A method for preparing potassium sulfate in water-salt system by combining full water-soluble potassium sulfate and common agricultural potassium sulfate

Abstract

This invention provides a method for the combined preparation of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in a water-salt system, belonging to the field of salt lake chemical technology. This invention uses potassium chloride flotation concentrate and soft potassium flotation concentrate as raw materials, resulting in low cost. This invention does not require significant modifications to existing water-salt system potassium sulfate production facilities, nor does it require the construction of new engineering facilities; the combined production of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate can be achieved using existing water-salt system potassium sulfate production facilities. Without increasing the water consumption of the original production system and ensuring system yield, this invention can produce 1 ton of fully water-soluble potassium sulfate product for every 9 tons of ordinary water-salt system potassium sulfate product. The fully water-soluble potassium sulfate product of this invention has a potassium oxide content ≥53.00%, meeting the requirements of the superior grade standard for agricultural potassium sulfate. The mother liquor can be circulated internally within the system, resulting in low production costs and strong market competitiveness.

Description

Technical Field

[0001] This invention relates to the field of salt lake chemical technology, and in particular to a method for the combined preparation of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in a water-salt system. Background Technology

[0002] Water-soluble fertilizers refer to single-element chemical fertilizers or compound fertilizers that are completely soluble in water. They are dissolved or diluted in water and used for irrigation, foliar fertilization, hydroponics, seed soaking, root dipping, and other applications. They are primarily used to supplement crops with essential nutrients (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and trace elements). Because water-soluble fertilizers are completely soluble in water, they offer advantages such as no residue, high absorption rate, convenient application, and easy absorption by crops. With the booming market for water-soluble fertilizers, more and more potash fertilizer manufacturers are developing similar new products.

[0003] There are two main production methods for agricultural potassium sulfate products in the market: the Mannheim process and the water-salt system process. Water-salt system potassium sulfate accounts for approximately 60% of the total potassium sulfate market, and its raw material is sulfate-type potassium-containing brine from salt lakes. The most representative salt lake in China is Lop Nur Salt Lake, which houses the world's largest potassium sulfate production facility. Compared to Mannheim process potassium sulfate, water-salt system potassium sulfate products have advantages such as high nutrient content, being environmentally friendly, and free of free acid. However, they also have disadvantages such as high insoluble content and slow dissolution rate. With the rapid development of integrated water and fertilizer management in China, reducing the insoluble content in water-salt system potassium sulfate products and producing fully water-soluble water-salt system potassium sulfate products is becoming increasingly important.

[0004] According to relevant data, the insoluble content of potassium sulfate in water-salt systems is around 0.5%, mainly consisting of clay, sand, and sodium sulfate. To remove this low content of insoluble matter, a separate purification and impurity removal unit for potassium sulfate in water-salt systems is constructed. However, this results in high production costs and significant potassium loss, leading to poor market competitiveness for the produced fully water-soluble potassium sulfate product. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for the combined preparation of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in a water-salt system. The method of this invention can realize the combined production of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate, with low production cost and strong market competitiveness.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for the combined preparation of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in a water-salt system, comprising the following steps:

[0008] (1) Mix potassium chloride flotation concentrate and soft potassium flotation concentrate to obtain flotation concentrate mixture;

[0009] (2) Wash the flotation concentrate mixture with potassium-containing mother liquor to remove sodium chloride from the flotation concentrate mixture and obtain mixed potassium;

[0010] (3) Mix the potassium mixture with hot water, heat to 84-88°C, stir to dissolve, and separate the solid and liquid to remove insoluble matter to obtain hot potassium mother liquor;

[0011] (4) Cool the hot potassium mother liquor for crystallization and solid-liquid separation to obtain a first solid and a first filtrate. The obtained solid is fully water-soluble potassium sulfate.

[0012] (5) The first filtrate is mixed with mixed potassium and heated to 39-43°C for conversion crystallization and solid-liquid separation to obtain a second solid and a second filtrate. The second solid obtained is ordinary agricultural potassium sulfate.

