Siemens puts SCRs to test • Siemens is already looking
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ahead to Euro-4 emission levels by running trials of a selective catalytic converter (SCR) with three truck manufacturers.
The SCR is designed to reduce nitrous oxide (NOx) and hydrocarbon emissions: 15 Euro-2 trucks from MAN, Mercedes and Iveco have been fitted with Siemens' SIN0x-catalytic system, which is said to lower NOx emissions to 2g/kWh and to slash hydrocarbons by 80%.
Urea is used as a reducing agent in the system; it is injected into the SCR at a rate equal to 4% of the diesel consumption.
The process is linked to the engine's electronic diesel control, and the units can be retrofitted to vehicles with EDC. The technology is derived from work done on power station emissions.
One of the benefits for operators is that an SCRequipped truck can be optimised for fuel economy. This leaves the catalytic converter to take care of the emissions, rather than compromising fuel consumption to meet the limits.
Siemens has not set a price for the SCR, but it predicts that gains in fuel economy will give a payback period of two years.
Rather than re-optimising for economy, the engines in the test trucks have been left set to meet Euro-2. This means that if the prototype SCR units fail during the test, the emission levels will remain legal.