You can purchase motors & helix for the feed system directly from Matene in Norway. The pipes for the feed system is standard PP plastic drain pipes that you find in your local shop (Bauhaus etc.).
If you don't have tools or skills to build your silo, ask your supplier of the pellet boiler do the job.
For installing the feed system you need a grinder to cut the shaftless helix in addition to a jig saw and other standard tools.
Particles in Motion
Typical package of a feed system for a bulk silo holding 6 tonnes of pellets.
The package contains motors, cables and other installation details. This package is shipped to your local post office.
Above: Motor for the silo conveyor. Note that this small motor can handle up to a six meter long silo conveyor with 10 inlets. For boilers more than 50kW, larger induction motors are used.
The motors have mechanical torque protection as well as thermal protection. The motor drives are designed especially to handle conveyors in series and long transport distances.
Above: Motor for the silo conveyor is located in the front of the conveyor and is "pulling" the pellets. There is need for an extra feeding screw to feed the vertical conveyor.
Above: Motor for the silo conveyor is located in the back and "pushing" pellets to the vertical conveyor. This is the simplest way but not always possible due to arrangement of the silo.
The screw conveyors work in series without the need for any intermediate storage & costly level control. Pellets can be fed from large silos directly to the pellet burner at the required capacity. The burner starts and stops the feed system intermittently. From the vertical conveyor, one or several ceiling conveyors can be connected to transport pellets through neighbour rooms and ultimately to your boiler. When feeding a boiler with built in pellet storage, for example Windhager, Fröling boilers or Mafa mini , Matene supplies level control for such boilers and storage tanks. The capacity for small house boilers range from 8kg/hour to 13kg/hour. Larger feed systems will feed more than 100kg/hour.
Here's how it works:
The pellets in the silo fall into the silo conveyor openings. These openings have a "flap"-control which creates "side intake" to the conveyor, this means that the silo conveyor never runs full of pellets. This method creates a very stable and gentle flow of pellets through the conveyor and it is possible to use miniature motors, even in long conveyors. What if the vertical conveyor suddenly stops? Well, the torque control witches off the motor in due time before it reaches maximum allowed torque and before it is allowed to block completely. The silo conveyor length should not exceed 6 meters and have a maximum of 10 inlets.
This is the small feed screw you see on the picture above to the left. This conveyor is needed if you choose a "pulling" silo conveyor. This conveyor can be longer than what is shown if you want the vertical conveyor placed on the front side of the silo.
The vertical conveyor is patent pending technology in several countries and was invented in 2005 after 4-5 years of development. By lifting the pellets vertically, it is very easy to arrange the silo and feed system. The boiler and burner becomes easily accessible and you don't need to crawl over a tilted conveyor.
From the outlet of the vertical conveyor, you can drop the pellets down to the boiler or you can transport the pellets further in any direction with a ceiling conveyor, also backwards through the silo. The feed system has the flexibiliy of vacuum feed systems but is not that noisy and costly.
The vertical conveyor like the fines (dust) that come with bulk pellets. In fact, the conveyor is filled and balanced at around 70% of fines after some time of operation. The fines are needed for the transport process as they are put into movement (fluidized) by the helix and the bulk density of the material is reduced creating room for new pellets. The pellets are slowly lifted upwards through the fines, just like air bubbles in water. The conveyor uses natural processes to move the pellets upwards, these processes are called fluidization and segregation. Fines are sifted downwards and outwards towards the periphery of the tube, the pellets upwards in the center of the tube. The need for net motor power for the operation is 3-4 Watts, next to nothing.
Example of fluidization: Snow avalanche in the mountains. The snow is compacted to the ground. Once put into movement, the snow particles become water-like, they flow like a river down the mountain side.
Example of segregation: Pour sand into gravel and shake, the sand falls down, the gravel is on top.
We hope you have a feeling that Matene can provide unique technology and are well qualified for supplying feed systems. We should mention that a thumb rule says that 90% of stops in a bio-energy plant is due to the quality of the biomass. In other words, the feed system is the critical component and this is where it stops. Once the biomass is fed into a burner, it will burn nearly anything.
Since the vertical conveyor is partly filled with fines, the conveyor prevents combustible gases to pass from the boiler backwards to the silo. This is an important safety feature. In addition, the drop out from the chute is at safe distance from the burner inlet and this keeps the combustible matter at safe distance to the burning chamber. The chute consists normally of a plastic hose that will melt off in case of a back-burn. If this happens, additional pellets will fall on the floor in case the burner is still asking for pellets.
The ceiling conveyor is a standard operating conveyor which operates at a higher speed than the silo conveyor. Ceiling conveyors up to 15 meters of length can be used. It is also possible to use more than one ceiling conveyor.