Monday, October 24, 2011

Measuring the HEAT...

Iron Smelting Furnace Temperatures
Short Shaft over Slag Pit

October 9, 2011 / DARC Smelt Team, Neil Peterson recording

On our last smelt, we set up to record furnace temperatures over the duration of the experiment.

The furnace was our standard short shaft type, roughly 25 cm interior diameter, 70 cm total height.
Walls were clay and straw cobb, about 10 cm thickness.
Fuel was hardwood charcoal (mainly oak) graded to .5 through 2.5 cm diameters.
Air volume via the tuyere (set at 20 cm above base) was roughly 800 litres per minute.

Holes were drilled through the furnace walls at roughly every 10 cm, starting at 10 cm above the interior base.
Measurements were taken using an industrial quality digital pyrometer (HH12B from Omega equipped with standard bare metal type K thermocouples).
The probes were inserted roughly 5 cm beyond the interior surface of the furnace wall.
Measurements were taken roughly every hour over the course of the smelt event.

Because the probes did not reach into the central core of the furnace, there is every possibility that the central furnace temperatures were even higher than what was recorded.
Our thermocoples failed (melted!) at roughly 1350 C. On several recordings, this temperature was reached.

Image : Neil takes readings, early in the smelt

Time Elapsedbasetuyereplus 10plus 20plus 30plus 40top
10 cm20 cm30 cm40 cm50 cm60 cm70 cm
12:06:06 653890749579343
13:051:05 10421335130011451002610
13:501:503281051plus 1350119511891014660
16:324:32 11241265 *909700719

Note : It has been suggested by some theoretical researchers that temperatures above 1200 C are impossible to achieve inside a charcoal fired furnace...

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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