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Boiler and steam system seminar short version 05 29-13
This document provides information on boiler operations and efficiency. It discusses that a typical steam system loses 70% of its energy, with 28% lost in the boiler room and 42% lost in distribution. It also outlines various boiler types including watertube, firetube, and electric boilers. Key factors that impact boiler efficiency like combustion efficiency, radiation losses, and excess air are examined. The document emphasizes the importance of proper boiler maintenance, controls, and feedwater conditioning to maximize efficiency.
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Boiler and steam system seminar short version 05 29-13
- 1. By Edward Moschetti Control Specialties 2503Monroe Drive Gainesville, GA 30507 770 532-7736 Toll Free 800 752-0556 Fax 770 535-0536 emoschetti@aol.com See our website at www.control-specialties.com for more information Boiler OperationsBoiler Operations 1
- 2. Steam The Original Recyclable Formof Energy 2
- 3. A Boiler isa Pressure Vessel With a Burner or Other Energy Source Used To Convert Thermal Energy From One Form to Another Example Burn Natural Gas to Generate Steam 3
- 4. Average Steam SystemEfficiency An energy survey and load balance on a typical steam system in average condition will yield the following losses Boiler Room Losses Stack losses 21% Blowdown losses 4% Boiler radiation losses 3% Total Boiler Room Losses 28% Distribution Losses Insulation losses 7% Steam leaks 6% Blowing steam traps 7% Flash steam losses 13% Return System losses 9% Total Distribution Losses 42% Total Steam System Losses 70% Placed in perspective, if you are spending $500,000 per year for boiler fuel, only about $150,000 of thermal work is being delivered into your product or process. Average Steam System Efficiency An energy survey and load balance on a typical steam system in average condition will yield the following losses Boiler Room Losses Stack losses 21% Blowdown losses 4% Boiler radiation losses 3% Total Boiler Room Losses 28% Distribution Losses Insulation losses 7% Steam leaks 6% Blowing steam traps 7% Flash steam losses 13% Return System losses 9% Total Distribution Losses 42% Total Steam System Losses 70% Placed in perspective, if you are spending $500,000 per year for boiler fuel, only about $150,000 of thermal work is being delivered into your product or process. 4
- 5. Steam Boiler Energy Sources •Natural gas •Oil •Wastegas •Coal •Wood •Other Steam Heating Hot Water Heating Autoclaves Heating Metal Platens Heating Rotating Dryers Heating Process Air HVAC Equipments Other Applications Process and HVAC Equipment Deaerator Feedwater 5 Boilers Convert Primary Energy Sources to Energy In the Form of Steam The Basic Steam Loop For the most efficient operations, boiler operations should be integrated with steam demand.
- 6. • Thermal energyis used in a wide range of applications to manufacture products as well as provide comfort during cold weather. Take a moment and glance around your current location and see if you can identify anything you might see which did not use thermal energy to produce it. • BTU is the amount of heat to raise one pound of water one degree Fahrenheit. • One pound of water yields one BTU of thermal energy when cooled one degree Fahrenheit. • One pound of steam yields approximately 1000 BTU’s when condensed. • Steam is a common heat transfer media due to the large amount of heat which can be transmitted through a pipe. Other heat transfer media are offered such as thermal oils. We will limit our discussions to steam and hot water for this presentation since the basic principals and equipment are similar. 6
- 7. ENERGY DATA ALLARE EQUAL TO 1,000,000 BTU • 1 MCF of natural gas • 1,000 cubic feet of natural gas • 1 decatherm of natural gas • 10 therms of natural gas • 293.1 KW of electricity • 7.29 gallons of # 2 oil • 10.93 gallons of propane • 1,000 lbs of steam • 29.31 boiler horsepower • 1 MCF of natural gas • 1,000 cubic feet of natural gas • 1 decatherm of natural gas • 10 therms of natural gas • 293.1 KW of electricity • 7.29 gallons of # 2 oil • 10.93 gallons of propane • 1,000 lbs of steam • 29.31 boiler horsepower 7
