The major methods used in coal mines and thermal plants to control dust pollution are
- Ventilation
- Water sprays
- Dust collectors
I). Ventilation:
The ventilation methods provide the best use of air in the vicinity of workers and in the vicinity of dust sources. There are different methods
- Dilution Ventilation:
In this method it is used to provide more air and dilute the dust. Most of the time the dust is reduced roughly in proportion to the increase in air flow, but not always.
- Displacement Ventilation :
In this method it is used to use the airflow in a way that confines the dust source and keeps it away from workers by putting dust downward of the workers.
II).Water Sprays :
There are 3 methods
1. Wetting :
By wetting of the coal adequate dust pollution can be controlled. Due to wetting the dust particles stay attached with surface of coal material.
2. High pressure sprays:
This method improves spray by raising the water pressure which may further causes to raise the efficiency per unit use of water. In this case there is a chance to get reduced 30 to 40% dust pollution?
3. Foam:
For dust control foam may be better than water. It provides dust reductions upto 20% to 60% compared to water. Foam also can produce similar results at lower water use that is the amount of water needed to make the foam is less than the equivalent water spray. Only drawback is high cost.
III).Dust Collectors :
The dust collectors play a vital role in dust reduction in mining and coal plants of thermal power plants. Dust collectors range from low-volume filtration to high volume wet collectors is used in various locations such as conveyor areas, tunnels, crusher areas and bunker areas. For dust collectors properly designed to trap respirable dust, the filtration efficiency is usually quite high in the range of 90-95%.
Methods generally implemented in thermal plants
Location | Method implemented |
Coal transportation | Wagons covered with tarpaulins |
Wagon tippling | Spraying water |
Conveyor streams | Dust collectors and sprinkling water |
Crusher houses | Dust collectors |
Bunkers | Dust collectors |
Coal yards | Sprinkling water |
COMPARISON OF VARIOUS SYSTEMS:
DUST CONTROL METHOD | Effectiveness (Low is10-30%, Moderate is 30-50%, High is 50-75%) | Cost and draw backs |
Dilution Ventilation | Moderate | High |
Displacement ventilation | Moderate to high | Moderate |
Wetting | Moderate | Low |
Foam | Moderate | High |
Water high pressure sprays | Moderate | Moderate |
Dust collectors | Moderate to high | Moderate to high |