steam saving

7/30/2019 STEAM Saving

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Energy Saving in Steam System


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IntroductionSTEAM

Most common medium for heat transfer and power generation wfollowing advantage

Easy to generate

Easy to use

Most economic method for heat transfer.

High heat content.

High specific heat

Highest heat transfer coefficient

Easy to control & distribute

Cheap & inertDue to this Steam is prevalent in many manufacturingfacilities


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According to the U.S. DOE Office of Industrial

Technologies Best Practices, Over 45% of all the

fuel burned by U.S. manufacturers is consumed toraise steam.Unlike traditional utilities, the cost of

steam is not typically measured or tracked. A

typical industrial facility can realize steam savings

of 20% by improving its steam system.


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The total steam system must be considered for energysaving.Upstream inefficiencies will affect processheating and cost of producing steam, whiledownstream inefficiencies (leaks, bad traps, poor load

control) can also affect process heating and havesevere effects on the boiler and cost of producingsteam. In general savings are found in:

Steam Generation through cogeneration applications, boiler

controls, and water treatment.

Steam Distribution through checking steam leaks, installing

insulation and proper steam trap maintenance.

Steam End Use through heat exchanger maintenance.

Steam Recovery through condensate return.


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Energy Loses in an Inefficient Steam System


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.

Energy Loses in an efficient Steam System


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Energy saving opportunities in steam

1.Monitoring of Steam traps :

Steam traps proper function is required as

If condensate, air & non condensable gases accumulates in pipe

line it reduces the capacity of lines ,equipment and heat transfe

area.

Excess condensate also causes "water hammer," and candamage pipes.

Non-condensable gases, such as oxygen and carbon dioxide,cause corrosion.

Steam that passes through the trap provides no heating service


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Thermodynamic Steam Traps

Inverted Bucket Steam Traps Ball Float Steam Traps

Types of Traps

Thermostatic Steam Trap
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Trap monitoring can be done by

Trap man.

Watching steam outlet.

Hearing sound.

Observing trap temperature.

Observations for condensate discharge:

Thermodynamic traps : Intermittent condensate discharge

Float type traps : Continuous condensate discharge

Inverted bucket traps : Intermittent condensate discharge

Thermostatic traps : Continuous condensate discharge /

Intermittent discharge based on load

2 Ti l ti t l k


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2.Timely arresting steam leakages

3 mm hole leaking steam at 5 bar is having approx. 15

kg/hr of steam loss.( i.e 120 tones of steam or 0.6 laces

of rupees)

3 mm hole leaking steam at 20 bar is having 60 kg/hr

of steam loss.( i.e 480 tones of steam or 3.8 laces of

rupees)

3 mm hole leaking steam at 40 bar is having 100

kg/hr of steam loss. ( i.e 800 tones of steam or 8.0 laces

of rupees)


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3. Providing dry steam for process

For industrial process heating dry saturated

steam to be supplied as : Wet steam reduces total heat value of steam.

Condensate water forms a wet film on heattransfer surface.

Condensate overload the traps & condensatesystem.

Super heated steam gives up heat at a rate

slower than the condensation heat transfer ofsaturated steam


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4. Utilizing Steam at the lowest acceptablepressure for the Indirect heating process

Proper selection of steam pressure is important as

Latent heat reduces with increase in steam pressure

Only latent heat takes part in the heating process.

Lower the steam pressure , lower the temperature & lessheat transfer

Steam should be always generated &distributed at the highest possiblepressure & utilized at a lowest pressure as

possible.


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5. Correct Insulation of steam pipelines &Hot process equipment

Proper insulation is very much important to avoid losses.

Condensate inside the insulation is dangerous. Cladding sheets should be proper.

Cladding joints should be at the bottom of pipeline.

Condition of insulation may be monitored by measuringsurface temperature.(


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QUANTITY OF HEAT LOSS AT DIFFERENTTEMPERATURES

Deg C Kcal/m2/hr

50 500

100 1350

200 3790

400 13640

Difference in Surface

temperature with

ambient

Heat Loss


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6. Proper Utilization of directly injectedsteam for heating

Silent points

No condensate recovery system is necessary

Heating is quick & the sensible heat of the system isalso used along with latent heat.

