Efficient steam systems - Generation to WHR

Efficient Steam Systems – Generation to Waste Heat

Recovery

Vizag – 8th December, 15

2

Fuel Prices and Calorific Value

Fuel Price (Rs./Kg) Calorific Value (Kcal/Kg)

Furnace Oil 30 10200

HSD 52 10800

Natural Gas 40 8500

Coal 7 5500

Petcoke 9 8000

Rice Husk 3.5 3200

Briquette 5.5 4000

Boiler Efficiency & Cost of Steam

Fuel Avg S:F Avg Cost of Steam (Rs./Kg)

Furnace Oil 12 2.25

HSD 13 4

Natural Gas 12 3.5

Coal 4.5 1.5

Petcoke 7 1.2

Rice Husk 3.2 1.2

Briquette 3 1.8

Optimal Steam Generation System

Meeting the process demands in a manner which is:

Copyright Forbes Marshall, 2009-

10

Steam & Condensate Loop

100% fuel

energy

80%

ste

am

3% distribution losses

77%

Process

consumption 57%

20%

Unburnt

Stack

Blowdown

Steam Generation-Boiler

House

• Criteria for Selection of Boiler

- Steam Demand : Peak /Average

load

- Steam Consumption pattern

- Fuel selection w. r. t. availability,

cost

- Feasibility of COGEN


10


10

Cost of operation-Solid fuel


10

Cost of operation–Oil\Gas

fuels


10

Measured Losses

Boiler Efficiency – Perception & Reality

86%

78%

74%

78%

70%

65%

60%

65%

70%

75%

80%

85%

90%

Oil Solid

Ideal

Indirect

Direct

8%

4% 8%

5%


10

An increase of 2% efficiency in a 5 TPH boiler results in a saving of 53,200 liters of

oil per year !

Factors affecting boiler

efficiency


10

Comparison of Efficiency Methods

• Direct Efficiency

• Useful Heat output / total heat input

• Covers all losses

• Simple to implement

• Instrument accuracy has a significant affect on final efficiency

• In Direct Efficiency

• Efficiency = 100 – Losses

• Considers Stack, Enthalpy, Radiation, Blowdown and unburnt losses

• Gives detailed break up of losses

• Not affected too much by instrument accuracy

Copyright Forbes Marshall, 2009-10

Real life scenario

• The measured efficiency of Process boilers varies a lot

Min. Avg. Max.

Direct Efficiency 61 % 72 % 82 %

Indirect Efficiency 63 % 78 % 84 %

• Efficiency is dynamic – It WILL keep on changing.


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What leads to variations

• Air temperature

• Fuel temperature

• Fuel pressure

• Moisture in fuel

• Loading pattern

• Changing calorific value of fuel

• Use of multiple fuels

Innovative Oil / Gas fired Boilers

Site Installations…




Manual Fired Boilers – Limitations !!

• Indirect Efficiency Guaranteed 73 – 77%

• Typical Direct Efficiency obtained 50-55%

– More heat loss by radiation and convection during fuel feeding cycle resulting in lesser actual efficiency

– Distribution of fuel on furnace grate is uneven leading to Empty pockets and fuel overloaded pockets possible

– Operators tend to overfeed resulting in incomplete combustion

• Manual fuel feeding is laborious and time consuming

• The operator gets exposed to hot flames

• These boilers can not be designed for higher pressure beyond 28 kg/cm2.

24

Observations in Manual Fired Boilers

• High stack temp of up to 249 Deg c @ 6 bar (g) causing heat carry over loss.

• High O2 percentage - ~ up 10 (charged) -19 (discharged)%

• Indirect efficiency – 65.3 % (@ 50% fix damper)

Direct efficiency–50 %

• Optimum Air : Fuel ratio is not maintained

25

26

Date Operating

hrs

Day wise Readings

Steam generation

(kg)

Avg steam load

(kg/h)

Wood consumptio

n (kg)

S:F

13/10/10 12 4355 363 1607.4 2.70

15/10/10 10 4503 450.3 1441.8 3.12

16/10/10 4 2333 584 834 2.79

26/10/10 10 4906 490.6 1790 2.74

28/10/10 10 4414 441.4 1840 2.39

30/10/10 11 6561 597 1785 3.67

*

31/10/10 12 7883 657 2050 3.84

*

1/11/10 – IInd shift

5 1892 378.4 920 2.05

AVERAGE Steam : Fuel Ratio 2.85

S:F Ratio with Manual Fired boiler

Gap Between Minimum and maximum S:F is 100% Gap between average and mimimum is 40%

Stack , 26%

Unburnt , 9.80%

Enthalpy, 11%

Radiation, 1.50% Ash, 1.75% Unaccounted,

0.25%

Losses in Percentage

Typical Break-up of Losses

• Stack Loss – Frequent Opening & closing of door ID Fan damper position same for all stages of operation of

boiler. • Unburnt Loss – Overfeeding of fuel resulting in low air for Burning which also leads to high amount of Unburnt generation. • Enthalpy Loss – Moisture in fuel & Air results in this loss. • Radiation Loss – Through Boiler Heating Surface areas – no Major control possible

Deep Dive into the Losses…..

