The main production method of artificial rutile
Principle
Corrosion reduction method is a method for selective addition to iron, the first oxide by solid titanium iron ore is reduced to metallic iron phase, and an aqueous electrolyte solution with the reduced ilmenite iron rust and separated, so that TiO 2 is rich in synthetic rutile. This method was successful in Australia, and now Western Titanium has built a plant with an annual capacity of 790,000 tons of corroded synthetic rutile. Corrosion production of synthetic rutile includes oxidative roasting, reduction, rust, acid leaching, filtration and drying. The process of producing artificial rutile by rust method is shown in Figure 1.
2 Oxidation roasting, Australia in the early stage of research and industrialization, pre-oxidation roasting before reduction, the raw material used is semi-weathered ilmenite (TiO 2 content is 54% ~ 55%, Fe 3 + / Fe 2+ = 0.6 ~ 1.2 ). The purpose of pre-oxidation calcination is to reduce the sintering of minerals during solid phase reduction. Pre-oxidation of ilmenite to form high-iron brookite and rutile:
4FeTiO 3 +O 2 ===2Fe 2 TiO 5 +2TiO 2
However, in the industrial production, the pre-oxidation process has been eliminated.
Oxidative roasting in Australia is carried out in a rotary kiln with fuel as fuel and the maximum temperature in the kiln is 1030 °C. Oxidative roasting in air, first oxidizing Fe 2+ in ilmenite to Fe 3+ , oxidation is incomplete, generally still contains 3% to 7% FeO. The oxidized ore is cooled to about 600 ° C, ie Enter the reduction kiln. [next]
3 reduction, ilmenite reduction is carried out in a rotary kiln, using coal as a reducing agent and fuel, Australia uses local cheap sub-bituminous coal, after the material is oxidized, the iron in the ilmenite is activated, which can increase the reduction rate and Reduction rate and anti-sintering. The reduction temperature is controlled at 1180~1200°C. Since the temperature is >1030°C, the solid carbon forms CO, the CO reduces Fe 3+ to Fe 2+ in the first stage, and the second stage reduces Fe 2+ to Fe. A portion of the TiO 2 is reduced. To prevent air from entering, the metal iron is oxidized. The reduction can reduce 93% to 95% of the iron to metallic iron. When the temperature exceeds 1200 ° C, severe sintering of the mineral occurs to cause the rotary kiln to loop. The temperature in the kiln is controlled by adjusting the rate of coal addition and the speed of ventilation. Its reaction formula is as follows:
Fe 2 O 3 ·TiO 2 +3C===2Fe+TiO 2 +3CO
Fe 2 O 3 ·TiO 2 +2CO===FeO·TiO 2 +Fe+2CO 2
FeO·TiO 2 +CO===Fe+TiO 2 +CO 2
In order to reduce the interference of manganese impurities on the reduction process, Australia added a certain amount of sulfur as a catalyst in the reduction process to make the MnO in the ore preferentially form sulfides, reduce the influence of manganese on the reduction of ilmenite, and the sulfide of manganese formed. It can be dissolved and removed in the subsequent acid leaching process, thereby improving the TiO 2 grade of the product.
The reduced ore discharged from the reduction kiln, the temperature is as high as 1140 ~ 1170 ° C, it must be cooled to 70 ~ 80 ° C, before screening and magnetic decoking, separation of coal ash and coke to obtain reduced ilmenite .
4 Corrosion, the rust process is an electrochemical corrosion process carried out in an electrolyte solution containing 1% NH 4 C1 or aqueous hydrochloric acid. Corrosion is an exothermic reaction and the temperature can be raised to 80 °C. The metal iron crystallites in the reduced ilmenite particles correspond to the anode of the primary battery, and the surface of the particles corresponds to the cathode. At the anode, Fe loses electrons and becomes Fe 2+ ions into the solution:
Fe-2e→Fe 2+
In the cathode region, oxygen in the solution accepts electrons to form OH-ions:
2H 2 O+O 2 + 4e→4OH -
The Fe 2+ ions dissolved in the particles diffuse along the micropores into the electrolyte solution on the outer surface of the particles, and at the same time pass air to further oxidize to form hydrated iron oxide fine particles precipitate:
The resulting hydrated iron oxide particles are particularly small, and depending on the physical properties of the reduced ore, they can be separated from the mother of the reduced ore to obtain a titanium-rich material.
