How Activated Carbon is produced from a chunk of Wood pile
The discarded wood pallets in shipping industries generated a massive industrial wooden waste. In a developed country like Hong Kong, 347 tons of domestic, commercial and industrial wood waste is generated every day (Ref: Hong Kong Environmental protection department,2005). One of the ways to use this wooden waste is to produce activated carbon out of it.
How is activated carbon made out of the pile of wood?
Wooden pieces are sun dried and cut into small pieces. They are then further dried at 105 degrees for 24 hrs. This char is then “activated” in a furnace at high temperatures of 1,700° to 1,800°F with steam with no oxygen. Oxidation will make wood turn into ash. A constant flow of nitrogen gas at 250 ml for 1 minute at 3 hr intervals is required. Nitrogen is to cool down the “Char”
The carbon + steam reaction results in producing hydrogen gas and carbon monoxide (C+H2O=H2 +CO). As the carbon monoxide gasses off it takes carbon atoms with it. Typically 3 pounds of raw charcoal will produce 1 pound of activated charcoal. The black carbonized wood (charcoal) is then pulverized to be able to pass through an 180-µm sieve. It is then passed through a magnetic rod to reduce iron content.
After the activated carbon is cooled, the next step is to remove soluble ash content. This procedure can be done by water or acid washing. The acid used is sulphuric acid in this case.
This carbon is then dried again and packed in bags for use.
The key factors in activation are the temperature control, quality of wood and the design of rotating furnace.
Traditionally, activated carbons are made into powders or fine granules. Powdered is made up of crushed or ground carbon particles, 95–100% of which will pass through a 50 to 80 /325 mesh sieve
Granular activated carbon is relatively larger in particle size compared to powdered activated carbon… GAC is preferred for all adsorption of gasses and vapors as their rates of diffusion are faster Granulated activated carbons are also used for water treatment, deodorizing and the separation of components in a flow system.
Why wood-based carbon is better
Steam activated carbon has high in purity and porosity. It is majorly used in pharmaceuticals companies to decolorize and deodorize medicines. It is vastly used in water treatment plants as well
|Powdered wood based carbon||Passing 100 Mesh (99%)
Passing 200 Mesh (85%)
Passing 300 Mesh (70%)
|Iodine (mg/g) Minimum||1000|
|Surface area (m2/g )Minimum||1000|
Carbonizing waste wood helps us filter the water we drink, breath the air purified by it,eat food purified through it; grow our food and flowers in it; go to war with it and heal sick bodies with it; preserve things in it; we take it with us to the bottom of the deepest oceans and out into space; swim in water washed with it;. Activated charcoal is called upon to clean up many of our technological mistakes. No wonder we naturally warm up to it.