CN106745095B - Utilize saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate - Google Patents

Abstract

The invention discloses a method for producing soda ash and co-producing gypsum and basic magnesium carbonate by using mirabilite and dolomite as raw materials. Integrating into the same reaction system, soda ash is produced under low voltage, normal temperature and pressure, and an optimized process plan is designed according to the huge difference in the solubility of precipitates produced by the combination of calcium and magnesium ions and different anions, so that the by-products in the soda production process can be transformed into It is a high value-added product that does not produce any three wastes in the process of preparing soda ash, gypsum, and basic magnesium carbonate. The invention solves the problems of unutilized chloride ions and low utilization rate of sodium ions in the preparation of soda ash by traditional chemical methods, realizes the production of soda ash with low energy consumption and high efficiency, and provides a brand-new method for the preparation of soda ash by chemical methods, overcoming The problems of high energy consumption, large environmental pollution, low efficiency and low added value of by-products existing in the soda ash preparation method in the prior art are solved.

Description

Method for producing soda ash and co-producing gypsum and basic magnesium carbonate by using mirabilite and dolomite

technical field

The invention relates to a method for preparing soda ash by using sodium sulfate as a source of sodium ions, in particular to a method for preparing soda ash and co-producing gypsum and basic magnesium carbonate by using sodium sulfate and dolomite as raw materials.

Background technique

Soda ash is one of the most important basic chemical raw materials, known as the "mother of chemical industry", its output and consumption are usually used as one of the indicators to measure a country's industrial development level. Soda ash is widely used in the construction field, chemical industry, metallurgical industry, printing and dyeing industry, leather industry, daily chemical field, and food industry. The glass industry in the construction field is the largest consumer sector of soda ash, consuming 0.2 tons of soda ash per ton of glass. In the chemical industry, it is used to make sodium silicate, sodium dichromate, sodium nitrate, sodium fluoride, baking soda, borax, and trisodium phosphate. In the metallurgical industry, it is used as a smelting flux, a flotation agent for ore dressing, and a desulfurizer in steelmaking and antimony smelting. Used as water softener in printing and dyeing industry. In the tanning industry, it is used for degreasing raw hides, neutralizing chrome tanned leather and increasing the alkalinity of chrome liquid. It is also used in the production of synthetic detergent additive sodium tripolyphosphate and other sodium phosphate salts. Food grade soda ash is used in the production of monosodium glutamate, pasta and so on.

Since 2001, China's soda ash consumption has been increasing year by year, indicating that China's soda ash demand still has great potential. With the growth of consumption and export, the production of soda ash is also increasing further.

The source of trona minerals in nature is lower than the market demand, and the index control of chloride content in the trona method seriously affects its development, so the trona method is not a long-term stable soda production process. At present, the industrial methods of producing soda ash at home and abroad mainly include the trona method, the Solvay soda method, and the Hou's soda method, and the Solvay soda method with a history of more than 140 years is still the most important chemical method in the world today. alkaline method. Since the Solvay soda production has taken the competitive advantage for more than 100 years, although people have made many attempts, there is no other chemical soda production method that can compete with the Solvay soda production method, but its inherent raw material utilization rate is low, The disadvantage of a large amount of waste liquid discharge still cannot be overcome. The energy consumption of producing soda ash is about 9.3GJ/t～13.6GJ/t, and the energy is mainly obtained by burning coal, which leads to a large amount of _CO2 emission, and the utilization rate of raw materials is low, and the utilization rate of raw material sodium is only about 75%, chlorine The ion utilization rate is 0%, and 10m ³ of waste liquid will be discharged for every 1t of soda ash produced. Hou's soda production method is an improvement made by famous Chinese chemists on the basis of Solvay's soda production method. This method increases the utilization rate of raw material sodium to more than 96%, but this method needs to build a synthetic ammonia plant (with greater energy consumption) or from Ammonia factories purchase raw materials at high cost. Hou's soda production method has great disadvantages in terms of economic cost.

According to my country's "13th Five-Year Plan", during the "13th Five-Year Plan" period (2016-2021), the soda ash industry will focus on energy conservation and emission reduction, and will focus on promoting 22 energy-saving technologies throughout the industry. Ecological and environmental protection level, promote industrial transformation and upgrading. The 22 energy-saving and emission-reduction technologies summarized by the industry association mainly include four aspects: general energy-saving technology for the soda ash industry, energy-saving technology for ammonia-soda method, energy-saving technology for combined soda method and energy-saving technology for trona. Among these 22 technologies, two core technologies are currently being promoted, which are the energy-saving technology of the horizontal belt alkali filtration series and the energy-saving technology of the powder flow caustic soda. But in fact, these 22 technologies were improved on the basis of the original Solvay soda production method and Hou's soda production method, and failed to touch the fundamental problems of energy saving and pollution.