5 acid leaching, using 4% sulfuric acid at 80 ° C under normal pressure, the above titanium-rich material is leached, wherein a part of the residual iron and manganese impurities are dissolved, filtered, washed, dried and cooled in a rotary kiln, ie An artificial rutile having a TiO 2 content of 92% can be obtained. The by-product iron oxide contains 1%~2% TiO 2 , the recovery rate of titanium in ilmenite is up to 98.5%, the consumption of rust inhibitor ammonium chloride is 11kg per ton, and the power consumption is 135KW·h. Australia and China adopt their own The composition of synthetic rutile products made from ilmenite is shown in Table 1.
Table 1 Reducing rust method artificial rutile product composition (mass fraction) Unit: %
ingredient | Australia | China | ||
Raw material titanium concentrate | Artificial rutile | Oxidized sand ore rutile | Rattan mine artificial rutile | |
ΣTiO 2 | 55.03 | 92.0 | 88.04 | 87.05 |
Ti 2 O 3 | 10.0 | |||
FeO | 22.20 | 4.63 | ||
Fe 2 O 3 | 18.80 | 6.35 | 8.70 | |
SiO 2 | 0.7 | 0.84 | 0.81 | |
CaO | 0.03 | 0.12 | 0.31 | |
MgO | 0.18 | 0.15 | 0.12 | 0.22 |
Al 2 O 3 | 0.7 | 1.29 | 0.10 | |
MnO | 1.43 | 2.0 | 1.17 | 1.04 |
S | 0.15 | 0.005 | 0.99 | |
P | 0.018 | 0.019 | ||
C | 0.15 | 0.028 | 0.029 | |
6 advantages of reducing rust method
a. The artificial rutile product has uniform particle size and stable color;
b. The amount of electricity used and ammonium chloride, hydrochloric acid and sulfuric acid are both small. When reducing, coal is mainly used as reducing agent and fuel, and cheap lignite can be utilized, so the product cost is low;
c. The three wastes are easy to be treated. The wastewater discharged during the rusting process is close to neutral (pH 6~6.5). The red mud can be used as ironmaking raw material after drying, and can be further processed into iron oxide red with less pollution.
7 Disadvantages of the reduction rust method: only suitable for the treatment of high grade ilmenite ore.
Due to the process of the reduction rust process itself, the product grade can only reach 92%. Later, foreign RGC improved in the process, adding an acid leaching process to increase the grade of TiO 2 from 92% to 94%, and reduce the content of radioactive elements of uranium and thorium in the product.
2. Hydrochloric acid leaching method
1 Principle, there are two slightly different methods for producing artificial rutile by dilute hydrochloric acid leaching method abroad. Among them, the widely used and representative one is the BCA hydrochloric acid circulating leaching method adopted by American Meikeji Company. This method mainly removes ilmenite by selectively leaching impurities such as iron, calcium, magnesium and manganese in dilute hydrochloric acid, thereby enriching TiO 2 and improving the grade. The main reactions are as follows:
FeO·TiO 2 +2HC1===TiO 2 +FeCl 2 +H 2 O
CaO · TiO 2 + 2HC1 === TiO 2 + CaC1 2 + H 2 O
MgO · TiO 2 + 2HC1 === TiO 2 + MgC1 2 + H 2 O
MnO·TiO 2 +2HC1===TiO 2 +MnC1 2 +H 2 O
During the leaching process, TiO 2 is partially dissolved. When the acid concentration of the solution is lowered, the dissolved TiOCl 2 is hydrolyzed to precipitate TiO 2 hydrate:
FeO·TiO 2 +4HC1===TiOC1 2 +FeC1 2 +2H 2 O
TiOC1 2 +(x+1)H 2 O===TiO 2 ·xH 2 O↓+2HC1
2BCA hydrochloric acid circulation leaching method continuously adds titanium iron concentrate and 3%~6% reducing agent (coal, petroleum coke) to the rotary kiln, and reduces Fe 3+ in the ore to Fe 2+ at 870 °C. The Fe 2+ accounts for 80%~95% of the total iron. In the process, 2% sulfur is added as a catalyst to increase the recovery rate of TiO 2. When the kiln is discharged, it should be rapidly cooled to 85~93 °C to prevent oxidation. The raw material is also cooled and added to the spherical rotary cooker, and leached with 18%~20% of regenerated hydrochloric acid for 4 hours, the leaching temperature is 130~143°C, the pressure is 0.25MPa, the rotation speed is 1r/min. Then the hydrochloric acid containing 18%~20% is used. The evaporant is injected into the cooker to provide the necessary heat to prevent the leachate from becoming thinner due to steam heating. After leaching, the solid phase was filtered and washed with a belt vacuum filter, and then calcined at 870 ° C in another kiln to prepare artificial rutile.
