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Preferred Utilities Mfg. Corp. 31-35 South St. Danbury CT www.preferred-mfg.com Electrical Energy & Fuel Savings Using Advanced Boiler Controls Preferred.

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Presentation on theme: "Preferred Utilities Mfg. Corp. 31-35 South St. Danbury CT www.preferred-mfg.com Electrical Energy & Fuel Savings Using Advanced Boiler Controls Preferred."— Presentation transcript:

1 Preferred Utilities Mfg. Corp South St. Danbury CT Electrical Energy & Fuel Savings Using Advanced Boiler Controls Preferred Utilities Manufacturing Corp

2 Introduction q Introduction q Fuel Savings n Stack Losses q Electrical Savings n Fan Basics n Fan and System Curves n VFD Basics q Savings Summary

3 Introduction This discussion focuses on upgrading existing burners from Jackshaft Control to FD Fan Variable Frequency Drives (VFD) Speed Control with Oxygen Trim to Save Energy and Provide Rapid Payback. VFD are currently being applied to motors through out industry.

4 Typical Applications q Firetube Boilers over 400 Bhp q Watertube Boilers q Boilers with Seasonal Load Swings: n Hospitals n Universities n Prisons n Airports n Military Bases

5 Fuel Savings

6 Combustion Efficiency

7 Chemistry: Air = O 2 + N 2 Fuel = C + H 3O 2 + N 2 + 2C + 4H  2CO 2 + 2H 2 O + N 2 Time + Temperature + Turbulence Excess Air Combustion Theory

8 Excess Air Required for Burners

9 Excess Versus Deficient Air

10 Variations in Air Composition q “Standard” air has LB. O 2 per FT 3 q Hot, humid air has less O 2 per cubic ft n 20% less at 95% RH, 120 O F, and 29.9 in. Hg q Dry, cold air has more O 2 per cubic ft n 10% more at 0% RH, 32 O F, and 30.5 in. Hg q Combustion controls must: n Adapt to changing air composition or n Allow at least extra excess air at “standard” conditions

11 Variations in Air Composition

12 At these ambient conditions the burner has extra O 2 & N 2

13 Control System Errors Combustion control system can not perfectly regulate fuel and oxygen flows. Therefore, extra excess air must be supplied to the burner to account for control system errors… n Hysteresis (non-repeatability): linkage slop, valves, dampers, and fuel pressure regulator n Fuel flow for a given valve position varies with temperature and pressure

14 Combustion Control Objectives q Maintain proper fuel to air ratio at all times n Too little air causes unburned fuel losses n Too much air causes excessive stack losses n Improper fuel air ratio can be DANGEROUS q Always keep fuel to air ratio SAFE q Interface with burner management for: n Purge n Low fire light off n Modulate fuel and air when safe to do so

15 Jackshaft Fuel-Air Ratio Control

16 Electrical Savings q Fan Basics q Fan and System Curves q Motor & Electrical Systems Basics q VFD Basics

17 VFD System Basics q Variable Frequency Drive n The Inputs are a 4-20mA FD Fan Speed Demand and Motor AC Voltage n Output is a “Variable Frequency” AC n Motor speed follows the 4-20mA input n Motor manufactures strongly recommend a Motor rated for Inverter Service for long life »These motors can with stand higher surge voltages

18 q VFD provides Electrical Energy Savings due to: n Oversized Fans n Oversized Motors n Partially Loaded Boilers n Minimizing Damper Hp Losses VFD System Basics

19 Centrifugal Fan Exploded View Reference 1

20 Vortex Dampers q Inlet vanes give an initial spin (or vortex) to air entering a centrifugal fan. By adjusting angle of vanes the degree of spin and volumetric output are regulated. Reference 3

21 Inlet Control Vanes Reference 2

22 Inlet or Outlet Dampers q Inlet or opposed blade dampers assure even distribution of air immediately downstream from the damper. By adjusting angle of blades the volumetric output are regulated. Reference 1

23 Flow vs Fan Hp Non-Vortex Dampers Vortex Damper Speed Control Reference 1

24 Fan Hp Summary q Dampers substantially increase Fan Hp and Fan kW Consumption. q Dampers are Evil! q Inlet Vortex Dampers waste less Hp than any type of inlet and outlet Blade Dampers. q Variable Speed Fans Control air flow with minimum fan shaft Hp. q Variable Speed Fans have been field proven in thousands of HVAC air handler applications.

