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RU-2861666-C1 - METHOD FOR PRODUCING CALCIUM HYPOCHLORITE

RU2861666C1RU 2861666 C1RU2861666 C1RU 2861666C1RU-2861666-C1

Abstract

FIELD: chemical industry. SUBSTANCE: provided is a method for producing calcium hypochlorite, which includes chlorination of a calcium hydroxide slurry with gaseous chlorine to obtain a solid phase containing calcium hypochlorite and a liquid phase containing active chlorine, separating the solid phase containing calcium hypochlorite, washing and drying it to obtain calcium hypochlorite. Part of the liquid phase containing active chlorine is mixed with calcium hydroxide to obtain the calcium hydroxide slurry sent for chlorination, or with the calcium hydroxide slurry sent for chlorination. Wherein, part of the liquid phase containing active chlorine is reacted with sodium hydroxide to obtain calcium hydroxide and a sodium chloride solution, the resulting calcium hydroxide is used to obtain the calcium hydroxide slurry sent for chlorination. The resulting sodium chloride solution is used to wash the solid phase containing calcium hypochlorite. The solution after washing the solid phase containing calcium hypochlorite is added to the liquid phase containing active chlorine. Variants of the method for producing calcium hypochlorite are provided. EFFECT: reducing the effect of the quality of the starting raw material on the purity of the product obtained in the process, increasing the efficiency of the calcium hypochlorite production process by reducing losses of chlorine, calcium and water. 24 cl, 8 dwg, 39 ex

Inventors

  • ANTONOV SERGEI ALEKSANDROVICH
  • Bannikov Vladimir Mikhailovich
  • Kurakov Andrei Aleksandrovich
  • Letuev Aleksandr Viktorovich
  • Riabtsev Aleksandr Dmitrievich

Dates

Publication Date
20260507
Application Date
20250616

Claims (20)

