Activation of Canadian coals in a fixed-bed reactor and an internally stirred horizontal kiln

Activation of a lignite, a subbituminous coal and a high-volatile bituminous coal was studied using a fixed-bed reactor and an internally stirred horizontal kiln (ISHK), the latter being designed to control dusting problems encountered in handling finely divided coal. The properties of the activated carbons were determined by measuring iodine, methylene blue and phenol numbers, specific surface areas, bulk density, mercury and nitrogen porosities and ash and mineral contents. The lignite, activated at lower temperatures (similar to 700 degrees C) in the ISHK system, developed a surface area of similar to 500 m(2) g(-1) with most of the adsorptive surface associated with micropores of radii < 1.8 nm. Products from this lignite in the ISHK and fixed-bed reaction systems operated at similar to 700 degrees C had iodine, phenol and methylene blue numbers of 494 and 520, 56 and 63, and 84 and 105, with yields of 47.2 and 29.2 wt%, respectively. The lignite gave the same quality of product in the ISHK at higher yields than in the fixed bed. The properties of the products from the subbituminous coal at 700 degrees C in the ISHK suggest that this coal is a good feedstock for the production of activated carbon. Activated carbon produced from the bituminous coal in the fixed bed in the range 800-850 degrees C had surface areas > 700 m(2) g(-1) and a methylene blue number of 175, higher values than the best obtained with the lower-rank coals. The activation temperature needed to achieve these results with this higher-rank coal is similar to 150 K higher than that for the low-rank coals.