| Abstrakt: |
Incineration of municipal solid waste (MSW) is a waste treatment method which can be sustainable in terms of waste volume reduction, as well as a source of renewable energy. During MSW combustion, increased formation of deposits on convection heating exchanger surfaces can pose severe operational problems, such as fouling, slagging and corrosion. These problems can cause lower heat transfer efficiency from the hot flue gas to the working fluid inside the tubes. In extreme cases, they can lead to capacity-limiting plugging and unscheduled shutdown. A study was performed where experiments were carried out to examine the ash deposition characteristics in a full-scale MSW circulating fluidized bed (CFB) incinerator, using a newly designed deposit probe which was fitted with six thermocouples and four removable half rings. The influence of probe exposure time and probe surface temperature (500, 560, and 700 °C) on ash deposit formation rate has been investigated. The results indicate that the deposition mass and collection efficiency achieve a minimum at the probe surface temperature of 560 °C. Ash particles are deposited on both, the windward- and leeward-sides of the probe by impacting and thermophoretic/condensation behavior. The major inorganic elements present in the ash deposits are Ca, Al and Si. Compared to ash deposits formed on the leeward-side of the probe, windward-side ash deposits contain relatively higher Ca and S concentrations, but lower on Al and Si. Among all cases at different surface temperatures, the differences in elemental composition of the ash deposits from the leeward-side are insignificant. However, as the surface temperature increases, the concentration of Al, Si, K and Na in the windward-side ash deposits are increasing but the Ca concentration is reduced. Finally, governing mechanisms are speculated on the basis of the experimental data, such as deposit morphology, elemental composition and thermodynamic calculations. [ABSTRACT FROM AUTHOR] |
