Experiments on mechanism of biomass ash slagging

In order to provide references and bases for solving the problem of slagging and agglomeration that occurs during biomass thermal chemical transformation of straw, experiments on combustion of three different kinds of straw were carried out in a muffle under five different temperatures. XRD, ion chromatography as well as EDX analysis have been conducted to measure the elemental compositions and phase of bottom ashes. The results indicated that KCl and K₂SO₄ are the main forms of alkali metals in rice straw bottom ashes under 700°C combustion temperature. K₂MgSi₅O₁₂ KAISi₃O₈, the glassy compounds, are the main forms of alkali metals in rice straw bottom ashes above 750°C. The content of alkali metals in rice straw bottom ashes is lowest, but its slagging is most serious. We concluded that the slagging degree of straw ash at low combustion temperature relates not only to the content of alkali metals but also to KCl:K₂SO₄ ratio. Under higher combustion temperature, the slagging degree was mainly determined by glassy Compounds derived from SiO₂, K₂O, AI₂O₃ and other metallic oxide.