CN118344250A - Resource recycling method for sodium citrate and sodium sulfate mixed solution - Google Patents

Resource recycling method for sodium citrate and sodium sulfate mixed solution Download PDF

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CN118344250A
CN118344250A CN202410481056.7A CN202410481056A CN118344250A CN 118344250 A CN118344250 A CN 118344250A CN 202410481056 A CN202410481056 A CN 202410481056A CN 118344250 A CN118344250 A CN 118344250A
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solution
sodium citrate
sodium sulfate
mother liquor
mother
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路娜
解永磊
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Saehan Tianjin Energy Saving And Environmental Protection Technology Co ltd
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Saehan Tianjin Energy Saving And Environmental Protection Technology Co ltd
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Abstract

The invention provides a resource recycling method of sodium citrate and sodium sulfate mixed solution, which comprises the following steps: firstly, carrying out freezing crystallization and solid-liquid separation on the mixed solution to obtain crude mirabilite and mother liquor A1, and determining a freezing crystallization temperature interval according to a concentration ratio interval of sodium sulfate and sodium citrate; then re-dissolving, evaporating and recrystallizing the obtained crude mirabilite to obtain refined anhydrous sodium sulfate; according to the mass ratio of sodium sulfate to sodium citrate in the mixed solution, determining that evaporating crystallization is carried out on the mother solution A1 by using the mother solution A1 or cooling crystallization is carried out on the mother solution A1 by using concentrated solution; and re-dissolving and re-crystallizing the coarse sodium citrate dihydrate obtained by crystallization to obtain the refined sodium citrate dihydrate. The method can carry out high-efficiency recovery treatment on the mixed solution with different sodium sulfate and sodium citrate concentration ratios, does not need to add additional medicament, has simple and easy process steps, wide application range and higher recovery rate, and can obtain a high-purity product.

Description

Resource recycling method for sodium citrate and sodium sulfate mixed solution
Technical Field
The invention belongs to the technical field of wastewater recovery treatment, and particularly relates to resource recovery and utilization of a sodium citrate and sodium sulfate mixed solution.
Background
Sodium-electricity positive electrode materials are generally prepared using a coprecipitation method, and specifically include: the method comprises the steps of taking sodium ferricyanide solution as a precipitator, carrying out coprecipitation reaction with transition metal solution, carrying out solid-liquid separation after the reaction, and drying to obtain the iron-based sodium-electricity anode material (FePB), wherein mother liquor after solid-liquid separation is a mixed solution containing sodium sulfate and sodium citrate, and one of the difficulties in separation of the system is that the proportion of sodium sulfate and sodium citrate components is unstable.
CN104557517B discloses a comprehensive treatment process of waste sodium citrate mother liquor, which comprises adding concentrated sulfuric acid into waste sodium citrate mother liquor, acidifying, settling, centrifuging to obtain anhydrous sodium sulfate and mother liquor, cooling and crystallizing the mother liquor, separating sodium sulfate decahydrate crystals, returning the crystallized liquor to a citric acid purification section for recovering citric acid, and recrystallizing the anhydrous sodium sulfate and sodium sulfate decahydrate crystals to obtain sodium sulfate. The method for treating the sodium citrate-sodium sulfate mixed solution in the patent needs to additionally introduce a concentrated sulfuric acid reagent to convert sodium citrate into citric acid and then separate the citric acid from sodium sulfate, and is only suitable for waste liquid generated in the citric acid production process, and the proportion of the sodium citrate-sodium sulfate mixed solution generated in other industries is different, so that the applicability of the technical scheme in the invention is limited.
In order to improve the recovery rate of simple substance salt and realize the resource recovery and reutilization of mixed salt solution, a resource recovery and reutilization method aiming at mixed solution with different sodium sulfate and sodium citrate concentration ratios is needed.
Disclosure of Invention
The invention aims to provide a resource recycling method for sodium citrate and sodium sulfate mixed solution.
To achieve the above object, the present invention proposes the following solution:
The invention provides a resource recycling method of sodium citrate and sodium sulfate mixed solution, which comprises the following steps:
S1, freezing and crystallizing the mixed solution, and then filtering and separating to obtain coarse mirabilite and mother liquor A1; the concentration TDS of the total dissolved solids in the mixed solution is more than or equal to 400g/L, the mass fraction of sodium sulfate is W 1, and the mass fraction of sodium citrate is W 2,0.6＜W1/W2 < 2; when W 1/W2 is more than or equal to 1.2 and less than 2, the temperature of freezing crystallization is-2~0 ℃; when W 1/W2 is more than or equal to 1 and less than 1.2, the temperature of freezing crystallization is 0-6 ℃; when W 1/W2 is more than 0.6 and less than 1, the temperature of freezing crystallization is 6-8 ℃;
S2, redissolving the crude mirabilite to obtain a sodium sulfate recrystallization solution, evaporating and recrystallizing, and filtering and separating to obtain refined anhydrous sodium sulfate and mother liquor A2;
S3, crystallizing the mother liquor A1 or the concentrated solution of the mother liquor A1, and carrying out solid-liquid separation to obtain crude sodium citrate dihydrate and mother liquor A3; when W 1/W2 is more than or equal to 1 and less than 2, evaporating and crystallizing by using a mother solution A1; when W 1/W2 is more than 0.6 and less than 1, cooling and crystallizing the concentrated solution of the mother solution A1;
S4, redissolving the crude sodium citrate dihydrate to obtain a sodium citrate solution, and evaporating and recrystallizing to obtain refined sodium citrate dihydrate and mother liquor A4.
