Mine Air Composition and Air Pollution

Course Outline

• The course covers the mining environment, air parameters, gases, dust/particulates, detection of gases and particulates, air pollution, heat in the work environment/thermal stress, water quality and pollution, instruments used in water quality analysis, and environmental impact assessment.

Course Aims

• The course introduces students to the concepts of the mining environment, environmental pollution, and management.
• The course helps students understand pollutants released by mining, their effects, and how they are measured and managed.

Course Assessment

• Quizzes/individual and group assignments accounts for 30% of the final grade.
• Class Exercises/Attendance accounts for 10% of the final grade.
• The final examination accounts for 60% of the final grade.

The Environment

• The environment can be defined as the physical and biological habitat that surrounds us and can be perceived through our senses.
• Most now define the term to include not only physical/chemical and biological aspects but also social, cultural, and economic aspects, effectively referring to the environment of people
• The characteristics of the environment consist of physical/chemical (air, water, and land), biological (fauna and flora), and human environment (social and economic systems) elements.
• The four environmental spheres are the atmosphere (air), hydrosphere (water), lithosphere (land), and biosphere (fauna and flora), which form an interlocked natural system per natural sciences and physical geography.
• Human environment is modifying or destroying natural conditions and is sometimes called the 'built environment,' compared to the natural environment.
• The environment is defined by demographics, manmade systems, structures, cultural, and heritage resources, it encompasses not only manmade systems but also cultural and heritage assets.
• The human factor in the environment is grouped into social and economic systems, or the social and economic spheres, per social sciences and human geography.
• The overall evaluation assessment of a new mining project includes all six environmental spheres, which are the overlapping areas of the three circles of sustainability.
• Each mining project influences these spheres, and they in turn influence the mine. Environmental Management
• Environmental or Resources Management involves managing human activities' impact on the environment, seeking practical ways to save resources and reduce negative impacts.
• It also focuses on study themes like environmental degradation, natural resource use, natural hazards, impact assessment, and the effects of urbanization and land use.

The Atmosphere – Air, Weather, and Climate

• Mining projects are affected by the climate conditions at their location.
• Factors such as temperature, precipitation, or lack thereof, visibility, wind, and their variations are vital in designing and operating mining facilities.
• Mining and mineral processing can influence climatic conditions and significantly affect local air quality, impacting human health and comfort.
• Understanding local climate and air quality is important.

The Atmosphere

• The atmosphere is the gaseous envelope around the Earth, being the most dynamic and changeable of the Earth's spheres
• (hydrosphere, biosphere, and lithosphere).
• It is a complex system of constant physical and chemical reactions.
• Many processes achieve dynamic balance.
• Includes balances between solar energy entering and radiant energy leaving, oxygen levels regulated by photosynthesis and respiration, and water levels managed by the hydrological cycle.

Atmosphere Constituents

• Key atmosphere constituents by volume are:
• Nitrogen (N2) at 78.1%.
• Oxygen (O2) at 20.9%.
• Water vapour (H2O) varies between 0-5%.
• Argon (Ar) at 0.9%.
• Carbon dioxide (CO2) at 0.03%.
• Trace constituents form the balance.

Atmosphere Temperature

• Air temperature has measurements via a thermometer, and uses degrees Celsius (°C) or Fahrenheit (°F).
• Temperature is an air parameter measured with a thermometer, degrees Celsius (°C) or Fahrenheit (°F).
• The maximum air temperature is near the Earth's surface in the troposphere as air temperature declines uniformly with altitude.
• The temperature declines at approximately 6.5 degrees Celsius per 1,000 meters; this is known as environmental lapse rate.
• The solar radiation's uneven heating, and the lateral temperature distribution from spherical shape of the Earth, influence climatic variation.
• Half the energy from solar radiation is absorbed by land and oceans.
• To maintain Earth's 16°C surface temperature, loss and gain must balance.
• Most energy gained is transferred to the atmosphere since most of the atmosphere is heated from below by the Earth.
• This effect creates convective motion.
• Measuring the climate at a specific location requires long-term meteorological observations, such as at a mine site.

Temperature Conversion

• Kelvin (K) = t(°C) + 273 K
• Rankine (R) = t(°F) + 459 R
• Celcius to Fahrenheit conversion is T(°C) = 5/9 • (T(°F) − 32)
• Fahrenheit to Celcius conversion is T(°F) = 9/5 • (T(°C) + 32)

Dry Bulb Temperature (Tdb)

• Denotes ambient air temperature.
• Measured by a shielded thermometer, indicating heat and proportional to air molecules' kinetic energy.
• Unlike wet bulb temperature, it does not reference moisture in the air.

