How do you calculate the Deaerator & HP heaters steam consumption???

DEAERATORS:

What is the function of Deaerator?

Functions of deaerator

To remove the dissolved oxygen from deaerator & bringing down to <0.005 ppm

To heat the feed water

To provide NPSH to Boiler feed pumps

Acts as surge for feed water storage device

2-Which steam is used for deaerator?

Saturated steam having pressure from 0.3 to 3 kg/cm2 and temperature 130 deg C to 200 deg C

3-What are the pipe lines connected to Deaerator & storage tank?

Inlet lines:

Make up water line

Condensate water line from CEP

Return condensate water from process

Recirculation water line from BFP

Balance leak off water lines from BFP

Condensate water from HP & LP heaters

Steam line from turbine extraction or PRDSH

Out let lines:

Feed water line to BFP suction

Deaerator overflow line

Deaerator storage tank drain line

Understanding with examples.

1-Calculate the steam consumption of deaerator based on following given data

Sl No.

Particular

UOM

Value

 

1

LP steam flow to deaerator at pressure 1.5kg/cm2G & temperature 135 deg C t

TPH

 

?

 

2

Feed water outlet temperature from deaerator

0C

 

105

 

3

Feed water outlet flow from deaerator

TPH

 

     125

 

4

CEP water flow to deaerator at temperature 50 deg C flow

TPH

 

120

 

5

Make up water to deaerator at temperature 25 deg C

TPH

 

5

        

 

 

 

 

 

 

 

 

 

Solution:

Enthalpy of steam at pressure 1.5 kg/cm2 & temperature 135 deg C = 653 kcal/kg

Enthalpy of CEP water at temperature 50 deg C = 50 kcal/kg

Enthalpy of makeup water at temperature 25 deg C = 25 kcal/kg

Enthalpy of deaerator outlet feed water = 106 kcal/kg

Mass of steam = (Feed water flow X Enthalpy –CEP flow X Enthalpy-Makeup water X Enthalpy) / (Enthalpy of steam-Enthalpy of deaerator outlet water)

Mass of steam      = 125 X 106 -120 X 50 -5 X 25 / (653-106)

Mass of steam = 13.02 MT

Read top-6-Power plant O&M books

2-Calculate the steam consumption of deaerator based on following given data

Sl No.

Particular

UOM

Value

 

1

LP steam flow to deaerator at pressure 2.5 kg/cm2G & temperature 150 deg C t

TPH

 

?

 

2

Feed water outlet temperature from deaerator

0C

 

128

 

3

Feed water outlet flow from deaerator

TPH

 

     210

 

4

CEP water flow to deaerator at temperature 45 deg C flow

TPH

 

30

 

5

Make up water to deaerator at temperature 25 deg C

TPH

 

20

6

Process return condensate at temperature 95 deg C

TPH

160

        

 

 

 

 

 

 

 

 

 

 

 Solution:

Enthalpy of steam at pressure 2.5 kg/cm2 & temperature 150 deg C = 658.4 kcal/kg

Enthalpy of CEP water at temperature 45 deg C = 45 kcal/kg

Enthalpy of makeup water at temperature 25 deg C = 25 kcal/kg

Enthalpy of deaerator outlet feed water = 129 kcal/kg

Enthalpy of return condensate water = 96 kcal/kg

Mass of steam = (Feed water flow X Enthalpy –CEP flow X Enthalpy-Makeup water X Enthalpy-Return condensate X Enthalpy) / (Enthalpy of steam-Enthalpy of deaerator outlet water)

Mass of steam      = (210 X 129 -30 X 45 -20 X 25-160 X 96) / (658.4-129)

Mass of steam = 18.66 MT

HP & LP heaters:











1-What are the applications of HP & LP heaters?

HP & LP heaters are used to heat the feed water & to improve the cycle efficiency

 

2-What are the various pipe lines connected to HP heaters?

Inlet lines:

1-Feed water inlet line

2-Bleed steam line from Turbine

Outlet lines:

1-Feed water outlet line

2-Condensate outlet line

Understanding with examples.

A HP heater is used to heat the 105 TPH feed water from 105 °C to 150 °C by using turbine bleed steam at 8 kg/cm2 and 200 °C. The condensate returning from heater is at 125 °C, calculate the quantity of steam used.

