CN109761800B - Method for removing oxalic acid by continuous crystallization in glyoxylic acid production process - Google Patents
Method for removing oxalic acid by continuous crystallization in glyoxylic acid production process Download PDFInfo
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- CN109761800B CN109761800B CN201811589152.4A CN201811589152A CN109761800B CN 109761800 B CN109761800 B CN 109761800B CN 201811589152 A CN201811589152 A CN 201811589152A CN 109761800 B CN109761800 B CN 109761800B
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Abstract
The invention relates to a method for removing oxalic acid by continuous crystallization in the production process of glyoxylic acid, belonging to the technical field of chemical synthesis. The method comprises the following steps: firstly, continuously adding the concentrated solution of the concentration process into a primary precooler, and after the temperature of a system is reduced to be below 40 ℃, flowing into a primary crystallizer for cooling crystallization; secondly, when the feed liquid in the primary crystallizer continuously flows and is cooled to below 35 ℃, the feed liquid enters a centrifugal machine for solid-liquid separation to obtain separation mother liquid and solid-phase oxalic acid with the oxalic acid content of less than 1.0 percent, and the separation mother liquid enters an underground tank; thirdly, pumping the separated mother liquor into a secondary precooler through a centrifugal pump, and when the temperature is reduced to about 10 ℃, feeding the separated mother liquor into a secondary crystallizer for secondary temperature reduction and crystallization; and fourthly, when the feed liquid in the secondary crystallizer continuously flows and is cooled to 0 to-5 ℃, feeding the feed liquid into a centrifuge for solid-liquid separation to obtain separated mother liquid and solid-phase oxalic acid with the oxalic acid content of less than 0.5%, and feeding the separated mother liquid into an underground tank.
Description
Technical Field
The invention relates to a glyoxylic acid production process, in particular to a method for removing oxalic acid by continuous crystallization in the glyoxylic acid production process, belonging to the technical field of chemical synthesis.
Background
Glyoxylic acid is an important chemical raw material, is mainly used as a flavoring agent and a fixative of cosmetics and is used for pharmacy. Currently, there are 4 preparation methods commonly used, specifically:
1. the oxalic acid electrolytic oxalic acid solution is electrolyzed and reduced to generate dilute glyoxylic acid solution, and then the dilute glyoxylic acid solution is evaporated, concentrated, frozen and filtered to be gradually concentrated, and finally the qualified product is obtained and packaged.
2. The oxidation method of glyoxal is that glyoxal is oxidized by air or oxygen under the action of catalyst to generate glyoxylic acid, and then the glyoxylic acid is refined and purified to obtain the finished product. In addition, dichloroacetic acid is condensed with sodium methoxide to obtain sodium dimethoxyacetate, and then the sodium dimethoxyacetate is hydrolyzed by hydrochloric acid to generate glyoxylic acid.
3. Putting sodium methoxide and methanol into a reaction tank by a dichloroacetic acid method, heating to 40-50 ℃, slowly dripping dichloroacetic acid, performing reflux reaction for 2 hours after the completion of condensation, then cooling to room temperature, filtering, washing with methanol, and combining washing filtrates to obtain a dimethoxy sodium acetate methanol solution. Concentrating the solution under reduced pressure to dryness, adding 2.8 parts of hydrochloric acid, heating in water bath, stirring to obtain paste to obtain hydrolysate, heating to 90 deg.C, cooling to about 10 deg.C, filtering, and separating to obtain the final product.
4. The ozonization reduction method of maleic anhydride dissolves maleic anhydride in formic acid, and then ozone is introduced for oxidation, and then zinc powder and the like are used for reduction to obtain glyoxylic acid.
The glyoxal oxidation method is commonly used, at present, the glyoxal nitric acid oxidation method in China completely adopts an intermittent kettle type production process, the quantity of equipment is large, the operation of workers is frequent, the labor intensity is high, the working environment is poor, the oxalic acid content in the product is high, the product is not easy to reach the standard, and the product quality stability is poor. Therefore, the defects in the existing production process are urgently needed to be changed, and the industrial production preparation method which can improve the working environment, improve the efficiency, improve the product quality, reduce the production cost and is safe and stable in operation is invented.
