CJEPSR Vol24 No5 March 2022-8

International Journal of Engineering Processing & Safety Research Vol. 24 No.
5
March, 2022.
Published by Cambridge Research and Publications
DESIGN AND FABRICATION OF A HORIZONTAL

WATER TUBE BOILER
SMART BELLO1, OLAWEPO B. B.1 AND AJAYI R.

POLAM2
1
Department of Mechanical Engineering Technology, School of Engineering
Technology. Auchi Polytechnic Auchi, Edo State. 2Department of Chemical
Engineering Technology, School of Engineering Technology. Auchi
Polytechnic Auchi, Edo State.
ABSTRACT
Introducing modern boiler concepts in the design of thermal power stations is
nowadays becoming mandatory, not only from an economic point of view of
new investments, but also as a significant and pro-active step towards the
reduction of greenhouse gases & dust emissions by the enhancement of
efficiency. The increase in the cycle efficiency in modern power station is mainly
achieved by increasing the steam parameters. In addition to elevated steam
parameters, other measures such as double reheat design and increased boiler
efficiency are the key factors to achieve the desired maximization in heat rates.
The aim of this project was to design and fabricate a water-tube boiler using a
diesel fired burner (C13H25)9 to generate 80kg of steam per hour. The boiler
tank is made of pure mild steel. Mild steel is used to fabricate the water tubes
and other parts such as the furnace, smokestack and return chamber that make
up the boiler. The heating surface area was increased for sake of efficiency and
fast steam generation by reversing the direction of the gas through a second
and third parallel tube (three pass). The boiler (which is fired by a diesel
burner) generates dry saturated steam at a pressure of 1 bar and temperature
of 111.4oC. It can be used for domestic and industrial purposes.
INTRODUCTION
Steam is a critical resource in today’s industrial world. It is used in the
production of goods and food, the heating and cooling of large buildings, the
running of equipment, and the production of electricity. The system in which
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International Journal of Engineering Processing & Safety Research Vol. 24 No.5
March, 2022.
steam is generated is called a boiler or a steam generator (Woodruff et al.,

2004). Steam generators may be of different shapes and sizes, depending on
their applications. Steam generators have been in use for a very long time and
over the course of time, various inventors and engineers have developed and
modified them for the purpose of academic study, as well as to suit the needs of
the modern man. As a result of their continuous success, many industries today
depend greatly on steam for the operation of their equipment and the production
of their goods.
Steam is therefore important in engineering and energy studies. In science and
engineering laboratories, there is sometimes the need to utilize steam or hot
water to generate power, to carry out tests or for other heating applications. This
steam or hot water can be obtained using boilers. Therefore, the purpose of this
project is to design a miniature water-tube laboratory boiler that can be
manufactured to meet the needs of schools for practical demonstrations and
teaching aid (Rajput, 2006).
A boiler is a closed vessel in which steam is produced from water by combustion
of fuel. According to the American Society of Mechanical Engineers (ASME),
a steam generating unit is defined as a combination of apparatus for producing,
furnishing or recovering heat together with the apparatus for transferring the
heat so made available to the fluid being heated and vaporized (Rajput, 2006).
Steam boilers is made up of two major parts, that is, the combustion chamber,
which provides heat by the combustion of fuel, and the heat exchanger which
transforms water into steam through heat exchange in the medium (Saidur et
al., 2010). Boiler types comprises of fire tube, water tube, modular, coil tube
and cast iron respectively. Steam boilers could be used for various services,
such as, steam process and heating, hot water heating, power generation,
petrochemical processes, chemical recovery, nuclear, just to mention a few
(Ray, et al., 2003).
Several boilers are designed to withstand the stress induced in the boilers
(Woodruff et al., 2004). In a boiler, water is heated, steam is generated or
superheated, or any combination thereof, under pressure or vacuum by the
application of heat resulting from the combustion of fuel (such as in a natural
gas boiler), electrical resistance heating or the recovery and conversion of
normally unused energy (Rawson, 2008). Many different solid, liquid and
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March, 2022.
gaseous fuels are fired in boilers. Sometimes, combinations of fuels are used to
reduce emissions or improve boiler performances. Fuels commonly fired in
boilers include fossil, biomass, and refuse-derived fuel (RDFs) as well as others
types of fuels and fuel combinations (Boiler Fuels and Emissions, 2009). For
effective teaching and learning, well equipped laboratories and subject rooms
are needed. However, many educational institutions lack the necessary
equipment for effective teaching and learning (Adeyinka, 1992).
The word 'boiler', in everyday use, covers a wide range of equipment, from
simple domestic hot water boilers to boilers housed within a power generation
plant to convert fossil fuel to electricity. Generally, domestic hot water boilers
do not produce steam and should operate at low pressure. While some
combination boilers now operate at the pressure of the incoming cold water
mains, this is still far below the normal operating pressure of steam-raising
boilers. As steam driven engines replaced the horse, as a means of motive
power, it followed that steam driven engines were rated in 'Horsepower'. Boiler
design progressed from what was essentially a kettle to a relatively large-
diameter flue pipe submerged in water - thus the first water-tube boiler, as
power and pressure requirements increased, boilers became larger and the
single-flue pipe became a larger number of smaller diameter flue tubes
combined with an external, or internal, furnace for the combustion of the fuel.
The modern-day 'modified Scotch Marine' boiler, generally comprising
horizontal steel furnace combustion chambers) and/or fire-tube convective
pass(es), in 'dry-back' or 'waterback' configurations, owes its heritage to these
early multi-tube boilers and their application in ships constructed on Scotland's
River Clyde (Rawson, 2008).
The primary application of the boiler was still motive power; whether for
pumping water from mines, driving machinery in mills, propelling steam
locomotives or ships. Therefore, boiler ratings were based on the size of the
steam engine that they were capable of driving. The quantity of steam required
to operate a 1 horsepower steam engine became known as 1 Boiler Horsepower.
(Note that the watertube boiler was not prevalent until after the first water-tube
boiler design patent of 1867; thus, the term Boiler Horsepower (Bhp) has been
associated with fire-tube boilers from the earliest days of boiler development)
(Rawson, 2008).
Boilers often contain elements that become corrosive when concentrated far
beyond normal values as a result of the design problem. The frequent
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March, 2022.
contributor to waste heat boiler problem is the uneven distribution of gases

