FLY ASH EROSION FLY ASH EROSION FLY ASH EROSION FLY ASH EROSION - - PowerPoint PPT Presentation

www.electricpowerexpo.com May 15‐17, 2012 – Baltimore, MD

FLY ASH EROSION FLY ASH EROSION FLY ASH EROSION FLY ASH EROSION CONTROL & PREVENTION CONTROL & PREVENTION CONTROL & PREVENTION CONTROL & PREVENTION RECENT DEVELOPMENTS RECENT DEVELOPMENTS RECENT DEVELOPMENTS RECENT DEVELOPMENTS JOHN DRENNEN, PE JOHN DRENNEN, PE JOHN DRENNEN, PE JOHN DRENNEN, PE DRENNEN ENGINEERING, INC. DRENNEN ENGINEERING, INC. DRENNEN ENGINEERING, INC. DRENNEN ENGINEERING, INC.

FLY ASH EROSION (FAE) FLY ASH EROSION (FAE)

LEADING CAUSE OF BTF PREVENTABLE… IN MOST CASES OLD TECHNOLOGY… & NEW TOOLS

FACTORS CONTRIBUTING FACTORS CONTRIBUTING TO INCREASED FAE TO INCREASED FAE

GAPS, OPENINGS TURNS IN FLOW PATH SOOTBLOWING FUEL CHANGE HIGHER LOAD PP CHANGES FUEL FIRING EQUIP ASH PLUGGING EROSION CONTROLS LOWER FLOW RESISTANCE CENTRIFUGAL SEPARATION FLY ASH SURGES MORE ASH HIGHER FLOW PREFERENTIAL FLOW TIME-TEMP HISTORY DECREASE FLOW AREA CAN MOVE PROBLEM

FAE EQUATION FAE EQUATION

E = C x

E = C x M x V M x V

n x C

x Cp



E – Erosion Rate



C – Correlation Const.



M – Mass Flux



V – Gas Velocity



n – exponent (2.5 - 3.5)

 Cp – Particle Size Adjustment

RELATIVE EROSION RELATIVE EROSION

E E1

1/E

/Eavg

avg = (M

= (M1

1/M

/Ma

a) x (V

) x (V1

1/V

/Va

a)

)

n n x (C

x (Cp1

p1/C

/Cpa

pa)

)

Relative Erosion Rates

(E1/Eavg, n=2.4)

0.0 0.5 1.0 1.5 2.0 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Relative Velocity Relative Solide Loading

(0.18) (0.47) (E1/Eavg=1.00) (1.86) (5.0)

LARGE BOILER LARGE BOILER >750 MW >750 MW FAE AREAS: FAE AREAS: PERIMETER PERIMETER IN IN-

• BANK

BANK APPROACH: APPROACH: CAVT CAVT COMPUTER MODEL COMPUTER MODEL

FAE

FLOW FLOW FLOW FAE

MID MID-

• SIZE BOILER

SIZE BOILER 200 200 -

• 750 MW

750 MW FAE AREAS: FAE AREAS: REAR PASS NEAR REAR PASS NEAR REAR WALL REAR WALL APPROACH: APPROACH: COMPUTER & PHYSICAL MODEL COMPUTER & PHYSICAL MODEL FOLLOW FOLLOW-

• UP CAVT

UP CAVT

SMALL BOILER SMALL BOILER < 200 MW < 200 MW FAE AREA: FAE AREA: ECON NEAR ECON NEAR REAR WALL REAR WALL APPROACH: APPROACH: COMPUTER MODEL COMPUTER MODEL

STEAM DRUM

FLOW (FROM STOKER)

MUD DRUM

FAE

APPROACH TO FAE REDUCTION APPROACH TO FAE REDUCTION

 IDENTIFY ROOT CAUSE

GAS & ASH DISTRIBUTION, OTHER…

 MEASURE / MODEL DISTRIBUTIONS

CAVT, COMPUTER, PHYSICAL MODEL

 REDISTRIBUTE FLOWS

FLOW MODIFICATION BAFFLES

COLD AIR VELOCITY TEST COLD AIR VELOCITY TEST

 Measure Gas Flow Distribution

FULL SCALE PHYSICAL MODEL

 Testing in Unit w/ Fans Running  Multiple Teams  Flow Visualization

COLD AIR VELOCITY TEST

• Multiple Teams at Different Planes
• One Person Measures, the Other Records Readings & Notes
• Safety Person for Each Team Outside at Same Plane
• Control Room Operator Sets and Monitors Flow and

Other Equipment to Support Test. Control Room

n i j k l m h g f e d c b a

COLD AIR VELOCITY TEST COLD AIR VELOCITY TEST

FLOW VISUALIZATION FLOW VISUALIZATION

FLOW VISUALIZATION FLOW VISUALIZATION

COLD AIR VELOCITY TEST COLD AIR VELOCITY TEST

n- Rear m l k j i h g f e d c b a- Front Left 2 3 4 5 6 Right 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00

Normalized Velocity Front-to-Rear Side-to-Side

Normalized Velocty vs. Position Normalized Velocity vs. Position (Column Averages)

0.0 0.5 1.0 1.5 2.0 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Relative Position (Left-to-Right) Normalized Velocity Normalized Velocity vs. Position (Row Averages)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.5 1.0 1.5 2.0

Normalized Velocities Relative Position (Front-to-Rear)

