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Incinerator slag formation and control of excursion temperatures
Stephen Greenwood1, Jack Geisenhoff
1Metropolitan Council, St. Paul, Minnesota, USA. steve.greenwood@metc.state.mn.us
Summary
Reducing incinerator slag requires understanding ash fusion. A new test revealed slag forms at lower temperatures than standard tests indicate, and water spray effectively controls slag formation.
Area of Science:
- Environmental Engineering
- Materials Science
Background:
- Incinerator slag formation poses operational challenges.
- Standard ash fusion tests (ASTM D-1857) do not accurately reflect real-world slagging temperatures in incinerators.
Purpose of the Study:
- To investigate factors influencing incinerator slag formation.
- To develop a more accurate method for determining ash fusion temperatures.
- To evaluate a water spray system for controlling slag formation.
Main Methods:
- A factorial test examined the impact of polymers, sludge ratios, and dewatering equipment on ash fusion.
- A novel test involved heating ash cubes to various temperatures and measuring compressive strength.
- A water spray system was implemented to manage temperature excursions.
Main Results:
- Standard test parameters (polymers, sludge ratio, dewatering equipment) did not affect initial deformation or softening temperatures.
- The new ash cube test demonstrated slag formation occurs at temperatures significantly lower than predicted by ASTM D-1857.
- The water spray system proved effective in controlling temperature excursions and mitigating slag formation, using less mass than air cooling.
Conclusions:
- Incinerator slag formation is a complex phenomenon influenced by factors not captured by standard ash fusion tests.
- A new testing methodology is crucial for accurately predicting and managing slagging.
- Water spray cooling is an efficient method for controlling high temperatures and preventing slag in incinerators.