across the inlet tubes at the hot end. This causes unequal stresses and distortion
and leads to mechanical stress and fatigue problems (Rawson, 2008).
The use of horizontal hairpin tube configurations with inadequate forced
circulation of water through the tubes often permits stratification of steam and
water. This often leads to stream blanketing of caustic corrosion problem.
Due to the high demand of electricity to power our electronics and other systems
which make use of electricity. We find the use of boiler to generate steam which
will be used to turn turbines useful. The turbine will on the other hand generate
electricity as its end product which every living thing will benefit from
(Rawson, 2008). In order to find alternative means to generate power apart from
solar, hydroelectricity generation, boiler is used to generate steam which will
be used to turn turbine and the material use for the production are locally
available and cheap. The objective of the project is to design and construct a
horizontal water tube boiler.
MATERIALS AND METHOD

Basic Design Requirements
Criteria which govern the design and manufacture of the water-tube boilers
include:
• Compliance with the ASME Boiler and Pressure Vessel Code.
• Compliance with required safety and installation Codes.
• The ability to meet the required efficiency and other performance
standards.
• The ability to meet the required level of pollutant emissions,
• Compliance with the requirements of the National Board of Boiler and
Pressure Vessel Inspectors through local
• The ability to meet the perceived needs of the customer in terms of
operational performance, reliability and maintenance costs.
• The ability to produce a competitively priced product
Water-tube boiler manufacturers have established over the years that these
criteria can be satisfied with varying heating surface specifications.
Design Specification
The water tube boiler consists of various components and it will be of great
importance to have a detailed specification before the design. The arrangement
of the water-tube boiler is illustrated below. The diesel burner used to heat up
the furnace of the water-tube has the following specifications:
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March, 2022.
• Mass firing rate = 2.5 – 5 kg/hr

• Orifice diameter for exit (d) = Ø0.0005 m
• Motor rating = 0.5 horse power.
The burner is connected to the furnace by the means of both external and
internal circular flange (a projecting collar, rim, or rib on an object for fixing it
to another object, holding it in place or strengthening it. Flanges are often found
on pipes and shafts) of both the burner and furnace respectively. The flange
specifications are given as follows;
• Outer diameter of circular flange (do) = Ø0.017 x 2 m
• Inner diameter of circular flange (di) = Ø0.013 x 2 m
• Number of opening for bolts and nuts of flange = 4 openings
• Diameter of the bolts and nuts used (db) = Ø00.014 m
The furnace which is located inside the boiler pressure vessel (shell) and
situated at one end of 5 section of longitudinal water-tubes connected to it
serially which elongates the path of the hot gases, thus expanding the heating
surface. The idea of placing the furnace inside the boiler shell is to maximize
the heat of the boiler rather than losing it to the surrounding. The furnace serves
as a pre-heater in this case as it raises the temperature of the water.
The water-tubes extend to a compartment known as the return chamber situated
at another end in the boiler vessel (shell). The return chamber itself which is
serving as an intermediary for hot gases transfer has another set of 5 water-tubes
connected to it in the same manner as that at the furnace. This was done to
further increase the heating surface area by making the gases reverse direction
through a second 5 sets of parallel tubes. The heat emitted by this other set of 5
longitudinal water-tubes at the return chamber goes out from a smoke stack.
The following are the specifications of the inner components in the boiler vessel
(shell):
i. Total of 15 pieces of water-tubes
ii. A furnace
iii. Two return chamber
iv. Smoke stack.
Design Consideration for Material Selection
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March, 2022.
For an intelligent design to be done, the knowledge of the materials available as

