A method for producing low-sodium carnallite and potassium chloride by utilizing high-sodium carnallite

Abstract

The invention discloses a method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite. Described method comprises: first will be rich in MgCl 2 The substance is mixed with fresh water and preheated to obtain a hot solvent; then, the high-sodium carnallite is selectively heat-dissolved with the hot solvent to obtain a high-temperature potassium-rich saturated liquid; and then the high-temperature potassium-rich saturated liquid is Carry out step-type airtight cooling and crystallization to obtain crude potassium chloride and low-temperature potassium saturated liquid; finally, evaporate the low-temperature potassium saturated liquid to obtain low-sodium carnallite, and then decompose and select the obtained low-sodium carnallite Dissolving treatment to obtain crude potassium chloride. The present invention ensures the high-efficiency and high-quality precipitation of potassium chloride through selective thermal dissolution and step-type closed cooling crystallization; at the same time, artificial potassium halite can be prepared by one low-temperature selective dissolution, avoiding multiple cycles Hot melt crystallization treatment; the method of the present invention has mild conditions, simple method, and is convenient for popularization and implementation of the technology.

Description

technical field [0001] The invention belongs to the technical field of inorganic salt industry, and in particular relates to a method for preparing low-sodium carnallite and potassium chloride from high-sodium carnallite. Background technique [0002] Potassium fertilizer is the basic material material for the stable growth of grain production. It can effectively improve the quality of agricultural products and improve the stress resistance of crops. It is one of the nutrients necessary for the growth of crops. With the reduction of arable land and the continuous growth of population, large-scale development of potassium resources and improvement of potassium fertilizer yield are of great significance to food security. [0003] The main type of potash fertilizer products is potassium chloride fertilizer, accounting for more than 90% of the total potash fertilizer. The raw materials for producing potassium chloride fertilizer mainly include potassium halite and carnallite or...

AI Technical Summary

Problems solved by technology

Further, the patent CN102442687B adopts cold decomposition in a rotary decomposer, selectively grades and separates coarse NaCl particles, and flotation the remaining pulp to obtain qualified KCl concentrate; the patent CN107188200B adopts a multi-stage screening system to separate the cold decomposition slurry, and then obtains Coarse-grained NaCl, coarse-grained KCl and fine-grained KCl slurry, the fine-grained KCl slurry is separated by flotation to obtain KCl concentrate; the two technologies have greatly improved the product quality of potassium chloride, although the production of potassium chloride by this technology is relatively economical Energy, less investment in building a factory, simple and easy to master technology, but the obtained product has a finer particle size, poor physical properties, low potassium yield, generally 50% to 60%, poor physical properties of the product, and poor physical properties in the product. The particle size greater than 100 mesh only accounts for 10% to 20%, and it is gradually difficult to adapt to the requirements of the international market. This technology is greatly affected by the type of carnallite ore. When the NaCl content in carnallite ore is high, the grade and yield of KCl will be greatly reduced. ;

[0007] (3) Reverse flotation-cold crystallization method: The technical process is that the carnallite ore is firstly subjected to reverse flotation to remove NaCl to obtain low-sodium carnallite. After the low-sodium carnallite is cold-decomposed and crystallized, it is screened, filtered and washed. , dry to obtain the potassium chloride product, the technical process can be found in figure 2 , on the basis of the original process, the patents CN104058427A and CN107572552A introduced a screening system before the reverse flotation, preferentially screened out large particles of NaCl, further reduced the content of NaCl in low-sodium carnallite, and ensured the stable operation of cold crystallization, although the Potassium chloride produced by the technology is of high quality, up to about 95%, and the product has a coarse particle size and good appearance, but its process is relatively complicated, the operation is not easy (especially the crystallization system), and the requirements for raw ore are high, and the dependence strong;

[0008] (4) Mixing halogen-speed-controlled crystallization method: This technology is the co-saturated mother liquor (carnallite saturation point) of potassium chloride, sodium chloride, and carnallite with magnesium chloride, sodium chloride, and carnallite. The mother liquor (saturation point of bischofite) is mixed, and low-sodium carnallite is precipitated due to the supersaturation of potassium and magnesium. After concentration and dehydration, it enters the crystallizer, and fresh water is added to decompose and crystallize to obtain high-grade potassium chloride. The technical process can be found in image 3 , although this technology has obvious advantages such as simple process flow, excellent product quality, low capital investment, low production cost, high operation recovery rate, high resource utilization rate, and no environmental pollution, but this technology uses decomposed mother liquor as raw material to produce The scale cannot be expanded arbitrarily, and it can only be attached to a large flotation plant with low output;

Although the insolation method makes full use of solar energy and does not add any chemicals, the product quality is good. The precipitated potassium chloride particle size is generally above 0.2mm and the purity is high, but the yield is low and is greatly affected by climate conditions;

[0010] (6) Cold decomposition-hot solution crystallization method: This technical process is to completely decompose carnallite with fresh water to obtain artificial potassium halite, and then remove it by hot solution of fresh water according to the principle that the solubility of sodium chloride and potassium chloride varies with temperature. Sodium chloride in artificial potassium rock salt, the mother liquor is cooled and crystallized to obtain potassium chloride, the technical flow chart can be found in Figure 5 , although the potassium chloride product obtained by this technology has a large and uniform particle size, good physical properties, high product purity, high recovery rate of potassium, and low equipment investment, but the energy consumption is large, the cost is high, the equipment corrosion is serious, and the process The operation is also more complicated, and it is generally suitable for promotion and use in areas with relatively cheap energy

[0011] On the basis of the original technology, the patent CN102583446B uses old brine to dissolve low-sodium carnallite ore at high temperature to obtain a hot solution, and the hot solution cools down to precipitate potassium chloride, but only for low-sodium carnallite, the solid mass ratio of the hot solution is increased, so that All low-sodium carnallite (including NaCl) enters the liquid phase, so the crude potassium obtained by cooling is actually still potassium halite, and the process effect is not good

Patent CN103193252B uses high-temperature potassium-rich brine to decompose carnallite to obtain artificial potassium halite, and then uses hot-melt crystallization process to process artificial potassium halite to produce potassium chloride. Since the concentration of K ions in hot-soluble brine is already very high, the light The decomposition efficiency of halide stone is extremely low; at the same time, except for a small amount of large-grained KCl, a large amount of the decomposed solid phase is still in the form of fine-grained potassium halite, and the overall effect is not good.

[0012] Generally speaking, the technical effect of producing potassium chloride from carnallite ore at this stage is closely related to the content of sodium chloride in carnallite ore. The higher the content of sodium chloride, the lower the yield and grade of potassium chloride, especially for High sodium carnallite ore, the actual effect is not ideal

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