boiler supercritical

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660 MW
SUPERCRITICAL BOILER ASHVANI
SHUKLA CI BGR ENERGY
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• POINTS OF DISCUSSION
• SUB CRITICAL SUPER CRITICAL BOILER
• SIPAT BOILER DESIGN
• BOILER DESIGN PARAMETERS
• CHEMICAL TREATMENT SYSTEM
• OPERATION
• FEED WATER SYSTEM
• BOILER CONTROL
• BOILER LIGHT UP
• START UP CURVES

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WHY SUPER CRITICAL TECHNOLOGY

• To Reduce emission for each Kwh of electricity
  generated Superior Environmental
• 1 rise in efficiency reduce the CO2 emission by
  2-3
• The Most Economical way to enhance efficiency
• To Achieve Fuel cost saving Economical
• Operating Flexibility
• Reduces the Boiler size / MW
• To Reduce Start-Up Time

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UNDERSTANDING SUB CRITICAL TECHNOLOGY

• Water when heated to sub critical pressure,
  Temperature increases until it starts
  boiling
• This temperature remain constant till all the
  water converted to steam
• When all liquid converted to steam than again
  temperature starts rising.
• Sub critical boiler typically have a mean (
  Boiler Drum) to separate Steam And Water
• The mass of this boiler drum, which limits the
  rate at which the sub critical boiler responds to
  the load changes
• Too great a firing rate will result in high
  thermal stresses in the boiler drum

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Role of SG in Rankine Cycle
Perform Using Natural resources of energy .
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UNDERSTANDING SUPER CRITICAL TECHNOLOGY

• When Water is heated at constant pressure above
  the critical pressure, its temperature will never
  be constant
• No distinction between the Liquid and Gas, the
  mass density of the two phases remain same
• No Stage where the water exist as two phases and
  require separation No Drum
• The actual location of the transition from liquid
  to steam in a once through super critical boiler
  is free to move with different condition
  Sliding Pressure Operation
• For changing boiler loads and pressure, the
  process is able to optimize the amount of liquid
  and gas regions for effective heat transfer.

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Circulation Vs Once Through
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No Religious Attitude
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BOILER DESIGN
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540C, 255 Ksc
568C, 47 Ksc
492C, 260 Ksc
457C, 49 Ksc
FUR ROOF I/L HDR
ECO HGR O/L HDR
HRH LINE
MS LINE
411C, 277Ksc
411C, 275 Ksc
SEPARATOR
STORAGE TANK
FINAL SH
FINAL RH
LTRH
DIV PANELS SH
PLATEN SH
VERTICAL WW
G
ECO JUNCTION HDR
LPT
IPT
LPT
305C, 49 Ksc
CONDENSER
HPT
ECONOMISER
ECO I/L
Spiral water walls
FEED WATER
BWRP
290C, 302 KSC
FUR LOWER HDR
FRS
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Steam
Partial Steam Generation
Complete or Once-through Generation
Steam
Heat Input
Heat Input
Water
Water
Water
Boiling process in Tubular Geometries
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SEPARATOR TANK
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PENTHOUSE
Eco. O/L hdr (E7)
LTRH O/L hdr (R8)
2nd pass top hdrs (S11)
Back pass Roof o/l hdr (S5)
SH final I/L hdr (S34)
SH final O/L hdr (S36)
F19
1st pass top hdrs
RH O/L hdr (R12)
RH I/L hdr (R10)
Platen O/L hdr (S30)
F28
Platen I/L hdr (S28)
F28
Div. Pan. O/L hdrs (S24)
Div. Pan. I/L hdrs (S20)
1st pass top hdrs
F8
Back pass Roof i/l hdr
S2
Separator (F31)
Storage Tank (F33)
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• SIPAT SUPER CRITICAL BOILER
• BOILER DESIGN PARAMETER
• DRUM LESS BOILER START-UP SYSTEM
• TYPE OF TUBE
• Vertical
• Spiral
• SPIRAL WATER WALL TUBING
• Advantage
• Disadvantage over Vertical water wall

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Vertical Tube Furnace

• To provide sufficient flow per tube, constant
  pressure furnaces employ vertically oriented
  tubes.
• Tubes are appropriately sized and arranged in
  multiple passes in the lower furnace where the
  burners are located and the heat input is high.
• By passing the flow twice through the lower
  furnace periphery (two passes), the mass flow per
  tube can be kept high enough to ensure sufficient
  cooling.
• In addition, the fluid is mixed between passes to
  reduce the upset fluid temperature.

