(576a) Gasification Reactivity of Model Refuse Derived Fuel (RDF) Char and Its Components in CO2 and Steam

Authors: 
Aluri, S., Georgia Institute of Technology
Agrawal, P. K., Georgia Institute of Technology
Muzzy, J. D., Georgia Institute of Technology
Sievers, C., Georgia Institute of Technology
Flick, D. W., The Dow Chemical Company
Stears, B., Dow
Henley, J., The Dow Chemical Company
The discarded portion of Municipal Solid Waste (MSW) is subjected to pre-processing steps (e.g., glass and metal separation) to produce Refuse Derived Fuel (RDF). For this study, a model RDF composition was established based on the EPA data and pyrolysis results of individual components in different categories, e.g., plastics, paper and food waste. Pyrolysis studies were carried out in a thermogravimetric analyzer (TGA) at atmospheric pressure and at temperatures between 25 â?? 800 °C with a heating rate of 20 K/min. Gasification of pyrolyzed feed was conducted at 800 °C using pure CO2 and steam as the gasification reagents.

Inorganic materials inherently present in the feed have an effect on the gasification reactivity. Alkali and alkaline earth metals were catalytically beneficial, while other inorganics, such as silicon and phosphorous, had an inhibiting effect. The three major inorganics affecting the gasification reactivity in the model RDF feed were potassium from orange peel, calcium from paper components and silicon from paperboard and rubber. Gasification behavior of the model RDF char in CO2 showed a synergistic effect, which is attributed to the redistribution of inorganic species during the gasification process. Potassium present in the orange peel char catalyzes the gasification of other RDF char components due to its mobility at high temperatures. This observation was verified by comparing the sum of individual gasification reactivities with mixed RDF char composite reactivity. Additionally, EDX of the chars confirmed redistribution of potassium during gasification.

The effect of the inorganics was also evident when steam was used as the gasifying agent. However, the transient reactivity profiles in steam were different as compared to those during CO2 gasification. Tissue paper (calcium-rich), orange peel (potassium-rich), rubber (silicon-rich) and model RDF were gasified in steam and the reactivity trends were compared to those observed during CO2 gasification. Both the type and amount of inorganics present had an effect on the gasification reactivity in different gasifying mediums. In addition to the effect of the inorganics, steam gasification reactivity profiles were affected by hydrogen inhibition. Various RDF components rich in different inorganic species thus exhibited varying reactivity trends during steam gasification.