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SYSTEMCirculating Water System Presentation Transcript
SYSTEMCirculating Water System Presentation Transcript
1.Circulating Water System
2.Cooling Water requirement
Bulk requirement of water is used in thermal plants for the purpose of cooling the steam in condensers. The requirement of water for this purpose is of the order of 1.5-to2.0 cusecs/MW of installation.
Where sufficient water is available once through system is used.
Where water supply is not consistent, closed loop cooling system with cooling tower is used.
Bulk requirement of water is used in thermal plants for the purpose of cooling the steam in condensers. The requirement of water for this purpose is of the order of 1.5-to2.0 cusecs/MW of installation.
Where sufficient water is available once through system is used.
Where water supply is not consistent, closed loop cooling system with cooling tower is used.
3.Circulating water scheme
A circulating water pump house
Intake channel
Trash rack
A chlorination plant
Traveling water screen
Connecting pipe line to condenser
Outlet channel
A cooling tower
A circulating water pump house
Intake channel
Trash rack
A chlorination plant
Traveling water screen
Connecting pipe line to condenser
Outlet channel
A cooling tower
4.Circulating water scheme
We shall discuss the open loop system first.
We shall discuss the open loop system first.
5.Function of each component
A circulating water pump house
It houses the main CW pumps. Vertical submergible pump with operating pressure around 1 Kg/ cm2.
The pump house resides on the fore bay.
The fore bay is flooded through intake system.
6.It is RCC open trench from where Raw water is taken through canal/reservoir.
The intake level is normally 10-15 ft. above from flood level of the water source and 12 m in depth.
7.Once through system
Chemical dosing done for disabling micro organism development inside the tube.
Condenser is fitted with 4 way valve to enable reverse flow through condenser when required.
Hot water coming out from condenser is allowed to pass through long outlet channel to get cool down before meeting the main stream of water.
Performance of condenser mainly depends on Inlet temp. to the condenser, Condenser tube fouling, Air ingress in condenser etc.
A circulating water pump house
It houses the main CW pumps. Vertical submergible pump with operating pressure around 1 Kg/ cm2.
The pump house resides on the fore bay.
The fore bay is flooded through intake system.
6.It is RCC open trench from where Raw water is taken through canal/reservoir.
The intake level is normally 10-15 ft. above from flood level of the water source and 12 m in depth.
7.Once through system
Chemical dosing done for disabling micro organism development inside the tube.
Condenser is fitted with 4 way valve to enable reverse flow through condenser when required.
Hot water coming out from condenser is allowed to pass through long outlet channel to get cool down before meeting the main stream of water.
Performance of condenser mainly depends on Inlet temp. to the condenser, Condenser tube fouling, Air ingress in condenser etc.
8.Types of CW systems
9.Hot Pond:
Hot Water from the condenser discharged to hot pond and provide source for the CT pump.
CT Pump
It takes suction from the Hot pond and discharged the water to the riser tubes of Cooling towers
Hot Water from the condenser discharged to hot pond and provide source for the CT pump.
CT Pump
It takes suction from the Hot pond and discharged the water to the riser tubes of Cooling towers
10. Cooling Tower - Introduction
A cooling tower is an air and water management device, which consists of fan stacks, fans, drift eliminators, fill and water/air distribution systems.
It uses principle of evaporation of water in unsaturated air.
A cooling tower is an air and water management device, which consists of fan stacks, fans, drift eliminators, fill and water/air distribution systems.
It uses principle of evaporation of water in unsaturated air.
11. Cooling tower is the most important equipment for closed cycle water recirculation system.
The efficiency of cooling tower has direct effect on condenser vacuum and in turn, the heat rate of the station.
1oC rise in cold water temperature in a 200MW unit corresponds to 5mm vacuum loss leading to 7.5 Kcal/kwh loss in heat rate and in 500MW, 5.74 Kcal/kwh loss in heat rate..
