RU2436732C2 - Method for complex treatment of calcium chloride and magnesium chloride type brines (versions) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemistry and can be used in processing hydro-mineral material. According to the first version, calcium carbonate and magnesium hydroxide are jointly deposited from brine to obtain a sodium chloride-containing solution which is evaporated. Sodium chloride crystals are dissolved in water and the sodium chloride solution undergoes electrolysis to obtain chlorine gas and a catholyte - sodium hydroxide solution. Chlorine gas is used to oxidise bromide ions. After carbonisation with carbon dioxide gas, the catholyte is used to deposit magnesium carbonate and hydroxide. The residue is repulped in calcium chloride solution and undergoes carbonisation to obtain calcium carbonate and magnesium chloride solution. The residue is separated. Magnesium carbonate is deposited from a portion of the magnesium chloride solution. The magnesium carbonate is calcined to obtain magnesium oxide and carbon dioxide gas. The other portion of the magnesium chloride solution is evaporated to obtain bischofite. After separating sodium chloride crystals, lithium carbonate is deposited from the solution. According to the second version, calcium carbonate is separately deposited from the brine, followed by magnesium carbonate. Chorine gas is used to obtain hydrochloric acid. A portion of magnesium carbonate is calcined to obtain magnesium oxide and the other portion is used to obtain bischofite.

EFFECT: invention enables complex processing of natural brine.

4 cl, 2 dwg, 2 tbl

Description

The invention relates to a method for processing hydromineral raw materials to produce chlorine, bromine, calcium carbonate and chloride, magnesium oxide and chloride, lithium carbonate with the utilization of solutions after the separation of all components.

An industrial method of producing chlorine is carried out by electrolysis of sodium chloride in electrolyzers of the diaphragm type [1].

A known method of producing chlorine and oxidizing agents based on it by electrolysis of a solution of sodium chloride, followed by trapping anode chlorine with water or alkali. As commercial products, chlorine water and a solution of sodium hypochlorite are obtained (patent 2315132 dated 10.10.05) [2].

The disadvantage of this method [2] is the use of commodity table salt (NaCl) as a starting reagent.

There is a method of producing bromine from highly mineralized natural brines, according to which the bromide ions contained in the brine are oxidized with chlorine, and elemental bromine is stripped with steam, the air-vapor mixture is condensed, the liquid bromine is separated and subjected to distillation purification from chlorine and water impurities. In this way, liquid bromine of grades A and B is obtained (patent 2108963 from 04/03/95) [3].

The disadvantage of this method [3] is the use of imported chlorine balloon as an oxidizing agent.

Known methods for producing magnesium oxide from bischofite (Akchurin T.K., Ananyin S.A., Nikitin I.I. Prospects for the development and processing technology of bischofite) [4] and from highly mineralized brines (Patent 2211803 from 06.26.01) [5] . The methods provide for the precipitation of magnesium in the form of hydroxide with milk of lime obtained by calcining limestone, followed by quenching of CuO with water and subsequent washing, pressing the precipitate to obtain Mg (OH) ₂ paste, by calcination of which various types of caustic (MgO) powder are obtained.

In the method [4], part of the precipitate of magnesium hydroxide is repulped in water and carbonized to obtain magnesia with carbon dioxide 3MgCO ₃ · Mg (OH) ₂ · 3H ₂ O. After its calcination at different temperatures, various types of magnesia are obtained, including periclase.

The disadvantages of the methods [4, 5] is the use of imported products for the deposition of magnesium and the formation of a finely divided, difficult to filter precipitate Mg (OH) ₂ .

A known method of producing bischofite from highly mineralized calcium chloride type brines, according to which the Mg (OH) ₂ paste obtained by the precipitation of magnesium, is repulped in a solution of calcium chloride (for this purpose, a mother liquor after precipitation of magnesium) is subjected to carbonization. In this case, calcium carbonate precipitates and a solution of magnesium chloride is formed, which is separated from the precipitate, evaporated and poured into drums, where bischofite crystallizes (Patent 2051865 from 02.20.92) [6].

