In last text, we discuss the first factor which influence biomass pellets, here we will discuss the rest factors together continuously.Mold temperature
The process of biomass briquetting is mainly the process of softening some organic components under certain temperature and pressure, so molding temperature is an important factor affecting biomass particle molding. Generally speaking, the temperature at which organic components in biomass begin to soften is 70 ℃ / 80 ℃, plastic bonding at about 160 ℃, and liquefaction at 240 ℃. So when the temperature reached 60 ℃, the material began to soften and the fluidity increased. With the increase of temperature, the resistance of material movement became smaller and the resistance of molding decreased. The pressure difference between normal temperature molding and hot forming is measured to be nearly 2 times. . However, the higher the temperature, the better, too high temperature will lead to biomass carbonization, which is not conducive to molding, and because of the non-uniform and uncontrollable carbonation, will affect the particle quality and calorific value.
Material layer thickness
When the material enters the extrusion area, a gap between the roller and the die is formed, which is the material layer thickness. The material layer thickness is a preprocessing stage before the material enters the extrusion area, when the roller has a precompression force on the material in the material layer. For the moulds with different diameters of die holes, the smaller clearance is generally used for the small diameter particles, and the larger clearance is used for the large diameter compaction particles.
The thickness of the material layer is not only related to the diameter of the finished product, but also affects the power consumption of the granulation process. Under the same conditions, the different layer thickness of the material will lead to the change of extrusion pressure, the thickness of the material layer is too small, the extrusion pressure is small, and the material entering the die hole is also less. The low productivity even causes the material to enter the mold hole too little to form the extrusion, cannot produce the particle; when the material layer thickness is too big, the extrusion pressure rises rapidly, the material enters the mold hole quantity too big, causes the particle to be too dense to discharge the material difficulty, the power increases, It even causes equipment failure caused by overload.
Extrusion speed directly affects the residence time of material in die hole. The residence time of the material in the die hole has a great influence on the molding quality. When the material is extruded in the die hole, the power per unit output is less, but the compaction degree of the production particle is not enough. The longer the material stays in the die hole, the longer the extrusion time is, the denser the particle structure is, the higher the particle quality is, but the relative unit energy consumption is also increased; at the same time, the compression is too dense and the friction is aggravated. Difficult to move, there will be overheating resulting in particle carbonization or die hole compaction and stop production. Extrusion speed roll rotation The reasonable extrusion speed and speed are the guarantee of continuous operation and low energy consumption.
Extrusion strength is the physical extrusion pressure on the material, which is the main factor of particle density. Only when the extrusion strength is high, some biomass in the raw material can be softened, and the friction heat produced under the higher extrusion strength also promotes the plasticization and adhesion of some components in the raw material. Thus, the particles are glued together. When the extrusion strength is insufficient, the raw material can not be extruded effectively and the particles can not be formed, and the excessive extrusion strength will aggravate the wear of the die, which is not conducive to the control of the cost.
Molding hole parameter
The molding hole parameter is a comprehensive factor, which is restricted by the ingredients of the raw material, the grain size of the raw material, the extrusion speed and the extrusion strength. In turn, it affects these factors, and influences the process of the particle forming. For example, the compression ratio of the type hole parameters, the larger compression ratio is higher than the extrusion speed, and the extrusion speed is reduced, and the material particles are reduced. The material with lower mass factor has a promoting effect, and the entrance form in the type hole parameter affects the quantity and speed of the material entering the type hole, and affects the change of the material layer thickness.
In this paper, the main influencing factors of granulation are analyzed. These factors have many influences on the granulation, and the composition of raw materials and the content of humidity directly determine the effect of granulation. The raw materials with high humidity must be treated by reducing the moisture content, otherwise, the granulation process can not be formed, the granulation process is a relatively strict control process, the temperature, the thickness of the layer can not exceed the required range, otherwise, the granulation process can not be normal. The equipment factor is also a complex comprehensive factor, in which the selection and adjustment of the orifice parameters can improve the adjustment of other factors. The suitable range of good molding parameters for the raw materials is wide, and the energy consumption per unit of the production process is also low. And the quality of particle forming is good. Through the optimization and improvement of molding equipment and pore parameters, the particle quality and output can be effectively improved, and the application and popularization of biomass particles can be promoted.