What is titanium sponge?
What is titanium sponge?
Sponge titanium is a kind of sponge titanium produced by metal thermal reduction. The purity% (mass) is generally 99.1-99.7. The total amount of impurity element% (mass) is 0.3-0.9, the impurity element oxygen% (mass) is 0.06-0.20, and the hardness (HB) is 100-157. According to the purity, it can be divided into five grades: whtio to mhti4. It is the main raw material of industrial titanium alloy. Titanium sponge production is the basic link of titanium industry. It is the raw material of titanium material, titanium powder and other titanium components. Turn ilmenite into titanium tetrachloride, and put it into a sealed stainless steel tank filled with argon to make them react with metal magnesium to get “titanium sponge“. This kind of porous “titanium sponge” can not be used directly, and they must be melted into liquid in an electric furnace before they can be cast into titanium ingot.
How is titanium sponge processed?
Titanium tetrachloride is mainly used to produce titanium sponge, titanium dioxide and titanium trichloride. There are many preparation methods, including boiling chlorination, molten salt chlorination and shaft furnace chlorination. Boiling chlorination is the main method to produce titanium tetrachloride (adopted by China, Japan and the United States), followed by molten salt chlorination (adopted by CIS countries), while shaft furnace chlorination has been eliminated. Boiling chlorination is generally based on high-grade titanium rich materials with low calcium and magnesium content, while molten salt chlorination can use materials with high calcium and magnesium content.
Boiling chlorination is a method to produce titanium tetrachloride by using fine titanium rich material and solid carbon (petroleum coke) reducing agent in the presence of high temperature and chlorine flow. This method has the characteristics of accelerating the process of mass transfer and heat transfer between gas and solid phases and strengthening production. The raw materials used for boiling chlorination at home and abroad are high titanium slag, natural rutile, artificial rutile, etc. The diameter of the newly built fluidized bed chlorination furnace in Fushun titanium plant and Zunyi Titanium plant is Φ 1.4m and Φ 2.4m respectively, and the unique non sieve plate chlorination technology is adopted, among which the designed daily output of Zunyi Titanium plant is 70t.
Molten salt chlorination
Molten salt chlorination is a method of preparing titanium tetrachloride by suspending the ground titanium slag or rutile and petroleum coke in molten salt medium (mainly composed of KCl, NaCl, MgCl2 and CaCl2) and introducing chlorine gas. Generally, the waste electrolyte of electrolytic magnesium can also be used to inject chlorine under the condition of 973k ~ 1073k, so the speed of chlorination reaction is affected by the nature and composition of the melt, the type of reducing agent, the nature of the raw material, chlorination temperature, chlorine concentration and penetration speed, melt height, carbon distribution and other factors.
Molten salt chlorination
The molten salt chlorination method was developed in 1960s in the former Soviet Union to produce titanium tetrachloride. This method is not only suitable for the raw material characteristics of the former Soviet Union (titanium slag contains about 6% CaO + MgO), but also has a furnace capacity of 20 t / m2 ~ 25 t / m2 titanium tetrachloride and a section area of 6 m2 in the molten salt section. The daily output of titanium tetrachloride in large-scale molten salt chlorination furnace is 120 t ~ 150 t, originally rectangular furnace, now it is changed into circular furnace. The size of circular molten salt chlorination furnace is Φ 5.0 M × 8.5 m, the inner diameter is 2.76 m, and the rectangle is 4.5 m × 3.5 m × 8.5 M. There is no dead angle in the round furnace, and the strength of the furnace body is increased. The furnace is overhauled once in three years, which is nearly one time longer than the service life of the rectangular furnace. Many kinds of titanium rich materials can be used for molten salt chlorination. In addition to the titanium slag containing calcium and magnesium, the titanium slag (TiO2 87% ~ 91%) melted by rutile (fe2o3tio2) is widely used, and rutile can also be used.
