This document provides an introduction to high pressure boilers. It discusses the unique features of high pressure boilers such as forced water circulation, small diameter tubes, and higher steam pressures and temperatures. It then summarizes several types of high pressure boilers including La-Mont, Benson, Loeffler, and Schmidt-Hartmann boilers. It also discusses supercritical boilers, fluidized bed combustion systems, and methods for superheat control and corrosion prevention in boilers.

1. PREPARED BY : AMIT V SHAH (ASST.PROFF , S.V.M.I.T ,BHARUCH )
YEAR : 2017 (7TH SEM MECHANICAL)
CHAPTER -2
HIGH PRESSURE BOILERS

2. CONTENTS:
• UNIQUE FEATERS AND ADVANTAGES
• ALL HIGH PRESSURE BOILERS
• SUPERCRITICAL BOILERS
• SUPERCHARGE & F.B.C
• METHODS OF SUPERHEAT CONTROL
• CORROSION IN BOILER AND IT’S
PREVENTION.
• GTU QUESTIONS

3. INTRODUCTION OF BOILER
DEFINATION :
 According to Indian Boiler Regulation (I.B.R) Act 2007,”Boiler is a closed pressure
vessel in which steam is generated with capacity exceeding 25 liters, gauge pressure
greater than or equal to 1 kg/cm2, and water is heated at 100oc or above”
 Steam boiler is a closed vessel in which heat produced by the combustion of fuel is
utilized to generate steam from water, at desired temperature and pressure.
APPLICATIONS OF BOILERS :
1. Power generation
2. Heating
3. Industrial processes

4. INTRODUCTION OF HIGH PRESSURE BOILERS
 Fire tube boiler : Steam is need 30 bar pressure.
 Water tube boiler : Steam is need 42 bar pressure.
 A boiler is called a high pressure boiler when it operates with a steam pressure
above 80 bar. The high-pressure boilers are widely used for power generation
in thermal power plants.
 Example: Lamont boiler, Benson boiler, loeffler boiler, Babcock and Wilcox
boiler , etc…
 Power plant necessary to generate steam at a high rate , high pressure , higher
efficiency , which is full fill by high pressure boiler.
 H.P.B generate 160 bar pressure and maximum steam temperature 540 degree.

5. FEATURES OF HIGH PRESSURE BOILERS:
 Forced circulation of water
 Large number of small diameter tubes
 Higher steam pressure and temperature
 Improved mode of heat transfer and heating
 Pressurized combustion
 Compactness
 High efficiency
 Once through construction

6. FEATURES OF HIGH PRESSURE BOILERS:
1. METHOD OF WATER CIRCULATION:
 Flow of water/steam takes place due to density
difference in natural circulation.
 With increase in boiler pressure density difference is
reduce and at critical pressure difference is same , so
natural circulation is not possible.
 Slow circulation of water causes Film boiling and hence
bubbles remain contact with metal tube which resist the
heat flow.
 In modern H.P.B , the circulation is maintained with
the help of boiler circulating pump which forces the
water through the boiler.
 Due to high velocity , heat transfer rate is increase.
 Evaporation capacity is increase so size and diameter of
boiler and tube is reduce.

7. FEATURES OF HIGH PRESSURE BOILERS:
2. TYPE OF TUBING:
 The most of H.P.B are water tube. If flow take place through
one long continues tube , the large pressure drop take place
due to friction.
 This is reduce by arranging the flow to pass through parallel
set of tubes.
 In force circulation boiler it is possible to prevent film boiling
 But , above 200 bar pressure the effectiveness of drum in
separating the saturated steam from water is reduce.
 This eliminated by using once through boiler.
 In this water is fed to the boiler at one end and superheated
steam discharge through the other end of boiler.
 Means , Eliminated the separating drum.

8. FEATURES OF HIGH PRESSURE BOILERS:
3. PRESSURIZED COMBUSTION:
 To increase the rate of heat release in the boiler furnaces it is essential to increase the rate of firing of the fuel.
 Hence it is necessary to use pressurized combustion system.
4. IMPROVED METHODS OF HEATING:
 Saving of latent heat of evaporation of water at pressure above critical.
 Heating of water by mixing the superheated steam.
 Velocity of hot gas and water are high and hence heat transfer rate from gas to water is increase.
 Utilization of the mode of heat transfer.

