The higher the carbon content of charcoal, the higher the calorific value, which is determined by the two factors: raw materials and charcoal burning, or it can be said by the chemical composition of charcoal. The burning time of charcoal produced by briquette machine is determined by chemical and physical factors. To extend the burning time of charcoal, the calorific value not only need to be large, it also requires a smaller contact surface area of charcoal and air. The surface area includes outer surface and the internal porosity.

There are two ways to improve the burning time of charcoal: one is to improve the molding pressure of briquette machine to improve the density and strength of the briquettes. The other is to improve the final carbonization temperature of the carbonizing furnace, and slow down the heating and cooling speed to reduce the contact area of charcoal and air so as to extend the time of burning charcoal.

If the burning time of charcoal is long, the quality is higher. The density and strength of briquettes should be increased to improve the combustion time. The carbonization temperature of carbonizing furnace should also be noticed to make the carbonized charcoal has high density and high hardness.

To ensure the quality of briquettes produced by briquette machine, the moisture content of raw materials should be between 5% and 12%. If the moisture content is less than 5%, the briquettes produced are not strong. While if moisture content is more than 12%, briquettes produced are soft and easy to bend. It also has low density. Usually, fresh materials (such as fresh bamboo, raw branches, etc.) contain about 50% water and they need to be dried by a dryer for 1-2 times. If the raw materials are dried in the open air or in the sun for 1-2 days, the drying times can be reduced by 1 time. In any case, we need to dry the raw materials more than once to meet the requirements of making briquettes.