Field of the invention

The invention relates to a feedstock composite comprising a metal oxide fraction and a carbonaceous fraction, a binder composition and the use thereof for obtaining the feedstock composite. Further, the invention refers to a method for obtaining the feedstock composite.

Technological background of the invention

Carbochlorination processes are those in which metal oxides are converted into their corresponding metal chlorides in the presence of chlorine gas and carbonaceous materials. The most common carbochlorination processes involve the processing of feedstocks such as ores and slags containing the oxides of refractory metals, among them, niobium, tantalum, tungsten, molybdenum and rhenium or oxides of rare earth metals like cerium, neodymium, samarium or of oxides of light metals such as aluminum, silicon, vanadium or titanium or other metals like zirconium. Metal chlorides often show relatively low vapor pressure and can be removed from the original solid matrices by sublimation or can be purified by fractionational sublimation or distillation thereby exploiting their varying boiling points, with or without the use of solvents. In addition, metal chlorides can also be purified by extraction or other separation methods.

Usually, metal chlorides are further processed to metals, metal alloys or purified oxides or hydroxides all of which are economically attractive. One of the most important carbochlorination process is the chloride process for the manufacture of titanium dioxide.

Titanium dioxide is either manufactured by the well-established sulfate process or the chloride process. The latter uses a titanium-containing feedstock which is subjected to a carbochlorination process. The thus obtained chlorides are subsequently separated by resublimation or distillation. The titanium tetrachloride is finally converted to titanium dioxide, and the chlorine which is set free from the afore-mentioned reaction is separated, and reused in the reaction with the titanium-containing feedstock. Amongst other reasons, the reuse of chlorine makes the chloride process economically attractive over the sulphate process. The coke of choice in this process is petroleum coke with a specific particle size. Due to its small particle size and low weight, fine petroleum coke is discharged from the reactor and is hence unsuitable for carbochlorination reactions per se. The same applies to green and sustainable cokes descending from renewable raw materials such as char coal and bio char due to its low particle density and low poured bulk density. In addition, the demand for petroleum coke increases continuously due to the attractiveness of the chloride process as compared to the sulphate process. The increasing demand leads to higher prices for petroleum coke. Alternative cokes are available at lower costs, but are due to facts given above unsuitable for carbochlorination processes.

Therefore, there is a need in the art for a feedstock for carbochlorination processes, especially for the titanium dioxide chloride process, with cokes other than petroleum coke having a specific physical properties rendering the material eligible.

Object and summary of the invention

It is the object of the invention to use carbonaceous material as feedstock in carbochlorination processes which is unsuitable due to its poured bulk density and the particle density.

This object is achieved by the feedstock composite, the binder composition, the use thereof, and a method for obtaining said feedstock composite.

This present invention provides a feedstock composite comprising a metal oxide fraction and a carbonaceous fraction, characterized in that the carbonaceous fraction has a poured bulk density of 0.8 g/cm ³ or less, preferably 0.7 g/cm ³ or less, and more preferably 0.6 g/cm ³ or less, and a particle density of 0.85 g/cm ³ to 1.15 g/cm ³ . This carbonaceous material can be selected among a broad variety of cokes which can be, for example, bio char or originate of pyrolyzed cokes and peats which would be unsuitable for carbochlorination reactions. As a result, expensive petroleum coke with the specific physical properties, amongst others, a poured bulk density of at least 0.8 g/cm ³ , is not the only eligible source as carbonaceous feedstock for carbochlorination reactions.

Therefore, in a first aspect, the invention relates a feedstock composite comprising a metal oxide fraction and a carbonaceous fraction, characterized in that the carbonaceous fraction has a poured bulk density of 0.8 g/cm ³ or less, preferably 0.7 g/cm ³ or less, and more preferably 0.6 g/cm ³ or less, and a particle density of 0.85 g/cm ³ to 1.15 g/cm ³ .

In as second aspect, the invention is directed to a binder composition comprising lignosulfonate, carboxymethylcellulose and water glass.

In a further aspect, the invention refers to the use of the binder composition as disclosed herein for obtaining a feedstock composite comprising a metal oxide fraction and a carbonaceous fraction.