  1. 1. A method for producing calcium hypochlorite, which comprises chlorinating calcium hydroxide pulp with gaseous chlorine to produce a solid phase containing calcium hypochlorite and a liquid phase containing active chlorine, separating the solid phase containing calcium hypochlorite, washing and drying it to produce calcium hypochlorite, wherein at least part of the liquid phase containing active chlorine is mixed with calcium hydroxide to produce calcium hydroxide pulp supplied for chlorination, or with calcium hydroxide pulp supplied for chlorination, wherein at least part of the liquid phase containing active chlorine is subjected to a reaction with sodium hydroxide to produce calcium hydroxide and a sodium chloride solution, the obtained calcium hydroxide is used to produce calcium hydroxide pulp supplied for chlorination, and the sodium chloride solution is used to wash the solid phase containing calcium hypochlorite, the solution after washing the solid phase, containing calcium hypochlorite, is added to the liquid phase containing active chlorine.
  2. 2. The method according to paragraph 1, characterized in that before washing the solid phase containing calcium hypochlorite with a sodium chloride solution, it is washed with water.
  3. 3. The method according to paragraph 2, characterized in that the solution, after washing the solid phase containing calcium hypochlorite with water, is added to the liquid phase containing active chlorine.
  4. 4. The method according to paragraph 1, characterized in that at least part of the sodium hydroxide and chlorine are obtained by electrolysis of a sodium chloride solution.
  5. 5. The method according to paragraph 4, characterized in that the sodium chloride solution for electrolysis is a calcium chloride brine.
  6. 6. The method according to paragraph 4, characterized in that the sodium chloride solution for electrolysis is a solution after washing the solid phase containing calcium hypochlorite.
  7. 7. The method according to claim 4, characterized in that the sodium chloride solution for electrolysis is a solution obtained in the reaction of a liquid phase containing active chlorine with sodium hydroxide.
  8. 8. The method according to paragraphs 4-7, characterized in that before electrolysis, the sodium chloride solution for electrolysis is purified to remove calcium, magnesium, and sulfate ions.
  9. 9. The method according to paragraph 8, characterized in that the purification of the sodium chloride solution from sulfate ions is carried out by precipitation, using barium chloride as the precipitant.
  10. 10. The method according to paragraph 8, characterized in that the purification of the sodium chloride solution from calcium and magnesium is carried out in two stages: in the first stage, reagent purification is carried out, calcium and magnesium are precipitated from the sodium chloride solution in the form of insoluble compounds CaCO 3 and Mg(OH) 2 , using sodium hydroxide and sodium carbonate as reagents; in the second stage, purification is carried out on an ion-exchange resin in sodium form.
  11. 11. The method according to paragraph 10, characterized in that the regeneration of the spent ion-exchange resin is carried out in two stages: first with a hydrochloric acid solution, then with a sodium hydroxide solution, wherein the solutions after resin treatment, containing calcium and magnesium, are mixed with the solution supplied for reagent purification from magnesium and calcium.
  12. 12. The method according to paragraph 4, characterized in that during the electrolysis process the anolyte is purified from active chlorine by introducing reducing agents, and then it is purified from calcium, magnesium and sulfate ions.
  13. 13. The method according to paragraph 12, characterized in that at least one of the substances selected from urea, hydroxylamine, hydrazine, hydrazine hydrate, ammonium carbonate, and formic acid is used as a reducing agent.
  14. 14. A method for producing calcium hypochlorite, which includes chlorinating calcium hydroxide pulp with gaseous chlorine to obtain a solid phase containing calcium hypochlorite and a liquid phase containing active chlorine, separating the solid phase containing calcium hypochlorite, washing and drying it to obtain calcium hypochlorite, wherein at least part of the liquid phase containing active chlorine is mixed with calcium hydroxide to obtain a calcium hydroxide pulp supplied for chlorination, or with a calcium hydroxide pulp supplied for chlorination, wherein the drying of calcium hypochlorite is carried out with heated air, which is saturated with water during the drying process and then cooled with the formation of condensate, wherein the condensate is used to wash the solid phase containing calcium hypochlorite, the solution after washing the solid phase containing calcium hypochlorite is added to the liquid phase containing active chlorine.
  15. 15. The method according to paragraph 14, characterized in that after washing the solid phase containing calcium hypochlorite using condensate, it is washed with a solution of sodium chloride.
  16. 16. The method according to claim 15, characterized in that the solution obtained after washing the solid phase containing calcium hypochlorite with a sodium chloride solution is added to the liquid phase containing active chlorine.
  17. 17. The method according to paragraph 14, characterized in that thermal energy is recovered by transferring it from a stream of water-saturated air to a stream of air entering the drying of calcium hypochlorite.
  18. 18. The method according to paragraph 17, characterized in that after transferring thermal energy from the flow of water-saturated air to the flow of air supplied for drying calcium hypochlorite, further cooling of the flow of water-saturated air is carried out in a heat exchanger-condenser with a refrigerant.
  19. 19. A method for producing calcium hypochlorite, which includes chlorinating calcium hydroxide pulp with gaseous chlorine to obtain a solid phase containing calcium hypochlorite and a liquid phase containing active chlorine, separating the solid phase containing calcium hypochlorite, washing it and drying it to obtain calcium hypochlorite, wherein at least part of the liquid phase containing active chlorine is mixed with calcium hydroxide to obtain a calcium hydroxide pulp supplied for chlorination, or with a calcium hydroxide pulp supplied for chlorination, while ensuring a concentration of calcium hydroxide in the pulp supplied for chlorination of from 1 to 4% of the pulp mass.
  20. 20. The method according to any one of paragraphs 1-19, characterized in that the calcium hydroxide included in the composition of the calcium hydroxide pulp is obtained from a calcium chloride brine by reaction with sodium hydroxide.

