See discussions, stats, and author profiles for this publication at: https://www.researchgate.

net/publication/323470420

Design and fabrication of blow down heat recovery system to improve energy
efficiency in steam boilers of petroleum refineries

Article · February 2018

CITATIONS READS

0 469

3 authors, including:

Raheek I. Ibrahim Abdulrahim Humod

University of Technology, Iraq University of Technology, Iraq
20 PUBLICATIONS 44 CITATIONS 37 PUBLICATIONS 32 CITATIONS

SEE PROFILE SEE PROFILE

Some of the authors of this publication are also working on these related projects:

Viscosity reduction techniques in Iraqi crude oil pipelines View project

The control on boilers tubes fouling View project

All content following this page was uploaded by Raheek I. Ibrahim on 14 April 2018.

The user has requested enhancement of the downloaded file.

 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

DESIGN AND FABRICATION OF BLOW DOWN HEAT RECOVERY

SYSTEM TO IMPROVE ENERGY EFFICIENCY IN STEAM
BOILERS OF PETROLEUM REFINERIES
Raheek I. Ibrahim1, Abdulrahim T. Humod2 and Najat A. Essa1
1
Departmentof Electromechanical Engineering, University of Technology, Baghdad, Iraq
2
Department of Electrical Engineering, University of Technology, Baghdad, Iraq
E-Mail: doctorraheek@yahoo.com

ABSTRACT
Blow down water is the part of water that is purposely drained during the boiler operation to limit the level of
impurities in boiler water to an acceptable level. So it is contains large quantity of heat energy. The aim of the present work
is to improve energy efficiency of steam boilers in the south refineries company/Al-Basrah. This aim has been achieved
through designed and manufactured of a heat exchanger consists of a shell and coiled tube unit to recover heat from surface
blow down water and reducing indirect losses. The blow down water (hot fluid) is supplied to the heat exchanger at
atmospheric pressure by passing it through the shell side and the feed water (cold fluid) in the coils tube side. These were
done as counter flow. A flow control valve is used to control the flow rate of hot blow down water inside the heat
exchanger. The experiments are done at the blow down water and feed water flow rates ranging between (0.06-0.14) m3/h
with 0.02 m3/h interval, and between (0.1-0.5) m3/h with 0.1m3/h interval, respectively. The experimental results proved
the effectiveness of the heat recovery system in improving the boiler efficiency where a percentage of 83.16% of the
energy is lost with blow-down water that can be recovered using heat-recovery unit with an energy saving of 103411.8
MJ/day. Which will save a mass of fuel equals to 482.46 ton/ year. The heat recovery unit is proved to be a good solution
for saving energy and reducing harmful emissions to the environment and it contributes to the maintenance of sewage
pipes from damage caused by the heat of discharge water by cooling the water before discharging it into the sewer system.

Keywords: boiler blow down, heat exchanger, heat recovery system, energy efficiency, indirect losses.

