Investigation on ash fusion behavior modification of wheat straw by sludge addition

Energy utilization of biomass has attracted great interests. To decrease ash-related issues during straw gasification and mitigate sludge environmental pollution, the influences of three sludges [aluminum plant sludge (APS), paper-making sludge (PMS), and municipal waste-water sludge (MWS)] on the ash fusion behaviors of wheat straw (WS) and their variation mechanisms under reducing atmosphere were investigated. The ash fusion temperatures (AFTs) of mixed WS increased following APS > PMS > WMS when they were equal. The ratio of bridging-oxygen bonds and nonbridging-oxygen bonds of WS mixture decreased more obviously with APS addition than that of MWS, causing the WS-APS mixture AFT increased more quickly than that of WS-MWS. The formations of high melting-point (MP) KAlSiO, MgAlO and their increasing contents by APS addition resulted in the AFT increased obviously; the increase in relative high MP CaMgSiO caused the AFT increase moderately with increasing PMS percentage; with MWS addition, the increasing CaMgSiO content led to a slow increase in the AFTs. The variations in liquid-phase content in the WS mixtures based on FactSage calculation were also explained the AFT variations.