Air Pollutants in the Mines
Aerosols - solid or liquid particles suspended in a gas.
Solids
Dust 1-100μm 1-20μm
- solid particulate matter suspended in a gas
- most common aerosol problem
Fumes <1μm
- products resulted from physicochemical process
combustion, sublimation, or distillation
Dust and fumes are usually the results of
combustion processes.
Smokes 0.01-1.0μm
- Formed by incomplete combustion
- visible and are distinguished from fumes
Liquids - consequence of high temperature and
humidity
Fog (denser) 100μm
- condensation of liquid or the dispersal of small
liquid droplets
Mists (lighter)
Smog (<1μm)
- a combination of smoke and fog
- Contains photochemical reaction products
combined with water vapor
Haze
- Similar to smog
Airborne dust can be divided into the following
types:
Inhalable - enter the respiratory system through the
nose and mouth (30–100 μm). pollen
Thoracic - These are particles that reach beyond the
larynx getting into the thorax. (<30 μm) coal dust
Respirable - particles penetrate to the unciliated
airways (<10 μm) bacteria,cigarette smoke
Dynamic Behavior of Aerosols
BROWNIAN MOTION – When aerosol particles are
less than 0.1 u.m in diameter and suspended in a
quiescent fluid, the process of Brownian motion
controls their behavior.
STOKES’ LAW - determine the settling velocity of
dust
particles greater than 1microns in diameter
REYNOLDS NUMBER - determining the
type of flow pattern as laminar or turbulent
Basic Psychrometry - the branch of thermodynamics
and climatology that studies mixtures of gases and
vapors.
-It relies on two essential parameters: temperature
and humidity.
Dry-bulb temperature (Td) - ordinary thermometer
measures dry-bulb temperature. air humidity and air
velocity, heat
radiation of nearby objects.
Wet-bulb temperature (Tw) - covered with a cotton
bulb moistened with water; temperature is affected
by the cooling effect of the water evaporating in the
air. If the air is drier, the bulb will dry faster and the
temperature will be lower.
Equivalent temperature (Te) - involves
environmental temperature, relative humidity and
air velocity.
Absolute humidity (AH) - mass of water vapor per air
mass unit.
Saturation humidity (SH) - maximum amount of
water vapor that a volume of air can contain at a
given temperature.
Relative humidity (RH) - ratio between the mass of
water vapor in the air and the maximum possible
mass of water vapor in the air at that temperature.
Saturated vapor pressure (Ps(w)) - pressure of a
vapour in equilibrium with its liquid phase.
Vapour pressure (Pv) - calculate air humidity
Specific volume (Ve, ν) - total volume of air plus
water vapor per unit mass of dry air.
Dew temperature (DT) - temperature to which air
must be cooled for it to become saturated with
water vapor.
Enthalpy (H) - amount of energy absorbed or
transferred by the air.
Heat Inside Mines
Geothermal Gradient - reason why the temperature
increases as one goes deeper into a mine.
Outdoor Climate - ground temperature and the
variation in the air temperature that is introduced
from the outside.
Air Self-compression - process by which a column of
descending air compresses and its temperature
increases.
Electromechanical Equipment - These machines
work;
most of it becomes heat.
Explosives - Heat released from explosives
Heat of the Rock Mass
Human Metabolism
Mine Waters
Other Sources - Oxidation reactions
CONTROL OF DUST
Concentration - determination of whether an aerosol
is harmful to human beings
Concentration - Reducing the concentration of dust
will also reduce the incident of lung disease
Particle size - determines where the particles will
reside within our respiratory tract
Exposure Time - Most of the diseases associated
with breathing mineral dusts manifest them-selves
over a relatively long period of time
Individual Susceptibility - dust exposure is certainly a
variable that will affect whether that person will
suffer from lung disease.