB with the gas phase neutralization section and the crystallizer panning leg is 1-5:1, preferably 1.5-4:1.
  • the crystallization zone of the DTB with a gas phase neutralization zone and the crystallizer is stirred at a rate of from 50 to 500 rpm, preferably from 100 to 300 rpm.
  • the temperature of the crystallization zone of the DTB neutralizing crystallizer with the gas phase neutralization section is 10-40 ° C, preferably 20-30 ° C.
  • the hydrolyzate containing potassium methionine is allowed to remain in the DTB of the gas phase and in the zone and in the crystallizer for 0.3 to 3 hours, preferably 0.5 to 2 hours, to enter the methyl sulfide containing the neutralization crystallizer.
  • the hydrolyzate flow meter of potassium potassium is 0.333-3.33 m3/h, preferably 0.5-2 m3/h.
  • the pressure in the DTB with a gas phase neutralization zone and the gas phase carbon dioxide in the crystallizer is from 0.3 to 1.2 MPa, preferably from 0.4 to 1.0 MPa.
  • the invention also provides a DTB neutralization crystallizer with a gas phase neutralization section for continuously preparing high bulk density methionine crystals, characterized by comprising:
  • a liquid distributor for forming a droplet or a fine stream containing a potassium methionine mixed solution in the upper neutral zone, and a gas distributor for supplying carbon dioxide gas,
  • the external circulation system is partially supplied to the panning leg, partially mixed with the hydrolyzate containing potassium methionine, and circulated to the draft tube plus the baffle evaporation and the crystallizer material inlet.
  • the DTB neutralizing crystallizer with a gas phase neutralization section further includes a drum filter that separates and washes the crystal slurry from the panning legs.
  • the invention is characterized in that the neutralization reaction of the potassium methionine-containing hydrolyzate and the carbon dioxide which easily generate the foaming phenomenon is transferred from the liquid phase to the gas phase, thereby fundamentally solving the problem that the liquid phase is easily foamed during neutralization.
  • the supersaturation of the methionine in the neutralization solution can be effectively controlled, thereby controlling A.
  • the amount of thione new nucleation is such that the methionine crystal can grow up, and finally a high bulk density methionine crystal product having a large particle size can be obtained.
  • the invention has the advantages that the reaction liquid containing potassium methionine is continuously neutralized and crystallized in the DTB in the gas phase and in the crystallizer, and the production process has good stability, high efficiency and stable product quality. Suitable for industrial production.
  • Figure 1 is an illustration of one embodiment of a DTB neutralization crystallizer with a gas phase neutralization section of the present invention.
  • the DTB neutralization crystallizer with gas phase neutralization section of the invention has the following structure: a liquid phase partial volume of 1 m 3 , designed according to a conventional DTB structure ratio; a gas phase partial volume of 0.6 m 3 , a diameter of 600 mm and a height of 2200 mm with an oval seal
  • the cylindrical body of the head is provided with a liquid distributor at the upper portion and a carbon dioxide gas distributor at the lower portion.
  • a hydrolyzate containing 19% potassium methionine at 28 ° C was passed at a flow rate of 1 m 3 /h (corresponding to a residence time of 1 hour), mixed with the externally circulated material, and cooled to 25 ° C through a cooler.
  • the liquid After entering the liquid distributor at the top of the crystallizer, the liquid is sprayed into the gaseous carbon dioxide in a fine stream to neutralize the reaction to become a neutralizing liquid and fall into the liquid level of the crystallizer.
  • the neutralizing liquid falling into the surface of the crystallizer has been heated to 28 ° C, stirred and mixed to grow on the crystallizer seeds, and a certain amount of new seed crystals are also produced due to the existence of supersaturation.
  • the crystal slurry pump was turned on, and the methionine crystal slurry was sent to the drum filter at a flow rate of 1.1 m 3 /h for filtration and washing, and the methionine filter cake was further
  • the methionine product can be obtained by continuous fluidized drying. After the operation was completely stabilized (about 4 hours), a methionine crystalline product having a bulk density of 811 kg/m 3 was obtained at a yield of 112 kg/h.
  • a saturated solution of 0.9 m 3 of methionine was previously added to the DTB in the gas phase neutralization section described in Example 1 and to the crystallizer, and 10 Kg of methionine seed crystal ground to 10 ⁇ m or less was further added.
  • Turn on the crystallizer stirring stir at a rate of 200 rpm, turn on the external circulation pump, adjust the flow rate of the external circulation liquid entering the panning leg to 1.5 m 3 /h, and the flow rate of the external circulation liquid mixed with the hydrolyzate containing potassium methionine is 20 m. 3 / h.
  • the circulation cooling is turned on to stabilize the temperature at 20 °C. Carbon dioxide is introduced from the gas distributor to a pressure of 0.4 MPa.
  • a hydrolyzate containing 19% potassium methionine at 20 ° C was introduced, and the flow rate was 0.5 m 3 /h (corresponding to a residence time of 2 hours), and after mixing with the externally circulated material, it was cooled to 18 by a cooler. After °C, it enters the liquid distributor at the top of the crystallizer, and the liquid is sprayed into the gaseous carbon dioxide in a fine stream to neutralize the reaction and become a neutralizing liquid and fall into the liquid level of the crystallizer.
