### How do you calculate power plant efficiency???

Efficiency of the power plant is calculated based on heat input and out put.

Power plant efficiency = Heat out put X 100 / Heat out put

In power plant, generally heat input is fuel, make up water and condensate return water from process.

Heat out put is power generation.

The formula for efficiency calculation is different for different plants.

Efficiency of the power plant is given as

Efficiency = 860 X 100 / Heat rate

1-For thermal power plants efficiency is calculated as;

Efficiency = 860 X Power generation / Heat input

Efficiency = 860 X PG X 100 / (Fuel consumption X Fuel GCV)

2-For co generation plants heat rate is calculated as;

Efficiency = 860 X Power generation X 100 / (Fuel consumption X GCV + Make up water X Make up water enthalpy + Return condensate water X Enthalpy-Process steam flow X Enthalpy)

3-Cogen plant Efficiency is also calculated as;

Efficiency = 860 X Boiler efficiency X 100 / Turbine heat rate

Calculation:

1.Calculate the efficiency of power plant having heat rate 3451 Kcal/kwh

Efficiency of the power plant = 860 X 100 / Heat rate

Efficiency of the power plant = 860 X 100 / 3451

Efficiency of the power plant = 24.92%

Read power plant O&M reference books

2.A 75 MW Thermal power plant consumes 1100 MT coal per day, calculate the plant efficiency, consider the GCV of coal 5000 Kcal/kg

Efficiency of the plant = 860 X 24 X 75 X 100 / (1100 X 5000)

Efficiency of the plant = 28.15%

3. A 29 MW thermal power plant is having Turbine of heat rate 2798 kcal/kwh, which consumes steam at the rate of 4.2 MT/MW from a boiler having efficiency 69%.Calculate the efficiency of power plant

Efficiency = 860 X Boiler efficiency X 100 / Turbine heat rate

Efficiency = 860 X 0.69 X 100 / 2798

Efficiency = 21.2%

4. A 30 MW biomass Co generation plant consumes 1750 MT fuel per day and supplies 2880 TPH steam to process at pressure 2 kg/cm2 & 135 deg C, in turn receives 90% return condensate at 119 deg C temperature.The make up water for this plant is 610 m3 at temperature 27 deg C.Calculate the efficiency of the plant, consider GCV of biomass fuel 2250 kcal/kg.

Efficiency of Co-gen plant  = 860 X Power generation X 100 / (Fuel consumption X GCV + Make up water X Make up water enthalpy + Return condensate water X Enthalpy-Process steam flow X Enthalpy)

Enthalpy of process steam at 2 kg/cm2 and 135 deg C is 652 kcal/kg

Enthalpy of return condensate water is 121 kcal/kg

Enthalpy of make up water at 27 deg C is 27.2 kcal/kg

Efficiency of Co-gen plant  = 860 X 30 X 24 X 100 / (1750 X 2250 + 610 X 27.2 + 2880 X 80% X 121 X 2880 X 652)

Efficiency of Co-gen plant  = 860 X 30 X 24 X 100 / (1750 X 2250 + 610 X 27.2 + 2880 X 80% X 121 - 2880 X 652)

Efficiency of Co-gen plant = 26.29%

5. A thermal power plant operating at 125 MW operating  at pressure 110 kg/cm2 and temperature 545 deg C.A AFBC boiler of efficiency 84% consumes 379 TPH Feed water at temperature 200 degC to generate 375 TPH steam.Calculate the efficiency of the thermal power plant.

We have, Turbine heat rate = (Inlet steam flow X Enthalpy-Feed water flow X Enthalpy) / Power generation

Turbine heat rate = 375 X 821-379 X 202) / 125

Turbine heat rate = 1850.5 kcal/kwh

Turbine efficiency = 860 X 100 / 1850.5

Turbine efficiency = 46.5%

Power plant efficiency = Turbine efficiency X Boiler efficiency = 46.5 X 0.84 =39.06%

For more calculations read Powerplant and calculations

# Practical Approach to Power Plant Operation and Maintenance

### How do you calculate the efficiency of pumps???

How do you calculate the efficiency of a pump?

Efficiency of the pump is the ratio of output power to the input power

Pump efficiency = Output power X 100 / Input power

Centrifugal pumps efficiency varies from 40% to 95% well.

Pump efficiency is equal to the power of the water/liquid produced by the pump divided by the pump’s shaft power input.

A pump’s output power is determined by how much water and how much pressure it delivers

On what factors pumps efficiency depends on?

