The titanium concentrate obtained from the ore dressing is the raw material for the production of titanium-rich material. There are many methods for preparing titanium-rich materials, which can be classified into two types according to the production process: fire method and wet method. Furnace fire comprising, selective chlorination method, a plasma melting method, thermal reduction method, a microwave, a wet method comprising the hydrochloric acid leaching, acid leaching, reducing corrosion process, iron chloride leaching and other chemical separation methods. At present, electric furnace smelting method, acid leaching method and reduction rust method are mainly used.
I. Research status of fire treatment of titanium concentrate
Furnace slag production method is a method of mixing a titanium ore and solid reducing petroleum coke or anthracite and the like, for smelting reduction in an electric furnace, the iron oxide in the titanium ore is selectively reduced to metallic iron, and The oxide of titanium is enriched to form titanium slag. The main reaction of titanium concentrate during electric furnace smelting is
2FeTiO 3 +CO=Fe+ FeTi 2 O 5 +CO 2 ;
The resulting FeTi 2 O 5 is further reduced, but the iron oxide cannot be all reduced to metallic iron, and a small amount remains in the titanium slag:
(3-x)FeTi 2 O 5 +5(1-x)CO=3(1-x)Fe+2(FexTi l =x )+Ti 2 O 5 +5(1−x)CO 2
The process of preparing titanium slag by electric furnace smelting is simple and mature, and the by-product iron can be directly used. The "three wastes" are few, but only iron can be removed, and non-iron impurities cannot be removed. The characteristics of titanium resources in China are low content of TiO 2 in titanium concentrate and high content of impurities, especially high content of calcium and magnesium . This determines the source of titanium in the domestic furnace (except a small amount of titanium concentrate ore). The slag can only be used as a raw material for the production of titanium dioxide by sulfuric acid.
Rotary kiln treatment method: Fan Xiaohui and others use the rotary kiln direct reduction technology for the Panzhihua titanium concentrate. By means of the catalytic action of the additive, the iron oxide in the titanium concentrate is fully reduced and the iron grain growth is promoted to realize Fe and Ti. Efficient separation. The test results show that the titanium-rich material TiO 2 grade is 74.68 when the additive dosage is 5%, the pellet preheating temperature is 700 °C, the preheating time is 15 min, the reduction temperature is 1100 °C, and the reduction time is 210 min. %, the recovery rate is 90.32%.
Selective chlorination method: using the difference in thermodynamic properties of titanium and iron in titanium concentrate and carbon chlorination, iron is preferentially chlorinated in a neutral or weak reducing atmosphere, volatilized in the form of FeCl 3 ; and titanium is not chlorinated Crystalline transformation occurs at high temperatures to produce artificial rutile. Industrial test was carried out using seashore sand ilmenite as raw material, and the reaction temperature in the furnace was successfully maintained above 950 °C. The obtained artificial rutile grade was 92.13%, and the average purity of FeC1 3 was 96.94%. When using Panzhihua ilmenite (its Mg0 and When the total amount of CaO is 5% to 7%), it is difficult to solve the problem that CaC1 2 and MgC1 2 are enriched at the bottom of the furnace to form a material, thereby reducing the operating life of the furnace.
Microwave heating reduction of titanium concentrate: Huang Mengyang and other microwave-heated reduction of titanium concentrate to obtain titanium-rich material for a kilogram expansion test. Using 20kg pellets, 14% carbon as the reducing agent, the reduction temperature is 1100～1150°C, the proportion of the additive is 5%, and the reduction time is 90min, the TiO 2 grade is 72.01. %, the recovery rate is 90.1% of titanium-rich material. Microwave is a kind of high-efficiency clean energy. It has the characteristics of fast heating, internal heating, selective heating and uniform heating. This process can avoid the problem of serious pollution and high energy consumption in the process of electric furnace smelting and reduction of titanium concentrate.
