Nooter Eriksen Presentation [2]

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Transcript of Nooter Eriksen Presentation [2]

American Electric Power BRO Forum July 2010

N NOOTER/ERIKSEN EPaul Gremaud and Shaun Siegel

Nooter/Eriksen HRSGs at American Electric Power FacilitiesOologah - 2 Units (1999) GE 7 FA turbines (3) pressure levels with supplemental firing Waterford - 3 Units (2000) GE 7 FA turbines (3) pressure levels with supplemental firing Stall - 2 Units (2007) just began commercial operation (7/2010) Siemens 501 FD2 turbines

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2010 AEP BRO Forum

Nooter/Eriksen HRSGs behind Siemens 501Fs and GE 7 FAsNooter/Eriksen has supplied HRSGs behind GE 7FA machines on 51 projects for a total of 115 HRSGs. Nooter/Eriksen has supplied HRSGs behind Siemens 501F machines on 41 projects for a total of 79 HRSGs. Nooter/Eriksen HRSGs are behind 42% of the Siemens 501F machines

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2010 AEP BRO Forum

Topics to be Addressed1. General Overview of the Thermal Design of a HRSG

2. Issues/Concerns With HRSGs

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2010 AEP BRO Forum

Part 1: Thermal Design of HRSGs An Overview HRSG materials Tube finning Heating surface configurations Economizer design Vapor lock Cold end corrosion Boiler pressure turndown

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2010 AEP BRO Forum

Tube Materials SA-213 T91 HP Superheaters and Reheaters where tube wall temperature exceeds T23/T22/T11 limits SA-213 T23 HP Superheaters with high MAWPs and tube wall temperatures with T22/T11 limits SA-213 T22/T11 HP Superheater and Reheater when tube wall temperatures above CS limits. LP evaporator for corrosion resistance.

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Tube Materials Continued Carbon Steel Evaporators and economizers where design temperatures are within carbon steel limits 2205 SS LP economizer, preheaters where water is non-deareated.

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2010 AEP BRO Forum

Finning Configurations Fin Density 2.5 7.0 fpi Fin Height 0.25 1.0 Fin Thickness 0.039 0.059 Fin Segment 0.1772 for stainless and 0.15625 for CS

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2010 AEP BRO Forum

Drum Separator Design Primary Separator - Sized for max sub-cooled flow Secondary Separator - Sized for max V2 Benefits over cyclone type -Wider range of operation

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2010 AEP BRO Forum

Water Side Characteristics Pinch Temperature difference between fluid and exhaust gas. Recommend minimum of 15F Approach Temperature difference between saturation temperature and temperature of incoming water. Design as small as 0F Coil Distribution Provide uniform heat transfer across row Increases pressure of evaporator or pump

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HRSG Heating Surface

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Heating Surface ConfigurationsHalf Circuit Single Circuit Double Circuit

Up Flow

Down Flow2010 AEP BRO Forum

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HRSG Heating Surface

Half Circuit Double Circuit

Up Flow Single Circuit

N E

Stall Module #2 NOOTER/ERIKSEN

Waterford Module #42010 AEP BRO Forum

Heating Surface Configurations Half Circuit Economizers and IP/LP Superheaters Single Circuit Economizers and Superheaters Double Circuit HP Superheaters and Reheaters

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2010 AEP BRO Forum

Competitor 1 Economizer Design

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2010 AEP BRO Forum

Competitor 1 Economizer Design Design disadvantages Requires vent at every top header Converge/diverge at every header Possible vapor lock in down flow tubes Potential for corrosion fatigue

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2010 AEP BRO Forum

Competitor 2 Economizer Design

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2010 AEP BRO Forum

Competitor 2 Economizer Design Design disadvantages Requires vent at every top header Converge/diverge at every lower header Possible air entrapment at end of headers Potential for corrosion fatigue

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N/E Typical Economizer Design

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2010 AEP BRO Forum

N/E Economizer Design Design advantages Does not require vents Converge/diverge at inlet and outlet headers Accommodates differential movement Accommodates steaming Operation, maintenance and repair. Design disadvantage Vapor lock

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Vapor Lock Vapor Lock When tube flow is not able to clear the return bend. Variables Heating surface arrangements Fluid temperature and pressure Flow through coil Most likely to occur in low pressure economizers

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Vapor Lock Cont.

