A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).

A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).

A process is disclosed for removing nitrous components from a raw liquid nitric acid stream to produce a bleached nitric acid product (55). The raw liquid nitric acid stream (37) is from an absorber (19) of a nitric acid process. The process comprises contacting the raw nitric acid liquid stream with an oxidising gas (12) in a bleaching stage (52). At least some of the gas effluent (12c) from the bleaching stage enters (12d) a combustion stage (15) of the nitric acid process. The oxidising gas (12) entering the bleaching stage (52) may comprise at least about one-third of an oxidising gas feed (12) to the nitric acid process. At least about one-tenth of the bleaching stage gas effluent (12c) may enter (12d) the combustion stage (15).

A process is disclosed for removing nitrous components from a raw liquid nitric acid stream to produce a bleached nitric acid product (55). The raw liquid nitric acid stream (37) is from an absorber (19) of a nitric acid process. The process comprises contacting the raw nitric acid liquid stream with an oxidising gas (12) in a bleaching stage (52). At least some of the gas effluent (12c) from the bleaching stage enters (12d) a combustion stage (15) of the nitric acid process. The oxidising gas (12) entering the bleaching stage (52) may comprise at least about one-third of an oxidising gas feed (12) to the nitric acid process. At least about one-tenth of the bleaching stage gas effluent (12c) may enter (12d) the combustion stage (15).

A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).

A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).

A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).

A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).

A process for recycling of a mixed acid containing nitrosyl sulfuric acid and sulfuric acid to obtain nitric acid and sulfuric acid, the process including adding (i) a dilute nitric acid to (ii) the mixed acid comprising nitrosyl sulfuric acid and sulfuric acid to effect the decomposition of the nitrosyl sulfuric acid and to obtain (iii) a liquid phase and (iv) a gaseous phase, adding steam to the liquid phase to separate (v) a purified sulfuric acid, and evaporate (vi) a mixture of concentrated nitric acid and nitrogen oxides, cooling the gas phase and the mixture of nitric acid and nitrogen oxides in order to separately obtain (vii) a purified nitric acid condensate and (viii) nitrogen oxides, absorbing nitrogen oxides (viii) in water to obtain dilute nitric acid (ix), and optionally, introducing at least part of the obtained dilute nitric acid (ix) into the process.

A process for recycling of a mixed acid containing nitrosyl sulfuric acid and sulfuric acid to obtain nitric acid and sulfuric acid, the process including adding (i) a dilute nitric acid to (ii) the mixed acid comprising nitrosyl sulfuric acid and sulfuric acid to effect the decomposition of the nitrosyl sulfuric acid and to obtain (iii) a liquid phase and (iv) a gaseous phase, adding steam to the liquid phase to separate (v) a purified sulfuric acid, and evaporate (vi) a mixture of concentrated nitric acid and nitrogen oxides, cooling the gas phase and the mixture of nitric acid and nitrogen oxides in order to separately obtain (vii) a purified nitric acid condensate and (viii) nitrogen oxides, absorbing nitrogen oxides (viii) in water to obtain dilute nitric acid (ix), and optionally, introducing at least part of the obtained dilute nitric acid (ix) into the process.