A self-balanced production method for preparing potassium sulfate by using high-nitrate and high-potassium wastewater

Abstract

The application provides a self-balanced production method for preparing potassium sulfate by using high-nitrate and high-potassium wastewater, which comprises the following steps: the wastewater is concentrated by MVR evaporation, and potassium mirabilite I and mother liquor I are obtained by separation; potassium mirabilite I, potassium chloride and water are subjected to conversion reaction II to obtain potassium sulfate and potassium mother liquor, the potassium mother liquor is added with sodium sulfate, and potassium mirabilite II and mother liquor II are obtained by conversion reaction I, evaporation and solid-liquid separation, and the potassium mirabilite II is sent back to the conversion reaction II; the mother liquor II is subjected to MVR evaporation crystallization to obtain industrial salt I, water and mother liquor III, the mother liquor III is added with water, and potassium mirabilite III and mother liquor IV are obtained by conversion reaction III; the potassium mirabilite III is sent back to the conversion reaction II; part of the mother liquor IV is mixed with the mother liquor I and is sent back to the MVR evaporation crystallization; part of the mother liquor IV is subjected to evaporation crystallization to obtain industrial salt II, water and mother liquor VI; and the obtained water is sent to a water storage device for reuse in the above steps. The high-purity potassium sulfate and the industrial salt are obtained by the reasonable process, the system water balance and the material balance are realized by the multi-stage reflux of the mother liquor and the recycling of the water, the water expansion is avoided, and the raw material consumption is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inorganic chemical industry, and particularly relates to a self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater. BACKGROUND

[0002] Potassium sulfate (K2SO4) is an important inorganic compound, which is widely used in various fields such as agriculture, industry and medicine. In the field of agriculture, it is mainly used as a potassium fertilizer to provide potassium elements for crops, especially for crops that are not suitable for chlorine, such as tobacco, watermelon, tea, etc., and crops that are suitable for sulfur, such as rapeseed, beans, etc., to avoid the quality decline caused by chlorine ions in potassium chloride. In the field of industry, it is used as a chemical raw material to produce potassium carbonate, potassium persulfate and other potassium salts, and as a clarifying agent to remove bubbles in the melt in glass manufacturing. In the field of medicine and other fields, it is used as a laxative ingredient, a swelling agent or a water-retaining agent for meat products, etc.

[0003] At present, the main production methods of potassium sulfate are the Mannheim method and the mirabilite method. The Mannheim method mainly uses potassium chloride (KCl) and sulfuric acid (H2SO4) as raw materials to react at a high temperature of 550-700°C to produce potassium sulfate (K2SO4) and hydrogen chloride gas. This method is mature in technology, but has high energy consumption, large equipment investment, serious equipment corrosion, high maintenance cost, difficult treatment of by-product hydrochloric acid, and great environmental pressure. The mirabilite method is a simple complex decomposition reaction between solid mirabilite (Na2SO4·10H2O) and solid potassium chloride, which produces potassium sulfate and sodium chloride. The single consumption of sodium sulfate and potassium chloride is ≥0.8 (calculated by tons of potassium sulfate), and the potassium recovery rate is less than 60%. The production cost is high, the product quality is unstable, the treatment technology of various mother liquors is not perfect, the scale production is limited, and the system runs unstably due to water expansion in the production process, resulting in economic loss.

[0004] At present, there is also a process for extracting potassium sulfate from wastewater, but the composition of the raw wastewater is relatively simple, mainly sodium sulfate and sodium chloride. However, there is no report on the extraction method of potassium sulfate from a multi-component system (such as high-nitrate and high-potassium wastewater, which mainly contains Na2SO4, NaCl and KCl). How to efficiently separate the economically valuable components (such as K2SO4) from such complex wastewater, achieve stable operation of the process, avoid water expansion of the system, reduce material consumption and production cost, and improve environmental and economic benefits, is still a key problem to be solved. SUMMARY

[0005] In view of this, in order to solve the above technical problems, the present application provides a self-balanced production method for preparing potassium sulfate by using high-nitrate and high-potassium wastewater. The high-nitrate and high-potassium wastewater is used as raw material, and through a reasonable process flow, high-purity potassium sulfate, industrial salt and miscellaneous salt are obtained. At the same time, through the circulation of mother liquor and water, and combined with process parameter regulation, the material balance and water balance of the system are realized, the water swelling phenomenon is effectively avoided, the stable operation of the system is ensured, and the raw material consumption is significantly reduced.

