In this posting, I shall endeavour to outline a small scale sustainable metal working industry based on a wood (or other biomass) resource. I have recently had the opportunity to explore techniques close to home in the affluent south of England, which may be directly relevant to the development of a small scale sustainable industrial base in the Developing Countries. Pre-requisites:
- A source of fuel based on a sustainable biofuel crop or biomass waste.
- A source of iron and steel scrap metal, including wrecked cars, oil drums, concrete steel reinforcing “re-bar”.
- General metalworking skills aided by simple machine tools including lathe, drill press, grindstone etc.
The first stage of the process is to turn the biomass fuel into useful heat energy, which will either be used directly for the smelting of metals or for the generation of mechanical power and thus electricity by means of simple converted electric motors/generators.
The energy conversion process begins with the gasification of the biomass fuel. This can be done quite simply using an up-draught gasifier made from old oildrums. An oil drum will hold approximately 100g of biomass, which can be gasified to form a powerful, fairly constant source of gas, and thus fairly constant heat source for either the melting of scrap metal, or driving some form of heat engine.
Using a design suggested by Alex English, 100kg of wood will produce a wood-gas burner capable of burning at a near constant 50kW for approximately 7.5 hours.
The oildrum gasifier is capable of supplying about 50kW of heat in the form of an intense gas flame for most of the working day on just one drum of firewood. At the end of the burn period the drum can be sealed airtight and allowed to cool, yielding approximately 20kg of charcoal, which may be used as a cooking fuel, or a fuel for metal smelting, or as a reducing agent to allow cast iron to be smelted from rusty steel scrap.
One oil drum would be used as the gasifier and a second drum lined with firebricks or clay would form a furnace capable of melting most ferrous and non-ferrous metals. This would allow simple castings to be produced, which could be sold for a profit, or incorporated into simple heat engines allowing mechanical work and electric power generation to be derived from the wood source.
By way of an example, a simple steam engine could be used as the energy converter, and again on just 1 drum of firewood, a 5hp double acting slide valve engine ( which may be produced from scrap metal and used automotive engine parts for under $100) would supply mechanical power for perhaps a workshop for almost all of the working day.
The mechanical power could be used for running simple lathes, mills, water pumping or generating electricity. The steam engine could even be fired from the waste heat from a forge hearth, and be used to drive bellows or mechanical hammers.
Over the next few months I intend to put together a demonstration of this integrated metalworking industry based on sustainable wood resources.
I have already located a suitable source of fuel, a good source of recyclable metal scrap, and viable steam engine technology which can be made to operate safely with minimum of attendance. In addition, I shall be looking for people who share similar interests or who have had direct experience of the technologies outlined above.
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