Wood Gas

No-weld design revisions

2011-06-13T03:47:00.000-07:00

For such a small gasifier, it has been decided to fuel it with charcoal rather than wood. This reduces the need for filtration as there are less unwanted tars and gases in a charcoal fired gasifier. However, a simple filter will still be constructed to remove the lower amounts of unwanted tars and gases.

In fact the filter will be the first part of the new gasifier to be built and will based on designs in the books "Convert Wood into Charcoal and Electricity" and "Producer Gas for Motor Vehicles".

After that a suitable radiator/cooler will be constructed and then both new components married to a no-weld version of the G3-I gasifier.

For now, some charcoal will be bought (or maybe obtained on Freecycle) to test the system. If it works then charcoal will be made by the retort method.

Leakier than a very leaky thing

2011-06-09T04:21:00.000-07:00

The no-weld gasifier was fired up, last night. Chunks of softwood off-cuts were used as fuel. Doused with a little meths, they were ignited and a fire took hold without any problems.

The lid with the blower was placed on top and smoke was soon seen coming from the gas outlet pipe and just about everywhere else too.

Sealing all the gaps with fire cement will mean that the gasifier innards will not be accessible. A redesign is in order so that gas doesn't leak out and the gasifier can be dismantled when necessary.

There are some interesting designs on YouTube that I will incorporate into my redesign. The G3-I is one such design that I am interested in. Although it is welded together, it is a simple design that might yield ideas for the no-weld gasifier.

No-Weld Gasifier Progress

2011-06-07T11:53:00.000-07:00

A little more progress on the no-weld gasifier. The centrifugal fan has been put on top of the hopper. Originally it was going to force air through the side, into the combustion (middle) chamber, but that would have required a stand to hold what is a very heavy fan.

On the table, to the right of the fan, you can see the variable mains supply that was built. This allows the speed of the fan to be altered for the correct amount of air throughput.

The fan was briefly switched on and surprisingly there was not much bleeding of air from unwarranted places. A draught was felt from the exit tube (top right of lower chamber). There are not that many holes in the grating so more will be made.

The fan will be bolted in place and some gasket material placed between it and the lid. A test firing is not too distant into the future.

A transition tube was added to the centrifugal fan, as can be seen in the image below.

As this is an experimental gasifier and not the final product then gaps will be filled with fire cement. The aim, with this gasifier, is to produce gas of whatever quality and then to take stock of the project so far.

The documentation for this project needs updating and will be carried out soon.

Some no-weld gasifier progress

2011-06-04T07:36:00.000-07:00

Time and commodity are beginning to come together, allowing us to get further with the "No-Weld Gasifier" project.

The stationary engine was completely rebuilt. Initially it worked but there was a remaining fault. The woodruff key slot for the flywheel was damaged by the previous owner and finally gave in. A new flywheel and drive shaft have been ordered and will replace the damaged ones, next week. Still, the engine looks a lot better than it did.

Today, a plywood flange was added to the centrifugal fan that was built for the project. The copper piping that was going to be used for venting air from the fan into the gasifier was quite narrow. Instead, some obtainium tinware will be riveted into a conduit between fan and gasifier. The plywood flange on the fan will help to join the fan to the conduit.

As soon as all of that is in place then the fan will be attached to the gasifier and we shall see if there are any holes in the system that will need plugging. Once air is entering the gasifier through the conduit and exiting only through the gas exhaust then a test firing with wood will be made. This should all be achieved by the end of the month.

After that it is a matter of filtering and cooling the wood gas afore connecting the gasifier to the engine. We have an alternator and all the necessary belts and pulleys to test the resulting generator.

Suffolk Engine Rebuild

2011-05-18T15:12:00.000-07:00

The engine has been stripped down and is in the process of being cleaned. There was a lot of coking to be removed. The piston head doesn't move from side to side so it looks as though the rings are not worn.

To the right, you see the air governor. The link between it and the throttle is missing so I need to fashion a replacement. The vane itself must have fallen off and was chewed up by the vanes of the flywheel so it will need to be patched up.

The exhaust muffler was completely rusted. I brushed off the surface rust with a rotary brass brush on a power drill. No sign of any clean metal so I painted the muffler with two coats Kurust. Now the muffler has a beautiful dark brown sheen and will be reused rather than buying a new one.

There is a lot more cleaning, painting and repair to be done afore the engine can have a trial run with petrol. After that it will be run on Butane then some thought on how to run it on wood gas.

A stationary engine for wood gasification

2011-05-10T12:02:00.000-07:00

A quick update. I am no further with my "No-Weld Gasifier" project so you won't find a "Part 4" on this website.

However, I did get a non-functioning lawnmower on Freecycle last week with which to use for a future wood gas electricity generation project and it will use the No-Weld Gasifier.

The particular lawnmower I received is a Model 24A Suffolk Super Colt. It is powered by a Suffolk Foundry 75G14 iron block engine. Ideal for conversion to a stationary engine.

I guess I have no excuse but to continue with the No-Weld project.

The lawnmower, a Suffolk Super Colt.

The 75G14 engine underneath its cowling. Recoil starter on the left. Spark plug atop.

Engine removed, begging for some attention. The air vane governor fell off but was kept by the previous owner. There were no linkages from the governor to the throttle so I will need to make some. The spark plug is dead, new one in the post.

Kelly Kettle wood gas modification

2010-10-17T04:07:00.000-07:00

I have owned a Kelly Kettle (see first photograph) for sometime. I use it for boiling water outdoors. There is also an attachment for the chimney whereby you can place a pot or pan to cook food too.

