Research Progress on Making Titanium Dioxide from High Titanium Slag

  High titanium slag, enrichment gained from the process of heating and smelting titanic iron ore in the furnace, has been widely used across China. Titanium Dioxide (TiO2), which has also been called titanium white, is a white inorganic pigment with stable physicochemical property strong persistent, nontoxicity, and the best opaqueness. At present, it is a widely-used pigment with the best property and has played an extremely significant role in the field of chemical industry production.

  Present Situation of Technology Development of Making Titanium Dioxide from High Titanium Slag in China

  China has abundant titanium resources. Most of the titanic iron ore of China has been used as raw material for making titanium dioxide through sulfuric acid method or for some other products of titanium industry.

  With the rapid development of China's titanium industry, there's an even greater demand on raw material s like high titanium slag, and therefore the output of the titanium slag has increased year by year. Currently, the major methods for making pigment of level-4 titanium white are sulfuric acid method, chlorination process, and hydrochloric acid method.

  The traditional technology for making titanium white has the disadvantages of long process flow, high cost, difficulties of dealing with by-product, and huge amount of three wastes (waste gas, waste water, and industrial residue), which carried a strong impact on impeding the development and promotion of the technology. Apart from the sulfuric acid method and chlorination process, other methods were failed to realize industrialization due to various technical matters.

  1. Sulfuric Acid Method

  The industry of making titanium dioxide from sulfuric acid began to rapidly development since 1930s. There are five steps and ten links in making titanium dioxide from sulfuric acid. The disadvantages of this method lie in the long production time, non-consecutive production links, complicated process flow, and low quality of titanium dioxide.

  The most serious problem is that there would produce two by-products--spent liquor of dilute FeSO4 and H2SO4-- which, turned to be the bottleneck of the development of the titanium white industry, would cause extremely serious pollution to environment with high cost cost-recovering.

  Therefore, it is significant to develop the technology of disintegrating ilmenite under the conditions of low acid concentration and low temperature, making use of recycled low-concentration waste acid, and reducing the exhaust emission. Nowadays, the cities more and more concern the environmental protection, many heavy-polluted factories were force to shut down and therefore the heavy-polluted technologies were also sifted out. It is extremely urgent to develop the technology of making clean titanium white.

  2.  Chlorination Process

  Compared with sulfuric acid method, the method of chlorination process was more advanced. This technology applied chlorine to disintegrate the raw materials and transformed titanium compound into TiCl4, and then run a reaction under high temperature to take TiCl4 into TiCl2 and Cl2. Recycling the produced Cl2 and turning the titanium dioxide into the titanium white.

  There are three phases in this method. The phase one is chlorination, the phase two is rectification, and the phase three is oxidation. The advantages of producing the titanium dioxide through chlorination process are short process flow, relatively high production capacity, few waste residue and high product quality. However, the raw materials of this method, most of which are toxic and corrosive, are more expensive and hard to get, and the wastes of this method are even harder to deal with.

  China began to study the titanium slag smelting since 1950s, and at present it has not applied the technology of making titanium dioxide from high titanium slag yet due to the serious environmental pressure. The domestic high titanium slag production was characterized by underdeveloped technology with high quantity of electric furnaces abut low quantity of output. Moreover, apart from few of the newly built furnace, many of the domestic electric furnaces are old and backward. Most of the domestic products have not got into the international market.

  Analysis on Prospect

  The consumption of titanium dioxide has been keep growing all around the world, and the demand on the high titanium slag has also increased year by year. In the recent years, the domestic titanium dioxide industry has been in a rapid development, and due to the high titanium content of the high titanium slag and low production of three wastes, the demand on the high titanium slag has leaped in China.

  The supply of the high titanium slag has still not adequate to the demand although the domestic output has increased yearly. And therefore China is highly dependent on the import in terms of high titanium slag. About a decade ago, there were only 12 factories enable to manufacture the high titanium slag. The number of the factories has increased afterwards, but the quality of their products was not very high. And then, the factories have rapidly increased to over 70.

  In the recent years, the enterprises that producing the titanium dioxide understood the advantages of the high titanium slag and began to use it to produce the titanium dioxide. Under this circumstance, the high titanium slag would be more widely used in the future, and the technology of making products like titanium dioxide from the high titanium slag would also turn to be more and more important with a very broad application prospect.

  *The article is edited and translated by CCM. The original version comes from China Academic Journal Electronic Publishing House.

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