[0013] Preferably, the potassium-containing mother liquor in step (2) comprises, by mass percentage, the following components:

[0014]

[0015] Preferably, the potassium-containing mother liquor in step (2) is the second filtrate obtained in step (5).

[0016] Preferably, the main component of the potassium chloride flotation concentrate includes potassium chloride, and the potassium chloride flotation concentrate contains K + The mass content is 24.2-30.0%, Na + The mass content is 6.1%–9.0%;

[0017] The main components of the soft potassium flotation concentrate include soft potassium magnesium vanadium, and the K in the soft potassium flotation concentrate + The mass percentage content is 14.1-17.5%, Na + The mass percentage content is 1.8%–4.0%.

[0018] Preferably, the mass ratio of potassium to sulfur in the flotation concentrate mixture is 1.25 to 1.3:1.

[0019] Preferably, in step (2), the mass ratio of the flotation concentrate mixture to the potassium-containing mother liquor is 1:1.5 to 1.7.

[0020] Preferably, in step (3), the mass ratio of mixed potassium to hot water is 1:2 to 2.1.

[0021] Preferably, in step (3), the K in the hot potassium mother liquor + The mass concentration is 8.1%–8.3%.

[0022] Preferably, the cooling crystallization temperature in step (4) is 25-30°C.

[0023] Preferably, in step (5), the mass ratio of the first filtrate to the mixed potassium is 1.7 to 1.9:1.

[0024] This invention provides a method for the combined preparation of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in a water-salt system, comprising the following steps: (1) mixing potassium chloride flotation concentrate and soft potassium flotation concentrate to obtain a flotation concentrate mixture; (2) washing the flotation concentrate mixture with potassium-containing mother liquor to remove sodium chloride from the flotation concentrate mixture to obtain mixed potassium; (3) mixing the mixed potassium with hot water, heating to 84-88°C, stirring to dissolve, and separating the solid and liquid to remove insoluble matter to obtain hot potassium mother liquor; (4) cooling and crystallizing the hot potassium mother liquor and separating the solid and liquid to obtain a first solid and a first filtrate, wherein the obtained solid is fully water-soluble potassium sulfate; (5) mixing the first filtrate with the mixed potassium, heating to 39-43°C, performing conversion crystallization and solid-liquid separation to obtain a second solid and a second filtrate, wherein the obtained second solid is ordinary agricultural potassium sulfate. This invention uses potassium chloride flotation concentrate and soft potassium flotation concentrate as raw materials, resulting in low costs. It requires no major modifications to existing water-salt system potassium sulfate production facilities, nor does it necessitate the construction of new engineering facilities; the existing water-salt system potassium sulfate production facilities can be used to achieve the combined production of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate. Without increasing the water consumption of the original production system and ensuring system yield, this invention can achieve the combined production of fully water-soluble potassium sulfate and ordinary potassium sulfate products. For every 9 tons of ordinary water-salt system potassium sulfate produced, 1 ton of fully water-soluble potassium sulfate product can be produced simultaneously. The fully water-soluble potassium sulfate product of this invention has a potassium oxide content ≥53.00%, meeting the requirements of the superior grade standard for agricultural potassium sulfate. The mother liquor can be internally circulated within the system, resulting in low production costs and strong market competitiveness. Attached Figure Description

[0025] Figure 1 This is a process flow diagram for the combined production of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in the water-salt system of this invention. Detailed Implementation

[0026] This invention provides a method for the combined preparation of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in a water-salt system, comprising the following steps:

[0027] (1) Mix potassium chloride flotation concentrate and soft potassium flotation concentrate to obtain flotation concentrate mixture;

[0028] (2) Wash the flotation concentrate mixture with potassium-containing mother liquor to remove sodium chloride from the flotation concentrate mixture and obtain mixed potassium;

[0029] (3) Mix the potassium mixture with hot water, heat to 84-88°C, stir to dissolve, and separate the solid and liquid to remove insoluble matter to obtain hot potassium mother liquor;

[0030] (4) Cool the hot potassium mother liquor for crystallization and solid-liquid separation to obtain a first solid and a first filtrate. The obtained solid is fully water-soluble potassium sulfate.

