Industrial Boilers .ppt power plant engg.

industrial 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