A cyclone filter should be the first level of filtration in any wood gas system. A typical cyclone will remove over 90% of the particulate matter from the gas stream. IT WILL NOT REMOVE TAR UNLESS THE TAR HAS CONDENSED INTO DROPLETS.
A cyclone works by spinning the gas so that the particles are trapped against the walls of the housing. The force on those particles varies according to the equation:
Force = Mass*(tangential velocity^2/spin radius)
The “squared” term indicates that the filtration will improve dramatically as the cyclone flow increases. If you actually do the math you will find that the force on a particle is over 300 times that of gravity at the point of best filtration. This is why I advocate cyclones over settling bins. Settling bins only apply a single force of gravity.
The cyclone actually has two “tornados” inside. There is an inner and an outer vortex. Any dirt that gets blown into the inner vortex is immediately thrown back into the outer vortex which is why these units are so effective.
If you would like to purchase a wood gas cyclone filter, I do build and sell them. Please see the Get Hardware drop down list.
I have had several inquiries regarding whether my cyclones can be used to measure flow. Below is the flow measurement rig I used to develop the calibration curves below:
I drew in a “best filtration” line strictly based on the 1D3D style cyclone numbers. There is NO testing behind that line. I will try to get to that later but I just have more important things to do first.
Now if you have purchased one of my cyclones and you would like to know the gas flow in your system you can determine it by simply reading the pressure drop across the device with a manometer.
Lastly, my flowmeter only goes to 25scfm which is why I have to project such an uncomfortably large amount.
My cyclones do work horizontally. I never thought to try it until one of my wood gas group members asked me about it. I got 85% efficiency on the first test. You can watch it here: