CN114307641A - High-purity solid automobile urea and preparation method thereof - Google Patents
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- 239000004202 carbamide Substances 0.000 title claims abstract description 156
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 title claims abstract description 155
- 239000007787 solid Substances 0.000 title claims abstract description 98
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 238000002425 crystallisation Methods 0.000 claims abstract description 102
- 230000008025 crystallization Effects 0.000 claims abstract description 102
- 238000001816 cooling Methods 0.000 claims abstract description 71
- OHJMTUPIZMNBFR-UHFFFAOYSA-N biuret Chemical compound NC(=O)NC(N)=O OHJMTUPIZMNBFR-UHFFFAOYSA-N 0.000 claims abstract description 44
- 210000002700 urine Anatomy 0.000 claims abstract description 38
- 238000004519 manufacturing process Methods 0.000 claims abstract description 9
- 239000002002 slurry Substances 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 29
- 239000013078 crystal Substances 0.000 claims description 23
- 238000001035 drying Methods 0.000 claims description 19
- 238000000926 separation method Methods 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 230000003134 recirculating effect Effects 0.000 claims description 4
- 239000000126 substance Substances 0.000 abstract description 6
- 239000002994 raw material Substances 0.000 abstract description 4
- 239000000047 product Substances 0.000 description 42
- 239000000243 solution Substances 0.000 description 17
- 239000007788 liquid Substances 0.000 description 9
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 9
- 238000001514 detection method Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 238000005086 pumping Methods 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 239000007789 gas Substances 0.000 description 5
- 239000012535 impurity Substances 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 3
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000012271 agricultural production Methods 0.000 description 1
- 150000001299 aldehydes Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- -1 containing biuret Chemical compound 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- DOTMOQHOJINYBL-UHFFFAOYSA-N molecular nitrogen;molecular oxygen Chemical compound N#N.O=O DOTMOQHOJINYBL-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
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- 238000006722 reduction reaction Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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Abstract
The invention belongs to the technical field of chemical industry, and discloses a preparation method of high-purity solid automobile urea, wherein dilute urine with lower biuret content is directly used as a production raw material, the dilute urine with initial concentration of 60-80% is selected, the end point temperature of cooling crystallization is controlled, the biuret content in a solid urea product can be effectively controlled to be far below a standard range, an ultrapure solid automobile urea product with yield of about 53% can be obtained by continuously adjusting and testing the end point temperature of cooling crystallization, the biuret content in the product is far below the national standard index value of automobile urea, and the biuret index of the urea solution for a subsequent automobile production vehicle directly utilizing the ultrapure solid automobile urea meets the requirements of an SCR system.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to high-purity solid automobile urea and a preparation method thereof.
Background
An SCR (Selective Catalytic Reduction) system using vehicle urea as a reducing agent utilizes the reaction of vehicle urea aqueous solution and nitrogen oxides in the tail gas of diesel vehicles such as heavy trucks, buses and the like to generate N2And H2O is used for purifying the tail gas, so that the nitrogen oxides discharged by the tail gas can reach the national IV emission standard or even higher emission standard. The working principle of the automobile urea is that the automobile urea is added into an SCR system, and the urea is decomposed into NH under the high-temperature environment (the temperature is higher than 300 ℃)3Can react quickly to generate N2And H2And O. The exhaust temperature of the diesel vehicle is generally 300-500 ℃, and NO is satisfiedxTemperature regulation required for nitrogen-oxygen reduction.
The solid automobile urea is environment-friendly special urea, has appearance characters of solid particles, powder or crystals, is a special raw material of AUS32 (nitrogen oxide reducing agent-urea solution of a diesel engine, which is called as automobile urea solution for short) and AUS40 (marine urea solution), and can be mixed with industrial desalted water according to a certain proportion to obtain the special urea for purifying the tail gas of the diesel engine. Different from agricultural urea and common industrial urea, the special urea for purifying the tail gas of the diesel engine has strict quality requirements on indexes such as biuret, aldehydes, insoluble substances, metal ions and the like. Just as urea can generate biuret as a byproduct in the production process, the biuret is a urea polymer and can cause the blockage of automobile exhaust pipes and catalyst frameworks, and the control is strict. Therefore, the biuret is one of the important indexes affecting the quality of the automobile urea product, and the content of the biuret in the product should be reduced as much as possible.
