1. Humidity Measurement Benefits in Power Plant Applications
Jeff Bossong, H2O

2. Objective of Presentation
H2O Technology
Power Plant Applications
“Fits” for The Sensor
Questions / Discussion

3. H2O Technology Absolute Humidity Sensor Advantages
Direct measurement of the water molecule
Dipole moment measuring effect
In-situ measurement
Advantages
High temperature operation – 1000 F
High particulate operation
Minimal maintenance
Corrosive and condensing environments are not an issue
Accurate
Robust (sensor life is 10 years minimum)

4. Installation Requirements
Probe sizes – 490 mm or 1,470 mm lengths
Flange - 4 inch, 150 lb. ANSI
Power – 110V, 5 Amps
Output Signal – mA isolated
Measurement unit – g/m3 corrected to 0C at process pressure
Other Units – Equations are provided (i.e., dew point, RH, humidity ratio)

5. Picture / Drawing

6. Installation

7. Power Plant Applications
Coal / Biomass Fired Boilers
Tube leak detection
Soot blower feedback
Heat rate calculations
Air heater in-leakage
Dry scrubber control
Environmental reporting
Wet scrubber stack protection
Optimization software input
Pulverizer control
Combined Cycle
Tube leak detection
Dew point measurement
Feed water temperature control
Environmental reporting
Power augmentation
Optimization software input

8. Combined Cycle Tube Leak Detection – HRSG Outlet
Evaporative Cooler Simulation
Assumed 98% RH when “On”
Calculated to actual 1 lb/s to 4 lb/s difference
10 to 14 minute lag time

9. Evap Cooler “On/Off” EVAPORATIVE COOLER STATUS Inlet Humidity lb/s
Combustion Humidity (lb/s)
Total Calc (lbs/s)
H2O Sensor ( lbs/s)
Stack Moisture (% Volume)
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10. Combined Cycle Dew Point Measurement – HRSG Outlet
Water dew point equation
Pd = (1-(0.0001*(SQRT((0.1*T)+1)+4)))*461.51*(T )*F*
Dp = ( *LN(Pd/6.1078))/( LN(Pd/6.1078))
T = Temperature in C
F = Absolute humidity at process conditions
Pd = Water vapor pressure
Dp = Dew point temperature
Water dew point temperature varies 111 to 120 F
Corrosion prevention during outages

11. CC Plant Water Dew Point

12. H2SO4 Determination Verhoff & Banchero Formula
Tds = 1000/( ln(p H2O) ln(p SO3) ln(p H2O) ln( p SO3))
Partial pressures are expressed as mmHg
Use humidity sensor as a direct input to equation
Use worst case constant for SO3 concentrations
Varies six degrees as a function of H2O concentration

13. CC Plant Verhoff Chart – NG-CC

14. Sulfur Dew Point Data - CC
SO3 PPM
H2O %
Tds (Celsius)
Tds (Fahrenheit)
0.1 9 10 12
0.5 1

15. Feed Water Temperature Control

16. Combined Cycle Environmental Reporting - Stack
Provides real time, accurate moisture concentration
EPA method 4 is not very accurate and data is a snapshot
Could hurt or help depending on humidity number used for reporting
Power Augmentation – Turbine Inlet
Improved accuracy of dew point temperature
Reduce factor of safety so inlet temperature can be lowered without condensation

17. Coal / Biomass Tube Leak Detection – Economizer Outlet
Our detection limit is 0.1 g/m3 at 0C
Volumetric flow rate: 372,000 m3/hr
Detection limit = leak / volumetric flow rate
Leak = .1*372,000
Leak = 37,200 g/hr
Leak = 1.37 lbs/min or 0.17 gallons per minute
Process noise includes ambient humidity, soot blows and fuel moisture
More process noise but lower air flow
In conjunction with laser based units

18. Coal / Biomass Economizer Outlet Soot blower feedback
Safety to assure steam is firing
Protect lances from bending and plant shutdown
Heat rate calculations
Fuel moisture variation
Air heater efficiency
Optimization software Input

19. Coal Biomass
Air Heater In-Leakage Rate – Economizer Outlet and Air Heater Outlet
Water doesn’t stratify like oxygen: more accurate, real time leakage rate
Equation
AHI * y + AHA * x = AHO * F , where F=x+y
x = (AHI-AHO)*F/(AHI-AHA)
AHI = H2O reading at air heater inlet
AHA = ambient humidity in g/m3 (manual or real time)
AHO = H2O reading at air heater outlet
F = flow leaving air heater
x = volumetric leakage rate
y = flow entering air heater
No flow measurement will still provide a relative difference

20. Verhoff Chart – Coal Plant

21. Sulfur Dew Point Data - Coal
SO3 PPM
H2O %
Tds (Celsius)
Tds (Fahrenheit) 1 9 10 12 5

22. Coal Biomass
Dry Scrubber Control – Scrubber Outlet, Baghouse Outlet or Stack
Control to an approach to adiabatic saturation temperature
Better SO2 removal at lower temperatures improves lime usage
Protects baghouse from corrosion
Moisture variables include soot blow, load change, fuel moisture, ambient air humidity and tube leaks
Dew point can vary up to 10 degrees depending upon time of year and conditions
GE Installations – Flint Creek and Braynton Point

23. Coal / Biomass Environmental Reporting – Stack
Improved accuracy of emissions
Wet scrubber stack protection
Control reheat or bi-pass after scrubber
Water carry over can increase moisture concentration past scrubber outlet dew point

24. Coal / Biomass Pulverizer Control – Pulverizer Outlet
Sensor is a real time input for mass and energy balance across the pulverizer
Sensor will also identify upset conditions like mill fires
Tests were done at GE Windsor

25. “Fits” for Sensor Operations Optimization Asset Performance Management
Thermal Performance
Outage Planning
Emissions Management & Reporting
Asset Performance Management
Tube Leak Detection
Evaporative Cooling Upsets

26. “Fits” for Sensor Coal Optimization Software (Neuco, Etapro…)
Thermal Performance
Tube Leak Detection with Laser Systems
Air Heater Leakage
Dry Scrubber Control
Emissions Management & Reporting
Pulverizer Optimization

27. Questions / Discussion