ADDING AN ECONOMIZER MMakes a Good akes a Good … · A3 Update on Economizers Your boiler may be sending large amounts of heat energy up the stack. Learn about modern economizer

THE SOURCE FOR ENERGY SOLUTIONS WWW.ENERGYSOLUTIONSCENTER.ORG

VOLUME 22 / I SSUE 3WINTER /09

ADDING AN ECONOMIZER

Makes a Good Makes a Good Boiler BetterBoiler Better

ple0911Sup1_Cover_ID 1ple0911Sup1_Cover_ID 1 11/10/2009 10:00:51 AM11/10/2009 10:00:51 AM

A3 Update on Economizers Your boiler may be sending large amounts of heat energy up the stack. Learn about modern economizer technologies which can put that wasted energy to work in your plant.

A6 Renewables and Natural Gas Renewable energy systems and natural gas are natural partners. With growing corporate commitments to green operation, it’s useful to fi nd a place for renewables in your operation, partnering with effi ciency natural gas.

A8 Heat Treating Effi ciency Heat treating is an important process in many industrial operations. Today’s heat treating furnaces and gas-fi red burners are more effi cient than ever before. If you haven’t updated your system, now may be the time.

A10 Save Energy Big-Time with Condensing Boilers Hot water boilers are major users of energy across the lines of industrial, commercial and residential customers. Today’s condensing boilers wring a big chunk of otherwise wasted energy out of the boiler exhaust.

A12 LEED Certifi cation for Industrial Buildings LEED certifi cation has captured a lot of attention today for its approaches to green design for commercial and institutional buildings. Now it’s a practical goal for industrial facilities as well.

on the cover

inside

Economizers have great potential to

improve the operating effi ciency of

industrial and commercial boilers.

This installation of a condensing

economizer is at a paper converting

plant. Photo Courtesy Combustion &

Energy Systems.

Gas Technology is a trademark of Energy Solutions Center Inc. and is published in cooperation with Reed Business Information.

Gas Technology is an educational supplement from: Energy Solutions Center Inc. 400 N. Capitol St., N.W. Washington, DC 20001 � (202) 824-7150

www.energysolutionscenter.org

David Weiss, Executive DirectorJake DelwicheContributing EditorComments may be directed to: Gas Technology Editor Plant Engineering Magazine 2000 Clearwater Dr. Oak Brook, IL 60523 � (630) 288-8789

Printed in the USA

energy solutions center websites

www.aircompressor.org

www.cleanboiler.org

www.energysolutionscenter.org

www.naturalgaseffi ciency.org

www.gasairconditioning.org

www.poweronsite.org

www.foodtechinfo.com

ple0911Sup1_TOC_ID A2ple0911Sup1_TOC_ID A2 11/10/2009 10:09:56 AM11/10/2009 10:09:56 AM

NEW ECONOMIZER DESIGNS

Selection the Key to an Effi cient Unit

Boiler Effi ciencyPump Up

This ConDex condensing economizer at a paper converting plant extracts 35 million Btuh from the exhaust of a 30 MW gas turbine.

ALTHOUGH BOILER ECONOMIZERS

have been in use since the mid-19th

century, recent improvements make them

better than ever at scavenging energy

that would otherwise be lost up the boiler

exhaust stack. Economizers are designed

to extract useful heat from the exhaust by

passing it through a heat exchanger cooled

by a liquid to absorb that heat energy. The

goal is to improve overall boiler effi ciency,

thereby reducing operating costs and

lowering plant emissions by reducing the

amount of fuel used.

Interest Continues to GrowAccording to Cameron Veitch of

Combustion & Energy Systems Ltd., a

major manufacturer of add-on economiz-

ers, his fi rm is seeing an unprecedented

level of interest in these systems. Accord-

ing to Veitch, who was a speaker at an

Energy Solutions Center-sponsored Tech-

nology & Marketing Assessment Forum in

Niagara Fall, Ontario in October, 2009,

“The opportunities are on both the large

and small-scale application ends of the

spectrum.” He explains that the concept

has been proven in many different indus-

tries, as well as in commercial opportuni-

ties such as hospitals and laundries.

Economizers can range in size from

giant sections for large utility boilers to

small barrel-size devices added to package

boilers. Some newer gas-fi red industrial

boilers now include an economizer section.

More common, however, is an economizer

designed for a specifi c installation and

sized for the available cooling liquid fl ow

and characteristics.

Two Classes of SystemsThe two general classes of economizers

are condensing and non-condensing units.

Condensing economizers are designed to

reduce the temperature of the exhaust gas

to below its dew point, thereby recovering

the latent heat of vaporization and increasing

boiler effi ciency dramatically. According to

Veitch, whose fi rm specializes in condens-

ing economizers with its ConDex units, a

condensing economizer can increase boiler

effi ciency from 10% to 20%.

