## the sporulation model for manganiferous ore dissolution - sciencedirect

This article develops a versatile structural model specifically suited to describe the dissolution kinetics in leaching processes involving nonporous ore particles. The model accounts explicitly for intraparticle heterogeneity by describing the interplay between the dissolution kinetics of the main solid reactant (e.g. metal oxide) and the dissolution/fragmentation of the solid matrix (gangue). The application to the dissolution of manganiferous ores is thoroughly addressed.

## simulation study on the mining conditions of dissolution of low grade solid potash ore in qarhan salt lake | scientific reports

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The output and grade of liquid potash minerals in Qarhan Salt Lake are decreasing year by year, which has become the main problem restricting the sustainable production of potassium fertilizer. The exploitation and utilization of low-grade solid potash ore, which is in the strata of the Qarhan Salt Lake, represents the fundamental framework for the sustainable development of Qarhan Salt Lakes potash fertilizer. PHREEQC is a simulation software for hydrogeochemistry. In this paper, PHREEQC was applied to simulate temperature, pH value and solvent chemical characteristics which affect the dissolution process of low-grade solid potash minerals. The simulation results indicate that the optimum temperature for ore dissolution is around 25C, because, around this temperature, the dissolving ability of solvents to low-grade solid potash minerals is enhanced, while the dissolving ability to halite remains basically unchanged, which is conducive to selective dissolution of low-grade solid potash. It is recommended the temperature is between 20 and 30. The simulation results show that, when the pH value of solvents is more than 9, although it is advantageous to selective dissolution of low-grade solid potash minerals, the solvent becomes strong alkali solution, which will cause environmental pollution and seriously corrode materials and equipment in actual production, so it is recommended the pH value of the solvent is adjusted between 6 and 8. The simulation results show that, when the values of K+, Na+, Mg2+, Ca2+, Cl and SO42 in the solvent are 0.1%, 2.9%, 3.77%, 0.05%, 15.72% and 0.13% respectively, the solubility of low-grade solid potash ores is stronger, which is more conducive to selective ore dissolution. It is suggested that in actual production, the chemical composition of solvents prepared with old brine and fresh water should be as close as possible to the above chemical composition characteristics.

Qarhan Salt Lake is the largest potash fertilizer production base in China with proven liquid potash mineral resources of 2.44108 tons and solid potash mineral resources of 2.96108 tons1. It is difficult to develop these solid potash minerals by traditional mining method of solid potash ore because of its scattered distribution, thin ore bed and low-grade. The solid potash minerals do not meet the formal and official requirements of industrial development, so are called low-grade solid potash ore (abbreviation LGSP ore, afterwards used often). For a long time, the main mining resource is liquid potash minerals in Qarhan Salt Lake. With the extension of mining time of liquid potash, the quantity and quality of iquid potash minerals decreased year by year, which became the main problem restricting the sustainable production of potash fertilizer2,3,4,5. As a results, the mining of LGSP ore through liquefaction becomes an important and feasible method to meet the sustainable production of potash fertilizer in Qarhan Salt Lake6.

Since 1990s, there have been some scholars or research institutes to study the development and utilization of LGSP ore. Qinghai Salt Lake Exploration and Development Institute7 studied the recoverable reserves of KCl in Qarhan Salt Lake and demonstrated the feasibility of LGSP ore dissolved by dilute brine. They mainly studied the relationship between time and dissolution rate of LGSP ore. Sun Dapeng and others8 proved that low-grade solid carnallite dissolved in the first mining area of Qarhan Salt Lake due to the continuous supply of low concentration brine in the periphery. Hao Aibing9 carried out a series of laboratory experiments on LGSP ore dissolution, and pointed out the importance of the concentration and composition of the solvent to the dissolution process, but he mainly used the NaCl solvent. Li Wenpeng and others10,11 carried out a numerical simulation study on the LGSP to simulate the dissolution process, and obtained the conclusion that the ion curve in the dissolution driving process is wave like. An Lianying et al.12 mainly studied the conversion rate and conversion speed were affected by the difference of potassium concentration in solid and liquid potash ore. Wang Wenxiang et al.13,14 studied and discussed the change of hydrodynamic field and hydrochemical field in the process of the solidliquid transformation of LGSP ore. In 2006, the Institute of Mineral Resources, Chinese Academy of Geological Sciences and QingHai Salt Lake Industry Co., Ltd., undertook the National High Technology Research and Development Program of China (863 Program), namely, Key Technologies for Liquefaction and Exploitation of LGSP Minerals in Qaidam Basin, taking the hard to mine LGSP ore in Qarhan Salt Lake as the research object, the LGSP ore mining technology was studied; the main research achievements include finding out the new combination characteristics and distribution rules of potash minerals in the potassium-bearing strata, and modifying the LGSP ore dissolving driving model15. Liu Dongqu and others16 simulated the dissolving effect of Mg2+ based solvent of the LGSP ore in Qarhan Salt Lake. Wang Xingfu and others17 pointed out that the dissolution conversion rate of LGSP ore increased with the increase of LGSPs grade. Li Xinmeng and others18 studied the relationship between the particle size and potassium content of LGSP minerals, and the results showed that the particle size of LGSP minerals decreases gradually, the content of potassium in minerals decreases. Wang Luohai et al.19 discussed the impact of solid to liquid technology of LGSP on resources and environment, indicating that solid to liquid technology has greatly increased the recoverable reserves of potassium resources, extended the service life of Qarhan Salt Lake, improved the utilization rate of Salt Lake resources, and realized the green development of Salt Lake resources. To sum up, although predecessors have made some important understandings and drawn some important conclusions, due to the complexity of hydrological and physicochemical conditions in the process of solidliquid transformation, and Salt Lakes are always dynamic change, the dissolved mechanism of LGSP ore is still not completely clear.

The dissolution process of LGSP ore in Qarhan Salt Lake is a physical and chemical reaction process of solvent and potash minerals. This process is affected by many factors such as temperature, pH, characteristics of solvent chemical components, solvent flow rate, salt layer structure and porosity. Until now, the factors of temperature and pH value on LGSP ores dissolution have not been studied and discussed and the most suitable solvent composition has not been found. In the past, researchers usually used traditional experimental methods to study the LGSP dissolution process, however, it is very complicated to study these variables by traditional experimental methods, which requires a lot of manpower, material and financial resources. The hydrogeochemical simulation technology developed on the basis of thermodynamics provides an effective and easy method and way for the study of such problems. Under the reliable parameters, some tedious experimental work can be simulated by computer in a short time20,21. A series of equations of Pitzer theory are used in part of hydrogeochemistry computer simulation software, which can describe the activity, ionic strength, dissolution equilibrium of different phase substance and charge balance of solution in high-salinity waters or brine. PHREEQC is one of the hydrogeochemical simulation software22. In this paper, we carried out the method of computer simulation (PHREEQC) and laboratory experiment to explore the influence of temperature, pH value and suitable solvent composition on the dissolution of LGSP minerals, which provides scientific basis for reasonable solution mining scheme.

