Production process for preparing potassium chloride by utilizing sylvite-containing carnallite

Abstract

The invention relates to a production process for preparing potassium chloride by utilizing sylvite-containing carnallite. The production process comprises the following steps: crushing raw ore; adding water of which the TDS / mg / L is less than 45000, the potassium-containing mother liquor and the blended mother liquor for crystallization; carrying out primary screening on the first-stage crystallization underflow, feeding an oversize product S1 to second-stage crystallization, and carrying out first-stage thickening on undersize slurry; the first-section dense underflow is conveyed to a flotation size mixing tank; adding water of which the TDS / mg / L is less than 45000, a flotation mother solution and a blended mother solution into the second-stage crystallization; second-stage crystallization underflow is subjected to secondary screening, oversize products S2 are conveyed to be ground, and undersize slurry is subjected to second-stage thickening; the second-section dense underflow is conveyed to a flotation size mixing tank; after ore grinding, materials are conveyed to a flotation size mixing tank; and adding fresh water and pulp mixing mother liquor into the concentrate K1, washing, and carrying out solid-liquid separation to obtain a potassium chloride product. The method is simple in process and high in product yield.

Description

Technical Field

[0001] The present invention relates to the field of a preparation method of potassium chloride, and particularly relates to a production process for preparing potassium chloride by using carnallite ore containing potassium rock. Background Art

[0002] Currently, carnallite ore is generally processed by a decomposition - positive flotation or decomposition crystallization - positive flotation process for the production of agricultural potassium chloride fertilizer. The addition of water in the process includes adding water at the front end of the process (i.e., the decomposition or decomposition crystallization process) to decompose carnallite and then perform flotation, such as the processes disclosed in CN107739037A, CN 102963912A, and CN 204079502U. There is also a method of adding water required for decomposing carnallite to the back end of the process for washing crude potassium and tailings. For example, CN112551553B discloses a high - recovery production process for extracting potassium chloride from carnallite ore.

[0003] The disadvantage of adding water to decompose carnallite at the front end of the process is that the amount of decomposed water is not easy to control. If the amount of water added is small, the concentration and viscosity of the decomposition liquid of MgCl 2 both increase, the decomposition rate becomes slower, the entrainment rate of impurities in the flotation foam increases, resulting in a significant decrease in the grade of crude potassium (the grade of crude potassium in Qarhan Salt Lake, Qinghai is generally between 58% and 70%), and the potassium chloride grade in the flotation tailings is 3 - 5.7%, resulting in a low potassium chloride recovery rate of the system. Adding water at the back end of the process also has problems of many water - using points and a large amount of water consumption. For example, in CN112551553B, water is added for washing after the first crystallization, and water is added for washing the tailings slurry and crude potassium after flotation, and there are still many water - using points with a low precision control level. In addition, in this process, the carnallite ore is crushed to ≤8mm, with high requirements for the crushing particle size, high requirements for equipment, and high cost investment. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] In view of the above - mentioned disadvantages and deficiencies of the prior art, the present invention provides a production process of potassium chloride with low cost and high recovery rate.

[0006] Technical Solution

[0007] To achieve the above object, an embodiment of the present invention provides a production process for preparing potassium chloride by using carnallite ore containing potassium rock, including:

[0008] Crushing the collected raw carnallite ore to ≤15mm;

[0009] Water with TDS / mg / L < 45000, potassium-containing mother liquor and blending mother liquor are added for crystallization. The amount of water added is 17% - 30% of the mass of the original ore with a particle size ≤ 15 mm after crushing. The amount of potassium-containing mother liquor added is 20% - 28% of the mass of the original ore with a particle size ≤ 15 mm after crushing. The overflow of the first-stage crystallization is controlled at 8% - 12%. The amount of blending mother liquor added is used to control the mass concentration of the underflow of the first-stage crystallization at 25% - 40%.

[0010] The underflow of the first-stage crystallization is screened once to obtain the oversize S1 and the undersize slurry. The oversize S1 is sent to the second-stage crystallizer for operation, and the undersize slurry is thickened in the first stage.

[0011] The underflow of the first-stage thickening is transported to the flotation pulp mixing tank. Part of the overflow of the first-stage thickening is returned to the first-stage crystallization as the blending mother liquor, and the excess overflow of the first-stage thickening is evaporated.

[0012] Water with TDS / mg / L < 45000, flotation mother liquor and blending mother liquor are added to the second-stage crystallization operation. The amount of water added in the second stage is 1.5% - 5.0% of the mass of the original ore with a particle size ≤ 15 mm after crushing. The amount of flotation mother liquor added is 50% - 65% of the mass of the original ore with a particle size ≤ 15 mm after crushing. The amount of blending mother liquor added is 65% - 75% of the mass of the original ore with a particle size ≤ 15 mm after crushing.

