02B HRSG [PDF]

Zitiervorschau

Heat Recovery Steam Generator Control Philosophy And Instrumentation

For Training Only

O&M Training 1

CONTROL PHILOSOPHY Permit the HRSG to follow the Gas Turbine Load AND lead the operation of the steam turbine. Achieved by carefully considering economizer steaming impacts, and drum level control. Specifically, in the HRSG evaporator, steam flow varies depending upon heat energy extracted from the gas turbine exhaust gas stream. The operator must bear in mind that at all times the gas turbine loading dictates the power output of the steam cycle. The HRSG is designed for sliding pressure and constant pressure operation. Maximum operating efficiency is obtained during sliding pressure operation. In the sliding pressure configuration the steam turbine throttle valves remain in the wide open position. This minimizes the pressure drop losses associated with constant pressure operation.

For Training Only

O&M Training 2

DRUM LEVEL CONTROL

™Drum water level control uses three element feedwater control. 9 Provides a continuous drum water mass balance, since every pound of steam or water removed from the evaporator must be replaced. ™Three elements 9 Steam flow from the HRSG, (pressure and temperature compensated) 9 Feed water flow into the HRSG, 9 Drum level (pressure and temperature compensated) ™Drum level is used for trimming the mass balance of steam flow and feedwater flow signals. ™Mass balance measurements are pressure corrected to compensate for temperature/pressure fluctuations. ™Steam flow signal reacts to changes in steam demand, causing a corresponding change in feed flow. Once the steam demand has stabilized, the drum level controller will maintain the desired level. ™To accommodate sliding pressure operation, the drum level pressure decreases in response to lower steam turbine throttle pressure. The lower pressure changes the steam specific volume through out the steam cycle components. For Training Only

O&M Training 3

SHRINK AND SWELL

"Shrink" and "Swell" are two terms associated with drum water level and steam and water specific volume characteristics. Shrink = The decline in drum water level that occurs when boiling decreases. When boiling decreases, the steam/water volume and the drum level decrease, because steam bubbles start collapsing. Swell = The increase in drum level due to increased boiling resulting from an increase in heat absorption. Essentially, swell occurs because steam bubbles formed increase the steam/water volume and, as a follow up, the drum level. Swell is a boiler start-up characteristic. Most boilers are started with a lower drum level. This allows the drum water to reach NWL after the increase in drum water level due to swell. If NWL is exceeded during start-up, the intermittent blowdown drain systems, or a decrease in the CT loading ramp rate should be used to manage the water level swell of the drum.

For Training Only

O&M Training 4

ATTEMPERATION

Attemperation • Why? Control Steam Temperature to within the limits. • Where? Before and after last Superheater. Attemperator Attemperators inject low solids water from the feed pumps. Attemperation control is a feed forward control loop. The primary control is achieved by measuring the final steam temperature and comparing it to a setpoint. The feed forward portion is measuring the attemperator outlet temperature and steam turbine load changes. The feed forward components assure attemperator system has adequate time to react to a change in operating conditions. To assure that wet steam is not admitted to the heating surface, the attemperator outlet setpoint prevents final stage steam temperature from falling within a certain degree of saturation temperature at anytime.

For Training Only

O&M Training 5

Drain and Blowdown System

The HRSG drain and blowdown system provides a means to: Continuously and Intermittently blowdown various sections of the HRSG for chemistry and sediment control, Drain the HRSG superheater and reheater sections during startup Drain the HRSG water sections for maintenance during shutdowns. All blowdown and drains except the water section drains are directed to a blowdown tank. The blowdown tank automatically drains to a blowdown sump. Water section drains go directly to the blowdown sumps. Continuous Blowdown A portion of the evaporator drum water is continuously removed by skimming the water and entrained solids from the surface of the water in the steam drum. Maintain the required total dissolved solids in the drum water to maintain proper steam purity. Intermittent Blowdown The intermittent blowoff line is designed for rapid removal of drum water either at startup (swell control) or for rapid changes in TDS control of the steam drum. During cold HRSG start-up, rapid load swings which result in rapid pressure decay of the steam system, the intermittent blowdown system is available to remove excessive amounts of feed water to control drum level and water solids for steam purity considerations. Intermittent blowdown is not normally needed after the unit is stabilized.

For Training Only

O&M Training 6

INSTRUMENTS

Various instruments required by the Code. Many instruments aid in reliable and safe operation. Instruments are shown on the P&ID Drawings. Instrumentation Used on the HRSG include: Pressure Indicators - required by the Boiler Code to provide a local indication of drum pressure. Pressure Transmitters - supplied to collect operating pressures for the control system. Temperature Indicators - give a local indication of temperature. Thermocouples - located in the piping system and HRSG ductwork to monitor critical temperatures. The thermocouples in the HP superheater and reheater attemperator are used by the attemperator systems to control final steam temperatures.

