Patent ID: 7217378

Claim:
A simple and efficient process for the preparation of pencil lead from spent pot liners or a waste material of aluminum industries, said process comprising: a. collecting spent pot liners from an aluminum smelter plant, b. crushing the liners into various sizes ranging between ½ inch to about 125 micron, c. adding chromic acid to the crushed liners with stirring for time duration ranging between 20–40 minutes at temperature ranging between 130–140° C. to obtain the reacted product, d. washing the reacted product with distilled water multiple times to provide a filtrated solid mass that is neutral, e. drying the neutral solid mass at temperature ranging between 80° C. and 120° C. for about 1 hour to obtain dry carbon powder, f. thermally shock-treating the dried mass for about 1–3 minutes in a pre heated furnace kept at temperature ranging between 900–980° C. to obtain a fine flowing graphite powder, g. mixing the powder with one or more binders, h. moistening the mixture with requisite amount of water to form a stiff dough, i. extruding the dough under pressure to obtain product in the form of a discs, j. drying the discs to the moisture content of less than 10%, k. heating the dried discs in an inert/reducing atmosphere in a furnace at temperature ranging between 400° C. and 1200° C. for a time duration ranging between 1 and 6 hours, l. cooling the heated discs to room temperature in about 20–50 hours, and m. obtaining the pencil lead.