The case for Selective Catalytic Reduction (SCR)
Environmental legislation has limited the emissions of Nitric Oxides and Dioxides due to their damage to human health – particularly the respiratory organs – and the environment through chemical reactions in the atmosphere that create smog, greenhouse gases and acid rain. As a means of reducing NOx levels in exhaust gases, a process known as DeNOx, engine manufacturers are now looking at Selective Catalytic Reduction (SCR) in order to hit their gas emission targets.
NOx can be reduced by Ammonia (NH3) or urea solutions, such as AdBlue or Diesel Exhaust Fluid (DEF), over a catalyst at high temperature. This chemical reaction results in the NOx gases being converted into nitrogen and water, which are both harmless. As the global population increases, so too will the emission of NOx gasses from the combustion of fossil fuels if exhaust treatment is not implemented. Legislation is the main driver for change.
Customised SCR systems from Bürkert
An SCR system consists of a reducing agent storage tank, a reducing agent feeding and dosing unit, a reactor with catalyst (downstream of the reducing agent injection) and a control system. The main fluidic task Bürkert is involved with is the precise dosing of reducing agent into the reactor. If the injection rate is too high, not all of the ammonia will react with the NOx and some ammonia will ‘slip’ through the catalyst and impair performance. If the rate is too low, the desired NOx reduction will not be achieved.
The reducing agent flow control is accomplished by using either a pump unit in combination with a pulse valve (time pressure dosing). This is usually used in on or off road applications and does not rely on using forced air to atomise the reducing agent into the exhaust stream. These systems are referred to as ‘airless’. The second option is a pump unit in combination with a dosing unit. Here, the dosing unit includes a flow sensor and control valve. This is usually used on larger diesel engines where ‘forced air’ is used to help atomise the reducing agent into the exhaust stream.
Bespoke SCR systems from our Systemhaus experts
By applying our years’ of experience and knowledge in the field of SCR technology, we can customise our standard products to better suit the environment in which they operate. This flexibility allows us to propose systems that will operate over wide electrical conditions in environments that could be subject to high ambient temperatures, vibrations or high dust and water ingress protection requirements. We can also advise on material compatibility and operational life expectancy. All of which ensures that the dosing system is tailored to your individual exact requirements.
For more information about Bürkert’s Selective Catalytic Reduction (SCR) systems, or to discuss your application requirements in more detail, please contact our sales team today on +44 (0) 1285 648 720 or email email@example.com.