The efficiency of cooling tower has direct effect on condenser vacuum and in turn, the heat rate of the station.
1oC rise in cold water temperature in a 200MW unit corresponds to 5mm vacuum loss leading to 7.5 Kcal/kwh loss in heat rate and in 500MW, 5.74 Kcal/kwh loss in heat rate..
12. Types of cooling Tower
Wet type
Dry type
Wet type cooling towers are two type
1.natural draft
2.mechanical draft
Mechanical draft may be devided in to two type
1.forced draft
2.induced draft
Both of these can be counter flow type or cross flow type.
Wet type
Dry type
Wet type cooling towers are two type
1.natural draft
2.mechanical draft
Mechanical draft may be devided in to two type
1.forced draft
2.induced draft
Both of these can be counter flow type or cross flow type.
13. Cooling Tower – in NTPC Ltd.
14. There are 75 cooling towers in operation in NTPC.
Induced Draught Cooling Towers
Cross flow type 24
Counter flow splash bar fill type 21
Counter flow film fill type 20
Natural Draught Cooling Towers
Natural draught type. 08
15.NATURAL DRAFT C.T.
It produces air flow through utilization of stack or chimney effect.pressure diff. causing air flow is given by p (pr head developed)=(p outer-p inner).H.g
The fill is located in the lower portion of shell with upper 85 to 90% of shell empty which is used to create chimney effect.
They are more suitable in the area of high relative humidity and low temp.
They may be of cross flow or counter flow.
16.MECHANICAL DRAFT C.T.
Forced draft
Advantage:-fan is subjected to less severe condition
Disadvantage:-recirculation more
Induced draft
Advantage:-min recirculation
Disadvantage:-fan is subjected to warm humid condition.
Induced Draught Cooling Towers
Cross flow type 24
Counter flow splash bar fill type 21
Counter flow film fill type 20
Natural Draught Cooling Towers
Natural draught type. 08
15.NATURAL DRAFT C.T.
It produces air flow through utilization of stack or chimney effect.pressure diff. causing air flow is given by p (pr head developed)=(p outer-p inner).H.g
The fill is located in the lower portion of shell with upper 85 to 90% of shell empty which is used to create chimney effect.
They are more suitable in the area of high relative humidity and low temp.
They may be of cross flow or counter flow.
16.MECHANICAL DRAFT C.T.
Forced draft
Advantage:-fan is subjected to less severe condition
Disadvantage:-recirculation more
Induced draft
Advantage:-min recirculation
Disadvantage:-fan is subjected to warm humid condition.
17.Counter flow :-fill is arranged over entire tower plan.fill is typically film type.
Advantage:-more thermal efficiency, smallest tower,lower capital cost, lower pumping head
Disad:-increased pressure drop requires more horse power of fan.
Cross flow:-fill is arranged at the outer perimeter.
Advantage:-large air inlet area hence pressure drop is less.
Disad:-high pumping head due to more height of fill.
Advantage:-more thermal efficiency, smallest tower,lower capital cost, lower pumping head
Disad:-increased pressure drop requires more horse power of fan.
Cross flow:-fill is arranged at the outer perimeter.
Advantage:-large air inlet area hence pressure drop is less.
Disad:-high pumping head due to more height of fill.
18.1.Rectangular type:-each cell indentical, more long area required, low capital cost,for plant upto 250mw.
2.Round type:-less recirculation, more capital cost,for plant more than 250mw.
19.Cooling Tower Thermal Design
Parameters are used to develop the tower design :
Water flow rate
Cooling range
Design Heat load
Design Wet-bulb temperature.
Recirculation and interference
DBT and relative humidity
2.Round type:-less recirculation, more capital cost,for plant more than 250mw.
19.Cooling Tower Thermal Design
Parameters are used to develop the tower design :
Water flow rate
Cooling range
Design Heat load
Design Wet-bulb temperature.
Recirculation and interference
DBT and relative humidity
20. DESIGN HEAT LOAD
Condenser and c.t. are designed on the basis of MCR load point.
