Abstract: The starting point is a process to improve the performance of the incineration of combustible waste material in an incineration chamber, whereby the waste material is conveyed to a burner flame where it is burned with combustion air at a temperature in the range from 1100° C. to 1700° C. [2012° F. to 3092° F.]. On this basis, in order to create a process that allows a capacity increase of installations employed for the exothermal incineration of waste materials, it is proposed according to the invention that at least part of the combustion air is replaced by an oxygen-rich gas having an oxygen content that is higher than that of air and that the oxygen-rich gas is mixed with a cooling medium.

Abstract: Process for the preparation of iron oxide pigments from the waste acid resulting from the preparation of titanium dioxide by the sulfate process, characterized in that in a first stage a partial neutralization of the sulfuric acid contained in the waste acid is performed with compounds from the group comprising metallic iron and/or iron compounds, the sulfuric acid is optionally further neutralized with a further alkaline compound, the precipitate containing Ti, Al, Cr and V compounds is separated from the resultant reaction product and an iron oxide yellow pigment or iron oxide black pigment is precipitated from the resultant iron sulfate-containing solution by addition of alkaline compounds as well as an oxidizing agent, each pigment being able to be baked to form an iron oxide red pigment.

Abstract: Process for the production of gypsum and also of an iron-oxide pigment from the waste acid that accumulates in the course of the production of titanium dioxide in accordance with the sulfate process, characterized in that in a first stage a partial neutralization of the waste acid is effected with a calcium compound subject to precipitation and optionally direct separation of gypsum, subsequently the remaining solution is neutralized further in a second stage subject to precipitation of a deposit containing Ti, Al, Cr, V and optionally Fe(III) and from the solution containing iron sulfate that is obtained after separation of the solids an iron-oxide pigment is produced in a third stage by addition of alkaline compounds and also of an oxidizing agent.

Abstract: Process for the production of gypsum and also of an iron-oxide pigment from the waste acid that accumulates in the course of the production of titanium dioxide in accordance with the sulfate process, characterized in that in a first stage a partial neutralization of the waste acid is effected with a calcium compound subject to precipitation and optionally direct separation of gypsum, subsequently the remaining solution is neutralized further in a second stage subject to precipitation of a deposit containing Ti, Al, Cr, V and optionally Fe(III) and from the solution containing iron sulfate that is obtained after separation of the solids an iron-oxide pigment is produced in a third stage by addition of alkaline compounds and also optionally addition of ammonia and also of an oxidizing agent, ammonia being liberated by addition of CaO and/or Ca(OH)2 from the solution containing (NH4)2SO4 that is obtained after separation of the iron-oxide pigment.

Abstract: The invention relates to a novel process for removing arsenic compounds using amino/ammonium-functionalized anion exchangers from the distillation bottoms obtained in the purification of hydrogen fluoride by distillation.

Abstract: A novel process for the continuous preparation of perfluorinated organic compounds by electrochemical fluorination of the parent non-fluorinated or partially fluorinated organic compounds using hydrogen fluoride having an arsenic content of less than about 10 ppm can be operated over a prolonged period of time without the electrode area-time yield decreasing over time.

Abstract: A novel process for the continuous preparation of perfluorinated organic compounds by electrochemical fluorination of the parent non-fluorinated or partially fluorinated organic compounds by means of hydrogen fluoride having an arsenic content of less than about 10 ppm can be operated over a prolonged period of time without the electrode area-time yield decreasing over time.

Abstract: The invention relates to a novel process for removing arsenic compounds from the distillation bottoms from hydrogen fluoride distillation in which the distillation bottoms are first concentrated by evaporation of hydrogen fluoride until the temperature at the bottom is from 40 to 60° C., and the residue is then reacted with calcium hydroxide, calcium oxide, or a mixture thereof to give, in a simple manner, a product capable of disposal in a landfill.

Abstract: Process for the preparation of sodium fluoride from sodium hydroxide solution and hydrogen fluoride or hydrofluoric acid, characterized in that <45% strength by weight, preferably 20 to 40% strength by weight, sodium hydroxide solution and hydrogen fluoride or hydrofluoric acid are introduced separately into a saturated NaF solution in which 4 to 50% by weight, preferably 5 to 30% by weight, of solid NaF are suspended and whose temperature is in the range from 20 to 80° C., preferably 30 to 60° C.

Abstract: 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.

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

Abstract: 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.

Abstract: 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.

Abstract: 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 %, whereina) the hot exhaust gases are cooled to temperatures below 135.degree. C. by scrubbing with 60-75% sulphuric acid,b) the exhaust gases from a) are cooled to 60.degree.-80.degree. C. by contact with 5-20% sulphuric acid,c) the exhaust gases from b) are desulphurized in contact with moist active charcoal to form sulphuric acid,d) the sulphuric acid formed in c) is raised to a concentration of 5 to 20% H.sub.2 SO.sub.4 in contact with the hot exhaust gases,e) the 5 to 20% sulphuric acid formed in d) is evaporated to a concentration of 60 to 80% H.sub.2 SO.sub.4 by the heat obtained from cooling the exhaust gases of a) andf) prior to stage e) HCl and/or HF is removed from a mixture of 5 to 20% H.sub.2 SO.sub.4 from d) with 60 to 80% sulphuric acid.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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(a) the hot exhaust gases are cooled to temperatures below 135.degree. C. by scrubbing with sulphuric acid,(b) sulphuric acid containing solids and dissolved metal sulphates is then separated from the exhaust gases from (a),(c) the exhaust gases from (b) are cooled to temperatures of 50.degree. to 70.degree. C. by scrubbing with 15 to 50% sulphuric acid,(d) and desulphurized with the formation of sulphuric acid,(e) and reheated to temperatures of 70.degree. to 90.degree. C. by scrubbing with 50 to 65% sulphuric acid while the sulphuric acid discharged from (c) is concentrated and(f) the sulphuric acid from stage (a) together with the solid particles contained therein is cooled with the pure sulphuric acid from (e) in heat exchangers.

Abstract: 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.