CLIMATEWISE BOILER AND STEAMEFFICIENCYWISE RULES



### PamelaHennanMilmoe Director, ClimateWise Program U.S. Environmental Protection Agency

ABSTRACT Climate Wise is an industrial energy efficiency program sponsored by the U.S. EPA, and supported by the U.S. DOE, working in partnership with more than 400 industrial companies. Many Climate Wise Partners are evaluating or implementing boiler and steam system efficiency measures and have requested assistance in quickly estimating the impacts of these projects through the 

### Wise Line. Climate Wise has developed the 

### Wise Rulesfor Industrial Efficiency (Wise Rules Tool Kit) to provide companies with simple rules ofthumb, or Wise Rules, for estimating potential energy, cost, and greenhouse gas emissions savings from key industrial energy efficiency
measures for a broad range of end uses, including boilers and steam systems. This paper presents excerpts from the Wise Rules Tool Kit on boiler and steam system efficiency measures.
INTRODUCTION TheWise Rules are a compilation ofsome ofthe best industrial energy efficiency infonnation from a variety of industrial, academic and government sources. The Wise Rules were developed from infonnation sources including the DOEIIAC database (8), the Rutgers University Office of Industrial Productivity and Energy Assessment, the Association of Energy Engineers and the Bonneville Power Administration, the EnergyEfficiency and Renewable Energy ClearinghouselNetwork (ERECIEREN), the Centre for the Analysis and Dissemination of Demonstrated Energy Technologies (CADDET), and Climate Wise Partners' own estimates. These data
sources are quite comprehensive and may 

### be new to many ClimateWise Partners. We have extracted core information from these materials to provide Climate Wise Partners with ready-to-use Wise Rules. Thoroughreferences are included to direct Partners to the original sources for more detailed treatment ofthe issues. The Wise Rules can help companies develop
a first cut estimate of project impacts and provide guidance on how to analyze efficiency measures in
more detail. Steven

### R. Winkelman SeniorAssociate ICF Kaiser Consulting Group

This paperpresents excerpts from theWise Rules Tool Kit on boiler and steam system efficiency
measures. This will include a discussion of boilers and steam systems, and sample Wise Rules presented in text, tabular, and graphical fonnats. The Wise Rules provide a range ofestimates ofenergy savings for broad categories of efficiency measures, (e.g., boiler maintenance), and more specific measures (e.g., adjusting air to fuel ratio). Savings estimates
are expressed both as a percent ofboiler fuel use and
as apercent ofan average facility's fuel consumption.
BOll..ERS Boilers are one ofthe most importantenergy uses in manufacturing, typically comprising over 25 percent of total manufacturing energy demand. A boiler generateshotwater or steam, typically from the combustion ofcoal, oil or natural gas. A network of pipes delivers steam (or hot water) to provideheat for
a variety of process and space heating applications. Once the heat has been extracted from the water or steam, another network of pipes returns the condensed water back to the boiler where it is cyclically reheated. There are several different types of boilers including natural draft, forced draft, hot water or steam, and fire tube or water tube. The typical boiler used in small-to-medium sized industrial operations is a forced draft steam boiler at 120-150 psi and approximately 

### ISO hp (equivalent to 5.0 MMBtulhr) (4). Typical boiler efficiencies range from about 70 to 85 percent depending on fuel type, configuration, and heatrecoverycapability (3).
BoilerSavingsby Industry Group Figure 1 illustrates the potential energy savings from boiler efficiency measures based on IAC audit recommendations (8). Boiler efficiency measures with an average savings of 3% offacility energy use and a simple payback of 9 months were recommended at 20% of the 4,300 facilities audited from 1990to 1997.



### 272Recommendation Rate

50% 6month payback 45%
40%
35%
30%
25%
20%
15%
10%

5%
0% 4 month payback • Recommendalion Rale

6month payback Energy Savings

9month payback

Figure I. Boiler Savings by Industry Group (8)

The Wise Rules Tool Kit provides a brief Ener Saving 70/<

60/1

50/1

40/1

30/1

20/1

10/1

00/1

overview of the efficiency measures considered. Following is a discussion of boiler tune-up and air/fuel ratio optimization measures and associated Wise Rules

BoilerTune-Upand AirlFuel Ratio Optimization Using the following instruments allows plant engineers to properly monitor and adjust boiler operating conditions: stack thermometers, fuel meters, make-up feed watermeters, oxygen analyzers, run-time recorders, energy output metering (steam flow, Btu output), and return condensate thermometers (6). Periodic measurement of flue gas oxygen, carbon monoxide, opacity, and temperature provides the fundamental data for a boiler tune-up. A typical tune-up might include a reduction of excess air (and excess oxygen, 02), boilertube cleaning, and re-calibration ofboiler controls.

