METHOD AND DEVICE FOR PROCESSING WASTE SULPHURIC ACIDS FROM NITRATION PROCESSES

Processing waste acid obtained from nitroaromatics production, preferably dinitrotoluene- or trinitrotoluene production, comprises: adding a pre-heated waste acid comprising sulfuric acid, water, nitric acid, nitrosylsulfuric acid and nitro-organics, into a stripping column in a counter-flow to the steam obtained from the bottom of the stripping column by heating a pre-concentrated sulfuric acid; separating nitric acid, optionally nitro-organics and the pre-concentrated sulfuric acid into at least one vapor phase; and processing the obtained nitric acid and the nitro-organics. Processing waste acid obtained from nitroaromatics production, preferably dinitrotoluene- or trinitrotoluene production, under recovery of concentrated and purified sulfuric acid and nitric acid, comprises: (i) adding a pre-heated waste acid comprising sulfuric acid and water (up to 80 wt.%), nitric acid, nitrosylsulfuric acid and nitro-organics, preferably dinitrotoluene and mononitrotoluene, into a stripping column in a counter-flow to the steam, which is obtained from the bottom of the stripping column by heating a pre-concentrated sulfuric acid in a first phase; (ii) separating nitric acid, optionally nitro-organics and the pre-concentrated sulfuric acid into at least one vapor phase; and (iii) supplying the obtained pre-concentrated sulfuric acid from the bottom of the stripping column for further purification to separate the highly concentrated nitro-organics in a first downstream stage, and processing nitric acid obtained from the nitric acid vapor phase, and the nitro-organics including the nitro-organics obtained during the further purification and concentration of the pre-concentrated sulfuric acid, and returning back to the nitration process in a second downstream stage. The step (i) comprises: adding the pre-heated waste acid into the stripping column for stripping in the counter-flow to the steam obtained from the pre-concentrated sulfuric acid in concentrating the stripping steam containing nitric acid in the counter-flow to the purified and optionally fresh concentrated sulfuric acid (75-97 wt.%, preferably 80-96 wt.%); and condensing the nitric acid vapors obtained from the top of the column of the first stage, and thus directly obtaining a highly concentrated form of nitric acid for returning back to the nitration process. An independent claim is also included for a device for performing the above method comprising: a first stripping column (K1) with a feeding line f