Salt production. Salt

The invention relates to a technology for the production of common salt from sodium chloride solutions of natural or artificial origin. The invention can be most effectively used in the production of edible table salt from brines of underground dissolution of rock salt. Edible table salt is obtained by crystallization during the evaporation of brines of underground salt dissolution in multi-shell evaporators. At the same time, impurities contained in rock salt pass into the finished product, reducing its quality. In addition, these impurities, mainly scale-forming calcium salts, such as sulfate and bicarbonate, complicate the evaporation process, being deposited on the internal heat exchange surfaces of the equipment in the form of scale, reducing its productivity and increasing energy consumption. To improve the quality of commercial edible table salt, as well as to prevent scale formation on the internal surfaces of heat exchange equipment, brines of underground dissolution of rock salt are subjected to chemical purification. Purification of brines consists in the conversion of impurities polluting table salt into insoluble compounds by adding special chemical reagents. After precipitation and separation of insoluble impurities, the purified brine is processed to obtain edible table salt of sufficiently high purity. However, chemical purification of brines leads to a significant increase in the cost of obtaining salt, as well as to the appearance of a large amount of industrial waste, which includes precipitated impurities, along with the table salt brine captured by them. At the same time, it is possible to obtain pure table salt by processing directly brines of underground dissolution of rock salt - the so-called crude brines. Special technology and appropriate equipment also make it possible to avoid scale formation on the heat exchange surfaces of the equipment. At the same time, the cost of obtaining salt is significantly reduced. However, this technical solution does not eliminate all the disadvantages of traditional methods of obtaining table salt from brines. In particular, the mother liquor remaining after isolation of the pure crystalline salt is also not disposed of. Sometimes this solution is returned to the wells of underground salt dissolution, which cannot be considered acceptable, since conditions are created for the gradual contamination of the original brine with undesirable impurities. In other cases, the mother liquor is thermodynamically discharged into special storage facilities, which leads to serious contamination. environment. In addition, it is obvious that the lack of technology for the rational processing of mother liquors reduces the degree of use of raw materials. Thus, when analyzing the known methods for obtaining table salt from brines, it is necessary to keep in mind the problems of the purity of the finished product, increasing the degree of use of raw materials, as well as environmental and economic issues. A known method for producing table salt includes chemical purification of the original brine from impurities, evaporation of the purified brine in a multi-shell evaporator, followed by separation of crystalline salt from the mother liquor and drying. Insoluble impurities that precipitate after chemical treatment in the form of sludge are separated from the brine, washed and sent for storage in special tanks (sludge storage) or discharged after dilution into natural reservoirs. When evaporated from the purified brine, table salt crystallizes. required quality . By cleaning the brine from scale-forming substances, scale formation on the heat transfer surfaces of the equipment is minimized and a sufficiently long inter-flushing cycle of its operation is ensured. The mother liquor after crystallization of sodium chloride, containing, in addition to sodium chloride, dissolved impurities, is removed from the process. The disadvantages of this method are the high operating and capital costs for cleaning the brine, as well as the need to discharge sludge from the chemical cleaning of the brine and the mother liquor after separating the crystalline salt. These discharges lead to environmental pollution and worsen the ecological situation around salt production plants. A known method of obtaining sodium chloride from raw materials contaminated with impurities, for example, halite dumps, by dissolving raw materials in circulating liquor to obtain a hot saturated sodium chloride solution, clarifying and isolating the final product from it, characterized in that, in order to simplify the method and obtain high quality table salt from crude brines, the product is isolated by multi-stage vacuum crystallization using mixing condensers irrigated in the head part with circulating mother liquor and, at the last stages, with a refrigerant, for example water. In this case, table salt is isolated from the solution by multi-stage vacuum crystallization at a decrease in temperature. Isolation of impurities from the original raw brine, formed by dissolving rock salt or halite dumps, is carried out by heating the raw brine with live steam to 105 o C. Due to the heating of the raw brine, the scale-forming impurities contained in it, which have reverse solubility, crystallize. After that, they are separated from the brine by settling, washed with water and removed from the process in the form of sludge. The disadvantage of this method is the low degree of separation of salt from the brine during vacuum crystallization due to a slight change in the solubility of sodium chloride depending on temperature. As a result, the amount of pumped solution increases, which leads to an increase in energy consumption. This also leads to the need to heat the brine when dissolving the feedstock with live steam. Another disadvantage of the method is the discharge of insoluble impurities in the form of sludge, which pollutes the environment. There is also a known method for producing pure table salt according to the UK patent. According to this patent, table salt is obtained by processing crude brine obtained by dissolving salt and containing scale-forming impurities, by heating the brine to a temperature exceeding its boiling point at atmospheric pressure, separating impurities on a hydraulic cylinder and isolating table salt. from purified brine as a result of vacuum crystallization upon cooling with the return of the mother liquor to dissolve the salt. At the same time, table salt is added to the heated crude brine to salt out impurities. This method makes it possible to exclude the chemical purification of the brine from impurities, as well as the previously described method, these methods are in many ways similar in their characteristics. Therefore, the known method for producing table salt has the same disadvantages as a low degree of salt release from brine during vacuum crystallization, an increase in energy costs due to the need to heat the solution with live steam, and also the discharge of impurities in the form of sludge. A known method for producing table salt from a brine contaminated with impurities according to the French patent According to this patent, impurities are isolated from the impure brine containing impurities by heating to a temperature exceeding the solubility limit of impurities, precipitation and separation of them, followed by evaporation of the brine and separation of crystalline salt from the solution. In the described way, table salt is obtained by evaporating brine in a multi-shell plant. Thus, the degree of salt separation from the brine relatively increases in comparison with its production by the vacuum crystallization method, and energy costs are reduced. At the same time, the crude brine is processed without pre-treatment with chemical reagents. Instead, scale-forming components from the brine are isolated by thermal softening before evaporation; pre-heating the brine to a temperature of 120-150 o C. To a temperature of 60 o C, the brine is heated in recuperative heat exchangers, and then in mixing heat exchangers with live steam, because brine heating in recuperative heat exchangers (with heat transfer through the wall) above 60 o C is excluded due to intensive scale deposition. Impurities released during heating of the brine are separated from the brine and, together with a solution containing soluble impurities, are removed from the process in the form of sludge. The disadvantage of this method is the need to heat the initial crude brine to separate impurities to high temperatures of 120-150 o C. As a result, the pressure at which the precipitate of impurities is separated from the brine increases to 0.5-3 kgf/cm 2 . At such a pressure, the equipment on which the precipitate of impurities is separated by settling is unstable. Small fluctuations in pressure cause the brine to boil and particles of impurities enter it, which leads to contamination of the production table salt. Another disadvantage of this method is the increase in energy consumption as a result of heating the brine and mixing heat exchangers in which the brine is diluted. To compensate for this dilution of the brine, you have to additionally spend thermal energy at the evaporation stage. In addition, the disadvantage of this method is the need to remove impurities from the lumen in the form of sludge, which pollutes the environment and leads to salt loss. Closest to the claimed method in terms of technical essence is a method for producing table salt, described in This method is taken as a prototype. The method consists in processing raw materials contaminated with impurities - crude brine of underground dissolution of rock salt, including evaporation of this brine in an evaporation plant to obtain a suspension containing 30-40% crystalline salt, thickening the one stripped off suspension and washing salt crystals with the original brine, returning the clarified solution to evaporation with the discharge of part of this solution to remove impurities, the classification of the thickened suspension in a hydraulic cylinder with the return of the overflow solution of the hydrocyclone to evaporation, the second washing of the crystalline salt from the hydrocyclone with the original brine, centrifugation of the salt with the return of the centrifuge to evaporation and drying of the salt. In the described way, table salt is obtained as a result of direct processing of crude brine obtained by underground dissolution of rock salt and contaminated with impurities, including scale-forming ones. This excludes the chemical purification of the brine from impurities, as well as the heat treatment of the brine to precipitate impurities from it before separating salt. The crude brine containing impurities is fed to a multi-effect evaporator unit consisting of four casings. In the process of evaporation from the brine, salt crystallizes, as well as scale-forming impurities, mainly calcium sulfate and carbonate. However, due to the fact that a special technological mode