Part-4: Lime saturation Factor LSF
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
Benefit of LOI?
1. Quality Control: LOI testing is a critical quality control measure that helps cement manufacturers ensure the consistency and quality of their products. It allows them to monitor the chemical composition of raw materials and the resulting cement clinker.
2. Determination of Volatile Components: LOI testing helps in quantifying the amount of volatile components, such as carbonates and chemically combined water, present in the raw materials. This information is essential for understanding how these components will behave during the cement manufacturing process.
3. Process Optimization: By knowing the LOI values of raw materials, cement plants can adjust their production processes to account for variations in the composition of these materials. This optimization can lead to more efficient and cost-effective production.
4. Control of Clinker Formation: High LOI values in raw materials can lead to excessive clinker formation in the kiln, which can negatively impact the production process. Monitoring and controlling LOI levels help prevent issues like over-burning or under-burning of clinker.
5. Consistency in Cement Properties: Cement with consistent LOI values tends to have consistent properties, which is crucial for construction projects where uniformity in cement performance is required.
6. Compliance with Standards: Many cement standards and specifications specify acceptable LOI limits. Ensuring that the cement product meets these limits is essential for compliance with industry standards and customer requirements.
7. Research and Development: LOI testing can also be valuable in research and development efforts. Researchers can use LOI data to explore new raw material sources or alternative cement formulations.
8. Environmental Impact: Understanding the LOI of raw materials can also be important from an environmental perspective. High LOI values may result in higher energy consumption during cement production, which can have environmental implications. By optimizing the LOI, cement plants can reduce energy consumption and emissions.
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