Nitric acid extraction and concentration method

Abstract

The invention belongs to the technical field of chemistry, and relates to a nitric acid extraction and concentration method, wherein dilute nitric acid is preheated by circulating sulfuric acid and then enters a nitric acid concentrating tower, the circulating sulfuric acid is further cooled and then enters the concentrating tower, the nitric acid is concentrated under the action of the sulfuric acid, so the concentrated sulfuric acid is formed and discharged from an overhead condenser, and a nitric acid product is obtained after nitric oxides are bleached and stripped by air; the dilute nitric acid is discharged from a reboiler of the nitric acid concentrating tower and is then vacuum concentrated, and the reboiler of the nitric acid concentrating tower adopts indirect steam heating; thedilute nitric acid undergoes first-class flash evaporation and then automatically flows into a sulfuric acid evaporator to be concentrated into a sulfuric acid product; and the whole technological process is simple and is easy to control, the operation load is low, raw materials are saved, the equipment is simple, the investment is less, the production efficiency is high, and the economic benefitis good.

Description

Technical field: [0001] The invention belongs to the technical field of chemistry, and relates to a method for extracting and concentrating nitric acid, in particular to a method for concentrating nitric acid using sulfuric acid as a dehydrating agent, which includes two processes of concentrating nitric acid and concentrating sulfuric acid. Background technique: [0002] Nitric acid is one of the important products in the chemical industry, widely used in chemical fertilizers, organic synthesis, dyes, explosives and metallurgical industries. The nitrification reaction in the field of explosives will produce a large amount of dilute nitric acid. These dilute acids need to be concentrated before recycling. In industry, magnesium nitrate or sulfuric acid is often used as a dehydrating agent to concentrate dilute nitric acid. Concentration of nitric acid by sulfuric acid method mainly includes two processes of concentration of nitric acid and concentration of sulfuric acid. Th...

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Problems solved by technology

Due to the use of more direct steam, the traditional process requires a large amount of sulfuric acid, which increases the load of sulfuric acid concentration; the drum type sulfuric acid concentration process shortens the life of the equipment due to corrosion problems, and the waste gas is difficult to treat, causing serious pollution to the environment

In "Ullman Encyclopedia of Industrial Chemistry" (volume A17, P293), a process flow of Plinke-NACSAL sulfuric acid method for concentrating nitric acid is introduced: sulfuric acid is added as reflux from the top of the concentration tower, and nitric acid vapor is discharged after passing through the rinsing tower; Sulfuric acid concentration adopts forced circulation heating and vacuum concentration; the exhaust gas produced by the concentration before and after is removed to the tail gas for absorption, and the vacuum concentration of sulfuric acid greatly reduces the pollution of acid gas to the environment. The disadvantages of this process are: a. There is no separation of nitric acid and sulfuric acid at the top of the nitric acid concentration tower In the section, a small amount of sulfuric acid may be entrained in the product; b. The energy of the material itself is not utilized (such as circulating sulfuric acid), which is wasteful; c. Under certain specific requirements (such as the organic matter in the acid needs high temperature to decompose), forced circulation can Heating to a higher temperature is more conducive to the decomposition of impurities, but for ordinary acids, there are more equipment in the forced circulation process, and the required heat source is of higher grade, which will increase the investment

[0003] Chinese patent CN1209282C discloses an improved sulfuric acid nitric acid concentration process, which integrates the heat, changes the original nitric acid concentration tower into two towers, and feeds part of the nitric acid to be concentrated after mixing with sulfuric acid, and the upper tower generates nitric acid vapor, The lower tower separates nitric acid and sulfuric acid, and the horizontal boiler in the tower needs direct steam to remove residual nitric acid, and the concentrated part of sulfuric acid is concentrated in a horizontal multi-chamber boiler in vacuum; this process reduces the consumption of cold and heat to a certain extent; more equipment is used , too much integration will easily make the operation unstable; the nitric acid concentration tower still needs to be fed with direct steam, which increases consumption; the sulfuric acid concentration acid gas is not washed, which will lead to high acid content and other disadvantages

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