- 8. Gas Cost (MCF)# 2 Oil (gallon) Propane (gallon) Electricity (KWH) $5.00 $.82 $.46 $.0171 8 If natural gas costs $5.00 per million BTU’s- •Number 2 oil would have to cost $.82 per gallon •Propane would have to cost $.46 per gallon •Electricity would have to cost $.0171 per KWH Energy Cross Over Costs
- 9. Gas Cost (MCF)# 2 Oil (gallon) Propane (gallon) Electricity (KWH) $5.00 $.82 $.46 $.0171 $6.00 $.82 $.55 $.0205 $7.00 $.96 $.64 $.0239 $8.00 $1.10 $.73 $.0273 $9.00 $1.24 $.83 $.0307 $10.00 $1.37 $.92 $.0341 $11.00 $1.51 $1.01 $.0375 $12.00 $1.64 $1.10 $.0409 Energy Cross Over Costs 9
- 10. Combustion Efficiency 10 Fuel Valve AirDamper Combustion Analyzer
- 11. Combustion Efficiency The optimumpoint for most boilers is 3% O2 11 Heat up the stack Smoke
- 12. Fuel to SteamEfficiency = Output BTUs Input BTUs Efficiency and Radiation Loss • Efficiency is the ratio of output from a piece of equipment as compared to the input • Radiation loss is the heat lost from the boiler shell • The larger the boiler, the larger the radiation loss • Typical values for radiation loss are ~ 4% of full capacity • Boilers are typically under fired and operate in the 40-60% load range • A boiler operating at a 50% firing rate would have a radiation loss of 8% • As an example assume the combustion efficiency is 81% and the blow down losses are 2% • The predicated Fuel to Steam Efficiency would be 71% (81%-8%-2%) 12
- 13. Radiation Loss 13 Radiation lossis rated as a percentage of 100% boiler output and is typically 4% for most firetube boilers Since the radiation loss off a boiler does not change, a boiler operating at a 75% firing rate will have a radiation loss of 6% as a percentage of boiler output. At a 50% firing rate, the radiation loss rises to 8%. The lower the percentage load, the higher the radiation losses become since fuel is being wasted to keep the boiler hot. Boilers which cycle in and out of operation have very high losses due to radiation and purge losses.
- 14. Boiler Size 200HP Firing Rate 50% Delivered HP 100 BHP Combustion Eff. 81% Radiation Loss 8% (50% firing rate doubles the radiation loss) Fuel to Steam Eff. 73% Gas Use (MCF/Hr) 4.73 Cost per Hour $33.11 6000 Hours/Year $198,660 14 Cost to Produce 100 BHP Using Various Boiler Sizes Gas Cost $7.00 per Million BTU’s 6000 Hours of Operation per year Boiler Specification of Radiation Loss-4%
- 15. Cost to Produce100 BHP Using Various Boiler Sizes Gas Cost $7.00 per Million BTU’s 6000 Hours of Operation per year Boiler Specification of Radiation Loss-4% Boiler Size 200 HP 135 HP 100 HP Firing Rate 50% 75% 100% Delivered HP 100 BHP 100 BHP 100 BHP Combustion Eff. 81% 81% 81% Radiation Loss 8% 6% 4% Fuel to Steam Eff. 73% 75% 77% Gas Use (MCF/Hr) 4.73 4.60 4.48 Cost per Hour $33.11 $32.20 $31.36 6000 Hours/Year $198,660 $193,200 $188,160 15 Multiply these figures for larger or smaller boilers
- 16. Lead Lag BoilerControls Firing Rate 50% 75% 100% Cost per Hour $33.11 $32.20 $31.36 16 Boiler 1 Boiler 2 Steam to Plant A Simple Example •Case 1-One boiler carries load at 100% firing rate with a cost of $31.36 per hour. •Case 2-Two boilers each firing at 50% carry the load with a cost of $33.11 per hour. •Lead Lag Savings is ~6% by using a lead lag controller. Lead Lag Controller
- 17. Blow Down Considerations •As water is boiled, sediment in the water settles and scum rises to the surface. • Surface blowdown deals with the surface contaminants. • Bottom blow down deals with the sediment. • Proper water treatment on a daily basis if critical to the service life of a boiler. 17 Conductivity based surface blowdown controller Heat exchanger bottom blowdown heat recovery system
- 18. Fuel to BoilerFuelto Boiler Steam to Plant Steam to Plant Boiler Consider Meters Consider Meters 18 Measuring Fuel to Steam Efficiency 1 GPM = 500 Lb/Hr Feedwater Meter Meter Meter
