Part-5: How to measure Clinker liquid phase during Clinkerisation process
The liquid has a critical role in Nodulisation of Clinker, Development of clinker minerals and their properties. Solid-solid reaction is very slow process while solid-liquid reaction kinetics is much faster, so without liquid phase the diffusion of Ca ions towards C₂S would be extremely slow, and the conversion of C₂S and free lime to C₃S would be almost impossible in the kiln.
The amount of liquid phase in the burning zone varies between 23% to 29%. Higher values can be damaging to most refractory bricks in the absence of a stable coating. As the brick is infiltrated and saturated with liquid, its elastic modulus (relation between stress and strain) increases and so does its tendency to spall off.
This simple fact explains why hotter than normal temperatures are so beneficial to clinkering and yet so harmful to the refractory lining as low viscosity liquid infiltrates the refractory lining faster, leading to its premature failure.
The ratio of the effective lime content to the maximum possible lime content in the clinker.
LSF = CaO x 100 / (2.8 SiO₂ + 1.2 Al₂O₃ + 0.65 Fe₂O₃) Typical range: 0.88 to 1.02
Alumina Modulus= Al₂O₃ / Fe₂O₃ Typical range: 1.0 to 1.7
Silica Modulus or Silica Ratio:
SiO₂ / (Al₂O₃+ Fe₂O₃)
Typical range: 2.1 to 2.7
1. It is the relation between the solids & liquids which favors their diffusion, and therefore will reduce the temperature of burning.
2. It is an indirect measurement of the liquid phase %.
3. If the SM is near to 2.0 then it generates an excess coating thickness, burning easiness and excess liquid phase.
4. If the SM is near to 3.0 then it generates a little coating thickness, little liquid phase and high thermal load in order to burn.
Effect High SM:
1. Result in hard burning & High fuel consumption
2. Difficult in Coating formation hence Radiation
3. Deteriorates the kiln lining
4. Increase C₂S & C₃S will reduce
5. Radiation from shell is high
6. Cause unsoundness of Cement (High Free lime)
7. Results in low setting & hardening of cement
Effect Low SM:
1. Increase liquid phase
2. This improve burnability of clinker & the formation of coating in the kiln
3. Better granulometry - less dust
4. Improve Cooler efficiency
5. Big Clinker ball, when too low
Loss on ignition (LOI) : To measure the amount of chemically combined water in a cement sample. This test helps in determining the amount of volatile components in the cement, such as carbonates and organic matter, which can impact the cement's quality and performance.
How to calculate LOI?
1. Sample Preparation: A representative sample of the cement clinker or raw material (Lime stone, Laterite, Gypsum, Shale, Coal, etc) is collected. The sample is usually ground to a fine powder to ensure uniformity.
2. Heating: The sample 1 to 100 gm is placed in a crucible or Covered Platinum crucibles (20-25ML), and it is heated (15-20 minute) in a controlled environment (often a high-temperature Muffle furnace) to a specific temperature, usually around 900 to 1000 °C.
3. Measurement: The weight of the crucible and sample before heating and the weight after heating are carefully measured. The difference in weight represents the loss of mass due to the removal of volatile components.
4. Calculation: The LOI is calculated as a percentage of the original sample weight (W2-W1) using the following formula:
LOI (%) = [W2- W3] × 100 / [W2-W1]
W1: Weight of empty crucible
W2: Initial weight of Crucible & sample
W3: Final weight of Crucible & sample
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