[0013] The underflow of the second-stage crystallization is screened twice to obtain the oversize S2 and the undersize slurry. The oversize S2 is sent to the grinding operation, and the undersize slurry is thickened in the second stage. All the supernatant of the second-stage thickening is returned to the second-stage crystallizer as the blending mother liquor.

[0014] The underflow of the second-stage thickening is transported to the flotation pulp mixing tank. Part of the overflow of the second-stage thickening is returned to the second-stage crystallization as the blending mother liquor, and the excess overflow of the second-stage thickening is transported to the grinding operation.

[0015] In the grinding operation, the oversize S2 controls the pulp mixing mass concentration at 50% - 65% through the overflow of the second-stage thickening, and the discharged material after grinding is transported to the flotation pulp mixing tank.

[0016] Flotation agent is added for flotation to obtain flotation concentrate and flotation tailings. The flotation concentrate and flotation tailings are filtered respectively to obtain concentrate filter cake K1 and tailings filter cake T1. The filtrate is returned to the second-stage crystallization operation as the blending mother liquor or returned to the flotation pulp mixing tank for pulp mixing.

[0017] The concentrate filter cake K1 is slurried, stirred and washed with water and washing mother liquor, and then solid-liquid separation is carried out to obtain potassium chloride products. Part of the separated filtrate is returned to the stirring and washing operation of the concentrate filter cake K1 for pulp mixing, and the excess filtrate is returned to the flotation operation.

[0018] In one embodiment, the screening particle size of both the first screening and the second screening is 0.6 mm - 1 mm.

[0019] In one embodiment, the potassium-containing mother liquor is brine with a KCl mass content of 6.00 - 13.0%, the KCl mass content in the blending mother liquor is 2.0 - 6.5%, the MgCl2 mass content is 21.3 - 26.6%, and the NaCl mass content is 2.0 - 3.0%.

[0020] In one embodiment, the mass concentration of the first-stage thickener underflow is 40% - 55%.

[0021] In one embodiment, the mass concentration of the second-stage crystallization underflow is 25% - 33%.

[0022] In one embodiment, the mass concentration of the slurry in the floating and adjusting pulp tank is controlled to be 26% - 33% by the opening degree of the thickener underflow valve.

[0023] In one embodiment, the flotation agent is a three-in-one flotation agent composed of octadecylamine, hydrochloric acid, and a foaming agent.

[0024] In one embodiment, the flotation agent is in an oil-wax shape, and when in use, the flotation agent is prepared into a solution with a mass fraction of 2% using 85°C water.

[0025] In one embodiment, the addition amount of the flotation agent is 130 g / t of raw ore - 200 g / t of raw ore.

[0026] In one embodiment, the potassium-containing mother liquor is the overflow mother liquor of the second-stage crystallization.

[0027] (III) Beneficial effects

[0028] The beneficial effects of the present invention are as follows: In the present invention, the collected carnallite containing primary potassium rock (with a potassium rock content of 1-8%) is crushed to ≤15 mm. Compared with the prior art where the raw ore is first crushed to a finer particle size, such as below 8 mm, the present application only needs to crush it to 15 mm, which can not only save equipment costs but also alleviate the problem of salt crystallization and blockage of the crushing equipment. The coarser particle size can slow down the decomposition of carnallite, control a large number of potassium chloride crystal nuclei, create conditions for the crystallization of potassium chloride, and achieve the purpose of controlled-rate crystallization. The amount of water added in the first-stage crystallization is 17-30% of the mass of the raw ore with a particle size of ≤15 mm after crushing. In the prior art, due to multiple water addition points for decomposition and difficult control of equipment water consumption, the E mother liquor is unsaturated and the system recovery rate is low. In the present application, the main water addition point is in the first-stage crystallization. The subsequent water addition amount is very small and is not discharged after addition but directly recycled, thus well controlling the water consumption. The discharged mother liquor is a saturated or supersaturated mother liquor, which can reduce the evaporation scale, reduce the potassium discharge amount, and improve the recovery rate. Two-stage crystallization is adopted. In the second-stage crystallization, refined potassium mother liquor and a small amount of water are added to fully decompose the insufficiently decomposed carnallite and improve the recovery rate. After two-stage crystallization, the carnallite can be fully decomposed. Almost all of the oversize materials after two-stage screening are potassium rock, and the potassium rock can be recovered after grinding, which can increase the recovery rate by at least 3%. Further, because some water will be mixed in during the flotation operation or filtration operation, resulting in an unsaturated mother liquor, the mother liquor generated during the flotation operation is not discharged but recycled in the system, reducing the potassium discharge amount and increasing the recovery rate.

