Char Technology
Char Technology produces high quality Soderberg electrode paste and char from its facility in Witbank, Mpumalanga. The group was prompted to build its own paste plant due to erratic and poor electrode performance using paste from other local suppliers. Devolatilised coal or more commonly referred to as char was introduced as a substitute for metallurgical coke within the Ferro-Alloys industry, due to the rapidly escalating price of metallurgical coke
African Carbon Group
Char, Retort Process
Raw materials are moved to the feed bin (Coal Hopper) by conveyor belt. The raw materials passes through three hydraulic sliding gates (Gas tight).
Once in the retort the coal is gravity fed through the retort at a temperature of +/- 650 ºC heated gas. The action of this heated gas on the descending coal, results in the liberation of the volatile matter from the coal.
The gaseous volatile (together with the burned gas) are drawn through the bed of coal surrounding the beehive to the top of the retort and out along a ducting to a large suction fan. Having passed through the fan the gasses are drawn through a heat exchanger, condenser and scrubber where the tar is cooled down and dropped into vessels which are pumped to a sump. The tar is pumped through a decanter where the solids are separated from the liquid tar.
Char, Grate Process
Low phosphorous, low sulphur metallurgical coal is loaded onto an incline conveyor. It then passes through a screen to remove -10mm coal fines and then enters the grate through the coal draw box. The coal is then fed onto the grate. Hot process gasses (volatiles) are drawn through the bed of coal and in so doing heat the coal. The volatiles are now drawn into a combustion chamber where it is combusted to an inert off-gas.
The devolatised coal, now called char, is removed from the soaking pit through a water spray system for cooling. It then falls onto a conveyor belt and is discharged into a char storage bin. The cooling water flows into a concrete channel and then into a concrete sump. It is then pumped back and recycled through the spray system.