A known method of producing calcium carbonate from the distillation liquid of soda production. Soda is used as a precipitant of CaCO ₃ , in particular, waste from soda production (Patent 2171227 dated 12.25.02) [7].

The disadvantage of the method of producing calcium carbonate is the use of commercial soda or solutions of soda - waste soda production.

A known method of producing granular calcium chloride in the complex processing of natural brines (Patent 2284298 from 12.30.04) [8]. The method allows cooling a brine of calcium chloride type to obtain a crystalline hydrate of the composition CaCl ₂ · 6H ₂ O with an impurity (at the level of 4-6%) MgCl ₂ · 6H ₂ O, then from the brine successively obtain lithium concentrate by sorption method in the form of a solution of LiCl, lithium carbonate , bromine and magnesium oxide.

The main disadvantage of this method is the absence of a chlorine recovery operation, the weight content of which in brines of this type reaches 70% of the content of all components. Of the other disadvantages, it should be noted that all reagents used in the technology are imported: limestone for the production of milk of lime for the deposition of magnesium, balloon chlorine for the oxidation of bromide ion and hydrochloric acid for the acidification of the brine in the operation for the production of bromine, soda for the deposition of lithium carbonate .

In its technical essence, this method is the closest to the proposed one and we have chosen as a prototype for the processing of brines of calcium and magnesium chloride types.

SUMMARY OF THE INVENTION

The technical result of the method is the involvement in the industrial turnover of a new type of raw material - natural brines of calcium chloride and magnesium types. Since these brines, along with CaCl and MgCl ₂ , contain significant amounts of chlorine, as well as bromine and lithium, their complex processing will significantly reduce the cost of the resulting products.

The technical result for brines of calcium chloride and magnesium chloride types is achieved by precipitation of calcium and magnesium with the simultaneous production of a mother liquor enriched with sodium chloride, which is evaporated to isolate NaCl crystals, the crystals are separated from the mother liquor, dissolved in the condensate formed by evaporation, and the concentrated solution sodium chloride NaCl≅300 g / l is sent to electrolysis to produce chlorine and catholyte - a solution of sodium hydroxide and sodium chloride, the latter carbonation with carbon dioxide to obtain soda-alkali and / or soda solution, which is used to produce bromine and precipitation of calcium and magnesium from the brine, and the mother liquor after evaporation and separating crystals of NaCl used for bromine and precipitation of lithium carbonate soda solution. For the carbonization of catholyte, carbon dioxide from the combustion of natural gas (flue gases) is used.

Since brines of calcium chloride and magnesium type have different ratios of calcium and magnesium chlorides (the name of the brine is taken according to the predominant component), their further processing is carried out taking into account this factor (options are proposed).

The technical result for calcium chloride and magnesium chloride brines with a high content of calcium chloride (up to 300 g / l and higher) is achieved by simultaneous precipitation of calcium and magnesium with a soda-alkaline solution, the precipitate of calcium carbonate and magnesium hydroxide in a solution of calcium chloride is subjected to carbonization with carbon dioxide. A solution of calcium chloride is prepared from a precipitate of CaCl ₂ · 6H ₂ O, which crystallizes from brine when it rises to the surface and is cooled in storage pools [8]. In this case, the reaction proceeds:

The precipitate of calcium carbonate precipitated from brine and obtained by reaction (1) is separated, and part of the magnesium chloride solution is used to precipitate magnesia with carbon dioxide soda-alkaline solution according to the reaction:

Then magnesia carbonate is calcined to obtain magnesium oxide and carbon dioxide:

Carbon dioxide is used to carbonize the pulp (see reaction 1). From the remaining part of the solution of magnesium chloride by evaporation get bischofite - MgCl ₂ · 6H ₂ O.

The mother liquor after evaporation and separation of NaCl crystals, enriched with bromine (NaBr) and lithium chloride, is first used to produce bromine, using electrolysis chlorine to oxidize bromide ions, after which the bromine is stripped with water vapor or air and condensed to produce liquid bromine. After bromine separation, lithium carbonate is precipitated from brine with a soda solution obtained after carbonization of catholyte (option).

