(1) Beneficiation and processing technology of soluble potassium salt ore
The main minerals for the preparation of potassium chloride are potash salts and carnallites. The potash salt has a single component, high solubility, and the most simple beneficiation process. Carnallite beneficiation process is more complex, the magnesium chloride must be removed carnallite obtained after further processing sylvite. The processing of sulphate ore is more complicated. In addition to the general beneficiation method, a certain chemical reaction is required to prepare potassium sulphate.
The ore processing method of the potassium salt mine, the chloride type ore usually has the following methods: hot solution method, flotation method, electrostatic method, gravity method, cold decomposition method and cold decomposition-flotation combined method. The basic principles of the various methods are:
The hot solution method utilizes potassium salt and rock salt to have different solubility in aqueous solution at different temperatures for separation. The method is to heat the co-saturated solution of the potassium salt and other salt minerals to a certain temperature, the potassium salt salt all enters the solution, and the solubility of the stone salt is substantially unchanged, and is separated by the solid phase residue, and then the solution is cooled and precipitated. Potassium chloride.
The flotation method is to sort by using the difference in surface wettability between potassium salt and stone salt. The method is to put a collector , a foaming agent, a catalyst and a medium adjusting agent into a saturated solution to form a film on the surface of the potassium chloride to be isolated from the solution, and when the small air bubbles pass, the potassium chloride particles are adsorbed in the bubble. Above, the bubble brings the potassium chloride crystal to the top of the flotation cell, scrapes the foam through the scraper, and is filtered and dried to be the finished product.
The electrostatic method is sorted by the difference in surface charging properties after heating, cooling and other methods of potassium salt and other associated salt minerals. Before sorting, the material is heated to 300-700 ° C, then cooled to 100-200 ° C, or treated with a special modifier to selectively change the charged nature of the mineral surface to achieve the purpose of sorting.
Heavy medium method (or gravity method): Separation in a specific medium by using the difference in density of potassium salts and other salt minerals. The method is to select a suspension solution between the potassium salt and the rock salt density, in which the stone salt is sunk and the potassium salt is floated to achieve the purpose of sorting.
Cold decomposition-flotation combination method: a combination of the above two methods. First, the slurry of the decomposition of carnallite is filtered, and the mother liquor is separated to obtain crude potassium which is similar to potassium salt. The potassium chloride is just separated from the carnallite, has a new ecological surface, and adds a certain amount of water. The product is obtained by flotation, dehydration and drying.
Typical examples of mineral processing are as follows:
1. Yunnan Yanyejing Potash Mine Ore Dressing Process
The Kanye Well Potash Mine is a deposit of potassium sulphate and stone salt closely coexisting. The main potassium-containing mineral is potassium salt, followed by carnallite. The existing small ore dressing plant of the mine adopts flotation method and processes 24,000 tons of ore annually. The selected ore is mainly a blue-gray type potash salt. The ore containing KCl is generally 10% to 25%, the NaCl content is generally 60% to 80%, the water insoluble matter is 3% to 8%; the original ore has a maximum particle size of 300 mm and the water content is 3% to 6%. The principle flow of the flotation process is shown in the figure below.
2. Qinghai Chaerhan Salt Lake brine beneficiation process
Qinghai Potash Fertilizer Plant, the annual production of potassium chloride fertilizer is about 40,000 tons, and the second plant has an annual output of 200,000 tons of potassium chloride fertilizer. Both of them use the carnallite cold decomposition-flotation combined process to produce potassium chloride. . The potassium-containing brine is pumped into the salt field, and the carnallite ore is produced by sun exposure, then water is decomposed, and the product is washed by flotation (Fig. 4.9.5). The chemical composition of the Yantian carnallite mine: KCl>16%, NaCl<26.25%, MgCl2<25.95%, CaSO4<0.5%, water insolubles 0.2%, free water<2%.