The iron and other metal chlorides in the mother liquor are leached and the chlorides are decomposed into hydrogen chloride and corresponding oxides by spray oxidation roasting. Wherein FeCl 2 is oxidized to iron oxide red:
The hydrochloric acid is absorbed by the washing water to obtain hydrochloric acid, and then the regenerated hydrochloric acid is returned to the leaching step to form a closed loop of hydrochloric acid. The process of preparing synthetic diamond by BCA hydrochloric acid circulation leaching method is shown in Fig. 2.
In the BCA process, an annual output of 100,000 tons of artificial rutile, if ilmenite with a TiO 2 content of 54% is used, the main iron oxide can be about 65,000 tons. The spherical autoclave is made of titanium alloy material, the acid evaporation is made of graphite equipment, and the other is steel lining equipment. [next]
Advantages of 3BCA hydrochloric acid circulation leaching method
a. Using ilmenite containing about 54% TiO 2 as raw material, artificial rutile with TiO 2 content of about 94% can be produced. The product has porosity and is a high-quality raw material for chlorination to obtain TiCl;
b. Suitable for treating various types of ilmenite;
. c leaching fast speed, high impurity capacity, not only iron, but also in addition to calcium, magnesium, aluminum and manganese and other impurities, a high-grade synthetic rutile;
d. Hydrochloric acid circulates, washes the washing water of the product, absorbs hydrogen chloride to form hydrochloric acid, and can be recycled. Only 150kg of hydrochloric acid can be added per ton of product. Since the mother liquor is regenerated by spray oxidation roasting and closed loop, the waste generated is less and the pollution is less.
The disadvantage of the 4BCA hydrochloric acid circulation leaching method is that the hydrochloric acid used is a highly corrosive acid, which is highly corrosive to equipment, and requires special anti-corrosion materials to manufacture equipment, so the investment is large; the energy consumption of the spray oxidation roasting regeneration hydrochloric acid is high.
The BCA process was later modified to produce artificial rutile with a TiO 2 content between 95% and 97% using low grade ilmenite. Improved ilmenite pretreatment technology and technology for regenerating hydrochloric acid from leaching mother liquor.
3. Sulfuric acid leaching method
1 principle, Japan Ishihara Industry Co., Ltd. uses India high-grade ilmenite (oxidized sand ore, TiO 2 content 59.5%, iron in the ore is mainly in the form of Fe 3+ ), first reduce the Fe 3+ with a reducing agent Fe 2+ is then subjected to pressure leaching by using sulfuric acid titanium dioxide to produce 22% to 23% of dilute waste sulfuric acid, so that it dissolves iron impurities in the ore to enrich TiO 2 . This method of producing artificial rutile originates from Ishihara Corporation, so it is called Ishihara. The stone method includes reduction, pressure leaching, filtration and washing, calcination and the like. Ishihara has already built a factory with an annual output of 100,000 tons of artificial rutile. The process of producing artificial rutile by dilute sulfuric acid leaching method is shown in Fig. 3.
