First, the chlorination process requirements for raw materials
At present, the chlorination process (including the production of titanium sponge) generally has two processes, namely, ebulli bed chlorination and molten salt chlorination. Most of the world's manufacturers use boiling bed chlorination. Only the former Soviet Union and China's Jinzhou plant use molten salt chlorination to produce TiCl 4 , and China's Jinzhou plant has achieved docking technology for chlorination and molten salt chlorination.
The materials used are different depending on the chlorination process. Foreign materials used in chlorination are classified into the following three categories.
①CP-A raw material Ti0 2 ≥90%, mostly synthetic rutile, natural rutile.
Ti0 2 ≥80% in 2CP-B raw material, high titanium slag smelted in electric furnace.
Ti0 2 ≥60%-80% in 3CP-C raw materials, mainly composed of high-titanium slag and high-grade titanium ore smelted in electric furnace.
The raw materials used for the sulphide chlorination are lower than those of the boiling chlorinated materials, especially the high titanium material CaO, and the MgO content can be relaxed a lot.
The world's chlorination plants use more CP-A materials, accounting for 60% of the total number of plants, accounting for 54.87% of the total production capacity; 7 factories using CP-B raw materials, accounting for 29.16% of the total number of factories, It accounts for 31.12% of the production capacity; only two factories under DuPont can use CP-C raw materials, with a production capacity of 450,000 tons/year, accounting for 15.5% of the total production capacity of the chlorination process.
The production capacity of the chlorination process in 2000 is shown in Table 1.
The production capacity of the nine plants using CP-A raw materials in the late 1970s has not yet produced a large production capacity of CP-C raw materials. Due to the limitation of sewage discharge, the production capacity of the CP-A plant was developed in the 1980s; by 1990, the CP-A plant operated more than the production capacity of the CP-C plant; by 2000, the total production capacity of the CP-A plant accounted for chlorine. 50% of the total production capacity of the chemical process. It can be seen that the use of high-quality titanium-rich materials for the production of TiCI 4 by the chlorination process has become a trend of development, while also meeting increasingly stringent environmental requirements. Only DuPont is still producing CP-C raw materials in Altamira (120,000 tons/year) in Mexico and Dreier plant (300,000 tons/year) in Mississippi, USA.
Among the titanium-rich minerals used in the boiling chlorination process, the most harmful impurities CaO, Mg0 content can not be too high, especially the CaO content can not be too high, otherwise it will affect the normal operation of the chlorination furnace.
American Titanium Products Company Patent 419179 proposes that if the content of CaO, MgO, Al 2 0 3 is controlled to 0.5%, 7.0% and 5.0% when the titanium slag is chlorinated, the boiling chlorination furnace can be operated normally and chlorine can be avoided. The furnace screen is clogged. In order to prevent high temperature chlorination in the furnace kiln furnace, the temperature above 1000 °C is controlled to produce CaCl 2 (boiling point 1900 ° C, melting point 731 ° C), MgCl 2 (boiling point 1412 ° C, melting point 714 ° C) to be smaller. The particles are carried out by the gas stream. [next]
China has used high-titanium slag smelting in Panzhihua Mine in the process of boiling chlorination without sieve. The content of MgO+CaO ≥12%, CaO content ≥1.0%, basically smooth, stable state, good reaction, smooth slagging The content of MgO+CaO in the bed material is as high as 30%-40%; it exceeds the “limit concentration†of 15% considered by foreign countries. The domestic slag-free chlorination furnace slag has a Ca content of 1.0% to 1.5% and a Mg content of 1.5% to 4.0%, which can operate normally.
The actual composition of the boiling bed material of a factory is shown in Table 2. The process control range is shown in Table 3. The chemical composition of the high-grade iron concentrate directly used in the chlorination process is shown in Table 4.
