The new type smoke-free carbonizing furnace is equipped with furnace flue gas recovery unit based on the original carbonizing furnace. It is dust and smoke free after flue gas recycling and the flue gas recovered can be lighted like liquefied petroleum gas for heating, cooking or used in the dryer. The new type smoke-free carbonizing furnace has dual efficacy. The material can be directly carbonized or made into briquette before they are carbonized.

1. With the volume of 3m3, the yield of charcoal is 40-60% with more than 95% of finished products.
2. Labor and time saving, one person can operate several carbonizing furnaces at the same time.

Moisture removal time is commonly 10 to 15 hours for earth kiln and 2-3.5 hours for mechanical kiln. Long heating time can prevent the briquette from cracking or affected with damp, ensuring the quality of carbonizing. When the temperature rises to 300 degrees, the furnace can produce large amounts of combustible gas. Normally, per kilogram of raw material can produce three cubic methane gas. These gases can make the furnace heating up. Ventilation of charcoal should be made first after discharging from the kiln to prevent the carbon dioxide poisoning. The charcoal discharged should be placed outside for more than 8 hours to prevent the resurgence and fire.

The working characteristics of carbonizing furnace: combustion type carbonizing furnace uses dry distillation carbonizing principle to make briquettes in the carbonizing furnace hypoxia, heating  and decomposition to generate combustible gas, tar and charcoal. Movable steel structure is used in carbonizing furnace. The exhaust pipe on the top of carbonizing furnace is in connection with the tar separator and induced draft fan with unique structure, large effective product, advanced carbonizing technology, short cycle, high yield, environmental protection and long service life, etc.

The carbonizing process can generally be divided into the following three temperature section:
1. The drying stage.
Starting from the ignition until the temperature rises to 160℃, then the water contained in briquette evaporates mainly rely on the additional heat and the heat generated by burning. The chemical composition of briquette is almost unchanged.
2. The initial carbonizing stage.
In this stage, heat is mainly generated by the burning of briquette to make the furnace temperature up to 160 ~ 280℃. At this point, the wood material has thermal decomposition reaction and its composition starts to change. The unstable composition, such as hemicellulose decomposes into CO2, CO and a small amount of acetic acid.
3. The comprehensive carbonizing stage (carbonizing temperature is 300 ~ 650℃).
There is dramatic thermal decomposition of wood material in this stage and generate a large amount of acetic acid, methanol, wood tar and other liquid products. Besides, it would produce the combustible gases such as methane and ethylene. The combustible gas burns in the oven. Thermal decomposition and gas combustion would produce lots of heat to make the temperature rise and make the wood material carbonized into charcoal at high temperature.