CN111233005A - Cyanamide freeze concentration method - Google Patents
Cyanamide freeze concentration method Download PDFInfo
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- CN111233005A CN111233005A CN202010091229.6A CN202010091229A CN111233005A CN 111233005 A CN111233005 A CN 111233005A CN 202010091229 A CN202010091229 A CN 202010091229A CN 111233005 A CN111233005 A CN 111233005A
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- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C3/00—Cyanogen; Compounds thereof
- C01C3/16—Cyanamide; Salts thereof
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Abstract
The invention discloses a method for freezing and concentrating cyanamide, which comprises the following steps: reacting lime nitrogen with water to perform hydrolysis reaction, introducing carbon dioxide gas with the concentration of more than 50% at a certain temperature and pH to perform carbonization and decalcification, and preparing a cyanamide solution with a certain concentration; then conveying the solution to a precooler to be precooled to-5 ℃; introducing the pre-cooled solution into a first-stage ice making machine for ice-liquid separation and concentration, and controlling the temperature of the solution to be below 7 ℃; then, introducing the mixture into a secondary ice machine to separate and concentrate ice and liquid, and controlling the temperature to be below 12 ℃; then introducing into a three-stage ice making machine for ice-liquid separation and concentration, and controlling the temperature to be 17 ℃ below zero; introducing into a four-stage ice making machine to separate and concentrate ice and liquid, controlling the temperature at minus 22 ℃, and finally obtaining cyanamide solution with the concentration of more than 30%; the process omits the concentration process of the conventional cyanamide process, reduces the initial equipment investment, saves the energy consumption of concentration process equipment, and simultaneously avoids all adverse effects of concentration on the product quality.
Description
Technical Field
The invention relates to the field of chemical product production, and particularly relates to a method for freeze concentration of cyanamide.
Background
Since the beginning of the last 50 th century, researchers have been focusing on freeze concentration, the technology of freeze concentration has been studied for a long time. The Eindhoven university of the Netherlands (Anguhenchen university) Thijssen et al successfully used Ostwald ripening to manufacture large ice crystals in the 70 s, and established mathematical models of ice crystal growth and seed size and addition, so that the freeze concentration technology is applied to industrial production. The Grenco freezing concentration equipment manufactured by the method is used for concentrating fruit juice, wine, dairy products and the like in the food industry, and high-quality products are obtained. With the intensive research of numerous scholars and the continuous improvement of experimental facilities, the research results of the freeze concentration technology are frequently reported in recent years. The domestic freeze concentration technology starts late, the application industry is centralized, the food industries such as fruit juice, wine brewing and the like are the main ones, along with the technical progress of freeze concentration and the domestic introduction and development of foreign advanced technologies, the freeze concentration technology has entered various industries in recent years, becomes an indispensable part of the concentration process, and the freeze concentration technology of chemical products has not been researched too much.
At present, 30% cyanamide solution is produced by adopting a process of one-time reaction and evaporation concentration. The method comprises the steps of reacting lime nitrogen with water to perform hydrolysis reaction, introducing carbon dioxide gas with the concentration of more than 50% to perform carbonization decalcification, controlling the reaction temperature to be 15-20 ℃, controlling the pH value of a solution to be 7.0-7.5 to prepare a 10% -16% cyanamide solution, filtering, adjusting the pH value of the cyanamide solution to be about 4.5 by using an H3PO4 solution with the content of 85%, and concentrating the solution to be 30% by using an evaporator. The method is characterized in that a thin film evaporator is adopted for concentration in the early stage of the production of the cyanamide, because the evaporator has high energy consumption, strict requirements on evaporation conditions and high evaporation temperature, the cyanamide is easily converted into the dicyandiamide, the product quality is unstable, and the evaporator has explosion danger in the evaporation process, the evaporator is gradually replaced by a novel energy-saving and high-efficiency evaporator (such as an MVR evaporator, a low-temperature vacuum evaporator and the like), the problems of the thin film evaporator are effectively improved, the evaporation concentration is more energy-saving, high-efficiency and safer, but the problem that the cyanamide is converted into the dicyandiamide due to high temperature in the evaporation process also exists. And the reduction of the evaporation temperature can lead to the problems of overlarge evaporation unit, increased initial investment cost, increased energy consumption, reduced evaporation efficiency and the like.