Kettle Kettles use small amounts of wood as is but from tinkering with wood gas I knew I could do better. Not only that but I have noticed that other peoples' kettles get quite dirty so I knew that a wood gas conversion would help there too.

In the second photograph, we see a standard MIDGE stove constructed from two suitable cans. The outer can fits the bottom of the kettle perfectly and the inner can is suited to the outer can of the MIDGE stove.

In the third photograph, we see a serpentine of metal scrap that keeps the MIDGE stove raised above the floor of the lower kettle chamber. This allows air

To start the kettle with this modification. Leave the top (water jacket chimney) off the lower part of the kettle. Put your wood into the MIDGE as you would do normally.

Light the MIDGE stove and when a fire is established, put the water jacket chimney on top of the lower kettle chamber as in the first photograph. Fresh fuel can be dropped into the MIDGE stove via the top of the chimney.

As you can see in the final photograph, the lower chamber is quite clean, unlike standard Kelly Kettles which are soon covered in tar.

Indoor wood gas stove

2010-05-03T13:02:00.000-07:00

After constructing a MIDGE stove, you may be tempted to use it indoors. However, that is not advisable as a MIDGE is a simple device and there are no guarantees that all noxious fumes will be combusted within the apparatus.

In the following photographs, we see a more professional installation from China that produces wood gas, in a more controlled manner, for indoor use on stoves. The stove is intended for remote farmers, unable to get bottled gas, to gasify their waste straw.
On the left, we see a downdraught gasifier, followed by a filtration cabinet with blower. Finally, on the right, there is a dual burner gas hob.

A detail drawing follows. Excuse the comedic machine translation by the manufacturer.
Constructing something similar for one's own use would not be difficult but all the usual precautions for using a gas oven should be taken.

A no-weld gasifier made from clay

2010-04-24T09:03:00.000-07:00

This is a fascinating set of videos showing the operation of a gasifier made largely of clay (plumbing is still performed with steel tubes) and scrap to produce gas for a 10kW generator.

Many people are put off by the thought of having to employ welding to build a gasifier. The idea of building a fully functioning downdraught gasifier without recourse to welding, and still being able to produce gas good enough for a generator, will hopefully get more people interested in building their own generator.

Build your own simple MIDGE gasifier (plans on the right-hand side) and see how simple it is to gasify wood. After you have understood the principles of gasification, and see how it applies to downdraught gasification, then it does not matter how you build a gasifier.

The camera work is not too steady but what there is to see is more than inspiring.

Video 1 - Overview of the generator in operation

Video 2 - Close-up of various aspects of the producer

Video 3 - A clearer look of the producer made from clay. One suspects that there are significant metal components inside the producer but sealing the outside with clay means there is no need for welding.

Power controller made safe

2009-04-14T09:45:00.001-07:00

The power controller for the 240V AC centrifugal fan has now been packaged in an earthed metal casing.

The speed of any 240V AC motor can now be controlled from standstill all the way up to full speed.

Power controller for centrifugal fan

2009-04-08T07:22:00.000-07:00

I happened upon a very useful AC power controller on eBay. The Kemo M028N power control cost about £22, which is a lot cheaper than the equivalent variac. The device can handle anything up to 4000 watts at 240V or 2000 watts at 110V. However, a heat sink and fan will have to be employed for high power devices.

The photo above shows a quick test using a light bulb. The light is dimmed to its lowest possible level. Now, I need to rewire my centrifugal fan to handle AC again, after converting it to DC a few weeks ago. At last I have a controlable fan. No more excuses to avoid completing my downdraught gasifier.

More fan progress

2009-03-26T14:16:00.000-07:00

With many projects on the go, finding time to work on the wood gas project is not easy. Over the past two weeks a photovoltaic system had to be set up. However, it gave me the chance to run the car air conditioning fan on the deep cycle battery and the result was much more promising than running the fan on a wall wart. The fan is a little over-powered so I will need to add a potentiometer to slow the fan down.

The fan I constructed from an electric leaf blower, and built a plywood case for, is now running on an old converted 386 PC power supply. The power supply has a +12V and -12V output and I am using this to run the fan on 24V. That fan is a little under-powered.

Interestingly, the car fan doesn't work well on the PC supply unit and the converted leaf blower doesn't work well on the deep cycle battery. Maybe someone reading this article knows the answer why.

The next thing to do is to build a transition for the car fan so that it can be connected to my no-weld gasifier. At long last I might be firing up the no-weld gasifier during the next week or two. I shall buy some charcoal and run the gasifier as an updraught gasifier just to check the seals and the power of the fans. Then the gasifier will be re-plumbed as a downdraught gasifier if the fans are up to the task. Charcoal is to be used as the planned gasifier will be a small one and charcoal is better than wood for that purpose. Of course, charcoal will have to be made on-site in future.

Constructing a centrifugal fan #3

2009-02-19T03:55:00.000-08:00

The fan is almost complete. All that is needed now is a way of taming its huge power. Controls for moderating air input and output will have to be constructed.

Update 1 - After discussing my problem with other wood gasers I have changed to a lower power DC supply. With a variable resistor I will be able to find the optimal speed. The next task will be to make a transition for the fan casing so it can be connected to the wood gasifier.

Update 2 - Well, the DC worked but made the fan rotate in the opposite direction. So I converted from AC to DC and from blower to vacuum cleaner. After some thought, I turned the coils round, that reversed the magnetic field and now we have a blower again. Now onto making a transition.

