Sammendrag
A small scale (30 kW thermal input) stratified downdraft gasifier is erected in the laboratory at the Norwegian University of Science and Technology (NTNU). The gasifier will be coupled to a gas engine to produce heat and power from biomass fuels. The paper describes the gasifier in detail (500 mm height and 100 mm diameter). One of the singularities of the gasifier design is that it allows for variation of the point of air injection and that air preheating is also possible. The gas engine was originally a diesel engine but it has been modified for producer gas and/or natural gas operation. These changes mainly affect the compression ratio and the fuel injection system. The paper describes the gas engine and explains the modifications. Experiments have been performed of gasification of wood pellets. The feeding rate was about 5 kg/h, giving an effect of 30 kW. The amount of air supplied to the reactor has been varied in the experiments, in addition to the location of the supply. The fuel gas composition has been measured with a GC. The amount of product gas obtained is about 12.5 Nm3/h and has a heating value of 4.9 MJ/Nm3. From these data, the power produced by the gas engine is expected to be about 5 kWe. The gas engine will be operated with mixtures of synthesis gas and natural gas and detailed measurements of cylinder pressure, compression ratio and heat released by the engine are planned in addition to emission measurements of CO, unburned hydrocarbons and NOx. The dependency of the results on the ratio of synthesis gas/natural gas will further be evaluated.
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