  • the neutralizing liquid falling into the liquid level of the crystallizer has been heated to 20 ° C, stirred and mixed to grow on the crystallizer seed crystal, and a certain number of new seed crystals are also produced due to the existence of supersaturation.
  • the crystal slurry pump was turned on, and the methionine crystal slurry was sent to the drum filter at a flow rate of 0.55 m 3 /h for filtration and washing, and the methionine filter cake was further
  • the methionine product can be obtained by continuous fluidized drying. After the operation was completely stabilized (about 8 hours), a methionine crystalline product having a bulk density of 816 kg/m 3 was obtained at a yield of 57 kg/h.
  • a saturated solution of 0.9 m 3 of methionine was previously added to the DTB in the gas phase neutralization section described in Example 1 and to the crystallizer, and 10 Kg of methionine seed crystal ground to 10 ⁇ m or less was further added.
  • Carbon dioxide was introduced from the gas distributor to a pressure of 1.0 MPa.
  • a hydrolyzate containing 19% potassium methionine at 35 ° C was introduced, and the flow rate was 2 m 3 /h (corresponding to a residence time of 0.5 hours), and after mixing with the externally circulated material, it was cooled to 30 ° C through a cooler.
  • the liquid distributor at the top of the crystallizer After entering the liquid distributor at the top of the crystallizer, the liquid is sprayed into the gaseous carbon dioxide in a fine stream to neutralize the reaction to become a neutralizing liquid and fall into the liquid level of the crystallizer.
  • the neutralizing liquid falling into the liquid level of the crystallizer has been heated to 35 ° C, stirred and mixed to grow on the crystallizer seed crystal, and a certain number of new seed crystals are also produced due to the existence of supersaturation.
  • the crystal slurry pump was turned on, and the methionine crystal slurry was sent to the drum filter at a flow rate of 2.2 m 3 /h for filtration and washing, and the methionine filter cake was further
  • the methionine product can be obtained by continuous fluidized drying. After the operation is completely stabilized (about 2 hours), a methionine crystalline product having a bulk density of 802 kg/m 3 can be obtained at a yield of 221 kg/h.
  • a saturated solution of 0.9 m 3 of methionine was previously added to the DTB in the gas phase neutralization section described in Example 1 and to the crystallizer, and 10 Kg of methionine seed crystal ground to 10 ⁇ m or less was further added.
  • the mold was stirred and the stirring speed was 50 rpm.
  • the external circulation pump was turned on to adjust the flow rate of the external circulation liquid entering the panning leg to 1.83 m 3 /h, and the flow rate of the external circulation liquid mixed with the hydrolyzate containing potassium methionine was 16.66. m 3 /h.
  • the circulation cooling is turned on to stabilize the temperature at 40 °C. Carbon dioxide is introduced from the gas distributor to a pressure of 1.2 MPa.
  • a hydrolyzate containing 19% potassium methionine at 40 ° C was introduced, and the flow rate was 0.333 m 3 /h (corresponding to a residence time of 3 hours), and after mixing with the externally circulated material, it was cooled to 39.5 through a cooler. After °C, it enters the liquid distributor at the top of the crystallizer, and the liquid is sprayed into the gaseous carbon dioxide in a fine stream to neutralize the reaction and become a neutralizing liquid and fall into the liquid level of the crystallizer.
  • the neutralizing liquid falling into the liquid level of the crystallizer has been heated to 40 ° C, stirred and mixed to grow on the crystallizer seed crystal, and a certain number of new seed crystals are also produced due to the existence of supersaturation.
  • the methionine product can be obtained by continuous fluidized drying. After the operation was completely stabilized (about 12 hours), a methionine crystalline product having a bulk density of 822 kg/m 3 was obtained at a yield of 36 kg/h.
  • a saturated solution of 0.9 m 3 of methionine was previously added to the DTB in the gas phase neutralization section described in Example 1 and to the crystallizer, and 10 Kg of methionine seed crystal ground to 10 ⁇ m or less was further added.
  • the mold was stirred and the stirring speed was 500 rpm.
  • the external circulation pump was turned on to adjust the flow rate of the external circulation liquid entering the panning leg to 3.67 m 3 /h, and the flow rate of the external circulation liquid mixed with the hydrolyzate containing potassium methionine was 16.66. m 3 /h.
  • the circulation cooling is turned on to stabilize the temperature at 10 °C. Carbon dioxide is introduced from the gas distributor to a pressure of 0.3 MPa.
  • a hydrolyzate containing 15% potassium methionine at 10 ° C was introduced, and the flow rate was 3.33 m 3 /h (corresponding to a residence time of 0.3 hours), and after mixing with the externally circulated material, it was cooled to 5 by a cooler. After °C, it enters the liquid distributor at the top of the crystallizer, and the liquid is sprayed into the gaseous carbon dioxide in a fine stream to neutralize the reaction and become a neutralizing liquid and fall into the liquid level of the crystallizer.
  • the neutralizing liquid falling into the liquid level of the crystallizer has been heated to 10 ° C, stirred and mixed to grow on the crystallizer seed crystal, and a certain number of new seed crystals are also produced due to the existence of supersaturation.
  • the crystal slurry pump was turned on, and the methionine crystal slurry was sent to the drum filter at a flow rate of 3.67 m 3 /h for filtration and washing, and the methionine filter cake was added.
