Method for continuous preparation of high bulk density methionine crystal

Abstract

The present disclosure relates to a method for continuous preparation of high bulk density methionine crystals. The process of the method is as follows: a hydrolysate solution, which is obtained from a reaction of 5-(?-methylmercaptoethyl) hydantoin and a potassium carbonate solution, is mixed with an external circulation material from a DTB neutralization crystallizer having a gas phase neutralization section; after being cooled, the mixture enters a liquid distributor of a neutralization region in the upper part of the crystallizer and is sprayed in the form of liquid droplet or trickle into carbon dioxide gas for neutralization reaction, and then naturally falls into a crystallization region in the lower part to be mixed with a material in the region; the obtained mixture grows on fine crystals in a system to form crystals having larger particle diameters, and meanwhile new crystal nucleuses are formed; in a deposition area in the middle part of the crystallization region, the crystals having larger particle diameters deposits into an elutriation leg, while the fine crystals circulate with the external circulation material, and a part of the external circulation material is used to elutriate the crystals in the elutriation leg, while another part of the same is used to be mixed with the hydrolysate solution; and the crystals in the elutriation leg are separated, washed and dried to obtain the high bulk density methionine product.

Claims

1. A method for continuous preparation of high bulk density methionine crystals, comprising the following steps: (1) mixing a hydrolysate solution containing potassium methionine obtained from a reaction of 5-(?-methylmercaptoethyl)hydantoin and a potassium carbonate solution with an external circulation material from a DTB neutralization crystallizer having a gas phase neutralization section to form a mixture material; the mixture material entering a liquid distributor of a neutralization region in an upper part of the crystallizer after being cooled and being sprayed in the form of liquid droplet or trickle to gas-liquid contact area to carry out a neutralization reaction with carbon dioxide gas so that obtaining a neutralization solution containing methionine; (2) making the neutralization solution naturally fall into a crystallization region in the lower part of the crystallizer to form crystals in the crystallization region, and then making the crystals having larger particle diameters deposited into a elutriation leg in a deposition area in the middle part of the crystallization region; (3) feeding the methionine crystals in the elutriation leg through a crystal mush pump into a rotary drum filter to be subjected to separation, washing and drying to obtain methionine products; wherein the external circulation material is initially a saturated methionine solution and the bulk density of the high bulk density methionine crystals is at least 800 kg/m.sup.3.

2. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein the crystallization process comprises growing on fine crystals already formed in the crystallization region to form crystals having larger particle diameters, while controlling the oversaturation to form new crystal nucleuses.

3. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein in the deposition area in the middle part of the crystallization region, fine crystals and a part of the methionine solution enter an external circulation pipe for cooling and circulation; and a part of the external circulation materials is used to elutriate the crystals in the elutriation leg, while another part of the external circulation materials is used to be mixed with the hydrolyzate solution containing potassium methionine.

4. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein the DTB neutralization crystallizer having a gas phase neutralization section has a gas phase space at an upper part, and a liquid distributor and a gas distributor are provided so that the liquid as a dispersed phase is subjected to a gas-liquid neutralization reaction in a carbon dioxide gas as a continuous phase.

5. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein a volume ratio of the hydrolyzate solution containing potassium methionine in the outer circulation pipe of the DTB neutralization crystallizer having a gas phase neutralization section to the outer circulation material is 1:5-50, and the temperature of the material after being mixed is reduced by a cooler by 0.5-5? C.

6. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein a volume ratio of the outer circulation material in the elutriation leg at the lower part of the DTB neutralization crystallizer having a gas phase neutralization section to the output volume of crystal mush is (1-5):1.

7. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein an agitation rate in the crystallization region of the DTB neutralization crystallizer having a gas phase neutralization section is 50-500 rpm.

8. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein the temperature of the crystallization region of the DTB neutralization crystallizer having a gas phase neutralization section is 10-40? C.

9. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein the hydrolyzate solution containing potassium methionine stays in the neutralization crystallizer for 0.3-3 hours.

