99 posts
TimePosted 25/08/2012 02:11:14
norew says

Formation of Boulder

Hi everyone, I would just like to know if there is some kind of relationship that exists between a high titration target i.e CaCo3 content of kiln feed or silica content and boulder formation. Or is it primarily attributed only to low O2 content at the kiln inlet. Thank you. Have a nice day.


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Ted Krapkat
537 posts
TimePosted 27/08/2012 06:41:30

re Formation of Boulder

Hello Norew,

In my experience the formation of boulders is related more to process instabilities rather than raw material chemistry. Boulders normally occur above the burning zone, well before any normal alumino-ferrite liquid phase is is present, in locations that are prone to high sulphur recirculation.

Some people have claimed that high MgO content of raw materials is a contributing factor. But I have never actually seen or heard of any example of boulder formation that was conclusively attributed to high MgO in kiln feed. If conditions in the kiln are right, boulders seem to form whether the MgO is high or low.

Provided that your high kiln feed CaCO3 and SiO2 levels were reasonably constant (ie constant LSF) it would be difficult to think of a mechanism that would result in CaCO3 and SiO2 content alone contributing to the formation of a boulder.

 See also this thread concerning a recent boulder problem;-