well as the properties they possess are very important For the selection of the
proper material to be used for the design of the water-tube boiler, we shall
consider the factors which affect the choice of material selected and used for
design and there reasons.
Factors considered are:

1. Suitability of the material for the working conditions in service,
considering characteristics such as; appearance, thermal conductivity,
rate of emissivity, strength, stiffness, creep, etc.
2. Availability of the material: the ease at which the materials are seen or
purchased in the market.
3. Workability of the material: considering possible methods of processing
material selected into desired shape such as; weldability, machinability,
formability, and workability.
4. Expected load or force as well as adequate strength in conformity so as
to function satisfactorily without failure.
5. Cost of the material (economic consideration).
Choice of Material
Based on the above considerations, the materials used for the design of the
water-tube boiler were thus selected and tabulated below;
Table 3.1: Materials Used and Reasons
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March, 2022.
Design of Component Parts of the Water Tube Boiler

Having completed the material selection for the water-tube boiler, the design of
the various parts of the boiler is typified by the following features;
• The volumetric boiler pressure vessel (tank or shell).
• The furnace.
• The water-tube.
• The return chamber.
• The smoke stack.
• Actual volumetric capacity of the boiler.
• Pressure gauge.
• Temperature gauge.
• Safety valve.
Design of the Volumetric Boiler Pressure Vessel

The boiler volumetric tank measures the quantity of water delivered to it at a
given time. It has a capacity of 292 liters and it is made of steel metal of 0.006
m thickness for pressure resistance, Ø0.62 m and length of 0.76 m three holes
were bored on the surface of the tank for both steam outlet (Ø0), turbine outlet
(Ø0.50 m) and exhaust or smokestack outlet (Ø0.05 m). A hole of Ø0.178m is
also provided at one end of the longitudinal section of the tank for the cylindrical
furnace placed inside it. Other dimensions are as follows;( (Baoyou, et al.,
2006).
Volumetric capacity of the drum (tank) = volume of cylinder + volume of
hemisphere.
2
𝑉 = 𝜋𝑟 2 × 𝐿 + 𝜋𝑟 3 −−−1
3
To know the maximum pressure and temperature of the boiler, using the hoop
law; We know that, Tensile stress of a mild steel = 60 Mpa Ultimate tensile
stress of a mild steel = 410Mpa.
Hoop stress of mild steel = 140Mpa Pressure of steam at 111.4oC (p) = 1.5bar
= 0.15Mpa
Thickness of pressure vessel (t) = 6mm Diameter of vessel (d) = 620mm
The hoop of stress of the steam
𝑝×𝑑
𝜎ℎ = −−−2
2𝑡
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March, 2022.
The estimated maximum pressure of the vessel

σmax × 2t
Pmax = −−−3
620
Design of the Furnace

The furnace made of mild steel located at one end of the boiler connected to a
heat supply (diesel burner located outside the boiler vessel) in this case by
means of a flange with specifications stated above, serves as the central system
for heat (hot gases) distribution to the water tubes. The furnace has a length of
0.40m, thickness 10mm and a diameter of 0.170m. Other dimensions are given
below;
𝜋𝑑 2
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑢𝑟𝑛𝑎𝑐𝑒 = ×𝐿 −−−4
4
0.172
=𝜋∙ × 0.40
4
= 0.0091 m3
Design of the Water-Tubes
The water-tubes made of mild steel is a total 15 in numbers and is sub-divided
into three sections namely
• Furnace section = 5 water-tubes of length 0.30m and diameter
0.030m each.
• Return chamber section = 5 water-tubes of length 0.30m and diameter
0.030m each.
• The third pass section (section to the smokestack) – 5 water-tubes of
length 0.50m and diameter 0.030m each.
Other dimensions are as shown;
Volume of the water-tubes in the furnace section
𝜋𝑑 2
4
0.032
=𝜋∙ × 0.3
4
= 0.001061 m3
Volume multiplied by the number of water-tubes on this section
Volume of water-tubes in the return chamber section
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March, 2022.
𝜋𝑑 2
4
0.032
=𝜋∙ × 0.3
4
= 0.001061 m3
Volume of water-tubes in the third passes section
Volume of water-tubes in the return chamber section
𝜋𝑑 2
4
0.032
=𝜋∙ × 0.5
4
= 0.001767 m3
Design of the Return Chamber