The technical result for magnesium chloride type brines with a low content of calcium chloride (10-50 g / l) is achieved by separate precipitation of calcium in the form of CaCO ₃ using a soda solution, then carbonate is precipitated with a soda or soda-alkaline solution (see reaction 2) , part of which is calcined to obtain magnesium oxide and carbon dioxide, another part of the precipitate is dissolved in hydrochloric acid to obtain a solution of magnesium chloride and crystallization of bischofite - MgCl ₂ · 6H ₂ O (option).

The technical result is achieved by the fact that hydrochloric acid to obtain a solution of magnesium chloride from magnesia carbon dioxide is obtained by trapping electrolysis of chlorine with an aqueous solution of a reducing agent. As a reducing agent, you can use ammonium salt, hydrazine, urea, etc.

The technical result is also achieved by the fact that the carbon dioxide formed during the calcination of magnesia carbon dioxide is used in the technological processes claimed to implement the method.

Thus, according to the proposed method, not only commercial products are obtained: chlorine, calcium carbonate, magnesium oxide, bischofite, bromine and lithium carbonate, but also the necessary reagents for implementing the method.

Distinctive features of the method of processing brines of calcium chloride and magnesium chloride types are:

1) expanding the range of products against the prototype method, namely obtaining scarce chlorine used both in the implementation of the method and in the form of commercial liquefied chlorine;

2) obtaining reagents for the implementation of a number of technological processes: soda and soda-alkaline solution, hydrochloric acid, carbon dioxide, condensate of water vapor formed during the evaporation of intermediate solutions;

3) the possibility of using options with different contents of CaCl ₂ in the brine: co-precipitation of calcium and magnesium in the form of calcium carbonate and magnesium hydroxide with large amounts of calcium chloride in the initial brine (option) or separate precipitation of calcium carbonate, magnesia carbon dioxide with small amounts of calcium chloride in source brine (option);

4) the ability to disseminate technology for the processing of any highly mineralized brines of calcium chloride, magnesium chloride and mixed types (for example, for bischofite brines of the Volgograd deposits).

All processes of the proposed technology are announced for the first time. The method of complex processing of any type of brines is waste-free and practically does not require commercial reagents, while the initial brine is processed completely.

List of drawings and tables

Figure 1. The technological scheme of the complex processing of natural brines of calcium chloride type to produce chlorine, calcium carbonate, magnesium oxide, bischofite, bromine and lithium carbonate.

Figure 2. Technological scheme of complex processing of natural brines of magnesium chloride type to produce chlorine, bischofite, magnesium oxide, lithium carbonate and calcium carbonate.

Figure 3. The compositions of the calcium chloride type brine of the Znamensky deposit (Irkutsk region) depending on the ambient temperature.

Figure 4. Compositions of brines of magnesium chloride type of the province of Qinghai (China) and the Volgograd deposit (Russia).

Information confirming the possibility of implementing the method of complex processing of natural brines of calcium chloride and magnesium chloride types are given in examples 1-4.

Example 1. Verification of the implementation of the method according to the scheme shown in figure 1, was carried out on brines of calcium chloride type Znamensky field. The compositions of the brine and bottom sediment CaCl ₂ · 6H ₂ About are shown in table 1 (figure 3).

The initial brine (V = 1 m ³ ) is slowly fed with a precipitating agent - catholyte after partial carbonization (V = 4 m ³ ) of the following composition: Na ₂ CO ₃ - 100 kg / m ³ ; NaOH - 25 kg / m ³ and NaCl - 100 kg / m ³ (see example 2). After 15-20 minutes of stirring the reaction mixture, the collective precipitate of calcium carbonate and magnesium hydroxide is separated from the solution, washed with demineralized water (condensate) at W: T = 2 and squeezed on the filter. Received 280 kg of CaCO ₃ (the degree of extraction is 95%) and 69 kg of Mg (OH) ₂ (the degree of extraction is 98%). The mother liquor (V = 5 m ³ ) contains 180 kg / m ³ NaCl, as well as lithium chloride and bromide ion. The mother liquor is evaporated 7.5 times to a volume of 0.65 m ³ , the precipitated NaCl crystals are separated from the solution and used to obtain a concentrated NaCl solution supplied to the electrolysis.