  • the methionine product can be obtained by continuous fluidized drying. After the operation was completely stabilized (about 1.2 hours), a methionine crystalline product having a bulk density of 805 kg/m 3 was obtained at a yield of 268 Kg/h.
  • Example 2 The other operation was the same as in Example 1, except that gaseous carbon dioxide was introduced from the liquid phase into the crystallizer.
  • a saturated solution of 0.9 m 3 of methionine was previously added to the DTB in the gas phase neutralization section described in Example 1 and to the crystallizer, and 10 Kg of methionine seed crystal ground to 10 ⁇ m or less was further added.
  • Turn on the mold stirring stir the speed at 100 rpm, turn on the external circulation pump, adjust the flow rate of the external circulation liquid entering the panning leg to be 1.1 m 3 /h, and the flow rate of the external circulation liquid mixed with the hydrolyzate containing potassium methionine is 10 m. 3 / h.
  • the circulation cooling is turned on to stabilize the temperature at 28 °C.
  • Carbon dioxide was introduced into the lower portion of the crystallizer liquid phase agitator to a pressure of 0.5 MPa.
  • a hydrolyzate containing 19% potassium methionine at 28 ° C was passed at a flow rate of 1 m 3 /h (corresponding to a residence time of 1 hour), mixed with the externally circulated material, and cooled to 25 ° C through a cooler.
  • the liquid falls into the liquid level of the crystallizer in a fine stream, is stirred and mixed with the liquid phase dissolved carbon dioxide, and then grows on the crystallizer seed crystal, and at the same time due to supersaturation. The existence of a certain number of new seeds will also occur.
  • the crystal slurry pump was turned on, and the methionine crystal slurry was sent to the drum filter at a flow rate of 1.1 m 3 /h for filtration and washing, and the methionine filter cake was further
  • the methionine product can be obtained by continuous fluidized drying. After the operation was completely stabilized (about 4 hours), a methionine crystalline product having a bulk density of 518 kg/m 3 was obtained at a yield of 111 kg/h.