Non-condensing economizers are

the choice where the goal is to extract a

large portion of the useful heat from the

exhaust while keeping the discharge

temperature above the dew point. This

type unit is chosen where there are

limitations on the amount of cooling liquid

available, or its temperature is such that it

cannot bring the exhaust gas below the

dew point. Generally, a non-condensing

economizer is less expensive to purchase

and install because it does not require

the use of corrosion-resistant materials as

does a condensing unit. Additionally, non-

W W W. E N E R G Y S O L U T I O N S C E N T E R . O R G g a s t e c h n o l o g y / W I N T E R 0 9 A 3

ple0911Sup1_CoverStory_ID A3ple0911Sup1_CoverStory_ID A3 11/10/2009 10:13:59 AM11/10/2009 10:13:59 AM

A 4 g a s t e c h n o l o g y / W I N T E R 0 9 W W W. E N E R G Y S O L U T I O N S C E N T E R . O R G

This ConDex condensing economizer extracts heat from the exhaust of three 250 hp boilers. Heat is used to pre-heat boiler makeup water.

Installation of a condensing economizer from Steam Plant Systems on the exhaust from two boilers using natural gas and waste solvents. The Tefl on®-covered heat exchanger is designed to prolong the life of the economizer while recovering 14 million Btuh.

...multiple boilers can be served with a single economizer package, as opposed to one economizer for each boiler – a much simpler installation that results in lower costs.Ron Nessen, President of Steam Plant Systems

“

”

condensing units do not need a condensate

collection, treatment and removal system.

According to Ron Nessen, President of

Steam Plant Systems, the manufacturer

of CHX Heat Exchangers, another option

for industrial energy users is a packaged

system that includes both a conventional

economizer and a condensing heat

exchanger. He points out, “The advantage

in doing this is that multiple boilers can be

served with a single economizer package,

as opposed to one economizer for each

boiler – a much simpler installation that

results in lower costs.”

Ideal for Natural Gas BoilersCondensing economizers are generally

not used on coal-fi red and oil-fi red boilers

because the wet tube heat exchange sur-

face will quickly accumulate ash and other

combustion byproducts, thus challenging

sootblower systems and increasing boiler

maintenance. Further the fl ue gases them-

selves are much more corrosive. However

because of their clean combustion, natural

gas boilers can take full advantage of con-

densing technology, and overall effi ciency

of a modern boiler can be increased from

80% to as high as 95%. Thus the paybacks

for installing a retrofi t condensing econo-

mizer are short – often less than one year.

The cooling liquid for either type econ-

omizer can be from many sources. In-

dustrial installations that consume large

amounts of steam need large volumes of

makeup water, which can be preheated in

the economizer before going to the boil-

er. Systems that reuse extensive amounts

of condensate can use the economizer

to preheat the condensate return liquid.

Industries that use hot water or other

liquids for process purposes can preheat

them in a condensing or non-condensing

economizer, depending on the volume

and temperature of water used. Generally

the return condensate in a steam heating

system is at a temperature too elevated for

condensing operation, but a non-condens-

ing economizer may be a practical solution

for increasing the effi ciency of the boiler.

Getting the Metallurgy RightVeitch notes that the metallurgy of the

heat exchanger must be compatible with

both the liquid stream being heated

and the properties of the fl ue gas being

condensed. On the circulating liquid side

of the tube, the heating process drives the

oxygen out of the liquid, which can bring

a risk of corrosion inside the water tubes.

On the exhaust gas side, even with natural

gas combustion, the condensate contains

carbonic acid from the exhaust gas being

cooled below its dew point. Because the

pH of this condensate is typically 3.0 to

3.5, the economizer must have corrosion

resistant tubes and enclosures.

Veitch gives as an example of a successful

installation a San Francisco area company

that was operating a 30 MW gas turbine

for site electric service. The effi ciency of

this operation jumped when they installed

a condensing economizer on the turbine

exhaust. The unit recovers 35 million Btuh

of energy from the turbine exhaust, all of

which is used for heating process water.



Even smaller exhaust streams can benefi t from waste heat recovery, as with this cylindrical economizer installed in-line on the exhaust from a 400 hp fi re-tube boiler in California.

CAIN INDUSTRIEShttp://www.cainind.com

COMBUSTION & ENERGY SYSTEMShttp://www.combustionandenergy.com

SOFAME TECHNOLOGIES INC.http://www.sofame.com/products.htm

STEAM PLANT SYSTEMS, INC.http://www.steamplantsystems.com

M O R E

i n f o

Condensing heat recovery is practical for

even a single, smaller boiler exhaust. For

example, a southern California company

installed a cylindrical in-stack condensing

economizer on the exhaust of a 400 HP

fi re-tube boiler. The heat recovered is used

to pre-heat boiler makeup water.

Tefl on® Coating the Heat ExchangerAccording to Nessen from Steam Plant

Systems, who was a speaker at an Energy

Solutions Center-sponsored conference

on condensing heat exchangers in Toronto

in 2008, corrosion resistance is a major

requirement. He indicated that much

research done in the 1980s indicated

that for condensing economizers, even

standard stainless steel heat exchangers

exposed to temperatures above 180° F

or exposed to fl ue gases from other than

natural gas fuels may have a shortened

life. For this reason, Steam Plant Systems

offers a Tefl on®-covered heat exchanger,

with a demonstrated service of over 25

years under corrosive conditions caused

by the fl ue gas.