[0006] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0007] A self-balanced production method for preparing potassium sulfate by using high-nitrate and high-potassium wastewater, comprising the following steps:

[0008] S1, the high-nitrate and high-potassium wastewater is concentrated by MVR evaporation to obtain water and slurry; the water is sent to a water storage device, and the slurry is subjected to solid-liquid separation to obtain potassium mirabilite I and mother liquor I;

[0009] S2, potassium chloride is added to the potassium mirabilite I, and the conversion reaction II is carried out by using the water supplied by the water storage device to obtain potassium sulfate and potassium mother liquor;

[0010] S3, sodium sulfate is added to the potassium mother liquor to carry out the conversion reaction I, and then the water is evaporated and the solid-liquid separation is carried out to obtain potassium mirabilite II and mother liquor II; the evaporated water is sent to the water storage device, and the potassium mirabilite II is sent to the conversion reaction II in step S2;

[0011] S4, the mother liquor II is subjected to MVR evaporation crystallization to obtain industrial salt I, water and mother liquor III; the water is sent to the water storage device, the conversion reaction III is carried out by adding the water supplied by the water storage device to the mother liquor III to obtain potassium mirabilite III and mother liquor IV; the potassium mirabilite III is sent to the conversion reaction II in step S2;

[0012] S5, a part of the mother liquor IV is mixed with the mother liquor I to obtain mother liquor V, and the mother liquor V is sent to step S4 for MVR evaporation crystallization;

[0013] S6, another part of the mother liquor IV is subjected to evaporation crystallization to obtain industrial salt II, water and mother liquor VI; the water is sent to the water storage device, and the mother liquor VI is solidified to obtain miscellaneous salt.

[0014] In some preferred embodiments of the self-balanced production method for preparing potassium sulfate by using high-nitrate and high-potassium wastewater, in the S1, the total dissolved solids of the high-nitrate and high-potassium wastewater are 80000-180000 mg / L, the Na + content is 12000-30000 mg / L, the K + content is 20000-40000 mg / L, the Cl - content is 40000-60000 mg / L, and the SO4 2-The content is 10,000–40,000 mg / L, and the total content of other impurities is 1,000–3,000 mg / L.

[0015] In some preferred embodiments of the self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater of the present invention, in step S1, the mass ratio of water obtained by MVR evaporation and concentration of the high-nitrate and high-potassium wastewater to the high-nitrate and high-potassium wastewater is 0.65 to 0.75:1; the Na in the mother liquor is... + With K + The mass ratio is 0.3–3:1, Cl - With SO4 2- The mass ratio is 4 to 11:1.

[0016] In some preferred embodiments of the self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater of the present invention, in step S2, the mass ratio of potassium chloride to water is 1:2 to 3.5; and the mass ratio of potassium mother liquor to potassium sulfate is 1.5 to 3:1.

[0017] In some preferred embodiments of the self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater of the present invention, in step S3, the mass ratio of potassium mother liquor to sodium sulfate is 4-9:1; the mass ratio of evaporated water to potassium mother liquor is 0.1-0.3:1; and the Na in mother liquor II... + With K + The mass ratio is 1~3:1, Cl - With SO4 2- The mass ratio is 4 to 8:1.

[0018] In some preferred embodiments of the self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater of the present invention, in step S4, the mass ratio of industrial salt I, water and mother liquor III is 1:1 to 5:6 to 12; the mass ratio of mother liquor III to water added to mother liquor III is 10 to 30:1.

[0019] In some preferred embodiments of the self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater of the present invention, in step S5, 10% to 60% of the total mass of mother liquor four is mixed with mother liquor one.

[0020] In some preferred embodiments of the self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater of the present invention, in step S6, the mass ratio of industrial salt II, water, and mother liquor VI is 1:1 to 6:8 to 15.

[0021] In some preferred embodiments of the self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater, 10% to 30% of the total mass of water in the water storage device is sent to step S2 for conversion reaction two, and 1% to 5% of the total mass of water in the water storage device is sent to step S4 for conversion reaction three.

[0022] In some preferred embodiments of the self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater, the product purity of potassium sulfate obtained in S2 is ≥98%, and the product purity of sodium chloride in industrial salt one obtained in S4 and industrial salt two obtained in S6 is ≥98.5%.

[0023] Compared with the prior art, the self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater has the following advantages:

[0024] (1) In the present application, the high-nitrate and high-potassium wastewater (mainly containing Na2SO4, NaCl and KCl) is used as raw material, and through a reasonable process flow, the valuable resources in the wastewater are efficiently extracted, and finally potassium sulfate, industrial salt and miscellaneous salt products are obtained, wherein the product purity of potassium sulfate is ≥98%, and the product purity of sodium chloride in industrial salt is ≥98.5%. This method not only helps to save natural mineral resources and reduce environmental pollution, but also effectively reduces the wastewater discharge load, and has significant environmental benefits. At the same time, more than 1000 yuan of economic benefits can be brought for every ton of potassium sulfate produced, showing good resource utilization prospects and economic benefits.

