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DeNOX systemsfor NOx reduction

SCR and SNCR solutions to reduce nitrogen oxides in flue gas and meet more stringent emissions requirements.
What is a DeNOX system?
Chemical reduction of NOx in flue gas by reagent injection, with or without catalyst, depending on the project emissions target.
A DeNOx system is a solution designed to reduce nitrogen oxides (NOx) present in the flue gas by injecting a reagent, normally ammonia or urea, which converts NOx into nitrogen and water. Depending on the technology used, this reaction can occur either without a catalyst (SNCR) or on a catalyst (SCR). The choice between the two options depends on the reduction target, the temperature available in the process, the composition of the fumes and the degree of environmental requirement of the installation.

Types of DeNOX systems

SCR – Selective catalytic reduction

Catalytic NOx reduction with reactor and catalyst to achieve higher efficiencies and more restrictive limits.
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SNCR – Selective Non-Catalytic Reduction

Non-catalytic NOx reduction by direct injection of reagent into a high temperature area of the process.
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When is a DeNOX system needed?
A DeNOx system is needed when an installation must reduce its NOx emissions to comply with stricter environmental limits.

High emissions

Strict limits

Continuous combustion

Thermal processes

Environmental requirements

Post-combustion integration

Applications

Our DeNOX systems are used in:

INDUSTRIAL BOILERS

PROCESS FURNACES

THERMAL OXIDISERS

WASTE INCINERATION

STEAM GENERATION

COMBUSTION FUMES

BIOMASS PLANTS

THERMAL PLANTS

INDUSTRIAL BURNERS

WASTE TO ENERGY

We’ll be with you every step of the way

  • Process engineering

  • Technology selection

  • System design

  • Energy integration

  • Installation and commissioning

  • Maintenance and support

Frequently Asked Questions

The main difference is that an SNCR system performs NOx reduction without a catalyst, taking advantage of a high temperature zone in the process, while the SCR uses a reactor with a catalyst to increase conversion efficiency. In general, SCR is selected when higher reduction levels are needed and SNCR when sufficient temperature and a compatible reduction target exist.

Nitrogen oxides (NOx) are generated during combustion mainly by three mechanisms:

  • Thermal NOx (thermal NOx)
    It is formed at high temperatures (>1,200-1,600 °C) when the nitrogen (N ) and oxygen (O ) of air react with each other. It is the dominant mechanism in most processes and increases rapidly with temperature and residence time in flame.
  • Fuel NOx
    It arises when the nitrogen contained in the fuel itself is released during combustion and oxidises to form NOx. Its importance depends on the nitrogen content of the fuel.
  • NOx “prompt”
    It is produced in the early stages of flame, by the reaction of nitrogen from air with radicals derived from fuel. Their contribution is usually small, except in very demanding emissions conditions.
A DeNOx system reduces NOx by injecting a reagent, normally urea or ammonia, into the flue gas stream. This reagent favours the chemical conversion of NOx to nitrogen and water. The reaction occurs directly in the gas in SNCR or on a catalyst in SCR, depending on the selected technology.
The SNCR is appropriate when the process has a high temperature zone suitable for the reaction and the NOx reduction target is compatible with a non-catalytic solution. It is a cheaper and simpler alternative than SCR, provided that the injection point can be correctly defined and operation can be maintained within the required thermal window.
The SCR is appropriate when the project requires a higher NOx reduction or particularly strict emission limits. When incorporating a catalyst, the reaction is more efficient than in SNCR, but the design must consider gas temperature, reactor location and the possible presence of substances that deteriorate the catalyst.
The performance of a DeNOx system depends on several factors: temperature, mixture of reagent, distribution in line, NOx load and, in the case of SCR, gas compatibility with catalyst. In SNCR, the temperature at the injection point is especially critical. In SCR, in addition, the reactor must work in a suitable thermal window.

Yes. A DeNOx system can be integrated with other gas train equipment such as thermal oxidisers, scrubbers, DeSOx, monitoring systems or additional treatment steps. This integration is especially important in projects where the aim is not only to reduce NOx, but also to adapt the whole process to more demanding environmental, operational and control requirements.

Direct thermal oxidation treats the stream in a chamber without prioritising heat recovery. Recuperative thermal oxidation incorporates heat exchange to improve efficiency. Catalytic thermal oxidation reduces the required temperature using a catalyst, but requires an assessment of fouling, chemical compatibility, and operating limits. The choice depends on the pollutant, operating conditions, energy, and environmental objectives.

Do you need to reduce your facility’s denox emissions?

Our technical team can help you define the most suitable solution for your process, choosing between SCR or SNCR technology according to the reduction objective, operating conditions and environmental requirements of the installation.
Request technical advice