PHREEQC, which evolved from the Fortran program PHREEQE, is a hydrogeochemical software developed by the U. S. Geological Survey22,23. PHREEQC version 3, which is the latest version, is written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC uses the following several aqueous solution models: The Lawrence Livermore National Laboratory model and WATEQ4F which are belong to two ion-association aqueous models, the Pitzer model and the SIT aqueous model. By using any of these aqueous models, PHREEQC can solve almost all equilibrium thermodynamics and chemical kinetics problems in the interaction system of water, gas, rock and soil, including water solute coordination, adsorptiondesorption, ion exchange, surface coordination, dissolutionprecipitation and oxidationreduction24. In addition, because of the application of Pitzer model, PHREEQC can simulate the high concentration electrolyte. PHREEQC can be carried out speciation and saturation-index calculations, one-dimensional transport calculations and batch-reaction, inverse modeling and so on24.

For multi solute electrolyte solutions, PHREEQC uses a series of equations to describe the activity of water, ionic strength, dissolution equilibrium of different phases, solution charge balance, element composition balance, mass conservation of adsorbent surface and so on. According to the users input command, PHREEQC will select some of the equations to describe the corresponding chemical reaction process. For example, the improved NewtonRaphson method is used for iterative solution; the RungeKutta method is used for PHREEQC to simulate the dynamic reaction process by integrating the reaction speed in time; for the one-dimensional convection dispersion process of multi-component chemical reaction, PHREEQC uses the split operation technique to calculate the chemical reaction terms count25.

Saturation indices (SI) is one of the most widely used indicators in hydrogeochemical research. It studies the saturation state of minerals in aqueous solutions. The SI of minerals in aqueous solution is defined as: SI=lgIAPlgKsp, where IAP is the activity product of related ions in mineral dissolution solution; Ksp is equilibrium constant of mineral dissolution reaction at a certain temperature. When SI=0, the mineral is in equilibrium in the aqueous solution; When SI<0, it means that the mineral is not saturated in the aqueous solution, and the mineral will be dissolved; when SI>0, it indicates that the mineral is in the supersaturated state in the aqueous solution, and the mineral will precipitate26.

First, using PHREEQC program simulates the most suitable temperature and pH value for the dissolution of LGSP minerals. Secondly, the simulation of solvent composition is carried out under the suitable temperature and pH value conditions. Finally, the laboratory experiment is set to verify the simulation results.

The possible mineral phases need to be determined before simulation. The most common salt minerals in Qarhan Salt Lake are halite, polyhalite, carnallite, gypsum and sylvite, and a small amount of calcite and dolomite are occasionally seen. The clastic minerals include quartz, mica, albite and chlorite13,14,27,28,29,30,31. The clastic minerals are insoluble minerals, calcite and dolomite are not common minerals, and the amount is very small. Therefore, the main mineral phases of Qarhan Salt Lake are gypsum, halite, polyhalite, carnallite and sylvite.

When simulating, only one factor is a variable and the others should be constant. First of all, the suitable temperature is simulated, so the pH and the solvent composition should be constant. After years of exploration, the solution mixed with old brine and Senie Lakes water is currently used as the solvent to dissolve LGSP ore6. The arithmetic mean values of K+, Na+, Mg2+, Ca2+, Cl, SO42 in the solvent were 0.23%, 1.60%, 3.69%, 0.05%, 15.23% and 0.13%, respectively6. The arithmetic mean value of pH is 6.5, and the arithmetic mean value of density is 1.184g/[email protected]@@6.

The precipitation and dissolution of minerals in water depend on their solubility to a large extent, and the solubility is greatly affected by temperature. Consequently, there should discuss the influence of temperature on the dissolving ability of solvents, and determine the most suitable dissolution temperature.

In the simulation, set pH=6.5, density=1.184g/cm3, pe=4 (default value), and select pitzer.dat database. The values of K+, Na+, Mg2+, Ca2+, Cl, SO42 are 0.23%, 1.60%, 3.69%, 0.05%, 15.23% and 0.13%, respectively.

The average temperature of Qarhan Salt Lake is about 25C in summer, the highest temperature in summer is 35.5C, the average temperature over the years is about 5.1C, the lowest temperature in winter is 29.7C, and the average temperature in winter is about 15C29. In addition, a maximum temperature of 40C is set for comparative study. Therefore, the simulated temperature is set to 29.7C, 15C, 5.1C, 25C, 35.5C and 40C respectively.

As shown in Fig.1, taking 25C as the demarcation point, when the temperature decreases from 25 to 29.7C, the SI of gypsum, carnallite and sylvite increases linearly with the decrease of temperature, which indicates that the dissolving ability of solvent to gypsum, carnallite and sylvite decreases with the decrease of temperature. When the temperature increases from 25 to 40C, the SI of gypsum, carnallite and sylvite decreases with the increase of temperature, but the decrease rate tends to be flat, which indicates that the solubility of gypsum, carnallite and sylvite increase with the increase of temperature, however, the increase is gradually to be weaker. The change for the SI curve of halite and polyhalite is relatively small, which indicates that the dissolving ability of solvent to halite and polyhalite is basically unchanged with the change of temperature. On the whole, the SI of polyhalite is the smallest, that is to say, the solvent has the strongest solubility to polyhalite. However, due to the formation of gypsum in the process of dissolution of polyhalite, in the case of no hydrodynamic or weak hydrodynamic condition, the polyhalite is easy to be wrapped by the formed gypsum, resulting in the stagnation of the dissolution of polyhalite32.

Above all, in the cold season with relatively low temperature, the solubility of solvent to carnallite and sylvite decreases, however, due to the weak effect of temperature on the dissolution ability of halite, the halite continues to dissolve in the cold season, which is not conducive to LGSP ore dissolution. However, some enterprises inject solvents into the field to dissolve LGSP minerals in winter. When the temperature is higher than 40C, although the dissolving capacity of the solvent to potash minerals increases, the increase is not very obvious, moreover, the higher the temperature is, the stronger the degree of evaporation will be, which is not conducive to ore dissolution. Consequently, the temperature that is around 25C is most suitable for LGSP dissolution. We recommend that the temperature range of LGSP dissolution is between 20 and 30C.

Qarhan Salt Lake is located in the Qinghai-Tibet Plateau, where the humid and hot air from South Asia is blocked by the Himalayas, so it cannot meet the cold air from Siberia, therefore, it cannot form precipitation conditions33. The climate in Qarhan Salt Lake belongs to the typical continental arid climate, which is windy and dry all the year round33. According to the meteorological data statistics collected by Qinghai Salt Lake Industry Co., the temperature of Qarhan Salt Lake from May to October is between 20 and 30C. In terms of actual production, selecting May to October with relatively high temperature is conducive to the dissolution of LGSP minerals.