is maintained during evaporation, there is no scale deposits on the heat transfer surfaces and no clogging of the heat exchange tubes of the evaporator with salt. This is achieved by keeping the concentration of solid crystalline salt equal to 30-40% in one stripped off suspension. At the same time, it contains crystals of scale-forming impurities, which play the role of a seed, on which impurities released from the brine are deposited. Maintaining the specified technological mode allows the evaporator plant to operate continuously for 15-30 days without a decrease in productivity. The use of a multi-shell evaporator for the production of table salt makes it possible to significantly reduce energy costs and reduce the cost of salt. One stripped off suspension containing crystals of sodium chloride and impurities is thickened in a sump. At the same time, in the clarified solution there are crystals of impurities, which are much smaller than the crystals of common salt and therefore leave with the clarified solution. The clarified solution, together with the impurity crystals contained in it, is mixed with the initial crude brine and fed to evaporation. During the evaporation process, the crystals of impurities present in the initial brine play the role of a seed and prevent scale formation on the evaporator tubes. A part of the clarified solution after thickening the one stripped off suspension, containing both dissolved and crystallized impurities, is discarded by withdrawing from the process. Thus, an excess amount of impurities coming with the initial crude solution is removed from the process. The thickened slurry, which contains about 50% solids, is washed with the original crude brine by mixing with it so that the solids concentration in the resulting slurry is about 25% This slurry is classified in a hydrocyclone with the return of the hydrocyclone overflow solution to evaporation. Table salt contained in the thickened hydrocyclone suspension is washed a second time with the original crude brine, separated from the solution in a centrifuge and dried. The salt-free solution is returned to evaporation. The edible table salt obtained by the described method is of high quality, with the exception of the increased calcium content, which reaches 0.1% for the salt of the Avan salt plant instead of 0.02% acceptable for the edible table salt "Extra" according to GOST 13830-91. The disadvantage of the known method is that in order to remove impurities from the process coming with the original crude brine, it is necessary to dump part of the stripped off solution into the sewer, polluting the environment. In this case, the discharged solution is saturated with table salt, which leads to the loss of a useful product, which is 10-15% of the salt in the original brine. Another disadvantage of the known method is the lack of purity of the resulting finished product. This is manifested in the fact that the calcium content in it is 5 times higher than required by the standard. In addition, the disadvantage of the known method is the "hanging" of salt on the walls of the sump when thickening one stripped off suspension containing salt crystals and impurities. The noted phenomenon leads to unreliable operation of the sump, violation of the settling regime, resulting in contamination of table salt with particles of impurities, in particular gypsum and chalk, causing an increase in calcium in the salt. The reason for this is the capture of small crystals of impurities by the coarse-grained salt condensed in the sump, as a result of which such table salt has an increased ability to adhere to the walls of the sump. Therefore, the quality of commercial salt is reduced. Based on the foregoing, it can be seen that the use of the prototype method does not allow to avoid discharges of industrial wastes that pollute the environment and lead to losses of the target product, and also does not make it possible to obtain high quality edible table salt. Mentioned disadvantages can be eliminated in the implementation of the claimed invention. At the same time, the technical result achieved is to improve the quality of commercial table salt by reducing the content of impurities in it, as well as the exclusion of industrial waste discharges, their complete utilization and an increase in the degree of use of raw materials. The claimed invention is a method for producing table salt from a raw material contaminated with impurities, for example, from a brine of underground dissolution of rock salt, including evaporation of this brine in an evaporator plant to obtain a suspension containing 30-40% crystalline salt, thickening the one stripped off suspension and washing salt crystals with the original brine with the return of the answer solution to evaporation, classification of the suspension in a hydrocyclone, the second washing of the crystalline salt, centrifugation of the salt with the return of the centrifuge to evaporation and drying of the salt. The listed features of the claimed method coincide with the features of the prototype method. The claimed method differs in that the stripped off suspension is subjected to classification in a hydrocyclone, which is diluted to a crystalline salt concentration of 10-20%, the hydrocyclone drain solution is divided into three parts, one of which, equal to 50-90% of the total solution flow, is sent to dilute the stripped off suspension, the other part, equal to 7-25% of the total flow, is sent for evaporation, the solid phase is separated from the remaining third part of the drain solution, and the mother liquor produces a second washing of crystalline common salt. The method also differs in that 30-90% of the mother liquor is evaporated at a separate stage until all salts are completely isolated from the solution, followed by their separation from the solution and drying. In addition, the method differs in that at a separate stage of evaporation, a part of the stripped off solution, which is 0.05-0.5 kg per 1 kg of salts, is separated from the stripped off suspension and removed from the process. The presence of distinctive features in the claimed invention indicates compliance with its criterion of "Novelty". In this application, the requirement of unity of invention is fulfilled, since all signs refer to one object - the method of obtaining table salt. The claimed invention meets the criterion of "inventive step". From the above description of the prior art, it follows that the applicant has not identified sources of information containing information about analogues and technical solutions that have features that match the distinctive features of the prototype of the claimed invention and have the same properties. Distinctive features of the claimed method have not been identified in other sources of information on methods and installations for producing table salt. The claimed set of essential features of the invention, together with the distinctive features of the claimed method, is in a direct causal relationship with the achieved technical result. According to the proposed method, table salt is obtained from raw materials contaminated with impurities, for example, from rock salt. This raw material is dissolved in water and the original crude brine is obtained, which is evaporated in an evaporator plant to obtain a suspension containing 30-40% crystalline salt. The evaporator plant can be multi-cascade, i.e. consisting of several evaporators connected in series for steam and solution, as well as single-case and thermal vapor compression. At the same time, as in the fact that in the other case, minimal energy consumption for salt production is ensured. One stripped off suspension is subjected to classification in a hydrocyclone, due to which salt crystals are separated from impurity crystals. The classification is based on the fact that these crystals have large differences in impurity sizes, several tens and even hundreds of times smaller than salt crystals. Therefore, impurities are in the overflow solution of the hydrocyclone, and crystalline table salt in a compacted suspension. At the same time, before classification, one stripped off suspension is diluted to a concentration of crystalline salt of 10–20%, which makes it possible to ensure almost complete separation of sodium chloride crystals and impurities. The dilution of the one stripped off suspension before being fed to the hydrocyclone is carried out by mixing with the overflow solution of the hydrocyclone. To do this, the hydrocyclone drain solution is divided into three parts, one of which, equal to 50-90% of the total solution flow, is sent to dilute the evaporated suspension. The other part of the hydrocyclone drain solution, equal to 7-25% of the total flow, is directed to evaporation. With this flow of the overflow solution of the hydrocyclone, crystalline impurities are fed to the evaporation, which, during evaporation, are a seed on which the crystallizing impurities stand out. This prevents scale formation on the heat transfer surfaces of the evaporators. The remaining third of the overflow solution of the hydrocyclone is directed to separate crystalline impurities from it. The suspension compacted in the hydrocyclone is mixed with the initial brine. Said process is carried out in a settler, in which the upward flow of the initial brine is used to wash salt crystals from the solid impurities remaining in them, as well as from the one stripped off solution having a high concentration of soluble impurities. In the sump, the process of thickening the evaporated sodium chloride suspension also takes place with the removal of the clarified solution for evaporation. With a clarified solution, impurities separated from table salt are returned to evaporation. The suspension condensed in the sump contains table salt washed from impurities. This salt is subjected to a second washing, for which the mother liquor is used after separating crystalline impurities from a portion of the hydrocyclone overflow solution. The washed salt is separated from the solution by centrifugation and dried to obtain production table salt. The centrifuge centrifuge is returned for evaporation. The second washing of common salt with the mother liquor can be carried out both by mixing the salt with the mother liquor, and by feeding the solution to the centrifuge during salt centrifugation. In the case of a large amount of impurities in the rock salt, 30-90% of the mother liquor after separation of crystalline impurities is evaporated in a separate stage. In this case, the solution is evaporated until all salts are completely isolated from it, followed by their separation from the solution and drying. The separation of salts from the solution is carried out by carrying out the operations indicated in the first paragraph of the claims for the claimed method, i.e. evaporation of the solution to obtain a suspension containing 30-40% crystalline salt, thickening and separating the salt from the solution by centrifugation with the