Effect of the Alkali Metals’ Existing Form on its Emission Characteristics during Biomass Combustion Process

As one kind of renewable energy, bio-energy attracts more and more scholars’ attention due to its good ignition, combustion characteristics and zero CO2 release during bio-energy combustion process, alkali metals’ emission could cause fouling, slagging, high temperature corrosion and ultra-fine particulate matter emission, which hazard equipment safety and human healthy. In this paper, the release characteristics of alkali metals during the combustion process of rice straw (RS) and sawdust (SD) was studied by the chemical desperation disposal method and in a vertical thermal balance furnace. Also, the concept of alkali metals’ release ratio was introduced. The Results indicated that increasing the combustion temperature leads to a bigger alkali metals’ release ratio. At the same temperature, the alkali metals release ratio of unwashed biomass is the largest, the acid-washed biomass is the smallest, and the water-washed biomass is in between them. Meanwhile, the existing forms of alkali metals cause different effect to the release ratio, i.e. the ionic form alkali metals release most greatly, the organic form smaller and the other forms the smallest.