EP2005 TID Almond Power-2005.01.17

7/29/2019 EP2005 TID Almond Power-2005.01.17

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A Babcock Power Inc. Company

Improving Emissions Performance

in Combined Cycle Equipment

Turlock Irrigation District

Almond Repowering Project

Distribution Grid Retrofit following GT Upgrade

Electric Power 2005

Track 8Gas Turbine Based Power Plants

Session 8C

Keith C. KaufmanSenior Thermal Engineer

Vogt Power International, Inc.


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Vogt Power International 4/6/052

The Problem:

Recent GT upgrade at TID Almond Power Station

GT change required replacement of CO and SCR systems

Following retrofit, plant did not achieve expected emissions

Large NH3 injection rates required to barely meet NOx limits.

Excessive ammonia slip

TID not satisfied with completed NELS models

Didnt adequately represent geometry

Recommended very complex distribution grid system

TID contracted VPI to model the existing system and

recommend options to correct the emissions performance

while minimizing impact on gas-side pressure drop


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Original Configuration with No Distribution Grid

Please note: Only inside gas path geometry is modeled.

GT Collector/Diffuser

SCR Catalyst

Modules

CO Catalyst Modules

Inlet Expansion Ductwork


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Analysis:

VPI used computational fluid dynamics (CFD) to evaluate both the

existing unit configuration and modified designs including a

distribution grid upstream of the CO catalyst modules.

Computational flow models were completed with Fluent 6.1

Inlet GT performance conditions were based on information provided

by TID

The GT inlet velocity profile was defined per an available analytical GE

velocity profile for the radial discharge LM6000.

Distribution grid variations were evaluated that would minimize theimpact on gas-side pressure drop while redistributing flow to both the

CO and SCR systems.


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Location of Key Result Planes

T4 Field Location

AIG Location

1ft Before SCR

Entering SCR

Modules

T2 Field Location

Inlet Duct Planes at

Column Line Locations

Note: T2 and T4 field locations were identified in the NELS Field

Test Preliminary Report


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Geometry Detail at CO and SCR Catalyst Modules

Stiffener Beam Spanning

Duct Width

Vertical Beams,Horizontal

Stiffeners, and

Splitter Plates at

SCR Modules

Vertical Beams and Splitter

Plates at CO Modules

CO catalyst and

support structure

SCR catalyst and

support structure


7/15Vogt Power International 4/6/057

Computational Mesh

Detail at CO and SCR

Modules



Flow patterns predicted for the original configuration confirm that the

flow approaching the CO catalyst is highly biased to the bottom and right

side of the unit

Stream Traces colored by

Velocity Magnitude (ft/s) Axial Velocity Contours (ft/s)



Contours of axial velocity highlight mal-distribution upstream of CO

catalyst and into the ammonia injection grid (AIG)

Axial

Velocity

(ft/s)

Axial

Velocity

(ft/s)

Axial

Velocity

(ft/s)

T2 Field Location Entering CO Modules AIG Location

Original Configuration



A two-zone distribution grid design was established that would:

Be sufficiently general for necessary GT

operating conditions.

Improve gas distribution at the CO, AIG,

and SCR. (+/-15% variation from average

at the T4 location) Minimize impact on gas-side pressure

drop across the unit while only requiring

construction of a single grid

(addl GSPD < 0.5WC)



Flow patterns following the grid are more regularly distributed into the

CO catalyst, and very uniform into the SCR system

VelocityMagnitude

(ft/s)

Distribution across height

and width is improved,

with backflow and cross-flow only observed

upstream of the grid.



Axial Velocity Contours with the final grid design show significantly more

uniform distributions into the CO and AIG

Axial

Velocity

(ft/s)

Axial

Velocity

(ft/s)

Axial

Velocity

(ft/s)

T2 Field Location Entering CO Modules AIG Location

Revised Configuration



Predicted velocities at the T4 location and entering the SCR catalyst meet

customer-specified requirements on gas distribution

Axial

Velocity(ft/s)

Axial

Velocity(ft/s)

T4 Field Location 1ft Before SCR Entering SCR Modules

Revised Configuration



Comparison of Measured Emissions Results

Pollutant

Emisions

ppmv

@15% O2lb/day

ppmv

@15% O2lb/day

NOx 2.90 115.0 2.70 112.2

CO 1.24 29.5 0.73 18.7NH3 6.00 88.8 0.70 10.5

Ammonia

Injectionlb/hr lb/day lb/hr lb/day

Range 15.7 - 22.7 376.8 - 544.8 11.2 - 11.5 268.8 - 276.0

Average 18.1 434.4 11.4 273.6

@45 MW Output

Before Retrofit

@50MW Output

After Retrofit

Original emissions testing completed on Nov. 20, 2003.

Follow-up testing after retrofit completed on Aug. 26. 2004

Factor of 8 decrease in ammonia slip

37% Average Reduction (50% Max. Reduction) inAmmonia Injection Requirements



VPI Applications for Computational Flow Modeling:

GT upgrades and impact on existing equipment

Inlet duct design and evaluation

Bypass stack design and performance

Duct burner placement and downstream mixing

Gas distribution into heating surface

Baffle design and comparison

Gas distribution into emissions equipment

Exhaust duct, stack breaching, and exhaust stack

EP2005 TID Almond Power-2005.01.17

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