For Training Only

O&M Training 7

INSTRUMENTS

Instrumentation Used on the HRSG include: Drum Water Level Indicators - required by the Boiler Code. Direct line of sight indicators or gauge glasses - Gauge glass observations must be unobstructed. The gauges can be viewed easily by direct line-of-sight at the HRSG operating platform. Level transmitters - provided on each of HP, IP and LP drum to monitor drum operating water level. The signal levels are monitored and alarms are generated to alert the operator of levels beyond those required for safe operation of the HRSG pressure levels and feed pump operation.

WARNING: NO BOILER SHOULD BE IN OPERATION WITHOUT AT LEAST TWO ACCEPTABLE, DEPENDABLE MEANS OF WATER LEVEL DETECTION IN SERVICE. DRUM LEVEL MUST BE CONTROLLED NEAR NORMAL WATER LEVEL AT ALL TIMES.

For Training Only

O&M Training 8

HRSG Operation Preparing for HRSG Operation Prior to starting the GT HRSG must be prepared to Start, HRSG Auxiliaries must be prepared to Start HRSG prepared to receive water, steam and gas flows. The following Major Systems must be verified In Service prior to HRSG Startup. Condensate System, Feedwater System, Plant Instrument Air System, Blowdown System, Steam Turbine on turning gear.

For Training Only

O&M Training 9

Low Pressure Steam System

Start Up From A Cold Piping State LP drum is filled to start-up level (MIN4) with the Feedwater control valve. Intermittent blowdown valve level opens and closes to control level at Start-Up Level (MIN4) Start-up = Warm-up of piping to avoid entrainment of condensate droplets into the steam turbine. Steam turbine is isolated - insufficient steam pressure, temperature and steam quality. When LP Steam is produced the LP drum level and overflow level is switched to the normal water level (NWL). As steam forms, drum water level increases. If water level > (MAX2), intermittent blowdown valve opens. Increasing thermal input – more steam is generated – LP Bypass Station begins to open. When the variable fixed set point has been reached – Pressure in the low pressure system increases in accordance with the variable pressure characteristic of the bypass station. Steam turbine control valve is opened when all conditions have been satisfied for loading of the steam turbine; Steam flow rate, Purity and Temperature. LP pressure bypass valve, which is set to pressure control, starts to close slowly in proportion to the steam quantity flowing to the turbine but still performing its pressure controlling task. Drain stations will open as long as the steam is NOT sufficiently superheated.

Warm / Hot Start For Training Only

The sequences for cold start also apply for a warm/hot start. O&M Training 10

Low Pressure Steam System

1. 4. 2. 5. 3.

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For Training Only

O&M Training 11

Low Pressure Steam System #1 LP Drum Level Control Level maintained by an automatic level control valve. Operator must verify that the level control valve is in automatic on the OM screen. Two level setpoints fed into the level control valve controller ¾ S/U LVL ¾ NORM LVL.

1.

Initial startup – S/U LVL SLC is Automatically Selected by the control system. Ensures drum level is NOT exceeded as the water swells.

4. S/U LVL mode ¾ Level control valve compares actual drum level to the S/U LVL setpoint only and adjusts to maintain level.

2.

5. As LP drum water is heated, water level will rise and pressure will build in the system. Steam will begin to flow to the LP superheater and out of the startup vent. Water level will drop and condensate will be fed through the level control valve to maintain the S/U LVL setpoint.

3.

LP steam flow > 15% of rated flow ¾ 3-element control logic will become active. (LP steam flow, LP drum condensate flow and LP drum water level). After 3 minutes of sustained 3 element control logic operation or when LP drum pressure > 3 bars, ¾ Level control valve setpoint changes from S/U LVL to NORM LVL (0 cm). ¾ Level control valve will raise the LP drum to the normal operating level.

6.

In 3-element control, if either steam flow or feedwater flow transmitters fail, the SLC NO 3 ELE will activate and remove the affected instrument from the calculation for controlling drum level. For Training Only

O&M Training 12

Low Pressure Steam System #2 LP Drum Continuous Blowdown Valve Motor Operated Continuous Blowdown Valve Allows blowdown of LP drum water to control chemistry in the drum during operation. The rate of blowdown is controlled by a precision manual throttle valve downstream of the motor operated valve. Operator must open and close the motor operated valve from the OM screen. ¾ Must OPEN the continuous blowdown valve within 30 minutes of gas turbine startup. 4. ¾ If the operator fails to open the valve within 30 minutes, a “CLOSED WARNING” will display on the alarm screen. The alarm will continue to re-display every 30 minutes until the valve is opened.