return of the clarified and mother liquor to evaporation. The table salt obtained in this case is, in terms of its quality, a salt of a lower grade than the main amount of salt, for example, fodder salt or salt for industrial applications . When processing feedstock containing a large amount of soluble impurities, at a separate stage of evaporation, a part of the stripped off solution is separated from the stripped off suspension and removed from the process, amounting to 0.05-0.5 kg per 1 kg of salts isolated at this stage. The separation of the stripped off solution from the suspension can be carried out by settling and thickening the suspension. Thus, table salt is almost completely isolated from the stripped off solution, leaving only soluble impurities in it. The solution withdrawn from the process can be used for further industrial applications, for example, for the production of salts contained therein, or for other purposes, such as use as a barrier fluid in oil production. The application of the claimed method makes it possible to obtain the highest quality edible table salt from the raw material contaminated with impurities. In this case, the impurities present in the feedstock are separated from the solution in the form of a solid crystalline precipitate, which can be processed into building gypsum. Thus, in this case, the discharge of industrial waste is excluded, since they are completely recycled. If the original brine contains a large amount of impurities, then part of the salt can be produced additionally in the form of technical or feed salt, and waste disposal will also be excluded. With a very high content of soluble calcium and magnesium salts in the initial brine, the claimed method allows them to be disposed of in the form of individual products or special commercial solutions. In all cases, a higher degree of use of raw materials is ensured and the discharge of industrial waste is excluded. The classification of one stripped off suspension in a hydrocyclone makes it possible to separate salt crystals from solid impurities with the greatest completeness. This is due to the fact that the crystallizing components differ significantly in size and, consequently, in mass. Salt crystals obtained by evaporation have an average size of 300-400 microns, and impurity crystals, which are gypsum and chalk, are not more than 5 microns. Therefore, table salt and impurities are well separated. Moreover, the separation of crystalline impurities from salt in the centrifugal field of the hydrocyclone occurs with much greater completeness than in the gravitational field of the sump, as is done in the prototype method. Dilution of one stripped off suspension before classification in the hydrocyclone to a concentration of crystalline salt 10 20% overflow solution of the hydrocyclone allows you to further increase the degree of separation of salt crystals and impurities. This excludes the presence of solid impurities in the intergrowths and agglomerations of salt crystals, which takes place in the prototype method when separating crystalline impurities from sodium chloride in more concentrated suspensions. As tests have shown, the classification of a suspension containing 10-20% salt crystals and solid impurities in the form of gypsum and chalk provides the highest degree of separation of these crystals, reaching 90-95%. If a suspension containing more than 20% of the solid phase is subjected to classification in a hydrocyclone, the separation of salt crystals and impurities is significantly worsened. About 20-30% of salt crystals, despite their large size, goes into the drain solution together with impurity crystals while increasing the proportion of impurities in the compacted suspension. A decrease in the concentration of the solid phase in the classified suspension below 10% leads to the capture of crystalline impurities by common salt in the compacted suspension due to the weak separation of the clarified solution from it. As a result, the degree of separation of sodium chloride and impurities is reduced to 60 - 70%. In addition, dilution of the one stripped off suspension to a solid phase concentration of less than 10% leads to an increase in the flow of the classified suspension and to an increase in the metal consumption of the hydrocyclone. Therefore, for the classification in the hydrocyclone of a suspension containing salt crystals and impurities, the most optimal and giving the best effect is the concentration of the solid phase 10 20% The drain solution of the hydrocyclone is divided into three parts. One of them, equal to 50–90% of the total solution flow, is sent to dilute the stripped off suspension in such a way that the concentration of crystalline salt in it before classification in the hydrocyclone would be equal to 10–20%. the value of the concentration of the solid phase in the suspension. So, if the dilution of the one stripped off suspension is directed to less than 50% of the total flow of the drain solution, then the concentration of the solid phase in the diluted suspension will be more than 20%, which will lead to a deterioration in the separation of salt crystals and impurities. If more than 90% of the total flow of the drain solution is used to dilute the evaporated suspension, then the content of solid salt in the suspension will be less than 10%. In this case, the separation of crystalline salt and impurities will also worsen, the flow of the suspension to the hydrocyclone will increase, and its metal consumption will increase. At the same time, it should be noted that the dilution of the one stripped off suspension by itself with a part of the hydrocyclone drain solution improves the separation of common salt crystals and impurities. This is due to the fact that a certain amount of the smallest salt crystals, captured by the solution flow, goes into the drain solution along with impurity crystals. The return and mixing of this solution with one stripped off suspension leads to the fact that the salt crystals captured by the drain solution mix with the crystals in the stripped off suspension and, during classification, leave with them in the compacted suspension of the hydrocyclone. The compacted suspension of the hydrocyclone, which contains a small amount of solid crystalline impurities, is washed with the original crude brine and thickened. Thus, table salt is completely washed from solid impurities, and, at the same time, from one stripped off solution with a high concentration of soluble impurities. As a result of washing and thickening, the stripped off solution in the suspension is replaced by a purer initial brine. After washing the salt crystals, the thickened suspension is fed to centrifugation. The classification of one stripped off suspension in a hydrocyclone with its dilution to a concentration of crystalline salt of 1020% according to the claimed method differs from the classification of the suspension according to the prototype method. The difference between classification operations in the claimed and known method is as follows. In the prototype method, the suspension thickened in the settler is diluted with the initial brine to a crystal concentration of about 25% i.e. about twice. At the same time, the dilute suspension entering the classification has a temperature of about 30 o C due to the mixing of cold (with a temperature of 15-20 o C) initial brine and stripped off pulp with a temperature of 50-55 o C. As a result, the viscosity of the solution, which contains salt crystals and impurities, separated during hydroclassification increases by almost 2 times, which leads to a significant decrease in the degree of separation of salt and impurities. In addition, the specified degree of separation is reduced by the fact that the concentration of the solid phase in the classified suspension is high, about 25% Therefore, the table salt obtained in the prototype method after classification in a hydrocyclone contains a large amount of crystalline impurities, in particular calcium, which reduces its quality. Unlike the prototype, classification according to the claimed method is stripped off suspension with a temperature of 47 55 o C, resulting in the viscosity of the solution is not very high. Along with this, the classified suspension has an optimal solids content of 10-20%. These factors provide a high degree of separation of salt crystals and impurities. The consequence of this is the high purity of the resulting table salt. Thus, the difference in the properties of the suspension classification operations in the claimed method and in the prototype is obvious. The separation of impurities in a hydrocyclone also differs in its properties from a similar operation according to the known method according to the British patent. In a known method, using a hydrocyclone, crystalline impurities are separated from the heated initial brine. That is, in fact, the hydrocyclone is used only to thicken the precipitate of impurities in the absence of crystalline salt and separate it from the brine, and not to hydraulically classify salt crystals and impurities, as in the claimed method. The second part of the drain solution of the hydrocyclone, equal to 725% of the total flow, is directed to evaporation. This solution contains crystals of impurities, separated from table salt. During evaporation, these crystals serve as a seed, on which solid impurities precipitate from solution. This prevents scale formation on the heat transfer surfaces of the evaporators. The indicated consumption interval of the drain solution is set based on the amount of scale-forming impurities in the feedstock and the dependence of their solubility in common salt solutions on temperature. Usually, crude brines can contain 0.1-0.4% calcium in the form of sulfate or bicarbonate, respectively, with a small amount of impurities in the crude brine, the proportion of the drain solution returned to evaporation is at least 7% The high content of impurities in the crude brine requires an increase in the proportion of the drain solution hydrocyclone up to 25% of the total solution flow. At the same time, for each specific case of obtaining table salt from rock salt of a particular deposit, there is its own optimal value for the proportion of the drain solution, which must be returned to evaporation to prevent scale formation. Lowering the proportion of the drain solution below the optimum for these conditions will lead to the fact that the seed present in the evaporated solution will not be enough to prevent scale formation. An increase in the proportion of the solution will lead to an increase in the amount of seed and table salt, make it difficult to separate it from the salt and, ultimately, lead to a decrease in the quality of the salt. The optimal value of the proportion of the hydrocyclone drain solution returned for evaporation to prevent scale formation is determined empirically in each specific case. To determine the indicated optimal values, we carried out work on obtaining