Moving around wood pellets in bags can take some time and for some people with limited mobility its simply not an option. In most places, you can have loose deliveries where the wood pellets are blown into some form of silo or store. But then you have to move the wood pellets from that silo to your wood pellet stove or boiler. Now, you could do it ‘old school’ like me with a bucket and shovel. However, in the 21st centry, most people are looking for something more automated. Therefore that’s where wood pellet vacuum systems come in.
The average 5 kW pellet stove will use around 1-3 tons of wood pellet fuel per year. This is a volume that for most people is not too much trouble to lift into the stove by hand with bags. However, pellet boilers generally start at 15 kW. For instance, our 25 kW pellet boiler consumes around 7 tonnes of wood pellets in a heating season. When it comes to these sorts of volumes many people look towards hoppers and silos to hold the wood pellets. Therefore more automated methods to get those wood pellets into the pellet boiler hopper.
Alternatives to Wood Pellet Vacuum Systems
The first alternative method is fixed augers. However, in many instances, this is not an easy retrofit and can also be very expensive. There are also flexible augers, these are easier to retrofit but are not as reliable as fixed augers. Also, flexible augers have their limitations due to length and getting around sharp angles. Therefore, that’s why in many cases wood pellet vacuum systems are a better fit. They are simpler, less expensive and can deal with long runs and changes in angles.
Below we are going to look at two wood pellet vacuum solutions. The first is an off-the-shelf product produced by Triotec and the second is an impressive DIY pellet vacuum build from the US.
Off-the-Shelf Triotec Wood Pellet Vacuum
The wood pellet vacuum system shown in the video above is the PIV 3 from Triotec. The PIV 3 is described as a compact and flexible solution for homes and production facilities. There are several components to the system which I’ll discuss below in reference to the image below:
How the PIV 3 Wood Pellet Vacuum System Works
The wood pellets are pulled through the hose at the base of the wood pellet hopper. The wood pellets are then carried up the cyclone separator. You will also notice a pipe which exits the top of the wood pellet hopper. This pipe is to let air into the hopper when the fan starts. Without this pipe, the wood pellet vacuum wouldn’t work.
The Cyclone Separator
A vacuum is generated within the cyclone by the separate fan. The wood pellets fall out of the air stream and into the base of the cyclone separator. An automated gate valve then opens to let the wood pellets out. A small motor and auger then collect the wood pellets and drop them through the short hose. The short hose will feed into the hopper of the pellet stove or boiler. Hence the cyclone separator will also have to be mounted over the pellet stove/boilers hopper.
The Fines (Dust) Bin
The air and fines (wood dust) are then pulled from the cyclone and separated again. The fines are deposited in the metal drum and the air will leave (via a filter) from the top of the fan unit. How quick the fines bin fills up will depend on two factors. Firstly, the grade of wood pellets purchased and how gently the wood pellet delivery driver off-loaded the pellets.
Reducing the amount of Fines
You see on a loose wood pellet delivery the driver can control the fan speed. A quicker fan speed will deposit the wood pellets into the hopper more quickly, however, it’s also more likely to break the wood pellets and create fines. Delivery drivers are sometimes in a rush to get to their next delivery. Therefore if possible try to supervise you wood pellet deliveries and monitor the condition of the wood pellets. If you see large volumes of fines dust, ask them to lower the pressure.
DIY Wood Pellet Vacuum System
As you can see from the PIV wood pellet vacuum system above, the process is actually very simple. You just need a fan with enough power to carry the wood pellets in an air stream. You also then need to be separate the fines and air. Otherwise, every time you use a wood pellet vacuum system you would be surrounded in clouds of dust.
Below is a pretty impressive DIY wood pellet vacuum set up from the US. This particular wood pellet vacuum system has been designed so bags of wood pellets do not need to be carried from the basement where they are stored up the house.
Dust Explosions need to be taken Seriously
As stated in the video if you are tempted to build your own DIY wood pellet vacuum system you need to take dust explosions seriously. If you do a quick bit of research on dust explosions, you will see why it needs to be taken seriously. Static charge can be built up as the wood pellet travel through the pipework. Therefore all wood pellet vacuum systems need to be properly earthed so sparks from static electricity build up are not an issue.
How to Improve the DIY Wood Pellet Vacuum System
First off, I want to congratulate the individual who built this wood pellet vacuum system, it’s a project I would also be proud of. However, from watching the video there is improvements which could be made.
As the wood pellets enter the hopper located upstairs in the property they are impacting against a hard surface. This is increasing the percentage of fines produced.
The first improvements to be made are to fit a rubber matt against the side of the hopper. This will reduce the impact on the wood pellets, reducing fines. Secondly, a cyclone separator could be used instead of a basic filter. Currently, the fines are not removed from the hopper. So these dusty wood pellets will also be loaded into the pellet stove. For some pellet stoves, wood pellets with a higher percentage of fines can lead to various issues, including clinker formations.
Quick Note on the Pellet Mole
In both of the wood pellet vacuum examples above the wood pellets are sucked from the bottom of the hopper. However, what if you wanted to retrofit an existing wood pellet store with a vacuum system? Well, one solution to that problem is the Pellet Mole (great name for this product).
So essentially the Pellet Mole is mounted in the ceiling of the wood pellet store and its lowered into position. As the volume of wood pellet reduced the Pellet Mole follows the wood pellets down. A small motor and agitator is fitted on the end which sweeps wood pellets to the vacuum hose. The Pellet Mole still needs a fan and cyclone dust separator to operate. However, its an interesting solution on how to retrofit an existing wood pellet store for a vacuum system.
Conclusions on Wood Pellet Fuel Vacuum Systems
I personally feel that wood pellet vacuum systems are a more flexible solution for most domestic situations compared to augers. One advantage augers do have is that they don’t create additional dust. However, if a well-designed cyclone separator is used in a wood pellet vacuum system, dust shouldn’t be an issue.
If you would like to learn more about wood pellets and about how they are made please visit my homepage. I’ve got a considerable number of posts on the wood pellet production process and how wood pellets are made.