This is a tank gsifier I built in 2004. It has an 8 inch tube in the centre and a 14 inch tank (old gas cylinder) of circulating water around the tube. Gasification takes place when wood is heated in an anaerobic (low oxygen) atmosphere. The wood itself is used to provide heating for gasification in this example. Primarily this gasifier was used for heating (around 8kW), and I used it for two year as part of a combined heating system for my house. Installed under a basic A-frame cover and a little insulation around the tank (not shown) it worked very well. The drawback is that it was difficult to automate the fuel supply and it required refilling every two and a half hours - not very practical. WARNING: Unless you know exactly what you are doing DO NOT touch a gas cylinder. You must also have the permission of the owner first. The gas cylinders I use have been damaged and are re-claimed from scrap. EVEN SCRAPPED OR EMPTY CYLINDERS ARE STILL EXTREMELY DANGEROUS - PLEASE BEWARE!! (Click on picture to enlarge)
Photo showing part construction of the tank gasifier. This particular gas cylinder was scrapped because a welding torch had almost melted through the cylinder around the neck. It is a miracle that the welder escaped with his life! Please see the warning about gas cylinders above. (Click on picture to enlarge)
This was an early experimental version of a gasifier. I started off with paint-pot sized gasifiers to prove the idea, and then moved on to this large model (40 inches high). There is no water cooling jacket, and the main tube is around 10 inches diameter and made from a piece of insulated stanless-steel chimney section. The gas it produced was immediately burned at the top and the heat was extracted using a standard cast-iron heat-exchanger taken from a domestic gas central-heating system. The flames are just visible between the tube and the heat collector shield. It was a superb gasifier but the tube eventually melted in a particularly hot firing. I also discovered that the fins in the heat exchanger clogged very quickly and required daily cleaning - not recommended! (Click on picture to enlarge)
This was my attempt at gasifier automation. This is a version of what I believe is known as a down-draft gasifier. Basically it is an upside-down version of the tank gasifier above. Fuel is supplied through a 6 inch tube at the top and moves down under gravity. There is a grate (stainless-steel kitchen colander) suspended on chains at the bottom of the tube, and the fuel is ignited in the grate. As gas forms it is immediately ignited in the water-jacket chamber, and the combustion gases are taken to the flue through a cast-iron gas central-heating heat-exchanger. This system worked well (around 10kW output) and, had I not discovered stoker-burners, I am sure I would have developed it further. Once again, a different solution is required for the heat-exchanger as the fins get clogged. (Click on picture to enlarge)