• A 

### good tune-up with preclSlon testing equipment can detect and correct excess air losses, smoking, unbumed fuel losses, sooting, and high stack temperatures, and result in boilerfuel savings of2% to 

### 20% (6). Each fuel type and firing method has an opti al air/fuel ratio. For example, optimum excess air fo a pulverized coal boiler is 15

- 20% (3

- 3.5% exc ss 02), and optimum excess air for a forced draft as boiler is 5 - 10% (l

- 2% excess 02) (7). The air/f¥el ratio should be adjusted to the manufacturer's recommendations. Because it is difficult to reach

### ~d maintain optimal values in most boilers, actual exctss air levels may need to be set higher than optimal

# !).

Manual or automatic oxygen trim can insure that e proper air/fuel mixture ratio is maintained (2).

• A 3% 

### decrease in flue gas 02 typic lly 

### produces a 2% 

### increase in boiler efficie cy (I).



### • Using over fire draft control systems to 

### control excess air can result in boiler el savings ranging from 2% 

### to 10% ( ith typicalequipmentcostsaround$1,500) ( ).

When boilers are operating at low loads excessair requirements may be greater than the

### opti~al levels and efficiency may be lower (7).



### 273

### • Using a characterizablefuel valve to match the airlJuel ratios across the load range can lead to

### fuel savings ranging from 2% 

### to 12% at low cost(6).

The Wise Rules also include DOElIAC data on specific efficiency measures. For example, air/fuel ratio optimization was recommended at 16 percent of facilities audited. The average energy savings across all industry sectors was 2,100 MMBtu or 2.4 percent of annual facility energy use. The average implementation cpst for these measures was $5,600 with a simplepaybackperiod ofthree months. Summary ofBoilerWise Rules The Wise Rules in Table 1 can be used to identify and estimate potential energy saving from boiler efficiency measures. In selecting alternative efficiency options and eliminating less attractive measures, consider the potential costs, savings, payback times and any secondary effects. When using the Wise Rules, remember that several of the
measures may overlap, or complement each other (e.g., tune-up and flue gas 02 reduction) and energy savings rates of overlapping measures may not be additive. In addition. multiple Wise Rules may address the same measure from multiple perspectives. For example Boiler Wise Rule I expresses savings from boiler load management as a percent of the boiler's energy use. while Boiler Wise Rule 2 expresses savings as a percent of the facility's total energy use. Wise Rules may not be comparable because they rely on different sources with different assumptions. Adjust the Wise Rules to match your circumstances. For example, you may want to scale the gross fuel cost savings to match your boiler size. To calculate savings for a 10 MMBtu/hr natural gas boiler, multiply gross fuel cost savings by a factor of ten. This scaling is applicable only to gross fuel cost savings expressed per MMBtulhr, e.g., Rule 2, but not Rule I in Table I. Implementation costs may not scale in a linearmanner. Similarly, you can adjust the savings numbers on the basis ofyour fuel prices and operating hours. For example. ifyour boileruses coal at a price of $1.50IMMBtu, divide the cost savings values in Table I by the per MMBtu price of natural gas. e.g., $2.30, and multiply by $1.50.



### 274

### Measure (lACRecommendationRate) Summary: Typical Efficiency Improvements, Which May Include Many orAll ofthe Measures Below (20%)

BoilerLoad Management I.Operate on high fire setting orinstall smallerboilers (1%)

2. Optimizeboiler size and boilerload Tune-Up and AirlFueI Ratio Optimization 3. Implement boilermaintenance (air/fuel ratio optimization, burner maintenance, boiler tube cleaning) (16%) 4. Implement comprehensive tune-up 5. Decrease flue gas 0') by 3% 6. Utilize overfire draft control 7. Utilize characterizable fuel valve 8. Convertto atomizing burners StackLosses and Waste HeatRecovery 9. Reduce net stack temperature by 40of 10. Utilize stackdampers II. Direct contact condensation heatrecovery 12. Pre-heatcombustion air (3%)

Blowdown Control and HeatRecovery 13. Minimize boilerblow down (1%)
14. Remove 1/32" to 1/8" depositfrom heat transfer surfaces 15. Utilize blowdown heatrecovery 16. Increase boiler feed water by I10 F J7. Utilize automatic blowdown control Table I. Summary ofBoilerEfficiency Measures 

