1. ACTIVE LEARNING PROCESS
Branch: Electronics & Communication
Guided By :
Prof. C O Yadav
Prepared By :
BINI MOL THOMAS 13BEECG069
VISHAL SALVI 13BEECG067
HARSHAL M.H 13BEECG064

2. Boilers

3. Objectives
1. Describe the theory, construction, and applications of boilers
2. Describe the common type of boilers
3. Explain how to assess the performance and efficiency of a boiler
4. Describe methods to improve boiler efficiency
5.List energy efficiency opportunities

4. Objectives Introduction – Purpose? Type of boilers Boiler Assessment
Energy efficiency opportunities

5. Introduction What is a Boiler?
Vessel that heats water to become hot water or steam
At atmospheric pressure water volume increases 1,600 times
Hot water or steam used to transfer heat to a process

6. Introduction Thermal Equipment/ Boilers BOILER
STEAM TO PROCESS
EXHAUST GAS
VENT
STACK
DEAERATOR
ECO- NOMI- ZER
PUMPS
Thermal Equipment/
Boilers
BOILER
VENT
BURNER
WATER SOURCE
BLOW DOWN SEPARATOR
FUEL
BRINE
CHEMICAL FEED
SOFTENERS
Figure: Schematic overview of a boiler room

7. What Type of Boilers Are There?
Types of Boilers
What Type of Boilers Are There?
Fire Tube Boiler
Water Tube Boiler
Packaged Boiler
Fluidized Bed (FBC) Boiler
Stoker Fired Boiler
Pulverized Fuel Boiler
Waste Heat Boiler
Thermal Equipment/
Boilers

8. Type of Boilers 1. Fire Tube Boiler Thermal Equipment/ Boilers
Relatively small steam capacities (12,000 kg/hour)
Low to medium steam pressures (18 kg/cm2)
Operates with oil, gas or solid fuels
Thermal Equipment/
Boilers
(Light Rail Transit Association)

11. Type of Boilers 2. Water Tube Boiler Thermal Equipment/ Boilers
Used for high steam demand and pressure requirements
Capacity range of 4,500 – 120,000 kg/hour
Combustion efficiency enhanced by induced draft provisions
Lower tolerance for water quality and needs water treatment plant
Thermal Equipment/
Boilers
(Your Dictionary.com)

12. Type of Boilers 3. Packaged Boiler Thermal Equipment/ Boilers
Comes in complete package
Features
High heat transfer
Faster evaporation
Good convective heat transfer
Good combustion efficiency
High thermal efficiency
Classified based on number of passes
Oil Burner
To Chimney
Thermal Equipment/
Boilers
The packaged boiler is so called because it comes as a complete package. Once delivered to a site, it requires only the steam and water pipe work, fuel supply and electrical connections to be made to become operational.
These boilers are classified based on the number of passes - the number of times the hot combustion gases pass through the boiler.
More specifically, it is a typical 3 pass, oil fired packaged boiler.
This is a packaged boiler.
Does anyone recognize what type of boiler this is? (Click once and name will appear)
Package boilers are generally of a shell type with a fire tube design so as to achieve high heat transfer rates by both radiation and convection.
The features of packaged boilers are:
Small combustion space and high heat release rate resulting in faster evaporation.
Large number of small diameter tubes leading to good convective heat transfer.
Forced or induced draft systems resulting in good combustion efficiency.
Number of passes resulting in better overall heat transfer.
Higher thermal efficiency levels compared with other boilers.
(BIB Cochran, 2003)

13. 4. Fluidized Bed Combustion (FBC) Boiler
Type of Boilers
4. Fluidized Bed Combustion (FBC) Boiler
Particles (e.g. sand) are suspended in high velocity air stream: bubbling fluidized bed
Combustion at 840° – 950° C
Fuels: coal, washery rejects, rice husk, bagasse and agricultural wastes
Benefits: compactness, fuel flexibility, higher combustion efficiency, reduced SOx & NOx
Thermal Equipment/
Boilers
The fluidized bed boilers
When an evenly distributed air or gas is passed upward through a finely divided bed of solid particles such as sand supported on a fine mesh, the particles are undisturbed at low velocity. As air velocity is gradually increased, a stage is reached when the individual particles are suspended in the air stream – the bed is called “fluidized”. With further increase in air velocity, there is bubble formation, vigorous turbulence, rapid mixing and formation of dense defined bed surface. The bed of solid particles exhibits the properties of a boiling liquid and assumes the appearance of a fluid – “bubbling fluidized bed”.
The fuels burnt in these boilers can include coal, washery rejects; rice husk and bagasse (sugar cane wastes) & other agricultural wastes.
The fluidized bed boilers have a wide capacity range- 0.5 T/hr to over 100 T/hr.
The fluidized bed combustion (FBC) takes place at about 840oC to 950oC.
Fluidized bed combustion (FBC) has emerged as a viable alternative and has significant advantages over a conventional firing system and offers multiple benefits:
compact boiler design
fuel flexibility
higher combustion efficiency
reduced emission of noxious air pollutants such as SOx (Sulfur oxides) and Nox (Nitrous oxides), both of which contribute to “acid rain”.
Three types of FBC boilers are explained on the next slides,

14. Type of Boilers 5. Stoke Fired Boilers a) Spreader stokers
Coal is first burnt in suspension then in coal bed
Flexibility to meet load fluctuations
Favored in many industrial applications
Thermal Equipment/
Boilers

