How to Determine the Quality of Finished Charcoal?
The determination of qualified finished charcoal is based on: calorific value, ash content, combustibility, and reducibility.
Charcoal Calorific Value: Generally between 6,500-8,000 kcal/kg. The higher the carbonization temperature, the greater the carbon content of charcoal, and the higher the calorific value.
Charcoal Ash Content: The ash content left after charcoal combustion varies with carbonization temperature, raw material type, bark proportion, carbonization method, and other factors. The higher the carbonization temperature, the greater the ash content. Charcoal from broadleaf forest carbonization has higher ash content than from coniferous forests, and bark contains more ash than wood.
Electrical Conductivity: When the furnace closing temperature exceeds 700°C, the atomic structure of the charcoal produced changes, forming a partial hexagonal ring planar layer structure similar to graphite atoms, thus possessing electrical conductivity. When the carbonization temperature is below 600°C, charcoal does not have electrical conductivity.
Charcoal Combustibility: When charcoal burns completely in air, it releases heat and produces CO2. Incomplete combustion releases CO. Reaction equations: C + O2 = CO2 + heat, 2C + O2 = 2CO + heat.
Charcoal Reducibility: Charcoal can serve as a reducing agent. For example: heating charcoal powder together with copper oxide can reduce it to red metallic copper.
The main component of charcoal is carbon, with very low ash content and a calorific value of about 27.21~33.49 MJ/kg. In addition, it also contains hydrogen, oxygen, nitrogen, and small amounts of other elements. Their content has little relationship with tree species, mainly depending on the final carbonization temperature. Charcoal is a hydrophobic substance with ash content within 6%, porosity occupying over 7% of charcoal volume, specific gravity generally 1.3~1.4. Calorific value depends on carbonization conditions, generally around 8,000 kcal/kg. The reduction capacity of charcoal is greater than that of coke. Charcoal has a large number of micropores and transitional pores, giving it not only a high specific surface area but also excellent adsorption properties once tar substances within the pores are removed.