One stripped off solution is used to extract bromine. For this, the bromide ion is oxidized with chlorine obtained by electrolysis of NaCl (see example 2), and elemental bromine is desorbed with water vapor. The steam-bromine mixture is condensed in a separation vessel and liquid bromine is separated (8.9 kg, the degree of bromine recovery is 96%). The brine after desorption of bromine is used to isolate lithium. To this end, it is added to a volume of 0.13 m ³ , NaCl crystals are separated, the resulting solution is purified from magnesium and calcium impurities by catholyte. Precipitation of Li ₂ CO _{3 is} carried out with a saturated soda solution (concentration 260 kg / m ³ ). The obtained precipitate of lithium carbonate is separated from the solution, washed with a triple amount of water to a residual content of Na in its composition of 0.2 wt.%, Which corresponds to the brand "technical Li ₂ CO ₃ ".

Example 2. NaCl crystals formed as a result of evaporation of the mother liquor after precipitation of the collective precipitate CaCO ₃ + Mg (OH) ₂ and as a result of the evaporation of the solution to isolate Li ₂ CO ₃ , as well as the solution after obtaining magnesia from carbon dioxide from MgCl ₂ solution (see example 3) served in the reactor for purification from impurities of magnesium and calcium (the content of magnesium and calcium in crystals of NaCl is 0.07 and 0.3 wt.%, respectively). To dissolve NaCl use demineralized water (condensate) to obtain a NaCl solution with a concentration of 225-250 kg / m ³ . The electrolysis of a NaCl solution (~ 4 m ³ ) gives chlorine and catholyte of the following composition (kg / m ³ ): NaOH - 100 and NaCl - 100. The resulting catholyte is subjected to carbonization by 75%, resulting in a partially carbonized catholyte composition (kg / m ³ ): Na ₂ CO ₃ - 100; NaOH - 25; NaCl - 100. For carbonization catholyte used balloon carbon dioxide - CO _2. In industrial conditions to be used for carbonization circulating CO _2; obtained by calcining magnesia with carbon dioxide (see example 3) and burning fuel.

Example 3. A collective precipitate of CaCO ₃ and Mg (OH) ₂ ~ 350 kg is subjected to pulping in a solution of calcium chloride at W: T = 4. To obtain a solution of CaCl ₂ precipitate of crystalline hydrate (300 kg) - CaCl ₂ · 6H ₂ O (mixed with MgCl ₂ · 6H ₂ O), dissolved in water. The content of calcium chloride, equal to 135 kg, corresponds to the stoichiometry of the formation of MgCl ₂ from Mg (OH) ₂ during pulp carbonization:

As a result of the reaction, an additional amount of CaCO ₃ (120 kg) and a 1.4 m ³ solution of magnesium chloride with a concentration of MgCl _{2 of} 90 kg / m ^{3 are formed} . Part of the solution (1/4) was evaporated to crystallize bischofite — MgCl ₂ · 6H ₂ O (~ 67 kg). The main part of the solution (1.05 m ³ ) is used to precipitate magnesia with carbon dioxide by carbonized catholyte:

The precipitate was separated, the mother liquor containing 115 kg of NaCl was returned to the electrolysis stage. The resulting magnesium carbonate (90 kg) is calcined at a temperature of 900 ° C to obtain 38 kg of MgO.

Thus, from a collective precipitate isolated from 1 m brine of calcium chloride type and 300 kg of crystalline hydrate CaCl ₂ · 6H ₂ O receive (kg): CaCO ₃ - 400; MgO - 38; MgCl ₂ · 6H ₂ O - 67; Br ₂ - 8.9; Li ₂ CO ₃ - 2.0; Cl ₂ - 350.