Preferably, in the step S2, the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 260-300 g/L; the temperature of the evaporation recrystallization is 80-100 ℃.
Preferably, in the step S2, when W 1/W2 is more than or equal to 1.2 and less than 2, the amount of the mother solution A2 is 18-22% of the sodium sulfate recrystallization solution;
preferably, in the step S2, when W 1/W2 is smaller than or equal to 1.2, the amount of the mother solution A2 is 15-18% of the sodium sulfate recrystallization solution.
Preferably, in the step S2, when W 1/W2 is more than 0.6 and less than 1, the amount of the mother solution A2 is 12-15% of the sodium sulfate recrystallization solution.
Preferably, in the step S2, when W 1/W2 is more than or equal to 1 and less than 2, the mother solution A2 is sent to a mother solution drying process, and the impurity salt is discharged after evaporation; when W 1/W2 is more than 0.6 and less than 1, the mother solution A2 is sent to a cooling crystallization process.
Preferably, in the step S3, the concentration is evaporation concentration, and the concentration multiple of the concentrated solution of the mother solution A1 is 2.0-2.2; the cooling crystallization temperature of the concentrated solution of the mother solution A1 is 40-45 ℃.
Preferably, in the step S3, the evaporation temperature of the mother solution A1 is 70-75 ℃; the amount of the mother solution A3 is 5-8% of that of the mother solution A1.
Preferably, in the step S3, when W 1/W2 is more than or equal to 1 and less than 2, the mother solution A3 is sent to a mother solution drying procedure, and the impurity salt is discharged after evaporation;
When W 1/W2 is more than 0.6 and less than 1, part of the mother liquor A3 is returned to be frozen and crystallized, part of the mother liquor A3 is discharged to a mother liquor drying system, the impurity salt is discharged after being evaporated, and the ratio of the reflux quantity to the discharge quantity in the mother liquor A3 is 3.1-3.6.
Preferably, in the step S4, the sodium citrate content in the sodium citrate recrystallization solution is 400-450 g/L;
the evaporating and recrystallizing temperature is 80-100 ℃.
Preferably, in the step S4, when W 1/W2 is more than or equal to 1 and less than 2, the amount of the mother solution A4 is 2-4% of the sodium citrate recrystallization solution;
when W 1/W2 is more than 0.6 and less than 1, the amount of the mother solution A4 is 1-3% of the sodium citrate recrystallization solution.
Preferably, in step S4, the mother liquor A4 is sent to a mother liquor drying process, and the evaporated salt is discharged.
Compared with the prior art, one or more of the technical schemes can achieve at least one of the following beneficial effects:
According to the method, no additional reagent is needed, the mixed solutions with different sodium sulfate and sodium citrate concentration ratios can be subjected to high-efficiency recovery treatment, anhydrous sodium sulfate and sodium citrate dihydrate in the wastewater are respectively recovered, the application range is wide, the process steps are simple and feasible, the method can be suitable for treating mother liquor wastewater for producing sodium citrate, and can also be used for treating wastewater produced in the wet synthesis of Prussian blue sodium electric anode material, for example, the Prussian blue wastewater with 15-30% of sodium sulfate mass fraction and 10-25% of sodium citrate mass fraction can be subjected to recovery treatment, the sodium sulfate and sodium citrate yield are high, the product purity is high, the sodium sulfate purity can reach more than 98%, and the sodium citrate dihydrate purity can reach more than 99%.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart for recycling resources of a sodium citrate-sodium sulfate mixed solution with W 1/W2 < 2, which is more than or equal to 1.2.
FIG. 2 is a flow chart for recycling resources of a sodium citrate-sodium sulfate mixed solution with W 1/W2 less than or equal to 1.2.
FIG. 3 is a flow chart for recycling the resources of the sodium citrate and sodium sulfate mixed solution with the W 1/W2 being more than 0.6 and less than 1.
