FR MULTIPLE EFFECT EVAPORATION

Multiple Effect Evaporator Problem
Guided By Prof. M.G.Desai Page | 1
“Study the steam economy of multiple effect evaporator
plant producing sodium sulphate and its Simulation ”
A PROJECT REPORT
Submitted by
-Rohan A. Kulkarni (110190105043)
- Mrugesh M. Bhandari (110190105058)
- Umang M. Patel (110190105070)
- Dhawnil K. Bhatia (110190105088)
In fulfilment for the award of the degree
Of
BACHELOR OF ENGINEERING
in
CHEMICAL ENGINEERING
Government Engineering College, Valsad
Gujarat Technological University, Ahmedabad
Chemical Engineering Department
2014

CERTIFICATE
Date:
This is to certify that the dissertation entitled “Study The Steam
Economy Of Multiple Effect Evaporator Plant Producing
Sodium Sulphate and its Simulation” has been carried out by
(1) Rohan A. Kulkarni (2) Mrugesh M. Bhandari (3) Umang M.
Patel (4) Dhawnil K. Bhatia under my guidance in fulfilment of the
degree of Bachelor of Engineering in chemical engineering 7th
Semester of Gujarat Technological University, Ahmedabad during
the academic year 2014-15.
Guide:
Prof. M. G. DESAI Prof. M. G. DESAI
Head of the Department

ACKNOWLEDGEMENT
We express my sincere and heartfelt gratitude to our guide Prof. M. G. Desai
for his constant and untiring guidance in carrying out my project work. His
motivation and support has helped us finish our work enthusiastically. His
constant encouragement and valuable advice in both academic and personal
front has helped us greatly in completing our project work successfully. We
would also like to acknowledge the contribution of the Department of Chemical
Engineering as a whole, and Prof. M.G.DESAI, HOD, Chemical Engineering,
G.E.C - Valsad, for having provided us with all the necessary Facilities.
- Rohan Kulkarni (110190105043)
- Mrugesh Bhandari (110190105058)
- Umang Patel (110190105070)
- Dhawnil Bhatia (110190105088)

ABSTRACT
During our visit to the ATUL LTD.,ANKLESHWAR we found in Multiple Effect
Evaporator plant that steam utility increases with the time for the production of
sodium sulfate.
Evaporators can minimize the production of regulated waste residues, and
increase the potential for recovering valuable materials from those wastes.
Multiple-effect evaporators (MEEs) are common to industries that concentrate
different products, regenerate solvents, or separate solid-liquid mixtures.
Since evaporation is the most energy-intensive stage in any industrial operation,
measures to reduce energy consumption in the evaporator are greatly beneficial
towards making an operation cost-effective.
Our aims are to find out the reason for the increase in steam utility, to find out its
suitable solution to reduce it out and simulation of Multiple Effect Evaporator. A
model for an evaporator used for the concentration of sodium sulfate solution is
developed using a set of non-linear equations derived from the mass and energy
balance relations. Excel is used for the designing of multiple effect evaporator

List of Figures
Sr.
No.
Name of figure Page
No.
1 Single effect evaporator 2
2 Multiple effect evaporator 4
3 Forward feed multiple effect evaporator 13
4 Backward feed multiple effect evaporator 14
5 Parallel feed multiple effect evaporator 15
6 Variables in evaporator, preheater, and flash box of effect i. 18
7 Forward-feed arrangement for a triple-effect evaporator 20
8 Backward-feed arrangement for a triple-effect evaporator 23
9 Boiling point elevation apparatus 27
10 Critical heat flux apparatus 29
11 Input data to be inserted by user for forward feed 34
12 Material balance of evaporator for forward feed 34
13 Parameters values obtained from calculations for forward feed 35
14 Values of Temperature and latent heat from steam table for
forward feed
35
15 Iterations for forward feed 36
16 Input data to be inserted by user or obtained from forward feed
for back ward feed
37
17 Material balance of evaporator for backward feed 37
18 Parameters values obtained from calculations for backward
feed
38
19 Values of Temperature and latent heat from steam table for
backward feed
38
20 Iterations for backward feed 39
List of Graph:
Sr. No. Graph Page No.
1. Temperature vs concentration graph 27