10. The method for continuous preparation of high bulk density methionine crystals according to claim 1, wherein a pressure of the gas-phase carbon dioxide in the DTB neutralization crystallizer having a gas phase neutralization section is 0.3-1.2 Mpa.

11. A DTB neutralization crystallizer having a gas phase neutralization section for continuous preparation of high bulk density methionine crystals, comprising: (1) a liquid distributor for forming the liquid droplets or trickles of mixed liquor containing potassium methionine and a gas distributor for supplying carbon dioxide gas that are provided in a neutralization region at an upper part, (2) a liquid guide shell and a stirrer provided in the middle part, (3) a crystal deposition area provided at a lower part, which includes an elutriation leg for depositing crystals, (4) an external circulation system for recycling potassium methionine solution in a crystallization region, and a part of the solution being supplied to the elutriation leg while another part of the same being mixed with the hydrolyzate solution containing potassium methionine and then circulating supply to a material inlet of the neutralization crystallizer, and wherein the bulk density of the high bulk density methionine crystals is at least 800 kg/m.sup.3.

12. The DTB neutralization crystallizer having a gas phase neutralization section according to claim 11, further comprising a rotary drum filter for separating and washing crystal mush from the elutriation leg.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an illustration of one embodiment of the DTB neutralization crystallizer having a gas phase neutralization section according to the present disclosure.

REFERENCE SIGNS

(2) 1 . . . liquid distributor 2 . . . gas distributor 3 . . . guide shell 4 . . . agitator arm 5 . . . rotary drum filter 6 . . . crystal mush pump 7 . . . external circulation pump 8, 9 . . . flow meter 10 . . . cooling heat exchanger 11 . . . external circulation outlet 12 . . . external circulation inlet 13 . . . CO.sub.2 gas inlet 14 . . . mother liquor 15 . . . crystal 16 . . . hydrolysate solution 17 . . . boiling surface 18 . . . cylindrical baffle 19 . . . elutriation leg A . . . gas-liquid contact neutralization region B . . . clarification region C . . . crystal deposition area D . . . large crystal concentrating region

(3) The present disclosure is specifically described with reference to non-limiting embodiments as follows.

DETAILED DESCRIPTION

Example 1

(4) The DTB neutralization crystallizer having a gas phase neutralization section of the present disclosure has the following configuration, including a liquid phase section having a volume of 1 m.sup.3 which is designed according to the structure proportion of conventional DTB; a gas phase section having a volume of 0.6 m.sup.3 in a shape of a cylindrical body with an elliptical sealed head, of which the diameter is 600 mm and the height is 2200 mm; a liquid distributor provided at the upper part; and a carbon dioxide gas distributor provided at the lower part.

(5) In the DTB neutralization crystallizer having a gas phase neutralization section of the present disclosure, 0.9 m.sup.3 of methionine saturated solution is added in advance, followed by 10 Kg of methionine crystal seed ground to having a diameter of no more than 10 micrometers. Then the crystallizer starts to stir at 100 rpm. Switch on the external circulation pump and adjust the flow rate of the external circulation solution entering the elutriation leg to 1.6 m.sup.3/h and the flow rate of the external circulation solution to be mixed with the hydrolyzate solution containing potassium methionine to 10 m.sup.3/h. After the circulation flow is stable, start circulation cooling to keep the temperature at 28? C. The carbon dioxide is introduced from the gas distributor till the pressure is up to 0.8 Mpa. At this moment, a hydrolyzate solution containing 19% of potassium methionine at 28? C. is introduced at a flow rate of 1 m.sup.3/h (i.e., the retention time of 1 hour). After mixing with the external circulation material, the mixture is cooled by a cooler to 25? C. and enters the liquid distributor at the top of the crystallizer. The liquid is sprayed in the form of trickle into gas carbon dioxide for neutralization reaction to become a neutralization solution and fall into the liquid surface of the crystallizer. The temperature of the neutralization solution fallen into the liquid surface of the crystallizer has increased to 28? C. After mixing with stirring, the crystal seeds in the crystallizer grow. At the same time, a certain amount of new crystal seeds will be produced due to the oversaturation.

