Abstract: A method for obtaining or recovering acids, in particular nitric acid and hydrofluoric acid, from solutions and/or metal salts of these acids containing solutions, comprising the steps of: a) spray-drying the solutions at temperatures below the decomposition temperature of the acids, the requisite energy for which is introduced via a gaseous heat-transfer medium, in order to obtain dry metal salts and gaseous acids; b) absorbing the gaseous acids formed in step a); c) separating out the dry metal salts formed in step a); optionally d) roasting the dry metal salts obtained in step a) at temperatures in the range from 400 to 900° C., in order to obtain metal oxides and gaseous acids; and e) absorbing the gaseous acids formed in step d).

Abstract: A method for reducing the levels of nitrogen oxides in the tail gas from a nitric acid production process by adding ozone to the absorber column of the production process. Nitric acid formation is also intensified by adding a mixture of secondary air and oxygen to the absorber column.

Abstract: A processes for the regeneration of a silver nitrate and nitric acid based electrolyte as used in certain silver refining processes is based on the hydrolytic removal of undesired metal-based compounds such as water insoluble hydrolysable base metal cations and water insoluble hydrolysable base metal nitrates from which the soluble silver nitrate and nitric acid based electrolyte may be separated. Water is added slowly to a dewatered electrolyte melt held at a predetermined, elevated, temperature while allowing nitric acid thereby formed to evolve and be separated from the melt while the water insoluble base metal salts are formed. The melt is then diluted with water to dilute the silver nitrate contained therein and the insoluble base metal salts are separated from the mixture by filtration.

Abstract: In a method for recovering acid from an aqueous etching mixture containing HF, HNO3, H2SiF6 and HNO2 which has been used for purifying polycrystalline silicon, the used etching mixture is distilled progressively so that approximately from 20 to 50 wt. % of the mixture is distilled off as dilute acid containing more than 90 wt. % of the silicon dissolved as hexafluorosilicic acid in a first fraction, and the water contained in the used etching mixture having been reduced by approximately 10-30 wt. %, this water-depleted mixture is then concentrated by evaporation to a residue of about 1 to 5 wt. % of the initial amount of used etching mixture during which a second fraction is distilled off, and the residue is disposed of.

Abstract: The invention relates to a process for recovering acids from product streams of organic syntheses, which comprises the steps a) neutralization of the acid with a base, b) removal of the base by means of adsorption, c) recovery of the acid.

Abstract: Disclosed is a method of removing nitric acid from an aqueous liquid containing various components such as vegetable extract, and nitrate ion is removed selectively without spoiling the taste or other components, by subjecting the aqueous liquid to chromatographic treatment with an amphoteric ion exchanger to separate nitrate ion from other components contained in the aqueous liquid. A nitric acid-reduced drink is produced by preparing a raw drink material comprising an extract or juice of plant tissue; removing nitric acid from the raw drink material with use of the method of removing nitric acid from an aqueous liquid as described above; and preparing a drink using the raw drink material after the removing of nitric acid.

Abstract: A process for treating acidic and metallic waste water, particularly the rinsing water and/or used acids from pickling plants. The process includes the step of adding an alkaline solution or gas to bind the free acids in the waste water, followed by separation of the waste water into a first partial stream with high metal content and a second partial stream with low metal content. To achieve a more economical embodiment, particularly in terms of favorable energy consumption, and also reduce the nitrate load as much as possible, the free acids are bonded by adding ammonia solution or gas, and the first partial stream with the high metal content is fed to a regeneration plant to undergo pyrohydrolytic treatment, preferably by spray roasting. The second stream can be recycled to a rinse station.

Abstract: A process for the removal of organic impurities from sulfuric acid utilizing either liquid or super critical carbon dioxide is provided. The process comprises providing a solution of sulfuric acid contaminated with at least one organic compound and subjecting the solution to countercurrent extraction with one of supercritical carbon dioxide and liquid carbon dioxide. Processes for removing organic contaminants from a waste stream generated in the manufacture of trinitrotoluene are also provided.

