CN102001693B - Process for preparing light magnesium oxide and calcium carbonate powder by utilizing dolomite acid method - Google Patents

Abstract

The invention discloses a process for preparing light magnesium oxide and calcium carbonate powder by dolomite acid method. Dolomite is crushed and ground into powder; it is dissolved in hydrochloric acid to make a solution whose main components are MgCl ₂ and CaCl ₂ ; after adjusting the pH value, Fe ³⁺ and Al ³⁺ ions in the solution are removed to make it pure MgCl ₂ and CaCl ₂ solution; react with ammonia gas to convert Mg ²⁺ into Mg(OH) ₂ precipitation, then filter, wash, dry, and calcinate to obtain light magnesium oxide powder; the filtrate is passed through ammonia , carbonization, to generate calcium carbonate crystals, and dry to make light calcium carbonate powder. The invention has reasonable design, low energy consumption, the purity of the prepared light magnesium oxide and calcium carbonate is above 98%, and the utilization rate of dolomite resources is above 95%, which is worthy of popularization and implementation.

Description

Preparation of Light Magnesium Oxide and Calcium Carbonate Powder by Dolomite Acid Method

technical field

The invention relates to a process for preparing light magnesium oxide and calcium carbonate powder by dolomite acid method.

Background technique

Dolomite is a relatively common carbonate rock, the main mineral component is dolomite. The proven dolomite resources in the world are more than 50 billion tons, and the high-quality dolomite reserves in China exceed 4 billion tons, which are distributed in Liaoning, Hebei, Shanxi, Sichuan, Hunan, Hubei, Henan, Shaanxi, Jilin, Jiangsu and other provinces district.

Light magnesia is an important industrial inorganic salt product, which can be used in the manufacture of ceramics, enamel, refractory crucibles and refractory bricks, etc. as a filler for polishing agents, adhesives, paints and paper; it is also used in glass, dyes, phenolic plastics and other industries. Therefore, light magnesium oxide is one of the most important and widely used products in the magnesium compound series.

Light calcium carbonate is also an important inorganic filler, widely used in rubber, plastics, coatings, papermaking, construction and other industries. The demand for light calcium carbonate in my country is large, and the product requires high quality.

At present, the utilization of dolomite in my country is concentrated in metallurgy, chemical industry, building materials and agriculture industries. Disadvantages such as high energy consumption, certain environmental pollution, and large waste discharge.

Contents of the invention

The object of the present invention is to provide a kind of technology that dolomite acid method prepares light magnesia and calcium carbonate powder. The invention makes full use of magnesium oxide and calcium oxide in dolomite to prepare high value-added products. The process has low energy consumption and is convenient for implementation and popularization.

To achieve the above object, the present invention takes the following technical solutions:

A kind of technology that dolomite acid method prepares light magnesia and calcium carbonate powder, adopts dolomite as raw material, comprises following preparation process:

(1), raw material pretreatment process: dolomite is crushed and ball-milled into dolomite powder;

(2) Dolomite acid-dissolving process: according to the molar ratio of HCl and dolomite being 2 to 2.1, dolomite powder is added to a hydrochloric acid solution with a mass percentage of 25% to 30% for dissolution, and after filtration, Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ , Fe ²⁺ and Cl ^- plasma solution, wherein the concentration of Ca ²⁺ and Mg ²⁺ is 1~2mol/L;

(3), impurity removal process: In the solution containing Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ , Fe ²⁺ and Cl ^- plasma obtained in step (2), the molar ratio of Fe ²⁺ and NaClO Ratio is 1: (2～4) add NaClO solution, pass into ammonia gas then, adjust pH value to be 5～7, after filtering, the filtrate that obtains is pure solution that contains MgCl ₂ and CaCl ₂ , and filter cake is Fe( OH) ₃ and Al(OH) ₃ are precipitated and discharged as solid waste;

(4), in the magnesium precipitation process by ammonia method: feed ammonia gas into the pure solution containing MgCl ₂ and CaCl ₂ , react at 40-70° C. for 1-3 h, wherein the molar ratio of ammonia gas to _MgCl is ( 2.5～3): 1, then filtered, the filter cake was washed and dried to obtain magnesium hydroxide precipitate; the filtrate was a solution containing NH ₄ ⁺ , Ca ²⁺ , Mg ²⁺ , Cl ^- and OH ^- ;

