Influence of impurity ions on rice husk combustion
Keywords:Rice husk ash, Transition metallic ions, Catalytic combustion, Catalyst
AbstractRice husk (RH) contains various impurity ions such as K+, Al3+, Fe3+, Mnn+ (n = 2 â€“ 4), and P-containing acid ions. In the present work, some of their oxides, formed in RH combustion, were found to exert a strong influence on the middle- and late stages of RH combustion, and consequently, strongly affected the structure and properties of the final ash. Very recently, we proved for the first time that the existence of the transition metallic ions in rice husk can lead to a decrease of about 70Â°C in the terminal combustion temperature (Ttc) of RH. This catalytic behavior was demonstrated by a Mn re-loading and catalytic combustion experiment. By leaching out most of the impurity ions from RH with HCl and subsequently re-loading some Mn2+ ions into the HCl-washed RH host for co-combustion, the Ttc of RH was also decreased. Ttc can be decreased by more than 100Â°C. This is of high benefit not only for the industrial combustion of RH, but also for the high value-added applications of the final MnOx-supported ash (x = 1 â€“ 2). This ash can, for example, be directly used as a complete combustion catalyst of other organics.
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