2 Reduction of petroleum coke as reducing agent, in the rotary kiln, the Fe 3+ in the ore is reduced to Fe 2+ , the reduction temperature is 900~1000 ° C, the time is 5h, and the Fe 2+ obtained by reduction should account for the total iron More than 95%, the kiln requires positive pressure operation (19.6~39.2Pa), and the raw material is cooled to 80 °C in the cooling kiln under the condition of air isolation. Separation was carried out by a magnetic separator to remove residual coke, and the remaining raw materials were used for leaching in the next process. [next]
3 Pressure leaching in a 80m 3 immersion tank lined with acid-resistant bricks, adding dilute sulfuric acid with a concentration of 22%~23%, adding the raw material at a solid-liquid ratio of 1:3, the pressure is 0.1~0.15MPa, the temperature The temperature is 120~130 ° C, and the mixture is leached for 8 hours, so that Fe 2+ in the ore is dissolved to form ferrous sulfate into the solution, and TiO 2 remains in the solid phase. Its reaction formula is as follows:
FeTiO 3 +H 2 SO 4 ===FeSO 4 +TiO 2 +H 2 O
During the acid leaching process, TiO 2 is partially dissolved and then water is resolved. The addition of TiO 2 hydrated colloid as a seed crystal can expand the concentration difference between the solid and liquid phases, thereby accelerating the leaching rate of iron and increasing the leaching rate. Control the particle size of the product and reduce the fine grain product. Since the leaching effect of sulfuric acid is inferior to that of hydrochloric acid, the primary leaching material contains partially incompletely leached minerals, which can be returned to the reduction or leaching process and reprocessed.
4 Filtration and washing The product after leaching is subjected to solid-liquid separation by a belt filter, and the separated solid phase is washed with water and dried to be a titanium-rich material. The separated liquid phase is a filtrate containing FeSO 4 used for the preparation of sulfuric acid and iron oxide red. Its reaction formula is as follows:
5 calcination, calcination can remove moisture and desulfurization in the titanium-rich material, calcination is carried out in another kiln under positive pressure (49~68.6Pa), the temperature of the kiln head is about 900 °C, and the calcined product is cooled and packaged, which is artificial Rutile finished product.
The composition of the raw material ilmenite concentrate and the product artificial rutile used by Japan Ishihara Industry Co., Ltd. is shown in Table 2.
Table 2 Composition of raw materials and products of the Shiyuan method (mass fraction) Unit: %
ingredient | raw material | product | |
Indian ilmenite concentrate | Common synthetic rutile | Artificial rutile for welding rod | |
TiO 2 | 59.62 | 96.1 | 95.9 |
FeO | 9.47 | ||
Fe 2 O 3 | 24.62 | 1.7 | 1.85 |
Al 2 O 3 | 1.32 | 0.46 | 0.35 |
Cr 2 O 3 | 0.16 | 0.15 | 0.18 |
CaO | 0.09 | 0.01 | 0.01 |
MgO | 0.28 | 0.07 | 0.05 |
MnO | 0.48 | 0.03 | 0.03 |
P 2 O 5 | 0.14 | 0.17 | 0.05 |
V 2 O 5 | 0.2 | 0.20 | 0.21 |
SiO 2 | 0.7 | 0.50 | 0.48 |
ZrO 2 | 0.86 | 0.15 | 0.16 |
SO 3 | 0.03 | 0.03 | |
The Shiyuan method produces artificial rutile, and each ton of product needs to consume 1.78 tons of the above-mentioned ilmenite and 98 kg of tar, and the recovery rate of TiO 2 can reach 90%.
6 advantages of the stone method
a. The stone method can not only remove iron from the ore, but also partially remove soluble impurities such as calcium, magnesium, aluminum and manganese, and obtain a high-grade product with a TiO 2 content of 96%;
b. The method utilizes the waste sulfuric acid of the sulfuric acid method titanium white production plant, which not only reduces the cost of the product, but also solves the three waste treatment problems of titanium white production;
c. The leached by-product FeSO 4 is used to process ammonium sulfate fertilizer and iron oxide red.
Disadvantages of the 7 stone method The method has poor leaching ability of dilute sulfuric acid and is only suitable for processing high quality ilmenite concentrate. If the grade of ilmenite concentrate is low, the process will be complicated and the quality of the product will be lowered. At the same time, the three wastes are large, and the sub-process is complicated.
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