1. Fuel System
13 April 2017

2. Presentation Plan Fuel oil System Oil burners Coal mills and feeder
Types of feeders
Classification of Mills
Features of different Mills
Burner arrangement
13 April 2017

3. Fuel oil System
Purpose: (a) to establish initial boiler light up. (b) to support the furnace flame during low load operation.
Fuel oil system Consists of
Fuel oil Pumps
Oil heaters
Filters
Steam tracing lines
Objective is to get filtered oil at correct pressure and temperature
13 April 2017

4. Atomization
Atomization breaks the fuel into fine particles that readily mixes with the air for combustion. Oil should be divided up into small particles for effective atomization. The advantages of atomization are:
a) Atomizing burners can be used with heavier grades of oil.
b) Can be adopted to large applications because of large capacity range.
c) Complete combustion is assured by the ability of the small particles to penetrate turbulent combustion.
13 April 2017

5. Classification: Oil burners
Oil burners are classified according to the method used for atomization, as follows:
a) Air-atomized burners
b) Steam-atomized burners
c) Mechanically atomized burners
Air atomizing system are not recommended for heavy oil system as they tend to chill the oil and decrease atomization quality
13 April 2017

6. Steam Atomization
This System uses auxiliary steam to assist in the atomization of the oil. The steam used in this method should be slightly superheated and free cf moisture. As in the air atomizing system, the steam used for atomizing as well as heating the fuel as it pass through the tip and into the furnace. The main advantages of steam atomizing burners over other are:
a) Simplicity of its design
b) Initial cost of installation is low
c) low pumping pressure
d) low preheating temperature.
Disadvantage is steam used in atomizing process
13 April 2017

7. Oil Burners The types of oil used in the oil burners are:
a) Light Diesel Oil
b) Heavyfuel oil
c) Low sulpher heavy stock (LSHS).
Heavy oil guns are used for stabilizing flame at low load carrying. Warm up oil guns are used for cold boiler warm up during cold start up and ignitor are used for start up and oil flame stabilizing.
13 April 2017

8. Oil Guns
The guns used in this system have two main components for atomization. They are:
a) Mixing plate
b) Spray Plate.
13 April 2017

9. Oil Gun Compartment
13 April 2017

10. Coal Mill & Feeder
13 April 2017

11. Components The Major components are : Coal Preparation Equipments
Feeders
Mills
Coal Firing Equipments
Burners
13 April 2017

12. Feeders Chain Feeder Chain Feeder Belt Feeder Table type belt Feeder
Volumetric Type feeder
Chain Feeder
Belt Feeder
Table type belt Feeder
Gravimetric Feeder
Chain Feeder
13 April 2017

13. Gravimetric Feeder
13 April 2017

14. 13 April 2017

15. Classification-As per Speed
Types of Mills
Medium Speed
High Speed
Low Speed
17 to 20 Rev/min
30 to 100 Rev/min
500 to 1000 Rev/min
Tube and ball mill
Bowl Mill, Ball and
Race mill
Beater Mill, Impact
Mill
13 April 2017

16. BOWL MILL Model no. Base capacity(T/Hr) 623XRP 18.4 703XRP 26.4AT
HGI -55
Total Moisture-10%
Fineness-70% THRU 200
MESH
13 April 2017

17. Features of Bowl Mills Grinding chamber Classifier mounted above it
Pulverization takes place in rotating bowl
Rolls rotating free on journal do the crushing
Heavy springs provide the pressure between the coal and the rolls
Rolls do not touch the grinding rings
Tramp iron and foreign material discharged.
13 April 2017

18. Pictures of Bowl Mill Coal Entry Classifiers To burners Hot Air
Flow from
PA Fan
Rollers
13 April 2017

19. Typical Mill (Pulveriser)
13 April 2017

20. Internal Details of a Mill
13 April 2017

21. BALL& RACE MILL(E MILL)
Model no Base
capacity(T/Hr) 7E
8.5E
8.5E
10E
10.9E
10.9E
10.9E
13 April 2017

22. TUBE MILL Model no. Base capacity(T/Hr) BBD4760 83 BBD4772 90
13 April 2017

23. Tube Mill Internals
13 April 2017

24. Feature of Tube Mill Operate at 17 to 20 Rpm
Coal Feed from both end of the Tube
Small Ball of 30,40, 50 mm Sizes are used
Hot air blown to move coal to classifiers at two elevations in boiler furnace
No Maintenance for long periods
Better availability so no spare mill required
Always a reserve of coal so there is no spark produced between Steel balls
Consumption of power is more
High Foundation and Initial cost of Equipment
13 April 2017