Pumps efficiency depends on

• In put power
• Output power
• Type of liquid
• Fluid temperature
• Flow
• Losses & leakages
• Fluid viscosity
• Pumps internal frictions

What do you mean by volumetric efficiency of a pump?

It is the ratio of actual flow delivered by the pump to the theoretical flow

How do you calculate the Mechanical or hydraulic efficiency of the pump?

Mechanical/Hyd.efficiency = Pump output power X 100 / Pump input power or pump shaft power

Mechanical efficiency is also calculated as

= Theoretical torque required to drive the pump X 100 / Actual torque provided to drive the pump

Calculations:

A centrifugal pump delivers 0.2 m3/sec flow at total head 27 m, calculate its hydraulic power. Assume density of water 995 kg/m3

Pump hydraulic power = Pump flow in m3/sec X pump total head in meter X Fluid density in kg/m3 X 9.81 m/sec2 / 1000

Pump hydraulic power = 0.2 X 27 X 995 X 9.81 / 1000

Pump hydraulic power = 52.7 KW

A centrifugal pump of capacity 0.05 m3/sec flow has to lift the water from 3.5 m deep well & has to discharge the water at 45 meter height. Calculate the pump efficiency if its shaft power is 30 KW

Assume water density 998 kg/m3

Pump hydraulic power = Pump flow in m3/sec X pump total head in meter X Fluid density in kg/m3 X 9.81 m/sec2 / 1000

Total head H = 45 + 3.5 = 48.5 meter

Pump hydraulic power = 0.05 X 48.5 X 998 X 9.81 / 1000

Ph = 23.74 KW

Pump efficiency =Pump hydraulic power X 100 / Pump shaft power

Pump efficiency =23.74 X 100 / 30

Pump efficiency =79.13%

A centrifugal pump of delivering  0.65 m3/sec flow at 75 meter discharge head, pump has positive suction head around 2.7 meter from overhead tank.Pump efficiency is 59%, calculate the motor input power if efficiency power if efficiency of motor is 92.5%.

Assume water density 1000 kg/m3

Pump hydraulic power = Pump flow in m3/sec X pump total head in meter X Fluid density in kg/m3 X 9.81 m/sec2 / 1000

Total head H = 75 -2.7 = 72.3 meter

Pump hydraulic power = 0.65 X 72.3 X 1000 X 9.81 / 1000

Ph = 461 KW

Pump efficiency =Pump hydraulic power X 100 / Pump shaft power = Ph X 100 / Ps

59 =461 X 100 / Ps

Ps = 781.35 KW

Motor efficiency = Pump shaft power X 100 / Motor input power =Ps X 100 / Pm

92.5 = 781.35 X 100 / Pm

Pm = 844.7 KW

A centrifugal pump of efficiency 63% develops hydraulic power 27.5 KW, calculate the motor efficiency if motor input power is 45 KW

Pump shaft power, Ps = Pump hydraulic power Ph / Efficiency of pump

Ps = 27.5 / 0.63 =43.65 KW

Motor efficiency = Pump shaft power X 100 / Motor input power

Motor efficiency= 43.65 X 100 / 45

Motor efficiency = 97%

For more articles on power plant Read

# Practical Approach to Power Plant Operation and Maintenance

### How to calculate ESP efficiency??

On what factors ESP efficiency depends on?

ESP efficiency depends on following factors.

• Dust collection area of ESP
• Dust particles size
• Dust or flue gas volume
• Resistivity of dust particles present in flue gas

What do you mean by Corona Power ratio?

Corona power ratio is the ratio of power consumed in watts to the flue gas flow in cubic feet per minute.

Corona power ratio = Power consumed by ESP in watts / Flue gas flow in CFM

This tells us about the energy consumed in filtering one cubic foot of flue gas per minute. The corona power ratio affects the efficiency of an electrostatic precipitator. Higher the corona power ratio, higher is the efficiency of the electrostatic precipitator

What do you mean by specific collecting area (SCA) & how do you calculate it?

It is the ratio of total collecting surface area of the ESP to the flue gas flow rate

SCA = Total collection area in m2 / Gas flow rate in m3/sec

SCA = m2/m3/sec

What do you mean by Aspect ratio in ESP?

It is the ratio of length of ESP to its Height

It should be in the range of 0.5 to 2

Calculation:

Calculate the aspect ratio of an ESP of total length 12 meter having its collecting plates height 11 meter.

