METHOD FOR PRODUCTION OF CONCENTRATED NITRIC ACID Russian patent published in 1997 - IPC

FIELD: chemical technology. SUBSTANCE: method involves concentration of origin diluted nitric acid which is carried out in rectification column in the presence of dehydrating materials. Thus super azeotropic acid and volatile product comprising steams of acid are prepared. Said super azeotropic acid is fed for its further concentration in the other rectification column. Thus product and vat residue are obtained, said vat residue is separated in two portions at their ratio (1.22-4.0):1 respectively. Waste solution of dehydrating materials is evaporated and mixed with less portion of said vat residue. Into thus prepared mixture larger portion of said vat residue and steams of acid from stage of concentration of diluted nitric acid are added, thus obtained mixture is fed to the stage of concentration of origin nitric acid. Origin diluted nitric acid is separated into two streams at their volume ratio (1-4):(1-4) before its concentration is carried out. One of said streams is directly fed for concentration, other is initially mixed with mixture of evaporated solution of dehydrating materials with less portion of vat residue and with steam of acid from the stage of concentration of diluted nitric acid. EFFECT: improved efficiency. 1 dwg, 1 tbl