25. Classifiers Distributors 2 No. Classifiers 4 No.
Ball and Tube Mill
RC Feeder
Drum Feeder
Coal entry to Drum
Classifiers Distributors
2 No.
Classifiers 4 No.
Hot Air
Entry
13 April 2017

26. Pictures of Tube Mill
Steel Balls
13 April 2017

27. Role of Mills
Produces Pulverized coal 80% of which passes through 200 mesh
Air mixed with Pulverized coal (PF) is carried to the coal nozzle in the wind box assembly.
PF from coal nozzle is directed towards the centre of boiler burning zone
Pre-heated secondary air enters boiler and surrounds the PF and help in combustion
13 April 2017

28. Why Pulverized Fuel?
The economic motives for the introduction and development of pulverized fuel firing are:
i) Efficient utilization of cheaper low grade coals.
ii) Flexibility in firing with ability to meet fluctuating loads.
iii) Elimination of breaking losses.
iv) Better response to automatic control.
v) Ability to use high combustion air temperature; increasing the overall efficiency of boiler.
vi) High availability.
13 April 2017

29. Mill Dampers and air system
PF temperature to be maintained 900C
All Shut off valves are required to be kept wide open during operation
Mill bearing is to be kept clean and no dust should enter
Low Primary air flow will cause unstable flame and high flow result in high mill reject
13 April 2017

30. Burner Arrangement
13 April 2017

31. Firing System
Direct Firing System: Coal is fed to the mill at controlled quantity. Hot air (temperature controlled) is permitted to flow through the mill. The air dries the coal and picks up the milled product and flows through the classifier rejecting higher size particle. The fine coal is carried through the coal burner to the combustion chamber.
Indirect Firing System: Mills are operated independent of boiler loading and pulverised coal is stored in the intermediate bunker. From the bunker it is taken to combustion chamber with the help of primary air fan. Boiler loading is controlled by the amount of pulverised fuel fed to boiler.
13 April 2017

32. Direct Firing
13 April 2017

33. Indirect Firing
13 April 2017

34. Coal Burners
Coal burners comprise of coal nozzle, steel tip, seal plate and tilting link mechanism.
Housed in coal compartment in all four corners of the furnace and connected with coal pipes.
One end (outlet) is rectangular and another end is cylindrical.
The burner can be tilted on a pivot pin
. The nozzle tip has separate coal and air passages.
Coal and air passages is divided into sevaral parts
13 April 2017

35. Methods of Fuel Firing
Vertical Firing : A number of rectangular fan shaped nozzles are set across the width of the furnace in an arch. Pulverised fuel mixture ignites under the arch and is directed vertically downwards to the bottom of the furnace where the gases are made to turn upwards to pass through the combustion chamber this gives a long path to the flame and is particularly suitable for coals of low volatile content.
Horizontal Firing: Horizontal firing with the turbulent type of burner are set up usually in the front (front wall fired) or rear walls of the furnace. Burner consists of an inner cone for primary air and fuel which is given a rotary motion as it passes through the burner.
Impact Firing : This is the arrangement with the type of burner used with slag tap furnaces where the ash is kept in a molten state on the furnace floor and tapped off as and when necessary.
Corner or tangential Firing: Burners are set at each corner of the furnace and are directed to strike the outside of an imaginary circle in the centre of the furnace.
13 April 2017

36. Tangential Firing System
13 April 2017

37. Arrangement
13 April 2017

38. Typical Flame
13 April 2017

39. 13 April 2017

40. Various Losses in A Boiler
Heat loss from furnace surface.
Unburned carbon losses.
Incomplete combustion losses.
Loss due to hot ash.
Loss due to moisture in air.
Loss due to moisture in fuel.
Loss due to combustion generated moisture.
Dry Exhaust Gas Losses.
13 April 2017

41. THANK YOU
13 April 2017