Sawdust pellets, also known as biomass pellet fuel, are mainly made from agricultural wastes such as wood, grains, peanut hulls, alfalfa, corn hulls, cottonseed hulls, and straws, which are crushed into wood chips, and then produced by a wood pellet machine. Forcibly extruding from the die hole according to a fixed diameter, and finally compressing it into wood pellets, is one of the most popular environmentally friendly energy sources today.
Due to the rise of wood pellet fuel, the biomass pellet production industry has been on fire. I feel that as long as I am given a pellet machine, wood pellets will be continuously transported from the conveyor belt to the whole country and even the whole world.
It’s just that in the production of wood pellets, more or less problems will be encountered, such as the following particle problems:
○The pellets are not formed or the forming rate is low
○Loose particles and powder
○Short or cracked particles
○The freshly pressed pellets are good, but after a while the pellets cracked…
There are many reasons for the cracks of the solid wood chips particles. It is recommended to follow the gradual investigation of the Bao Shell roller ring die, and prescribe the right medicine to easily solve the problem of particle cracking.
The moisture content of the raw materials used for production is about 13-20%. If it is too high or too low, the wood pellets will not be formed or formed badly. Because of the characteristic hardness of the raw materials and other reasons, the specific value should be based on your actual production situation.
The particle size of the raw material is also the reason why the wood pellets are not formed. Sawdust with a particle size between 1-5mm is easier to shape, and the produced sawdust particles have a smoother appearance and relatively low cracks. If the particle size of the raw material is too large and exceeds the aperture of the mold, it will be squeezed into the mold in one piece during the production process, resulting in poor adhesion and breakage at the contact position of the particles and particles, and short particles.
The compression ratio of the ring die of the wood pellet machine is an important parameter basis for measuring the compression molding time and compression strength of wood pellets. A small compression ratio will result in a shorter compression time and low compression strength. It is easy for the pellets to be out of shape or not to be molded.
The gap between the ring die and the pressure roller is normally 0.1-0.3mm between the outer diameter of the pressure roller and the high point of the ring die. The equipment will not jingle when idling. After feeding, the pressure roller rotates and the pressure roller shell reverses to feed the material. . If the gap is too large, the pressure will not be enough to be extruded; if the gap is too small, the density and smoothness of the backlog may be better, but it will increase the friction of the ring die pressing roller, reduce the service life of the ring die and affect the pelleting Machine output.
In addition, I want to remind everyone that with the wear between the pressure roller and the ring die, the gap between the pressure roller and the ring die needs to be adjusted at any time. Generally, it is adjusted once every 7 days. This should be judged according to the actual production situation. The die roller is not corrected after working for a long time, making the axis of the die roller not parallel, and the gap between the pressure roller and the ring die will be large on one side and small on the other, which will cause unbalanced force on the material.
The temperature of the equipment is too high or too low, which will have an important impact on the molding density of the particles and the effect after molding. If the temperature is too low, the input heat is reduced, which is not enough to make the material shape, and it will increase the power consumption of the pellet machine; if the temperature is too high, the surface of the pellet fuel will be thermally decomposed severely, cracks will appear, the strength of the pellet fuel will decrease, or even be unable to form. .
Investigation reason six: ring die wear
After the ring die reaches its service life, it reaches a critical point. At this time, the inner wall of the ring die hole has been worn and the diameter of the hole has become larger, and the produced particles will be deformed and cracked or directly powdered. In addition, after the inner wall of the ring die hole is worn, the inner surface roughness becomes larger, which reduces the smoothness of the particle surface and hinders the feed and extrusion of the material, which will reduce the output of the particle.