  • the present invention utilizes a reaction solution containing potassium methionine for continuous neutralization crystallization in the DTB in the gas phase and in the crystallizer, and a potassium methionine-containing hydrolyzate which is liable to cause foaming.
  • the neutralization reaction with carbon dioxide is transferred from the liquid phase to the gas phase, which fundamentally solves the problem of easy foaming during neutralization of the liquid phase.
  • the production process has good stability, high efficiency, and stable product quality, and is very suitable for industrial production.

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Abstract

本发明涉及一种连续制备高堆积密度甲硫氨酸结晶的方法，其过程是：将5-(β-甲巯基乙基)乙内酰脲与碳酸钾溶液反应得到的水解液与来自带气相中和段的DTB中和结晶器的外循环物料混合、冷却后进入该结晶器上部中和区的液体分布器中，以液滴或细流状喷洒到二氧化碳气体中进行中和反应并自然下落到下部的结晶区后与区内物料混合，并在体系中的细小结晶上生长形成粒径较大的晶体，同时也会形成新的晶核；在结晶区中部的沉降区，较大粒径的结晶沉入淘洗腿，细小结晶则随外循环物料一起进行循环，外循环物料部分用于对淘洗腿中的结晶进行淘洗，部分用于与水解液混合；将淘洗腿中的结晶进行分离、洗涤，再经干燥，即可得到高堆积密度甲硫氨酸产品。

Description

一种连续制备高堆积密度甲硫氨酸结晶的方法 技术领域
本发明属于化工生产技术领域。具体的，本发明涉及一种连续制备高堆积密度甲硫氨酸结晶的方法，主要涉及新的一种甲硫氨酸的结晶工艺和改进的结晶装置。
背景技术
甲硫氨酸是动物生长所必须的氨基酸之一，也是目前唯一含硫的氨基酸，是重要的饲料添加剂品种。甲硫氨酸产品有固体和液体二种形式，目前占世界甲硫氨酸市场主导地位的是固体甲硫氨酸。
目前甲硫氨酸主要采用化学法合成。按照原料路线分主要有丙二酸酯法、丙烯醛法、氨基内酯法等。目前安迪苏、曹达、住友、德固赛等世界甲硫氨酸主要生产厂家主要采用丙烯醛法，该法采用丙烯醛和甲硫醇为原料生产甲硫基丙醛，甲硫基丙醛再进行缩合、水解、酸化结晶生产甲硫氨酸，但是不同的厂家都有不同的水解和酸化结晶路线。安迪苏采用NaOH进行水解，生产蛋氨酸钠，再用硫酸酸化结晶得到甲硫氨酸，同时副产硫酸钠；曹达采用氢氧化钙进行水解，用盐酸酸化结晶得到甲硫氨酸，同时副产氯化钠和碳酸钙。上述水解、酸化结晶路线由于副产较多和其中杂质的存在，使得结晶成为粉末状，不便于分离，且烘干、包装、使用时容易产生粉尘。
相比之下，德固赛的水解、酸化结晶路线较有优势。该工艺采用氢氰酸与甲硫基丙醛缩合制备甲硫基乙基乙内酰脲，再用碳酸钾水解、二氧化碳酸化结晶得到甲硫氨酸，副产的二氧化碳、碳酸氢钾可以循环使用，从而大幅度减少了固体废物排放量，是一种清洁的生产路线。
在使用上述工艺制备甲硫氨酸的过程中，酸化结晶过程一直是研究的重 点。由于使用气态二氧化碳酸化，酸化过程中的甲硫氨酸悬浮液有非常严重的起泡现象，导致之后结晶过程中晶核过多，结晶颗粒非常细小，在一般情况下经常是鳞片状的结晶，这种鳞片状的结晶极易碎裂，导致固液分离性非常差。严重的起泡现象时常会导致生产过程的中断，使得生产无法正常进行。
目前存在着采用改进的设备、改进的工艺或者添加特定的辅助物质等手段来避免起泡现象的产生的各种研究。
专利文献1作为早期专利公开了一种甲硫氨酸结晶工艺。该工艺是通过在碳酸钾存在的条件下，将5-(β-甲巯基乙基)乙内酰脲水解，接着向水解液中通入二氧化碳进行中和、结晶，将析出的甲硫氨酸分离，浓缩滤液可以套用到5-(β-甲巯基乙基)乙内酰脲的水解过程。但是在该文献记载的条件下进行中和、结晶有比较严重的起泡现象发生，导致最终得到的甲硫氨酸结晶呈鳞片状，堆积密度小。如果通过重结晶来改善甲硫氨酸晶型，需要额外的装备和能耗，不是一种经济的方法。
为解决用气体二氧化碳中和所产生的起泡问题，专利文献2中采用向甲硫氨酸碱金属盐的水溶液中加入除泡剂的方法，加入浓度为1000-10000ppm。这样得到的甲硫氨酸为多孔球形晶体，粒径大多数在100-200μm，微孔内有附着物和母液残留。为了得到符合市场质量要求的产品，就需要较多的水来洗涤，从而增加了能耗，降低了过程的经济性。
专利文献3也使用添加剂(谷蛋白、聚乙烯醇、甲基纤维素等)来控制起泡现象。该文献指出，在水解过程中溶解在母液中的一部分甲硫氨酸会形成甲硫氨酸聚合物，该聚合物对结晶和重结晶过程中析出的结晶晶型会产生影响。通过对水解液在160-200℃下加热1-5小时，使得甲硫氨酸聚合物分解，来控制聚合物的含量。在所述的甲硫氨酸结晶方法下，所得到的结晶为粒状或者厚板状，其堆积密度为625kg/m3。该文献中通过对水解液进行加热，虽然使得甲硫氨酸聚合物水解，但所得到的结晶颗粒堆积密度依然不高。且长 时间加热水解液增加能耗，降低生产装置的生产能力。
