Hydro-gasified Coal Chars' Property Assessment for Hydrogen Synthesis Suitability

抄録

Property assessment of the hydro-gasified char was undertaken. The char was pre-pared using a high-pressure drop tube reactor under hydrogen atmosphere and rapid pyrolysis conditions. For comparison purposes, another type of char was also prepared under N₂ atmosphere (N₂-char). From the results, the coal conversion was found to increase with increasing pressure in the case of the hydro-gasified char but decreased in the case of N₂-char. The char reactivity decreased slightly with an increase in pressure for the hydro-gasified char but remained almost constant for the N2-char. Generally, hydrogasified char was more reactive than the N₂-char at lower pyrolysis pressures, but the tendency reversed as pyrolysis pressure increased. Results also show the depend-ency of the reaction rate constant on pressure to be proportional to the 1/4th power of the total pressure at 1, 273K. The hydrogasified char was found to have an activation energy of 68 kJ/mol. As for the effect of hydrogenation on the particle surface area, results showed that the surface area increases with an increase in the pyrolysis pres-sure. Further, it was found that, as the pyrolysis pressure increases, more pores are made but with smaller pore diameters. On the other hand, upon increasing H₂/coal feed ratio, the coal conversion was found to increase while char reactivity decreased. The corresponding effect was not observed from the N2-char thus exhibiting the so called “rapid carbon” of about 15‰ at H₂/coal ratios greater than 1.0. Comparison of char from this work to that from a relatively larger equipment (ca. 2.5 ton/day) revealed that the chars' properties are quite similar in many ways and that drop tube results can serve as useful indicators in the scale-up of the hydrogasification process.