Example 4. Verification of the implementation of the method according to the scheme shown in figure 2, was carried out on brines of magnesium chloride type, simulating the composition of brines in the deposits of Qinghai province, China (figure 4, table 2).

Natural brine, along with MgCl ₂ , contains insignificant amounts of calcium chloride (0.97 kg / m ³ ), so it is purified before magnesium is precipitated. A saturated soda solution (~ 1 kg Na ₂ CO ₃ ) is introduced into the model starting brine (v = 1 m ³ ) to remove calcium, and the precipitate is separated. Then, for the precipitation of magnesia by carbon dioxide according to reaction 2 shown in example 3, carbonized catholyte is introduced (V = 3.2 m ³ ). The precipitate is separated and washed (320 kg of the precipitate are washed with 1 m ^{3 of} water, W: T = 3). The mother liquor containing 864 kg of NaCl is evaporated to a volume of 0.35 m ³ . From 760 kg of NaCl crystals obtained by evaporation of the solution, a solution is prepared and sent to electrolysis.

From an evaporated NaCl solution, lithium carbonate is precipitated with carbonized catholyte, 4.1 kg of Li ₂ CO ₃ are obtained, while the degree of lithium extraction is 80%. The bulk of carbon dioxide magnesia in an amount of 240 kg (75% of the weight of the precipitate) is calcined at 900 ° C to obtain 105 kg of MgO.

The rest of the magnesia carbon dioxide (80 kg) is dissolved in hydrochloric acid to obtain a solution of MgCl ₂ , from which bischofite (about 180 kg MgCl ₂ · 6H ₂ O) is then isolated by evaporation:

Hydrochloric acid is obtained by capturing chlorine with a solution of a reducing agent - an aqueous solution of urea. For these purposes, about 20% of the chlorine obtained from the electrolysis of NaCl is used.

Thus, in the processing of a brine of magnesium chloride type obtained (kg): MgO - 105; MgCl ₂ · 6H ₂ O - 180; Cl ₂ - 200; HCl - 60; Li ₂ CO ₃ - 4.1.

A method of processing brines of magnesium chloride type can be extended to brines of the Volgograd field that do not contain lithium. In this case, magnesium products, chlorine, hydrochloric acid are obtained.

Industrial application

The proposed method of complex processing of brines of calcium chloride type allows you to get a wide range of marketable products: chlorine, salts of calcium and magnesium, magnesium oxide, bromine, lithium carbonate. Brines of this type are a new, previously unused source of chlorine. Calcium chloride type feedstock is widespread within the Siberian platform.

In the north-west of the People's Republic of China (Qinghai Province), magnesium chloride type brines containing lithium chloride are common. From the brines of the magnesium chloride type according to the proposed technology, chlorine, magnesium oxide, bischofite and lithium carbonate are obtained.

In contrast to the known methods for processing calcium chloride type brines (obtaining magnesium oxide - RF patent No. 2211803; calcium chloride - RF patent No. 2284298; bromine - RF patent No. 2171862; bischofite - RF patent No. 2051865; lithium compounds - RF patents No. No. 2050330, 2193008, 2196735) in the proposed method uses new techniques based on the use of reagents obtained by electrolysis of sodium chloride produced from the same raw materials. Chlorine, catholyte (NaOH + NaCl solution), hydrochloric acid obtained from chlorine, carbonate-alkaline solutions obtained from catholyte by its carbonization are used as reagents. All operations are based on precipitation methods, taking into account local climatic conditions and regional characteristics.

The brine field is usually accompanied by gas condensate deposits. This will allow the construction of a processing brine plant to use the infrastructure common with the gas producer, as well as produced natural gas for the needs of the enterprise (for evaporation and calcination operations). All this allows us to conclude about the industrial utility of the proposed method.

Information Sources Used

1. N.S. Frumina, N.F. Lysenko, Chernova M.A. Chlorine. - M .: Science-1983.

2. RF patent No. 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. 20.01.08. Bull.№2.

3. RF patent No. 2108963 from 04/03/95. The method of producing bromine. / A.G. Vakhromeev, L.F. Volodchenko, A.G. Zhilina, A.I. Ovchinnikova. Publ. 04/20/98. Bull. No. 11.