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Spiral Tube Furnace

• The spiral design, on the other hand, utilizes
  fewer tubes to obtain the desired flow per tube
  by wrapping them around the furnace to create the
  enclosure.
• This also has the benefit of passing all tubes
  through all heat zones to maintain a nearly even
  fluid temperature at the outlet of the lower
  portion of the furnace.
• Because the tubes are wrapped around the
  furnace to form the enclosure, fabrication and
  erection are considerably more complicated and
  costly.

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• SPIRAL WATER WALL
• ADVANTAGE
• Benefits from averaging of heat absorption
  variation Less tube leakages
• Simplified inlet header arrangement
• Use of smooth bore tubing
• No individual tube orifice
• Reduced Number of evaporator wall tubes Ensures
  minimum water flow
• Minimizes Peak Tube Metal Temperature
• Minimizes Tube to Tube Metal Temperature
  difference
• DISADVANTAGE
• Complex wind-box opening
• Complex water wall support system
• tube leakage identification a tough task
• More the water wall pressure drop increases
  Boiler Feed Pump Power
• Adherence of Ash on the shelf of tube fin

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BOILER DESIGN PARAMETERS
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BOILER OPERATING PARAMETER
FD FAN 2 NoS ( AXIAL ) 11 kv / 1950 KW 228 mmwc 1732 T / Hr
PA FAN 2 Nos ( AXIAL) 11 KV / 3920 KW 884 mmwc 947 T / Hr
ID FAN 2 Nos ( AXIAL) 11 KV / 5820 KW 3020 T / Hr
TOTAL AIR TOTAL AIR 2535 T / Hr 2535 T / Hr
SH OUT LET PRESSURE / TEMPERATURE / FLOW SH OUT LET PRESSURE / TEMPERATURE / FLOW 256 Ksc / 540 C 2225 T / Hr 256 Ksc / 540 C 2225 T / Hr
RH OUTLET PRESSURE/ TEMPERATURE / FLOW RH OUTLET PRESSURE/ TEMPERATURE / FLOW 46 Ksc / 568 C 1742 T / Hr 46 Ksc / 568 C 1742 T / Hr
SEPARATOR OUT LET PRESSURE/ TEMPERATURE SEPARATOR OUT LET PRESSURE/ TEMPERATURE 277 Ksc / 412 C 277 Ksc / 412 C
ECONOMISER INLET ECONOMISER INLET 304 Ksc / 270 C 304 Ksc / 270 C
MILL OPERATION MILL OPERATION 7 / 10 7 / 10
COAL REQUIREMENT COAL REQUIREMENT 471 T / Hr 471 T / Hr
SH / RH SPRAY SH / RH SPRAY 89 / 0.0 T / Hr 89 / 0.0 T / Hr
BOILER EFFICIENCY BOILER EFFICIENCY 87 87
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Coal Analysis

• High erosion potential for pulverizer and
  backpass tube is expected due to high ash
  content.
• 2. Combustibility Index is relatively low but
  combustion characteristic is good owing to high
  volatile content.

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Ash Analysis

• Lower slagging potential is expected due to low
  ash fusion temp. and low basic / acid ratio.
• 2. Lower fouling potential is expected due to
  low Na2O and CaO content.

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AIR AND FLUE GAS SYSTEM
AIR PATH Similar as 500 MW Unit
FLUE GAS PATH
No Of ESP Passes 6 Pass No Of Fields /
Pass 18 No Of Hopper / Pass 36 Flue
Gas Flow / Pass 1058 T/ Hr
1-7 fields ? 70 KV. 89 field ? 90 KV
COMMISSIONING DEPARTMENT, NTPC-SIPAT
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FUEL OIL SYSTEM
Type Of Oil LDO / HFO Boiler Load
Attainable With All Oil Burner In Service 30
Oil Consumption / Burner 2123 Kg /
Hr Capacity Of HFO / Coal 42.1
Capacity Of LDO / Coal 52.5 HFO
Temperature 192 C
All Data Are At 30 BMCR
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SOOT BLOWERS
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SAFETY VALVE
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• DESIGN BASIS FOR SAFETY VALVES
• Minimum Discharge Capacities.
• Safety valves on Separator and SH Combined
  capacity 105BMCR
• (excluding power operated impulse safety valve)
• Safety valves on RH system Combined capacity
  105 of Reheat
• flow at BMCR
• (excluding power operated impulse safety valve)
• Power operated impulse safety valve 40BMCR at
  super-heater outlet
• 60 of Reheat flow at BMCR at RH outlet