Condenser and c.t. are designed on the basis of MCR load point.
21. Design Wet-bulb Temperature
The impact the design wet-bulb temperature has on the size and power requirements of a cooling tower is critical to optimizing the cooling tower economics.
In the majority of applications, the design duty of an evaporative cooling tower is based upon an acceptable/required cold water return temperature
If investment and operational costs were not a concern, the ideal design wet-bulb temperature would be equal to, or higher than, the highest local wet-bulb temperature recorded.
In this way, the returned water temperature would never be higher than the acceptable/required cold water temperature.
Design W.B.T.=DESIGN AMBIENT D.B.T.-RECIRCULATION ALLOWANCE.
The impact the design wet-bulb temperature has on the size and power requirements of a cooling tower is critical to optimizing the cooling tower economics.
In the majority of applications, the design duty of an evaporative cooling tower is based upon an acceptable/required cold water return temperature
If investment and operational costs were not a concern, the ideal design wet-bulb temperature would be equal to, or higher than, the highest local wet-bulb temperature recorded.
In this way, the returned water temperature would never be higher than the acceptable/required cold water temperature.
Design W.B.T.=DESIGN AMBIENT D.B.T.-RECIRCULATION ALLOWANCE.
22. Component Design : Fills
The component most likely to provide improvement in tower performance is the fill packing.
The earliest and most common designs utilized splash type fills
Film type counter flow designs using relatively low cost PVC materials.
The new film type designs provide energy savings both in fan power and pump head through the high surface areas per cubic feet of fill.
The component most likely to provide improvement in tower performance is the fill packing.
The earliest and most common designs utilized splash type fills
Film type counter flow designs using relatively low cost PVC materials.
The new film type designs provide energy savings both in fan power and pump head through the high surface areas per cubic feet of fill.
23. TYPES OF FILLS
Splash type consisting of splash
Bars used for crossflow and
Counterflow.
Film type consisting of thin film of
Sheets used mostly for counterflow
Splash type consisting of splash
Bars used for crossflow and
Counterflow.
Film type consisting of thin film of
Sheets used mostly for counterflow
24. FILM FILLS
Film fill consists of flat or formed sheets to provide a surface upon which water and air come in contact for heat exchange.
Film fill consists of flat or formed sheets to provide a surface upon which water and air come in contact for heat exchange.
25. Drift Eliminators
A cooling tower drift eliminator is a low pressure, momentum filter.
Components are arranged to force the air leaving the fill section to make a series of directional changes.
Water droplets, which cannot negotiate these turns, impinge on the surface of the eliminator, from which they are collected and drained back into the wet side of the tower.
The designer's goal is to provide the maximum drift elimination at reasonable cost and minimum pressure loss.
The design of drift eliminators has undergone tremendous improvement in the last decade.
New eliminator configurations accomplish this improvement while actually reducing eliminator pressure losses
A cooling tower drift eliminator is a low pressure, momentum filter.
Components are arranged to force the air leaving the fill section to make a series of directional changes.
Water droplets, which cannot negotiate these turns, impinge on the surface of the eliminator, from which they are collected and drained back into the wet side of the tower.
The designer's goal is to provide the maximum drift elimination at reasonable cost and minimum pressure loss.
The design of drift eliminators has undergone tremendous improvement in the last decade.
New eliminator configurations accomplish this improvement while actually reducing eliminator pressure losses
26. Cellular eliminators are typically constructed of PVC sheets vacuum formed into very precise, compound shapes, with an integral honeycomb strength. The compound shape allows significant improvements in drift eliminations and the use of cellular structure appreciably reduces the pressure losses through the eliminator when compared to either the wood lath or wave form eliminators.
The net free are of well-designed, modern cellular eliminators is in excess of 95%.
The net free are of well-designed, modern cellular eliminators is in excess of 95%.