[0025] (2) In the present application, through water recycling, recycling of various mother liquors, and precise control of key process parameters, material balance and water balance in the system are realized, which is conducive to stable operation of the system and avoidance of water swelling, and provides protection for long-period stable operation of the system, and is also conducive to uniformity and control of product quality. In addition, in terms of reducing raw material consumption, the method significantly improves the utilization rate of raw materials, so that the unit product consumption of sodium sulfate and potassium chloride is controlled at a low level, the single consumption of sodium sulfate is ≤0.75 (based on tons of potassium sulfate), the single consumption of potassium chloride is ≤0.65 (based on tons of potassium sulfate), and the comprehensive utilization rate of potassium is increased to more than 75%, thereby greatly reducing production cost and enhancing the economic efficiency and sustainability of the overall process. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0027] Figure 1 The self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater described in Embodiment 1 of the present application is shown in the figure;

[0028] Figure 2 A material balance schematic diagram of the self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater according to Embodiment 1 of the present application. DETAILED DESCRIPTION

[0029] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples are conventional biochemical reagents unless otherwise specified; and the experimental methods described are conventional methods unless otherwise specified.

[0030] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0031] Embodiment 1

[0032] As shown in Figure 1 and 2 , the self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater includes the following steps:

[0033] S1, the high-nitrate and high-potassium wastewater with a flow rate of 600 m 3 / d and a mass flow rate of 654094 kg / d is fed into an MVR evaporation and concentration device, and after being concentrated by the MVR evaporation, water and slurry are obtained; the water is fed into a water storage device, and the slurry is subjected to solid-liquid separation to obtain potassium mirabilite I and mother liquor I; wherein, the total dissolved solids (TDS) of the high-nitrate and high-potassium wastewater is 126100 mg / L, the Na + content is 27924.5 mg / L, the K + content is 24154.4 mg / L, the Cl - content is 40925.8 mg / L, the SO4 2- content is 32157.4 mg / L, and the content of other impurities such as NH4 + , NO3 - , etc. is 1276 mg / L; the mass ratio of the obtained water to the high-nitrate and high-potassium wastewater is 0.72:1; the mass fraction of Na + in the mother liquor I is 9.53%, the mass fraction of K + is 3.86%, the mass fraction of Cl - is 15.66%, the mass fraction of SO4 2- is 3.48%, i.e., the mass ratio of Na + to K + is 2.5:1, and the mass ratio of Cl - to SO4 2- is 4.5:1;

[0034] S2, potassium glauber salt is converted with potassium chloride and water supplied from the water storage device to obtain potassium sulfate and potassium mother liquor; wherein the mass ratio of potassium chloride to water is 1:2.5, and the extracted water accounts for 15% of the total water mass of the water storage device; the mass ratio of potassium mother liquor to potassium sulfate is 2.3:1;

[0035] S3, potassium mother liquor is converted with sodium sulfate, and then water is evaporated and solid-liquid separation is performed to obtain potassium glauber salt II and mother liquor II; the evaporated water is sent to the water storage device, and the potassium glauber salt II is sent to step S2 for conversion reaction II; wherein the mass ratio of potassium mother liquor to sodium sulfate is 5.4:1; the mass ratio of evaporated water to potassium mother liquor is 0.14:1; the mass ratio of Na + and K + in the mother liquor II is 2:1, and the mass ratio of Cl - to SO4 2- is 5.9:1;

[0036] S4, mother liquor II is subjected to MVR evaporation and crystallization to obtain industrial salt I, water and mother liquor III; the water is sent to the water storage device, and the mother liquor III is converted with water supplied from the water storage device to obtain potassium glauber salt III and mother liquor IV; the potassium glauber salt III is sent to step S2 for conversion reaction II; wherein the mass ratio of industrial salt I, water and mother liquor III is 1:3.2:10.3; the mass ratio of mother liquor III to the water added to the mother liquor III is 26.1:1, and the extracted water accounts for 2% of the total water mass of the water storage device;

[0037] S5, 49% of the total mass of mother liquor IV is exchanged with mother liquor I to obtain mother liquor V, and the mother liquor V is sent to step S4 for MVR evaporation and crystallization;

[0038] S6, the remaining part of the mother liquor IV is sent to an evaporation and crystallization device, and industrial salt II, water and mother liquor VI are obtained through evaporation and crystallization; the water is sent to the water storage device, and the mother liquor VI is solidified to obtain miscellaneous salt; wherein the mass ratio of industrial salt II, water and mother liquor VI is 1:3.2:9.1.