Constructing a centrifugal fan #2

2009-02-16T07:20:00.000-08:00

The centrifugal fan is almost complete. As the fan runs on 240V AC a lot of care is being taken to make sure the fan does not endanger anyone.

The following photo shows the fan and a plywood former for a length of thin steel that will act as outside of the fan casing.

The next photo shows the rear of the fan with the AC motor. As you can see there are plenty of bolts holding everything together.

All that remains is for the front face and sides of the casing to be completed.

Handbook of Biomass Downdraft Gasifier Engine Systems

2009-02-07T05:57:00.000-08:00

I am adding the Handbook of Biomass Downdraft Gasifier Engine Systems to my list of gasification reading materials.

This document is available for sale on some websites but it's actually in the public domain.

The handbook covers all aspects of gasifier designing, building and use of woodgas as an engine fuel source.

PDF document - Handbook of Biomass Downdraft Gasifier Engine Systems

Generator powered by updraught gasifier

2009-02-04T04:30:00.000-08:00

Here is a simple but very effective gasifier running a generator. The gasifier would appear to use a forced-draught as air input as there is a blower rather than a sucker.

The wood gas is taken from directly above the pyrolysis layer so it would make this an updraught gasifier rather than a downdraught gasifier, which takes gas from below the pyrolysis layer.

Normally, an updraught gasifier is not to be recommended but the use of charcoal rather than wood makes for a cleaner gas. Looking at the flame in the combustion chamber, there is certainly a blue flame there.

Later in the video, we see the wood gas being successfully ignited.

It is good to see such a simple but effective gasifier in operation.

Constructing a centrifugal fan #1

2008-11-21T06:09:00.000-08:00

A centrifugal fan is essential for running a downdraught gasifier. However, searching for a fan can almost be impossible or too expensive if you are lucky enough to find one. After purchasing How to Design and Build Centrifugal Fans enough information is at hand to build a fan from scrap materials.

In the picture below we can see one side of a fan cut out of a piece of plywood. The correct dimensions for the fan required are taken from the book.

In the next picture we can see two plywood framing pieces cut out for both sides of the fan. Below the framing pieces a sheet of light gauge steel has been cut from a vegetable oil can that will act as a shield to protect the plywood.

Centrifugal fans

2008-11-14T04:13:00.000-08:00

Probably the hardest task, when making a gasifier, is the blowing/suction fan. Thanks to the famous Gingery engineering family there is help at hand. How to Design & Build Centrifugal Fans for the Home Shop is packed with everything you need to know about constructing the right fan for the task at hand.

There are five chapters; fundamentals, design, construction, testing & measurement and applications.

After experimenting with various fans, that were woefully underpowered, I am sure this new book acquisition will help me to build the right fan. The applications chapter even has details on building a cyclone separator, ideal for cleaning ash out of your wood gas.

The book can be bought from Amazon - How to Design and Build Centrifugal Fans

Wartime gas-powered van on Jersey Island

2008-07-18T09:02:00.000-07:00

This is a photograph of a gas-powered van on Jersey Island, prior to occupation by German forces.

The gas used was coal gas rather than wood gas and was pumped into the gas bag, on top of the vehicle, prior to travel. The vehicle's range was about 30 miles.

Prior to the discovery of North Sea gas, towns in the United Kingdom were supplied with coal gas, which was produced by the gasification of coal.

click image to enlarge

Operating Engines on Woodgas

2008-06-25T02:15:00.000-07:00

I have found a very useful slide show on wood gasification. There are 100 slides covering all aspects of wood gas theory, history and operation. No stone left unturned, a recommended read.

Slideshare - Operating Engines on Woodgas

Constructing a blower - continued

2008-06-20T15:12:00.001-07:00

The blower has been completed.

First, the end of the drum holding the fans was trimmed and tabbed so that it could accept the other end of the blower enclosure.

A hole was drilled in the drum end so that the wires from the fan could be fed to the outside. The wires are visible just below the bolts holding the fan in place.

The bottom off another 20-litre drum was cut off. This end of the enclosure was measured to provide just enough clearance above the fan.

Two holes were drilled into this part of the enclouse. These holes take tank connectors and act as the gas inlet and outlet.

The two ends of the enclosure were pressed together and the blower tested. The aperture for the gas inlet is a little small. It will enlarged when the rest of the gasifier is built.

Constructing the blower has given rise to some ideas for its integration into the gasifier so they will now be investigated.

Constructing a blower

2008-06-16T13:08:00.000-07:00

This is a work in progress and will be appended to the No-Weld Gasifier instructions in due course.

A blower is important in gasifier manufacturer, either for blowing air in or drawing wood gas out.

In the case of a downdraught gasifier, the blower is used in place of an engine to draw wood gas out of the gasifier until the gas is of sufficient quality for the engine to be started.

As part of the no-weld ethos, a blower has been constructed from scrap. In this case a car air-conditioner fan and vegetable oil drums were used.

In the first photograph we see a typical car fan.

The intention is to build a metal casing around the fan. Gas can then be drawn via an inlet pipe and forced out by the fan through an outlet pipe to a flare. At the flare the gas can be bunt to determine its quality. To facilitate the construction of the blower the two halves of the fan casing were prized apart so that the fan could be bolted into the blower housing.

The "squirrel cage" of the fan can clearly be seen. At the rear is the motor and other end of the rotor shaft. This shaft would rub off the intended metal casing so the assembly had to be held clear.

In the next photo you can just about make out a sandwich of plywood which holds the fan proud of the metal drum. The fan was bolted to the drum through the plywood sandwich.

