阅读说明：本技术 一种从不合格柠檬酸钠母液中提取苹果酸的工艺方法 (Process method for extracting malic acid from unqualified sodium citrate mother liquor ) 是由 于海彬 厉成伟 魏彩霞 范开明 张念臻 张志海 于 2020-12-08 设计创作，主要内容包括：本发明属于不合格柠檬酸的处理技术领域,具体涉及一种从不合格柠檬酸钠母液中提取苹果酸的工艺方法,将不合格柠檬酸钠母液先经絮凝、过滤、酸化、冷结晶、固液分离、色谱分离获得提余液；提余液再分别经中和、浓缩、铵化、酸化、结晶、过滤等步骤获得苹果酸粗品；苹果酸粗品再分别经溶解、蒸发结晶、离心、烘干等步骤获得成品苹果酸。本发明既保证了柠檬酸钠不合格母液主要成分柠檬酸得以有效回收,提高车间整体收率,降低环保负荷,又获得了附加值较高的副产品苹果酸。本发明提取苹果酸的工艺切实可行,获得的产品苹果酸纯度高、质量好。(The invention belongs to the technical field of treatment of unqualified citric acid, and particularly relates to a process method for extracting malic acid from unqualified sodium citrate mother liquor, which comprises the steps of flocculating, filtering, acidifying, cold crystallizing, performing solid-liquid separation and performing chromatographic separation on the unqualified sodium citrate mother liquor to obtain raffinate; respectively carrying out neutralization, concentration, ammonification, acidification, crystallization, filtration and other steps on the raffinate to obtain a malic acid crude product; and respectively carrying out the steps of dissolving, evaporating and crystallizing, centrifuging, drying and the like on the malic acid crude product to obtain the finished malic acid. The method ensures that the main component citric acid of the unqualified sodium citrate mother liquor can be effectively recovered, improves the overall yield of a workshop, reduces the environmental protection load, and obtains the byproduct malic acid with higher added value. The process for extracting the malic acid is feasible, and the obtained malic acid product has high purity and good quality.)

1. A process method for extracting malic acid from unqualified sodium citrate mother liquor is characterized by sequentially comprising the following steps:

(1) adding a flocculating agent into the unqualified sodium citrate mother liquor for flocculation and filtration;

(2) acidifying the filtrate;

(3) carrying out cold crystallization on the acidizing fluid, wherein the cold crystallization time is controlled to be 12-16h, and the end point temperature is controlled to be 8-12 ℃;

(4) carrying out solid-liquid separation on the crystal slurry to obtain a byproduct sodium sulfate;

(5) heating the mother liquor of solid-liquid separation, performing chromatographic separation, and recovering citric acid;

(6) neutralizing the raffinate subjected to chromatographic separation, controlling the pH value to be 5.0-8.0, and concentrating until the concentration of the solution is 50-70%;

(7) transferring the concentrated solution into a crystallizer, introducing carbon dioxide and ammonia gas, and stopping when the pH value of the solution is 6.0-8.0;

(8) adjusting the pH value of the solution in the crystallizer to be 1.0-3.0 and the temperature to be 8-15 ℃, and selectively crystallizing malic acid;

(9) carrying out solid-liquid separation on the crystallized malic acid to obtain a malic acid crude product;

(10) and refining the malic acid crude product to obtain a finished product malic acid.

2. The process method for extracting malic acid from the unqualified sodium citrate mother liquor according to claim 1, wherein the flocculant in the step (1) is cationic polyacrylamide, the addition ratio is 20-40 g/ton of sodium citrate, the flocculation time is 30-60 minutes, and the filtration is plate filtration or plate-and-frame filter pressing.

3. The process method for extracting malic acid from the unqualified sodium citrate mother liquor according to claim 1, wherein the acidification treatment in the step (2) adopts 60-80% by mass of sulfuric acid, and the addition amount of the sulfuric acid is controlled so that the molar ratio of the sulfuric acid to the sodium citrate is 3.05-3.1: 2.

4. The process method for extracting malic acid from the unqualified sodium citrate mother liquor according to claim 1, wherein the solid-liquid separation in the step (4) adopts a plastic-lined flat plate centrifuge.

5. The process for extracting malic acid from the unqualified sodium citrate mother liquor as claimed in claim 1, wherein the chromatographic separation in step (5) is performed by a chromatographic column, and the separation medium is XA-345 anion resin.

6. The process method for extracting malic acid from the unqualified sodium citrate mother liquor according to claim 1, wherein the neutralization treatment in the step (6) is performed by using sodium hydroxide, and the concentration is performed by multi-effect concentration which is 3-5 effect concentration.