In view of this, the invention is particularly proposed.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides high-purity solid automobile urea and a preparation method thereof. The preparation method of the invention can obviously reduce the biuret content in the product.
In order to achieve the purpose, the invention adopts a technical scheme that:
a preparation method of high-purity solid automobile urea comprises the following steps:
carrying out circulating cooling crystallization on the dilute urine with the first concentration to form slurry with urea crystals;
sending 15-25% of the slurry with urea crystals to a crystallization cyclone, and returning the rest slurry to the crystallizer to continuously participate in the cooling crystallization process;
and (3) carrying out concentrated liquid-solid separation on the slurry sent to the crystallization cyclone to obtain ultrapure solid automotive urea with the water content of less than or equal to 2.5 percent and the biuret content of less than or equal to 0.15 percent, and drying.
Further, the first concentration is 60-80% by mass percentage concentration.
Further, the first concentration is 60% or 70% or 75% or 78% by mass.
Further, the first concentration is 8% by mass.
Further, the crystallization initial temperature of the circulating cooling circulating crystallization is 70 ℃, and the cooling crystallization end temperature is 40-60 ℃.
Further, the cooling crystallization end point temperature of the circulating cooling circulating crystallization is 40 ℃ or 45 ℃ or 50 ℃ or 55 ℃ or 60 ℃.
Further, the cooling crystallization end point temperature of the circulating cooling circulating crystallization is 40 ℃.
Furthermore, the water content of the product after the dryer is less than or equal to 0.2 percent, and the biuret content is less than or equal to 0.15 percent.
The invention also discloses high-purity solid automobile urea obtained by adopting any one of the preparation methods.
Compared with the prior art, the invention has the following beneficial effects:
1) the invention directly uses the dilute urine with lower biuret content as the production raw material, selects the dilute urine with the initial concentration of 60-80 percent, and controls the end point temperature of cooling crystallization, so that the biuret content in the solid urea product can be effectively controlled to be far lower than the standard range, and the ultra-pure solid automobile urea product with the yield rate of about 53 percent can be obtained through continuous adjustment and experiment of the end point temperature of cooling crystallization, the biuret content in the product is far lower than the national standard index value of automobile urea, and the biuret index of the urea solution for producing the automobile by directly utilizing the ultra-pure solid automobile urea subsequently meets the requirement of an SCR system.
2) The preparation process of the invention has no vacuum equipment and less equipment. The temperature in the cooling crystallization process can be reduced by a certain value, and the required usage amount of the raw material urine is reduced.
3) The ultra-pure solid automobile urea prepared by the method can be directly used for producing the automobile urea solution with industrial desalted water according to a certain proportion, and compared with the automobile urea solution prepared from common granular urea, the automobile urea solution prepared from the ultra-pure solid automobile urea has lower impurity components mainly comprising biuret. The technology of the invention is not limited by regional conditions and can be continuously produced in batches.
4) The invention can not generate waste water in the process of preparing the ultra-pure solid automobile urea, and the residual mother liquid after the cooling and crystallization process can be directly returned to a first-stage evaporator for recycling, thereby playing a certain role in energy consumption and environmental protection.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In one embodiment of the present invention, a method for preparing high purity solid urea for vehicles is provided, comprising the steps of: carrying out circulating cooling crystallization on the dilute urine with the first concentration to form slurry with urea crystals; 15-25% of the total weight of the slurry with urea crystals is sent to a crystallization cyclone, and the rest slurry (namely 75-85%) returns to a crystallizer to continuously participate in the cooling crystallization process; and (3) carrying out concentrated liquid-solid separation on the slurry sent to the crystallization cyclone to obtain ultrapure solid automotive urea with the water content of less than or equal to 2.5 percent and the biuret content of less than or equal to 0.15 percent, and drying.
Wherein the first concentration is 60-80% by mass. In some preferred embodiments, the first concentration is a concentration of 60% or 70% or 75% or 78% by mass. In some more preferred embodiments, the first concentration is a concentration of 8% by mass.