Disclosure of Invention
The invention aims to provide a method for continuously crystallizing and removing oxalic acid in the production process of glyoxylic acid, which has the advantages of less residual oxalic acid, stable quality, easy control and operation, high capacity, low operation cost and the like.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the method for removing oxalic acid by continuous crystallization in the production process of glyoxylic acid specifically comprises the following steps:
step one, continuously adding a concentrated solution in a concentration process into a primary precooler, and after the temperature of a system is reduced to be below 40 ℃, flowing into a primary crystallizer for cooling crystallization;
step two, when the feed liquid in the primary crystallizer continuously flows and is cooled to below 35 ℃, the feed liquid enters a centrifugal machine for solid-liquid separation to obtain separated mother liquid and solid-phase oxalic acid, the oxalic acid content of which is lower than 1.0 percent, the oxalic acid is recycled after being washed and dried, and the separated mother liquid enters an underground tank;
pumping the separated mother liquor in the primary crystallization equipment into a secondary precooler through a centrifugal pump, and cooling to about 10 ℃ or below, and then feeding the mother liquor into a secondary crystallizer for secondary cooling crystallization;
and step four, when the feed liquid in the secondary crystallizer continuously flows and is cooled to 0 to-5 ℃, the feed liquid enters a centrifugal machine for solid-liquid separation to obtain separated mother liquid and solid-phase oxalic acid, the oxalic acid content of which is lower than 0.5%, the oxalic acid is washed with water and dried and then recycled, and the separated mother liquid enters an underground tank.
Preferably, the mass concentration of the glyoxylic acid in the concentrated solution after concentration and dehydration is 33 to 36 weight percent.
The primary crystallization temperature is 25-30 ℃, and the primary crystallization time is 15-30 minutes. Further, the flow rate of the primary crystallization was controlled at 25L/min.
The secondary crystallization temperature is 0 to-5 ℃, and the secondary crystallization time is 15 to 30 minutes. Further, the flow rate of the secondary crystallization was controlled at 20L/min.
The mass concentration of the glyoxylic acid contained in the oxalic acid after twice crystallization is less than or equal to 0.02 percent.
Compared with the prior art, the invention has the beneficial effects that:
1, the product quality is obviously improved, the oxalic acid content in a finished product is less than or equal to 0.5 percent, and the real oxalic acid content in domestic products is more than or equal to 1.0 percent;
by adopting the continuous sampling detection in the reproduction process of the device, the average data can reach the following values:
primary crystallization mother liquor: glyoxylic acid 36.8 percent and oxalic acid 0.97 percent;
secondary crystallization mother liquor: glyoxylic acid 37.3% and oxalic acid 0.36%.
2, the domestic problem that the glyoxylic acid is simultaneously crystallized when the glyoxylic acid is crystallized at the temperature of below 0 ℃ is thoroughly solved;
3, the quality is stable;
and 4, the labor intensity of workers is reduced, the working environment is improved, and the operating cost is reduced.
In addition, the invention adopts a DCS control, continuous feeding, discharging and automatic separation process method, thereby improving the working efficiency and the stability of the product; mainly reduces the oxalic acid content in the finished product; the production cost increase and the generation of solid waste caused by removing the oxalic acid by adopting a calcium salt method can be avoided.
Drawings
FIG. 1 is a schematic view of the structure of a two-stage continuous crystallization apparatus according to the present invention,
wherein, 1 a primary precooler, 2 a primary crystallizer, 3 a centrifugal machine, 4 underground tanks, 5 centrifugal pumps, 6 a secondary precooler and 7 a secondary crystallizer.
Detailed Description
The technical solution of the present invention will be further specifically described below by way of specific examples. It is to be understood that the practice of the invention is not limited to the following examples, and that any variations and/or modifications may be made thereto without departing from the scope of the invention.
In the present invention, all parts and percentages are by weight, unless otherwise specified, and the equipment and materials used are commercially available or commonly used in the art. The methods in the following examples are conventional in the art unless otherwise specified.
