A novel method of calcium dissolution-crystallization-polymerization for stabilization/solidification of MSWI fly ash.

Municipal solid waste incineration fly ash (MSWI FA) stabilization/solidification using calcium carbonate (CaCO3) oligomer is an efficient, low-carbon disposal method. The insoluble Ca in FA was converted to free-Ca, utilizing for CaCO3 oligomer preparation, which was crystallized and polymerized by thermal induction to develop continuous cross-link or bulk structures for stabilization/solidification of potentially toxic elements (PTEs, e.g., lead (Pb) and zinc (Zn)). Experimental results showed that the weakly alkaline acid-leaching suspension provided an excellent condition for the generation of CaCO3 oligomers, with Pb and Zn immobilization reaching over 99.4%. With the acid strengthening of the suspension, H+ took the lead in protonating with TEA and limiting the capping action of TEA, which was harmful to the synthesis of CaCO3 oligomers. Ethanol with a low dielectric constant was considered an ideal solvent for oligomer production, and triethylamine (TEA) as a capping agent established hydrogen bonds (N⋯H) with protonated CaCO3. H2O molecules competed with the protonated CaCO3 molecules for TEA with ethanol concentration decreasing, resulting in erratic precipitation of CaCO3 molecules and significantly elevated leaching risk of Pb and Zn. The sequential extraction procedure, pH-dependent leaching, and geochemical analysis results revealed that the dissolution/precipitation of Ca, Pb, and Zn in treated FA was mostly controlled by the carbonate mineral phases. Moreover, the low boiling points of ethanol and TEA can be recovered for recycling. The gel-like, flexible combination of CaCO3 oligomers and FA particles formed by FA offers great resource utilization potential via a controlled crystallization polymerization process.

Product regulation and catalyst deactivation during ex-situ catalytic fast pyrolysis of biomass over Nickel-Molybdenum bimetallic modified micro-mesoporous zeolites and clays.

Ni-Mo bimetallic modified micro-mesoporous zeolite catalysts were prepared and employed in the process of ex-situ catalytic fast pyrolysis (CFP) of poplar to produce liquid fuel. Clay catalysts were incorporated to further improve the products quality. The mass yield of monocyclic aromatic hydrocarbons (MAHs) increased under the catalysis of composite catalysts AZM and NiMo/AZM. HAP&Zeolite dual catalyst system reduced coke yield of NiMo/AZM to 5.01 wt%. Through real-time monitoring of gas products, the catalytic performance of zeolites began to decrease after the ratio of biomass and catalyst was more than 1. A series of characterization results futher demonstrated that AZM and NiMo/AZM possessed more stable catalytic ability and higher catalytic activity during the whole CFP process. N2 adsorption-desorption measurement and Raman characterization illustrated the formation and structure of coke, catalyst deactivation and the protective mechanism of mesopores on micropores.