专利文献4中提出使用带有导流管的析晶槽，通过半分批结晶的方法来获得甲硫氨酸结晶。其过程是先将15-40％甲硫氨酸盐水溶液同凝聚剂(山梨聚糖月桂酸酯，聚乙烯醇或者羟丙基甲基纤维素)一起进行分批中和结晶20-40min用来长晶种，之后再加入剩余的60-85％甲硫氨酸盐水溶液连续中和结晶40-90min用来长晶体。在该文献记载的条件下所得到的甲硫氨酸晶体的堆积密度为550kg/m3，依然不高。
专利文献5中提出，可以通过第一反应釜无搅拌水解和第二反应釜继续加热来降低水解液中副产物甲硫氨酸聚合物的量，使用聚乙烯醇作为絮凝剂，同时将一次结晶母液套用于水解液中再循环，从而获得一种堆积密度高的甲硫氨酸晶体。在结晶温度10-30℃，二氧化碳压力0.1-1MPa下进行中和结晶得到甲硫氨酸结晶的堆积密度为703kg/m3。其中通过对于水解液进行两次加热处理，所得到的结晶堆积密度与对比例相比仅提高5％，而经过两次热处理所需设备、能耗增加。
专利文献6中采用真空结晶方法对甲硫氨酸粗品进行重结晶以提高结晶的堆积密度。其过程是将粗甲硫氨酸同溶剂和添加剂在100℃下溶解，之后送入真空结晶釜，温度通过真空度进行控制，一级结晶控温60-70℃，二级结晶控温30-50℃，最后得到堆积密度为640kg/m3的甲硫氨酸晶体。但是重结晶步骤需要将粗品甲硫氨酸重新加热溶解、降温，并伴随着大量的液体循环，从而增加能耗，降低过程的经济性。
另有多篇专利都是使用添加剂来消除甲硫氨酸结晶过程中的起泡现象。专利JP10306071中提出在使甲硫氨酸的钾盐水溶液用酸中和时，在谷蛋白的共存下使甲硫氨酸结晶从而消除泡沫的方法；在特公昭43-22285中是使甲硫氨酸盐溶液在可溶性纤维素衍生物的共存下进行中和结晶从而消除泡沫的结晶方法；在特公昭43-24890中使得甲硫氨酸盐溶液在醇类、酚类以及酮类 的共存下进行中和结晶从而消除泡沫的方法；在特公昭46-19610中使甲硫氨酸盐溶液在添加了阴离子性和非离子性表面活性剂的溶液中进行中和结晶从而消除泡沫的方法；在JP2921097中则披露了使甲硫氨酸的钾盐水溶液在聚乙烯醇共存下吸收二氧化碳气体进行中和结晶从而消除泡沫的方法。
综上所述，在用甲硫氨酸盐溶液以二氧化碳进行中和结晶时，结晶过程中的起泡现象是影响中和结晶结果的重要因素。为了避免或者消弱起泡现象以获得理想的晶体，大多数现有技术中都采用在结晶过程中加入消泡剂、凝絮剂等添加剂，这些添加剂中有一部分会附着在晶体表面，随甲硫氨酸产品带出，另一部分则残留在母液中随母液进行循环套用，这部分添加剂的循环套用会改变母液中添加剂的比例，也可能因为受热变质成为不明物质，从而对后续中和结晶过程造成影响，增加中和结晶过程的不稳定性。此外，仅仅通过加入添加剂，无法获得高堆积密度的甲硫氨酸结晶产品。也有文献报道采用重结晶步骤来提高甲硫氨酸结晶的堆积密度，但重结晶过程需增加设备、能耗，从而降低生产过程的经济性。
引证文件列表
专利文献
专利文献1：特公昭54-9174
专利文献2：DE19547236
专利文献3：CN1589259
专利文献4：CN1274717
专利文献5：CN101602701
专利文献6：WO2013139562
发明内容
发明要解决的问题
本发明旨在解决现有技术中各种甲硫氨酸结晶生产方法所存在的容易产生气泡、堆积密度不高、以及使用添加剂时会影响结晶过程等问题，通过使用一种带气相中和段的DTB中和结晶器，将容易产生起泡现象的液相中和过程转移到气相中进行，从而从根本上解决了中和过程的起泡问题。同时通过对结晶过程过饱和度的控制，可以有效控制晶核的形成，从而可以得到高堆积密度的甲硫氨酸产品。
用于解决问题的方案
本发明的一个方案为一种连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于包括以下工序：
(1)将5-(β-甲巯基乙基)乙内酰脲与碳酸钾溶液反应得到含甲硫氨酸钾的水解液与来自带气相中和段的DTB中和结晶器的外循环物料混合形成混合物料，混合物料经冷却降温后进入所述结晶器上部中和区的液体分布器中，以液滴或细流状喷洒到气液接触区与二氧化碳气体进行中和反应，得到含甲硫氨酸的中和液；
(2)所述中和液自然下落到所述结晶器下部的结晶区中，在结晶区内形成晶体，在结晶区中部的沉降区，较大粒径的结晶沉入淘洗腿；
(3)将淘洗腿中的甲硫氨酸结晶通过晶浆泵送入转鼓过滤器中进行分离、洗涤、干燥，得到甲硫氨酸产品；
所述外循环物料最初为饱和甲硫氨酸溶液。
所述高堆积密度的甲硫氨酸结晶的堆积密度为至少800kg/m3以上。
其中优选先将5-(β-甲巯基乙基)乙内酰脲与碳酸钾溶液反应得到含甲硫氨酸钾的水解液预冷，然后与来自中和结晶器的相同温度的外循环物料混合形成混合物料。
进一步地，优选晶体的形成过程包括：所述中和液进入结晶区后通过结晶器中的搅拌与结晶区内物料混合，并且在体系中已形成的细小结晶上生 长，形成粒径较大的晶体，同时由于甲硫氨酸溶液处于过饱和度的状态，能形成新的晶核。
进一步地，优选在所述结晶区中部的沉降区中，细小结晶与部分甲硫氨酸溶液进入外循环管路，一起进行冷却降温、循环；外循环物料部分用于对淘洗腿中的结晶进行淘洗，部分用于与含甲硫氨酸钾的水解液混合。