NOMENCLATURE:
Symbol
used
Parameter Unit
Mf Feed flow rate kg/s
D0 Steam flow rate kg/s
L Flow rate of liquor stream kg/s
Di Flow rate of vapor stream kg/s
CS Condensate flow rate of steam/vapor kg/s
Cp Specific heat KJ/kg °C
H Enthalpy of liquor KJ/kg
H Enthalpy of vapor KJ/kg
λ Heat of vaporization/latent heat KJ/kg
A Heat transfer area of an effect m2
U Overall heat transfer coefficient KW/m2
K
Tf Feed temperature ˚C
Ti Temperature of ith
effect ˚C
T0 Steam temperature ˚C
∆T Temperature drop ˚C
X Solid concentration -
Q Heat flux KW/m2
XDM Dry matter concentration -
Subscripts:
1 – 3 Effect number
F Feed
0 Steam
L Liquor
V Vapor
TABLE OF CONTENT

Acknowledgement iii
Abstract iv
List of figures v
Nomenclature vi
Table of content vii
CHAPTER 1: INTRODUCTION 2
1.1 Introduction to Evaporator
1.2 Introduction to Multiple Effect Evaporator
1.3 Performance Measure
1.4 Application of Evaporators
1.5 Boiling Point Elevation
1.6 Introduction to Sodium Sulfate
1.7 Application of Sodium Sulfate
CHAPTER 2: LITERATURE SURVEY 10
2.1 History of Multiple Effect Evaporator
2.2 History of sodium sulfate
2.3 Production of Sodium sulfate:
CHAPTER 3: Feeding of Multiple Effect Evaporators 13
3.1 Forward feed
3.2 Backward feed
3.3 Parallel feed
3.4 Process Description
Chapter 4: Process Modeling 17

4.1 Forward flow calculations
4.2 Backward flow calculations
4.3 Effect of feed system on economy
Chapter 5: Practical works 26
5.1 Boiling Point Elevation Experiment
5.2 Heat Flux Experiment
Chapter 6: Descaling agents 30
6.1 General description
6.2 Purpose of chemical cleaning
6.3 Features
6.4 Notes regarding safety in descaling operations
Chapter 7: Simulation by using Excel 32
7.1 Introduction to Simulation
7.2 Procedure for solving problem of forward feed by using
excel
7.3Procedure for solving problem of backward feed by using
excel
7.4 Uses of using our excel iteration method
Conclusion 40
References 41

MULTIPLE EFFECT EVAPORATION

Chapter 1: Introduction
1.1 Introduction to Evaporator
1.1.1 Concept of Evaporation and evaporator:
 Evaporation is a widely used method for the concentration of aqueous
solutions, involves the removal of solvent from a solution by boiling the
liquor in a suitable vessel, generally an evaporator, and withdrawing the
vapor. In majority of processes solvent is water.
 Evaporation is usually
treated as the separation of a liquid
mixture into a liquid product
(concentrate or thick liquor) and a
vapor byproduct, although in special
cases such as water treating and
desalination, the vapor is the product
instead of the thick liquor.
 Evaporators are kind of heat
transfer equipment where the
transfer mechanism is controlled by
natural convection or forced
convection.
 If the solution contains
dissolved solids, the resulting strong
liquor may become saturated so that
crystals are deposited or crystals can
further be formed by using
crystallization after concentrating
the solution.
 Evaporation is a transport phenomenon in which vapors or vapor mixtures
are in contact with the liquids, and a large amount of energy is released or
absorbed with the phase change, which is known as the latent heat.
 Liquors which are to be evaporated may be classiﬁed as follows:
(a) Those which can be heated to high temperatures without
decomposition, and those that can be heated only to a temperature of about
330 K.
Figure-1 Single effect evaporator

