Final report on spent solution in hydro

INTRODUCTION
1.1 Scope
To study the basic operation of control room .To study cooling tower and determine
cooling tower efficiency. Selecting the right cooling tower structure and material..To
study the type of the fan and material is used in cooling tower. To improve efficiency of
exhaust.. To determine flow rate of spent ( acidic zinc sulphate solution ).Maintenance and
cleaning requirements in cell house area.
1.2 Methodology
Study which type of cooling tower is being used, study its type of structure for cooling
tower, components of cooling tower (air inlet, drift eliminators, fans, tower materials).For
mathematical calculation of cooling efficiency of cooling tower calculate inlet
temperature ,outlet temperature, wet bulb temperature and obtain multiple readings and
take average of all the readings Study type of blades ,blade material, capacity of face
cooler, material requirements ,laws of fan, characteristics of fan, maintenance and
cleaning requirements in cell house .Study basic leaching process ( acidic zinc sulphate
solution), type of material used on which volumetric flow of spent take place(corrosive or
non corrosive), calculate flow rate manually ,take multiple readings and take mean of all
the readings.

2 COOLING TOWER
2.1Introduction
Cooling towers are a very important part of many industries. The primary task of a cooling tower
is to reject heat into the atmosphere. They represent a relatively inexpensive and dependable
means of removing low-grade heat from cooling water. The make-up water sources used to
replenish water lost to evaporation. Hot water from heat exchangers is sent to the cooling tower.
The water exits the cooling tower and is sent back to the exchangers or to other units for further
cooling.
Fig no. 1 closed loop cooling tower system [1]

2.2 Types of cooling tower
Cooling towers fall into two main categories:
 Natural draft
 Mechanical draft.
Natural draft towers use very large concrete chimneys to introduce air through the media .Due to
the large size of these towers, they are generally used for water flow rates above 45,000m3/hr.
These types of towers are used only by utility power stations. Mechanical draft towers utilize
large fans to force or suck air through circulated water. The water falls downward over fill
surfaces, which help increase the contact time between the water and the air - this helps
maximise heat transfer between the two. Cooling rates of Mechanical draft towers depend upon
their fan diameter and speed of operation. Since, the mechanical drift cooling towers are much
more widely used, the focus is on them in this chapter.
Mechanical draft towers are available in the following airflow arrangements
1. Counter flows induced draft.
2. Counter flow forced draft.
3. Cross flow induced draft.
 In the counter flow induced draft design, hot water enters at the top, while the air is
introduced at the bottom and exits at the top. Both forced and induced draft fans are
used.
 In cross flow induced draft towers, the water enters at the top and passes over the fill.
Their, however, is introduced at the side either on one side (single-flow tower) or
opposite sides(double-flow tower). An induced draft fan draws the air across the wetted
fill and expels it through the top of the structure.
The Figure 2 illustrates various cooling tower types. Mechanical draft towers are available in a
large range of capacities. Normal capacities range from approximately 10 tons,2.5 m3/hr flow to
several thousand tons and m3/hr. Towers can be either factory built or field erected - for example
concrete towers are only field erected. Many towers are constructed so that they can be grouped
together to achieve the desired capacity. Thus, many cooling towers are assemblies of two or
more individual cooling towers or "cells." The number of cells they have, e.g., an eight-cell
tower, often refers to such towers. Multiple-cell towers can be lineal, square, or round
depending upon the shape of the individual cells and whether the air inlets are located on the
sides or bottoms of the cells.

Fig 2 Types of cooling tower [1]

2.3 Description and design features
The ZACT (zincobre atmospheric cooling tower) is based on following characteristics.
Design PLS Max flowrate per unit 165 m3/hr
Normal flowrate per unit 138 m3/hr
Inlet temperature Max 80 °C
Outlet temperature 34°C
Design wet bulb temperature 28°C
Cooling air flow Max 360000 m3/hr

