il iof steam presentation (1)

7/29/2019 IL IOF Steam Presentation (1)

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Steam Systems

Technology Concept


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US DOE Industries of the Future Workshop Series

Steam System Background

Primary industrial energy source process heating

pressure control

mechanical drive

space heating

Significant consumer of natural gasOver 45% of all fuel burned by U.S. manufacturers is

consumed to raise steam. DOE Best Practices

Great energy & cos t

savings potent ia l!$$$


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Why Use Steam?

Extremely Uniform HeatingAbsolute Temperature Limit on Heated Surfaces

High Heat Delivery

Fast Recovery from Cold SpotsHeats Unusually Shaped Heat Exchangers Uniformly


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Classes of Steam

Low Pressure Heating Steam 15 psig Used Mainly for Space Heating Systems and Single Effect

Absorption Chillers

Actual Code is More Restrictive

Medium Pressure Steam: 15-150 psig Used in Hospitals, District Steam Systems, Some Industrial

Heating

High Pressure: Above 150 psig Strictly Industrial and Power Generating Applications

Each Class has Piping and Valve Requirements Increase in Expense with Each Higher Class


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Steam System Operation

GenerationDistribution

End Use

Condensate Recovery & Feed WaterSystems


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Generation

Boilers Fire-tube or water-tube

Heat recoverygenerators Turbine exhaust

Furnace exhaust

Typical Boiler


7/55US DOE Industries of the Future Workshop Series

Generation

Water tube

fuel burned within combustionchamber

combustion gas surroundswater tubes within vessel

Fire tube

fuel burned in combustionchamber

combustion gases flowthrough tubes

water surrounds tubes



Generation

Fire tube Scotch Marine most

popular

Two, three, and four passdesigns

Constant pressure withwide load fluctuations

Steam pressure limited tounder 350 psig

Preferred between 3,500to 35,000 lbs/hr (120 Bhp

1,200 Bhp)



Generation

Water tube Fuel burned within combustion

chamber

Combustion gas surroundswater tubes within vessel

Low water content allows rapidsteam production

Capable of high pressure andsuperheated steam

Preferred ranges are below3,500 lbs/hr (120 Bhp) andabove 35,000 lbs/hr (1,200 Bhp)

Source: Cleaver Brooks



Generation

Modular Boilers Array of smaller boilers meet

load more effectively withoutcycling

Improved combustionefficiency

Reduced jacket losses

Fin tube design less durable

Piping and controls important

Mostly for commercialmarkets

Source: ES Magazine March, 2001



Generation

Heat recovery steamgenerators (HRSGs) Create steam using a heat

exchanger in a hot gas flow

Turbine exhaust

Furnace exhaust Can produce superheated

steam

Can produce high pressuresteam



Distribution & End Users

Distribution Systems Distribution lines Pressure reduction

Pressure reduction valve Backpressure turbine

End Use Components Heat exchangers

Mechanical drives

Steamsparging/injectionequipment



Recovery & Feed Water

Condensate Recovery System Steam traps Collection tanks

Flash steam recovery

Pumps

Feed Water System Deaerator

Economizer



Steam System Schematic



Typical Applications

Steam is not commonly used for spaceheating only

hot water systems are less maintenance intensive

Exceptions

Hospitals need steam for sterilizers

Older district heating systems

Industrial plants which require process steam



Efficient Steam Systems

Proper performance yields Low operating costs

Minimal downtime

Reduced emissions

Effective process control

Effective maintenance is the best strategy!!


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Why make a change?

Great energy & cos t savings po tent ia l!

$$$

Save energy (20% or more)

Reduce downtimeEliminate maintenance crises

Improve process control

Minimize safety hazards


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Why make a change?

INEFFICIENT STEAM SYSTEM


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Why make a change?

EFFICIENT STEAM SYSTEM


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Technology Common SystemImprovements


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Benchmarking

Profile your existing system

Separating process boiler load from seasonal heating Steam System Assessment Tool (US DOE)

Calculating the cost of steam ($/ thousand lbs) Fuel Water

Chemicals

DOE steam cost estimating resource:http://www.oit.doe.gov/bestpractices/steam/pdfs/tech_brief_true_cost.pdf

Rough est imate:

Total Steam Cos t ($/MMBtu ) = Fuel Cos t ($/MMBtu ) x 130%


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Common Problem Areas

Incorrect air/fuel ratio combustion inefficiency

Lack of insulation

Insufficient trap maintenance

Steam leaks

No heat recovery

Insufficient water treatment/blowdown issues

Frequent boiler cycling

Water hammer

Poor record keeping Gas usage

Steam production


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EXHAUST(CO2, H2O & N2)

PERFECTCOMBUSTION

Air/Fuel Ratio Combustion Efficiency

In theory . . .

AIR (O2 & N2)

FUEL (C2H)


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EXCESS O2

Left over oxy gen carr ies heat away from boi ler

EXHAUST(CO

2, H

2O & N

2)

Combustion

AIR (O2 & N2)

FUEL (C2H)

Air/Fuel Ratio Combustion Efficiency

In the real world . . .