9. LA-MONT BOILER
 It is first forced circulation boiler.
 It is introduced by La-Mont in 1925 in which pump
is used for forced circulation.
 Type of boiler : water tube , forced circulation ,
HPB
 Steam generating capacity : 45 to 50 tones / hr
 Pressure and temperature : 120 atm. And 500̊̊ c

10. LA-MONT BOILER
 The feed water from the hot well is pumped to boiler drum through economizer.
 In the economizer , the feed water absorb the sensible heat from the flue gases passes over the
economizer.
 The water from the drum is pumped to radiant and convection evaporator , and again to drum.
 The feed water in radiant evaporator absorb radiant heat and in convective evaporator absorb
convective heat and it evaporates.
 The steam collected in the upper part of separating steam drum and then passes through super heater
where it becomes superheated.
 The super heated steam then supplied to prime mover.
 The atmospheric cold air is pre-heated in the air-preheater by the flue gases before discharge through
chimney.
 The heated air from air pre heater is supplied to the combustion chamber.

11. LA-MONT BOILER
FLUE GAS PATH
WATER / STEAM PATH
COMBUSTION
CHAMBER
RADIENT
EVAPORATOR
CONVECTIVE
EVAPORATOR
SUPERHEATER ECONOMIZER
AIR
PREHEATER
CHIMNEY ATMOSPHERE
STEAM
CIRCULATION
PUMP
HOT WELL
FEED WATER
PUMP
ECONOMIZER STEAM DRUM
RADIENT
EVAPORATOR
CONVECTIVE
EVAPORATOR
STEAM DRUM SUPERHEATER STEAM TURBINE

12. LA-MONT BOILER
ADVANTAGES:
 Small diameter tubes are used, so that high heat transfer rate is maintained.
 The multiple tubes circuit gives flexibility for suitable location of heat transfer equipment's.
 Due to the forced circulation , high evaporation rate is achieved.
DISADVANTAGES:
 There is a formation and attachment of bubbles on the inner surface of the heating tubes. This reduce the
heat flow and steam generation.
 Salt and sediments are deposited on the inner surface of water tubes which reduce the heat transfer and steam
generating capacity.

13. BENSON BOILER
 It is introduced by benson.
 If the boiler pressure is raised above critical
pressure(225 atm) , the steam and water have same
density so bubbles will not be formed.
 Hence, the difficulty experienced in case of La-
mont boiler as danger of bubbles formation can be
easily eliminated.
 It is also called as once through boiler.
 Because water is fed into the boiler at one end and
superheated steam discharge through other end.
Without use of drum.
 Type : H.P.B , forced circulation , Once through
boiler , Water tube boiler.

14. BENSON BOILER
 The feed water supplied by feed pump at a pressure higher than 225 atm.
 This water passed through economizer then radiant evaporator , where most of water is evaporated.
 The remaining water is evaporated in convective evaporator and converted into steam.
 The steam is passed through the superheated and finally supplied to the prime mover.
ADVANTAGES:
 Generation of steam at pressure higher than critical pressure so do not required any evaporator drum.
 There is no drum , so total weight of the boiler is reduce. And cost is also reduce.
 Natural circulation boiler requires expansion joints but it does not required in Benson boiler. Hence Benson
boiler can be started very quickly because of welded joints.
 Erection of the boiler is easier and quicker.
 At part and over load it can be operated economically by varying temperature and pressure.
 High generation rate of steam.
DISADVANTAGES:
 Salt deposition and sediment on the inner surface of water tubes.
 Danger of overheating.

15. LOEFFLER BOILER
 In La-mont and Benson boiler , the major
difficulty experienced is deposition of salt
and sediment on inner surface of tubes.
 This difficulty is solved in LOEFFLER
BOILER by preventing the flow of water
into the boiler tubes.
 The most of steam is generated outside the
tubes and in evaporating drum using parts
of superheated steam coming from the
boiler.
 In this boiler more steam circulation is used
rather than of water in other boiler.
 Hence , steam is heat carrying and heat
absorbing medium.
 Type of boiler : forced circulation , H.P.B
and water tube boiler.