(b) Those which yield solids on concentration, in which case crystal size
and shape may be important, and those which do not.
(c) Those which, at a given pressure, boil at about the same temperature as
water, and those which have a much higher boiling point.
 A characteristic of mass transfer in these phenomena is that it is always
accompanied by an energy transfer (usually heat transfer) due to the phase
change, and in this respect it is quite different from ordinary mass transfer,
which is not accompanied by an energy transfer.
 Evaporation is achieved by adding heat to the solution to vaporize the
solvent.
 The heat is supplied to provide the latent heat of vaporization and by
adopting methods for recovery of heat from the vapor, it has been possible
to achieve good steam economy.
 The normal heating medium is generally low pressure exhaust steam from
turbines, special heat transfer ﬂuids or ﬂue gases are also used.
 The design of an evaporation unit requires the practical application of data
on heat transfer to boiling liquids, together with a realization of what
happens to the liquid during concentration.
 The material of construction of an evaporator may be any kind of steel.
Special materials like copper, stainless steel, nickel, aluminium may be
used depending upon the specific properties of the solution to be
concentrated.
 The multiple effect evaporation system is formed by a sequence of single
effect evaporators, where the vapor formed in one effect is used in the next
effect.
 The vapor reuse in the multiple effect system allows reduction of the brine
and the temperature to low values and prevent rejection of large amount of
energy to the surrounding, which was the main drawback of the single effect
system.
 If a single evaporator is used for the concentration of any solution, the vapor
issuing out of it is condensed and discarded it is called a single effect
evaporator system.
 If more than one evaporator is used in series for the concentration of any
solution, the vapor coming out of one effect is used as a heating medium in
the steam chest of the next effect, it is called a multiple effect evaporator
system.
 Single effect evaporation is simple but the steam utilization is not effective,
while multiple effect evaporators evaporate more quantity of water for the
same amount of steam consumed in the evaporation process.

 This brings a saving in the steam cost, but at the same time, the cost of
material and installation of the evaporator system increases because of the
large number of effects involved.
 For optimum cost the maximum number of effects in a multiple effect
evaporator usually should not exceed seven, because beyond this, the
material and installation cost of the evaporator effects increases more than
the saving achieved in the steam cost.
 If a single evaporator is used for the concentration of any solution, it is
called a single effect evaporator system and if more than one evaporator is
used for the concentration of any solution, it is called a multiple effect
evaporator system.
 The thermal separation technology offers effective solutions to many
customer concerns such as:
i) Energy cost monitoring
ii) Production of highly purified crystalline products
iii)Disposal of industrial waste streams through concentration
iv) Recovery of valuable volatile fractions.
1.2 Introduction to Multiple effect evaporator
1.2.1 Concept of Multiple Effect Evaporator
 Evaporators are classified by the number of effects. If more than one
evaporator is used for the concentration of any solution, it is called a
multiple effect evaporator system.
 In a single-effect evaporator, steam provides energy for vaporization and the
vapor product is condensed and
removed from the system.
 In a double-
effect evaporator, the vapor product
off the first effect is used to provide
energy for a second vaporization
unit.
 In a multiple effect
evaporator the vapor from one
evaporator is fed into the steam
chest of the other evaporator. This
cascading of effects can continue for
many stages.
 Multiple-effect evaporators
can remove much larger amounts
of solvent than is possible in a single
effect.Figure 2 Multiple effect evaporator

 The energy consumption to evaporate an aqueous solution is fairly
significant; therefore, in order to reduce the energy cost, systems such as
multiple effect evaporation and thermal vapor recompression are often
used.
 The steam consumption of the evaporator unit can be reduced by using the
vapor from the first chamber to heat the second one.
 In such a system, the heat from the original steam fed into the system is
reused in the successive effects.
 The thermodynamic principle of the multi-effect evaporator consists in a
series of reboilers operating at different pressures; the water evaporated at
one stage is condensed and used as the heat source for another stage.
 Due to its strong integration with the process, it is worth to analyze the
integration of the multi-effect evaporator with the rest of the process.
 The objective of Multiple effect evaporator system is to concentrated the
thin liquor of sodium sulfate to thick liquor which could be further be
crystallized in a centrifuge to give a solid product.
 Large amount of water must be evaporated in order to maximize net
calorific value in the boiler.
 The objective of this study has been to identify the opportunity of reducing
the energy consumed in the evaporator section of a sodium sulfate salt
producing plant in Atul ltd., Ankleshwar.
 Normally, all effects in an evaporator will be physically the same in terms
of size, construction, and heat transfer area. Unless thermal losses are
significant, they will all have the same capacity as well.
 Evaporator trains may receive their feed in several different ways. The feed
order is not related to the numbering of effects. Effects are always
numbered according to decreasing pressure (steam flow).
1.3 Performance Measure:
 There are three main measures of evaporator performance:
1. Capacity (kg vaporized / time)
2. Economy (kg vaporized / kg steam input)
3. Steam Consumption (kg / hr)
 Note that the measures are related, since
Consumption = Capacity/Economy.
 Economy calculations are determined using enthalpy balances.
 The key factor in determining the economy of an evaporator is the number
of effects.
 The economy of a single effect evaporator is always less than 1.0.

