Kronos, Inc.

Kronos Titan-g.m.b.h.

Rheox Inc.

Kronos (u.s.a.), Inc.

Nl Industries

Achim Hartmann

Hans Thumm

Dieter Schinkitz

Achim M Kulling

Franz Rosendahl

Siegfried Blumel

Hans-Hermann Luginsland

Dietrich W Schonherr

Edgar Klein

Donald G Cole

Herman Trub

Hermann B Trub

Erwin Schmeir

Ulrich Rothe

An improvement to the chloride process of making titanium dioxide. By recycling some of the cyclone dust, the yield in the chlorination of titanium-containing raw materials can be increased. In order to prevent silica accumulation in the fluidized bed, the cyclone dust is divided into two fractions. An economic solution is described of a single-stage separation of the cyclone dust in a hydrocyclone, the majority of the titanium dioxide occurring in the hydrocyclone underflow, although the separation is not sharp. By grinding and drying the solids from the hydrocyclone underflow, the titanium dioxide particles returned to the lower region of the fluidized-bed reactor are rapidly chlorinated, while the quartz and coke particles are rapidly discharged again from the fluid bed, so that no silica contamination occurs.

Process for increasing the yield in the manufacture of titanium dioxide by the chloride process

The hydrolysis of carbonyl sulfide is substantially improved by utilizing titanium dioxide particles as a catalyst. It is especially favorable, if the titanium dioxide particle are sintered and treated with sodium hydroxide or sodium aluminate. Through such a treatment, the catalyst can be regenerated and reutilized.

Process utilizing titanium dioxide as a catalyst for the hydrolysis of

To improve the separation of dispersedly precipitated sulfur from a washing solution used in the oxidative washing of hydrogen sulfide containing waste gases, the suspension is heated before filtration to about 45.degree. C. to 70.degree. C. Such heating causes the sulfur contained in the solution to coagulate into large flocks and form a mass of high purity sulfur which is largely non-thixotropic. This mass, often called a filter cake, can be washed and utilized in a large number of ways as a source of sulfur.

Process for the filtration of suspensions containing sulfur

In the preparation of metal chlorides from their elements to be used as additives in processes of making titanium dioxide by the chloride process, a titanium tetrachloride stream is directed to sweep over the lined inner wall of a metal chloride generator to act as a protective film, which considerably increases the life of the generator. Furthermore, the titanium tetrachloride is further heated, which is highly desirable in the chloride process. When the titanium tetrachloride is optionally conducted in advance through ducts in the lining of the inner walls of the metal chloride generator, its temperature can be further raised.

Metal chloride generator and improved process for the production of

In the preparation of a suspension with a high content of titanium dioxide, which has been produced according to the chloride process, a finely divided titanium dioxide is slurried, in unflocculated condition without use of a dispersing agent, dechlorinated and then filtered. The content of multivalent anions can be controlled in the slurry before the filtration through suitable dechlorinating agents, particularly hydrogen peroxide and/or sodium hydrogen sulfite, and thereby the solid content in the filter cake and the consistency of the filter cake are advantageously influenced. If, on one hand, no or only few multivalent anions are present, a thixotropic filter cake with a high solids content is obtained in a pressure filtration. The filter cake is converted into a titanium dioxide suspension with a high solids content through feeding into a titanium dioxide suspension to which a dispersing agent has been added. If, on the other hand, a rigid filter cake is desired by, for example, a vacuum filtration, a minimum quantity of multivalent anions is necessary for the formation of the rigid filter cake. The solids content is, however, lowered in comparison to the thixotropic filter pastes. Where this minimum quantity of multivalent anions is exceeded, the solids content declines further. The rigid filter cakes can be rendered flowable through the direct admixing of dispersing agent. Hydrogen peroxide is particularly preferred as a dechlorinating agent.

Process for preparing high solids content titanium dioxide suspension

Small quantities of an alkali metal salt control additive, along with the addition of a rutile promotion additive, preferably aluminum trichloride as ruffle promoter, is added in the oxidation of titanium tetrachloride into the titanium dioxide burner reaction zone. Metal used to make aluminum trichloride is introduced into a aluminum chloride generator reactor in a main branch, and the alkali metal salt is introduced in a subsidiary branch in a controlled addition provided by a 'dilution' mixture of the salt in aluminum powder and preferably by applying additional agents which improve the flee-flowing properties of the mixture such as, for example, anhydrous potassium oleate.

Process for the use of rutile promoter and control additives in the

The production of titanium dioxide by the sulphate process generates waste substances such as the wash filtrates, which are formed in the washing of titanium dioxide hydrate, and waste gases which contain sulphur dioxide. In this improved process the wash filtrate is used to remove the sulphur dioxide from the waste gas while the sulphuric acid content of the wash filtrate is raised and the sulphuric acid-containing process solution thus obtained is used within the scope of the titanium dioxide production process. The waste gas and the wash filtrate are passed countercurrently through a series of several washing steps and are contacted with each other by introducing the wash liquid into the waste gas in a finely divided form in scrub towers. The sulphuric acid content of the washing fluid is stepwise changed from washing stage to washing stage. The sulphur dioxide content of the waste gas is reduced to values that may be discharged into the ambient atmosphere. The sulphuric acid-containing process solution is returned to the digestion tank and/or used for dissolving the digestion cake.