[0031] (5) The first filtrate is mixed with mixed potassium and heated to 39-43°C for conversion crystallization and solid-liquid separation to obtain a second solid and a second filtrate. The second solid obtained is ordinary agricultural potassium sulfate.

[0032] This invention mixes potassium chloride flotation concentrate and soft potassium flotation concentrate to obtain a flotation concentrate mixture. In this invention, the potassium chloride flotation concentrate is preferably obtained from the decomposition and flotation of carnallite. In this invention, the main component of the potassium chloride flotation concentrate preferably includes potassium chloride, and the remaining components preferably include potassium magnesium sulfate and sodium chloride; in this invention, the potassium chloride flotation concentrate contains K... + The preferred mass content is 24.2–30.0%, more preferably 26.0–28.0%, Na + The preferred mass content is 6.1-9.0%, more preferably 7.0-8.0%.

[0033] In this invention, the source of the soft potassium flotation concentrate is preferably the flotation concentrate obtained after conversion and flotation of potassium mixed salt ore. In this invention, the main components of the soft potassium flotation concentrate preferably include soft potassium magnesium vanadium, and the remaining components are preferably sodium chloride; in this invention, the K in the soft potassium flotation concentrate... + The preferred mass percentage content is 14.1–17.5%, more preferably 15–16%, Na + The preferred mass percentage is 1.8% to 4.0%, more preferably 2% to 3%.

[0034] The present invention has specific requirements for the mixing method, and any mixing method well known to those skilled in the art can be used, such as stirring. In the present invention, the mass ratio of potassium to sulfur in the flotation concentrate mixture is preferably 1.25 to 1.3:1, more preferably 1.26 to 1.28:1.

[0035] After obtaining the flotation concentrate mixture, the present invention uses a potassium-containing mother liquor to wash the flotation concentrate mixture to remove sodium chloride from the flotation concentrate mixture, thereby obtaining mixed potassium. In the present invention, the potassium-containing mother liquor is unsaturated with sodium chloride.

[0036] In this invention, the potassium-containing mother liquor preferably comprises, by weight percentage:

[0037]

[0038] In this invention, the potassium-containing mother liquor is preferably the second filtrate obtained in step (5).

[0039] In this invention, the mass ratio of the flotation concentrate mixture to the potassium-containing mother liquor is preferably 1:1.5 to 1.7, and more preferably 1:1.6.

[0040] This invention does not impose any special requirements on the washing method; any washing method well-known to those skilled in the art can be used. In this invention, the washing temperature is preferably 33–38°C, and the washing time is preferably 0.5 hours.

[0041] After obtaining the mixed potassium, the present invention mixes the mixed potassium with hot water, heats it to 84-88°C, stirs to dissolve, and performs solid-liquid separation to remove insoluble matter, obtaining a hot potassium mother liquor. In the present invention, the temperature of the hot water is preferably 30-35°C. In the present invention, the mass ratio of the mixed potassium to the hot water is preferably 1:2-2.1. The present invention does not have special requirements for the mixing method; any mixing method well known to those skilled in the art can be used, such as stirring.

[0042] In this invention, the stirring rate during the stirring and dissolving process is preferably 150-300 r / min, more preferably 200-250 r / min, and the stirring time is preferably 60-70 min.

[0043] In this invention, the solid-liquid separation method is preferably filtration.

[0044] In this invention, in the hot potassium mother liquor, K + The preferred mass concentration is 8.1% to 8.3%, more preferably 8.2%.

