Process for Producing Ti and Apparatus Therefor

Abstract

A process for producing Ti, comprising a reduction step of reacting TiCl4 with Ca in a CaCl2-containing molten salt having the Ca dissolved therein to thereby form Ti particles, a separation step of separating the Ti particles formed in said molten salt from said molten salt and an electrolysis step of electrolyzing the molten salt so as to increase the Ca concentration, wherein the molten salt increased in Ca concentration in the electrolysis step is introduced into a regulating cell to thereby render the Ca concentration of the molten salt constant and thereafter the molten salt is used for the reduction of TiCl4 in the reduction step. In the present invention, the Ca concentration of the molten salt to be fed to the corresponding reduction vessel can be inhibited from fluctuating and, at the same time, can maintain high concentration levels. Further, a large volume of the molten salt can be treated continuously. Therefore, the reduction reaction of TiCl4 can be efficiently performed, and the process can be effectively utilized in the production of Ti by Ca reduction as a production process for realizing Ti production on an industrial scale.

Description

TECHNICAL FIELD[0001]The present invention relates to a process for producing metallic Ti by reduction treatment of TiCl4 with Ca and to an apparatus for use in that process.BACKGROUND ART[0002]A common industrial process for producing metallic Ti is the Kroll process comprising reducing TiCl4 with Mg. In this Kroll process, metallic Ti is produced via a reduction step and a vacuum separation step. In the reduction step, liquid-form TiCl4 fed from above into a reaction vessel is reduced by molten Mg, whereupon granular metallic Ti is formed and it then gradually settles downward to give spongy metallic Ti. In the vacuum separation step, the unreacted Mg and the byproduct MgCl2 are removed from the spongy metallic Ti in the reaction vessel.[0003]In the production of metallic Ti by the Kroll process, it is possible to produce high-purity products. However, since the process is a batch-wise one, the production costs increase and the prices of the products become very high. One of the c...

AI Technical Summary

Benefits of technology

[0011]As mentioned above, a number of research and development works have so far been made concerning processes for producing Ti other than the Kroll process. In particular, in the OYIK method proposed by the present inventors, Ca in molten salt is consumed with the progress of the reduction reaction of TiCl4 but when that molten salt is electrolyzed, Ca is formed in the molten salt; when the thus-obtained Ca is reused in the reduction reaction, Ca replenishment from outside becomes unnecessary and, furthermore, it is unnecessary to isolate Ca singly, thereby enhancing the economical efficiency.

Problems solved by technology

However, since the process is a batch-wise one, the production costs increase and the prices of the products become very high.

One of the causes for the increased production costs is the difficulty in increasing the rate of feeding of TiCl4.

While several reasons therefor are conceivable, one is that when the rate of feeding of TiCl4 is excessively increased, TiCl4 is supplied from above onto the MgCl2,failing to move downwards and staying on the liquid surface and, therefore, the supplied TiCl4 is partly discharged from the reaction vessel in the form of unreacted TiCl4 gas and / or insufficiently reduced TiCl3 gas, among others, resulting in decreasing utilization efficiency of TiCl4.

Therefore, cooling will not be able to keep up with the supply of TiCl4 when supplied at a high rate; this is also a major reason for the rate of feeding of TiCl4 being restricted.

Further, due to the wettability (stickiness) of molten Mg, the Ti powders formed settle in a flocculated manner and are sintered and grown in grain size during settling by the heat which the high-temperature molten liquid has, rendering it difficult to recover those out of the reaction vessel.

As a result, the production of metallic Ti cannot be carried out continuously, and the productivity is impeded.

However, the process described in Document 1 cited above cannot be put into a commercial use as the process for producing Ti since the metallic Ca powders to be used as the reducing agent are very expensive and, if they are purchased and used, the production costs will become higher as compared with the Kroll process.

In addition, it is very difficult to handle Ca which is highly reactive; this is also an important factor hindering the industrial use of the Ti production process by Ca reduction.

However, the use of high-purity TiO2, which is expensive, is inevitable in this process.

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