Exact details for attaching the fan to the drum will not be given as every car fan is different. It will be necessary for the builder to discover the best way for themselves.

The next stage of construction is to fit the other half of the drum and then attach the inlet and outlet pipes. The blower can then be tested to determine its suitability.

MIDGE stove update

2008-06-10T00:10:00.000-07:00

This article details changes we made to the original MIDGE stove. When building a wood gasifier, care must always be taken to prevent air from entering from where it should. If air is permitted to enter from anywhere other than where it should then the gasifier will not operate properly and can even explode under certain circumstances.

When first built, the combustion chamber rested precariously on four bolts attached to the outer chamber.

The weight of the combustion chamber pushed down on the bolts and allowed a sizeable air gap to appear between the top of the combustion chamber and the top lid. This gap allowed cold air to get to the secondary air holes from the top rather than entering through the primary air holes at the bottom.

To remedy this problem the hole on cowling lid was widened by cutting small tabs around the circumference of the hole so that the hole the combustion chamber could just pass through. The tabs were then folded back onto combustion chamber to lock it in place.

The area around the tabs was then sealed with fire cement to ensure there were no air gaps, as can be seen in the following photo.

Not only did this reduce the air gap but also meant that the supporting bolts could be removed from under the combustion chamber as the cowling lid now supported the combustion chamber.

Another test firing was performed. The air throughput was much enhanced resulting in much higher temperatures being read.

In the following photo we see a burn with a stove pipe on top of the stove, which increases the air throughput.

The draught was such that red hot particles of ash were ejected from the combustion chamber. A draught control that changes the size of the primary air intake may be needed. The very bright colour of the combustion shows great heat being generated. Small jets of gas can be seen emanating at the perimeter where the secondary air holes meet the wood gas.

Commercial MIDGE stoves are a waste of money

2008-05-27T07:55:00.000-07:00

Not only are commercial MIDGE stoves a waste of money but they also go against the spirit of wood gasification. Self-reliance is the key to wood gasification, the ability to provide for yourself and for others in times of hardship.

If there was an energy crisis then popping down to the shop for a MIDGE stove is not an option. There won't be any. Nor will there be an Internet for you to purchase one on either.

Another reason for not buying a commercial MIDGE stove is that for some reason they come with an integral battery operated fan to produce a stronger draught. The battery operated fan also goes against the spirit of wood gasification. Where are you going to get batteries from in an emergency?

A well-built gasifier simply doesn't need a forced draught. I have boiled water and cooked meals on my MIDGE stove. That is all they are meant to do and a handmade one does the job perfectly.

Read the plans. Find some cans. Make gas!

MIDGE stove plans - The Complete MIDGE (pdf)

No-weld downdraught gasifier #3

2008-05-27T07:23:00.000-07:00

In this section we complete the combustion tube inside the combustion chamber. Then we marry the combustion chamber to its shroud.

You will remember that we had introduced the combustion tube into the hole at the bottom of combustion chamber. Tabs were cut to hold the tube in place.

After checking that the tube has an idea fit we remove it. Four holes are drilled into the side walls of the combustion tube. These holes will take a bolt each so that they take the weight of the tube.

Next, a restraining band is made from a thin strip of steel (such as was leftover when cutting the 20-litre drum. Four holes are drilled into this band so that it can be held in place by the four bolts on the side wall of the combustion tube.

Holes are drilled into the bottom, closed end, of the combustion tube. This allows ash to fall out of the tube.

A disk of metal sheet is cut and entered into the combustion tube. It rests upon the bolt heads and acts as a throat inside the combustion tube. A hole (or holes) will be cut into this to allow char to fall into the combustion tube.

The combustion tube is placed back into the combustion chamber such that the tabs holding the tube in place are caught between the tube and the restraining band. This band holds the combustion tube firmly in place.

The combustion chamber was turned upside-down and the gap between the combustion tube and chamber sealed to prevent air from bypassing the char.

Here we can see the combustion tube sitting on top of the shroud we made in section #1. On top of the combustion chamber sits a hopper. Details of the hopper will be given in section #4.

No-weld gasifier sections:

#1 - Introduction - materials and tools, building the combustion chamber shroud

#2 - Building the combustion chamber

#3 - Completing the combustion tube

No-weld downdraught gasifier #2

2008-05-27T06:27:00.000-07:00

In this section we detail the construction of the combustion chamber. This is where air from the outside meets hot char to form wood gas.

The combustion chamber is made from two ends of a 20-litre vegetable oil drum. A whole drum is too big so we just cut off what is needed from either end and then join the two ends together.

In the following photo we can see an old drum being cut with tin snips. Drill a hole (using a low setting on your drill) in the side of the drum so that the tin snips can be inserted into the drum wall. I won't give dimensions here. It is up to you to decide what sizes you need depending on what tins and drums you have available. Read the whole of this article before starting work.

Here we can see the two ends of the drum. Keep the strip of metal between the two ends as that will come in useful later.

The bottom end of the drum has tabs cut into its wall section. This allows the top end of the drum to be pushed over the tabs and locked in place.

Now, a hole is cut into the bottom of the drum. The hole has a diameter about 2 centimetres smaller than your chosen combustion tube.

Here we see the completed hole. The hole doesn't have to be accurate, just smaller than the combustion tube. You then cut tabs so that they can be bent up and cling to the combustion tube. This will help hold the tube in place.

Here we see the tabs bent up and clasping the inserted combustion tube. The tube is a tin of about 15 cm diameter with one end open and the other closed.

