RU2715193C1 - Ilmenite concentrate processing method - Google Patents

Abstract

FIELD: production technology.

SUBSTANCE: invention can be used in processing natural titanium-containing material to obtain anatase modification titanium dioxide. Ilmenite concentrate processing method involves its exposure by means of a sulphatising reagent with subsequent separation of titanium compounds from iron compounds. Opening is carried out in solid phase by roasting concentrate with excess of ammonium sulphate as sulphatising reagent at 360–400 °C for 4.0–4.5 h. Formed product is leached with water at ratio T:I = 1:5.0–5.5 to obtain a solution containing iron and titanium sulphates. Insoluble residue is separated. Thermal hydrolysis of the obtained solution is carried out at 80–90 °C for 1.5–2.0 h. Titanium dioxide is obtained in form of a fine crystalline sediment of anatase modification, which is settled for 2–3 hours, separated from the solution by filtration and dried. After extraction of titanium dioxide solution is used to produce iron syrup.

EFFECT: invention increases efficiency of processing ilmenite concentrate while improving environmental safety and reducing harmful effects on the human body by reducing the number of steps, performing opening in a solid phase, eliminating the use of sulfuric acid.

4 cl, 3 ex

Description

The invention relates to the processing of natural titanium-containing raw materials, mainly ilmenite concentrate, with the production of anatase titanium dioxide, which is used in the paint and varnish and pulp and paper industries, in the production of plastics and rubber products, in the cosmetic and pharmaceutical industries.

A known method for producing technical titanium dioxide, including the decomposition of ilmenite concentrate with concentrated sulfuric acid (concentration of H ₂ SO ₄ more than 92%), the dissolution of solid sulfatization products, the recovery of iron (III) cations in solution with metallic titanium, the purification of solutions from sludge by sedimentation, followed by control filtration crystallization of excess iron (II) sulfate in the form of iron sulfate and purification of solutions from it, hydrolysis and calcination of the hydrolyzate (SU 986859, publ. 1983.01.07). The disadvantages of this method include the high costs associated with the use of "fresh" sulfuric acid, the consumption of which for the production of titanium dioxide is 4000-4500 kg / t of the target product, and the need to dispose of a large amount of environmentally unsafe waste.

Also known is a sulfate method for producing titanium dioxide containing 99.67 wt. % TiO ₂ and impurities in the amount of: Fe - 0.07%, S <0.02% (RU 2315123, publ. 2008.01.20), including the processing of titanium-containing material, mainly ilmenite, by leaching in an autoclave a solution containing 400-700 g / l sulfuric acid, in the presence of metallic iron as a reducing agent at a temperature of 95-120 ° C to obtain leach liquor, precipitation of iron sulfate from the liquor, extraction of titanyl sulfate with a solvent, hydrolysis of the extracted titanyl sulfate, followed by firing of the solid phase hydrolysis at temperatures e 1000 ° C with the formation of the final product in the form of titanium dioxide. In this case, at least a portion of the raffinate from the solvent extraction step is used at least as part of the leach solution in the initial leach step. The known method does not allow to provide a sufficiently high degree of titanium extraction (the degree of extraction after the second leaching stage is 72-87%), while the reason for the noticeable loss of titanium dioxide is the use of dilute solutions, which causes significant volumes of material flows. In addition, the presence of a large number of acidic effluents makes the known method environmentally unsafe. Extraction and stripping at a high temperature, firing of titanium hydroxide at 1000 ° C also make a significant contribution to increasing its danger to human health and the environment and, in addition, increase its energy intensity and cause a decrease in efficiency.

As a prototype, a method for processing titanium-containing material in the form of sphene, perovskite or ilmenite concentrate with a particle size of not more than 40 μm (RU 2571904, 2015.12.27), including leaching with sulfuric acid with a concentration of 600-800 g / l in the presence of a reducing agent in the form of iron, was selected shavings at a temperature of 130 ° C for 5 hours to obtain a suspension, which is filtered to separate the solid residue from the sulfuric acid leaching solution containing titanium and iron compounds. After that, the extraction processing of said solution is carried out with a mixture containing 90 vol. % high molecular weight aliphatic alcohol and 10 vol. % tertiary amine, at a temperature of 20 ° C and the ratio of the volumes of the organic and aqueous phase O: B = 4-6: 1 in 3 countercurrent steps with a translation of 55-65 wt. % sulfuric acid in the organic phase, and compounds of titanium, iron and residual sulfuric acid in the aqueous phase. An aqueous reextraction of the organic phase is carried out to obtain a sulfuric acid solution. The aqueous phase is treated with direct electric current at a current density of 0.02-0.10 A / cm ² to ensure that the content of Ti ₂ O _{3 is} not more than 5 g / l and is subjected to thermal hydrolysis in boiling mode with the addition of titanium nuclei in the amount of 1% the ratio of TiO ₂ in solution for 6 hours to form a precipitate of titanium hydroxide, which is washed with water and calcined at 870-900 ° C to obtain titanium dioxide. The degree of extraction of titanium from ilmenite concentrate was 88.1% TiO ₂ .

