How to measure the hydration activity of calcined lime in a lime kiln
The hydration activity of lime is an important indicator for measuring its quality, which directly affects its application effect in building materials, chemical industry and other fields. The hydration activity of calcined lime can be determined by the following methods:
1. Hydration temperature rise method (most commonly used)
Principle: Lime (CaO) reacts with water to release heat. The higher the activity, the faster the reaction rate, and the more significant the temperature rise.
Steps:
Take 50g of dry quicklime powder and place it in an insulated container;
Add 200mL of distilled water at 20 ℃, stir quickly and record the temperature change;
Measure the maximum temperature rise (Δ T) and the time to reach the peak (t).
Judgment criteria: The higher the Δ T and the shorter the t, the better the activity. Generally, high-quality lime with Δ T ≥ 60 ℃ and t ≤ 10 minutes.
2. Hydrochloric acid titration method
Principle: Active CaO reacts with hydrochloric acid to calculate the effective calcium content based on the amount of hydrochloric acid consumed.
Steps:
Dissolve 1g of lime sample in 100mL of distilled water;
Titrate with 1mol/L hydrochloric acid until pH=7, and record the consumption (V);
Calculate the effective CaO content (%)=(V × 0.028)/sample mass × 100.
Judgment criteria: The effective CaO of industrial lime is usually ≥ 90%.
3. Conductivity method
Principle: After lime hydration, the concentration of Ca ² ⁺ and OH ⁻ affects the conductivity. The higher the activity, the faster the conductivity increases.
Steps:
Mix lime samples with water and monitor changes in conductivity in real-time;
Draw a conductivity time curve, the larger the slope, the higher the activity.
precautions
The sample needs to be sealed and moisture-proof before testing;
When comparing different batches of lime, it is necessary to control the same experimental conditions (water temperature, stirring speed, etc.).
The above method can accurately evaluate the activity of lime, guide the optimization of calcination process, and improve product quality.