(5) Magnesium hydroxide calcining process: calcining the dried magnesium hydroxide at 600-800°C for 1-2 hours to obtain light magnesium oxide products;

(6) Calcium carbonate powder production process: inject ammonia gas into the solution containing NH ₄ ⁺ , Ca ²⁺ , Mg ²⁺ , Cl ^- , OH ^- at room temperature, keep the pH of the solution ≥ 7.5, and then use volume The CO ₂ with a percentage greater than 40% is carbonized, and the carbonization time is 45 to 90 minutes. The filter cake after filtration is precipitated by calcium carbonate, and then washed and dried to obtain light calcium carbonate powder products.

In the process of preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention, in the step

In (1), crushing and ball milling into a dolomite powder below 200 mesh, that is, the particle size of the dolomite powder is less than 74 μm.

In the process of preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention, in the step

In (6), the filtered filtrate is an ammonium chloride solution containing a small amount of calcium and magnesium ions, which is concentrated into ammonium chloride crystals by evaporation, and the ammonium chloride crystals are decomposed to obtain hydrogen chloride and ammonia gas, wherein the hydrogen chloride returns to the step

Recycling in the dolomite acid-dissolution process of (2); In the calcium carbonate powder production process of the ammonia method magnesium precipitation process and/or step (6) in the impurity-removing process of step (3) and step (4), the ammonia is returned Recycling.

The advantages of the present invention are:

The process design of the preparation of light magnesium oxide and calcium carbonate powder by the dolomite acid method of the present invention is reasonable, the energy consumption is low, the purity of the prepared light magnesium oxide and calcium carbonate is more than 98%, and the utilization rate of dolomite resources is greater than 95%. %, it is worth promoting and implementing.

Description of drawings

Fig. 1 is the process flow diagram of the preparation of light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention.

Detailed ways

The process for preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention uses dolomite as raw material, and the production process includes raw material pretreatment, dolomite acid dissolution, impurity removal, ammonia precipitation of magnesium, and magnesium hydroxide calcination and calcium carbonate preparation process.

After the dolomite is crushed and ball-milled, it is added into a hydrochloric acid solution with a mass fraction of 25% to 30% to dissolve. Take the supernatant, add a small amount of NaClO solution, then pass through ammonia gas to adjust the pH value between 5 and 7, and filter to obtain pure MgCl ₂ and CaCl ₂ solutions. Then feed ammonia gas into it, react for 1 to 3 hours, filter, filter cake, wash and dry to obtain magnesium hydroxide precipitate; the precipitate is calcined to obtain light magnesium oxide powder product; the filtrate is passed through ammonia gas, carbonized, filtered, After washing and drying, a light calcium carbonate powder product is obtained.

In the process of preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention, in the raw material pretreatment process, after the dolomite is crushed, it is ball-milled to below 200 mesh, that is, the particle size of the dolomite powder is The diameter is less than 74 μm.

In the process of preparing light magnesia and calcium carbonate powder by dolomite acid method of the present invention, in the described dolomite acid dissolution process, dolomite powder is added to the hydrochloric acid solution with a mass fraction of 25% to 30% Dissolve and filter to obtain a solution containing Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ , Fe ²⁺ , Cl ^- and other ions. The solution enters the impurity removal process.

In the technique for preparing light magnesia and calcium carbonate powder by dolomite acid method of the present invention, described impurity removal operation comprises adding NaClO solution by Fe ²⁺ and NaClO molar ratio is 1: (2～4), then Infuse ammonia gas to adjust the pH value between 5 and 7, and obtain pure MgCl ₂ and CaCl ₂ solutions through filtration. The solution enters the ammonia magnesium precipitation process.

In the process of preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention, in the described magnesium precipitation process by ammonia method, the concentration of Ca ²⁺ and Mg ²⁺ in the solution is 1-2 mol/L. Ammonia gas was introduced into it, reacted at 40-70°C for 1-3 hours, and then filtered, the filter cake was washed and dried to obtain magnesium hydroxide precipitate; the filtrate contained NH ₄ ⁺ , Ca ²⁺ , Mg ²⁺ , Cl ^- , OH ^- solution, enter the calcium carbonate preparation process.

