Method for preparing potash-containing potassium-magnesium fertilizer from kieserite

Abstract

The application discloses a method for preparing potash magnesium fertilizer by using potassium salt sylvite, and comprises the following steps: (1) adding raw materials; (2) stirring and converting by heating; (3) separating mother liquor by belt vacuum filtration and keeping warm; (4) cooling and crystallizing the mother liquor by heating; (5) ore flotation; (6) product washing and drying; and (7) tailing treatment. + , Mg 2+ , SO4 2‑ resources to a tailing pond, resulting in resource loss; or the fine crystals of bloedite are precipitated by cooling in the flotation process of the mother liquor by heating, the flotation environment is deteriorated, the concentrate quality is reduced, and filtration is difficult, so that fine treatment of resources is realized; the method is simple, the problem of difficult conversion of the potassium salt sylvite is avoided, the product quality is good, the production efficiency is high, the resource utilization rate is high, and the economic benefit is good.

Description

Technical Field

[0001] This invention relates to a method for utilizing potassium mixed salts, specifically a method for utilizing potassium mixed salts containing potassium salt and magnesium alum. Background Technology

[0002] A magnesium sulfate subtype brine salt field system typically consists of three parts: halite pools, potassium halite pools, and sulfate mixed salt pools. In the actual production process of the sulfate mixed salt pools, some scrap ore is often not harvested in time. The sulfate mixed salt from these scraps is then left to dry for extended periods, leading to the reaction of some eschar (MgSO4·7H2O) with potassium chloride (KCl) to form potassium magnesium alum (KCl·MgSO4·3H2O). Currently, due to the scarcity of potassium resources in brine, most potassium salt production enterprises face a situation of having no usable ore. The remaining scrap potassium ore must also be put into production to solve this predicament. This portion of the potassium mixed salt ore contains potassium magnesium alum, which has a low conversion efficiency to soft potassium magnesium alum (K2SO4·MgSO4·6H2O) at room temperature, resulting in poor flotation performance, low yield, and inability to meet the normal production needs of the enterprises.

[0003] Currently, researchers have conducted extensive research on potassium extraction processes using mixed potassium salts. At present, mixed potassium salt ore obtained from sulfate-type brine through evaporation mainly consists of carnallite, magnesia hydrate, esperidin, and sodium chloride. The main processing method for this type of mixed potassium salt ore is: cold decomposition of the mixed potassium salt – flotation – conversion to produce potassium sulfate. CN1696059A discloses a method for converting a single mixed potassium salt raw material into soft potassium magnesium alum, and then using the soft potassium magnesium alum as a raw material to produce potassium sulfate through conversion. This invention has the advantages of single raw material, short process flow, and recyclable conversion mother liquor, but it requires a sulfur-to-potassium ratio (S / K ratio) higher than 2.46 in the raw material. CN104193425A discloses a two-stage flotation process for low-grade potassium mixed salts. Using the mother liquor at point C as the flotation mother liquor and cations as collectors, a first-stage flotation is performed to obtain potassium chloride concentrate. Then, an anionic collector is added to the first-stage slurry for a second-stage flotation to obtain minerals such as soft potassium magnesium alum, potassium magnesium alum, anhydrous potassium magnesium alum, and esperidin. Finally, all the concentrates from both stages are combined and added to fresh water for a conversion reaction to produce potassium magnesium sulfate fertilizer. This invention has a simple process flow, but the potassium chloride concentrate grade is low and the recovery rate is not high. CN201110420163.1 discloses a process for producing potassium magnesium sulfate fertilizer from muddy potassium mixed salt ore. This involves crushing, washing, and grinding the primary potassium mixed salt ore, adding a fine mud inhibitor, and then flotating to enrich the potassium mineral soft potassium magnesium alum. The resulting concentrate is washed with fresh water and dried to obtain the finished potassium magnesium sulfate fertilizer. The inventions mentioned above are all for the development of conventional potassium mixed salt processes. However, potassium mixed salt containing potassium salt and magnesium alum is fundamentally different from conventional potassium mixed salt. The potassium-containing minerals in the raw ore are different, and room temperature conversion is difficult to achieve.