27. Air-Water Distribution System Design
Water Distribution:
Assured performance is a function of nozzle design, nozzle installation pattern, nozzle distance, and the structural cleanliness of the spray chamber.
To provide the primary function of precise water distribution, the nozzle must be designed with other considerations in mind:
The location of counter flow nozzles and the potential for poor quality circulating water demands that the nozzle system be designed to minimize fouling.
The nozzle must be capable of providing uniform distribution over a wide range of flows, without significant loss in nozzle performance.
The nozzle must be capable of efficient operation while consuming a minimum of expensive pump energy.
Water Distribution:
Assured performance is a function of nozzle design, nozzle installation pattern, nozzle distance, and the structural cleanliness of the spray chamber.
To provide the primary function of precise water distribution, the nozzle must be designed with other considerations in mind:
The location of counter flow nozzles and the potential for poor quality circulating water demands that the nozzle system be designed to minimize fouling.
The nozzle must be capable of providing uniform distribution over a wide range of flows, without significant loss in nozzle performance.
The nozzle must be capable of efficient operation while consuming a minimum of expensive pump energy.
28.2) Air Distribution: Three variables control the distribution of air to the fill in a counter flow configuration.
The first is the air inlet geometry.
Pressure Ratio : The pressure ratio reflects the ratio of resistance to available entering air energy. The higher the ratio, the better entering air will be spread out before entering the fill. The lower the pressure ratio, the less uniform, and less stable the distribution of air flow becomes. The degradation of air flow uniformity is readily apparent, particularly at the inlet.
(Pressure Ratio = Static Pressure / Velocity Pressure at Air Inlet)
The third is the fan coverage over the eliminators
The first is the air inlet geometry.
Pressure Ratio : The pressure ratio reflects the ratio of resistance to available entering air energy. The higher the ratio, the better entering air will be spread out before entering the fill. The lower the pressure ratio, the less uniform, and less stable the distribution of air flow becomes. The degradation of air flow uniformity is readily apparent, particularly at the inlet.
(Pressure Ratio = Static Pressure / Velocity Pressure at Air Inlet)
The third is the fan coverage over the eliminators
29.Fan Design
Each fan has only one design point which is established by a specific air flow, total pressure, air density, and fan speed.
The factors that must be known when replacing a fan on an existing installation are:
Fan diameter.
Installed motor horsepower.
Gear reduction ratio of gear reducer.
Shaft size or gear reducer model.
Some estimate of elevation above sea level of installation.
Each fan has only one design point which is established by a specific air flow, total pressure, air density, and fan speed.
The factors that must be known when replacing a fan on an existing installation are:
Fan diameter.
Installed motor horsepower.
Gear reduction ratio of gear reducer.
Shaft size or gear reducer model.
Some estimate of elevation above sea level of installation.
30.Cooling Tower Performance
31. Cooling Tower Performance
Cooling Tower Effectiveness=Actual Cooling/Maximum Cooling Possible =Range/(Range +Approach)
Cooling Tower Capacity = mass flow rate X specific Heat x Temperature Difference
Evaporation Loss in cub mtr/Hr = 0.00085x1.8xcirculation rate x Temperature Diff.
Cycle of Concentration = Dissolve solid in circulating water/Dissolve solid in make up water
Blow Down =1-1.5 percent of total water flow
To replenish the losses make up water 2-2.5% of water flow is added
Cooling Tower Effectiveness=Actual Cooling/Maximum Cooling Possible =Range/(Range +Approach)
Cooling Tower Capacity = mass flow rate X specific Heat x Temperature Difference
Evaporation Loss in cub mtr/Hr = 0.00085x1.8xcirculation rate x Temperature Diff.
Cycle of Concentration = Dissolve solid in circulating water/Dissolve solid in make up water
Blow Down =1-1.5 percent of total water flow
To replenish the losses make up water 2-2.5% of water flow is added
32. COOLING TOWER(BTPS)
33.MOTOR
34.COOLING TOWER
35.MOTORS
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