Production of highly concentrated nitric acid, comprises mixing dilute nitric acid with uncooled sulfuric acid, extracting and bleaching the nitric acid, heating the dilute nitric acid and evaporating water from the dilute nitric acid

摘要

The sulfuric acid is overheated by a heat exchanger (W2) and indirectly heated with steam. The overheated sulfuric acid is re-concentrated by flash evaporation of the water in vacuum processed evaporator. The dilute nitric acid is preheated on boiling temperature. The nitric acid is released with air in column of nitrous gas. The nitrous containing exhaust gas is cleaned under pressure by oxidation with atmospheric oxygen and absorption in water under recuperation of dilute nitric acid. The concentrated nitric acid is produced from dilute nitric acid by extractive rectification with the sulfuric acid. A packed column or packing column from enameled steel is used for the extractive rectification. The nitric acid concentration in the dilute nitric acid is greater than 65%. The highly concentrated nitric acid (greater than 99%) is extracted from extractive column (K1). The dilute nitric acid produced with absorption vapor is driven back for rectification and mixed with the concentrated sulfuric acid before rectification.