RU2456239C1 - Method of producing calcium bromide from natural bromine-containing calcium chloride-type brines - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry. The method of producing calcium bromide from natural bromine-containing brines involves oxidation of bromide ions contained in the brine with chlorine, desorption of bromine vapour, capturing bromine with a calcium reagent in the presence of a reducing agent. The calcium reagent used is calcium carbonate which is extracted from brine after crystallisation of CaCl₂·6H₂O with a MgCl₂·6H₂O impurity. To obtain calcium carbonate, a residue of CaCl₂·6H₂O and MgCl₂·6H₂O is used, which is dissolved in water and the solution is purified from magnesium hydroxide. After precipitation of calcium carbonate, the mother solution, which contains sodium chloride, undergoes electrolysis to obtain chlorine and a catholyte containing sodium hydroxide. Calcium carbonate is precipitated from brine using said catholyte with simultaneous carbonisation of the reaction mixture or with the catholyte after carbonisation thereof. Purification from magnesium hydroxide is also carried out with the obtained catholyte. Chlorine obtained from electrolysis is used to oxidise bromide ions to molecular bromine. The vapour-bromine mixture is used as the brominating agent for calcium carbonate pulp in a solution of a reducing agent. The reducing agent used is hydrazine or hydroxylamine or derivatives thereof.

EFFECT: invention enables to use highly mineralised brines to obtain reagents for producing calcium bromide in a single process scheme.

2 cl, 1 dwg, 1 tbl, 3 ex

Description

The invention relates to a method for processing hydromineral raw materials to produce calcium bromide and reagents for its production.

A known method of producing calcium bromide from bromine-containing mineralized water, in which the absorption of bromine after oxidation of the bromide ion and blowing it with air is a solution of calcium bromide containing urea and calcium hydroxide. The resulting product contains 55% CaBr ₂ ; the bromine yield is 99.9% (A.S. 1286521) [1].

A known method of producing calcium bromide from bromine-containing water after the oxidation of bromide ions with chlorine and air blowing, in which the absorption process is carried out in two stages: in the first stage, a solution of calcium hydroxide containing an equivalent amount of urea is fed, and in the second, a solution of calcium hydroxide with urea equivalent to the bromine content in the solution. The resulting solution of calcium bromide is evaporated to obtain crystals of CaBr ₂ · 6H ₂ O; the product contains 60.0-64.7% CaBr ₂ . The degree of bromine recovery is 77-79% (A.S. 1516465) [2].

A known method of obtaining a mixture of solutions of metal halides of the second group, in which the bromine-containing water is acidified, oxidized with bromide ion, chlorine is blown off with air, bromine is absorbed in the presence of urea in two absorbers, in the first, a suspension of Mg (OH) _{2 is} used as an absorber, the second is a suspension of Ca (OH) ₂ . After filtration, the solutions are mixed to obtain solutions of CaBr ₂ and MgCl ₂ (ρ = 1.7-1.9 g / cm ³ ). The resulting mixture is used for the preparation of drilling fluids (A.S. 1641774) [3].

There is also known a method of producing calcium bromide, in which the absorption of bromine from the bromine-air mixture is carried out with a solution containing urea at pH = 3-4, and subsequent processing of the resulting solution is carried out with milk of lime to pH = 5.0-6.5. This allows you to reduce the content of chlorine impurities in the product and increase the life of the column (US Pat. 1836846) [4].

This method is the closest to the proposed solution and we have chosen as a prototype.

The disadvantages of all methods, including the prototype, is the use of slightly saline water with a bromine content of not more than 0.3 kg / m ³ , and bromine is captured from the bromine-air mixture using lime milk obtained after calcining a natural mineral - limestone.

Distinctive features of the proposed method is the use of highly saline brines (Σ salts ~ 500 kg / m ³ ) containing 8-10 kg / m ^{3 of} bromine and 200-400 kg / m ³ of calcium chloride. This allows one to obtain reagents for the production of calcium bromide: chlorine and calcium carbonate in a single technological scheme.

SUMMARY OF THE INVENTION

To develop the method, we used a chloride-calcium brine of the Znamenskoye deposit (Irkutsk region) of a composition typical of the Siberian platform brines with a bromine content of ≈ 8.7, Σ salt ≈ 560 (the brine after being raised to the surface was supersaturated with the content of calcium chloride).

The technical result is achieved by the fact that the brine after rising to the surface and spontaneous crystallization of CaCl ₂ · 6H ₂ O in the storage pools [5] is separated from the precipitate, magnesium is precipitated from the brine, calcium carbonate is precipitated after separation of Mg (OH) ₂ , and the mother liquor after separating CaCO ₃ containing mainly NaCl, is electrolyzed to produce chlorine and catholyte (NaOH), is used to precipitate the catholyte magnesium and catholyte after the carbonization or carbonization simultaneous reaction mixture used for the precipitation of calcium carbonate .