25 q Adjustable Frequency Drive (AFD) q Adjustable SPEED Drives (ASD) q VARIABLE Frequency Drives (VFD) q VARIABLE SPEED Drives (VSD) q Inverters q Frequency Converters q Drives q Different names for the same thing. Variable Frequency Drives

26 Motor Speed Control

27 Pulse Width Modulation (PWM) q On or Off, voltage does NOT modulate. q PWM allows IGBT’s to run cool for long life, so all VFD’s use PWM. q However, PWM dV/dt causes spike voltages

28 q dv/dt - Change in Voltage over Time n Poor Drives - up to 3500V/us n Good Drives - 900V/us on 500 feet q Lower Peak Voltages Extend Motor Insulation Life Voltage Spikes

29 Do we need a VFD rated Motor ? q NO n 230 V Motors q Strong Probability: NO n 460 V motors with: < 50 ft wire run, good drives almost eliminate problems. n However, you can NOT guarantee it. Motor age and heat naturally degrade the motor wire insulation. The customer should know that there is a small risk. n If motor insulation fails, the VFD is not damaged, but the user must pay to have the motor re-wound or replaced. q YES n 575 V Motors

30 Combustion Air Fan Hp Savings Reference 1 Combustion Air Flow, %Full Load Motor Power(HP) Input, % Full Load Variable Speed Control Damper Control HP Savings

31 Savings Summary Fuel Savings Electrical Savings +

32 q Fuel Savings: n Seasonal Air Density and Humidity Changes n Fuel Pressure and Temperature Changes n Fuel Btu and Viscosity Variations n Worn Linkage Components (Hysteresis) q Electrical Savings: n Minimizing Damper Pressure Drop - damper is 100% open for maximum kWh savings, (Partially closed at low fire to maximize burner turndown) n Oversized Fans n Oversized Motors n Partially Loaded Boilers Energy Savings

33 Advanced Burner Control

34 Energy Savings q Important Factors n Boiler Size? n Loading Service? n Exit Gas Temperature? (Boiler Pressure Determines) n Electrical Cost? (10 cents, 4 cents?) n Fuel Cost? n Utility Rebate?

35 Unique Energy Savings Tool q Savings Estimate Based on: n Boiler size n Motor HP n Air Damper Type n Current O2 Level n Projected O2 Level n Flue Gas Temperature n Seasonal Loading Data n Fuel Cost n Electrical Cost

36 If You Can’t Get Field Data

37 q % O2 Improvement = % q Heating Boiler Seasonal Loading = n Boiler Firing Rate 0%20%40%60%80% 100% n % Per Year25%5%20%15%30%5% q Process Boiler Seasonal Loading = n Boiler Firing Rate 0%20%40%60%80% 100% n % Per Year5%5%20%20%30%20% q Natural Gas Cost $4.50 / 1000ft3 q Fuel Oil Cost $0.90 / gal q Electricity Cost $0.75 kWh q Flue Gas Temperatures - 10 psi-350 F, 120 psi-475 F Conservative Assumptions

38 Things You Need To Know q Utility Energy Rebates n North East Utilities, CL&P - offers a 50 % rebate of the VFD price and cost of installation. n They use standard numbers. n They require paper work to be submitted n Local VFD rep will be able to give the local rebate offer.

39 Large Firetube Scenario q Steam Boiler: 600 bhp 10 psi (193 F), 350 F flue gas temp. 20 ppm, 60 hp fan motor, parallel blade outlet damper controls air flow q Utilities Cost: Fuel Gas: $4.5 / 1000 ft3) / Electricity: 5 cents / kwh q Operation: Process boiler, 50 weeks a year service, »Shutdown - 10 % of year / 20 % Load - 20 % of year »40 % Load - 20 % of year / 60 % Load - 20 % of year »80 % Load - 20 % of year / 100 % Load - 10 % of year q Oxygen Trim Improvement: Field service engineer has determined that the burner excess air performance can be improved as follows: »20 % Load - 6% to 4.5 % O2 / 40 % Load - 6% to 4.5 % O2 Wet »60 % Load - 5% to 3.5 % O2 / 80 % Load - 4% to 2.5 % O2 Wet »100 % Load - 4% to 2.5 % O2 Wet q Utility Rebate: 50% of VFD Cost and installation »(use VFD list price as an estimate) »Existing Jackshaft Actuator: 150in-lbs

40 Large Firetube Scenario

41

42 Installed System Payback

43 300 Bhp Payback vs.O2 Decrease

44 Preferred Utilities Manufacturing Corp For further information, contact... Preferred Utilities Manufacturing Corporation South Street. Danbury CT T: (203) F: (203)


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