Process for the production of titanium dioxide

A process for purifying an acidic technical-grade iron chloride solution formed from cyclone dust from the production of TiO.sub.2 in accordance with the chloride process by adjusting the pH with a first neutralizing agent and thereafter introducing the pH adjusted solution in a controlled manner into a solution containing a second neutralizing agent. In this process undesired ions which are to be separated, such as chromium, vanadium, zirconium and/or niobium, precipitate in the form of efficiently filterable hydroxides which can be separated industrially under economical conditions by filtration. The filter cake is non-hazardous and can safely be disposed of by dumping. Calcium carbonate is the preferred neutralizing agent, and the pH adjustment may also advantageously be effected by using scrap iron or by using iron sinters with reduction of any Fe(III) ions before the second neutralization step.

Process for purifying a technical iron chloride solution by selective

A finely divided chloride process titanium dioxide prepared without the use of a dispersing agent. The slurry is dewatered via filtration, and the resulting filter cake is made flowable with an anionic dispersing agent. In order to attain a filter cake with very high solids content, the slurry should contain no, or only very few, multivalent anions. The conditions regarding the content of multivalent anions of the slurry are achieved by selection of suitable dechlorinating agents, especially hydrogen peroxide. The filter cake is thixotropic and is made flowable by the fact that it is put into the 'diluted' dispersing agent, especially into a part of the titanium dioxide suspension to which the required quantity of dispersing agent has previously been added. Titanium dioxide suspensions with solids content of approximately 78% are thereby obtained and are of particular use in the paper industry.

High solids content titanium dioxide suspension

This invention provides a process for the recovery of purified ferrous chloride resulting as a by-product during the production of titanium dioxide by the chloride process. The process involves a two-step cooling of a filtered solution containing ferrous chloride and other material in a manner to crystallize the ferrous chloride as a pure product. Such product can then be sold commercially including to companies involved in the waste water treatment business.

Production of purified iron chloride by a vacuum process in the

A process for the production of titanium dioxide through the reaction of vaporous TiCl.sub.4 with oxygen under a pressure of between 2.4 and 3.4 bar, and a corresponding apparatus are used to achieve long permanent operation times. The oxygen required is indirectly preheated to between 850.degree. and 1000.degree. C. In a reaction chamber closed at one end, configured inside for advantageous flow and lined at least partly with refractories, the indirectly preheated oxygen is further heated by direct contact with very hot combustion gases of an auxiliary flame to temperatures, as is required, for the spontaneous reaction with the TiCl.sub.4 introduced downstream into the reaction chamber. Through an annular passage in the inner peripheral wall of the reaction chamber directly at its front wall, the indirectly preheated oxygen enters the chamber uniformly distributed over its circumference, and the oxygen flow is controlled to obtain a Reynolds' number of between 15,000 and 20,000 in the annular passage and to obtain a ratio of Reynolds' number to inner diameter, in millimeters, of the reaction chamber of between 25 and 50 to 1.

A process for the removal of chlorine from off-gases which continuously or sporadically contain small amounts of chlorine by scrubbing the off-gases with a ferrous chloride-containing aqueous solution in a scrubbing system. The solution used is obtained by dissolving a solids mixture which results from the chlorination of a titaniferous and ferriferous feedstock material and which contains essentially ferrous chloride. This solution is used in particular for the scrubbing of off-gases formed in the production of titanium dioxide by the chlorination of titaniferous and ferriferous feedstock material, thus generating titanium tetrachloride and ferrous chloride, and by the reaction of the titanium tetrachloride with oxygen-containing gases. It is preferably the solids mixture separated in this process from the chlorination mixture in a condensation step that is dissolved in the process of the invention, and at least part of the resulting solution is used for the scrubbing of the off-gases. Known devices can be used for scrubbing, e.g., packed columns.

Process for the removal of chlorine from off-gases

A process for the production of coarse scrubbing aggregates of TiO.sub.2 particles by vapor phase oxidation of titanium tetrachloride. The particle aggregates of sizes above 0.15 mm are separated from the TiO.sub.2 fines by wet screening on a moving screen, calcined and returned to the process. In a preferred embodiment of the process, the titanium dioxide prior to calcination is admixed with 0.01 to 0.3% by weight alkaline hydroxides (related to anhydrous TiO.sub.2), hard particle aggregates of sizes between 0.2 to 2.0 mm being generated that are returned to the hot reaction mixture and used for the prevention of deposit formation on the surfaces of the heat exchanger. The process can be carried through in such a way that the quantities of coarse scrubbing TiO.sub.2 aggregates per unit of time consumed by abrasion and newly formed by sintering are equal, their percentages in recycling TiO.sub.2 thus remaining constant which simplifies the TiO.sub.2 production process.

Process for the production of coarse, scrubbing aggregates of titanium

The invention concerns a device for the cooling of hot gaseous solids suspensions, particularly for the cooling of hot gaseous TiO.sub.2 suspensions resulting from the production of titanium dioxide by vapor phase oxidation of titanium tetrachloride. The device consists of a number of coaxially connected constructional units, each of which consists of three jacketed tubes, i.e., tubes 1, 2 and 3, which are coaxially connected in such a way that tube 1 conically tapers toward tube 2 and that tube 3 is larger in diameter than tube 2. Heat transfer is twice as high in the device of the invention as in a comparable conventional cooling tube of uniform inner diameter; moreover, the demand of scrub solids needed to prevent the formation of deposits on its walls is reduced to one third of the quantity needed in a conventional cooling tube.

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Pulheim, Germany

Achim Hartmann