In recent years, with the practice of potassium salt production, the Chemical Industry Design and Research Institute of the Ministry of Chemical Industry has newly developed two new processes:
(1) The sodium bicarbonate of K+, Na+, Mg2+/Cl-, H2O quaternary system is pumped into the salt field, and evaporated in the sun to greatly increase the concentration before crystallizing the potassium-containing mineral carnallite. The brine (corresponding to the composition of the E-point of the phase diagram of the phase diagram) is sent to the processing plant to match the old halogen (corresponding to the composition of the F-point of the phase diagram), and the NaCl is extremely fine from the brine in the instant of halogenation. The particles crystallize out, and the potassium in the brine crystallizes out of the brine in the form of carnallite crystals, but the particles are coarser. Fine-grained sodium chloride is easily removed from the overflow, and the remainder is carnallite (low-sodium carnallite) containing a small amount of sodium chloride. Adding water to the low-sodium carnallite to control the decomposition rate of the carnallite, so that most of the magnesium chloride is dissolved in water, the final product potassium chloride (potassium chloride content up to 98%) is obtained. If you need to improve the purity, you can clean it with fresh water.
Fig. 2 Process for preparing potassium chloride by cold decomposition of carnallite in Qinghai potash plant-flotation combined method
In 1995, two 10,000-ton production units were built. Potassium chloride to produce quality products, intermediate products hyponatremia carnallite electrolyzed have been used as a raw material of magnesium metal. The process not only can obtain high-quality potassium chloride products, but also saves the salt field area, eliminates the recovery process of carnallite, shortens the production cycle, and the equipment can be fully localized.
(2) Dissolving and recrystallizing the salted carnallite to prepare potassium chloride: pumping the raw halogen into the sodium salt pool, and concentrating it to the carnallite by evaporation, then pumping it into the halogen pool, pumping the old halogen to the halogen, and halogenating After precipitation of carnallite, when a certain thickness is reached (30~50 cm), the halogenation is stopped, the brine in the pool is drained, and fresh brine is added to dissolve the carnallite. When it is close to saturation, it is pumped into the potassium salt pool for evaporation and concentration to precipitate KCl. The KCl is dehydrated and dried to obtain a potassium salt product; when the potassium salt pool brine reaches saturation, it is discharged back to the sodium salt pool for recycling production. The brine after the precipitation of the carnallite into the halogen pool is discharged into the second-stage carnallite pool, and the second-stage carnallite is concentrated by evaporation, a part of the terminal brine is discharged, and the other part is discharged into the old brine to adjust the brine and adjust the sodium salt pool brine. The carnallite precipitated in the second-stage carnallite pool, after draining the surface water, is added with fresh water for dissolution, and the dissolved solution is discharged back to the sodium salt pool for recycling production.
The process is an intermediate test scale and has been in operation for several years. The advantage is that it completely uses the salt field to complete the whole process of potassium chloride production, which saves the equipment of the beneficiation workshop; the disadvantage is that the water quality and production process of the brine are all carried out in the open air and are greatly affected by the climate.
3. Production process of Nongle polyhalite mine in Quxian County, Sichuan
After the ore powder is added to the roasting furnace and heated and calcined by the flue gas, the dust is collected and collected by the first-stage cyclone separator, and then recycled by the water washing tower, and the exhaust gas is vented. The calcined clinker is added to the solution tank in which the circulating liquid has been discharged, and after 30 minutes, the slurry enters the compacting machine for filtration and washing, and the gypsum residue after washing and drying is sampled, and then washed with water, and the gypsum residue is naturally discharged. After dehydration, it is sent to the brick making workshop for brick making or discharging. The filtrate is pumped into the double-effect vacuum evaporator by vacuum filtration. After the specific gravity reaches the process requirements, it is placed in a crystallizing tank to cool the crystal. The product is packaged by centrifugation and then packaged. After crystallization, the mother liquor is driven into the double-effect evaporator. The new supplemental filtrate continues to evaporate and concentrate.
The process is a pilot research and development project of 2 000 t/a of high-concentration potassium and magnesium fertilizer made of polyhalite. Using a polyhalite with a K2O content of about 5%, the dissolution rate of K2O is over 90%.
(ii) Comprehensive utilization of insoluble potassium-containing resources
Potassium aluminum silicate and potassium-rich rock is widely distributed in our country, huge reserves. In order to open up mineral resources of potash resources, a large amount of work has been carried out to extract potash from potassium-containing aluminosilicates and potassium-rich rocks. Although it is still in the stage of expanding trials and promotion, it has made a good start. Examples have been successfully tested utilization of the production of potassium sulphate Zhejiang Pingyang alum stone mine, Shanxi Province Wenxi potassium feldspar production and comprehensive utilization of potash, potassium carbonate and cement technology, production and utilization of potassium nepheline Yunnan old crafts.
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