Nessen indicates that heat recovery

system packages consisting of a conven-

tional economizer plus a condensing heat

exchanger can raise boiler effi ciency to

well over 90%. “This is true if they are

correctly engineered and designed, and

there is a suffi cient heat sink for the

condensing heat exchanger.” He points

out that his company’s latest CHX

System state-of-the-art package that is

due to start up in the last quarter of 2009

will result in a boiler effi ciency improve-

ment of 16.4%. He adds, “This will break

the 95% boiler combustion effi ciency

barrier – the fi rst of its kind.”

Specify the Right SystemIndustrial boiler operators considering

adding an economizer to an existing

boiler should get help from a qualifi ed

mechanical engineer, who will work with

economizer manufacturers to select exactly

the right type and size of system. Generally

an economizer can be added to a system

with relatively little boiler down-time.

The incoming water in a condensing

economizer needs to be from fi ve to

ten degrees below the dew point of the

exhaust gas, which is commonly between

125° and 150° F. Thus if the calculated

dew point of the gas is 135° F, the engineer

must calculate if there is an ample fl ow of

water at 128° F or lower. At higher water

temperatures, some heat recovery will

still take place, but the high effi ciency of a

condensing system will not be achieved.

Watch Liquid TemperaturesIn normal operation, it is important to keep

the circulating liquid temperatures within

the design range. It makes little sense to

pay the premium price for a condensing

economizer, and then operate it at fl uid

temperatures above the condensing point.

It is an even bigger problem to operate

a system that was designed as non-

condensing operation with circulating

liquids at temperatures that will allow

condensing. In this situation, corrosion and

damage to equipment will quickly result.

If you are currently operating a gas-fi red

boiler without an economizer, and you

can make use of a stream of heated liquid,

you need to be looking at this technology.

Whether yours is a small 150 hp unit or

a large central boiler plant, opportunities

exist for you to dramatically improve plant

effi ciency and reduce overall emissions.

The time for an economizer is defi nitely

here today. GT



Augmenting Your Energy Resources

A Place for Renewables

A compact biogas processing plant at a large dairy farm upgrades raw biogas to make it a direct replacement for natural gas.

IN INDUSTRIAL ENERGY PLANNING

HARNESSING THE POWER OF WIND,

solar, biofuels and other renewables prom-

ises to reduce our dependence on fossil

fuels. Energy production from these sources

is increasing and warrants a closer look.

Wind and ethanol applications continue

to grow. Of special interest to industry is

the combined use of clean natural gas and

emerging bio-fuel technologies.

Ethanol Use Is Now WidespreadEthanol motor fuels and fuel supplements,

along with biodiesel, now replace a

signifi cant amount of refi ned petroleum

in North America and around the world.

The use of ethanol in motor fuels varies

widely among states and provinces in

North America. In Corn Belt states ethanol

is commonly used as a 10% blend into

gasoline, and many gas stations also offer

85% ethanol motor fuels for vehicles

meeting Flexible Fuel design standards.

According to the U.S. Department of

Energy (DOE), the Energy Independence

and Security Act of 2007 (EISA) calls for

unprecedented growth in the U.S. biofu-

els industry over the next decade. The U.S.

already annually produces over 9 billion

gallons of ethanol, about a quarter of the

amount called for by EISA by 2022. However

DOE emphasizes that much of the future

growth in renewable fuels must come from

sources other than grain-based ethanol.

Electric Utilities Look to Meet Renewable RequirementsRenewable energy sources also meet a

growing proportion of the generation needs

of electric utilities and other industries. In

many U.S. states, utilities are required to

add increasing proportions of renewable

sources to their generation portfolios. This

requirement is being achieved with wind

farms, solar stations and the use of renew-

able fuels in thermal generation plants.

Industries Study Renewable TrendsIndustrial users want to know the implica-

tions of this seeming boom in renewable

energy. How will it affect industrial en-

ergy planning, and what specifi c opportu-

nities does it represent for industry in the

U.S. and Canada? Various state and federal

government programs encourage, or in

some cases require, the increased use of

renewable energy sources. A recently

announced “Retrofi t Ramp-up” program

under the Recovery Act earmarks $454 mil-

lion for DOE programs for energy effi ciency,

including a strong emphasis on renewable

energy projects for residential, commercial,

industrial and community energy users.

In California, fl eet operators of more

than 15 vehicles are required to specify

alternative fuels for new vehicle purchases.

These include ethanol, biodiesel and

solar-electric vehicles, along with the

more widely chosen compressed or liquid

natural gas (CNG and LNG) options. Using

alternative fuels, energy users can also help

meet corporate “green energy” goals.

Wind farms are popping up in many parts

of North America and elsewhere. Solar col-

lectors of various types can be seen in many

areas, particularly in sunnier regions. Be-

cause of the variable characteristics of wind

energy, some utilities and other owners are

choosing to have a reliable backup system.

Natural gas-fi red engines or combustion tur-

bines neatly meet this requirement, allowing

the assurance of energy when it is needed.