table salt from rock salt of various deposits. The results of these works have shown that the optimal values of the proportion of the drain solution in the processing of raw brines with different compositions of impurities are in the stated range of 7–25%. This portion is typically 3-30% of the total hydrocyclone overflow. The separation of solid impurities from the solution allows them to be removed from the process. Moreover, according to the proposed technical solution with solid crystalline impurities removed from the process, the minimum amount of sodium chloride solution is lost, because the solution separates from the crystals. Whereas in the prototype critical impurities are removed from the process along with the solution, i.e. there is a loss of solution, reducing the degree of use of raw materials to 85-90% and polluting the environment. (It should be noted that in the prototype, along with the solution, soluble impurities are removed from the process). Thus, due to the separation of impurities from the solution, the inventive method makes it possible to eliminate the loss of the solution, increase the degree of use of raw materials to almost 100%. Solid impurities separated from the solution can be processed into a commercial product, for example, building gypsum. At the same time, environmental pollution by production waste is excluded and their complete utilization is carried out. Quantitatively for the drain solution of the hydrocyclone, sent to separate solid impurities from it, is determined depending on the presence of impurities in similar raw materials. This stream of solution is selected in such a way as to remove from the process all scale-forming impurities present in the original crude brine with the separated precipitate of impurities. Based on this, an interval of 3-30% of the total flow of the drain solution is obtained. When separating impurities from the drain solution of the hydraulic cylinder, the flow rate of which is in the given range, it is ensured that almost all scale-forming impurities that may be in the rock salt of various deposits are removed from the process. When separating the solid phase from the drain solution of the hydrocyclone, only crystallizing scale-forming impurities, such as gypsum and chalk, are removed from the process. Soluble impurities, such as calcium chloride, magnesium and potassium compounds, remain in the mother liquor, which is not removed from the process. Moreover, the concentration of soluble impurities in the mother liquor increases in proportion to the degree of evaporation of the original brine. If this solution is withdrawn from the cycle along with crystalline impurities, then such a solution will repeat the prototype method, in which a one stripped off solution containing soluble impurities is produced, together with solid crystalline impurities. However, there will be a loss of salt, reducing the degree of use of raw materials and polluting the environment. To eliminate these negative consequences of removing soluble impurities from the process in the claimed method, it is proposed to perform a second washing of common salt with mother liquor after separation of crystalline impurities. The second washing of the salt with the mother liquor will remove soluble impurities from the process that are present in the feedstock in the industrial commercial salt. During the second washing of table salt, the crystalline salt separated from impurities is mixed, which is in a solution similar in composition to the original crude brine with the mother liquor. As mentioned above, the mother liquor has a high content of insoluble impurities, exceeding the content of these compounds in the original brine by 8200 times. Moreover, the last value, which is the degree of evaporation of the brine to obtain a production salt, is set based on the composition of the feedstock of the required content of soluble impurities in the commercial salt. As a result of washing, sodium chloride is in a solution of an average composition, which, although having a sufficiently high content of soluble impurities, is nevertheless lower than in a one stripped off solution. When such a salt is centrifuged, the crystals separated from the solution will contain a certain amount (usually 2-6%) of the centrate, i.e. the solution from which the salt was separated. In this case, the quality of the salt will be determined precisely by the amount of impurities in the centrate, which are in the salt crystals. Therefore, the degree of evaporation of the brine in each particular case is set such that the concentration of soluble impurities in the mother liquor would make it possible to remove with the commercial salt the amount of impurities that came with the original brine. Thus, the application of the claimed method will eliminate the loss of salt, increase the degree of use of raw materials and eliminate environmental pollution. Washing common salt with mother liquor can be carried out either by mixing a suspension containing crystalline salt with mother liquor, followed by compaction of the suspension and feeding it to centrifugation, or by directly feeding mother liquor to a centrifuge. As a result of washing the salt with the mother liquor after centrifugation, it will contain a solution containing less impurities than the mother liquor. However, the resulting commercial salt in its quality will meet the commercial requirements. There are cases when the feedstock contains a large amount of impurities. The processing of such raw materials in order to obtain top quality table salt according to known methods does not allow to avoid discharges of the mother liquor, i.e., salt losses and environmental pollution. In this case, we propose to evaporate 30 90 of the mother liquor after separation of crystalline impurities at a separate stage until all salts are completely isolated from the solution, followed by their separation from the solution and drying. The remaining mother liquor is used for the second salt wash. Separation of salts from part of the mother liquor also makes it possible to obtain common salt from it. However, this salt is of a lower quality than the base salt. Therefore, the mother liquor for the separation of salts from it is evaporated in a separate stage so as not to contaminate the main product with a salt of lower quality. At the same time, the salt from the mother liquor contains the main amount of impurities proportional to the proportion of this solution sent to obtain the salt. This reduces the amount of impurities that come with the mother liquor for the second washing of the salt. Due to this, the main amount of table salt is of high quality in terms of purity. The specific value of the share of the mother liquor directed to the extraction of salt depends on the composition of the feedstock. The work carried out by us to obtain table salt from various kinds raw materials showed that for the raw materials most contaminated with impurities, the value of this proportion does not exceed 90%. At the same time, common salt obtained from the mother liquor is a salt of lower quality and may not be of food, but of technical qualification. For raw materials less contaminated with impurities, the indicated value of this share is 30% or more, and the resulting table salt corresponds in quality to the highest grade of industrial salt or the lower grades of food salt. At the same time, in all cases when it is necessary to obtain salt from a part of the mother liquor, the proportion of this solution directed to the separation of salts is in the declared limit of 30–90%. from which more than 90% salt is extracted will lead to contamination of the resulting salt above all permissible items. Such salt is not used and will have to be dumped, polluting the environment and wasting salt. If the proportion of the mother liquor is 30%, then this will lead to the fact that not all impurities will be removed in the salt released, but only part of them. The rest of the impurities will be in the main table salt, thereby reducing its quality. Thus, the processing of a part of the mother liquor into table salt makes it possible to exclude the discharge of a solution of table salt, completely utilizing it, and to exclude environmental pollution. The inventive method allows processing for table salt and such feedstock, in which, among a large number of impurities, a significant part of them is contained in a soluble form. This excludes the transition of these impurities into a solid crystalline phase, which can be separated from the solution and removed from the process. In this case, if part of the mother liquor is processed at a separate stage of evaporation, the released salt will be contaminated beyond the permissible limits with precisely those impurities that are in a soluble form. In the claimed technical solution, it is proposed to separate a part of the stripped off solution from the suspension stripped off at a separate stage of evaporation and remove it from the process. Evaporation of part of the mother liquor, which contains a large amount of soluble impurities, leads to the fact that almost all the salt contained in it is released from the solution in the form of crystals, and only these impurities are in the dissolved form. This fact is explained by the mutual nature of solubility in a system containing table salt and soluble calcium and magnesium salts, which make up the bulk of soluble impurities. Separation from the one stripped off suspension of part of the stripped off solution, in which there are soluble impurities, makes it possible in this way to remove them from the process and obtain table salt of satisfactory quality at a separate stage of evaporation. At the same time, the mother liquor is evaporated so that in the solution withdrawn from the process the total concentration of calcium and magnesium salts would be 30-35%. This concentration of these salts makes it possible to almost completely salt out the salt from the solution and does not lead to significant contamination of the crystalline salt with soluble impurities. At the same time, the noted concentration of salts makes it possible to use the output solution for further industrial applications. One of the ways to use this solution is to obtain from it dissolved salts in solid form. Another way to use this solution may be to use it as a barrier fluid used to displace oil from wells during oil production. The only condition in this case is the condition that the density of this solution exceeds 1300 kg/m 3 . This requirement fully ensured by the fact that the concentration of salts in the solution must exceed 30%. In quantitative terms, the part of the stripped off solution separated from the suspension and removed from the process is 0.05-0.5 kg per 1 kg of emitted candles. The specified ratio range is determined by the concentration of soluble impurities in the feedstock. Moreover, if less than 0.05 kg of stripped off solution per 1 kg of salts is removed from the process, the