The known method is complex, due to its multi-stage (leaching, extraction and reextraction of sulfuric acid, multiple filtering, evaporation and crystallization, electrolysis of raffinate, hydrolysis, washing and firing, as well as neutralization and regeneration). In addition, the use of concentrated sulfuric acid containing 600-800 g / l H ₂ SO ₄ , and heated to a temperature of 130 ° C, not only complicates the method, but also makes it unsafe for the environment and the health of workers. Removing the excess acid that is necessary before the stage of hydrolysis of titanium sulfate, extraction at a ratio of O: B = (4-6): 1 and reextraction lead to the formation of large quantities of diluted sulfuric acid, which must be neutralized and disposed of, to its leak into the environment and inevitable losses that reduce the effectiveness of the method.

The objective of the invention is to create an environmentally friendly, while quite simple and effective method of processing ilmenite.

The technical result of the method consists in increasing the efficiency of the method while increasing its environmental safety and reducing the harmful effects on the human body by reducing the number of stages, without using sulfuric acid and performing the autopsy process in the solid phase.

The specified technical result is achieved by a method of processing ilmenite concentrate to obtain titanium dioxide, including opening it with a sulfatizing reagent followed by separation of titanium compounds from iron compounds, in which, unlike the known method, the opening is carried out in the solid phase by calcining the concentrate with an excess of ammonium sulfate as a sulfatizing reagent at a temperature of 360-400 ° for 4.0-4.5 hours, the resulting product is leached with water at a ratio of T: W = 1: 5.0-5.5 to obtain a solution containing iron and titanium sulfates, the undissolved residue is separated from it, after which, by thermal hydrolysis of the resulting solution at a temperature of 80-90 ° C for 1.5-2.0 hours receive anatase titanium dioxide in the form of a precipitate, which is separated from the solution by a known method.

Mostly thermal hydrolysis is carried out in the presence of a reducing agent, which provides the transition of ferric to ferrous.

From the solution remaining after separation of titanium dioxide, iron sulfate is obtained by a known method.

Ammonia released into the gas phase is captured and returned to the circulation in the form of ammonium sulfate.

The method is as follows.

After grinding, the ilmenite concentrate is mixed with an excess of ammonium sulfate (NH ₄ ) ₂ SO ₄ . The resulting mixture at a speed of 2.5 deg / min is heated to a temperature in the range of 360-400 ° C and maintained at the achieved temperature for 4.0-4.5 hours.

It was found that the interaction of the main components of ilmenite concentrate with ammonium sulfate (NH ₄ ) ₂ SO ₄ during firing in the indicated temperature range can be represented by equations (1-3):

Ammonia released into the gas phase can be trapped using a saturator and returned to the circulation in the form of ammonium sulfate.

The product obtained after firing in the form of a homogeneous free-flowing powder of gray-greenish color, which, according to x-ray phase analysis, mainly contains a mixture of ammonium double sulfate and iron NH ₄ Fe (SO ₄ ) ₂ and double ammonium sulfate and titanium (NH ₄ ) ₂ TiO ( SO ₄ ) ₂ , leached with water at a ratio of T: W = 1: 5.0-5.5 with continuous stirring for 30-40 minutes. In this case, ammonium bisulfate formed as a result of decomposition of ammonium sulfate:

(NH ₄ ) ₂ SO ₄ → NH ₄ HSO ₄ + NH ₃

provides a leach solution pH of 2.

Under these conditions, titanium and iron sulfates pass into the solution. Then, the resulting mixture was filtered to separate an insoluble residue, which, according to X-ray phase analysis, contained a small amount of unreacted ilmenite, quartz, and a mixture of iron oxides and hydroxides Fe ₂ O ₃ and FeOOH.

The leach solution is subjected to thermal hydrolysis by heating to a temperature of 80-90 ° C and holding at the achieved temperature for 1.5-2.0 hours. When heated, hydrolysis of titanium sulfate occurs with the precipitation of fine crystalline titanium dioxide anatase modification, which after settling for 2-3 hours is separated from the solution by filtration and dried.

Iron sulfate can be obtained from the remaining solution by a known method.

In an advantageous embodiment of the method, thermal hydrolysis is carried out in the presence of a reducing agent, which converts ferric to ferrous iron, which improves the purity of the target product and the whiteness of the resulting titanium pigment by reducing the iron content from 3.2 to 1.6%, in terms of per element.

As a reducing agent, the calculated amounts of oxalic acid or sodium sulfite solution are added to the solution with the addition of sulfuric acid, which is necessary to create pH = 2.