[0029] In summary, the mother liquor discharged in the present application is only the overflow of the first-stage crystallizer, and this mother liquor is in a saturated or supersaturated state, solving the problem in the traditional process that the mother liquor discharged from the tailing filtrate is unsaturated due to some water entering the mother liquor through the generally selected horizontal belt filter for tailing filtration equipment, resulting in the dissolution of part of the potassium and a low system recovery rate; through two-stage crystallization and grinding, the system recovery rate is further improved. The present application can make the recovery rate of the potassium chloride system reach more than 81.95%, the potassium chloride grade ≥95%, and the KCl grade of the tailings is controlled below 1.0%. Compared with the prior art where the potassium chloride recovery rate is 55% and the KCl in the tailings is 6.5%, the recovery rate and grade are greatly improved, and the present application has a low cost, a simple process, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the production process flow for producing potassium chloride using carnallite ore containing potassium rock according to an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to better explain the present invention for easy understanding, the present invention will be described in detail below through specific embodiments.

[0032] Please refer to Figure 1, an embodiment of the present invention provides a production process for preparing potassium chloride from carnallite ore containing potassium feldspar rock, including the steps:

[0033] S1. Crush the collected native carnallite ore to ≤15 mm.

[0034] Crush the collected native carnallite ore containing potassium feldspar rock (with a potassium feldspar rock content of 1-8%) to ≤15 mm. Compared with the prior art, which first crushes the raw ore to a finer particle size, such as below 8 mm, the present application only needs to crush it to 15 mm. This can not only save equipment costs but also alleviate the problem of salt crystallization and blockage of the crushing equipment. The coarser particle size can slow down the decomposition of carnallite, control a large number of potassium chloride crystal nuclei, create conditions for the crystallization of potassium chloride, and achieve the purpose of controlled-rate crystallization.

[0035] S2. Add water with TDS / mg / L < 45000, potassium-containing mother liquor, and conditioning mother liquor for crystallization. The water addition amount is 17-30% of the mass of the raw ore with a particle size of ≤15 mm after crushing. The potassium-containing mother liquor addition amount is 20%-28% of the mass of the raw ore. Control the overflow rate of the first-stage crystallization to be 8%-12%. The conditioning mother liquor addition amount is used to control the bottom flow concentration of the first-stage crystallization to be 25%-40%.

[0036] Specifically, in one embodiment, the potassium-containing mother liquor is brine with a KCl mass content of 6.00-13.0%. The KCl mass content in the conditioning mother liquor is 2.0-6.5%, the MgCl2 mass content is 21.3-26.6%, and the NaCl mass content is 2.0-3.0%.

[0037] Preferably, the overflow mother liquor of the second-stage crystallization can be used as the potassium-containing mother liquor. Preferably, the liquid filtered in flotation can be used as the conditioning mother liquor. Using the solutions generated in the process as corresponding functional liquids can save costs and improve efficiency.

[0038] In the first-stage crystallization, the water addition amount is 17-30% of the mass of the raw ore with a particle size of ≤15 mm after crushing. In the prior art, due to multiple decomposition water addition points and difficult control of equipment water consumption, the E mother liquor is unsaturated and the system recovery rate is low. In the present application, the main water addition point is controlled in the first-stage crystallization. The subsequent water addition amount is very small and is not discharged after addition but directly recycled, thus well controlling the water consumption, ensuring that the discharged mother liquor is saturated or supersaturated mother liquor. This can reduce the evaporation scale, reduce the potassium emission, and improve the recovery rate.

[0039] S3. Screen the bottom flow of the first-stage crystallization once to obtain the oversize S1 and the undersize slurry. The oversize S1 is sent to the second-stage crystallizer for operation, and the undersize slurry is subjected to first-stage thickening.

[0040] Specifically, in one embodiment, the screening particle size of the primary screening is 0.6 mm to 1 mm.

[0041] S4. Transport the underflow of the first thickening to the flotation pulp preparation tank. Part of the overflow of the first thickening is returned to the first crystallization as the blending mother liquor, and the excess overflow of the first thickening is evaporated.

[0042] The excess overflow of the first thickening is the only discharge point of this application. Due to the design of the liquid addition amount and the crushing of the original ore particle size in the front, the discharged mother liquor is a saturated or supersaturated mother liquor, which can reduce the evaporation scale, reduce the potassium discharge amount, and improve the recovery rate.

[0043] Specifically, in one embodiment, the mass concentration of the underflow of the first thickening is 40% to 55%.