concentration of salts in the solution will significantly exceed 35%, which, firstly, will lead to salt contamination, and secondly, will cause an increase in the temperature depression of the evaporated solution and , as a consequence of this, an increase in the surface of the evaporator equipment, i.e. increase in capital costs. If, however, more than 0.5 kg of solution is removed per 1 kg of salts, then the concentration of salts in the solution will not reach 30%, the density of the solution will be less than 1300 kg / m 3, it will contain a lot of sodium chloride and it will be difficult to find an industrial application of this solution, which will cause it to be reset. Therefore, the optimal value of the amount of stripped off solution removed per 1 kg of salt released is a value in the range of 0.05-0.5 kg. Thus, soluble impurities will be removed from the process in the form of a solution suitable for further industrial use, and table salt obtained at a separate stage of evaporation will be of satisfactory commercial quality. The claimed method for producing table salt meets the criterion of "industrial applicability", since no elements of the proposed technical solution contradict its technical reproducibility and application in industry. The proposed method is illustrated by the diagram shown in the figure. Rock salt contaminated with impurities (1) is dissolved with water or condensate from the evaporator (2). The resulting crude brine (3) is sent to evaporation (4). Evaporation of the crude brine is carried out until a suspension containing 30-40% crystalline salt (5) is obtained. One stripped off suspension is diluted with a hydrocyclone drain solution (11) to a concentration of crystalline salt of 10-20% (6). The diluted suspension (7) is classified on a hydrocyclone (8). The hydrocyclone drain solution (9) is divided into three parts (10), one of which, equal to 50-90% of the total solution flow, is sent to dilute the one stripped off suspension (11). The other part of the hydrocyclone drain solution, equal to 7-25% of the total flow, is directed to evaporation (12). The compacted suspension of the hydrocyclone (13) is washed with the original crude brine (14) and thickened (15), and the clarified solution (16) is returned to evaporation. The thickened suspension of the washed salt (17) is subjected to a second washing (18), for which the mother liquor (19) is used after separating the solid phase of crystalline impurities from the overflow solution of the hydrocyclone. The suspension of the washed salt (20) is fed to centrifugation (21) with centrifuge return (22) to evaporation. The wet salt (23) separated from the solution is fed to the dryer (24), after which the finished product is edible table salt (25) of high quality. From the third, remaining part of the drain solution of the hydrocyclone (26) separate the solid phase (27). The separated crystalline impurities (28) are removed from the process. At the same time, they can be processed into building gypsum. The mother liquor (29) obtained after separation of impurities is divided into two parts (30). One part of the mother liquor (19) is fed to the second salt washing, and the other (31), equal to 30-90% of the total flow (according to paragraph 2 of the claims) is sent for evaporation at a separate stage (32) until all salts are completely isolated from the solution From the one stripped off suspension (33) (according to paragraph 3 of the claims), a part of the stripped off solution (34) is separated, amounting to 0.05-0.5 kg per 1 kg of salts released, and removed from the process in the form of a solution of soluble impurities (35). From the one stripped off suspension (36), the salts separated from the solution (37) are separated with the return of the stripped solution (38) to evaporation. The wet salt (39) separated from the solution is fed to a dryer (40), after which a by-product table salt (41) of a lower quality than the basic salt is obtained. Examples of the invention. Example 1. The crude brine containing 305 g/l NaCl, 3.6 g/l CaSO 4 , 0.08 g/l MgCl 2 and 0.06 g/l KCl was obtained by underground dissolution of rock salt from the Shedok deposit in the Krasnodar region. When processing 1000 kg/h of raw brine, 500 kg/h is fed to the evaporator plant (the remaining 500 kg/h of the original raw brine is fed to washing the hydrocyclone slurry). Before evaporation of the initial crude brine, it is mixed with a hydrocyclone drain solution, a clarified solution from thickening and washing the one stripped off suspension, centrifuge centrifuge after separation of common salt from the solution and washing with a solution after washing the gypsum with water. As a result, 1460 kg/h of the solution is fed to the evaporation. In the evaporation plant, 727 kg/h of water is evaporated from the solution and 733 kg/h of stripped off suspension is obtained, which contains 36% of crystalline salt. The temperature of the stripped off solution 48-50 o C, it contains 26% common salt, 0.5% calcium sulfate, 1.3% magnesium chloride and 1% calcium chloride. In this case, the degree of concentration of the solution by impurities is 195. The consumption of heating steam for the evaporator plant is 230 kg/h. The one stripped off suspension is diluted with a hydrocyclone overflow solution to a crystalline salt concentration of 18% and classified in a hydrocyclone. After classification in a hydrocyclone, 1032 kg/h of overflow solution is obtained. The hydrocyclone drain solution is divided into three parts. The first part in the amount of 725 kg/h, i.e. about 70% of the total amount of this solution is used to dilute the evaporated suspension before classification. The second part of the overflow solution of the hydrocyclone is fed to evaporation, equal to 207 kg/h, i.e. about 20% of the total. The suspension compacted in the hydrocyclone in the amount of 421 kg/h is fed into the settling tank-thickener. In this apparatus, the salt crystals are thickened and washed with the initial crude brine, the amount of which is 500 kg/h. The clarified solution from the settler-thickener in the amount of 416 kg/h is fed to evaporation, and the thickened suspension is fed to a centrifuge to separate common salt from the solution. During centrifugation, a second washing of the salt is carried out, for which the mother liquor is used after the gypsum has been separated from it. The centrifuge centrifuge in the amount of 338 kg/h is returned for evaporation, and the peeled table salt is fed for drying. After drying, 252 kg/h of table salt is obtained, which contains 0.004% Ca ion, 0.009% SO 4 ion, 0.005% Mg ion and 0.007% K ion. In terms of its composition, the resulting salt meets the requirements of GOST 13830-91 "Edible table salt" for edible table salt of the highest grade "Extra", because the content of impurities does not exceed the limits allowed by the standard (components for Ca-ion 0.02% for SO 4-ion 0.16% for Mg-ion 0.01% and for K-ion 0.02%). From the remaining, the third part of the drain solution of the hydrocyclone, equal to 100 kg/h separate the solid phase of crystalline gypsum. To do this, gypsum crystals are precipitated in a special sump, after which the suspension with gypsum crystals is subjected to filtration. As a result of settling and filtering gypsum, 94 kg/h of mother liquor is obtained, with which salt is washed in a centrifuge. During filtration, the gypsum precipitate is washed with water from salt in an amount of 2 kg/h. After washing, the resulting washing solution is fed to evaporation. Filtered from the solution and the washed precipitate of gypsum is removed from the process. After filtration, 4 kg/h of gypsum precipitate is obtained, which contains 90% CaSO 4 2H 2 O, i.e. in its composition, the gypsum removed from the process corresponds to GOST 4013-82 for grade II gypsum stone for the production of binders. The results of the implementation of the claimed method in obtaining table salt from the crude brine of the Shedok deposit (according to clause 1 of the claims) example 1, as well as in obtaining salt from the brine of the Gusev deposit (according to clause 2 of the claims) example 2 and the Avan deposit (according to clause 1) 3 claims) example 3 are given in the table. As can be seen from the table, the application of the proposed method in the production of table salt from raw materials from various deposits makes it possible to produce edible table salt of the highest quality grade "Extra" according to GOST 13830-91, thereby increasing its quality compared to the prototype. Moreover, the share of high-quality salt of the "Extra" variety, depending on the degree of contamination of the feedstock, ranges from 90 to 100%. At the same time, discharges of industrial wastes of solid impurities and sodium chloride solution are excluded. Instead of dumping waste, as happens in the prototype, the proposed method allows them to be completely recycled, releasing gypsum suitable for the production of binders, as well as lower quality table salt. Thus, the degree of use of raw materials increases to almost 100% compared with the prototype. In addition, when processing raw materials especially contaminated with soluble impurities, the claimed method makes it possible to remove from the process a solution containing a high concentration of soluble impurities suitable for further industrial use. The technical and economic advantages of the proposed method for producing table salt in comparison with the prototype are as follows. 1. The method allows to improve the quality of produced table salt, obtaining 90-100% food table salt of the "Extra" grade according to GOST 13830-91, which satisfies all the requirements of the standard in terms of the content of impurities. 2. The application of the claimed method leads to the prevention of industrial waste discharges of solid impurities and sodium chloride solution, polluting the environment and worsening the ecological situation in the area of salt production. 3. The claimed method makes it possible to withdraw from the process of obtaining sodium chloride and utilize the impurities present in the feedstock. These contaminants that contaminate table salt are removed as by-products, ready for further industrial use. 4. Due to the application of the claimed method, the degree of use of the feedstock increases to almost 100%, while in the prototype only 85-90% of the raw materials are used. At the same time, depending on the degree of contamination of the feedstock, from 90 to 100% of the resulting salt meets the quality requirements for the highest quality edible table salt of the Extra grade according to GOST 13830-91. The rest of the salt is either food salt of a lower grade or industrial salt. Thus, obtaining table salt according to the claimed method leads to an increase in the quality of produced table salt, the prevention of industrial waste discharges with their disposal in the form of by-products, and an increase in the degree of use of raw materials.

