Abstract A process for the preparation of nitric acid of different concentrations, and preferably of a concentration below 75 percent (weak acid) and of about 98 percent (highly concentrated acid) comprising oxidizing catalytically ammonia and air under pressure to form nitrous gas, oxidizing the NO contained in the gas in a first oxidation step with subsequent chemical absorption of the oxidized NO into a nitric acid obtained in a preceding covering step, whereby a weak nitric acid is formed, and oxidizing the NO remaining in the nitrous gas in a second oxidation step completely to NO2, removing the NO2 from the gas by physical absorption into highly concentrated nitric acid, separating the NO2 from the nitric acid, liquefying the NO2 and oxidizing the liquefied NO2 with aqueous nitric acid to obtain highly concentrated nitric acid.
Process according to claim 1 wherein the residual gas remaining after separation of said NO2 is contacted with said weak nitric acid formed in the process, at a temperature in excess of 40* C.
Claim 2
Dependent Claim
13 words
Process according to claim 1 which comprises subjecting said weak acid to rectification.
Claim 3
Dependent Claim
19 words
Process according to claim 1 which comprises introducing additional water into said chemical absorption of said oxidized nitrous gas.
Claim 4
Dependent Claim
31 words
Process according to claim 1 which comprises utilizing at least a part of said weak nitric acid formed in the chemical absorption in the formation of said highly concentrated nitric acid.
Claim 5
Dependent Claim
30 words
Process according to claim 1 wherein at least a part of the nitric acId formed in said cooling step is used in the formation of said highly concentrated nitric acid.
Claim 6
Dependent Claim
22 words
Process according to claim 1 which comprises simultaneously preparing nitric acids of a concentration below 75 percent and of about 98 percent.
Claim 7
Dependent Claim
21 words
Process according to claim 1 which comprises conducting said process at a pressure of from about 4 to about 10 atm.
Claim 8
Dependent Claim
19 words
Process according to claim 1 which comprises separating the absorbed NO2 from the highly concentrated nitric acid by distillation.