Example (b):
the secondary continuous crystallization equipment used for the method is formed by connecting primary crystallization equipment and secondary crystallization equipment in series, the primary crystallization equipment and the secondary crystallization equipment have the same composition, and the primary crystallization equipment comprises a primary precooler 1, a primary crystallizer 2, a centrifuge 3 and an underground tank 4 which are sequentially connected with the primary precooler; the pipeline of the underground tank is connected with a centrifugal pump 5, the centrifugal pump is connected with a secondary precooler 6 of secondary crystallization equipment, and the precooler of the secondary crystallization equipment is sequentially connected with a secondary crystallizer 7, a centrifugal machine and the underground tank.
The method for removing oxalic acid by continuous crystallization in the production process of glyoxylic acid comprises the following specific steps:
taking a concentrated solution obtained in the concentration process, wherein the mass concentration of glyoxylic acid in the concentrated solution is 33-36 wt%;
introducing the concentrated solution into a primary precooler 1 at a speed of about 25L/min, cooling to below 40 ℃ by the primary precooler, and entering a primary crystallizer 2 for cooling crystallization. The concentrated solution continuously flows in the crystallizer to reduce the temperature for about 20 minutes, and enters a centrifuge 3 for solid-liquid separation when the temperature of the feed liquid is less than or equal to 30 ℃. The oxalic acid obtained by separation is automatically washed, dried, packaged and recycled; the mother liquor obtained by separation enters an underground tank 4, is pumped into a secondary precooler 6 through a centrifugal pump 5 and is continuously cooled through the precooler at the speed of about 20L per minute until the material temperature is less than or equal to 10 ℃, and then enters a secondary crystallizer 7 for brine cooling crystallization.
And continuously flowing the mother liquor in a secondary crystallizer to reduce the temperature for about 20 minutes, and when the temperature of the feed liquid is less than or equal to minus 3 ℃, feeding the feed liquid into a centrifugal machine to carry out solid-liquid separation. And (4) automatically washing and drying the oxalic acid obtained by separation, and packaging. The frozen mother liquor obtained by centrifugation is processed in the next process.
In the continuous crystallization process, the detection results are as follows:
1, primary separation of mother liquor: glyoxylic acid 35.96%, oxalic acid 0.98%
Secondary separation of mother liquor: glyoxylic acid 36.45%, oxalic acid 0.38%
2, primary separation of mother liquor: glyoxylic acid 36.21% and oxalic acid 0.99%
Secondary separation of mother liquor: glyoxylic acid 36.78% and oxalic acid 0.35%
3, primary separation of mother liquor: glyoxylic acid 36.35 percent and oxalic acid 0.95 percent
Secondary separation of mother liquor: glyoxylic acid 36.81% and oxalic acid 0.37%.
The mass concentration of the glyoxylic acid contained in the oxalic acid after twice crystallization is less than or equal to 0.02 percent.
Comparative example:
under the same condition, the result of the data of the sample obtained by the intermittent crystallization process is as follows:
1, primary separation of mother liquor: glyoxylic acid 32.96%, oxalic acid 1.12%
Secondary separation of mother liquor: glyoxylic acid 33.45%, oxalic acid 0.82%
2, primary separation of mother liquor: glyoxylic acid 33.21% and oxalic acid 1.16%
Secondary separation of mother liquor: glyoxylic acid 33.78%, oxalic acid 0.81%
3, primary separation of mother liquor: glyoxylic acid 32.35%, oxalic acid 1.13%
Secondary separation of mother liquor: glyoxylic acid 32.81% and oxalic acid 0.85%.
According to the detection results, the product prepared by the method has stable quality, high yield and lower oxalic acid content, and the process method is suitable for industrial large-scale production.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.