[0044] S5. Add water with TDS / mg / L < 45000, flotation mother liquor, and blending mother liquor to the second crystallization operation. The addition amount of the second-stage water is 1.5% to 5.0% of the mass of the original ore with a particle size ≤ 15 mm after crushing, the addition amount of the flotation mother liquor is 50% to 65% of the mass of the original ore with a particle size ≤ 15 mm after crushing, and the addition amount of the blending mother liquor is 65% to 75% of the mass of the original ore with a particle size ≤ 15 mm after crushing.

[0045] Adding refined potassium mother liquor and a small amount of water in the second crystallization can fully decompose the carnallite that has not been fully decomposed, improve the yield. After the carnallite passes through the second crystallization, it can be fully decomposed. The oversize material of the second screening is almost all potassium rock, and the potassium rock can be recovered after grinding, and the yield can be increased by at least 3%.

[0046] S6. Perform secondary screening on the underflow of the second crystallization to obtain the oversize material S2 and the undersize pulp. The oversize material S2 is sent to the grinding operation, and the undersize pulp is thickened for the second time. The supernatant of the second thickening is all returned to the second crystallizer as the blending mother liquor;

[0047] The screening particle size of the secondary screening is 0.6 mm to 1 mm.

[0048] S7. Transport the underflow of the second thickening to the flotation pulp preparation tank. Part of the overflow of the second thickening is returned to the second crystallization as the blending mother liquor, and the excess overflow of the second thickening is transported to the grinding operation;

[0049] In one embodiment, the mass concentration of the underflow of the second crystallization is 25% to 33%.

[0050] S8. In the grinding operation, the oversize material S2 controls the pulp mass concentration to 50% to 65% through the overflow of the second thickening, and the discharged material after grinding is transported to the flotation pulp preparation tank;

[0051] After two-stage crystallization decomposition, the oversize material is potassium rock ore with coarser particle size (which cannot be decomposed during crystallization decomposition). By grinding it to an appropriate particle size, potassium rock can be separated through flotation, thereby improving the product yield.

[0052] S9. Add a flotation agent for flotation to obtain flotation concentrate and flotation tailings. Filter the flotation concentrate and flotation tailings respectively to obtain concentrate filter cake K1 and tailings filter cake T1. The filtrate is returned to the two-stage crystallization operation as a blending mother liquor or returned to the flotation pulp conditioning tank for pulp conditioning.

[0053] Specifically, in one embodiment, the mass concentration of the slurry in the flotation pulp conditioning tank is controlled to be 26% - 33% by the opening degree of the underflow valve of the thickener. The flotation agent is a three-in-one flotation agent composed of octadecylamine, hydrochloric acid, and a foaming agent. In one embodiment, the flotation agent is in an oily wax-like form and is prepared into a solution with a mass fraction of 2% using 85°C water when in use. In one embodiment, the addition amount of the flotation agent is 130 g / t of raw ore - 200 g / t of raw ore.

[0054] During the flotation operation or filtration operation, some water will be mixed in, resulting in the unsaturation of the mother liquor. The mother liquor generated during the flotation operation is not discharged but recycled in the system, reducing the potassium discharge and increasing the recovery rate.

[0055] S10. After the concentrate filter cake K1 is slurried, stirred, and washed with water and washing mother liquor, solid-liquid separation is carried out to obtain potassium chloride products. Part of the separated filtrate is returned to the slurry mixing and washing operation of the concentrate filter cake K1 for pulp conditioning, and the excess filtrate is returned to the flotation operation.

[0056] The present invention will be further described below with reference to embodiments. The raw materials used in the embodiments of the present invention are the underground primary carnallite ore of a potassium salt mine in Africa.

[0057] Composition of the primary carnallite ore in Examples 1 - 3

[0058]

[0059] Example 1

[0060] Collect the underground primary carnallite ore containing potassium rock in Laos and crush it to -15 mm.

[0061] The crushed carnallite ore with a particle size of ≤15 mm (the original ore quality mentioned in this article refers to the crushed carnallite ore with a particle size of ≤15 mm) is transported to a primary crystallizer for crystallization by a belt conveyor. At the same time, water with a TDS / mg / L < 45000 and potassium-containing mother liquor (derived from the overflow L2 mother liquor of the secondary crystallization) and conditioning mother liquor (overflow from the primary thickener) are added to the primary crystallizer. The water is 30% of the original ore mass, L2 is 20% of the original ore mass, and the addition amount of the primary thickener overflow is 40% of the original ore mass. It circulates in the primary crystallizer for about 2 hours, and the height of the overflow port in the crystallizer is controlled so that the overflow amount of the primary crystallizer is 12%. The slurry circulates in the crystallizer for 2 h, and the conditioning mother liquor is the mother liquor at point E, the saturation mother liquor point of potassium rock, carnallite, and potassium chloride at 25°C.

