In-Situ Reforming of Tar from the Rapid Pyrolysis of a Brown Coal over Char

Reforming of nascent tar from the rapid pyrolysis of a brown coal over char prepared from the same coal was Studied at 750-900 degrees C. The reforming was very rapid and extensive, allowing only benzene (0.02% on a coal C basis), naphthalene (0.001%), and phenanthrene (0.0001%) to escape from the char bed at an empty-bed gas residence time of less than 170 ms and 900 degrees C, respectively. Reforming even at 750 degrees C converted 96% of heavy tar (boiling point temperature > 336 degrees C) into noncondensable gases and coke deposit over the char. Decreasing conversion of the tar into coke with increasing temperature suggested that the tar was reformed in a sequence of coking and steam gasification of the coke rather than direct steam reforming over the char. The reforming at 900 degrees C gave a negative coke yield due to progress of coke/char gasification faster than the coke deposition. Results of this work thus showed a possibility of complete tar reforming by intensification of contact between the char and volatiles even In the absence of it catalyst.