During the pH simulation, it can be seen from the above simulation that the temperature has better to be set at 25C. The density is 1.184g/cm3, pe is 4 (default value), and select pitzer.dat database. The values of K+, Na+, Mg2+, Ca2+, Cl, SO42 are 0.23%, 1.60%, 3.69%, 0.05%, 15.23% and 0.13%, respectively. The initial pH of the solvent was 6.5. The pH values were adjusted by adding HCl or NaOH to 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 6.5, 7.0, 8.0, 9.0, 10.0, 11.0 and 12.0, respectively.

The only pH related reaction in the solvent is sulfate, the reaction form as follows: $${\mathrm{SO}}_{4}^{2-}+{\mathrm{H}}^{+}={\mathrm{HSO}}_{4}^{-}$$. When pH is about 2, the activities of $${\mathrm{SO}}_{4}^{2-}$$ and $${\mathrm{HSO}}_{4}^{-}$$ are similar. Only at a lower pH value, the pH of the solvent will affect the activity of sulfate and the mineral saturation index (SI). As shown in Fig.2, when the pH value of the solvent is gradually reduced from 6.5 to 1.0, the mineral saturation index (SI) of gypsum, halite, polyhalite, carnallite and sylvite is basically unchanged, which indicates that in the process of solvent acidification, the mineral dissolving capacity of the solvent to gypsum, halite, polyhalite, carnallite and sylvite is basically unchanged. When the pH value of solvent increases from 6.5 to 12, especially after pH > 10, the mineral saturation index (SI) of gypsum, polyhalite, carnallite and sylvite graduaaly decreases, and the mineral saturation index (SI) of halite increases, which indicates that in the process of solvent alkalization, especially when the solvent is strongly alkaline solution, the dissolving ability of solvent to gypsum, polyhalite, carnallite and sylvite is enhanced, and the dissolving ability of solvent to halite is weakened. Why do these phenomena appear? It is mainly caused by the following reasons: chloride or sulfate minerals containing calcium and magnesium will dissolve in strong alkaline solutions and precipitate in the form of portlandite (Ca(OH)2) and brucite (Mg(OH)2). Taking polyhalite (K2MgCa2(SO4)42H2O) as an example, the following reaction will occur in strong alkaline solution: K2MgCa2(SO4)42H2O+2NaOH=2CaSO4+Mg(OH)2+2K++2Na+ +2$${\mathrm{SO}}_{4}^{2-}$$ + 2H2O. Therefore, with eh increase of the alkalinity of the solvent, the dissolving ability of the solvent to LGSP ore will be enhanced. In addition, due to the increase of Na+ in the solution, the same ion effect leads to the increase of mineral saturation index of halite, thus the dissolving ability of the solvent to halite decrease. The mineral saturation index of other Na+bearing minerals will also increase, as shown in Fig.3.

It can be seen from the above when the pH value decreases from 6.5 to 1, the dissolving ability of the solvent to LGSP minerals remains basically unchanged. When the pH value increase from 6.5 to 12, especially from 9 to 12, when the solvent shows strong alkalinity, the dissolving ability for LGSP minerals is strengthened. Although the dissolving ability for LGSP minerals is enhanced, because the strong alkaline solution pollutes the environment and seriously corrodes materials and equipment in actual production, the strong alkaline solvent is not suitable for LGSP dissolution. Therefore, the pH value of solvent maintained around 6.5 is suitable for LGSP minerals dissolution. In terms of actual production, we recommend the pH value of solvent is adjusted between 6 and 8.

A suitable solvent is very important for the dissolving of LGSP ore. If the concentration of the solvent is too low or fresh water is used directly, a large amount of surrounding rock, mainly halite, will be dissolved, which will cause the collapse of salt bed. The collapse of salt bed will affect the permeability and porosity of the strata, and also form geological disasters and threaten the personal safety of field works. If the concentration of solvent is too high, salt minerals will be easy to crystallize and precipitate, which will block the pore passageway and affect the porosity, thus affecting the permeability of salt bed. The ideal solvent is to dissolve the LGSP ore selectively, but try not to dissolve other minerals such as halite. Therefore, it is very important to select a suitable solvent for the mining of LGSP ore.

Is the previous solvent (defined as the initial solvent) used in the dissolution of LGSP minerals in Qarhan Salt Lake the best suitable solvent? It can be used PHREEQC program to simulate whether the initial solvent is the most fitful. Based on the above simulation, set the temperature=25C, pH=6.5, pe=4 (default value), and select pitzer.dat database. Only change the chemical composition of the solvent to simulate. Through dozens of simulations with PHREEQC program, it was found that when the concentration of K+, Na+, Mg2+, Ca2+, Cl and SO42 of the solvent (defined as simulated solvent) are 0.1%, 2.9%, 3.77%, 0.05%, 15.72% and 0.13%, respectively (see Table 1), the solubility of LGSP minerals is stronger (see Table 2 for details).

It can be seen from Table 2 that the mineral saturation index (SI) of the simulated solvent for halite and gypsum increases, while the mineral saturation index (SI) for carnallite, polyhalite and sylvite decreases. Compared with the initial solvent, the dissolving ability of the simulated solvent to halite and gypsum is weakened, while to carnallite, polyhalite and sylvite is enhanced, which is conducive to LGSP dissolution. In addition, in the ore-bearing layer of Qarhan Salt Lake, potash minerals often occur between the pores of halite crystal particles in the form of disseminated4,34,35,36,37. The simulated solvent can dissolve a small amount of halite, which can release the potash minerals between the pores of halite crystal particles into the solution. Because it does not cause a large amount of halite to dissolve, it will not cause salt layer collapse. To sum up, the simulated solvent may be more suitable for LGSP dissolution, which can be verified by the following laboratory experiments.

Experimental ore sample: the ore samples used in the experiment were collected from Qarhan Salt Lake and were from the same ore-bearing layer. The ore samples were mixed evenly, then they were divided into two equal parts.

According to the Table 1, 2L initial solvent and simulated solvent were prepared respectively, and the pH of the two solvent were adjusted to 6.5. Since the concentration of Ca2+ and SO42 were pretty low in the initial solvent and simulated solvent, meanwhile, gypsum is difficult to soluble in solutions. Consequently, Ca2+ and SO42 in either the initial solvent or simulated solvent were not added.

Two parts of ore samples with the same mass (850g each) were weighed and put into two 2L beakers respectively. The prepared initial solvent and simulated solvent (1L each) were poured into two beakers respectively. The two beakers were placed in a constant temperature incubator at 25C. The liquid phase samples were taken from two beakers respectively every 1h, and 5mL each time. The experiment lasted 8h, and 8 liquid samples were taken from each beaker, 16 liquid samples in total.

