High temperature behavior of electrostatic precipitator ash from municipal solid waste combustors

Area of Science:

• Waste Management
• Materials Science
• Environmental Engineering

Background:

• Municipal solid waste (MSW) flue gas residues necessitate treatment before disposal or reuse.
• Vitrification is a key process for solidifying and stabilizing these residues.
• Understanding high-temperature behavior is crucial for effective vitrification.

Purpose of the Study:

• To investigate the high-temperature behavior of MSW flue gas residues.
• To determine melting points and mass loss during vitrification.
• To identify volatile and retained elements during the process.

Main Methods:

• Laboratory experiments up to 1400°C.
• Thermogravimetric analysis.
• X-ray diffraction, chemical, and electron microprobe analyses.
• Utilizing CaO content and CaO-SiO2-Al2O3 ternary diagrams to estimate liquidus temperature.

Main Results:

• Electrostatic precipitator (ESP) ash melts between 1202-1272°C; semi-dry scrubber residues melt much higher (1900-2300°C).
• Liquidus temperature can be estimated using CaO content and ternary diagrams.
• Significant mass loss (18 wt.%) occurs by 1300°C, primarily below 1000°C due to volatile elements (C, Cl, S, Na, K, Hg, Cd, Pb, Cu).
• Cd, Pb, and Cu likely evaporate as chlorides; Zn, Cr, Ni, Sb, and Sn remain in the vitrified product.

Conclusions:

• The study provides critical data on the thermal behavior of MSW flue gas residues during vitrification.
• Melting temperatures and volatile element behavior are characterized.
• The findings support the optimization of vitrification processes for MSW residue management.