[0004] Potassium-containing magnesium sulfate ore differs from conventional potassium-containing mixed salt ores. Its main potassium-containing mineral is potassium-containing magnesium sulfate (KCl·MgSO4·3H2O), which is difficult to convert at room temperature, leading to challenges in mineral utilization. Currently, the main processing method for this type of ore is to blend a small portion into conventional potassium-containing mixed salt ores for conversion. However, the blending ratio is low, resource utilization is limited, and the resulting soft potassium-containing magnesium sulfate has a fine particle size, which deteriorates the flotation system environment, affects flotation indicators, and leads to poor concentrate grade and filtration difficulties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for efficiently preparing potassium-magnesium fertilizer using potassium mixed salt containing potassium salt magnesium alum.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: A method for preparing potassium magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate, comprising the following steps:

[0007] (1) Raw material addition: Add E mother liquor and raw ore to the reaction tank, with or without adding fresh water; the raw ore is potassium mixed salt containing potassium salt magnesium alum; the potassium mixed salt ore containing potassium salt magnesium alum mainly contains potassium salt magnesium alum, potassium chloride, sodium chloride, esperidone salt and other minerals;

[0008] (2) Heating and stirring conversion: The reaction tank is heated and stirred to obtain a slurry; the increased temperature promotes the conversion of potassium magnesium alum in the potassium mixed salt to soft potassium magnesium alum, and the increased temperature increases the K content in the mother liquor. + Mg 2+ Cl - SO4 2- The plasma solubility causes the potassium salt magnesium alum in the solid phase to transform into soft potassium magnesium alum, precipitating KCl and NaCl crystals, while the liquid phase is transformed into a new mother liquor, forming a new equilibrium.

[0009] (3) Belt vacuum filtration and heat preservation separation of mother liquor: The slurry obtained in step (2) is separated into solid and liquid under heat preservation conditions. The liquid obtained is the mother liquor with temperature rise E. The solid obtained is soft potassium magnesium alum solid ore.

[0010] (4) Cooling and crystallizing the heated mother liquor: Cooling the heated mother liquor E to crystallize the solid phase, which is soft potassium magnesium alum crystal, i.e., potassium magnesium fertilizer product, and the liquid phase is the cooled mother liquor; through the crystallization process, large-particle high-quality soft potassium magnesium alum product can be obtained.

[0011] (5) Flotation of mineral materials: The soft potassium magnesium alum solid ore obtained in step (3) is mixed with E mother liquor to obtain a slurry; flotation reagents are added to the slurry for flotation to obtain concentrate froth; the flotation adopts a closed-circuit flotation process of roughing, cleaning and scavenging, cleaning middlings and scavenging concentrate returned to roughing.

[0012] (6) Product washing and drying: The concentrate foam is mixed with fresh water for washing, and solid-liquid separation is performed. The resulting solid phase is potassium magnesium fertilizer, and the resulting liquid phase is washing mother liquor.

[0013] (7) Tailings treatment: Add water, which is insufficient to form an unsaturated solution, to the tailings slurry obtained by flotation in step (5). After clarification, take the supernatant as the flotation tailings.

[0014] The components of the mother liquor E are located in Na. + K + Mg 2+ / / Cl - SO4 2- —In the metastable phase diagram of the H2O pentahydrate-salt system, soft potassium magnesium sulfate, potassium chloride, and espresso salt share the saturation point E.

[0015] Preferably, in step (1), the potassium mixed salt K containing potassium magnesium alum is... + The content is 3.5–9.5 wt%, Mg 2+ Content is 2.5–10.5 wt%, SO4 2- Content 7.5–23.5 wt%.

[0016] Preferably, in step (1), the mass ratio of the mother liquor E to the raw ore is 1.2 to 0.6:1.

[0017] Preferably, in step (1), the mass ratio of fresh water to raw ore is 0 to 0.4:1.

[0018] Preferably, in step (2), the temperature is raised to 40-70°C.

[0019] Preferably, in step (2), the stirring time is 60 to 180 minutes.

[0020] Preferably, in step (4), the cooling crystallization temperature is 10-25℃ and the crystallization time is 1-5h.

[0021] Preferably, in step (5), the concentration of the slurry is 20-35 wt%.

[0022] Preferably, in step (5), the amount of flotation reagent used for roughing is 40-120 g / t of raw ore, no reagent is added for cleaning, and the amount used for scavenging is 20-60 g / t of raw ore.

