Method for producing an aqueous calcium polysulphide solution

Abstract

The invention relates to the production of an aqueous solution of calcium polysulphide (CaSn) for use in agriculture and the building industry. The technical result consists in that, when in direct contact with water, a sulphur melt does not lose the qualities of the initial raw components thereof when heated above a critical point (the temperature at which the crystal lattice type changes, i.e. polymorphic transformation occurs) and subsequently subjected to rapid cooling. Furthermore, the size of the sulphur particles in the working solutions of calcium polysulphide is from 20 to 40 nm, which allows particles of elemental sulphur to penetrate into the structure of plants and to be directly involved in nourishing the plants and protecting them from disease. Sulphur is comminuted by melting with calcium oxide, wherein cheap lump sulphur is used instead of ground sulphur, with sulphur activation occurring in addition to dispersion at this step, thus increasing the speed of production of a polysulphide solution and increasing product yield. The technical result is achieved in that the claimed method for producing a calcium polysulphide solution includes melting calcium oxide with lump sulphur at a temperature of 155°С and a ratio of 1:2 parts by weight, then cooling the obtained melt by direct contact with water in a ratio of 3:8 parts by weight, with the vessel containing the melt being vibrated at a frequency of 40-60 Hz, and subjecting the mixture itself to hydrothermal synthesis at a temperature of 85-90°С for 90 minutes.

Description

[0001] Method for obtaining an aqueous solution of calcium polysulfide

[0002] The invention relates to the production of an aqueous solution of calcium polysulfide (CaSn) for use in agriculture as a fertilizer and feed additive, as well as in the construction industry.

[0003] Unlimited reserves of local natural (limestone) and man-made (petroleum sulfur) raw materials provide the opportunity to implement technologies for sulfur-containing import-substituting multifunctional products for use in agriculture as fertilizers with fungicidal, acaricidal and pesticidal properties, and in the construction industry - as water repellents and intensifiers of phase formation processes.

[0004] Calcium polysulfide solution is the most effective form of sulfur-containing fertilizer for introducing sulfur in a form directly accessible to plants, which will allow realizing the most important reserve for increasing agricultural productivity, improving crop quality and protecting plants from diseases and pests.

[0005] A method for producing calcium polysulfide by direct interaction of metal with sulfur at high temperatures (250-350°C) is known (USSR A.S. No. 1129186, IPC C01 B 17 / 2, issue 15.12.84).

[0006] The synthesis of calcium polysulfide by this method is complicated by the insufficiently high stability of CaSn at elevated temperatures.

[0007] A method for producing calcium polysulfide is known (patent of the Republic of Kazakhstan No. 4817 for a utility model, March 27, 2020), which consists of calcining limestone-shell rock at a temperature of 850-900 ° C, obtaining calcium oxide, and jointly grinding the calcium oxide formed during calcination with granulated sulfur at a mass ratio of 0.33-0.40. The resulting mixture is stirred in water at 80-85 ° C, while the mass of water in the resulting mixture is 70-75%.

[0008] However, low-temperature calcination of shell limestone produces calcium oxide, the high activity of which in air leads to rapid carbonization, which complicates long-term storage and use of this method for producing calcium polysulfide at a distance from the calcination site. A known method for producing a calcium polysulfide solution is the interaction of calcium oxide and sulfur in a solvent (Patent of the Russian Federation No. 2256602 for invention, 01.05.2006), which consists in the fact that, in order to intensify, reduce the reaction temperature and increase the yield of the target product, the process is carried out with continuous supply of gaseous hydrogen sulfide to the solution under low pressure at a reaction mass temperature of 50-80 ° C. To remove residual H2S, the solution is purged with nitrogen at 60 ° C.

[0009] In the examples of the methods given, it is recommended to introduce pure hydrogen sulfide into the reaction, which is artificially obtained for the reaction by burning a mixture of paraffin and sulfur, however, when hydrogen sulfide is involved in the synthesis from sulfur removal processes, other undesirable impurities enter the system, such as mercaptans, which give an unpleasant odor to lime-sulfur solutions and make them a poor-quality product.

[0010] A method for obtaining a calcium polysulfide solution is also known (Patent of the Russian Federation No. 2523478 for invention, 20.07.2014), which proposes obtaining calcium polysulfide in the form of aqueous, aqueous-alcoholic and alcoholic solutions. The method assumes that hydrogen sulfide is fed into the reaction mixture along with sulfur, calcium hydroxide and water to reduce the amount of waste and obtain a high-quality product.