1. INTRODUCTION perfect candidate for the introduction of waste heat-

Energy efficiency has become an important recovery system. Greater energy savings come with the
feature of process industry with rising cost of energy and use of heat-recovery system where they can recover up to
the more stringent environmental regulations being 90% of the heat energy that would otherwise be lost down
implemented worldwide, today the most prominent targets the drain [5].There are two types of blow down heat
of modern technology to improve the efficiency of energy recovery systems depending primarily on boiler operating
technology in industrial processes particular industries that pressure, one simply includes heat exchanger arranged for
generate their own steam need to optimize their energy counter flow with the continuous blow down on one side
generation and use by making all the measures are taken to and makeup water on the other, and these are only
reduce energy loss [1].Steam boiler is one of the largest employed with low pressure steam systems. For high
equipment which consumes energy greatly, the boiler pressure steam systems the blow down heat recovery
efficiency is dependent upon decreasing of various indirect equipment includes flash tank and heat exchanger. Heat
losses of a boiler. Thus the quantity of energy entering the recovery at high pressure boilers is used to heat boiler
boiler by consumption of fuel can be maximum utilized makeup water before entering the deaerator, while it is
for generation of steam and the cost of steam can be used to heat water inside the deaerator at low pressure
reduced ultimately through utilization of several methods steam boilers. This lowers the cost to operate the deaerator
to increase industrial boiler efficiency that can be and improves the efficiency of steam boiler. Also, the heat
implemented relatively easily by minimizing the indirect recovery system achieves a typical requirement of
losses [2]. The main areas for improvement of boiler reducing the temperature of the blow down water before it
efficiency result from “reduction in blow down water and reaches the sewer drain, therefore eliminates the need to
blow down heat recovery”. Boiler blow down water is dilute blow down with cold-water before it enters the
water wasted from the steam boiler while the boiler is drainage system. Heat recovery systems provide fairly
running to avoid concentration of impurities during quick recovery depending on the volume of the blow
continuing evaporation of steam [3]. Since the blow down down. Many boilers can be linked to a single heat recovery
process is carried out during the boiler operation so the unit [6]. 90 percent of heat energy that would be lost down
blow-down water is at the same pressure and temperature the drain can be recovered with the use of an efficient heat
of that the boiler. Blow down water is at boiler exchange unit. There are two types of blow-down,
temperature; hence as it increases it means fuel wastage discontinuous (intermittent)and continuous: Discontinuous
[4]. System of heat recovery is used to decrease energy (intermittent) blow-down: is done by manually operating a
losses that result from boiler blow down. Each boiler with valve connected to drainage line to adjust (suspended
continuous blow-down passing 5% of the steam rate is a solids, TDS, pH, Silica and Phosphates concentration)

874
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

inclusive of any sludge created in the boiler water within 85% of total wasted fuel was recovered. This recovered
prescribed limits. Manual blow-down valve and discharge energy was supplied to feed water to raise the water
line are located at the bottom or low point of the boiler, temperature. S. Arunkumar, et al. 2014 [10], a system of
where any sludge formed would tend to settle [7, heat recovery was designed to reduce the losses. The
8].Continuous blow down: It is the continuous removal of experimental measurements were carried out by using
water from the boiler to remove concentrations of minerals plate type heat exchanger, with 20 plates, design pressure
dissolved in the boiler water. It offers many features that of 10 kg/cm2, and area of heat exchanger was 2.5 m2,
are not provided by the use of intermittent blow down required 3% blow down of steam. The results showed that
alone. Blow down water is discharged from the position of 6.61kJ/day total energy was saved in the process. Vandani,
the highest dissolved solids in boiler water. The steam and et al. 2015[11], they investigated the system of heat
water rising in the boiler are separated so the water at that recovery on a power plant using the flash-tank to restore
point has the highest concentration of solids more than lost energy from blow-down water. Results showed that,
anywhere else in the boiler. By doing so, the TDS the net generated power increased by 0.72% when a blow
concentration can be held near the limit, that reduces the down recovery mechanism was used, and energy
amount of blow down water and the amount of energy efficiency of the system raised by about (31.68-31.91) %.
removed from the boiler through blow down process. As a As well, the results showed that energy and exergy
result, the quality of boiler water can be maintained at efficiencies of the system increased by 0.23 and 0.22
suitable level of TDS at all times. Also, a maximum of respectively, the exergy efficiency of a system reached
dissolved solids may be discharged with minimal loss of (30.66%). Thus, the objective of the present work is to
heat and water from the boiler. Another main advantage of improve the energy efficiency of a steam boiler in the
continuous blow down is the recovery of a large quantity south refineries company located in Al-Basrah- Iraq. This
of its heat content by using the blow down flash tanks and has been achieved by designing and manufacturing of a
heat exchangers. Control valve settings must be regulated heat recovery system includes special design of shell and
orderly to increase or decrease the blow-down with coiled tube heat exchanger. It has been utilized to recover
reference to control test results and to maintain close the heat from the surface blow down water and saving in
control of boiler water concentrations at all times [4, 7]. fuel consumption for steam demand, in addition to
Several studies focused on blow down heat recovery environmental protection from blow down hot water that
systems. Gupta, et al. 2011 [9], They suggested an has been discharged to sewer system.
automatic blow-down system set up, which consisted of
continuous monitoring for conductivity. This automatic 2. EXPERIMENTAL SETUP FOR HEAT
system can save energy wasted by continuous system. D. RECOVERY SYSTEM
Madhav, et al. 2013 [5], presented a design and
mathematical modeling of the heat recovery system 2.1 Experimental system
consists from flash vessel and a heat exchanger designed Figure-1 is a schematic diagram of the
to minimize the heat losses. According to their studies, experimental rig. The main parts used in the experimental
approximately (49)% of energy at boiler blow down can system are: boiler, feed water tank, feed water pump,
be returned. Sunudas and Prince 2013 [4], studied electrical control panel, heat recovery unit, and automatic
experimentally the optimization of bottom blow down and control system which consist of: conductivity monitor,
blow down heat recovery by installation of an automatic throttle valve and automatic control circuit. The measuring
blow down system. The experimental analysis conducted devices are conductivity monitor, flow meter, temperature
in steam boilers in textile industries showed that nearly controller, thermocouples, an oscilloscope and a digital
1.5% of fuel was wasted through blow down and nearly an multimeter.

