Industrial Boilers.ppt power engineering

boilers

1. Industrial Boilers
Steam generators
Closed vessels
made of steel and
used for generation of steam
vaporizing water
combustion of fuels
eg. coal,coke,oil,wood,saw dust and begesse etc.
Steam used for producing power,for industrial
process work or for heating proposes.

2. Requirements of a Perfect
Steam Boilers
Should be absolutely reliable,capable of producing
maximum steam at required pressure for minimum of
fuel consumption,with minimum attention and minimum
initial cost and operating cost.
Simple constructions
Quick starting from cold
Strong enough against temp. stress & strains
Well design combustion chamber
Less floor area, space & light weight
Best gauges,safety valves and other mountings
Easily accessible for inspection,cleaning and repairs

3. Classification of Steam
Boilers
Vertical or Horizontal
Stationary(Power plant,industrial,central heating and
combined power and heating
boilers.),Portable,Locomotive or Marine
Internally Fired or Externally Fired (Lancashire and
Locomotive Boilers)
Solid,Liquid or Gas Fired
Fire(Smoke)Tube:Water is outside the tubes while the
hot gases are inside the tubes
eg.Vertical,Cochran,Lancashire,Cornish,Locomotives,etc
) or Water Tube: Contain a large number of small tubes
through which water circulates,the fire and hot gases
being outside of the tubes.eg.Babcock and Wilcox,
Stirling and High pressure Boilers etc.)

4. Vertical Boilers
Used in small factories,small water supply
plants,cranes,excavators,winch engines in
mines and on sites of temporary nature such
as construction work etc.
Required minimum floor space,not required
elaborate foundations,and is portable.
Cheap,easy to start but inefficient due to large
wastage of fuel and less heating surface.
Vertical Boilers are:Simple(having one to three
cross tubes), fire tubes and water tubes types.

5. Simple Cross tube vertical
boiler
consists of a cylindrical shell surrounding a cylindrical fire box.
heating surface is about 8-10 times the grate area.
50% efficiency

6. Cochran Boiler
It is well design of a Vertical multitubular fire tube boiler
Improvement over the simple vertical boiler as it
provides greater heating surface.
Total heating surface area is about 10-25 times the
grate area
Efficiency 70-75%
Ranges from 1m dia.X2m high,evaporation 20kg/hr to
3m dia X6m high,evaporation 3000kg/hr.

7. Cochran Boiler contd….

8. Lancashire Boiler
Is horizontal smoke tube boiler size range
from a shell 2m diaX6m long to 3m diaX10m
long
Working pressure range are up to 20kgf/cm2
Ratio of heating surface to grate area is 24-30
Efficiency is about 56% without economizer
and 75% with economizer.
Similar to Cornish boiler,in Lancashire Boiler
two flue tubes but in Cornish boiler only one
flue tubes are there.

9. Lancashire Boiler contd……

10. Lancashire Boiler contd……

11. Locomotive Boiler
Is an internally fired multitubular fire tube boiler

12. Babcock and Wilcox water
tube Boiler
Water tube boiler having lager pressure ranges and
larger sizes.
Three main parts, steam and water drum,water tubes
and furnace.

13. Stirling Boiler
Example of water tube boiler where bent tube are used
instead of straight tube which are used in Babcock and Wilcox
boiler

14. High Pressure Boilers
Two types-Natural circulation & Forced circulation
Boilers

15. High Pressure Boilers
contd………
La-Mont Boiler( Forced circulation Boiler)

16. Once-Through Forced
Circulation Boiler
Does not required a steam and water drum,saving in weight
Supercritical Pressure Boiler
Two types-Benson and Ramzin

17. Ramzin Boiler

18. Loeffler Boiler
Indirect heating is combined with forced circulation

19. Velox boiler
Fire tube forced circulation Boiler

20. Fire tubes Vs water tubes
Boilers
Fire tubes boilers has a large volume of water,therefore
more flexible and can meet the sudden demand of
steam without much drop of pressure.
Fire tubes boiler is rigid and of simple mechanical
construction,so greater reliability and low in first cost.
Fire tube boilers can be made in smallest sizes therefore
simple to fabricate and transport, occupies less floor
space but more height.
Due to mostly externally fired water tubes boiler so
furnace can be altered considerably to meet the fuel
requirements.
Water tubes boilers are more readily accessible for
cleaning,inspection and repairs,compared to the fire
tube boilers.
Modern trend is in the favors of water tube boiler due to
continuous increase in capacities and steam pressures.

21. Boiler Mountings and
Accessories
Fitting and devices which are necessary for the safety
and control are knows as boiler mountings
Fitting or devices which are provided to increase the
efficiency of the boiler and help in the smooth working
of the plant are knows as boiler accessories.
Fittings which are essential from the
safety point of view are as follows,
Water level indicators
Safety valves
Combined high steam and low water safety valve
Fusible plug

22. Boiler Mountings and
Accessories contd….
Fittings which are essential from the
control point of view are as follows,
Pressure gauge
Junction or stop valve
Feed check valve
Blow-off cock
Man hole and Mud Box
The important accessories are
Superheater
Economiser
Air-preheater
Feed pump or injector