Wet Bulb Temperature (Twb)

• The temperature a parcel of air would have if cooled to saturation (100% relative humidity) through water evaporation, with latent heat supplied by the air parcel.
• It is the temperature of adiabatic saturation.

Dew Point Temperature (Tdp)

• When air is completely saturated, water vapor starts to condense.
• Moisture remains airborne when the temperature is above the dew point.
• If the dew point temperature is close the the dry air temperature humidity is considered high.
• The dew point temperature is well below the dry air temperature – the relative humidity is low.
• The dew point temperature is always lower than the dry bulb temperature, being equal with 100% relative humidity.
• When air temperature changes, the dew point remains constant unless change takes place through and is added or water is removed from the air.

Wet Bulb Global Temperature (WBGT)

• This is a heat stress measure in sunlight.
• It takes into account;
• Temperature
• Humidity
• Wind Speed
• Sun Angle
• Cloud Cover
• Industrial hygienists, athletes, and the military use it to determine appropriate exposure levels to high temperatures.
• WBGT = 0.7 Tw + 0.3 Tg + 0.1 Td.
• Tw is wet bulb temperature.
• Tg is globe temperature (measured using a black globe thermometer for radiant temperature).
• Td is dry bulb temperature (actual air temperature).
• Air temperature has measurements in either °C or °F.

Pressure

• Pressure is the force exerted perpendicular to an object's surface per unit area.
• The measurements are in N/m² or Pa.
• Pressure may be measured as Absolute or Gauge (Pressure Difference).
• Barometric pressure or is the absolute pressure and is measured with a barometer.

Humidity

• This is the ammount of water vapor in the air.
• The higher the air temperature, the more water vapour it can contain.
• When air saturates with water vapor at a certain temperature.

Absolute Humidity

• Absolute humidity measures the quantity of water vapour, is expressed in g per m³ of air.
• Absolute Humidity = Mass of water vapour (g) / Volume of air (m³).

Relative Humidity (φ)

• It is the ratio of the mass of water to the total mass of moist air, or the ratio of vapour pressures of air (P) at a given condition to saturation (Psat).
• When the air is saturated, it cannot hold any more water vapor.
• The relative humidity is 100%.
• RH = Actual water vapour pressure (P) / Saturated water vapour pressure at that temperature (Psat) × 100.

Specidfic Humidity (x)

• This is the weight (in kg or g) of water vapour per unit weight of dry air.
• Unlike relative humidity, it is not dependent on changes in temperature.
• x = 0.622 × φρws / (p-pws)100%
  • x = specific humidity (humidity ratio) of air vapor mixture (kgH20/kgdry air) .
  • q = relative humidity (%).
  • Qws = density of water vapor (kg/m³).
• Q = density of the moist or humid air (kg/m³).
• High humidity can negatively affect chemical plants and refineries using furnaces, including processes like steam reforming and wet sulfuric acid.
• Humidity decreases oxygen concentrations in the atmosphere and flue gas, affecting fan intake.
• Typically dry air is 20.9% oxygen, but 100% rH means air is 20.4% oxygen

Precipitation

• Precipitation is a variable that is critical for establishing water balances and their variability.
• It includes liquid (rain) and solid (snow, hail) as well as deposed dew or frost forms.
• Observed variable is precipitation depth, defined as the depth of liquid water accumulated during a defined
• time interval on a horizontal surface and is measured in mm per time interval.
• Precipitation also drives land surface hydrology like incoming solar radiation drives thermal regimes.
• Reliable, high resolution records of precipitation are critical inputs for the design of mining projects.
• For most applications, average data is sufficient for the water cycle and budget.

The Mine Atmosphere

• Air quality and noise can be affected by atmospheric parameters.
• The composition, temperature, and humidity of pumped air change as it passes through underground mining excavations.
• Compared to surface air, mine air contains less O₂, more N₂/CO₂ because of oxidation and CO₂ release from rocks.
• Harmful mixtures of dust, vapours, and explosive gases are are often present in this atmosphere.
• O₂ content should be over 20%, and CO2 below 0.5-1%. Mine Gases
• Contamination through other gases contamination, such as CO, SO2, H2S, CH4, NOx and excess CO2 is also common.
• This contamination is an issue due to gasses being trapped in a confined space.
• Gasses can often form an explosive, combustible or toxic state.
• It is key to manage the the toxic or explosive mixture of different gases
• Mixtures of gases found in mine environments are called damps.