The technical result is achieved in that a precipitate of CaCl ₂ · 6H ₂ O mixed with MgCl ₂ · 6H ₂ O is dissolved in water, the solution is purified from magnesium chloride with catholyte, and CaCO _{3 is} precipitated from a solution of calcium chloride using catholyte during pulp carbonization, the mother liquor NaCl is used for electrolysis to produce chlorine and sodium hydroxide (catholyte) [5].

The technical result is achieved by the fact that precipitated calcium carbonate is used to produce calcium bromide by bromination of CaCO ₃ pulp in a reducing agent solution. Hydrazine or hydroxylamine or their derivatives are used as reducing agent.

The technical result is also achieved by the fact that the brine after spontaneous crystallization of CaCl ₂ · 6H ₂ O is used to produce bromine after the bromide ion has been oxidized with electrolytic chlorine, elemental bromine is desorbed with steam, and the bromine mixture is used as a brominating agent.

Thus, the hallmarks of the method are:

1) the use of a new type of raw material for producing calcium reagent - CaCO ₃ - from natural brines of calcium chloride type instead of limestone;

2) obtaining from the same raw material source of reagents for the implementation of the method - gaseous chlorine and catholyte (NaOH);

3) obtaining calcium bromide by direct interaction of calcium carbonate with bromine in the presence of a reducing agent;

4) the use of a precipitate of CaCl ₂ · 6H ₂ O with an admixture of MgCl ₂ · 6H ₂ O formed after the brine was raised to the surface for the subsequent production of calcium carbonate.

List of drawings and tables

Figure 1. Technological scheme for producing calcium bromide from brine.

Table 1. The composition of the brine and sediment after cooling.

Information confirming the possibility of implementing the method of producing calcium bromide is presented in figure 1 and in the following examples.

Example 1. 60 l of brine (Table 1) supersaturated in the content of calcium chloride, composition (kg / m ³ ): CaCl ₂ - 397; MgCl ₂ - 130; Σ MeCl ≈ 26 (Me - Li, Na, K) was cooled in a container for crystallization of the precipitate CaCl ₂ · 6Н ₂ О (mixed with MgCl ₂ · 6H ₂ O ~ 10%). The precipitate was separated from brine and dissolved in water. The resulting solution had the following composition (g / l): CaCl ₂ - 192; MgCl ₂ - 7.8; υ = 90 l. Catholyte, a NaOH solution (see Example 3) was added to the solution to precipitate magnesium:

The Mg (OH) ₂ precipitate was separated from the solution, catholyte was added to the reaction mixture and subjected to carbonization:

The resulting precipitate was separated, washed with a small amount of water (W: T = 2: 1) and fed to the reactor to produce calcium bromide. The content of Mg and Na impurities in the sediment was 0.01%.

Without preliminary purification of the solution from MgCl _2, up to 3% magnesium carbonate was contained in the CaCO ₃ precipitate.

Example 2. In the brine after separation of CaCl ₂ · 6H ₂ O (20 l) of the composition (kg / m ³ ) CaCl ₂ - 330; MgCl ₂ - 115; Br ^{- -} 9,3; Σ NaCl, KCl, LiCl ≈ 26, catholyte was added to precipitate magnesium (see reaction 1). The precipitate was separated. Catholyte was added to the remaining brine and the reaction mixture was carbonized (see reaction 2). The precipitated CaCO ₃ precipitate was washed with water and fed to obtain CaBr ₂ . A NaCl solution with a NaCl content of 154 kg / m ^{3 was} evaporated 1.3 times and fed to electrolysis.

Example 3. Electrolysis of a NaCl solution was carried out in a membrane electrolyzer of its own design [5]. In this case, chlorine and catholyte NaOH (140 g / l NaOH) were obtained.

The resulting chlorine was captured by brine composition (kg / m ³ ): CaCl ₂ = 330; MgCl ₂ = 115; Br ^- = 9.3; Σ NaCl, KCl, LiCl = 25.7. (Table 1). In this case, the bromide ion was oxidized to elemental bromine, which was desorbed with steam [6].

Example 4. To obtain calcium bromide, the resulting steam-bromine mixture (example 3) was captured by pulp of calcium carbonate obtained in examples 1, 2 with an aqueous solution of a reducing agent (hydrazine):

Calcium bromide is obtained as a 50-55% solution. The binding of bromine to calcium bromide occurs almost 100%.