16. LOEFFLER BOILER
 The high pressure feed pump draws water through the economizer and deliver it into the evaporating
drum.
 An evaporator drum is out side the boiler. In this feed water is evaporated by mixing superheated
steam coming from superheated.
 The stream circulating pump draws saturated stream from the evaporator drum.
 The steam passes through radiant and convective super heaters where it is heated to required
temperature.
 Steam coming from super heater , about 1/3 of superheated steam is supplied to steam turbine and the
remaining 2/3 superheated steam is supplied to evaporator drum to evaporator the feed water.
ADVANTAGES:
 The evaporator tubes in this boiler carries superheated steam , so there is no salt deposition on the
surface of tubes.
 Boilers are compact in design.
 High steam generating capacity.
 This boiler is suitable for marine applications.

17. SCHMIDT-HARTMANN BOILER
 The boiler have a multi circuit as primary
and secondary which reduces the problem of
overheating and salt deposition in the tubes.
 Feed pump is used to supply the water to a
drum which discharged saturated steam to
the super heater.
 The main feed water (impure) is evaporated
as a pressure of 60 bar in the secondary
circuit.
 The pure distilled water is evaporated at
pressure above 100 bar in primary circuit.
 In this boiler energy (heat) exchange between
two fluids at different pressure.

18. SCHHMIDT-HARTMANN BOILER
 In primary circuit steam is produced from distilled water , this steam passes through a submerged heating
coil which is located in an evaporator drum.
 This high pressure steam in this coil of primary circuit has a sufficient energy to generate steam from
impure water in the evaporating drum.
 The steam produced in the evaporator drum passes through the super heater and then supplied to the
steam turbine.
 Due to the heat transfer , the steam of primary circuit is condensed and falls down into the low pressure
feed pre heater on its way giving up heat to the impure feed water.
 Hence temperature of feed water increases to its saturation temperature.
 Therefore , only latent heat is supplied in the evaporator drum.
 The water and steam in the primary circuit flow is taken place due to density difference.
ADVANTAGES:
 Salt deposition in the evaporating drum is easily brushed off.
 No problem of over heating.
 Take wide fluctuation of load.
 Without priming the water take place in the evaporator.

19. SUPERCRITICAL BOILER
 Designer work for reducing the cost of
electric power generation.
 Cost is increase with increase the fuel cost
, designer try to compensate the rising fuel
prize and try another methods for cost
reduction.
 The best method is supercritical boiler for
cost reduction.
 In super critical boiler the boiler working
under pressure above critical pressure.
 A sub critical boiler (conventional ) consist
of three heating surfaces as economizer ,
evaporator , super heater while in
supercritical boiler consists only
economizer and super heater.

20. SUPERCRITICAL BOILER
 In conventional boiler water is heated below critical pressure , hence heat added to water is utilized to
increase temperature of water up to their saturation temperature.
 If more heat added to this water boiling will begin at constant temperature.
 Bubbles of steam begin to form in the water and rise above the water level drum.
 Further heating of saturated steam , steam become superheated.
 If the pressure of water or steam raised . Enthalpy of evaporation is reduce.
 At critical pressure enthalpy of evaporation become zero.
 It means that if the water is pressurized with the help of feed pump up to critical pressure and then heat is
added to it , the water will be directly converted into steam and there is no bubbling action as water
changes to steam.
 EX. Once through Boiler.
 In this boiler when water is heated at constant super critical pressure suddenly it is converted into steam.
 In supercritical boiler high pressure water enter in the tube inlet and leaves at the outlet as the superheated
steam.
 Since there is no drum , but there should be a transition section where the water is likely to flash in order to
accommodate the large increase in volume.

21. SUPERCRITICAL BOILER
ADVANTAGES:
 Heat transfer rate are large compare to subcritical boilers.
 There is no drum , less heat capacity of the generator and hence more stable and give better response.
 There is no two phase mixture and hence the problem of erosion and corrosion are minimized.
 Super critical boiler can generate peak loads by changing the pressure of operation.
 There is great ease of operation and their comparative simplicity and flexibility made them adaptable
to load fluctuation.
 Higher thermal efficiency.
DISADVANTAGES:
 Expensive material is required.
 The additional problem is created due to the separation of solid impurities as phase changes. These
solid remain in the tubes and block the passage for the flow of feed water . So , it is necessary to treat
water thoroughly before supply to the boiler.

22. SUPER CHARGED BOILER
 When the combustion is carried out under
high pressure in the combustion chamber by
supplying the compressed air then rate of
heat transfer increased and heating surfaces
required is reduces.
 This theory used in super charged boiler.
ADVANTAGES:
 It required less heat transfer surfaces.
 Due to small heat capacity of the boiler ,
boiler plant gives better response to control.
 Rapid start of boiler is possible.
 The part of the gas turbine output can be
used to drive other auxiliaries.
 Comparatively less number of operation
required.
DISADVANTAGES:
 It required tight passage for high pressure
gas.

