When we examine more closely to the wood pellet surface that we will look smooth, slippery and shiny. Even as smooth surface, slick and shiny that there are people who say that wood pellets are specially coated. Obviously this statement is groundless because especially not supported with a strong argument. Production of several tons, tens to hundreds to thousands of tons per day of wood pellets will produce the number of units very much. How about coating process? And how many substances are used so that the coating and still economically? Altogether these people can not give an answer.
Smooth surface, slippery and shiny is really due to the lignin in the wood tends to be resin that have plastic property. If mold is stretched and the temperature increased, the heat and absence of air condition in the shell will cause pyrolysis is characterized by outer skin darkened by carbonized. This appears more clearly in the process of screw briquetteproduction, which also features on heater in the die so that the outer skin of the briquette carbonized.
The main components of biomass are cellulose compounds, hemiselulose and lignin. Each of these compounds has a different thermal decomposition temperature. Carbonization occurs when compounds of lignin in the biomass decomposes at a temperature of about 400 C. The table looks like this below.