Aspect ratio (AR) = Length of ESP / Height of ESP

Aspect ratio (AR) = 12/11 =1.09.

What is the treatment time in ESP having flue gas flow rate 90 m3/sec at velocity 0.7 m/sec.ESP having total 4 nos of fields each of length 3.5 meter.

We have, total length of ESP = 3.5 X 4 = 14 meter

Velocity of flue gas in ESP = 0.7 m/sec

So, total Treatment time for flue gas = 14 / 0.7 =20 seconds

Read power plant O&M reference books

An ESP consumes 7 KW power for treating flue gas of 17 m3/sec, calculate its Corona power ratio.

Corona power ratio = Power consumed by ESP in watts / Flue gas flow in CFM

We have flue gas flow = 17 m3/sec = 599.9 X 60= 35994 CFM

CPR = 7000 / 35994 = 0.2

An ESP handles total flue gas at the rate of 61920 m3 /h., its specific collecting surface area is 131.9 m2/m3/sec, calculate the efficiency of ESP if ash particles migration velocity is 5.46 cm/sec.

Solution:

Given that,

Flue gas flow in ESP, Q = 61920 m3/hr / 3600 = 17.2 m3/sec

Total collecting area A= 131.9 X 17.2 =2268.68 m2

Migration velocity of dust particles, V = 5.46/100 = 0.0546 m/sec

Efficiency of ESP = 1–eˆ (-AV/Q) X 100

= 1– eˆ (-2268.68 X 0.0546/17.2) X 100

ηESP = 99.92%

Read more>>> for such calculations powerplant & Calculations

### How do you calculate the efficiency of Economiser in Boiler??

What is the Economiser in power plants?

It’s the heat exchanger used in Boilers to recover the heat from exhaust flue gases.

What are the functions of economisers in Boilers?

Functions of economisers:

It recovers the heat from flue gas leaving the boiler, there by reduces the losses

It helps in raising the feed water temperature, there by reduces the fuel consumption

It increases the Boiler efficiency

It lowers the power plant operation cost

What are the different types of economisers?

Types of economisers

Pressurized economisers

Non pressurized economisers

Steaming type

Non steaming pipe

What do you mean by steaming type economisers?

Economisers where only sensible heat is added to feed water

What do you mean by non-steaming type economisers?

Economisers where sensible heat and part of latent is added to feed water

Efficiency Calculations:

 ηEco. = (Economiser outlet feed water temperature Two-Economiser inlet feed water temperature Twi)  X 100 / (Economiser inlet flue gas temperature Tfi- Economiser inlet feed water temperature Twi)

Example:

Calculate the economiser effectiveness, whose feed water inlet & outlet temperatures are 160 Deg C & 240 Deg C respectively & flue gas inlet & outlet temperatures 390 deg C & 220 deg c respectively.

Solution:

Twi = 160 deg C

Two = 240 deg C

Tfi = 390 deg C

Tfo = 220 deg C

ηEco = (Two-Twi) X 100 / (Tfi-Twi)

ηEco = (240-160 ) X 100 / (390-160)

ηEco= 34%

In an non steaming economiser of efficiency 51%, feed water inlet and outlet temperatures are 105 deg c & 160 deg C respectively, calculate the flue gas temperature entering the economiser

Solution:

Twi = 105 deg C

Two = 160 deg C

Tfi = 370 deg C

Tfo = ? deg C

ηEco= 51%

ηEco = (Two-Twi) X 100 / (Tfi-Twi)

51= (160-105 ) X 100 / (Tfi-105)

Tfi X 51-105 X51 = 5500

Tfi = 212.8 deg C

A economiser inlet feed water & flue gas temperature are 125 deg C and 405 deg C respectively, calculate the feed water leaving the economiser, consider efficiency of economiser 43%

Solution:

Twi = 125 deg C

Two = ? deg C

Tfi = 405 deg C

ηEco= 43%

ηEco = (Two-Twi) X 100 / (Tfi-Twi)

43= (Two-125 ) X 100 / (405-125)

12040 = 100 X Two-12500

Two = 245.4 deg C

For more calculations related to power plant read Powerplant & Calculations

### How do you calculate the efficiency of Air pre heater (APH) in Boilers??

APH is an auxiliary used in steam generators or boilers to increase the Boiler efficiency and to reduce the fuel consumption.

There are different types of air heaters. Major types are tubular & regenerative air preheater.

These may be installed horizontally or vertically as per requirement.