23. FLUIDIZED BED COMBUSTION (FBC)SYSTEM
 Oil and gas prize is continuously increase since last few years. And also low Sulphur fuel oil and
natural gas are not available for power generation in near future.
 So , all the industry is diverted towards coal as a main fuel.
 But , burning of pulverized coal has some problems such as , partial size of coal is limited to 70-100
microns , also design for coal and oil burning is different.
 Also , pulverized fuel fired furnace required high generating temperature in the furnace. So , it create
problem of over heating , slag formation , ash and salt deposition , formation of SO2 and NO2.
 FBC rapidly emerged as a variable option to pulverized coal and stoker fired for the combustion of
solid fuels.
 In FBC has a capability to use vide range of solid fuel like.. Low grade fuel , biomass , or municipal
waste.
 So , it is also called FUEL FLEXIBLE SYSTEM.
 SO2 emission should be controlled without use of scrubber , because in this combustion is below 1100
degree so SO2 emission less.
 Due to lower temperature slagging problem is minimized.

24. FLUIDIZED BED COMBUSTION (FBC)SYSTEM
Principle of FBC system.
 A fluidized bed is composed of fuel and inert
material contained with an atmospheric or
pressurized vessel.
 When air or other gas flows upward through bed ,
the bed solid particles are distributed.
 if velocity increased further a stage is reached
when particles are suspended in the gas stream
and bed becomes turbulent and rapid mixing of
particles . The behavior of this mixture of solid
particles and air or gas is like a fluid.
 Burning of a fuel in such a stage is known as
fluidized bed combustion.

25. FLUIDIZED BED COMBUSTION (FBC)SYSTEM
 The main function of inert material (DOLOMITE) is to control bed temperature.
 The heat release by the combustion is first used in keeping up the temperature of the inert material
and the balance is absorb by the evaporator tube. Hence bed operate at a temperature 800 – 900.
 Another function is to absorb SO2 and Nox production.
 Ex.. Lime stone , Dolomite , Fused alumina , Sintered ash.
PROBLEMS
 Short residence time of fuel in bed.
 Poor lateral mixing of fuel and air.
 Fine solid particles leaving the furnace along with the flue gases.
 Very difficult to remove ash and in combustible.

26. FLUIDIZED BED COMBUSTION (FBC)SYSTEM
ADVANTAGES:
 Use any type of low grade fuel including municipal waste hence , it is a cheaper method for power
generation.
 Combustion temperature is control accurately.
 No formation of nitrogen oxide.
 Use inert material for removing slagging and over heating.
 The size of the coal does not effect on the operation and performance.
 FBC system can response rapidly.
 Due to better heat transfer , higher thermal efficiencies , the unit size and hence capital costs are reduce.
DISADVANTAGES:
 There may be problems in distribution of coal and dolomite.
 The direct contact between hot fuel and evaporator tubes causes erosion of the tubes.
 High pressure air required to fluidization of the bed.

27. FLUIDIZED BED COMBUSTION (FBC)SYSTEM
CLASSIFICATIONS
1. Atmospheric FBC
Boiler :
(1) Classical
(2) Circulation
2. Pressurized FBC Boiler

30. HEATING SURFACE AND THEIR LOCATION IN BOILER
The boiler consist
following heating surface:
1. Evaporator
2. Super heater
3. Re heater
4. Economizer
5. Air pre heater.
The boiler consist
following Zones:
1. Radiating zone
2. High temperature
convection zone
3. Low temperature
convection zone

31. SUPERHEATERS
FUNCTION :
 The function of super heater is to remove the moisture from the saturated steam coming from the
boiler.
 The steam produced in the boiler is nearly saturated . This steam should not be used in the steam
turbine because the dryness fraction of the steam leaving the boiler will be low.
 This result in the presence of moisture which causes corrosion and erosion of turbine blades.
ADVANTAGES:
 The steam turbine efficiency increased by approximately 2 % of each percent of moisture removed.
 The superheating increases overall cycle efficiency as well as avoids to much condensation in the last
stages of turbine which reduce blade erosion and corrosion.
 Super heated steam has a higher heat content and hence capacity to work is increased.