In the process of preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention, in the magnesium hydroxide calcining process, the magnesium hydroxide precipitate is calcined at 600-800°C for 1-2 hours to obtain Light magnesium oxide powder products.

In the process for preparing light magnesia and calcium carbonate powder by dolomite acid method of the present invention, the calcium carbonate production process includes passing the calcium-containing solution into ammonia gas and CO with a volume fraction greater than 40% at room temperature. _2. Get calcium carbonate precipitate, then wash and dry to get light calcium carbonate powder product.

In the process of preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention, the remaining filtrate is ammonium chloride solution containing a small amount of calcium and magnesium ions, which can be concentrated into ammonium chloride crystals by evaporation. Ammonium chloride crystals can be decomposed to produce hydrogen chloride and ammonia, which are returned to the acid hydrolysis process for recycling.

The process for preparing light magnesium oxide and calcium carbonate powder by dolomite acid method of the present invention mainly includes raw material pretreatment, dolomite acid dissolution, impurity removal, ammonia precipitation of magnesium, magnesium hydroxide calcining and calcium carbonate preparation processes. Its basic technological process is shown in Figure 1. As shown in Figure 1, dolomite powder is added to hydrochloric acid to dissolve, and the filtrate obtained after filtration is a solution containing Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ , Cl ^- , etc.; the filter cake is a small amount of residue. In a solution containing Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ , Cl ^-, etc., add NaClO and feed NH ₃ , after filtration, the obtained filter cake contains Fe(OH) ₃ and Al(OH) ) ₃ waste residue; the filtrate is a solution containing Ca ²⁺ , Mg ²⁺ , and Cl ^- . Pass NH ₃ into the solution containing Ca ²⁺ , Mg ²⁺ , and Cl ^- , and after filtration, the filter cake is precipitated as Mg(OH) ₂ ; the filtrate is a solution containing Ca ²⁺ , Cl ^- , NH ₄ ⁺ , OH ^- . Mg(OH) ₂ is precipitated and calcined to obtain magnesium oxide powder and H ₂ O; NH ₃ is introduced into the solution containing Ca ²⁺ , Cl ^- , NH ₄ ⁺ , OH ^- , carbonized with CO ₂ and filtered to obtain carbonic acid Calcium powder and NH ₄ Cl solution.

Experimental raw material: a dolomite ore sample (LD-09) from a certain origin, the chemical composition analysis results are shown in Table 1.

The chemical composition analysis result (w _B /%) of table 1 dolomite ore (LD-09)

(1) Dolomite is ball-milled and sieved to a particle size of <74μm, weighed 100g, and dissolved in 268g of 30% hydrochloric acid solution to obtain Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ^{3 +} , Fe ²⁺ , Cl ^- plasma solution and a small amount of waste residue. X-ray powder diffraction analysis results show that the main phase of the waste residue is silicon dioxide.

(2) Add 2mL of 9wt% NaClO solution to the solution containing Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ , Fe ²⁺ , and Cl ^- ions, then feed ammonia gas to adjust the pH value between 5 and 7 After filtering, a pure solution containing MgCl ₂ and CaCl ₂ is obtained, and a small amount of solid waste discharged is mainly Fe(OH) ₃ and Al(OH) ₃ precipitates.

(3) Feed ammonia gas into the pure solution containing MgCl ₂ and CaCl ₂ , react at 40-70° C. for 1.5-2.5 h, wherein the molar ratio of ammonia gas to MgCl ₂ is 3: 1; then filter, The filter cake was washed and dried to obtain about 28g of magnesium hydroxide precipitate; the filtrate was a solution containing NH ₄ ⁺ , Ca ²⁺ , Mg ²⁺ , Cl ^- , OH ^- .

(4) Calcining the above-mentioned magnesium hydroxide at 800° C. for 1-2 hours to obtain about 19 g of light magnesium oxide product. Comparing its chemical composition analysis results with the chemical industry standard HG/T 2573-2006 of the People's Republic of China, it can be seen that the performance indicators of the product meet the first-class product standard of the light magnesium oxide industrial product industry.