Contents of the invention

Aiming at the deficiencies and current situation of the used soda production method in the existing industry, the purpose of the present invention is to propose a new soda production technology——utilize Glauber's salt and dolomite to produce soda ash and co-produce gypsum and basic magnesium carbonate. It overcomes the problems of high energy consumption, high waste discharge in the production process, high production cost, and low utilization rate of raw materials in the existing soda production technology, and at the same time efficiently utilizes calcium and magnesium resources in dolomite.

The basic idea of the present invention is to realize the separation of products while promoting the reaction through membrane electrolysis, integrate multiple reaction processes into the same reaction system, and produce soda ash at low voltage, normal temperature and pressure, and simultaneously combine calcium and magnesium ions with different anions Combined with the huge difference in the solubility of precipitates, an optimized process scheme is designed to transform the by-products in the soda-making process into high-value-added products, and no three wastes are produced in the process of preparing soda ash, gypsum, and basic magnesium carbonate.

For above-mentioned purpose, the method that utilizes Glauber's salt and dolomite to produce soda ash co-production gypsum and basic magnesium carbonate provided by the invention mainly comprises the following steps:

(1) Place the cation exchange membrane in the electrolytic cell, divide the electrolytic cell into an anode area and a cathode area, add a sodium salt solution in the anode area as the anolyte and be a reaction raw material, and add a saturated sodium bicarbonate solution in the cathode area as the cathode Electrolyte, apply a direct current between the anode electrode and the cathode electrode, the hydrogen ions ionized by the bicarbonate in the catholyte are reduced to hydrogen gas on the cathode electrode and generate carbonate in the catholyte, while the anolyte The free-flowing sodium ions in the medium pass through the cation exchange membrane under the action of current to reach the cathode area and combine with the carbonate in the catholyte to form sodium carbonate to obtain a sodium carbonate solution. The hydrogen ions generated by hydrogen oxidation on the anode electrode are combined with the anolyte The acidic solution generated by the combination of sodium salt anions;

(2) When the hydrogen ions in the solution in the anode area rise to the set concentration, export the solution in the anode area, add dolomite to react, the reaction generates a mixed solution containing calcium salt and magnesium salt while releasing carbon dioxide, and then add Glauber's salt to react , when the calcium salt in the mixed solution is converted into sodium salt, the product calcium sulfate precipitate is generated, the calcium carbonate precipitate is filtered and dried to obtain the product gypsum, and the filtrate is mixed with the sodium carbonate solution in the cathode area in part of step (1) , when the magnesium salt is converted into a sodium salt, the product magnesium carbonate precipitate is generated, and the magnesium carbonate precipitate is cooled, filtered, and dried to obtain a powder basic magnesium carbonate product, and the filtrate is converted into a solution rich in sodium salt and circulated back to the anode area;

(3) a part of the sodium carbonate solution generated in the cathode area in step (1) is used for the preparation of basic magnesium carbonate in the step (2), and the remaining sodium carbonate solution is pumped into the carbon dioxide absorption tower, and the sodium carbonate in the solution is blown into The carbon dioxide in the carbon dioxide absorption tower reacts to obtain a saturated sodium bicarbonate solution while producing sodium bicarbonate crystals. After filtration, the filtrate is circulated back to the cathode area, and the sodium bicarbonate crystals are calcined to produce soda ash.

In the above embodiment, the sodium salt solution added to the anode area in step (1) is a sodium salt solution, preferably a sodium salt solution with a sodium salt concentration of 0.1mol/L to 10mol/L; the anion of the sodium salt can be It is an organic acid ion or an inorganic acid ion, that is, one of formate ion, acetate ion, oxalate ion, chloride ion, sulfate ion, nitrate ion and the like.

In the above embodiment, the thenardite in step (2) can be a natural mineral thenardite or an industrial product; the thenardite is preferably added in the form of an aqueous solution with a sodium sulfate concentration of 0.1 mol/L to 10 mol/L.