The return chamber made of mild steel which serves as an intermediary
of heat transfer between the above mention sets of water-tubes has a length of
0.15m and diameter of 0.30m.
The volume of the return chamber
𝜋𝑑 2
4
0.32
=𝜋∙ × 0.15
4
= 0.010603 m3
Design of the Smokestack (Exhaust)

The smokestack made of mild steel used to transport the flue out of the system
has a length of 0.20 m and diameter of 0.15 m (Cengel and Boles, 2006).
The volume of the smokestack
𝜋𝑑 2
4
0.152
=𝜋∙ × 0.2
4
= 0.0035343 m3
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March, 2022.
Actual Volumetric Capacity of the Boiler

Actual capacity (i.e. volume) of the boiler = volume of the drum - total volume
of the inner compartment of the boiler.
Volumetric capacity of the drum = 292 liters
𝑇𝑜𝑡𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒𝑡𝑟𝑖𝑐 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑖𝑛𝑛𝑒𝑟 𝑐𝑜𝑚𝑝𝑎𝑟𝑡𝑚𝑒𝑛𝑡𝑠
= 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑓𝑢𝑟𝑛𝑎𝑐𝑒 + 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟
− 𝑡𝑢𝑏𝑒𝑠 𝑜𝑛 𝑒𝑎𝑐ℎ 𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑠
+ 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑟𝑒𝑡𝑢𝑟𝑛 𝑐ℎ𝑎𝑚𝑏𝑒𝑟
+ 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑚𝑜𝑘𝑒𝑠𝑡𝑎𝑐𝑘
= {0.0091 m + (0.001061 m3 + 0.001061 m3 + 0.001767 m3) + 0.010603 m3 +
3
0.0035343 m3}
= 0.0271263 m3 Therefore,
Actual capacity of the boiler = 0.2918431m3-0.0271263m3 = 0.2647168m3 =
264.721iters
Thermal Design Calculation

The thermal design calculation involves the heat transfer from all heat sources
located in the boiler as outlined:
• Furnace heat transfer calculation.
• Water-tubes heat transfer calculation
• Return chamber heat transfer calculation.
• Smokestack calculation.
Furnace Calculation
The sensible heat loss of flue gas at furnace exit =
= 𝑚 × 𝐶𝑝 × ∆𝑇 − − − 10
Where; m = mass of flue gas (kg)
Cp = specific heat of flue gas
T = (flue gas temperature - ambient temperature) in oC
Theoretical air required from air fuel ratio
Mass of flue gas [mg (P)] = ma + mf
Heat loss = Mp x Cp x ∆T
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March, 2022.
Radiation heat transfer from furnace

𝑄𝑟𝑎𝑑 = 𝜀𝜎(𝑇ℎ4 − 𝑇𝑐4 )𝐴𝑐 − − − 11
Where; qrad = heat transfer per unit time (W)
𝜎 = Stefan Boltzmann const = 5.6703 x l0-8 (w/m2k4)
𝜀 = emissivity of material (mild-steel) used = 0.32
Th, = hot body absolute temperature (K) = temperature of water = 565oC =
838ok
Tc = cold surroundings absolute temperature = temperature of furnace = 30oC
= 303ok
Ac = area of the object (m2)
d = l 70mm: Ac = 0.02271m2
Convective heat transfer from furnace

𝑄𝑐𝑜𝑛𝑣 = ℎ𝑐 × 𝐴 × ( ∆𝑇) − − − 12
Where; hc - convective heat transfer coefficient (w/m2k) = 250w/m2k
d = heat transfer diameter (m) = 0.17m,
𝜋𝑑 2
𝐴= = 0.02271 𝑚2
4
∆𝑇 = (temperature of furnace - temperature of water) ok
L = length of furnace = 40cm = 0.4m
Conduction heat transfer from furnace