- 19. Boiler Losses Combustion Efficiency75-86% Radiation and Convection Losses 0.3-6% Boiler Design and Load Management 2-7% Scale Buildup in Boiler 7-11% Excess Boiler Blowdown 0.1-1% Excess Air 0-7.5% Range of Efficiency 42.5-76.6% (Source ASHRAE Journal September 1994) Boiler Losses Combustion Efficiency 75-86% Radiation and Convection Losses 0.3-6% Boiler Design and Load Management 2-7% Scale Buildup in Boiler 7-11% Excess Boiler Blowdown 0.1-1% Excess Air 0-7.5% Range of Efficiency 42.5-76.6% (Source ASHRAE Journal September 1994) 19
- 20. Watertube Boilers •Efficiencies to76-80% •Gas, oil, coal and other solid fuels •15,000 lb/hr and up •Large site built units for power generation and very large loads •Expensive to purchase and maintain •The choice for large to very large applications 20
- 21. Firetube Boilers •Efficiencies to78-81% •Gas, oil, and propane fired •Limited options on solid fuels •10-1200 BHP (1 BHP=34.5 lb/hr) •Work horse boiler for a wide range of applications •Moderate cost to purchase and install •Construction and design spec’s can affect price 21
- 22. Electric Boilers andHeaters •Efficiencies to 98-99% •Electrode and resistance types •Sizes up to 1000 BHP •No products of combustion •No alternate fuel options •Expensive to operate •Expensive to install-power side •RTP rates can be very expensive •Power company will add incentives 22
- 23. Electric Boilers andHeaters •Efficiencies to 98-99% •Electrode and resistance types •Sizes up to 1000 BHP •No products of combustion •No alternate fuel options •Expensive to operate •Expensive to install-power side •RTP rates can be very expensive •Power company will add incentives 23 Electric Boilers-a few thoughts •Sold on the basis of 98-99% efficient, zero emissions, and simple installation.
- 24. Electric Boilers andHeaters •Efficiencies to 98-99% •Electrode and resistance types •Sizes up to 1000 BHP •No products of combustion •No alternate fuel options •Expensive to operate •Expensive to install-power side •RTP rates can be very expensive •Power company will add incentives 24 Electric Boilers-a few thoughts •Sold on the basis of 98-99% efficient, zero emissions, and simple installation. •1.02 BHP = 10 kWh A 200 BHP boiler would require a 2000 kWh power source. •Cost of steam = 293.1 x kWh rate for an electric boiler ($.07 x 293.1 = $20.52 per million BTU’s. •Cost of steam for a gas fired boiler = (Gas cost)/(Efficiency) $5.00 at 80% = $6.25 per million BTU’s. •Power audits used to understand steam loads and switch customers from natural gas. •Carbon footprint for natural gas about 25% less than coal and oil.
- 25. Summary of BoilerTypes • Watertube Boilers (Many Brands) • Firetube Boilers (Many brands) • Low Volume Watertube Boilers (Miura) • Steam Generators (Clayton) • Electric Boilers (Many Brands) • Old Boilers • Best suited for high volume steam production from 25,000 lb/hr up to building sized boilers. • Size range up to ~ 1200 HP (41,400 lb/hr). Most boilers installed are FT’s . • Modular concept with high efficiency and PLC based control. Small footprint and good for retrofit applications. • High efficiency coupled with high range of operating pressures. Small footprint and good for retrofit applications. • Suitable in specialized applications such as no boiler stack possible, small loads, point of use need for steam, no flame requirement and others. • New Boilers 25
- 26. Boiler Link-less Controls ImproveBoiler Efficiency 3-5% Most boilers use a mechanical system to manage the air fuel mixture. Mechanical combustion systems are hard to maintain, drift in adjustment and lead to extra fuel being burned to operate your boilers. 26
- 27. Servo operator for airdamper Servo Operator for gas valve Servo operator for FGR controlsServo operator for oil valve Control Panel Full feature PLC controller allows for precise programming of fuel, air, FGR and number 2 oil setting. •Complete data display of boiler operations. •Easily integrated with building management control systems. 27
- 28. 28 Boiler Stack Economizers Boilerstack economizers will typically increase combustion efficiency by ~ 4%. The typical temperature drop across a stack economizer is ~ 100 F. The heat removed from the stack gas is used to boost the feedwater temperatures into the boiler or preheat boiler feedwater. Stack dewpoint must be carefully considered to prevent acid formation in the stack.
