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1 SURNAME AND INITIALS

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SURNAME AND INITIALS :MBUTHUMA N

STUDENT NO : 217110177

SEMESTER AND YEAR : S2 2018

SUBJECT : THERMODYNAMICS II

ASSIGNMENT :ONE

TITLE OF AN ASSIGNMENT : BOILERS

LECTURER : DR S HASSAN

DUE DATE : 18 OCTOBER 2018

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TABLE OF CONTENTS
INTRODUCTION ……………………………………………………………………….….3
FLAME TUBE BOILER ………………………………………………………………….4-6
WATER TUBE BOILER ………………………………………………………………..6-10
WATER TREATMENT………………………………………………………………..11-12
COMPARISSONS BETWEEN WATER AND FLAME TUBE BOILER……………….13
CONCLUSION……………………………………………………………………..……..14
REFERENCE LIST………………………………………………………………………..15

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Introduction
Steam Generator, well known as boiler is an equipment designed to boil liquid to steam. Steam is
produced by means of transfer of heat to water and combustion, this is provided by an enclosed vessel
acknowledged as a boiler. The functional steam or hot water under pressure is aimed at transferring
the heat to a process. Heat is transferred to a process using water as a cheap medium. The volume of
water upsurges about 1,600 times when it is boiled, the force produced is just about the similar as that
of an explosive of gunpowder. At this point the boiler becomes really dangerous tools that has to be
used with caution. Evaporation come about when a liquid is heated up to a vaporous phase.
(Forbesmarshall.com, 2018)

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The boiler system is made up of:
1. Feed water system
2. Steam system
3. Fuel system
Water is provided inside the boiler by means of feed water and is automatically directed to meet the
steam demand. The feed water is the water that is supplied to the boiler and then is vaporized to
steam. The sources of water feed are the returned condensed steam from the process and raw water
coming outside plant processes and boiler room. Produced steam is collected and directed by the
steam system. The steam is then controlled using a piping system to the point of use. Pressure gauges
are then used to check steam pressure and is controlled using valves. (Kabir, 2018)
Flame tube boiler

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Working principle of a flame tube boiler
The fuel is burnt inside a furnace in a flame tube boiler. Passing through the fire tubes is the hot gas
produced in the furnace. The heat energy of gases is transferred to the water surrounds them. This
results to a steam generation in the water, it comes up naturally and is stored upon the water in same
vessel of fire tube boiler. Then the utilizable steam for desirable purpose is taken out from the steam
outlet, through the feed water inlet water is fed into the boiler (Kabir, 2018)
Advantages of a flame boiler
? Easy to operate, use, clean and maintain
? Can be used in small scales industries
? The water is supplied in shell and outside tubes while hot gas is supplied inside tubes so the
water volume cannot be shaken easily when the fire tube boiler is running
? It is cheaper when compared to water tube boiler (Kabir, 2018)

Disadvantages of fire tube boiler
? There is a limit for steam generation capacity
? Steam cannot be produced at high pressure
? Heat exchanger does not use thermal radiator thus the efficiency of steam is bad
? In case of leakage of hot water or gas collected inside occurs it may cause serious accident

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? The time to raise a temperature and pressure is less than that required to fill water, from the
furnace side. (Kabir, 2018)
Types of flame tube boilers:
? Cornish boiler
? Lancashire boiler
? Locomotive boiler
? Scotch marine boiler
? Admiralty-type direct tube boiler
? Horizontal return tubular boiler
? Immersion fired boiler
? Velcon boiler
? Vertical fire-tube boiler (Kabir, 2018)

Water tube boiler
Water tube boiler is another type of a boiler in which the heating of water happens inside the tubes
and hot gases surrounding them. An opposite of flame tube boiler where by hot gasses pass through
tubes that surrounded by water. (Kabir, Kabir and profile, 2018)

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Working principle of water tube boiler
The working principle of this type of a boiler is easy. It has mainly two drums, the lower drum known
as mud drum and the upper drum know as steam drum. Riser tube and down-comer are tubes that
connect these two drums. The steam is produced by heating water in the mud drum and riser tube
connected to the mud drum and the steam naturally comes to the upper drum. Steam is then separated
from water naturally and store above the surface of water. At the upper drum cold water is fed through
the feed water inlet. Cold water is heavier than hot water in the lower drum and in the riser, hot water
is then pushed upwards through riser by cold water. (Kabir, Kabir and profile, 2018)

