METHOD FOR PRODUCING CONCENTRATED NITRIC ACID AND INSTALLATION FOR CARRYING OUT A METHOD OF THIS TYPE

摘要

The invention relates to a method for producing a nitric acid with a concentration of 75 to 99.9 % from a more dilute nitric acid. According to said method, a nitric acid with a concentration of approximately 45 to 70 % is rectified in contact with a liquid extraction agent in order to prevent the formation of a nitric acid-water-azeotrope, the vapors of the concentrated nitric acid are condensed and a concentrated nitric acid is obtained. The extraction agent is also reprocessed by reconcentration and returned to the extractive rectification process. The nitric acid to be concentrated is fed into said extractive rectification process, which is preferably carried out in two columns (K1.0, K1.1), as a boiling liquid or in a partially evaporated form, using the quantities of heat (W2, W5) that are available throughout the method. Nitric acid is added to the extraction agent before being fed into the extractive rectification process. The energy required is supplied to the extractive rectification process by indirect heating (W4, W8) and the extraction agent is supplied to the extractive rectification process in as concentrated a form as possible in order to minimize the quantity of extracting agent in the circuit and maximize energy use while ensuring maximum dilution of the extraction agent leaving the extractive rectification process.