The metals contained in a solid biomass fuel form ash after combustion in a furnace, which lowers the thermal efficiency and causes clinker problems. Therefore, there is a great merit if demineralization can be carried out when raw materials are crushing to make pellets or briquettes. In this study, bamboo, which is a promising biomass resource, is used as a sample, was washed with water and hydrochloric acid. The influences of washing method（washing in static water, washing with stirrer, washing with ultrasonic waves）, sample grain size and hydrochloric acid concentration on ash removal, potassium and iron removal in the ash were investigated. And the influence of washing method was compared to that with cypress, which is one of the wood sample. As a result, with the bamboo sample, the amount of ash was greatly reduced by washing with static water for 5 min., and a higher ash removal effect was observed in both by washing with stirrer and with ultrasonic waves. Ash removal effects between washing with stirrer and with ultrasonic waves were almost the same. On the other hand, with the cypress sample, washing with ultrasonic waves showed a higher ash removal effect than that with stirrer. Almost no effect of hydrochloric acid concentration and the sample grain size on ash removal with the bamboo sample was observed in the scope of the present study. It was found that washing with water has a great effect to remove potassium from the bamboo sample. It was observed that iron in bamboo samples was hardly removed by washing with water, but decreased by using hydrochloric acid.

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