Lime and Pollution Control Systems
Lime (also called quicklime) is the common term for calcium oxide (CaO). It's produced commercially by high-temperature (approx. 2000 °F) calcification of limestone, where the following reduction occurs:
The reaction also occurs in reverse, and the lime will slowly revert back to limestone when exposed to carbon dioxide. Lime is very hygroscopic and reacts vigorously and exothermically with water. When lime reacts with water, it forms calcium hydroxide, or hydrated lime by the following reaction:
Principal Uses of Lime
- Soil stabilization - Quicklime, when mixed with silicon-containing clays, undergoes an ion-exchange reaction and converts the clay to a cement-like substance. The reaction occurs with hydrated lime, and water and lime are both consumed.
- Neutralization of acids - The pH of lime in water is about 12, making it a moderately strong base and a good agent for the reduction of acidity.
- Drying up muddy sites - Lime's hygroscopic properties make it effective for drying wet areas.
Safety Information: Lime is not considered harmful, but the dust is an irritant and thermal burns can occur on the skin due to the exothermic reaction with water.
Dust Emission Control
Dust emission of quicklime and hydrated lime can occur during dry transfers, such as truck unloading or transfer of the material to a slurry mixer. Proper dust collection systems are essential for:
Truck Unloading Stations
- Enclosed unloading systems with appropriate ventilation
- Dust collection hoods positioned at transfer points
- Proper ducting to maintain adequate conveying velocities
Transfer Points to Slurry Mixers
- Enclosed conveyor systems
- Local exhaust ventilation at mixing stations
- Dust-tight connections between equipment
Material Handling Considerations
- Use of appropriate filter media resistant to alkaline conditions
- Proper hopper design to prevent material buildup
- Explosion protection measures where applicable
BCE Engineering Solutions: Our lime handling dust collection systems are designed to address the unique challenges of lime dust, including its hygroscopic nature, alkalinity, and potential for irritation. We implement proper ventilation, filtration, and material handling solutions to ensure safe and efficient operations.