 Given that,

Qf = 105 TPH

Tf1 = 105 °C

Tf2 = 150 °C

Hg at pressure 8 kg/cm2 & temperature 200 °C =677 kcal/kg

Enthalpy of condensate water Hf = 126 kcal/kg

Heat lost by the steam = Heat gained by feed water

Ms X (Hg-Hf) = Mw X (Tf2-Tf1)

Ms X (677-126) = 105 X (150-105)

Ms = 8.57 TPH

 

For such posts Pl.read

How to calculate the cost of steam???

 

In power plant, calculation of cost of steam is very vital in commercial point of view. Following are the parameters which affect the cost of steam.

  1. Steam pressure
  2. Steam temperature
  3. GCV of fuel
  4. Price of fuel
  5. And Boiler efficiency

Following gives you the relation among steam cost & above all parameters & vice versa

  • Steam cost increases as the enthalpy or heat content in steam increases and vice versa
  • Steam cost increases as the GCV of fuel decreases and vice versa
  • Steam cost increases as the fuel price increases & vice versa
  • Steam cost increases as the Boiler efficiency decreases & vice versa

Understanding with examples.

1.Calculate the cost of steam per kg, which is been using for Steam turbine having pressure 121 kg/cm2 & temperature 550 deg C.The boiler of efficiency 75% uses coal of GCV 4200 kcal/kg to produce this steam.Cosnsider the price of coal is Rs 5000/MT

Enthalpy of steam at above pressure & temperature H = 830.43 kcal/kg

Boiler efficiency b= 75%

GCV of coal = 4200 kcal/kg

Now, cost of steam = Heat content in steam in kcal/kg  X Fuel price / (GCV of fuel in kcal/kg X Boiler efficiency b)

                                     = 830.43 X 5000 / (4500 X 0.75)

                                     = 1230.26 rupees / MT of steam or Rs 1.23 / kg of steam

 2.Calculate the cost of steam per kg, which is been using for chemical process plant having pressure 5 kg/cm2 & temperature 180 deg C.The boiler of efficiency 65% uses biomass of GCV 2800 kcal/kg to produce this steam.Cosnsider the price of biomass is Rs 2400/MT

Enthalpy of steam at above pressure & temperature H = 670 kcal/kg

Boiler efficiency b= 65%

GCV of coal = 2800 kcal/kg

Now, cost of steam = Heat content in steam in kcal/kg X Fuel price / (GCV of fuel in kcal/kg X Boiler efficiency b)

                                     = 670 X 2400 / (2800 X 0.65)

                                     = 883.51 rupees / MT of steam or Rs 0.88 / kg of steam

3. Calculate the cost of saturated steam given to sugar process for juice boiling plant having pressure 1.5 kg/cm2 & temperature 130 deg C.The boiler of efficiency 68% uses bagasse (biomass) of GCV 2200 kcal/kg to produce this steam.Cosnsider the price of biomass is Rs 2500/MT

Enthalpy of steam at above pressure & temperature H = 650 kcal/kg

Boiler efficiency b= 68%

GCV of coal = 2200 kcal/kg

Now, cost of steam = Heat content in steam in kcal/kg X Fuel price / (GCV of fuel in kcal/kg X Boiler efficiency b)

                                     = 650 X 2500 / (2200 X 0.68)

                                     = 1086.22 rupees / MT of steam or Rs 1.086 / kg of steam

 

 Deaeartor & HP heaters steam consumption calculations

 

 Questions & Answers on steam blowing

 

Questions & Answers on Boiler Hydraulic test











1-According to which law or regulation Boiler hydraulic tests are conducted?

Boilers hydraulic tests are conducted as per IBR 1950 Regulation 379

2-Why do Boilers Hydraulic tests are conducted?

  • To ensure there is no leakages in joints after erection & welding works
  • To ensure the healthiness of pressure parts & correctness of workmanship
  • To identify the weakness & defect of pressure parts
  • To complete the compliance of Boiler inspector authority
  • To avoid any incidents during boiler start up or operation

3-When shall you conduct Boiler Hydraulic tests?