[0039] The overall material balance table of Example 1 is shown in Table 1, the overall water balance table is shown in Table 2, and the benefit estimation is shown in Table 3.

[0040] Table 1

[0041]

[0042] Table 2

[0043]

[0044] Table 3

[0045]

[0046] Note: The income is simply estimated by the items listed in the table. The unit consumption is calculated by tons of potassium sulfate. The relevant data in the annual quantity is calculated by 300 days of annual production.

[0047] The purity of the potassium sulfate product prepared in Example 1 is 98.5%, and the purity of the sodium chloride product in the industrial salt is 98.5%. From the material balance diagram of Figure 2 0.42 (calculated by tons of potassium sulfate), the potassium chloride consumption is 0.65 (calculated by tons of potassium sulfate), and the comprehensive utilization rate of potassium in the wastewater neutralization and added potassium chloride is 77%. Through water recycling, recycling of various mother liquors, etc., material balance and water balance are achieved, so that the system can run stably and water swelling can be avoided. According to the estimation in Table 3, 1235 yuan can be obtained per ton of potassium sulfate (estimated by the items listed in the table), which has high economic benefits.

[0048] Example 2

[0049] The self-balanced production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater includes the following steps:

[0050] S1, the high-nitrate and high-potassium wastewater with a flow rate of 600 m 3 / d and a mass flow rate of 654094 kg / d is sent to the MVR evaporation and concentration device, and after evaporation and concentration by the MVR, water and slurry are obtained; the water is sent to the water storage device, and the slurry is subjected to solid-liquid separation to obtain potassium mirabilite one and mother liquor one; wherein, the total dissolved solids (TDS) of the high-nitrate and high-potassium wastewater is 121500 mg / L, the Na + content is 20000 mg / L, the K + content is 35000 mg / L, the Cl - content is 50000 mg / L, the SO4 2- content is 15000 mg / L, and the content of other impurities such as NH4 + , NO3 - , etc. is 1500 mg / L; the mass ratio of the obtained water to the high-nitrate and high-potassium wastewater is 0.75:1; the mass ratio of Na + and K + in the mother liquor one is 1.5:1, the mass ratio of Cl - and SO4 2- is 6:1;

[0051] S2, potassium chloride and water supplied by the water storage device are added to the potassium mirabilite one to carry out conversion reaction two, and potassium sulfate and potassium mother liquor are obtained; wherein, the mass ratio of potassium chloride to water is 1:2.5, and the water extracted accounts for 13% of the total water mass in the water storage device; the mass ratio of the potassium mother liquor to the potassium sulfate is 2.3:1;

[0052] S3, sodium sulfate is added to the potassium mother liquor for a conversion reaction one, and then water is evaporated and solid-liquid separation is performed to obtain potassium mirabilite two and mother liquor two; the evaporated water is sent to a water storage device, and the potassium mirabilite two is sent to step S2 for a conversion reaction two; wherein the mass ratio of the potassium mother liquor to the sodium sulfate is 5:1; the mass ratio of the evaporated water to the potassium mother liquor is 0.12:1; the mass ratio of Na + and K + in the mother liquor two is 1.8:1, the mass ratio of Cl - and SO4 2- is 6.3:1;

[0053] S4, the mother liquor two is subjected to MVR evaporation crystallization to obtain industrial salt one, water, and mother liquor three; the water is sent to a water storage device, and the mother liquor three is added with water supplied by the water storage device for a conversion reaction three to obtain potassium mirabilite three and mother liquor four; the potassium mirabilite three is sent to step S2 for a conversion reaction two; wherein the mass ratio of the industrial salt one, the water, and the mother liquor three is 1:4:11; the mass ratio of the mother liquor three to the added water is 25:1, and the extracted water accounts for 1.5% of the total water mass of the water storage device;

[0054] S5, 45% of the total mass of the mother liquor four is exchanged with the mother liquor one to obtain mother liquor five, and the mother liquor five is sent to step S4 for MVR evaporation crystallization;

[0055] S6, the remaining part of the mother liquor four is sent to an evaporation crystallization device, and evaporation crystallization is performed to obtain industrial salt two, water, and mother liquor six; the water is sent to a water storage device, and the mother liquor six is subjected to solidification to obtain miscellaneous salt; wherein the mass ratio of the industrial salt two, the water, and the mother liquor six is 1:4:10.