𝐾𝑐 × 𝐴 × ∆𝑇
𝑄𝑐𝑜𝑛𝑑 = − − − 13
𝑙
Where; Kc = thermal conductivity coefficient (w/mk) = 59w/mk
l = length of furnace
Th - hot body absolute temperature
(K) = temperature of water
Tc = cold surroundings absolute temperature = temperature of furnace
Ac = area of the object (m2)
Efficiency of Furnace
Thermal efficiency of the furnace by direct method;
Mf = fuel consumption or mass flow rate
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March, 2022.
𝑇ℎ𝑒𝑟𝑚𝑎𝑙 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑢𝑟𝑛𝑎𝑐𝑒

Heat output from the burner
= × 100 −−
Heat in the fuel consumed (heat input)
− 14
Heat output from burner = 55kw
𝐻𝑒𝑎𝑡 𝑖𝑛 𝑡ℎ𝑒 𝑓𝑢𝑒𝑙 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑
kJ
GCV of diesel ( )
kg
= × 100 − − − 15
kg
fuel consumption rate ( )
hr
Radiation heat transfer from furnace to the Return Chamber Section
𝑄𝑟𝑎𝑑 = 𝜀𝜎(𝑇ℎ4 − 𝑇𝑐4 )𝐴𝑐 − − − 16
Convective heat transfer from furnace to the Return Chamber Section

𝑄𝑐𝑜𝑛𝑣 = ℎ𝑐 × 𝐴 × ( ∆𝑇) − − − 17
d = heat transfer diameter (m) = 0.17m,
𝜋𝑑 2
𝐴= = 0.02271 𝑚2
4
∆𝑇 = (temperature of furnace - temperature of water) ok
L = length of furnace = 40cm = 0.4m
Conduction heat transfer from furnace to the Return Chamber Section

𝐾𝑐 × 𝐴 × ∆𝑇
𝑄𝑐𝑜𝑛𝑑 = − − − 18
𝑙
Where; Kc = thermal conductivity coefficient (w/mk) = 59w/mk
𝜋𝑑2
d = heat transfer diameter (m) 0.03 = d x 5 = 0.15m, 𝐴 = = 0.017671m2
4
∆T = (temperature of furnace - temperature of water) °k
L = length of furnace 0.3 = Lx5 = 1.5m
59 × 0.0177 × 535
𝑄𝑐𝑜𝑛𝑑 = = 371.87w
1.5
Return Chamber Heat Transfer Calculation
Radiation Heat Transfer
𝑄𝑟𝑎𝑑 = 𝜀𝜎(𝑇ℎ4 − 𝑇𝑐4 )𝐴𝑐 − − − 19
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March, 2022.
Convective Heat Transfer

𝑄𝑐𝑜𝑛𝑣 = ℎ𝑐 × 𝐴 × ( ∆𝑇) − − − 20
Conduction Heat Transfer

𝐾𝑐 × 𝐴 × ∆𝑇
𝑄𝑐𝑜𝑛𝑑 = − − − 21
𝑙
Where; Kc = thermal conductivity coefficient (w/mk)
Amount of Steam Generated

The amount of steam generated is calculated from the formula below;
𝑞𝑡
𝑀𝑠 =
ℎ𝑒
Where: Ms - mass of steam (kg/h)
qt = calculated total heat transfer (kw)
he = evaporation energy of steam (kj/kg)
From steam table; under saturated steam of Psat at 111.4oC
Boiler Efficiency
This is also known as 'input - output method' (Cengel and Boles, 2006)
due to the fact that it needs only the useful output (steam) and the heat input
(i.e. fuel) for evaluating the efficiency. This efficiency can be evaluated using
the formula;
ℎ𝑒𝑎𝑡 𝑜𝑢𝑡𝑝𝑢𝑡
𝐵𝑜𝑖𝑙𝑒𝑟 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = × 100
ℎ𝑒𝑎𝑡 𝑖𝑛𝑝𝑢𝑡
37.93
= × 100
55
= 68.96%
≈ 69%
Construction of the Water Tube Boiler

A horizontal steam and water drum which is supported by a steel structure at a
certain height and is independent of brick works. A bundle of steel tubes were
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March, 2022.
connected to the uptake header (water box) by a short tube and the rear end is
connected to the down take header (water box) by a long tube. In between the
headers, a number of small-diameter steel tubes are fitted at angle of 5° to 15°
with the horizontal to promote the water circulation. These steel tubes are
arranged in the combustion chamber in a zigzag way so that more surface area
of the tube is exposed to hot gases. The combustion chamber is the space above
the grate, below the front end of the drum where combustion of fuel takes place.
This chamber enclosed by brickwork and is lined from inside by fire bricks.
Doors are provided to give access for cleaning, inspection and repairing. The
combustion chamber is divided into three separate compartments above the
furnace is the hottest and the last chamber is of lowest temperature. This makes
the path of hot gases longer before leaving the boiler through the chimney. The
super heater is placed between the drum and water tubes. Dampers are provided
at the rear end of the chamber to regulate the fresh air supply for maintaining
proper combustion of fuel. The safety and control devices are also provided
(Kitto and Stuitz, 2005).
Operation of the Water Tube Boiler