In this example, the chemical composition analysis results of the prepared light magnesium oxide powder are shown in Table 2.

The chemical composition analysis result (w _B /%) of table 2 light magnesia products

(5) The calcium-containing solution prepared in (3) is passed into ammonia gas at room temperature to keep the solution alkaline, and then the _CO gas with a concentration of more than 40vt% is carbonized, and the carbonization time is 1h. After filtering and washing, light Quality calcium carbonate is about 37g. Comparing its chemical composition analysis results with the chemical industry standard HG/T 2567-2006 of the People's Republic of China, it can be seen that the performance of the product meets the first-class product standard of the industrial active precipitated calcium carbonate industry. In this example, the chemical composition analysis results of the prepared light calcium carbonate powder are shown in Table 3.

The chemical composition analysis result (w _B /%) of table 3 light calcium carbonate products

Claims (3)

1. a scud acid system prepares the technology of light magnesium oxide and calcium carbonate powder, it is characterized in that employing scud is raw material, comprises following preparation section:

(1), raw materials pretreatment operation: the scud fragmentation is become the scud powder with ball milling;

(2), scud acid dissolves operation: by HCl and rhombspar mol ratio is 2～2.1, and it is to dissolve in 25%～30% the hydrochloric acid soln that the scud powder is joined mass percent, obtains containing Ca after the filtration ²⁺, Mg ²⁺, Fe ³⁺, Al ³⁺, Fe ²⁺And Cl ^-Ion solution, wherein, Ca ²⁺And Mg ²⁺Concentration is 1～2mol/L;

(3), removal of impurities operation: contain Ca what operation (2) obtained ²⁺, Mg ²⁺, Fe ³⁺, Al ³⁺, Fe ²⁺And Cl ^-In the ion solution, press Fe ²⁺With the NaClO mol ratio be 1: (2～4) add NaClO solution, feed ammonia then, and regulating pH value is 5～7, and through filtration, the filtrating that obtains is the purified MgCl of containing ₂And CaCl ₂Solution, filter cake is Fe (OH) ₃And Al (OH) ₃Deposition emits as solid slag;

(4), in the heavy magnesium operation of ammonia process: to the purified MgCl that contains ₂And CaCl ₂Solution in feed ammonia, at 40～70 ℃ of following reaction 1～3h, wherein, ammonia and MgCl ₂Mol ratio is (2.5～3): 1, and through filtering, filter cake obtains magnesium hydrate precipitate through washing drying again; Filtrating is for containing NH ₄ ⁺, Ca ²⁺, Mg ²⁺, Cl ^-And OH ^-Solution;

(5), Marinco H calcination process: dried Marinco H is calcined 1-2h down at 600～800 ℃, promptly make the light magnesium oxide goods;

(6), calcium carbonate powder production technique: will contain NH ₄ ⁺, Ca ²⁺, Mg ²⁺, Cl ^-, OH ^-Solution at room temperature feed ammonia, maintenance solution is pH>=7.5, uses percent by volume greater than 40% CO again ₂Carbonization, carbonization time are at 45～90min, and the filter cake after the filtration is ZG 301, through washing, drying, promptly make light calcium carbonate powder goods again.

2. scud acid system as claimed in claim 1 prepares the technology of light magnesium oxide and calcium carbonate powder, it is characterized in that, in step (1), fragmentation becomes the rhombspar powder below 200 orders with ball milling, and promptly the particle diameter of scud powder is less than 74 μ m.

3. scud acid system as claimed in claim 1 prepares the technology of light magnesium oxide and calcium carbonate powder; It is characterized in that in step (6), filtrate filtered is the ammonium chloride solution that contains small amount of calcium, mg ion; Become ammonia chloride crystal through evaporation concentration; This ammonia chloride crystal obtains hydrogenchloride and ammonia through decomposition, and wherein, recycle in the operation is dissolved in the scud acid that hydrogenchloride returns step (2); Ammonia returns recycle in the calcium carbonate powder production technique of the heavy magnesium operation of ammonia process and/or step (6) of removal of impurities operation, step (4) of step (3).

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