The raw brine from the brine field continuously enters the raw brine tank pos. E18 with a capacity of 2000 m3. From the tank by centrifugal pumps type X 200-150-400 pos. H29 is supplied for heating to a group of heat exchangers. In the heat exchangers pos. T4 brine is heated up to 40ºC due to the heat of the condensate from the secondary steam of the evaporators.

After passing the heating unit, the brine enters the central part of the sump damper pos. X10, where it is mixed with a soda-caustic reagent and a working solution of PAAG. The settling tank piping scheme provides for their operation in autonomous and sequential mode. Soda-caustic reagent is supplied in the amount of 0h8 m3/hour.

After mixing the crude brine and the soda-caustic reagent, sparingly soluble compounds are formed: calcium carbonate CaCO3 and magnesium hydroxide Mg(OH)2. The solubility of calcium carbonate decreases with increasing temperature, and therefore, to reduce the residual content of calcium ions, it is recommended to clean the brine at a temperature of 30-40ºC. In addition, as the temperature rises, larger and well-settling calcium carbonate crystals are formed, which is very important for the subsequent settling of the brine.

Purified brine must contain:

CaI+ ions not more than 0.05 g/dmi;

MgI+ ions not more than 0.04 g/dmі;

excess CO3ІЇ not more than 0.15 g/dm³;

excess OH is not more than 0.1 g/dmi.

In the sump, CaCO3 and Mg(OH)2 are formed and the brine is clarified from these sediments. Settling tanks are single-tiered with a central rake drive and a central inlet of the liquid to be settled.

Through a drain funnel installed in the upper peripheral part of the drain trough of the sump (in sequential mode of operation), the clarified brine flows by gravity into the tanks of the purified brine pos. E20 with a capacity of 2000 m3 each.

To intensify the sludge process of the treated brine, PAAG is used with a working concentration of 0.001-0.1%, which is fed into the settling tanks thickeners by pumps pos. H30. The sludge from the sedimentation tanks, thickening, continuously descends into the sludge collector pos. E19. Sludge from the collections, partially diluted with water 1:10 to a solid phase concentration of up to 18%, goes to the sludge storage.

Brine purified from calcium and magnesium salts in an amount of up to 240 m3 from tanks by centrifugal pumps of the X280 / 29T type pos. H32 is supplied to the evaporation section and in the amount of 25-100m3 per shift to the reagent section for the preparation of reagents.

Three evaporators are installed in the evaporator section, including one standby one.

The initial purified brine in the amount of up to 240 m³/hour (based on two working evaporators) with a temperature of 18-35ºC from the tanks with pumps of the X 280/29-T type, pos. H32 is fed into the feed tanks pos. E21 with a capacity of 100 m3 each, part of the purified brine in the amount of 25-40 m3/hour is sent to the centrifugation department for salt washing in brandes thickeners and centrifuges.

The recirculating mother brine is also supplied to the feed tanks in the form of a part of the drain from the Brandes thickeners and centrifuge centrifuge.

The mixture of the initial purified brine with the recirculating mother brine necessary to remove the solid phase from the installation called the feed brine is fed respectively to each evaporator unit pos. K6 in parallel to all evaporators.

Before being fed into the evaporator, the feed brine is heated in a shell-and-tube heat exchanger pos. T5 with a heat exchange surface of 75 m².

The heating of the feed brine before it is fed into the 1 evaporator of the evaporator plant is carried out by the condensate of the heating steam of the 1st building and the secondary steam of the 2nd-4th buildings. The brine moves through the pipe space, the condensate from the heating chambers - through the annulus. The main flow of the feed brine is fed into the irrigation rings located in the upper part of the separators of the evaporators, a small part of this brine in the amount of 2-4 m3/hour is fed into each of the surge tanks to prevent the deposition of common salt on them.

During evaporation in the apparatuses, salt crystallization occurs, while the flow rate of the feed brine in each apparatus is set in such a way (24-32 m3 / h) that mass fraction the solid phase in one stripped off suspension (pulp) of each evaporator was equal to 30-40%. At a mass fraction below 30%, the cost of heating steam for obtaining salt increases and salt deposits form on the walls of the evaporator separator, which leads to a reduction in the interwash period of the evaporator. With a mass fraction above 40%, the heat transfer in the evaporators deteriorates and the productivity of the evaporator decreases, in addition, the size of salt crystals decreases.

The evaporated pulp flows from body to body by gravity through the overflow tank. This is facilitated by a consistent decrease in pressure across the housings. The decrease in pressure leads to partial self-evaporation of the solution in subsequent vessels and additional release of secondary vapor in them.

From the fourth (last) evaporator production saline pulp containing 30-40% of the mass. crystalline table salt, in the amount of 60-90 m³ / hour with a pump type GrT 160/31.5 pos. H31 is pumped to the centrifugation department in thickeners of the "Brandes" type pos. X11.

The pressure in the heating chamber of the first evaporator is maintained in the range of 0.15-0.22 MPa. Steam consumption per evaporator unit is up to 30 t/h.

The secondary steam from the first evaporator enters the heating chamber of the second evaporator, the pressure in which should not exceed 0.7 MPa. Subsequent evaporators are heated by the secondary steam of the previous evaporator. From the fourth evaporator, the secondary steam enters a barometric condenser with a diameter of 2.0 m.

The condensate of the heating steam of the first evaporator is cooled in heat exchangers, then pumped out to the boiler room.

Secondary steam condensate from the heating chamber of the second evaporator enters the heating chamber of the third evaporator, and then from it to the heating chamber of the fourth evaporator, from where it is supplied to other production needs.

For the utilization of vapors and non-condensed gases in barometric condensers, recycled water with a temperature not exceeding 28ºC is used. Heated water from barometric condensers enters tanks - water seals with a capacity of 10 m³ each with a temperature not exceeding 50ºC and is then fed to fan cooling towers. Chilled water is collected in a cold water receiver and fed to vapor recovery in barometric condensers.

Non-condensable gases from the heating chamber of the first evaporator are discharged into the heating steam pipeline of the second evaporator. From the heating chamber of the second evaporator, non-condensable gases are discharged to the heating steam pipeline of the third evaporator, from the third heating chamber to the heating steam pipeline of the fourth evaporator, and from the fourth heating chamber to the barometric condenser. The outlet is made through the central pipe located in the annulus of the heating chamber.

