The carbonization process of a carbonization furnace can generally be divided into the following three temperature sections:
Drying stage
From the start of the ignition until the furnace temperature rises to 160 ° C, the water contained in the mechanism rod is mainly evaporated by the amount of external heating and the heat generated by its own combustion. The chemical composition of the mechanism rods remains almost unchanged.
Initial stage of carbonization
This stage mainly depends on the combustion of the rod itself to generate heat, so that the furnace temperature rises between 160 and 280 ° C. At this time, the wood material undergoes a thermal decomposition reaction, and its composition begins to change. Among them, unstable composition, such as hemicellulose decomposition to produce CO2, CO and a small amount of acetic acid and other substances.
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Full carbonization stage
The temperature at this stage is 300-650 ° C.
During this stage, the wood material undergoes rapid thermal decomposition, while a large amount of liquid products such as acetic acid, methanol, and wood tar are generated. In addition, flammable gases such as methane and ethylene are generated, and these flammable gases are burned in the furnace. Thermal decomposition and gas combustion generate a large amount of heat, which increases the furnace temperature, and carbonizes carbon materials at high temperatures.
In order to calcine high-temperature charcoal, in addition to the above three stages, we also need to increase the heat so that the temperature in the furnace continues to rise to about 800 ° C to 1000 ° C, so that the volatile substances remaining in the charcoal can be discharged and the charcoal can be improved The carbon content increases the graphite structure of carbon and enhances its electrical conductivity.
Carbonization is an important part of mechanism charcoal. The carbonization process is the core of the manufacturing technology of mechanism charcoal. It's like building a building. Good raw materials are the foundation of the building and the part below the ground. The carbonization technology in the carbonization process is the above-ground part of the building. Carbonization is divided into three stages: low temperature exhaust temperature, high temperature calcination, and cooling. When the salary stick enters the carbonization furnace, it carries about 8% of water, which is the enemy of carbonization. Because the mechanism salary stick is most afraid of dampness, water in the salary stick will seriously affect the carbonization quality. Therefore, the ebb tide time is essential. Tide exhaust time is generally 10-15 hours for earth kiln and 2-3.5 hours for mechanical kiln. Long heating time can prevent the moisture stick from cracking and ensure the quality of carbonization. When the furnace temperature rises to 300 degrees, a large amount of combustible gas can be generated in the furnace. For every kilogram of raw material, three cubic meters of methane gas can be produced. These gases can be used to heat the furnace. The heat source that can be discharged for drying above 400 degrees is required to be sealed during the heat preservation and calcination phase. The oxygen-free closed fire can be achieved by self-ignition cooling or water cooling. After the charcoal exits the kiln, ventilate the charcoal first to prevent carbon dioxide poisoning. The charcoal leaving the kiln should be left outdoors for more than 8 hours. Prevent dead ash from re-igniting and cause fire.
In summary, during the entire process of burning charcoal, we always deal with heat at all times, that is, we need to consume a part of energy in order to increase the economic value and use value of charcoal.
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