Abstract: A method process to convert inhibited red fuming nitric acid (IRFNA) and/or nitrogen tetraoxide to either dilute or concentrated (98%+) nitric acid. The method describes a process to remove all of the normal inhibitors (if required), that have been reported to been used in IRFNA. The process described will provide nitric acid free of contaminates which are undesirable when using the nitric acid in reactions to produce other products.

Abstract: A distilling apparatus and method use a two step distillation and purification process for processing a waste liquid, such as an impure sulfuric acid solution, to form a highly concentrated sulfuric acid solution. First, the waste liquid is stored in a concentrating column, where it is heated. A condenser, which uses the waste liquid as a cooling medium, condenses the vapor generated by the heater. The condensed vapor is passed through a filter, which separates impurities out of the waste liquid, prior to feeding the waste liquid back into the concentrating column. Water is then removed from the waste liquid via a distilling process. The resulting concentrated liquid is then fed to a purifying column, where it is again heated, to remove residue, and condensed, resulting in a highly pure waste liquid.

Abstract: A distilling apparatus and method use a two step distillation and purification process for processing a waste liquid, such as an impure sulfuric acid solution, to form a highly concentrated sulfuric acid solution. First, the waste liquid is stored in a concentrating column, where it is heated. A condenser, which uses the waste liquid as a cooling medium, condenses the vapor generated by the heater. The condensed vapor is passed through a filter, which separates impurities out of the waste liquid, prior to feeding the waste liquid back into the concentrating column. Water is then removed from the waste liquid via a distilling process. The resulting concentrated liquid is then fed to a purifying column, where it is again heated, to remove residue, and condensed, resulting in a highly pure waste liquid.

Abstract: In a method of regenerating a spent pickling solution composed of nitric acid and hydrofluoric acid and containing metal fluorides and metal nitrates, the pickling solution is heated in a reactor to about 300-1,000° C., the metal fluorides and the metal nitrates are pyrohydrolized, and the metal oxides formed as a result are removed as a granulate, and the gas produced in the fluodized bed reactor is dedusted, cooled and fed to an acid recovery unit. The spent pickling solution is initially separated in a separating process into a partial flow with free acid and into a partial flow enriched with metal salts, and the partial flow enriched with free acid is fed to the acid recovery unit and the partial flow enriched with metal salts is fed to the fluidized bed reactor.

Abstract: A process for regenerating spent acid liquor feeds an acid liquor into a reactor having a first heating zone for evaporating a substantial portion of the liquid from the spent acid to produce acid vapors and metal salts without decomposing the acid. The metal salts are transferred to a second heating zone where the salts are roasted to form metal oxides. The acid vapors from the primary roasting furnace are then transferred to an absorption column to regenerate the acid. The first heating zone is operated at a temperature below the decomposition temperature of the acid and the metal salts. The second heating zone operates at a higher temperature to completely oxidize the metal salts.

Abstract: A method for oxidizing HCl to produce pure chlorine gas by reacting HCl with a mixture of sulfuric and nitric acids. Chlorine gas is evolved. Spent nitric and sulfuric acids are first regenerated by contact with air or oxygen. After regeneration, the entire stream of regenerated acid, or major portion thereof, is reconcentrated. The concentration of sulfuric acid occurs at lower strengths (60%-80%) and temperatures. The concentrated acid may be used to oxidize more HCl. Heat evolved by the regeneration of the spent acids is carried into the acid concentration stage.

Abstract: Nitrogen oxides are removed from a waste gas stream by contacting the waste gas stream with ammonia, thereby reducing the nitrogen oxides to nitrogen. Residual nitrogen oxides and unreacted ammonia in the waste gas stream leaving the nitrogen oxides reducing step are oxidized to nitrogen pentoxide or nitric acid by contacting this gas stream with ozone. Contact of the ozone and waste gas is preferably carried out in the presence of an aqueous solution at a pH above about 9 and at a temperature above about 75° C., and this step is preferably carried out in the presence of an ammonia-oxidizing catalyst.