Biogas Potential for IndustryIndustry looks for other ways to effectively

use renewable fuels. One interesting

option is to supplement natural gas

usage with biogas products from on-site

or nearby digesters. Biogas is the general

term for methane-rich gas byproducts of

anaerobic digesters – the types used in

many municipal and private wastewater

treatment plants, and increasingly with

agricultural and some industrial wastes.

Biogas is also now widely being reclaimed

from municipal solid waste landfi ll sites.

Industries that produce potential

digester fuels – food processing wastes for

example – can install a digester on site to

process the wastes and to generate biogas.

Such a system is installed at Gills Onions in

ple0911Sup1_Renewables_ID.indd A6ple0911Sup1_Renewables_ID.indd A6 11/10/2009 11:36:17 AM11/10/2009 11:36:17 AM


M O R E

i n f oDOE BACKGROUND INFORMATION ON BIOGASwww.afdc.energy.gov/afdc/fuels/emerging_biogas.html

DOE INFORMATION ON RETROFIT RAMP-UPapps1.eere.energy.gov/news/daily.cfm/hp_ news_id=202

INFORMATION ON CHP FROM WASTEWATER TREATMENT PLANTSwww.chpcentermw.org/06-04_wwtf.html

LINK TO NATURAL RESOURCES CANADA FOR INFORMATION ON ALTERNATIVE FUELSwww.nrcan-rncan.gc.ca/com

ENERGY SOLUTIONS CENTER CHP AND ENERGY EFFICIENCY RESOURCEwww.PowerOnsite.org and www.NaturalGasEffi ciency.org

A digester for food-processing waste at Gills Onions in California generates a biogas stream to supply fuel cells which generate electricity for plant operations as well as a stream of hot water for food processing.

Oxnard, California. The company, a major

producer of peeled, sliced and chopped

onions, is a major user of electricity and

natural gas for processing and refrigeration.

They enlisted the help of their natural

gas supplier, SoCalGas, along with other

partners, in developing a sophisticated

digester and gas collection system to convert

what previously was a waste product – onion

peels and juice – to generate gas to supply

a fuel cell to meet a signifi cant proportion

of plant electric needs. Byproduct heat from

the fuel cell helps provide hot water for the

onion prep operation.

If your facility does not have potential to

supply a digester, it is sometimes practical to

import biogas from other nearby producers

via short, dedicated pipelines. This raw

digester or landfi ll biogas is not a direct

substitute for natural gas. Biogas streams

include water vapor, carbon dioxide,

hydrogen sulfi de and other components

that require removal before injection into

natural gas distribution systems.

However. if properly handled, biogas can

be directly used as a burner fuel for boilers

or other applications. Some reciprocating

engine designs allow it to be used with

minimal treatment as a fuel for electric

generation or mechanical shaft power. In

all cases it is necessary to verify the charac-

teristics of the fuel and, where needed, to

provide appropriate pre-treatment.

Dharan Punwani of Avalon Consult-

ing was a presenter at the Technology &

Market Assessment Forum sponsored by

the Energy Solutions Center in Salt Lake

City in June 2009. His fi rm specializes in

renewable fuels applications. He indicates

that biogas fuels now are produced by a

wide range of digester types, ranging from

covered lagoons to highly mechanized

multistage drum units.

Gas Treatment Often DesirablePunwani points out that the unwanted

components of raw biogas

can removed by chemical

and thermal treatments,

potentially producing a fuel

that is interchangeable with

conventional natural gas.

He notes that a particularly

unwelcome contaminant

of landfi ll gas and some

wastewater treatment sludges are siloxanes

– manmade chemicals that are widely used

in household and commercial products.

These can form crusty silicon oxide scale

in combustion equipment. Siloxanes

should be removed if these gases are used

in engine or turbine generation because

the siloxane components can damage this

equipment.

Another large volume source of potential

biogas is livestock waste. Feedlots and

large dairy, swine and poultry operations

dispose of millions of tons of animal waste

annually. Increasingly these operations

are using anaerobic digestion processes to

reduce soil and water contamination and

meet community odor control standards.

In many cases, these operations cannot

themselves use the large volumes of biogas

produced. Industrial energy users can look

for potential partnerships with such nearby

biogas producers. Such a partnerships

can be done by purchasing either the raw

biogas, a treated and upgraded gas product,

or electricity generated at the digester site.

Look for Nearby Landfi ll Gas Sources Alternatively, industrial energy users can

look for nearby landfi ll gas producers to

supplement their fuel sources. Again,

it is important to carefully evaluate the

range of characteristics of the biogas and

its suitability for the proposed industrial

application. As noted above, landfi ll gas

often requires special treatment before it

can be used as an engine fuel.

Conserved Energy Also a Green ChoiceUnquestionably, the greenest energy source

of all is energy that is never consumed.

Plenty of opportunities remain for improving

process effi ciency, reclaiming waste heat,

and taking advantage of combined heat and

power (CHP) systems to use every energy

unit more effi ciently. We will need many

of these strategies to achieve the levels of

energy independence and effi ciency we all

want. Now is a good time to begin assessing

what is available to you. GT

ple0911Sup1_Renewables_ID A7ple0911Sup1_Renewables_ID A7 11/10/2009 10:23:59 AM11/10/2009 10:23:59 AM


NATURAL GASHEAT TREATING ADVANCEMENTS

New Burners, Controls Make For Big Savings

The indication is that the new burners produced a 25% improvement in thermal effi ciency.

