PROCESS FOR THE SIMULTANEOUS MANUFACTURE OF HIGHLY CONCENTRATED NITRIC ACID AND DILUTED NITRIC ACID

摘要

The invention relates to a process for the simultaneous preparation of highly concentrated and dilute nitric acid by catalytic combustion of ammonia with air, heat recovery from the hot combustion gas containing the nitrogen oxides with deposition of an acid condensate, chemical absorption of nitrogen oxides from the combustion gas using the acid condensate and formation of dilute acid, physical absorption of nitrogen oxides from the combustion gas using nitric acid of at least azeotropic concentration, desorption of the nitrogen oxides from the acid and reaction with water-containing nitric acid and air or oxygen to give over-azeotropic or highly concentrated acid, which is worked up thermally to give pure highly concentrated acid. According to the invention, the process is characterised in that the combustion of ammonia is carried out in a pressure range from 2 to 15 bar, the combustion gas in combination with customary heat recovery is cooled to a temperature in the range from 100 to 180 DEG C, the thermal work-up step is heated using the gas cooled to that extent with deposition of an acid condensate, and the gas is then passed on to the absorption steps.