Black Damp

• Atmosphere of carbon dioxide and nitrogen in a lack of oxygen, carbon dioxide will result in suffication.
• Mining term for the suffocating mix of carbon dioxide and unbreathable gasses poisoning, asphyxiation and ultimately death.
• Blackdamp is present where coal is and is hard to distinguish, increasing risk of missed warnings and serious harm.
• Prevention and identification are essential for mine safety.

White Damp

• It is carbon monoxide (CO) and is very poisonous
• A domestic canary was was a common warning sign due carbon monoxide affecting smaller animals faster.

Stink Damp

• This is Hydrogen Sulfide (H2S), a colorless gas with sweetish taste, and a distinctive odor of rotten eggs.
• The minimum to smell this gas us 0.01% in air.
• The gas is more poisonous than CO.

Fire damp

• Mining term for set of explosive gases found in mines and is primarily methane (CH4).
• Methane is often an interchangeable term miners talk about firedamp.
• All dangerous gases must be detected through a flame.
• If it gets to close the whole gas supply may ignite.

After Damp

• This is Gaseous products and smoke from a fire or explosion: including CO, CO2, water vapor, nitrogen, oxygen, hydrocarbons and hydrogen.

Mine Gas Prevention

• Mine gases can occur from: blasting residue, mine fires, liberation from rock, decaying timbers, or timber oxidation.
• Mining gases can also come from: water absorption of oxygen plus diesel and gasoline motors in enclosed areas.
• Mine gases can be dissolved in thermal water or through chemical reactions of mining reagents.
• Positive ventilating currents prevent dangerous gas pile ups, except during fires.
• Gases may be toxic, explosive, or combustible; inert gases can displace oxygen.

Mine Gases by Type

• Firedamp is predominately methane, it is is colorless & odorless (Methane / CH4)
• Whitedamp is carbon manoxide (CO) and is colorless odorless and toxic.
• Black damp is carbon dioxide (CO2) and it's odorless or has a slight acrid smell and is toxic.
• Stinkdamp is Hydrogen Sulfide (H2S), colorless with a rotten egg smell and is explosive as well as toxic.

Gas mitigation

• Damps are released during drilling, blasting etc.
• Diesel, gasoline motors and timber decay also produce damps.
• Best prevention involves quality ventilation and early detection, High CO2
• Is inert and comes from organic compounds in the presence of oxygen.
• It is produced via people and animals too.
• Colorless & odorless, can cause a distinctly acid taste.
• The gas that does not burn.

Inert Gas

• Carbon dioxide's specific gravity is 1.5189, and it can be found in abandoned parts of mines.
• The gas builds up through human breathing or fire explosions due to liberated coal beds or through water.

The effects of various percentages of Carbon Dioxide

• Level Percentages in Respiration
• 0.05 Slight.
• 0.5 Maximum for 8-hour day.
• 2.0 50 percent.
• 3.0 100 percent.
• 5.0 300 percent and laborious.
• 10.0 Cannot endure for a few minutes.
• 18.0 Rapid death.
• These CO2 effects occur when oxygen is normal and the individual is at rest, working or moving increases effects.

Methane (CH4)

• Is encountered in practically all coal mines; comes from decomposed matter underwater and absent air.
• Its emissions in a coal mine come from "blowers", and coal cracks, often released with irregularities such as clay veins.
• It will accumulate at the mine roof and mixes with the flowing currents of air.
• Specific gravity is 0.555; lighter than air and found near the roof.
• Its ignition temperature is 537 °C as methane is a colorless, odorless, and tasteless gas, with a sulfide odor.
• Is an explosive gas when in still air containing 5 to 15 percent w/ 12+ percent oxygen.
• Known methane occurrences should be diluted via adequate ventilation.
• Is most often located through a methane detector.
• There is no direct effect to humans.
• It may displace breathable air. , displacing the oxygen.
• Circuits must be isolated when methane hits 1.0 percent.
• Miners must be withdrawn at 1.5 percent.

Explosive limits

• This gas should not exist with blasting of any kind and decreases the lower explosive limits.

Carbon Monoxide (CO)

• One of the most hazardous gases in miners
• Product of combustion, often from diesel
• Has explosive reactions between 12.5 to 74 percent if ignited.
• Only slightly soluble in water.
• Specific gravity is 0.967, slightly less than air.
• Ignition is at 609 °C.