875
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

The main parts assembling in the heat recovery

system are:

Shell: Shell is the container for the coil tubes and

liquid is distributed around the tube. It is created from tube
or rolled sheet and soldered plate metal. For economical
aspects, low carbon steel is commonly used; also other
materials can be appropriate for maximum temperature or
erosion resistance. Utilizing commonly obtainable shell
pipe is of (24) inch diameter leads to reduced cost and
facility at industrialization, partially because they
generally are more completely round than rolled and
soldered shells [12].
Coiled tube: Tube outside diameter of 3/4 and 1 Figure-2. Coil tube configuration.
inches are very common to design a compact heat
exchanger. Coil tube designs can be an effective use of 2.2 Design procedure for shell and coiled tube heat
space in heat transfer applications as shown in Figure- exchanger
2[12, 13]. A simple procedure to calculate the design
Connecting pipes: Four pipes are connected for equations for a shell and coiled tube heat exchanger shown
cold water inlet, cold water outlet, hot water inlet, and hot in Figure-3, is used a differential cross section is
water outlets [12]. considered for the coiled tube heat exchanger Figure-4.
Thermocouple: It is a temperature measuring Then a counter current flow Logarithmic Mean
device consisting of two dissimilar conductors that contact Temperature Difference (LMTD) method is used to solve
each other at one or more spots. It produces a voltage the design parameters. The liquid inflows are inside the
when the temperature of one of the spots differs from the coil and the annulus, heat transfer takes place through the
reference temperature at other parts of the circuit [12]. coil wall [14].

876
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

consecutive coils turns measured from centre to centre in

(mm) taken as:

p=1.5do (4)

Where: (do) is the outside diameter of coiled tube

(mm).
To calculate the curvature ratio:

δ=di/Dc (5)
Figure-3. A heat exchanger (Shell and coiled tube) [15].
Where: (di) is the internal diameter of coiled tube (mm).

The inside diameter of the tube being fixed, by

knowing the mass- flow rate (ṁ), fluid average density,
the average velocity (u) can be calculated from the
following equation:

ui=ṁi⁄ρA (6)

Ac= π/4 di2 (7)

The Reynolds numbers for the cold and hot fluid

can be calculating from equation:

Rei=(ρ uidi)/µ (8)

Where: (Re) is the critical Reynolds number

(transition laminar/turbulent flow) for a helical tube.
Figure-4. Schematic cross section view of coiled
tube HE. [14]. Reo= (ρ uoDh)/µ (9)

