Preferred Utilities Manufacturing Corp

1
Preferred Utilities Manufacturing Corp
Electrical Energy Fuel Savings Using Advanced
Boiler Controls
Preferred Utilities Mfg. Corp. 31-35 South St.
Danbury CT www.preferred-mfg.com
2
Introduction

• Introduction
• Fuel Savings
• Stack Losses
• Electrical Savings
• Fan Basics
• Fan and System Curves
• VFD Basics
• 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

• Firetube Boilers over 400 Bhp
• Watertube Boilers
• Boilers with Seasonal Load Swings
• Hospitals
• Universities
• Prisons
• Airports
• Military Bases

5
Fuel Savings
6
Combustion Efficiency
7
Combustion Theory

• Chemistry
• Air O2 N2
• Fuel C H
• 3O2 N2 2C 4H Þ 2CO2 2H2O N2
• Time Temperature Turbulence
• Excess Air

8
Excess Air Required for Burners
9
Excess Versus Deficient Air
10
Variations in Air Composition

• Standard air has 0.0177 LB. O2 per FT3
• Hot, humid air has less O2 per cubic ft
• 20 less at 95 RH, 120OF, and 29.9 in. Hg
• Dry, cold air has more O2 per cubic ft
• 10 more at 0 RH, 32OF, and 30.5 in. Hg
• Combustion controls must
• Adapt to changing air composition or
• Allow at least extra excess air at standard
  conditions

11
Variations in Air Composition
12
Variations in Air Composition
At these ambient conditions the burner has extra
O2 N2
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
• Hysteresis (non-repeatability) linkage slop,
  valves, dampers, and fuel pressure regulator
• Fuel flow for a given valve position varies with
  temperature and pressure

14
Combustion Control Objectives

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

15
Jackshaft Fuel-Air Ratio Control
16
Electrical Savings

• Fan Basics
• Fan and System Curves
• Motor Electrical Systems Basics
• VFD Basics

17
VFD System Basics

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

18
VFD System Basics

• VFD provides Electrical Energy Savings due to
• Oversized Fans
• Oversized Motors
• Partially Loaded Boilers
• Minimizing Damper Hp Losses

19
Centrifugal Fan Exploded View
Reference 1
20
Vortex Dampers

• 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

• 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

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

25
Variable Frequency Drives

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

26
Motor Speed Control
27
Pulse Width Modulation (PWM)

• On or Off, voltage does NOT modulate.
• PWM allows IGBTs to run cool for long life, so
  all VFDs use PWM.
• However, PWM dV/dt causes spike voltages

28
Voltage Spikes

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

29
Do we need a VFD rated Motor ?

• NO
• 230 V Motors
• Strong Probability NO
• 460 V motors with lt 50 ft wire run, good drives
  almost eliminate problems.
• 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.
• If motor insulation fails, the VFD is not
  damaged, but the user must pay to have the motor
  re-wound or replaced.
• YES
• 575 V Motors

30
Combustion Air Fan Hp Savings
Damper Control
Motor Power(HP) Input, Full Load
Variable Speed Control
Combustion Air Flow, Full Load
Reference 1
31
Savings Summary
Fuel Savings

Electrical Savings
32
Energy Savings

• Fuel Savings
• Seasonal Air Density and Humidity Changes
• Fuel Pressure and Temperature Changes
• Fuel Btu and Viscosity Variations
• Worn Linkage Components (Hysteresis)

• Electrical Savings
• Minimizing Damper Pressure Drop - damper is 100
  open for maximum kWh savings, (Partially closed
  at low fire to maximize burner turndown)
• Oversized Fans
• Oversized Motors
• Partially Loaded Boilers

33
Advanced Burner Control
34
Energy Savings

• Important Factors
• Boiler Size?
• Loading Service?
• Exit Gas Temperature? (Boiler Pressure
  Determines)
• Electrical Cost? (10 cents, 4 cents?)
• Fuel Cost?
• Utility Rebate?

35
Unique Energy Savings Tool

• Savings Estimate Based on
• Boiler size
• Motor HP
• Air Damper Type
• Current O2 Level
• Projected O2 Level
• Flue Gas Temperature
• Seasonal Loading Data
• Fuel Cost
• Electrical Cost

36
If You Cant Get Field Data
37
Conservative Assumptions

• O2 Improvement 1 - 2
• Heating Boiler Seasonal Loading
• Boiler Firing Rate 0 20 40 60 80 100
• Per Year 25 5 20 15 30 5
• Process Boiler Seasonal Loading
• Boiler Firing Rate 0 20 40 60 80 100
• Per Year 5 5 20 20 30 20
• Natural Gas Cost 4.50 / 1000ft3
• Fuel Oil Cost 0.90 / gal
• Electricity Cost 0.75 kWh
• Flue Gas Temperatures - 10 psi-350 F, 120 psi-475
  F

38
Things You Need To Know

• Utility Energy Rebates
• North East Utilities, CLP - offers a 50 rebate
  of the VFD price and cost of installation.
• They use standard numbers.
• They require paper work to be submitted
• Local VFD rep will be able to give the local
  rebate offer.

39
Large Firetube Scenario

• Steam Boiler 600 bhp capacity _at_ 10 psi (193 F),
  350 F flue gas temp.
• 20 ppm, 60 hp fan motor, parallel blade outlet
  damper controls air flow
• Utilities Cost Fuel Gas 4.5 / 1000 ft3) /
  Electricity 5 cents / kwh
• 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
• 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
• 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
Large Firetube Scenario
42
Installed System Payback
43
300 Bhp Payback vs.O2 Decrease
44
Preferred Utilities Manufacturing Corp
For further information, contact... Preferred
Utilities Manufacturing Corporation 31-35 South
Street. Danbury CT T [phone] F
[phone] www.preferred-mfg.com