charcoal stove.
Charcoal is essentially wood which has been burned in the
absence of oxygen. This exothemic reaction drives off all the
volatile hydrocarbons leaving a friable substance which is up to
90% pure carbon.
Charcoal has many uses as well as barbeques! Charcoal was
traditionally used for iron smelting until it was found how to use
coke which is derived from coal. Charcoal is used in stick form by
artist and the small particles and dust, known as fines, are used as
a soil improving substance by gardeners.
Activated charcoal is charcoal which has been treated with
additional oygen to open up millions of tiny pores within the
structure of the carbon. This acts like a sponge or selective filter
and will adsorb gases, odours and remove dyes from liquids.
The UK uses about 60,000 tonnes of charcoal each year. Sadly
most of this (97%) comes from Indonesian Mangrove forests and
is leading to the destruction of these forests. Five tonnes of wod
are required to make one tonne of charcoal, and 2/3 of the energy
stored in the wood is lost to the atmosphere. Charcoal burning in
Indonesia may have been a contributing factor to the forest fires
which burnt for months in 1997.
There are about 400 small scale charcoal burners in Britain
perhaps producing 5 tonnes per year. This is produced from
sustainable woodland often using coppiced trees. The increase in
UK charcoal burning has brought many areas of derelict
woodland back into sustainable management, and encouraged the
growth of plants, in the newly opened up woods.
There is one such wood, 300 metres from my house, and this has
been neglected for 50 years. I hope that soon we will be able to
get a professional charcoal burner to assist with its future
management.
One such wood, is Steward Wood in Devon has recently
benefitted from an ongoing new woodland management scheme.
Click here for information on Coppicing and Charcoal burning
in Steward Wood
Wood Gas
The volatile compounds are flammable in their own right and are
collectively known as wood gas or producer gas. They can be
burnt as a by product of the charcoal making process and form a
very useful alternative fuel. In WW2, many of the cars running in
Scandanavia were fitted with wood gasifiers, which were about
the size of a dustbin. The producer gas was first filtered and
cooled and then piped into the carburettor of the petrol engine.
This allowed Norway and Sweden to rema mobile even at the
height of the petroleum fuel shortages. Follow these links, for
more information: WW2 Wood Gasification..
Building a Wood Gasifier
Full constructional details for a stratified, downdraft gasifier,
suitable for automotive use.
scrapped and thought that the boiler would make a convenient test bed for
some wood gasification and charcoal burning experiments.
Various fuels will be tried, including sawmill waste, shredded tree waste, wood
chips, peat and general garden compost.
The intention is to build a multifuel stove with reasonably constant heat output
that can be used for domestic heating purposes and for providing a heat
source for a Stirling engine driven generator.
Around the outside is an annular water jacket with a 1.5" gap. The height of
the combustion chamber is 26" and the whole unit stands on a mount so that
there is about 12" between the chamber and the ground.
A 6" diameter porthole allows access from the front and this is fitted with a 2"
diameter glass window so that combustion may be observed. It also gives a
convenient access panel for lighting the fuel with the propane torch.
The inside of the boiler was first lined with refractory bricks salvaged from
some electric storage heaters. These are very high density and act as a heat
store. Once lined, the combustion space was reduced to a 9" diameter
pentagonal chamber.
A 9" stainless steel collander bought for a couple of pounds in a cheap kitchen
shop, makes a good hearth to burn the charcoal.
A vacuum cleaner motor fitted with a speed controller makes an ideal blower
fan. Running on ac mains it generates a very powerful blast, but on 12V dc it
gives a gentle fan breeze.