[0062] The bottom flow of the primary crystallization is transported to a screening machine with a screening particle size of 0.6 mm to obtain the oversize S1 and the undersize slurry. The oversize S1 is sent to the secondary crystallization operation, and the undersize slurry is subjected to primary thickening. The concentration of the bottom flow of the primary thickener is controlled at 45%, and the primary bottom flow is transported to a flotation pulp mixing tank. The overflow from the primary thickener is stored in a storage tank. Part of the overflow from the primary thickener goes to the primary crystallization as the conditioning mother liquor, and the excess mother liquor goes to the mother liquor evaporation device for evaporation.

[0063] The oversize S1 from the primary screening is transported to the secondary crystallizer, and water and flotation mother liquor are added to the secondary crystallizer as the driving force for secondary decomposition. At the same time, the subsequent overflow from the secondary thickener is added as the conditioning mother liquor. The addition amount of water in the secondary stage is 1.5% of the original ore mass, the addition amount of the flotation mother liquor is 58% of the original ore mass, and the addition amount of the conditioning mother liquor is 72.5% of the original ore mass. The concentration of the bottom flow of the secondary crystallizer is controlled at 25%.

[0064] The bottom flow of the secondary crystallization is transported to a screening machine with a screening particle size of 0.6 mm to obtain the oversize S2 and the undersize slurry. The oversize S2 is sent to the grinding operation, and the undersize slurry is subjected to secondary thickening. The concentration of the bottom flow of the secondary thickener is controlled at 45%, and the bottom flow of the secondary thickener is transported to a flotation pulp mixing tank. The overflow from the secondary thickener is stored in a storage tank. Part of the overflow from the secondary thickener goes to the secondary crystallization as the conditioning mother liquor, and part of the mother liquor goes to the grinding operation.

[0065] Part of the overflow from the secondary thickener is added to the oversize S2 to adjust its concentration to 50%, the grinding time is controlled at 6 min, and the discharge of the grinding mill is transported to a flotation pulp mixing tank.

[0066] The slurry in the floating and adjusting slurry tank is adjusted to a mass concentration of 26% with the mother liquor from the floating mother liquor tank, and flotation reagents are added. The dosage of the reagents is 130 g / t of the original ore. The flotation operation adopts the operation sequence of one roughing, two scavenging and one cleaning, and the middlings are returned in sequence to obtain flotation concentrate and flotation tailings. The flotation concentrate and flotation tailings are filtered respectively to obtain the filter cakes as concentrate filter cake K1 and tailings filter cake T1. The filtrate is stored in the floating mother liquor storage tank for use in the second-stage crystallization to adjust the mother liquor or floating and adjusting slurry.

[0067] After adding water and washing mother liquor to the filter cake K1 and adjusting the slurry, it is stirred and washed for 40 minutes, and the obtained slurry is separated into solid and liquid. The solid phase is wet potassium chloride material, which is dried to obtain potassium chloride product with a potassium chloride content of 96% and a recovery rate close to 82%. The mother liquor obtained after separation is partially returned to the filter cake K1 washing operation for slurry adjustment as the washing liquid, and the excess mother liquor is returned to the roughing operation.

[0068] Example 2

[0069] Collect the underground primary carnallite ore in Laos and crush it to -15 mm.

[0070] The crushed carnallite is transported to the first-stage crystallizer by a belt conveyor. At the same time, water with TDS / mg / L < 45000, the overflow L2 mother liquor from the second-stage crystallization and the overflow from the first-stage thickener are added to the first-stage crystallizer. The water addition amount is 17% of the mass of the original ore, L2 is 28% of the mass of the original ore, and the addition amount of the first-stage thickener overflow is 25% of the original ore. It circulates in the first-stage crystallizer for about 2 hours, and the height of the overflow port in the crystallizer is controlled so that the overflow amount of the first-stage crystallizer is 8%. The slurry circulates in the crystallizer for 2 h, and the theoretical adjusted mother liquor is the saturated mother liquor point E mother liquor of potassium rock, carnallite and potassium chloride at 25°C.

[0071] The underflow of the first-stage crystallization is transported to a screening machine with a screening particle size of 0.8 mm to obtain the oversize material S1 and the undersize slurry. The oversize material S1 is sent to the second-stage crystallization operation, and the undersize slurry is subjected to first-stage thickening. The concentration of the underflow of the first-stage thickener is controlled at 45%, and the first-stage underflow is transported to the floating and adjusting slurry tank. The overflow from the first-stage thickener is stored in the storage tank, and part of the overflow from the first-stage thickener goes to the first-stage crystallization as the adjusted mother liquor, and the excess mother liquor goes to the mother liquor evaporation device for evaporation.