Thickening of the salt pulp from 30-40% to 40-60% of the mass. on the solid phase is carried out in thickeners of the "Brandes" type, and the separation of the solid phase - on the filtering horizontal centrifuges of the type S FGP 1201T-01 pos. C23 with pulsating sludge discharge. Washing of salt from the mother brine is carried out with purified brine in thickeners of the "Brandes" type. The consumption of purified brine for washing is 25-35 m 3 /hour. Washed and centrifuged salt with a moisture content of 2-3% of the mass. goes to conveyor belts. Wet salt on the conveyor is treated with a solution of potassium ferrocyanide (PCC) as an anti-caking agent.

The FCC solution is prepared in a tank, where a sample of crystalline potassium ferrocyanide, condensate and compressed air are supplied to mix and dissolve the FCC. From the tank, the FCC solution flows by gravity through the pipeline through the nozzles to the wet salt conveyor pos. Fri 24. Passing through the conveyor, the salt is partially mixed and fed to the dryer.

The flow rate of the FCC solution is controlled automatically, depending on the amount of salt entering the conveyor. Salt consumption is determined using scales (indicator scales) on the conveyor.

Wet table salt with a content of 2.5 ± 0.5% of the mass. Н2О and a temperature of 40 ± 5ºС are distributed by conveyors to bunkers pos. x12. From the bunker, table salt is fed by a feeder and a mechanical caster into the "fluidized bed" apparatus pos. T3, where salt is dried with hot air. Air is supplied to the apparatus by a pipe blower after preheating in the air heater pos T1.

The air is supplied to the air heater in the amount of 11000 ± 2000 nm/h for one drying unit at a pressure of 4000 ± 500 Pa.

In the air heater, the air is heated by flue gases from the combustion of natural gas in burners of the GMG type - 2 M furnaces pos. T 2. When the gas is turned off, high-sulphur fuel oil grade M-100 can be used as fuel. Before combustion, fuel oil is heated by steam at a pressure of 0.6 MPa to 120°C. Air for burning fuel oil, gas (for the burner), for cooling the vaults of the furnace afterburning is supplied by a fan of the VDN type - 11.2 pos. B 33-34 under a pressure of 2000 ± 500 Pa. In this case, the air flow rate for the burners is 5000 ± 1000 nmi/h, and for blowing the vaults and afterburning - 1600 ± 200 nmi/h.

Combustion of natural gas or fuel oil in the furnace occurs at a discharge of 50 ± 20 Pa and temperatures up to 1300ºC. The specified vacuum is maintained by a smoke exhauster pos. B36.

A decrease in vacuum can lead to the release of hot flue gases into the room, an increase in vacuum leads to an increased suction of cold air into the furnace, which can lead to a breakdown of the torch.

Furnace (flue) gases in the mixing chamber of the furnace pos. T2 are mixed with exhaust (after the air heater) return flue gases having a temperature of 180 ± 10ºC. As a result of mixing, the temperature of the flue gases decreases to 550 ± 50ºС, with this temperature they enter the pipe space of the air heater to heat the drying agent, where they are cooled from 550 ± 50ºС to 180 ± 10ºС, and injected into the packed adsorber pos. K8, where gases are cleaned from sulfur-containing compounds, after which the latter are smoked with a DN-12.5 smoke exhauster N = 75 kW, n = 1500 rpm with a capacity of 37000 m3 / h pos. X13 are emitted into the atmosphere through a common gas duct and two chimneys with a diameter of 600 mm. The height of the first chimney is 45 m, the height of the second chimney is 31.185 m. Reducing the temperature of flue gases below 170ºС leads to the formation of acid corrosion of gas pipelines and chimneys, and an increase in temperature above 200ºС leads to failure of the smoke exhauster. Part of the cooled flue gases is supplied by the same smoke exhauster to the mixing chamber of the furnace to maintain their temperature in front of the air heater in the range of 550 ± 50ºС.

Adsorber pos. K8 is irrigated with soda. The resulting wastewater are sent to the collection of industrial waste pos. E16, from where they are thrown into the sewer.

Dried table salt from the apparatus "KS" through the overflow chute enters the apparatus "KS" for cooling. Air for cooling is supplied to the apparatus by a fan. Cooled table salt is unloaded onto the conveyor pos. PT27, from where it is fed to vertical elevators of the TsG type - 400 pos. PT28 and further to electromagnetic vibrating screens for separating the pellet formed during drying.

Large salt particles (more than 1.2 mm) and lumps that have not passed through the holes in the sieve fabric of vibrating screens pos. E22, descend from it and by gravity in the amount of 320 ± 50 kg / h enter a vertical mixer with a capacity of 10 m і to dissolve the okata pos. E14.

The solution formed in the amount of 3-6 m і 5-10% is pumped out by pumps of the type AX 45/54 into the collection of industrial waste pos. E15.

Magnetic traps are installed on conveyors at the site for pouring salt from vibrating screens onto conveyors. Installation is made in 2 tiers: upper -3 magnets, lower -4 magnets. The main flow of salt with particle sizes less than 1.2 mm is fed to inclined belt conveyors KLS - 800 pos. PT26 supplying salt to the salt packing and packing shop.

The dusty air leaving the apparatus "KS" enters the gas cleaning system. Cleaning is carried out in two stages: preliminary cleaning from the largest particles is carried out in cyclones pos. K7 and cleaning from fine dust particles in the bag filter pos. F9.

The spent drying agent with =70±10ºС and dust content of 12-50 g/nm³ under a discharge of 200±50 Pa is fed into a battery cyclone for cleaning. The air purified in the battery cyclone to a concentration of 12-17g/nm³ t=68±8ºС in the amount of (16±4)x10³nm³/hour under a discharge of 1500±500Pa is sucked in by the fan pos. B35 and is fed under a pressure of 4500 ± 500 Pa for cleaning into a bag filter.

Salt dust is removed from the battery cyclones with the help of chutes equipped with flashing lights (sluice gates) and fed into the container pos. E17, where recycled water enters. The resulting saline water is directed to a pit located in the brine field. The fine dust trapped in the bag filter is fed to belt conveyor pos. PT25, from where it enters the washout tank.

The spent drying agent finally cleaned of the smallest particles of salt dust at a temperature of 110ºC is fed into the air heater pos. T1, where it is heated to a temperature of 300ºC and returned to the "KS" dryer.

The technological scheme for the production of sodium chloride is presented in Appendix C.

The formation of salt brines is possible with systematic irrigation with water and gradual erosion of underground chambers in the salt layer, or flooding of the chambers. In this case, the resulting concentrated brine is pumped out.

A more advanced method of leaching through boreholes is also used. This method consists in the fact that a pipe of a smaller diameter (75—100 mm) is inserted into a well fixed with a string of steel casing pipes with a diameter of 150–250 mm. Water is pumped into the salt bed through one of these pipes using a high-pressure centrifugal pump (20–25 atm). It dissolves salt and in the form of brine is squeezed out to the surface through another pipe. There are two modes of operation of wells - countercurrent, when water is supplied through the outer pipe, and the brine rises to the surface through the inner one (Figure 1 a), and direct-flow, when water is supplied through the inner pipe, and the brine is squeezed out through the outer pipe. The depth of the wells and the pressure under which water is supplied to it depend on the depth of the salt reservoir or underground source of brine. The productivity of such a well is about 10–25 m3 of brine per hour. (Sometimes water is fed into the well by gravity; in this case, the brine, which has a high density, cannot reach the surface due to the pressure of the water column, and it is pumped out by a deep pump lowered into the well to a level determined by the density difference between the brine and water.)

The chamber formed in the salt layer when it is washed away by water through a borehole gradually acquires a shape close to the shape of an overturned cone, since as a result of natural convection, the side surface, and especially the ceiling of the chamber, dissolves faster than the bottom covered with saturated brine and mechanical sludge. impurities. Therefore, the side surface becomes progressively flatter and then covered with a layer of waste rock preventing further leaching. The intensity of brine formation decreases, and the operation of the well has to be stopped when the generatrix of the cone reaches an angle of 30–40°. As a result, the reserves of the deposit with this method of exploitation are used no more than 5-15%.