As shown in Fig.4, the change trend of Na+ and Cl is basically the same. Compared with the initial solvent, the net increase of Na+ and Cl is relatively small when use the simulated solvent, so the solubility of Halite by the simulated solvent is low, which is good to the salt bed, for not cause the collapse of the salt layer. Compared with the initial solvent, the net increase of K+ is relatively high and increases relatively quickly when use the simulated solvent. In the process of ore dissolution by the two solvents, the change of Mg2+ is small. In the process of preparing of the two solvents, Ca2+ and SO42 were not added. But after 8h of ore dissolving, Ca2+ and SO42 were detected in the two solutions, and their change trends were basically the same, indicating that gypsum or polyhalite were dissolved. In addition, compared with the initial solution, the net increase of Ca2+ and SO42 was relatively higher when the simulated solvent was used to dissolve the ore samples. Li+ and B3+ were also not added during the preparation of the two solvents, however, a small amount of Li+ and B3+ were detected in the solution after 8h of ore dissolution, indicating that there was a small amount of Li+ and B3+bearing minerals dissolved.

From the above analysis, compared with the initial solvent, the simulated solvent is more favorable for selective dissolution of LGSP minerals. Therefore, in the actual production, the chemical composition of the solvent prepared with old brine and Senie Lake water should be as close as possible to the simulated solvent.

In the dissolving process of LGSP minerals in Qarhan Salt Lake, the temperature should be around 25C, and it be recommended the temperature is between 20 and 30C, which is the most suitable for dissolving ore. Around this temperature, the dissolving ability of the solvent to LGSP minerals is enhanced, and the solubility of halite is basically unchanged, which is conducive to the selective dissolution of LGSP ore. Considering the natural conditions of Qarhan Salt Lake, selecting May to October with relatively high temperature is in favor of the dissolution of LGSP minerals.

In the dissolving process of LGSP minerals in Qarhan Salt Lake, when pH is more than 9, the dissolving ability of solvent to gypsum, polyhalite, carnallite and sylvite is strengthened, and the dissolving ability to halite is weakened, which is beneficial to selective dissolution of LGSP ore. However, with the pH value increasing, although the dissolving ability of LGSP minerals is increased, the solvent becomes strong alkaline solution which pollutes the environment and seriously corrodes materials and equipment in actual production. Therefore, in terms of actual production, it be recommended the pH value of solvent is adjusted between 6 and 8.

In the dissolving process of LGSP minerals in Qarhan Salt Lake, when the chemical compositions of solvent, K+, Na+, Mg2+, Ca2+, Cl and SO42, are 0.1%, 2.9%, 3.77%, 0.05%, 15.72% and 0.13%, respectively, the dissolving ability of solvent to LGSP minerals is enhanced, which is more favorable to selective dissolution of LGSP minerals. In actual production, the chemical composition of the solvent prepared with old brine and Senie Lake should be as close as possible to the composition showed above.

In order to better study the dissolving process of LGSP minerals, the interaction between temperature, pH and solvent chemical characteristics should be considered. We plan to do the orthogonal simulated experiment in terms of temperature, pH value and solvent chemical characteristics in the future. In addition, we will also do other factors that affect the dissolving process of LGSP minerals, such as porosity of the strata.

Li, B. T. et al. Acomparative study of material composition of solid sylvite before and after liquefaction and its significance in Bieletan area of Qarhan Salt Lake, Qinghai, China. Miner. Depos. 29(4), 669683 (2010).

Sun, D. P. & Lv, Y. P. A preliminary investigation on carnallite-resolving experiment for intercrystal brines in the first exploitation area of Qarhan Salt Lake, Qinghai, China. J. Salt Lake Sci. 3(4), 4043 (1995).

Li, W. P. The model of dissolving and driving exploitation and the software development in Qarhan Salt Lake. PhD dissertation, Graduate School of Chinese Academy of Geological Sciences, Beijing (1991).

Li, W. P., & Liu, Z. Y. The model research of dissolving and driving exploitation in Qarhan Salt Lake. In Proceeding of the Sixth International Salt Lake Conference (Geological Publishing House, Beijing, 1994).

Parkhurst, D. L. & Appelo C. A. J. Users guide to PHREEQC (Version 2)A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations. U.S. Geological Survey, Water-Resources Investigations Report 994259, 312 p (1999).

Parkhurst, D. L. & Appelo, C. A. J. Description of Input and Examples for PHREEQC Version 3A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations. U.S. Geological Survey, Modeling Techniques (Book 6), Groundwater (Section A), Chapter 43 (2013).

Mark, R. & Nicolas, S. Calculation of pH and mineral equilibria in hydrothermal waters with application to geothermometry and studies of boiling and dilution. Geochim. Cosmochim. Acta 48(7), 14791492 (1984).

Institute of Mineral Resources of Chinese Academy of Geological Sciences. The report of key technologies for liquefaction and exploitation of low-grade solid potassium minerals in Bieletan area, Qinghai (2013).

This paper is supported by Natural Science Foundation of Qinghai Province, China (Granted No. 2019-ZJ-917), the Thousand-Personal Project of Senior and Innovation Talents for Qinghai Province, China, the State-Key Research Development Project, China Resource Exploration and Mining Technology in The Deep Strata of Salt Lake (Granted No. 2018YFC0604801), Special Project for Basic Scientific Research Business Expenses of Central Public Welfare Scientific Research Institutes (Granted No. KK2005 and No. KK2016), and National Mineral Resources Investigation and Comprehensive Evaluation (Granted No. DD20190606). We would like to thank Mr Chunlian Wang, Jiuyi Wang and Dr. Lijian Shen for their support and help to the research. The field work was also assisted and supported by Wang Luohai and Yan Qunxiong of Qinghai Salt Lake Industry Co., Ltd.

R.L. wrote the main mannuscript text. C.L. provied the ideals for this manuscript. P.J. reviewed this manuscript. Y.H. did the analyzed work for this Manuscript. W.L. and S.W. sampled the samples from the field.

Li, R., Liu, C., Jiao, P. et al. Simulation study on the mining conditions of dissolution of low grade solid potash ore in Qarhan Salt Lake. Sci Rep 11, 10539 (2021). https://doi.org/10.1038/s41598-021-88818-z

## method to control carnallite ore dissolution

SUBSTANCE: invention can be used in production of synthetic carnallite. Proposed method comprises adjusting ore feed depending upon the content of useful component in inlet flows and measurement of temperature. Besides solvent flow rate, solvent density and content of magnesium chloride therein and content of potassium chloride in carnallite ore flow are measured. Parametres thus obtained allow determining carnallite ore flow rate from the relationship indicated below to make setting to be incorporated with ore consumption control system: where Gore is the consumption of carnallite ore, t; Gsol is the consumption of solvent, t; is the content of potassium chloride in carnallite ore, %; is the content of free potassium chloride not bound in carnallite, %; is the content of magnesium chloride in saturated solution set by enterprise operating conditions to make 28.50.5%; is the content of magnesium chloride in solvent, %.

The invention relates to a technique of managing the processes of dissolution of carnallite ores containing carnallite, potassium chloride and sodium and other impurities, and can be used in the production of synthetic carnallite - raw materials for the production of magnesium metal.