Disclosure of Invention
The invention solves the problems that in the prior art, the existing film evaporator is adopted for concentration in the early stage of cyanamide production, and because the evaporator has high energy consumption, strict requirements on evaporation conditions, high evaporation temperature, unstable product quality and explosion danger in the evaporation process, the cyanamide is easily converted into dicyandiamide, the evaporator is gradually replaced by a novel energy-saving and high-efficiency evaporator (such as an MVR evaporator, a low-temperature vacuum evaporator and the like), the novel evaporator effectively improves the problems of the film evaporator, so that the evaporation concentration becomes more energy-saving, high-efficiency and safer, but the problem that the cyanamide is converted into dicyandiamide in the evaporation process because of higher temperature also exists. The single-step reduction of the evaporation temperature can lead to the problems of overlarge evaporation unit, increased initial investment cost, increased energy consumption, reduced evaporation efficiency and the like, and the method for freeze concentration of the cyanamide is provided.
The invention is realized by the following technical scheme:
a method for freeze concentration of cyanamide, comprising:
s1, reacting lime nitrogen with water to perform hydrolysis reaction, introducing carbon dioxide gas with the concentration of more than 50% at a certain temperature and pH to perform carbonization and decalcification, and preparing a cyanamide solution with a certain concentration;
s2, conveying the cyanamide solution prepared in the last step to a precooler for precooling, and precooling the temperature of the cyanamide solution from normal temperature to minus 5 ℃ after passing through the precooler;
s3, introducing the cyanamide solution precooled to minus 5 ℃ into a primary ice making machine for ice-liquid separation and concentration, and controlling the temperature of the cyanamide solution to minus 7 ℃;
s4, introducing the separated cyanamide solution at minus 7 ℃ into a secondary ice making machine for ice-liquid separation and concentration, and controlling the temperature to be minus 12 ℃;
s5, introducing the separated cyanamide solution at the temperature of minus 12 ℃ into a three-stage ice making machine for ice-liquid separation and concentration, and controlling the temperature to be minus 17 ℃;
s6, introducing the separated cyanamide solution at minus 17 ℃ into a four-stage ice making machine for ice-liquid separation and concentration, controlling the temperature at minus 22 ℃, and enabling the concentration of the finally obtained cyanamide solution to be more than 30%;
s7, adjusting acid of the finally obtained cyanamide solution with the concentration of 30%, separating out the cyanamide solution with high purity and less impurities, wherein the obtained cyanamide solution is low in temperature and beneficial to storage;
s8, carrying out solid-liquid separation on a small amount of cyanamide solution contained in the ice separated in the S3-S6 steps, putting the separated liquid into a first-stage ice making machine for ice-liquid separation and concentration again, recovering the cyanamide solution in the ice, fully utilizing the cold energy and trace cyanamide in the ice, participating in the preparation reaction of the cyanamide, further reducing the energy loss and saving the cost, wherein the cold source required by the concentration process is provided by a low-temperature water chilling unit.
Further, the dicyandiamide freezing concentration method is characterized in that the whole concentration system is controlled by a PLC (programmable logic controller), and the reaction time, the reaction temperature and the reaction PH value of each process step are controlled by the PLC according to process requirements.
Further, the cyanamide freezing concentration method is characterized in that the temperature of the hydrolysis reaction of lime nitrogen and water is controlled to be 15-20 ℃.
Further, in the method for freezing and concentrating cyanamide, the pH of a hydrolysis reaction solution generated by the action of lime nitrogen and water is controlled to be 7.0-7.5.