In the next section we will complete the combustion tube and show the combustion chamber and shroud joined together.

No-weld gasifier sections:

#1 - Introduction - materials and tools, building the combustion chamber shroud

#2 - Building the combustion chamber

Ferrocement resources

2008-05-26T09:16:00.000-07:00

In a previous post we mentioned the possibility of using ferrocement as a way of building a no-weld gasifier. At the moment we are using lighter gauges of steel and bolting together our no-weld gasifier. To create airtight seals we are using fire cement.

It is not too far a step to start using ferrocement to seal the gasifier from air and wood leakages. There are also advantages to using ferrocement as a way of protecting the lighter steel gauges from excessive heat, which cause buckling.

For the time being we will continue without ferrocement and consider its use after a test run.

Ferrocement - resources

Electricity generator running on wood gas

2008-05-26T06:17:00.000-07:00

This is a very good presentation about what can be achieved with a simple wood gas powered generator.

Heating water with wood gas

2008-05-23T06:46:00.000-07:00

I was experimenting with Big MIDGE last night. Attempting to find out the minimum amount of wood chips I would need to boil 1 litre of water. Not much was the answer. Approximately 200g is the amount of wood chips required.

It is surprising how efficient these MIDGE stoves are. They produce no smoke, can be used indoors so long as there is adequate ventilation, and produce little ash. They give off an awful lot of heat and most of it is directed precisely where you want it.

Upcoming experiments include constructing a heating coil from copper pipe and attempting to heat a larger mass of water using the thermosiphon effect. I would like to heat enough water for one or two showers, washing the dishes and a cup of coffee per day.

Ultimately I would like a larger gasifier that during the course of a day can heat a large heat store. This store would be a heavily insulated tank holding 10,000 or more litres of water. The intention would be to heat the store to provide enough heat for a week of hot water and underfloor heating.

A wood gasifier is ideal for this as it is very efficient. Most of the heat generated would go into the store. The wood chips would be simply created from waste wood mass. There would be no need to fell large trees, which could then be sold on for income rather than my burning here. Besides, chainsaw work, bucking and splitting does my back no good at all.

Operating a wood gas stove

2008-05-23T06:40:00.000-07:00

I have created a better video of the MIDGE stove in operation. I'm no Orson Welles but I do come in on budget.

The stove is a particular type of gasifier known as an 'inverted downdraught gasifier'. Essentially, that makes it an upside-down downdraught gasifier. The difference being that the wood gas is immediately burnt in the inverted gasifier but in the normal configuration it is tapped off for running an internal combustion engine.

The inverted downdraught gasifier in its most basic form consists of one can suspended inside another. The outer can acts as a cowling permitting air to enter its primary air holes where it can pass into the inner can. The inner can has holes at the bottom, in the form a grating which aids combustion of the fuel, and a ring of secondary air holes at the top which create an air/fuel mixture with the wood gas.

Fuel consists of wood chips. This permits easy fuel collection from broken tree boughs and the sort of waste that owners of log burning fires reject. The chips are packed down into inner combustion can and a small amount of some flammable liquid (spirit or paraffin) is dripped on top so as to get the fuel to sustain a hot flame long enough for char formation.

A fire is lit on top of the fuel, which results in a char layer forming. Beneath this layer is the pyrolysis layer where wood is converted into hot wood gas. Combustion continues down through the wood chips, converting the chips into charcoal which is then reduced to wood gas. The wood gas rises up, meets hot air at the secondary air holes and ignites.

You can think of a MIDGE stove as a device for making charcoal, which is then reduced to various volatile gases and a small amount of ash. The operation is very efficient, is virtually smokeless and yields little ash.

YouTube - Wood Gas Stove

No-weld downdraught gasifier #1

2008-05-21T06:08:00.000-07:00

Much is made of wood gasifiers being useful in emergencies. However, most are made in today's time of relative plenty. Constructors have ample time to source materials and then weld them together with state of the art equipment.

What if we were in an emergency? What if the materials available were not of a high grade? What if welding facilities were either not available or inappropriate given the materials we had? All of these questions made me think of building a no-weld gasifier, using common materials that anyone might have and tools that could easily be found.

In these times of dwindling resources, scrap metal is snapped up by scrap dealers and is hard to find. In an emergency, looking for quality scrap metal might not be an option. Here are some typical scrap tins that you might find in your house or on a rubbish tip.

Tools used were the kind that can either be found around the home or easily procured. No welding was permitted so fixings either had to be bolted together or merely rested on top of each other. Sealing to prevent gas escaping or air getting to where it shouldn't be had to be done with fire cement, which can be found in most hardware stores.

The larger tins are 20-litre vegetable oil drums and are ideal for building the main housings for a gasifier. These drums can easily be cut with tin snips but care must be taken when cutting thin steel as any jagged edges can easily scratch your skin. The metal will not clean and any dirt can enter wounds and cause infection.

This photo shows the top cut off a drum. A serrated edge can clearly be seen.

Serrated edges can be cut into tabs and then tapped down so that no sharp edges are in harm's way.

A firm surface under that part of the drum being tapped prevents the drum being put out of shape.

The result is an open-topped drum that can be used to house the combustion chamber of a gasifier. The fitting at top left of the drum is a tank connector. Any wood gas produced will be sucked out through this port.

Close-up of the tank connector. Connecting it is simply a matter of making a hole in the drum and screwing both parts of the connector either side of the drum wall. No welding required.

In the next section we will build the combustion chamber that sits inside this gas collection drum.