Advantages of water tube boiler
These types of boilers are essentially used in large thermal thus they have a number of different
advantages. (Kabir, Kabir and profile, 2018)
? There more numbers of water tubes used they help in archiving larger heating surfaces
? Movement of water is much faster than that of a flame tube boiler because of conventional
flow, thus the rate of heat transfer is high which results into higher efficiency
? Very high pressure in order of 140 kg/cm2 can be obtained smoothly. (Kabir, Kabir and profile,
2018)

Types of water boilers

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? Babcock & Wilcox boiler
? Stirling boiler
? La-Mont boiler
? Benson boiler
? Yarrow boiler
? Loeffler boiler (Kabir, Kabir and profile, 2018)

Water tube boiler components

Steam drum
Steam drum may be an assortment vessel for steam & water. Here water & steam is
separated. Its steam separators. Steam goes from prime facet to superheater & water goes
from the lowest through down comer Mud drum, then to chamber bottom ring headers (bottom
of chamber water wall). It has 2 sorts of exhausting arrangement (a) CBD- continuous blow down
used once Si02 or TDS is on the upper facet. (b) Emergency blow down is employed once drum
level is high. Boiler mountings and accessories just like the valve, water level gauge and gauge,
feed water recess affiliation area unit put in on this drum. Drum internals includes cyclone

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separators baffle plates rose pipe and therefore the dry pipe. The most perform of the steam
drum is to supply water storage and house to separate steam from water. (Functions, 2018)

Mud or water drum
Mud or water drum the lower drum is straightforwardly connected to upper steam drum with huge no
of straight tubes bundles called kettle bank tubes. Solids and mud can settle in this mud drum for
evacuation through occasional blow down. A few times desuperheater coil too introduced in this drum
to recoup warm from superheated steam. Depleting course of action of this drum is through one or
two evaporator blow down associations to control tds or to completely deplete the evaporator when
out of benefit. (Functions, 2018)
Water walls
Tubing course of action around the heater to extricate warm from fuel to produce steam is called
water divider circuit. These water dividers can be orchestrated in line course of action or amaze
course of action. Water dividers get the warm from radiation and around assimilate the 50% of the
overall warm created within the heater. (Functions, 2018)
Super heater
In the event that the temperature of the steam is over its immersion temperature at that point it is
called superheated steam. The super radiator (warm exchanger) is utilized to extend the temperature
of the steam. These are bundles of tall quality tube which can bear temperature 600C Depending upon
the fabric of tubes Generally SA-213 is utilized. In most mechanical water tube boilers the
superheater is put where vent gasses make their turn from the brilliant to the convection segment of
the kettle. There are three sorts of super radiators convection, brilliant and conv-radient super
radiators. (Functions, 2018)

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Economiser
Economizer (heat exchanger) is the evaporator adornment utilized to recoup the warm of pipe gas that
taking off the kettle by warming bolster water. The proficiency of an evaporator can be expanded with
an economizer. 60C rise in nourish water temperature with the assistance of economizer can spare up
to 1% of fuel. Regularly economiser is utilized some time recently the discuss radiator in vent gas
path of the kettle to extend the evaporator effectiveness. (Functions, 2018)
Air heater
Air is provided to an evaporator for combustion is pre warmed with the assistance of discuss radiator
by recouping the warm of squander vent gas that takes off the economizer. 20C rise in temperature of
combustion discuss can spare up to 1% of total fuel. Preheated discuss is additionally required for the
operation of pulverized coal furnaces. Primary discuss is required for drying coal within the
pulverizer. Air radiators are classified into two primary sorts’ recuperative Discuss radiators and
regenerative Discuss radiators. (Functions, 2018)

Boiler fans
For combustion of fuel within the boiler heater discuss is drawn from the environment and pushed
through the conduits with constrained draft fan to heater where discuss responds with fuel and gotten
to be pipe gas, the pipe gas is at that point extricated from the heater with the assistance of Initiated
draft fan. The fan utilized in huge water tube boilers are FD fans, ID fans, Essential discuss fans, and
Auxiliary discuss fans and Gas distribution fans. Other fundamental water tube kettle parts are
burning gear burners and heater and gas cleaning gadgets like ESP Violent wind Separators and pack
channels. (Functions, 2018

