Effective Boiler Effective Boiler UtilizationUtilization

Why go to all the Why go to all the trouble ?trouble ?

Steam is an easy method for Steam is an easy method for transferring heat energy from a heat transferring heat energy from a heat source to a heat load.source to a heat load.

Addition of heat and moisture into Addition of heat and moisture into the material improves processing.the material improves processing.

Goal is to produce a gelatinized Goal is to produce a gelatinized material with improved feed value.material with improved feed value.

Benchmark your cost of Benchmark your cost of steam production.steam production.

Determine your annual fuel cost based Determine your annual fuel cost based on utility bills.on utility bills.

Install a steam flow meter or water flow Install a steam flow meter or water flow meter in your facility and calculate your meter in your facility and calculate your steam generation costs.steam generation costs.

Compare your actual costs with the Compare your actual costs with the benchmark.benchmark. (Use a water flow meter on water feed into (Use a water flow meter on water feed into

the boiler will also cover boiler blow down the boiler will also cover boiler blow down effects.)effects.)

Performing BenchmarkPerforming Benchmark

You will need to You will need to know the know the following.following. Operating boiler Operating boiler

pressure.pressure. Feedwater Feedwater

Temperature.Temperature. Type of fuel used.Type of fuel used. Cost of fuel.Cost of fuel.

FeedFeed WateWaterr

TemTempp

Op Op Pressure Pressure (PSIG)(PSIG)

5353 101101 162162 198198

6060 1160.1160.77

1112.1112.22

1051.1051.88

1016.1016.22

8080 1165.1165.00

1116.1116.55

1056.1056.11

1020.1020.55

9090 1166.1166.99

1118.1118.44

1058.1058.00

1022.1022.44

100100 1167.1167.66

1119.1119.11

1058.1058.77

1023.1023.11

Energy Required to Produce One Pound of Saturated Steam, Btu.

Benchmark ContinuedBenchmark ContinuedFuel Type and Fuel Type and Sales UnitSales Unit

Energy Energy Content, Content, Btu/Sales unitBtu/Sales unit

CombustionCombustion Efficiency, %Efficiency, %

Natural Gas, Natural Gas, MMBtuMMBtu

1,000,001,000,0000

85.785.7

Natural Gas, Natural Gas, Thousand Thousand cubic feetcubic feet

1,030,001,030,0000

85.785.7

Distillate/Distillate/No.2 Oil, No.2 Oil, gallongallon

138,700138,700 88.788.7

Residual/Residual/No.6 Oil, No.6 Oil, gallongallon

149,700149,700 89.689.6

Coal, TonCoal, Ton 27,000,027,000,00000

90.390.3

ExampleExample Producing 100 psig steam, Producing 100 psig steam,

101 Deg F feed water, and 101 Deg F feed water, and $7.50/MMBtu Natural gas.$7.50/MMBtu Natural gas.

Steam Cost = Steam Cost = ($7.50/MMBtu/10($7.50/MMBtu/1066 Btu/MMBtu) * 1,000 lb * Btu/MMBtu) * 1,000 lb * 1,119.1 Btu/lb/0.8571,119.1 Btu/lb/0.857

Steam Cost = $9.79/1,000 lb Steam Cost = $9.79/1,000 lb steamsteam

Factors Effecting Steam Factors Effecting Steam Cost’s.Cost’s.

Feed Water Temperature.Feed Water Temperature. Heat Transfer (Chemistry).Heat Transfer (Chemistry). Burner EfficiencyBurner Efficiency Steam ApplicationSteam Application Distribution System.Distribution System.

Steam TrapsSteam Traps Condensate ReturnCondensate Return InsulationInsulation

Feed Water TemperatureFeed Water Temperature

Proper feed water temperature control Proper feed water temperature control can be a major factor when looking at can be a major factor when looking at improving steam system efficiencies. improving steam system efficiencies.