No-weld gasifier sections:

#1 - Introduction - materials and tools, building the combustion chamber shroud

#2 - Building the combustion chamber

Ferrocement gasifier

2008-04-26T01:55:00.000-07:00

Not everyone has access to heavy gauge steel or to welding facilities. Part of our research is to investigate "no-weld" methods for producing fuel grade wood gas.

One such method is the use of ferrocement, a composite material of cement and wire or mesh. An effective gasifier could be built from cement with wood formers to hold the cement in place whilst it cures. The gasifier would be reinforced with easily bent strategically placed steel bars. Steel tubing for air intake and gas output could be accurately positioned before the cement was added.

Such a gasifier would lighter than the equivalently sized all-steel gasifier, would be as strong as steel and free of gas leaking holes. Many ocean going yachts have been made with ferrocement hulls and are a testament to the strength and flexibility of this material.

Online instruction booklet - Low Cost Charcoal Gasifiers for Rural Energy Supply

Scrapheap challenge

2008-03-04T07:14:00.000-08:00

Today, I drove around town looking for scrap to finish a project. The project entails building a wood gasifier to run a small engine without resorting to welding. By not welding I am limited to thinner gauge steel, which is more available and, more importantly, free.

By driving around trying to hunt for scrap metal you get an idea of how lucrative the scrap metals business is. If it's ore being mined from the ground or scrap metal in a yard you can be sure that most of it is heading to China and you will have to dig deep into your pocket to convince people otherwise. And if it isn't ore or scrap, such as telephone cables, bronze war memorials or graveyard plaques then it's probably heading to China anyway via a foundry run by a criminal gang. Such are the record breaking prices for metals.

I went to a car breaking yard. Nothing much there. I did see a pair of air-conditioning blowers that would be good for a gasifier but I have a blower already. Anyway, the breaker would have wanted £10 for them and this week is meant to be an ultra-belt-tightening week. I then went to a hardware store to look at some pipe fittings, just to see what was available. Nothing bought. Then I ate a packed lunch. No eating out. Money in the bank.

On the way back home I passed a pub, I slowed down as I passed the back gate and there they were, a pile of vegetable oil cans. A U-turn and a chat with the pub's cook secured the whole lot. Well, I took two for now as I wish to build a cage for my blower and a filter barrel for the gasifier. I can collect the rest in a day or two.

Fuelling the gasifier will not be a problem. Thankfully, China doesn't want our waste wood just yet as it does with all our other waste. Though it is only a matter of time. There are plenty of skips overflowing with wooden pallets all over town. Everyone in the UK is still happy to flick a switch and pay well over the odds for their energy. That will come to pass too.

Producing wood chips for a MIDGE stove

2008-02-28T08:48:00.000-08:00

The beauty of a MIDGE stove is the ease of fuelling as well as the ease of operation. What could be easier than picking up dead twigs, burning them and making a meal?

Although a MIDGE stove will run on broken twigs you can pack more wood (and hence heat) into a MIDGE stove by chipping the wood beforehand.

To that end a garden shredder is used. Simply feed dead branches and twigs into the shredder and bag the chips until they are needed. Do not bag chipped green wood as this will rot. Green chips can be left out in the sun under a plastic sheet to bake in the sun. Leave a gap under the sheet for moisture to evaporate.

Making charcoal

2008-02-27T08:37:00.000-08:00

Wartime automotive gasifiers used charcoal as fuel more often than wood. This permitted a cleaner fuel to be made as charcoal is about 85-98% carbon with few volatiles.

In tandem with a charcoal fuelled gasifier, a steam injector was used to produce a gas that was virtually 100% carbon monoxide and hydrogen and little else. A wood fuelled gasifier contains its own water in the wood itself.

For small applications charcoal fuel may be more preferable than wood as charcoal is lighter and packs more energy for a given mass than wood. For a wood gas driven motorbike, a small gasifier is required and for that charcoal is the better fuel.

Making Charcoal - instructions

Generator gas

2008-02-09T01:24:00.001-08:00

This Swedish book details the use of wood gas generators in cars during the 1940s.

Whilst it is a review copy and not 100% complete, it can be seen on Google Books and provides a wealth of knowledge.

The book can still be purchased in print form, from various sellers.

Google Books - Generator gas — the Swedish experience from 1939–45

Driving on wood gas

2008-01-26T00:47:00.000-08:00

This is a rare Swedish video in English. Scandinavians are masters at the art of running cars on wood gas but their videos tend to be in their native language. All credit to the Vedbil team.

One thing to remember is that automotive gasification does not have to be as messy as the Vedbil car. This team is obviously having fun with engineering and have put aesthetics to one side for the moment. Driving a car on wood gas does not necessarily mean dirt and a car that looks like something out of Back to the Future.

Simplified wood gas stove

2008-01-23T11:54:00.000-08:00

Here is a slight variation on the MIDGE stove theme. The design is from a paper by The Biomass Energy Foundation entitled A Wood-Gas Stove for Developing Countries. The main difference between this stove and the MIDGE is this stove uses a stacked can system.

Combustion is carried out in a single walled can, unlike the MIDGE can-in-can method. Wood gas rises to the top of this can to another (upper can) suspended slightly above the lower combustion can.

Between the two cans there is a separation gap (by way of metal spacers between the two cans) where air from outside is sucked in and ignites in the upper can. Inside the upper can there is a third can, known as a 'wick', which holds the flame within the stove. The 'wick' is a can, suspended inside the upper can, with the lower end open and the upper end sealed.

A detailed description of this stove and its performance can be found in the paper A Wood-Gas Stove for Developing Countries.