The water in Babcock and Wilcox boilers pumped by a feed pump and it enters
the drum through the feed check valve up to the prespecified level so that the
headers and tubes are always flooded. When the combustion takes place above
the grate, the products of hot gases come out and rush through each
compartment of the combustion chamber. Hence, the rear part of the tubes has
lowest temperature and the front part of the tubes as highest temperature. Due
to continuous heat supply, some of the water gets vaporized into steam inside
the tubes and mixture of water and steam enters the boiler drum through the
uptake header. The cold water from the boiler drum comes down through the
uptake header and enters the lower end of the water tubes for getting heated
further. This natural circulation is called thermosiphon system (Baoyou, et al.,
2006).
The steam generated gets collected in the steam space above water space in the
boiler drum. In order to remove all water particles from the steam, it is finally
through the superheating. The superheated steam is then available for use.
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March, 2022.
RESULTS AND DISCUSSION

The fabricated water tube boiler was tested to evaluate its performances,
efficiency and determine its evaporation ratio. The purpose of the performance
test is to determine the actual performance and efficiency of the oiler and
compare it with design values or norms. It is an indicator for tracking day-to-
day and season-to-season variations in boiler efficiency and energy efficiency
improvements.
When the burner is turned on and ignition occurs which produces the required
water in the furnace inside the furnace, a hot flue gas is produced which is forced
through the water tubes (by the he p of blower in the burner) and heat is thus
transferred into the water which in turn results in production of the required
steam that may be used for industrial purposes.
Result
The result in this case is a torque produced at a steam pressure of 1.5bar and a
steam temperature of 111.4oC also raising the temperature of the water from
30oC to a generated steam quantity of 61.34kg/hr, with a diesel quantity of
5.2Htres/hr. The efficiency of the burner after getting an adequate combustion
air/fuel ratio and heat delivery from the burner resulted into 64.3%. The
efficiency of the boiler was also calculated to be 69%. The detailed description
of other parts are shown in table 4.1.
Table 4.1: Summary of details and operational data of steam boiler

S/N DETAILS DESCRIPTION OF VALUES
1 Orientation Horizontal
2 Type of tube Water tube
3 Type of firing Internally fired
4 Type of circulation Natural circulation
5 Type of pressure Low pressure
6 Stationary or portable Stationary
7 Single or multi – tube Multi tube
8 Number of water tubes 3
9 Operating feed water temperature 80oC
10 Operating steam temperature 151.8oC
139
March, 2022.
11 Operating steam pressure 500 kN/m2 (5 bar)

12 Combustion fuel Diesel
13 Operating steam capacity 5.65 tons/hr
14 Firing rate 483.84 kg/hr
15 Boiler capacity 18.87 GJ/hr
16 Material used for boiler shell Mild steel A 36
17 Materials used for boiler insulation Brick
Discussion of the Results

Good boiler design practices must take into account the operation of the boiler
and not simply the heat transfer, parameters that a good boiler design addresses
include;
a. Ample furnace volume must be included to absorb a significant portion of
Radiative heat transfer and allow the low NOx burner designs to function.
b. Optimized pressure drop across the boiler convective passes, the pressure
drop determines the fan size required for the boiler application.
c. Ample steam storage and steam height. The volume of steam and distance
from the steam nozzle to the normal water level determine to a very large
extent the steam quality and the amount of water that will be carried over
into the system. Boiler design and optimization programs have been
written to determine the performance of water-tube boilers. These
programs can be applied to analyze a wide variety of the boiler scenarios
for many different boiler applications extending from simple gas water
systems to complex waste heat applications.
In-flame gas temperature data for lire-tube boilers has been obtained.
The data follows expected trends and has been very useful in the validation of
predictive optimization models. This data is compared to predicted results from
computational fluid dynamic combustion models and good agreement has been
found. This data is used to optimize furnace and heat transfer surfaces for typical
water-tube boilers. Gas temperatures measured at the entrance to the convective
tube surfaces provided excellent data that validated the heat transfer sub-models
augmented surface tubes have proven to be a valuable resource in the design of
water-tube boilers for many special applications. The advantages of thee
augmented tube are that it allows the designer to include larger steam storage
140
March, 2022.
and steam height resulting in higher steam quality and rapid load swing
handling ability. Using the augmented tube also allows the designer to have a
lower overall pressure drop with a boiler efficiency that is still over 81%. The
augmented tube boiler may be used to reduce the boiler shell diameter and still
maintain standard steam volumes, steam heights, and boiler efficiency.
The following are the features of the fabricated water tube boiler that makes it
more advantageous than others:
1. Generation of steam is much quicker due to small ratio of water content
to steam content. This also helps in reaching the steaming temperature in
short time.
2. Its evaporative capacity is considerably larger and the steam pressure
range is also high-200 bar.
3. Heating surfaces are more effective as the hot gases travel at right angles
to the direction of water flow.
4. The combustion efficiency is higher because complete combustion of
fuel is possible as the combustion space is much larger.
5. The thermal stresses in the boiler parts are less as different parts of the
boiler remain at uniform temperature due to quick circulation of water.
6. The boiler can be easily transported and erected as its different parts can
be separated.
7. Damage due to the bursting of water tube is less serious. Therefore, water
tube boilers are sometimes called safety boilers.
8. All parts of the water tube boilers are easily accessible for cleaning,
inspecting and repairing.
9. The water tube boiler's furnace area can be easily altered to meet the fuel
requirements diesel fuel
Diesel Fuel Specifications