Further, the concentration of the cyanamide solution prepared by the hydrolysis reaction of lime nitrogen and water is controlled to be 10-16%.
At present, the process of one-time reaction, evaporation and concentration is mostly adopted for producing 30% cyanamide solution. The method comprises the steps of reacting lime nitrogen with water to perform hydrolysis reaction, introducing carbon dioxide gas with the concentration of more than 50% to perform carbonization decalcification, controlling the reaction temperature to be 15-20 ℃, controlling the pH value of a solution to be 7.0-7.5 to prepare a 10% -16% cyanamide solution, filtering, adjusting the pH value of the cyanamide solution to be about 4.5 by using an H3PO4 solution with the content of 85%, and concentrating the solution to be 30% by using an evaporator. Because the evaporator has high energy consumption, strict requirements on evaporation conditions and high evaporation temperature, cyanamide is easily converted into dicyandiamide due to the high evaporation temperature, the product quality is unstable, and the evaporator has explosion danger in the evaporation process, the evaporator is gradually replaced by a novel energy-saving and high-efficiency evaporator (such as an MVR evaporator, a low-temperature vacuum evaporator and the like), the novel evaporator effectively improves the problems of a thin film evaporator, so that evaporation concentration becomes more energy-saving, high-efficiency and safer, but the problem that cyanamide is converted into dicyandiamide due to the high temperature in the evaporation process also exists. And the reduction of the evaporation temperature can lead to the problems of overlarge evaporation unit, increased initial investment cost, increased energy consumption, reduced evaporation efficiency and the like. The process comprises the steps of carrying out three-time circulating reaction to enable the solution to reach more than 30%, filtering to obtain more than 10% of cyanamide solution through one-time reaction, continuously taking the cyanamide solution as mother liquor to carry out secondary feeding reaction, filtering to obtain more than 20% of cyanamide solution through the secondary reaction, carrying out three-time feeding reaction, and filtering to obtain more than 30% of cyanamide finished product. The invention provides a method for freezing and concentrating cyanamide, which comprises the steps of reacting lime nitrogen with water to generate hydrolysis reaction, introducing carbon dioxide gas with the concentration of more than 50% at a certain temperature and pH to perform carbonization and decalcification, and then preparing a cyanamide solution with a certain concentration; the method comprises the steps of pre-cooling a 15% cyanamide solution by a pre-cooler, pre-cooling the solution from normal temperature to minus 5 ℃, then entering a first-stage ice maker to separate and concentrate ice and liquid, controlling the temperature to minus 7 ℃, then entering a second-stage ice maker to separate and concentrate ice and liquid, controlling the temperature to minus 12 ℃, then entering a third-stage ice maker to separate and concentrate ice and liquid, controlling the temperature to minus 17 ℃, then entering a fourth-stage ice maker to separate and concentrate ice and liquid, controlling the temperature to minus 22 ℃, then easily reaching the concentration of the cyanamide solution to more than 30%, and then adjusting acid, wherein the purity of the separated liquid is high, impurities are few, and the temperature of the liquid is low, so that the storage is facilitated. The separated ice also contains a small amount of cyanamide solution which can be subjected to solid-liquid separation, the separated liquid can be put into a first-stage ice making machine for ice-liquid separation and concentration again, the concentration loss is reduced, the cost is saved, the cold quantity and the trace amount of the cyanamide in the separated ice are fully utilized to participate in the preparation reaction of the cyanamide, the energy consumption is further reduced, and the cost is saved. The cold source required by the concentration process is provided by a low-temperature water chilling unit.
In summary, the following beneficial effects of the invention are:
1. the method for freezing and concentrating the cyanamide omits the concentration process of the conventional cyanamide process, reduces the initial equipment investment, saves the energy consumption of concentration process equipment, and avoids all adverse effects of concentration on the product quality.
2. The invention relates to a method for freezing and concentrating cyanamide, which avoids the phenomenon that the quality of a product is influenced because the cyanamide is polymerized into dicyandiamide due to the rise of temperature in the traditional process by using a freezing and concentrating technology.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a process flow diagram of the present invention.