2.4 Operating principle
A cooling tower may be consider as a heat exchanger in which liquid and air are in direct
contact with on another. Heat is transferred from liquid drops to surrounding air by the transfer
of sensible latent heat. and Liquid is sprayed into the air at the top of the tower. Counter flow
cold air comes from exterior and passes through the tower volume .The Mist Eliminator Module
filters the exhaust hot air to avoid the environmental contamination and to reduce the loss of
liquid by evaporation. The heat transference is produced by the different enthalpy of air and
liquid. The transference depends on the contact surface among many other factors ( in liquid
temperature, wet bulb temperature, liquid flow rate, air flow etc). The surface of contact
depends on the size of sprayed drops. The aim of the ACT is to improve overall parameter to
increase heat transfer coefficient. This leads us to change the traditional square shape ,with
poor efficiency near the corners, to a circle shape, with a homogeneous distribution of air and
liquid flows. On the other hand, the tower height depends upon the necessary time of contact
between the liquid drops and the air. The liquid coming out of the nozzles takes some length to
achieve the good distribution inside the tower. Then, it needs time transfer the heat to the
counter flow air. Thus, for the present design, the height of the cooling tower was chosen to
ensure that all these requirements are met an oversize of 15%. To ease the manufacturing
process, the circle shape is achieved with a regular octagon made of flat walls (panels) . There
are two aspects that condition the dimensions of this “ circle” shape: the fan dimensions and
mainly, the room needed to spread the liquid flow inside the tower properly. The pressure of
the liquid and its viscosity determines the droplet size and spreading characteristics of a nozzle.
Since the viscosity of the liquid does not suffer almost any change by the content of solids, the
dimension of octagon does not change from a Zn electrolyte solution cooling tower..Tangential
flow full cone spraying nozzles are used to achieve an extremely uniform area distribution of
the sprayed liquid.
The important parameters, from the point of determining the performance of cooling towers, are:
i) "Range" is the difference between the cooling tower water inlet and outlet temperature.
ii) "Approach" is the difference between the cooling tower outlet cold water temperature
and ambient wet bulb temperature. Although, both range and approach should be monitored,
the 'Approach' is a better indicator of cooling tower performance.
iii)"Range" is the difference between the cooling tower water inlet and outlet temperature

2.5 Cooling Tower Efficiency
The cooling tower efficiency can be expressed as
μ = (ti - to) 100 / (ti - twb)
where
μ = cooling tower efficiency (%)
ti = inlet temperature of water to the tower (o
C, o
F)
to = outlet temperature of water from the tower (o
C, o
F)
twb = wet bulb temperature of air (o
C, o
F)
Fig no. 3 Graphical representation of the cooling tower characteristics [3]

Fig no. 4Actual cooling tower structurein plant [2]

Table
ATMOSPHERIC COOLING TOWER COMPONENTS
MAIN
ASSEMBLY
SECONDARY
ASSEMBLY
DRAWINGS IDENTITY NO.
PIPE &
SPRAYING
SYSTEM
HEADERS 1
CAMLOCKS 2
FEXIBLE HOSE 3
FLANGED ELBOW 4
NOZZLE
PP DISTRIBUTION
RING
5
PP FEEDINGPIPE
PIPE SUPPORTS
WALKWAYS GRATING MESH
GRATING FRAME
SUPPORT OF
WALKWAY
HANDRAL
FAN BLADES (6) 6
HUB 7

GEAR MOTOR 8
GEAR MOTOR
SUPPORT
9
FAN PILLAR 10
MIST
ELIMINATORS
MODULES
(MEM)
MIST ELIMINAT FOR
BLADES
11
STEEL STRUCTURE 12
FRP LATERAL
PANELS
13
STRUCTURE FRP LATERAL
PANELS
14
AIR DUCT 15

Fig no. 5 Schematic structureof forced cooling tower [2]
2.6 Methodology
 Take thermometer clean its bore using cotton.
 Using thermometer first take inlet temperature of spent ( acidic zinc sulphate solution)
which is pumped from tank house ( contains acidic zinc sulphate solution coming after
electrolysis) using centrifugal pump to the cooling tower.
 Now measure temperature of spent solution coming out from cooling tower in an open
runnel.
 Take cotton dip into tap water and attach to bore of thermometer and whirl in air of cell
house area and note down wet bulb temperature.
 Take multiple reading in an interval of a hour.
 Calculate cooling tower efficiency for each time and take mean efficiency and it should
be in between desired cooling tower efficiency according to plant design parameter

