Granular activated carbon manufacture from sub-bituminous coal treated with dilute inorganic acid: direct activation method

摘要

Granular activated carbon is manufactured from sub-bituminous coal by crushing and screening the as received coal containing about 10 to about 25% moisture by weight to produce 8/30 mesh granules, treating the granules with a dilute aqueous solution of inorganic acid at a concentration from about 1 to about 25% by weight to reduce the volatile content and thereby increase the fixed carbon content, the particular concentration being selected to provide the desired activity and porosity of the activated carbon, comprising: mixing the granules with the acid, washing off the acid, and drying the granules at least partially to a moisture content below about 25% by weight. The granules are mixed with from 0 to about 15% by weight of coal tar pitch. The so treated granules are ground to form fine powder of not less than about 60% by weight -325 mesh, preferably more than about 65% by weight -325 mesh, which is compressed into shapes, such as pellets or thin corrugated sheets under high pressure, and then granulated to reform 6/20 mesh granules. These reformed granules are then directly activated, without prior charring and devolatilization, by directly heating to and at a temperature higher than the devolatilizing temperature in an atmosphere containing a gaseous activating agent.