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

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

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

FAE EQUATION FAE EQUATION n x C  E = C x E = C x M x V M x V x C p 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 n x (C n E 1 /E avg = (M 1 /M a ) x (V 1 /V a ) x (C p1 /C pa ) E 1 /E avg = (M 1 /M a ) x (V 1 /V a ) p1 /C pa ) Relative Erosion Rates (E1/Eavg, n=2.4) 2.0 Relative Solide Loading 1.5 (5.0) 1.0 (1.86) 0.5 (0.18) (0.47) (E1/Eavg=1.00) 0.0 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Relative Velocity

LARGE BOILER LARGE BOILER >750 MW >750 MW FAE AREAS: FAE AREAS: PERIMETER PERIMETER IN- -BANK BANK IN FAE APPROACH: APPROACH: CAVT CAVT COMPUTER MODEL COMPUTER MODEL

FLOW MID- -SIZE BOILER SIZE BOILER MID 200 - - 750 MW 750 MW 200 FAE AREAS: FAE AREAS: REAR PASS NEAR REAR PASS NEAR REAR WALL REAR WALL FLOW FAE APPROACH: APPROACH: COMPUTER & PHYSICAL MODEL COMPUTER & PHYSICAL MODEL FLOW FOLLOW- -UP CAVT UP CAVT FOLLOW

STEAM SMALL BOILER SMALL BOILER DRUM < 200 MW < 200 MW FAE AREA: FAE AREA: ECON NEAR ECON NEAR REAR WALL REAR WALL MUD DRUM FAE APPROACH: APPROACH: FLOW (FROM STOKER) COMPUTER MODEL COMPUTER MODEL

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

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

COLD AIR VELOCITY TEST COLD AIR VELOCITY TEST

FLOW VISUALIZATION FLOW VISUALIZATION

FLOW VISUALIZATION FLOW VISUALIZATION

Normalized Velocty vs. Position Normalized Velocity vs. Position (Row Averages) 2.00 1.0 1.75 Rear 1.50 COLD AIR VELOCITY TEST COLD AIR VELOCITY TEST Normalized Velocity 0.9 1.25 1.00 0.8 0.75 0.50 0.7 Left 2 Relative Position (Front-to-Rear) 3 0.25 4 Side-to-Side 5 0.6 0.00 6 n- m l k j Right i h g Rear f e d c b a- Front 0.5 Front-to-Rear 0.4 Normalized Velocity vs. Position (Column Averages) 0.3 2.0 Normalized Velocity 1.5 0.2 1.0 0.1 0.5 Front 0.0 0.0 0.5 1.0 1.5 2.0 0.0 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 Normalized Velocities Left Right Relative Position (Left-to-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

2-1/2-D CFD Model Geometry FLOW FLOW HTSH FAE Nominal 1 Ft Wide Slice FLOW Model Outlet Inlet Div Wall

3-D MODEL ECON BANKS INLET OUTLET TO AH PA DUCT EXTRACTION ASSYMETRIC

Gas Velocity 3-Baffles

INLET – 2350°F TEMPERATURE OUTLET – 700°F

30 & 53 MICRON PARTICULATE

PARTICULATE 74, 88, 105 MICRON

PARTICULATE 177, 210 MICRON

Relative Mass Loading w/ Size Correction Rear Pass at Operating Conditions 5.0 No Baffles 3 Baffles 4.0 Relative M ass & Size Ratio 3.0 2.0 Uniform ash / size distribution = 1.0 40% REDUCTION 1.0 0.0 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 Distance, Rear-to-Front (Ft) Front Rear

FLOW MID- -SIZE BOILER SIZE BOILER MID 200 - - 750 MW 750 MW 200 FAE AREAS: FAE AREAS: REAR PASS NEAR REAR PASS NEAR REAR WALL REAR WALL FLOW FAE APPROACH: APPROACH: COMPUTER & PHYSICAL MODEL COMPUTER & PHYSICAL MODEL FLOW FOLLOW- -UP CAVT UP CAVT FOLLOW

2-1/2-D CFD Model Geometry 400 MW Screen Tubes Hanger Tubes LTSH HTSH Nominal 1 Ft Wide Slice Model Outlet Inlet Div Wall

PARTICULATE: 10, 100, 150 MICRON BASELINE OUTLET INLET

BASELINE RELATIVE FAE TOP LTSH BANK INLET 20 Mass Wtd. Mass & Part. 18 Peak at Wall Gap 16 21x Ideal Adjustment to Account 14 Relative Erosion Rate for Larger Particle Shift to Rear of Pass 12 10 8 6 4 2 0 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)

CFD Model Geometry MAIN DIAGONAL SCREEN & TUBE BEND BAFFLES LADDER VANE BAFFLE 6 2 7 3 1 5 4 Div Wall FLOW FLOW

EMS BAFFLE 10, 23, 100  Particle Tracks

NEW FAE Controls Relative Erosion at Upper Rear LTSH Inlet 10.0 Mass Wtd. Mass & Part. 8.0 Realitive Erosion Rate 6.0 Peak in Front Sect No Major Particle Due to Jet off Vanes Shift to Rear 4.0 Rear Sect. Below Avg. 2.0 0.0 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)

STEAM SMALL BOILER SMALL BOILER DRUM < 200 MW < 200 MW FAE AREA: FAE AREA: ECON NEAR ECON NEAR REAR WALL REAR WALL MUD DRUM FAE APPROACH: APPROACH: FLOW (FROM STOKER) COMPUTER MODEL COMPUTER MODEL

FLOW VISUALIZATION FLOW VISUALIZATION

Trajectories for 10 Micron Ash Particles 18.0 17.0 16.0 15.0 14.0 13.0 Normalized Erosion Rate 12.0 Economizer Inlet Plane 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Economizer Tube Row Number

Trajectories for 10 Micron Ash Particles 5.0 Economizer Inlet Plane 4.0 Normalized Erosion Rate 3.0 2.0 1.0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Economizer Tube Row Number

OTHER ISSUES OTHER ISSUES  IN BANK FAE  TUBE ALIGNMENT  PLUGGING  TEMPERATURE

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

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

& FLOW TO SIDEWALL GAP TUBE ALIGNMENT Offset SH tube Sidewall

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 QUESTIONS AND ANSWERS J. DRENNEN DRENNEN ENG, INC