STEAM AND STEAM BOILER MSBTE DIPLOMA IN MECHANICAL ENGINEERING THERMAL ENGINEERING

1. UNIT 3- STEAM AND STEAM BOILER
MR. Dhammadip A. KAMBLE
M.E. (Mech. Design Engg.)

2. Application of steam
 Process Heating
 Atomization of Fuel
 Power Generation
 Humidification
 Drying the Product

3. Steam Generation at Constant Pressure

4. Formation of Steam (Temperature-
Enthalpy Diagram)

5. Formation of Steam (Temperature-
Enthalpy Diagram)
 Induction stage : AB shows the heating of water up to boiling temperature. The heat
required to raise the temperature of water (1 kg mass) from 0°C to boiling point (B) is
known as sensible heat of water.
 Warming stage: BC shows the change of state from liquid to steam. The heat absorbed
during this stage is FG, known as latent heat of vaporization (h18).
 Evaporation stage: CD shows the superheating process. The heat absorbed during this
stage is GI I, known as heat of superheat. Line AH represents the total heat required to
go up to superheated point D.

6. Temperature- Entropy Diagram for
Steam Generation Process

7. Mollier Diagram (H-S Chart)

8. Mollier Diagram (H-S Chart)

9. Types of Heat
 Sensible Heat- The heat that can be sensed by thermometer i.e. change in
temperature can be observed.
Sensible heat= m Cp (T2-T1)
 Latent Heat- The heat required to convert a solid into a liquid or vapour, or a
liquid into a vapour, without change of temperature.
1. Latent heat of vaporization 2. Latent heat of condensation

10. Conditions of Steam
 Dry Saturated Steam-If saturated steam does not contain any water, it is known as Dry
Saturated Steam.
 Wet Steam- If saturated steam contains liquid particles, it is known as Wet Steam.
 Superheated Steam- If the temperature of the steam is greater than that of the boiling
point corresponding to the pressure of steam generation, the steam is known as
Superheated Steam.
 Degree of Superheat- The difference (tsup – tsat) is called the degree of superheat, e.g.,
steam at a pressure of 10 bar has a saturation temperature of 179.9°C and if the
temperature of steam is 200°C the degree of superheat is 200 – 179.9 = 20.1°C.
 Dryness Fraction- The dryness fraction of a wet steam may also be defined as the
amount of dry steam in unit amount of wet steam. If 1 kg of wet mercury vapour
contains 0.12 kg of droplets of liquid mercury, it has a dryness fraction of (1 – 0.12) =
0.88.
x=Ms/Ms+Mw

11. Steam Boiler
 A boiler or steam generator is a device used to create steam by applying heat
energy to water.

12. Classification of Boiler

13. Cochran Steam boiler

14. Cochran Steam boiler
 Cochran Boiler is one of the best types of vertical multi- tubular boiler and has a
number of horizontal fire tubes. They have cylindrical shell with a dome shape top
where the space is provided for steam.
1. Shell
 A shell is the main body of the boiler. They having vertical axis cylindrical drum with
hemispherical dome type shell at the top. This hemisphere gives higher volume to
increase steam capacity.
2. Grate
 It is the stage on which the strong fuel is singed.
3. Combustion chamber
 The consuming of fuel happens in the burning chamber.

16. Lamont Boiler

17. LoefflerBoiler

18. LoefflerBoiler
 In Lamont boiler, a major problem was experienced which is the salt and sediment
deposition in the inner surface of the water tube through which water the flows.
 Lamont boilers also have overheating problems due to the salt deposits.
 The Loeffler boiler is an internally fired furnace with forced circulation, high pressure
and water tube boiler. In Loeffler boiler, 75% of superheated steam is used to evaporate
the water within the evaporator drum and the remaining 25% of the steam from the
super heater is utilized by the turbine. Steam circulating pump is employed to circulate
steam inside the boiler.
Working Principle of Loeffler Boiler-
 Its main working principle is to evaporate the feed water by means of superheated
steam from the super heater. The hot gases from the furnace are used for superheating.
The total produced superheat steam is used in two ways. About 75% is used to
evaporate the water and 25% is used to drive the prime mover of the turbine.

