First, the moisture content
Because charcoal is a highly absorptive substance, it will absorb moisture in the air during stacking and increase its moisture content. Therefore, the moisture content of charcoal does not have any impact on its own quality. The customer requires that the lower the moisture content of charcoal, the better, in order to increase its economic value. Generally speaking, the moisture content of freshly produced charcoal is less than 3%.
The charcoal content of charcoal will vary with the type of raw material and carbonization temperature. Generally speaking, compared with low-density wood such as poplar and tung wood, the hard carbon content of the former is higher than the latter at the same carbonization temperature. The carbon content of the same raw material at high temperatures is higher than that at low temperatures. The charcoal content of charcoal is usually less than 75%. We take pine as an example. When the carbonization temperature reaches 380 ° C, its carbon content is 76%, when the temperature reaches 500 ° C, the carbon content is 85%, and when the temperature reaches 600 to 700. At ℃, the carbon content reaches 92%.
3. Ash content (ash content)
Ash is the white or pink substance remaining after the charcoal has been completely burned, which is what we usually call ash. Its size directly affects the use and economic value of charcoal. For example, straw, rice husks, and other materials contain large ash content and are not easy to fall off during combustion, resulting in low temperature during combustion, which is not suitable for people’s life and industrial carbon. Of course, it is desirable that the ash content of charcoal be as small as possible to expand its use.
The ash content of charcoal will vary with the carbonization process and temperature. But as far as wood or its scraps are concerned, the difference in ash content after charcoal formation is not large. Generally speaking, under the same conditions as above, the charcoal-fired from the broad-leaved forest is higher than that from the coniferous forest, and the raw materials with a large proportion of bark are burned. The charcoal ash content is also large. The usual charcoal ash is 1 to 4%.
4. Volatile fraction (volatile content)
The content of volatile matter depends on the carbonization temperature. Depending on the application, we can burn low and medium temperature charcoal as well as high-temperature charcoal. The former emits volatiles such as CO, CO2, H2, CH4 and gaseous carbohydrates during high-temperature calcination, and their content is generally 12-20%. The above-mentioned volatile matter released by the high-temperature charcoal is less, and its content is generally less than 5%.
The energy released per kilogram of charcoal under specific conditions is expressed in kcal. The calorific value of charcoal is directly related to the charring temperature and holding time. Under the same conditions of carbonization temperature and holding time, the charcoal calorific value of different raw materials is also different. Generally speaking, the carbonization temperature is high, the holding time is long, the carbon content is also large, and the calorific value is naturally high. When the carbonization temperature is less than 450 ° C, the calorific value of charcoal made from wood and its corner waste is usually between 6500 and 7000 kcal / kg. The calorific value of straw and rice husk charcoal is generally about 6000 kcal/kg. When the carbonization temperature is greater than 600 ° C, the calorific value of the charcoal made from the above materials can be increased by 500 to 1000 kcal.