Description

Field of technology The invention relates to the field of inorganic chemistry, namely to the technology of producing calcium hypochlorite. State of the art In world practice, the production of calcium hypochlorite, in particular, is based on the interaction of calcium hydroxide with elemental chlorine according to the reaction: 2Ca(OH) 2 +2Cl 2 →Ca(OCl) 2 +CaCl 2 +2H 2 O+234.1 kJ/mol (Ca(OCl) 2 ) As a rule, it is not the solid-phase calcium hydroxide that is chlorinated, but rather lime milk - a suspension consisting of the solid phase of calcium hydroxide and an aqueous solution of Ca(OH) 2 . During the chlorination of lime milk, various crystalline forms of calcium hypochlorite are released into the solid phase, depending on the Ca(OH) 2 concentration, temperature, amount of chlorine absorbed, and other factors. This explains the variety of methods for its production. The simplest process is the chlorination of 30% lime milk, first implemented by the German company Griesheim-Elektron; patent DE 373847 C "Process for producing calcium hypochlorite compounds" was received for this method (priority date 09.11.2021). The process was carried out at 40-50°C until the residual Ca(OH) 2 content in the chlorination product was 0.5-1.0%. The chlorinated mass was filtered using a specially designed press with an operating pressure of 15 kg/cm. The pressed mass was crushed and dried in two stages: in a pneumatic dryer in the first stage and in a drum dryer in the second stage. The need for high pressure and unique filtration equipment has significantly limited the adoption of this method. In order to obtain calcium hypochlorite crystals suitable for filtration using traditional equipment, it was proposed to introduce sodium chloride into the chlorinated mass at the final stage of the chlorination process. This technical solution is described in patents US 1754473 A “Production of calcium hypochlorite” (priority date 04.08.1926) and GB 378847 A “Improvements in the production of calcium hypochlorite” (priority date 16.05.1931). This method was used by the French company Krebs in its calcium hypochlorite production technology, producing a commercial product with an active chlorine content of up to 70% by weight. However, a significant drawback of this method is the requirement to use only high-purity Ca(OH) 2 , which in turn necessitated the production of Ca(OH) 2 exclusively from high-purity calcite (with a CaCO3 content of at least 98%). This is due to the fact that the content of the main impurities found in limestone (Mg, Fe, Si, Al) must be kept to a minimum, as they reduce the yield and quality of calcium hypochlorite. This significantly limits the raw material base for the product. Other disadvantages of these methods are the periodicity of the production process and high losses of chlorine. A prior art method, described in patent RU 2543214 C2, "Method for the Comprehensive Processing of Natural Salts of the Chloride-Magnesium Type" (priority date April 11, 2013), addresses the main drawbacks of the above-described methods by eliminating the need for lime produced from limestone. This method produces calcium hypochlorite via an exchange reaction between calcium chloride, obtained from natural brine in the form of a concentrated aqueous solution of CaCl2 , and a sodium hypochlorite solution, produced by the absorption of chlorine in a sodium hydroxide solution produced by membrane electrolysis of a solution of table salt. The resulting product is dried at 80°C, and the mother liquor from the exchange reaction is recycled, returning NaCl and CaCl2 to the production process. The main advantage of this method is the ability to produce calcium hypochlorite continuously and eliminate the need for a discontinuous chlorination step, minimizing chlorine losses. However, this method can only be implemented in practice within the context of integrated processing of multi-component calcium-containing natural brines. Furthermore, the direct yield of calcium hypochlorite in the exchange reaction does not exceed 47%, necessitating the loss of a large amount of active chlorine during processing of the mother liquor from the exchange reaction. The method also eliminates the possibility of using lime produced from sources other than brine as feedstock. The method was further refined (Russian Patent No. 2637694, 2017) to increase the yield of Ca(OCl) 2 and enable the product to be produced not only in integrated processing facilities for polycomponent natural calcium-containing chloride brines but also autonomously using other calcium sources. Patent RU 2637694 C2, "Method for producing calcium hypochlorite during integrated processing of natural polycomponent supersaturated calcium-magnesium chloride brine" (priority date December 6, 2017), was granted for the refined method. The stated goal was achieved by organizing independent, continuous production of two solutions: sodium hypochlorite-chloride and calcium hypochlorite-chlor