[0011] The method allows increasing the yield of the product, but is complicated in multi-stage execution and requires the supply of hydrogen sulfide to the reaction mass. It is difficult to obtain and store hydrogen sulfide specifically, but if it is obtained in the processes of sulfur removal from hydrocarbons, then along with hydrogen sulfide, the volume also contains other gases (CO2, mercaptans, etc.), which can negatively affect not only the course of the reaction, but also give the final product an unpleasant odor.

[0012] A method for producing calcium polysulfide is known (Pozin M.E. Technology of mineral salts, fertilizers, pesticides, industrial salts, oxides and acids). 4.1. Moscow: Chemistry, 1974. - P. 502). The method involves the interaction of calcium oxide with sulfur in water at 100 ° C and a component weight ratio of S: CaO: H2O = 10: 5: 85. Lime is preliminarily slaked, and then sulfur is introduced in the form of a paste obtained by thoroughly grinding sulfur with added water. As a result of the reaction, CaS4 and CaSs (64-67%) and by-products are formed - calcium thiosulfate CaS2O3 (23-28%) and calcium carbonate CaCO3 (0.3-1.1%). About 5-11% of sulfur remains unreacted. The disadvantages of this method are: high temperature of 100 °C required for the interaction of calcium oxide with sulfur in water and a significant amount of by-products (about 30% of the total mass).

[0013] The closest analogue of the claimed invention is a method for producing calcium polysulfide (RU Patent No. 2777173 for invention, 01.08.2022), which makes it possible to obtain a concentrated solution of calcium polysulfide with a density reaching 1.25-1.28 g / cm 3 , and also eliminate the problem of hydrogen sulfide disposal and its release into the environment.

[0014] The solution to the technical problem is achieved by the fact that the method for obtaining calcium polysulfide, including the interaction of calcium oxide and crushed sulfur in water, is carried out at a temperature of 40-50 °C with an increase to 80 °C, held for 2-3 hours and stopped when the density of the resulting aqueous solution of calcium polysulfide reaches 1.18-1.20 g / cm 3 . The resulting hydrogen sulfide contained in the absorber water and the aqueous solution of calcium polysulfide are returned to the process and reacted until the density of the aqueous solution of calcium polysulfide reaches 1.25-1.28 g / cm 3The method uses crushed sulfur with an average particle size of 40 microns.

[0015] However, it is known that the process of obtaining highly dispersed sulfur has economic and technological difficulties due to its potential for explosion during milling, product sticking to equipment, dusting and the risk of fire during storage.

[0016] The objective of the present invention is to develop a method for obtaining a calcium polysulfide solution that eliminates the need to use highly dispersed sulfur, reduces the amount of by-products and increases the density of the solution in comparison with known ones.

[0017] The technical result is that the sulfur melt, in direct contact with water, does not lose the quality of the original raw materials when heated above the critical point (temperature of the change in the type of crystal lattice, i.e. polymorphic transformation) and subsequent rapid cooling. At the same time, the size of sulfur particles in working solutions of calcium polysulfide from 20 to 40 nm ensures the penetration of elemental sulfur particles into the structure of plants and direct participation in nutrition and protection of plants from diseases.

[0018] The technical result of the proposed method is achieved by obtaining a calcium polysulfide solution, including fusing calcium oxide with lump sulfur at a temperature of 155°C, in a ratio of 1:2 parts by weight, cooling by direct contact of the alloy with 8 parts by weight of water, the container with which vibrates at a frequency of 40-60 Hz (2400-3600 rpm) and subsequent hydrothermal synthesis of the mixture at a temperature of 85 - 90°C for 90 minutes.

[0019] In addition, crushing sulfur by fusing with calcium oxide, where cheap lump sulfur is used instead of grinding, at this stage, in addition to dispersion, sulfur is activated, which increases the speed of obtaining calcium polysulfide solution and increases the yield of the product.

[0020] Figure 1 shows the product of cooling in water of an alloy of sulfur with calcium oxide.

[0021] The proposed method for producing calcium polysulfide involves the use of lump sulfur. Its production is technologically simple and is carried out by feeding liquid sulfur through a heated pipeline to a warehouse where sulfur blocks are poured. The solidified blocks, 1-3 meters high, are broken into smaller pieces and transported to the customer.

[0022] The basis of the invention is the technology of fusing sulfur with calcium oxide and hydrothermal synthesis based on the alloy and water to obtain calcium polysulfide, which decomposes in an aqueous environment with the release of elemental sulfur in a nanodispersed state.

[0023] Crushing sulfur by fusing with calcium oxide, where cheap lump sulfur is used instead of grinding, in addition to dispersion, sulfur is activated, increasing the speed of obtaining a calcium polysulfide solution and increasing the product yield.