(6) After the hydrolyzate solution containing potassium methionine has been introduced for 6 min, the crystal mush pump is switched on to feed methionine crystal mush into the rotary drum filter at a flow rate of 1.1 m.sup.3/h for filtering and washing. Methionine products will be obtained after continuous fluidization desiccation of filter cake. After the operation has become totally stable (taking about 4 hours), methionine crystal products can be obtained at a yield of 112 Kg/h, of which the bulk density is 811 kg/m.sup.3.

(7) Foaming phenomenon is not observed during the whole process of continuous operation for 24 hours.

Example 2

(8) In the DTB neutralization crystallizer having a gas phase neutralization section of Example 1, 0.9 m.sup.3 of methionine saturated solution is added in advance, followed by 10 Kg of methionine crystal seed ground to having a diameter of no more than 10 micrometers. Then the crystallizer starts to stir at 200 rpm. Switch on the external circulation pump and adjust the flow rate of the external circulation solution entering the elutriation leg to and the flow rate of the external circulation solution to be mixed with the hydrolyzate solution containing potassium methionine to 20 m.sup.3/h. After the circulation flow is stable, start circulation cooling to keep the temperature at 20? C. The carbon dioxide is introduced from the gas distributor till the pressure is up to 0.4 Mpa. At this moment, a hydrolyzate solution containing 19% of potassium methionine at 20? C. is introduced at a flow rate of 0.5 m.sup.3/h (i.e., the retention time of 2 hours). After mixing with the external circulation material, the mixture is cooled by a cooler to 18? C. and enters the liquid distributor at the top of the crystallizer. The liquid is sprayed in the form of trickle into gas carbon dioxide for neutralization reaction to become a neutralization solution and fall into the liquid surface of the crystallizer. The temperature of the neutralization solution fallen into the liquid surface of the crystallizer has increased to 20? C. After mixing with stirring, the crystal seeds in the crystallizer grow. At the same time, a certain amount of new crystal seeds will be produced due to the oversaturation.

(9) After the hydrolyzate solution containing potassium methionine has been introduced for 12 min, the crystal mush pump is switched on to feed methionine crystal mush into the rotary drum filter at a flow rate of 0.55 m.sup.3/h for filtering and washing. Methionine products will be obtained after continuous fluidization desiccation of filter cake. After the operation has become totally stable (taking about 8 hours), methionine crystal products can be obtained at a yield of 57 Kg/h, of which the bulk density is 816 kg/m.sup.3.

(10) Foaming phenomenon is not observed during the whole process of continuous operation in 24 hours.

Example 3

(11) In the DTB neutralization crystallizer having a gas phase neutralization section of Example 1, 0.9 m.sup.3 of methionine saturated solution is added in advance, followed by 10 Kg of methionine crystal seed ground to having a diameter of no more than 10 micrometers. Then the crystallizer starts to stir at 400 rpm. Switch on the external circulation pump and adjust the flow rate of the external circulation solution entering the elutriation leg to 4 m.sup.3/h and the flow rate of the external circulation solution to be mixed with the hydrolyzate solution containing potassium methionine to 10 m.sup.3/h. After the circulation flow is stable, start circulation cooling to keep the temperature at 35? C. The carbon dioxide is introduced from the gas distributor till the pressure is up to 1.0 Mpa. At this moment, a hydrolyzate solution containing 19% of potassium methionine at 35? C. is introduced at a flow rate of 2 m.sup.3/h (i.e., the retention time of 0.5 hour). After mixing with the external circulation material, the mixture is cooled by a cooler to 30? C. and enters the liquid distributor at the top of the crystallizer. The liquid is sprayed in the form of trickle into gas carbon dioxide for neutralization reaction to become a neutralization solution and fall into the liquid surface of the crystallizer. The temperature of the neutralization solution fallen into the liquid surface of the crystallizer has increased to 35? C. After mixing with stirring, the crystal seeds in the crystallizer grow. At the same time, a certain amount of new crystal seeds will be produced due to the oversaturation.

