'Weathering Heights' - Oct 30 IRON SMELT

 Those who have been following the work on Icelandic / Hals - Phase 3 have seen that the originally intended set of experiments has been modfied :

Part A / June 2021- full build using Icelandic simulated clay mixture, thin walls with sod cone support

June - after extraction

Part B / September 2022 - repair and re-use of furnace, after exposure to weather.

September - after extraction

Part C / (June 2022) - repair and re-use of furnace after over wintering

Part D / (continuing) - long term observation of furnace as it naturally erodes. 

State of the furnace 9/21/21

 

A combination of factors contributed to more damage to this furnace than had originally been foreseen. Additionally, September at Wareham was exceptionally wet (September 14 saw 5.5 cm on that one day alone, where the historic average for the entire month was 7.8 cm). Combined, the remaining clay liner had slumped forward 17 degrees over the first three weeks since the September 4 firing. Although it was perhaps possible to recover and repair this furnace, it certainly would never have survived in viable condition over an entire winter exposure. 

For that reason, it was decided to skip the spring re-use, and proceed directly to Part D - recording the furnace as it weathers over coming years. (The hope is for a full decade of observations, which will certainly depend on my own longevity!)

 The next smelt will mark the start of another long duration exposure project. 

Another 'clean' sand pad had been built earlier this summer, 8 x 8 feet square. This was framed by standard 2 x 4 lumber, set on narrow edge, then filled with course sand. On to this was built a 'standard Short Shaft' furnace, clay / sand / manure mix walls, set on a low stone block plinth. (This build detailed in an earlier blog post, first segment). On consideration of the possible recording scheme detailed below, an additional 15 cm of wall height was added. The total shaft height (above 10 cm plinth) is now roughly 85 cm, with an expected stack height (above tuyere) at 65 cm. (Re-cycled clay material included both ash and charcoal fines, resulting in the colour seen below)

 

Finished clay build - chalk lines at 10 cm

The intent is to run a 'typical' smelt, using roughly 30 kg of DD-1 analog (red oxide with 10% flour binder). Then leave the furnace plus any debris created in place. As there are no special problems expected from this well proven build, layout or ore, the smelt itself is most likely to follow the pattern of (many) earlier experiments.

The acquisition of several accurate instruments by Neil Peterson has suggested adding some more detailed measurements as the experimental element during the actual smelt. To this end, a number of new fittings were created (as detailed in an earlier blog post, lower segment).

• A new air volume gauge will allow for recording 'in line' amounts (in finer detail than required)
• The existing air pressure gauge, although an older dial / analog type, can be included
• A 'Y' fitting equipped with a simple one way valve will permit the existing 'Norse Smelt Bellows' to be integrated into the air system. As the current high volume air blower is normally fitted with a sliding air gate, it will be possible to switch to human powered air supply over frequent (if short duration) periods over the whole smelting cycle. 
• The furnace itself will be equipped with two sets of small diameter holes, allowing for frequent internal temperature measurements. Spaced every 10 cm of shaft height, one set above the tuyere, the other located at 90 degrees.

The projected outline would be to have :

• Air volume recorded constantly (via computer lap top input), but most likely reported as 5 minute intervals.
• Air pressure recorded as a rough visual average every 5 minutes
• Human Bellows utilized for a five minute period, once every 30 minutes, with operators alternating. 
• Temperatures recorded individually over the set of ports, once every 30 minutes. 

It is expected that once the extraction process starts, further measurements will not prove possible. An attempt to video the extraction will also be made.

Combined with the normal cycle of charcoal and ore additions (typically something every two minutes) plus the usual clearing of slag blockages and tapping events, this will make for a fairly busy activity level for this smelt! 

Note : The details on the two Phase 3 smelt experiments were documented in a more formal style, available as a PDF : Phase 3 : P3 A & B

The full web site has a number of individual reports covering the Phase 3 work.