2.B.2 - Nitric Acid Production

Short description

Category Code Method AD EF
2.B.2 T2 PS D
Key Category: -/- - - - - - - - - - - - - - -

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T = key source by Trend L = key source by Level

D Default
T1 Tier 1 / Simple Methodology *
T2 Tier 2*
T3 Tier 3 / Detailed Methodology *
CS Country Specific
M Model
* as described in the EMEP/EEA Emission Inventory Guidebook - 2019, in the group specific chapters.
AD - Data Source for Activity Data
NS National Statistics
RS Regional Statistics
IS International Statistics
PS Plant Specific data
As Associations, business organisations
Q specific Questionnaires (or surveys)
M Model / Modelled
C Confidential
EF - Emission Factors
D Default (EMEP Guidebook)
C Confidential
CS Country Specific
PS Plant Specific data
M Model / Modelled

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 nine nitric acid plants.

Activity data

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, with one producer as exception who 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.

Emission factors

Different T2 default NOx emission factors based on different technology types and abatement systems are used from the EEA Emission Inventory Guidebook 2019 (EF for medium and high pressure processes and for catalytic reduction of low, medium and high pressure process)1). The applied emissions factors are listed in Table 1.

Table 1: Tier 2 emission factors of NOx for source category 2.B.2 Nitric acid production, in [kg/t]

EF Process
7.5 medium pressure process
3 high pressure process
0.4 low, medium and high pressure process, catalytic reduction


With activity data and emission factors remaining unrevised, no recalculations were carried out compared to Submission 2022.

Planned improvements

No category-specific improvements are planned.

1) EEA, Oct 2019: : EMEP/EEA air pollutant emission inventory guidebook 2019, Part B: sectoral guidance chapters, 2.B Chemical industry: pp.21-23, Table 3.11, Table 3.12 and Table 3.14.