7. The process method for extracting malic acid from the unqualified sodium citrate mother liquor according to claim 1, wherein the concentration of dissolved ammonia in the solution obtained by introducing carbon dioxide and ammonia gas into the concentrated solution obtained in the step (7) is 5-10 ppm.

8. The process for extracting malic acid from unqualified sodium citrate mother liquor according to claim 1, wherein the regulator used for regulating pH in step (8) is ammonium bisulfate.

9. The process for extracting malic acid from the unqualified sodium citrate mother liquor according to claim 1, wherein the solid-liquid separation in step (9) is filtration.

10. The process method for extracting malic acid from the unqualified sodium citrate mother liquor according to claim 1, wherein the refining process in the step (10) comprises the steps of dissolving in water, evaporative crystallization, centrifugation and drying, wherein the temperature of the evaporative crystallization is controlled to be 60-80 ℃, the vacuum degree is controlled to be-0.08-0.09 MPa, the solid content reaches 40-50%, and the malic acid is dried by adopting clean air at 50-80 ℃ after centrifugal separation.

Technical Field

The invention belongs to the technical field of treatment of unqualified citric acid, and particularly relates to a process method for extracting malic acid from unqualified sodium citrate mother liquor.

Background

Malic acid, also called 2-hydroxysuccinic acid, can directly participate in human metabolism due to its special position in the metabolic pathway of substances, and can be directly absorbed by human body, so as to provide energy to human body in short time, relieve fatigue, and exert the effects of resisting fatigue and recovering physical strength rapidly. The malic acid has wide effects and effects, has the effects of expelling toxin and beautifying, has the effect of losing weight and slimming, can accelerate intestinal tract movement in a human body, can effectively prevent and relieve constipation diseases, and can reduce the content of fat in the human body.

The citric acid mother liquor contains a certain amount of heteropolyacid, sodium citrate is usually produced by using the citric acid mother liquor, along with continuous concentration and crystallization, the heteropolyacid in the sodium citrate mother liquor is continuously converted and accumulated, the circulation is carried out to a certain degree, the unqualified sodium citrate mother liquor is discharged, the citric acid yield is reduced due to the discharge of the sodium citrate, the COD (chemical oxygen demand) of the unqualified sodium citrate mother liquor is very high, the environment-friendly treatment load can be increased, the heteropolyacid in the mother liquor mainly exists in a malic acid form, the content can reach 10%, the heteropolyacid is directly discharged, the resource is wasted, and the environment-friendly treatment load is increased. In the prior patents, no report about the extraction of malic acid from unqualified sodium citrate mother liquor is found.

Disclosure of Invention

Aiming at the technical problems existing at present, the invention provides a process method for extracting malic acid from unqualified sodium citrate mother liquor, aiming at recovering citric acid from unqualified sodium citrate mother liquor and simultaneously extracting malic acid with higher added value, improving the comprehensive economic benefit of enterprises, reducing the load of wastewater treatment and reducing pollution.

The technical scheme of the invention is as follows:

a process method for extracting malic acid from unqualified sodium citrate mother liquor sequentially comprises the following steps:

(1) adding a flocculating agent into the unqualified sodium citrate mother liquor for flocculation and filtration;

(2) acidifying the filtrate;

(3) carrying out cold crystallization on the acidizing fluid, wherein the cold crystallization time is controlled to be 12-16h, and the end point temperature is controlled to be 8-12 ℃;

(4) carrying out solid-liquid separation on the crystal slurry to obtain a byproduct sodium sulfate which can be directly sold;

(5) heating the mother liquor of solid-liquid separation, performing chromatographic separation, and recovering citric acid;

(6) neutralizing the raffinate subjected to chromatographic separation, controlling the pH value to be 5.0-8.0, and concentrating until the concentration of the solution is 50-70%;

(7) transferring the concentrated solution into a crystallizer, introducing carbon dioxide and ammonia gas, and stopping when the pH value of the solution is 6.0-8.0;

(8) adjusting the pH value of the solution in the crystallizer to be 1.0-3.0, and the temperature to be 8-15 ℃, and selectively crystallizing malic acid;

(9) carrying out solid-liquid separation on the crystallized malic acid to obtain a malic acid crude product;

(10) and refining the malic acid crude product to obtain a finished product malic acid.

For the citric acid production process, the concentration of the produced sodium citrate is relatively stable, and the amount of the flocculating agent and the amount of the sulfuric acid and the like can be further determined according to the content of the sodium citrate.

Preferably, the flocculating agent in the step (1) adopts cationic polyacrylamide, the adding proportion is 20-40 g/ton sodium citrate, the flocculating time is 30-60 minutes, and the filtration adopts plate filtration or plate-and-frame filter pressing.

