Page 135 - Advanced Mine Ventilation

116 Advanced Mine Ventilation

Table 8.5 Dust Deposition in Human Lungs

Percentage of All Respirable
Coal Type Dust Deposited in Lungs (%)
Anthracite 76
Low-volatile bituminous coal 58
High-volatile bituminous coal 53
Lignite 56

particles (below 1 mm) constitutes 72% of respirable dust for anthracite compared with
only 39% for high-volatile bituminous coal.
This has a serious health implication. Using the lung deposition curve of Chapter 7,
it can be concluded that “lung dose” of respirable dust is significantly higher for
anthracite mines compared with high-volatile bituminous coal mines even if the total
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respirable dust is maintained at 1.5 or 2.0 mg/m in both mines.
Although a rigorous quantitative estimate of percentage deposition of dust in lungs
is not feasible for lack of lung deposition efficiency values for particles below 0.5 mm,
a close approximation can be made by assuming that all dust particles below 0.5 mm
have a 100% deposition efficiency. Thakur [1,12] has calculated the percentage of total
respirable dust deposited in human lungs as shown in Table 8.5.
Thus for the same level of respirable dust in the mine air, a mine worker in an
anthracite mine will receive a dust dose that is 1.43 times higher than that of a mine
worker in a high-volatile bituminous coal mine. This indicates that anthracite miner’s
lungs will be damaged faster and partially explains why the rate of CWP is globally
higher in anthracite mines. There are other reasons (chemical composition) for this
anomaly that will be discussed later in the chapter.

8.5 Determination of Mass Distribution for Fine Coal
Dust Particles

In recent years, many sophisticated instruments have appeared in the market that mea-
sure the number or the surface area of particles (such as light scattering instruments),
but they fail to produce true mass distribution of the fine respirable dusts. Instruments
that measure the electrical conductivity claim to measure the volume of the particles
but do not yield a true mass distribution. The only reliable device that gives good
mass distribution is the Andreasen pipette [13]. Fig. 8.3 shows the Andreasen pipette.
The apparatus consists of a graduated cylinder, w; with a stopper, L, that has a hole
in it; a pipette, P, that can hold 10 cc of fluid; and a three-way cock, T, that enables the
sample to be withdrawn and discharged into a container, A. Thakur [12] used this
apparatus extensively to measure the mass distribution of 18 coal samples with excel-
lent results. If the concentration of solids is kept less than 1% by volume, 2%e5% ac-
curacy can be achieved [10].