It has been used in Ukraine for more than 40 years. It is not only suitable for the high content of MgO and Cao in titanium concentrate in Ukraine, but also has the following advantages: 1) high unit productivity of chlorination plant, up to 20 t / m2 · d ~ 25 t / m2 · D TiCl4; 2) low chlorination temperature (800 ℃), many impurities will not enter TiCl4 due to chlorination; 3) recovery rate of titanium from furnace burden to titanium tetrachloride is high (95%); molten salt itself has the function of purifying TiCl4, obtaining TiCl4 with low impurity content, total content of vanadium, chlorine, silicon, carbon and other impurities ≤ 2%; the product of TiCl4 is more than 98%, which can make AlCl3, FeCl3, Cao, MgO and SiO2 And other impurities remain in the molten salt medium, and then discharged; 4) the requirements for the particle size composition of raw materials are not high, and the titanium slag with small particle size can be used; 5) the reaction process does not produce CoCl2, and the waste gas has no explosion risk. The content of Cl2 and HCl in the waste gas is very small, and the pollution to the environment is also small.
Shaft furnace chlorination is a method of preparing titanium tetrachloride by grinding the chlorinated titanium slag (or rutile) and petroleum coke, mixing it with binder, making a pellet and coking it, stacking the pellet in shaft chlorination furnace, acting as solid layer and chlorine gas, which is also called fixed layer chlorination or pellet chlorination. This method has been basically eliminated.
Mg reduction method
The essence of magnesium reduction is to make titanium tetrachloride react with magnesium metal in argon atmosphere at 880 ℃ ~ 950 ℃ to obtain sponge like titanium and magnesium chloride. Magnesium chloride and excess magnesium in sponge titanium are removed by vacuum distillation, so as to obtain pure titanium. The molten magnesium can be recovered by distillation condensate, and magnesium chloride can be recovered by molten salt electrolysis. The preparation of titanium from titanium tetrachloride is divided into two steps: reduction and distillation. For a long time, reduction and distillation are carried out step by step, but tend to be combined and large-scale.
The main reactions of magnesium reduction are as follows:
In the reduction process, trace impurities in TiCl4, such as AlCl3, FeCl3, SiCl4 and vocl3, are reduced by magnesium to form corresponding metals, which are all mixed in sponge titanium. The impurities such as potassium, calcium and sodium mixed in magnesium are also reducers. They reduce TiCl4 and generate corresponding impurity chlorides. The reduction process of magnesium includes: gasification of TiCl4 liquid → external diffusion of TiCl4 and liquid mg → adsorption of TiCl4 and Mg molecules on the active center → chemical reaction on the active center → crystallization nucleation → growth of titanium crystal → desorption of MgCl2 → external diffusion of MgCl2. The key step in this process is crystallization and nucleation, accompanied by heterogeneous nucleation.
Magnesium reduction products after MgCl2 discharge contain 55% ~ 60% titanium, 25% ~ 30% magnesium, 210% ~ 15% MgCl2, and a small amount of TiCl3 and ticl2. Magnesium and MgCl2 in sponge titanium are separated by distillation.
In the vacuum distillation process, the reduction product sponge titanium was sintered at high temperature for a long time, gradually densified, the pores gradually narrowed, the dendrite structure disappeared, and finally became a lump, commonly known as titanium lump.
What is titanium sponge used for?
Titanium sponge is the product in its purest form and is used as the base of for titanium alloys, billets, ingots etc.
What are the benefits of titanium sponge?
- Resistance to corrosion
- Fire and shock resistant
- Light weight
- Low cost of maintenance
Titanium sponge producers
There are nearly as few quoted titanium sponge producers as there are quoted ilmenite and rutile producers. And production of sponge is currently concentrated in just six countries, with China being both the largest producer and the one with the largest production capacity.
In terms of the titanium sponge market, the United States, Europe and South Korea are the main export destinations for Chinese-produced titanium sponge. In recent years, titanium sponge output has gradually declined in the United States, where titanium product manufacturers including TIMET are experiencing short supply of the material. As for the European market, it relies entirely on imported titanium sponge. Currently, VSMPO-AVISMA and ATI are the main producers of aerospace titanium sponge in the European and American markets. Chinese titanium sponge enterprises mainly focus on the production of industrial titanium sponge.
Source: China Titanium Pipe Manufacturer: www.titaniuminfogroup.com