“”

NATURAL GAS HAS LONG been

the fuel of choice for most heat treating

applications, and that’s not about to

change. But the technology for gas-fi red

heat treating is evolving rapidly, with

major changes coming in heightened

burner effi ciency, reduced emissions,

closer fl ame and temperature control, and

extended service intervals. We’ll explore

some of these key changes.

Heat Treating Widely UsedHeat treating is a tool commonly used

in metal fi nishing and fabrication. The

actual objective may be hardening, tem-

pering, annealing, stress relief, or other

modifi cations of the metal. Heat treat-

ment, followed by an appropriate cool-

ing procedure, changes the characteris-

tics of the metal, making it harder, softer,

tougher, more malleable or more ductile.

The prevalent heat source for such treat-

ments is natural gas. The actual treatment

is done in a furnace, cabinet or oven. Both

ferrous and non-ferrous metals commonly

receive heat treatment.

John Dormire is Vice President Sales

and Marketing at Bloom Engineering Co.,

a long-standing supplier of heat treating

equipment for steel. He notes, “In past years

the heat treat industry usually relied on in-

expensive, ineffi cient small cold air burners

for their heat treat processes. Now, nearly all

producers are looking at improving energy

effi ciency, reducing greenhouse gases and

reducing NOx emissions as well.” Dormire

indicates that suppliers like his fi rm have

improved their product line to maximize

effi ciency while reducing emissions. He ex-

plains, “Bloom has traditionally excelled in

very high temperature processes, such as

steel reheating, and has successfully taken

this technology to lower temperature heat

treating applications.”

Because large amounts of heat energy

are often needed, industrial operators today

look for systems with maximum effi ciency.

It is practical to improve the effi ciency of

an existing system by re-evaluating process

schedule and operating temperature. In

some cases, energy can be saved by staged

heating to eliminate excessive energy use.

In some cases the heating enclosure can be

modifi ed to reduce heat losses. For many

operators, entirely new processes for heat

treating have high promise for improving

treatment and reducing energy use.

Vacuum Furnace TechnologyAn example of such an emerging

technology is a new design for a natural

gas-fi red vacuum furnace. This technology

was described by Benjamin Bernard,

Director of Business Development for

Surface Combustion Inc., at a Technology

& Market Assessment Forum (TMAF)

sponsored by the Energy Solutions Center

in Salt Lake City in June, 2009. Surface

Combustion is a supplier of a broad range

of equipment types for heat treating.

The new technology is a high temperature

vacuum carburizing furnace that uses

advanced burner, control and carbon

source technology for superior results

and high effi ciency. Carburizing is a heat

treatment process in which iron or steel is

heated in the presence of another material

which liberates carbon as it decomposes.

Using carburization, the outer surface of

the steel will have higher carbon content

than the original material. When the iron

or steel is cooled rapidly by quenching, the

higher carbon content on the outer surface

becomes hard, while the core remains soft

and tough.

The new process uses a vacuum chamber

to prevent other atmospheric gases from

interfering with the process, and uses a

technology called VringCARB® to release

the carbon at a temperature of 1900° F.

The heat is provided by high-effi ciency

gas-fi red silicon carbide radiant tubes.

The system uses a very stable, high purity,

saturated hydrocarbon, cyclohexane, as

the carburizing medium.

Better Treatment with Less EnergyThis new process was installed in 2006 at

MMS Thermal Processing in Davenport,

Iowa, and has proven to be very success-

ful, resulting in increased production and

reduced energy use. For this application,

Surface packaged its new VringCARB®

capability in a circular machine confi gu-

ration.This technology not only provides

a more effective carburizing treatment,

but reduces the energy requirement for

the process.

In many cases the best step to improve

heat treating operations is to use existing

furnaces but improve the burner and

control technology and adjust or replace

ple0911Sup1_HeatTr_ID A8ple0911Sup1_HeatTr_ID A8 11/10/2009 10:27:39 AM11/10/2009 10:27:39 AM


BLOOM ENGINEERINGhttp://www.bloomeng.com

ECLIPSEhttp://www.eclipsenet.com

FIVES NORTH AMERICANhttp://www.namfg.com

GAS TECHNOLOGY INSTITUTEhttp://www.gastechnology.org

PYRONICShttp://www.pyronics.com

SURFACE COMBUSTION INC.http://www.surfacecombustion.com

A regeneratively-fi red heat treat furnace for a forging application. Photo courtesy Bloom Engineering.

M O R E

i n f o

Single-Ended Radiant Tube burners installed in pipe heat treating application.

burners and controls to increase effi ciency.

Commonly this has the added benefi t

of reducing burner emissions, making it

easier to meet mandatory or voluntary

emission targets.

