62235-mt----thermal Power Plants

NR

Code No: 62235/MT

M.Tech. – II Semester Regular Examinations, September, 2008 THERMAL POWER PLANTS (Power Engineering & Energy Systems) Time: 3hours

Max. Marks:60 Answer any FIVE questions All questions carry equal marks ---

1.a) b)

2.a) b)

Draw a neat diagram of multi-retort underfeed stoker and explain its working. Discuss its merits over other types of stokers. Draw a line diagram of pneumatic ash handling system and explain the difficulties encountered in its design and operation. When this system is preferred over other system? What factors are mainly considered in the design of a boiler used in power plant? Discuss the significance of each with details. Sketch different types of air heaters mention their field of application and discuss their relative merits and demerits.

3.a)

List out the causes of losses in system turbines mention the preventive measures to be taken to reduce them b) In a reaction stage of steam turbine the nozzle angle is 200 and the absolute velocity of steam at inlet to the moving blades is 240 m/s. The blade velocity is 210 m/s. If the balding is designed for 50% reaction, determine: i) the blade height at inlet and exit ii) the enthalpy drop per kg of steam in the moving blades and in the complete stage iii) the diagram power for a stream flow of 1kg/s and iv) the diagram efficiency.

4.a) b)

Discuss the part load behavior of combined cycle plant and compare with conventional gas turbine plants of the same capacity. What is PFBC combined cycle? Explain its operation with a line diagram.

Contd…2

Code No: 62235/MT 5.a) b)

6.a) b)

::2::

Explain a barometric condenser. What is the function of the tail pipe? A surface condenser receives 200t/h of steam at 400C with 10% moisture. The cooling water enters at 330C and leaves at 380C. The pressure inside the condenser is found to be 0.078 bar. Neglecting any sub cooling, determine: i) the condenser cooling water flow in kg/s ii) air ejector capacity in kg/s and iii) the surface area of the condenser. Take U0=2970 W/m2K. Why Dry type cooling systems are preferred over water cooling system in modern power plants? Cooling water enters a cooling tower at a rate of 1000 Kg/hr and 700C. Water is pumped from the base of the tower at 240C and some makeup water is added afterwards. Air enters the tower at 150C, 50% RH, 1.013 bar and is drawn from the tower saturated at 340C, 1bar. Calculated the flow rate of the dry air in Kg/h and the makeup water required per hour.

7.a) b)

Explain the effect of load factor on the cost of electricity generated. How is the load-duration curve constructed?

8.a)

Method used to control NOx increases CO in the flue gases. What is the reason? What method is used to control both? What are the different methods presently adopted in the world to reduce the future effects of greenhouse effect?

b)

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