[0023] Preferably, in step (5), the flotation reagent is an anionic flotation reagent.

[0024] More preferably, in step (5), the flotation reagent is sodium dodecyl sulfonate.

[0025] Preferably, in step (6), the volume ratio of fresh water to concentrate foam is 0.1-0.5:1.

[0026] Preferably, in step (7), the weight ratio of tailings to water is 1:0.1-0.4. Tailings refer to the solid portion of the tailings slurry.

[0027] Preferably, the mother liquor obtained in step (4), the washing mother liquor obtained in step (6), and the flotation tail liquor obtained in step (7) are returned to step (1) or step (5) as E mother liquor. The mother liquor obtained in step (4), the washing mother liquor obtained in step (6), and the flotation tail liquor obtained in step (7) can be used as E mother liquor.

[0028] This invention innovatively employs a process of "heating conversion + heat preservation solid-liquid separation + mother liquor cooling crystallization + solid flotation" to remove potassium from potassium mixed salt containing magnesium alum. + Mg 2+ SO4 2- The resources are extracted in two steps, which ensures the smooth production of potassium and magnesium fertilizer while maximizing the processing and utilization of resources.

[0029] Beneficial effects of this invention:

[0030] (1) This invention promotes the conversion of potassium salt and magnesium alum by heating, and the solid and liquid phases of the conversion are treated separately to ensure efficient resource recovery and avoid the mother liquor from carrying away potassium during heating. + Mg 2+ SO4 2- Resources are lost when they are sent to tailings ponds; or the mother liquor is heated and then cooled during flotation to precipitate fine crystals of soft potassium magnesium alum, which deteriorates the flotation environment, leading to a decline in concentrate quality and difficulty in filtration. Therefore, it is necessary to achieve refined processing of resources.

[0031] (2) The process of this invention is simple, avoids the problem of difficult conversion of potassium salt and magnesium alum, and has good product quality, high production efficiency, high resource utilization rate and good economic benefits. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments.

[0033] The raw materials used in the embodiments of the present invention are all obtained through conventional commercial channels.

[0034] The flotation reagent used in each embodiment is sodium dodecyl sulfonate, an anionic flotation reagent.

[0035] Example 1

[0036] This embodiment describes a method for preparing potassium-magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate, comprising the following steps:

[0037] (1) Raw material addition: A potassium mixed salt ore containing potassium salt and magnesium sulfate, the original ore composition is K + 5.89%, Na + 22.30%, Mg2+ 3.19%, SO4 2- 16.27%, Cl - 37.00%, others 15.35%; weigh 100.0 kg of the above-mentioned sulfur-potassium mixed salt, 8.0 kg of fresh water, and 90.0 kg of the mother liquor after cooling from the previous batch of solid conversion (E mother liquor) and mix them in a heating tank to form a slurry; the composition of the E mother liquor is located in Na + K + Mg 2+ / / Cl - SO4 2- —In the metastable phase diagram of the H2O pentacetic acid-salt system, soft potassium magnesium sulfate, potassium chloride, and espresso salt share a saturation point E, and its composition is K. + 2.55%, Na + 2.26%, Mg 2+ 5.00%, SO4 2- 5.86%, Cl - 16.07%, H2O 68.26%;

[0038] (2) Heating and stirring conversion: Heating to 50℃ and stirring for 120 min to obtain slurry, completing the conversion of potassium magnesium alum to soft potassium magnesium alum, and the liquid phase is converted into new mother liquor;

[0039] (3) Belt vacuum filtration and heat preservation separation of mother liquor: Solid-liquid separation is carried out under heat preservation conditions. The obtained solid material, 95.00 kg, is soft potassium magnesium alum solid ore, and its content composition is: K + 4.61%, Na + 24.55%, Mg 2+ 2.18%, SO4 2- 14.13%, Cl - 38.43%, others 15.60%; the resulting liquid was 103.0 kg of heated E mother liquor, and its composition was: K + 3.59%, Na + 2.44%, Mg 2+ 5.52%, SO4 2- 7.92%, Cl - 15.52%, H2O 62.82%; the solid material will be sent to the flotation section; the heated mother liquor will be sent to the crystallizer for cooling and crystallization;

