SU990757A1 - Process for producing dust-free potassium fertilizers - Google Patents

Description

(54) METHOD FOR OBTAINING SPRAYLESS

POTASSIUM FIXTURES

The invention relates to a technology for the processing of sylvinites, can be used in potash plants in the production of potassium chloride by the halurgy method to obtain a non-dusting, coarse-grained, potash fertilizer from sylvinites by dissolving them and crystallizing potassium chloride from the resulting solution.

Known methods for the crystallization of potassium chloride from solutions obtained by dissolving sylvinites, using the apparatus of adjustable vacuum-crispallisation: devices with a suspended layer and devices with circulating suspension lj.

These methods make it possible to obtain large crystals up to 1–3 mm, but the equipment used has a low productivity, the metal and energy intensity of the process is several times larger than with conventional horizontal vacuum crystallizers.

The closest in technical essence and the achieved result is a method of obtaining potash fertilizers by processing sylvinite ores by dissolution, followed by separation of potassium chloride from the resulting solution by a multi-stage vacuum crystallizer to obtain a suspension with sodium chloride 0.97-0.98, classification solid phase on the coarse and telokkrollicheskie fractions, drying and dusting coarse

10 fraction, which is the final product. Dust, obtained by dedusting a large fraction, and a fine-crystalline fraction, obtained as a result

15 of the classification of the solid phase, is treated with water and acute parsm and in the form of a slurry with a temperature of -90-10 ° C is supplied to the beginning of the process of vacuum crystallization together

20 initial solution after solution of sylvinites 2.

The total amount of fine-crystalline and dust fractions returned to the beginning of the crystallization process is 20-80% or on average 50% by weight of the finished product. Consequently, per 1 ton of product returns to a crystallization of 0.5 t of potassium chloride, with 85%

30 or 0.42 tons of this amount before. It is dissolved visually and then recrystallized. Thus, the solution load on the vacuum crystallization unit increases; by 42%, which requires in the same amount an increase in the volume of equipment of the vacuum crystallization plant and other equipment: solvents, settlers, centrifuges, pumps, etc. All this will lead to a 42% increase in capital investment, electricity and heat consumption (steam). The purpose of the invention is to increase the economic efficiency of the processes of consolidation of cribtals of commodity products and utilization of dust fractions. This goal is achieved by the fact that according to the method of obtaining dust-free potassium silt stones from sylvinites by dissolving them, crystallization of potassium chloride from the forming hot saturated solution in a multi-stage vacuum crystallization unit to obtain a suspension with a sodium chloride concentration of 0.97 -0.98 the subsequent classification of the solid phase of the suspension into the coarse-crystalline and crystalline fractions of their separation from the suspension, the drying and drying of the coarse-crystal fraction uu for crystallization in a multistage vacuum crystallization-ionized installation serves 80-85 ma hot saturated solution, and the remaining 15-20 wt% of sol ra mixed with fine-grained and dusty fractions, The mixture was cooled with mixing of re vacuo. and attached to the main stream of the suspension entering the classification. Example 1. 80% by weight of a hot saturated solution obtained by dissolving sylvinite is fed to the beginning of a 14-stage vacuum crystallization unit. The solution, bypassing from step to step, is cooled from 90-100 to 20-30 ° C in the first 12 steps of the installation to produce a potassium chloride suspension, the solution in which has a NaCI saturation level of 0.97-0.98. A suspension with a temperature of 20–30 ° C from the 12th step is transferred to hydroclassification and thickening into a six-cone settling tank. A coarse-grained fraction with a size range of 0.0–0.7 mm in the last 2 cones — a fine-grained fraction with a crystal size less than 0.2 mm — is collected in the first cones along the 4 cones. The crystalline fraction is filtered on centrifuges, washed with water, dried and dedusted by air in air classifiers. 20% by weight of a hot saturated solution obtained by dissolving sylvinite is mixed with a fine-crystalline fraction after hydro-classification and thickening and with dust fractions separated during drying and air dedusting of a large fraction. The resulting suspension with a temperature of 70-80s is fed for cooling to the last two (13th and 14th) stages of the vacuum crystallization unit. The cooled suspension after the 14th stage is combined with the suspension after the 12th stage and again fed to the hydroclassification and condensation into a six-tonnage settling tank for separating fine and coarse fractions. Then the cycle repeats. The result is a marketable product with a grain size of 0.2-0.8 mm. Dust fractions less than 0.2 mm are absent. The content of the COP in the product 98-99%. As can be seen from the example, neither the solid nor the liquid phase returns to the beginning of the crystallization process. The dissolution of part of the crystallization of the CS and its recrystallization are not carried out either. Thus, the load on the vacuum crystallization unit for solution and solid phase does not increase, which is a significant advantage over the known method. PRI me R. 2. The 14-stage vacuum crystallization unit is supplemented with a single vacuum crystallizer. Then the process will be carried out as follows. 85% by weight of the hot saturated solution obtained during the dissolution of sylvinite is fed to a 14-stage vacuum crystallization unit for cooling from 90-100 to 20-30 C n of crystallization. with potassium chloride. The resulting suspension with a temperature of 20-30 from the last 14th stage of the installation is fed to the classification unit in a hydroseparator or hydrocyclone, where the solid phase of the suspension is divided into a large fraction with a crystal size of 0.2-0.7 mm and a small fraction with a crystal size less than 0 2 mm. A coarse fraction with a small amount of solution is directly filtered through or filtered, washed with water, dried and dedusted in air classifiers, dust F1 actions formed in this process are caught in a cyclone. A slurry with a small fraction of crystals is concentrated in a settling tank to a solids content in a thickened suspension of 40-50%. 15 wt.% Of the hot saturated solution obtained by dissolving sylvinite is mixed with a thickened suspension of the fine fraction and with dust fractions captured in. cyclones during the drying and dusting of a large fraction. The resulting suspension with a temperature of 70-75 ° C is fed for cooling to 20-25, C into an additional vacuum crystallizer. The cooled suspension is mixed with the suspension after the 14th stage and together with it is fed for classification into a hydroseparator or a -hydrocyclone to separate the coarse and fine fractions. solid phase. The cycle is then repeated. The result is a product with a crystal size of 0.2–0.8 mm with no dust crystals with a size of less than 0.2 mm. The content of KS in the product is 98-99%. Here, too, the crystalline and dust fractions e are not returned to the beginning of the crystallization process, and these fractions are dissolved, followed by the subsequent crystallization of the CS from solution. The performance of potassium chloride per unit of volume of the vacuum crystallization unit does not reduce c. All this gives considerable advantages. Example 3. Two vacuum crystallizers with a volume of 100 l each are used .. In sylvite, a hot () saturated solution with the composition,%: 15.8 NaCI and 63.90, is prepared in the tank. The solution from the test tank is at a rate of 200 l / h. 165 l / h or 82.5 wt.% Of this solution are continuously fed to the first vacuum crystallizer. The solution of the crystalline mash is cooled under vacuum to 750 mm Hg. to 25 ° C. The resulting potassium chloride suspension with the degree of saturation of the solution according to NaCI 0.97 arrives at the hydroclassification into a precipitate. A condensed suspension is taken from the bottom of the settling tank, the solid phase of which consists of crystals with a size of more than 0.2 mm (0.2-0.7 mm) This suspension is fed to filtration, with simultaneous washing of the crystallized water and drying. From the top of the settling tank by gravity A suspension is taken, the solid phase of which contains crystals with a size of less than 0.2 mm. The suspension is concentrated in an additional 1 settling tank to a solids content of 45% and transferred to a mixer. From a tank with a hot saturated solution, the mixer is fed for mixing with the fine fraction 35 l solution; which is 17.5 wt.% of the total amount of solution resulting from