Widely known methods of dissolving potassium carnallite ores in the circulating hot solvent liquor - see, for example, galurgia, Abbadesse, L., Chemistry, 1972, s-479; Solikamsk carnality, collection of scientific papers, Vol.2, S.-Petersburg, LICK, 2007, s-121, which are by definition methods of chemical analysis of the compositions of carnallite ore and dissolving liquor with subsequent control of ore ratio:lye on the basis of the calculation of the material balance of the process of dissolution.

There is a method of process control leaching of potassium chloride from multicomponent materials by controlling the feed of raw material to solvent, the apparatus depending on the concentration of potassium chloride in the raw material and regulating the water content of the solvent liquor by changing the water flow into the tank rastvortsev the liquor, the supply of raw materials and water regulated depending on the concentration of magnesium chloride in the raw and cold liquor - see speaker of the USSR 1271824, CL 01D 3/04; G05P 27/00.

The proposed method of control of the process of dissolution of potassium ores aimed at stabilizing the water balance of the process of dissolution of potassium chloride and inefficient in the production of synthetic carnallite, and the proposed equation does not apply when managing the process of dissolution of carnallite ores.

A known method of controlling the process of dissolution of the salt ore such as carnallite, by stabilizing the flow of the original solution and controlling the feed of ore depending on the content of useful component in the input flow and temperature measurement of a ready solution - prototype - see speaker of the USSR 1256776, CL B01F 1/00; G05D 27/00, publ. 15.09.86, bull. No. 34.

According to the method additionally measure the mineral content in the finished solution and depending on the temperature of the prepared solution and the content of useful component in source and finished solutions regulate the flow of ore in dependence shown in speakers.

The method is complex, as it requires the use of methods of analytical control and does not take into account the presence of solvent liquor magnesium chloride. In addition, stabilization of the flow of the original, rastvora.pri processing carnallite ores hampered by combining the liquor flows from the stages of the crystallization of carnallite and countercurrent washing clay-salt slurry.

The goal is solved by the fact that in contrast to the known method further measure the flow rate of solvent fluid, its density and the content of magnesium chloride, the content of potassium chloride in the stream carnallite ore, according to the obtained parameters are calculated according to the following dependence of the optimal consumption carnallite ore and the calculated value serves as the task management system flow of ore:

In the above equations the dimension included in the equation technological parameters: the concentration of MgCl2the density of the solution and its temperature is balanced by the dimensionality of the factors facing options and free members.

The essence of the method as a technical solution consists in the following. The process control method of the dissolution of carnallite ores is carried out by controlling the feed of ore depending on the content of useful component in the input flow and temperature measurement. In contrast to the known method the proposed method additionally measure the flow rate of solvent solution, the weight, the content of magnesium chloride and the content of potassium chloride in the stream carnallite ore.

In the manufacture of synthetic carnallite solvent solution is formed from the mother liquor produced after extraction from it si the Tethyan carnallite - the target product and solution after hot countercurrent washing clay-salt slurry - PTP. The flow and composition of the solvent solution varies due to uneven unloading thickeners clay-salt slurry and the solid content in the discharged suspension, as well as due to temperature fluctuations suspension vacuum crystallization setup - internals.

At existing carnallite factories (OJSC Uralkali and OJSC Silvinit) managing the process of dissolution of carnallite ore is carried out by compliance with the specified maintenance ratio ore:solvent solution, periodically making this ratio amendments in the chemical composition of the hot clarified saturated solution of arriving at the UWC for crystallization of synthetic carnallite.

However, analyses of the chemical composition of the ore and the clarified solution is not coming to production in a timely manner due to the length of their run, so the management process of dissolution is not always effective. The situation is aggravated by the fact that variations in the content of natural carnallite ore reaches 10%, and the sampling of carnallite in the analysis are not always representative for polydispersed particle size distribution of the ore.

The analysis of the work of departments dissolution of carnallite factories, about the Eden authors, showed that carnallite ore is a mixture of minerals such as carnallite (KCl, MgCl2H2O), halite (NaCl), sylvite (KCl), anhydrite (CaSO4) and clay minerals (CONCENTRATION). In the process of dissolution of the ore in the solvent solution is the dissolution of carnallite, while other water-soluble minerals pass into the liquid phase only when the solvents, water is supplied, for example when washing bucket elevators.

The authors found that the content of carnallite ore varies widely due to the specifics of the ore, while the content Silvina changes slightly and is only 0.5-1.2%. This observation allowed us to determine the content in the ore of carnallite (magnesium chloride), defining operational flow carnallite ore content of potassium chloride radiometric method.

Carnallite can be regarded as a compound consisting of KCl and MgCl26H2O. Determining the flow of ore content of potassium chlorideand subtracting from it the amount of free Silvinawhich is determined analytically 1 per day and is changing slightly, determine the current content in the ore MgCl26H2O for readings.

Upon the dissolution of carnallite ore important characteristic is the content of MgCl2in a hot saturated solution. This value is regulated and depends on the specifics of the ore processing plant and, as a rule, is 28.50,5%. Determining the content of MgCl2-in solvent solution, for example, analytically and knowing its consumption - Gp.p-pwe determine the optimal current consumption MgCl26H2O required to obtain a saturated solution of routine composition:

Table 1no PP.Temperature 40CTemperature 65CTemperature 90CThe content of MgCl2, %The density of the solution, , t/m3The content of MgCl2, %The density of the solution, , t/m3The content of MgCl2, %The density of the solution, , t/m3115,21,25015,11,25615,0the 1.265216,81,25316,71,25916,6were 1,268318,31,25618,21,26318,1 1,271419,81,26019,71,26719,61,275521,41,264of 21.21,27121,11,279622,9were 1,26822,71,27522,61,283724,41,27324,21,28024,11,288825,81,28025,71,28625,51,293

Carrying out the processing of the experimental data table with the derivation of the equation by standard techniques of mathematical analysis using Excel, received for these temperature dependencies of the content MgCl2in solution from the lotnosti. R2- the value of the accuracy of the approximation.

To determine the density dependence of the solution from the content of magnesium chloride on the condition of saturation of a solution of the chlorides of potassium and sodium the selected temperature of 40, 65 and 90C. the Choice of temperature is determined by the minimum value of carnallite factories: temperature carnallite suspension internals after ~40C, the temperature of the solvent solution, coming to the surface heaters, ~65C and the temperature of the clarified hot saturated solution of arriving at the UWC, ~90C.

When processing the data array to determine the density dependence of the solution from the content MgCl2for the extended sample temperatures (>3) auxiliary coefficients to determine a, b and C can be adjusted. Therefore, the auxiliary coefficients a, b and C are presented in a General form:

Thus, measuring the operational flow of solvent solution, its temperature, density and determining its content of magnesium chloride, and in the flow of carnallite ore total content of potassium chloride and 1 times in 24 hours - the content of potassium chloride, which is not connected in carnallite, analytical method and applying these parameters to the controller, the equations calculate the optimal consumption carnallite ore dissolution and calculated values serves as the task management system flow of ore.