[0072] The oversize material S1 from the first-stage screening is transported to the second-stage crystallizer, and water and floating mother liquor are added to the second-stage crystallizer as the driving force for the second-stage decomposition. At the same time, the subsequent overflow from the second-stage thickener is added as the adjusted mother liquor. The water addition amount in the second stage is 5.0% of the mass of the original ore, the addition amount of the floating mother liquor is 65% of the mass of the original ore, and the addition amount of the adjusted mother liquor is 75% of the mass of the original ore. The concentration of the underflow of the second-stage crystallizer is controlled at 33%.

[0073] The underflow of the second-stage crystallization is transported to a screening machine with a screening particle size of 0.8 mm to obtain the oversize material S2 and the undersize slurry. The oversize material S2 is sent to the grinding operation, and the undersize slurry undergoes second-stage thickening. The concentration of the underflow of the second-stage thickener is controlled at 45%, and the underflow of the second-stage thickener is transported to the flotation pulp conditioning tank. The overflow of the second-stage thickening is stored in a storage tank. Part of the overflow of the second-stage thickening goes to the second-stage crystallization as the blending mother liquor, and part of the mother liquor goes to the grinding operation.

[0074] Grinding operation: Part of the overflow of the second-stage thickening is added to the oversize material S2 to adjust its concentration to 50%, the grinding time is controlled at 6 min, and the discharge of the grinding mill is transported to the flotation pulp conditioning tank.

[0075] The slurry in the flotation pulp conditioning tank is adjusted to a concentration of 26% using the mother liquor from the flotation mother liquor tank, and flotation reagents are added. The dosage of the reagents is 165 g / t of raw ore. The flotation operation adopts the sequence of one roughing, two cleaning, and one scavenging with the middlings returned in sequence to obtain the flotation concentrate and the flotation tailings. The flotation concentrate and the flotation tailings are filtered respectively to obtain the concentrate filter cake K1 and the tailings filter cake T1. The filtrate is stored in the flotation mother liquor storage tank for use as the blending mother liquor for the second-stage crystallization or for flotation pulp conditioning.

[0076] After adding water and the washing mother liquor to the concentrate filter cake K1 and adjusting the slurry, it is stirred and washed for 40 minutes. The obtained slurry is separated into solid and liquid phases. The solid phase is the wet potassium chloride material, which is dried to obtain the potassium chloride product with a potassium chloride content of 96% and a recovery rate close to 82%. The mother liquor obtained after separation is partially returned to the concentrate filter cake K1 washing operation for slurry adjustment, and the excess mother liquor is returned to the roughing operation.

[0077] Example 3

[0078] Collect the underground primary carnallite ore in Laos and crush it to -15 mm.

[0079] The crushed carnallite is transported to the first-stage crystallizer using a belt conveyor. At the same time, water with a TDS / mg / L < 45000, the overflow L2 mother liquor of the second-stage crystallization, and the overflow of the first-stage thickening are added to the first-stage crystallizer. The water is 17.25% of the mass of the raw ore, L2 is 25.52% of the mass of the raw ore, and the addition amount of the overflow of the first-stage thickening is 35% of the mass of the raw ore. It circulates in the first-stage crystallizer for about 2 hours. The height of the overflow port in the crystallizer is controlled so that the overflow of the first-stage crystallizer is 10.05%. The slurry circulates in the crystallizer for 2 h. The theoretical blending mother liquor is the mother liquor at point E, which is the saturation mother liquor point of potassium rock, carnallite, and potassium chloride at 25°C.

[0080] Transport a section of crystalline underflow to a screening machine with a screening particle size of 1.0 mm to obtain oversize product S1 and undersize slurry. The oversize product S1 is sent to the second-stage crystallization operation, and the undersize slurry is subjected to first-stage thickening. Control the bottom flow concentration of the first-stage thickener to be 45%, transport the first-stage bottom flow to the flotation pulp conditioning tank, store the first-stage thickening overflow in a storage tank, send part of the first-stage thickening overflow to the first-stage crystallization as the blending mother liquor, and send the excess mother liquor to the mother liquor evaporation device.

[0081] Transport the oversize product S1 from the first-stage screening to the second-stage crystallizer, add water and flotation mother liquor in the second-stage crystallizer as the driving force for the second-stage decomposition. At the same time, add the subsequent second-stage thickening overflow as the blending mother liquor. The addition amount of water in the second stage is 2.5% of the mass of the original ore, the addition amount of flotation mother liquor is 50% of the mass of the original ore, the addition amount of the blending mother liquor is 65% of the mass of the original ore, and control the bottom flow concentration of the second-stage crystallizer to be 25%.