1.

2.

¾ Must CLOSE the continuous 5. blowdown valve within 20 minutes of gas turbine shutdown. ¾ If the operator fails to close the valve within 20 minutes, an “OPEN WARNING” will display on the alarm screen. The alarm will continue to re-display every 20 minutes until the valve is closed.

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For Training Only

O&M Training 13

Low Pressure Steam System #3 LP Feedwater Block Valve ™ Motor Operated Block Valve Upstream of the Level Control valve ™ Ensures positive isolation of water into the LP Drum. ™ With Controller in AUTOMATIC, ¾ Block valve will open and stay open when LP drum level is in its normal operating range. ¾ Valve will close If LP drum level increases to “Imminent Trip HIHI” setpoint. ¾ As level decreases below the reset level value, block valve will 4. reopen.

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For Training Only

O&M Training 14

Low Pressure Steam System #4 LP Startup Vent Block Valve

1. 4. 2. 5. 3.

™ Motor Operated Vent Valve Downstream of the Superheater ™ Provides a flow path of steam during startup of the LP section of the HRSG. ¾ Prevents potential overheating of the superheater ™ With Controller in AUTOMATIC, ¾ Vent valve will open when the gas turbine is in operation and the LP Drum indicates a rise in pressure of 0.5 bar from its initial pressure when the gas turbine is started. ¾ Vent valve will close when: 6. 9 LP Steam Block valve is open, 9 Condenser is ready for steam, 9 LP Bypass Pressure Controller is in AUTO and 9 LP Bypass valve is 10% open. For Training Only

O&M Training 15

Low Pressure Steam System #5 LP Steam Block Valve

1. 4. 2. 5. 3.

™ Motor Operated Block Valve Downstream of the Startup Vent ™ Isolates LP Section of the HRSG from the LP steam header. ™ Must be opened and closed by the operator from the OM screen. ™ ™ Has a protective close feature for future application when a second HRSG is provided. When installed, if the second HRSG is in service and the first HRSG LP Steam Block Valve is closed for more than 3 minutes, a protective feature will6.not allow the operator to open the valve from the OM screen. It will have to be open locally once pressure across the valve is locally equalized.

For Training Only

O&M Training 16

Low Pressure Steam System #6 LP Drum Intermittent Blowdown Block Valve ™ Motor Operated Block Valve ™ Provides a means to isolate the LP Intermittent Blowdown Control valve which controls excessive drum level during startup and transients during normal operations. ™ Automatically opened when blowdown control valve demanded position is greater than 10% and the position demand is greater than 5% of the valve’s actual position. ™ Automatically closed when 4. blowdown control valve position demand is less than 5% of actual position or the valve position demand is less than 10%. 2.

1.

5. 3.

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For Training Only

O&M Training 17

Intermediate And Reheater Pressure Steam System Start Up From A Cold Piping State If the economizer is partly or fully drained - Vents are manually opened during filling. System is filled via the feedwater bypass valve, when the feedwater isolating valve is closed. Vent valves are manually closed when filling of the economizer is complete (visual check). If the current drum level is below the start-up level ¾ Open the feedwater isolating valve. ¾ Close the feedwater bypass valve. ¾ Open the feedwater control valve and fill the IP Drum to the start-up level. If the current drum level is above the start-up level ¾ The intermittent blowdown valve level is switched over to start-up level (MIN5). ¾ Some water maybe blown down to the HRSG blowdown system LBH. IP steam isolating valve is opened after filling and prior to the start-up. When the condenser and other necessary systems are ready for service, the steam generator is started up. Intermittent blowdown valve is switched over to normal water level. IP Economizer is fed with a minimum flow rate of ~ 5 kg/s to protect the evaporator from flashing during GT start up. After steam production has been established, ¾ IP feedwater control station is switched over to 3 element control. ¾ Intermittent blowdown valve of the IP drum is switched over to blowdown level. For start-up, the GT exhaust gas temperature is controlled to maintain main steam temperature within the range required by the steam turbine. If the temperature cannot be controlled in GT premix operation the steam temperatures can be controlled by activating the spray attemperators. For Training Only

