SCR Catalysts for a Fresh Breeze Rather than Bad Air

Decentralized energy generation for the energy transition

Electricity and heat from combined heat and power (CHP) stations fueled by gas – biogas, natural gas, sewage gas or landfill gas – are contributors to the energy transition. For this type of power generation to be clean, exhaust gas treatment is necessary.

The exhaust gas from gas that is combusted to produce electricity contains CO₂ as well as nitrogen oxide (NO_x).

The Ordinance for the Implementation of the Federal Immission Control Act (BImSchV) continuously adapts the limits for nitrogen oxide emissions from CHP plants. Under the BImSchV’s current version, the maximum NO_x emission for a CHP plant with 1 to 50 MW output is 100 mg/m³.

Clean air protects our climate and our health – thanks to a SCR catalyst retrofit

To stay below the new limit value, exhaust gas needs to be treated. Selective catalytic reduction (SCR) is a process used to reduce nitrogen oxide, which is well-known from the AdBlue exhaust gas purification process used in Diesel vehicles.

An aqueous urea solution is added to a stream of hot exhaust gas, which releases ammonia from the urea. The ammonia is then reacted onto a catalyst, producing nitrogen and water.

Catalysts for CHP plants help meeting the revised legal requirements

Emission Partner GmbH & Co. KG from Ramsloh near Oldenburg, Germany is the first independent manufacturer of catalysts that fully concentrates on the development, production and sale of exhaust gas purification processes for gas engines. Their customers include decentralized power generators such as municipal utilities, CHP plant manufacturers and biogas plant operators.

Emission Partner are experts for the entire process of exhaust gas treatment, from combustion gas quality monitoring to exhaust gas processing and monitoring of limit values.

Urea requires a metering pump with high leak-tightness

To ensure that the aqueous, alkaline urea solution is accurately dosed, Emission Partner use KNF liquid transfer pumps in this process. And this is the right decision, because KNF has plenty of experience with this exhaust gas purification process using urea. The KNF Group has already sold more than one million diaphragm liquid pumps for automotive applications, where their durability is put to the test in 10,000 operating hours on average.

Emission Partner have selected a diaphragm liquid pump from the FEM 1.09 series for exhaust gas purification in CHP plants. These pumps are known to require little maintenance, be robust and durable. The full EPDM diaphragm provides the ideal solution for achieving the leak-tightness needed in this case. Thanks to the KNF modular system, every pump series model can be quickly and easily adapted to suit the specific needs of the application.

Immission protection around the clock

The SCR catalyst works round the clock – and so do all of its components, among them the KNF pump in the urea dosing line.

The urea pump transfers the reduction agent from the active tank to the dosing line with a flow rate of 35 ml/min. A finely controllable stepping motor ensures the reliable transfer of the volume through the FEM 1.09 diaphragm pump. This means overcoming a mean overpressure of 2 bar.

To make the NO_x reduction effective, the volume of urea must be adapted to the concentration of nitrogen oxide in the exhaust gas at any given time. The provision of the accurate volume of urea through the FEM 1.09 liquid transfer pump is controlled linearly via the frequency or voltage used. This ensures that the right amount of urea is always ready for transfer so that the harmful nitrogen oxide can be reduced to a level below the limit value for the protection of humans, the environment and the climate.

The result is fresher, healthier air for us all.