The Gas Producer

SUSTAINABLE ENERGY

THE  WOOD  FIRED  GAS  PRODUCER

The first internal combustion engines ran on producer gas as petrol (gasoline) was considered too dangerous. In the great depression of the 1930’s many of those who could not afford to buy petrol used producer gas. In World War 2, with severe petrol rationing, there were tens of thousands of units in use. A transport disaster was alerted. After the war they were consigned to the tip as they tested the patience of many amateur users. In those days they were nearly all charcoal fired as wood was plentiful and labour cheap.The gas producer was only ever used in the past to bridge a crisis. That will be the pattern in the future also. Using wood can never be a permanent means of energy as wood is an expendable item.In 1987-88 Margaret and I did a twelve months trip around Australia using a gas producer as pictured above. It was a learning experience with plenty of tests and trials. We had the engine out three times and the gas producer in pieces five times. We do not claim to be an authority on this unusual machine but we learned through our tests and trust that we can help you to avoid mistakes by what we learned. The gas producer is not an economic answer but the means of surviving an economic crisis.

TIME TO PREPARE

As many people can currently see a crisis ready to explode, and probably more than the 1930’s, it is a very sensible strategy to consider preparing now to build a gas producer. Once the crisis hits it could be too late.I see a need not just for transport in the outback but also for locally sustainable workshops that can have a gas producer driven standby power supply unaffected by the inability to pay bills. These workshops could build power units for other workshops and so on. Transport of food will be a vital need whilst communities prepare for locally sustainable food production.

OVER 1000 DEGREES C.

Making charcoal takes time and wastes at least 20% of the energy as the tar and resin vapours go up in smoke. The charcoal unit operated at around 850 degrees C. whilst the wood fired unit operates from 1000 to 1100 degrees C.  It burns all the tar and resin vapours into usable gas.

STEAM IMPORTANCE

The gas we are talking about is sometimes called water gas as the addition of super heated steam produces the optimum amount of hydrogen which is the main power of the fuel. Several chemical equations take place in the breaking down of hydrocarbons such as tar and resin etc. but a simple one to understand is C + H2O > CO  + H2.

OPTIMUM H2 IS THE AIM

The H2 (hydrogen) is the one that we are after. CO (carbon-monoxide) will drive a vehicle at no more than 50 – 60 km/hr. With H2 at the optimum level you can reach 80 km/hr or more; we have reached that speed within two minutes of lighting up. You must be prepared to have the patience of Job and get filthy dirty as you go through the learning process. You will easily understand why most gas producers ended up at the tip as soon as petrol was available after the war. When it is the only means of getting from A to B you will endure all the trials. Reckon on no more than 10% less than LP gas power.

OUTBACK USE

In the aboriginal outback areas we are looking at transport and power generation for pumping water for food production. There are thousands of tonnes of dead mulga wood so fuel is no problem. Close to the big cities and towns there are usually laws to prevent us from gathering dry wood. When we are looking at a crisis time and literal survival of people there will be no such laws or at least no-one to police them.

CONSTRUCTION OF THE GAS PRODUCER

Do not plan for too much elaborate expenditure. The only electronic component should be the ignition for the spark. It needs to be as manual as possible. When choosing a vehicle go for one at least twenty years old. Any old petrol six cylinder vehicle will be easy to convert. More recent vehicles are so crammed up under the bonnet.

THE OUTER CYLINDER

We have used the old galvanized 44 gallon petrol drum. It is the ideal diameter but needs to be 20cm higher. Also now they are very hard to find. I suggest to roll a 1.5 or 2mm cylinder as shown in the diagram. Weld in the base      and a flange around the top so that the inner cylinder and cone can be lifted out for maintenance. Steel for the base should be 3-4 mm.

THE INNER CYLINDER HOPPER

This would also be best in 2mm mild steel. We recommend a slight taper to prevent wood and charcoal jamming. We had a parallel hopper on our trip and wood jam and charcoal cavities were our worst problem on smooth highways.