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COMMISSIONING DEPARTMENT, NTPC-SIPAT
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BOILER FILL WATER REQUIREMENT
Main Feed Water Pipe ( FW Shut Off Valve to ECO I/L HDR) 28.8 m3
Economizer 253.2 m3
Furnace ( Eco Check Valve to Separator Link) 41.5 m3
Separators Link 13.8 m3
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CHEMISTRY
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OXYGENATED TREATMENT OF FEED WATER
WATER CHEMISTRY CONTROL MAINTAINS PLANT HEALTH.

• Dosing of oxygen(O2) or Hydrogen peroxide
  (H2O2) in to feed water system.
• Concentration in the range of 50 to 300 µg/L.
• Formation of a thin, tightly adherent ferric
  oxide (FeOOH) hydrate layer.
• This layer is much more dense and tight than
  that of Magnetite layer.

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DOSING POINTS
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AVT Dosing Auto Control
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OWT Dosing Auto Control
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OPERATION
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FEED WATER SYSTEM
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FEED WATER SYSTEM

• MODES OF OPERATION
• BOILER FILLING
• CLEAN UP CYCLE
• WET MODE OPERATION (LOAD lt 30 )
• DRY MODE OPERATION (LOAD gt 30 )
• DRY TO WET MODE OPERATION ( WHEN START UP SYSTEM
  NOT AVAILABLE)

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BOILER FILLING LOGIC

• If the water system of the boiler is empty
  (economizer, furnace walls, separators), then the
  system is filled with approximately 10 TMCR (
  223 T/Hr) feed water flow.
• When the level in the separator reaches
  set-point, the WR valve will begin to open.
• When the WR valve reaches gt30 open for
  approximately one minute, then increase feed
  water flow set-point to 30 TMCR ( approx 660
  T/Hr).
• As the flow increases, WR valve will reach full
  open and ZR valve will begin to open.
• The water system is considered full when
• The separator water level remains stable for
  two(2) minutes
• and
• The WR valve is fully opened and ZR valve is
  gt15 open for two(2) minutes
• After completion of Filling, the feed water flow
  is again adjusted to 10 TMCR for Clean up cycle
  operation

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BOILER INITIAL WATER LEVEL CONTROL (UG VALVE)

• The boiler circulating pump is started following
  the start of a feed water pump and the final
  clean-up cycle.
• This pump circulates feed water from the
  evaporator outlet back to the economizer inlet.
• Located at the outlet of this pump is the UG
  valve which controls economizer inlet flow during
  the start-up phase of operation.
• Demand for this recirculation, control valve is
  established based on measured economizer inlet
  flow compared to a minimum boiler flow set point.

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• Boiler Clean-up
• When the feedwater quality at the outlet of
  deaerator and separator is not within the
  specified limits, a feedwater clean-up
  recirculation via the boiler is necessary.
• During this time, constant feedwater flow of 10
  TMCR ( 223 T/Hr) or more is maintained.
• Water flows through the economizer and
  evaporator, and discharges the boiler through the
  WR valve to the flash tank and via connecting
  pipe to the condenser.
• From the condenser, the water flows through the
  condensate polishing plant, which is in service
  to remove impurities ( Like Iron its Oxide,
  Silica, Sodium and its salts ), then returns to
  the feed water tank.
• The recirculation is continued until the water
  quality is within the specified limits.