It can be seen from the composition of the foreign bed material that the chlorination rate of SiO 2 is very low and is enriched in the bed material. On the contrary, CaO and MgO are taken out after chlorination, and the control in the bed is still relatively low (<1.0). %) to prevent the clogging of the orifice of the sieve plate by the cake. Even in the process of the CP-C, the high-grade TiO 2 content ≥ 60% of the titanium concentrate is used, but the content of CaO, MgO is still very low, wherein the Mg0 content ≤ 0.5%, CaO content ≤ 0. 10% . It is required that the content of Mg0+Ca0 does not exceed 0.6%, otherwise it is difficult to control normally in the system, which affects the quality of chlorination.
In this regard, according to foreign requirements for boiling chlorination, the current highest quality ilmenite, preferably high titanium slag, cannot meet the requirements of boiling chlorination. However, China's current non-screen plate chlorination furnace technology has certain advanced nature. At present, the daily production of TiCI 4 of Φ1200-1400mm furnace is only 25-40 tons. Because there is no demand, it can not develop the TiCI 4 250 tons or more. Boiling chlorination furnace. Therefore, domestic large-scale boiling chlorination furnace still needs to solve the problem. [next]
Second, the preparation technology of chlorination raw materials
The most important feature of the chlorination titanium white raw material is that the Ti0 2 content is high, the CaO, MgO content is low, and especially the CaO content is lower.
1. Preparation of CP-C raw material (high-grade titanium concentrate) CP-C raw material is characterized by Ti0 2 content) 60%, CaO, MgO content is low, CaO content is <0.10%, CaO+MgO content is ≤1.2%.
Titanium is rich in resources and widely distributed, almost all over the world. More than 140 kinds of titanium minerals have been discovered, but only a few of them have practical value at present, mainly rutile and ilmenite, followed by white titanium, magnesia and red ilmenite.
The theoretical content of the titanium oxide is FeTi0 3 , wherein the theoretical content of Ti0 2 is 52.63%. Impurities (such as Cr, Al, Mg, etc.) may be formed by various conditions depending on the conditions of formation, that is, m[(Fe·Mg·Mn)·Ti0 2 ]·n[(Fe·Cr·A1) 2 0 3 〕.
Titanium deposits with mining value can be divided into two major categories: rock and sand. Rock deposits can be divided into two types, namely, massive minerals formed by magma differentiation and rutile minerals in alkaline rocks.
Titanium raw material mining and processing operations are shown in Figure 1.
Despite the strict beneficiation , there are still not many ilmenites that can be used for CP-C. Due to the limitation of chlorination technology and the requirement of environmental waste reduction, the production of raw materials using CP-C is decreasing, and it is developing towards CP-B and CP-A. [next]
2. Preparation of CP-B raw materials The CP-B raw materials used in the chlorination process are mainly high-titanium slag smelted by electric furnace.
Production Principle: ilmenite with a reducing agent petroleum coke or brown coal, adding a certain amount of a binder such as asphalt, paper pulp having mixed ingredients, was melted in an electric furnace at 1650-1700 deg.] C temperature reached, so that iron as a main The metal which can be reduced by carbon is reduced to form an alloy under the melt, and the upper layer is molten Ti0 2 . It is periodically discharged into the slag package outside the furnace, separated after cooling, and the titanium slag of the upper layer is crushed and finished, and the iron beads are selected to obtain a titanium-rich material called high titanium slag.
In the ilmenite smelting high-titanium slag, in addition to the high content of Ti0 2 , it is required to have high iron content, and the titanium-rich material containing Ti0 2 can be obtained after melting in an electric furnace.
Titanium slag produced by foreign titanium slag smelter does not pursue excessive reduction to produce low-priced titanium compounds, and increases Ti0 2 content, but basically makes iron completely reduced and precipitated, saving electricity and high yield. Therefore, the Ti0 2 content in such a product is normally between 70% and 80%. For example, the South African RBM slag is a high titanium slag having a relatively high Ti0 2 content. The chemical composition of the raw materials of the chlorination method is shown in Table 5.
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