Method for complex processing of concentrate leucoxene

 

(57) Abstract:

The invention relates to the production of titanium dioxide pigment of leucoxene concentrate. For a comprehensive processing of leucoxene concentrate for creating environmentally friendly and waste-free production, leucoxene concentrate is mixed with the carbonaceous reducing agent in an amount to provide carbides of metals, and heated at a temperature of 1,600-2,000oWith, and crushed carbide sintered treated with an aqueous solution of nitric acid of density not less than 1,05 g/cm3at a temperature of 35-75oWith the separation of silicon carbide, then precipitated from a solution of the metal hydroxides. table 1.

The invention relates to the production of titanium dioxide pigment of leucoxene concentrate.

Currently pigmentary titanium dioxide produced by sulfuric acid method [1] using as raw ilmenite (44-56% of TiO2, 25-35% Fe), perovskite (50,0% TiO2, 35,0 CaO, 3,6 Fe2O3) concentrates and slags (56-70% of TiO2, 5-12% FeO), melted in electric furnaces of the titanium containing ores. The method involves the decomposition of concentrates or slag serratore salts of titanium and iron. At subsequent stages, the solution is separated from the slurry containing insoluble in the acid oxides of the metals, then from the solution produce iron in the form of crystals of ferrous sulfate. A filtered solution of salts of titanium evaporated under vacuum at a temperature below 70-75oWith and subjected to hydrolysis at the boiling temperature to obtain a precipitate of hydrate of titanium dioxide, which is separated from the mother liquor (hydrolysis of sulfuric acid and calcined at temperatures of 900-950oFor obtaining of titanium dioxide pigment.

The disadvantage of this method is that the sulfuric acid decomposition traditional titanium concentrates is carried out at high temperature 180-200oC. forming a great number of unusable waste in the form of sludge (not decomposed concentrate), iron sulphate hydrolysis of sulfuric acid (20-23% H2SO4), gaseous oxides of sulfur and acidic wastewater.

The disadvantages of this method are aggravated by the use leucoxene concentrates containing 45-53% of TiO2; 38-46% SiO2; 1,5-2,8% Fe2O3; 2.4 to 5.4% of Al2O3because of the decomposition requires a higher temperature (250-280oFrom [2]). This mn is mA containing SiO2and Al2O3insoluble in sulfuric acid, which is not utilized.

The closest in technical essence adopted for the prototype of the invention, sulfuric acid is a method of obtaining a pigment titanium dioxide [3] of leucoxene concentrate, including the recovery annealing at temperatures 1200-1350oWith the formation of anatase (Ti3O5) and quartz. This allows to reduce the temperature of the subsequent sulfuric acid decomposition of leucoxene concentrate with 250-280oWith up to 180-200oWith and obtain pigmentary titanium dioxide according to the existing technology.

The disadvantage of this method consists in the formation of large quantities of sludge containing SiO2and Al2O3that is not utilized. In addition, this method has all the weaknesses inherent in the sulfuric acid process for the preparation of titanium dioxide pigment.

The objective of the invention is to develop a method for complex processing of leucoxene concentrate for creating environmentally friendly, waste-free production of pigmentary titanium dioxide with the formation of by-products for use in various sectors of leucoxene concentrate, including his firing with the carbonaceous reducing agent, and grinding the obtained SPECA and its leaching of mineral acid according to the invention leucoxene concentrate is mixed with the carbonaceous reducing agent in an amount to provide carbides of metals, and heated at 1600-2000oWith, and crushed sintered treated with an aqueous solution of nitric acid of density not less than 105 g/cm3at a temperature of 35-75oWith the separation of silicon carbide, then precipitated and the solution of the metal hydroxides. Leucoxene concentrate is mixed with the carbonaceous reducing agent in an amount to provide recovery of all components of the raw materials to metal carbides, and heated at atmospheric pressure and a temperature of 1,600-2,000oC. the Obtained carbide sintered pulverized and treated with an aqueous solution of nitric acid with a density of not less than 1,05 g/cm3at a temperature of 35-75oC. When this occurs, the dissolution of carbides of metals for reactions

TiC + 8HNO3Ti(NO3)4+ 4NO2+ 4H2O + C,

Fe3C + 8HNO33Fe(NO3)2+ 2NO2+ 4H2O + C,

Al4C3+ 16HNO34Al(NO3)3+ 2NO2+ 8H2O + 3C.