In a yet further aspect, the invention relates to a method for obtaining the feedstock composite as disclosed herein, comprising the steps of a) providing a raw mixture of titaniferous material and a carbonaceous material, wherein the carbonaceous material possesses a poured bulk density of 0.8 g/cm ³ or less, preferably 0.7 g/cm ³ or less, and more preferably 0.6 g/cm ³ or less, and b) agglomerating the raw mixture to obtain the feedstock composite.

Further advantageous embodiments of the invention are stated in the dependent claims.

Description of the invention

These and other aspects, features and advantages of the invention become obvious to the skilled person from the study of the following detailed description and claims. Each feature from one aspect of the invention can be employed in any other aspect of the invention. Numerical ranges stated in the format "from x to y" include the mentioned values and the values that are within the respective measuring accuracy as known to the skilled person. If several preferred numerical ranges are stated in this format, it is a matter of course that all ranges formed by the combination of the various end points are also included.

In a first aspect, the invention relates to a feedstock composite comprising a metal oxide fraction and a carbonaceous fraction, wherein the carbonaceous fraction has a poured bulk density of 0.8 g/cm ³ or less, preferably 0.7 g/cm ³ or less, and more preferably 0.6 g/cm ³ or less, and a particle density of 0.85 g/cm ³ to 1.15 g/cm ³ . The poured bulk density of the carbonaceous fraction is preferably not less than preferably 0.3 g/cm ³ or less, and more preferably 0.2 g/cm ³ . The feedstock possess preferably a poured bulk density of from 0.7 g/cm ³ to 2.0 g/cm ³ , more preferably of from 0.9 g/cm ³ to 1.7 g/cm ³ , and more even preferably of from 1.2 g/cm ³ to 1.5 g/cm ³ . In a preferred embodiment, the feedstock composite possesses a poured bulk density of from 0.7 g/cm ³ to 2.0 g/cm ³ , preferably of from 0.9 g/cm ³ to 1 .7 g/cm ³ , and more preferably of from 1 .2 g/cm ³ to 1 .5 g/cm ³ . In yet another preferred embodiment, the feedstock composite possesses the form of a particle, and preferably the particle has a size of from 0.1 mm to 6.0 mm, preferably of from 0.3 mm to 4.0 mm, and more preferably of from 0.5 mm to 3.0 mm rendering the composite highly suitable for carbochlorination processes.

“Poured bulk density”, as used herein relates to the mass per volume of the composite feedstock and a continuous fluid filling the voids between the composite feedstock, wherein the fluid is air and the individual components of the feedstock material must not dissolve into each other. The procedure described in DIN 53468 was used to determine the poured bulk density. “Particle density”, as used herein relates to the mass per volume of a solid. The procedure described in ISO 12154 was used to determine the poured bulk density.

The carbonaceous fraction is preferably selected from the group consisting of fine petroleum coke, recycled petroleum coke, bio char, char coal, pyrolyzed brown coal, pyrolyzed peat, and pyrolyzed coke can be used. Further, substances such as cokes generated from organic recycled materials or secondary or tertiary raw materials by e.g. pyrolysis and similar processes that generate coke, hydrothermally generated coke (HTC) from sewage sludge, manure, wood, straw or other agricultural residues, appropriate fractions of municipal waste. “Fine petroleum coke”, as used herein refers to a petroleum coke with a poured bulk density of 0.5 g/cm ³ or less, preferably 0.4 g/cm ³ or less.