### AverageEnergySavings*

2.8% oftotal facility energy use**

7.4% oftotal facility energy use**
2% to 50%

2.4% oftotal facility energy use**
2% to 20% 2% 2% to 10% 2% to 12% 2% to 8%

I % to 2% 5% to 20% 8% to 20% 2.6% oftotal facility energy use**

1.6% oftotal facility energy** 2% to 8%
2% to 5% 1% 2% to 20% 

### AverageAnnualCost SavingsperMMBtuJhr and

### (Paybackt $7,200 (9 months) [total

dollars, not on aper MMBtufhrbasis]** $19,900 (23 months) [total dollars, not on a per MMBtu/hrbasis]** $230to $5,750*** $2,460 (5 months) [total dollars, not on a pe MMBtu/hrbasis]** $230to $2,300*** $230*** $230to $1,400*** $230to $1,400*** $230 to $920***
$140 to $230*** $580to $2,300*** $920 to $2,300*** $5,200(8 months) [total dollars, not on aper MMBtu/hrbasis]**
$8,500(11 months)**
$230 to $920*** $230to $580*** $140*** $230to $2,300*** !
,

Table Notes: 

### • Percenl ofboilerenergy use, unless noted 

### •• Energy savings are as a percent oftotal facility energy use. Cost savings (fuel,O&M,etc.) are expressed in dollars, not in dollars per MMBruIhrofboiler size. 

## ••• Based on a natural gas boiler with 80% efficiency, operating 5.000hrsIyr, with a gas price of**~$2.30IMMBtu.** These are gross fuel savings only and do not include capital, maintenanceorothercosts (savings).

STEAM SYSTEMS maintenance, repairing steam leaks, insulation.
a measures

### , and 

### p p**~"r** Steam s

### ystem efficienc

### y im

### provements are condensate va or recom ression logical complement to boiler efficiency measures. Useful energy escapes from steam distribution systems from malfunctioning steam traps, steam leaks, and radiative losses from steam lines, condensate lines, and storage tanks. Each of these
areas presents opportunities for energy savings. Based in data from the DOElIAC database (8), steam system efficiency measures were recommended a 13% of the 4,300 facilities audited with an averag anticipated savings of 2% of a facility's total energ use and a simple payback of6 months.

The Wise Rules Tool Kit provides a brier Steam system efficiency measures that may be of overview of the efficiency measures considered' interest to Climate Wise Partners include steam trap



### 275 I

### Following is a discussion of steam leak repair and insulation measures and associated Wise Rules. Repairing SteamLeaks Repairing leaks in steam pipes, condensate return lines, and fittings can yield significant energy and cost savings. Steam leaks increase boiler fuel use because additional steam must be generated to make up for the wasted steam. Leaky condensate return lines increase make-up water requirements and increase boiler fuel use because make-up water is cooler than condensate return water and more energy is required to heat the boiler feedwater. Savings will depend on factors such as boiler efficiency, annual operating hours, and boilerpressure (4).



### • The cost ofhigh pressure steam leaks 

### (125 psi) can rangefrom $660 to $2,200per leak per year (8,760 hrs). The cost of low pressure steam leaks 

### (15 psi) can range from $130 to $480per leakperyear (8,760 hrs) (5).
Steam leak repair was recommended at two percent of the DOElIAC facilities audited (8). The average energy savings across all industry sectors was 2,200MMBtu or0.9 percent ofannual facility energy use. The average implementation cost for these
measures was $6,100 with a simple payback period of three months. Improved Insulation Often insulation is removed to make repairs and is not replaced. Uninsulated surfaces in boiler and steam systems can reach 450 

### OF. These high temperatures can threaten employee safety and can be fire hazards. Table 2. presents annual costs of heat loss per 100

### feet ofuninsulated steampipe. SteamPressure Costper 100ftofpipeperyear (8760hr) 25DSi $1,600 50DSi $1,900 75 psi $2,100 100DSi $2,300 