[0040] (4) Heating and cooling of the mother liquor for crystallization: The mother liquor heated by step E is pumped to a crystallizer for cooling and crystallization. After cooling to 20°C, crystallization is carried out for 4 hours, yielding 7.0 kg of large-particle soft potassium magnesium alum crude product. Its composition is: K + 17.20%, Na + 2.20%, Mg 2+6.34%, SO4 2- 43.25%, Cl - 6.68%, H2O 24.33%; Crude potassium magnesium fertilizer product K from the cooling crystallization process + The process recovery rate was 20.46%; the mass of the mother liquor after cooling was 95.5 kg, and its composition was: K + 2.62%, Na + 2.12%, Mg 2+ 5.12%, SO4 2- 6.08%, Cl - 16.11%, H2O 67.95%; the crude soft potassium magnesium sulfate product enters the washing and drying process, and 1.50 kg of fresh water is added to obtain 5.86 kg of high-quality potassium magnesium fertilizer product, whose composition is: K + 20.07%, Na + 0.87%, Mg 2+ 6.18%, SO4 2- 48.79%, Cl - The potassium content was 1.13%, meeting the requirements for first-grade potassium-magnesium fertilizer, with a potassium recovery rate of 18.97%. The washing mother liquor was 2.64 kg, and its composition was: K... + 2.60%, Na + 2.79%, Mg 2+ 4.88%, SO4 2- 6.42%, Cl - 1.13%; The washing mother liquor and the cooled mother liquor are returned to step (1) for use as E mother liquor;

[0041] (5) Flotation of mineral materials: The solid material obtained in step (3) is transferred to a mixing tank and 276.0 kg of the previous batch of flotation tailings is added for slurry conditioning. The slurry concentration is adjusted to 25.0 wt%. After slurry conditioning, the slurry enters the flotation machine for soft potassium magnesium alum flotation. The flotation process adopts a roughing-cleaning-scavenging flotation process. The middlings of the cleaned ore and the scavenging concentrate are combined and returned to the roughing operation. Sodium dodecyl sulfate anionic is used as the collector. The roughing concentration is 80 g / t of raw ore and the scavenging concentration is 30 g / t of raw ore. 42.89 kg of concentrate foam is obtained, of which 21.80 kg is concentrate product. Its composition is: K + 15.83%, Na + 3.08%, Mg 2+ 6.33%, Cl - 7.04%, SO4 2- 42.62%, H2O 25.10%; tailings slurry 290.8 kg, of which tailings mass is 73.2 kg, its composition is: K + 1.17%, Na + 31.21%, Mg2+ 0.92%, Cl - 46.11%, SO4 2- 4.81%, others 14.55%; flotation concentrate K + The process recovery rate was 58.63%;

[0042] (6) Product washing and drying: The concentrate foam was transferred to a mixing tank, 6.50 kg of fresh water was added, and the mixture was stirred for 30 min at 20°C for washing. The mixture was then transferred to a centrifuge for solid-liquid separation and drying to obtain 16.79 kg of potassium-magnesium fertilizer product. The composition of the product was: K + 18.68%, Na + 0.88%, Mg 2+ 5.32%, Cl - 1.50%, SO4 2- 50.54%; meeting the requirements for qualified potassium-magnesium fertilizer, with a potassium recovery rate of 53.23%; 10.58 kg of filtrate was obtained, which was the washing mother liquor, with the following composition: K + 2.73%, Na + 2.79%, SO4 2- 7.51%, Cl - 15.19%, H2O 66.79%; Potassium magnesium fertilizer products are sent to the finished product workshop, and the filtrate is pumped to step (1) as E mother liquor or sent to the mother liquor recovery tank;

[0043] (7) Tailings treatment: The tailings slurry obtained in step (5) is mixed with 25.0 kg of fresh water and pumped to the tailings pond via pipeline. After the tailings slurry is allowed to settle, the supernatant is taken as the flotation tailings and used in the next batch of flotation.

[0044] This process yields 5.86 kg of Grade I potassium-magnesium fertilizer with a potassium recovery rate of 18.97% and 16.79 kg of qualified potassium-magnesium fertilizer with a potassium recovery rate of 53.23%, for a total potassium recovery rate of 72.70%, achieving efficient recovery and production of potassium and magnesium resources.