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FEED WATER QUALITY PARAMETER FOR START UP
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• MODE OF OPERATION
• WET MODE
• Initial Operation Of Boiler Light Up. When
  Economizer Flow is maintained by BCP.
• Boiler Will Operate till 30 TMCR on Wet Mode.
• DRY MODE
• At 30 TMCR Separator water level will become
  disappear and Boiler Operation mode will change
  to Dry
• BCP Will shut at this load
• Warm Up system for Boiler Start Up System will
  get armed
• Boiler will turn to once through Boiler

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SYSTEM DESCRIPTION ( WET MODE OPERATION)

• Flow Control Valve ( 30 Control Valve )
• Ensures minimum pressure fluctuation in Feed
  Water Header
• It measures Flow at BFP Booster Pump Discharge
  and compare it with a calculated flow from its
  downstream pressure via a function and maintains
  the difference 0
• 100 Flow Valve To Boiler
• Remains Closed
• BFP Recirculation Valve
• It Measures Flow at BFP Booster Pump Discharge
• Ensures minimum Flow through BFP Booster Pump
• Closes when Flow through BFP Booster Pump
  discharge gt 2.1 Cum
• Open When Flow through BFP Booster Pump Discharge
  lt 1.05 Cum
• ( Minimum Flow will be determined by BFP Speed
  via BFP Set limitation Curve)

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• UG Valve
• Maintain Minimum Economizer Inlet Flow ( 30
  TMCR Approx 660 T/Hr)
• Maintain DP across the BRP ( Approx 4.0 Ksc)
• It Measures Flow Value from Economizer Inlet Flow
  Transmitter
• WR / ZR Valve
• Maintains Separator Storage Tank Level
• It Measures value from the Storage tank Level
• Storage Tank Level
• 3 Nos Level Transmitter has been provided for
  Storage tank level measurement
• 1 No HH Level Transmitter has been provided

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SYSTEM DESCRIPTION ( DRY MODE OPERATION)

• Following System will be isolated during Dry Mode
  Operation
• FCV ( 30 )
• Start Up System Of Boiler
• WR / ZR Valve
• Storage Tank
• BRP
• BRP Recirculation System
• BFP Recirculation Valve
• Following System will be in service
• UG Valve ( Full Open)
• 100 FW Valve ( Full Open)

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SYSTEM OPERATION ( DRY MODE OPERATION)

• START UP SYSTEM
• In Dry Mode Start Up System Of Boiler will become
  isolated
• Warming System for Boiler Start Up system will be
  charged
• Separator Storage Tank level will be monitored by
  Separator storage tank wet leg level control
  valve ( 3 Mtr)
• TRANSITION PHASE - Changeover of FW Control
  valve (30 to 100 Control )
• 100 FW Flow valve will wide open
• During the transition phase system pressure
  fluctuates
• The system pressure fluctuation will be
  controlled by 30 FW Valve. After stabilization
  of system 30 CV Will become Full Close
• FEED WATER CONTROL
• It will be controlled in three steps

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FEED WATER DEMAND ( DRY MODE OPERATION)

• FINAL SUPER HEATER SPRAY CONTROL
• Maintain the Final Steam Outlet Temperature ( 540
  C)
• PLATEN SUPER HEATER SPRAY CONTROL
• Primary purpose is to keep the final super heaer
  spray control valve in the desired operating
  range
• Measures the final spray control station
  differential temperature
• It Compares this difference with Load dependent
  differential temperature setpoint
• Output of this is the required temperature
  entering the Platen Super Heater Section (Approx
  450 C)
• FEED WATER DEMAND
• FEED FORWARD DEMAND
• It is established by Boiler Master Demand.
• This Demand goes through Boiler Transfer Function
  where it is matched with the actual Evaporator
  Heat Transfer to minimize the temperature
  fluctuations

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FEED WATER DEMAND ( DRY MODE OPERATION)

• FEED BACK DEMAND
• Work With two controller in cascade mode
• FIRST CONTROLLER
• One Controller acts on Load dependent average
  platen spray differential temperature
• Its Output represents the desired heat transfer /
  steam generation to maintain the desired steam
  parameters and Flue gas parameters entering the
  Platen section
• SECOND CONTROLLER
• Second Controller acts on the load dependent
  Separator Outlet Temperature adjusted by Platen
  spray differential temperature
• This controller adjust the feed water in response
  to firing disturbances to achieve the separator
  O/L Temperature
• THE RESULTING DEMAND FROM THE COMBINED
  FEEDFORWARD AND FEEDBACK DEMANDSIGNAL DETERMINED
  THE SETPOINT TO THE FEED WATER MASTER CONTROL
  SETPOINT

