steam engg and energy conservation

7/31/2019 Steam Engg and Energy Conservation

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Copyright Forbes Marshall, 2006-07

STEAM ENGINEERINGAND ENERGY CONSERVATION


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Standard Steam Circuit - Energy Balance

Boiler ProcessPlant Plant

Power PRDS

Plant Unit

Fluegases

Blow

down

HP steam PRS unit

Condensate

losse

s

losses

Fuel

100%

15%

5%

80%

3%

55% to process

20%

2%


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Energy Conservation in Steam Systems

52 years of Steam Engineering experience in SteamGeneration, Distribution and Utilisation

Steam as the best source of process heat

The Cost of steam- Rs.400 to 1600 per tonne

- Anything from 5% to 50% of total

discretionary production cost


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Why Steam remainsthe best source of Process Heat

A plentiful raw material

Non-toxic, requiring no special handling

Requires no pumping - flows over long distances

naturally Simple temperature control, by simple pressure

control

Considerably cheaper than electricity or thermic

fluid


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Good Steam Engineering means

Proper sizing, insulation, routing and trapping

High pressure distribution and reduction at the pointof use

Separating condensate and venting air Proper process trapping

Condensate return

Temperature control

Efficient boiler operation


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Boiler Efficiency is the beginning

Excess air control

Proper capacity-utilisation and boiler balancing

Automatic blowdown control

Close performance monitoring for tube cleaning and

other maintenance


7/23Copyright Forbes Marshall, 2006-07

Making Boiler Efficiency Automatic

A textile mill operates two 10 tph boilers

Automatic blowdown control will save Rs.6.5 Lakhsper year (payback < 3 months)

Flue-gas trim can increase efficiency by 2% easily(payback < 1 year)

Shutting a third boiler run just in case saves Rs.2.5

lakhs per year

A Boiler Efficiency package pays for itself in sixmonths



Steam Trap Selection ...

A continuous discharge Float Trap in place of anintermittent discharge TD - upto 4 x processefficiency - payback in days

A thermostatic trap in place of a TD or FT on tracing

lines - payback in six months

A TD in place of an IB on a main-line - payback fromsaving radiation losses alone in 12 months



... and Steam Trap Monitoring

What is the cost of a leaking Steam Trap ?

An automatic on-line trap monitoring system for 50

critical traps will cost say 6 Lakhs One 1 trap failed open will waste that much in nine

months (8 Lakhs per year)



Metering for Energy-conservation

How much steam is worth metering ?

- 1 tph of steam @ 7000 hrs per year will cost

Rs.35 Lakhs (For SF boilers) and Rs 100 L (ForOF boilers)

Does usage demand high turndown ?

Density compensation is critical

- An uncompensated meter sized for 10.5 bar,operating at 7 bar will have an error > 15%



How Much Condensate is Worth Returning ?

1 tph of condensate at 3 bar will save Rs.6 Lakhs inthe fuel bill each year

And reduce the dearating of a 2 tph boiler from 15%to 5% (so you get a 200 kg boiler for free)

And Rs.30,000 in ones water-treatment cost for DMwater

And reduce heat-pollution And save water (about 600 tankers each year !)



Compressed Air - the ignored utility

Compressed Air is free, right ...

- A 1 mm hole @ 6 bar leaks Rs.80 per day or

Rs.2800 per year- A 10 mm hole @ 6 bar leaks Rs.8,000 per day !

1 mm = Corrosion leak

2 mm = Gasket leak

10 mm = Broken or cracked pipe/hose



Compressed Air in a Spinning Mill

5 leaks cost Rs.1 Lakh per year

Installing Reducing valves and nozzles on cleaninghoses pays for itself in days

Air separators and drain traps drastically improve

Air quality



Energy Conservation in a Paper Mill

The mill makes a loss of Rs.4 Crores each year

Operates at 55% of rated capacity

The problem is scaling and poor condensateremoval from the drying cylinders

An automatic dryer package (and other smallerimprovements) could save 30% of steam consumed

and almost double output A thermo-compressor can pay its way in days



Thermocompressors pay back quick

A 50 tpd paper machine

- A 12 Lakhs investment with documented

savings of 25 Lakhs per year

- A saving of 0.4 kg (18% minimum) per kg ofpaper

Turbine exhaust from a sugar mill to a distillery

- A 20 Lakhs investment with savings of 64

Lakhs

- Takes care of the total steam need of the

distillery


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The Big Things Matter

A good boiler will

- raise dry steam

- have an efficiency > 82% in normal operation

- be easy to maintain - just brushing soot out

of tubes can increase boiler output by 10%for the same fuel-input

- operate efficiently without manual

supervision

- be correctly sized for capacity (a new 2 tphboiler will pay for itself in a year if one is

using a 4 tph for future expansion) and

operated at rated pressure


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The Big Things Matter - 2

Thermocompressors give you steamfor free

Boiler Efficiency Analysers automates

high efficiency


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The Big Things Matter - 3

Metering where every last 250 kg of steam goes

Condensate return and flash steam recovery havetypical paybacks under 3 months

Trap selection, sizing and performance monitoringdirectly boosts machinery output, reduces

maintenance and downtime, and even pays for itselfin six months

Generating and distributing steam at max pressureand reducing it at the point of use


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The Little things mean big savings

A few Air Vents dramatically reduces cycle time byshortening start-up time in batch processes

A Separator directly increases machine output byremoving condensate and so boosting heat transfer

A Balanced-pressure trap on tracing lines harvestsome sensible heat too

A Sight glass helps one set the SLR on a trap - anddirectly increases drying machine speed


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The Little things mean big savings - 2

A weekly brushing of boiler tubes can save 2% ofones fuel bill

Daily monitoring of boiler efficiency and waterquality helps diagnose problems

A Deaerator Head reduces dissolved oxygen and so

reduces corrosion (=leaks!) of pipes and fittings

Automatic Blowdown Control costs < Rs 1 Lakhpays for itself in months, and improves steam quality

Fix leaks and insulation before you give us any

business !


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So Where Does One Start ?

Priority 1 is Housekeeping

- Leaks

- Insulation

- Air Vents- Main-line traps

- Separators to improve steam quality

Priority 2 is Trap Selection

- FTs as Process Traps - the payback is days


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Priorities in Energy Conservation

Third is Diagnosis

- Metering where every 1 tph and 250 kg of

steam goes

Fourth is Condensate Return and Condensate andFlash Steam Recovery

Fifth is Pressure and Temperature Control

- Are these opportunities ?


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Copyright Forbes Marshall 2006 07

Priorities in Energy Conservation

And last is Capital Investment

- New Boilers and Burners- The Cogen option

- Automated plant control systems

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