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NOx reduction by SCR

Nitrogen oxides have a negative impact on the environment and human life.

They can be removed by a process called selective reduction catalysis, in which an aqueous urea solution is sprayed into the hot flue gas, resulting in the conversion of nitrogen oxides to non-toxic nitrogen and water vapor. Today’s diesel- and the gas-fuelled industry faces a significant problem with atmospheric emissions of nitrogen oxides (NOx). Our SCR systems are designed with efficiency and ergonomics in mind, which, combined with the use of the best materials, allows them to meet the most stringent emission limits while ensuring reliable operation. Thanks to the closed-loop dosing system, we can ensure that urea consumption is kept at the lowest possible level to reduce NOx, which directly translates into reduced operating costs, and our computational fluid dynamics tools help us to determine the best place to install the urea dosing nozzle.

Our SCR system

Our SCR system

Here are some considerations to consider before purchasing an SCR system:

  • Location of the SCR system- if the SCR system is to be operated outdoors, it is worth considering water-impermeable thermal insulation. In such cases, we provide welded insulation.
  • We recommend not moving the SCR system too far away from the turbine outlet, typically this is 3-5 metres. This will ensure that the system operates within the correct temperature range (typically 250-500 oC).
  • At genset start-up, dust emissions are very high; if a catalytic substrate with a high channel density is used (e.g. CPSI>200), individual channels may become clogged. This will result in an increase in exhaust back pressure and consequently a reduction in engine power. Obviously, NOX reduction efficiency will also decrease.
  • If particulate emissions are too high, the SCR should be fitted with a soot blower system.
  • Urea can be used in a 32.5% and 40% solution. The 32.5% solution freezes at a temperature of around -11°C, if SCR is to be used at these temperatures, the system should be equipped with heated urea lines. The 40% solution freezes at 0 °C and is mainly used in the marine industry.
  • Low sulphur fuel is currently used in Europe. If a engine with an SCR system is intended for outside the EU, it is worthwhile to know which fuel will be used. A high sulphur content and low exhaust temperature leads to the formation of ammonium bisulphate, which causes clogging and deactivation of the SCR catalytic converter.
  • Preliminary numerical calculations made by the company supplying the SCR are able to determine many of the operating parameters and also select the minimum mixer pipe section and mixer geometry.

Contact us

Our team is happy to answer any questions.