Method and apparatus for producing titanium dioxide

Abstract

A process for reacting titanium tetrachloride vapors with oxygen to produce titanium dioxide wherein the oxygen is introduced into the reactor in at least two points. The process has the ability to control properties, such as particle size, of the raw pigment produced. The temperature of the oxygen introduced to the reactor at the further inlet point is above, below, or at the same temperature of the oxygen introduced at the first inlet point. The further inlet point can be located before or after the all the titanium tetrachloride has been introduced into the reactor. The titanium tetrachloride is introduced at a relatively low temperature, below about 427° C., and the reaction temperature in the reactor is at least about 700° C. The process includes the use of an auxiliary fuel such as carbon monoxide, methane, propane, butane, pentane, hexane, benzene, xylene, toluene, or combinations thereof for increasing the temperature in the reactor. Still further, the process for producing titanium dioxide provides for the addition of aluminum chloride to the reactor. Advantageously, the process allows the pressure in the reactor to be above atmospheric pressure and range between about 0.15 MPa and 4.0 MPa above atmospheric pressure during the production of titanium dioxide. A reactor is also provided with an aluminum chloride generator for heating the titanium tetrachloride and delivering aluminum chloride to the reactor.

Description

[0001]This application is a continuation-in-part of application Ser. No. 08 / 687,280, filed Jul. 25, 1996, now U.S. Pat. No. 5,840,112.BACKGROUND OF THE INVENTION[0002]The present invention relates to a process for producing titanium dioxide by reacting titanium tetrachloride vapors with oxygen and to an improved reactor for use in such a system. The process and reactor of the present invention provides the ability to control properties, such as particle size, of the titanium dioxide product.[0003]It is well-known that titanium tetrachloride reacts with oxygen in the vapor phase to form titanium dioxide and that this reaction is initiated by heating the reactants to a suitable temperature. However hot titanium tetrachloride is highly corrosive and therefore many useful materials of construction for heat exchangers used to heat titanium tetrachloride are rapidly corroded. In practice this generally imposes an upper limit of about 400° C. (752° F.) on the temperature to which titanium ...

AI Technical Summary

Benefits of technology

[0006]According to the present invention, a reactor for producing titanium dioxide by reacting titanium tetrachloride vapors with oxygen comprises a means for forming a first reaction zone and an oxidizing gas introduction assembly for receiving oxygen at a predetermined temperature level and passing oxygen into the first reaction zone. The oxidizing gas introduction assembly comprises a conduit having an upstream and a downstream end and an opening extending therethrough intersecting the upstream and the downstream ends where oxygen is passable through the opening in the conduit for passing into the first reaction zone. The reactor further comprises a first titanium tetrachloride introduction assembly for receiving titanium tetrachloride vapors at a first predetermined temperature and passing titanium tetrachloride vapors into the first reaction zone for reacting with oxygen to produce a mixture including titanium dioxide. Still further, the reactor comprises a means for passing the titanium tetrachloride vapor at the predetermined temperature into the first

Problems solved by technology

However hot titanium tetrachloride is highly corrosive and therefore many useful materials of construction for heat exchangers used to heat titanium tetrachloride are rapidly corroded.

The use of these methods introduce unwanted impurities such as, for example, carbonaceous residues from the fuel or metallic impurities from the electrodes used for the electrical discharge.

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