[0045] After obtaining the hot potassium mother liquor, the present invention cools and crystallizes the hot potassium mother liquor and separates the solid and liquid to obtain a first solid and a first filtrate. The obtained solid is fully water-soluble potassium sulfate. In the present invention, the cooling and crystallization temperature is preferably 25-30°C, more preferably 26-28°C. In the present invention, the cooling rate is preferably 60 min. In the present invention, during the cooling and crystallization process, potassium chloride crystallizes with soft potassium magnesium vanadium to precipitate potassium sulfate crystals.

[0046] In this invention, the solid-liquid separation method is preferably centrifugal filtration. After solid-liquid separation, the resulting first solid is a fully water-soluble potassium sulfate wet material. Preferably, the fully water-soluble potassium sulfate wet material is dried to obtain the fully water-soluble potassium sulfate product. This invention does not have special requirements for the drying method; any drying method well-known to those skilled in the art can be used.

[0047] After obtaining the first filtrate, the present invention mixes the first filtrate with mixed potassium, heats it to 39-43°C, and performs conversion crystallization and solid-liquid separation to obtain a second solid and a second filtrate. The obtained second solid is ordinary agricultural potassium sulfate. In the present invention, the mass ratio of the first filtrate to the mixed potassium is preferably 1.7-1.9:1, more preferably 1.8:1. The present invention does not have special requirements for the mixing method; any mixing method well known to those skilled in the art can be used, such as stirring.

[0048] In this invention, the conversion crystallization is preferably carried out in an upward-pushing, downward-lifting crystallizer. During the conversion crystallization process, potassium chloride and soft potassium magnesium vanadium are converted into potassium sulfate. In this invention, the solid precipitated during the crystallization process is agricultural potassium sulfate in a common aqueous salt system.

[0049] In this invention, the solid-liquid separation method is preferably centrifugal filtration. In this invention, the second solid obtained after solid-liquid separation is ordinary agricultural potassium sulfate wet material. Preferably, the ordinary agricultural potassium sulfate wet material is dried to obtain the ordinary agricultural potassium sulfate product.

[0050] In this invention, the second filtrate is preferably reused as a washing liquid for flotation concentrate mixture, which can realize internal circulation of the system and reduce production costs.

[0051] The fully water-soluble potassium sulfate product obtained by this invention has a potassium oxide content of ≥53.00%, which meets the requirements of the superior grade standard for agricultural potassium sulfate; the ordinary agricultural potassium sulfate product obtained has a potassium oxide content of ≥52.00%.

[0052] The process flow diagram for the combined production of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate in this invention is as follows: Figure 1 As shown.

[0053] The following detailed description, in conjunction with embodiments, illustrates the method for the combined preparation of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1

[0055] K was obtained after decomposition and flotation of carnallite ore. + Content is 25.6%, Na + A potassium chloride flotation concentrate with a content of 8.45% was converted into potassium mixed salt ore and then floated to obtain K. + The content is 15.1%, Na + A soft potassium flotation concentrate with a content of 1.86% was thoroughly mixed with two flotation concentrates at a mass ratio of 1.5:1 to obtain a flotation concentrate mixture with a potassium-to-sulfur ratio of 1.27:1.

[0056] Flotation concentrate mixture and potassium-containing mother liquor (composition: Na)+ 0.7%, K + 7.6%, Mg 2+ 2.2%, SO4 2- 5.6%, Cl - 10%) were mixed and stirred at a mass ratio of 1:1.5, and the mixture was washed to remove sodium chloride impurities from the flotation concentrate mixture to obtain K. + The content is 26.6%, SO4 2- A mixed potassium solution with a content of 25.25%;

[0057] Potassium hydroxide was mixed with fresh water at a mass ratio of 1:2, heated to 85°C for 60 minutes to dissolve, and insoluble matter was removed using a sedimentation centrifuge to obtain potassium hydroxide. + High-temperature mother liquor with a content of 8.21% was subjected to a process of cooling and crystallization at 26℃, concentration, centrifugation, and drying to obtain a fully water-soluble potassium sulfate product with a potassium oxide content of 53.10%, which meets the requirements for superior grade potassium sulfate.

