Study Of The Dynamic Characteristics Of Ash Deposition And Slag During Biomass And Coal Co-Firing

Biomass is a kind of clean and renewable energy source, with the coal mixed combustion can realize large-scale and high-efficiency use of biological mass, but because biomass is rich in alkali metal, it is easily lead to produce solid phase deposition and corrosion problems during the mixed fuel combustion process. A method of theory combining with practice is adopted in this paper, For getting in-depth study about solid phase depositionary characteristics during the process of biomass and coal mixed combustion, advanced test method is used, such as SEM、XRD and EPMA.Through the analysis of ash contents in the dust generated during coal combustion with biomass, the results show that every material content in the dusts are increase with the increased content of biomass presenting as nonlinear changes. Along with the increase of biological mass content, alkali metal of K, Na and alkaline metal Mg, Ca content increase, K in 2%~18%, and Na in 1%~6%, it is In relation to high content of alkali metal and alkaline metal in the biomass;the content of Si in the ash is more stable, it is in 50%~60%, the biomass mixture ratio, reaction temperature and reaction time don’t have a major influence to Si content. Al is another important element in the ashes, Its content is only second to Si content, Al become 20%~8% and it’s content is decreased as biomass content adding.XRD analysis reached some conclusions that alkali metal and alkaline metal have a significant contribution to fouling and slagging during the process of biomass and coal mixed combustion, potassium feldspar, albite, sodium sulfate and calcium feldspar have a primarily position, and the first three kind of materials itself have strong viscosity and lower melting point, these features make deposition appearing molten state in the lower temperature.EPMA analysis discovered Si, Al and Ca is the key elements of depositions, in the situation of different mixture proportion or different reaction time, the effect on the main elements content in the deposition would be modest. Si and Al have similar distribution, it is visible that aluminosilicate and Fe elements play an important role during the process of deposition. Potassium feldspar exist in the interior of the deposition, it make the structure of the deposition more stable. Most of stable Ca compounds is in the interior of the depositions. The viscosity of Potassium feldspar and sodium sulfate formed in the depositions surface make depositions to concentrate more easily.