进一步地，优选所述带气相中和段的DTB中和结晶器在上部存在气相空间，设置液体分布器和气体分布器，将液体作为分散相在作为连续相的二氧化碳气体进行气-液中和反应。
进入所述带气相中和段的DTB中和结晶器外循环管路中的含甲硫氨酸钾反应液(水解液)与外循环溶液体积比为1:5-50，优选1：10-30；混合后的物料经冷却器温度降低0.5-5℃，优选降低1-3℃，循环冷却后稳定在20-40℃。
进入所述带气相中和段的DTB中和结晶器淘洗腿的外循环溶液与晶浆出料量的体积比为1-5:1，优选1.5-4:1。
所述带气相中和段的DTB中和结晶器的结晶区搅拌速率为50-500rpm，优选100-300rpm。
所述带气相中和段的DTB中和结晶器的结晶区温度为10-40℃，优选20-30℃。
所述含甲硫氨酸钾的水解液在所述带气相中和段的DTB中和结晶器中停留0.3-3小时，优选0.5-2小时，以进入所述中和结晶器的含甲硫氨酸钾的水解液流量计为0.333-3.33m3/h，优选为0.5-2m3/h。
所述带气相中和段的DTB中和结晶器中气相二氧化碳的压力为0.3-1.2Mpa，优选0.4-1.0Mpa。
本发明还提供一种连续制备高堆积密度甲硫氨酸结晶的带气相中和段的DTB中和结晶器，其特征在于包括：
(1)设置在上部中和区的形成含甲硫氨酸钾混合液的液滴或细流的液体分布器、供给二氧化碳气体的气体分布器，
(2)设置在中部的液体导流筒和搅拌器，
(3)设置在下部的结晶沉降区，沉降区包括沉淀晶体的淘洗腿，
(4)外循环系统，部分用于供给到淘洗腿，部分与含甲硫氨酸钾的水解液混合并循环供给至导流筒加挡板蒸发中和结晶器物料入口。
进而，所述的带气相中和段的DTB中和结晶器还包括分离、洗涤来自淘洗腿的晶浆的转鼓过滤器。
本发明的特征在于：通过将容易产生起泡现象的含甲硫氨酸钾的水解液与二氧化碳的中和反应从液相转移到气相，从根本上解决了液相中和时容易起泡的问题；同时，通过将含甲硫氨酸钾水解液与外循环溶液混合稀释后再与气相二氧化碳中和的方法，可以有效控制中和液中甲硫氨酸的过饱和度，从而可以控制甲硫氨酸新晶核的产生数量，使得甲硫氨酸晶体能够长大，最终可以得到粒径较大的高堆积密度甲硫氨酸结晶产品。
发明的效果
本发明的优点是：利用含甲硫氨酸钾的反应液在所述带气相中和段的DTB中和结晶器中进行连续中和结晶，生产过程稳定性好、效率高，产品质量稳定，适合工业化生产。
附图说明
图1为本发明所述带气相中和段的DTB中和结晶器的一种实施方式的图例。
附图标记说明
1……液体分布器 2……气体分布器  3……导流筒
4……搅拌桨     5……转鼓过滤器  6……晶浆泵
7……外循环泵    8、9……流量计   10……冷却换热器
11……外循环出口 12……外循环入口 13……CO2气体入口
14……母液       15……结晶       16……水解液
17……沸腾表面   18……筒形挡板   19……淘洗腿
A……气液接触中和区
B……澄清区
C……结晶沉降区
D……大晶体富集区
以下结合非限制性的实施例对本发明进行详细说明。
具体实施方式
实施例1
本发明的带气相中和段的DTB中和结晶器具有如下结构：液相部分容积为1m3，按常规DTB结构比例设计；气相部分容积为0.6m3，为直径600mm、高2200mm带椭圆封头的圆筒体，上部设置液体分布器，下部设置二氧化碳气体分布器。
在上述本发明的带气相中和段的DTB中和结晶器中预先加入0.9m3甲硫氨酸饱和溶液，再加入磨细至10微米以下的甲硫氨酸晶种10Kg。开启结晶器搅拌，搅拌速率100rpm，开启外循环泵，调整进入淘洗腿的外循环液流量为1.6m3/h，与含甲硫氨酸钾的水解液混合用的外循环液流量为10m3/h。循环流量稳定后，开启循环冷却，使其温度稳定在28℃。从气体分布器通入二氧化碳，使其压力达到0.8Mpa。此时，通入28℃含甲硫氨酸钾19％的水解液，其流量为1m3/h(相当于停留时间为1小时)，与外循环物料混合后，经冷却器冷到25℃后进入结晶器顶部的液体分布器中，液体以细流状喷洒到气体二氧化碳中进行中和反应成为中和液并落入到结晶器的液面。落入到结晶器的液 面的中和液已升温到28℃，经搅拌混合在结晶器晶种上生长，同时由于过饱和度的存在，也会产生一定数量的新晶种。
通入含甲硫氨酸钾的水解液6min以后，开启晶浆泵将甲硫氨酸晶浆以1.1m3/h流量送入转鼓过滤器进行过滤、洗涤，甲硫氨酸滤饼再经连续流态化干燥即可得到甲硫氨酸产品。待操作完全稳定后(约需4小时)，可以以112Kg/h的产量得到甲硫氨酸结晶产品，其堆积密度为811kg/m3。
连续操作24小时，全过程均未发现起泡现象。
实施例2
在实施例1所述的带气相中和段的DTB中和结晶器中预先加入0.9m3甲硫氨酸饱和溶液，再加入磨细至10微米以下的甲硫氨酸晶种10Kg。开启结晶器搅拌，搅拌速率200rpm，开启外循环泵，调整进入淘洗腿的外循环液流量为1.5m3/h，与含甲硫氨酸钾的水解液混合用的外循环液流量为20m3/h。循环流量稳定后，开启循环冷却，使其温度稳定在20℃。从气体分布器通入二氧化碳，使其压力达到0.4Mpa。此时，通入20℃含甲硫氨酸钾19％的水解液，其流量为0.5m3/h(相当于停留时间为2小时)，与外循环物料混合后，经冷却器冷到18℃后进入结晶器顶部的液体分布器中，液体以细流状喷洒到气体二氧化碳中进行中和反应成为中和液并落入到结晶器的液面。落入到结晶器的液面的中和液已升温到20℃，经搅拌混合在结晶器晶种上生长，同时由于过饱和度的存在，也会产生一定数量的新晶种。
