Reformed natural gas (RNG) - Operation and development of plant

A steam reforming unit has been developed during this project. The unit converts natural gas into reformed natural gas (RNG), which contain hydrogen. The RNG is combusted in an SI engine, which produces power and heat. Hydrogen was supposed to reduce hydrocarbon emissions and increase the combustion efficiency. An efficient control strategy has been developed, and the plant has been operating automatically without problems for more than one week. An increase in power efficiency of 0,5% was achieved, but almost no reduction in hydrocarbon emissions. However, the engine was unable to operate at excess air ratios beyond 2, where 10% reduction in unburned hydrocarbon emissions was seen. It is believed that larger plants, which operates with more excess air, will demonstrate more reduction in unburned hydrocarbons with RNG. An increase in compression ratio with RNG over NG is possible since the engine operates more stable on RNG. This could further improve power efficiency with 2-3%. The payback time for the plant was calculated to be 81 years without the effect from increased compression ratio. This does not support implementation of the plant in practice