Scheme of leaching of a salt reservoir through a drilling brine well
(a - countercurrent, b - hydraulic cut)

Source: Pozin M.E. "Technology of mineral salts"

The operation of wells can also be carried out by a combined countercurrent-direct-flow method. The main stage here is forward flow, when the salt layer is “washed out” with the formation of a large amount of brine; at a shorter stage of countercurrent operation, the well is “flushed” with the removal of most of the insoluble particles from it. The duration of the cycle of alternating the direction of flows inside the well is, for example, 2 hours with the ratio of the duration of the “washout” and “flushing” modes ranging from 7: 1 to 3: 1.

More perfect is the operation of wells with a hydraulic cut (Fig. 1 b). In this case, air or oil is injected into the well along with water. First maintain the water level at a constant height of 1-1.5 m from the face. In this case, the dissolution occurs only along the circumference of the chamber, while the ceiling is protected “from the action of water by a thin layer of“ non-solvent ”- air or oil. A cut is formed - an approximately flat cylindrical chamber 1-1.5 m high and 100 m or more in diameter. (It is more likely that during the leaching of the hydraulic cut, the shape of the resulting cavity in the salt deposit corresponds to the shape of a hyperboloid of revolution.) After that, air or oil is squeezed onto the day surface, raising the level of the brine, and the ceiling of the chamber is intensively dissolved. Deposition of waste rock on the dissolving surface is excluded, and the use of the deposit reserves increases.

The most progressive is stepwise leaching, especially for the development of salt reservoirs containing many insoluble inclusions. In this case, first, erosion is carried out not in the form of a cut, i.e., a flat slot, but in the form of a cone with its apex down. Then, periodically increasing the level of water supply and changing the level of brine withdrawal, a stepwise dissolution of salt is carried out, so that the leaching chamber takes a shape close to a cylinder, with a base in the form of a funnel and a vaulted roof. Insoluble inclusions accumulate in the lower part of the chamber. The degree of use of the salt reservoir increases dramatically.

The salt layer is fed with water to wash it out and the brine is pumped out through different wells - water is supplied through one, brine is pumped out through the others. With such a group system of well operation, the salt recovery factor especially increases with sequential development of reserves by dip and with the use of failed funnels formed as a result of leaching. This reduces the number of water intake wells and significantly increases the amount of water supplied.

The voids formed during underground leaching can be the cause of the collapse of the roof of the chambers - the subsidence and collapse of post-salt rocks. Therefore, the salt extraction method can be used only if the cover layers are sufficiently strong.

After the extraction of salt by underground leaching in specially equipped shops, the brines are cleaned from calcium and magnesium salts in a special tank. In this way, the best edible salt "Extra" is produced. In salt refineries, it is called the vacuum process. In a simplified representation, it looks like this: Fresh water is pumped through wells into the salt column lying underground. The salt dissolves in it, and the brine is already pumped up by the pumps. It is first cleaned, and then sent to the chambers, where a reduced pressure is created - a vacuum. At a pressure less than atmospheric, the brine begins to boil at lower temperatures than usual and actively evaporates. Salt crystals precipitate. They are separated from the liquid by a centrifuge. Manufacturers receive very finely ground salt. With special sprayers, if necessary, iodine component and anti-caking components are added to it.

Extra white salt color; shades of grayish, yellowish, etc. are allowed for other varieties. The maximum content of Na2SO4 in terms of dry matter for the extra variety is 0.2%, for other varieties 0.5%.

The process of producing vacuum salt implies highly efficient equipment and the optimality of the technological process at all its stages. This technology reduces production costs and improves the environmental safety of production.

Salt production is a very good business idea. Salt is always a tradable and rather liquid commodity, which practically does not deteriorate, has a constant demand and an infinite shelf life. All these qualities indicate that salt is an ideal commodity, and salt processing and its subsequent sale is a good and cost-effective idea to start your business.

But the production process directly depends on the type of salt itself.
One of the healthiest is sea salt. It contains various very useful minerals. Sea salt is obtained by evaporating sea water, because it contains a huge list of salts with various additives.

If doing salt production, then in this case it is necessary to carefully consider business plan .

In order to obtain table salt, halite, or rock salt, is needed. Basically, first they develop halite deposits, and then, after a whole specific processing process, table salt is obtained from the mined rock salt. But besides this method, the evaporation of salt from salt water is also practiced. It can be both sea water and water of saline reservoirs - lakes or ponds. However, this alternative method becomes profitable only in cases of a large number of the above reservoirs.

Halite is the mineral from which table salt is made. It, like any mineral, contains foreign inclusions in the form of sand, earth or some metal parts. For this reason, as soon as raw salt enters the plant, it first goes through several stages of purification. First, it is washed twice with various types of devices, then it goes through the crushing stage, and at the end it is washed twice again. At the same time, the magnetic separator screens out metal impurities that may be in the halite. After the salt has passed the stage of purification from impurities, it is dried using a special centrifuge.

In order to obtain large iodized salt, the resulting semi-finished product is sent to the unit for adding iodine, and then to vibration drying. If coarse salt should not be iodized, then the step of adding iodine is skipped, and the salt directly enters the vibration dryer. In the event that fine table salt is needed, then after the semi-finished product has passed the stage of adding iodine and vibration drying, it is sent to the crusher. If the fine salt is not to be iodized, then this processing step is excluded from the production process.

After the process of adding iodine and crushing, the salt is dried. This happens with the help of hot air, which is blown into the furnace by an industrial fan. Also, at this stage, you can add other excipients. These may be some food additives that resist caking of table salt, iodides, carbonates, fluorides. Fluoride supplementation is useful for preventing dental disease. At the same time, the total amount of food additives in salt should not exceed 2-3% (as a percentage).

After all auxiliary substances are added to the salt, it is completely ready for packaging.

Video - how sea salt is mined and produced:

Productivity 1 t/h. Salt (sodium chloride) is an important element that ensures the vital activity of man and the animal world. Salt production, since ancient times, was considered a profitable and noble business.
We offer you to choose a complete set of the salt production plant that best meets your requirements.
We have three plant configurations: Econom, Standard and Full.
Distinctive features of the Econom configuration is the maximum use of natural environment conditions. This plant has low energy consumption. Technological process susceptible to changes in environmental conditions. Reacts negatively to changes or deterioration in the chemical composition of salt, incl. insoluble impurities. Manufactured products are of variable quality and high level manual labor. Requires constant quality control. The production cycle finished product is 7-14 days.
The Standard package is the best offer for manufacturers working on raw materials with high characteristics of the feedstock. In this configuration, the method of double cleaning of raw materials is used, which makes it possible to produce high quality products. The line is semi-automatic. Has a low rate of manual labor. The production cycle is 4-6 hours. Let out production corresponds to GOST, and also allows to trade with large federal customers and to sell salt for Export to the countries of the former CIS.
The Full package has the highest automation ratio. Production of products is based on the method of deep processing of raw materials. This line is susceptible to severe pollution, which allows you to trade with the largest foreign customers. The production cycle is 4-6 hours. Production meets standards ISO quality. Finished products comply with GOST. This configuration allows you to trade with large federal customers and sell salt for export to the countries of the former CIS, as well as the countries of the Near and Far Abroad.

Plan-scheme of the Econom assembly plant

Plan-scheme of the plant of the Standard and Full configuration

Conclusion: in terms of return on investment, the Econom equipment line looks the most attractive. It has the smallest amount of initial investment, with the fastest return on investment. However, when choosing a configuration, it is also necessary to take into account the dependence of the production process on external factors.
Plants of the Standard and Full configuration are an order of magnitude more resistant to changes in external factors, and therefore have a more stable manufacturing process. This, in turn, makes it possible to achieve a constant high quality of products and, as a result, the possibility of trading with large customers.
The client needs to independently assess the market in which he is going to work and who he is potential client. Further, based on this, choose the most complete package that suits you.

Salt production. Salt

Read also

Where to find a job with a good salary: top high-paying jobs in Belarus Job ads in Belarus

Work and employment in the UK

How to write a letter of recommendation

THE BELL