[0058] The first filtrate obtained after cooling and crystallization, along with the aforementioned mixed potassium, was fed into a potassium sulfate crystallizer at a mass ratio of 1.8:1. The crystallization temperature was 42℃, and the crystallization time was 90 min. After centrifugation and drying at the bottom of the crystallizer, ordinary agricultural potassium sulfate with a potassium oxide content of 52.12% was obtained. The second filtrate obtained after centrifugation was used for washing the subsequent flotation concentrate mixture.

[0059] The elemental composition of the obtained ordinary agricultural potassium sulfate and fully water-soluble potassium sulfate is shown in Table 1.

[0060] Table 1. Elemental composition of ordinary agricultural potassium sulfate and fully water-soluble potassium sulfate

[0061]

[0062] Example 2

[0063] K was obtained after decomposition and flotation of carnallite ore. + A potassium chloride flotation concentrate with a content of 27% was mixed and washed with the second filtrate obtained in Example 1, and then filtered to obtain Na. + Similarly, after washing and filtering the wet potassium chloride concentrate with a content of 2.6%, Na is obtained. + A wet soft potassium content of 1.80% was used. The two washed materials were mixed in a certain proportion to form a potassium-sulfur ratio of 1.3. This potassium mixture was then mixed with hot water at a mass ratio of 1:2 and thermally dissolved at 85℃ to generate potassium sulfate (K). + The high-temperature mother liquor with a content of 8.17% was cooled at 35°C to precipitate potassium sulfate. After filtration and drying, a fully water-soluble potassium sulfate product was obtained, with a potassium oxide content of 53%, which meets the requirements for superior grade potassium sulfate.

[0064] After potassium sulfate precipitates, the filtrate is mixed with mixed potassium at a mass ratio of 1.8:1, and heated to 42°C for conversion crystallization. Subsequent operations are the same as in Example 1, and finally ordinary agricultural potassium sulfate with a potassium oxide content of 52.3% is obtained.

[0065] Example 3

[0066] K was obtained after decomposition and flotation of carnallite ore. + The content is 26.5%, Na + A potassium chloride flotation concentrate with a content of 7.86% was converted to potassium mixed salt ore and then floated to obtain K. + The content is 14.8%, Na + A soft potassium flotation concentrate with a content of 2.32% was thoroughly mixed with two flotation concentrates at a mass ratio of 1.6:1 to obtain a flotation concentrate mixture with a sulfur-potassium ratio of 1.28:1.

[0067] Flotation concentrate mixture and potassium-containing mother liquor (composition: Na) + 0.7%, k + 7.6%, Mg 2+ 2.2%, SO4 2- 5.6%, Cl - 10%) were mixed and stirred at a mass ratio of 1:1.6, and the mixture was washed to remove sodium chloride impurities from the flotation concentrate mixture to obtain K. + The content is 26.2%, SO4 2- Mixed potassium with a content of 25.07%;

[0068] Potassium hydroxide was mixed with fresh water at a mass ratio of 1:2.02, heated to 85°C for 60 minutes to dissolve, and insoluble matter was removed using a sedimentation centrifuge to obtain potassium hydroxide. + High-temperature mother liquor with a content of 8.26% was subjected to a process of cooling and crystallization at 27℃, concentration, centrifugation, and drying to obtain a fully water-soluble potassium sulfate product with a potassium oxide content of 53.18%, which meets the requirements for superior grade potassium sulfate.

[0069] The first filtrate obtained after cooling and crystallization, along with the aforementioned mixed potassium, was fed into a potassium sulfate crystallizer at a mass ratio of 1.75:1. The crystallization temperature was 42℃, and the crystallization time was 90 min. After centrifugation and drying at the bottom of the crystallizer, ordinary agricultural potassium sulfate with a potassium oxide content of 52.24% was obtained. The second filtrate obtained after centrifugation was used for washing the subsequent flotation concentrate mixture.