Boiler Hydraulic tests are carried out;

  • After erection of new Boiler
  • After replacement of drum gaskets
  • After any repair works in pressure parts
  • After repair of replacement of critical (root valve, MSSV, MSNRV) valves
  • Yearly as per Boiler inspector compliance
  • After any alteration or modification in pressure parts

4-At what pressure do you take the Boiler Hydraulic test?

Boiler Hydraulic tests should be taken at pressure 1.25 times the maximum operating pressure or Design pressure of the Boiler

5-When shall you carryout Boiler hydraulic test at 1.5 times the maximum operating pressure or Design pressure of the Boiler?

If all the Boiler components are not tested in manufacturer premises as per Regulation 268, then Boiler hydraulic test should be conducted at pressure 1.5 times the maximum operating pressure or Design pressure of the Boiler.

6-What is the recommended temperature of Water for Boiler Hydraulic test?

The temperature of the water used as medium of pressure testing shall not be less than 20°C and greater than 50°C.

7-What are the desired parameters of water used for Boiler Hydraulic test?

Boiler water parameters

  • PH-8.5-9.2
  • Conductivity-5-10 mic S/cm
  • Silica-0.02 ppm
  • Hardness-Nil

8-Up to what time you are going to hold the Boiler at Hydraulic test pressure?

Boiler can be held up to 30 minutes at rated Hydraulic test pressure

9-When shall you conclude the completion of Boiler Hydraulic test?

The boiler shall satisfactorily withstand maximum allowable operating pressure without appreciable leakage or undue deflection or distortion of its parts for at least 10 consecutive minutes.

10-Is test pressure affects the Boiler ageing?

Yes, Boiler hydraulic test pressure should be reduced based on their ageing

11-What you will do if you observed any defects or deflection in Boiler parts during hydraulic test?

In such cases, Boiler hydraulic test should be stopped immediately & pressure shall be released

12-Is Pneumatic testing of Boilers is recommended before hydraulic test?

Yes pneumatic test of Boiler is done at pressure around 2-3 kg/cm2 to ensure leakages to avoid loss of DM water.

13-What is the rate of pressure rising during Boiler Hydraulic test?

It is around 3 to 3.5 kg/cm2/minute

14-Explain the Boiler Hydraulic test procedure

Preliminary checks

  • Ensure Boiler erection & maintenance related works are completed
  • Ensure Boiler feed pumps are healthy & ready to use (Ensure 1W+1S)
  • Ensure Initial water fill up line & pumps are ready to use
  • Ensure required quantity of DM water is available
  • Ensure DM water parameters are normal
  • Ensure DM temperature is 20 deg C to 50 deg C
  • Ensure Pressure gauges are mounted at steam drum, super heater & any other required location
  • Ensure the transmitters/pressure parts whose operating /hydraulic pressure is not recommended for hydraulic test are isolate
  • Ensure sufficient number of competitive team is available for conducting test
  • Ensure safety valves gags are available & kept near safety valves
  • Ensure, hydraulic test planning is done properly

Procedure:

  • Keep open Boiler’s all drum, super heater & economiser header air vent valves.
  • Ensure all drain valves of drum & headers are closed
  • Fill the Boiler, by initial fill up line by starting Deaerator or feed water tank make up pump.
  • If Boiler is completely empty, it will take 2 to 3 hours’ time to fill the Boiler (It depends on size of initial fill up line)
  • After filling the Boiler water will come out from vents of economiser, drum & super heater header.
  • Initial close the economiser header vents
  • Then close the Super heater & drum vents at pressure > 2 kg/cm2 to ensure air present in water is vented out completely (Sequence of vent closing should be from bottom elevation to top)
  • After closing the vents slowly raise the Boiler pressure by starting Boiler feed water pump or reciprocating pump (For newly erected Boilers, feed pumps may not available, so in such cases separate positive displacement pumps of required head are made available)
  • Ensure, initially the pressure rising rate is 3-3.5 kg/cm2/minute up to 25% of Hyd.test pressure, after that raise the pressure at rate 1 to 2 kg/cm2 / minute.
  • AT pressure 4 to 5 kg/cm2, flush the pressure gauge impulse lines & mount pressure gauges
  • After reaching Boiler pressure 90-95% of the operating pressure, mount the gags & apply force to ensure gags are fitted properly
  • Then continue pressurizing until Boiler pressure reaches the hydraulic test pressure. Ensure hydraulic test pressure not crossed the 6% of maximum allowable pressure
  • Hold this pressure for 30 minutes & then release the pressure to normal operating pressure
  • Then inspect all the joints, valves glands, other pressure parts for leakages & deflection.
  • Once found normal, release the Boiler pressure through blow down valves
  • AT pressure 10-15 kg/cm2 flush Boiler bottom headers
  • Remove the gags
  • Open the vent valves

