The co-gasification of coal and biomass has received much attention in recent years due to the increasing energy demand and environmental crisis. However, the amount of the alkali metals releasing to the gas phase should be suppressed in order to reduce the operational problems related to alkali metals corrosion and slagging. On the other hand, the increasing amount of alkali metals should be provoked to transform and exist in modes of occurrence that have a catalytic effect for an efficient co-gasification process. Alkali metals are widely considered to be a good catalyst for gasification of both coal and biomass; however, the catalytic mechanism has been controversial. For example, one of the most popular and widely supported mechanisms proposed is the electron transfer mechanism, in which the phenolate structure C-O-K is the reactive intermediate phase. There are quite a few studies on this kind of structure in gasification process of carbon with the potash as a catalyst. However, there is not yet a direct evidence how the alkali metals migrate and fix to coal char in the co-gasification process and their catalytic role in the process. It can be speculated that the alkali metals fixed in coal char structure may be combined with oxygen in the oxygen containing functional groups to form phenolate structure of catalytic effect during coal char gasification. The above assumption is based on the knowledge about the structure of coal char which is characterized by a variety of oxygen containing functional groups, as well as on the knowledge about the mechanism of catalytic gasification by alkali metals alkoxide structure. Therefore, the purpose of this study focuses on the quantitative analysis of the oxygen containing functional groups based on Boehm titration method to obtain the amount of major types of oxygen-containing functional groups in the coal char, namely carboxyl, lactones, phenolic hydroxyl and carbonyl groups. The results of this investigation will elucidate the forms of alkali metals formation in the char and their contribution to the gasification process.

Behavior and catalytic effects of alkaline metals during co-gasification of coal and biomass

253rd National Meeting (2017)

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