The RASERT BurnerAnother interesting development in

burner technology is the the Reverse

Annulus Single Ended Radiant Tube

(RASERT) burner, a new low-emissions

energy effi cient burner technology. This

improvement offers up to a 69% net NOx

emissions reduction over conventional

burner technologies. The reduction is

achieved from both a lower average

internal fl ame temperature and a 17%-

27% increase in fuel effi ciency. The

RASERT burner was developed by Fives

North American Manufacturing and the

Gas Technology Institute (GTI).

Field Demonstration at Steel MillSoCal Gas is co-sponsoring an ongoing fi eld

demonstration of this burner technology

on an annealing furnace at a steel mill in

southern California. According to Steve

Simons from SoCal Gas, the deployment

of the ten RASERT tubes was at a furnace

at California Steel Industries. Following

modifi cation of the initial design, an

additional retrofi t was made on another

furnace section, and has been in operation

for over a year.

Simons says, “The indication is that the

new burners produced a 25% improvement

in thermal effi ciency. The owner is now

studying possible further use of this

technology.” The RASERT technology is

also being demonstrated in a batch heat

treating operation at Akron Steel Treating.

Both of these demonstration installations

were achieved through collaboration of

private companies, natural gas industry

research and demonstration groups, and

state government agencies.

Recuperative Design Conserves EnergyOne of the keys to improved burner

effi ciency is the use of recuperative designs.

The recuperative principle is to reuse the

heat from each burner exhaust to preheat

combustion air or the fuel-air mixture.

An example of a current recuperative

design is the SER AutoRecupe indirect-

fi red burner by Eclipse, which came out in

2007. This unit has the burner and integral

recuperator coaxially mounted inside a

radiant tube.

This design allows the effi cient

transfer of heat from the exhaust to the

combustion air supply, which provides

high preheat temperatures. Eclipse offers

metal or silicon carbine tubes for furnace

temperatures from 1830° to 2400° F.

These tubes can be used wherever high

effi ciency, low emissions, and superior

temperature uniformity are necessary.

An example of the energy savings and

improved production achievable with a

burner retrofi t is at Rock River Heat Treat

in Rockford, Illinois. In a furnace rebuild,

the company replaced previous tubes with

six AutoRecupe burners with ceramic

inner and metallic outer tubes. With the

new arrangement, the same size load can

now be processed in a shorter time. This

has meant two to three extra loads per

day using the same amount of fuel.

Manufacturer Working with CustomersThis kind of savings in energy and increases

in production are now widely available.

John Dormire from Bloom indicates that his

fi rm’s practice is to work with its customers

to identify specifi c process requirements,

then work to design a custom system to

meet these needs. He stresses the impor-

tance of understanding each customer’s

needs. “Our customers get better value for

their equipment, and solutions are specifi -

cally designed for their products.”

For their part, he urges customers,

“Make sure your suppliers understand

your goals, and assure that the equipment

supplier meets that goal.” Dormire believes

that the industry will continue to improve

heat treating equipment. “In the future, we

are likely to see lower fuel use, very low

NOx emissions, and improved temperature

uniformity, all in one package.” GT

ple0911Sup1_HeatTr_ID.indd A9ple0911Sup1_HeatTr_ID.indd A9 11/10/2009 10:37:53 AM11/10/2009 10:37:53 AM

The modular characteristic of many modern condensing hot water boilers allows them to be operated in the condensing range for maximum effi ciency. Photo courtesy Cleaver-Brooks.

A Better Solution for Hot Water Systems

NEW DESIGNS FOR INDUSTRIAL AND COMMERCIAL

hot water boilers feature advanced heat exchanger designs and

materials that extract more heat from the fl ue gases. With today’s

emphasis on minimizing fuel use and reducing emissions, these

developments get to the heart of boiler effi ciency and are im-

portant enhancements. A major step has been improvements in

condensing boilers. In these, the temperature of the fl ue gases is

reduced to the point where some of the water vapor in the fl ue

gas produced during combustion condenses back into liquid form,

releasing its latent heat.

Growing Interest in Condensing UnitsAccording to Alan Wedal of Cleaver-Brooks, a manufacturer of

this type product, energy users are increasingly selecting condens-

ing hot water boilers, especially in process hot water and build-

ing heating applications. He indicates, “Owners are having great

success with the use of condensing boilers, provided the system

design allows them to get cold enough water for the condensing

mode.” Wedal adds that using a condensing boiler can lead to ef-

fi ciencies as high as 99%. “This will vary depending on the return

water temperature. It will also vary by manufacturer.”

Because they can offer such dramatic improvements in boiler

effi ciency, these boilers offer signifi cant energy-savings poten-

tial. However, Wedal notes, condensing boilers are too often sold

for applications where they are not suitable. An example of this

might be where the boiler is sold to provide circulating hot water

for building heat, but the design return water is above the con-

densing point.

Wedal explains, “Many building owners have been sold on the

concept of condensing boilers and install them, but later fi nd that

the savings they expected were not there because building com-

fort levels cannot be supported at the temperatures necessary for

condensing operation. In these cases they have paid a premium

for little or no effi ciency gain.”

