Abstract: A method for the post-combustion of exhaust gases comprising carbon monoxide from metallurgical processes includes conditioning the exhaust gas prior to post-combustion by metering a combustion gas and/or one additional gas in feedback-controlled fashion. The feedback control depends on the composition of the exhaust gas dependent on the exhaust gas volume flow. A device for post-combustion of exhaust gas during vacuum treatment of liquid steel comprises a flare stack at an exhaust outlet, means for feeding combustion gas to the flare stack, means for feeding an inert gas into the exhaust gas channel of the vacuum pump, means for ascertaining the exhaust gas volume flow and/or for measuring the exhaust gas velocity within the exhaust gas channel, means for analyzing the exhaust gas composition, means for metering the combustion gas and the inert gas, and means for feedback control of the metering of the combustion gas and/or the inert gas dependent on the exhaust gas composition.

Abstract: Process for producing a nitric acid of a concentration from 75 to 99.9% from a more diluted nitric acid, wherein a nitric acid of a concentration of about 45 to 70% is rectified in contact with a liquid extraction medium to prevent the formation of a nitric acid-water-azeotropic mixture, and the vapors of the concentrated nitric acid are condensed and a concentrated nitric acid is obtained and wherein additionally the extraction medium is reconstituted through reconcentration and returned into the extractive rectification, wherein the nitric acid to be concentrated is fed as a boiling liquid or partially vaporized to the extractive rectification preferably carried out in two columns (K 1.0, K 1.