To compute the coefficients of heat transfer at the Where: (Dh) is the hydraulic diameter of shell
coil and the annulus. The following transactions must be side, can be calculated as:
known [15], [16], [17]: Input and output temperatures for
fluid are known. Consequently, relative values of viscosity Dh=(D2-πDcdo2γ (-1))/ (D2+ πDc do γ(-1)) (10)
(µ), thermal conductivity (k), isobaric specific heat
capacity (Cp) and density (ρ) can be obtained from D is the shell diameter in (mm), γ is the non-
databases and then used to calculate the average values. dimensional pitch,
The quantity of heat transfer rate or heat potential
is computed through utilization of the equations of energy γ=p/ (πDc) (11)
balance:
Nusselt number:
Q=ṁ ×Cp× (∆ T) (1)
Nui=0.023Re0.85 Pr0.4 (di/Dc) 0.1 (12)
Where: (𝘘) is the energy-absorbed (kJ/s), (ṁ) is
the waste water quantity (kg/s), (Cp) is the specific-heat of The coefficient based on internal diameter of the
water (kJ/kg.k), (∆T) is the substance temperature rise ̊C. coil is obtained through:

ṁ=ρ×V̇ (2) hi=(Nui .k)/di (13)

Where: V ̇ is the volume flow rate in (m3/h), and ρ is the Where: (hi) is the convective heat transfer
density in (kg/m3). coefficient of coiled tube (kJ/kg).
The coil length (L) necessary to make (N) turns: The Dean Number De: is dimensionless.
Calculated from the following relation:
Lc=N ×Dc×π (3)
De=Rei (di/Dc)0.5 (14)
Where: (N) is the number of coil turns, (P) is the
tube pitch which represents the distance between

877
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

To calculate the velocity of the fluid through shell The volume of shell is calculated from equation:
side:
V shell=Vcoil+Va (27)
uo=ṁo⁄(ρA ) (15)
Where:( Va) is the volume of the annulus.
The Nusselt number is calculated from the
relation: V a=π /4 DedoLc (28)

Nuo=0.023Re0.8Pr0.4 (16) Where: (De) is the shell side equivalent diameter,

calculated from equation:
The overall heat transfer coefficient is calculated
from the following equation: De= (4ṁ/πρ u) 0.5 (29)

Uo= Qaverage / (Ao×∆Tlm) (17) To calculate the diameter of the shell:

Where: Q average= (Q hot+Qcold)/2 (18) D shell= √ 4Vshell/πLs (30)

Ao= πdoLshell (19) To calculate the pressure drop:

Ao: is the outside surface area of the heat exchanger. ∆PD= 2×F×Lc×ρ×ui2)/di (31)
∆Tlm is the logarithmic mean temperature difference,
calculated for a counter flow heat exchanger as: Where: F is the fraction factor, calculated by
using Reynolds Number as in the following equation:
∆Tlm=((Th1-TC2)-(Th2-TC1))/ln ((Th1-TC2)/ (Th2-TC1) (20)
F= (7.2/ Rei0.5) ×(di/ Dc) 0.25 (32)
Where: (Th1& Th2) are the inlet and outlet
temperatures of hot fluid in ̊C, and (T C1&TC2) are the inlet 2.3Assembly
and outlet temperatures of cold fluid in ̊C. Heat exchanger (shell and coiled tube) type is
The coefficient of convective heat transfer shell- manufactured as shown in Figure-5 to be used for heat the
side (ho) can be obtained from the following equation: make-up water that enters at near ambient temperature,
and cools the blow down water before it is drained to
1/Uo=Ao/ (hiAi) +Aoln(do/di)/(2πkLcoil)+1/ho (21) sewer. the shell that is constructed from 316L stainless
steel pipe with 13.6 cm inner diameter, 14 cm outer
Where: (do) is the external diameter, and Lc is the diameter, with 2 mm pipe thickness, and 43 cm length.
coil length. Two holes were drilled in the shell with a diameter of 25
While (Ai and di) are the internal surface of the mm, for input and exit water (blow down water). Two
coiled tube and the internal diameter, and (k) the thermal nipples were welded in the holes have a diameter of 20
conductivity of the material. mm for connecting pipes. Two nipples were also welded
Area of the coil: in two flange plates for connecting pipes to the helical
tube with a diameter of 25 mm for flow of cold water
A= π d Lc (22) (feed water). Two coiled tubes (316L stainless steel), are
inserted in the shell side. Each coiled tube has 10 mm
To determine the required area needed for heat outer diameter, 7 mm inner diameter and 1 mm thickness
transfer by overall heat transfer coefficient: pipe. Both coil pipes have 30 cm length and 15 turns. The
diameter of outer coil is 11 cm, while the diameter of inner
A=Q⁄U∆Tlm (23) coil is 8 cm. The distance between the two coils is 1.5 cm,
with 20 mm pitch for each coil. In the present work the
To calculate the number of coil turns (N): blow down water (hot fluid) flows in the shell side and
make-up water (cold fluid) is supplied through coiled tube
N=A / (πdo (L/N)) (24) side. The heat exchanger was insulated by aluminum foil
thermal insulation, with a thickness of 10 mm to reduce
The actual number of coil turns needed n, is heat dissipating to the environment. Two flow meters are
simple N rounded to the next highest integer. installed upstream of the heat exchanger to measure the
To calculate the length of the shell Lshell: flow rate of the hot stream and cold stream. Two PVC ball
valves are used to control the flow rate of cold and hot
Lshell=p .N (25) water inside the flow meters. To measure the inlet and
outlet temperatures of cold and hot water, four k- type
The volume of coil is calculated from equation: thermocouples were inserted in the small holes drilled in
the inlet and outlet tubes of heat exchanger and closed to
V coil= π/4 do2.Lc (26) prevent any leakage, thermocouples has been joined to

878
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

digital temperature indicator, which is installed in the electrical control unit.

Figure-5. Experimental setup.

3. EXPERIMENTAL PROCEDURE increases. Also it’s noted that, as the volumetric flow-rate
To operate and assess the pilot plant designed for of blow down water increases at specific volumetric flow-
heat recovery from blow down water. A number of rate of feed water, the outlet temperature of blow down
experiments were carried out to recover the latent heat in water increases. Figure-7 shows the effect of the flow rate
the waste water discharged during the surface blow down of feed water on the feed water outlet temperature for
process. The blow down water was supplied to the heat different volumetric flow rates of blow down water. It is
exchanger at atmospheric pressure. The experiments were observed that feed water outlet temperature increases
conducted by passing feed water (cold fluid) through coils when volumetric flow-rate of the feed water increases
tube and the blow down (hot fluid) in the shell side; this because more cooling is generated by increasing volume
was done for counter flow operation. Measuring the heat flow-rate of cold-water leads to increase heat transfer rate
gained by feed water 𝘘F.W and heat lost by blow down to the cold water. The Figure shows outlet temperature of
water 𝘘B.D has been done by keeping the flow rates of feed feed water initially increases and then decreases as the
water constant, while, blow down flow was changed from volumetric flow-rate of feed water increases. Figure-8
0.06 m3/h to 0.14 m3/h with 0.02 m3/h interval. Next the shows the outlet temperature of feed water with variation
flow rates of blow down water was kept constant and the of volumetric flow-rate of blow-down water for different
flow rates of feed water was varied from 0.1 m3/h to 0.5 volumetric flow-rates of feed water. It is illustrated that
m3/h with 0.1m3/h interval. All of the data contained in the feed water outlet temperature increases when
this work are based on average values of five experiments volumetric flow-rate of blow down increases inside the
conducted. shell side for each corresponding volumetric flow rate of
feed water. Therefore the rate of heat transfers increases
4. RESULTS AND DISCUSSIONS when blow down water the volumetric flow rate increases.
This leads to an increase in the outlet temperature of
4.1 Effect of flow rates on outlet temperatures of blow feedwater. Figure-9 illustrates the variation of the outlet
down water and feedwater temperature of blow down water with volumetric flow-rate
The experiments were carried out to measure the of blow-down water for different feed water volumetric
change in outlet temperature of feed water supplied to the flow-rates. It’s observed that, outlet temperature of
steam boiler and outlet temperature of blow down water discharge water (blow down water) increases with
discharged to the sewer may be influenced by volumetric increasing volumetric flow rate of blow down water. It
flow rates of feed water and blow down water through also shows that when volumetric flow-rate of feed water is
heat exchanger. Figure 6 shows the effect of variation of maintained at lower value of 0.1 m3/h, the outlet
feed water volumetric flow rate on outlet temperature of temperature of blow down water is maximum. But, when
blow down water for different volumetric flow rate of volumetric flow-rate of feed water increases, outlet
blow down water. It is clear that as the outlet temperature temperature of blow down water decreases
of blow down water decreases, the flow-rate of feed water correspondingly until it reaches the lowest temperature at
increases, because of the increase in the heat transfer from a flow-rate of feed water equals to 0.5 m3/h.
hot water to cold water as the cold water flow-rate