[0056] It is detected that the purity of the potassium sulfate product prepared in Example 2 is 98.7%, and the purity of the sodium chloride product in the industrial salt is 98.7%. The single consumption of sodium sulfate is 0.53 (calculated based on tons of potassium sulfate), the single consumption of potassium chloride is 0.62 (calculated based on tons of potassium sulfate), and the utilization rate of potassium is 79%. Through water recycling and recycling of various mother liquors, material balance and water balance are achieved, so that the system can be stably operated and water swelling can be avoided. Ton of potassium sulfate can obtain a profit of 1289 yuan, and has high economic benefits.

[0057] The above only describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater, characterized in that, Includes the following steps: S1. High-nitrate and high-potassium wastewater is concentrated by MVR evaporation to obtain water and slurry; the water is sent to a water storage device, and the slurry is separated into potassium sulfate and mother liquor. S2. Potassium chloride and water supplied by the water storage device are added to potassium sodium sulfate to carry out conversion reaction 2, resulting in potassium sulfate and potassium mother liquor. S3. Sodium sulfate is added to the potassium mother liquor to carry out conversion reaction one. After evaporation of water and solid-liquid separation, potassium sulfate II and mother liquor II are obtained. The evaporated water is sent to a water storage device, and potassium sulfate II is sent to step S2 to carry out conversion reaction two. S4. Mother liquor 2 is evaporated and crystallized by MVR to obtain industrial salt 1, water and mother liquor 3; water is sent to a water storage device, and water supplied by the water storage device is added to mother liquor 3 to carry out conversion reaction 3 to obtain potassium sulfate 3 and mother liquor 4; potassium sulfate 3 is sent to step S2 to carry out conversion reaction 2. S5. A portion of Mother Liquor 4 is mixed with Mother Liquor 1 to obtain Mother Liquor 5. Mother Liquor 5 is sent to step S4 for MVR evaporation and crystallization. S6. Another part of the mother liquor 4 is evaporated and crystallized to obtain industrial salt 2, water and mother liquor 6; the water is sent into a water storage device, and the mother liquor 6 is solidified to obtain mixed salt.

2. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: In S1, the total dissolved solids of the high-nitrate and high-potassium wastewater is 80,000–180,000 mg / L, and Na... + The content is 12000–30000 mg / L, K + The content is 20,000–40,000 mg / L, Cl - The content is 40,000–60,000 mg / L, SO4 2- The content is 10,000–40,000 mg / L, and the total content of other impurities is 1,000–3,000 mg / L.

3. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: In S1, the mass ratio of water obtained from the MVR evaporation and concentration of high-nitrate and high-potassium wastewater to the total high-nitrate and high-potassium wastewater is 0.65–0.75:1; the Na in the mother liquor is... + With K + The mass ratio is 0.3–3:1, Cl - With SO4 2- The mass ratio is 4 to 11:

1.

4. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: In step S2, the mass ratio of potassium chloride to water is 1:2 to 3.5; the mass ratio of potassium mother liquor to potassium sulfate is 1.5 to 3:

1.

5. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: In step S3, the mass ratio of potassium mother liquor to sodium sulfate is 4–9:1; the mass ratio of evaporated water to potassium mother liquor is 0.1–0.3:1; the Na in mother liquor II... + With K + The mass ratio is 1~3:1, Cl - With SO4 2- The mass ratio is 4 to 8:

1.

6. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: In step S4, the mass ratio of industrial salt I, water, and mother liquor III is 1:1 to 5:6 to 12; the mass ratio of mother liquor III to water added to mother liquor III is 10 to 30:

1.

7. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: In step S5, 10% to 60% of the total mass of mother liquor four is mixed with mother liquor one.

8. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: In S6, the mass ratio of industrial salt II, water, and mother liquor VI is 1:1 to 6:8 to 15.

9. The self-balancing production method for preparing potassium sulfate using high-nitrate and high-potassium wastewater according to claim 1, characterized in that: 10% to 30% of the total water mass is extracted from the water storage device and sent to step S2 for conversion reaction two; 1% to 5% of the total water mass is extracted from the water storage device and sent to step S4 for conversion reaction three.

10. The self-balancing production method for preparing potassium sulfate from high-nitrate and high-potassium wastewater according to any one of claims 1 to 9, characterized in that: The potassium sulfate obtained in S2 has a purity of ≥98%; the sodium chloride obtained in industrial salt I in S4 and industrial salt II in S6 has a purity of ≥98.5%.

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