JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV POWER PLANT ENGINEERING Previous Question Paper (February/March - 2022 - R18)
Answer any five questions
All questions carry equal marks
Main
Describe the different types of overfeed stokers and discuss the merits and demerits of each over others.
Answer
Overfeed stokers feed coal onto the fuel bed from above. The primary types include:
- Chain-Grate Stoker: Coal is fed onto a moving endless chain grate. It is simple, handles a wide range of coals, and has low maintenance. However, it is limited to smaller capacities and has lower efficiency compared to modern systems.
- Traveling-Grate Stoker: Similar to chain-grate but uses a separate grate surface. It allows for better air distribution and higher combustion rates, though it is mechanically more complex.
- Spreader Stoker: Coal is thrown into the furnace by a rotating rotor. It provides rapid response to load changes and burns a portion of coal in suspension, leading to higher efficiency. The main demerit is the high amount of fly ash produced, requiring robust dust collection systems.
Explain in detail with the help of line diagram, the implant handling of coal along with coal dust and its control.
Answer
Coal handling involves a series of processes to move coal from the receiving point to the furnace. The sequence typically includes: unloading, preparation (crushing), transfer (conveyors), and storage.
The process flow is as follows:
- Unloading: Coal is received via rail or truck and unloaded into hoppers.
- Crushing: Large lumps are crushed to a uniform size (typically 20-40 mm) to ensure efficient combustion.
- Conveying: Belt conveyors or bucket elevators transport coal to the bunker.
- Storage: Dead storage (long-term) and live storage (bunker) are maintained to ensure continuous supply.
Coal dust management is critical due to explosion risks and environmental hazards. Control methods include:
- Dust Suppression: Using water sprays at transfer points to dampen coal.
- Dust Extraction: Installing local exhaust ventilation and bag filters at conveyor discharge points to capture airborne particles.
- Enclosure: Keeping conveyors and transfer chutes covered to prevent dust migration.
Explain the advantages and working details with the help of a neat diagram the fluidized bed combustion.
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Explain the principle of operation of pulverized coal burning system used in the grate of a steam boiler.
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What do you understand by supercharging? Under what conditions, the supercharging is advisable. Justify.
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Draw the layout of gas turbine power plant along with the auxillary components and discuss the limitations.
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Differentiate between open cycle gas turbine power plant and closed cycle gas turbine power plant.
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Explain the construction and operational features of different types of dams constructed in India.
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Draw the hydrological curve and discuss its importance in the establishment of hydro power generation unit.
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How to select the better location for hydropower plants? Also discuss the methods to achieve the required water head in the dams.
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Differentiate between nuclear fusion and nuclear fission and discuss the suitable fertile material required for both the reactions.
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How does the fast breeder reactor function? Explain it with a suitable diagram and discuss its applications.
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What do you understand by the term radiation hazards? Explain different methods to minimize the radiation hazards.
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Explain different standards maintained by Indian government in order to control the pollutions from the thermal power plants.
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Draw the same load curve of any power plant and discuss the methods to estimate the demand factor, load factor and diversity factors.
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A steam power plant has installed capacity of 120 MW and a maximum demand of 100 MW. The coal consumption is 0.4 kg per kWh and the cost of the coal is Rs 80 per ton. The annual expenses of salaries and other overhead expenses excluding coal are Rs 5 crores. The plant works on load factor 0.5 and the capital cost of the power station is Rs 4 crores. If the rate of interest and depreciation is 10%, then calculate the cost of power generation for kWh.
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