Worldwide Pollution Control Association

Transcription

1 Worldwide Pollution Control Association FirstEnergy ESP Seminar November 27 th 28 th, 2007 Visit our website at

2 Effects of Temperature on ESP Performance Environmental & Energy Research Department Southern Research Institute Joseph D. McCain. Senior Staff Physicist Environment & Energy Research Department Southern Research Institute

3 Temperature affects ESP performance in three ways It changes the volume flow through the ESP. It changes the resistivity of the ash. It changes the adhesion and cohesion properties of the ash.

4 Deutsch-Anderson equation for the collection efficiency of an ESP p = exp(-v k *A/V) where p = fractional penetration of precipitator collection efficiency A = total collecting area V = flue gas flow rate v k = the effective migration velocity of the particles A/V = Specific Collection Area (SCA) [ collection efficiency of ESP = 100*(1 - p)]

5 Examples to follow are based on an ESP with four sections of uniform length. The SRI ESP model was used to estimate performance over a temperature range of 250 F to 375 F with constant mass flow of gas and inlet particulate matter. The SCA was 288 sq.ft./kacfm at 300 F Opacities were calculated based on a stack diameter of 30 feet. First: Vary only volume flow using a fixed ash resistivity of 1X10 10 ohm-cm.

6 Emission Rate, lb.mmbtu Emission Rate PM Pm2.5 Concentration, grains/dscf Temperature, F

7 Opacity, % Temperature, F

8 Electrical Effects In dust layer: Electric Field = (current density) x (resistivity) If Electric Field > Breakdown field strength, then corona initiation occurs in dust layer. Breakdown for moderately high resistivities => sparkover very high resistivities => back corona (ρ ~ ohm-cm) (ρ ~ ohm-cm)

9 Spark Rate, sec -1 Field data from a pilot ESP with temperature change 50 Spark Rate Temperature Inlet temperature, deg. F 0 10:19 12:19 14:19 16:19 18:19 20:19 Time 0 S OUTHERN RESEARCH I N S T I T U T E

10 Field data from a pilot ESP with temperature change Secondary Current, ma Temperature Increased Here Secondary Voltage, KV :19 12:19 14:19 16:19 18:19 20:19 Time 0 S OUTHERN RESEARCH I N S T I T U T E

11 1.E+11 Initial Temperature Resistivity, ohm-cm 1.E+10 1.E+09 Final Temperature 1.E Temperature, deg. F S OUTHERN RESEARCH I N S T I T U T E

12 Next: Allow resistivity and gas volume to vary with temperature Calculations were done for two ashes. 1. A hard-to-condition ash from a low sulfur, Eastern bituminous coal 2. An easy to condition Eastern bituminous coal

13 Again, the examples to follow are based on an ESP with four sections of uniform length. The SRI ESP model was used to estimate performance over a temperature range of 250 F to 375 F with constant mass flow of gas and inlet particulate matter. The SCA was 288 sq.ft./kacfm at 300 F Opacities were calculated based on a stack diameter of 30 feet. SOUTHERN RESEARCH I N S T I T U T E Environment & Energy Division

14 Hard to Condition Ash

15 1.E+12 Resistivity, ohm-cm 1.E+11 1.E+10 0 ppm 1 ppm 4 ppm 10 ppm 20.0 ppm 1.E Temperature, F

16 Average Secondary Voltage, kv Secondary Voltage Secondary Current Density Current Density, na/cm^ Temperature, F

17 Emission Rate, lb/mmbtu Emission Rate PM PM2.5 Concentration, grains/dscf Temperature, F

18 Opacity, % Temperature, F

19 Easy to Condition Ash SOUTHERN RESEARCH I N S T I T U T E Environment & Energy Division

20 1.E+12 1.E+11 Resistivity, ohm-cm 1.E+10 1.E+09 1.E+08 0 ppm 1.0 ppm 4 ppm 10 ppm 1.E Temperature, F

21 Temperature, F Average Secondary Voltage, kv Secondary Current Density, na/cm^2 Secondary Voltage Secondary Current

22 Emission Rate, Lbs/MMbtu lbs/mmbtu, 1ppm SO3 PM2.5, gr/dscf, 1ppm SO3 lbs/mmbtu, 4ppm SO3 PM2.5, gr/dscf, 4ppm SO PM2.5 concentrations, grains/dscf Gas Temperature, F

23 ppm SO3 4ppm SO3 12 Opacity, % Gas Temperature, F

24 Effect of temperature spreads across ESPs following rotary air heaters. Typical temperature spread is around 60 to 100 F

25 1.E+12 D1 C1 3 3 D2 2 C2 B1 B2 B3 B4 4 A1 A2 A3 A Green Arrow = Good Performance Orange Arrow = Impaired Performance Red Arrow = Very Poor Performance Resistivity, ohm-cm 1.E+11 1.E+10 1.E+09 0 ppm 1 ppm 4 ppm 10 ppm 20.0 ppm Temperature, F Hard to Condition Ash

26 D1 D2 1.E+12 0 ppm 1.0 ppm 4 ppm 10 ppm C1 C2 1.E+11 B1 B2 B3 B4 A1 A2 A3 A4 Resistivity, ohm-cm 1.E E+09 Green Arrow = Good Performance Orange Arrow = Impaired Performance Red Arrow = Poor Performance SOUTHERN RESEARCH I N S T I T U T E 1.E Temperature, F Easy to Condition Ash Environment & Energy Division

27 Effects of Ash Adhesion and Cohesion Higher temperatures tend to result in lower adhesion and cohesion. Only limited quantitative data is available. Data was collected during a multi-plant study of rapping losses. Sites used included four units with cold-side precipitators and two with hot-side precipitators. SOUTHERN RESEARCH I N S T I T U T E Environment & Energy Division

28 Example of the effect of ash adhesion and cohesion Inlet Grains/dscf Outlet Grains/dscf Emission Rate lb/mmbtu Outlet PM Grains/dscf Outlet PM Grains/dscf Opacity % SOUTHERN RESEARCH I N S T I T U T E Using Coldside Rapping Model Using Hotside Rapping Model Environment & Energy Division

29 Typical ESP Performance vs. Resistivity from EPRI Operating VI Correlations Avg kv Avg na/cm2 Opacity, % E+09 1.E+10 1.E+11 1.E+12 1.E+13 Resistivity, ohm-cm SOUTHERN RESEARCH I N S T I T U T E Environment & Energy Division

30 Questions?? SOUTHERN RESEARCH I N S T I T U T E Environment & Energy Division