[0045] Example 2

[0046] This embodiment describes a method for preparing potassium-magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate, comprising the following steps:

[0047] (1) Raw material addition: A potassium mixed salt ore containing potassium salt and magnesium sulfate, the original ore composition is K + 8.06%, Na + 18.62%, Mg 2+ 3.60%, SO4 2- 21.86%, Cl -30.37%, others 17.49%; 100.0 kg of the above-mentioned sulfur-potassium mixed salt, 5.0 kg of fresh water, and 80.0 kg of the mother liquor after cooling from the previous batch of solid conversion (E mother liquor) were weighed and mixed in a heating tank to form a slurry; the composition of the E mother liquor is located in Na + K + Mg 2+ / / Cl - SO4 2- —In the metastable phase diagram of the H2O pentagonal aqueous salt system, soft potassium magnesium sulfate, potassium chloride, and espresso salt share the saturation point E, and the composition is K. + 2.55%, Na + 2.26%, Mg 2+ 5.00%, SO4 2- 5.86%, Cl - 16.07%, H2O 68.26%;

[0048] (2) Heating and stirring conversion: Heating to 45℃ and stirring for 90 min; slurry is obtained; the liquid phase is converted into new mother liquor;

[0049] (3) Belt vacuum filtration and heat preservation separation of mother liquor: Solid-liquid separation was carried out under heat preservation conditions. The obtained solid material, 91.30 kg, was soft potassium magnesium alum solid ore, and its content composition was: K + 7.28%, Na + 19.22%, Mg 2+ 3.36%, SO4 2- 19.38%, Cl - 32.47%, others 18.29%; the resulting liquid was 113.70 kg of heated E mother liquor, and its composition was: K + 3.47%, Na + 2.48%, Mg 2+ 5.33%, SO4 2- 7.67%, Cl - 16.04%, H2O 65.01%; the solid material will be sent to the flotation section; the heated mother liquor will be sent to the crystallizer for cooling and crystallization;

[0050] (4) Heating and cooling of the mother liquor for crystallization: The mother liquor heated by step E is pumped to a crystallizer for cooling and crystallization. After cooling to 15°C, crystallization is carried out for 3 hours, yielding 8.07 kg of large-particle soft potassium magnesium alum crude product. Its composition is as follows: K + 17.25%, Na + 3.22%, Mg 2+ 5.67%, SO4 2- 42.15%, Cl - 7.82%, H2O 17.27%; Crude potassium magnesium fertilizer product K from the cooling crystallization process+ The process recovery rate was 17.27%; the mass of the mother liquor after cooling was 105.63 kg, and its composition was: K + 2.40%, Na + 2.31%, Mg 2+ 4.87%, SO4 2- 5.10%, Cl - 16.55%, H2O 68.77%; the crude soft potassium magnesium sulfate product enters the washing and drying process, and 2.15 kg of fresh water is added to obtain 6.47 kg of high-quality potassium magnesium fertilizer product, whose composition is: K + 20.02%, Na + 0.87%, Mg 2+ 6.11%, SO4 2- 51.17%, Cl - The potassium content was 0.96%, meeting the requirements for first-grade potassium-magnesium fertilizer, with a potassium recovery rate of 16.08%. The washing mother liquor was 3.75 kg, and its composition was: K... + 2.43%, Na + 2.49%, Mg 2+ 4.88%, SO4 2- 6.12%, Cl - 15.19%; The washing mother liquor and the cooled mother liquor are returned to step (1) for use as E mother liquor;

[0051] (5) Flotation of mineral materials: The solid material obtained in step (3) is transferred to a mixing tank and 213.03 kg of the previous batch of flotation tailings is added for slurry preparation. The slurry concentration is adjusted to 30.0 wt%. After slurry preparation, the slurry enters the flotation machine for soft potassium magnesium sulfate flotation. The flotation process adopts a roughing-cleaning-scavenging flotation process. The middlings from the cleaned ore and the scavenging concentrate are combined and returned to the roughing operation. Sodium dodecyl sulfate, an anionic reagent, is used as the collector. The roughing concentration is 100 g / t of raw ore, and the scavenging concentration is 40 g / t of raw ore. 71.45 kg of concentrate froth is obtained, of which 32.58 kg is concentrate product. Its composition is: K + 16.52%, Na + 2.08%, Mg 2+ 6.18%, Cl - 5.69%, SO4 2- 42.23%, H2O 26.30%; tailings slurry 313.6 kg, of which tailings mass is 73.20 kg, its composition is: K + 1.24%, Na + 23.67%, Mg 2+ 1.71%, Cl - 40.86%, SO4 2-7.32%, others 8.60%; flotation concentrate K + The process recovery rate was 66.78%;