Effects of percentages of CO

• Percentages and what will eventually take place within the body given it has spread:
• 0.01 produces symptoms of poisoning.
• 0.02 produces slight symptoms after hours.
• 0.04 headache and discomfort usually occur within hours.
• With an 8 hour period the percentage must not exceeded 0.005 /50 ppm.
• With moderate exercises, the specific signs a conditions are these with percentage increases
  • 0.12 slight heart palpitation (30min), tendency to stagger (1.5hr), and confusion of mind (2hr).
• In concentrations of 1.20 to 0.25 can result to unconsciousness within (30min). , those one may have little or no warning before collapsing.

C0 Poisoning

• CO exposure occurs quickly or over a period of time
• CO is absorbed from air in lungs form loose association with haemoglobin of red blood cells.
• O₂ must first exist with a stable, high-affinity compound of haemoglobin
• Haemoglobin takes in CO over oxygen even small percentage. If exposed to h concentrations, there may be few symptoms.
• CO is dangerous as the rate of absorption increases depend upon
  • Concentration
  • Exercises
  • Health
  • Temp/humidity
  • Air movement

How to treat CO Poisoning

• Move the person to fresh air.
• If respiration ceased, give artificial respiration until the patient can be sustained only by a machine.
• Administer O₂ with 20-30 minute lessions every 1-2hr
• Keep victim warm with blankets, etc.
• Keep victim lying down to to allow rest and recovery.

Carbon Monoxide (CO) Exposure

• How the exposure ammounts effect the body after being absorped
• CO Ppm and alowable Lenth of exposure
• 50 Allowable for exposure of hours.
• 400-500 Can inhale for 1 hr w without appreciable effect.
• 600-700 Noticeable effects in 1 hr
• 1000-1200 Unpleasant/Dangerous 1-1hr
• 1500-2000 Death Possible 1hr
• Greater than 4000 Death can occour in <1hr

Nitrogen Oxide (NOx)

• Nitrogen is in mines through burning/detenation explosives.
• The oxide can detected thru order or color, which has a reddish color and has (NO2) fumes.
• Dynamite gases are approx. 11.9 are oxides of nitrogen.
• Diesel also produces oxides of nitrogen.
• Threshold limit is 5ppm.

NOx Exposure Effects

• Effects of Nitrogen percentage
  • Min Allowance 0.0005%
  • Throat irratation is caused 0.006%
  • Causing cough at 0.01%
  • Becoming Dangerous % 0.01-0.015
  • Rapidly fatal would be % 0.02-0.07
• A person exposed to high percentage after exposure can feel nothing for eight hours, lungs later fill fluids and asphyxia.

SO2

• Sulfur Dioxide (SO2) is has production via sulfide ores (pyrites).
• Also can come out from the exploitations od sulfide ore dust, and some diesel fuels.
• Has a strong sulfur odor which may irratate. Affect is the same which has nitrogen oxide which lung have pulmonary adema.

Sulfure exposure Effects

• Symptoms of percentage from Sulfur
• Max limit day 0.0005%
• Couch and nose irritation is from around % 0.002
• Being endured for a while would be around % 0.015
• Impossible to breath % 0.04
• Gas is highly-soluble.
• Heavy- specific is around % 0.264
• Colorless with a distinctly acid taste.

Detection and Limit

• The Thres hold is 5ppm.

H2S

• (Hydrogen Sulfide). -One of the most deadly
• Only found in small trace's.
• The smell is distinctive: rotten egg odor
• High concentrations result in loss Smell.
• It is poisoness color less gas given low even in small concentrations.
• At low points in mind has a Specific Gravity of 1.1763.
• Ignition:260°C

The effects if being inhalaed

• Immediate asphyxiation (high amounts).
• In low amount: inflamation, respiratory,bronchitis, penumonia and adema.

The Immediate effect

• With eye effect, that leads to immediatey collapse, if exposure leads to from 0.06 to 0.01% and death will occurs quickly.
• Exposure shouldnt exceeds 0.001 /10ppm .
• Can be detected by hydrogen sulphide: detectors paper wth acetate is black quickly in sulphide present. If explosion with result gases, will vary along by along other sulfur gases
• Ranges 4.3 /46 .

Ranges with (H₂S) by percentage in time

• Time and Percentage of results 10 - 0.001 Maximum day allowable 50-100 subacute is 0.005-0.010 the I hour mild , respiratory 200-300 Acute -1 to to ,irritation and respitory i 1 hour 500 to 700 1 to5 hours leads unconscious. greater above in mins that will lead to deaths

Dust/Particlate

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Explore mine air characteristics, acceptable CO2 levels, and the effect of mining on the climate. Differentiate types of air pollution, describe factors influencing atmospheric dynamics and air quality, and discuss contaminants found in mine air.