Detailed Description
Some embodiments of the present invention provide a resource recycling method of a sodium citrate-sodium sulfate mixed solution, including:
S1, freezing and crystallizing the mixed solution, and then filtering and separating to obtain coarse mirabilite and mother liquor A1; the concentration TDS of the total dissolved solids in the mixed solution is more than or equal to 400g/L, the mass fraction of sodium sulfate is W 1, and the mass fraction of sodium citrate is W 2,0.6＜W1/W2 < 2; when W 1/W2 is more than or equal to 1.2 and less than 2, the temperature of freezing crystallization is-2~0 ℃; when W 1/W2 is more than or equal to 1 and less than 1.2, the temperature of freezing crystallization is 0-6 ℃; when W 1/W2 is more than 0.6 and less than 1, the temperature of freezing crystallization is 6-8 ℃;
S2, redissolving the crude mirabilite to obtain a sodium sulfate recrystallization solution, evaporating and recrystallizing, and filtering and separating to obtain refined anhydrous sodium sulfate and mother liquor A2;
S3, crystallizing the mother liquor A1 or the concentrated solution of the mother liquor A1, and carrying out solid-liquid separation to obtain crude sodium citrate dihydrate and mother liquor A3; when W 1/W2 is less than or equal to 1 and less than or equal to 2, 5-12% sodium sulfate is contained in the mother solution A1 (when W 1/W2 is less than or equal to 1.2, 8-12% sodium sulfate is contained, and when W1/W2 is less than or equal to 1.2 and less than or equal to 5-8% sodium sulfate is contained), the mother solution A1 is used for evaporative crystallization, and part of the mother solution (namely all the mother solution after the evaporative crystallization is discharged) is discharged, so that the crude sodium citrate dihydrate with relatively high purity can be obtained; when W 1/W2 is more than 0.6 and less than 1, the mother solution A1 is an unsaturated solution, the mother solution A1 is concentrated to obtain a concentrated solution of the mother solution A1, and a large amount of mother solution is discharged when evaporation crystallization is performed due to the fact that the sodium sulfate content in the concentrated solution of the mother solution A1 is more than 12% and the content is higher, so that the concentrated solution of the mother solution A1 is used for cooling crystallization;
S4, redissolving the crude sodium citrate dihydrate to obtain a sodium citrate solution, and evaporating and recrystallizing to obtain refined sodium citrate dihydrate and mother liquor A4.
In the part S2, when the concentration of the dissolved total solid TDS in the mixed solution is low, the original solution should be concentrated to the specified range of TDS.
In a part of preferred embodiments, in the step S2, the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 260-300 g/L; the temperature of the evaporation recrystallization is 80-100 ℃.
Because the crude mirabilite contains sodium citrate, part of mother solution is required to be discharged (namely mother solution A2 is discharged) for evaporation and recrystallization in order to ensure the purity of the sodium sulfate; in a part of preferred embodiments, in the step S2, when W 1/W2 is less than or equal to 1.2 and less than 2, the amount of the mother solution A2 is 18-22% of the sodium sulfate recrystallization solution; when W 1/W2 is more than or equal to 1 and less than 1.2, the amount of the mother solution A2 is 15-18% of the sodium sulfate recrystallization solution; when W 1/W2 is more than 0.6 and less than 1, the amount of the mother solution A2 is 12-15% of the sodium sulfate recrystallization solution.
In the step S2, when W 1/W2 is smaller than or equal to 1 and smaller than 2, the mother solution A2 is sent to a mother solution drying procedure, and the impurity salt is discharged after evaporation; when W 1/W2 is more than 0.6 and less than 1, the mother solution A2 is sent to a cooling crystallization process.
In a part of preferred embodiments, in step S3, the concentration is evaporation concentration, and the concentration multiple of the concentrated solution of the mother solution A1 is 2.0-2.2.
In a preferred embodiment, in step S3, the cooling crystallization temperature of the concentrated solution of the mother liquor A1 is 40 to 45 ℃.
In a part of preferred embodiments, in the step S3, the evaporation temperature of the mother liquor A1 is 70-75 ℃; the amount of the mother solution A3 is 5-8% of that of the mother solution A1.
In a part of preferred embodiments, in the step S3, when W 1/W2 is less than or equal to 1 and less than 2, the mother solution A3 is sent to a mother solution drying process, and the impurity salt is discharged after evaporation.
In a part of preferred embodiments, in the step S3, when W 1/W2 is less than 0.6 and less than 1, part of the mother liquor A3 is returned to perform freezing crystallization, part of the mother liquor is discharged to a mother liquor drying system, the mixed salt is discharged after evaporation, and the ratio of the reflux amount to the discharge amount in the mother liquor A3 is 3.2-3.6.
In a part of preferred embodiments, in the step S4, the sodium citrate content in the sodium citrate recrystallization solution is 400-450 g/L.
In a part of preferred embodiments, in step S4, the evaporation recrystallization temperature is 80 to 100 ℃.
