Circular concentration method for treating dilute nitric acid produced by nitrotoluene waste sulfuric acid

Abstract

The invention discloses a circular concentration method for treating dilute nitric acid produced by nitrotoluene waste sulfuric acid. The circular concentration method comprises a start-up phase and aproduction stage, wherein the production stage comprises the following steps: cooling 15%-40% low concentration dilute nitric acid produced from a denitration condenser for waste sulfuric acid treatment, and mixing the dilute nitric acid with concentrated nitric acid with a mass friction higher than or equal to 50% until the density of the mixture is larger than that of nitrotoluene; separating free nitrotoluene liquid, and concentrating by virtue of a nitrogen oxide compressor unit until the concentration is higher than or equal to 50%; applying a part of concentrated sulfuric acid with theconcentration higher than or equal to 50% to subsequent density adjustment, and discharging the other part into a finished product tank region; and compressing and absorbing nitrogen oxide gas by virtue of a nitrogen oxide compressor, absorbing nitrogen oxide gas by virtue of a nitrogen oxide absorbing tower, and discharging until nitrogen oxide gas reaches the standards. The circular concentration method is applicable to the separation and concentration of nitrotoluene in low-concentration dilute nitric acid with middle in the treatment of waste sulfuric acid, so that the use value of low-value dilute nitric acid is increased, the production balancing problem of dilute nitric acid is well solved, and the treatment economy of waste sulfuric acid is increased.

Description

Technical field [0001] The invention relates to a waste acid concentration chemical process, in particular to a cyclic concentration method of dilute nitric acid produced by processing nitrotoluene waste sulfuric acid. Background technique [0002] At present, the most advanced waste sulfuric acid treatment technology in the world is the vacuum concentration of waste sulfuric acid and the pressure absorption of nitrogen oxides; the denitration process of vacuum concentration of waste sulfuric acid generally produces condensed dilute nitric acid with a concentration of 15%-40%, such as waste sulfuric acid For nitrotoluene waste acid, the dilute nitric acid contains a large amount of free nitrotoluene; the nitrogen oxide produced in the denitration process of waste sulfuric acid is condensed and then sent to the nitrogen oxide pressurized nitrogen oxide absorption tower for absorption, which is generally used 0.65mPa working pressure, absorption of nitrogen oxides emission concentr...

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Problems solved by technology

[0003] Dilute nitric acid contains a lot of free nitro compounds; the density range of dilute nitric acid is 1.1kg / L-1.25kg / L, and the density of nitro compounds is about 1.19kg / L. The densities of the two materials are very similar, and it is difficult to achieve free Continuous separation of nitro compounds from dilute nitric acid; in the subsequent nitration production, a large amount of nitro compounds are wasted and combined side reactions produce

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