879
VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

Figure-6. Difference of outlet temperature of blow down water withVolumetric

flow-rate of feedwater at different volumetricflow ofblow down water.

Figure-7. Difference of outlet temperature of feed water for volumetric flow-rate

of feedwater at different volumetric flow-rate of blow-down water.

Figure-8. Variation of outlet temperature of feed water for volumetric inflow rate
of blow down water at different volumetric flow rate of feed water.

880
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

Figure-9. Variation of outlet temperature of blow down water for volumetric inflow
rate of blow-down water atdifferent volumetric inflow rate of feed water.

Figure-10 shows the effect of variation increases gradually with increasing volumetric inflow rate
volumetric flow rates of feed water on heat energy lost by of blow-down water, because when the flow-rate of blow-
the blow-down water when keeping the shell side flow down increases, there is a large amount of heat transferred
rate is constant. It is observed that with increasing to the feed water. Figures (12 and 13) show the
volumetric flow-rate of feed water rate, the heat energy relationship between the heat energy lost 𝘘B.D and heat
lost from blow-down water increased because as the energy gained 𝘘F.W with the volumetric flow rate of blow-
volumetric feed water increases there is more heat being down water and feed water. It’s observed that the heat
transferred from the blow-down water. Figure-11 displays energy lost 𝘘B.D and heat energy gained 𝘘F.W increase
the effect of variation in the volumetric flow rate of blow- when the flow-rates of blow-down water and feed water
down water around (0.06 - 0.14) m3/h with an interval of increases respectively, because a heat energy rate is a
0.06 on heat energy gained by the feed water𝘘F.W. It is function of mass flow rate, when the mass flow rate
observed that the heat energy gained by feed water increases it leads to increases in the heat energy rate.

Figure-10. The effect of feed water flow rates on heat energy lost from blow
down water 𝘘B.D (watt).

881
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

Figure-11. The effect of blow down water flow rates on heat energy
gained by feed water 𝘘F.W (watt).

Figure-12. The effect of blow down water flow rates onheat energy lost 𝘘B.D (watt).

Figure-13. The effect of feed water flow rates on heat energy gained 𝘘F.W (watt).

4.2 Effect of heat recovery unit utilization volumetric flow rate of blow down water is discharged
According to the operating conditions in the from the bottom of flash tank to the drain at 90 ̊C. By
south refineries company/AL-Basrah. A 21 m3/h