Preferably, the acidification treatment in the step (2) adopts 60-80% of sulfuric acid by mass concentration, and the adding amount of the sulfuric acid is controlled in such a way that the molar ratio of the sulfuric acid to the sodium citrate is 3.05-3.1: 2.

And (4) performing solid-liquid separation in the step (4) by adopting a plastic-lined flat plate centrifuge.

Preferably, the chromatographic separation in step (5) is performed by means of a chromatographic column, the separation medium being an XA-345 anionic resin.

Preferably, the neutralization treatment in the step (6) utilizes sodium hydroxide treatment, and the concentration adopts multi-effect concentration, namely 3-5-effect concentration.

Preferably, the concentration of dissolved ammonia in the solution obtained by introducing carbon dioxide and ammonia into the concentrated solution obtained in the step (7) is 5-10 ppm.

Preferably, the adjusting agent used to adjust the pH of the solution in step (8) is ammonium bisulfate.

Preferably, the solid-liquid separation in step (9) is filtration.

Preferably, the refining process in the step (10) comprises the steps of adding water for dissolution, evaporating for crystallization, centrifuging and drying, wherein the temperature of the evaporating for crystallization is controlled to be 60-80 ℃, the vacuum degree is controlled to be-0.08-0.09 MPa, the solid content reaches 40-50%, and the purified air at 50-80 ℃ is adopted for drying after centrifugal separation.

In the invention, the unqualified sodium citrate mother liquor is added with a flocculating agent for flocculation and filtration, impurities such as protein, colloid and the like are removed, the unqualified sodium citrate mother liquor is subjected to acidification pretreatment, the main component is citric acid, cold crystallization and solid-liquid separation are utilized to obtain sodium sulfate, the cold crystallization is adopted to control time and end point temperature, so that higher crystallization rate can be obtained, the crystal forming is better, the required time is short, and the energy consumption is saved. The chromatographic separation in the step (5) is completed through a chromatographic column, and the separation medium is resin XA-345 anion resin with high selectivity to citric acid, and the principle is that under the acidic condition, the citric acid and other miscellaneous acids have different residence time on the resin, and the citric acid is selectively recovered in stages, so that the citric acid is recovered separately, and the main component of malic acid in the raffinate; neutralizing the raffinate obtained by chromatographic separation by using sodium hydroxide, wherein the pH value is controlled to be 5.0-8.0, preferably 6.0-7.5, and the neutralization treatment is carried out to convert malic acid into corresponding sodium salt which can react with carbon dioxide and ammonia gas in the subsequent process; if the pH value is too low, the ammonia loss is large, and if the pH value is too high, the carbon dioxide loss is also large; after neutralization treatment, organic acid is converted into organic acid salt, the solubility is increased, and in order to further reduce the volume of the solution and facilitate subsequent ammonification reaction, the solution needs to be concentrated in multiple effects, and the concentration is carried out in 4-5 effects. Because ionization balance exists, the pH value of the solution is still maintained to be 5.0-8.0, and carbon dioxide and ammonia gas play a role to the maximum extent in the subsequent steps. Similarly, in order to prevent the concentrated liquid from being excessively accumulated and causing crystallization, the concentration of the concentrated liquid is controlled to be 50-70%.

Transferring the concentrated solution into a closed crystallizer, and for subsequent transformation and acidification, mixing carbon dioxide and ammonia gas at room temperature according to the ratio of 1: and (3) introducing the solution into a crystallizer at a molar ratio of 1, wherein the introduction of carbon dioxide and ammonia gas is equivalent to the substitution of ammonium bicarbonate, but the introduction of gas can reduce the introduction of water and avoid the reduction of the concentration of the solution, and the reaction is completed when the concentration of dissolved ammonia in the solution reaches 5-10 ppm, wherein the pH value of the solution is 6.0-8.0. The malate has carboxyl and hydroxyl groups and is easy to participate in the reaction, while other heteropolyacids have low content and limited participation degree, so the malate is completely converted into ammonium salt, and the main components of the malate ammonium salt and the sodium salt of other heteropolyacids are adopted.

After the conversion of the ammonium malate salt is finished, adding a pH regulator ammonium bisulfate into the crystallizer, controlling the pH value to be 1.0-3.0, preferably 1.0-2.5, wherein most of the ammonium malate salt can be converted into malic acid under the condition, and the main component of the solution is sodium salts of malic acid and other miscellaneous acids.