Every fuel has a unique composition and energy content described by its fuel
specifications presented in Table 4.2. Knowing the fuel specifications is
essential for determining various combustion parameters.
141
March, 2022.
Table 4.2: Fuel specifications for diesel

Property Value
% Carbon (C ) 85.54
% Hydrogen (H) 12.46
HHV (Gross heating value) kJ/kg 45, 482.52
LHV (Net Heating Value) kJ/kg 42, 790.21
CO2 max 15.60
% Sulphur (S) 1.60
% Moisture (M) 0
% O2 [100 – (C+H+S+M)] 0
Dimensional details of Designed Steam Boiler

Determined dimensional details of the designed steam boiler are presented in
Table 4.3.
Table 4.3: Summary of dimensional details
S/N Details Description/value
1 Diameter of boiler shell 0.5 m
2 Length of boiler shell 1m
3 Thickness of insulation 0.0625 m
4 Diameter of water tubes 0.035 m
5 Length of water tubes 0.6 m
6 Thickness of water tubes 2.5 m
7 Thickness of boiler shell 6.25 mm
8 Volume of fuel tank 0.027 m3
Thermodynamic details of Designed Steam Boiler

Determined thermodynamic details of the designed steam boiler are presented
in Table 4.4.
Table 4.4: Thermodynamic properties of material streams of the boiler

Substances Mass flow Temperature Enthalpy Entropy
o
rate (kg/s) ( C) (kJ/kg) (kJ/kgk)
Air ma 2.2848 40.00 313.26 1.7446
Fuel mf 0.1344 1, 051.31 42, 790.21 2.0185
142
March, 2022.
Hot products mp 2.4192 186.67 2, 673.09 4.0922