In the above embodiment, the particle size of the dolomite in step (2) is generally controlled to be greater than 10 mesh, preferably within the range of 10-500 mesh.

In the above embodiment, the source of the carbon dioxide blown into the carbon dioxide absorption tower described in step (3) is preferably provided by the carbon dioxide generated by adding the acidic solution in the anode area to the dolomite reaction in step (2).

In the above embodiment, the anode electrode in step (1) is preferably a gas diffusion electrode. It is preferable to use the hydrogen generated by the cathode as the source of hydrogen for the anode gas diffusion electrode. The hydrogen generated by the cathode electrode in step (1) is preferably passed through the hydrogen buffer tank to the anode electrode as a source of hydrogen after gas-liquid separation and drying.

In the above embodiment, the material of the cathode electrode in step (1) includes one of metal platinum, metal palladium and metal nickel.

In the present invention, the hydrogen generated by the cathode electrode is used as the hydrogen source of the anode electrode, and the carbon dioxide generated by the reaction of the acidic solution generated in the anode area and the dolomite is used as the carbon dioxide source of the carbon dioxide absorption tower, and then the mirabilite is reacted with the dolomite to produce soda ash and co-produce gypsum The total reaction with basic magnesium carbonate is as follows:

Na ₂ SO ₄ +CaMg(CO ₃ ) ₂ →CaSO ₄ +Na ₂ CO ₃ +4MgCO ₃ Mg(OH) ₂ 5H ₂ O

In the above-mentioned technical scheme, the process of utilizing mirabilite and dolomite to produce soda ash for co-production of gypsum and basic magnesium carbonate mainly includes the following several reaction processes:

1. Acid hydrolysis of dolomite:

CaMg(CO ₃ ) ₂ +HX→CaX+MgX+H ₂ O+CO ₂ ;

2. Add Glauber's salt to produce calcium carbonate precipitation:

CaX+ _{Na2SO4 →} CaSO4 ₊ NaX;

3. Preparation of precipitated basic magnesium carbonate:

MgX+Na ₂ CO ₃ → 4MgCO ₃ Mg(OH) ₂ 5H ₂ O+NaX;

4. Membrane electrolysis produces sodium carbonate:

Na ⁺ +OH ^- +NaHCO ₃ +H ₂ O→Na ₂ CO ₃ ;

5. Absorb _CO2 to produce supersaturated sodium bicarbonate:

Na ₂ CO ₃ +CO ₂ +H ₂ O→NaHCO ₃ ;

6. Calcination of sodium bicarbonate solid to produce soda ash:

NaHCO ₃ →Na ₂ CO ₃ +CO ₂ +H ₂ O

The present invention uses mirabilite and dolomite to produce soda ash and co-produces gypsum and basic magnesium carbonate. Electric energy is used as external energy to break the reaction balance. The cation exchange membrane separates the generated sodium carbonate solution from the acid solution, and at the same time utilizes cation exchange The membrane exchanges the sodium ions in the sodium salt NaX to the cathode area, so that the weakly acidic _CO2 is used to produce strongly acidic HX acid, and then the produced HX acid is used to react with dolomite to form a high-concentration Ca/Mg salt solution. Generate CO ₂ , and the generated CO ₂ is used as carbon source raw material for making soda ash. It solves the problems that the chlorine ions cannot be utilized and the utilization rate of the sodium ions is low when the traditional chemical method is used to prepare the soda ash. Under the condition of normal temperature and pressure, only 0.8V voltage is needed to carry out the reaction, which realizes the production of soda ash with low energy consumption and high efficiency, and provides a new method for solving the chemical method to prepare soda ash. These characteristics fundamentally solve the problems of high energy consumption and waste in the existing soda production industry, and meet the needs of the soda production industry in the "13th Five-Year Plan" at the current stage.

The method proposed by the present invention to produce soda ash and co-produce gypsum and basic magnesium carbonate by using mirabilite and dolomite has high added value of the product, simple process, low energy consumption, large output, short production cycle, and production energy consumption of 5.3GJ/t -7.7GJ/t, the utilization rate of raw material sodium is greater than 90%, and there is no discharge of waste liquid and waste residue. Compared with the traditional chemical method to produce soda ash, it has huge industrial application value. The co-produced gypsum of the present invention does not contain various impurities such as phosphorus and fluorine, has very high purity, can be directly used as building materials, and has high cost performance; the co-produced basic magnesium carbonate has a very high added value, and the market price is more than 3,000 yuan/ It can be used as a chemical coolant, as a raw material for preparing high-purity magnesia and magnesium salt series products, as an additive and improver for food and various chemical products, and can also be used for the manufacture of high-grade glass products, magnesium salt, pigments, paints and daily necessities. With chemicals etc.

