Efficient steam systems - Generation to WHR

Efficient Steam Systems –
Generation to Waste Heat
Recovery
Vizag – 8th December, 15

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%steam
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–OilGas
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.

10
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

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

 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 IntellGeneral 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
2-
3
mi
nu
te6% Stack
O
6% Stack
O

With IntellGeneral operating practice
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
te6% Stack
O
6% Stack
O

General operating practice With Intell
PHASE III: AFTER FEEDING (contd.)
• High feeding frequency
• Light grey/light Brown smoke
observed
4-
5
mi
nu
te
2-
3
mi
nu
te6% Stack
O
6% Stack
O
• 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.

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

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

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
10
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

10
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
TOFTIntegrated design for base
and Cover
PRODUCT MARKING
Aesthetic Features

Modern Float Trap Assembly
TOFT
TOFT VIEWS

10
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

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

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

Efficient steam systems - Generation to WHR

Efficient steam systems - Generation to WHR

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