In a part of preferred embodiments, in the step S4, when W 1/W2 is less than or equal to 1 and less than 2, the amount of the mother solution A4 is 2-4% of the sodium citrate recrystallization solution.
In a part of preferred embodiments, in the step S4, when 0.6 < W 1/W2 < 1, the amount of the mother liquor A4 is 1 to 3% of the sodium citrate recrystallization solution.
In a part of preferred embodiments, in step S4, the mother liquor A4 is rich in sodium sulfate, and is sent to a mother liquor drying process, and the impurity salt is discharged after evaporation.
The invention will be described more fully hereinafter with reference to the accompanying drawings and preferred embodiments in order to facilitate an understanding of the invention, but the scope of the invention is not limited to the following specific embodiments.
Unless defined otherwise, all technical and scientific terms used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present invention.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or may be prepared by existing methods.
Example 1
In the embodiment, the mass content of sodium sulfate is 19.77%, the mass content of sodium citrate is 18.27%, and W 1/W2 is approximately equal to 1.08.
① And (3) delivering the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature at 2 ℃ in the freezing crystallization system, and carrying out solid-liquid separation to obtain 1.05t of coarse mirabilite containing water and 0.95t of freezing mother liquor.
② Adding pure water into the crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 80 ℃, carrying out solid-liquid separation and drying to obtain 348.1kg of anhydrous sodium sulfate, wherein the purity is 98.5%, the discharge amount of mother liquor is 15% of the sodium sulfate recrystallization solution, and all the solution is sent into a mother liquor drying system.
③ The frozen mother solution is sent into an evaporative crystallization system for evaporative crystallization at 75 ℃, then 385.5kg of crude sodium citrate dihydrate and 59kg of mother solution are obtained after solid-liquid separation, and the mother solution is sent into a mother solution drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare a sodium citrate recrystallization solution, adding pure water for dissolution, preparing the sodium citrate recrystallization solution, wherein the concentration of the sodium citrate is 450g/L, then sending the sodium citrate into an evaporation recrystallization system, evaporating and crystallizing at 90 ℃, carrying out solid-liquid separation and drying to obtain 341.4kg of refined sodium citrate dihydrate, wherein the purity is 99.1%, the discharge amount of mother liquor is 4% of the sodium citrate recrystallization solution, and sending all the mother liquor into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 86.7%, and the sodium citrate yield is 81.3%.
Example 2
In the embodiment, the mass content of sodium sulfate in the sodium citrate and sodium sulfate mixed solution 2t is 17.67%, the mass content of sodium citrate is 17.49%, and W 1/W2 is approximately equal to 1.01.
① And (3) delivering the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature at 2 ℃ in the freezing crystallization system, and carrying out solid-liquid separation to obtain 0.95t of coarse mirabilite containing water and 1.05t of freezing mother liquor.
② Adding pure water into crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 80 ℃, carrying out solid-liquid separation and drying to obtain 301.9kg of anhydrous sodium sulfate with the purity of 98.5%, discharging mother liquor with the discharge amount of 15% of the sodium sulfate recrystallization solution, and sending the whole solution into a mother liquor drying system.
③ The frozen mother solution is sent into an evaporative crystallization system for evaporative crystallization at 75 ℃, then 364.5kg of crude sodium citrate dihydrate and 60kg of mother solution are obtained after solid-liquid separation, and the mother solution is sent into a mother solution drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare a sodium citrate recrystallization solution, wherein the concentration of sodium citrate is 450g/L, then sending the sodium citrate into an evaporation recrystallization system to be evaporated and crystallized at 90 ℃, obtaining 324.9kg of refined sodium citrate dihydrate after solid-liquid separation and drying, wherein the purity is 99.2%, the discharge amount of mother liquor is 4% of the sodium citrate recrystallization solution, and sending all the mother liquor into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 84.1%, and the sodium citrate yield is 80.9%.
Example 3
In the embodiment, the mass content of sodium sulfate is 17.98%, the mass content of sodium citrate is 15.1%, and W 1/W2 is approximately equal to 1.19.
① And (3) delivering the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature at 2 ℃ in the freezing crystallization system, and carrying out solid-liquid separation to obtain 0.98t of coarse mirabilite containing water and 1.02t of freezing mother liquor.
② Adding pure water into the crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 80 ℃, carrying out solid-liquid separation and drying to obtain 315.1kg of anhydrous sodium sulfate, wherein the purity is 98.5%, the discharge amount of mother liquor is 15% of the sodium sulfate recrystallization solution, and all the solution is sent into a mother liquor drying system.