 Multiple effect evaporators have higher economy but lower capacity than
single effect.
 The thermal condition of the evaporator feed has an important impact on
economy and performance.
 If the feed is not already at its boiling point, heat effects must be
considered.
 If the feed is cold (below boiling) some of the heat going into the
evaporator must be used to raise the feed to boiling before evaporation can
begin; this reduces the capacity.
 If the feed is above the boiling point, some flash evaporation occurs on
entry.
1.4 Application of evaporators
 Evaporators are integral part of a number of process industries namely Pulp
and Paper, Chloro-alkali, Sugar, pharmaceuticals, Desalination, Dairy and
Food processing, etc.
 Evaporators find one of their most important applications in the food and
drink industry.
 The goal of evaporation is to concentrate a target liquid, and this needs to
be achieved for many different targets today.
 One of the most important applications of evaporation is that on the food
and drink industry. Many foods that are made to last for a considerable
amount of time or food that needs a certain consistency, like coffee, need
to go through an evaporation step during processing.
 It is also used as a drying process and can be applied in this way to
laboratories where preservation of long-term activity or stabilization is
needed (for enzymes for example).
 Evaporation is also used in order to recover expensive solvents such as
hexane which would otherwise be wasted.
 Another example of evaporation is in the recovery of sodium hydroxide in
Kraft pulping.
 Cutting down waste handling cost is another major application of
evaporation for large companies. If up to 98% of wastes can be vaporized,
industry can greatly reduce the amount of money that would otherwise be
allocated towards waste handling.
 Evaporation is also used in pharmaceutical industry as to get a concentrated
product and to improve the stability of the products.
 Evaporation is also used in the concentration of the sodium salts that are
obtained as a by-product from the production of p-cresol.
 In an air-conditioning process, evaporation is used to allow the coolant,
Freon, to evaporate from liquid to gas while absorbing heat.

1.5 Introduction to Sodium Sulfate
Sodium Sulfate:
Molecular Formula: Na2SO4
Chemical Formula:
Molar Mass: 142.04 g/mol (anhydrous)
322.20 g/mol (decahydrate)
Appearance: White Crystalline Solid
Density: 2.664 g/cm3
(anhydrous)
1.464 g/cm3
(decahydrate)
Melting Point: 884 °C (1,623 °F; 1,157 K) (anhydrous)
32.38 °C (decahydrate)
Boiling Point: 1,429 °C (2,604 °F; 1,702 K) (anhydrous)
Solubility in water: anhydrous:
4.76 g/100 ml (0 °C)
42.7 g/100 ml (100 °C)
Solubility: Insoluble in ethanol,
Soluble in glycerol and hydrogen iodide.
Crystal Structure: Orthorhombic or Hexagonal (anhydrous)
Monoclinic (decahydrate)
 Sodium sulfate is the sodium salt of sulfuric acid.
 When anhydrous, it is a white crystalline solid of formula Na2SO4 known
as the mineral thenardite.
 The decahydrate Na2SO4·10H2O is found naturally as the mineral
mirabilite.

1.6 Physical and Chemical Properties:
 Sodium sulfate is chemically very stable, being unreactive toward most
oxidizing or reducing agents at normal temperatures. At high temperatures,
it can be converted to sodium sulfide by carbothermal reduction:
Na2SO4 + 2 C → Na2S + 2 CO2
1.6.1 Acid-Base:
 Sodium sulfate is a neutral salt, which forms aqueous solutions with pH of
7.Sodium sulfate reacts with sulfuric acid to give the acid salt sodium
bisulphate.
Na2SO4 + H2SO4 ⇌ 2 NaHSO4
1.6.2 Solution and ion exchange:
 Sodium sulfate has unusual solubility characteristics in water. Its solubility
in water rises more than tenfold between 0 °C to 32.384 °C, where it
reaches a maximum of 497 g/L.
 Sodium sulfate is a typical ionic sulfate, containing Na+ ions and SO42−
ions.
 The existence of sulfate in solution is indicated by the easy formation of
insoluble sulfates when these solutions are treated with Ba2+ or Pb2+ salts:
Na2SO4 + BaCl2 → 2 NaCl + BaSO4