FEMA simplified wood gas generator in action

2008-01-08T06:23:00.000-08:00

This is a very well produced video of the FEMA simplified wood gas generator.

Construction of a simplified wood gas generator

2008-01-08T06:08:00.000-08:00

These are a popular set of plans for constructing a simplified wood gas generator for fuelling internal combustions engines. They were developed by the US Federal Emergency Management Agency (FEMA) so that people could continue to use internal combustion engines during a fuel shortage.

The design is simpler to build than the FAO design but many constructors believe it not to produce gas of as good a quality therefore cleaning/filtering the gas is very important.

Documents in HTML and PDF.

Producer Gas for Motor Vehciles

2008-01-01T11:43:00.000-08:00

Published in 1942, Producer Gas for Motor Vehicles is a fine book on automotive wood gas. It is probably too complete a book, covering commercial gas producing equipment at a time when petrol supply to the general public was rationed.

However, the book includes photographs and line drawings for all the producer gas plants of the day. If you want ideas on building your own producer plant and how to integrate it then this is the book to have.

If you wish to buy this book then I recommend you contact Lindsay Books in the US or Camden Books in the UK, where I bought my copy. Neither company lists the book now but they might have a copy lying around somewhere.

Wood gas as engine fuel

2007-12-23T02:23:00.000-08:00

The document "Wood gas as engine fuel" is a must read for anyone wishing to build a wood gasifier. It concentrates on downdraught gasification, which is best type of gasifier for fuel grade wood gas.

The document by the Food and Agriculture Organisation of the United Nations (FAO) covers all aspects of building gasifiers for fuelling engines. The document can be found on the FAO website at http://www.fao.org/docrep/t0512e/t0512e00.htm.

A PDF document can also be found at ftp://ftp.fao.org/docrep/fao/t0512e/t0512e00.pdf

The Complete MIDGE

2007-12-20T07:14:00.001-08:00

The Complete MIDGE is a PDF document detailing how to build a wood gas stove. All you need to make a MIDGE stove are waste cans, some tin snips, a drill with high speed drill bits. There is plenty of scope for experimentation and you are encouraged to do so.

The Complete MIDGE - PDF document

Retort gasification

2007-12-17T04:57:00.001-08:00

Can you see the problem with this form of gasification?

This form of gasification uses a retort, which is a closed container with a vent and external source of heat. And yes, the gas hob, the retort is sitting upon, is putting as much energy in (if not more) than is being produced in the form of wood gas.

A retort is an interesting way to get into gasification and doesn't require much work to get you started. However, the gas produced will have a lot of tar in it and will be of no use for running engines with. It would be a waste of time and effort scrubbing the gas because of the amount of tar in it.

A MIDGE stove on the other hand consumes most of its own tar. Better still, a downdraught gasifier heats the wood above it so that tars drip down into the combustion area and are converted to wood gas.

We recommend that you build a MIDGE stove first and then move on to a downdraught gasifier. A retort is only suitable for making charcoal and is best fired with a renewable energy source such as a wood fire.

Wood gas stove in operation

2007-12-16T02:44:00.000-08:00

A video made earlier in the year. It shows the constituent parts, fuelling and operation of the stove.

MIDGE stove improvements

2007-01-10T07:01:00.000-08:00

Today was spent modifying the gasifier. After the air intake had been improved it was necessary to seal the rest of the gasifier to prevent leakage of air to where is wasn't wanted.

Previously, the combustion chamber rested precariously on four bolts attached to the outer chamber.

The weight of the combustion chamber pushed down on the bolts and allowed a sizeable air gap to appear between the top of the combustion chamber and the top lid. This gap disrupted the flow of air through the secondary air holes in the combustion chamber.

To remedy this problem the hole at the top of the cowling was widened by cutting small tabs around the circumference of the hole so that the hole the combustion chamber could just pass through. The tabs were then folded back onto combustion chamber to lock it in place.

Not only did this reduce the air gap but also meant that the supporting bolts could be removed from under the combustion chamber as the cowling now supported the combustion chamber.

A new ring of secondary air hole were drilled into the combustion chamber and the gasifier reassembled.

Another test firing was performed. The air throughput was much enhanced resulting in much higher temperatures being read.

The draught was such that red hot particles of ash were ejected from the combustion chamber. A draught control that changes the size of the primary air intake may be needed. The very bright colour of the combustion shows great heat being generated.

Future Experiments

Aluminium Foundry - Because of the immense heat being generated an experiment to melt aluminium in a crucible will be carried out. The crucible will require a lid so that the combustion chamber can be charged with additional fuel during the melt.

Automated Refuelling - During today's burn additional fuel was dropped by hand into the combustion chamber via the stove pipe. It was necessary to drop small amounts often rather than one large charge of fuel otherwise the combustion of wood gas was terminated and smoke was generated in its stead. This was remedied with a single drop of paraffin but was not ideal. An auger dropping pellets into the stove pipe would be ideal. Knowing the rate of refuelling required depends on many variables that will need to be discovered through experiment.

Warning!

Make sure you take all necessary precautions. Especially when you smell a new odour. A new smell in your nostrils means something new has happened. When I returned to the house to wash my hands I noticed in the mirror that I had melted some of my hair!

MIDGE stove - test runs #3 & #4

2007-01-07T07:23:00.000-08:00

As suspected, it was a lack of air that was causing the smoking and the extinction of wood gas.

The existing primary air holes were enlarged but the wood gas was again extinguished after a quarter of the fuel had been burnt.