③ And sending the frozen mother liquor into an evaporative crystallization system for evaporative crystallization at 75 ℃, obtaining 376.5kg of crude sodium citrate dihydrate and 56kg of mother liquor after solid-liquid separation, and sending all the mother liquor into a mother liquor drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare a sodium citrate recrystallization solution, wherein the concentration of sodium citrate is 450g/L, then sending the sodium citrate into an evaporation recrystallization system to be evaporated and crystallized at 90 ℃, obtaining 282.2kg of refined sodium citrate dihydrate after solid-liquid separation and drying, wherein the purity is 99.1%, the discharge amount of mother liquor is 4% of the sodium citrate recrystallization solution, and sending all the mother liquor into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 86.3%, and the sodium citrate yield is 81.3%.
Example 4
In the embodiment, the mass content of sodium citrate and sodium sulfate is 15.77%, the mass content of sodium citrate is 19.07% and W 1/W2 is approximately equal to 0.83.
① And (3) sending the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature in the freezing crystallization system at 6 ℃, and carrying out solid-liquid separation to obtain 1.51t of coarse mirabilite containing water and 3.49t of freezing mother liquor.
② Adding pure water into crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 80 ℃, carrying out solid-liquid separation and drying to obtain 644.7kg of anhydrous sodium sulfate, wherein the purity is 98.5%, the discharge amount of mother liquor is 12% of the sodium sulfate recrystallization solution, and all the solution is sent into a mother liquor drying system.
③ The frozen mother liquor was fed to an evaporative concentration system and concentrated 2.1 times at an evaporation pressure of 101.3 kpa.
④ Cooling and crystallizing the concentrated solution C at 40 ℃, filtering and separating to obtain 995kg of crude sodium citrate dihydrate and 720kg of cooled mother liquor, refluxing 548kg of cooled mother liquor to a freezing and crystallizing system, discharging 172kg of cooled mother liquor to a mother liquor drying system, and discharging the mixed salt after evaporating.
⑤ Adding pure water into crude sodium citrate dihydrate to prepare a sodium citrate recrystallization solution, adding pure water for dissolution, preparing the sodium citrate recrystallization solution, wherein the concentration of the sodium citrate is 450g/L, then sending the sodium citrate into an evaporation recrystallization system, evaporating and crystallizing at 90 ℃, carrying out solid-liquid separation and drying to obtain 893.8kg of refined sodium citrate dihydrate, wherein the purity is 99.1%, the discharge amount of mother liquor is 3% of the sodium citrate recrystallization solution, and sending all the mother liquor into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 80.5%, and the sodium citrate yield is 81.5%.
Example 5
In the embodiment, the mass content of sodium citrate and sodium sulfate mixed solution is 5t, the mass content of sodium sulfate is 15.25%, the mass content of sodium citrate is 24.59%, and W 1/W2 is approximately equal to 0.62.
① And (3) sending the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature in the freezing crystallization system at 6 ℃, and carrying out solid-liquid separation to obtain 1.40t of coarse mirabilite containing water and 3.60t of freezing mother liquor.
② Adding pure water into the crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 80 ℃, carrying out solid-liquid separation and drying to obtain 620.1kg of anhydrous sodium sulfate with the purity of 98.5%, discharging the mother liquor with the discharge amount of 12% of the sodium sulfate recrystallization solution, and sending the whole solution into a mother liquor drying system.
③ The frozen mother liquor was fed to an evaporative concentration system and concentrated 2.1 times at an evaporation pressure of 101.3 kpa.
④ Cooling and crystallizing the concentrated solution C at 40 ℃, filtering and separating to obtain 1350kg of crude sodium citrate dihydrate and 617kg of cooled mother liquor, refluxing 508kg of cooled mother liquor to a freezing and crystallizing system, discharging 109kg of cooled mother liquor to a mother liquor drying system, and discharging the impurity salt after evaporating.
⑤ Adding pure water into crude sodium citrate dihydrate to prepare a sodium citrate recrystallization solution, adding pure water for dissolution, preparing the sodium citrate recrystallization solution, wherein the concentration of the sodium citrate is 450g/L, then sending the sodium citrate into an evaporation recrystallization system, evaporating and crystallizing at 90 ℃, carrying out solid-liquid separation and drying to obtain 1139.1kg of refined sodium citrate dihydrate, wherein the purity is 99.1%, the discharge amount of mother liquor is 3% of the sodium citrate recrystallization solution, and sending all the mother liquor into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 80.1%, and the sodium citrate yield is 80.6%.
Example 6
In the embodiment, the mass content of sodium citrate and sodium sulfate is 15.75% and 16.07% respectively, and W 1/W2 is approximately equal to 0.98.
① And (3) sending the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature in the freezing crystallization system at 6 ℃, and carrying out solid-liquid separation to obtain 1.45t of coarse mirabilite containing water and 3.55t of freezing mother liquor.
② Adding pure water into crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 80 ℃, carrying out solid-liquid separation and drying to obtain 652.8kg of anhydrous sodium sulfate, wherein the purity is 98.5%, the discharge amount of mother liquor is 12% of the sodium sulfate recrystallization solution, and all the solution is sent into a mother liquor drying system.