882
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

using the heat recovery system we can conserve the energy Where ρ= 980.56 kg/m3
losses in the south refineries company. Heat energy saving with heat recovery 𝘘 =
The values of heat energy lost 𝘘B.D and heat 4308.825 MJ/h
energy gained 𝘘F.W were calculated by using equations (1) Percentage of heat recovered= 4308.82578
and (2). Where physical properties of water specific heat /5180.848117 = 83.16%. Figure-14 shows the heat energy
Cp (kJ/kg. k) and density ρ (kg/m3) are calculated at the lost with blow down water by using the heat recovery unit
atmospheric pressure: and without the use of heat recovery unit. It is observed
that the quantity of heat lost with blow down water has
Heat energy lost to the drains 𝘘 = ṁ ×Cp× ∆ T decreased with the use of heat recovery unit.
where ρ= 983.21 kg/m3
𝘘 = (21× 983.21) × 4.182 × (363 – 303) Amount of fuel saving with heat recovery system
Blow down mass flow rate to drain ṁ = 20.64741 Gross calorific value x mass of fuel = ṁ ×Cp× ∆
T/h. T
Heat energy rate lost to the drain = 5180.848117 Mass of fuel = [(21x994.8) x1x29)]/ 11000 =
MJ/h 55.075745 kg/h
Heat energy recovered through the use of heat Mass of fuel saving per day= 1321.81789
exchanger: kg/day= 1.32181 ton/day which is equal to 482.460 ton/
𝘘 = (21× 980.56) × 4.185 × (363 – 313) year.

Figure-14. The heat energy lost with blow down water 𝘘B.D(watt) at feed water
flow rate 0.1 m3/hby using heat recovery unit and without using of
a heat recovery unit.

5. CONCLUSIONS down water from flash tank which is discharged at a

From the obtained results it can be concluded that temperature above 90 ̊C. It means, 482.46 ton/ year in fuel
the best condition for volume flow rate of blow down (natural gas) can be saved. Reduction in fuel consumption
water = 0.14 m3/h and volumetric flow rate of feed water = means increased efficiency of boiler and reduced
0.1 m3/h. Where, at this level of flow rate for feed water environmental pollution. It also neglects the need for blow
and blow down water gave the highest value of heat down cooling before discharging to the sewer system.
exchange. Outlet temperature of blow down water
decreases with increased the volumetric flow-rate of feed ACKNOWLEDGEMENT
water. The output temperature of blow down water The authors would like to express grateful thanks
increased with increasing volumetric flow-rate of blow- to The Iraqi Ministry of Oil/ South Refineries Company/
down water. The heat energy gained by feed water 𝘘F.W Al-Basrah for the financial support and practical
increased when the flow-rate of the side of coiled tube are information in accordance with graduate research grant
fixed with a change in the volumetric flow rate of shell (No. 1/ 2016).
side. Outlet temperature of feed water decreased with
increasing mass flow-rate of feedwater. The proposed List of symbols
design of the heat recovery unit which consists of a shell Ac Area of coiled tube (cm2)
and coiled tube heat exchanger, contributed to recover Ao Outside surface area of the helix (cm2)
nearly 83.16% of energy wasted with discharged blow Cp Specific heat (J/kg.k)