Note
1. Reading was taken on 9th day after scheduled cleaning and maintenance ( in every 15 days)
of cooling tower in an interval of a hour.
OBSERVATION TABLE NO. 1
Sr. no. Parameters Value
1 Type Forced draft
2 Tower size(diameter) 6700mm
3 Impeller fan (diameter) 3962mm
4 Air flow rate 96 m3/s
5 Pressure 90 pa
6 No. of blades 6
7 Power 37kw
8 Supply voltage 415v 50 hz
9 Fan speed 250 rpm
OBSERVATION TABLE NO.2
Sr
no.
Inlet (ti )
Temperature
Outlet (to )
temperature
Wet bulb
(twb )
temperature
Cooling
efficienciy
(μ %)
1 52.1 34.3 30.1 80.90
2 52.2 34.5 29.8 79.01
3 52 34 30 81.81
4 52.8 34.6 30.3 80.80
5 53 35 30.8 81.08
Mean efficiency 80.72
2.7 Tower material

In the early days of cooling tower manufacture, towers were constructed primarily of wood.
Wooden components included the frame, casing, louvers, fill, and often the cold water basin. If
the basin was not of wood, it likely was of concrete. Today, tower manufacturers fabricate
towers and tower components from a variety of materials. Often several materials are used to
enhance corrosion resistance, reduce maintenance, and promote reliability and long service life.
Galvanized steel, various grades of stainless steel, glass fiber, and concrete are widely used in
tower construction as well as aluminum and various types of plastics for some components.
Wood towers are still available, but they have glass fiber rather than wood panels (casing)over
the wood framework. The inlet air louvers may be glass fiber, the fill may be plastic, and the
cold water basin may be steel. Larger towers sometimes are made of concrete. Many towers–
casings and basins–are constructed of galvanized steel or, where a corrosive atmosphere is
problem, stainless steel. Sometimes a galvanized tower has a stainless steel basin. Glass fiber is
also widely used for cooling tower casings and basins, giving long life and protection from the
harmful effects of many chemicals. Plastics are widely used for fill, including PVC,
polypropylene, and other polymers. Treated wood splash fill is still specified for wood towers,
but plastic splash fill is also widely used when water conditions mandate the use of splash fill.
Film fill, because it offers greater heat transfer efficiency, is the fill of choice for applications
where the circulating water is generally free of debris that could a plug the fill passage ways.
Plastics also find wide use as nozzle materials. Many nozzles are being made of PVC, ABS,
polypropylene, and glass-filled nylon. Aluminum, glass fiber, and hot-dipped galvanized steel
are commonly used fan materials. Centrifugal fans are often fabricated from galvanized steel.
Propeller fans are fabricated from galvanized, aluminum, or moulded , glass fiber reinforced
plastic.
2.8 Maintenance operation on cooling tower
 This section lists the most important options to improve energy efficiency of cooling
towers.
 Follow manufacturer’s recommended clearances around cooling towers and relocate or
modify structures that interfere with the air intake or exhaust.
 Optimize cooling tower fan blade angle on a seasonal and/or load basis.
 Correct excessive and/or uneven fan blade tip clearance and poor fan balance.
 In old counter-flow cooling towers, replace old spray type nozzles with new square spray
nozzles that do not clog.
 Install nozzles that spray in a more uniform water pattern
 Clean plugged cooling tower distribution nozzles regularly
 Balance flow to cooling tower hot water basins
 Control cooling tower fans based on exit water temperatures especially in small units
 Check cooling water pumps regularly to maximize their efficiency
 The following maintenance operations will be carried out in every 15 days:
1 Spears and nozzle cleaning