[0052] (6) Product washing and drying: The concentrate foam was transferred to a mixing tank, 8.15 kg of fresh water was added, and the mixture was stirred for 30 min at 15°C for washing. The mixture was then transferred to a centrifuge for solid-liquid separation and drying to obtain 26.13 kg of wet potassium-magnesium fertilizer product. The composition of the product was: K + 19.07%, Na + 0.98%, Mg 2+ 5.32%, Cl - 1.50%, SO4 2- The potassium recovery rate was 49.71%, meeting the requirements for qualified potassium-magnesium fertilizer, with a potassium recovery rate of 61.83%. 14.09 kg of filtrate was obtained as the washing mother liquor, with the following composition: K... + 2.73%, Na + 2.79%, Mg 2+ 4.81%, SO4 2- 7.51%, Cl - 15.19%, H2O 66.97%; the filtrate is pumped to step (1) for use as mother liquor E or sent to the mother liquor recovery tank;

[0053] (7) Tailings treatment: The tailings slurry obtained in step (5) is mixed with 20.00 kg of fresh water and pumped to the tailings pond via pipeline. After the tailings slurry is allowed to settle, the supernatant is taken as flotation tailings and used in the next batch of flotation or sent to the mother liquor recovery tank.

[0054] This process yields 6.47 kg of Grade I potassium-magnesium fertilizer with a potassium recovery rate of 16.08%; and 26.13 kg of qualified potassium-magnesium fertilizer with a potassium recovery rate of 61.83%, for a total potassium recovery rate of 77.92%, achieving efficient recovery and production of potassium-magnesium resources.

[0055] Example 3

[0056] This embodiment describes a method for preparing potassium-magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate, comprising the following steps:

[0057] (1) Raw material addition: A potassium mixed salt ore containing potassium salt and magnesium sulfate, the original ore composition is K + 8.32%, Na + 20.73%, Mg 2+ 2.70%, SO4 2- 17.77%, Cl -34.25%, others 16.23%; Weigh 100.0 kg of the above-mentioned sulfur-potassium mixed salt, 0.0 kg of fresh water, and 100.0 kg of the mother liquor after cooling from the previous batch of solid conversion (E mother liquor) and mix them in a heating tank to form a slurry; The composition of the E mother liquor is located in Na + K + Mg 2+ / / Cl - SO4 2- —In the metastable phase diagram of the H2O pentagonal aqueous salt system, soft potassium magnesium sulfate, potassium chloride, and espresso salt share the saturation point E, and the composition is K. + 2.55%, Na + 2.26%, Mg 2+ 5.00%, SO4 2- 5.86%, Cl - 16.07%, H2O 68.26%;

[0058] (2) Heating and stirring conversion: Heating to 55℃ and stirring for 90 min; slurry is obtained; the liquid phase is converted into new mother liquor;

[0059] (3) Belt vacuum filtration and heat preservation separation of mother liquor: Solid-liquid separation was carried out under heat preservation conditions. The obtained solid material, 92.30 kg, was soft potassium magnesium alum solid ore, and its content composition was: K + 7.52%, Na + 22.13%, Mg 2+ 2.10%, SO4 2- 16.51%, Cl - 36.96%, others 17.59%; the resulting liquid was 105.11 kg of heated E mother liquor, and its composition was: K + 3.74%, Na + 2.44%, Mg 2+ 5.48%, SO4 2- 7.98%, Cl - 15.42%, H2O 64.94%; the solid material will be sent to the flotation section; the heated mother liquor will be sent to the crystallizer for cooling and crystallization;

