Small-Scale biomass power plant with Stirling engine (STE) was developed in this R&D. In wood powder combustion test, air ratio could be down to 1.1 without increasing CO and unburned carbon. Combustion efficiency was higher than 99.9% at air ratio of 1.1. NOx emission was 100 ppm (6%O2) at air ratio of 1.1, and 200 ppm (6%O2) at air ratio of 2.5. As results of start-up and shut-down tests, operating performance and safety were quite excellent. It looks easy to establish a full-automatic control and operation system. Ash fouling problem in the heater head of STE was clearly found during wood powder burning. As a result, higher dust loading, higher combustion temperature, and also higher STE inlet gas temperature result larger amount of ash deposit. That is, potassium in wood fuel evaporates in burner zone, and it is accumulated at the surfaces of STE heater tubes. Ca, Si and another ash components are accumulated with together at this moment at the tube surfaces. At the final stage, continuous operation of about 7 hours with cyclone collector was carried out reducing ash fouling. We calculated energy balance, power generation efficiency is 20% in case that preheating air temperature is 600℃.