4. T.K. Akchurin, S.A. Ananyina, I.I. Nikitina Prospects for development and bischofite processing technology of the Volgograd deposits - Volgograd, VolgGASA - 1995 - P.195.

5. RF patent No. 2211803 dated 06/26/01. A method of producing magnesium oxide from natural brines. / A.D. Ryabtsev, A.G. Vakhromeev, L.T. Menzherez and others Publ. 09/10/03. Bull. Number 25.

6. RF patent No. 2051865 from 08.20.92. The method of obtaining bischofite. / N.P. Kotsupalo, V.D. Belykh. Publ. 01/10/96. Bull. No. 1.

7. RF patent No. 2171227 of 02.25.02. A method of obtaining a chemically precipitated chalk. / A.V. Belkin, N.N. Falkovsky, I.Yu. Ilatovsky. Publ. 07/27/01. Bull.№21.

8. RF patent No. 2284298 from 12.30.04. A method of producing granular calcium chloride in the complex processing of natural brines / A.D. Ryabtsev, N.P. Kotsupalo, L.T. Menzherez and others Publ. 09/27/06. Bull.№27 (prototype).

Claims (4)

1. The method of complex processing of natural brines of calcium chloride and magnesium chloride types, including the production of magnesium oxide and chloride, as well as bromine and lithium carbonate, characterized in that the brine is first precipitated together with calcium carbonate and magnesium hydroxide, while obtaining a mother liquor containing sodium chloride, which is subjected to evaporation to isolate crystals of sodium chloride, the crystals are separated, dissolved in water to obtain a concentrated solution of sodium chloride, which Rye is electrolyzed to produce gaseous chlorine and a catholyte-sodium hydroxide solution; chlorine gas is used to oxidize bromide ions contained in an evaporated solution, followed by desorption of elemental bromine; catholyte after carbonization with carbon dioxide and obtaining a solution of carbonate and sodium hydroxide is used to precipitate calcium carbonate and magnesium hydroxide; the precipitate is repulped in a solution of calcium chloride and subjected to carbonization to obtain calcium carbonate and a solution of magnesium chloride, the precipitate is separated off, magnesium carbonate is precipitated from a portion of the magnesium chloride solution with a solution of carbonate and sodium hydroxide, which is then calcined to obtain magnesium oxide and carbon dioxide; another part of the magnesium chloride solution is evaporated to crystallize bischofite; from the solution after separation of the crystals of sodium chloride, lithium carbonate is precipitated with the solution after carbonization of catholyte. 2. A method of complex processing of natural brines of calcium chloride and magnesium chloride types, including the production of magnesium oxide and chloride, as well as lithium carbonate, characterized in that calcium carbonate is separately precipitated from the brine, and then carbon magnesia, while obtaining a mother liquor containing sodium chloride , which is subjected to evaporation to isolate crystals of sodium chloride, the crystals are separated, dissolved in water to obtain a concentrated solution of sodium chloride, which is subjected to elec trolysis to obtain gaseous chlorine and catholyte-sodium hydroxide solution; chlorine gas is used to produce hydrochloric acid, and catholyte after carbonation with carbon dioxide and a solution of carbonate and sodium hydroxide is used to precipitate magnesia from carbon dioxide, part of which is calcined to produce magnesium oxide; another part of magnesia is dissolved in hydrochloric acid to obtain a solution of magnesium chloride, followed by crystallization of bischofite; the solution after separation of the crystals of sodium chloride is used to precipitate lithium carbonate solution after carbonization of catholyte. 3. The method according to claim 2, characterized in that hydrochloric acid for producing magnesium chloride is obtained by trapping gaseous chlorine with an aqueous solution of a reducing agent — a carbon ammonium salt, or hydrazine, or urea. 4. The method according to claims 1 and 2, characterized in that the carbon dioxide formed during the calcination of magnesia with carbon dioxide is used for carbonization of catholyte.

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