JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II MINE ENVIRONMENTAL ENGINEERING – I Previous Question Paper (March - 2022 - R16)

To determine the composition, we first identify the excess nitrogen and carbon dioxide that constitute the black damp. Black damp is defined as an atmosphere deficient in oxygen and enriched with carbon dioxide and nitrogen. Given the air composition (20.95% O₂, 0.03% CO₂, 79.02% N₂), we use the oxygen deficiency method.

1. Calculate the nitrogen associated with the measured oxygen (16.52%):

2. Calculate the excess nitrogen (N₂ in sample - N₂ in air):

3. Calculate the total black damp (Excess N₂ + CO₂ in sample - CO₂ in air):

4. Calculate the percentage of air in the sample:

5. Composition of black damp (normalized to 100%):

Methane drainage is the process of capturing methane gas from coal seams before or during mining to reduce the concentration in the ventilation air and improve safety. The primary methods include:

• Pre-drainage: Boreholes are drilled from the surface or underground into the virgin coal seam ahead of mining. The gas is extracted using vacuum pumps, often assisted by hydraulic fracturing or directional drilling to increase permeability.
• Post-drainage: This involves capturing gas from the goaf (gob) or adjacent strata after coal extraction. Boreholes are drilled into the caved roof strata where methane accumulates due to pressure relief.
• Cross-measure drilling: Boreholes are drilled from the ventilation roadways into the roof or floor strata to intersect gas-bearing layers, allowing the gas to be piped out before it enters the working face.

The extracted gas is transported through a dedicated pipeline system to the surface, where it is either utilized for power generation, industrial heating, or safely flared to prevent atmospheric release.