 

 Read Boiler refractory dry out procedure

 

 Questions & Answers on steam blowing

 

 

 

 

Interview questions and answers on Boiler fans

 

1-What do you mean by fan & and what are the various fans used in power plant Boilers?

Fan is a Mechanical device , used to move volume air, vapour or flue gas at specific static pressure

Fans used are;

1-Induced draft fan (ID fan)

2-Forced draft fan (FD fan)

3-Secondary air fan (SA fan)

4-Cinder reinjection fan (CR fan)

2-What type of fans used in Boiler?

Generally centrifugal radial, forward & backward curved fans















3-What are the function of Boiler fans in Boiler

SL No.

Fan type

Functions

1

ID fan

1-To suck & expel the flue gas from Boiler

2-To maintain negative & balanced draft in furnace

2

FD fan

1-To provide combustion air for Boiler

2-To maintain balanced draft in Boiler

3-To maintain fluidisation on bed

3

SA fan/PA fan

1-To carry fuel into the furnace or bed

2-To assist fuel in suspension burning (OFA)

3-To spread the fuel in case of Biomass Boilers

4

CR fan

To re-inject unburnt fuel from Bank, Economiser & APH back into the furnace

 know about POWERPLANT SAFETY

4-Which type of fan is more efficient & why?

Centrifugal backward curved is more efficient as they do not over load & speed controlling is very easy. Fan operates beyond the maximum efficiency point at lower in put power

5-Differentiate between forward & backward curved centrifugal fans

Sl No.

              Backward curved

              Forward curved

1

Less number of blades

More number of blades

2

For this type of impeller, flow is produced in a radial direction because the impeller develops static pressure across the longer length of blade.  On the front side of the blade a positive pressure is generated pushing the air outwards and on the reverse side of the blade a negative pressure is generated

For this type of impeller, flow from the impeller is produced in a tangential direction.  The forward curve of the blade imparts kinetic energy to the air requiring a scroll housing to convert the kinetic energy into static pressure

3

Does not over load the motor at higher flow rates

Overloads the motor at higher flow rate

4

High pressure

Low pressure

5

Lower & medium flow rate

Higher flow

6

Higher efficiency

Lower efficiency

 6-What are the various parts of Boiler fans (centrifugal type)?

  • Parts of Boiler fans
  • Casing
  • Inlet cone
  • Evase
  • Inlet box
  • Impeller blade
  • Impeller shroud
  • Impeller back plate
  • Shaft & coupling
  • Bearings

7-What are the material of composition (MOC) of Fan’s various parts

SL No.

Particular Fan part

MOC

1

Casing

Mild steel IS 2062

2

Inlet cone

& inlet box

Mild steel IS 2062

3

Evase

Mild steel IS 2062

4

Impeller blade

SAILMA 350

5

Impeller shroud

SAILMA 350

6

Impeller back plate

SAILMA 350

7

Shaft

EN-8

 8-What is thickness of fans casing

Casing of ID fans is 8mm & that of FD, SA & PA fans is 6mm

9-What are factors considered for Boiler fans design?

Following factors are considered while designing the Boiler fans

  • Required flow
  • Inlet & outlet static pressure
  • Total pressure
  • Operating & design temperature
  • Density of gas/air
  • Dust load
  • Relative humidity
  • Nose level
  • Fan speed

 10-What type of bearings used for Boiler fans?

Generally, spherical roller bearings for fans having speed up to 1500 TPM

11-What are the various instruments used for fans?

Draft sensor (draft transmitter)

Flow meter (Aerofoil)

Temperature sensors

12-What are the protections given for fans?

