Summer Training Report at IPGCL Figure 6; Heat Recovery Steam Generator at PPCL Evaporator Section: The most important component would, of course, be theEvaporator Section. So an evaporator section may consist of one or more coils. Inthese coils, the effluent (water), passing through the tubes is heated to the saturation point for the pressure it is flowing. Superheater Section : The Superheater Section of the HRSG is used to dry thesaturated vapour being separated in the steam drum. In some units it may only beheated to little above the saturation point where in other units it may be superheatedto a significant temperature for additional energy storage. The Superheater Sectionis normally located in the hotter gas stream, in front of the evaporator. Economizer Section: The Economizer Section, sometimes called a preheater or preheat coil, is used to preheat the feedwater being introduced to the system toreplace the steam (vapour) being removed from the system via the superheater or steam outlet and the water loss through blowdown. It is normally located in thecolder gas downstream of the evaporator. Since the evaporator inlet and outlettemperatures are both close to the saturation temperature for the system pressure,the amount of heat that may be removed from the flue gas is limited due to theapproach to the evaporator, whereas the economizer inlet temperature is low,allowing the flue gas temperature to be taken lower.The steam turbine-driven generators have auxiliary systems enabling them to work satisfactorily and safely. The steam turbine generator being rotating equipment generally hasa heavy, large diameter shaft. The shaft therefore requires not only supports but also has to bekept in position while running. To minimize the frictional resistance to the rotation, the shafthas a number of bearings. The bearing shells, in which the shaft rotates, are lined with a lowfriction material like Babbitt metal. Oil lubrication is provided to further reduce the friction between shaft and bearing surface and to limit the heat generated. Submitted by Priyanshu DixitD x t . s h a n u @ g m a i l . c o m 1 2
Summer Training Report at IPGCL Figure 7: Block Diagram of a Power Plant Which Utilizes the HRSG Condenser
The surface condenser is a shell and tube heat exchanger in which cooling water iscirculated through the tubes. The exhaust steam from the low pressure turbine enters the shellw h e r e i t i s c o o l e d a n d c o n v e r t e d t o c o n d e n s a t e ( w a t e r ) b y f l o w i n g o v e r t h e t u b e s . S u c h condensers use steam ejectors or rotary motor -driven exhausters for continuous removal of air and gases from the steam side to maintain vacuumFor best efficiency, the temperature in the condenser must be kept as low as practicalin order to achieve the lowest possible pressure in the condensing steam. Since the condenser Submitted by Priyanshu DixitD x t . s h a n u @ g m a i l . c o m 1 3
Summer Training Report at IPGCL temperature can almost always be kept significantly below 100 ο C where the vapour pressureo f w a t e r i s m u c h l e s s t h a n a t m o s p h e r i c p r e s s u r e , t h e c o n d e n s e r g e n e r a l l y w o r k s u n d e r vacuum. Thus leaks of non-condensable air into the closed loop must be prevented. Plantsoperating in hot climates may have to reduce output if their source of condenser cool ingwater becomes warmer; unfortunately this usually coincides with periods of high electricaldemand for air conditioning. The condenser uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a river. Figure 8: A Typical Water Cooled Condenser Figure 9: Showing Exclusive Inside View of Tube Type Condenser Installed at IPGCL Gas Turbine Station Deaerator
Submitted by Priyanshu DixitD x t . s h a n u @ g m a i l . c o m
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Summer Training Report at IPGCL A steam generating boiler requires that the boiler feed water should be devoid of air and other dissolved gases, particularly corrosive ones, in order to avoid corrosion of themetal. Generally, power stations use a deaerator to provide for the removal of air and other d i s s o l v e d g a s e s f r o m t h e b o i l e r f e e d w a t e r . A d e a e r a t o r t yp i c a l l y i n c l u d e s a v e r t i c a l , d o m e d d e a e r a t i o n s e c t i o n
m o u n t e d o n t o p o f a horizontal cylindrical vessel which serves as thedeaerated boiler feedwater storage tank. Figure 10: Deaerator Practical considerations demand that in as t e a m b o i l e r / s t e a m t u r b i n e / g e n e r a t o r u n i t thecirculating steam, condensate, and feed water should be devoid o f d i s s o l v e d g a s e s , particularly corrosive ones, and dissolved or suspended solids. The gases will give rise tocorrosionof the metal in contact thereby thinning them and causing rupture. The solids will d e p o s i t o n t h e h e a t i n g s u r f a c e s g i v i n g r i s e t o l o c a l i s e d h e a t i n g a n d t u b e r u p t u r e s d u e t o overheating. Under some conditions it may give rise to stress corrosion cracking. CoolIngTowers Cooling towers are heat removal devices used to transfer process waste heat to t h e atmosphere.Cooling towers may either use theevaporationof water to remove process heat and cool the working fluid to near thewet-bulb air temperatureor rely solely on air to coolthe working fluid to near thedry-bulb air temperature. Common applications include coolingthe circulating water used in oil refineries, c h e m i c a l p l a n t s ,p o w e r s t a t i o n s and b u i l d i n g c o o l i n g . T h e t o w e r s v a r y i n s i z e f r o m s m a l l r o o f t o p u n i t s t o v e r y l a r g e hyperboloid structures(as in Image 1) thatcan be up to 200 metres tall and 100 metresin diameter, or rectangular structures (as in Image 2) that can be over 40 metres tall and8 0 m e t r e s l o n g . S m a l l e r t o w e r s a r e normally factory-built, while larger ones areconstructed on site. Figure 11: Fan of Induction Type Cooling Tower Submitted by Priyanshu DixitD x t . s h a n u @ g m a i l . c o m 1 5
Summer Training Report at IPGCL Figure 12: Outside View of Cooling towersFigure1 3: Inside Views of Cooling Tower Left Hand and Right Hand Respectively. Submitted by Priyanshu DixitD x t . s h a n u @ g m a i l . c o m 1 6
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