2 substituting drift eliminator
3 cleaning of drift eliminator
4 collecting basin cleaning and flushing
3 COOLING TOWER FAN
3.1Introduction
Fans provide air for ventilation and industrial process requirements. Fans generate a pressure to
move air (or gases) against a resistance caused by ducts, dampers, or other components in a fan
system. The fan rotor receives energy from a rotating shaft and transmits it to the air.The purpose
of a cooling tower fan is to move a specified quantity of air through the system, overcoming the
system resistance which is defined as the pressure loss. The product of air flow and the pressure
loss is air power developed work done by the fan; this may be also termed as fan output and
input kW depends on fan efficiency. The fan efficiency in turn is greatly dependent on the
profile of the blade. An aerodynamic profile with optimum twist, taper and higher coefficient of
lift to coefficient of drop ratio can provide the fan total efficiency as high as 85–92 %. However,
this efficiency is drastically affected by the factors such as tip clearance, obstacles to airflow and
inlet shape, etc. As the metallic fans are manufactured by adopting either extrusion or casting
process it is always difficult to generate the ideal aerodynamic profiles. The FRP blades are
normally hand moulded which facilitates the generation of optimum aerodynamic profile to meet
specific duty condition more efficiently. Cases reported where replacement of metallic or Glass
fibre reinforced plastic fan blades have been replaced by efficient hollow FRP blades, with
resultant fan energy savings of the order of 20–30% and with simple pay back period of 6 to 7
months. Also, due to lightweight, FRP fans need low starting torque resulting in use of lower HP
motors. The lightweight of the fans also increases the life of the gear box, motor and bearing is
and allows for easy handling and maintenance.
3.2Scope
The application covers the technical requirements of the cooling tower fans for cooling gypsum
saturated spent solution in the tank house

3.3 Types of axial flow fan
Tubeaxial:-fans have a wheel inside a cylindrical housing, with close clearance between blade
and housing to improve airflow efficiency. The wheel turn faster than propeller fans, enabling
operation under high-pressures 250 – 400 mm WC. The efficiency is up to 65%.
Vaneaxial:-fans are similar to tubeaxials, but with addition of guide vanes that improve
efficiency by directing and straightening the flow. As a result, they have a higher static pressure
with less dependence on the duct static pressure. Such fans are used generally for pressures up to
500 mmWC. vaneaxials are typically the most energy-efficient fans available and should be used
whenever possible.
Propeller:- fans usually run at low speeds and moderate temperatures. They experience a large
change in airflow with small changes in static pressure. They handle large volumes of air at low
pressure or free delivery. Propeller fans are often used indoors as exhaust fans. Applications
include air-cooled condensers and cooling towers. Efficiency is low approximately 50% or less.

Fig no.6 Types of axial fans [1]

AXIAL-FLOW FANS
Type Characteristics Typical applications
Propeller Low pressure, high
flow, low
efficiency, peak
efficiency close to
point of free air
delivery ( zero static
pressure)
Air-circulation,
ventilation, exhaust
Tube- axial Medium pressure,
high flow, higher
efficiency than
propeller type, dip
in pressure flow
curve before peak
pressure point
HVAC, drying
ovens, exhaust
systems
Vane- axial High pressure,
medium flow, dip in
pressure-flow curve,
use of guide vanes
improves efficiency
exhausts
High pressure
applications
including HVAC
systems
3.4 Design criteria in plant
Duty
The equipment shall be suitable for continuous operation,24 hours a day, all year around under
following conditions:

 Continuous operation at extremes of ambient temperature
 Continuous operation in an external environment containing high level of acid mist
 Continuous operation fully exposed to the elements
 High-pressure hose washdown with the fan stopped
3.5 Design life
Number of towers 10
Number of fans 1 per cell
Type Forced draft
Tower size( diameter) 6.74m
Fan suction Acid mist from tank house, direct suction
3.6Environmental design conditions
Dry bulb temperature 37°C
Wet bulb temperature 28°C
Annual rainfall 850mm
Environment So2/so3 mist
Design wind speed 47 m/s
Seismic zone II
3.7 Main design parameter
Air flow rate 100m2 /s
Impeller diameter 3.962m
Turning speed 250/min
Minimum static pressure 90ps
Number fan blades 6 unts.
3.8 Technical specification
 The spent cooling towers are designed to cool gypsum saturated electrolyte, which is
circulating in a zinc electrolysis. The cooling towers shall operate in parallel.
 Particular attention has to be paid to the protection of the fan against acid mist, since the
air for cooling is selected from tank house. This air is loaded with acid mist. A protection