TBE carborundum material in the production of refractories, melting silicon and the deoxidation of steel. Released during the acid treatment SPECA nitrous gases containing oxides of nitrogen, used for the production of nitrogen fertilizers (ammonium, potassium or calcium nitrate) by existing industry methods.

The filtrate, containing salts of titanium, iron, aluminum, is heated to a temperature above 85oFor the implementation of thermal hydrolysis of titanium salts with obtaining a precipitate of hydrate of titanium dioxide, which is then recycled to pigmentary titanium dioxide in a known manner. The remaining filtrate containing hydrolytic nitric acid, salts of titanium, iron, aluminium and other heavy metals, treated with alkaline additives such as CaO, for sequential deposition of hydrates of titanium dioxide aluminium, iron and heavy metals with obtaining the solution of calcium nitrate, which is evaporated and used as a nitrogen fertilizer. Aluminum hydroxide utilized in the production of coagulants and hydroxide of iron in ferrous metallurgy.

The advantage of the proposed method over the prototype is as follows:

the process of acid treatment of leucoxene carbidizing SPECA PR is EMA, hydrolysis of sulphuric acid, sulphate of iron.

Examples of the method.

The method was verified in laboratory conditions with the use of leucoxene concentrate containing (wt.): TiO246,8; SiO246,0; Fe2O32,6; Al2O33,5; CaO 0,3; MgO Of 0.5.

Leucoxene concentrate was mixed with graphite, taken in the stoichiometric ratio for the restoration to metal carbides and with an excess of 5% was heated at temperatures of 1500, 1600 and 2000oC for 1 hour. Obtained at a temperature of 2000oWith carbide spectrum was treated with a solution of nitric acid of a density of 1.31 g/cm3at temperatures of 25-30, 35-40, 60-75 and 80-85oC. eye-Catching nitrous gases were used to produce calcium nitrate by their absorption lime milk with a concentration of CaO 100-130 g/l

Filtered from silicon carbide solution was heated at a temperature of 85-95oFor precipitation of hydrate of titanium dioxide. It was separated from the solution, washed and progulivali in air at a temperature of 950oC. the Filtrate containing gidrolizu nitric acid, salts of titanium, aluminum, iron and other heavy metals neutralized by sequentially depositing of hydroxylysine in the table, which shows that the lower temperature limit carbidization of leucoxene concentrate (1600oC) due to the fact that at lower temperatures (1500oC) not achieved full conversion of SiO2in silicon carbide. The upper limit of carbidization limited temperature 2000oC, because at higher temperatures causes dissociation of silicon carbide, which leads to decrease in the content of SiC in carbide Speke and increase energy costs.

The lower temperature limit leaching carbide SPECA solution of nitric acid (35oC) due to the low dissolution rate of titanium carbide. The upper limit (75o(C) is related to the fact that at higher temperatures begins the hydrolysis solution with precipitation of hydrate of titanium dioxide. This leads to a decrease of the extraction of titanium in the target product and the deterioration of the powder of silicon carbide. The lower limit of the density of nitric acid solution of 1.05 g/cm3due to the fact that at lower densities solution, the dissolution rate of titanium carbide is small due to the low concentration of HNO3in the solution. Extraction of titanium in the solution of carbidizing SPECA by leaching with nitric acid 98,5% Poluchenie. It is suitable for use as fertilizer.

Thus, the proposed method of processing leucoxene concentrates enables the creation of non-waste technology for pigment titanium dioxide associated with the production of valuable by-products in the form of a powder of silicon carbide, nitrogen fertilizer and hydroxides of metals. As a result of this expanded resource base pigment industry and will improve the environmental situation around these industries.

Method for complex processing of leucoxene concentrate, including his firing with the carbonaceous reducing agent, and grinding the obtained SPECA and its leaching with a mineral acid, wherein leucoxene concentrate is mixed with the carbonaceous reducing agent in an amount to provide carbides of metals, and heated at 1600 2000oWith, and crushed carbide sintered treated with an aqueous solution of nitric acid of density not less than 1,05 g/cm3at a temperature of 35 to 75oWith the separation of silicon carbide, then precipitated from a solution of the metal hydroxides.

 

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21 cl, 22 dwg, 1 tbl

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2 dwg, 5 ex

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21 cl, 4 dwg, 8 tbl, 5 ex

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