SCR technology for reducing NOx emissions

SCR Technology can achieve more than 95% NOx reduction. SCR is the absolute NOx control system.

SCR technology for reducing NOx emissions

Selective Catalytic Reduction (SCR) is a method to reduce the level of nitrogen oxides (NOx) with the help of a catalyst.

SCR technology can achieve more than 95% NOx reduction in combustion processes and can meet stricter incoming legislation.

It is the absolute NOx control system.

With SCR technology:

  • The temperature of the flue gas is much lower than in SNCR systems
  • A catalyst is needed to reduce nitrogen oxides with the help of a reducing agent ( anhydrous ammonia, ammonia solution, urea solution). The NOx and ammonia enter the catalyst, causing the NOx to react with the ammonia to produce elemental nitrogen and water. It ensures that you reach good NOx control level, up to 95% reduction
  • The reagent consumption is optimized
  • Investment costs are high (Capex) given the catalyst but also its whole installation
  • The maintenance costs are high as you regularly need to renew the catalyst – when it shows signs of decreasing performance

When choosing SCR technology it is also important that you choose a reliable reagent supplier for ammonia or urea to ensure you are always meeting your legal requirements in terms of NOx emission reduction.

A reliable supplier guarantees continuous deliveries of the reagent. Without the reagent, your NOx control unit will stop as you will be over the emissions limits prescribed for your site according to the Clean Air Act.

Furthermore the quality of the reagent is particularly important to meet the strict demands of your catalyst supplier to ensure a long and maintenance free life-time of your catalyst.

Yara has been producing and delivering its reagents to clients for over two decades from our unique network of production plants which offer a constant back-up in sourcing, thus guaranteeing both supply and quality.

When choosing how to reduce NOx emissions, the feasibility and the economy of SNCR technology should also be investigated. The investment cost of an SNCR system is only a fraction of a complete SCR installation.

Ed Wells
Ed Wells
VP, Environmental Solutions, North America

Reliability and quality

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

Yara has been offering reagents and solutions to operators with SCR systems for almost two decades, and has experience and knowledge of how to avoid the challenges below.

Choose quality reagents to avoid SCR catalyst contamination

When you are operating your SCR system, it is very important to avoid using contaminated reagent. Since a contaminated reagent can lead to catalyst poisoning, it is important to ensure you are using the right quality of reagent, and that it is shipped and stored correctly. A catalyst poisoning/break-down may lead to premature replacement at a high cost.

Accurately calculated reagent injection is key for efficient NOx reduction

SCR systems require uniform distribution of ammonia and NOx in the gas stream to work optimally. Un-even gas distribution/ poor mixing may lead to insufficient NOx reduction and high ammonia slip. It is also important to determine the proper reagent dosage for all process conditions. Typically, all future operating conditions must be known beforehand to properly design and tune an SCR system.

Avoid ammonia slip with the right temperature and injection

Ammonia slip is an industry term for ammonia passing through the SCR reactor without reacting with the NOx gases. This can occur if ammonia is over-dosed, if the mixing upstream of the catalyst is not sufficient (uneven ammonia and NOx distribution) , if temperatures are too low for the catalyst to be sufficiently active or if the catalyst has lost too much activity by poisoning. Ammonia slip linked to SCR represents unnecessary costs and is not good for the environment.

Reagent injection

Yara: the expert for cost efficient and reliable operation of your SCR system

Our NOx Control reagents under our NOxCare brand are of a high quality. Most of our ammonia is made from natural gas, the cleanest hydrocarbon source available. We deliver the reagent of your choice from our unique network of production plants offering a constant back-up in sourcing, thus guaranteeing both supply and quality.

Reducing your costs

Want to reduce your operating costs for your SCR reagent?

Choice of reagent, dosing and injection have an important role in the economy of the SCR operations. Our experts will provide you with technical support and advice to ensure that your SCR installation is run in a cost efficient way. It is important to set the injection and flow in the proper manner so you use only what you need. Your costs in ammonia and urea can be optimized with our help and information.

Contact one our experts if you have any questions on how you can operate and optimize your SCR system by using the right reagent.