Examples of specific implementation of the method

Example 1

5 g of ilmenite concentrate containing 44.0% TiO ₂ , 30.8% FeO and 14.3% Fe ₂ O ₃ were mixed with 24.5 g of ammonium sulfate (NH ₄ ) ₂ SO ₄ , the resulting mixture was heated at a rate of 2 , 5 deg / min to a temperature of 360 ° C and kept at this temperature for 4 hours. Received 22 g of the product in the form of a homogeneous free-flowing powder of gray-greenish color, containing a mixture of ammonium double sulfate and iron NH ₄ Fe (SO ₄ ) ₂ and double ammonium sulfate and titanyl (NH ₄ ) ₂ TiO (SO ₄ ) ₂ .

Water was added to the product obtained by opening the ilmenite concentrate at a ratio of T: W = 1: 5 (22 ml of product 110 ml of water) and thoroughly mixed for 30 minutes. Then, the resulting mixture was filtered to obtain a leach solution, the pH of which is 2, and an insoluble precipitate, according to x-ray phase analysis, including a small amount of unreacted ilmenite, quartz, and a mixture of iron oxides and hydroxides Fe ₂ O ₃ and FeOOH.

According to atomic absorption analysis, the concentration of titanium in the solution was 11.28 g / l, iron - 13.52 g / l. The yield of titanium and iron in solution during aqueous leaching was 94.0 and 85.0%, respectively. A 0.11 L leach solution was subjected to thermal hydrolysis by heating to a temperature of 90 ° C with holding at the reached temperature for 1.5 hours. When heated, the solution became cloudy, a white crystalline precipitate gradually formed. After cooling and settling for 3 hours, the mixture was filtered. The mass of the filtered and dried precipitate, which is anatase-modified titanium dioxide, was 1.98 g. The degree of titanium extraction from ilmenite concentrate was 90%, and the purity of Ti ₂ obtained was 84.9%. The content of iron impurity calculated on Fe ₂ O ₃ is 9.2% .9 (in terms of element - 3.2%).

In this example, the hydrolysis of titanium sulfate was carried out without adding a reducing agent to the solution. As a result, the titanium dioxide precipitate had a brownish tint due to sorbed particles of ferric compounds.

Example 2

Ilmenite concentrate was treated with ammonium sulfate at a temperature of 400 ° C for 4.5 hours. The further process was carried out analogously to example 1, except for the stage of thermal hydrolysis, which was carried out in the presence of a reducing agent for the conversion of Fe (III) to Fe (II). To 0.11 L of a solution containing 11.28 g / L of titanium and 13.52 g / L of iron, calculated as an element, a reducing agent, 3 g of oxalic acid, was added. The solution was heated to a temperature of 80 ° C and kept at this temperature for 2 hours. Upon heating, the solution became cloudy and a white fine crystalline precipitate gradually formed. After cooling and settling for 2 hours, the reaction mixture was filtered. The mass of the filtered and dried precipitate, which is anatase-modified titanium dioxide, was 1.97 g. The degree of titanium extraction from ilmenite concentrate was 89.5%. The purity of the obtained TiO ₂ is 96.9%, white. The content of iron impurity per element is 2.3%.

Example 3

The process was carried out analogously to example 2, but instead of oxalic acid, to 0.11 l of a solution containing 11.28 g / l of titanium and 13.52 g / l of iron, 3 g of sodium sulfite and 1 ml of sulfuric acid were added to acidify the solution to pH = 2. As a result, after filtration and drying, a precipitate of anatase titanium dioxide with a mass of 1.97 g was obtained. The degree of extraction of titanium from ilmenite concentrate was 89.5%. The purity of the obtained TiO ₂ is 98.2%, the color is white. The impurity content of iron per element is 1.6%.

Claims (4)

1. A method of processing ilmenite concentrate to produce titanium dioxide, including opening it with a sulfatizing reagent, followed by separating the titanium compounds from iron compounds, characterized in that the opening is carried out in the solid phase by calcining the concentrate with excess ammonium sulfate as a sulfatizing reagent at a temperature of 360 -400 ° C for 4.0-4.5 hours, the resulting product is leached with water at a ratio of T: W = 1: 5.0-5.5 to obtain a solution containing iron and titanium sulfates, after separation from it an insoluble residue by thermal hydrolysis of the resulting solution at a temperature of 80-90 ° C for 1.5-2.0 hours receive titanium dioxide in the form of a crystalline precipitate of modification of anatase, which is settled for 2-3 hours, then separated from the solution by filtration and dried. 2. The method according to p. 1, characterized in that the thermal hydrolysis is carried out in the presence of a reducing agent, providing the transition of ferric to ferrous iron, which is used as oxalic acid or a solution of sodium sulfite with the addition of sulfuric acid, necessary to create a pH of 2. 3. The method according to p. 1, characterized in that from the solution remaining after separation of titanium dioxide, get iron sulfate. 4. The method according to p. 1, characterized in that the ammonia emitted during firing of ilmenite concentrate in the gas phase is captured and returned to the circulation in the form of ammonium sulfate.