O&M Training 18

Intermediate And Reheater Pressure Steam System Start Up From A Cold Piping State Start-up of the reheat steam piping system mainly consists of piping warm-up to avoid entrainment of condensate droplets into the steam turbine. Initially during start up, the steam turbine is isolated from the reheater main steam system due to insufficient steam pressure, temperature and steam quality. The drains are closed once the steam is sufficiently superheated. Increasing thermal input – more steam is generated – IP Bypass Station begins to open. When the fixed set point has been reached – Pressure in the IP system increases in accordance with the variable pressure characteristic of the bypass station. Steam turbine control valve is opened when all conditions have been satisfied for loading of the steam turbine; Steam flow rate, Purity and Temperature. IP bypass valve, which is set to pressure control, starts to close slowly in proportion to the steam quantity flowing to the turbine. After the IP bypass station has been closed, the load is increased in accordance with the allowable load change gradients of the steam turbine. The pressure set point of the IP station is increased 45 psig above the steam pressure set point resulting from the actual steam mass flow. The IP bypass station opens upon a sudden rise in pressure. The IP bypass station prevents exceeding of the design pressure prior to the safety valve.

For Training Only

O&M Training 19

Intermediate And Reheater Pressure Steam System Start Up From A Cold Piping State Warm / Hot Start The same sequences for the cold start apply for preparation for a warm/hot start. The drain valves may be opened only after the HRSG is heated and a pressure increase has been initiated. The drains are closed in accordance with the same criteria as a cold start. The IP bypass valve opens when a pressure increase is detected. It maintains the correct pressure until the variable pressure characteristic has been reached. The combustion turbine is then loaded according to the steam conditions required by the steam turbine with the allowable gradients for the heat recovery steam generator and the steam turbine.

For Training Only

O&M Training 20

Intermediate And Reheater Pressure Steam System 1.

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O&M Training 21

Intermediate And Reheater Pressure Steam System #1 IP Feedwater Block Valve 1.

2. 9.

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3. ™ Motor Operated Block Valve Upstream of the Level Control valve ™ Ensures positive isolation of water into the IP Drum.

5.

™ With Controller in AUTOMATIC, ¾ Block valve will open and stay open when: 9 A boiler feedwater pump is running, 9 IP Feedwater Startup Block Valve is open and 9 Differential pressure across feedwater block valve is < 3.5 bars. ¾ If the pressure instruments before or after the block valve fail, the valve will open when a boiler feedwater pump has been running for > 5 minutes ¾ Valve will close when: 9 The boiler feedwater pump is off, or 9 IP drum level reaches the HI-HI trip level with the CT shutdown, or 9 IP boiler feedwater pump pressure drops below 28.5 bars.

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For Training Only

O&M Training 22

Intermediate And Reheater Pressure Steam System #2 IP Feedwater Startup Block Valve 1.

2. 9.

8.

3.

™ Solenoid Operated Block Valve ™ Provides a means to equalize pressure across the IP Feedwater Block Valve prior to opening.

5.

™ With Controller in AUTOMATIC, ¾ Startup Block valve will open when: 9 A boiler feedwater pump is running, and 9 IP Discharge Pressure from pump is > 32 bar. ¾ If the pressure transmitter for the IP discharge pressure fails, the valve opens within a short time period on indication that a boiler feedwater pump is in service

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For Training Only

O&M Training 23

Intermediate And Reheater Pressure Steam System #3 HRH Intermediate and Final Desuperheater Block Valve 1.

2. 9.

8.

3. 5.

™ Solenoid Operated Block Valves ™ Provide positive isolation of IP feedwater to their corresponding control valves. ™ HRH Final Desuperheater Block Valve With Controller in AUTOMATIC, ¾ Block valve will OPEN when: 9 A boiler feedwater pump is in service, 9 Final HRH steam has > 25° superheat, 9 Final HRH temperature is > 305°C, 9 HRH temperature before desuperheater is > 305°C, 9 Total HRH steam flow > 35%, and 9 Final desuperheater control valve is demanded open. ¾ Block valve will CLOSE IF any of the previous conditions are not met. For Training Only

4.

™ HRH Intermediate Desuperheater Block Valve With Controller in AUTOMATIC, ¾ Block valve will OPEN6.when: 9 A boiler feedwater pump is in service, 9 Final HRH steam has > 25° superheat, 9 Intermediate HRH temperature is > 305°C, 9 HRH temperature before desuperheater is > 305°C, 9 Total HRH steam flow > 35%, 9 Intermediate desuperheater outlet temperature has > 5° superheat, and 7. 9 Intermediate desuperheater control valve is demanded open. ¾ Block valve will CLOSE IF any of the previous conditions are not met. O&M Training 24

Intermediate And Reheater Pressure Steam System #4 IP Drum Level Control 1.

Level maintained by an automatic level control valve. Operator must verify that the level control valve is in automatic on the OM screen. 2. Two level setpoints fed into the level control valve controller 9. ¾ S/U LVL ¾ NORM LVL.

