METHOD OF REGENERATING NITRIC ACID Russian patent published in 1997 - IPC

FIELD: nitric acid recovery. SUBSTANCE: invention concerns regeneration of nitric acid from raffinates containing acetic acid. Process includes rectification and/or scrubbing of nitric acid in column with withdrawal of acetic acid into low-acidic distillate from column zone where vapor flow exceeds that of phlegm flowing down the trays. Acetic acid is contained either in process solution fed onto one of top trays of column, or in secondary steam from evaporation of this solution fed into middle part of column. Excess of vapor flow is created either by evaporating process solution not containing acetic acid along with solution from which acetic acid were already distilled off, or by way of combining vapor flows from both solutions as rectification proceeds, or by way of giving additional water stream into rectification still. Regenerated concentrated nitric acid is produced via scrubbing with a separate water stream and withdrawal of regenerate from tray of column, whereas phlegm containing impurities is by-passed into column still omitting scrubbing zone. EFFECT: achieved one-step recovery of nitric acid. 5 cl, 1 dwg, 1 tbl