Primitive Technology: Smelting Iron In Brick Furnaces

By | October 31, 2022

The orange slime is a type of bacteria that precipitates iron oxide dissolved in ground water Collecting the iron bacteria Pouring iron bacteria into a porous clay pot Over time the water seeps out. Clear water on top is bailed out. Taking out concentrated ore to leach in another smaller pot Iron bacteria congealing Drying iron bacteria near fire to be used as iron ore later Iron ore balls drying for storage Crushing the ore into powder closer to smelting time Powdered ore allows the heat and carbon monoxide to penetrate the smaller particles more effectively Ore ready for smelting Making charcoal in a pit, stacking the wood over top Making alternating layers of firewood Leaning wood against pile to stop horizonal logs rolling off Light from the top with hot coals Fire front burns down the pile against the flow of rising gasses, carbonizing the wood to charcoal without burning it The coals fall into the pit when the first layer burns and collapses Un-burnt logs are lifted to the top with a stick to carbonize more fully in the air When they break apart and no longer give off flames the coals are extinguished with water Allowing the residual heat to evaporate excess water This method is simple and quick, while the resultant charcoal is non-dusty (good for lungs) and is of sufficient quality for smelting. Making the tuyere for the furnace from clay molded over a log Narrowing tuyere with a thinner stick Making bricks from ordinary mud in a ceramic brick mold Drying and turning bricks Placing tuyere at the front of a small pit about 12.5 cm deep and putting bricks on their sides around to form a furnace. The front is left open with a half brick Plastering front of furnace with mud. The nose of the tuyere penetrates about 2.5 cm into the furnace The next layer of bricks is staggered over the joints of those below for stability 3 layers in total Plastering gaps between bricks with mud to stop the gases coming out the sides instead of up through the ore 37.5 cm tall and about an 18.5 cm square inner cross section The centrifugal blower for the furnace Pre-heating furnace for smelt (1 hour burning wood) Filling the furnace with charcoal (12 double handfuls of charcoal)

Adding the first charge of ore (2 single handfuls of iron bacteria) Powering the blower for about 5-7 minutes Carbon monoxide starts to burn above the furnace in a violet tinged flame, a sign of the reducing atmosphere inside the fuel bed (good for reducing ore to metal) 2nd charge: 3 double handfuls charcoal/2 single handfuls ore Another 5-7 minutes blower 3rd charge: 3 double handfuls charcoal/2 single handfuls ore 4th charge: 3 double handfuls charcoal/2 single handfuls ore 5th charge: 3 double handfuls charcoal/2 single handfuls ore 6th and final charge: 3 double handfuls charcoal/2 single handfuls ore Kept blowing for about half an hour afterwards to burn down to tuyere level Extinguishing furnace to get result out Note, the brick furnace is easy to disassemble to access the product Mass of slag and iron prills attached to the brick wall directly under the tuyere nose Dislodging slag and iron Some decent sized prills, though not as good as previous smelts though due to a seasonal change in the iron bacteria quality (more mud this time) Getting the large prills out first Crushing the slag to get more out Using a crude panning technique with a pot to get out the small pieces (on the advice of viewers of this channel) Resultant iron yield (about 15 g) Trying a larger tuyere (5cm as opposed to 2.5 cm) Again, building a furnace from bricks makes it quick, easy, portable and re-useable. The same smelting process with the larger tuyere It's about the same yeild of iron (15 g) but smaller pieces Trying a circular brick furnace. Furnace is the same height but has a diameter about 22 cm (larger cross-sectional area) Bricks are stacked on their ends and joints sealed vertically. The same smelt again, 5 cm diameter tuyere but circular furnace Again some ok sized prills about the same yield. I'll probably stick to the square furnace as it's the easiest to build and gives the same result Adding up all the iron from various smelts into one pot

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