The present invention uses dolomite and Glauber's salt as raw materials for preparation, and the source of raw materials is very rich. Dolomite is a carbonate mineral rich in calcium and magnesium with the chemical expression CaMg(CO ₃ ) ₂ . Dolomite is very rich in my country, and its ore reserves are more than 4 billion tons, mainly distributed in Shanxi, Shandong, Liaoning, Hunan, Hebei, Sichuan Basin, Tarim Basin and other regions. At present, the large-scale utilization of dolomite is very limited, so The price is low, about 200 yuan/ton.

Sodium sulfate decahydrate (Na ₂ SO ₄ ·10H ₂ O) is commonly known as Glauber's salt, anhydrous sodium sulfate is commonly known as Anhydrous Glauber's salt, and is often referred to as Glauber's salt in general. Glauber's salt is rich in mineral resources, and the proven reserves in China alone have reached 20 billion tons. According to the estimate of the United States Geological Survey, the total output of sodium sulfate in the world is about 6 million tons/a. However, the utilization methods of thenardite are very limited, which leads to the decline of the use of thenardite year by year. It is of great strategic and practical significance for the development of the national economy to strengthen the research on the comprehensive utilization of thenardite and explore ways to transform the resource advantages of thenardite into economic advantages.

The global annual consumption of soda ash is more than 30 million tons. If sodium sulfate is used as a source of sodium ions for the preparation of soda ash, it will find a broad way out for the utilization of mirabilite. Over the years, researchers at home and abroad have been exploring new ways of making soda from mirabilite. , according to literature statistics, there are as many as 20 or 30 patents for Glauber's salt soda production in China in recent years, but almost all of them focus on traditional methods and have not achieved substantial breakthroughs.

Gypsum has the characteristics of high whiteness, light weight, low thermal conductivity, non-flammability, moisture absorption, low shrinkage, and earthquake resistance. Therefore, it is widely used in building materials. Gypsum can be used for building decoration materials and sculpture materials; it can also be used for the production of raw materials for cementing materials, including building gypsum and anhydrous gypsum cementing materials, as well as high-strength gypsum, filler gypsum, and calcareous gypsum cementing materials; it can also be used for the production of plasterboard . At present, most of the gypsum used in construction is phosphogypsum. Phosphogypsum is a by-product mainly composed of CaSO ₄ ·nH ₂ O obtained from the reaction of phosphate rock and sulfuric acid in the production process of wet-process phosphoric acid. It contains various impurities such as phosphorus and fluorine. , which affects the performance of phosphogypsum, so that it cannot be directly applied to the production of gypsum building materials and high-end products, and must be pretreated, which increases the application cost. The gypsum co-produced by the method of the invention overcomes the disadvantages of phosphogypsum, is a by-product of soda ash production, and has low production cost.

The invention proposes a method for producing soda ash by using mirabilite and dolomite to co-produce gypsum and basic magnesium carbonate, which has great economic value and social value and can be used for soda ash production technology in industrial production.

It should be noted that for the present invention, in the preferred embodiment of the specific embodiment of the present invention, the types of the anode electrode and the cathode electrode are all in the form of including but not limited to, and those skilled in the art can use the embodiment according to actual needs. The anode and cathode electrodes that are not described in the above all belong to the protection scope of the present invention under the premise of conforming to the purpose of the content of the present invention. Moreover, those skilled in the art can modify the operating parameters such as power supply voltage, electrolyte concentration, heating, etc., as well as the distribution and shape of the cathode area and anode area of the electrolytic cell according to the existing technology of electrolysis and ion exchange membrane. Under the premise of the purpose of the content of the present invention, all belong to the protection scope of the present invention.

Except in the examples or where otherwise expressly stated, the numerical values used in the specification and claims are to be regarded as variable in all cases by the term "about". Accordingly, unless stated to the contrary, the numerical values set forth in the specification and claims are approximate values that may vary according to the desired properties of the present invention.

Description of drawings

Fig. 1 is the process flow chart of method embodiment 1, 2, 3 of the present invention.

Fig. 2 is a schematic diagram of the principle of the membrane electrolysis reaction process in the method embodiments 1, 2, and 3 of the present invention.