(12) After the hydrolyzate solution containing potassium methionine has been introduced for 3 min, the crystal mush pump is switched on to feed methionine crystal mush into the rotary drum filter at a flow rate of 2.2 m.sup.3/h for filtering and washing. Methionine products will be obtained after continuous fluidization desiccation of filter cake. After the operation has become totally stable (taking about 2 hours), methionine crystal products can be obtained at a yield of 221 Kg/h, of which the bulk density is 802 kg/m.sup.3.

(13) Foaming phenomenon is not observed during the whole process of continuous operation in 24 hours.

Example 4

(14) In the DTB neutralization crystallizer having a gas phase neutralization section of Example 1, 0.9 m.sup.3 of methionine saturated solution is added in advance, followed by 10 Kg of methionine crystal seed ground to having a diameter of no more than 10 micrometers. Then the crystallizer starts to stir at 50 rpm. Switch on the external circulation pump and adjust the flow rate of the external circulation solution entering the elutriation leg to 1.83 m.sup.3/hand the flow rate of the external circulation solution to be mixed with the hydrolyzate solution containing potassium methionine to 16.66 m.sup.3/h. After the circulation flow is stable, start circulation cooling to keep the temperature at 40? C. The carbon dioxide is introduced from the gas distributor till the pressure is up to 1.2 Mpa. At this moment, a hydrolyzate solution containing 19% of potassium methionine at 40? C. is introduced at a flow rate of 0.333 m.sup.3/h (i.e., the retention time of 3 hours). After mixing with the external circulation material, the mixture is cooled by a cooler to 39.5? C. and enters the liquid distributor at the top of the crystallizer. The liquid is sprayed in the form of trickle into gas carbon dioxide for neutralization reaction to become a neutralization solution and fall into the liquid surface of the crystallizer. The temperature of the neutralization solution fallen into the liquid surface of the crystallizer has increased to 40? C. After mixing with stirring, the crystal seeds in the crystallizer grow. At the same time, a certain amount of new crystal seeds will be produced due to the oversaturation.

(15) After the hydrolyzate solution containing potassium methionine has been introduced for 18 min, the crystal mush pump is switched on to feed methionine crystal mush into the rotary drum filter at a flow rate of 0.366 m.sup.3/h for filtering and washing. Methionine products will be obtained after continuous fluidization desiccation of filter cake. After the operation has become totally stable (taking about 12 hours), methionine crystal products can be obtained at a yield of 36 Kg/h, of which the bulk density is 822 kg/m.sup.3.

(16) Foaming phenomenon is not observed during the whole process of continuous operation in 24 hours.

Example 5

(17) In the DTB neutralization crystallizer having a gas phase neutralization section of Example 1, 0.9 m.sup.3 of methionine saturated solution is added in advance, followed by 10 Kg of methionine crystal seed ground to having a diameter of no more than 10 micrometers. Then the crystallizer starts to stir at 500 rpm. Switch on the external circulation pump and adjust the flow rate of the external circulation solution entering the elutriation leg to 3.67 m.sup.3/h and the flow rate of the external circulation solution to be mixed with the hydrolyzate solution containing potassium methionine to 16.66 m.sup.3/h. After the circulation flow is stable, start circulation cooling to keep the temperature at 10? C. The carbon dioxide is introduced from the gas distributor till the pressure is up to 0.3 Mpa. At this moment, a hydrolyzate solution containing 15% of potassium methionine at 10? C. is introduced at a flow rate of 3.33 m.sup.3/h (i.e., the retention time of 0.3 hours). After mixing with the external circulation material, the mixture is cooled by a cooler to 5? C. and enters the liquid distributor at the top of the crystallizer. The liquid is sprayed in the form of trickle into gas carbon dioxide for neutralization reaction to become a neutralization solution and fall into the liquid surface of the crystallizer. The temperature of the neutralization solution fallen into the liquid surface of the crystallizer has increased to 10? C. After mixing with stirring, the crystal seeds in the crystallizer grow. At the same time, a certain amount of new crystal seeds will be produced due to the oversaturation.

(18) After the hydrolyzate solution containing potassium methionine has been introduced for 1.8 min, the crystal mush pump is switched on to feed methionine crystal mush into the rotary drum filter at a flow rate of 3.67 m.sup.3/h for filtering and washing. Methionine products will be obtained after continuous fluidization desiccation of filter cake. After the operation has become totally stable (taking about 1.2 hours), methionine crystal products can be obtained at a yield of 268 Kg/h, of which the bulk density is 805 kg/m.sup.3.