15. Type of Boilers 5. Stoke Fired Boilers
b) Chain-grate or traveling-grate stoker
Coal is burnt on moving steel grate
Coal gate controls coal feeding rate
Uniform coal size for complete combustion
Thermal Equipment/
Boilers
A type of FBC boiler: This picture illustrates a chain grate or traveling grate stoker.
Coal is fed onto one end of a moving steel grate. As the grate moves along the length of the furnace, the coal burns before dropping off at the end as ash.
The coal-feed hopper runs along the entire coal-feed end of the furnace. A coal gate is used to control the rate at which coal is fed into the furnace by controlling the thickness of the fuel bed.
Coal must be uniform in size as large lumps will not burn out completely by the time they reach the end of the grate.
(University of Missouri, 2004)

16. 6. Pulverized Fuel Boiler
Type of Boilers
6. Pulverized Fuel Boiler
Pulverized coal powder blown with combustion air into boiler through burner nozzles
Thermal Equipment/
Boilers
Combustion temperature at °C
Benefits: varying coal quality coal, quick response to load changes and high pre-heat air temperatures
A type of FBC boiler: Pulverized Fuel Boiler
One of the most popular systems for firing pulverized coal is the tangential firing using four burners corner to corner to create a fireball at the center of the furnace. This is shown in the figure.
The coal is pulverized to a fine powder until less than 2% of the coal is +300 micro meter and 70-75% is below 75 microns for bituminous coal.
The pulverized coal is then blown with part of the combustion air into the boiler plant through a series of burner nozzles.
The combustion takes place at temperatures ranging between degrees Celsius depending mainly on the coal grade. The particle residence time in the boiler is typically 2 to 5 seconds and the particles have to be small enough to be completely combusted during this time period
This system has many advantages :
ability to fire varying quality of coal
quick responses to changes in load
use of high pre-heat air temperatures etc.
Tangential firing

17. Independence Steam Electric Station - Newark, AR
Operation: Unit 1 - January 1983/Unit 2 - December 1984
Fuel: Low-sulfur coal mined near Gillette, Wyoming Capability: 1,678 megawatts

18. Type of Boilers 7. Waste Heat Boiler Thermal Equipment/ Boilers
Used when waste heat available at medium/high temp
Auxiliary fuel burners used if steam demand is more than the waste heat can generate
Used in heat recovery from exhaust gases from gas turbines and diesel engines
Thermal Equipment/
Boilers
Agriculture and Agri-Food Canada, 2001

19. Assessment of a Boiler 1. Boiler performance
Causes of poor boiler performance
Poor combustion
Heat transfer surface fouling
Poor operation and maintenance
Deteriorating fuel and water quality
Heat balance: identify heat losses
Boiler efficiency: determine deviation from best efficiency
Thermal Equipment/
Boilers

20. Assessment of a Boiler Heat Balance Thermal Equipment/ Boilers
An energy flow diagram describes geographically how energy is transformed from fuel into useful energy, heat and losses
Thermal Equipment/
Boilers
Stochiometric
Excess Air
Un burnt
FUEL INPUT
STEAM OUTPUT
Stack Gas
Ash and Un-burnt parts of Fuel in Ash
Blow Down
Convection & Radiation

21. Assessment of a Boiler Heat Balance Thermal Equipment/ Boilers
Balancing total energy entering a boiler against the energy that leaves the boiler in different forms
Thermal Equipment/
Boilers
12.7 %
BOILER
Heat loss due to dry flue gas
8.1 %
Heat loss due to steam in fuel gas
100.0 %
1.7 %
Heat loss due to moisture in fuel
A Heat balance is an attempt to balance the total energy that enters a boiler against the energy that leaves it.
This figure illustrates the different typical losses that occurs while generating steam.
(Question) Does anyone have any suggestions of what the two major heat losses are? (Discussion)
(Click once and answer reveals) They are dry fly gas that represents a heat loss of 12.7% and heat loss as a result of steam in the flue gas of 8.1%.
(Click once for other heat losses to appear) Other heat losses are due to moisture in the fuel and in the air, as well as unburnts in residue and radiation.
(Click once) This leaves 73.8% of heat that goes to steam generation.
Fuel
0.3 %
Heat loss due to moisture in air
2.4 %
Heat loss due to unburnts in residue
1.0 %
Heat loss due to radiation & other unaccounted loss
73.8 %
73.8 %
Heat in Steam

22. Assessment of a Boiler Heat Balance Thermal Equipment/ Boilers
Goal: improve energy efficiency by reducing avoidable losses
Avoidable losses include:
Stack gas losses (excess air, stack gas temperature)
Losses by unburnt fuel
Blow down losses
Condensate losses
Convection and radiation
Thermal Equipment/
Boilers
The goal of a Cleaner Production and/or energy assessment must be to reduce the avoidable losses, i.e. to improve energy efficiency.
The following losses can be avoided or reduced:
Stack gas losses: Excess air (reduce to the necessary minimum which depends from burner technology, operation, operation (i.e. control) and maintenance) and Stack gas temperature (reduce by optimizing maintenance (cleaning), load; better burner and boiler technology).
Losses by unburnt fuel in stack and ash (optimize operation and maintenance; better technology of burner).
Blow down losses (treat fresh feed water, recycle condensate)
Condensate losses (recover the largest possible amount of condensate)
Convection and radiation losses (reduced by better insulation of the boiler).

23. Assessment of a Boiler 1. Boiler Efficiency Thermal Equipment/ Boilers
Thermal efficiency: % of (heat) energy input that is effectively useful in the generated steam
Thermal Equipment/
Boilers

24. Boiler efficiency () = hf /hg
Assessment of a Boiler
Boiler Efficiency: Direct Method
Boiler efficiency () = hf /hg
Heat Input * 100%
Heat Output
Thermal Equipment/
Boilers

25. THANK YOU....