1-gas diffusion electrode (anode electrode), 2-cation exchange membrane, 3-cathode electrode, 4-hydrogen buffer tank, 5-carbon dioxide absorption tower.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the content of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1

The process and principle of this embodiment are shown in Figures 1 and 2. The electrolytic cell is divided into two areas, the anode area and the cathode area, by the cation exchange membrane 2 which only allows cations to pass through but prevents anions from passing through. Add 40ml of NaAc solution with a concentration of 3.2mol/L as the anolyte in the anode area, and add 120ml of saturated NaHCO solution with a concentration of _1.14mol /L in the cathode area as the electrolyte and simultaneously as the reaction raw material, load 400mA direct current. A gas diffusion electrode is used as the anode electrode 1 , and a metal nickel electrode is used as the cathode electrode 3 . Every 10 to 20 minutes, use a needle syringe to extract 0.5ml of anolyte to measure the concentration of hydrogen ions. When the concentration of hydrogen ions in the solution is higher than 3.168mol/L, take out the negative electrolyte and anolyte respectively. At this time, the anolyte is HAc solution with a concentration of 3.168mol/L, the catholyte is a mixed solution containing 0.08mol/L NaHCO ₃ and 1.06mol/L Na ₂ CO ₃ .

Gained 40ml anode acid solution is introduced into the acidolysis reactor and reacted with 500 mesh 24g dolomite for 1h, and the _CO produced by dissolving is introduced into the carbon dioxide buffer tank 4, and the solution is filtered to obtain 40ml of 0.79mol/L _Ca (Ac) and 0.79 mol/L Mg(Ac) ₂ mixed solution. The mixed solution was introduced into a reactor containing 4.4872 g of Glauber's salt, reacted under stirring at 300 rpm for 1 hour, and filtered. The filter cake was dried at 75°C and weighed 5.045 g (CaSO ₄ ·2H ₂ O, gypsum). The filtrate was further introduced into a reactor containing 3.35g Na ₂ CO ₃ , under strong stirring for 1 hour, settled for 1 hour, and filtered. The filter cake was dried at 75°C and weighed 3.07 g (4MgCO ₃ ·Mg(OH) ₂ ·5H ₂ O, basic magnesium carbonate). Now the obtained filtrate is tested and analyzed as can be seen, the solution is 35ml of NaAc solution with a concentration of 3.2mol/L. At this point, the solution was replenished to 40 ml and reinjected into the anode area of the electrolytic cell.

The solution obtained in the cathode area is passed into the carbon dioxide absorption tower 5, and the CO ₂ obtained by the acid hydrolysis of the dolomite from the anode solution is introduced into the absorption tower through the carbon dioxide buffer tank 4. After the absorption is completed, the turbid solution is separated by precipitation and filtration. After analysis, the obtained filtrate was 110 ml of saturated NaHCO ₃ with a concentration of 1.14 mol/L. After the filter cake was dried at 110°C and roasted at 370°C, XRD analysis showed that the filter cake was Na ₂ CO ₃ and weighed 6.72g. The resulting filtrate is replenished and returned to the cathode area of the electrolytic cell.

During the whole process, the efficiency of electrolysis, acid decomposition of dolomite, production of basic magnesium carbonate, and absorption of _CO2 are all above 97%, and the production efficiency of pure gypsum is above 95%.

Example 2

The technical process of this embodiment is shown in Figures 1 and 2. The electrolytic cell is divided into two areas, the anode area and the cathode area, by the cation exchange membrane 2 which only allows cations to pass through but prevents anions from passing through. Add 40ml of NaAc solution with a concentration of 1.6mol/L as the anolyte in the anode area, and add 60ml of saturated NaHCO solution with a concentration of _1.14mol /L in the cathode area as the electrolyte while serving as the reaction raw material, and load 400mA direct current. A gas diffusion electrode is used as the anode electrode 1 , and a metal nickel electrode is used as the cathode electrode 3 . Every 10 to 20 minutes, use a needle syringe to extract 0.5ml of anolyte to measure the concentration of hydrogen ions. When the concentration of hydrogen ions in the solution is higher than 1.52mol/L, take out the cathode and anode electrolytes respectively. At this time, the concentration of the anolyte is 1.52 mol/L HAc solution, the catholyte is a mixed solution containing 0.08mol/L NaHCO ₃ and 1.06mol/L Na ₂ CO ₃ .