通入含甲硫氨酸钾的水解液12min以后，开启晶浆泵将甲硫氨酸晶浆以0.55m3/h流量送入转鼓过滤器进行过滤、洗涤，甲硫氨酸滤饼再经连续流态化干燥即可得到甲硫氨酸产品。待操作完全稳定后(约需8小时)，可以以57Kg/h的产量得到甲硫氨酸结晶产品，其堆积密度为816kg/m3。
连续操作24小时，全过程均未发现起泡现象。
实施例3
在实施例1所述的带气相中和段的DTB中和结晶器中预先加入0.9m3甲硫氨酸饱和溶液，再加入磨细至10微米以下的甲硫氨酸晶种10Kg。开启结晶器搅拌，搅拌速率400rpm，开启外循环泵，调整进入淘洗腿的外循环液流量为4m3/h，与含甲硫氨酸钾的水解液混合用的外循环液流量为10m3/h。循环流量稳定后，开启循环冷却，使其温度稳定在35℃。从气体分布器通入二氧化碳，使其压力达到1.0Mpa。此时，通入35℃含甲硫氨酸钾19％的水解液，其流量为2m3/h(相当于停留时间为0.5小时)，与外循环物料混合后，经冷却器冷到30℃后进入结晶器顶部的液体分布器中，液体以细流状喷洒到气体二氧化碳中进行中和反应成为中和液并落入到结晶器的液面。落入到结晶器的液面的中和液已升温到35℃，经搅拌混合在结晶器晶种上生长，同时由于过饱和度的存在，也会产生一定数量的新晶种。
通入含甲硫氨酸钾的水解液3min以后，开启晶浆泵将甲硫氨酸晶浆以2.2m3/h流量送入转鼓过滤器进行过滤、洗涤，甲硫氨酸滤饼再经连续流态化干燥即可得到甲硫氨酸产品。待操作完全稳定后(约需2小时)，可以以221Kg/h的产量得到甲硫氨酸结晶产品，其堆积密度为802kg/m3。
连续操作24小时，全过程均未发现起泡现象。
实施例4
在实施例1所述的带气相中和段的DTB中和结晶器中预先加入0.9m3甲硫氨酸饱和溶液，再加入磨细至10微米以下的甲硫氨酸晶种10Kg。开启结晶器搅拌，搅拌速率50rpm，开启外循环泵，调整进入淘洗腿的外循环液流量为1.83m3/h，与含甲硫氨酸钾的水解液混合用的外循环液流量为16.66m3/h。循环流量稳定后，开启循环冷却，使其温度稳定在40℃。从气体分布器通入 二氧化碳，使其压力达到1.2Mpa。此时，通入40℃含甲硫氨酸钾19％的水解液，其流量为0.333m3/h(相当于停留时间为3小时)，与外循环物料混合后，经冷却器冷到39.5℃后进入结晶器顶部的液体分布器中，液体以细流状喷洒到气体二氧化碳中进行中和反应成为中和液并落入到结晶器的液面。落入到结晶器的液面的中和液已升温到40℃，经搅拌混合在结晶器晶种上生长，同时由于过饱和度的存在，也会产生一定数量的新晶种。
通入含甲硫氨酸钾的水解液18min以后，开启晶浆泵将甲硫氨酸晶浆以0.366m3/h流量送入转鼓过滤器进行过滤、洗涤，甲硫氨酸滤饼再经连续流态化干燥即可得到甲硫氨酸产品。待操作完全稳定后(约需12小时)，可以以36Kg/h的产量得到甲硫氨酸结晶产品，其堆积密度为822kg/m3。
连续操作24小时，全过程均未发现起泡现象。
实施例5
在实施例1所述的带气相中和段的DTB中和结晶器中预先加入0.9m3甲硫氨酸饱和溶液，再加入磨细至10微米以下的甲硫氨酸晶种10Kg。开启结晶器搅拌，搅拌速率500rpm，开启外循环泵，调整进入淘洗腿的外循环液流量为3.67m3/h，与含甲硫氨酸钾的水解液混合用的外循环液流量为16.66m3/h。循环流量稳定后，开启循环冷却，使其温度稳定在10℃。从气体分布器通入二氧化碳，使其压力达到0.3Mpa。此时，通入10℃含甲硫氨酸钾15％的水解液，其流量为3.33m3/h(相当于停留时间为0.3小时)，与外循环物料混合后，经冷却器冷到5℃后进入结晶器顶部的液体分布器中，液体以细流状喷洒到气体二氧化碳中进行中和反应成为中和液并落入到结晶器的液面。落入到结晶器的液面的中和液已升温到10℃，经搅拌混合在结晶器晶种上生长，同时由于过饱和度的存在，也会产生一定数量的新晶种。
通入含甲硫氨酸钾的水解液1.8min以后，开启晶浆泵将甲硫氨酸晶浆以 3.67m3/h流量送入转鼓过滤器进行过滤、洗涤，甲硫氨酸滤饼再经连续流态化干燥即可得到甲硫氨酸产品。待操作完全稳定后(约需1.2小时)，可以以268Kg/h的产量得到甲硫氨酸结晶产品，其堆积密度为805kg/m3。
连续操作24小时，全过程均未发现起泡现象。
比较例
其他操作同实施例1，只是将气体二氧化碳从液相通入到结晶器中。
在实施例1所述的带气相中和段的DTB中和结晶器中预先加入0.9m3甲硫氨酸饱和溶液，再加入磨细至10微米以下的甲硫氨酸晶种10Kg。开启结晶器搅拌，搅拌速率100rpm，开启外循环泵，调整进入淘洗腿的外循环液流量为1.1m3/h，与含甲硫氨酸钾的水解液混合用的外循环液流量为10m3/h。循环流量稳定后，开启循环冷却，使其温度稳定在28℃。在结晶器液相搅拌器下部通入二氧化碳，使其压力达到0.5Mpa。此时，通入28℃含甲硫氨酸钾19％的水解液，其流量为1m3/h(相当于停留时间为1小时)，与外循环物料混合后，经冷却器冷到25℃后进入结晶器顶部的液体分布器中，液体以细流状落入到结晶器的液面，经搅拌混合与液相溶解的二氧化碳中和以后在结晶器晶种上生长，同时由于过饱和度的存在，也会产生一定数量的新晶种。