(19) Foaming phenomenon is not observed during the whole process of continuous operation in 24 hours.

Comparative Example

(20) The experiment is carried out in the same way with Example 1, except the gas carbon dioxide is introduced into the crystallizer from the liquid phase.

(21) In the DTB neutralization crystallizer having a gas phase neutralization section of Example 1, 0.9 m.sup.3 of methionine saturated solution is added in advance, followed by 10 Kg of methionine seed ground to having a diameter of no more than 10 micrometers. Then the crystallizer starts to stir at 100 rpm. Switch on the external circulation pump and adjust the flow rate of the external circulation solution entering the elutriation leg to 1.1 m.sup.3/h and the flow rate of the external circulation solution to be mixed with the hydrolyzate solution containing potassium methionine to 10 m.sup.3/h. After the circulation flow is stable, start circulation cooling to keep the temperature at 28? C. The carbon dioxide is introduced from the gas distributor till the pressure is up to 0.5 Mpa. At this moment, a hydrolyzate solution containing 19% of potassium methionine at 28? C. is introduced at a flow rate of 1 m.sup.3/h i.e., the retention time of 1 hour). After mixing with the external circulation material, the mixture is cooled by a cooler to 25? C. and enters the liquid distributor at the top of the crystallizer. The liquid falls in the form of trickle into the liquid surface of the crystallizer. After mixing with stirring, the liquid neutralizes with carbon dioxide dissolved in a liquid phase so that the crystal seeds in the crystallizer grow. At the same time, a certain amount of new crystal seeds will be produced due to the oversaturation.

(22) After the hydrolyzate solution containing potassium methionine has been introduced for 6 min, the crystal mush pump is switched on to feed methionine crystal mush into the rotary drum filter at a flow rate of 1.1 m.sup.3/h for filtering and washing. Methionine products will be obtained after continuous fluidization desiccation of filter cake. After the operation has become totally stable (taking about 4 hours), methionine crystal products can be obtained at a yield of 111 Kg/h, of which the bulk density is 518 kg/m.sup.3.

(23) During continuous operation in 24 hours, foaming phenomenon occurs in the whole process. Defoamer needs to be added continuously to maintain the continuous neutralization and crystallization process.

(24) TABLE-US-00001 TABLE 1 Flow rate of external Flow rate of circulation hydrolyzate solution to be Temperature solution mixed with of external Pressure containing Agitation hydrolysate circulation of carbon potassium Bulk rate solution solution dioxide methionine Yield Density (rpm) (m.sup.3/h) (? C.) (MPa) (m.sup.3/h) Kg/h kg/m.sup.3 Foaming Example 1 100 10 28 0.8 1 112 811 Not found Example 2 200 20 20 0.4 0.5 57 816 Not found Example 3 400 10 35 1.0 2 221 802 Not found Example 4 50 16.66 40 1.2 0.333 36 822 Not found Example 5 500 16.66 10 0.3 3.33 268 805 Not found Comparative 100 10 28 0.5 1 111 518 obvious Example 1

(25) Referring to Table 1, in the production method of Comparative Example 1, the conditions for the operation is substantially the same with the method of the present application. Comparative Example 1 differs from the present application merely by introducing carbon dioxide in liquid phase, which result in obvious foaming phenomenon. Thus, the methionine crystal product obtained by Comparative Example 1 is affected; and the bulk density cannot meet with the requirement of the present application.

INDUSTRIAL APPLICABILITY

(26) By continuous neutralization and crystallization using a reaction solution containing potassium methionine in a DTB neutralization crystallizer having a gas phase neutralization section, the present disclosure transfers neutralization reaction of the hydrolyzate solution containing potassium methionine and carbon dioxide which is easy to generate a foaming phenomenon from liquid phase to gas phase. Thus, the production process attains good stability and high efficiency. The product obtained has a stable quality. Therefore, the method of the present disclosure is suitable for industrial production.