Hybrid May Be a Better SolutionWedal points out that a better solution for these facilities might be

to use a hybrid system, allowing a less expensive non-condensing

boiler to operate in the winter heating season to supply 180° F wa-

ter, and then using a smaller condensing boiler to handle shoulder

seasons where lower supply temperatures may be acceptable. He

adds, “We have seen cases where this type system can be installed

for 1/3 less than the cost of a completely condensing boiler system,

without any effect on the operation of the building heat.”

As Wedal mentions, modern natural gas-fi red condensing

boilers can have energy effi ciencies in the high 90s, whereas

conventional non-condensing models have energy effi ciencies

of only 70 to 85%, and many boilers over 20 years old may

operate at only 55 to 70%. If these older boilers can be replaced

by condensing units, the payback will be short and the energy

savings dramatic.

Problems with Oil-fi red CondensingGenerally, natural gas burning boilers are better suited to

condensing operation than those with oil combustion. The typical

dew point for oil combustion fl ue gas is lower — 116°F compared

to about 140°F for natural gas — making water vapor in the fl ue

gas more diffi cult to condense and the energy savings smaller. Oil-

fi red condensing boilers are more expensive than equivalent gas-

fi red systems.

Getting Below the Dew PointFor water vapor in the fl ue gases to condense, the temperature

of the fl ue gas must be brought below the water dew point of the

A 1 0 g a s t e c h n o l o g y / W I N T E R 0 9 W W W. E N E R G Y S O L U T I O N S C E N T E R . O R G

ple0911Sup1_Boilers_ID A10ple0911Sup1_Boilers_ID A10 11/10/2009 10:43:20 AM11/10/2009 10:43:20 AM

This installation of a condensing boiler illustrates an acid-resistant stainless stack and PVC condensate drain lines. Photo courtesy the Veissmann Group.

Cutaway view of a Cleaver-Brooks ClearFire condensing hot water boiler. Illustration courtesy Cleaver-Brooks.

fl ue gas. For this to occur, the return water

temperature to the boiler proper must be

below approximately 140°F, or another

cooling liquid must be introduced.

In some industrial operations, this is

easily achieved. For example industries

such as commercial laundries and food

processing plants may consume a large

proportion of the heat in the circulating

water so feedwater temperatures are low.

Return feeds from heat exchangers that

supply potable water heaters are another

source of cool water.

Newer Technology Makes Condensing PracticalNew commercial and industrial condens-

ing boilers feature designs to help the

boiler stay in the condensing mode as

long as possible. Digital burner controls

now allow burners to modulate to keep

fi ring rates within the condensing range.

An example is the ClearFire Condensing

(CFC) boiler manufactured by Cleaver-

Brooks, in sizes from 750 to 2,500 MBtuh.

This fi retube design has a fully modulat-

ing burner and also a variable speed fan to

keep fl ue exhausts in the range to support

condensing.

According to Wedal from Cleaver-

Brooks, another advantage of the CFC unit

is in the heat transfer design. It utilizes a

stainless fi retube with an Alufer® insert.

This aluminum insert helps “suck” the heat

out to the tube wall more effectively. This

increases the heat transfer rate compared

to a bare tube.

Changes have been made to condensing

boilers to enhance their capabilities, allowing

mechanical designers the ability to drive a

boiler into condensing mode even when the

heating loop has an outlet temperature of

180° F and a 20° temperature differential.

This is done with a second return water port,

so a second source of colder water can be

brought in to lower the water temperature

to the condensing point.

Multiple Boilers Widely UseA strategy now being widely used in

commercial and industrial settings is to

install multiple hot water boilers. Groups

of six or more units are not unusual.

This allows a supervisory fi ring system to

fi re only the necessary number of boilers

for daily or seasonal needs, at rates that

optimize condensing and therefore the

overall effi ciency of the system.

Another supplier of condensing water

heating boilers is Gasmaster Industries,

offering units ranging in size from 200 to

12,000 MBtu per hour. Hussain Mantri

from Gasmaster spoke at a Technology

Marketing & Assessment Forum sponsored

by the Energy Solutions Center in October,

2008. Mantri stressed the exceptionally

high operating effi ciencies available with

this equipment – as high as 97% when

the inlet water temperature ranges from

60° to 70° F, as would be common with

many applications.

Mantri gave as an example of potential

energy savings an installation at a con-

dominium community, Minto Gardens,

in Toronto. He noted that installing two

condensing boilers for heating rather than

conventional boilers had a payback of less

than three years, with an annual savings

of $65,000. The Minto Gardens project

received a LEED Silver rating, in part

because of the energy effi ciency of the

heating and cooling plant.

Building codes forbid discharge of these

boiler fl ues into a masonry stack because

the wet, acidic character of the exhaust has

the potential to damage masonry joints.

Condensate must be similarly handled

in acid-resistant pathways. In some cases

the condensate may be drained through a

drum or tank fi lled with limestone gravel

or a similar material to help neutralize

its acidity before going to wastewater

treatment.