The crystallization initial temperature of the circulating cooling circulating crystallization is 70 ℃, and the cooling crystallization end temperature is 40-60 ℃. In some preferred embodiments, the cooling crystallization end temperature of the cyclic cooling cyclic crystallization is 40 ℃ or 45 ℃ or 50 ℃ or 55 ℃ or 60 ℃. In some more preferred embodiments, the cooling crystallization end temperature of the recirculating cooling recirculating crystallization is 40 ℃.
The water content of the product after the dryer is less than or equal to 0.2 percent, and the biuret content is less than or equal to 0.15 percent.
According to the invention, the required substances are obtained in a targeted manner by using dilute urine with different initial concentrations, cooling and crystallizing, observing the fluidity of the urea solution, and combining the profitability of the product obtained after crystallization with the impurity index parameters of the product mainly containing biuret obtained according to data.
The method only needs to adopt one-time cooling according to the concentration and the solubility of the urea and the biuret at different temperatures by controlling the end point temperature of cooling crystallization, greatly saves the consumption of fuel in the preparation process and greatly improves the production efficiency. And comparing the yield of the product obtained after crystallization (the amount of ultra-pure solid automobile urea/the amount of urea in the dilute solution) to obtain the required substances in a targeted manner.
The common urea contains a small amount of impurities such as biuret and the like in the production process, and the influence on the general industrial production or agricultural production is not great. However, in the production of automotive urea requiring high purity, even a small amount of impurities can substantially affect the final product and the use effect. Therefore, the invention aims to control the quality index of urea mainly containing biuret, and can be quickly completed in one process, and simultaneously can reduce energy consumption.
The method only needs to adopt one-time cooling according to the concentration and the solubility of the urea and the biuret at different temperatures by controlling the end point temperature of cooling crystallization, greatly saves the consumption of fuel in the preparation process and greatly improves the production efficiency. And comparing the yield of the product obtained after crystallization (the amount of ultra-pure solid automobile urea/the amount of urea in the dilute solution) to obtain the required substances in a targeted manner.
The method can effectively control the biuret content in the solid urea product to be far below the standard range, and can obtain the ultra-pure solid automotive urea product with the yield rate of about 53 percent through continuous adjustment and experiment of the cooling crystallization end point temperature.
The invention, when using the above parameters, has various combinations, can control the biuret content of the product within the range far lower than the national standard, and is different from the yield (ultra-pure solid vehicle urea amount/urea amount in dilute solution) of the product obtained by adopting different cooling crystallization end point temperatures. According to the embodiment, the yield is quite different when the cooling temperature is different. The lower the cooling temperature, the higher the profitability; the higher the concentration of the solution, the higher the yield.
In one embodiment of the invention, the ultra-pure solid automobile urea prepared by using dilute urine with the concentration of 78%, selecting the end point temperature of cooling crystallization to be 40 ℃, and performing the steps of cooling crystallization, concentration, centrifugal separation, drying and the like has the biuret content far lower than the national standard, and can obtain the high-purity solid automobile urea.
In another embodiment of the invention, the diluted urine with the concentration of 78% is adopted, the end temperature of cooling crystallization is selected to be 45 ℃, and the ultra-pure solid automobile urea prepared by the steps of cooling crystallization, concentration, centrifugal separation, drying and the like has the biuret content far lower than the national standard and can obtain the high-purity solid automobile urea.
In another embodiment of the invention, the diluted urine with the concentration of 78% is adopted, the final temperature of cooling crystallization is selected to be 50 ℃, and the ultra-pure solid automobile urea prepared by the steps of cooling crystallization, concentration, centrifugal separation, drying and the like has the biuret content far lower than the national standard and can obtain the high-purity solid automobile urea.
In another embodiment of the invention, the diluted urine with the concentration of 78% is adopted, the end temperature of cooling crystallization is selected to be 55 ℃, and the ultra-pure solid automobile urea prepared by the steps of cooling crystallization, concentration, centrifugal separation, drying and the like has the biuret content far lower than the national standard and can obtain the high-purity solid automobile urea.