The equations cover the range of variation of process parameters for any of the carnallite plant processing of natural ore. The content of magnesium chloride in a hot saturated carnallite solution arriving at the UWC is set by regulation and is 28.50,5% MgCl2however , if necessary - for example, for synthetic carnallite with a high content of NaCl and KCl, MgCl content2this solution can be changed.

From the description of the invention it is seen that when implementing the present invention solves the problem the forgiveness process due to operational management by automating the flow of carnallite ore, supplied to the dissolution, depending on the ore composition, flow rate and solvent composition of the solution and other parameters.

The method is as follows. The mother liquor obtained after the separation from it of synthetic carnallite formed during crystallization at the UWC, together with a solution after countercurrent washing clay-salt slurry - PTP and in the form of a solvent solution is heated and served on the dissolution of carnallite ore in AIDS-solvents.

The signals from the transducers are received at the controller and the PC, where calculate the optimal values of consumption of ore depending on the current technological options, and then enter the flow control ore dissolution.

To calculate the optimal consumption carnallite ore fed to the dissolution, based procedural content MgCl2in hot saturated carnallite solution Gp.p-p=Vp.p-p=2501,286Therefore, the consumption of carnallite ore will be 94,93 t 250 m3solvent solution and the ratioExample 2.The readings taken in accordance with example 1, but the content of magnesium chloride in a solvent solution calculated density of the solution and its temperature:- density solution1,286 t/m3the temperature of the solution65CA=-a1t2+a2t-a3=-2,6064652+362,541265-16129,0189=-3575,8809B=a1t2in2t+b3=6,6448652-920,896065+41226,0191=9442,0591C=c1t2-c2t+c3=4,2357652-584,766065+26316,8009=6202,84341. The process control method of the dissolution of carnallite ores by regulating the supply of ore, depending on the content of useful component in the input flow and temperature measurement, characterized in that it further measure the flow rate of solvent fluid, its density and the content of magnesium chloride, the content of potassium chloride in the sweat is ke carnallite ore and derived parameters are calculated according to the following dependence of the optimal consumption carnallite ore and the calculated value serves as a job management system ore consumption: where Gore- consumption of carnallite ore t;Gp R-Rthe flow of solvent solution, t;the content of potassium chloride in carnallite ore, %;is the content free of potassium chloride, which is not connected in carnallite, %;the content of magnesium chloride in a saturated solution, %, as defined by regulations of the enterprise and is 28.50,5%;the content of magnesium chloride in a solvent solution, %.2. The method according to claim 1, characterized in that the content of magnesium chloride in a solvent solution determined analytically or estimated in terms of density and temperature of the solution.

1. The process control method of the dissolution of carnallite ores by regulating the supply of ore, depending on the content of useful component in the input flow and temperature measurement, characterized in that it further measure the flow rate of solvent fluid, its density and the content of magnesium chloride, the content of potassium chloride in the sweat is ke carnallite ore and derived parameters are calculated according to the following dependence of the optimal consumption carnallite ore and the calculated value serves as a job management system ore consumption: where Gore- consumption of carnallite ore t;Gp R-Rthe flow of solvent solution, t;the content of potassium chloride in carnallite ore, %;is the content free of potassium chloride, which is not connected in carnallite, %;the content of magnesium chloride in a saturated solution, %, as defined by regulations of the enterprise and is 28.50,5%;the content of magnesium chloride in a solvent solution, %.

2. The method according to claim 1, characterized in that the content of magnesium chloride in a solvent solution determined analytically or estimated in terms of density and temperature of the solution.

SUBSTANCE: invention can be used in production of potassium chloride using a halurgic method. The method of controlling this process involves controlling flow of water into the solution for crystallisation depending on the concentration of potassium chloride and its temperature. Flow of the solution and content of crystalline sodium chloride and magnesium chloride, flow of water for diluting the clarified saturated solution, flow of evaporated water in housings of the vacuum-crystallisation installation and temperature of the liquid phase in the said installation housings are also measured. Flow of water into the solution for crystallisation in the housing of the installation is calculated from the obtained parametres and the calculated values are entered as settings into the water flow control system: where is flow of water in the i-th housing or groups of housings of the vacuum-crystallisation installation, where i=1, 2, 3, 4N depends on the number of housings, is flow of evaporated water in the i-th housing, t; is flow of water in housings which should be removed from the solution to obtain potassium chloride saturation KCl=1 and sodium chloride saturation NaCl=1, t; is flow of evaporated water in housing 1 until potassium chloride saturation KCl and sodium chloride saturation NaCl equal 1, t.

SUBSTANCE: invention can be used in production of potassium chloride. Proposed method comprises control over ore feed subject to content of useful component in inlet flows, measurement of ready solution temperature, density, temperature and consumption of dissolving solution. Additionally, content of potassium chloride in ready solution is measured after its defecation, as well as its consumption. Obtained data and temperature are used to determine roe feed to correct its main flow in compliance with the following relation, and calculated magnitudes are entered in proportioner control system: where Gore is ore consumption that corrects its main flow, t, symbol indicates a necessity to increase or decrease primary consumption of silvinite ore consumption; Gread sol is consumption of clarified solution, t; CKCIread sol is content of potassium chloride in clarified solution, %; CKCIore is content of potassium chloride in silvinite ore, %; KCIread sol is saturation of clarified solution with respect to potassium chloride.

SUBSTANCE: invention can be used in chemical-recovery industry. Coke is loaded into coke-cooler plenum 8. Circulating gases are removed from coke-cooler plenum 8 with the help of draft system 7 and supplied into waste heat boiler 2. Produced superheated steam is removed from waste heat boiler 2 along steam line 9. Downstream waste heat boiler 2 circulating gases again arrive into coke-cooler plenum 8. In order to control actual flow rate of circulating gases and maintenance of superheated steam temperature at specified level, data obtained from superheated steam temperature sensor 1, sensor 3 of circulating gases temperature at the inlet to waste heat boiler 2, sensor 4 of circulating gases temperature at the outlet from waste heat boiler 2 and sensor 5 of circulating gases flow rate is sent to control unit 6. After processing of obtained data, control unit 6 generates signal of draft system 7 control.

SUBSTANCE: present invention relates to versions of a method of stabilising the hydroformylation process and a device for realising the said method. One version of the method involves reaction of one or more reagents, carbon monoxide and hydrogen in the presence of a hydroformylation catalyst to obtain an exhaust gas stream and a reaction product stream which contains one or more products, in which the method described above is realised at such partial pressure of carbon monoxide that, the rate of reaction increases when partial pressure of carbon monoxide falls, and falls when partial pressure of carbon monoxide increases; and in which the following steps of the process for stabilising the rate of reaction, total pressure, speed of the exhaust gas stream, reaction temperature or combinations thereof are carried out, process steps including at least one of the following process control schemata, selected from: Scheme A: (a1) setting a given total pressure; (a2) determination of total pressure and determination of the difference between the measured total pressure and the given total pressure; and (a3) based on the pressure difference measured at step (a2), manipulation of the stream of incoming gas which contains carbon monoxide in order to balance the measured total pressure to virtually the given total pressure; and Scheme B: (b1) setting a given speed of the exhaust gas stream; (b2) determination of the speed of the exhaust gas stream and determination of the difference between the measured speed of the exhaust gas stream and the given speed of the exhaust gas stream; and (b3) manipulation of the speed of incoming gas which contains carbon monoxide based on the difference in the speed of the exhaust gas stream measured at step (b2) in order to equalise the determined speed of the exhaust gas stream virtually with the given speed of the exhaust gas stream.