③ The frozen mother liquor was fed to an evaporative concentration system and concentrated 2.1 times at an evaporation pressure of 101.3 kpa.
④ Cooling and crystallizing the concentrated solution C at 40 ℃, filtering and separating to obtain 890kg of crude sodium citrate dihydrate and 692kg of cooled mother liquor, refluxing 508kg of cooled mother liquor to a freezing and crystallizing system, discharging 184kg of cooled mother liquor to a mother liquor drying system, and discharging the mixed salt after evaporating.
⑤ Adding pure water into crude sodium citrate dihydrate to prepare a sodium citrate recrystallization solution, adding pure water for dissolution, preparing the sodium citrate recrystallization solution, wherein the concentration of the sodium citrate is 450g/L, then sending the sodium citrate into an evaporation recrystallization system, evaporating and crystallizing at 90 ℃, carrying out solid-liquid separation and drying to obtain 741.6kg of refined sodium citrate dihydrate, wherein the purity is 99.1%, the discharge amount of mother liquor is 3% of the sodium citrate recrystallization solution, and sending all the mother liquor into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 81.7%, and the sodium citrate yield is 80.3%.
Example 7
In the embodiment, the mass content of sodium sulfate is 17.32%, the mass content of sodium citrate is 14.41%, and W 1/W2 is approximately equal to 1.20.
① And (3) delivering the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature at 0 ℃ in the freezing crystallization system, and carrying out solid-liquid separation to obtain 1.42t of coarse mirabilite containing water and 1.58t of freezing mother liquor.
② Adding pure water into the crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 90 ℃, carrying out solid-liquid separation and drying to obtain 478.5kg of anhydrous sodium sulfate, wherein the purity is 98.5%, the discharge amount of mother liquor is 18% of the sodium sulfate recrystallization solution, and all the solution is sent into a mother liquor drying system.
③ The frozen mother solution is sent into an evaporative crystallization system for evaporative crystallization at 75 ℃, then 433.2kg of crude sodium citrate dihydrate and 71kg of mother solution are obtained after solid-liquid separation, and the mother solution is sent into a mother solution drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare sodium citrate recrystallization solution, wherein the concentration of sodium citrate is 464g/L, then sending the solution into an evaporation recrystallization system to be evaporated and crystallized at 90 ℃, obtaining 406.4kg of refined sodium citrate dihydrate after solid-liquid separation and drying, the purity is 99.1%, the discharge amount of mother liquor is 2% of the sodium citrate recrystallization solution, and sending the whole solution into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 90.7%, and the sodium citrate yield is 81.8%.
Example 8
In the embodiment, the sodium citrate and sodium sulfate mixed solution 4t contains 16.70% of sodium sulfate by mass and 10.42% of sodium citrate by mass, and W 1/W2 is approximately equal to 1.60.
① And (3) delivering the mixed solution phase into a freezing and crystallizing system, wherein the freezing and crystallizing system keeps the crystallization temperature at-1 ℃, and obtaining 1.81t of coarse mirabilite containing water and 2.19t of freezing mother liquor after solid-liquid separation.
② Adding pure water into crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 90 ℃, obtaining 622kg of anhydrous sodium sulfate after solid-liquid separation and drying, wherein the purity is 98.6%, the discharge amount of mother liquor is 20% of the sodium sulfate recrystallization solution, and all the solution is sent into a mother liquor drying system.
③ The frozen mother liquor is sent into an evaporative crystallization system for evaporative crystallization at 75 ℃, 446kg of crude sodium citrate dihydrate and 109kg of mother liquor are obtained after solid-liquid separation, and the mother liquor is sent into a mother liquor drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare a sodium citrate recrystallization solution, adding pure water for dissolution, preparing the sodium citrate recrystallization solution, wherein the concentration of the sodium citrate is 450g/L, then sending the sodium citrate into an evaporation recrystallization system, evaporating and crystallizing at 90 ℃, carrying out solid-liquid separation and drying to obtain 388.1kg of refined sodium citrate dihydrate, wherein the purity is 99.1%, the discharge amount of mother liquor is 3% of the sodium citrate recrystallization solution, and sending all the mother liquor into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 91.8%, and the sodium citrate yield is 80.9%.
Example 9
In the embodiment, the mass content of sodium sulfate is 20.18%, the mass content of sodium citrate is 10.20%, and W 1/W2 is approximately equal to 1.98.
① And (3) delivering the mixed solution phase into a freezing and crystallizing system, wherein the freezing and crystallizing system keeps the crystallization temperature at-2 ℃, and obtaining 2.81t of coarse mirabilite containing water and 2.19t of freezing mother liquor after solid-liquid separation.