In another embodiment of the invention, the diluted urine with the concentration of 78% is adopted, the final temperature of cooling crystallization is selected to be 60 ℃, and the ultra-pure solid automobile urea prepared by the steps of cooling crystallization, concentration, centrifugal separation, drying and the like has the biuret content far lower than the national standard and can obtain the high-purity solid automobile urea.
In another embodiment of the invention, the ultra-pure solid automobile urea prepared by preparing dilute urine with the concentration of 78% into 75% dilute urine according to a certain proportion with industrial desalted water, selecting the end point temperature of cooling crystallization to be 40 ℃, and performing steps of cooling crystallization, concentration, centrifugal separation, drying and the like has the biuret content far lower than the national standard, and can obtain high-purity solid automobile urea.
In another embodiment of the invention, the diluted urine with the concentration of 78% is prepared into 70% diluted urine by mixing with industrial desalted water according to a certain proportion, the final temperature of cooling crystallization is selected to be 40 ℃, and the ultra-pure solid automobile urea prepared by the steps of cooling crystallization, concentration, centrifugal separation, drying and the like has the biuret content far lower than the national standard and can obtain high-purity solid automobile urea.
In another embodiment of the invention, the ultra-pure solid automobile urea prepared by preparing the dilute urine with the concentration of 78% into 65% dilute urine according to a certain proportion with industrial desalted water, selecting the cooling crystallization temperature end point to be 40 ℃, and performing cooling crystallization, concentration, centrifugal separation, drying and other steps has the biuret content far lower than the national standard, and can obtain the high-purity solid automobile urea.
The product obtained by the invention can be hardened to a certain extent by being stacked for a long time, but can be in a loose state after being thrown. During the dissolving process of preparing the urea aqueous solution for vehicles, a large amount of heat is absorbed, and the urea aqueous solution can be quickly and completely dissolved after being continuously stirred and has good clarity.
In order to better understand the technical scheme provided by the invention, the following specific examples respectively illustrate the preparation method and performance test of high-purity solid vehicle urea provided by the above embodiment of the invention.
Example 1
A high-purity solid automobile urea and a preparation method thereof comprise the following steps:
(1) feeding diluted urine with the concentration of 78% of urea and the temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization in a circulating mode, wherein the crystallization end point temperature of the cooling crystallization is 40 ℃, and then placing the urea into a material receiving groove to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer by a pump, wherein 20 percent of the total weight of the slurry is sent to a crystallization cyclone, and 80 percent of the total weight of the slurry is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 60.23%. The detection shows that the biuret content of the product is 0.14 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Example 2
A high-purity solid automobile urea and a preparation method thereof comprise the following steps:
(1) feeding diluted urine with the concentration of 78% of urea and the temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization in a circulating mode, wherein the crystallization end point temperature of the cooling crystallization is 45 ℃, and then placing the urea into a material receiving groove to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer by a pump, wherein 15 percent of the total weight of the slurry is sent to a crystallization cyclone, and 85 percent of the total weight of the slurry is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 55.19%. The detection shows that the biuret content of the product is 0.10 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Example 3
A high-purity solid automobile urea and a preparation method thereof comprise the following steps:
(1) feeding diluted urine with the concentration of 78% of urea and the temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization in a circulating mode, wherein the crystallization end point temperature of the cooling crystallization is 50 ℃, and then placing the urea into a material receiving groove to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer by a pump, wherein 25 percent of the total weight of the slurry is sent to a crystallization cyclone, and 75 percent of the total weight of the slurry is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 48.67%. The detection shows that the biuret content of the product is 0.12 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Example 4
A high-purity solid automobile urea and a preparation method thereof comprise the following steps:
(1) feeding diluted urine with the concentration of 78% of urea and the temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization in a circulating mode, wherein the crystallization end point temperature of the cooling crystallization is 55 ℃, and then placing the urea into a material receiving groove to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer by a pump, wherein 18 percent of the total weight of the slurry is sent to a crystallization cyclone, and 82 percent of the total weight of the slurry is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 39.44%. The detection shows that the biuret content of the product is 0.11 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Example 5