Claims (4)
1. A method for removing oxalic acid by continuous crystallization in the production process of glyoxylic acid is characterized by comprising the following steps:
step one, continuously adding a concentrated solution obtained in the concentration process into a primary precooler, and after the temperature of a system is reduced to be below 40 ℃, flowing into a primary crystallizer for cooling crystallization; the mass concentration of the glyoxylic acid in the concentrated solution is 33-36 wt%;
step two, when the feed liquid in the primary crystallizer continuously flows and is cooled to below 35 ℃, the feed liquid enters a centrifugal machine for solid-liquid separation to obtain separated mother liquid and solid-phase oxalic acid, the oxalic acid content of which is lower than 1.0 percent, the oxalic acid is recycled after being washed and dried, and the separated mother liquid enters an underground tank;
pumping the separated mother liquor obtained in the last step into a secondary precooler through a centrifugal pump, and when the temperature is reduced to below 10 ℃, feeding the separated mother liquor into a secondary crystallizer for secondary cooling crystallization;
step four, when the feed liquid in the secondary crystallizer continuously flows and is cooled to 0 to-5 ℃, the feed liquid enters a centrifuge for solid-liquid separation to obtain separated mother liquid and solid-phase oxalic acid with the oxalic acid content of less than 0.5 percent, the oxalic acid is washed with water and dried and then recycled, and the separated mother liquid enters an underground tank;
the primary crystallization temperature is 25-30 ℃, and the primary crystallization time is 15-30 minutes; the secondary crystallization temperature is 0 to-5 ℃, and the secondary crystallization time is 15 to 30 minutes.
2. The method for removing oxalic acid by continuous crystallization in the production process of glyoxylic acid according to claim 1, characterized in that: the method adopts secondary continuous crystallization equipment to remove oxalic acid, the equipment is formed by connecting primary crystallization equipment and secondary crystallization equipment in series, the primary crystallization equipment and the secondary crystallization equipment have the same composition, and the primary crystallization equipment comprises a primary precooler, a primary crystallizer, a centrifuge and an underground tank which are sequentially connected with the primary precooler; the underground tank pipeline is connected with a centrifugal pump, the centrifugal pump is connected with a secondary precooler of secondary crystallization equipment, and the precooler of the secondary crystallization equipment is sequentially connected with a secondary crystallizer, a centrifugal machine and the underground tank.
3. The method for removing oxalic acid by continuous crystallization in the production process of glyoxylic acid according to claim 1, characterized in that: the mass concentration of the glyoxylic acid contained in the oxalic acid after twice crystallization is less than or equal to 0.02 percent.
4. The method for removing oxalic acid by continuous crystallization in the production process of glyoxylic acid according to claim 1, characterized in that: the flow rate of the primary crystallization was controlled at 25L/min, and the flow rate of the secondary crystallization was controlled at 20L/min.
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| CN111647911B (en) * | 2020-03-27 | 2022-09-13 | 昆明理工大学 | Process for removing magnesium ions in electrolytic manganese anolyte |
| CN114684879A (en) * | 2020-12-25 | 2022-07-01 | 中核四0四有限公司 | One-pass oxalic acid oxidation method |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3132006A1 (en) * | 1981-08-13 | 1983-03-03 | Chemische Werke Hüls AG, 4370 Marl | Process for preparing glyoxylic acid |
| CN1740133A (en) * | 2005-09-29 | 2006-03-01 | 王金锋 | Technological process of purifying and refining glyoxylic acid |
| CN102786410A (en) * | 2012-07-26 | 2012-11-21 | 湖北省宏源药业有限公司 | Treating method and apparatus for reaction solution produced in synthesis of glyoxalic acid through nitric acid oxidation of glyoxal |
| CN103896761A (en) * | 2014-03-18 | 2014-07-02 | 湖北省宏源药业有限公司 | Method for composite oxidation and synthesis of glyoxalic acid |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3132006A1 (en) * | 1981-08-13 | 1983-03-03 | Chemische Werke Hüls AG, 4370 Marl | Process for preparing glyoxylic acid |
| CN1740133A (en) * | 2005-09-29 | 2006-03-01 | 王金锋 | Technological process of purifying and refining glyoxylic acid |
| CN102786410A (en) * | 2012-07-26 | 2012-11-21 | 湖北省宏源药业有限公司 | Treating method and apparatus for reaction solution produced in synthesis of glyoxalic acid through nitric acid oxidation of glyoxal |
| CN103896761A (en) * | 2014-03-18 | 2014-07-02 | 湖北省宏源药业有限公司 | Method for composite oxidation and synthesis of glyoxalic acid |
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