Patent ID: 6969446

Claim:
A process for the production of a nitric acid with a concentration of 75 to 99.9% from a more diluted or an impure starting nitric acid, comprising the steps of: contacting a starting nitric with an amount of extractive medium for rectification by feeding the nitric acid of a concentration of about 45 to 70% in a form selected from the group consisting of boiling liquid and in partially vaporized state or separated into vapor and liquid, into an extractive rectification under pressure condition selected from the group consisting of atmospheric pressure, hyperbaric pressure and vacuum and under prevention of forming a nitric acid and water azeotrope, obtaining nitric acid vapors from the rectification step and condensing the vapors to thereby obtain a concentrated nitric acid, reconstituting the extractive medium by reconcentration and returning the extractive medium to the extractive rectification, enriching at least 50% of the amount of extractive medium with nitric acid in an amount of 0.1 to 60% of the starting nitric acid before feeding it into the extractive rectification, and supplying the extractive medium in high concentration to the extractive rectification, while at the same time as the extractive medium, which is in a condition of low concentration, is flowing from the extractive rectification, a circulation amount of extractive medium is minimized, and wherein energy required for the extractive rectification heating is supplied through indirect heating from available process streams of the entire process, wherein the extractive rectification is carried out in two columns separated by an input site for the starting nitric acid, or in a concentration column which is divided into two column portions, wherein the rectification of the starting nitric acid and the yield of the concentrated nitric acid vapor is carried out in a first one of the two columns, and a separation of the nitric acid from the extractive medium is carried out in a second one of the two columns.