Different organic acid crystallization conditions are different and have selectivity, and the malic acid has low solubility when the pH value is 1-2.5, which is the optimal crystallization condition. The crystallization temperature is too high or too low, so that the yield of the malic acid is reduced, and the purity is poor, so that the crystallization temperature is 8-15 ℃.

After obtaining a malic acid crude product, adding water to dissolve, evaporating and crystallizing, centrifuging, drying and other refining processes to obtain a malic acid product, wherein the evaporation temperature is controlled at 60-80 ℃, the vacuum degree is controlled at-0.08-0.09 MPa, the solid content reaches 40-50%, and after centrifugal separation, clean air at 50-80 ℃ is adopted to dry the malic acid product to obtain a finished product malic acid with the purity of 99-100%.

In the invention, sodium hydroxide is neutralized, and all the acid is converted into sodium salt, so that the salt formation of the mixed acid is realized, the solubility of malate is improved, and the concentration is further improved, and the higher the concentration of the malate is, the more the subsequent reaction is favorably carried out; introducing carbon dioxide and ammonia gas, wherein the mixed acid salt does not participate in the reaction, and only the malic acid sodium salt is converted into ammonium salt; only the ammonium malate salt can be converted into malic acid by adopting ammonium bisulfate, and the sodium salt of the heteropolyacid is not converted. The above operation is carried out, and the final purpose is to obtain malic acid and sodium salt of the heteropolyacid, and then carry out subsequent selective crystallization to realize the purification of the malic acid.

In conclusion, the method provided by the invention not only ensures that the main component citric acid of the unqualified sodium citrate mother liquor can be effectively recovered, improves the overall yield of a workshop, reduces the load of environmental protection treatment, but also obtains malic acid with higher added value. The process for extracting the malic acid is feasible, the obtained malic acid product has high purity and good quality, and the economic benefit of an enterprise is improved; the obtained malic acid has high purity and good quality.

Drawings

FIG. 1 is a process flow diagram of the process of the present invention.

Detailed Description

The following detailed description of specific embodiments of the present invention is provided to illustrate and explain the present invention and to be understood not to limit the present invention.

In the following examples the chromatographic separation is performed by means of a chromatographic column with separation medium XA-345 anion resin, the percentages being mass percentages.

Example 1

A process method for extracting malic acid from unqualified sodium citrate mother liquor comprises the following steps:

(1) flocculating the unqualified sodium citrate mother liquor by using cationic polyacrylamide, wherein the addition amount of the cationic polyacrylamide is 25 g/ton of sodium citrate, the flocculation time is 35 minutes, and then filtering by using a plate-type closed filter;

(2) acidifying the filtrate with 60% sulfuric acid at a molar ratio of sulfuric acid to sodium citrate of 3.05: 2;

(3) carrying out cold crystallization on the acidizing fluid, wherein the crystallization time is 12h, and the end point temperature is 12 ℃;

(4) carrying out solid-liquid separation on the crystal slurry to obtain a byproduct sodium sulfate with the purity of 99.0 percent and other quality indexes meeting the national standard requirements;

(5) heating the mother liquor, performing chromatographic separation, recovering citric acid, and returning the citric acid to the existing ion exchange workshop for further purification;

(6) neutralizing raffinate with sodium hydroxide to adjust pH value to 6.0, concentrating to 60% with four-effect concentration evaporator at 80 deg.C under-0.085 MPa;

(7) transferring the concentrated solution into a crystallizer, and introducing carbon dioxide and ammonia gas, wherein the molar ratio of the carbon dioxide to the ammonia gas is 1: 1, converting malate into ammonium salt, wherein the pH value is 6.5;

(8) adding ammonium bisulfate into the crystallizer to adjust the pH value to 2.5, controlling the temperature to be 15 ℃, and separating out malic acid crystals;

(9) filtering and washing the malic acid crystals, and transferring the malic acid crystals into a material melting tank;

(10) further carrying out evaporative crystallization, centrifugation and drying on the malic acid feed liquid to obtain a finished product malic acid, wherein the evaporation temperature is controlled at 60 ℃, the vacuum degree is controlled at-0.08 MPa, the solid content reaches 40%, and drying the malic acid feed liquid by adopting clean air at 80 ℃ after centrifugal separation; the average amount of finished L-malic acid obtained from each ton of unqualified sodium salt mother liquor is 35kg, the purity of malic acid is 99.2%, and other indexes meet the national standard requirements.