32. SUPERHEATERS
SLAGGING OF THE SUPER HEATER:
 In modern steam power plant , the combustion temperature is higher than the fusing temperature of
ash.
 So , there is a tendency of the ash to collect in fluid form on the super heater tubes and this is known as
slagging of super heater.
 This problem is minimized by following methods:
1) Place radiant super heater as possible as close to furnace.
2) Provide bank of water filled tubes in front of convective super heater to restrict radiation heat transfer
as well as to limit slag accumulation on the convective super heater.
3) Utilize combined convection – radiation super heater.

33. SLAGGING OF SUPERHEATERS

34. CLASSIFICATION OF SUPERHEATERS
1. BASED ON MODE OF HEAT TRANSFER.
 Convective super heater.
 Radiant super heater.
 Combined radiant and convective super heater. (Pendant super heater )
2. BASED ON MODE OF HEAT TRANSFER.
 Over deck super heater.
 Inner deck super heater.
 Inner tube super heater.
 Inner bank super heater.

35. CONVECTIVE SUPER HEATER.
 It is located in the convective zone of the furnace usually before economizer.
 The convective super heater absorbs heat from flue gases through convection.
 The convective super heater gives rising characteristics means the temperature of super heater
increase with increase the steam out put , because with the increase the steam out put both gas
flow over super heater tubes and steam flow inside the tubes increase which causes increase in
heat transfer rate and mean temperature difference.

36. RADIANT SUPER HEATER.
 Radiant super heater is located in the furnace between the furnace wall.
 It absorb heat from burning fuel through radiation.
 It has two main disadvantage (1) tubes get over heated due to high temperature of furnace ( 2 )
temperature of the super heater falls with increase in steam out put , because with increase in
steam out put , the furnace temperature rise at a much less rate than the steam out put.

37. COMBINED OR PENDANT SUPER HEATER.
 In this both radiant and convection super heaters are arranged in series in the path of flue gases.
 Radiant super heater receives heat by radiation , and convection super heater receives heat by
convection.
 About ¾ th of convective surface made counter flow while the remaining ¼ th is parallel flow.
 If the entire coils are counter flow then exit end of the super heater coil will be subjected
maximum temperature difference.(outside maximum temperature of gas and inside maximum
temperature of steam ).
 Hence , parallel flow exit end of super heater protect against over heating and metal failure.

40. REHEATERS
 FUNCTION : it’s function is to re superheat the partially expanded steam from the turbine.
 So , steam remains dry as far as possible through the last stage of the turbine.
 The re heater is generally located before or after the convective super heater in the convective
zone of utility boilers.
 In modern high pressure boilers , re heater generally in two section . The primary section is
placed in the convective zone. And secondary section is placed just at the furnace exit hanging
from top.

41. ECONOMIZERS
 FUNCTION : it’s function is to preheated the feed water using the hot gas leaving the boiler.
 “A Device , which increases the temperature of feed water using waste heat of flue gases
leaving the boiler through chimney.
ADVANTAGES:
 It improve the efficiency of boiler. ( 1% of efficiency is improve by increasing the temperature of
feed water by 6 degree )
 It reduced the losses of heat with the flue gases.
 It reduce the consumption of fuel.
 It reduce thermal stress in the boiler due to reduced temperature differential in the boiler.

43. CLASSIFICATION OF ECONOMIZERS
1. BASED ON CONSTRUCTION.
 Plain tube type
 Gilled tube type
2. BASED ON PART OF STEAM GENERATION.
 Steaming type
 Non – steaming type
3. BASED ON LOCATION OF ECONOMIZER.
 Independent economizer
 Integral economizer

45. AIR PRE-HEATERS
 FUNCTION : it’s function is to recover the heat from the flue gases and this heat is utilized to
increased the temperature of air before it supply to the furnace.
ADVANTAGES:
 It increase the temperature of the furnace gases , improve combustion rate and efficiency.
 Drop 20-22 degree in the flue gases temperature increase boiler efficiency 1%.
 Pre heating air facility the burning of poor grade of fuel thus permitting a reduction in excess air.
 It increase steam generating capacity per unit m2 of boiler surface.
 Increase the thermal efficiency of plant and saving the fuel.
 In case of pulverised coal combustion hot air can be used to dry coal , to transport pulverized coal
to burners and accelerate combustion.
CLASSIFICATION :
1. Recuperative : (1) Plate type (2) Tubular type
2. Regenerative : (1) stationary (2) rotary (Ljungstrom)