AIR (O2 & N2)

Excess air introduced to prevent incomplete combustion


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Steam System Exercises Air/Fuel Ratio

Optimum combustion air = increased efficiency Too much air = excess heat loss in stack

Too little air = wasted fuel

Worksheet example (use boiler chart on next slide):


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Steam System Exercises Air/Fuel Ratio

Net Stack Temp = Stack temp reading ambient air temp


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Insulation

Lack of insulation

unnecessary heat loss

Wet insulation heat loss

Condensate return lines need insulation too.

3E Plus available at www.pipeinsulation.org

*Based on 8,000 hours of operation, 85% efficient boiler, mineral fiber insulation withall purpose jacket


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Insulation

What about insulating valves?

Removable insulation is available

costfuelhours(btu/hr)savingsenergySavings


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Steam traps

Expect 15% to 30% failure every 3 to 5 years

Easily tested using ultrasonic equipment

Steam trap example problem

GO

TOSupplementalSt

eamTrapInfo


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Steam Leaks

Easy to find

Hard to fix

2 5 10 15 25 50 75 100 125 150 200 250 300

1/32 0.31 0.49 0.7 0.85 1.14 1.86 2.58 3.3 4.02 4.74 6.17 7.61 4.05

1/16 1.25 1.97 2.8 3.4 4.6 7.4 10.3 13.2 16.1 18.9 24.7 30.4 36.2

3/32 2.81 4.44 6.3 7.7 10.3 16.7 15.4 29.7 36.2 42.6 55.6 68.5 81.5

1/8 4.5 7.9 11.2 13.7 18.3 29.8 41.3 52.8 64.3 75.8 99 122 145

5/32 7.8 12.3 17.4 21.3 28.5 46.5 64.5 82.5 100 118 154 190 226

3/16 11.2 17.7 25.1 30.7 41.1 67 93 119 145 170 222 274 326

7/32 15.3 24.2 34.2 41.9 55.9 91.2 126 162 197 232 303 373 443

1/4 20 31.6 44.6 54.7 73.1 119 165 211 257 303 395 487 579

9/32 25.2 39.9 56.5 69.2 92.5 151 209 267 325 384 500 617 733

5/16 31.2 49.3 69.7 85.4 114 186 258 330 402 474 617 761 905

11/32 37.7 59.6 84.4 103 138 225 312 399 486 573 747 921 1095

3/8 44.9 71 100 123 164 268 371 475 578 682 889 1096 1303

13/32 52.7 83.3 118 144 193 314 436 557 679 800 1043 1286 1529

7/16 61.1 96.6 137 167 224 365 506 647 787 928 1210 1492 1774

15/32 70.2 111 157 192 257 419 580 742 904 1065 1389 1713 2037

1/2 79.8 126 179 219 292 476 660 844 1028 1212 1580 1949 2317

Steam Leak Rates Through Holes (lbm/hr)

Steam Pressure (psig)Orifice

Diameter

(inches)

The table can also be used to determine steam losses through

steam traps that have failed open.


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Heat recovery options

Blowdown HeatRecovery

Vent Condensers

Economizer/Recuperator


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Economizers and Recuperators

Recuperators Recover heat to

combustion air

Require steadyboiler loading

Economizers Recover heat to

boiler feed water

Require continuousfeed water flow Boiler Recuperator


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Boiler Recuperator

Boiler efficiency indirectly proportional to stack tempCauses of excess stack temps:

Excess air

Fouled waterside surfaces

Fouled fireside surfaces

Overfiring Insufficient heat transfer surface

High steam pressure

Only insufficient heat transfer surface or high pressure justify arecuperator:

Excess air - adjust air/fuel ratio

Fouled surfaces - can be detected by visual inspection

Overfiring

Flue temp must be at least 50F over the minimum allowable


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Boiler Recuperator

Boiler conditions: 450F stack temperature

80 inlet air

4% O2 in stack

Current natural gas consumption: 67,286 MMBtu/year

Current natural gas cost: $5.90/MMBtuTo find the potential savings from a recuperator:

Net stack temp: 450 - 80 = 370

Net stack temp w/recuperator: 280F

New efficiency current efficiency = efficiency gain

83.0% - 80.7% = 2.3%

continued


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Boiler Recuperator

continuedEnergy Savings:

= current use x (1- (old efficiency/new efficiency))

= 67,286 MMBtu x (1 (0.807 / 0.830))

= 1,865 MMBtu/yr

Cost savings: = energy savings x energy cost

= 1,865 MMBtu/yr x $5.90/MMBtu

= $11,000/yr


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Vent Condensers

Recover flash steam or fugitive steam Condensate tanks

Deaerators


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Blowdown Heat Recovery

Requires continuous mid-drum blow down

Intermittent mud-drum blowdown can be accommodated

Approx imate Savings:

Boiler

Deaerator

FlashSeparator

Mud-drum

blowdown

Mid-drum

blowdown

FeedWater

FlashSteam

Vent

Heat

Exchanger

Blow

Down

Makeup

Water

Preheatedfeed water

CondensateReturn

4.0%blowdownsavingsenergy%


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Water treatment/blowdown issues