8.

3.

5.

Initial startup – S/U LVL SLC is Automatically Selected by the control system. Ensures drum level is NOT exceeded as the water swells.

4.

S/U LVL mode ¾ Level control valve compares actual drum level to the S/U LVL setpoint only and adjusts to maintain level. As IP drum water is heated, water level will rise and pressure will build in the system. Steam will begin to flow to the IP superheater and out of the startup vent. Water level will drop and feedwater will be fed through the level control valve to maintain the S/U LVL setpoint.

6.

IP steam flow > 15% of rated flow ¾ 3-element control logic will become active. (IP steam flow, IP drum feedwater flow and IP drum water level). After 3 element control logic operation with CT in Service or when IP drum pressure > 5 bars, and IP drum pressure indicates a 3.5 bar rise from initial drum pressure with the CT in service ¾ Level control valve setpoint changes from S/U LVL to NORM LVL (0 cm). ¾ Level control valve will raise the IP drum to the normal operating level. In 3-element control, if either steam flow or feedwater flow transmitters fail, the SLC NO 3 ELE will activate and remove the affected instrument from the For Training Only calculation for controlling drum level.

7.

O&M Training 25

Intermediate And Reheater Pressure Steam System #5 IP Drum Continuous Blowdown Valve Motor Operated Continuous Blowdown Valve 1. Allows blowdown of IP drum water to control chemistry in the drum during operation.

2. The rate of blowdown is controlled by a precision manual throttle valve downstream of the motor operated valve. 9. Operator must open and close the motor operated valve from the OM screen. 3. 30 minutes of gas ¾ Must OPEN the continuous blowdown valve within turbine startup. ¾ If the operator fails to open the valve within 30 minutes, a “CLOSED WARNING” will display on the alarm screen. The alarm will continue to re-display every 30 minutes until the valve is opened.

8.

5.

4.

¾ Must CLOSE the continuous blowdown valve within 20 minutes of gas turbine shutdown. ¾ If the operator fails to close the valve within 20 minutes, an “OPEN WARNING” will display on the alarm screen. The alarm will continue to re-display every 20 minutes until the valve is closed.

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For Training Only

O&M Training 26

Intermediate And Reheater Pressure Steam System #6 IP Economizer Vent Valve Motor Operated Vent Valve 1. Buildup of non condensable gases in the economizer tubes can reduce heat transfer. The vent valve ensures adequate cooling by keeping the economizer tubes full of water.

2.

™ With Controller in AUTOMATIC, Economizer Vent valve will open when: 9. ¾ IP drum pressure drops below a preset value (~ 1.72 bar), ¾ A boiler feedwater pump is in service and 3. ¾ The IP feedwater block valve is open.

8.

5.

4.

™ With Controller in AUTOMATIC, Economizer Vent valve will close when: ¾ As pressure builds in the IP drum above the minimum preset pressure setpoint (~ 1.72 bar), ¾ The IP feedwater block valve is closed, or ¾ The boiler feedwater pump is shutdown.

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For Training Only

O&M Training 27

Intermediate And Reheater Pressure Steam System #7 IP Drum Intermittent Blowdown Block Valve ™ Motor 1. Operated Block Valve ™ Provides a means to isolate the IP Intermittent Blowdown Control valve which controls excessive drum level during startup and transients during normal operations. 2. 9.

8. ™ Automatically opened when blowdown control valve demanded 3. position is > 3%. ™ Automatically closed when blowdown control valve position demand is < 3%.

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O&M Training 28

Intermediate And Reheater Pressure Steam System #8 IP Steam Vent Valve 1.

2. 9.

8.

3. 5.

™ Motor Operated Vent Valve Downstream of the Superheater ™ Provides a flow path of steam during startup of the IP section of the HRSG. ¾ Prevents potential overheating of the superheater ™ With Controller in AUTOMATIC, ¾ Vent valve will open when the gas turbine is in operation and the IP Steam Control Valve closed and the IP Drum pressure less than 2 bar. ¾ Vent valve will close when any one of these conditions are not met.

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For Training Only

O&M Training 29

Intermediate And Reheater Pressure Steam System #9 CRH Equalization Control Valve 1.

2. 9.

8.

3. 5.

™ Motor Operated Valve ™ Provides to balance out CRH steam flow during two HRSG operations. ¾ Ensures that the exact amount of steam flow is returned to each HRSG that is taken from them. ™ Under the current design, no balancing is required with one HRSG. Therefore the current purpose of the CRH Equalization Control Valve is to isolate the CRH to the HRSG when the control valve position demand drops below 5%. When Valve demand is greater than 5%, the CRH Equalization Control Valve will open.

