Ecopure® SCR - Selective catalytic reduction
Knowing and Understanding the Need for NOx Control
NOx is a term used to describe exhaust gases consisting primarily of nitrogen oxide (NO) and nitrogen dioxide (NO2). NOx emissions are a concern because they contribute to the formation of acid rain and, either directly or through the creation of ozone, lead to harmful effects on human health. The combustion of fossil fuels has been determined as a major source of NOx emissions.
Dürr Will Provide the Necessary Engineering Capabilities
Dürr engineers will analyze your NOx abatement requirements, and then configure an optimum solution of equipment and process. Key factors used to achieve maximum results include:
- Air stream and constituents
- NOx type and concentration:
Fuel NOx is formed by oxidation of nitrogenous matter contained in the airstream/process
Thermal NOx is formed by oxygen reacting with nitrogen from the air at very high temperatures
- Utility costs
- Regulatory requirements
Dürr Systems has the technical ability for NOx abatement alone or include VOCs and HAPs in the process. NOx abatement systems can be retrofitted into existing processes as an economical way to meet tighter emissions regulations (tailpipe systems) or designed into greenfield facilities as an integral part of the process. Dürr has the management ability to handle the entire NOx abatement project in a turnkey fashion from conceptual design through installation and start-up.
The Right System to Remove NOx
Selective Catalytic Reduction (SCR) technology is a process designed to reduce the emissions of oxides of nitrogen. In SCR, ammonia (NH3) is added through an ammonia injection grid to the process exhaust containing NOx emissions. This creates a homogenous mixture which is then passed over a bed of catalyst. The catalyst promotes a reaction between NH3, NOx, and the excess oxygen (O2) in the exhaust stream, forming nitrogen (N2) and water (H2O).
Choosing the Proper System Elements with Dürr
The basic building blocks used to configure an Ecopure® SCR system include:
- SCR catalyst
- Ammonia injection grid
- Ammonia control systems
- NOx analyzers
- Heat recovery equipment
- Auxiliary burners
Flue gas purification
Ecopure® SCR systems are also used for the thermal Ecopure® VAR direct fired thermal oxidizer application if the non-selective catalytic reduction (SNCR) cannot be applied directly in the burning chamber, because of the high NOx concentrations and the resulting high necessary efficiency of the Denox system. The Ecopure® SCR can be furthermore realized as flue gas purification stage after the thermal oxidation as tail end solution.
The Precise Catalyst Makes All the Difference
The reduction of NOx is dependent on the volume, depth, density, operating temperature and type of SCR catalyst. The major factors influencing catalyst selection include process gas temperature and potential contaminants such as sulphur and particulate. The ammonia injection part of an Ecopure® SCR system needs to be designed to ensure complete mixing of the ammonia with the fue gas as an aid to the conversion process. When creating the homogenous mixture, either anhydrous ammonia (compressed gas), aqueous ammonia (water solution) or urea may be used for the reduction process.