(1) Feeding diluted urine with the concentration of 78% of urea and the temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization in a circulating mode, wherein the crystallization end point temperature of the cooling crystallization is 60 ℃, and then placing the urea into a material receiving groove to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer, wherein 22% of the total weight of the slurry is sent to a crystallization cyclone and 78% is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 37.51%. The detection shows that the biuret content of the product is 0.12 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Example 6
A high-purity solid automobile urea and a preparation method thereof comprise the following steps:
(1) feeding dilute urine with the concentration of 75% of urea and the temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization in a circulating mode, wherein the crystallization end point temperature of the cooling crystallization is 40 ℃, and then placing the urea into a material receiving groove to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer by a pump, wherein 24 percent of the total weight of the slurry is sent to a crystallization cyclone, and 76 percent of the total weight of the slurry is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 53.51%. The detection shows that the biuret content of the product is 0.14 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Example 7
A high-purity solid automobile urea and a preparation method thereof comprise the following steps:
(1) feeding dilute urine with the concentration of 70 percent and the temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization by circulation, wherein the crystallization end point temperature of the cooling crystallization is 40 ℃, and then placing the dilute urine into a material receiving groove to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer, wherein 16% of the total weight of the slurry is sent to the crystallization cyclone and 84% is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 33.27%. The detection shows that the biuret content of the product is 0.12 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Example 8
A high-purity solid automobile urea and a preparation method thereof comprise the following steps:
(1) feeding dilute urine with urea concentration of 65% and temperature of 70 ℃ into a stirring crystallizer through a urine pump, performing cooling crystallization by circulation, wherein the crystallization end point temperature of the cooling crystallization is 40 ℃, and then placing the dilute urine into a material receiving tank to form slurry with urea crystals;
(2) pumping the slurry with urea crystals from the bottom of the crystallizer by a pump, wherein 19 percent of the total weight of the slurry is sent to a crystallization cyclone, and 81 percent of the total weight of the slurry is returned to the crystallizer;
(3) concentrating by a crystallization cyclone and separating liquid from solid by a centrifugal machine to obtain an ultra-pure solid automobile urea product with certain moisture, and drying the ultra-pure solid automobile urea product in a rotary drum dryer. The yield of ultra-pure solid automotive urea obtained from the above process was about 29.41%. The detection shows that the biuret content of the product is 0.13 percent and is far less than 0.8 percent of the national relevant urea standard for solid vehicles.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. The preparation method of the high-purity solid automobile urea is characterized by comprising the following steps of:
carrying out circulating cooling crystallization on the dilute urine with the first concentration to form slurry with urea crystals;
sending 15-25% of the slurry with urea crystals to a crystallization cyclone, and returning the rest slurry to the crystallizer to continuously participate in the cooling crystallization process; and
and (3) carrying out concentrated liquid-solid separation on the slurry sent to the crystallization cyclone to obtain ultrapure solid automotive urea with the water content of less than or equal to 2.5 percent and the biuret content of less than or equal to 0.15 percent, and drying.
2. The method of claim 1, wherein the first concentration is between 60% and 80% by mass.
3. The method of claim 2, wherein the first concentration is 60% or 70% or 75% or 78% by mass.
4. The method of claim 3, wherein the first concentration is 78% by mass.
5. The method for preparing high-purity solid automotive urea according to claim 1, wherein the crystallization initial temperature of the circulating cooling circulating crystallization is 70 ℃ and the cooling crystallization end temperature is 40-60 ℃.
6. The method for preparing high purity solid vehicular urea according to claim 5, wherein the cooling crystallization end point temperature of the circulating cooling circulating crystallization is 40 ℃ or 45 ℃ or 50 ℃ or 55 ℃ or 60 ℃.
7. The method of claim 6, wherein the cooling crystallization end point temperature of the recirculating cooling recirculating crystallization is 40 ℃.
8. The method according to claim 1, wherein the post-dryer product has a moisture content of 0.2% or less and a biuret content of 0.15% or less.
9. A high purity solid automotive urea obtained by the production method according to any one of claims 1 to 8.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116082194A (en) * | 2022-12-31 | 2023-05-09 | 江苏可兰素环保科技有限公司 | Process for removing biuret from urea |
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Application publication date: 20220412 |