Blending effect of sewage sludge and woody biomass into coal on combustion and ash agglomeration behavior

• Published in: Fuel (Guildford) 2018-08, Vol.225, p.266-276
• Main Authors: Namkung, Hueon, Lee, Young-Joo, Park, Ju-Hyoung, Song, Gyu-Seob, Choi, Jong Won, Choi, Young-Chan, Park, Se-Joon, Kim, Joeng-Geun
• Format: Article
• Language: English
• Subjects: Agglomeration; Ash; Ash agglomeration; Ashes; Biomass; Biomass burning; Blending effects; Burnout; Co-combustion; Coal; Combustion; Electric power generation; Energy dispersive X ray spectroscopy; Melt temperature; Mineral phase; Phosphorus; Power plants; Scanning electron microscopy; Sewage sludge; Shrinking core model; Sludge; Thermogravimetric analysis; Volatilization; Woody biomass; X-ray diffraction; X-ray spectroscopy
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2018.03.109

•The combustion and ash agglomeration characteristics of coal and BSW mixture were investigated.•Addition of BSW into the coal lowered the combustion temperature profiles during non-isothermal heating conditions.•Carbon and reagent gas reaction occurred on exterior and interior of the particle during char combustion.•BSW containing high phosphorus contents made a high agglomeration tendency and low melting mineral phase. The co-combustion of sewage sludge and woody biomass is a key issue in coal power plants. Different combustion and ash behaviors of sewage sludge and woody biomass cause unpredictable operating concerns. In this study, the combustion and ash agglomeration behavior of blended fuel of sewage sludge and woody biomass (BSW) were investigated while coal co-combusted with it. Thermogravimetric analysis (TGA) revealed that adding a high amount of BSW into the coal lowered volatilization, ignition, and burn-out temperature. The char combustion reactivity of coal differed from that of BSW. The shrinking core model (SCM) and volumetric reaction model (VRM) were used to fit the char combustion reactivity of coal and BSW. In the case of ash agglomeration behavior, BSW addition led to increasing particle agglomeration at fouling temperatures. In particular, phosphorus composition influenced particle growth, which was verified using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) analysis. Furthermore, the ash mixture ratio of BSW and coal changed the intensity of the phosphorus-bearing mineral phase from X-ray diffraction (XRD) analysis, and finally influenced the melting temperature of the ash.