THE CONE OR FIREBOX

The cone which is the hot box should be at least ¼ inch mild steel plate. It can be made in hexagonal shape in two sections by crimping in a press. When welding together, and the cone to the hopper, the inside joins should be ground smooth to prevent wood jamming or charcoal cavities. The hot air and steam inlet must be through a stainless steel insert with about a ¾inch hole. Weld a small strap around the square insert and then using the oxy tap it over the insert to seal. Do not weld stainless steel to mild steel as the different expansion rates at 1000 degrees C  will cause cracking. Also do not try a mild steel air and steam inlet otherwise the ¾ ‘’ hole will finish up as 2-3 ‘’ diameter.

COOLING JACKET

If you have the extra time a cooling jacket as shown will not only avoid distortion of the mild steel plate but give extra super heated steam which means more hydrogen and a more efficient fuel. However, without the jacket and just one hole we had enough performance to satisfy our needs.

THE IMPORTANT LID

The top of the hopper must be welded and flanged to the top of the outer cylinder. The flange must be sealed with exhaust putty. It must be possible to lift out the hopper and cone for maintenance. The cylinder base for the lid must be a precision fit to the lid which is pressed down at the centre with a disk sealing effect. Do not use heat to cut out the lid as any distortion will render it useless. The seal needs to be as perfect as steel on steel can be. The whole system operates an engine vacuum so we do not want cold air to enter at the wrong place. We have a unique design for levering and locking the lid as described in the attached photograph.

RAKING OUT HATCH

After a day’s travel, the next morning when all has cooled down, it is time to rake out the ashes across a screen to recover the charcoal to light up for the next day. The seal for the rake out hatch should, like the lid, be as near perfect as possible, but quick and easy to operate.

LOADING HOPPER

Once the screened charcoal is returned to the hopper there should be enough to make a heap on the floor and come above the lighting hole in the cone. Then wood can be added through the top. About a couple of domestic wheelbarrow loads should fill the hopper. We found to cut to about 20cm lengths is OK.

LIGHTING HOLE

The air and steam inlet must be flanged on both sides of the outer cylinder wall with the inside flange threaded. This enables an easy removal of the hopper and firebox for maintenance. A cap at the end enables a lighted taper to light the charcoal through the insert hole. Charcoal ignites almost instantly as the engine vacuum commences.

OPERATING TEMPERATURE

The firebox temperature needs to be as high as possible to produce the optimum amount of hydrogen. The resulting fuel gas needs to be as low as possible to deliver to the engine. Every 30 degrees C decrease in temperature means 10% less volume and therefore a richer fuel. So after the gas leaves the gas producer we aim at as near to air temperature as possible. The hotter the gas from the firebox the more steam will come from the automatic steam generator. In the process of the hot carbon reducing the steam to H2 and CO it is also cooling. So the temperature in the firebox is governed by the automatic steam generator. We are told that the firebox runs at between 1000 and 1100 degrees C.

STEAM GENERATOR

It is a very simple design, just a piece of 50mm stainless steel exhaust inside the next size up. Hot gas from the top outlet of the outer cylinder of the gas producer, passes through a jacket of water creating super heated steam. The water level can be adjusted by raising or lowering a small reservoir of water with a float valve. There needs to be a cleaning hatch with a gasket to remove salt from any brackish water used. The outside tube needs to be closed in top and bottom with the oxy., and stainless steel welded for seal.