② Adding pure water into the crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 90 ℃, carrying out solid-liquid separation and drying to obtain 942.2kg of anhydrous sodium sulfate, wherein the purity is 98.5%, the discharge amount of mother liquor is 22% of the sodium sulfate recrystallization solution, and sending the whole solution into a mother liquor drying system.
③ And sending the frozen mother liquor into an evaporative crystallization system for evaporative crystallization at 75 ℃, obtaining 550kg of crude sodium citrate dihydrate and 175kg of mother liquor after solid-liquid separation, and sending all the mother liquor into a mother liquor drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare sodium citrate recrystallization solution, wherein the concentration of sodium citrate is 450g/L, then sending the solution into an evaporation recrystallization system to be evaporated and crystallized at 90 ℃, obtaining 471kg of refined sodium citrate dihydrate after solid-liquid separation and drying, the purity is 99.3%, the discharge amount of mother liquor is 4% of the sodium citrate recrystallization solution, and sending the whole solution into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 91.97%, and the sodium citrate yield is 80.3%.
Comparative example 1
In the comparative example, the sodium citrate-sodium sulfate mixed solution 2t, the sodium sulfate mass content is 15.77%, the sodium citrate mass is 19.71%, and W 1/W2 is about 0.80, and the separation is carried out by using a method that W 1/W2 is less than 1.2.
① And (3) delivering the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature at 2 ℃ in the freezing crystallization system, and carrying out solid-liquid separation to obtain 1.15t of coarse mirabilite containing water and 0.85t of freezing mother liquor.
② Adding pure water into crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 90 ℃, carrying out solid-liquid separation and drying to obtain 243kg of anhydrous sodium sulfate with the purity of 98.5%, and sending the mother liquor discharge amount of 18% of the sodium sulfate recrystallization solution into a mother liquor drying system.
③ And sending the frozen mother liquor into an evaporative crystallization system for evaporative crystallization at 75 ℃, obtaining 398kg of crude sodium citrate dihydrate and 47.5kg of mother liquor after solid-liquid separation, and sending the mother liquor into a mother liquor drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare sodium citrate recrystallization solution, wherein the concentration of sodium citrate is 450g/L, then sending the solution into an evaporation recrystallization system to be evaporated and crystallized at 90 ℃, obtaining 370kg of refined sodium citrate dihydrate after solid-liquid separation and drying, wherein the purity is 99.1%, the discharge amount of mother liquor is 2% of the sodium citrate recrystallization solution, and sending the whole solution into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 75.9%, and the sodium citrate yield is 81.6%.
Comparative example 2
In this comparative example, the sodium sulfate mixed solution 2t has a sodium sulfate mass content of 19.98%, a sodium citrate mass content of 15.1%, and a W 1/W2. Apprxeq.1.32. The separation is carried out by a method that W 1/W2 is more than or equal to 1 and less than 1.2.
① And (3) delivering the mixed solution phase into a freezing crystallization system, keeping the crystallization temperature at 2 ℃ in the freezing crystallization system, and carrying out solid-liquid separation to obtain 1.2t of coarse mirabilite containing water and 0.8t of freezing mother liquor.
② Adding pure water into crude mirabilite to carry out dissolution to prepare sodium sulfate recrystallization solution, wherein the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 280g/L, then sending the solution into an evaporation recrystallization system to carry out evaporation crystallization at 90 ℃, obtaining 355kg of anhydrous sodium sulfate after solid-liquid separation and drying, wherein the purity is 99%, the discharge amount of mother liquor is 18% of the sodium sulfate recrystallization solution, and all the solution is sent into a mother liquor drying system.
③ The frozen mother liquor is sent into an evaporation crystallization system for evaporation crystallization at 75 ℃, 307.5kg of crude sodium citrate dihydrate and 90.5kg of mother liquor are obtained after solid-liquid separation, and the mother liquor is all sent into a mother liquor drying system.
④ Adding pure water into crude sodium citrate dihydrate to prepare sodium citrate recrystallization solution, wherein the concentration of sodium citrate is 450g/L, then sending the solution into an evaporation recrystallization system to be evaporated and crystallized at 90 ℃, obtaining 252kg of refined sodium citrate dihydrate after solid-liquid separation and drying, wherein the purity is 99.1%, the discharge amount of mother liquor is 2% of the sodium citrate recrystallization solution, and sending the whole solution into a mother liquor drying system.
