1992 Volume 71 Issue 2 Pages 107-115
We tried to estimate the amount of hydrogen radical transferred from gas phase to coal fragments during flash hydropyrolysis of coal. A known amount of hydrogen was supplied to the reactor only while the coal particles were heated to a reaction temperature. The hydrogen unreacted and the product gases were all collected in a gas holder. Then the amount of hydrogen transferred from gas phase to coal radicals were successfully measured from the hydrogen balance. Its value reached over 12mol/kg-coal at 920°C for the pyrolysis of Morwell (MW) brown coal under 5MPa of H2.
Next, the flash pyrolysis of coal swollen by tetralin, which was effective to increase the conversion and the tar yield in an atmospheric pressure of He, was performed under high pressure. This pyrolysis method was also effective in 5MPa of He, and was more effective in 5MPa of H2, indicating the presence of combined effect of hydrogen and tetralin.
Comparing the product distribution during the flash pyrolysis of the MW coal and the tetralin swollen MW coal in He and H2 atmospheres, the mechanism of hydrogen transfer from the additives to coal was clarified. The hydrogen radical from high pressure hydrogen is utilized only to stabilize hydrocarbon gases at high temperatures. On the other hand, the hydrogen radical deriving from tetralin is mainly transferred to tar fragments at rather low temperatures. The combined effect of hydrogen and tetralin was found to be realized by a rapid hydrogen transfer from gaseous hydrogen to coal fragments via tetralin.