Steam-activation is primarily used for coconut charcoal and coal.
In the production of steam-activated charcoal, first the coconut shell or coal is heated to create a char. This char is then “activated” in a furnace at high temperatures of 1,700° to 1,800°F with steam in the absence of oxygen. In the steam-activation process, all volatile compounds are removed, and at the same time layer after layer of carbon atoms are pealed off, enlarging the existing internal pores, and leaving behind a carbon skeleton. The carbon + steam reaction results in producing hydrogen gas and carbon monoxide (C+H2O=H2 +CO). As the carbon monoxide gases off it takes carbon atoms with it. Typically 3 pounds of raw charcoal will produce 1 pound of activated charcoal. This is a perfect example of the saying “Less is More”. Less carbon atoms yields More internal space.
How to Make Steam-Activated Charcoal ?
Once the activated charcoal is cooled off, to remove the soluble ash content, it may be either “water-washed”* (which requires a lot of water) or it is “acid-washed” (to remove the acid-soluble ash content) and then repeatedly “water-washed” to remove any trace of the acid solution.
(*Not to let anything go to waste, the charcoal “vinegar” is sometimes collected and sold as commercial ascetic acid or processed into table vinegar.)
Because of the very high temperatures required for steam activation (600 – 1,200 °C), temperatures you cannot achieve in a conventional oven (260 °C), this method is all but limited to industrial technology.
Another huge limiting factor is the cost of production. The world uses a tremendous amount of Activated Charcoal annually and so production needs to be on an industrial scale that can produce millions of tons of AC at a very low price.
This is typically done in large rotating steel cylinder kilns (up to 180ft long producing up to 12.5 metric tonnes/hour) with a sophisticated delivery system of heat and steam. If money were not an issue, then individuals would need to first design an even more sophisticated miniature version. There would be the issue of washing/rinsing, the disposal of waste ash from the pyrolysis, managing the exhaust gasses, and other challenges. The net product would far exceed the cost of the mass-produced product, and quality would likely also be an issue, since cooking temperatures and times are quite critical. Aside form the fascination of building one’s own, it seems the cost would be prohibitive to make steam-activated charcoal “at home”.
So, how can you make steam activated charcoal? It should be obvious that, for small personal quantities, you are not set up for the technical challenges or the financial outlay. Well then, how can you make chemically activated charcoal? Is it less expensive and easier?