[0060] (4) Heating and cooling of the mother liquor for crystallization: The mother liquor heated by step E is pumped to a crystallizer for cooling and crystallization. After cooling to 20°C, crystallization is carried out for 3 hours, yielding 7.90 kg of large-particle soft potassium magnesium alum crude product. Its composition is: K + 17.00%, Na + 3.11%, Mg 2+ 6.83%, SO4 2- 41.94%, Cl - 7.73%, H2O 17.27%; Crude potassium magnesium fertilizer product K from the cooling crystallization process+ The process recovery rate was 16.14%; the mass of the mother liquor after cooling was 97.21 kg, and its composition was: K + 2.61%, Na + 2.43%, Mg 2+ 5.20%, SO4 2- 5.47%, Cl - 16.78%, H2O 67.51%; the crude soft potassium magnesium sulfate product enters the washing and drying process, and 1.98 kg of fresh water is added to obtain 6.45 kg of high-quality potassium magnesium fertilizer product, whose composition is: K + 20.13%, Na + 0.75%, Mg 2+ 6.18%, SO4 2- 48.37%, Cl - The potassium content was 1.40%, meeting the requirements for first-grade potassium-magnesium fertilizer, with a potassium recovery rate of 15.60%. The washing mother liquor was 3.43 kg, and its composition was: K... + 2.47%, Na + 2.38%, Mg 2+ 4.68%, SO4 2- 6.02%, Cl - 16.23%; The washing mother liquor and the cooled mother liquor are returned to step (1) for use as E mother liquor;

[0061] (5) Flotation of mineral materials: The solid material obtained in step (3) is transferred to a mixing tank and 215.37 kg of the previous batch of flotation tailings is added for slurry preparation. The slurry concentration is adjusted to 30.0 wt%. After slurry preparation, the slurry enters the flotation machine for soft potassium magnesium sulfate flotation. The flotation process adopts a roughing-cleaning-scavenging flotation process. The middlings from the cleaned ore and the scavenging concentrate are combined and returned to the roughing operation. Sodium dodecyl sulfate, an anionic reagent, is used as the collector. The roughing concentration is 100 g / t of raw ore, and the scavenging concentration is 40 g / t of raw ore. 71.45 kg of concentrate froth is obtained, of which 33.47 kg is concentrate product. Its composition is: K + 16.31%, Na + 2.14%, Mg 2+ 5.23%, Cl - 6.87%, SO4 2- 42.07%, H2O 27.38%; tailings slurry 236.22kg, of which tailings mass is 58.83kg, its composition is: K + 1.32%, Na + 28.67%, Mg 2+ 0.51%, Cl - 49.73%, SO4 2-2.28%, others 17.45%; flotation concentrate K + The process recovery rate was 65.60%;

[0062] (6) Product washing and drying: The concentrate foam was transferred to a mixing tank, 10.71 kg of fresh water was added, and the mixture was stirred for 30 min at 20°C for washing. The mixture was then transferred to a centrifuge for solid-liquid separation and drying to obtain 24.99 kg of potassium-magnesium fertilizer product. The composition of the product was: K + 19.75%, Na + 1.03%, Mg 2+ 5.12%, Cl - 1.67%, SO4 2- The potassium recovery rate was 45.58%, meeting the requirements for qualified potassium-magnesium fertilizer, with a potassium recovery rate of 59.73%. 17.98 kg of filtrate was obtained as washing mother liquor, with the following composition: K... + 2.58%, Na + 2.65%, Mg 2+ 4.46%, SO4 2- 7.32%, Cl - 15.04%, H2O 67.95%; the filtrate is pumped to step (1) for use as mother liquor E or sent to the mother liquor recovery tank;

[0063] (7) Tailings treatment: The tailings slurry obtained in step (5) is mixed with 23.00 kg of fresh water and pumped to the tailings pond via pipeline. After the tailings slurry is allowed to settle, the supernatant is taken as flotation tailings and used in the next batch of flotation or sent to the mother liquor recovery tank.

[0064] This process yields 6.45 kg of Grade I potassium-magnesium fertilizer with a potassium recovery rate of 15.60%; and 25.27 kg of qualified potassium-magnesium fertilizer with a potassium recovery rate of 59.73%, for a total potassium recovery rate of 75.33%, achieving efficient recovery and production of potassium and magnesium resources.

