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Chemical knowledge

Processing Method of Barite

2016/01/27 Bmschem

1 High whiteness fine and superfine powder processing

High whiteness fine barite powder is made by crushing, washing, whitening barite ore. The powder keeps the crystal structure of ore. Barite powder is widely used in paints, rubber, plastics, papermaking, ceramics and other industries. As a kind of high quality filler, it is used by some domestic medium-sized coating factory to manufacture various kinds of oil paints instead of titanium dioxide.

The technological process of fine barite powder is as follows.

Jaw crusher raymond mill gas-liquid grader(-15μm)→ roaster 870℃ (Clinker) → water washing→ dilute acid pickling→ pulping→pickling and reducing in reactor (100℃)→ filter pressing→ water washing→ filter pressing→ drying (170℃) → crushing→ packaging→ product

Barite ore is sedimentary stratiform deposite and according to chemical analysis, its mineral compositions are: 94.78% of BaSO4, 2.1% of acid soluble matter, 0.72% of Si, 0.56% of organic carbon, 0.43% of Ca, 0.12% of Fe, 0.10% of Al, 0.17% of Mg.

After several times crushing, ores turn into superfine material in micron-size. Roast in calcinator for 2.5h and become clinker. Remove alkali by water washing and pulping after dilute acid pickling. Then suklfuric acid and aluminite powder (acid soluble, bleaching) are added into reaction still. Stir and react for 2.5 h at boiling temperture and obtain bleaching material. After soluble salts being washed by water, filter pressing, stoving (170℃), finished products are obtained. The technical performance of the products meets the quality index of IS03262 B grade barite.

The chemical reaction process of acid dissolution and reduction in reaction still is as follows.

Acid dissolution: use sulfuric acid to dissolve coloured elements of impurity

[Fe₂O₃]+3H₂SO₄=Fe₂(SO₄)₃+3H₂O

[MnO]+H₂SO₄=MnSO₄+H₂O

[NiO]+H2SO₄=NiSO₄+H₂O

Bleaching: aluminum powder is added and then hydrogen is produced to reduce Fe²⁺ and bleach.

2Al+3H₂SO₄=Al₂(SO₄)₃+3H₂

Fe₂(SO₄)₃+H₂=2FeSO₄+H₂SO₄

Bleaching and superfine grinding are key technologies in the above physical and chemical machining method. Bleaching, which includes roasting (to remove carbon) and acid pickling (to remove coloured elements of impurity), requires to master calcination temperature and time, the acid concentration, bleaching time, the adding quantity and times of reductant. Superfine grinding should select and use high efficiency mill and appropriately select pertinent parameters.

Sichuan province southeast geology team used barite powder technology in high-quality barite processing (the barite is from someplace of Sichuan province) and obtained ultra-fine powder: BaSO₄≥98%，F(xiàn)e₂O₃≤0.05%，ZBD whiteness≥90%, ≥98% of powder’s finess≤2μm. This ultra-fine powder is used in papermaking, rubbber, paint and plastic production, which can totally replace precipitated barium sulphate. With good basic performance, this product has a broad application prospect in industry.

2 Manufacturing barium salt products

Make use of barite to produce barium salt products: barium carbonate, barium chloride, barium hydroxide, barium nitrate, barium sulfate, barium titanate, barium molybdate and some fine chemicals, except lithopone.

(1) Lithopone: it is white powder and insoluble in water with 0.3～0.5μm average particle size. Not react with hydrogen sulfide and alkali liquor, while react with acid liquor to release hydrogen sulfide. Lithopone will change color in long term solarization and return the color under dark place. The raw materials of producing lithopone, except barite, are zinc oxide, silfuric acid, pulverized coal, etc. The main chemical reaction is as follows.

ZnO+H₂SO₄=ZnSO₄+H₂O

BaSO₄+2C=BaS+2CO₂

ZnSO₄+BaS=ZnS•BaSO₄

(2) Barium carbonate: the principal raw materials are barite, limestone and coal. Technological process: Barite and pulverized coal→ crushing→ roasting→ heating steam to extract→ clarification→ carbonization→ adding sodium carbonate, desulfurization and washing with steam→ filtration→ drying → packaging.

(3) Barium chloride: barium chloride is white lustrous monoclinic crystal.When heated to 113℃, it lost water and become white powder. It is soluble in water and its solubility increases with the increase of temperature. Its aqueous solution is bitter and salty, which is toxic to human, animals and insects.

The main raw materials are barite, coal, hydrochloric acid or chlorine, calcium chloride, etc. The preparation methods are hydrochloric acid method, calcium chloride method, chlorination process. Hydrochloric acid method: barite and pulverized coal react with hydrochloric acid after reduction roasting to produce barium chloride. Calcium chloride method: barium chloride is made by reduction roasting at first, then leaching, desulfurization and other processing system. The chlorination process: barium sulfide liquid reacts with chlorine to form barium chloride solution, then process and get barium chloride.

(4) Barium hydroxide: barium hydroxide is white tetragonal system, easily soluble in hot water, and the solution is strongly alkaline. Anhydrous barium hydroxide is white lustrous and poisonous amorphous powder.

Caustic soda method is mainly used in industrial production, which is to make barium hydroxide by the reaction of caustic soda and barium chloride solution, evaporation, crystallization and separation. The major chemical reaction is as follows:

BaCl₂+2NaOH→Ba(OH)₂+2NaCl

(5) Barium nitrate: barium nitrate is colorless or white cubic crystal, soluble in water and concentrated sulfuric acid, decomposing at high temperature, poisonous. Decompose into oxide and glow green during combustion. It is mainly produced by concentrated nitric acid and barium carbonate. It is also produced by nitric acid (50%) and barium sulfide. First grade product contains more than 99.0% of barium nitrate. Second grade contains not less than 98.5%.

(6) Precipitated barium sulfate (barium sulfate): it is white crystalline powder, almost insoluble in water, soluble in oleum and liquated alkali. It is easily mixed with potassium permanganate, calcium carbonate or alkali metal nitrate to form mixed crystal. If heated with carbon, it can be reduced to barium sulfide.

The production methods are barite refining process and mirabilite-barium sulfide method. The former is roasting barite with pulverized coal then reacting with Na₂SO₄. While the latter is made up by the reaction of barium sulfide and mirabilite, filter pressing, drying and separating.