Typical steam system

Systems with high quality water treatment

Reducing blowdown saves

Energy Water costs

Chemical costs

Blowdown


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Boiler Short Cycling

Boiler cycle: Pre-purge fan removes combustible gases from boiler

Firing interval

Post-purge gases removed again

Idle period

Problem: heat is removed during purges


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Short cycling Occurs when an oversized boiler quickly satisfies heat

demands

Boiler shuts down until next demand

Causes:

Boiler oversized for expansions that never happened Energy conservation measures have reduced heat

demand

Space heating based on design-basis temperatureconditions

Space heating sized for quick recovery from nightsetbacks


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Illustration of a typical boiler short-cycling:

Green areas represent energy that will be wasted while the boiler is not firingbut the fan is in pre-purge or post-purge phase.


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Illustration of an improved boiler cycle:

Note the reduction in wasted energyfrom eliminating short-cycling.


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Replacement and alternative technologies

Backpressure Turbines Replace pressure reducing valves

Produce electrical power by reducing steampressure

Require >5,000 lbs/hr steam flow >100 psig pressure drop across turbine


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IAC implementation trends and analysis


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Application of New Technologies/Concepts

Combustion analysis testing equipment

Removable valve insulation

Trap analysis with ultrasonic equipment

Steam flow metering

Gas sub-meteringContinuous blow down and conductivity metering

Exhaust stack economizers

Modular boiler systems

Direct contact water heaters


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Technology - Next Steps


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How to start

Steps in evaluating your system

Best Practices

Monitoring needs

Implementation

TREAT STEAM LIKE A FOURTH UTILITY!


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Steps in evaluating your system

Utility bill analysis

Steam trap inventory

Combustion testing

Ensure all insulation is in good shape

Optimize boiler blowdownMonitor boiler cycling during periods of low demand

Check for applications for new technologies


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-

5,000

10,000

15,000

20,000

25,000

30,000

Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May

GasUse(MMBtu)

Natural Gas Utility Profile

Heating Load

Process

Load


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Best Practices

Combustion testing (quarterly)

Steam trap testing (annually) Inventory / maintenance history

Steam leak reporting mechanism for all staff

Insulation standards formalized

Benchmarking


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Monitoring needs

Monitor and track boiler system data Daily Natural Gas Usage (meter on each boiler)

Daily Steam Production (meter on boiler water feed)

Daily Water Usage (meter on make-up water feed)

Chemical Costs (compare to water usage)

Boiler cycles

Stack temperature


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Implementation of Improvements

Implementation requires participation

Production staff

Maintenance staff

Management staff

Improving system performance

Assessing the entire system (supply and demand)

Identifying opportunities

Quantifying benefits and costs

Implementing most feasible projects


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ISO 14000

Formalized method for identifying and documentingprocess improvements

Can be used for benchmarking

Proper use can lead to significantly reduced energycosts

All program goals are set by company


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Assessing your current system

In house assessment Tools available from US DOE Steam Challenge Program

Steam equipment manufacturers

Private energy service companies

Energy Resources Center @ UIC

US DOE Industrial Assessment Centers



GO

TOA

s

sessm

en

tResou

rcesLis

ting


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Assessment Resources

Energy Resources Center @ UIC www.erc.uic.edu - can provide

expertise in industrial steam systems, also will perform energyassessments for industrial clients.

Industrial Assessment Centers http://www.oit.doe.gov/iac/ - will provideenergy assessments (including steam systems) free of charge toqualified industrial clients.

US DOE Steam Challenge Program

http://www.oit.doe.gov/bestpractices/steam/ - provides a wide range oftechnical assistance materials, tools, and services to the industrialmarket.

National Association of Energy Service Companieshttp://www.naesco.org/ - trade organization of companies that willperform energy audits and finance improvements.

Steam System Survey Guidehttp://www.oit.doe.gov/bestpractices/steam/pdfs/steam_survey_guide.pdf- guide to assessing industrial steam systems.

Rutgers IAC Self Assessment Guidehttp://iac.rutgers.edu/manuals/selfassessment.pdf- guide to assessingindustrial plants for energy efficiency.BACK
http://www.erc.uic.edu/http://www.oit.doe.gov/iac/http://www.oit.doe.gov/bestpractices/steam/http://www.naesco.org/http://www.oit.doe.gov/bestpractices/steam/pdfs/steam_survey_guide.pdfhttp://www.oit.doe.gov/bestpractices/steam/pdfs/steam_survey_guide.pdfhttp://iac.rutgers.edu/manuals/selfassessment.pdfhttp://iac.rutgers.edu/manuals/selfassessment.pdfhttp://www.oit.doe.gov/bestpractices/steam/pdfs/steam_survey_guide.pdfhttp://www.oit.doe.gov/bestpractices/steam/pdfs/steam_survey_guide.pdfhttp://www.naesco.org/http://www.oit.doe.gov/bestpractices/steam/http://www.oit.doe.gov/iac/http://www.erc.uic.edu/

il iof steam presentation (1)

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