re bolder formation
How high is your clinker MgO content?
It is hard to understand how high MgO could cause boulder formation on its own. MgO does contribute to the liquid phase, which might increase the quantity of liquid phase enough to increase the degree of clinker nodulisation, but only if the quantity of aluminate and ferrite liquid phase was already very high. However, MgO tends to lower both the viscosity and surface tension of the liquid phase, resulting in smaller average clinker nodule sizes, so there are two opposing factors at play with regard to the effect of MgO on nodulisation..
What is your calculated clinker liquid phase (at 1450 deg.C)?
re bolder formation
Thank you for your information.
Your clinker MgO content is certainly rather high, however MgO can only contribute a maximum of about 2 - 3% to the liquid phase, the remainder then normally occurs as free MgO or periclase within the clinker matrix.
Your liquid phase at 1450C is slightly high, but still within the normal range for liquid phase (23-28%). However, it would be helpful if you could reduce your liquid phase to say 25%.
So, based on your MgO content and liquid phase, I would not say that MgO is a contributing factor.
Have you tested the chemical composition of these boulders? In particular, have you broken open the balls an examined the interior, both chemically and physically? The K2O, SO3, Cl- and LOI content at the centres of the boulders can tell you a lot about their origin. Have a look at this thread for more information;- http://www.cemnet.com/Forum/thread/150028?page=1
Increasing the kiln rotation speed may reduce the nodulisation size of the clinker and reduce boulder formation, but only if the cause of the boulders is a nodulisation problem. Examining the boulders interior will tell you if their origin is over-nodulisation, or buildups coming into the kiln from the kiln inlet.
Do you have a high SO3 recirculation and frequent buildups in the kiln inlet?