A system for producing nitric acid at reduced power consumption, including an air compressor producing a compressed air stream; a source of pressurized oxygen-rich gas having a pressure higher than the pressure of the compressed air stream; a mixing apparatus for mixing the oxygen-rich gas/compressed air stream mixture with an ammonia gas stream; an ammonia converter to provide in a NO.sub.x gas/steam mixture; a water cooler/condenser for separating and condensing steam from NO.sub.x gas in the gaseous NO.sub.x gas/steam mixture; an absorption tower downstream the water cooler/condenser, for absorbing NO.sub.x gases in water, to provide in a stream of raw nitric acid-containing residual NO.sub.x gas and a tail gas including NO.sub.x gases. The system further includes a mechanism for splitting the tail gas into a first tail gas stream and a second tail gas stream; and a mechanism for adjusting the amount of tail gas being split.

A system for producing nitric acid at reduced power consumption, including an air compressor producing a compressed air stream; a source of pressurized oxygen-rich gas having a pressure higher than the pressure of the compressed air stream; a mixing apparatus for mixing the oxygen-rich gas/compressed air stream mixture with an ammonia gas stream; an ammonia converter to provide in a NO.sub.x gas/steam mixture; a water cooler/condenser for separating and condensing steam from NO.sub.x gas in the gaseous NO.sub.x gas/steam mixture; an absorption tower downstream the water cooler/condenser, for absorbing NO.sub.x gases in water, to provide in a stream of raw nitric acid-containing residual NO.sub.x gas and a tail gas including NO.sub.x gases. The system further includes a mechanism for splitting the tail gas into a first tail gas stream and a second tail gas stream; and a mechanism for adjusting the amount of tail gas being split.

A vertical bleaching tower for removing dissolved nitrogen oxides from an aqueous nitric acid solution using a stripping gas such as air, nitrogen, oxygen or combinations thereof in a process for producing nitric acid, comprising a structured packing; a liquid distributor comprising a feed box having a serrated weir for distribution of the aqueous nitric acid solution comprising the dissolved nitrogen oxides through upward-pointing serrations of the serrated weir into perforated trays of the liquid distributor and located above the structured packing for distributing the aqueous nitric acid solution comprising the dissolved nitrogen oxides to the structured packing; an inlet and outlet, both suitable for aqueous nitric acid solution; and an inlet and outlet, both suitable for the stripping gas. The present invention further comprises a bleaching method for removing dissolved nitrogen oxides from an aqueous nitric acid solution in a vertical bleaching tower.

A method for preparing electronic grade inorganic acids includes: introducing alkali metal salts into a waste acid solution containing hydrofluoric acid, nitric acid and water to obtain hydrogen fluoride vapor, and a distillation residue mixture containing nitric acid, water and the alkali metal salts; subjecting the first distillation residue mixture to evaporation treatment, and then introducing an alkali earth metal nitrate salt into the resultant nitric acid/water mixture followed by distillation treatment so as to obtain nitric acid vapor; and removing mist droplets in the hydrogen fluoride and nitric acid vapor, followed by condensation treatment and concentration adjustment so as to obtain electronic grade hydrofluoric acid and nitric acid.

A method for preparing electronic grade inorganic acids includes: introducing alkali metal salts into a waste acid solution containing hydrofluoric acid, nitric acid and water to obtain hydrogen fluoride vapor, and a distillation residue mixture containing nitric acid, water and the alkali metal salts; subjecting the first distillation residue mixture to evaporation treatment, and then introducing an alkali earth metal nitrate salt into the resultant nitric acid/water mixture followed by distillation treatment so as to obtain nitric acid vapor; and removing mist droplets in the hydrogen fluoride and nitric acid vapor, followed by condensation treatment and concentration adjustment so as to obtain electronic grade hydrofluoric acid and nitric acid.