Energetic, bio-oil, biochar, and ash performances of co-pyrolysis-gasification of textile dyeing sludge and Chinese medicine residues in response to K2CO3, atmosphere type, blend ratio, and temperature

Abstract

Hazardous waste stream needs to be managed so as not to exceed stock- and rate-limited properties of its recipient ecosystems. The co-pyrolysis of Chinese medicine residue (CMR) and textile dyeing sludge (TDS) and its bio-oil, biochar, and ash quality and quantity were characterized as a function of the immersion of K₂CO₃, atmosphere type, blend ratio, and temperature. Compared to the mono-pyrolysis of TDS, its co-pyrolysis performance with CMR (the comprehensive performance index (CPI)) significantly improved by 33.9% in the N₂ atmosphere and 33.2% in the CO₂ atmosphere. The impregnation catalyzed the co-pyrolysis at 370°C, reduced its activation energy by 77.3 kJ/mol in the N₂ atmosphere and 134.6 kJ/mol in the CO₂ atmosphere, and enriched the degree of coke gasification by 44.25% in the CO₂ atmosphere. The impregnation increased the decomposition rate of the co-pyrolysis by weakening the bond energy of fatty side chains and bridge bonds, its catalytic and secondary products, and its bio-oil yield by 66.19%. Its bio-oils mainly contained olefins, aromatic structural substances, and alcohols. The immersion of K₂CO₃ improved the aromaticity of the co-pyrolytic biochars and reduced the contact between K and Si which made it convenient for Mg to react with SiO₂ to form magnesium-silicate. The co-pyrolytic biochar surfaces mainly included -OH, -CH₂, C=C, and Si-O-Si. The main phases in the co-pyrolytic ash included Ca₅(PO₄)₃(OH), Al₂O₃, and magnesium-silicate.