27/01/05 New Technology
Stirring things up - especialy zircon cords ?
“Can zircon cords be removed by stirrers” – a question that is often posed. The answer is complex, but explicit. In the majority of cases stirring will NOT eliminate visible zircon cord in the production.
The answer is complex because it involves flow patterns in furnaces, working end s and forehearths. However, the relevant facts can be summarised as follows :
The contaminated glass flows along the bottom of the forehearth channel in almost all cases – a fact verified by the experience of more than 60 operating forehearth drains
This bottom glass is not affected by stirrers unless the stirrers are located VERY close (less than about 5 millimeters) to the channel bottom. Even then, there is no certainty that all the contaminated glass will be moved.
Stirring this close to the channel bottom results in increased wear of the channel bottom refractory
The stirrers themselves are also subject to wear, and so any positive effect that may be obtained is not stable, but decreases with time as the stirrers degrade.
These comments are based on experimental work carried out about 5 years ago during the development of the forehearth CONTI-DRAIN®. The basic laws of physics have not changed in the intervening period.
A detailed explanation of the subject of zircon cords, entitled “ The SORG CONTI-DRAIN® system to eliminate zircon cords“ is available as a download on this web site, under Info Service