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For Training Only

O&M Training 30

High Pressure Steam System Start Up From A Cold Piping State Drains and Vents of the HP system are opened. HP drum is filled to start-up level. Intermittent blowdown valve level is switched over to start-up level. When the condenser and other necessary systems are ready for service, the steam generator is started up. Intermittent blowdown valve is switched over to normal water level. HP Economizer is fed with a minimum flow rate of ~ 10% of normal flow to protect the evaporator from flashing during GT start up. If HP drum water level rises above normal water level, the HP intermittent blowdown valve opens. After steam production has been established, ¾ HP feedwater control station is switched over to 3 element control. ¾ Intermittent blowdown valve of the HP drum is switched over to blowdown level. Initially during start up, the steam turbine is isolated from the main steam system due to insufficient steam pressure, temperature and steam quality. The drains are closed once the steam is sufficiently superheated. With increasing thermal input, the HP bypass station will begin to open when a certain pressure level is achieved (typically 90 to 120 psig). Once the position set point is reached, the pressure in the high pressure system rises in accordance with the variable pressure characteristic of the bypass station. Steam turbine control valve is opened when all conditions have been satisfied for loading of the steam turbine; ¾ Steam flow rate, ¾ Purity and ¾ Temperature. HP bypass valve, which is set to pressure control, starts to close slowly in proportion to the steam quantity flowing to the turbine. After the HP bypass station is closed, the load will be increased in accordance with the allowable load change gradients of the steam turbine, the steam generator and the pipes. For Training Only

O&M Training 31

High Pressure Steam System

Warm / Hot Start The same sequences for the cold start apply for a warm/hot start. The drain valves may be opened after the HRSG is in operation. The drains are closed in accordance with the same criteria as in the cold start. The HP bypass valve opens when a pressure rise is detected. It maintains the previous setpoint until the variable pressure characteristic has been reached. The combustion turbine is then run up corresponding to the steam conditions required by the steam turbine in accordance with the allowable gradients for the heat recovery steam generator and the steam turbine.

For Training Only

O&M Training 32

High Pressure Steam System

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O&M Training 33

High Pressure Steam System #1 Press Hold SLC 6.

2. 3.

4. 5. 1. ™ Sub Loop Controller ™ Operator Activated ™ Should be “Turned ON” prior to Start up. 11. ™ When Turned ON: ¾ Limit pressure setpoint for HP bypass valve, ¾ Limit pressure setpoint for HP vent valve, and 10. ¾ Limit CT load control to prevent exceeding a pressure and temperature limit on the HP section. ™ If NOT Turned ON: ¾ Operator is responsible for ensuring pressure and thermal limits are not exceeded during startup and operation.

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O&M Training 34

High Pressure Steam System #2 HP Feedwater Block Valve 6.

2. 3. ™ Motor Operated Block Valve Upstream of the HP Level Control valve 4. into the HP Drum. ™ Ensures positive isolation of water 5. ™ With Controller in AUTOMATIC, ¾ Block valve will open and stay open when: 9 A boiler feedwater pump is running, 1. 9 HP Feedwater Startup Block Valve is open and 9 Differential pressure across feedwater block valve is < 3.5 bars. ¾ If the pressure instruments before or after the block valve fail, the 11. valve will open when a boiler feedwater pump has been running for > 5 minutes ¾ Block Valve will close when: 10. 9 The boiler feedwater pump is off, or 9 HP drum level reaches the HI-HI trip level with the CT shutdown, or 9 HP boiler feedwater pump pressure drops below 118.5 bars.

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O&M Training 35

High Pressure Steam System #3 HP Startup Block Valve 6.

2. 3. ™ Solenoid Operated Block Valve 4. ™ Provides a means to equalize pressure across the HP Feedwater Block Valve prior to opening. 5. 1.

™ With Controller in AUTOMATIC, ¾ Startup Block valve will open when: 9 A boiler feedwater pump is running, and 9 HP Discharge Pressure from pump is > 122 bar. ¾ If the pressure transmitter for the IP discharge pressure fails, the valve opens within a short time period on indication that a boiler 11. feedwater pump is in service

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For Training Only

O&M Training 36

High Pressure Steam System #4 HP Bypass Desuperheater Block Valve 6.

2. 3.

4. 5. Block Valve ™ Solenoid Operated ™ Isolates feedwater to the HP Bypass valve when not required for operation.

1.

11.

™ With Controller in AUTOMATIC, ¾ Block valve will open when: 9 HP Bypass valve position demand reaches 5% increasing. 8.

7.