883
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

d distance (cm) [5] D. Madhav, L. Ramesh, M. Naveen. 2013. Heat

Dc Helix diameter (mm) recovery through boiler blow down tank. Int. J. of
De Dean number Engineering Trends and Technology (IJETT). Vol. 4I.
Dh Hydraulic diameter (m)
di Inside diameter of clean riser tube (m) [6] Wayne C. Turner and Steve Doty. 2006. Energy
do Outside diameter of coil (mm)
Management Hand book. Sixth edition, United State.
GCV Type of fuel and gross calorific value of the fuel
(kcal/kg)
[7] Kiran G. Gayakwad, Prof.V.H.Patil, Dr.C.R.Patil.
L Tube length (m)
Lc Length of coil (m) 2016. Experimental study on heat recovery from
ṁ Mass flow rate (Kg/s) continuous blow down water and reduced feed water
ṁB.D Mass flow rate of B.D water (Kg/h) consumption by utilizing it In CFBC boiler. Int.
N Theoretical number of turns of coiled tube Journal of Engineering Research and Applications. 6:
De Shell side equivalent diameter (mm) 15-19.
P Tube pitch (mm)
PB Boiler operating pressure (N/m2) [8] Paul Eichamer. 2011. Industrial fired boilers for
Prprandtl number general refinery and petrochemical service. American
Rc The helix radius (mm)
Re Reynolds number dimensionless Petroleum Institute.
TDS Total dissolve solid (ppm)
Th1 Inlet temperature of hot fluid (̊C) [9] Rahul Dev Gupta, Sudhir Ghai, Ajai Jain. 2011.
Th2 outlet temperature of hot fluid (̊C) Energy efficiency improvement strategies for
U overall heat transfer coefficient (w/m2.k) industrial boilers: A Case Study. Journal of
u Fluid average velocity (m/s) Engineering and Technology. 1: 52-56.
V Volume (m3)
X Thickness of coil wall (mm) [10] S. Arunkumar, R. Prakash, N. Jeeva, M. Muthu, B.
𝘘 Heat energy (watt) Nivas. 2014. Boiler blow down heat recovery. IOSR
T temperature (Celsius) Journal of Mechanical and Civil Engineering (IOSR-
ρ density (kg/m3)
JMCE). 11: 83-85.
𝑉̇ Volumetric flow rate (m3/h)
Cp Specific heat of water (kJ/kg.k) [11] Amin Mohammadi Khoshkar Vandani, Mokhtar Bidi,
B.D Blow down
FW Feed water Fatemeh Ahmadi. 2015. Exergy analysis and
𝘘B.D heat energy lost (watt) evolutionary optimization of boiler blow down heat
𝘘F.W heat energy gained (watt) recovery in steam power plants. Journal of Energy
LMTD Logarithmic Mean Temperature Difference Conversion and Management. 106: 1-9.

REFERENCES [12] Dr. B. Jayachandriah, M. Uday kumar, R.Jagaesh,

T.M Vamsi Krisha. 2011. Fabrication and design of
[1] Ernst W., Mariëlle Corsten and C. Galitsky. 2015. spiral tube heat exchanger. American Int. J. of
Energy efficiency improvement and cost saving Contemporary Scientific Research.
opportunities for petroleum refineries. An Energy
Star® Guide for energy and plant managers, U.S.A. [13] Amitkumar S. Puttewar, A.M. Andhare. 2015. Design
and thermal evaluation of shell and helical coil heat
[2] S. Panda, P.S. Ratha, Dr. N. K. Barpanda. 2014. exchanger. Int. J. of Research in Engineering and
Intelligent system for efficiency enhancing program Technology. Vol. 4.
of thermal power plant: A Case Study. Int. J. of
Advanced Research in Electrical, Electronics and [14] Marija Lazova, Henk Huisseune, Alihan Kaya, Steven
Instrumentation Engineering. 3(10). Lecompte, George Kosmadakis and Michel De Paepe.
2016. Performance evaluation of a helical coil heat
[3] Keerthi R Lekshmi, Vandana S Pillai. 2015. Boiler exchanger working under supercritical conditions in a
blow down analysis in an industrial boiler. IOSR solar organic Rankine cycle Installation. J. of
Journal of Engineering (IOSRJEN). 5: 22-28. Energies.
[4] Sunudas T, M G Prince. 2013. Optimization of boiler [15] N. Jamshidi, M. Farhadi, D.D. Ganji, K. Sedighi.
blow down and blow down heat recovery in textile 2013. Experimental analysis of heat transfer
sector. Int. J. of Engineering Research and enhancement in shell and helical tube heat
Applications. 3: 35-38.

884
 VOL. 13, NO. 3, FEBRUARY 2018 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

exchangers. J. of applied thermal engineering. 51:

644-652.

[16] Giacomo Bonafoni, Roberto Capata. 2015. Proposed

design procedure of a helical coil heat exchanger for
an Orc energy recovery system for vehicular
application. J. of Mechanics, Materials Science and
Engineering.

[17] M.R. salimpour. 2009. Heat transfer coefficients of

shell and coiled tube heat exchangers. J. of
Experimental Thermal and Fluid Science. 33, pp. 203-
207.

885

View publication stats