Compare Benchmark calculation for 90 Compare Benchmark calculation for 90 psig steam at 53 Deg vs 162 Deg F feed psig steam at 53 Deg vs 162 Deg F feed water.water.54 Deg F = $10.21/1,000 lb of steam54 Deg F = $10.21/1,000 lb of steam162 Deg F = $9.26/1,000 lb of steam162 Deg F = $9.26/1,000 lb of steamA difference of $0.95/1,000 lb of steam A difference of $0.95/1,000 lb of steam productionproduction

Feed Water TemperatureFeed Water Temperature There are a several ways to increase There are a several ways to increase

the feed water temperature in the the feed water temperature in the system. Two of the most common system. Two of the most common methods would be:methods would be:

1.1. Direct Steam injection into the feed Direct Steam injection into the feed water make-up tank with water make-up tank with thermostatically controlled valve.thermostatically controlled valve.

2.2. Install Feedwater Economizer.Install Feedwater Economizer.

3.3. Proper condensate return and Proper condensate return and blowdown heat exchangers.blowdown heat exchangers.

Feed Water TemperatureFeed Water Temperature Direct Steam Direct Steam

Injection.Injection.

Steam injected Steam injected directly into the feed directly into the feed water tank can be water tank can be used as a heat source, used as a heat source, but it is important to but it is important to remember that this is remember that this is also a heat load on the also a heat load on the boiler and will not boiler and will not provide a high energy provide a high energy savings.savings.

EconomizerEconomizer

Generally, boiler Generally, boiler efficiency can be efficiency can be increased by 1% increased by 1% for every 40 Deg. F for every 40 Deg. F reduction in flue reduction in flue gas temperature. gas temperature.

**Economizers have limits for Economizers have limits for both cold end corrosion and both cold end corrosion and exhaust gas temperatures exhaust gas temperatures that must be observed.that must be observed.

Heat TransferHeat Transfer Proper Boiler Chemistry control is Proper Boiler Chemistry control is

critical in efficient boiler operation as critical in efficient boiler operation as well as boiler safety.well as boiler safety.

1/501/50thth of an inch of hard scale buildup of an inch of hard scale buildup on boiler tubes can result in an increase on boiler tubes can result in an increase in fuel usage of up to $20,000/in fuel usage of up to $20,000/ year.year.

Find a reliable boiler chemistry Find a reliable boiler chemistry company and perform tests as required.company and perform tests as required.

Burner EfficiencyBurner Efficiency

The purpose of the burner is to mix The purpose of the burner is to mix molecules of fuel with molecules of air. A molecules of fuel with molecules of air. A boiler will run only as well as the burner boiler will run only as well as the burner performs. Burners are designed to performs. Burners are designed to maximize combustion while minimizing maximize combustion while minimizing the release of emissions.the release of emissions.

An efficient natural gas burner requires An efficient natural gas burner requires only 2 to 3% excess oxygen, or 10 to 15% only 2 to 3% excess oxygen, or 10 to 15% excess air. excess air.

Burner EfficiencyBurner Efficiency Flue Gas AnalyzersFlue Gas Analyzers

The percentage of The percentage of oxygen in the flue gas oxygen in the flue gas can be measured by can be measured by inexpensive gas inexpensive gas absorbing test kits. absorbing test kits.

More expensive More expensive analyzers are available analyzers are available that display % Oxygen, that display % Oxygen, stack gas temp., and stack gas temp., and boiler efficiency. These boiler efficiency. These are recommended for are recommended for boilers with annual boilers with annual fuel costs over fuel costs over $50,000.$50,000.

Oxygen Trim SystemsOxygen Trim SystemsIf fuel composition is If fuel composition is highly variable or in highly variable or in cases where steam flows cases where steam flows are highly variable, an are highly variable, an online oxygen analyzer online oxygen analyzer should be considered.should be considered.