47. DIFFERENTIATE AIR PREHEATER
RECUPERATOR AIR PREHEATER
 In this heat exchanger two fluids are
separated by heat transfer surface. There is
continuously het transfer take place.
 Static construction , there is only nominal
leakage through joints.
 It required more space
 Less pressure drop for both air and flue gas
 It does not required power since there is no
any rotating parts.
 The clean surface is difficult.
 It become very large as boiler capacity
increases. Hence , for large power plant
large size air pre heater required.
 More investment and operating cost.
 Scale deposition reduce heat transfer.
REGENERATIVE AIR PREHEATER
 In this heat exchanger cold fluid and hot fluid
alternately occupy same space. There is a
discontinuously heat transfer take place.
 Heat transfer surface are rotated , hence leakage
through sealing arrangement at the moving surface
is high.
 It is very compact air preheater.
 Large pressure drops for both air and flue gases.
 It needs power to rotate the matrix rotor.
 The cleaning the surface is not difficult.
 It is very economically used for high capacity boilers
and plants.
 Minimum initial and operating costs.
 Scale deposition does not reduce the heat transfer.

48. STEAM TEMPERATURE OR SUPER HEAT
CONTROL
 Reduction in steam temperature reduction in plant efficiency.
 Increase temperature over design value then over heating and failure of super heater , re heater tubes and turbine blades.
 Hence , accurate control in temperature is important for efficient power plant operation.
 The main variables affecting the super heater temperature are :
 Furnace temperature
 Mass flow rate of flue gases
 Cleanliness of heating surface
 Variation of load on the plant.
 The super heat of steam can be controlled by following method.
1. Combined radiant – convective super heater.
2. DE super heating and attemperation.
3. Pre-condensing of steam.
4. By pass the furnace gas around the super heater.
5. Gas recirculation.
6. Tilting burner in the furnace.
7. Auxiliary burners.
8. Twin furnace.

53. GTU QUESTIONS:
S.N QUESTIONS MARK YEAR
1 State desirable to control the super heat temperature. Explain desuperheater method. 3 2016
2 Explain working of Schmidt-Hartmann boiler with neat sketch. 7 2016
3 What is the function of super-heaters? Sketch and explain different super heaters briefly 7 2015
4 Explain any two from the following boiler accessories with neat sketch. (i) Air-preheater (ii) Economizer (iii) Re-heaters. 7 2015
5 Explain with neat sketch construction and working of Lamont Boiler 7 2014
6 Explain types of Super heater and state the various methods used for controlling the superheat temperature of steam. 7 2014
7 Explain with neat sketch, construction and working of La Mont Boiler. 7 2013
8 Explain with neat sketch construction and working of Benson Boiler. 7 2013
9 With neat sketch explain different types of super heaters. 7 2012
10 Discuss status of Fluidized bed combustion boilers worldwide and list its
advantages and disadvantages.
7 2012
11 Draw a line diagram of a benson boiler. State the main difficulties experienced in the La Mont boiler and how it is
prevented?
6 2016

54. GTU QUESTIONS:
S.N QUESTIONS MARK YEAR
12 Explain any two method of controlling temperature of super heated steam. 4 2016
13 Differentiate between Superheater, Reheater and air Preheater. 3 2016
14 Draw a neat sketch of once through drum less boiler. What are its advantages over conventional high pressure boilers? 7 2015
15 Explain working principal of fluidized bed boiler with necessary diagram. How Sulphur and Nitrogen emissions are
controlled in fluidized bed boiler.
7 2015
16 Why temperature of steam needs to be controlled in thermal power plant? Name different methods to control the
temperature of steam and explain any two in detail.
7 2015
17 Explain with neat sketch, construction and working of La Mont Boiler. 7 2014
18 Explain the constructional difference between Low pressure and High
pressure boiler
7 2014
19 What are the reasons of corrosion in a boiler and how it is control? 7 2014
20 Explain Loeffler boiler with a schematic. State the difficulty experienced in La-Mont and Benson boiler. How is it solved?
Mention its advantages.
7 2013
21 Name different methods of controlling the superheat temperature of steam. Explain the operation of spray type
attemperator.
3 2013
22 With neat sketch explain construction and working of Fluidized bed combustion boiler and list its advantages and
limitations.
7 2012