Current Scenario

• Variety of Boiler designs like Wet Back/Semi Wet Back & Dry Back

• Converted external furnace boilers with deaerated capacity & with Big gap in efficiency

• Quality of Accessories used on Solid fired boilers ????

• No Automation provided, hence total reliance on operator skills

D:%5CA%5CCompact%20Boiler%5Cpresent-blrs%5CBoilerCD%5CJNM%20Boilers%20(D)%5CVideos%5CMarshal_B.avi

O2 Levels – 9 – 11% Excess Air - @70%

Furnace pressure – Between -5 to - 8 mmWC

What should we AIM for ?

Fuel Feeding practices

•The boiler operator looks at steam pressure and does the fuel feeding accordingly.

•Stoker mostly overfeeds fuel as per his convenience & Grate space. Irrespective of plant load, the grate is usually filled fully. This results in high un-burnts and stack loss

Current Operating Practices in Manual Fired boilers

Fuel Feeding practices

• After feeding, the window is closed & fuel burns incompletely for some time leading to high unburnts as can be seen from the black chimney smoke colour during feeding

• Thereafter, the fuel burns and is fed at a later stage by that time stack losses start to happen.


Need Of The Hour based on Today’s Limitations in the Industry

• To provide information & Alerts – to assist the boiler operator for efficient boiler operation.

• To provide information to utility manager on – How the boiler was operated on Daily, weekly & monthly basis.

• To generate MIS so as to follow better operating practices in boiler house for reduced fuel bills

• To provide periodic maintenance alerts to enhance life of boiler & reduce on forced break downs.







With Intell

General operating practice

PHASE I: IMMEDIATELY AFTER FEEDING

• Fuel is overfed

• Bed not evenly spread

• Black/dark grey smoke

observed

• High unburnt loss (High CO

levels)

• Stack O2 levels: 0-5%

• Fuel feed optimised

• Bed is evenly spread

• Light grey/light Brown observed

• Low CO levels


4-

5

mi

nu

te

s

2-

3

mi

nu

te

s 6% Stack

O2

6% Stack

O2

With Intell


PHASE II: AFTER FEEDING (contd.)

• Large interval between fuel

feeds

• Uneven bed

• Greyish-white smoke observed


• High feeding frequency

• Light grey/light Brown smoke

observed


10-

14

mi

nut

es

8-

10

mi

nu

te

s 6% Stack

O2

6% Stack

O2


With Intell

PHASE III: AFTER FEEDING (contd.)

• High feeding frequency

• Light grey/light Brown smoke

observed


4-

5

mi

nu

te

s

2-

3

mi

nu

te

s 6% Stack

O2

6% Stack

O2

• Large interval between fuel

feeds

• Uneven bed

• White smoke observed

• High stack loss (High O2%

levels)


Furnace Draft pressure

• Boiler Furnace draft is maintained by guess-work and there is no measurement of it. Improper Boiler draft results in improper combustion and risk of back firing and increased unburnt loss.

• Manual damper adjustments are based on expertise and vigilance


So what can be done go close to level of comitted Indirect Efficiency levels??

• Continuous Monitoring of Boiler parameters

• Generating Pop ups for corrective actions to be taken by boiler operator

• Provide History & trends to utility manager for the boiler operations, which can suggest a necessary change in operations of boiler

38

Intelligent Boiler

39

PLC Based HMI Display with POP UPS

Facts & Figures!! • 2% decrease in O2 leads to 4% increase in Boiler Efficiency.

• Every 6 deg C increase in Feed water temperature means 1% less fuel bill.

• 20 Deg C variation in stack temperature from optimum value means 1% increased fuel consumption

• Presence of 1% unburnt represents 2.5% excess fuel consumption.

• 3mm soot deposition on tubes increases fuel consumption by 2%

• Maintaining optimum water TDS avoids scaling, moisture carryover in steam & increase operating Efficiency.

Pop ups

1. Feed fuel

2. Close the door

3. Open damper

4. Close damper

5. Clean the tubes

6. Reduce feed

7. Stir/poke the fuel bed

8. Check condensate recovery

9. Avoid sudden loading

10. Excess steam demand

11. Possible back fire

12. Improve water quality

13. Drain mobrey

14. Mobrey not drained

15. Clean the TDS sensor

Safety

Boiler Efficiency

Good operating practices

Feed fuel

Condition:

1. Steam pressure is lesser than the set lower limit.

2. Gap between stack temperature & steam temperature is less than 50 C

3. Boiler door is closed

Condition:

Door open for more than 5 minutes.