¾ Block valve will close when: 9 HP Bypass valve position demand reaches 3% decreasing.

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For Training Only

O&M Training 37

High Pressure Steam System #5 HP Interstage and Final Desuperheater Block Valves 6.

2. 3.

4. 5. 1.

™ Solenoid Operated11. Block Valves ™ Provide positive isolation of HP feedwater to their corresponding control valves. 10. ™ Final Desuperheater Block Valve With Controller in AUTOMATIC, ¾ Block valve will OPEN when: 9 A boiler feedwater pump is in service, 9 Final HP steam has > 25° superheat, 9 Final HP temperature is > 325°C, 9 HP temperature before desuperheater is > 305°C, 9 Total HP steam flow > 25%, and 9 Final desuperheater control valve is demanded open. ¾ Block valve will CLOSE IF any of the previous conditions are not met. For Training Only

8. ™ HP Interstage Desuperheater Block Valve With Controller in AUTOMATIC, ¾ Block valve will OPEN when: 9 A boiler feedwater pump is in service, 9 Final HP steam has > 25° superheat, 9 HP temperature before desuperheater is > 305°C, 9 Total HP steam flow > 25%, 9 Interstage desuperheater outlet temperature 9. and has > 5° superheat, 9 Interstage desuperheater control valve is demanded open. ¾ Block valve will CLOSE IF any of the previous conditions are not met.

7.

O&M Training 38

High Pressure Steam System #6 HP Drum Level Control Level maintained by an automatic level control valve. Operator must2.verify that the level control valve is in automatic on the OM screen. 3. Two level setpoints fed into the level control valve controller ¾ S/U LVL ¾ NORM LVL.

6.

4.

Initial startup – S/U LVL SLC is Automatically Selected by the control system. 5. Ensures drum level is NOT exceeded as the water swells. S/U1.LVL mode ¾ Level control valve compares actual drum level to the S/U LVL setpoint only and adjusts to maintain level. As HP drum water is heated, water level will rise and pressure will build in the system. Steam will begin to flow to the HP superheater and out of the startup 11. vent. Water level will drop and feedwater will be fed through the level control valve to maintain the S/U LVL setpoint.

8.

7.

10. flow > 15% of rated flow HP steam ¾ 3-element control logic will become active. (HP steam flow, HP drum feedwater flow and HP drum water level). After 3 element control logic operation with CT in Service or when HP drum pressure > 10 bars, and HP drum pressure indicates a 7 bar rise from initial drum pressure with the CT in service ¾ Level control valve setpoint changes from S/U LVL to NORM LVL (0 cm). ¾ Level control valve will raise the HP drum to the normal operating level. In 3-element control, if either steam flow or feedwater flow transmitters fail, the SLC NO 3 ELE will activate and remove the affected instrument from the calculation for controlling drum level. For Training Only

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O&M Training 39

High Pressure Steam System #7 HP Economizer Vent Valve 6.

2. 3.

4. 5. 1.

Motor Operated Vent Valve Buildup of non condensable gases in the economizer tubes can reduce heat 11. The vent valve ensures adequate cooling by keeping the economizer transfer. tubes full of water.

8.

7.

™ 10.With Controller in AUTOMATIC, Economizer Vent valve will open when: ¾ HP drum pressure drops below a preset value near saturation temperature, ¾ A boiler feedwater pump is in service ¾ The HP feedwater block valve and Startup Block Valves are open and ¾ HP drum level control valve is greater than 1.5% open.

9. ™ With Controller in AUTOMATIC, Economizer Vent valve will close when: ¾ As pressure builds in the HP drum above the minimum preset temperature setpoint , ¾ The HP feedwater block valve or Startup Block Valve is closed, or ¾ The boiler feedwater pump is shutdown. For Training Only

O&M Training 40

High Pressure Steam System #8 HP Drum Continuous Blowdown Valve 6.

2. 3.

4. 5. Motor Operated Continuous Blowdown Valve 1. Allows blowdown of HP drum water to control chemistry in the drum during operation. The rate of blowdown is controlled by a precision manual throttle valve downstream of the motor operated valve. Operator must open and close the motor operated valve from the OM screen. 11. ¾ Must OPEN the continuous blowdown valve within 30 minutes of gas turbine startup. ¾ If the operator fails to open the valve within 30 minutes, a “CLOSED 10. WARNING” will display on the alarm screen. The alarm will continue to re-display every 30 minutes until the valve is opened. ¾ Must CLOSE the continuous blowdown valve within 20 minutes of gas turbine shutdown. ¾ If the operator fails to close the valve within 20 minutes, an “OPEN WARNING” will display on the alarm screen. The alarm will continue to re-display every 20 minutes until the valve is closed.

