Page 165 - Advanced Mine Ventilation

Respirable Dust Control 145

ventilation is done with auxiliary fans and tubing, it can be either exhaust or blowing.
Sometimes, a combination of both is used for optimum results.

10.3.4 Remote Operation of a Continuous Miner
The last resort for dust control is to operate the continuous miner remotely. With
exhaust ventilation as shown in Fig. 10.3, the operator can stay in the intake air and
3
be exposed to less than 1 mg/m of respirable dust. Goodman and Listak [8] measured
a reduction of 80% in dust exposure compared with the dust exposure at the mining
machine by placing the operator about 50 ft away from the mining machine.

10.4 Dust Control in Longwall Faces

The sources of dust on longwall faces are the intake air, the stage loaders and crushers,
the shearers, and the shields. The intake air is a minor source of dust unless the belt air
is used on the face. Confinement and water sprays usually at less than 70 psi pressure
can generally keep the contribution of stage loader dust to a minimum. The dust
created by shield movement is also minimized by mounting water sprays on the
shields. The biggest source of dust on longwall faces is the shearer. Table 10.3 gives
a summary of data obtained from 13 US longwall faces [9].
Shield movement is always behind the shearer. It comes into consideration when
the shearer is cutting from head gate to tail gate and shields are advanced upstream
from the shearer operators.

10.4.1 Water Infusion
Excellent dust control can be achieved by drilling the longwall panel horizontally for
degasification (to be discussed later in this book) and using the horizontal boreholes for
water infusion ahead of mining. Slow infusion of water at 70 to 300 psi has given
excellent results, often reducing the dust generation by 80% [10]. Larger and sharper
cutting bits also reduce dust generation by reducing the specific energy of cutting coal.
Use of very high pressure water (5000 to 10,000 psi) to assist coal cutting has also

Table 10.3 Dust Sources on Longwall Faces

Average Dust
3
Source Average (%) Concentration (mg/m )
Intake air 9 0.33
Stage loader and crusher 15 0.78
Shields 23 1.80
Shearer 53 3.50