The resulting 40ml anode acid solution is introduced into the acidolysis reactor and reacted with 500 mesh 24g dolomite for 1h, and the _CO produced by dissolving is introduced into the carbon dioxide buffer tank 4, and the solution is filtered to obtain 40ml of 0.38mol/L _Ca (Ac) and 0.38 mol/L Mg(Ac) ₂ mixed solution. This solution was introduced into a reactor containing 2.16 g of Glauber's salt, reacted under stirring at 300 rpm for 1 hour, and filtered. The filter cake was dried at 75°C and weighed 2.60 g (CaSO ₄ ·2H ₂ O, gypsum). The filtrate was further introduced into a reactor containing 1.34g Na ₂ CO ₃ , under strong stirring for 1 hour, settled for 1 hour, and filtered. The filter cake was dried at 75°C and weighed 1.53 g (4MgCO ₃ ·Mg(OH) ₂ ·5H ₂ O, basic magnesium carbonate). Now the obtained filtrate is tested and analyzed as can be seen, the solution is 35ml of NaAc solution with a concentration of 1.59mol/L. At this point, the solution was replenished to 40 ml and reinjected into the anode area of the electrolytic cell.

Pass the solution obtained from the cathode into the carbon dioxide absorption tower 5, and introduce the _CO2 obtained from the acid hydrolysis of the dolomite from the anode solution into the absorption tower through the carbon dioxide buffer tank 4. After the absorption is completed, the turbid solution is separated by precipitation and filtration. After analysis, the obtained filtrate was 110 ml of saturated NaHCO ₃ with a concentration of 1.14 mol/L. After the filter cake was dried at 110°C and roasted at 370°C, XRD analysis showed that the filter cake was Na ₂ CO ₃ and weighed 6.74g. The resulting filtrate is replenished and returned to the cathode area of the electrolytic cell.

During the whole process, the efficiency of electrolysis, acid hydrolysis of dolomite, production of basic magnesium carbonate, and absorption of _CO2 are all above 95%, and the production efficiency of pure gypsum is above 95%.

Example 3

The technical process of this embodiment is shown in Figures 1 and 2. The electrolytic cell is divided into two areas, the anode area and the cathode area, by the cation exchange membrane 2 which only allows cations to pass through but prevents anions from passing through. Add 40ml of NaCl solution with a concentration of 3.2mol/L in the anode area as the anolyte, and add 120ml of saturated NaHCO solution with a concentration of _1.14mol /L in the cathode area as the electrolyte and simultaneously as the reaction raw material, after loading 400mA direct current. A gas diffusion electrode is used as the anode electrode 1 , and a metal nickel electrode is used as the cathode electrode 3 . Use a needle syringe to extract 0.5ml of anolyte every 10 to 20 minutes to measure the concentration of hydrogen ions. When the concentration of hydrogen ions in the solution is higher than 3.168mol/L, take out the cathode and anode electrolytes respectively. At this time, the concentration of the anolyte is 3.168 mol/L HAc solution, the catholyte is a mixed solution containing 0.08mol/L NaHCO ₃ and 1.06mol/L Na ₂ CO ₃ .

Gained 40ml anode acid solution is introduced into the acidolysis reactor to react with 500 mesh 24g dolomite for 1h, and the _CO produced by dissolving is introduced into the carbon dioxide buffer tank 4, and the solution is filtered to obtain 40ml of 0.81mol/L _Ca (Ac) and 0.79 mol/L Mg(Ac) ₂ mixed solution. This solution was introduced into a reactor containing 4.4872 g of Glauber's salt, reacted under stirring at 300 rpm for 1 hour, and filtered. The filter cake was dried at 75°C and weighed 5.046 g (CaSO ₄ ·2H ₂ O, gypsum). The filtrate was further introduced into a reactor containing 3.35g Na ₂ CO ₃ , under strong stirring for 1 hour, settled for 1 hour, and filtered. The filter cake was dried at 75°C and weighed 3.07 g (4MgCO ₃ ·Mg(OH) ₂ ·5H ₂ O, basic magnesium carbonate). At this moment, the obtained filtrate was tested and analyzed, and the solution was 35 ml of NaCl solution with a concentration of 3.2 mol/L. At this point, the solution was replenished to 40 ml and reinjected into the anode area of the electrolytic cell.