The metal oxide fraction can be any metal oxide used as starting material of carbochlorination process comprised of any metal of interest such refractory metals, among them, niobium, tantalum, tungsten, molybdenum and rhenium, rare earth metals like cerium, neodymium, samarium or light metals such as aluminum, silicon, vanadium or titanium or other metals like zirconium. Preferably, the ores and slags containing the above can be used. Preferably, the metal oxide fraction is a titaniferous fraction, and that the titaniferous fraction is selected from the group consisting of natural rutile, synthetic rutile, titaniferous slag, recycled titaniferous slags, residual slags, and ilmenite. The residual slag can originate from the iron and steel industry. In order to improve the adhesion of the fraction of the feedstock composite, at least one binder can be used selected from the group consisting of sodium chloride, sodium carbonate, bentonite, water glass, carbon black, soth, polyvinyl alcohol, plasticizers, lignosulfonate, carboxymethylcellulose, starch, starch ether, tars, bituminous, molasse, natural resin, pitch, gelatin, and tannin. Starch ether can be obtained from Agrana Beteilungs-AG in Vienna, Austria. Preferably, a binder composition comprising lignosulfonate, carboxymethylcellulose, water glass and bentonite, preferably the ratio of lignosulfonate, carboxymethylcellulose, water glass and bentonite is 1 : 2 : 2 : 2 to 1 : 3 : 4 : 4 is employed which is advantageous in carbochlorination processes. Preferably, the feedstock composite further comprises 1 wt.% to 20 wt.%, preferably 3 wt.% to 17.5 wt.%, and more preferably 7.5 wt.% to 13 wt.% of the at least one binder or the binder composition with respect to the total weight of the feedstock composite.

In another aspect, the invention relates to a binder composition comprising lignosulfonate, carboxymethylcellulose, water glass, and bentonite. Preferably, the ratio of lignosulfonate, carboxymethylcellulose, water glass, and bentonite is of from 1 : 2 : 2 : 2 to 1 : 3 : 4 : 4 is used.

In yet another aspect, the invention is directed to the of the binder composition as disclosed herein for obtaining a feedstock composite comprising a metal oxide fraction and a carbonaceous fraction, preferably for obtaining a feedstock composite as described herein. Even more preferably, the binder composition according to the invention is employed for obtaining a feedstock composition for the titanium dioxide chloride process.

In a further aspect, the invention related to a method for obtaining the feedstock composite comprising a metal oxide fraction and a carbonaceous fraction, comprising the steps of a) providing a raw mixture of a metal oxide material and a carbonaceous material, wherein the carbonaceous material possesses a poured bulk density of 0.8 g/cm ³ or less, preferably 0.7 g/cm ³ or less, and more preferably 0.6 g/cm ³ or less, and b) agglomerating the raw mixture to obtain the feedstock composite. The agglomeration in step b) can be accomplished by compacting and/or extrusion and/or wet extrusion, preferably extrusion. Further, pressure agglomeration, dry agglomeration, tumble growth agglomeration, heating or sintering can also be used.

Preferable, step after step a) and prior to step b), the raw mixture is confected by drying, wetting and/or pre-agglomeration. This step is conducted to prepare the raw mixture for the step b). Apparatuses and techniques are known in the art, for example, a disc pelletizer. The particle size of the feedstock can also be adjusted by common reduction techniques.

The metal oxide fraction can be any metal oxide used as starting material of carbochlorination process comprised of any metal of interest such refractory metals, among them, niobium, tantalum, tungsten, molybdenum and rhenium, rare earth metals like cerium, neodymium, samarium or light metals such as aluminum, silicon, vanadium or titanium or other metals like zirconium. Preferably, the ores and slags containing the above can be used. Preferably, the metal oxide fraction is a titaniferous fraction, and that the titaniferous fraction is selected from the group consisting of natural rutile, synthetic rutile, titaniferous slag, recycled titaniferous slags, residual slags, and ilmenite. The residual slag can originate from the iron and steel industry.

In order to improve the adhesion of the fraction of the feedstock composite, at least one binder can be added in step a) selected from the group consisting of sodium chloride, sodium carbonate, bentonite, water glass, carbon black, soth, polyvinyl alcohol, plasticizers, lignosulfonate, carboxymethylcellulose, starch, starch ether, tars, bituminous, molasse, natural resin, pitch, gelatin, and tannin. Starch ether can be obtained from Agrana Beteilungs-AG in Vienna, Austria. Preferably, a binder composition comprising lignosulfonate, carboxymethylcellulose, water glass and bentonite, preferably the ratio of lignosulfonate, carboxymethylcellulose, water glass and bentonite is 1 : 2 : 2 : 2 to 1 : 3 : 4 : 4 is employed which is advantageous in carbochlorination processes. Preferably, the feedstock composite further comprises 1 wt.% to 20 wt.%, preferably 3 wt.% to 17.5 wt.%, and more preferably 7.5 wt.% to 13 wt.% of the at least one binder or the binder composition with respect to the total weight of the feedstock composite.