Start permissive,

Inlet Damper close

Bearing temperature normal

Bearing vibration normal

Protections:

High bearing vibrations trip > 7mm/sec

High bearing temperature trip>90 deg C (for journal & rolling contact bearings)

High/low static pressure

Over load

13- Explain the terms static pressure, total pressure and velocity pressure.

Static Pressure is

Resistance to flow

Equal in all directions

Can be Positive or Negative

Independent of air velocity

Measured by pressure tap perpendicular to airflow

Used for fan selection

 

Total Pressure is

 

A fluid in motion will exert a Total Pressure on an object in its path.

Total Pressure measured by pressure tap pointed directly into the air stream.

Used to find velocity pressure.

Velocity Pressure

Cannot be measured directly.

A Pitot tube uses both Static pressure and Total pressure taps.

Used for measuring CFM in a system.

Total Pressure = Static Pressure + Velocity Pressure

17- What is the differential static pressure?

 It is the difference between the static pressure at fan inlet and out let

18- What are the flow control methods employed in fans?

 Controlling inlet guide vanes

Discharge damper control method

 V belt position change on pulley (If fan is stepped pulley driven type)

 Incorporating Variable Frequency Drives (VFD) to fan motors to control the speed

19-Calculate the differential static pressure of ID fan, whose inlet static pressure is -300 mmwc & outlet 0 mmwc

We have,

Differential static pressure = Outlet static pressure-Inlet static pressure = 0-(-300) = 300 mmwc

20- Calculate the differential static pressure of FD fan, whose inlet static pressure is -10 mmwc & outlet 250 mmwc

Differential static pressure = Out let static pressure-Inlet static pressure = 250-10= 240 mmwc

21-What size of FD air duct is required to get flow 70 m3 /sec. at 11 m/sec. speed?

We have,

 Volumetric flow = Area of duct (M2) X Velocity of air (m/sec.)

Area of duct = 70 / 11 = 6.36 M2

 

22- State the relation between fan’s flow, static pressure, and speed and power consumption.

Following are the some affinity laws related to fans:

A. Fan speed is directly proportional to its flow.

(N1/N2) = (Q1/Q2)

Where N1 & N2 are speed RPM & Q1 & Q2 are flow in M3/hr

B. Static pressure is directly proportional to square of the speed.

(SP1/SP2) = (N1/N2)2

Where, SP1 & SP2 are static pressure at two different speed/RPM

C. Power consumption is directly proportional to cube of speed.

(P1/P2) = (N1/N2)3

Where, P1&P2 are power consumption at speed N1 & N2

23-Calculate the power consumed by an ID fan if its speed reduced from 900 RPM to 750 RPM, take 120 KW power consumption at 900 RPM

As per affinity law

(P1/P2) = (N1/N2)3

(120/P2) = (900/750)3

P2 = 69.44 KW

24-Calculate the anticipated static pressure when FD fan RPM is increased from 1100 RPM to 1175 RPM, static pressure at 1100 RPM is 220 mmwc

As per affinity law

(SP1/SP2) = (N1/N2)2

(220/SP2) = (1100/1175)2

SP2 = 268.3 mmwc

25-Boiler ID fan of flow capacity 55 m3/sec having static inlet pressure & efficiency are  is 300mmwc & 78% respectively, calculate the rated power required to run the fan if motor of efficiency 96% is used to drive the fan.

We have,

Motor rated power = Flow (M3/sec) X Static differential pressure (mmwc) / (102 X Fan static efficiency X motor efficiency)

Motor rated power P = 55 X 300 / (102 X 0.78 X 0.96)

Motor rated power P =216.03 KW

26-A Boiler FD fan of capacity 24m3/sec having total pressure 265 mmwc & Mechanical efficiency 82%, then calculate the fan shaft input power

Fan shaft power = Flow (M3/sec) X Total differential pressure (mmwc) / (102 X Fan mechanical efficiency)

Fan shaft power = 24 X 265 / (102 X 0.82) =76.04 KW

27-Calculate the rated capacity of Boiler FD fans based on following data.

SL No.