THE WET FILTER

To achieve the optimum amount of hydrogen it is inevitable that at times there is a little too much steam. As the gas cools this condenses back into water and makes a dry filter very difficult. We concluded that a wet filter was the way to go.In outback Australia saline water from bores is very corrosive and so it is advisable to use stainless steel for the cylinder, mesh and lid. The hot gas enters just beneath the mesh and rises up through the dripping wet 1cm. diameter coke or stone screenings. The outlet is above the coke. The cylinder and lid and base could be about 1.3mm steel which is plenty strong enough to withstand the vacuum. A water pump is needed to circulate through the shower `rose’. The number of holes in the rose and the size of the holes will depend on the pump output of at least fifteen gallons per minute. In the marine industry there are 12v bilge pumps available. Make sure of the continuous rating before purchasing.

SILICON DUST

Filtration must be 100% for the engine to last. In the dust from the ash there is a fine silicon powder which would be as abrasive as corundum grinding paste. Even though the wet filter is very effective you still need a secondary filter under the bonnet with like a vacuum cleaner type bag made of a blanket material.

CAR RADIATOR

To further condense moisture and cool the gas it can be passed through a car radiator mounted to catch the breeze or if stationary use with an electric fan. Condensed moisture could trickle back to the sump. Also at a low spot in the 50mm delivery line to the engine a water trap can be installed.

CLEANING SLUDGE, AVOIDING DUST & TAR SPLASH

After shutting down the gas producer the sludge plug can be drained and the water left to settle overnight so that the clean water can be returned to the sump. Condensed steam should maintain the level. The wet filter is much cleaner to handle than a dry filter with all the charcoal dust. We found that after raking out the charcoal it took about three showers to clean the pores of our skin. When raking out the hopper make sure the wind is blowing the dust away from you. When raising the lid on the hopper be careful to park so that the hot tar splash does not spray on the vehicle. It takes paint remover to clean it off.

FROM GAS PRODUCER TO ENGINE

It is best to mount the gas producer at the rear of a trailer with the wood storage in front. We learned the hard way. Occasionally the heat from the gas producer ignited our half ton of wood behind. Also in re-loading the hopper with wood we suffered constant tar splash on the vehicle.The ideal vehicle would be a station wagon with a pack-rack. The 50mm gas line can be mounted over the top and then down to the engine with much better cooling than underneath near the hot road. A piece of 50mm spring reinforced hose and clamp are needed to connect from the trailer to the vehicle at the drawbar.

TO THE CARBURETOR

The gas must first be delivered to the secondary filter and then to two butterflies, one for the foot accelerator for the gas and one for the air mixture which is operated manually by a hand lever on the dash. The gas/air mixture then goes through a very shallow closed in channel (10mm deep) to fit underneath the carburetor with a matching hole so that with a couple of gaskets the petrol carby can still operate. The channel is also drilled so that the holding down lengthened bolts for the carby can be tightened down. Small pieces of tube (just less than 10mm) must be inserted inside the channel so that it does not distort when tightened down. The gas goes into this channel and enables a dual system of petrol or gas.

SPARK CONTROL

Producer gas has a long explosion and so the spark must be advanced a few degrees. On our transit van we put longer bolts with a short spring to hold down our distributor. We wired a clamp around the distributor and a lever to the dash with two slotted positions –one for gas and one for petrol. We usually started with half a carby of petrol to generate the vacuum and then after about a minute or so we were on producer gas. One can use high speed heater blowers which will draw enough vacuum to light the charcoal. If petrol were unavailable there are many alternative but cumbersome ways to get started.

ECONOMY

On our 20,000 km trip  we achieved about 2,000 km per ton of firewood. With optimum steam I believe we could reach 2,500 km. The amount of water needed to produce the steam for `water gas’ is about the same volume as the petrol that would have been used. We have had up to 240 km per hopper of wood and down to about 80 km with quick burning pine wood. We have used old tyre treads (not the steel weave), coal and even sugar cane. Dry cow manure in fact anything dry and combustible will generate producer gas. We only found one stretch of about 200 km around Australia where there were no dry sticks of wood. We carried enough for 1000 km.Remember that the gas producer is for a temporary transition in a crisis. It is not complicated to build. It just takes plenty of patience. It will take you anywhere in time if not on time.