Close the door

Possible Back-fire

Condition:

Furnace pressure goes positive

Intell – Management Tool!! • Min – Max values of

important parameters can be seen on Daily/weekly/Monthly basis

• History & Trends of two years of operation of boiler can be seen

• Data on Number of alarms generated, addressed can be seen.

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Summary Screen

• Gives a summary for current day and last day of the number of alarms

occurred and how was the health associated to a particular parameter. • The heath number is an indication of the response time of the operator

Incorporate automated feeding for feeding fuel in Furnace

Feed only the required quantity of fuel

Ensure even spread of fuel over the bed

Modulation of air to fuel ratio

Control the air flow during operation cycle

47

How do we ACHIEVE this?

Automation –Need of Hour!!

Automation of –

• Fuel feeding mechanism

• Damper movement

Objective..

49

Capacity – 1/2/3/4/4.5TPH Pressures – 10.54 / 14.5 / 17.5 kg/cm2(g) Fuel – Briquette/Coal/Wood Chips

MS-HD DTB


10

Online Efficiency Monitoring


10

Online Efficiency Monitoring


10

Generation Opportunity Description

Generate steam at rated pressure Operating at lower pressure results in reduced output and carryover.

Minimize excess air Reduces the amount of heat lost up the stack, allowing more of the fuel

energy to be transferred to the steam

Clean boiler heat transfer surface Promotes effective heat transfer from the combustion gases to the

steam

Maintain high feedwater temperature High Feedwater temperature drives out dissolved oxygen

Size feedwater tank correctly As thumb rule, feedwater tank should be sized to be 1.5 times the peak

steam demand

Avoid oversizing the boiler Oversizing leads to frequent On-Off cycles in a boiler which lowers

boiler efficiency

Monitor Boiler Parameters Continuous monitoring of boiler parameters for optimized boiler

efficiency

Install heat recovery equipments (feedwater

economizers/combustion air preheaters,

blowdown heat recovery)

Recovers available heat and transfers it back to the system by

preheating feedwater or combustion air.

Similarly apart from controlling blowdown, heat can be recovered from

blowdown that is done.

FM Solid Fuel Fired Boilers

Hinged

Doors for

ease of

maintenance


Factory

Insulation &

Cladding


Structurals &

Platforms –

Packaged

Boiler

Feed Water

Pumps on Skid


600 kg/ hr

Boiler

(Dryback)


Packaged

Boiler)


Twin Flue

Boiler

Ash Doors




Individual Lines

for Feed Water




Site Installations

Schreiber Dynamix Dairy Baramati

PO Date – 8th April 2013

Commissioning Date – 4th Dec 2013


10

Steam Distribution • Pipe Sizing & Layout

- Check adequacy & recommend improvement

- Identify redundant piping & optimise layout for reduced losses.

• Insulation

- Check adequacy & estimate losses

- Recommend improvements

• Air Venting

- Identify locations

- Recommend right type, size & quantity

• Metering

- Identify locations

- Recommend right type & size.

• Trapping

- Trap survey & recommendations

- Estimation of loss through leaks

- Recommendations of trap monitoring

Steam pipe layout


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Steam

CORRECT

INCORRECT

Steam

Steam Mains –Condensate

drain


10

Condensate to Steam trap

INCORRECT

Flow

Flow

CORRECT

Condensate to Steam trap

Steam

Pocket

Importance of Correct Pipe

Sizing


10

Insulation


10

Need for Air Venting


10

Air Venting….


10


10

Distribute at High Pressure This will have the following advantages:

– Smaller bore steam mains needed so less heat (energy) loss due to

smaller surface area.

– Lower capital cost of steam mains, both materials such as pipes, flanges

and support work and labour.

– Lower capital cost of insulation (lagging).

– Dryer steam at point of usage due to drying effect of pressure reduction

taking place.

– Boiler can be operated at higher pressure corresponding to its optimum

operating condition, thereby operating more efficiently.

– Thermal storage capacity of boiler increases, helping to cope more

efficiently with fluctuating loads, & a reduced risk of priming & carryover


10

Pressure Reducing Station


10

Electro-pneumatic Temp

control

KE valve with PN actuator and EP5 Positioner

SX65 Controller

EL2270 Sensor

Pneumatic power and electronic intelligence

on a steam to liquid heat exchanger


10

Trapping Issues

Not Fit For Purpose

Plant Start Up

Not in service


10

Commonly Prevailing • Failed Closed

• Failed open

• Not in service

• Not fit for purpose

• Installation


10

The cost of Leaks??

Cost of Steam Leaks….


10

Copyright Forbes Marshall, 2009-10

Maintenance addresses only 20%!