[0024] A positive factor in the sharp cooling of sulfur in water are the phase transitions of sulfur: at 155 °C - 8zh - liquid sulfur; when cooled to 119 °C, it passes into SM - monoclinic sulfur; at 95.5 °C into rhombic - Sp. With these polymorphic transformations, a decrease in the volume of the sulfur crystal lattice by 14% is observed, which contributes to the emergence of brittleness and dispersibility of granules. Bringing the original raw mixture to a physical state in the form of a porous, brittle, cracked conglomerate ensures one-stage production of calcium polysulfide with a density of 1.24 g / cm 3 at a temperature of 90°C for 90 minutes and an increase in the yield of the finished product up to 80%.

[0025] Hydrothermal synthesis waste is a mixture of the following substances: water-soluble calcium polysulfide and insoluble calcium sulfite (Ca3O3), unreacted elemental sulfur, calcium carbonate (CaCO3) and calcium hydroxide Ca(OH)2, which can be processed into fertilizers containing valuable plant nutrients - sulfur and calcium, according to the Method for obtaining sulfur-containing fertilizer from calcium polysulfide production waste and the fertilizer obtained in this way (RU 2744183, published 03.03.2021).

[0026] Example 1

[0027] The initial components used were technical lump sulfur and technical calcium oxide in the form of powder with a residue on sieve No. 02 close to zero, which corresponds to a specific surface of 3500 - 5000 cm 2 / G.

[0028] A sand bath is installed on an electric stove, onto which an enamel container with a capacity of 10 liters is placed, 5 kg of lump sulfur is poured, which melts at a temperature of 135 ° C. After the sulfur has completely melted, 2.5 kg of powdered technical calcium oxide are introduced in small portions with continuous stirring, then the temperature is raised to 155 ° C, at which sulfur has a minimum viscosity and the mixture is homogenized for 10 minutes.

[0029] A container with 20 liters of water is installed and secured on a vibrating table (oscillation amplitude, mm 0.35±0.05, vibrator type, VI-99B power, kW - 0.5, operating voltage, V 380 - current frequency, Hz-50.). During vibration, the molten mass is poured into the container with water. The container is moved to an electric stove, closed with a lid with a reflux condenser and at a temperature of 90 ° C for 90 minutes with continuous stirring, hydrothermal synthesis of a calcium polysulfide solution is carried out. The resulting reaction mixture is poured into a 50-liter container for settling and decantation. As a result, a calcium polysulfide solution in the amount of 18.0 liters with a pronounced dark cherry color and a density of 1.24 g / cm was obtained. 3 and sediment in the amount of 9.5 liters, having a dark green color and high dispersion.

[0030] Example 2

[0031] The process of obtaining a calcium polysulfide solution differs from Example 1 in that the mixture of raw components is placed in a ceramic container, the process of fusion of the components of the mixture is carried out in a microwave oven for 12 minutes. As a result, the alloy of sulfur and calcium oxide is formed 4 times faster than in the example! , which reduces the total time for obtaining a calcium polysulfide solution by 35 minutes.

[0032] Example 3

[0033] Differs from Example 1 in that a mixture of essential oils and organic compounds extracted from plants in an amount of 0.05 to 0.1% of the volume is introduced into the finished calcium polysulfide solution in order to eliminate discomfort from the smell of hydrogen sulfide during use. This mixture not only masks the unpleasant smell, replacing it with a more pleasant one, but the oil vapors and organic compounds promote the adhesion of calcium polysulfide solution drops to the treated surfaces. The biological activity of sulfur is preserved.

[0034] Example 4

[0035] Differs from Example 1 in that the resulting granulate of the sulfur and calcium oxide alloy is collected from the cooling tank onto a mesh conveyor and moved to a drum dryer for drying at a temperature of no more than 60°C, then packaged and sent to the place of use. At the place of use, the granulate is mixed with water in a ratio of 3:8 and heated (to a temperature of 90°C with continuous stirring for 90 minutes). This technological method will avoid the need and danger of transporting the liquid alkaline solution of calcium polysulfide to the place of use.

Claims

Invention formula A method for producing an aqueous solution of calcium polysulfide, in which calcium oxide and crushed sulfur react in water, characterized in that calcium oxide is fused with lump or granulated sulfur at a temperature of 155°C, in a ratio of 1:2 parts by weight, then the resulting alloy is cooled by direct contact with water in a ratio of 3:8 parts by weight, and the container in which the alloy is located is vibrated at a frequency of 40-60 Hz, and the mixture itself is subjected to hydrothermal synthesis at a temperature of 85-90°C for 90 minutes.

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