Thread: cullet shortage
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Old 03-20-2018, 04:03 PM
Durk Valkema Durk Valkema is offline
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3 years that is very short, recuperated so gas fired I presume.
The borax sure dos not help but what you are seeing is Nephelin formation.
The moment melting temperatures dropped with the low melting batch we saw this phenomena, before only seen in flue area's at the right temperature. We used to race up to 1300+ C charge and melt at 1340 to 1360 C (2380 F charge, melt at 2450-2480F) Now charging 1240 C lingering at 1270 C or 2320 F the calcium in the castibles with the AlumoOxide react with the Alkaline, all of them forming Neph that has a differend expantion so it forms nasty flakes.
They used a very bad castible on that furnace, things are a bit better with the low cement materials but this issue is persistent.
Really 3 years is crazy. We have a client melting 26 metric tonne a year in one single (had a premature one only once) Magma crucible holding 500lbs GLASMA batch, melting 4 times a week. We set the furnace in 2008, you see the Neph formation and we changed the gathering plate 3 years ago, it has another 10 years in it.
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