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DRY TO WET MODE OPERATION ( START UP SYSTEM NOT
AVAILABLE)

• The combined Feed Forward and Feed back demand (
  as calculated in dry mode operation) will be
  compared with minimum Economizer Flow
• This ensures the minimum flow through Economizer
  during the period when start up system is
  unavailable
• Output of the first controller is subjected to
  the second controller which monitors the
  Separator Storage tank level ( Since the system
  is in Wet Mode now)
• The output of the second controller is the set
  point of Feed water master controller.
• The Feed back to this controller is the minimum
  value measured before the start up system and
  Economizer inlet.

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WATER STEAM PATH

• BLR PATH ( WHEN WET MODE)
• Separator - Backpass Wall Extended Wall - SH
  Division - Platen SH - Final SH - HP By-pass -
  Cold R/H Line - Primary R/H (Lower Temp R/H) -
  Final R/H - LP By-pass - Condenser
• BLR Path (When Dry Mode)
• Primary Eco - Secondary Eco - Ring HDR - Spiral
  W/W - W/W Intermediate HDR - Vertical W/W -
  Separator - Backpass Wall Extended Wall - SH
  Division - Platen SH - Final SH - HP TBN - Cold
  R/H Line - Primary R/H (Lower Temp R/H)- Final
  R/H - IP and LP TBN - Condenser

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Wet Mode and Dry Mode of Operation
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SH Temperature Profile

PLATEN SH
FINAL SH
DIV SH
440
480
540
486
451
406
DSH1
DSH2
3
15


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BOILER CONTROL
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BOILER LOAD CONDITION

• Constant Pressure Control
• Above 90 TMCR The MS Pressure remains constant
  at rated pressure
• The Load is controlled by throttling the steam
  flow
• Below 30 TMCR the MS Pressure remains constant
  at minimum Pressure

• Sliding Pressure Control
• Boiler Operate at Sliding pressure between 30
  and 90 TMCR
• The Steam Pressure And Flow rate is controlled by
  the load directly

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CONSTANT PRESSURE VS SLIDING PRESSURE

• Valve throttling losses occur because the boiler
  operates at constant pressure while the turbine
  doesn't.
• The most obvious way to avoid throttling losses
  therefore is to stop operating the boiler at
  constant pressure!
• Instead, try to match the stop valve pressure to
  that existing inside the turbine at any given
  load.
• Since the turbine internal pressure varies
  linearly with load, this means that the boiler
  pressure must vary with load similarly.
• This is called .sliding pressure operation..
• If the boiler pressure is matched to the pressure
  inside the turbine, then there are no valve
  throttling losses to worry about!
• While sliding pressure is beneficial for the
  turbine, it can cause difficulties for the
  boiler.
• ADVERSE AFFECT
• As the pressure falls, the boiling temperature
  (boiling point) changes. The boiler is divided
  into zones in which the fluid is expected to be
  entirely water, mixed steam / water or dry steam.
  A change in the boiling point can change the
  conditions in each zone.
• The heat transfer coefficient in each zone
  depends upon the pressure. As the pressure falls,
  the heat transfer coefficient reduces. This means
  that the steam may not reach the correct
  temperature. Also, if heat is not carried away by
  the steam, the boiler tubes will run hotter and
  may suffer damage.

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• CHALLANGES
• The heat transfer coefficient also depends upon
  the velocity of the steam in the boiler tubes.
• Any change in pressure causes a change in steam
  density and so alters the steam velocities and
  heat transfer rate in each zone.
• Pressure and temperature cause the boiler tubes
  to expand. If conditions change, the tubes will
  move. The tube supports must be capable of
  accommodating this movement.
• The expansion movements must not lead to adverse
  stresses.
• The ability to use sliding pressure operation is
  determined by the boiler
• Boilers can be designed to accommodate sliding
  pressure.
• When it is used, coal fired boilers in the 500 to
  1000 MW class normally restrict sliding pressure
  to a limited load range, typically 70 to 100
  load, to minimize the design challenge. Below
  this range, the boiler is operated at a fixed
  pressure.
• This achieves an acceptable result because large
  units are normally operated at high load for
  economic reasons.
• In contrast, when sliding pressure is used in
  combined cycle plant, the steam pressure is
  varied over a wider load range, typically 50 to
  100 load or more