can be realized via drive casting, which has an opening for the fan shaft and another to
suck the needed outdoor air for the drive cooling.
 Forced draught cooling towers are formed by a vertical cylindrical body with the spray
nozzles and the mist eliminators on top and the basin and the horizontal cylindrical fan
duct on bottom. Gypsum saturated spent solution will be fed under pressure to the spray
manifold, on top of cooling tower. Several nozzles will spray the GSPS into the tower,
where a counter flow air stream will cool it down. The resulting cooled spent solution
including the precipitated gypsum will be collected in a basin at the tower’s base and
cleared through the hole at the bottom.
 The towers are erected on a concrete basin . No fill (package) is intended inside the
cooling tower due to the expected gypsum scale on the internal components.
 Fans geared motors will be located on top of approx. 3.5m high concrete pillar, which
will be braced to avoid resonance phenomenon. Fan’s hubs will be directly coupled to the
output shaft of the gearboxes.
3.9 Fan suction side:
The fan will be located inside an horizontal cylindrical duct, which will link the tank house to the
inside of the cooling tower. The duct shape will be cone. Cooling towers suck air from the
electrolysis. A safety grid (approx 95% clearness) will cover all surface the duct inlet
The cooling towers in two lines of five are located parallel (approx. 17.5 m in between) with the
fan suction sides looking east and west
3.10 Fan discharge side:
There are two important pressure drops of the air, one caused by the spraying purified solution
inside the cooling tower and the other one caused by the mist eliminator layers.
There are two mist eliminator layers with approx 30.5 m2 free way section through each one.
This area could be reduced by 10% due to gypsum build up.

3.11 Fan characteristics
The following table shows, as an example, the air flow that corresponds to each fan speed
in a real ACT. These values are only for the selected fan (for specific, diameter, blade tip
angle, fan type, obstacles and crosswind).This table may be helpful for plant operator to
estimate the air corresponding. The second graph shows, for the same fan how static
pressure decreases with fan rpm
Fan rpm Air m3
/s Pressure (pa)
250 95 80
245 92.5 75.9
240 90 71.8
235 87.5 67.8
230 84.9 64
225 82.4 60.1
220 79.8 56.4
215 77.2 52.8
210 74.5 49.2
200 69.1 42.3
190 63.5 35.7
180 57.7 29.5
170 51.5 23.5
160 44.8 17.8
150 37.2 12.3
145 32.8 9.5

Graph no.1 [2]
Graph no. 2 [2]

3.12 Fan laws
The fans operate under a predictable set of laws concerning speed, power and pressure. A change
in speed (RPM) of any fan will predictably change the pressure rise and power necessary
to operate it at the new RPM.
Fig no. 7 Fan laws [2]

3.13 Fan design and selection criteria
Precise determination of air-flow and required outlet pressure are most important in proper
selection of fan type and size. The air-flow required depends on the process requirements;
normally determined from heat transfer rates, or combustion air or flue gas quantity to be
handled. System pressure requirement is usually more difficult to compute or predict.Detailed
analysis should be carried out to determine pressure drop across the length, bends, contractions
and expansions in the ducting system, pressure drop across filters, drop in branch lines, etc.
These pressure drops should be added to any fixed pressure required by the process (in the case
of ventilation fans there is no fixed pressure requirement). Frequently, a very conservative
approach is adopted allocating large safety margins, resulting in over-sized fans which operate at
flow rates much below their design values and, consequently, at very poor efficiency.
Once the system flow and pressure requirements are determined, the fan and impeller type are
then selected. For best results, values should be obtained from the manufacturer for specific
fans and impellers. The choice of fan type for a given application depends on the magnitudes of
required flow and static pressure. For a given fan type, the selection of the appropriate impeller
depends additionally on rotational speed. Speed of operation varies with the application. High
speed small units are generally more economical because of their higher hydraulic efficiency and
relatively low cost. However, at low pressure ratios, large, low-speed units are preferable.
3.14 Material required
The fan’s hub and all its parts (including fasteners) shall be made of stainless steel, grade ASI
316 or better
Fan blades shall be made of a fibre reinforced resin. These should be suitable to withstand acid
mist passing through the fan in a continuous operation. The manufacture shall provide
information about these construction materials.