19. PartsofLoefflerBoiler
1. Economizer
 Economizer is used to heating the water before it is entering into the drum. The process of preheating water
increases the overall efficiency of the boiler.
2. Evaporating Drum
 The evaporating drum is placed at the bottom of the boiler. It has a mixing nozzle. In this, the feed water is
transformed into saturated steam with the help of superheated steam in the super heater.
3. Steam Circulating Pump
 Steam circulating pump is also known as centrifugal pump. It exists between evaporating drums and radiant
super heater. It transmits steam in the boiler.
4. Radiant Super heater
 In radiant super heater, It superheats steam by the method of radiation generated by the burnt fuel in the
boiler.
5. Convection Super heater
 In the convection super heater, it superheats steam by the method of convection to the desired temperature
of about 500° C.
6. Mixing Nozzle
 It is located inside the evaporated drum. It mixes the steam and feed water from the super heater and
evaporates them.

20. BoilerDraught
 Draught is the pressure difference which is necessary to draw the required quantity of
air for combustion and to remove the flue gases out of the system.

21. Classificationofboilerdraught

22. Induceddraught

23. Forceddraught

24. Balanceddraught

25. Boilermountings
 Boiler mountings are a set of safety device installed for the safe operation of a
boiler.
A) safety fittings
1. safety valves
2. water level indicator
3. fusible plug
B) Control fittings
1. steam pressure gauge
2. Feed check valves
3. Steam stop valves
4. Blow off Cock

26. Functionsofboilermountings
1. Water Level Indicator
Location: This fittings may be seen in front of the boiler.
Function: To indicate the water level inside the boiler.
Water level indicator are generally two in number.
2. Pressure Gauge
Location: It is fixed in front of the boiler.
Function: To measure the pressure of the steam inside of the steam boiler.
Pressure gauges generally used are of Bourdon type
3. Safety valve
Location: These are attached to the steam chest
Function: To blow off the steam for preventing explosions when the pressure of the steam
inside of the boiler exceeds the working pressure.
Safety Valve generally used are of Spring loaded safety valve.

27. Functionsof boilermountings
4. Steam Stop valve
Location: It is usually fitted to the highest part of the shell by means of a flanges.
Function: a) To control the flow of steam from the boiler to the main steam pipe. b) To shut off the
steam completely when required
5. Blow off cock
Location: It is located at the bottom of the boiler.
Function: To empty the boiler whenever required & To remove the mud, scale or sediments
accumulated at the bottom of the boiler.
6. Feed check valve
Location: It is fitted to the shell slightly below the normal water level of the boiler. It is a non
return valve, fitted to a screwed spindle to regulate the lift.
Function: To regulate the supply of water, which is pumped into the boiler by the feed pump.
7. Fusible plug
Location: It is fitted to the crown plate of the furnace or the fire box.
Function: To put off the fire in the furnace of the boiler when the level of water in the boiler falls to
an unsafe limit and thus avoids the explosion which may place due to overheating of the furnace
plate.

28. Boileraccessories
1. Economizer- An Economizer is a device used to heat feed water by utilizing the heat in the
exhaust flue gases before leaving through the chimney.
2. Super heater- It is an important devices of a steam generating unit. Its purpose is to increase
the temperature of saturated steam without raising its pressure. It is generally an integral
part of a boiler and is places in the path of hot flue gases from the furnace.
3. Air Preheater- Air preheater used to recover heat from exhaust flue gases. It installed
between the economizer and chimney. Air for combustion purpose passes from the air
preheater. It increases combustion air temperature with the help of exhaust flue gases. Air
passes through the heater tubes and flue gases pass over the outside of the heater tubes.
Thus heat transfer takes place from flue gases to air required for combustion.
4. Steam Injector- An injector is a simple device used to supply feed water into the boiler. It has
no moving parts and water is supplied into the boiler by the action of steam flowing
through nozzles.

29. Differencebetweenboilermountingsandaccessories

30. Fusibleplug

31. Airpreheater

33. Numerical onmollierdiagram
 1. A steam compressed from 0.1 bar and 200 C to 0.5 bar at constant entropy. Using
mollier chart find change in enthalpy during the process.

34. Numerical onsteam table
 Determine the enthalpy, entropy, specific volume and internal energy for 1 kg of steam
at 7 bar if its conditions are- 1. 85% dry 2. superheated up to 100 C assume Cp=2.1
KJ/Kg K for superheated steam. Use steam table.
 Hwet=hf+xhfg
 Hsup= hg+Cp(Tsup-Tsat)
 Swet= Sf+xSfg
 Ssup=Sg+Cp ln (Tsup/Tsat)
 Vwet=xVg
 Vsup= Vg* Tsup/Tsat