Steam activation is used throughout for the activation of carbon made from peat, coal,
coconut shells, lignite, anthracite, or wood. First, the raw material is converted into carbon by heating. When coal is used as the raw material in steam activation, it always consists of small graphic-like plates, rather like potato crisps. The crisps are flat or a little curved, just like potato crisps, 0.35 nm thick and a few nm in width and length. The crisps are in disarray, as in a bag of potato crisps.
Water steam +130°C is then blown in at a coal temperature of approx. 1000°C. Some of the crisps (“in the bag”) become gas and leave pores (empty space) behind. The form this takes depends largely on the raw material used. A hard material, like coconut shell, leaves almost nothing but micro pores, while a soft material like peat always get many meso pores as well.
Short activation period many micro pores.
Medium actication period, many meso pores.
Long activation period, many large meso- and macro pores.
If we continue for a long period to blow in more steam, more and more crisps turn to gas and leave empty spaces (pores) behind. First we get micro pores. As the process continues, the surrounding crisps also turn to gas and the pores develop into meso pores.
If we continue still further, we get a macro pore. This is usually already found in the structure of the raw material, so we do not need to make more. Wood, peat, and coconut shell have definite cellular structures that are maintained throughout the entire activation process.