Bayer Aktiengesellschaft

Metallgesellschaft Aktiengesellschaft

Bayer Akteingesellschaft

Gunter Lailach

Rudolf Gerken

Karl-Heinz Schultz

Gerhard Wiederhoft

Gunter Linde

Eckhard Bayer

Wolfgang D Muller

Wolfgang Dietz

Andreas Bulan

Peter Woditsch

Hugo Grimm

Jurgen Kischkewitz

Hans-Joachim Schittenhelm

Fritz Rodi

Kai Butje

Harro Witt

Karl H Dorr

Gunther Teichmann

Walter Bockmann

Heinz Neumann

Peter Clasen

Walter Gutsche

Dieter Becher

Wolfgang Larbig

Walter Deissmann

Gunter Buss

Wolfgang Rens

Rudolf Hornung

Process for the preparation of sodium fluoride from sodium hydroxide solution and hydrogen fluoride, characterized in that at least 45% strength by weight, in particular 50% strength by weight, sodium hydroxide solution and anhydrous hydrogen fluoride are introduced separately into a saturated NaF solution in which 4 to 50% by weight, preferably 5 to 30% by weight, solid NaF are suspended and the temperature of which is in the range from 20 to 80.degree. C., preferably 30 to 60.degree. C.

Process for the preparation of sodium fluoride

The invention relates to a process for re-processing deactivated DENOX catalysts on the basis of Ti/V/Mo/W mixed oxides.

Process for producing mixed oxide powders from deactivated denox

A process for the thermal decomposition of metal sulphate mixtures at temperatures from 800.degree. to 1100.degree. C. under oxidizing conditions, in which the metal sulphate mixtures are mixed with roasting residue and reacted together with fuels in the decomposition reactor to form roasting residue and SO.sub.2 -containing gases from roasting wherein the roasting residue admixed with the sulphate mixture is the finely divided fraction of the resulting roasting residue which is separated from the stream of gas in an electrostatic gas purification apparatus and returned to the decomposition reactor. This procedure has an advantageous influence on the formation of coarse roasting residue and also significantly reduces the proportion of undecomposed, water soluble sulphates in the roasting residue.

Process for the thermal decomposition of metal sulphates

A process for the preparation of titanium dioxide by the sulphate process in which titanium raw materials are decomposed with sulphuric acid, the resulting titanyl sulphate is hydrolyzed, the waste acid is separated from the hydrolyzate and evaporated to a concentration of 60 to 70%, sulphuric acid is separated from the solid metal sulphates, and the sulphuric acid which has been concentrated by evaporation is used again for the decomposition of the titanium raw material, the improvement wherein the 60 to 70% sulphuric acid is concentrated to 70 to 80% H.sub.2 SO.sub.4 in a further evaporation stage and the concentration of a part of this sulphuric acid is raised to a concentration of 98 to 99% H.sub.2 SO.sub.4 by the absorption of SO.sub.3 and then used together with the remainder of the above-mentioned 70 to 80% sulphuric acid for the decomposition of titanium raw materials.

Process for the preparation of titanium dioxide

A process for the purification of hot exhaust gases containing dust, sulphur dioxide and/or hydrogen chloride and/or hydrogen fluoride and having a water vapor partial pressure of at least 15 volume %, wherein

Process for the purification of exhaust gases

In the production of TiO.sub.2 pigments by the steps of digesting titanium-containing raw materials with sulfuric acid, hydrolyzing the titanyl sulfate obtained, separating the waste acid from the hydrolyzate, bleaching the hydrolyzate and calcining the hydrolyzate after addition of rutilizing nuclei and standardizing chemicals to form TiO.sub.2 pigments, and recovering sulfuric acid from the waste acid, the improvement which comprises employing as the rutilizing nuclei nuclei produced from part of the bleached and then washed hydrolyzate, which nuclei are added to the remainder of the bleached and washed hydrolyzate before calcination.

Process for the production of TiO.sub.2 pigments

A process for the recovery of sulphuric acid from waste acids containing metal sulphates by evaporative concentration and separation of the metal sulphates from the suspension obtained by evaporation, the improvement wherein vapors leaving the evaporators together with droplets of sulphuric acid containing metal sulphates and solid metal sulphates are condensed by direct contact with cooled contaminated vapor condensate, cooling of this vapor condensate which is circulated as cooling medium is carried out in a flash evaporator and the vapors leaving the flash evaporator free from metal sulphates and sulphuric acid are directly or indirectly condensed by means of cooling agent.

Process for the concentration of sulphuric acid containing metal

A process for the preparation of an improved quality TiO.sub.2 pigment by hydrolysis of titanyl sulphate, isolation of the hydrolysis product form the waste acid produced during the hydrolysis, washing of the hydrolysis product and calcination of the hydrolysis product to form the TiO.sub.2 pigment, wherein the hydrolysis of the titanyl sulphate is carried out using separately produced hydrolysis nuclei which have been produced by a reaction of titanium salts with alkaline reagents, and in which waste acid and/or wash liquid containing waste acid is added after at least 50% of the total duration of the hydrolysis process.

Process for the recorvery of sulphuric acid in the production of

A process for the separation of metal sulphates from dilute sulphuric acid by evaporative concentration of the sulphuric acid to a concentration of from 55 to 75% by weight H.sub.2 SO.sub.4, cooling of the resulting solution or suspension and mechanically separating the solid metal sulphates and/or hydrogen sulphates, wherein an Fe(III) content of at least 0.01% by weight is ensured before the separation.

Process for separating metal sulphates from sulphuric acid

A process for the removal of dust and sulphur dioxide from hot exhaust gases which have a low hydrogen halide content and the reheating of the purified exhaust gases, wherein

Process for the purification and reheating of exhaust gases

A process for the production of TiO.sub.2 pigments by the sulfate process by digestion of titanium-containing raw materials with sulfuric acid, hydrolysis of the titanyl sulfate formed, purification of the hydrolyzate and calcination of the hydrolyzate in rotary kilns, wherein the calcination conditions are regulated through adjustment of the SO.sub.2 content of the waste gases issuing from the rotary kilns used for calcination.

Process for the production of titanium dioxide pigments

A process for heating up moist gases containing hydrogen halides comprising removing the hydrogen halides from the gases by partial condensation of the water vapor, separating out the condensate and heating up the resultant gas in indirect or recuperative heat exchangers.

Process for heating up moist gases containing hydrogen halides

Cleaned flue gases normally accumulate as steam-saturated gases with temperatures of from 40.degree. to 55.degree. C. after wet cleaning processes for the removal of sulfur and/or nitrogen compounds. Before being let off through a stack, however, these gases have to be heated to at least 72.degree. C. This invention relates to a process for reheating flue gases after wet cleaning.

Process for cleaning flue gases

A process for the preparation of sulphur dioxide by the thermal decomposition of metal sulphates in a fluidized bed reactor with sulphur-containing reducing agents and energy suppliers, characterized in that a mixture comprising the metal sulphates, the sulphur-containing reducing agents and 75 to 99% of the energy suppliers is fed into the fluidized bed reactors and the remainder of the energy suppliers is introduced separately into the fluidized layer of the fluidized bed reactor.

Process for the preparation of sulphur dioxide

Energy required for the calcining or drying operations in the production of titanium dioxide by the sulfate process and the chloride process is at least in part provided by burning by-product offgases containing carbon monoxide obtained in the chlorination of titanium-containing raw materials under reducing conditions.

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Krefeld, Germany

Gunter Lailach