After the above treatment process, the sodium sulfate yield of the sodium citrate-sodium sulfate mixed solution is 87.95%, and the sodium citrate yield is 72.6%.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (10)

1. The resource recycling method of the sodium citrate and sodium sulfate mixed solution is characterized by comprising the following steps of:
S1, freezing and crystallizing the mixed solution, and then filtering and separating to obtain coarse mirabilite and mother liquor A1; the concentration TDS of the total dissolved solids in the mixed solution is more than or equal to 400g/L, the mass fraction of sodium sulfate is W 1, and the mass fraction of sodium citrate is W 2,0.6＜W1/W2 < 2; when W 1/W2 is more than or equal to 1.2 and less than 2, the temperature of freezing crystallization is-2~0 ℃; when W 1/W2 is more than or equal to 1 and less than 1.2, the temperature of freezing crystallization is 0-6 ℃; when W 1/W2 is more than 0.6 and less than 1, the temperature of freezing crystallization is 6-8 ℃;
S2, redissolving the crude mirabilite to obtain a sodium sulfate recrystallization solution, evaporating and recrystallizing, and filtering and separating to obtain refined anhydrous sodium sulfate and mother liquor A2;
S3, crystallizing the mother liquor A1 or the concentrated solution of the mother liquor A1, and carrying out solid-liquid separation to obtain crude sodium citrate dihydrate and mother liquor A3; when W 1/W2 is more than or equal to 1 and less than 2, evaporating and crystallizing by using a mother solution A1; when W 1/W2 is more than 0.6 and less than 1, cooling and crystallizing the concentrated solution of the mother solution A1;
S4, redissolving the crude sodium citrate dihydrate to obtain a sodium citrate solution, and evaporating and recrystallizing to obtain refined sodium citrate dihydrate and mother liquor A4.
2. The method for recycling and reusing resources of a sodium citrate-sodium sulfate mixed solution according to claim 1, wherein in the step S2, the concentration of sodium sulfate in the sodium sulfate recrystallization solution is 260-300 g/L; the temperature of the evaporation recrystallization is 80-100 ℃.
3. The method for recycling resources of a sodium citrate-sodium sulfate mixed solution according to claim 1, wherein in the step S2, when W 1/W2 is less than or equal to 1.2 and less than 2, the amount of the mother solution A2 is 18-22% of the sodium sulfate recrystallization solution;
When W 1/W2 is more than or equal to 1 and less than 1.2, the amount of the mother solution A2 is 15-18% of the sodium sulfate recrystallization solution;
When W 1/W2 is more than 0.6 and less than 1, the amount of the mother solution A2 is 12-15% of the sodium sulfate recrystallization solution.
4. The method for recycling and reusing resources of sodium citrate and sodium sulfate mixed solution according to claim 1, wherein in the step S2, when W 1/W2 is less than or equal to 1 and less than 2, the mother solution A2 is sent to a mother solution drying procedure, and the impurity salt is discharged after evaporation; when W 1/W2 is more than 0.6 and less than 1, the mother solution A2 is sent to a cooling crystallization process.
5. The method for recycling sodium citrate-sodium sulfate mixed solution according to any one of claims 1-4, wherein in step S3, the concentration is evaporation concentration, and the concentration multiple of the concentrated solution of the mother solution A1 is 2.0-2.2;
the cooling crystallization temperature of the concentrated solution of the mother solution A1 is 40-45 ℃.
6. The method for recycling sodium citrate-sodium sulfate mixed solution according to any one of claims 1 to 4, wherein in step S3, the evaporation temperature of the mother liquor A1 is 70 to 75 ℃; the amount of the mother solution A3 is 5-8% of that of the mother solution A1.
7. The method for recycling sodium citrate-sodium sulfate mixed solution according to any one of claims 1-4, wherein in step S3, when W 1/W2 is less than or equal to 1 and less than 2, the mother liquor A3 is sent to a mother liquor drying process, and the evaporated mixed salt is discharged;
When W 1/W2 is more than 0.6 and less than 1, part of the mother liquor A3 is returned to be frozen and crystallized, part of the mother liquor A3 is discharged to a mother liquor drying system, the impurity salt is discharged after being evaporated, and the ratio of the reflux quantity to the discharge quantity in the mother liquor A3 is 3.1-3.6.
8. The method for recycling sodium citrate-sodium sulfate mixed solution according to any one of claims 1 to 4, wherein in step S4, the sodium citrate content in the sodium citrate recrystallization solution is 400 to 450g/L;
the evaporating and recrystallizing temperature is 80-100 ℃.
9. The method for recycling sodium citrate-sodium sulfate mixed solution according to any one of claims 1-4, wherein in step S4, when W 1/W2 is less than or equal to 1 and less than 2, the amount of the mother liquor A4 is 2-4% of the sodium citrate recrystallization solution;
when W 1/W2 is more than 0.6 and less than 1, the amount of the mother solution A4 is 1-3% of the sodium citrate recrystallization solution.
10. The method for recycling sodium citrate-sodium sulfate mixed solution according to any one of claims 1-4, wherein in step S4, the mother liquor A4 is sent to a mother liquor drying process, and the evaporated mixed salt is discharged.
CN202410481056.7A 2024-04-22 2024-04-22 Resource recycling method for sodium citrate and sodium sulfate mixed solution Pending CN118344250A (en)

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