Nowadays nitric acid plants are currently based on the same basic chemical operations:
- Oxidation of ammonia with air resulting nitric oxide
- Oxidation of the nitric oxide to nitrogen dioxide and absorption in water resulting a solution of nitric acid
Low pressure increase the efficiency of the first step, whereas the efficiency of the second step is favoured by high pressure.
The above considerations, in combination with economic reasons generates to two types of nitric acid plant, single pressure plants and dual pressure plants. In the single pressure plant, the oxidation and absorption steps take place at essentially the same pressure. In dual pressure plants absorption takes place at a higher pressure than the oxidation stage.
Monitoring of emissions plays an important part in environmental management for nitric acid plants. It is a good practice to perform continuous monitoring that can lead to rapid detection of process upsets and can give the operators the possibility to correct and restore the optimum standard operating conditions as quickly as possible.
Overall, fertilizers accounted for almost 80% of total nitric acid consumption, with ammonium nitrate accounting for more than 96% of that. Other nonfertilizer applications include production of nitrobenzene, TDI, adipic acid, and nitro-chlorobenzenes.