Particular

Value

1

Boiler capacity

100 TPH

2

Coal consumption

17 TPH

3

Coal to air ratio

1:6

4

Fan inlet static pressure

5 mmwc

5

Draft loss in ducts from Fan to APH

15 mmwc

6

Draft loss in APH

80 mmwc

 

Draft loss aerofoil flow meter

25 mmwc

7

Draft loss in ducts from APH to plenum

20 mmwc

8

Draft loss in Grate

50 mmwc

9

Static efficiency of the fan

75%

10

Motor efficiency

95%

11

Air temperature

28 deg C

 

Solution,

Total air required for burning the coal in Boiler = 17 X 6 =102 TPH

Take 20% extra margin on air flow , then air flow = 102 X 120% = 122.4 = 123 TPH

Convert air flow from TPH to m3/sec

Density of air at temperature 28 deg C = 273 X 1.293 / (28+273) = 1.17 kg/m3

Where, 1.293 is density of air at 0 deg C

Air flow = 123000 kg/hr /1.17 =29.2 m3/sec

Based on above flow we can select, two fans of capacity 29.2/2 = 14.6 or 15 m3/sec

Now calculate the total static pressure required to over come the resistance in air flow path

Pressure/draft loss drop = Draft loss in APH inlet ducts + Draft loss in flow element + Draft loss in APH + Draft loss in APH to grate ducts + Draft loss in grate

= 15 + 80 +25 + 20 + 50 = 190 mmwc

Take 20% extra margin on draft

Discharge static pressure = 190 X 120% = 228 = 230 mmwc

Now calculate the motor rated power, P = Flow (M3/sec) X Static differential pressure (mmwc) / (102 X Fan static efficiency X motor efficiency)

P = 15 X (230-5) / (102 X 0.75 X 0.95) = 46.43 KW

Take 15% extra margin on motor capacity

Then, compensated rated motor power = 46.43 X 115% =53.4 KW

Select nearest standard size motor i.e 55 KW

Therefore for boiler of capacity 100 TPH, FD fans capacity 55 KW X 2 are required

28-Why does ID fan trip during Boiler operations?

Reasons are

1-Over load

2-High bearing vibrations

3-High bearing temperature

4-Electrical& Instrumentation related issues like short circuit, mal functions etc

5-Low drum level

6-High Boiler pressure & temperature (if interlocks are provided)

7-Low pressure (more negative pressure) in furnace

29-Why does FD fans trip during Boiler operations?

Reasons are

1-Over load

2-High bearing vibrations

3-High bearing temperature

4-Electrical& Instrumentation related issues like short circuit, mal functions etc

5-High drum level

6-High Boiler pressure & temperature (if interlocks are provided)

7-Low pressure (more negative pressure) in furnace

8-Upon tripping of ID fan

30-What will happen if Boiler ID fan trips (one fan out of two)?

1-Same stream FD fan trips

2-Same stream SA fan trips

3-If pressure drops fuel feeding system trips

4-Boiler pressure becomes low & eventually boiler load reduces

31-What will happen if Boiler FD fan trips (one fan out of two)?

1-Same stream SA fan trips

2-If pressure drops fuel feeding system trips

3-Boiler pressure becomes low & eventually boiler load reduces

32-What are the maintenance activities that you will carryout on Boiler fans

  • Fans cleaning
  • Casing thickness checking
  • Impeller inspection, includes Shroud plate, blade and back plate thickness checking
  • Wear liner inspection and hard facing
  • Inlet cone inspection
  • Drive end non drive end bearings overhauling and grease replacement
  • Shaft run out checking
  • Coupling inspection
  • Shaft ultrasonic continuity test
  • Suction and discharge dampers and pneumatic cylinders overhauling
  • Motors servicing
  • Realignment
  • Manhole doors and inspection doors proper sealing
  • Fan trial and dynamic balancing at site

33-Write down the start of steps of Boiler fans

Start-up checks

  • Ensure all the maintenance activities are carried out on fans and equipments are normalized
  • Ensure all the instruments like bearing temperature sensor, vibration sensor etc are fitted & showing readings in DCS
  • Ensure none of the interlocks are bypassed
  • Ensure Fans suction & discharge dampers are in closed condition
  • Ensure coupling & bearing cooling fan guards are fitted properly
  • Ensure local emergency push button is healthy & in good condition
  • Give clearance to DCS or electrical person to start at 10% initially
  • Check abnormal sound from fan casing, bearing & couplings, if found normal open discharge damper slowly & subsequently suction damper

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