APROVIS used a two-stage exhaust gas heat exchanger unit for the district heating network – one for each engine with one high-temperature stage and one low-temperature stage. The SCR catalytic converters reduce the proportion of nitrogen oxides to < 200 mg/Nm3 and the proportion of carbon monoxide to < 267 mg/Nm3, each in relation to 5% oxygen. The NOX values are measured continuously at the SCR catalytic converter’s outlet. Urea injection is regulated based on these measured values, resulting in minimum consumption and low operating costs. The exhaust gas mass flow per engine is 50,400 kg/h.