- 29. Feedwater Conditioning Removing O2and CO2 29 Deaerator Pressure Vessel Boils feedwater to drive off gases 225-227 F Water Temperature Operating Pressure 5-7 psig Feedwater Heater Non code Vessel Chemicals added to bind gases 190-200 F Water Temperature Operating Pressure O psig O2 Causes Oxygen Pitting on Boiler Tubes CO2+H20 = Carbonic Acid Corrosion Red Brown Rust
- 30. Boiler Feedwater Pumps 30 NPSH NetPositive Suction Head (NPSH) Required distance in feet to prevent pump cavitation Cavitation occurs when water is pumped out faster than it can enter the pump which leads to water vapor forming inside the pump which destroys seals and impellers
- 31. Water Softeners Typical MakeUp Water Spec’s 0 CaCo3 Hardness pH 7-9 Less than.5 ppm O2 Less than 30 mg/L Chlorides Less than 30 mg/L Silica Below .5 mg/L Iron Below .5 mg/L Manganese 31
- 32. Blow Down Separators ColdWater Inlet Surface and Bottom Blowdown from Boilers Steam to Outside Vent 160 F Boiler and Cooling Water to Drain 32
- 33. Older Boilers • Theaverage boiler in service is typically 30+ years old. • Consider an 1979 automobile to a 2009 model. • Older boilers can be upgraded with linkage less controls, economizers, and better PLC based control systems. • Boilers should be tuned at least twice per year. • Boilers should be matched to the connected load. • Two boilers running in parallel to carry a load wastes fuel. • Lead lag systems typically reduce fuel use by at least 5%. • Consider setting back or shutting down boilers over a weekend-do the math. • Water treatment is critical to boiler life. • Water softeners are critical to boiler life. • Consider meters to provide a basis of system health. 33
- 34. Boiler Considerations-Before YouBuy Be Aware • First cost vs. long term cost. A boiler will use 3-4 times the purchase cost of the boiler installed in energy per year. • Understand boiler efficiency vs. manufacturer claims. • Be aware of efficiency claims by other utility companies. • Match the boiler to the connected load. • Emission requirements. All boilers over 10 million BTU’s must be air permitted and low NOx. • Fuel options and back up. • If a single boiler installation, will failure of the boiler shut down operations? • Space and installation issues? • In most states, the installer must be licensed and the boiler permitted. • Avoid buying a boiler. Buy a boiler room. 34
- 35. Average Steam SystemEfficiency An energy survey and load balance on a typical steam system in average condition will yield the following losses Boiler Room Losses Stack losses 21% Blowdown losses 4% Boiler radiation losses 3% Total Boiler Room Losses 28% Distribution Losses Insulation losses 7% Steam leaks 6% Blowing steam traps 7% Flash steam losses 13% Return System losses 9% Total Distribution Losses 42% Total Steam System Losses 70% Placed in perspective, if you are spending $500,000 per year for boiler fuel, only about $150,000 of thermal work is being delivered into your product or process. Average Steam System Efficiency An energy survey and load balance on a typical steam system in average condition will yield the following losses Boiler Room Losses Stack losses 21% Blowdown losses 4% Boiler radiation losses 3% Total Boiler Room Losses 28% Distribution Losses Insulation losses 7% Steam leaks 6% Blowing steam traps 7% Flash steam losses 13% Return System losses 9% Total Distribution Losses 42% Total Steam System Losses 70% Placed in perspective, if you are spending $500,000 per year for boiler fuel, only about $150,000 of thermal work is being delivered into your product or process. 35