JNTU
JNTU B.Tech III UNDERGROUND COAL MINING TECHNOLOGY Previous Question Paper (August - 2022 - R18)
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Main
Explain the factors affecting choice of mining methods.
Answer
The selection of a suitable mining method for an underground coal mine is a critical decision that influences the economic viability, safety, and efficiency of the operation. The choice is governed by a combination of geological, technical, and economic factors:
- Geological Factors: The thickness and inclination of the coal seam are primary determinants. Thin seams may favor longwall mining or mechanized bord and pillar, while steeply dipping seams require specialized methods like breast stoping or sub-level caving. The depth of the seam affects the magnitude of rock pressure, influencing the size of pillars and the choice of support systems.
- Geotechnical Properties: The strength and stability of the roof, floor, and coal seam itself dictate the method. Weak roof conditions often necessitate caving methods or intensive artificial support, whereas strong, competent rock may allow for larger spans and room and pillar layouts.
- Gas and Hydrological Conditions: High methane emission rates require methods that facilitate efficient ventilation and drainage, such as longwall mining with bleeder systems. Similarly, the presence of water-bearing strata or aquifers may restrict certain caving methods to prevent inundation.
- Economic Factors: Capital availability, market demand, and the required rate of production are decisive. Highly mechanized methods like longwall mining require massive initial capital investment but offer lower operating costs per tonne at high production volumes.
- Safety and Regulatory Requirements: Methods must comply with statutory safety standards regarding ventilation, dust control, and strata control. The risk of spontaneous heating or coal bumps may rule out certain methods that leave large amounts of coal in the goaf.
- Resource Recovery: The objective of maximizing coal extraction often favors caving methods over pillar-based methods, which may leave significant coal reserves locked in permanent pillars.
What is the importance of determination of Proximate analysis of Coal?
Answer
Proximate analysis is essential for evaluating the commercial value and combustion characteristics of coal. It provides the following critical data:
- Moisture Content: Indicates the amount of water present, which reduces the effective calorific value and increases transportation costs.
- Volatile Matter: Determines the ignition characteristics and flame length; higher volatile matter makes coal easier to ignite but produces more smoke.
- Ash Content: Represents the non-combustible mineral residue. High ash content lowers the heating value, increases handling costs for waste, and causes slagging or fouling in boiler furnaces.
- Fixed Carbon: Provides a measure of the solid combustible material, which is the primary source of heat during combustion.
These parameters collectively dictate the suitability of coal for specific industrial applications such as power generation, coking, or gasification.
Explain the procedure of determination of Fixed Carbon of coal.
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Describe the general principle of Bord and Pillar Development with a sketch.
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Explain the limitations of Bord and Pillar method.
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What are the different mining processes and systems in Bord and Pillar method?
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Explain one development panel with a production capacity of 450 T per day. The thickness of the coal seam is 3m and the gradient is 1 in 8. Assume other conditions as per the requirement.
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Explain principle and designing of pillar extraction.
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What are the automatic tripping features incorporated in LHD?
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A coal seam having the following parameters: Seam thickness: 3.2 m, Gradient: 1 in 5, Depth: 200 m. Suggest a suitable method of extraction of pillars mentioning the requirement of equipment, manpower, method of supporting, manner of extraction and rate of extraction. Assume other conditions.
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Discuss about continuous and cyclic systems in Longwall Mining.
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What are the different methods of underground coal gasification?
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Explain the common method of underground coal gasification.
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