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Boiler water treatment
There mainly three objectives that a treatment and conditioning of boiler feed water must satisfy:
? Corrosion protection
? Continuous heat exchange
? Production of high quality steam
External treatment is important because it’s when impurities are removed from the water. When the
boiler system question is in and there are high impurities to be tolerated the external treatment is done.
There is a number of external treatment including softening, evaporation, deaeration, membrane
contractors etc. they can be used clean feed water. (Lenntech.com, 2018)
Internal treatment in is a type of treating where by impurities inside the boiler system. Inside the
boiler proper or the feed lines it is where reactions occur. The use of internal treatment is independent
to the external treatment but it can also be used in conjunction with the external treatment. Its aim is
to prevent boiler water foaming and act against feed water hardness, condition sludge, scavenge
oxygen. (Lenntech.com, 2018)
External treatment
Feed water is made up of daerate and the water treatment facility purity. Pure vapour is sometimes
produced by pre-treating water by evaporation and is condensed and used for boiler feed purposes.
Different types of evaporators are used to mention one which is very simple is a tank of water through
which coils of steams pass to heat water to the boiling point. Passing through coils in a second tank of
water of the vapour to produce additional heating and evaporation it helps to increase the efficiency.
When a steam is ready to use evaporators are suitable. If solids dissolved in the raw water are very
high, evaporators have certain advantages over demineralization. (Lenntech.com, 2018)
Internal treatment
Internal treatment is able to establish different treatment when boilers operate at low or moderate
pressure, when good quality raw water is available and when large amounts of condensed steam are
used for feed water. The aim of an internal treatment is to prevent any feed-water hardness from
precipitating on the boiler metal as scale, makes matter such iron oxide to be non-adherent to the
boiler metal. In prevention of boiler corrosion internal treatment plays a part by eliminating the
oxygen from water whilst providing alkalinity. In other words or in few words internal treatment is
aimed at preventing corrosion and topping of feed water system and act against corrosiveness in the
steam condensate systems. (Lenntech.com, 2018)

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There are different types of used for internal treatment of water mainly used, include phosphate-
dispersants, polyphosphate-dispersants also called softening chemicals. Natural and synthetic
dispersants, sequestering agents, oxygen scavengers, anti-forming. (Lenntech.com, 2018)
Phosphate-dispersants also referred to as softening chemicals, in order to neutralize the hardness of
water these chemical they form tricalcium phosphate, but first they react with alkalinity of the boiler
water. Tricalcium phosphate can be easily removed from the bottom of the boiler by blowing it down
and be disposed regularly on daily basis. (Lenntech.com, 2018)
Natural and synthetic dispersants, these products they upturn the dispersive properties of the
habituation products. These dispersive come in many form they can be natural polymers (tannins) or
they can be synthetic polymers (polyacrilates, polystyrene, sulphonates, etc.). (Lenntech.com, 2018)
Sequestering agents, the function of these products is to inhibit and implement the threshold effect.
Oxygen scavengers, the function of these products is to remove dissolved oxygen and oxides. They
also reduce the chemical reactivity of metal surfaces. When choosing a product and the dose it will
depend if the deaerating heater is used or not. (Lenntech.com, 2018)
To amend the surface tension of a liquid and to protect against carrying over of fine water particles in
the steam and to remove the foam, anti-foaming agents play this above mentioned role.
(Lenntech.com, 2018)

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Comparison between flmae tube boiler and water tube boiler.
In Fire-tube boilers hot vent gasses pass through tubes and water encompasses them. In Water-
tube boilers water passes through tubes and hot pipe gasses encompass them. These are worked
at moo weights up to 20 bar. The working weight is tall sufficient, up to 250 bar in super basic
boilers. The rate of steam era and quality of steam are exceptionally moo, subsequently, not
reasonable for control era. The rate of steam era and quality of steam are superior and
reasonable for control era. Stack variances cannot be dealt with. Stack vacillations can be
effectively taken care of. It requires more floor region for a given yield. It requires less floor
range for a given yield. These are bulky and troublesome to transport These are light in weight,
subsequently transportation isn’t a issue. Generally proficiency is up to 75%. By and large
proficiency with an economizer is up to 90%. Water doesn’t circulate in a unequivocal course.
Course of water circulated is well characterized.

