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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 1.1), by utilizing the amounts of heat available to the entire process (W1, W2, W5), wherein, before feeding into the extractive rectification nitric acid is added to the extraction medium, and the energy required for the extractive rectification is supplied through indirect heating (W4, W8) and the extraction medium supplied in most concentrated form to the extractive rectification, so that simultaneously at the greatest possible dilution of the extraction medium flowing from the extractive rectification, the circulation amount of extraction medium is minimized and the utilization of energy maximized.

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