Nugget of Knowledge: Wood Gas for Driving Vehicles
This is also the answer to ScrapLabs Challenger – #1
The Challenger : http://blog.scraplabs.in/?p=41
The Winners : http://blog.scraplabs.in/?p=106
The solution to this challenger is rather amazing!
Wood, say match-stick, is basically very close to hydrocarbon (like sugar). So when it burns it burns like any other hydrocarbon substance would! It is a two-step process. The carbon and hydrogen molecules contained in wood disintegrate on burning and are converted to Carbon-monoxide and Hydrogen gas. Now, both these gasses are combustible. So, in the second step Carbon-monoxide is converted to carbon-dioxide and Hydrogen gas is converted to water.
To start the fire on a match we rub the gunpowder coated end of the matchstick against a rough surface to generate heat. When the gunpowder reaches its ignition temperature it starts burning (oxidizing). This reaction is highly exothermic (burning gives out heat). This generated heat starts heating the wood of matchstick right next to the gunpowder coated area and turns the Hydro-carbon molecules to CO and H2.
Both of these gasses are hot right now and hence start rising up. As they move up, they come in contact of the fire that was already burning alongside and ignite.
Note that when wood got gasified it didn’t burn instantly. The gasses (CO & H2) had to rise up and come in contact with existing flame to start burning themselves. Hence a small gap between the matchstick and the flame is seen 🙂
This keeps going on till the wood runs out.
Now you might be able to relate to a few things –
- The reason why there is no gap initially (when gunpowder coated portion burns) but it shows up as flame moves towards the other end of the stick.
- The reason we need to hold matchstick in a certain inclined manner to make it burn properly.
- Flame likes to go up rather than coming down a matchstick.
Being said that, let me take you on a historical journey.
In World War 2 as the Germans and Britishers were slugging it out in the forests on the borders of France and UK they faced a tragic problem which, if not solved, may cost them the war. The problem was availability of fuel for their tanks, trucks and other vehicles.
However, the Germans had found a farmer who knew a technique to use wood to drive vehicles! Shocking. Beautiful. Amazing!
He had designed a setup which allowed the wood to half-burn only. He would stop the combustion reaction just after step 1 and obtain the gasses (CO & H2). He would then use this gas to drive Vehicles (like CNG or LPS that we use now-a-days). Don’t believe me? See for yourself!
In-fact they were also used to drive cars, trucks, buses in cities! But soon after the war was over the technology got lost in the tides of time. It is really sad that it was not used on a large scale. It is found out that it is less polluting and has a lower carbon foot print over other fossil fuels like diesel, petrol, etc. The primary reason being that it has very low composition of oxides of nitrogen and sulphur. Hence the smoke of a wood-gas engine is far less toxic.
I was able to find a few enthusiasts who still make such vehicles just for fun.
Interesting right? 🙂