Nitric Acid Rectification

SABAR [Strong acid by azeotropic rectification] A process for making nitric acid by the atmospheric oxidation of ammonia. The nitrous gases from the oxidation are absorbed in azeotropic nitric acid in the presence of oxygen under pressure ... 

In 1957 Hercules Inc. started the first unit that produced concentrated nitric acid for commercial sales using magnesium nitrate as the extractive agent. In this process (see Figure 2) the weak nitric acid product from an AOP is fed to the appropriate tray of a distillation column. A concentrated solution of magnesium nitrate and water is fed to the proper tray in sufficient quantity to enrich the vapors to a concentration greater than 68 wt % nitric acid. The overhead product from the column is concentrated (98-99.5 wt %) nitric acid. A portion of the concentrated nitric acid is returned as reflux to aid in rectification. The... 

As mentioned earlier in this chapter, the SABAR process absorbs nitrous gases in azeotropic nitric acid in the presence of oxygen and then makes strong acid by azeotropic rectification. Some of the key reactions in this process are illustrated by Eq. (9.15) and Eq. (9.16). 

The SABAR (Strong Acid By Azeotropic Rectification) process makes nitric acid by the atmospheric oxidation of ammonia. Davy McKee developed the process and built plants based on this technology from 1974 to 1986. 

In Davy McKee s Sabar process (Strong Acid By Azeotropic Rectification) the nitrous gases from the oxidation of nitrogen(ll) oxide are absorbed in azeotropic (ca. 68 to 69%) nitric acid in the presence of atmospheric oxygen (at 6 to 13 bar) and superazeotropic acid is formed ... 

The manufacture of concentrated nitric acid (98—99%) can be done by two methods, direct and indirect. The indirect method, mainly used in the United States, is performed industrially by two different systems, the sulfuric acid and magnesium nitrate processes. Both processes involve the dehydration of nitric acid with concentrated H2S04 or Mg(N03)2. The sulfuric acid process has acute corrosion problems. This process utilizes azeotropic rectification to produce concentrated nitric acid. 

The second involves the absorption of N02/N0 in concentrated HNO3 (Re action 3.17). This produces a superazeotropic acid which then is distilled to produce concentrated nitric acid. Examples of these processes are the Uhde CNA (concentrated nitric acid) process and Davy McKee s SABAR (Strong Acid By Azeotropic Rectification) process. 

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