[Gasification] stratified downdraft pressure

[JOHN GOODWIN]

Dear list,

I have made a stratified downdraft gasifier as described by Dr Reed at http://www.gengas.nu/byggbes/intro.shtml. Using a small blower, it works, and I have large quantities of flammable gas. I unfortunatley also have quantities of tar and steam coming through the filter, using wood chip of about 10% moisture.

Being new to this, please feel free to correct me at any point. Please also excuse my mixing units.

I assume that the tar and steam are present because the temperatures in the reduction tube are too low for the water gas reaction to fully complete, and too low for the tar to crack. From this I assume I need more suction from my fan.

I have used a 10" reduction tube. From table 2.2, http://www.gengas.nu/byggbes/52.shtml this is suited to a 160 cubic inch engine (2.6 litre). At 2000 RPM, a 2.6l engine is drawing 5200 litres per minute. I understand that producer gas and air need mixing at approximatley 50:50, so would be drawing 2600 litres (91 cubic feet) per minute from the gasifier.

So therefore, I am looking for a 100 cubic feet/min suction fan. How many inches water suction does this fan need to generate in order to achieve the neccessary temperatures in the reduction tube? Does anyone have any good sources of cheap fans (UK 240v, 50Hz).

One more beginners question, when using a simple U bend to measure water guage, is the suction the difference between the gasifier side and atmospheric side levels of water, or the difference between the gasifier side and the starting level of water?

Many thanks,

John