Sponge titanium production technology
Na reduction method
Four titanium chloride is mainly used for the production of sponge titanium, titanium dioxide and titanium trichloride. There are many methods of preparation, such as boiling chlorination, molten salt chlorination and shaft furnace chlorination in 3 ways. Boiling chlorination is the main method for the production of four titanium chloride (China, Japan, the United States), followed by molten salt chlorination (CIS countries), and the shaft furnace has been eliminated. In the process of boiling chlorination, the high grade titanium rich material with low content of calcium and magnesium is used as raw material.
1, boiling chlorination
Boiling chlorination is a method for preparing four titanium chloride by using fine particle titanium rich material and solid carbon (petroleum coke) reducing agent, which is subjected to chlorination under the action of high temperature and chlorine flow. The method can accelerate the mass transfer and heat transfer of gas-solid phase, and strengthen the production characteristics. At present the use of raw materials with high boiling chlorination slag, natural rutile and rutile etc.. The diameter of the newly developed boiling chlorination furnace in Fushun titanium plant and Zunyi titanium plant is 1.4 m and phi m, respectively, which is unique in the technology of no sieve plate chlorination, in which the Zunyi titanium plant is designed to produce a total of about four titanium chloride (T), which is about 70 mg / day.
2, molten salt chlorination
Molten salt chlorination is a method for preparing four titanium chloride in the medium of the molten salt (mainly composed of KCl, NaCl, MgCl2 and CaCl2), and by the incorporation of chlorine gas. Waste electrolyte usually can be used in electrolytic magnesium, under the condition of 973K~1073K filled with chlorine, the chlorination reaction velocity by the melt properties, composition, reducing agent, raw material properties, chlorination temperature, chlorine concentration and inlet velocity, melt height, carbon content and other factors. The best molten salt composition in cis four titanium chloride production is shown in table 4.
Molten salt chlorination is the successful development of the former Soviet Union in 1960s, with four production methods of titanium chloride, the raw material characteristics of this method is not only applicable to the former Soviet Union (titanium slag containing CaO+MgO about 6%), the furnace production capacity of 20 t/m2 ~25 t/m2 four titanium chloride, molten salt section area is 6m2. Large molten salt Nissan four titanium chloride was 120 t~150 T, was a rectangular furnace instead of circular furnace, circular molten salt size with a diameter of 5 m * 8.5 m, inner diameter is 2.76 m, rectangular is 4.5 m x 3.5 m x 8.5 M. There is no dead corner in the circular furnace, the furnace body strength is increased, the 3 year overhaul is more than 1 times, and the service life of the rectangular furnace is prolonged by nearly 1 times. Molten salt chlorination can use a variety of titanium rich materials, in addition to containing calcium and titanium slag, is now widely used by the 87%~91% (Fe2O3 3TiO2) smelting of titanium slag (TiO2), can also use rutile.
Ukraine by the molten salt chlorination production has been 40 years of history, is not only suitable for the feature of MgO, titanium concentrate with high content of CaO, but also has the following advantages: 1) chloride units with high productivity, up to 20 t/m2 - D ~25t/m2 - D TiCl4; 2) chloride in low temperature is 800 DEG C, a lot of impurities not enter the TiCl4 for chloride; 3) from the charge to four titanium chloride titanium industry, the recovery rate is high, up to 95%; molten salt purification itself has the role of TiCl4, TiCl4 low impurity content, vanadium, silicon, carbon, chlorine and other impurities total content less than 2%; preparation of TiCl4 products is more than 98%, can make AlCl3, FeCl3, CaO, MgO and SiO2 impurities remain in molten salt medium, and then discharged; 4) composed of less demanding on the granularity of raw materials, titanium slag can use fine granularity; 5) the reaction process does not produce waste gas COCl2, no danger of explosion. The content of Cl2 and HCl in the exhaust gas is very small, and the pollution is not great.
3, shaft furnace chlorination
The shaft will be titanium slag is chloride chloride (or rutile) and petroleum coke fine grinding, adding binder and mixing group and the coking briquette made will, stacked in the vertical chloride furnace, a method of solid state layer and chlorine to produce four titanium chloride, also known as fixed layer or conglomerates chloride chloride at present, the basic law has been eliminated.
Two, Mg reduction method
The essence of magnesium reduction is at 880 DEG ~950 DEG under argon atmosphere, let four titanium chloride and magnesium were obtained by the reaction of sponge titanium and magnesium chloride, magnesium chloride removal in titanium sponge and excess magnesium by vacuum distillation to obtain pure titanium by distilled condensate molten metal recovery magnesium, magnesium chloride by molten salt electrolysis recovery of magnesium and chlorine. Preparation of titanium from refined four titanium chloride is divided into reduction and distillation of the two steps. In a long period of time, reduction, distillation are carried out step by step, and has been the trend of integration, large-scale.
1, magnesium reduction
The main reaction of magnesium reduction:
In the reduction process, the trace impurities in TiCl4, such as AlCl3, FeCl3, SiCl4, VOCl3, etc., are all reduced to the corresponding metal by magnesium reduction. The impurities, such as potassium, calcium, sodium, etc., are also reducing agents, which reduce the TiCl4 and produce the corresponding impurity chloride. Magnesium reduction process includes: TiCl4 liquid, gas and liquid gasification TiCl4 Mg diffusion of TiCl4 and Mg molecules adsorbed on the active center, in the active center of chemical reaction, nucleation, crystal growth, titanium MgCl2 desorption, diffusion MgCl2. The key step in this process is crystallization nucleation, which is accompanied by heterogeneous nucleation.
2, vacuum distillation
After the reduction of MgCl2, 55%~60%, 25%~30%, MgCl210%~15%, and TiCl3 and TiCl2 were used in the reduction of magnesium and MgCl2 in titanium sponge.
In the process of vacuum distillation, the titanium sponge, which was reduced to the product, was subjected to a long period of high temperature sintering, and the densification of the product gradually decreased, and the capillary pores were gradually reduced.
3, magnesium reduction, distillation process and equipment
Large titanium metallurgical enterprises are magnesium titanium joint ventures, most manufacturers use reduction distillation integrated process. This process is known as the combination method or the semi combination method, which realizes the closed loop of the raw material Mg-Cl2-MgCl2.
Reduction distillation integrated equipment, divided into inverted "U" and "I" type two. Inverted "U" type equipment is to restore the tank (distillation tank) and condensate tank with the valve between the pipe connection, set up a special heating device, the whole system before the reduction of the equipment assembled. "System I" integration process such as reduction in the one-time pre assembled, which is called the combined method of equipment; and first assembled reduction equipment, to be reduced while hot finished, then the system equipment condensate tank assembled by distillation operation is called on equipment, with magnesium plug "transition segment link.