SCR technology

Flue gas treatment for NOx by Selective Catalytic Reduction

Flue gas treatment for NOx

Selective Catalytic Reduction (SCR) technology reduces emissions of oxides of nitrogen (NOx) by using a catalyst. SCR technology can achieve a reduction of up to 95% of NOx in the combustion process and can thus meet the more stringent future legislation. New legislation will come into force under the European Directive on Industrial Emissions in 2016. The SCR process is the most efficient technology as it provides the best conversion rate.

With SCR technology:

  • The flue gas temperature at the injection point is much lower than with an SNCR system. The application temperature is ideally located around 350°C 
  • The catalyst is used to favor the reduction reactions of NOx with the selected reducing agent (anhydrous ammonia, aqueous ammonia solution or urea solution) to produce nitrogen and water, thereby limiting the side reactions. It is guaranteed to deliver good reduction results, by up to 95% reduction 
  • The reagent consumption is optimized by molar ratio close to one between the reagent and NOx to be treated.

A suitable reagent and a reliable supplier are needed for the optimum operation of the SCR system

If you choose SCR technology, the choice of reagent is essential for the optimal performance of your NOx treatment.

  • The quality of the reducing agent is important because the pollutant content or catalyst poisons must be minimal. The catalyst manufacturer demands reagent specifications that must be respected in order to optimize the lifetime of the catalyst and ensure it exceeds the validity of the contractual warranty. At Yara we make sure you have the right quality of reagent for your SCR catalyst
  • In addition, it is important to choose a reliable supplier that can ensure continuous supply of the reagent, urea or ammonia. If there is a failure in the supply of reagent, the consequences are that your processing unit cannot operate. This causes an interruption in your business as it cannot meet the legal requirements in terms of reduction of NOx emissions, which are included in your site permit, in accordance with the IPPC Directive and the Directive on Industrial Emissions.

Poor quality reagent or unreliable deliveries of reagents to your site can have negative effects on your NOx control system

Yara has produced and supplied reducing agents to its customers, through its NOxCare range, for more than twenty years. Our unique network of production sites offers security of supply, ensuring both quality and reliability. Our factories deliver urea or ammonia for NOx reduction nationwide.

Yara has provided reducing agents and solutions to SCR system operators around the world for almost twenty years. Yara brings you its expertise and can follow you in all stages of the implementation of an SCR system.

Select a quality reducing agent to prevent deactivation of your SCR catalyst

When you use your SCR system, it is very important to avoid the use of contaminated reagent. Contaminated reagent can deactivate the catalyst, therefore, it is important to make sure you use a good quality reagent, delivered and stored correctly. Deactivated catalysts can lead to premature and costly replacement of your SCR system which reduces NOx (nitrogen oxides). Yara provides products that have been developed to ensure compatibility with all SCR catalysts., and we control our reagent’s attributes through our quality system. All our production sites are ISO 9001, 14001 and 18001 certified.

Precise calculation of reagent injection is key to an effective NOx reduction solution

To optimize their operation, SCR systems require a uniform distribution of ammonia and NOx in the flue gas stream. An uneven distribution of gas can lead to a reduction in NOx that is not sufficient and a significant ammonia slip occurs. It is also important to determine the correct dosage of the reducing agent for all possible configurations of the process. Typically, all future operating configurations are known prior to the design and development of your SCR system.

Prevent ammonia slip with correct temperature and ammonia injection

Ammonia slip is an industry term that describes the passage of ammonia through the SCR catalyst without reacting with the NOx gas. This can happen if: 

  • There is an overdose of ammonia 
  • The mixture upstream of the catalyst is not sufficient (irregular distribution of ammonia and of NOx) 
  • Temperatures are too low for the catalyst to be sufficiently active or if the catalyst is completely or partially deactivated due to its deterioration

Ammonia slip brings SCR unnecessary costs and is not good for the environment. With Yara’s expertise, we can ensure Ammonia slip is prevented.

Yara: the expert in cost effective and reliable SCR system operation

Our reagents for reducing NOx, marketed under the brand NOxCare, are of the highest quality. The vast majority of our ammonia is produced from natural gas which is considered a cleaner process. We deliver the reducing agent of your choice from our network of plants, giving you the assurance of a reliable supply. Choosing Yara is a guarantee of both reliability and quality.

Want to reduce your operating costs for your SCR reagent?

The choice of the reducing agent, the dosage and the injection method have a significant economic impact on the cost of your SCR operations. Our experts will advise you and provide appropriate technical support to ensure the cost efficient operation of your SCR installation. It is important to precisely calculate and adjust the injection and flow properly, so that only the necessary amount of reducing agent is used. Costs of ammonia and urea reagents can be optimized with our help and information.

To learn how to use and optimize your SCR system by using the right reagent: contact one of our experts.

When you choose a technology to reduce NOx emissions, the feasibility and cost of SNCR technology must also be considered. The investment cost of an SNCR system is much lower than that of a complete SCR system and its effectiveness may be sufficient for your needs.

Learn more about Yara's SNCR systems to reduce NOx emissions.