Claims (2)

990757 tank. The resulting suspension with a temperature is fed to a cooling to 25 ° C in the second vacuum cristizlizator. The cooled suspension is attached to the suspension from the first vacuum crystallizer and together with it is fed to the hydro-classification for separation of the coarse and crystalline fractions, filtration, washing, drying and dusting of the coarse-crystalline fraction. The result is a product that does not contain dust-like crystals with a size of less than 0.2 mm. The size of the crystals lies in the range of 0.2-1.2 mm, the arithmetic average size of the crystal is 0.6 g mm, the content of CS in crystals is 98.8% crystal strength 93.5%. The preparation of dust-free potassium fertilizer, by a known method, is achieved by separating fine fractions from crystallized KS, dissolving 85% of their mass, returning the solution with the remaining part of the fractions to crystallize and repeat. crystallization of potassium chloride from solution. A large mass of potassium chloride — up to 42% of the mass of the final product — is subjected to such recrystallization. Because of this, for carrying out the process according to a known method, an increase of 42% in capital costs, an additional consumption of electricity and heat (steam) is required. According to the proposed method, in order to obtain desiccated potash fertilizers, the fine-dispersed fractions are also separated from the KCC crystallisate, but do not dissolve or recrystallize them. Accordingly, the increase in capital expenditures, the additional consumption of electricity and heat are not required. DETAILED DESCRIPTION A method for producing de-dusting sylvinite potash fertilizers by dissolving them, including crystallization of potassium chloride from a hot saturated solution in a multi-stage vacuum crystallization plant to obtain a suspension with a degree of saturation: sodium chloride solution 0.97-0.98, followed by solid classification suspension phases to the coarse and crystalline fractions, their separation from the suspension, washing, drying and dusting the coarse crust fraction characterized in that, in order to increase the efficiency of the process of enlarging crystals 80-85% by weight of hot and dry solution are fed to the vacuum installation and the remaining 15–120% by weight of this piacTBor mixed with q of fine-crystalline and dusty mixture, while mixing is cooled under akumG and attached to the axial flow . suspension entering the classification. . Sources of information taken into account during the examination 5 1. Pozin M.Ye. Mineral salt technology. T. 1, M., Himi, 1970, p. 151-154. 2. USSR author's certificate 781194, cl. C 05 D 1/04, 1978. 10