通入含甲硫氨酸钾的水解液6min以后，开启晶浆泵将甲硫氨酸晶浆以1.1m3/h流量送入转鼓过滤器进行过滤、洗涤，甲硫氨酸滤饼再经连续流态化干燥即可得到甲硫氨酸产品。待操作完全稳定后(约需4小时)，可以以111Kg/h的产量得到甲硫氨酸结晶产品，其堆积密度为518kg/m3。
连续操作24小时，全过程均发现有明显起泡现象，需要不断加入消泡剂来维持中和结晶过程的连续进行。
表1
Figure PCTCN2015098368-appb-000001
由表1可知，比较例1的生成方法中，其操作条件基本与本申请的方法相同，不同仅在于以液相通入二氧化碳，结果发现有明显起泡现象，影响了获得的甲硫氨酸结晶产品的质量，堆积密度达不到本申请的要求。
产业上的可利用性
本发明通过利用含甲硫氨酸钾的反应液在所述带气相中和段的DTB中和结晶器中进行连续中和结晶，将容易产生起泡现象的含甲硫氨酸钾的水解液与二氧化碳的中和反应从液相转移到气相，从根本上解决了液相中和时容易起泡的问题，生产过程稳定性好、效率高，产品质量稳定，非常适合工业化生产。

Claims (12)

  1. 一种连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于包括以下工序：
    (1)将5-(β-甲巯基乙基)乙内酰脲与碳酸钾溶液反应得到含甲硫氨酸钾的水解液与来自带气相中和段的DTB中和结晶器的外循环物料混合形成混合物料，混合物料经冷却降温后进入所述结晶器上部中和区的液体分布器中，以液滴或细流状喷洒到气液接触区与二氧化碳气体进行中和反应，得到含甲硫氨酸的中和液；
    (2)所述中和液自然下落到所述结晶器下部的结晶区中，在结晶区内形成晶体，在结晶区中部的沉降区，较大粒径的结晶沉入淘洗腿；
    (3)将淘洗腿中的甲硫氨酸结晶通过晶浆泵送入转鼓过滤器中进行分离、洗涤、干燥，得到甲硫氨酸产品；
    所述外循环物料最初为饱和甲硫氨酸溶液。
  2. 如权利要求1所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于结晶过程包括在结晶区内已形成的细小结晶上生长，形成粒径较大的晶体，同时控制过饱和度，以形成新的晶核。
  3. 如权利要求1所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于所述结晶区中部的沉降区中，细小结晶与部分甲硫氨酸溶液进入外循环管路，一起进行冷却降温、循环；外循环物料部分用于对淘洗腿中的结晶进行淘洗，部分用于与含甲硫氨酸钾的水解液混合。
  4. 如权利要求1或2所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于所述带气相中和段的DTB中和结晶器在上部存在气相空间，设置液体分布器和气体分布器，使液体作为分散相在作为连续相的二氧化碳气体中进行气-液中和反应。
  5. 如权利要求1或2所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于进入所述带气相中和段的DTB中和结晶器的外循环管路中的含 甲硫氨酸钾的水解液与外循环物料的体积比是1:5-50，混合后的物料经冷却器温度降低0.5-5℃。
  6. 如权利要求1或2所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于进入所述带气相中和段的DTB中和结晶器下部淘洗腿的外循环物料与晶浆出料量的体积比为(1-5)：1。
  7. 如权利要求1或2所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于所述带气相中和段的DTB中和结晶器的结晶区的搅拌速率为50-500rpm。
  8. 如权利要求1或2所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于所述带气相中和段的DTB中和结晶器的结晶区的温度为10-40℃。
  9. 如权利要求1或2所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于所述含甲硫氨酸钾的水解液在所述中和结晶器中停留为0.3-3小时。
  10. 如权利要求1或2所述的连续制备高堆积密度甲硫氨酸结晶的方法，其特征在于所述带气相中和段的DTB中和结晶器中气相二氧化碳的压力为0.3-1.2Mpa。
  11. 一种连续制备高堆积密度甲硫氨酸结晶的带气相中和段的DTB中和结晶器，其特征在于包括：
    (1)设置在上部中和区的形成含甲硫氨酸钾混合液的液滴或细流的液体分布器、供给二氧化碳气体的气体分布器，
    (2)设置在中部的液体导流筒和搅拌器，
    (3)设置在下部的结晶沉降区，沉降区包括沉淀晶体的淘洗腿，
    (4)外循环系统，用于回收循环结晶区的甲硫氨酸溶液，部分用于供给到淘洗腿，部分与含甲硫氨酸钾的水解液混合并循环供给至所述中和结晶 器物料入口。
  12. 如权利要求11所述的带气相中和段的DTB中和结晶器，其特征在于还包括分离、洗涤来自淘洗腿的晶浆的转鼓过滤器。
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