Feed water mw 1.5692 80.00 334.90 1.0750
Steam, ms 1.5692 151.80 2, 749.00 6.8220
Exhaust fuel gas 2.4192 150.10 225.77 2.0449
mg
Conclusion
The water tube boiler designed was projected from the conceptual physical
geometry tube boilers which elucidated the primary units making up a boiler.
Thermodynamics, heat transfer and strength of materials analysis subjected to
temperature and pressure variations were conducted in the theoretical
framework of the laboratory fire-tube steam boiler. Conclusively, a simple
laboratory water tube steam boiler is herein presented for fabrication, testing
and further improvement. Production of a simple steam boiler of this sort will
enable the availability of portable and affordable steam boilers for steam
generation processes, especially in school laboratories. The availability of steam
boilers in school laboratories will enhance students’ learning process, especially
in the area of thermodynamics, heat transfer and energy studies.
Recommendation
Having achieved the set objectives of this work, the following recommendations
are therefore made from the work:
i. Safety. The boiler is safe under operating conditions.
ii. Accessibility. The various parts of the boiler are accessible for repair and
maintenance.
iii. Capacity. The boiler should is capable of supplying steam according to
the requirements.
iv. Efficiency. To permit efficient operation, the boiler should be able to
absorb a maximum amount of heat produced due to burning of fuel in
the furnace.
v. It is simple in construction and its maintenance cost is low.
vi. Its initial cost is low.
vii. The boiler has joints exposed to flames.
143
March, 2022.
Although the objective of this work was achieved, there is need to modify the
already existing work in order to achieve higher efficiency:
i. Other pre-heater devices should be applied.
ii. Feed water pump should be applied for higher efficiency.
REFERENCES
Adeyinka A. A., “Current Problems of Educational Development in Nigeria”, [online],
Available: https://www.unilorin.edu.ng/journals/education/ pdf, Accessed: October 30,
2010, 1992.
American Society of Mechanical Engineers (ASME) 2010 Boiler and Pressure Vessel Code
(BPVCK http://go.asmc.org /bpvc10.
Baoyou, Z., Zhonghong, L., Yuexian, C. & Xigang, F. (2006). Analysis of a boiler pipe
rupture, Engineering Failure Analysis, 13: 75-79, 2006.
Cengel, Y. A. and Boles, M. A., (2006) "Thermodynamics: An Engineering" Approach, 5 th
Edition, McGraw Hill, Companies Inc.
Department of Energy (DOE) Fundamentals Handbook "Thermodynamics, heat transfer, and
fluid flow" U.S. Department of Energy, Washington, D.C. [Online].
Husain, A. & Habib, K. (2005). Investigation of tubing failure of super-heater boiler from
Kuwait Desalination Electrical Power Plant, Desalination, 183: 203-208, 2005.
Khajavi, M.R., Abdolmaleki, A.R., Adibi, N. & Mirfendereski, S. (2007). Failure analysis of
bank front boiler tube, Engineering Failure Analysis, 14: 731-738, 2007.
Kitto, J. B. and Stuitz, S. C., (2005) "Steam: Its Generation and Use", 41st Edition, the
Babcock and Wilcox Company, Barberon, Ohio, U.S.A.
Rajput R.K., (2006) "Thermal Engineering", Laxmi Publications (P) Ltd., New Delhi.
Rawson W.R., “Boiler. The Encyclopedia of Earth”, [online], Available:
http://www.eoearth.org/article/Boiler, Accessed: November 1, 2010, 2008.
Ray, A.K., Sahay, S.K. & Goswami, B. (2003). Assessment of service exposed boiler tubes,
Engineering Failure Analysis, 10: 645-654, 2003.
Saidur, R., Ahamed, J. U. and Masjuki, H. H., “Energy, Exergy and Economic Analysis of
Industrial Boilers”, Energy Policy, Vol. 38, pp2188–2197, 2010.
Srikanth, S., Das, S.K., Sasikumar, C. & Ravikumar, B. (2007). Failure of evaporator tubes
initiated by lamellar tearing during the commissioning of a waste heat recovery boiler,
Engineering Failure Analysis, 14: 262-278, 2007.
Woodruff E.B., Lammers H.B. and Lammers T.F., “Steam Plant Operation”, 8th Edition. The
McGraw-Hill Companies, Available: www.digitalengineeringlibrary.com, Accessed:
September 7, 2010, 2004.
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International Journal of Engineering Processing & Safety Research Vol. 24 No.

DESIGN AND FABRICATION OF A HORIZONTAL

SMART BELLO1, OLAWEPO B. B.1 AND AJAYI R.

steam is generated is called a boiler or a steam generator (Woodruff et al.,

contributor to waste heat boiler problem is the uneven distribution of gases

MATERIALS AND METHOD

• Mass firing rate = 2.5 – 5 kg/hr

Design Consideration for Material Selection

For an intelligent design to be done, the knowledge of the materials available as

Factors considered are:

Design of Component Parts of the Water Tube Boiler

Design of the Volumetric Boiler Pressure Vessel

The estimated maximum pressure of the vessel

Design of the Furnace

Design of the Return Chamber

Design of the Smokestack (Exhaust)

Actual Volumetric Capacity of the Boiler

Thermal Design Calculation

Radiation heat transfer from furnace

Convective heat transfer from furnace

Conduction heat transfer from furnace

𝑇ℎ𝑒𝑟𝑚𝑎𝑙 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑢𝑟𝑛𝑎𝑐𝑒

Convective heat transfer from furnace to the Return Chamber Section

Conduction heat transfer from furnace to the Return Chamber Section

Where; qrad = heat transfer per unit time (W)

Convective Heat Transfer

Conduction Heat Transfer

Amount of Steam Generated

Construction of the Water Tube Boiler

Operation of the Water Tube Boiler

RESULTS AND DISCUSSION

Table 4.1: Summary of details and operational data of steam boiler

11 Operating steam pressure 500 kN/m2 (5 bar)

Discussion of the Results

Diesel Fuel Specifications

Table 4.2: Fuel specifications for diesel

Dimensional details of Designed Steam Boiler

Thermodynamic details of Designed Steam Boiler

Table 4.4: Thermodynamic properties of material streams of the boiler

Hot products mp 2.4192 186.67 2, 673.09 4.0922

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