1. Prepared By:- Nisarg Amin
Topic:- Improving Boiler Availability

2. Improving Boiler
Availability

3. Boilers are widely used in power
generation, chemical & process industries
They’re used mainly for generating steam
at high pressures & temperatures for a
variety of purposes
Its development began in the 18th century
Industrial Revolution
Being fairly mature technology, today’s
boilers have become very efficient at
converting the thermal energy in coal, oil
or natural gas to heat water & form steam
at high pressure & temperature
This presentation seeks to explore the
methods available to maintain & improve
the boiler efficiency
Introduction

4. Main Areas for Improvement
Combustion Management
Feedwater Management
Steam Distribution Management

5. Combustion Efficiency Management
Boiler burns fuel efficiently if following 3 conditions aremet:
It burns fuelcompletely
It uses as little excess air as possible to do it
It extracts as much heat as possible from the combustiongases
The first 2 conditions are met by careful control of excess air in theboiler

6. Control of Excess Air
In general, boiler efficiency decreases for excess oxygen above 2-3% or excessair
above 10-15%
Optimum excess air is recommended for each type of boiler on the basis of fuel
used

7. Combustion Control
Usual causes of deficient combustion:
Improper Draft: Remedied by DraftControl
Improper Air-Fuel Mixture

8. Draft Control
Pitfalls of Improper Draft:
Insufficient Draft: Prevents adequate air supply for combustion; Results insmoky,
incomplete combustion
Excessive Draft: Larger volume of air & flue gas moves quickly through the furnace;
Less time for heat transfer, High flue gas exit temperature; Contributes to maximum
heat loss
Ideal Draft: Controlled such that boiler operates at 2-4% excessoxygen
Close Draft Regulation difficult due to burners’ requirement of properair-fuel
mixture

9. Air-Fuel Mix Control
Stoichiometric air-fuel mix depends on masses
Fact to be considered: Density of air & gaseous fuels changes withambient
temperatures
Control challenging due to:
Inadequate tolerance of burner controls
Faultyburners
Improper Fuel Deliverysystem

10. Reclaiming Boiler Heat Losses
Residual heat in flue gas is the main heat loss
Residual heat used in following ways:
Economisers: Feedwaterpreheated
Flue gas condensing by water: Water absorbs flue gasheat
Combustion Air Preheat: Combustion air preheated for better combustion
Flue Gas Recirculation: Recirculated with incoming air-fuel mix; decreases NOx
emissions
Heat Cascading: Exhaust heat used in lower temperature applications

11. Feedwater Management
Boiler feedwater consists of:
Returnedcondensate
Make-upwater
Make-up water is the main source of contaminants, making condensate recovery
important
Condensate recovery important due to the following:
Losing hot condensate results in heat loss of fuel
More the condensate recovery, lesser will be the make-up water, lesser the need for
water treatment
More condensate recovery implies lower blowdown & associated losses

12. Steam Distribution Management
Steam distribution equipment must supply high quality steam at requiredpressure
& flow rate with minimum heat loss
Key Components of Steam Distribution System:
Steam distributionpiping
Valves &Flanges
Insulation
Steam Traps
AirVents
DripLegs
Strainers

13. Important Concerns of Steam Distribution Management
Optimum PipeSizing
ProperInsulation
PluggingLeaks
Steam Traps & Associated Pipelines
Steam Use inHeating
Steam Distribution Management

14. Optimum Pipe Sizing
Affected by Steam Velocities:
Superheated: 50-70 m/s
Saturated: 30-40 m/s
Wet/Exhaust: 20-30m/s
Velocities lesser than 15 m/s at shorter pipebends
Standard data tables available to help selection of appropriate pipesizes
Steam piping size based on ‘permissible velocity’ & ‘available pressuredrop’
considerations
Condensate piping size designed based on the assumption of only water flow at
starting conditions, despite mostly carrying two-phase flow in practice

15. Proper Piping Design & Maintenance
Ensure right sizing of pipes
Oversized Pipes: Increase capital, maintenance & insulation costs; Increase surface
heat losses
Undersized Pipes: Require higher pressure & pumping energy; Have higher rates of
leakage
Get rid of redundant & obsolete pipework
Fix Steam Leaks
Keep track of facility-wide & individual process-unit steambalances
Piping at equipment connections should accommodate thermal responses during
system start-ups & shutdowns
Steam separators should be installed to ensure dry steam throughout theprocess
equipment & branch lines

16. Done to avoid excessive heat loss to atmosphere
Important Insulation Properties: Thermal conductivity, Strength,Abrasion
resistance, Workability, and Resistance to water absorption
Common Insulating Materials:
Steam Piping: Calcium Silicate, Fiberglass, Perlite, Cellular Glass
Steam Distribution Components/Attachments: Fiberglass, Fabric InsulationBlankets
Smaller the pipe diameter, thinner the insulation
Higher the temperature of the insulated pipe, higher the return on investment
Running pipes in groups reduces heat losses
Air movement & Draft increase heat losses of un-insulatedpipes
Proper Insulation of Steam Piping

17. Steam Traps & Associated Pipelines
Steam traps distinguish condensate from steam & remove thecondensate
Types of steam traps, classified based on:
Density difference: Known as mechanical traps; Include float traps & bucket traps
Temperature difference: Known as thermostatic traps; Include Balanced-pressure traps,
Bimetal traps & Liquid expansion traps
Flow characteristics: Known as thermodynamic traps
Steam Traps Maintenance:
Periodic Cleaning & Checking for wear
Fixing strainers ahead of the steam traps to avoid damage by scale & dirt
Steam traps handling more air require more frequent inspection & proper venting

18. Steam Use in Heating
Steam can be used in various ways as follows:
Providing Dry steam forProcess
Using steam at lowest pressures required by end-user
Heating by DirectInjection
Proper Air Venting: Done to avoid reduced heat transfer performance due toair
films

19. Summary
The three important phases of operation to be managed for high boiler efficiency
are:
Combustion
Feedwater
SteamPiping
Good draft control, air-fuel mixture control results in high boilerefficiency
Maintaining low amount of dissolved solids & acids helps in maintaining high
efficiency & prolonging equipment life
Proper piping design & maintenance helps in increasing boilerefficiency

20. THANK YOU!