The oxygen “Trim” The oxygen “Trim” system provides system provides feedback to the burner feedback to the burner controls to automatically controls to automatically minimize excess minimize excess combustion air and combustion air and maximize the fuel-to-air maximize the fuel-to-air rationration

Steam ApplicationSteam Application Boiler systems in the feed industry have Boiler systems in the feed industry have

few similarities with industrial boiler few similarities with industrial boiler systems. One of the main differences is systems. One of the main differences is with the condensate return system. with the condensate return system. Commercial boiler systems can return Commercial boiler systems can return over 90% of the condensate while boiler over 90% of the condensate while boiler systems in the feed industry typically systems in the feed industry typically return less than 5% condensate into the return less than 5% condensate into the feed water system.feed water system.

In short, almost all of the steam delivered In short, almost all of the steam delivered into the distribution system is used or lost.into the distribution system is used or lost.

Steam ApplicationSteam Application Performing the Benchmark test we Performing the Benchmark test we

learned that even the best situation will learned that even the best situation will result in a given steam production cost.result in a given steam production cost.60 psig - 198 deg F - $7.50/MMBtu = $8.89/1000 lb 60 psig - 198 deg F - $7.50/MMBtu = $8.89/1000 lb steamsteam100 psig – 198 deg F - $7.75/MMBtu = $8.95/1000 lb 100 psig – 198 deg F - $7.75/MMBtu = $8.95/1000 lb steamsteam

By insuring that we are not over-By insuring that we are not over-steaming, we can achieve enough heat steaming, we can achieve enough heat input to cook while minimizing the total input to cook while minimizing the total steam contribution. steam contribution.

Steam ApplicationSteam Application60 psig – 198 Deg F - 60 psig – 198 Deg F -

$7.50/MMBtu$7.50/MMBtu$8.89/1,000 lb of steam$8.89/1,000 lb of steam

Adding 6% moisture in the Adding 6% moisture in the steam chest requires steam chest requires approx. 127 lbs of steam approx. 127 lbs of steam application. At $0.0089 per application. At $0.0089 per pound of steam that means pound of steam that means that adding 6% moisture that adding 6% moisture (127 lbs) will have a cost of (127 lbs) will have a cost of $1.13 per ton.$1.13 per ton.

Compare this to adding Compare this to adding only 3% moisture, 62 lbs, only 3% moisture, 62 lbs, and a cost of $0.55 per ton.and a cost of $0.55 per ton.

100 psig – 198 Deg F - 100 psig – 198 Deg F - $7.50/MMBtu$7.50/MMBtu

$8.95/1,000 lb of steam$8.95/1,000 lb of steam

Adding 6% moisture in the Adding 6% moisture in the steam chest requires approx. steam chest requires approx. 127 lb of steam application. 127 lb of steam application. At $0.0090 per pound of At $0.0090 per pound of steam, that means that adding steam, that means that adding 6% moisture (127 lbs) will 6% moisture (127 lbs) will have a cost of $1.14 per ton.have a cost of $1.14 per ton.

Compared to $0.56 per ton Compared to $0.56 per ton for 3%for 3%

The higher pressure also The higher pressure also insures that enough heat will insures that enough heat will be added for cooking with the be added for cooking with the reduced stem additionreduced stem addition

Steam ApplicationSteam Application

Steam Flow Meters: Steam Flow Meters: There are a number of There are a number of steam flow meters that steam flow meters that can be installed in the can be installed in the distribution system to distribution system to allow operators to allow operators to monitor and adjust monitor and adjust steam application within steam application within specified ranges to specified ranges to insure adequate cooking insure adequate cooking while minimizing the while minimizing the pounds applied.pounds applied.

There are a few options when looking at monitoring steam application. The object is to provide enough heat input for cooking while minimizing pounds added.

Distribution SystemDistribution System

The steam distribution system The steam distribution system includes everything from the boiler includes everything from the boiler discharge valve out to the processing discharge valve out to the processing units and any condensate return units and any condensate return system that may be in place. system that may be in place.