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• As stated, in coal-fired plant, sliding pressure
  is normally restricted to a limited load range to
  reduce design difficulties.
• In this range, the boiler pressure is held at a
  value 5 to 10 above the turbine internal
  pressure. Consequently, the governor valves
  throttle slightly.
• The offset is provided so that the unit can
  respond quickly to a sudden increase in load
  demand simply by pulling the valves wide open.
• This produces a faster load response than raising
  the boiler firing rate alone.The step in load
  which can be achieved equals the specified margin
  ie 5 to 10.
• The throttling margin is agreed during the
  tendering phase and then fixed.
• A margin of 5 to 10 is usually satisfactory
  because most customers rely upon gas turbines,
  hydroelectric or pumped storage units to meet
  large peak loads.
• The throttling margin means that the full
  potential gain of sliding pressure is not
  achieved.
• Nevertheless, most of the throttling losses which
  would otherwise occur are recovered.

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• ADVANTAGES
• Temperature changes occur in the boiler and in
  the turbine during load changes. These can cause
  thermal stresses in thick walled components.
• These are especially high in the turbine during
  constant-pressure operation. They therefore limit
  the maximum load transient for the unit.
• By contrast, in sliding pressure operation, the
  temperature changes are in the evaporator
  section. However, the resulting thermal stresses
  are not limiting in the Once through boiler due
  to its thermo elastic design.

In fixed pressure operation , temperature change
in the turbine when load changes, while in
sliding-pressure operation ,they change in the
boiler
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• The enthalpy increase in the boiler for
  preheating, evaporation and superheating changes
  with pressure.
• However, pressure is proportional to output in
  sliding pressure operation
• In a uniformly heated tube, the transitions from
  preheat to evaporation and from evaporation to
  superheat shift automatically with load such that
  the main steam temperature always remains
  constant.

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Sliding Pressure

• At loads over 25 of rated load, the water fed by
  a feed-water pump flows through the high pressure
  feed-water heater, economizer ,furnace water
  wall, steam-water separator, rear-wall tubes at
  the ceiling, and super heaters, The super heaters
  steam produced is supplied to the turbine.
• At rated and relatively high loads the boiler is
  operated as a purely once through type. At
  partial loads, however, the boiler is operated by
  sliding the pressure as a function of load.

24.1 Mpa
9.0 Mpa
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CONSTANT PRESSURE Vs VARIABLE PRESSURE BOILER
CHARACTERSTIC
Variable Pressure
Constant Pressure
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• Benefits Of Sliding Pressure Operation ( S.P.O)
• Able to maintain constant first stage turbine
  temperature
• Reducing the thermal stresses on the component
  Low Maintenance Higher Availability
• No additional pressure loss between boiler and
  turbine.
• low Boiler Pr. at low loads.

WHY NOT S.P.O. IN NATURAL/CONTROL CIRCULATION
BOILERS

• Circulation Problem instabilities in
  circulation system due to steam formation in down
  comers.
• Drum Level Control water surface in drum
  disturbed.
• Drum (most critical thick walled component)
  under highest thermal stresses

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BOILER LIGHT UP
The Basis of Boiler Start-up Mode
Mode Basis Restart Hot Warm Cold
Stopped time 2Hr Within 612Hr 56Hr Within 96Hr Above
SH Outlet Temp 465? above 300? above 100? above 100? below
Separator Tank pr 120200?/? 30120?/? 30?/? below 0?/?
Starting Time
STARTING TIME
Startup Mode Light off ?TBN Rolling(minutes) Light off ? Full Load(minutes)
Cold 120 420 Except Rotor and Chest Warming Time
Warm 90 180 "
Hot - -
Restart 30 90
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• PURGE CONDITIONS
• No Boiler Trip Condition Exists
• All System Power Supply Available
• Unit Air Flow gt 30 BMCR
• Nozzle Tilt Horizontal and Air Flow lt 40
• Both PA Fans Off
• The Following Condition Exist At Oil Firing
  System
• The HOTV / LOTV Should Be Closed
• All Oil Nozzle Valve Closed
• The Following Condition Exists at Coal Firing
  System
• All Pulverisers are Off
• All Feeders are Off