### Table 2. Annual Costs ofHeat Loss per 100 feet of Uninsulated Steam Pipe (5) Sector-Specific SavingsEstimates from Steam SystemEfficiencyMeasures in the lAC Database Table 3 provides sector-specific savings estimates from steam system efficiency measures in the lAC Database (8). As indicated in Table 3, the average savings across all industries (SIC 20-39) from measures such as steam trap replacement, leak repair, insulation, and improved operations was 2.1 percent of total facility energy use with an average simple payback of 6 months. At a fabricated metals plant (SIC 34), system efficiency measures might reduce total facility energy use by 3.0 percent. Steam system efficiency measures recommended in the DOEIIAC audits had the largest relative impact in the fabricated metals industry (SIC 34), but were most frequently recommended in the textile mill products industry (SIC 22). Summary ofWise Rules for Steam Systems The Wise Rules in Table 4 can be used to identify and estimate potential energy saving from steam system efficiency measures. When identifying attractive options and eliminating weak ones, considerpotential costs, savings, paybackperiods and any secondary effects. When using the Wise Rules, remember that some measures may overlap or complement each other (e.g., steam trap maintenance and steam pipe insulation) and energy savings rates may not be additive. Multiple Wise Rules may address the same efficiency measure from different perspectives. For example, Steam Rules I and 2 express savings from steam trap maintenance as a percent of a 

### facility's total energy use, and as a percentof

### boilerenergy use.

27651

2 2 2 2 2 2 3 3 20­ TabIe 3. Sector-Specific SavingsEstimates from Steam SystemEfficiencyMeasures in the lAC Database (8) Note: Includes traps, rondensate, leaks, insulation, and operations (1990-1997). C Industry AverageEnergySavings Recomme

ndation Rate (%) (% oftotal facility energy use) Annual (MMBtu)

0 Food 27% 1.7% 1,540 2 Textile Mill Products 32% ].6% 2,480 3 Aooarel & TextileProducts 26% 1.7% 620 4 Lumber& Wood Products 15% 1.5% 3,930 6 Paper 25% 1.3% 2,220 8 Chemicals 26% 2.7% 7,170 0 Rubber and Plastics 10% 2.4% 1,850 4 Fabricated Metals 8% 3.0% 1,800 39 AverageAcrossIndustries 14% 2.1% 2,420 AverageIrnplementation Costs $2,600 $6,890

$990 $2,940 $3,870 $3,370 $2,860 $2,610 $3,350 Average Annual

Cost Savings

$5,530 $7,940 $1,950 $5,480 $8,020 $13,550

$9,190 $5,510 $7,120 Averae:e Simple Payback (months) 6 10 6 6 6 3 4 6 6

Measure (IAC Recommendation Rate) Summary:Typical Efficiency Improvements, Which May Include Many orAll ofthe Measures Below (13%) SteamTrapMaintenance I. Implement steam trap maintenance program (I%)

2. Steamtrao maintenance LeakRepair 3. Repair steam leaks (2%)
4. Repair high pressure (125 psi) leaks Repair low pressure ( 15 psi) leaks Insulation 5. Improve insulation ofsteam lines (7%)

OtherMeasures 6. Recompress low pressure vapor
7. Reduceheat loss from condensate (4%) Average Energy Savings*

2% oftotal facility energy use

3.4% oftotal facility energy use 10-20% ofboiler fuel use
1.0% oftotal facility energy use

1.0% oftotal facility energy use
90-95% ofenergy needed to

raise the steam in a boiler 1.3% oftotal facility energy use AverageAnnual Cost**Savin~s** and (Pavback) $7,100 (6 months)

$17,400 ( 2 months)

10-20% ofboilerfuel costs $6,100 (3 months)
$660

- $2,200perleak$130

- $480 oerleak
$1,600

- $2,300oer 100ft $2,800 (10 months)

$6,700 (8 months)

Table 4. Summary ofSteam System EfficiencyMeasures Table note: 

### *Percentofstearn systemenergy use, unless noted.

REFERENCES 

### 5. Rutgers University Office of Industrial Productivity 1. 3M Company, "Rules of Thumb: Quick Methods of Energy Assessment, "Useful Rules ofThumb for Resourc Evaluating Energy ReductionOpportunities," 1992. Conservation and Pollution Prevention," March 1996.

2. Garay, P.N., Handbook ofIndustnal Power and Steam 6. TaplIn, H.R., BOIler Plant and DlStnbutlOn System Systems, FairmontPress. OptimizationManual, FairmontPress, 1991.
3. O'Callaghan, P., Energy Management, McGraw-Hill, 7. Turner, W.e., Energy Management Handbook, 3rl England, 1993, p. 198. Edition, Fairmont Press, 1997.
4. Rutgers University, Office ofIndustrial Productivity and 8. U.S. Department ofEnergy, Industrial Assessment Energy Assessment, Modem Industrial Assessments: A Database, July 1997. Training Manual, Version LOb, December 1995.



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