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2.B.2 - Nitric Acid Production
During the production of nitric acid (HNO3), nitrogen oxide is produced unintentionally in a secondary reaction during the catalytic oxidation of ammonia (NH3). HNO3 production occurs in two process stages:
- Oxidation of NH3 to NO and
- Conversion of NO to NO2 and absorption in H2O.
Details of the process are outlined below:
Catalytic oxidation of ammonia
A mixture of ammonia and air at a ratio of 1:9 is oxidised, in the presence of a platinum catalyst alloyed with rhodium and/or palladium, at a temperature of between 800 and 950 °C. The reaction according to the Oswald process is as follows:
4 NH3 + 5 O2 –> 4 NO + 6 H2O
Simultaneously, nitrogen, nitrous oxide and water are formed by the following undesired secondary reactions:
4 NH3 + 3 O2 –> 2 N2 + 6 H2O
4 NH3 + 4 O2 –> 2 N2O + 6 H2O
All three oxidation reactions are exothermic. Heat may be recovered to produce steam for the process and for export to other plants and/or to preheat the residual gas. The reaction water is condensed in a cooling condenser, during the cooling of the reaction gases, and is then conveyed into the absorption column.
In Germany, there are currently seven nitric acid plants.
As this source category is a key category for N2O, plant specific activity data is collected here according to the IPCC guidelines.
This data is made available basically via a co-operation agreement with the nitric acid producers and the IVA (Industrieverband Agrar). As the data provided by the producers has to be treated as confidential, it is anonymised by the IVA before submitting it to the UBA. However, one producer is delivering its data directly to the UBA. After checking this specific data, it is merged with that provided by the IVA.
According to the IVA, catalytic reduction is used as an abatement method in some of the plants.
For NOx the default emission factor from the EEA Emission Inventory Guidebook of 10 kg/t NH31) is used.
With activity data and emission factors remaining unrevised, no recalculations have been carried out compared to last year's submission.
For pollutant-specific information on recalculated emission estimates for Base Year and 2018, please see the pollutant specific recalculation tables following chapter 8.1 - Recalculations.
Germany is in contact with the IVA with the aim to get a Country-specific EF for the NOx emissions. It is expected that the Country-specific EF will be lower than the Default EF.