20%

Maintenance

Procedures

40%

Improper

Selection/

Installation

20%

Site Conditions

20%

Manufacturing

Defects


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Steam Trap Selection Criteria

Steam Application Present type of Trap Benchmark Key Selection Factor

Steam Main Line Drain Thermodynamic (TD) Thermodynamic (TD) Quick condensate

removal

Steam Tracing for product line

Thermodynamic (TD) Balance Pressure

Thermostatic (BPT) Energy

Conservation

Copper Tracing for instrument tracing

No Traps Thermostatic (MST) Energy

Conservation

Process Heating Equipments

TD / IB / FT Mechanical (Float

Trap - FT) Process Efficiency

and time

Pump Casing Thermodynamic (TD) Thermodynamic (TD) Quick condensate

removal

Steam trap selection….


10


10

Compact Steam Trapping Station

Estimated weight : 13 kg 4.0 kg

Assembly Parts & Labor

5 ea. 600# rated globe or gate valves 1 ea. Line strainer

8 ea. Sch 80 nipples 16 ea 1/2’’ welds

2 ealine “tee” 1 ea. Steam trap

1 ea. elbow

CONVENTIONAL

720mm 160 mm

245mm

Modern Process Trap Assembly

TOFT Integrated design for base

and Cover PRODUCT MARKING

Aesthetic Features

Modern Float Trap Assembly

TOFT

TOFT VIEWS


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Glandless Piston Valves

FEATURES

– CLASS VI, BUBBLE TIGHT SHUT-OFF

Ensures Positive Isolation

– SS REINFORCED GRAPHITE SEALING RINGS

Asbestos free Sealing rings,

– FORGED CS BODY FOR SIZES UPTO 1 ½”

Max. Pressure : 78 Kg/cm2

Max. Temperature : 427 °C

OPTIMIZING HEAT RECOVERIES

Waste Heat Recovery

• Important & unexplored area for reducing energy

• Around 20 to 50% industrial energy input is lost as

– Waste heat from hot exhaust gases

– Cooling water

– Hot liquor from equipments

Recovering waste heat provides attractive opportunity for emission free and less costly energy resource!


10

Condensate Recovery

To Drain!

Condensate contains 25% of

Total Energy Supplied – Using

this can make a difference


10

• Monetary Value

• Water Charges

• Effluent Restrictions

• No Boiler Derating

•Reduced water treatment costs

Every 6 deg increase in feed water temp from return of hot condensate & recovery of flash steam cuts your fuel bill by 1 %

As per our audit findings Average CR factor in industry is 50-60%(energy recovered still less) & very few recover Flash steam

Why Return Condensate?

Monetary values for

Condensate


10

Higher FW Temp. leads to fuel

savings


10


10

• Back Pressure on Steam Traps

•Flash Steam vented

•Drop in Condensate Temp

•Electrical cost of pumping – besides pump problems

•Too many components to maintain

Conventional Method - CR


10

Effective CR

FW Tank size matters….


10

Illustration:

Consider 4KL of condensate at 90 deg C held up in a tank. Now even a 10 deg. C drop here means a loss of 32KL of

FO or 91tons of coal annually!


10

Heat Content-Steam &

Condensate


10

Thermocompressor


10

Thermocompressor

Heat Recovery Potential

100 %

Energy

37%

utilize

d

63%

Waste

54.22%

Energy

Dye bath

Liquor

Condensate

Flash

Cooling Water

12.84% 14.85%

17.78%

Not considering losses the Process Heat Recovery in Dyeing m/c

Heat Recoveries - At a glance

Textile

Dye Liquor Heat Recovery

Cooling Water Recovery

CRP condensate Recovery

Stenter Exhaust Recovery

Vent Heat from Drum Washer

Brewery Wort vapor Heat Recovery

Wort Cooling Water Recovery

Recovering heat from Bottle Washer drain

SEP & Oil Refi

Heat from waste water boiler

Recovering heat from Bleached Oil, Neutral Oil, Crude Oil

Soap water to preheat hot water

Recovering heat from oil to generate hot water and preheat miscella

Textiles

Brewery

SEP & Oil Refinery

Dome Drain Heat Recovery

Hot water Heat Recovery

Blow through Steam Recovery

Tyre

Heat recovery from Dye liquor of Yarn Dyeing machine

At a large integrated textile mill From drain to savings

Dye liquor at 90 oC when used for heating soft water for process lead to annual savings of 21 lakhs with payback of just 2 months!!

CRP Hot Water Recovery

At a large integrated textile mill From drain to savings

Recovering the CRP hot water to heat DM water lead to savings of 1.5 Crores with payback period of 1 month!


10

Act fast and grow your Profits!!!

Fuel prices would continue to spiral

upwards……. & so would your losses!

Find out where you stand.


10

Thank you

Date post:	16-Apr-2017
Category:	Engineering
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Efficient steam systems - Generation to WHR

Engineering