Example 2

A process method for extracting malic acid from unqualified sodium citrate mother liquor comprises the following steps:

(1) flocculating the unqualified sodium citrate mother liquor by using cationic polyacrylamide, wherein the addition amount of the cationic polyacrylamide is 30 g/ton of sodium citrate, the flocculation time is 45 minutes, and then filtering by using a plate-and-frame filter press;

(2) acidifying the filtrate with 70% sulfuric acid at a molar ratio of sulfuric acid to sodium citrate of 3.1: 2;

(3) carrying out cold crystallization on the acidizing fluid, wherein the crystallization time is 15h, and the end point temperature is 10 ℃;

(4) carrying out solid-liquid separation on the crystal slurry to obtain a byproduct sodium sulfate with the purity of 99.1 percent and other quality indexes meeting the national standard requirements;

(5) heating the mother liquor, performing chromatographic separation, recovering citric acid, and returning the citric acid to the existing ion exchange workshop for further purification;

(6) neutralizing raffinate with sodium hydroxide to adjust pH value to 7.0, concentrating to 70% with five-effect concentration evaporator at 85 deg.C under-0.09 MPa;

(7) transferring the concentrated solution into a crystallizer, introducing carbon dioxide and ammonia gas, and converting malate into ammonium salt, wherein the molar ratio of the carbon dioxide to the ammonia gas is 1: 1, pH value is 7.0;

(8) adding ammonium bisulfate into the crystallizer to adjust the pH value to 2.2, controlling the temperature to be 12 ℃, and separating out malic acid crystals;

(9) filtering and washing the malic acid crystals, and transferring the malic acid crystals into a material melting tank;

(10) the malic acid liquid is further evaporated, crystallized, centrifuged and dried to obtain the finished product malic acid, wherein the evaporation temperature is controlled at 65 ℃, the vacuum degree is controlled at-0.05 MPa, the solid content reaches 45%, the malic acid liquid is dried by clean air at 70 ℃ after centrifugal separation, the finished product L-malic acid obtained by each ton of unqualified sodium salt mother liquor is 45kg, the purity of the malic acid is 99.5%, and other indexes meet the national standard requirements.

Example 3

A process method for extracting malic acid from unqualified sodium citrate mother liquor comprises the following steps:

(1) flocculating the unqualified sodium citrate mother liquor by using cationic polyacrylamide, wherein the addition amount of the cationic polyacrylamide is 35 g/ton of sodium citrate, the flocculation time is 60 minutes, and then filtering by using a plate-type closed filter;

(2) acidifying the filtrate with 80% sulfuric acid at a molar ratio of sulfuric acid to sodium citrate of 3.08: 2;

(3) carrying out cold crystallization on the acidizing fluid, wherein the crystallization time is 16h, and the end point temperature is 8 ℃;

(4) carrying out solid-liquid separation on the crystal slurry to obtain a byproduct sodium sulfate with the purity of 99.1 percent and other quality indexes meeting the national standard requirement, and directly selling the product;

(5) heating the mother liquor, performing chromatographic separation, recovering citric acid, and returning the citric acid to the existing ion exchange workshop for further purification;

(6) neutralizing raffinate with sodium hydroxide to adjust pH value to 7.5, concentrating to 65% with four-effect concentration evaporator at 85 deg.C under-0.092 MPa;

(7) transferring the concentrated solution into a crystallizer, and introducing carbon dioxide and ammonia gas, wherein the molar ratio of the carbon dioxide to the ammonia gas is 1: 1, converting malate into ammonium salt, wherein the pH value is 7.5;

(8) adding ammonium bisulfate into the crystallizer to adjust the pH value to 1.8, controlling the temperature to be 10 ℃, and separating out malic acid crystals;

(9) filtering and washing the malic acid crystals, and transferring the malic acid crystals into a material melting tank;

(10) the malic acid liquid is further evaporated, crystallized, centrifuged and dried to obtain the finished product malic acid, wherein the evaporation temperature is controlled at 80 ℃, the vacuum degree is controlled at-0.09 MPa, the solid content reaches 50%, the malic acid liquid is dried by using clean air at 60 ℃ after centrifugal separation, the finished product L-malic acid obtained by each ton of unqualified sodium salt mother liquor is 40kg, the purity of the malic acid is 99.4%, and other indexes meet the national standard requirements.

According to the process method, 30-50 kg of finished L-malic acid can be extracted from each ton of unqualified sodium salt mother liquor on average, the purity of the finished malic acid is more than or equal to 99%, and all indexes meet the relevant national standards. The method ensures that the citric acid which is the main component of the unqualified sodium citrate mother liquor can be effectively recovered, improves the overall yield of a workshop, reduces the load of environmental protection treatment, and obtains the malic acid with higher added value. The process for extracting the malic acid is feasible, the obtained malic acid product has high purity and good quality, and the economic benefit of an enterprise is improved; the obtained malic acid has high purity and good quality.