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) KAlSiO4, MgAl2O4 and their increasing contents by APS addition resulted in the AFT increased obviously; the increase in relative high MP Ca3MgSi2O8 caused the AFT increase moderately with increasing PMS percentage; with MWS addition, the increasing CaMgSiO4 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.

Automated summary

The study found that the addition of aluminum plant sludge had the greatest impact on the ash fusion temperature of wheat straw, while municipal waste-water sludge had the least impact. The influence of different sludges on wheat straw ash fusion was mainly caused by changes in the ratio of oxygen bonds and the content of certain substances.