Presentation on theme: "Preferred Utilities Manufacturing Corp"— Presentation transcript:
1Preferred Utilities Manufacturing Corp Electrical Energy &Fuel Savings UsingAdvanced Boiler ControlsThis presentation is designed to be a general seminar on combustion. It not only deals with controls as supplied by Preferred, but general topics on boilers, burners, emissions, etc. While not designed to be “commercial,” it uses Preferred products as its base for descriptions. (indicates advance slide)Preferred Utilities Mfg. Corp.31-35 South St. • Danbury • CT
2Introduction Introduction Fuel Savings Electrical Savings Stack LossesElectrical SavingsFan BasicsFan and System CurvesVFD BasicsSavings Summary
3IntroductionThis 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.
4Typical Applications Firetube Boilers over 400 Bhp Watertube Boilers Boilers with Seasonal Load Swings:HospitalsUniversitiesPrisonsAirportsMilitary Bases
7Combustion Theory Chemistry: Air = O2 + N2 Fuel = C + H 3O2 + N2 + 2C + 4H Þ 2CO H2O + N2Time + Temperature + TurbulenceExcess Air The chemistry of combustion is gone over. Air consists primarily of oxygen and nitrogen as individual molecules. Fossil fuels contain primarily carbon and hydrogen, though they can include other elements such as sulfur, nitrogen, etc. The formula given is the ideal reaction; in reality, there are other reactions that occur, some of which will be discussed. Combustion requires time, temperature, and turbulence. Enough time for the reaction to occur, sufficient temperature to ignite the fuel and start the process, and turbulence to assure mixing of fuel and oxygen. The formula given assumes all fuel comes into contact with all oxygen. We introduce extra air to assure that this happens. Too much excess air will cause good combustion but low efficiency as you will be heating this air rather than the water in the boiler.
10Variations in Air Composition “Standard” air has LB. O2 per FT3Hot, humid air has less O2 per cubic ft20% less at 95% RH, 120OF, and 29.9 in. HgDry, cold air has more O2 per cubic ft10% more at 0% RH, 32OF, and 30.5 in. HgCombustion controls must:Adapt to changing air composition orAllow at least extra excess air at “standard” conditions
12Variations in Air Composition At these ambient conditions the burner has extra O2 & N2
13Control System ErrorsCombustion 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 regulatorFuel flow for a given valve position varies with temperature and pressure
14Combustion Control Objectives Maintain proper fuel to air ratio at all timesToo little air causes unburned fuel lossesToo much air causes excessive stack lossesImproper fuel air ratio can be DANGEROUSAlways keep fuel to air ratio SAFEInterface with burner management for:PurgeLow fire light offModulate fuel and air when safe to do so
16Electrical Savings Fan Basics Fan and System Curves Motor & Electrical Systems BasicsVFD Basics
17VFD System Basics Variable Frequency Drive The Inputs are a 4-20mA FD Fan Speed Demand and Motor AC VoltageOutput is a “Variable Frequency” ACMotor speed follows the 4-20mA inputMotor manufactures strongly recommend a Motor rated for Inverter Service for long lifeThese motors can with stand higher surge voltages
18VFD System Basics VFD provides Electrical Energy Savings due to: Oversized FansOversized MotorsPartially Loaded BoilersMinimizing Damper Hp Losses
20Vortex DampersInlet 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.Vortex dampers are only on the inlet of a fan.Vortex Dampers spin the air as it enters the rotating fan wheel.These dampers consume less kWh than a parallel blade damper.Upgrading to VFD control provides moderate kWh savings.Vortex dampers are round with pie shaped blades that rotate about radial shafts.Reference 3
22Inlet 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.Parallel Blade Dampers can be on either the inlet or discharge (or both sides) of the fan.This damper adds pressure drop (and motor kWh usage) as the flow decreases.These dampers consume more kWh than Vortex dampers and VFD's.Upgrading to VFD control provides large kWh savings.Cleaver Brooks firetube & watertube fans generally have discharge dampers.Older Coen register burners generally have discharge dampers.Webster burners use a parallel blade inlet damper.Reference 1
23Flow vs Fan Hp Non-Vortex Dampers Vortex Damper Speed Control Reference 1
24Fan Hp SummaryDampers 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.
25Variable Frequency Drives Adjustable Frequency Drive (AFD)Adjustable SPEED Drives (ASD)VARIABLE Frequency Drives (VFD)VARIABLE SPEED Drives (VSD)InvertersFrequency ConvertersDrivesDifferent names for the same thing.
27Pulse Width Modulation (PWM) On or Off, voltage does NOT modulate.PWM allows IGBT’s to run cool for long life, so all VFD’s use PWM.However, PWM dV/dt causes spike voltages
28Voltage Spikes dv/dt - Change in Voltage over Time Poor Drives - up to 3500V/usGood Drives - 900V/us on 500 feetLower Peak Voltages Extend Motor Insulation Life
29Do we need a VFD rated Motor ? NO230 V MotorsStrong Probability: NO460 V motors with: < 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.YES575 V Motors
30Combustion Air Fan Hp Savings Damper ControlHP SavingsMotor Power(HP) Input, % Full LoadVariable Speed ControlCombustion Air Flow, %Full LoadReference 1
32Energy Savings Fuel Savings: Electrical Savings: Seasonal Air Density and Humidity ChangesFuel Pressure and Temperature ChangesFuel Btu and Viscosity VariationsWorn 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 FansOversized MotorsPartially Loaded Boilers
37Conservative Assumptions % O2 Improvement = %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 =% Per Year 5% 5% 20% 20% 30% 20%Natural Gas Cost $4.50 / 1000ft3Fuel Oil Cost $0.90 / galElectricity Cost $0.75 kWhFlue Gas Temperatures - 10 psi-350 F, 120 psi-475 F
38Things You Need To Know Utility Energy Rebates North East Utilities, CL&P - offers a 50 % rebate of the VFD price and cost of installation.They use standard numbers.They require paper work to be submittedLocal VFD rep will be able to give the local rebate offer.
39Large Firetube Scenario 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 flowUtilities Cost: Fuel Gas: $4.5 / 1000 ft3) / Electricity: 5 cents / kwhOperation: Process boiler, 50 weeks a year service,Shutdown - 10 % of year / 20 % Load - 20 % of year40 % Load - 20 % of year / 60 % Load - 20 % of year80 % Load - 20 % of year / 100 % Load - 10 % of yearOxygen 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 Wet60 % Load - 5% to 3.5 % O2 / 80 % Load - 4% to 2.5 % O2 Wet100 % Load - 4% to 2.5 % O2 WetUtility Rebate: 50% of VFD Cost and installation(use VFD list price as an estimate)Existing Jackshaft Actuator: 150in-lbs