Research On The Slagging Characteristics Of Guangdong Typical Crop

Because biomass ashes contain a lot of alkali metal, it is quite easy to cause slag duringbiomass combustion. In this paper, the slagging characteristics of three Guangdong typicalcrops （rice straw, bagasse and sugarcane leaves） was studied to provide guidance to the actualoperation of biomass power plants.First, effect of ashing temperature on the characteristics of biomass ash was studied. Itwas found that the biomass ash content at high temperature was less than low temperature, forthe higher the temperature, the more fully the biomass combustion, and many of inorganicelements in the form of organic matter volatilized more easily at high temperature. BySEM-EDX it was also found that the alkali content at815℃was lower than575℃, whichindicated that alkali metal （K, Na） volatilized easily at high temperatures. And it wasdetermined by XRD that alkali metal （K） migrated into the gas phase in the form of KClvapor.Next, three crops were burned in a tubular furnace at different temperatures （600℃to900℃）, and their slagging degree were evaluated through5slagging identification index ofash melting point, acid-base ratio, alkali index, Si ratio and Si/Al ratio. The results showedthat rice straw is easy to slagging and single slagging identification index does not accuratelyreflect the actual burning slagging. Therefore, a biomass fuel combustion slagging predictionmodel based on fuzzy neural network was established and the simulation results wereconsistent with the experimental results, which indicated that the model is reliable andeffective.After mastering the slagging degree of the three crops combustion, using FactSage tosimulate their combustion conditions of different temperatures and adding different additives（CaO, Al₂O₃）. Combined with the previous experiments, the biomass combustion slaggingmechanism and resistance to slagging mechanism of the additives were analysised. Becausethe rice straw combution produces large amounts of molten K₂O, which is easy to generateliquid potassium silicate once contacting with SiO₂, and then cause low temperature eutectic,resulting in slagging. The additives of CaO and Al₂O₃can slow down the slagging degree. CaO mainly consume large amounts of SiO₂by reacting with SiO₂to generate solidCa₃Si₂O₇（s） and MgOCa₃O₃Si₂O₄（s） with a high melting point, thereby inhibiting thegeneration of large K₂Si₄O₉（liq）. Al₂O₃is serving dual purposes: to capture potassium in thebottom ash and to neutralize reactive silica into a more high melting temperature andfavorable phase, such as KAlSiO₄and KAlSi₂O6.