MOLECULAR-HYDROGEN EVOLUTION AS A CONSEQUENCE OF ATMOSPHERIC OXIDATION OF COAL .3. THERMOGRAVIMETRIC FLOW REACTOR STUDIES

Large bituminous coal piles stored outdoors for long periods of time c an undergo autocatalytic autogenous heating. Associated with the low t emperature (50-150-degrees-C) oxidation of the coal is the chemisorpti on of oxygen and the emission of CO and H2O. This process is accompani ed by residual gas evolution, mainly CO and low molecular weight hydro carbons. Low temperature simulations in the laboratory (50-150-degrees -C) have shown that an appreciable amount of molecular hydrogen, H-2 ( few hundred ppm volume), is also evolved. Flow reactor thermogravimetr ic analysis of the low temperature coal oxidation process has been per formed with two different bituminous coals; one from Northern Appalach ia in the USA, and the other from the Ruhr Basin of Germany. It has be en observed that the emission of H-2 occurs at temperatures as low as 50-degrees-C and that, as has been previously suggested, this reaction is an oxidation correlated process. Furthermore the emission of H-2 i s a fast process, occurring within a few minutes from the onset of hea ting the coal sample. Prior to the evolution of the aforementioned gas es, an increase in the coal sample weight is observed due to oxygen ch emisorption. The mechanism and a parameter study is discussed in detai l.