How did these work theory or practice?

Saw an article on facebook about these gas generators that burnt wood without much air thereby generating hydrogen methane and CO2

apparently 50 million were sold during the 2nd WW

does anyone have any experience of them?

I have heard of them, but I have no idea how they work. But I would like to know. Maybe it's the same principle as a rocket stove. The wood is burnt in the bottom of the stove, and then the gases re-ignited (or something) as they rise up the flue to produce much more heat and very little ash.

A little !The key with wood gasification is the feed stock, using wood chippings, if not very dry will cause the production of moisture and tar that has to be filtered out before combustion. The experiments I know of had big problems with clogged filter bagsand were deemed a failure ! Those conducting the tests seemed to have litte understanding of basic combustion and the heat loss due to moisture.Being a green experiment, tax funded success  was not vital and nothing NEW was going to be found. Such units are commercially available today but they are aimed at places where there is a dry and readily available feedstock, nut shells Etc. The "gas" was used to fuel a diesel generator. Noel

Edited By noel shelley on 05/06/2023 20:28:30

The useful gas they generate is a mixture of hydrogen and carbon monoxide (CO) not carbon dioxide (CO2). Basically the same as the old town gas. They both types of producer gas. One significant environmental issue is that they produce a lot of water contaminated with organic chemicals including tars. This liquid requires special treatment which takes yet more power that hs to come from somewhere. They also have practical limitations.

I believe some types used coke, so eliminating the tar problem.

Back in the days when we were allowed to have 'real' chemistry sets as children, I remember one experiment was to make town gas by heating matchsticks in a test tube, corked and with a piece of glass tube forming a jet where the gas could be lit. It produced a surprising amount of tar which then needed cleaning out, but it did serve as a dire warning against smoking! The matchsticks became charcoal, or something vey close to it.

I guess the principle is the same as used in the gas generators shown.

Rob

You could probably use wood or Coal in them.

Messy byproducts though, like bitumen, might even be enough to do your driveway with

As usual nowadays there are youtube instructions for making your own.
The number of 50million is way out, maybe 50k.
There is a display attending some steam shows with a coal based version running a big open crank engine. The whole set up being a commercial product from the '30s.

During the war petrol was rationed and they where also fitted to cars. Shown here on a 1930 Ford Model A.

The coke burner on the back made gas to run the car. Note bags of coke on running board.

In our village when I was a teenager there was a sawmill that had an engine that ran on sawdust. I think 'suction gas engine' would throw up some googlings.

Look up GASOGEN on the internet or GASOGEN for cars etc. There are some modern pickup trucks in USA using them.

In Norway wood gas generators was used during WW 2 to fuel the cars of ordinary people. You didn't get as much power as you would from petrol but at least you could drive your car. I think grey alder was the best wood to use.

More about wood gas generators here.

Thor

It was quite some time ago but Dick Strawbridge had a programme called Planet Mechanics. They converted a land rover to run on wood gas and if I remember right drove it through London. You may still be able to watch it as the program seems to be streaming on National Geographic.

I also remember seeing online a WWII booklet from some US agricultural department on how to convert your tractor to wood gas.

I think the secret of how it works is that the top of the combustion chamber is sealed and the air is injected just above the grate. The air flows down through the combustion zone. This means the initial combustion gasses are passed over white-hot carbon. This converts the carbon dioxide, water and unburnt gasses to carbon monoxide, hydrogen and methane.

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When I did school chemistry we spent an inordinate amount of time on these. Wikipedia gives a good explanation of both.

I must be a little younger because our old textbook covered it in detail, but the new one didn't. I think because town gas made from coal was going to be replaced with North Sea gas. Many British towns had a gas works, all gone now!

Producer gas for vehicles was a shortage-driven war time thing. Oil had to be convoyed to the UK past U-boat wolf packs and many seamen died doing it. On arrival top priority was given to the military, and civilians only got a small ration of 'Pool Petrol' - a variable quality mix of leftovers! Led to a great deal of criminality. On the other hand coal and wood were available locally, not rationed, and could be manipulated to drive a vehicle. There's an episode of Dad's Army where Corporal Jones van is shown with a kind of barrage balloon strapped on top. These were filled with coal gas. Both systems worked, but not well!

Curiously a more advanced version of the producer process is used on a very large scale today. Not on vehicles! Huge chemical plant convert Natural Gas rather than coal or wood and the Hydrogen is used to make Nitrogenous fertilizer, over 200 million tons per year. As the high productivity of modern farming depends on fertilizers, we'd all starve without it.

Dave

I lived in South Lincolnshire during WW11, Boston area, and we had gas powered buses, single decker's, they towed a trailer/gas unit and I remember seeing one with an inflatable bag on the roof. I also remember seeing fire/flames at the back of the unit when the driver put in some coke where a small door was. No one was in a hurry those days, just pleased to get a ride, better than walking, or got on your bike. For us youngster a penny each way, into town, adults three pence return. john

There is a long tradition of people mis-selling gasifer and pyrolysis technology for the treatment of MSW (Municipal Solid Waste) and other material streams with excessive heterogeneity, as a result of which very reputable companies (who should know better) end up loosing their shirts as a result to the tune of hundreds of millions (or 1.3 billion in the case of air products).

There's a particularly savage review paper by an engineer at Loughborough Uni which highlights some of the more egregious and dangerous failures by developers of such projects to study the vast literature on the subject derived from the town gas era, followed by an exchange of short communications with a researcher who objected to the paper in which the author of the review proceeds to pull the objectors mathematical treatment of experimental results apart...

It's rare you see that kind of thing in the scientific literature, and it gives me great amusement.

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At the same time there's a curious German professor (notable for being dressed in a Dinner Jacket and Birkenstock's when I was first introduced to him) who has developed a pyrolysis reactor with an integral screw auger of a particularly complex geometry which mixes the solid char from the process to form an auto-catalytic bed facilitating the correct reaction conditions to allow the moisture in the feedstock to then hydrolyse the tar fraction produced by the initial breakdown of materials.

The result is that it condenses a stream of remarkably clean hydrocarbons (which due to the hydrolysis are a mixture of aliphatic hydrocarbons and their oxygenates) out of the hydrogen stream.

He has probably been altogether too cautious in approaching the commercialisation of that technology, despite having several successful pilot plants running now.

During WW2, petrol for road vehicles was in very short supply, (You ad to be in a special,occupation ,such a special constable, or farmer ) to have a permit to obtain it., My father was a specvial constable and worked for the Ministry of War Transport, so he qualified for a small quantity!

Public transport resorted to towing trailers making producer gas for their petrol engines. the gas was of low calorific value, and so reduced the power of the low compression engines then available.

Any vehicle over 3 tons unladen weight was not supposed to excedd 20 mph. And away from prying eyes, a diesel lorry would be harf pressed to exceed 30.

But it enabled vehicles to run, which was better than nothing!.

Steam lorries, such as Sentinels, were capable of quite high speeds. Bulmers, ran a Sentinel S6 until after the war.

Post was, with many petrol engines being badly worn, and high petrol prices, Perkins would coinvert a lorry from petrol to diesel powere within a day, or sell conversion kits to do this. (About £550 in the mid /late 40s )

Shortly afterwards, Ford and Bedford introduced their own diesel engines, as did the Rootes Group with their 2 stroke TS3..

Howard