[0070] Example 4

[0071] K was obtained after decomposition and flotation of carnallite ore. + A potassium chloride flotation concentrate with a content of 26.8% was mixed and washed with the second filtrate obtained in Example 1, and then filtered to obtain Na. + A wet potassium chloride feedstock with a content of 2.1% was used; after washing the soft potassium concentrate, Na was obtained by filtration.+ The wet soft potassium content is 2.5%; the two washed materials are mixed in a certain proportion to form a mixed potassium with a potassium-sulfur ratio of 1.28. The mixed potassium is mixed with hot water at a mass ratio of 1:2.2 and then dissolved at 85°C to generate a high-temperature mother liquor with a potassium content of 8.2%. After cooling the high-temperature mother liquor at 40°C, potassium sulfate is precipitated. After filtration and drying, a fully water-soluble potassium sulfate product is obtained with a potassium oxide content of 53.5%, which meets the requirements for superior grade potassium sulfate.

[0072] After potassium sulfate precipitates, the filtrate is mixed with mixed potassium at a mass ratio of 1.85:1, and heated to 42°C for conversion crystallization. Subsequent operations are the same as in Example 1, and finally ordinary agricultural potassium sulfate with a potassium oxide content of 52.00% is obtained.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a water-salt system of fully water-soluble potassium sulfate and ordinary agricultural potassium sulfate, comprising the following steps: (1) Potassium chloride flotation concentrate and soft potassium flotation concentrate are mixed to obtain flotation concentrate mixture; the mass ratio of potassium to sulfur in the flotation concentrate mixture is 1.25~1.3:1; (2) The flotation concentrate mixture is washed with potassium-containing mother liquor to remove sodium chloride from the flotation concentrate mixture and obtain mixed potassium; (3) Mix the potassium mixture with hot water, heat to 84~88℃, stir to dissolve, separate the solid and liquid to remove insoluble matter, and obtain hot potassium mother liquor; (4) Cooling and crystallizing the hot potassium mother liquor and separating the solid and liquid to obtain a first solid and a first filtrate. The obtained solid is fully water-soluble potassium sulfate. The cooling and crystallization temperature is 25~30℃. (5) The first filtrate is mixed with mixed potassium, heated to 39~43℃, and transformed crystallization and solid-liquid separation are carried out to obtain the second solid and the second filtrate. The second solid obtained is ordinary agricultural potassium sulfate. The main component of the potassium chloride flotation concentrate is potassium chloride, and the potassium chloride flotation concentrate contains K + The mass content is 24.2~30.0%, Na + The mass content is 6.1%~9.0%; The main components of the soft potassium flotation concentrate include soft potassium magnesium vanadium, and the K in the soft potassium flotation concentrate + The mass percentage content is 14.1~17.5%, Na + The mass percentage content is 1.8~4.0%.

2. The method according to claim 1, characterized in that, The potassium-containing mother liquor in step (2) comprises, by mass percentage, the following components: That + 0.5~0.8%; K + 7.0~9.0%； Mg 2+ 2.0~2.8%; SO4 2- 4.5~7%; Cl - 10.0~13.0%。 3. The method according to claim 1, characterized in that, The potassium-containing mother liquor in step (2) is the second filtrate obtained in step (5).

4. The method according to claim 1, 2 or 3, characterized in that, In step (2), the mass ratio of the flotation concentrate mixture to the potassium-containing mother liquor is 1:1.5~1.

7.

5. The method according to claim 1, characterized in that, In step (3), the mass ratio of mixed potassium to hot water is 1:2~2.

1.

6. The method according to claim 1 or 5, characterized in that, In step (3), K in the hot potassium mother liquor + The mass concentration is 8.1-8.3%.

7. The method according to claim 1, characterized in that, The cooling and crystallization temperature in step (4) is 25~30℃.

8. The method according to claim 1, characterized in that, In step (5), the mass ratio of the first filtrate to the mixed potassium is 1.7~1.9:1.

Images