The drum measure is huge and harm caused by bursting is huge. In case any water tube is
harmed, it can be effortlessly supplanted or repaired. Basic in plan, simple to erect and moo
support taken a toll. Complex, plan, troublesome to erect and tall upkeep fetched. Indeed less
expertise administrators are adequate for proficient operation. Gifted administrators are
required for operation. The treatment of nourish water isn’t exceptionally fundamental, as
overheating due to scale arrangement cannot burst thick shell.Treatment of nourish water is
exceptionally fundamental as little scale stores interior the tubes can cause overheating and
bursting. Utilized in prepare industry. Utilized in expansive control plants. (Team and Team,
2018)

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Conclusion
Water-tube and fire-tube boilers are total alternate extremes in terms of the area of the water
relative to the hot gasses coming about in water-tubes boilers being intrinsically more productive in
terms of the warm exchange. Producers of fire-tube condensing boilers have created different
strategies to overcome this inalienable shortage, where the warm exchange efficiencies are
comparative for both plans. At moo yield capacities, fire-tube condensing boilers have a littler
impression when compared to a water-boiler of the same capacity. It ought to be famous that the
evaporator exhibitions can be comparable in any case of whether employing a water-tube or fire-
tube, where efficiencies of up to 95% can be accomplished, depending on the producer and
arrangement. In any case, at higher capacities, water-tube boilers may beat their fire-tube partner in
terms of effectiveness and reaction time.
Too, at these higher capacities, the measure and weight of the fire-tube boilers may essentially
increment compared to the water-tube plan. Most imperatively, water-tube boilers are inalienably
more secure in operation than their fire-tube partners where a genuine issue may result in an blast
of the fire-tubes evaporator; whereas the water-tube evaporator may result in a tube leak. There is
no culminate condensing evaporator plan within the world, on the off chance that there was one,
we would as it were be fabricating and promoting as it were that one plan. It is hence imperative to
have an understanding of the distinctive sorts of condensing boilers and how each plan may be
advantageous to meet the prerequisites of your framework.

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Reference List

Boilers.guide. (2018). Working Principle | Boilers Guide. Online Available at:
http://www.boilers.guide/working-principle/ Accessed 17 Oct. 2018.
Person, Fire Tube Boiler | Operation and Types of Fire Tube Boiler. Electrical Engineering and
Technology. Available at: https://www.electrical4u.com/fire-tube-boiler-operation-and-types-of-fire-
tube-boiler/ Accessed October 17, 2018.
Electrical4u.com. (2018). Water Tube Boiler | Operation and Types of Water Tube Boiler. online
Available at: https://www.electrical4u.com/water-tube-boiler-operation-and-types-of-water-tube-boiler/
Accessed 17 Oct. 2018.
Electrical4u.com. (2018). Water Tube Boiler | Operation and Types of Water Tube Boiler. online
Available at: https://www.electrical4u.com/water-tube-boiler-operation-and-types-of-water-tube-boiler/
Accessed 17 Oct. 2018.
Kabir, R. (2018). Fire Tube Boiler. online Mech-engineeringbd.blogspot.com. Available at: http://mech-
engineeringbd.blogspot.com/2016/07/fire-tube-boiler.html Accessed 17 Oct. 2018.

Lenntech.com. (2018). Boiler water treatment – Lenntech. online Available at:
https://www.lenntech.com/applications/process/boiler/boiler-water-treatment.htm Accessed 17 Oct.
2018.
Forbesmarshall.com. (2018). What is a Boiler: Introduction to Boilers. online Available at:
https://www.forbesmarshall.com/fm_micro/news_room.aspx?Id=boilers;nid=177 Accessed 18 Oct.
2018.
Functions, W. (2018). Water tube boiler parts and functions – Boilersinfo. online Boilersinfo. Available
at: https://boilersinfo.com/water-tube-boiler-parts-functions/ Accessed 18 Oct. 2018.
Team, M. and Team, M. (2018). Comparison Between Fire Tube and Water Tube Boiler. online ME
Mechanical. Available at: https://me-mechanicalengineering.com/comparison-between-fire-tube-
boiler-and-water-tube-boiler/ Accessed 18 Oct. 2018.