The effect of process parameters on the carbon dioxide based production of activated carbon from lignite in a rotary reactor

Activated carbons were prepared from raw lignite applying a physical activation method with CO2 in a rotary tube furnace. The effects of process parameters were determined namely; temperature, activation time, preoxidation time, CO2 flow rate, heating rate and rotation rate. In general micropore rich activated carbons were produced and the operating parameters had a significant influence on the product. BET surface areas were found to range from 331.5 m2/g to 696.4 m2/g, the total pore volume from 0.1768 cm3/g to 0.4446 cm3/g and yield from 61.06% to 11.06%. Raising CO2 flow rate significantly increased the BET surface area of the product. The operation mode of the reactor was important. The BET surface area of the sample produced with rotation of the reactor is approximately 16% higher than the sample produced without rotation of the reactor, although it appears insensitive to the absolute speed of rotation. It was concluded that rotation of the reactor is an effective way to enhance the production of activated carbon, in terms of increasing surface area without a significant reduction in yield.