Process and plant for preparing nitric acid

A plant for producing nitric acid by the Ostwald process, comprising:

• a primary air compressor;
• a secondary air compressor disposed in a conduit tract separate from the primary air compressor such that the secondary air compressor is independent of the primary air compressor;
• an ammonia oxidation reactor configured to react ammonia with atmospheric oxygen as primary air to afford a product gas mixture including a NOx-containing gas stream at a first pressure, wherein the primary air compressor is configured to bring the primary air to the first pressure;
• an NOx compressor disposed on a same shaft as the primary air compressor, wherein the NOx compressor is configured to compress the NOx-containing gas stream to a second pressure that is higher than the first pressure;
• an absorption apparatus configured to absorb the NOx-containing gas stream in water at the second pressure;
• a bleaching apparatus configured to bleach nitric acid with bleach air as secondary air, wherein the bleaching is performed at an operating pressure that is closer to the first pressure than the second pressure, wherein the secondary air compressor is configured to bring the secondary air to the operating pressure;
• and
• a bleach air compressor or a bleach air compressor stage disposed downstream of the secondary air compressor and downstream of the bleaching apparatus, wherein the bleach air compressor or the bleach air compressor stage is configured to bring a laden gas stream from the bleaching apparatus to the second pressure at which absorption of an NOx-containing gas stream occurs in water, wherein the bleach air compressor or the bleach air compressor stage operates independently of the NOx compressor.