RU2841813C1 - Method of extracting calcium chloride from brines of chloride-calcium and chloride-magnesium type - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry and processing of natural brines to obtain calcium chloride. Method involves preliminary extraction of magnesium chloride in form of its hydroxide from chloride-calcium and chloride-magnesium type brines. Further, calcium chloride is deposited. Organic solvent which is an aliphatic amine – triethylamine, is added to the brine in amount of 10-15 wt.%. Deposition process is carried out at temperature of partial or complete dissolution of the aliphatic amine in the aqueous phase. Further, the solid phase – calcium chloride – is separated from the filtrate and heated to stratification temperature into an aqueous and an organic phase, which does not exceed 25-30 °C.

EFFECT: wider existing raw material base, high efficiency of extracting calcium chloride, high rate of extraction and low content of magnesium compounds in the crystallising precipitate.

4 cl, 1 tbl, 1 ex

Description

Field of technology

The invention relates to the chemical industry and, specifically, to the processing of natural brines to expand the existing scope of application.

State of the art

A method for isolating CaCl ₂ ⋅H ₂ O from brines by cooling them to a temperature of minus 25°C is known, which was used in the production of magnesium oxide (RU patent 2211803, IPC C01F5/06, published 10.09.2003). However, this technical solution requires expensive equipment and high energy costs.

A method is known for isolating calcium chloride from highly mineralized brines supersaturated in calcium chloride content (CaCl ₂ concentration of 350-370 g/l), which is carried out with deep cooling and spontaneous crystallization of CaCl ₂ ⋅H ₂ O with an admixture of MgCl ₂ ⋅H ₂ O, which results in a decrease in the calcium chloride concentration to 150-200 g/l, i.e. by 40-60%, with the simultaneous production of 500-600 kg of a mixture of CaCl ₂ ⋅H ₂ O (90-93%) and MgCl ₂ ⋅H ₂ O (7-10%) from 1 m ³ of brine. The sediment is separated from the solution by centrifugation and granulated using known methods (RU patent 2284298, IPC C01F11/24, published 09/27/2006).

In its technical essence, this method is the closest to the one we propose and was chosen as a prototype. The main disadvantages are the use of expensive cryohydrate equipment and high energy costs. In addition, the salt is contaminated with magnesium compounds.

Disclosure of the essence of the invention

The technical problem of the invention is the development of a method for extracting calcium chloride from hydromineral sources by salting them out with preliminary removal of magnesium compounds in the form of hydroxide from the brine.

The technical result consists in increasing the efficiency of calcium chloride extraction due to its introduction at positive temperatures, at a high speed, while reducing the content of magnesium compounds in the crystallizing sediment (i.e., while improving the quality of the resulting product).

The specified technical result is achieved by preliminary removal of magnesium compounds from the brine in the form of hydroxide, followed by the introduction of a substance into the newly formed system that reduces the solubility of calcium chloride (salting-out process), which leads to its release in the form of crystal hydrate.

The theoretical aspects of this approach are presented in the works of V.V. Danilina // Phase equilibria, salting out effects and extractive crystallization of salts in ternary salt-water-amine systems. Abstract of dissertation, Saratov, 2023.

Implementation of the invention

The initial brine is preliminarily purified from heavy metals and magnesium chloride. The process of calcium chloride extraction is carried out by salting out with an organic solvent, partially soluble in water, for which, according to its physicochemical properties, as well as safety, energy and fund saving requirements, an aliphatic amine - triethylamine (TEA) is used. The salting out agent is taken in the amount of 10-15% of the brine mass. A decrease in the triethylamine content in the forming system below 10 wt.% leads to a decrease in the amount of crystallizing crystal hydrate, and an excess of the salting out agent by 15% does not change the amount of the precipitated sediment. This justifies the choice of the concentration range of the amine used. When dissolved in water, TEA interacts with it to form triethylammonium hydroxide, which is a strong base. Note that a decrease in temperature increases the solubility of the amine in water, therefore the salting out process is preferably carried out at 5-10 ° C. When TEA dissolves, the water structure changes due to the redistribution of the ratio of hydrogen protons and hydroxide anion, which determines the effectiveness of the salting-out agent. This process continues until the calcium ion concentration decreases to 35-40 g/l of brine (crystallization degree 70-80%). The precipitated salt is separated from the liquid phase by filtration or centrifugation, dried and sent to the granulation process.

An example of a specific application is illustrated by the isolation of calcium chloride crystal hydrate CaCl ₂ ⋅H ₂ O from the brine of the Znamenskoye deposit (Irkutsk region) (Table 1).

Table 1

Chemical composition of the brine of the Znamenskoye deposit (Irkutsk region)

Element Li ⁺ Na ⁺ K ⁺ Mg2 ⁺ Ca ²⁺ Br ^- Content, g/l 0.45 2.4 4.3 31.2 154.3 9.8

1 liter of brine (ρ=1.41 g/ ^cm3 ) is purified from heavy metal salts (mainly Fe2 ⁺ , Mn2 ⁺ ) by adjusting the pH to approximately 8.5 and simultaneously introducing an oxidizer (sodium hypochlorite) or by aeration. The solution is stirred, followed by filtration of the released hydroxides. Then 75 g of calcium oxide are added to it. This forms 70 g of magnesium hydroxide, which is also separated by filtration. 140 g of triethylamine are added to the filtrate and the resulting system is stirred with a gradual decrease in temperature to 5°C for 30 min. Under these conditions, 840 g of calcium chloride crystal hydrate is released from the brine, separated on the filter or by centrifugation. The resulting filtrate is heated to 25-30°C, settled and the organic phase of triethylamine is separated, followed by sending it to a new salting-out cycle. The crystal hydrate is sent for drying or, if necessary, for granulation.

The above allows us to state that the method allows us to significantly simplify and reduce the cost of the process of obtaining calcium chloride from brines with a high salt concentration.

The developed salting-out agent, determination of the optimal amount of salting-out agent and conditions for the extraction of salt from the composition of the heterogeneous system "brine-triethylamine" ensure high efficiency and cost-effectiveness of the processes of extraction of calcium chloride crystallohydrate from brines. In addition, the method allows to involve natural hydromineral raw materials - highly mineralized brines of chloride-calcium and chloride-magnesium type - in industrial circulation.

Claims (4)

1. A method for extracting calcium chloride from calcium chloride and magnesium chloride brines, including precipitation of calcium chloride, characterized in that magnesium chloride is first removed from the brine in the form of its hydroxide, and then, to precipitate calcium chloride, an organic solvent is added to the brine, which is an aliphatic amine - triethylamine, in an amount of 10-15 wt.%, and the precipitation process is carried out at a temperature of partial or complete dissolution of the aliphatic amine in the aqueous phase, the solid phase - calcium chloride, is separated from the filtrate and heated to a temperature of stratification into aqueous and organic phases, which does not exceed 25-30 °C. 2. The method according to item 1, characterized in that the precipitation process is carried out at a temperature of 5-10°C. 3. The method according to item 1, characterized in that the brine is pre-cleaned of heavy metals. 4. The method according to claim 1, characterized in that triethylamine is separated from the aqueous phase and reused in a new cycle of the precipitation process.