In some design of APH air flows outside the tubes and flue gas inside the tubes where as in some cases air flows inside the tubes and flue gas outside of the tubes.

The main functions of APH is to reduce the flue gas temperature to allowable limit that is coming out from Boiler and to increase combustion air temperature.

The efficiency of the APH are calculated from two ways one is from air side other from gas side.

APH gas side efficiency

ηAPHg = (Flue gas inlet temp.Tfi-Flue gas outlet temp.Tfo) X 100 / (Flue gas inlet temperature tfi-Air inlet temperature Tai)

APH air side efficiency

ηAPHa = (Air outlet temp.Tao-Air inlet temp.Tao)) X 100 / (Flue gas inlet temperature tfi-Air inlet temperature Tai)

Calculate the APH gas side & air efficiency if its flue gas inlet and out let temperature are 230 deg C and 145 deg C and air inlet and out let temperatures are 28 deg C & 180 deg C respectively.

ηAPHg = (Flue gas inlet temp.Tfi-Flue gas outlet temp.Tfo) X 100 / (Flue gas inlet temperature tfi-Air inlet temperature Tai)

ηAPHg =(230-145) X 100 / (230-28)

ηAPHg = 42.1%

ηAPHa = (Air outlet temp.Tao-Air inlet temp.Tao)) X 100 / (Flue gas inlet temperature tfi-Air inlet temperature Tai)

ηAPHa = (180-28) X 100 / (230-28)

ηAPHa = 75.24%

A Tubular type APH is having air side efficiency 79%, its flue gas and air inlet temperature are 225 deg and 30 deg C respectively, calculate the APH outlet air temperature

We have,

ηAPHa = (Air outlet temp.Tao-Air inlet temp.Tao)) X 100 / (Flue gas inlet temperature tfi-Air inlet temperature Tai)

79% = (Tao-30) X 100 / (225 – 30)

Tao-30 = 0.79 X 195

Tao = 184.05 deg C

A Tubular type APH is having gas side efficiency 39%, its flue gas and air inlet temperature are 225 deg and 30 deg C respectively, calculate the APH outlet flue gas temperature

We have,

ηAPHg = (Flue gas inlet temp.Tfi-Flue gas outlet temp.Tfo) X 100 / (Flue gas inlet temperature tfi-Air inlet temperature Tai)

39% = (225-Tfo) X 100 / (225-30)

0.39 X 195 = 225-Tfo

Tfo = 148.95 deg C

### Reasons for Priming, Foaming and carryover in Boilers

Priming:

1. What do you mean by the term Priming?

Priming means carryover of water particle in the steam

2. What are the reasons for Priming?

Reasons for priming;

• Improper design of Boiler and steam drum
• Maintaining high drum level
• Sudden load raise due to steam demand
• Foaming in feed water
• Miss operation of Boiler
• Sudden lifting of Boiler safety valve or start up vent CV
• More impurities in Boiler water

3. What are the impacts of Priming?

Impacts of Priming;

• Lower steam efficiency
• Water hammering
• Super heater coil failure due to thermal shock
• Turbine high vibration & blade failure

How do you avoid priming in Boilers?

Priming can be avoided by;

• Proper operation of boiler
• Maintaining drum level in between 45 to 55%
• Avoiding foaming
• Proper designing of Boiler

Carryover:

What do you mean by the term carryover?

Carryover is the carryover of solid, liquid & gaseous contaminants with water and steam leaving the drum due to incomplete separation of water and steam in steam drum.

What are the major reasons for carryover?

Reasons for carryover;

• Defects in steam and water separators
• Foaming
• Higher drum level
• Boiler steam drum construction defects

What are the effects of carryover on Boiler components?

Contamination in steam leads to deposition of solid scale on Super heater coils & control and regulating valves.

Foaming:

What do you mean by the term foaming?

Foaming is the formation of unbroken bubbles on the surface of the boiler water inside the boiler drum.

The bubbles may be in thin layer with few bubbles overlying each other or it may build up throughout the steam space.

What are the reasons for foaming?

•  High suspended solid concentration
•  High alkalinity concentration
•  High dissolved solid concentrations in the boiler water
•  Oil and organic contaminants in the boiler water
• High impurities
• High dosage of chemicals
• High water level

How do you avoid foaming?

• Timely blow down & maintaining desired water quality
• Maintaining constant load on Boiler
• Avoiding high water level
For more articles read Power plant and calculations