The boiler blow down system, while The boiler blow down system, while not actually part of the distribution not actually part of the distribution system may also offer some efficiency system may also offer some efficiency options and should be looked at.options and should be looked at.

Distribution SystemDistribution System

Steam TrapsSteam Traps Every distribution system should include Every distribution system should include

steam traps.steam traps. Steam traps provide a means for removing Steam traps provide a means for removing

water droplet and condensate from the water droplet and condensate from the header prior to utilizing the steam for header prior to utilizing the steam for heating.heating.

While extremely important in turbine While extremely important in turbine applications, they also are important in our applications, they also are important in our process to insure the highest energy and best process to insure the highest energy and best quality steam is being applied.quality steam is being applied.

Steam TrapsSteam Traps Steam loss from Steam loss from

traps.traps. Steam traps should Steam traps should

be tested to insure be tested to insure they are not cold they are not cold plugging or failing plugging or failing open allowing steam open allowing steam to escape directly to escape directly into the CR lineinto the CR line

Four ways to test: Four ways to test: Temp., Sound, Temp., Sound, Visual, ElectronicVisual, Electronic

Traps should be Traps should be tested monthly to tested monthly to Quarterly.Quarterly.

Trap Orifice Trap Orifice Diameter, Diameter, InchesInches

Steam loss, Steam loss, lb/hrlb/hr

100 psig100 psig

1/321/32 3.33.3

1/161/16 13.213.2

1/81/8 52.852.8

3/163/16 119119

¼¼ 211211

3/83/8 475475

Condensate ReturnCondensate Return

Returning hot condensate to the Returning hot condensate to the boiler makes sense for several boiler makes sense for several reasons. reasons.

1.1. The more condensate that is returned, the The more condensate that is returned, the less make-up water is required.less make-up water is required.

2.2. Chemicals and Chemical treatment costs.Chemicals and Chemical treatment costs.

3.3. Fuel savings with higher temperature Fuel savings with higher temperature make-up water.make-up water.

4.4. Reduced boiler blowdown with return of Reduced boiler blowdown with return of high purity water.high purity water.

InsulationInsulation

Un-insulated steam piping is a constant Un-insulated steam piping is a constant source of wasted energy.source of wasted energy.

Proper insulation can typically reduce Proper insulation can typically reduce energy losses by 90% and help insure energy losses by 90% and help insure proper steam pressure at processing proper steam pressure at processing equipment.equipment.

Any surface over 120 Deg. F should be Any surface over 120 Deg. F should be insulated including boiler surfaces, insulated including boiler surfaces, steam piping and fittings, and CR lines.steam piping and fittings, and CR lines.

InsulationInsulation

Proper insulation can Proper insulation can provide a great deal provide a great deal of energy savings of energy savings when properly selects when properly selects and maintained.and maintained.

Use insulating Use insulating jackets for valves, jackets for valves, flanges and traps. A flanges and traps. A 6-inch gate valve may 6-inch gate valve may have more than 6 sq. have more than 6 sq. feet of surface area.feet of surface area.

Pipe Size, Inches

MMBtu/yr loss per 100 feet

0.5 160

1 240

2 400

4 700

6 985

8 1270

10 1550

12 1820

ConclusionConclusion There are obviously a number of factors There are obviously a number of factors

that effect boiler utilization and efficiency.that effect boiler utilization and efficiency. If you don’t know what your cost of steam If you don’t know what your cost of steam

production is, how can you improve it.production is, how can you improve it. If your not monitoring your steam usage, it If your not monitoring your steam usage, it

is impossible to tell if you are being is impossible to tell if you are being efficient.efficient.

Use the various resources available to you Use the various resources available to you for better steam and boiler utilizationfor better steam and boiler utilization

ResourcesResources

www.eere.energy.gov/industry/bestpracticesThis site has a lot of information available and can be a This site has a lot of information available and can be a great resource for improving efficiencies.great resource for improving efficiencies.