SUBSTANCE: group of inventions related to oil industry, to dosing methods and equipment of reagents, such as demulsifying agents and corrosion inhibitors - oil development and preparation at fields and can be used at oil treatment and water preliminary discharge plants. Preliminary equalise pressure in a reagent tank and accompanying oil gas pipeline. Then regulate reagent flow rate, compare measured with flow metre reagent flow rate value in regulator with reagent flow rate target value, and according hose values difference create a control signal to a control valve, installed on pipe connecting nozzle to the tank. Device contains sealed tank with reagent, located over the pipeline top generating line. A section of a smaller diametre with nozzle mounted into the pipeline. The nozzle connected to the tank via pipeline, with reagent flow metre, connected to the regulator, reagent target flow rate signal transferred to the second end it, and outlet connected with control valve, installed on the pipe connecting nozzle to the tank. The reagent tank connected to the accompanying oil gas pipeline with equaliszing line.

SUBSTANCE: invention relates to a method of automatic control of ion-exchange sorption of amino acids from waste water and can be used in chemical, food and other industries. The method of automatic control of ion-exchange sorption of amino acids from waste water involves controlling concentration of components of waste water, measuring flow of liquid solutions and their level in reservoirs. Information on flow of the process of ion-exchange sorption of amino acids from waste water is sent to sensors for monitoring level in containers of incoming water, distillate and desorbing solution, acidity of incoming water and during its flow into ion-exchange columns, temperature of the distillate and desorbing solution, concentration of the target component in the incoming water and water at the outlet of the ion-exchange columns and flow through secondary devices, a microprocessor and digital-to-analogue converters to actuating mechanisms for changing parametres of operation of the equipment depending on selected criteria.

SUBSTANCE: first version of the method involves the following steps: distillation of a mixture which contains methyl iodide and acetaldehyde in a distillation apparatus in order to obtain an overhead fraction and a residue, measuring density of the said overhead fraction, determination of relative concentration of methyl iodide, acetaldehyde or both in the overhead fraction based on the measured density and regulation of at least one process variable, associated with the said distillation apparatus. As a response reaction to the said measured density or relative concentration calculated from the measured density, the said process variable is selected from heating intensity, column pressure, the composition fed, condensate composition and coefficient of flow reversal.

SUBSTANCE: stated invention is related to method and device, and may be used in the field of automation of mixed air flows parametres control in ventilation systems. Device for method realisation comprises metres of initial values of temperature and moisture content of mixed flows, metre of barometric pressure, outlets of which are connected to inputs of initial parametres processing and setting. Besides outlet of initial parametres processing and setting is connected to inlet of functional converter of temperature differences, and outlet of functional converter is connected with inlet of computing unit. Also outlet of computing unit is connected to inlet of temperature difference sign analysis unit, outlet of which is connected to inlet of outlet signal generator. Device outlet is outlet of outlet signal generator.

SUBSTANCE: method involves measurement of a temperature parametre, comparison the actual temperature parametre with a given parametre and, depending on the difference value, reduction of this value by changing flow of fuel to burners of the corresponding section coil pipe of the furnace. The temperature parametre used is the temperature profile along the coil pipe and the given temperature profile for each section of the coil pipe is calculated using the formula where t - is relative temperature along the coil pipe, %; k- raw material conversion (gas + petrol), % per raw material; L - is the effective length of the coil pipe from its beginning to the ith point of measurement, % of the total length of the coil pipe of the furnace; - is a coefficient of the formula; j - a coefficient index.

SUBSTANCE: invention refers to the method for operating mode of caprolactam production from benzene carried out in the plant with one process line including the stations of benzene hydrogenation with hydrogen, cyclohexane oxidation with oxygen, cyclohexanone rectification, oximation, cyclohexanone oxim rearrangement to caprolactam, neutralisation of the reaction mixture with ammonia and mixing of caprolactam. The said stations are connected with pumps, pipelines with sensors and valves for consumption control of benzene, hydrogen, cyclohexanone, hydroxylamine sulphate and oleum, sensor of acid value and pH-metre of caprolactam. The said line contains additionally the second process line of caprolactam production from phenol including the stations of phenol hydrogenation with hydrogen, dehydrogenation of cyclohexanol with circulation circuit including: pump - station of cyclohexanol dehydrogenation - station of cyclohexanone rectification - pump, station of cyclohexanone rectification, oximation with hydroxylamine sulphate, rearrangement of cyclohexanon oxim to caprolactam and neutralisation of the reaction mixture with ammonia connected by pumps and pipelines with sensors and valves for control of benzene, hydrogen, cyclohexanone, hydroxylamine sulphate and oleum consumption, sensor of acid value and pH-metre of caprolactam and contains the device of benzene-phenol ratio connected with stations of benzene and phenol hydrogenation, oxidation and dehydrogenation; device of cyclohexanone distribution to the oximation stations connected with rectification stations and (through the cyclohexanone mixing tank) with the oximation stations; device of crystalline caprolactam switch-over to liquid caprolactam connected with caprolactam mixer, concentrator of crystalline caprolactam and tank of liquid caprolactam. The total caprolactam capacity, benzene-phenol ratio, cyclohexanone distribution to oximation stations, shipping of crystalline and liquid caprolactam to customers are set up; the consumption of benzene, phenol, hydrogen, cyclohexanone, hydroxylamine sulphate and oleum are corrected with corresponding valves.

SUBSTANCE: invention relates to chemistry and can be used in production of mineral salts. An aqueous solution of a mixture of potassium nitrate and magnesium chloride is heated until dissolution of the solid phase, where content of the mixture of magnesium nitrate and potassium chloride in the aqueous solution is 48.0-52.0 wt % mass ratio KCl:Mg(NO3)2 is in the range (41.5-47.0):(53.0-58.5) respectively. The obtained mixture is cooled to temperature close to room temperature in order to crystallise potassium nitrate which is then separated from the mother solution through filtration. The mother solution is evaporated until formation of a dihydrate of magnesium chloride and the remaining mother solution which is saturated with magnesium nitrate is used to prepare the initial mixture.

SUBSTANCE: aqueous solutions of metal chlorides are successively treated with an oxidant and a calcium chloride source and/or barium chloride source with molar ratio of oxidant and divalent iron ions in the range (0.95-1.90):1.0 and molar ratio of calcium chloride and/or barium chloride and sulphate ions in the range (0.9-1.1):1.0 with subsequent coprecipitation of a hydrate of iron (III) oxide and calcium sulphate and/or barium sulphate at pH of the reaction medium between 5.0 and 9.5 and separation of the liquid and solid phase of the suspension.