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 below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Examples
As shown in fig. 1, a method for freeze concentration of cyanamide, comprising: reacting lime nitrogen with water to perform hydrolysis reaction, introducing carbon dioxide gas with the concentration of more than 50% at a certain temperature and pH to perform carbonization and decalcification, and preparing a cyanamide solution with a certain concentration; conveying the cyanamide solution prepared in the last step to a precooler for precooling, and precooling the temperature of the cyanamide solution from normal temperature to minus 5 ℃ after passing through the precooler; introducing the cyanamide solution precooled to minus 5 ℃ into a primary ice machine for ice-liquid separation and concentration, and controlling the temperature of the cyanamide solution to minus 7 ℃; introducing the separated cyanamide solution at the temperature of minus 7 ℃ into a secondary ice machine for ice-liquid separation and concentration, and controlling the temperature to be minus 12 ℃; introducing the separated cyanamide solution at the temperature of minus 12 ℃ into a three-stage ice making machine for ice-liquid separation and concentration, and controlling the temperature to be minus 17 ℃; introducing the separated cyanamide solution at the temperature of minus 17 ℃ into a four-stage ice making machine for ice-liquid separation and concentration, controlling the temperature to be minus 22 ℃, and finally obtaining the cyanamide solution with the concentration of more than 30%; the finally obtained cyanamide solution with the concentration of 30% is subjected to acid adjustment to separate out the cyanamide solution with high purity and less impurities, and the obtained cyanamide solution is low in temperature and beneficial to storage; and (2) carrying out solid-liquid separation on a small amount of cyanamide solution contained in the ice separated in the steps S3-S6, putting the separated liquid into a primary ice making machine for ice-liquid separation and concentration again, recovering the cyanamide solution in the ice, fully utilizing the cold energy and trace cyanamide in the ice to participate in the cyanamide preparation reaction, further reducing the energy loss and saving the cost, wherein the cold source required by the concentration process is provided by a low-temperature water chilling unit, the whole set of concentration system is controlled by a PLC (programmable logic controller), the hydrolysis reaction temperature of the lime nitrogen under the action of water is controlled to be 15-20 ℃, the pH of the hydrolysis reaction solution under the action of the lime nitrogen under the action of water is controlled to be 7.0-7.5, and the concentration of the cyanamide solution prepared after the hydrolysis reaction of the lime nitrogen under the action of water is controlled to.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (5)
1. A method for freeze concentration of cyanamide, comprising:
s1, reacting lime nitrogen with water to perform hydrolysis reaction, introducing carbon dioxide gas with the concentration of more than 50% at a certain temperature and pH to perform carbonization and decalcification, and preparing a cyanamide solution with a certain concentration;
s2, conveying the cyanamide solution prepared in the last step to a precooler for precooling, and precooling the temperature of the cyanamide solution from normal temperature to minus 5 ℃ after passing through the precooler;
s3, introducing the cyanamide solution precooled to minus 5 ℃ into a primary ice making machine for ice-liquid separation and concentration, and controlling the temperature of the cyanamide solution to minus 7 ℃;
s4, introducing the separated cyanamide solution at minus 7 ℃ into a secondary ice making machine for ice-liquid separation and concentration, and controlling the temperature to be minus 12 ℃;
s5, introducing the separated cyanamide solution at the temperature of minus 12 ℃ into a three-stage ice making machine for ice-liquid separation and concentration, and controlling the temperature to be minus 17 ℃;
s6, introducing the separated cyanamide solution at minus 17 ℃ into a four-stage ice making machine for ice-liquid separation and concentration, controlling the temperature at minus 22 ℃, and enabling the concentration of the finally obtained cyanamide solution to be more than 30%;
s7, adjusting acid of the finally obtained cyanamide solution with the concentration of 30%, separating out the cyanamide solution with high purity and less impurities, wherein the obtained cyanamide solution is low in temperature and beneficial to storage;
s8, carrying out solid-liquid separation on a small amount of cyanamide solution contained in the ice separated in the S3-S6 steps, putting the separated liquid into a first-stage ice making machine for ice-liquid separation and concentration again, recovering the cyanamide solution in the ice, fully utilizing the cold energy and trace cyanamide in the ice, participating in the preparation reaction of the cyanamide, further reducing the energy loss and saving the cost, wherein the cold source required by the concentration process is provided by a low-temperature water chilling unit.