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2010 AEP BRO Forum

Cold End Corrosion When exhaust gas temperature goes below the sulfur dew point or contacts a surface colder than the dew point Control the inlet feedwater temperature above dew point Three methods of prevention Preheat evaporator (patent pending) Recirculation External heat exchanger

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Cold End Corrosion PreventionRecirculation

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Cold End Corrosion PreventionExternal heat exchanger

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Boiler Pressure Turndown Boiler performance envelope is based on the original design Minimum of 50% of HP base load pressure Potential problems with turndown Velocity in pipes Velocity in evaporators Stability in evaporators

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2010 AEP BRO Forum

Part 2: Issues/Concerns With HRSGs HRSG Inlet Duct Liner Issues Distribution Grid Issues Condensate Management Desuperheater Drain Pots & Coil Drains Improvements to Address Cycling of HRSGs Flow Accelerated Corrosion Backpressure Issues/Economizer Surface Reduction

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Inlet Duct Floor and Sidewall DetailsFloor is typically sloped 10-18 degrees Floor and sidewall liners have additional stiffening

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Inlet Duct Floor and Sidewall DetailsInlet Duct Floor and sidewalls are stiffened up to the distribution grid or the first coil.

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Inlet Duct Liner Damage

Deformed Liner Plate

Catastrophic damage to floor liner

Catastrophic damage to sidewall liner

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Inlet Duct Liner SolutionsWhat can be done when you have inlet duct liner damage?

Add stiffeners on the casing sidewall or floor Add intermediate liner pins Increase the thickness of the liner plate Install additional batten channels Additional liner stiffening backup angles

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2010 AEP BRO Forum

Inlet Duct Distribution GridWhat is it? Stiffened, Flat Plate with 40% to 60% open area Usually made from 300 series stainless steel Located in the inlet duct

What is the purpose of the distribution grid? Used to get proper flow distribution in the HRSG Typically required for units with supplemental firing

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Typical Distribution Grid

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Typical Distribution Grid Components

Gas Flow

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2010 AEP BRO Forum

Distribution Grid Damage

Pin Weld Failure at Sidewall

Support pedestal failure at weld to casing

Local deformation at support plate

Shear block weld failure2010 AEP BRO Forum

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Some Potential Grid Modifications (Incorporated into New Designs)Modifications can and have been made to address many grid failure issues. Addition/modification of the floor restraints Addition/modification of the sidewall restraints Addition of a gusset at the sidewall restraint plate Move location of sidewall restraint remove the offset Addition of stiffener bars on grid fabric

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Reheater and HP Superheater Condensate ManagementModifications have been made to address removal of condensate during startup, operation, and shutdown. ASME Section I 2004 edition 2006 addenda 1. Includes new section PHRSG 2. Contains mandatory requirements for DSHR drain pots

3. Contains mandatory requirements for RH & SH drainsIf condensate is not removed bad things happen!

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Condensate Management - DrainingBuckled tubes caused by uneven condensate clearing in coils or piping

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Condensate Management

Steam cooled tubes

No steam flow, hot tubes

Water

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Condensate ManagementNow what actually happens to cause this? Steam flow is low or prior to initiation of steam flow Water filling lower header and tubes blocks steam With low steam flow, only a few tubes clear Cleared tubes are steam cooled High expansion differences between hot and cool tubes Cooler tubes go into tension and potentially yield At cool down, tubes go into compression and buckle If there are bends, very high bending stresses created Normally no failure if the tubes are straight2010 AEP BRO Forum

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Condensate ManagementAvoid condensate moving between pressure levels or from other components Multiple pressure levels connected via blowdown or flash tank or other collection device It is possible to pressurize the collection device forcing water back into lower pressure components It is also possible to move condensate due to pressu