[0082] Transport the second-stage crystalline underflow to a screening machine with a screening particle size of 0.6 mm to obtain oversize product S2 and undersize slurry. The oversize product S2 is sent to the grinding operation, and the undersize slurry is subjected to second-stage thickening. Control the bottom flow concentration of the second-stage thickener to be 45%, transport the bottom flow of the second-stage thickener to the flotation pulp conditioning tank, store the second-stage thickening overflow in a storage tank, send part of the second-stage thickening overflow to the second-stage crystallization as the blending mother liquor, and send part of the mother liquor to the grinding operation.

[0083] Add part of the second-stage thickening overflow to the oversize product S2 and adjust its concentration to 50%, control the grinding time to be 6 minutes, and transport the discharge of the grinding mill to the flotation pulp conditioning tank.

[0084] The slurry in the flotation pulp conditioning tank is adjusted to a concentration of 26% with the mother liquor from the flotation mother liquor tank, add flotation reagents, and the addition amount of the reagents is 180 g / t of the original ore. The flotation operation adopts the operation sequence of one roughing, two cleaning, and one scavenging with the middlings returned in sequence to obtain flotation concentrate and flotation tailings. Filter the flotation concentrate and flotation tailings respectively to obtain concentrate filter cake K1 and tailings filter cake T1, and store the filtrate in the flotation mother liquor storage tank for use as the blending mother liquor for the second-stage crystallization or flotation pulp conditioning.

[0085] After adding water and washing mother liquor to the concentrate filter cake K1 and adjusting the pulp, stir and wash for 40 minutes, separate the solid and liquid of the obtained slurry, the solid phase is wet potassium chloride material, and after drying, potassium chloride product is obtained with a potassium chloride content of 96% and a recovery rate close to 82%. The mother liquor obtained after separation is the washing liquid, part of which is returned to the pulp conditioning operation of the concentrate filter cake K1 for washing, and the excess mother liquor is returned to the roughing operation.

[0086] Combined with specific embodiments, it can be seen that in the present invention, the carnallite containing native potassium rock (with potassium rock content of 1-8%) collected is crushed to ≤15 mm. Compared with the prior art where the raw ore is first crushed to a finer particle size, such as below 8 mm, in this application, it only needs to be crushed to 15 mm, which can not only save equipment costs but also alleviate the problem of salt deposition and blockage of the crushing equipment. The coarser particle size can slow down the decomposition of carnallite, control a large number of potassium chloride crystal nuclei, create conditions for the crystallization of potassium chloride, and achieve the purpose of controlled-rate crystallization. The amount of water added in the first-stage crystallization is 17-30% of the mass of the raw ore with a particle size of ≤15 mm after crushing. In the prior art, due to multiple water addition points in the decomposition process and difficult control of equipment water consumption, the E mother liquor is unsaturated and the system recovery rate is low. In this application, the main water addition point is in the first-stage crystallization, and the subsequent water addition amount is very small and not discharged after addition, but directly recycled, thus well controlling the water consumption. The discharged mother liquor is a saturated or supersaturated mother liquor, which can reduce the evaporation scale, reduce the potassium discharge amount, and improve the recovery rate. Two-stage crystallization is adopted, and refined potassium mother liquor and a small amount of water are added in the second-stage crystallization, which can fully decompose the carnallite that has not been fully decomposed, improve the recovery rate. After two-stage crystallization, the carnallite can be fully decomposed, and almost all of the oversize materials from the second-stage screening are potassium rock, which can be recovered after grinding, and the recovery rate can be increased by at least 3%. Furthermore, because some water is mixed in the flotation operation or filtration operation, resulting in an unsaturated mother liquor, the mother liquor generated in the flotation operation is not discharged but recycled in the system, reducing the potassium discharge amount and improving the recovery rate.

[0087] All in all, the mother liquor discharged in this application is only the overflow of the first-stage crystallizer, and this mother liquor is in a saturated or supersaturated state, solving the problem in the traditional process of discharging from the tailings filtrate. Since horizontal belt filters are generally selected for tailings filtration equipment, some water enters the mother liquor, resulting in an unsaturated mother liquor that dissolves part of the potassium, and the system recovery rate is not high. Through two-stage crystallization and grinding, the system recovery rate is further improved. This application can make the recovery rate of the potassium chloride system reach more than 81.95%, the potassium chloride grade is 95%, and the tailings KCl grade is controlled below 1.0%. Compared with the prior art where the potassium chloride recovery rate is 55% and the tailings KCl is 6.5%, the recovery rate and grade are greatly improved, and this application has low costs, a simple process, and is suitable for industrial production.