Claims

1. A method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts, characterized in that, Includes the following steps: (1) Raw material addition: Add E mother liquor and raw ore to the reaction tank, with or without adding fresh water; the raw ore is a potassium mixed salt containing potassium salt and magnesium alum; the potassium mixed salt containing potassium salt and magnesium alum K + The content is 3.5–9.5 wt%, Mg 2+ Content is 2.5–10.5 wt%, SO4 2- Content 7.5–23.5 wt%; (2) Heating and stirring conversion: The reaction tank is heated and stirred to obtain a slurry; the temperature is raised to 40-70℃; the stirring time is 60-180 min; (3) Belt vacuum filtration and heat preservation separation of mother liquor: The slurry obtained in step (2) is separated into solid and liquid under heat preservation conditions. The liquid obtained is the mother liquor with temperature rise E, and the solid obtained is soft potassium magnesium alum solid ore. (4) Cooling and crystallizing the heated mother liquor: Cooling and crystallizing the heated mother liquor E, the solid phase is soft potassium magnesium alum crystals, i.e. potassium magnesium fertilizer products, and the liquid phase is the cooled mother liquor; the cooling and crystallizing temperature is 10-25℃, and the crystallization time is 1-5h; (5) Flotation of mineral materials: The soft potassium magnesium alum solid ore obtained in step (3) is mixed with E mother liquor to obtain a slurry; flotation reagents are added to the slurry for flotation to obtain concentrate froth; the flotation adopts a closed-circuit flotation process of roughing, cleaning and scavenging, cleaning middlings and returning scavenged concentrate to roughing. (6) Product washing and drying: The concentrate foam is mixed with fresh water for washing, and solid-liquid separation is performed. The obtained solid phase is potassium magnesium fertilizer, and the obtained liquid phase is washing mother liquor. (7) Tailings treatment: Add water, which is insufficient to form an unsaturated solution, to the tailings slurry obtained by flotation in step (5). After clarification, take the supernatant as the flotation tailings. The components of the mother liquor E are located in Na. + K + Mg 2+ / / Cl - SO4 2- —In the metastable phase diagram of the H2O pentahydrate-salt system, soft potassium magnesium sulfate, potassium chloride, and espresso salt share the saturation point E.

2. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to claim 1, characterized in that, In step (1), the mass ratio of the mother liquor E to the raw ore is 1.2 to 0.6:1; the mass ratio of the fresh water to the raw ore is 0 to 0.4:

1.

3. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to any one of claims 1 to 2, characterized in that, In step (5), the concentration of the slurry is 20-35 wt%; the amount of flotation reagent used for roughing is 40-120 g / t of raw ore, no reagent is added for cleaning, and the amount used for scavenging is 20-60 g / t of raw ore.

4. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to claim 3, characterized in that, In step (5), the flotation reagent is sodium dodecyl sulfonate.

5. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to any one of claims 1 to 2 and 4, characterized in that, In step (6), the volume ratio of fresh water to concentrate foam is 0.1-0.5:

1.

6. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to claim 3, characterized in that, In step (6), the volume ratio of fresh water to concentrate foam is 0.1-0.5:

1.

7. The method for preparing potassium magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate according to any one of claims 1 to 2, 4, and 6, characterized in that, In step (7), the weight ratio of tailings to water is 1:0.1-0.

4.

8. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to claim 3, characterized in that, In step (7), the weight ratio of tailings to water is 1:0.1-0.

4.

9. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to claim 8, characterized in that, In step (7), the weight ratio of tailings to water is 1:0.1-0.

4.

10. The method for preparing potassium magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate according to any one of claims 1-2, 4, 6, 8-9, characterized in that, The mother liquor obtained in step (4), the washing mother liquor obtained in step (6), and the flotation tail liquor obtained in step (7) are returned to step (1) or step (5) as E mother liquor.

11. The method for preparing potassium magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate according to claim 3, characterized in that, The mother liquor obtained in step (4), the washing mother liquor obtained in step (6), and the flotation tail liquor obtained in step (7) are returned to step (1) or step (5) as E mother liquor.

12. The method for preparing potassium-magnesium fertilizer from potassium-containing magnesium sulfate mixed salts according to claim 5, characterized in that, The mother liquor obtained in step (4), the washing mother liquor obtained in step (6), and the flotation tail liquor obtained in step (7) are returned to step (1) or step (5) as E mother liquor.

13. The method for preparing potassium magnesium fertilizer from potassium mixed salt containing potassium magnesium sulfate according to claim 7, characterized in that, The mother liquor obtained in step (4), the washing mother liquor obtained in step (6), and the flotation tail liquor obtained in step (7) are returned to step (1) or step (5) as E mother liquor.