Ultimate test for Producer Gas
Doug Williams, Fluidyne Gasification, New Zealand, August 5, 2007
Since I began working with producer gas in 1976, the question of it's quality, and how to measure it in a way that clarifies it's purity, has never in my mind, been answered by gas analysis. I have seen many gas analysis presented to prove a gasifiers function, and therefore justify claims of how this gas can be used, but this can hide a multitude of problems within the gas making phenomena.
Because the cost of gas testing was completely outside of our development budget here in New Zealand, we chose the engine as the instrument to test our gas for condensable tar free, in the vacuum of the inlet manifold, and have a combustible gas content that fitted calculations of electrically generated output. We were assisted by the old DSIR Government Laboratory with a couple of free tests to get going, but from then on, used the engine to prove the gas quality, which eventually provided the Fluidyne Engine Tables http://www.fluidynenz.gwprojects.org/ As our work was directed to engine powered electrical generation, it was quickly established to be reliable, and the need for costly gas analysis as an ongoing proof of gas quality, was not required.
Over the last ten years since this forum began, I have consistently said that you can make tar free gas from wood, not low tar gas, which some prefer to use to describe producer gas. It is therefore a day of reckoning for me personally, as the gas I make meets the ultimate challenge, to be non toxic to CO eating bacteria. There is no hiding behind hot gas to conceal the toxic condensate, and zero tolerance to any uncracked hydrocarbons.
We have all hopes and aspirations to see producer gas have a meaningful role to replace liquid fossil fuels, so when a New Zealand research company LanzaTech contacted me to discuss their project www.lanzatech.co.nz I was surprised to see how important it was to their work, to access good quality producer gas right on their door step. Their first requirement was to access syngas, in the belief that this was the only way to get a tar free gas. Made from oxygen, the cost of obtaining even a small amount of CO in laboratory cylinders, was incredibly expensive, and the prospect of using producer gas as an alternative was an exciting prospect. The only problem was to get the producer gas.
The thought of opening the storage shed to get at my gasifier and engine generator, down the back of my farm in the middle of a very wet winter, was not one of my best ideas. Stored for 18 months, according to myths, the engine would be eaten away with acids, or stuck solid with tar. The gasifier might need repairs, after all it is nearly 20 years old, and so on! The engine is a 1949 four cylinder car engine, we built into a generator set in 1982-3, and used for uncountable hours on producer gas. I fitted a battery, a squirt of gasoline and it fired in about four turns. The gasifier fired up in standard time, of 10 seconds to ignite the bed, 3 minute to combustible gas, 3.5 minutes to get the engine started, and 4 minutes to get full power output. This is a testament for using very dry fuel wood.
The next step was to get the gas into cylinders, so with the aid of a $250 compressor, the gas was drawn while the engine ran at full power 5.5 kWe to give us a standard gas, and we filled the cylinders to 100psi. Several purges of the new cylinders ensured a reasonably true sample was acquired for the lab testing programme, and because they are installing gas analysis equipment, a modern update of the gas from these small gasifiers can be provided.
CO eating bacteria, are not new, and similar projects have been tried, or might even still be active, but this new work by LanzaTech can only widen the choices and ways to replace our fossil liquid fuels. Good or bad, I promise to keep you informed of the outcomes.