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• MFT CONDITIONS
• Both ID Fans Off
• Both FD Fans Off
• Unit Air Flow lt 30 TMCR
• All Feed Water Pumps Are Off For More Than 40 Sec
• 2 / 3 Pressure Transmitter indicate the furnace
  pressure High / Low for more than 8 sec ( 150
  mmwc / -180 mmwc))
• 2 / 3 Pressure Transmitter indicate the furnace
  pressure High High / Low - Low ( 250 mmwc / -
  250 mmwc)
• Loss Of Re-heater Protection
• EPB Pressed
• All SAPH Off
• Economizer Inlet Flow Low For More Than 10 Sec
  (223 T/Hr)
• Furnace Vertical Wall Temperature High For more
  than 3 Sec (479 C)
• SH Pressure High On Both Side (314 KSc)
• SH Temperature High For More Than 20 Sec ( 590 C)
• RH O/L Temperature High For More Than 20 Sec (
  590 C)
• Separator Level Low-Low During Wet Mode ( 1.1 M)
• Separator Level High-High During Wet Mode ( 17.7
  M)

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• MFT Relay Tripped
• Loss Of Fuel Trip It Arms when any oil burner
  proven.
• it occurs when all of the following
  satisfied
• All Feeders Are Off
• HOTV Not Open or all HONV Closed
• LOTV Not Open or all LONV Closed
• Unit Flame Failure Trip It Arms when any Feeder
  Proves
• it occurs when all 11 scanner elevation
  indicates flame failure as listed below ( Example
  is for only elevation A)
• Feeder A Feeder B is Off with in 2 Sec Time
  Delay
• following condition satisfied
• Any oil valve not closed on AB Elevation
• 3 /4 valves not proven on AB Elevation
• Less Than 2 / 4 Scanner Shows Flame
• Both Of The Following Condition Satisfied
• Less Than 2 / 4 Scanner Flame Shows Flame
• 2 / 4 Oil Valves not open at AB Elevation

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• Boiler Light Up Steps
• Start the Secondary Air Preheater
• Start one ID fan, then the corresponding FD fan
  and adjust air flow to a min. of 30 TMCR
• Start the scanner air fan.
• Adjust fan and SADC to permit a purge air flow of
  atleast 30 of TMCR and furnace draft of approx.
  -12.7 mmWC.
• When fans are started, SADC should modulate the
  aux. air dampers to maintain WB to furnace DP at
  102 mmWC(g).
• Check that all other purge permissives are
  satisfied.
• Place FTPs in service.
• Check The MFT Conditions

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SYSTEM / EQUIPMENT REQUIRED FOR BOILER LIGHT UP

• FURNACE READINESS
• PRESSURE PARTS
• SCANNER AIR FAN
• BOTTOM ASH HOPPER READINESS
• FUEL FIRING SYSTEM
• START UP SYSTEM
• SEC AIR PATH READINESS
• FD FAN
• SAPH
• WIND BOX / SADC
• FLUE GAS SYSTEM
• ESP PASS A , B
• ID FAN

80
SYSTEM / EQUIPMENT REQUIRED FOR BOILER LIGHT UP

• CONDENSATE SYSTEM
• CONDENSER
• CEP
• CPU
• FEED WATER SYSTEM
• D/A
• MDBFP A
• VACCUME SYSTEM
• SEAL STEAM SYSTEM
• TURBINE ON BARRING

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83
Evaporator heat absorption
84
?Reduced number of evaporator wall tubes.
? Ensures minimum water wall flow.
85
SPIRAL WALL ARRAMGEMENT AT BURNER BLOCK AREA
86
Support System for Evaporator Wall

• Spiral wall ? Horizontal and vertical buck stay
  with tension strip
• Vertical wall ? Horizontal buck stay

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Key source

• NTPC SIPAT
• DOSSAN BOILER
• BGR ENERGY

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