2. The method for freeze concentration of cyanamide according to claim 1, wherein the whole concentration system is controlled by PLC.
3. The method for freeze concentration of cyanamide as claimed in claim 1, wherein the temperature of hydrolysis reaction between the lime nitrogen and water is controlled to be 15-20 ℃.
4. The method for freeze concentration of cyanamide as claimed in claim 1, wherein the pH of the solution in which the reaction of lime nitrogen with water is hydrolyzed is controlled to 7.0-7.5.
5. The method for freeze concentration of cyanamide as claimed in claim 1, wherein the concentration of the cyanamide solution prepared by hydrolysis reaction of lime nitrogen with water is controlled to 10-16%.
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| CN202010091229.6A CN111233005A (en) | 2020-02-13 | 2020-02-13 | Cyanamide freeze concentration method |
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| CN202010091229.6A CN111233005A (en) | 2020-02-13 | 2020-02-13 | Cyanamide freeze concentration method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112723385A (en) * | 2020-12-30 | 2021-04-30 | 宁夏嘉峰化工有限公司 | Production method of high-quality 50% cyanamide |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB883319A (en) * | 1958-10-02 | 1961-11-29 | Kiichiro Sugino | Improvements in or relating to the production of cyanamide |
| CN1366466A (en) * | 2000-04-20 | 2002-08-28 | 梁保民 | Freeze concentration for aqueous solutions |
| CN102936211A (en) * | 2012-11-13 | 2013-02-20 | 宁夏宝马化工集团有限公司 | Method for continuously producing dicyandiamide |
| CN103922365A (en) * | 2014-04-10 | 2014-07-16 | 宁夏宝马化工集团有限公司 | Method for efficient synthesis of hydrogen cyanamide employing lime nitrogen |
| CN104445276A (en) * | 2014-12-08 | 2015-03-25 | 古浪鑫辉化工有限公司 | Method for efficiently preparing monocyanamide solution |
| CN206027694U (en) * | 2016-08-24 | 2017-03-22 | 宁夏宝马化工集团有限公司 | Lime nitrogen is hydrolysised and is cooled off reation kettle |
-
2020
- 2020-02-13 CN CN202010091229.6A patent/CN111233005A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB883319A (en) * | 1958-10-02 | 1961-11-29 | Kiichiro Sugino | Improvements in or relating to the production of cyanamide |
| CN1366466A (en) * | 2000-04-20 | 2002-08-28 | 梁保民 | Freeze concentration for aqueous solutions |
| CN102936211A (en) * | 2012-11-13 | 2013-02-20 | 宁夏宝马化工集团有限公司 | Method for continuously producing dicyandiamide |
| CN103922365A (en) * | 2014-04-10 | 2014-07-16 | 宁夏宝马化工集团有限公司 | Method for efficient synthesis of hydrogen cyanamide employing lime nitrogen |
| CN104445276A (en) * | 2014-12-08 | 2015-03-25 | 古浪鑫辉化工有限公司 | Method for efficiently preparing monocyanamide solution |
| CN206027694U (en) * | 2016-08-24 | 2017-03-22 | 宁夏宝马化工集团有限公司 | Lime nitrogen is hydrolysised and is cooled off reation kettle |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112723385A (en) * | 2020-12-30 | 2021-04-30 | 宁夏嘉峰化工有限公司 | Production method of high-quality 50% cyanamide |
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Application publication date: 20200605 |