Industrial applicability

The proposed method for producing calcium bromide allows you to use a new source of raw materials - bromine-containing brines of calcium chloride type. Raw materials of this type are widespread within the Siberian platform. After brining, saturated with CaCl ₂ (t = 30-40 ° С), it is fed to the pools, where it is cooled and its equilibrium state is established under natural conditions, which is accompanied by the precipitation of a part of calcium chloride in the sediment - in the form of CaCl ₂ · 6Н ₂ О, mixed with MgCl ₂ · 6H ₂ O, which is present in the bottom phase.

To obtain calcium carbonate, both a brine and a precipitate of CaCl ₂ · 6H ₂ O were used. In contrast to the known methods, the preparation of calcium bromide in the proposed method was carried out by direct contact of the precipitated calcium carbonate with a steam-bromine mixture in the presence of a reducing agent. In the method, all reagents (chlorine, catholyte) for the implementation of the method were obtained from the same brine. For carbonization, flue gas generated during fuel combustion is used.

Given the high demand for calcium bromide as a weighting fluid for drilling fluids, CaBr ₂ production at oil and gas drilling sites may have wide regional demand.

Information sources

1. A.S. 1286521 from 06.27.85. The method of producing calcium bromide. / A. Nuryev, A. Khadzhimamedov, V.I. Ksenzenko and others Publ. 01/30/87. Bull. Number 4.

2. A.S. 1516465 from 08.27.87. The method of producing calcium bromide. / R.A. Sarkarov, M.E.Yusupova. Publ. 10/23/89. Bull. Number 39.

3. A.S. 1641774 dated 08.12.87. A method of obtaining a mixture of solutions of metal halides of the second group. /R.F. Sarkarov, M.E. Yusupova and A.I. Ovchinnikov. Publ. 10/15/91. Bull. No. 14.

4. Pat. RF 1836846 from 02.14.90. A method of obtaining a solution of calcium bromide. / A. Nuriev, A. Khadzhimamedov, A. Khudaiberdyev and other publ. 10/10/95. Bull. No. 28. Prototype.

5. Pat. RF 2315132 dated 10/10/05. A method of producing chlorine and chlorine-containing oxidizing agents and a plant for its implementation. / A.D. Ryabtsev, N.M. Nemkov, V.I. Titarenko, etc. Publ. 01/20/08. Bull. No. 20.

6. Ksenzenko V.I., Stasinevich D.S. Chemistry and technology of bromine, iodine and their compounds. - M .: - Chemistry. - 1995 .-- 303 p.

Table 1 Composition of brines and crystalline hydrate of calcium chloride Name Quantity, m ³ (kg) Content, kg / m ³ Σ salts, kg / m ³ CaCl ₂ MgCl ₂ Mecl Br The brine after rising to the surface, supersaturated in the content of CaCl ₂ (t = 30-40 °). 1,0 397 130 26 8.7 562 The equilibrium brine after precipitation of CaCl ₂ · 6H ₂ About (average annual composition). 0.96 330 115 26 9.3 480.3 Content% kg / m ³ CaCl ₂ MgCl ₂ H ₂ O The precipitate of crystalline hydrate CaCl ₂ · 6Н ₂ О (MgCl ₂ · 6Н ₂ О (bottom phase) 75-600 (depending on t of ambient air) 44 5 51 Not up to date one hundred% MeCl - Σ NaCl, KCl, LiCl in terms of NaCl.

Claims (2)

1. The method of producing calcium bromide from natural bromine-containing brines, including the oxidation of bromide ions contained in the brine, chlorine, desorption of bromine with steam, capture of bromine with a calcium reagent in the presence of a reducing agent, characterized in that the calcium chloride brine is used as a raw material for the production of a calcium reagent type or precipitate of CaCl ₂ · 6H ₂ O mixed with MgCl ₂ · 6H ₂ O isolated from the brine after dissolving it in water, from which magnesium hydroxide is precipitated, and the brine after separation of Mg (OH) _{2 is} used to obtain calcium carbonate; the mother liquor after separation of calcium carbonate, containing mainly NaCl, is subjected to electrolysis to produce chlorine and catholyte - a solution of NaOH; catholyte is used to precipitate magnesium hydroxide, and catholyte after its carbonization or while carbonization of a mixture of brine and catholyte is used to precipitate calcium carbonate; chlorine obtained by electrolysis is used to oxidize bromide ions to molecular bromine; and the steam-bromine mixture is used as the brominating reagent of the pulp of calcium carbonate in a solution of a reducing agent upon receipt of calcium bromide. 2. The method according to claim 1, characterized in that hydrazine, or hydroxylamine, or their derivatives, are used as reducing agent in the bromination of pulp.

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