Pass the solution obtained from the cathode into the carbon dioxide absorption tower 5, and introduce the _CO2 obtained from the acid hydrolysis of the dolomite from the anode solution into the absorption tower through the carbon dioxide buffer tank 4. After the absorption is completed, the turbid solution is separated by precipitation and filtration. After analysis, the obtained filtrate was 110 ml of saturated NaHCO ₃ with a concentration of 1.14 mol/L. The filter cake was dried at 110°C, and after roasting at 370°C, XRD analysis showed that the filter cake was Na ₂ CO ₃ and weighed 6.75g. The resulting filtrate is replenished and returned to the cathode area of the electrolytic cell.

During the whole process, the efficiency of electrolysis, acid decomposition of dolomite, production of basic magnesium carbonate, and absorption of _CO2 are all above 99%, and the production efficiency of pure gypsum is above 95%.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (10)

1. It is 1. a kind of using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, it is characterised in that main bag Include following steps：

   (1) cation-exchange membrane is placed in electrolytic cell, electrolytic cell is divided into anode region and cathodic region, sodium salt is added in anode region Solution is as anolyte and is reaction raw materials, and cathodic region adds saturated sodium bicarbonate solution as catholyte, in sun Apply direct current between pole electrode and cathode electrode, the hydrogen ion that the bicarbonate radical in catholyte ionizes out is in cathode electrode On be reduced to hydrogen and carbonate generated in catholyte, the sodium ion at the same time flowed freely in anolyte exists Cathodic region is reached through cation-exchange membrane under the function of current and generation sodium carbonate is combined with the carbonate in catholyte, obtain carbonic acid Sodium solution, the sodium salt anion binding generation in the hydrogen ion and anolyte of oxidation of hydrogen generation is acid on the anode electrode Solution；

   (2) anode region solution is exported after the hydrogen ion in the solution of anode region rises to setting concentration, adds dolomite and reacted, Reaction generates the mixed solution containing calcium salt and magnesium salts while carbon dioxide is discharged, and adds saltcake reaction afterwards, makes Calcium salt in mixed solution generates product calcium sulfate precipitation while being changed into sodium salt, calcium sulfate precipitation is filtered, drying obtains Product gypsum, filtrate and the sodium carbonate liquor in cathodic region in part steps (1) carry out hybrid reaction, are changed into sodium salt making magnesium salts While generate product carbonic acid magnesium precipitate, carbonic acid magnesium precipitate is through cooling, filtering, dry and obtain powder basic magnesium carbonate product, filter Liquid is changed into the solution rich in sodium salt and is recycled back into anode region；

   (3) the sodium carbonate liquor part generated cathodic region in step (1) is used for the preparation of basic magnesium carbonate in step (2),

   Remaining sodium carbonate liquor is pumped into carbon dioxide absorption tower, sodium carbonate in solution and blasts in carbon dioxide absorption tower Carbon dioxide reaction, obtain producing sodium acid carbonate crystallization while saturated sodium bicarbonate solution, filtrate cycle returns cloudy after filtering Soda ash is made in polar region, sodium acid carbonate crystallization after calcining.
2. 2. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：The sodium salt solution that step (1) middle-jiao yang, function of the spleen and stomach polar region adds is sodium-salt aqueous solution, and the concentration of sodium salt is 0.1mol/L ~10mol/L.
3. 3. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：The anion of the sodium salt be formate ion, acetate ion, oxalate denominationby, chlorion, sulfate radical from One kind in son, nitrate ion.
4. 4. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：Saltcake described in step (2) is natural minerals saltcake or industrial production product saltcake.
5. 5. it is according to claim 4 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：The saltcake is added using being configured to the aqueous solution of the sodium sulfate concentration as 0.1mol/L~10mol/L.
6. 6. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：The granularity of dolomite described in step (2) is 10~500 mesh.
7. 7. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：The carbon dioxide that carbon dioxide absorption tower is blasted in step (3) adds anode region acid by dolomite in step (2) Property solution reaction is generated.
8. 8. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：Anode electrode described in step (1) is gas-diffusion electrode.
9. 9. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：Hydrogen caused by cathode electrode passes through hydrogen gas buffer after gas-liquid separation and drying described in step (1) Anode electrode is passed through as hydrogen source.
10. 10. it is according to claim 1 using saltcake and the method for dolomite preparing soda coproduction gypsum and basic magnesium carbonate, It is characterized in that：The material of cathode electrode described in step (1) is one kind in metal platinum, Metal Palladium and metallic nickel.