[0088] In the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0089] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A production process for preparing potassium chloride using carnallite ore containing potassium rock, characterized in that: include: The collected primary carnallite ore is crushed to ≤15mm; Add water with TDS / mg / L <45000, potassium-containing mother liquor and blending mother liquor for crystallization, the amount of water added is 17-30% of the mass of the original ore with a particle size of ≤15mm after crushing, the amount of potassium-containing mother liquor added is 20%-28% of the mass of the original ore with a particle size of ≤15mm after crushing, the overflow rate of the first stage of crystallization is controlled to be 8%-12%, and the amount of blending mother liquor added is used to control the mass concentration of the first stage of crystallization underflow to be 25%-40%; The first stage crystallization bottom flow is screened once to obtain the screened material S1 and the screened slurry. The screened material S1 is sent to the second stage crystallizer for operation, and the screened slurry is thickened in one stage; The dense underflow of the first stage is transported to the flotation slurry tank, part of the dense overflow of the first stage is returned to the first stage crystallization as the blending mother liquor, and the excess dense overflow of the first stage is evaporated; Add water with TDS / mg / L < 45000, flotation mother liquor and blending mother liquor to the second stage crystallization operation. The amount of water added in the second stage is 1.5% to 5.0% of the mass of the original ore with a particle size of ≤15mm after crushing, the amount of flotation mother liquor added is 50% to 65% of the mass of the original ore with a particle size of ≤15mm after crushing, and the amount of blending mother liquor added is 65% to 75% of the mass of the original ore with a particle size of ≤15mm after crushing; The second stage crystallization bottom flow is screened twice to obtain the screened material S2 and the screened slurry. The screened material S2 is sent to the grinding operation, and the screened slurry is thickened in the second stage. The supernatant of the second stage thickening is returned to the second stage crystallizer as the blending mother liquor. The second stage thickening underflow is transported to the flotation slurry tank, part of the second stage thickening overflow is returned to the second stage crystallization as the blending mother liquor, and the excess second stage thickening overflow is transported to the grinding operation; During the grinding operation, the screen material S2 is controlled by the second-stage thickening overflow to adjust the slurry mass concentration to 50% to 65%, and the discharge material after grinding is transported to the flotation slurry tank; Flotation agent is added for flotation to obtain flotation concentrate K1 and flotation tailings T1. After the flotation concentrate K1 is slurried with water and washing mother liquor, stirred and washed, the solid-liquid separation is performed to obtain the potassium chloride product. The filtrate after separation is returned to the stirring and washing operation of the concentrate filter cake K1 for slurry preparation, and the excess filtrate is returned to the flotation operation.

2. The production process for preparing potassium chloride by using carnallite ore containing potassium rock according to claim 1, characterized in that: The screening particle sizes of the primary screening and the secondary screening are both 0.6 mm to 1 mm.

3. The production process for preparing potassium chloride by utilizing carnallite ore containing potassium rock according to claim 1, characterized in that: The potassium-containing mother liquor is brine with a KCl content of 6.0-13.0% by mass, and the KCl content in the blending mother liquor is 2.0-6.5% by mass, the MgCl2 content is 21.3-26.6% by mass, and the NaCl content is 2.0-3.0% by mass.

4. The production process for preparing potassium chloride by utilizing carnallite ore containing potassium rock according to claim 1, characterized in that: The mass concentration of the dense underflow is 40% to 55%.

5. The production process for preparing potassium chloride by utilizing carnallite ore containing potassium rock according to claim 1, characterized in that: The mass concentration of the second stage crystallization bottom flow is 25% to 33%.

6. The production process for preparing potassium chloride by using carnallite ore containing potassium rock according to claim 1, characterized in that: The mass concentration of slurry in the flotation slurry mixing tank is controlled to be 26% to 33% by the opening and closing degree of the thickener underflow valve.

7. The production process for preparing potassium chloride by utilizing carnallite ore containing potassium rock according to claim 1, characterized in that: The flotation agent is a three-in-one flotation agent consisting of octadecylamine, hydrochloric acid and a frother.

8. The production process for preparing potassium chloride using carnallite ore containing potassium rock according to claim 7, characterized in that: The flotation agent is in the form of oil wax. When used, the flotation agent is prepared into a solution with a mass fraction of 2% by using 85° C. water.

9. The production process for preparing potassium chloride by utilizing carnallite ore containing potassium rock according to claim 7, characterized in that: The amount of flotation agent added is 130g / t to 200g / t of raw ore.

10. The production process for preparing potassium chloride by using carnallite ore containing potassium rock according to claim 1, characterized in that: The overflow mother liquor of the second stage crystallization is used as potassium-containing mother liquor.

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