Solid Phase Deposition Character Of Biomass Derived Fuel In The Gasification Process

Biomass as a kind of clean and renewable energy source, co-gasified with the plastic canrealize large-scale and high-efficiency use of biomass. However, biomass has high levels ofalkali metals, which can easily lead to solid phase deposition and corrosion problems duringthe mixed fuel gasification process. Eventually, it will adversely affect the service life and thesafety production of gasification boiler. A method of theory combining with practice isadopted in this paper. For getting in-depth study about solid phase deposition characteristicsduring co-gasification of biomass and plastic (PE/PVC), advanced test method is used, suchas AFT、SEM-EDS、XRD and XRF.Through the analysis of ash contents during biomass co-gasification with PE, the resultsshow that every material content in the ash increased with the increasing content of PE/PVCpresenting as nonlinear changes. During the co-gasification of biomass (cornstalk straws andrice straws) and PE, the degree of disintegration of gasified ash was gradually increased withthe increase in polyethylene (PE), thus facilitating the gasification. Changes in relativecontents of acidic oxides (SiO2+P2O5+Al2O3) and basic oxides (Na2O+K2O+CaO+MgO+Fe2O3) had a similar influence on DT of the gasified ashes for both mixtures (CS+PE,RS+PE) with a distinctive effect on their ST. Additional increase in PE had no influence onthe mineral species in the gasified ash. The softening temperature (ST) of co-gasification ashof corn straw and polyvinyl chloride (PVC) prediction by using the ternary phase diagram isfeasible, but the prediction error was existed.When the content of PE was80%during co-gasification of the biomass (RS, CS) andpolyethylene (PE), the ash formation characteristics was better. When the content of PVC was20%during co-gasification of the rice straw and PVC, the ash formation characteristics wasbetter and the negative effect of Cl was small. The ash formation characteristics was betterwhen the biomass derived fuel was gasified at800℃.With the increase of PE/PVC content, the co-gasification ash surface of biomass (rice straw, corn straw) and PE/PVC changed from the smooth structure and compact to theloose floc or lamellar structure gradually. Addition of PE/PVC has advantageous inalleviating fouling and slagging tendency of gasification ash. Through the XRD analysis, itcan be found that the smooth and dense surface gray was included in the low melting pointminerals, such as K, Na silicate minerals and the flocculent and the lamellar structurecontained higher melting point minerals, such as Ca, Mg and other silicate minerals.By modify the fouling and slagging prediction model Ratio-slag viscosity index, thenew forecasting model SF(+K, Na)=SR/exp (K2O+Na2O) was established. The model hashigher prediction accuracy by using the experimental data to validate. It has betterapplicability to prediction the co-gasification ash of biomass (rice straw, corn straw) andPE/PVC fouling and slagging.