Not useful where agitation is not acceptable.

Ideally injected steam should be condensed completely(steam pressure between 0.5 to 1.0 kgf/cm2) as thebubbles rise through the liquid. If pressure are high,the velocity of the steam bubbles will also be high andthey will not get sufficient time to condense beforethey reach the surface.

7 STEAM PIPE SIZING


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7. STEAM PIPE SIZING

Steam pipes should be laid by the shortest possibledistance.

Provision for proper draining of condensate. The pipes should run with a fall (slope)of not less than 12.5

mm in 3 meter in the direction of flow.

Large pockets in the pipes to enable water to collect

Drain pockets should be provided at every 30 to 50 metersand at any low point in the pipe network.

Expansion loops are required to take care of the expansionof pipes when they get heated up.

Automatic air vents should be fixed at the dead end of

steam mains, which will allow removal of air, which will tendto accumulate.

.


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Proper sizing of steam pipelines help inminimizing pressure drop.

A higher pipe size will reduce the pressure dropand thus the energy cost. However, higher pipesize will increase the initial installation cost.

By use of smaller pipe size, even though the

installation cost can be reduced, the energy

cost will increase due to higher-pressure drop.


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Pressure drop change is inversely proportional to

the 5th power of diameter change.

Hence, care should be taken in selecting the

optimum pipe size.


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8. Reduction of Scaling and Soot Losses Soot buildup on tubes side or Scale on water side

Acts as an insulator against heat transfer

Elevates stack temperature and heat loss

1% efficiency loss with 4.4oC increase in stacktemperature

Indicated by high exit gas temperatures at normal

excess air level Water side deposits require review of water treatment

procedures and tube cleaning

It is time to clean soot deposits when flue gas

temperature rise 20o

C above temperature for newlycleaned boiler

Check and record stack temperature regularly


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0.25 mm thick air film offers the same resistance toheat transfer as a 330mm thick copper wall

A 3mm thick soot deposition on the heat transfer

surface can cause in fuel consumption to the tune of2.5%

A 1mm thick scale (deposit) on the water side couldincrease fuel consumption by 5 to 8%

9. Reduction of Boiler Steam Pressure


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9. Reduction of Boiler Steam Pressure

Lower steam pressure gives a lower saturated steam temperature

and without stack heat recovery, a similar reduction in the

temperature of the flue gas temperature results. Potential 1 to2% improvement.

Steam is generated at pressures normally dictated by the highes

pressure / temperature requirements for a particular process. In

some cases, the process does not operate all the time, and there

are periods when the boiler pressure could be reduced.

Adverse effects, such as an increase in water carryover from the

boiler owing to pressure reduction, may nullify any potentiasaving. Pressure should be reduced in stages, and not more tha

a 20 percent reduction should be considered.

d


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10. Condensate Recovery

Ensure condensate is returned or re-used inthe process .

For every 60c rise in the feed watetemperature by condensate recovercorresponds to approximately 1 % saving ofuel consumption in the boiler .


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Thanks


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Thermodynamic traps

Unaffected by steam temperature and pressurefluctuations

No adjustment is needed, robust & simple

Only one moving part

Can withstand water hammer & vibration Compact & light weight

Do not work well with low inlet or high dischargepressure

Noisy operation


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Disc steam trap


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Float type traps

Continuous discharge of condensate atsteam temperature

Ideal for application with large condensateload

Can be worked as automatic air vent.

Susceptible to damage with water hammer

Not suitable with superheated steam.


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THERMOSTATIC TRAPS

Valve is fully open on start up allowing air tobe discharge freely & maximum condensateremoval. Suitable for tracing line application

due to large capacity. Element susceptible to damage by water

hammer.

Not suitable with superheated steam.


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Float and thermostatic steam trap


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Inverted bucket steam traps Can withstand high pressure.

High tolerance to water hammer.

Small discharge hole at top of bucket

means that air discharge is low. Water seal is necessary hence require

priming.


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steam saving

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