For Training Only

8.

7.

9.

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High Pressure Steam System #9 HP Drum Intermittent Blowdown Valve 6.

2. 3.

4. 5. 1.

8.

11.

7.

™ Motor Operated Block Valve ™10. Provides a means to isolate the HP Intermittent Blowdown Control valve which controls excessive drum level during startup and transients during normal operations. ™ Automatically opened when blowdown control valve demanded position is > 5%. ™ Automatically closed when blowdown control valve position demand is < 3%.

For Training Only

9.

O&M Training 42

High Pressure Steam System #10 HP Superheater Steam Block Bypass Valve 6.

2. 3.

4. 5. 1.

11.

10.

8.

7.

™ Motor Operated Block Valve ™ Provides a means to equalization of pressure across the HP Superheat Steam Block Valve to prevent damage due to high differential pressure. ™ Automatically opened when the SLC HRSG SETUP FOR IN SERVICE is activated from the Water/Steam Overview OM 9. screen. ™ Automatically closed when the HP Superheat Steam Block Valve indicates it is open.

For Training Only

O&M Training 43

High Pressure Steam System #11 HP Superheater Steam Block Valve 6.

2. 3.

4. 5. 1.

11.

10.

8.

7.

™ Motor Operated Block Valve ™ Provides a means to isolate the HRSG HP section from the plant’s HP steam system during periods of shutdown. ™ Automatically opened when differential pressure across the valve reaches < 7 bar. ™ Automatically closed when the gas turbine is shutdown. 9.

For Training Only

O&M Training 44

Duct Burner System

1. 2. 3. 4. 5.

For Training Only

O&M Training 45

Duct Burner System #1 Duct Burner Start SLC 1. ™ Allows the duct burner to be placed into service once the gas turbine is online and is on outlet temperature control (OTC). ™ Duct Burner will Start When: ¾ SLC is activated, ¾ Duct burner PLC is OK, ¾ Duct burner fan is in service and ¾ HRSG is in service (GT OTC is active). 4. ™ SLC will command the Duct Burner PLC to activate the duct burner 5. startup sequence.

For Training Only

2. 3.

O&M Training 46

Duct Burner System #2 Duct Burner Stop SLC 1. ™ Commands the Duct Burner PLC to shutdown the duct burner system. ™ SLC can be activated by: ¾ The operator, ¾ The PLC Burner Management Master Fuel Trip or ¾ Abnormal conditions with the steam plant. 9 Gas turbine trip, 4. 9 High HP steam pressure, 118 bar 9 HI-HI HP steam temperature, 557 > 60 s, 560 >3 s 9 Steam turbine trip or 9 Low HP drum level. -15.24

For Training Only

2. 3.

5.

O&M Training 47

Duct Burner System #3 Duct Burner MFT Reset SLC 1. ™ Provides the operator a means to reset the duct burner system PLC remotely after any trip of the duct burner. ™ Prior to starting the duct burner, the operator should reset the system with this SLC.

2. 3.

4. 5.

For Training Only

O&M Training 48

Duct Burner System #4 & 5 Duct Burner Fans SLC/ASO 1. 2. 3. 4. 5.

#4 Duct Burner Fans SLC ™ Turns on the selected fan to provide cooling to the flame scanners. ™ SLC can be activated by: ¾ The operator, ¾ Automatically when gas turbine exhaust temperature increases to 60°C. ™ Selected fan will continue to run until gas turbine exhaust temperature drops to 55°C for 5 minutes #5 Duct Burner Fans ASO ™ Allows the operator to select which fan should be the primary and starts that fan when the SLC Duct Burner Fans is active. ™ If primary fan fails to indicate proper operation, the ASO will automatically start the backup fan and provide an alarm. For Training Only

O&M Training 49

Shutdown and Part-Load Behavior On a load reduction of the gas turbine, the gas turbine exhaust gas flow rate is reduced to approximately 70% at nearly constant exhaust gas temperature in the first phase. The exhaust gas flow rate is then held constant and the exhaust gas temperature is reduced as a function of combustion inlet temperature. The main steam temperature starts to rise slightly. The interstage spray attemperators limit the main steam temperature. The main steam temperature drops proportionally to the gas turbine exhaust gas temperature only when additional load is reduced on the gas turbine. The heat recovery steam generator adapts to the characteristics of the gas turbine. The low pressure system is operated in the variable fixed pressure mode over the load range. For the shutdown of the steam turbine, the turbine inlet valves are closed. Additional steam produced in the heat recovery steam generator is routed to the condenser via the bypass stations.

For Training Only

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