LITRE WEIGHT OF CLINKER

Clinker liter weight on lower side means low burning, low strength in clinker and expansion problem in clinker. When the liter weight of clinker is on lower side, we have to check the following two things. they are

KILN SYSTEM

Burning zone temperature may be low or fluctuating due to faulty burner pipe, inadequate fuel rate or drop in fuel quality.

The degree of calcination of the kiln feed may be too low. Much lower values would cause un-calcined hot meal to enter the kiln, reducing the burning zone temperature and causing dusty clinker.

Change in quality of feed coal like ash content and NCV of coal.

How do you blend your pet coke and coal? Since these two fuels have such large differences in ash (and energy) content, fluctuations in blending of the fuels could increase the LSF or the clinker, resulting in high free limes.

What about the kiln inlet temperature… do you measure it? If so, has it changed significantly or become very variable?

Pet coke contains a lot of sulphur which normally results in strongly increased SO3 recirculation. If this recirculation becomes high enough, quite a lot of CaSO4 can form as the SO3 reacts with CaO in the incoming hot meal. This CaSO4 breaks down in the burning zone releasing SO3 which returns to the pre heater and CaO which remains in the clinker, thus increasing the clinker LSF in the burning zone, resulting in increased free limes. 

High sulphur recirculation also increases the chances of rings and build-ups in the system.  Do you have frequent meal “flushes” through the kiln or slabs of unburnt preheater build-up falling into the kiln inlet?

RAW MIX CHEMISTRY

Chemically, your kiln feed already appears easy to burn, so the problem may lie with oversize quartz (>32um) or calcite (>90um).

Have any of your raw materials changed recently, e.g. sourced from a different location in the mine or purchased from a different supplier?

Are you using more of a quartz-rich corrective or limestone containing a lot of quartz seams, or a harder limestone.

Variations in kiln feed quality such as widely varying LSF or SM could cause clinker free lime to increase intermittently. How often do you measure your kiln feed chemistry and what is the standard deviation (SD) of your kiln feed LSF and SM on an hourly and on a daily basis?

At 17%, your raw meal 90um residue is still a little bit high. Depending on the capability of your raw mill, I would recommend 12% on 90um and 1% on 212um.