3.15 Maintenance operation on fan
Operation Condition/
frequency
Procedure Specific safety
rule
Inspection of blades
possible deposits
and damages
Once in every
month
Proper lubrication,
prevent breakdown
from vibrations,
moisture and
fouling
During the
performance of
maintenance
activities at the fan,
the impeller should
be fastened and the
electric connection
of e- motor should
be disconected
Impeller: paint
inspection to
prevent corrosin
Atleast once a year
New paint
coating if it is
damaged
corroded away.
paint type shall
be at least equal
to the original
paint
Do not start any
maintenance
activities until the
fan has been
shutdown and it is
dead. This shall be
done such that the
power cannot be
switched on
unintentionally or
inexpertly during
maintenance
Impeller
:verifiication of
tightening tourque
of the bolts
connections. blades
angle verification
At least once a year When starting up the
fan again, all legal
requirements
regarding safety
distances from both
live and rotating
parts and regarding
safety guard shall
be compiled with
Impeller:to replace
corroded bolts and
nuts in time
Atleast once a year Visiual inspection:
Replacement if
required

4 FLOW RATE OF SPENT (ACIDIC ZINC SULPHATE)
SOLUTION
4.1 Design parameter
Current supplied during electrolysis of
spent
165amp.
Maximum flow rate of spent 11 m³/s
Minimum flow rate of spent 8 m³/s
4.2 Methodology
 Measure the length and depth in which spent(acidic zinc sulphate solution) is flowing
using metallic tape measure which is cuboidal in shape.
 Calculate area in which spent is flowing.
 Take small piece of cardboard (approx. 2×2cm)
 Put that piece of cardboard at rear end.
 Note the time taken to travel a small piece of cardboard to front end using stop watch.
 Calculate velocity for each time.
 Calculate flow rate for each time.
 Take multiple readings.
 Calculate mean flow rate of all the readings.
Note
1. Reading was taken on 22nd day after scheduled cleaning and maintenance ( in every 15
days) of spent solution flow rate and cell house in an interval of a hour

OBSERVATION TABLE NO. 3
Sr no. Length
(L)
metre
Depth
(D)
metre
Area
(A)
Metre
square
Time
(T)
second
Velocity
(V=L/T)
Metre per
second
Flow rate
(Q=A.V)
Metre
cube per
second
1 3.26m 1.2m 3.912 1.60 2.43 9.52
2 3.26m 1.2m 3.912 1.60 2.44 9.58
3 3.26m 1.2m 3.912 1.58 2.47 9.69
4 3.26m 1.2m 3.912 1.62 2.41 9.44
5 3.26m 1.2m 3.912 1.61 2.42 9.47
Mean flow rate 9.54

CONCLUSION
It was a wonderful and learning experience for me while working
on this project. This project took me through the good industrial
working experience and while working in maintenance department
I have learnt about cooling tower, calculating efficiency of cooling
tower, material required , cooling tower fan ,characteristics of fan
in industry, calculating flow rate of spent solution and got brief
idea of control room functioning.

SCHEDULE
18/5/2015 Safety training
25/5/2015 Cell house area visit, control room area visit
1/6/2015 Project analysis, project related study
8/6/2015 To calculate cooling efficiency of cooling tower
15/6/2015 To calculate velocity of air cooler
22/6/2015 To calculate flow rate of spent
29/6/2015 Project documentation ,project report submission
9/7/2015 Project presentation
REFRENCES
 Bureau of energy efficiency
 Manual by host organization
 Cheresources.com

Final report on spent solution in hydro

More Related Content

What's hot (20)

Similar to Final report on spent solution in hydro (20)

Recently uploaded (20)

Final report on spent solution in hydro