Condensing hot water boilers offer

important improvements in effi ciency,

however are practical only where the

return water can be held below the water

dew point. A careful system evaluation is

needed to determine if this condition exists,

or can be created. In the right applications,

a condensing hot water boiler is a great

money-saving solution. GT

M O R E

i n f oBURNHAM BOILERShttp://www.burnham.com

CLEAVER-BROOKShttp://www.cleaver-brooks.com

GASMASTER INDUSTRIEShttp://www.gasmaster-ind.com

ENERGY SOLUTIONS CENTERwww.CleanBoiler.org

NATURAL RESOURCES CANADA INFORMATION ON BOILERShttp://oee.nrcan.gc.ca/industrial/equipment/boilers

VEISSMANN GROUPhttp://www.viessmann.com

W W W. E N E R G Y S O L U T I O N S C E N T E R . O R G g a s t e c h n o l o g y / W I N T E R 0 9 A 1 1

ple0911Sup1_Boilers_ID.indd A11ple0911Sup1_Boilers_ID.indd A11 11/10/2009 11:02:30 AM11/10/2009 11:02:30 AM

A 1 2 g a s t e c h n o l o g y / W I N T E R 0 9 W W W. E N E R G Y S O L U T I O N S C E N T E R . O R G

MOST OF US HAVE HEARD OF

LEED certifi cation for building design.

LEED stands for Leadership in Energy

and Environmental Design. LEED was

developed by the U.S. Green Building

Council in 1998, and now these design

criteria are used widely for certifying

building designs in the U.S., Canada,

México, and many other countries. These

criteria have evolved over the years as

green building knowledge has increased

and new tools become available.

Measuring Up to LEEDThe purpose of LEED is to promote “green

buildings” by establishing recognized design

measures, with a goal of improving whole-

site designs, recognizing environmental

design leadership, stimulating competition,

and raising public awareness of green build-

ing benefi ts. Tthe goal is to transform the

entire building process and market.

LEED specifi cations score “green building”

designs in the following six areas:

Sustainable sites

Water effi ciency

Energy and atmosphere

Materials and resources

Indoor environmental quality

Innovation in the design process

Points are granted for specifi c achieve-

ments in each of these areas. Points are

totaled for the complete building and if

the building receives a minimum required

number of points, it is classifi ed as “LEED

Certifi ed” with additional higher grades

of LEED Silver, LEED Gold, or the high-

est, LEED Platinum. Until the last few

years, most of the LEED attention went to

commercial and institutional facilities,

whose architects and owners saw them as

showcases of their green commitment. As

LEED has evolved, these specifi cations are

now appropriate for a much wider range

of building types, including industrial

buildings.

Natural Gas a Natural PartnerEffi cient use of energy, minimizing

emissions and the use of recycled materials

are prominent in LEED industrial building

designs. Natural gas is a good energy

source because of its low emissions,

high effi ciency, and fl exibility for use in

equipment that also uses renewable fuels.

Many natural gas utilities have experience

working with owners who are looking for

LEED certifi cation.

LEED building designers have learned

that signifi cant points can also be obtained

by minimizing construction debris, plan-

ning site drainage to reduce discharges to

wastewater treat-

ment systems, and

intelligent design

to reduce the im-

pact of employee,

customer and de-

livery traffi c. In

some cases, entire

industrial parks

are being built to

LEED specifi ca-

tions.

The $25 mil-

lion Perry Avenue

Building at Brooklyn Navy Yard is the

nation’s fi rst multi-level green industrial

facility. According to Steve Closson

from National Grid, the facility, which

is on track to receive LEED certifi cation,

incorporates many green features including

high-effi ciency natural gas boilers and a

demonstration photovoltaic powered 10

kW generation system, which was designed,

fi nanced, developed and constructed by

National Grid. The building also features

refl ective roofi ng, use of rain water in toilets,

recycled building materials, high-effi ciency

lighting fi xtures and natural ventilation

systems. The three-story building is leased

to SurroundArt, which operates a Museum

Resource Campus to serve the art industry

and institutions in the City of New York and

beyond.

Getting StartedWhile attaining the highest LEED rating

– Platinum – may be diffi cult for many

industrial sites, it is increasingly common

to hear about LEED-certifi ed industrial

buildings that make positive contributions to

the corporate image, and more importantly,

cast a lighter footprint on the planet.

It is essential to select architects and en-

gineers that understand and are committed

to the LEED process, and to perform site

and facility development from the begin-

ning with the LEED goal in mind. For a

successful LEED process, start with an

architect and engineer with experience in

the specifi cation process who also under-

stands your business and its needs. GT

LEED Certifi cationFOR INDUSTRIAL BUILDINGSStriving For the Best

M O R E

i n f oCANADA GREEN BUILDING COUNCILhttp://www.cagbc.org

U.S. GREEN BUILDING COUNCILhttp://www.usgbc.org

The Perry Avenue building at the Brooklyn Navy Yard incorporates a wide range of green design elements, including high effi ciency natural gas-fi red boilers, and a photovoltaic electric generation system.

ple0911Sup1_Leed_ID A12ple0911Sup1_Leed_ID A12 11/10/2009 10:46:04 AM11/10/2009 10:46:04 AM

Documents

ADDING AN ECONOMIZER MMakes a Good akes a Good … · A3 Update on Economizers Your boiler may be sending large amounts of heat energy up the stack. Learn about modern economizer