SUBSTANCE: magnesium chloride and worked out melted electrolyte of magnesium and chlorine preparation electrolytic process are loaded to the vessel in magnesium/chlorine mass ratio equal 1:(1-1,2) respectively. The components are mixed, heated up to temperature exceeding the crystallisation temperature of mixture salts at 200-400C. Obtained synthetic carnallite in the melt form is decanted, the clarified part is separated and supplied to the electrolytic magnesium and chlorine preparation process. The aforementioned vessel is chlorator melting pot or the stationary carnallite furnace.

SUBSTANCE: present invention pertains to metallurgy and chemistry of inorganic substances. According to the invention serpentinite is leached with hydrochloric acid. The suspension is filtered, obtaining magnesium chlorate solution and silicon dioxide. Impurities are removed from the magnesium chlorate solution through neutralisation, obtaining a nickel-iron concentrate. Carnallite is produced from the purified magnesium chlorate solution and spent electrolyte. The carnallite is dehydrated and subjected to electrolysis, obtaining magnesium, chlorine and spent electrolyte. The nickel-iron concentrate is leached by 10-15% hydrochloric acid at temperature 80C and pH 3-5. The suspension is filtered, obtaining an iron-containing residue and a solution, containing nickel chloride. Nickel compounds are extracted from the solution containing nickel chloride by treatment with a solution of sodium hydroxide at pH=8.0-8.5. The residue is washed in water soluble salts-chlorides, dried and calcinated, obtaining a nickel concentrate.

SUBSTANCE: hydrates of chlorides of alkali earth metals are obtained by evaporation or drying water solutions of chlorides of alkali earth metals at temperature ranging from 115 to 250C in the presence of a reducing compound, taken in quantity of 0.005-0.1% of the mass of the anhydrous metal chloride. The reducing compound can be a compound, chosen from a group consisting of urea, formaldehyde, formaldehyde polymers, hydrazine-hydrate, hydrazine hydrochloride, sodium hydrosulphide, sodium sulphite, potassium sulphite, sodium hydrosulphite, sodium nitrite, in form of individual compounds or in form of different mixtures.

SUBSTANCE: naturally occurring brine is heated in a vessel to 95-105C at pressure not higher than atmospheric and crystallization is then carried out on the surface of rotary drum disposed in the vessel and heated to 105-117C. Process is effected in continuous operation mode.

SUBSTANCE: the invention is pertaining to the method of production of the artificial carnallite. The method of production of the carnallite includes mixing of the heated concentrated solutions containing potassium and magnesium chlorides, with the potassium chloride in the mass ratio of the solution equal to MgCl2:KCl = (3.2-7.9):1, cooling of the suspensions with crystallization, filtration the carnallite crystallizate, dissolution in the mother liquor at the temperature of 115 of the waste electrolyte of the magnesium production and feeding of the produced solution for lixiviation of the magnesium chloride from the ore in the chamber of the underground lixiviation. Dissolution of the waste electrolyte of the magnesium production is conducted in the part of the mother liquor in the presence of the water or the sewage of the magnesium production containing magnesium, potassium, sodium chlorides for maintaining the water balance of the process of production of carnallite with reception of the solution containing 4-7 % of potassium chloride. The share of the magnesium chloride in the solution at the chamber outlet of the underground lixiviation is maintained at the level of 28-30 %.The solution received at the outlet of the chamber of the underground lixiviation is subjected to evaporation up to the share of MgCl2 in it at the level of 30-33 % and feed for mixing with the suspension of potassium chloride in the remained heated mother liquor. The method increases the share of extraction of potassium from the raw materials and the recycling solutions into the target product.

SUBSTANCE: method for chemically removing impurities from chlorine-magnesium melt comprises steps of melting solid dehydrated carnallite in vessel; treating prepared chlorine-magnesium melt by means of chemical reagent and agitating it; using as chemical reagent magnesium granules in salt envelope containing, mass%: metallic magnesium, 50 -95; chlorides of magnesium, potassium, calcium produced from salt casting waste materials of magnesium production by disintegration and separation to magnesium granules in salt envelope and to salt phase. Chemical reagent is fed onto surface or under layer of chlorine-magnesium melt. Chlorine-magnesium melt is treated in chlorinator or in furnace or in vacuum-ladle.

EFFECT: lowered consumption of chemical reagent for removing impurities from melt and therefore lowered expenses due to using relatively cheap reagent -magnesium granules in salt envelope, reduced outbursts to environment.

SUBSTANCE: the invention is pertaining to the method of production of the enriched carnallite by its separation from the accompanying ores and impurities. The method of preparation of the carnallite for the electrolysis includes reduction of the carnallite ore, its air separation with partition of the carnallite and the halite, the two-stage dehydration of the carnallite. After reduction the carnallite ore is subjected to dressing within two stages in series: at first using the air separation in the furnaces of the fluidized layer at the temperature in the layer of 20-250 and the gases speed in the layer of 1.5-7.0 m per second, then the produced carnallite is treated with the heavy suspension in the hydrocyclone. As the heavy suspension use the heavy brine of the potassium chloride with the density of 1.5-1.9 g/dm3. The invention allows to improve the quality and to increase extraction of the carnallite from the carnallite ore.

SUBSTANCE: the invention is pertaining to the method of production of the synthetic carnallite for the electrolytic production of magnesium and chlorine and may be used in the nonferrous metallurgy and chemical industry. The method of production of the synthetic carnallite provides for dissolution of the spent electrolyte containing the magnesium chloride, potassium chloride, sodium chloride in the mother liquor of production of the carnallite up to the complete dissolution of the potassium chloride at the temperature of 90-115 with the following filtration for separation of the non-dissolved sediment containing sodium chloride and production of the clarified carnallite-saturated solution. From the received solution the carnallite is crystallized by refrigeration with the speed of 17-25/h. The produced suspension is thickened and filtered for separation of the mother-liquor from the carnallite. The carnallite is dehydrated, dried and returned for intercalation in the dehydrated carnallite. The invention allows to produce the synthetic carnallite of the bigger size and with the low share of impurities.

SUBSTANCE: invention can be used in production of potassium chloride. Proposed method comprises control over ore feed subject to content of useful component in inlet flows, measurement of ready solution temperature, density, temperature and consumption of dissolving solution. Additionally, content of potassium chloride in ready solution is measured after its defecation, as well as its consumption. Obtained data and temperature are used to determine roe feed to correct its main flow in compliance with the following relation, and calculated magnitudes are entered in proportioner control system: where Gore is ore consumption that corrects its main flow, t, symbol indicates a necessity to increase or decrease primary consumption of silvinite ore consumption; Gread sol is consumption of clarified solution, t; CKCIread sol is content of potassium chloride in clarified solution, %; CKCIore is content of potassium chloride in silvinite ore, %; KCIread sol is saturation of clarified solution with respect to potassium chloride.

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