SUNDAY - April 13
Wareham
Test 2 - DARC Dirt One
This is a fast extra test smelt being interjected into our normal series. I wanted to have a good controled test of the bog ore analog that Gus developed. His Harder-Gissing Machining had donated enough of the Spanish Red iron oxide for two full scale tests. The test on the first batch I ran at Smeltfest with Skip and Jake Keen was not conclusive. Mainly because we ran an experimental ore into an experimental smelter (two major variables on the furnace). The results pointed to problems with the furnace, and also suggested a possible important variable on the ore itself. (And no - I have not written up that experiment yet).
So yesterday I mixed up a second batch of the analog. Should give us about 50 lbs of finished material - certainly enough for a full smelt test. This is spread on the sheets for drying, I will be moving these into the sun as its available over the week hoping to just air dry this batch (as opposed to the problematic baking in Vandy's oven!). I did take a look at the dump for a gas fired oven, figuring it would be easy to convert into a propane fired drier for the ore - no dice. (I did grab up some oven racks against a possible future construction of this.)
One error from the Smeltfest Test - the ore was somewhat over pounded, resulting in a fair amount of fine dust. I had originally intended to screen the crushed cake to pull this dust off (and just add it to the next mix) - but that step was not undertaken. I will be making up the required widow screen sieve today.
I also have 50 kg of charcoal remaining from Smeltfest (plus now can get at the trailer where the remains from last years operations are stored). So fuel is on hand and prepared as well.
I had gone to the dump specifically to try to find a half sized metal barrel. I did get exactly the right size. I want to prepare a more durable version of the Econo Norse smelter. I will line the inside of the barrel with the fire bricks, then pack the corners with a clay and charcoal fines mix. This should give us a heavy - but easily moveable - variation on our proven smelter design. By using the more refractory clay / charcoal mix, there should be far less clay slag formed than we get with the sand /ash black fill. I will be using our normal ceramic tube tuyere, standard set up (5 cm insert / 22 degree down).
One very important variable made obvious with the first test of the analog was the stack height. Skip had built a taller than usual furnace, almost the same size as Jormungand from Smeltfest 06. (It actually WAS Jormungand - repaired and extended from two years ago.) The fine particle size of the red iron oxide proved to suffer from the same working dynamic as we have seen from the hematite grit. So the tendancy (based on that single test!) is for the iron to pick up considerable carbon in the stack. This can be corrected (based on past experience?) on reducting the stack height to the optimal (40 cm) and slightly increasing ore amounts. Keeping track of burn times to the shorter end of the range will also help.
One last equipment note. I have set up the high volume blower that I ordered earlier in the year and had delivered to Lee's. I ran the anenometer on the air blast, the result was 166 KPH. If I have the math correct, the top end volume with this unit is 1350 litres per minute. (The best we could get out of the vacumn blower was about 950). Air will certainly not be a problem! I will make measurements of volumes delivered through the new sliding gate I made up earlier in the year so we have those numbers on hand.
Neil and I have a long teaching day on Friday, plus I have a late night theater opening that evening. For that reason I have decided to move this test smelt to SUNDAY. If any of you can make it up despite the short notice, all would be welcome. No problem if no one else shows. Normal hours: Preheat for 9 AM, expect extraction in the latter afternoon.
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