No.138 Yingxie Road,Jinshui District,Zhengzhou, Henan Province, China
Biomass wood pellets mill
Biomass wood pellets mill production steps :
- reception and intermediate storage of the sawdust;
-drying and possibly intermediate storage again;
-screening for foreign materials such as stones and metal;
-hammer-milling and possibly intermediate storage;
-pressing of the pellets;
-cooling of the pellets;
-screening of fines;
Biomass wood pellet production process
Reception in biomass wood pellets mill production:
At reception all sawdust coming in should be weighed on the weighbridge and samples taken to determine the moisture content.
For s torage it is p referable to s eparate wet an d dry sawdust. Wet sawdust can be stored for a short period out in the open. The moisture content is not too badly affected if some rain falls on the base material, and wet sawdust does not blow about as easily.
Dry sawdust should be stored indoors immediately to prevent the material getting wet. If the material is stored outside, the sawdust can blow about and create dust hazards. Very high levels of dust are encountered in buildings as dry sawdust is being unloaded. All personnel, including the delivery vehicle driver, should wear a P3 dust mask at all times during and after unloading. Vehicle windows should be k ept closed while they are inside the building.
In large plants that handle a lot of sawdust, under-pressure in the building is created to retain the dust inside. The exit gate from the building is equipped with an airbrush system that blows sawdust from the outside of the vehicles before they leave.In the reception building it is possible to mi x the sawdust befo re it goes in to the hammer-mill, so hardwood sawdust could be mixed in at this stage.
Dryingin biomass wood pellets mill production:
The wet sawdust needs to be dried before hammer-milling as wet sawdust requires much more energy to reduce the particle size than when it is dry. There is also a significant risk of screens becoming clogged or smeared.
Drying can either be done in a drum drier, a so-called flash drier that works wi th high temperatures, or on a flatbed drier, which works at a relatively low temperature. The first option is b etter suited for f ine material, while coarse material needs a lower temperature. So, if chips are going to be mixed in, a flatbed drier is preferable.
It is likely that the throughput capacity of the drier will be less t han the r est of the system , so there should be a facility for intermediate storage of dried sawdust after the drier.
The heat for the drier can be supplied by any kind of fuel, e.g. gas, o il or even biomass. The biomass boil er could use bark, wood chips, short rotation coppice or other wood waste that is not suitable for pellet production.
Screeningin biomass wood pellets mill production:
Before the sawdust can be passed to the hammer-mill for homogenising, it has to be screened for stones, pie ces of metal, plastic etc. Stone is usually rem oved by a stone trap, where the sawdust passes at speed over an opening. Sawdust should also be passsed over a magnet t hat removes metal o bjects. Foreign particles in th e sawdust are likely to damage the press or could conceivably cause sparks in the hammer-mill, which might lead to a dust explosion.
Hammer-millingin biomass wood pellets mill production:
The homogenising of th e sawdust to an even-sized feedstock for the pellet presses takes place in the hammer-mill. Here small lumps of wood, dead knots, etc. are pulverised, so that they can pass through the matrix of the presses. The mixing of the material is also completed here. The hammer-mill should be equipped with a venting hatch to the outside of the building. If a dust explosion occurs, the membrane in the e scape ha tch will bl ow out a nd ventilate part of the pressure to the outside of the building. The opening of the vent on the outside of the building needs to be located at a sufficient height or cordoned off in a way th at reduces the propensity for in jury to any bystander or passer-by in the event of an explosion.
Again, the hammer-mill will not necessarily have the same capacity a s the p resses, so there should b e an intermediate store o f hammer-milled ma terial. This material is very fine and very dry, so precautions against fire should be taken. This part of the building should only be entered when wearing a face mask with a P3 dust filter.
Biomass wood pellet mill
Pellet pressing in biomass wood pellets mill production:
Many presses need the sawdust to be warmed up to 120-130°C using dry steam. The heat makes the lignin in the wood b ecome more p lastic w hich helps to stick th e particles together. T he sawdust is extruded through a matrix and the pellets are cut off on the outside of the matrix.
The matrix can either be standing, with the pressure rollers moving on its inside, or can be lying down with the rollers moving over the matrix in a revolving fashion. The wood is pressed through the matrix under very high pressure.
Vegetable oil is added to lubricate the last pellets at the end of a working period. The matrix will then slowly cool off with the lubricated pellets in the holes of the matrix. If this is not done, the last pellets may become stuck in the matrix, making it difficult to start the press again. The oil-saturated pellets can be returned to the press again the next time it is due to be stopped.
Usually the presses are kept operating overnight, because the matrix and the whole machine operate best at an elevated temperature. Many pellet plants operate from Monday morning until Friday afternoon on a continuous basis. This is another reason for having intermediate storage following drying and hammer-milling, otherwise the press can run out of raw material if it is in continuous operation for periods of up to five days.
Coolingin biomass wood pellets mill production:
Once the pellets leave the press, they are plastic and hot. During cooling, the pellets become rigid and lose moisture, so that the final moisture content after the cooler can be as low as 6%. They will take up moisture from the surrounding air and stabilise at a content of between 8 and 10%.
After cooling the pellets are transported by conveyor belt to the storage shed, where they condition.
Packaging and delivery of biomass wood pellets
After above,you can get biomass wood pellet.Package and delivery them,you will get abundant profit.