In recent years, there have been many studies on the treatment of titanium concentrates, but the progress made is not significant, because the fire treatment is more effective for the separation of ferrotitanium, and the non-ferrous impurities in the titanium concentrate reduce the quality of the titanium slag. . Therefore, in order to break through the limitations of the fire treatment of titanium concentrate, it is necessary to reduce the content of impurities in the titanium concentrate, especially the removal of Mg0 and CaO.
2. Research status of wet processing of titanium concentrate
The acid leaching method firstly reduces the titanium concentrate, converts the iron into ferrous iron, and then leaches the reduced product with the dilute acid, then the iron enters the human liquid phase, and the titanium is concentrated in the solid phase. Acid leaching includes both hydrochloric acid leaching and sulfuric acid leaching. Acid leaching can not only leaching iron, but also impurities such as Mg, Ca, Al, etc., so acid leaching can obtain titanium-rich material with high TiO 2 content, which is suitable for the treatment of Panzhihua high-calcium and magnesium-type titanium concentrate.
Sulfuric acid leaching method: The leaching of sulfuric acid with titanium concentrate as raw material will produce industrial “three wastes†which are difficult to control and pollute the environment. The country has listed it as a restricted industry. 'The use of titanium slag as raw material can reduce acid consumption, solve the problem of by-product ferrous sulfate, reduce environmental pressure and increase equipment production capacity.
Hydrochloric acid leaching method: According to different conditions of acid leaching, it can be divided into high pressure leaching method (Benillite) and atmospheric pressure leaching method (Murso). China's preparation of synthetic rutile has formed two major processes - pre-oxidation - fluidization atmospheric pressure leaching process and combined pressure and leaching process. The pre-oxidation-fluidization atmospheric pressure leaching process can solve the refinement problem of the ore in the leaching process by pre-concentrating the titanium oxide concentrate, and maintain the particle size of the artificial rutile; the smelting and the combined pressure leaching process improves the leaching by pressure leaching effect. Wang Zengjie et al. prepared artificial rutile by using the hydrochloric acid atmospheric direct leaching process for the Panzhihua titanium concentrate, and obtained a product with a TiO 2 content of 94.9%.
The domestic reduction-corrosion method for the production of synthetic rutile began in the 1970s. In 1978, the semi-industrial test of the Guangxi coastal sea-altered ilmenite was successfully carried out and passed the technical appraisal. In 1980, a trial production workshop with an annual output of 2000t rutile was built. Some domestic factories have also established small production workshops, but the production capacity is extremely small, and no scale benefits are formed. The products are mainly used for the production of welding electrodes. The reduction-corrosion method needs to use high-quality titanium concentrate as raw material. The key technology lies in the reduction of titanium concentrate, which requires high reduction temperature, serious ore ringing in the rotary kiln, and the production cannot be continuously carried out, resulting in an increase in cost.
Third, other new processes
Sun Yan et al. combined with the advantages of microwave heating and the advantages of acid leaching method, proposed a new process of microwave heating selective leaching modified titanium-containing material to obtain high-quality titanium-rich material. The surface of the particles after microwave heating reduction is developed with fine pores, loose structure, and sufficient contact with the leaching agent, and the leaching agent is easy to penetrate into the material to strengthen the reaction. After leaching, the grade of titanium-rich material can reach 96.08%, and the leaching time is shortened by 67%-75% compared with the conventional method.
The Institute of Process Engineering of the Chinese Academy of Sciences has proposed a new process for the clean production of titanium dioxide by the sub-molten salt method. The sub-molten salt method utilizes a pseudo-uniform reaction to decompose ore in a high-concentration medium flowing under normal pressure, which can enhance the reaction, mass and heat transfer, and obtain a higher ore decomposition rate at a lower temperature. The process is applied in the separation of ilmenite, and the titanium in the ilmenite can be selectively and efficiently converted into titanate at a low temperature. After hydrolysis and satin burning, titanium dioxide is obtained, and elements such as iron, calcium and magnesium are not The slag phase is formed by reacting with the sub-molten salt system to realize the selective separation of titanium and iron, and the iron slag can be further resourced, which opens up a new way for the comprehensive utilization of high-calcium-magnesium-type titanium resources in China.
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