Rear Front Left Right

COMPUTER MODELING COMPUTER MODELING COMPUTER MODELING

• 2-D OR 3-D

DEPENDS ON SYMMETRY

• AMBIENT TEMPERATURE (CAVT)
• OPERATING CONDITIONS

W/ HEAT EXTRACTION

• GROSS FLOW DISTRIBUTION

GAS AND PARTICULATE

• ESTIMATE RELATIVE FAE RATE
• DETAILED AREA MODELS

Inlet Outlet Nominal 1 Ft Wide Slice Model Div Wall

2-1/2-D CFD Model Geometry

HTSH

FLOW FLOW FLOW FAE

3-D MODEL

PA DUCT EXTRACTION ASSYMETRIC

INLET OUTLET TO AH ECON BANKS

Gas Velocity 3-Baffles

TEMPERATURE INLET – 2350°F OUTLET – 700°F

PARTICULATE 30 & 53 MICRON

PARTICULATE 74, 88, 105 MICRON

PARTICULATE 177, 210 MICRON

0.0 1.0 2.0 3.0 4.0 5.0 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Distance, Rear-to-Front (Ft) Relative M ass & Size Ratio

No Baffles 3 Baffles

Relative Mass Loading w/ Size Correction Rear Pass at Operating Conditions

40% REDUCTION

Front Rear

Uniform ash / size distribution = 1.0

FLOW FLOW FLOW FAE

MID MID-

• SIZE BOILER

SIZE BOILER 200 200 -

• 750 MW

750 MW FAE AREAS: FAE AREAS: REAR PASS NEAR REAR PASS NEAR REAR WALL REAR WALL APPROACH: APPROACH: COMPUTER & PHYSICAL MODEL COMPUTER & PHYSICAL MODEL FOLLOW FOLLOW-

• UP CAVT

UP CAVT

Hanger Tubes Inlet Screen Tubes Outlet LTSH Nominal 1 Ft Wide Slice Model Div Wall

2-1/2-D CFD Model Geometry

HTSH 400 MW

INLET

BASELINE

PARTICULATE: 10, 100, 150 MICRON

OUTLET

2 4 6 8 10 12 14 16 18 20 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0

Distance, Front-to-Rear (Ft) Relative Erosion Rate

Mass Wtd. Mass & Part. Adjustment to Account for Larger Particle Shift to Rear of Pass

Peak at Wall Gap 21x Ideal

BASELINE

RELATIVE FAE TOP LTSH BANK INLET

FLOW FLOW 1 2 3 5 4 6 7

CFD Model Geometry

MAIN DIAGONAL SCREEN & TUBE BEND BAFFLES Div Wall

LADDER VANE BAFFLE

EMS BAFFLE 10, 23, 100  Particle Tracks

0.0 2.0 4.0 6.0 8.0 10.0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 Distance, Front-to-Rear (Ft) Realitive Erosion Rate

Mass Wtd. Mass & Part.

Relative Erosion at Upper Rear LTSH Inlet

NEW FAE Controls

No Major Particle Shift to Rear

Rear Sect. Below Avg.

Peak in Front Sect Due to Jet off Vanes

SMALL BOILER SMALL BOILER < 200 MW < 200 MW FAE AREA: FAE AREA: ECON NEAR ECON NEAR REAR WALL REAR WALL APPROACH: APPROACH: COMPUTER MODEL COMPUTER MODEL

STEAM DRUM

FLOW (FROM STOKER)

MUD DRUM

FAE

FLOW VISUALIZATION FLOW VISUALIZATION

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Economizer Tube Row Number Normalized Erosion Rate

Trajectories for 10 Micron Ash Particles

Economizer Inlet Plane

0.0 1.0 2.0 3.0 4.0 5.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Economizer Tube Row Number Normalized Erosion Rate

Trajectories for 10 Micron Ash Particles

Economizer Inlet Plane

OTHER ISSUES OTHER ISSUES

 IN BANK FAE  TUBE ALIGNMENT  PLUGGING  TEMPERATURE

Particle Tracks Through Bank

Particle Sizes Shown () : 44, 62, 88, 125, 177, 250, 420 Highest Particle Impact Zone Particles are deflected off of top row and then again by 4th row into Rows 5-8, where the most serious FAE occurs.

FAE LOCATIONS

Particles are deflected by top row and 4th row tubes into Row’s 5 - 8, where most serious FAE occurs.

Particle Tracks at Top of Bank

Particle Sizes Shown () : 44, 62, 88, 125, 177, 250, 420 Flow

Sidewall Offset SH tube

FLOW TO SIDEWALL GAP & TUBE ALIGNMENT

PLUGGING DUE TO SOOTBLOWING PLUGGING DUE TO SOOTBLOWING

PLUGGING DUE TO CARRYOVER PLUGGING DUE TO CARRYOVER

ASH DEFLECTION SCREENS ASH DEFLECTION SCREENS

OVERHEATING OVERHEATING

SUMMARY SUMMARY

STEPS TO REDUCE FAE  IDENTIFY LOCATIONS – FAE – ROOT CAUSE  GET FLOW DISTRIBUTIONS GAS AND FLY ASH CAVT, COMPUTER OR PHYSICAL MODEL  CORRELATE FAE TO FLOW DISTRIBUTIONS  SELECT BAFFLES TO REDISTRIBUTE FLOW  GET MODIFIED DISTRIBUTIONS W/ BAFFLES  CAUTIONARY ITEMS PLUGGING, TEMPERATURE

FLY ASH EROSION FLY ASH EROSION CONTROL & PREVENTION CONTROL & PREVENTION

• J. DRENNEN

DRENNEN ENG, INC

QUESTIONS AND ANSWERS