For test run #4, more air holes were added to the bottom of the outer container.

When the stove pipe was put on top of the stove a forceful draught could be heard, which resulted in better combustion. No smoke was seen to be generated.

The ignited gas jets from the secondary holes at the top of the combustion chamber could clearly be seen.

The fuel used consisted of wood chippings from a garden shredder. This appears to be a better fuel than the wood "pellets" with regards to starting a fire. However, another test with the updated stove will be carried out tomorrow as the pellets are denser than the chippings and so can give off more heat energy per burn.

The pellets could also be kept back and used in some automated refuelling operation for a stove that is already in operation. The reasoning being that the pellets are of uniform size and an auger or similar could administer a given amount of pellets every so often. The stove could then sustain heat for as long as required.

Though the stove pipe improved the draught, the length of the pipe makes the stove less useful. Future experiments will involve finding the minimum pipe length that provides an adequate draught, allows access to the combustion chamber for refuelling and permits a water coil to be so positioned that water can be heated.

MIDGE stove - test run #2

2007-01-06T07:22:00.000-08:00

Another test of the wood gasifier was performed today. The results were completely different to yesterday. The hole at the top of the cowling was widened and the fuel had wood chips added on top instead of cloth.

Almost immediately wood gas was generated. It was ignited intermittently and created small explosions that almost blew the flame out. It was like listening to a steam engine leaving a station with the sound of the steam slowly puffing. Five minutes later a larger explosion blew the cover off the top. The top was replaced. After 10 minutes the flame went out and a lot of smoke billowed out until the fuel had been consumed.

Tomorrow, wood chips will be used instead of pellets and the primary air holes will be made larger.

MIDGE stove - test run #1

2007-01-05T07:20:00.000-08:00

The stormy weather had calmed today and so we were presented with an opportunity to give the wood gasifier stove a test run. Plans for this can be found simply by performing a search for "midge stove". We used a 20 litre vegetable oil can picked up from a restaurant for the outer container and a 1 kilogramme coffee can for the inner combustion chamber.

The top cowling is the bottom off another 20 litre oil can. These cans are very plentiful and we hope to use another one for the construction of an aluminium foundry. The hole at the top is a little narrow and will be widened for the next firing so that is corresponds with the diameter of the combustion chamber.

The fuel used was rhododendron "pellets". Whips of willow, birch and rhododendron are coppiced on the land here and cut into 25 mm lengths and range in width from 8 to 12 mm.

For this test run, 500 g of pellets were used.

The top layer of pellets were doused with paraffin oil and on top of that was placed a piece of cotton cloth, also doused in oil. The cotton was then lit.

After 10 minutes, the flame died down and a pyrolysis layer could be seen quite clearly beneath a layer of charcoal.

By using an infra-red thermometer we noted that the sides of the combustion chamber were at almost 600 C. The pyrolysis layer was much higher and was off the scale. The outer chamber temperature was over 100 C.

There was a period when a large amount of smoke was generated. Some stirring of the fuel with a metal rod stopped this and combustion continued as before. It is believed that a "bridge" had formed and prevented air from reaching the pyrolysis zone.

The total burn time was approximately 1 hour. The remaining ash was weighed and found to be 7 g or 1.4% of the initial mass of fuel. This means that 98.6% of the fuel was combusted.

With the outer can reaching over 100 C we wonder if a water jacket could be used to gather this heat for heating a hot water cylinder. This would be in addition to a coil in the much hotter combustion chamber.

Would the removal of heat affect the combustion? Further experiments will be needed to check this.

The next firing will be carried out after the cowling hole has been widened and the outer container air holes have been widened too.

A different fuel will also be tried in a later test, namely fine wood chips from a garden shredding machine.

How to convert wood into charcoal and electricity

2005-08-28T07:02:00.000-07:00

I am currently reading a book by Richard H. Buxton with the aforementioned title. Detailing the manufacture of charcoal (as the author's coke supply was not good enough for his smelting work) and producer gas for running an internal combustion engine, it is very instructive. There are plenty of diagrams and photographs. The retort method for creating charcoal was one that I wished to use for generating producer gas and this book is very detailed in that respect. There are more typing errors than pages but it doesn't affect one's understanding.

It can be purchased by US residents here at Lindsay Books or from here at Camden by European customers.

I recommend Camden for its wide range of books covering alternative technology, steam and stirling engines.

Contact details

2004-12-14T03:14:00.000-08:00

If you would like to contact me through e-mail then please leave a moderated comment here with your e-mail address in it.

Any moderated comment with your e-mail address will not be published on this blog but replied to via e-mail.

Thank you.

What is wood gas?

2004-01-16T08:10:00.000-08:00

Wood gas is formed from the thermal gasification of biomass or other carbon containing materials such as coal in a gasifier. It is the result of a high temperature reaction (>700 °C), where carbon reacts with steam or a limited amount of air or oxygen producing carbon monoxide, hydrogen, and carbon dioxide.

In some gasifiers the actual gasification process is preceded by pyrolysis, where the biomass or coal turns into char releasing hydrocarbon rich tars and methane. Other gasifiers are fed with previously pyrolysed char in the form of charcoal.

Wood gas is flammable gas because of the carbon monoxide, hydrogen and methane content.

Before and during the Second World War there were many commercial suppliers of gas producers for motor vehicles due to the rationing of petrol. Today there are a growing band of enthusiasts converting cars to wood gas due to increasing fuel prices.

Other uses for wood gasifiers include cooking stoves that use less wood than a conventional wood stove and heating of domestic hot water supply.