1.7 Application of sodium sulfate:
 Sodium sulfate is a very cheap material, approx. $30 per ton in 1970. The
largest use is as filler in powdered home laundry detergents, consuming
approximate 50% of world production. This use is waning as domestic
consumers are increasingly switching to compact or liquid detergents that
do not include sodium sulfate.
 Another formerly major use for sodium sulfate, notably in the US and
Canada, is in the Kraft process for the manufacture of wood pulp. Organics
present in the "black liquor" from this process are burnt to produce heat,
needed to drive the reduction of sodium sulfate to sodium sulphide.
 The glass industry provides another significant application for sodium
sulfate, as second largest application in Europe. Sodium sulfate is used as
a fining agent, to help remove small air bubbles from molten glass. It fluxes
the glass, and prevents scum formation of the glass melt during refining.
The glass industry in Europe has been consuming from 1970 to 2006 a
stable 110,000 tons annually.
 Sodium sulfate is important in the manufacture of textiles, particularly in
Japan, where it is the largest application. Sodium sulfate helps in
"levelling", reducing negative charges on fibers so that dyes can penetrate
evenly. Unlike the alternative sodium chloride, it does not corrode the
stainless steel vessels used in dyeing. This application in Japan and US
consumed in 2006 approximately 100,000 tones.

CHAPTER 2: LITERATURE SURVEY
2.1 History of Multiple Effect Evaporator
 The origins of the multiple effect evaporation dates back to the 19th
century with the growth of the sugar industry, where it was necessary to
devise an efficient evaporation process to produce good quality sugar
crystal at low prices.
 The invention of the multiple effect evaporator is generally credited to
Norbert Rillieux. He developed a multiple pan evaporation system for use
in sugar refining.
 Rillieux was born in Louisiana and trained in France. Most of his working
career was spent in the U.S., although he later returned to Europe where he
is buried in the famous Pere Lachaise cemetery in Paris.
 The first desalination plants were of the evaporation type their use was
not expanded to full industrial scale because of limited design and
operating experience.
 Efforts have been made by many researchers such as Khanam et al.(2010),
Jorge et al.(2010), to cut down the steam consumption in a multiple-effect
evaporator by different operating strategies like feed, condensate and
product flashing, vapor compression, vapor bleeding, feed and steam
splitting or using an optimal feed flow sequence.
 Harper and Tsao (1972) carried out optimization of multiple effect
evaporator and they modified the feed flow pattern. Their work was
extended by Nishitani and Kunugita (1979) who considered all possible
feed flow sequences to optimize a MEE system.
 All the mathematical models are solved by developing a set of non-linear
equations originating from the corresponding mass and energy balance
relations.
 When the operating strategy of a system is changed, a whole new set of
equations results. This problem was addressed by Stewart and Beveridge
(1977). They developed a generalized cascade algorithm which could be
solved irrespective of the operating strategy involved in the operation.
 Many different operating strategies such as flashing, vapor compression,
have been studied in literature. In the present work, vapor bleeding as an
energy reduction scheme has been elaborated.

2.2 History of sodium sulfate:
 The hydrate of sodium sulfate is known as Glauber's salt after the
Dutch/German chemist and apothecary Johann Rudolf Glauber (1604–
1670), who discovered it in 1625 in Austrian spring water. He named it sal
mirabilis (miraculous salt), because of its medicinal properties: the crystals
were used as a general purpose laxative, until more sophisticated
alternatives came about in the 1900s.
 In the 18th century, Glauber's salt began to be used as a raw material for
the industrial production of soda ash (sodium carbonate), by reaction with
potash (potassium carbonate). Demand for soda ash increased and the
supply of sodium sulfate had to increase in line. Therefore, in the
nineteenth century, the large scale Leblanc process, producing synthetic
sodium sulfate as a key intermediate, became the principal method of soda
ash production.
2.3 Production of Sodium sulfate:
2.3.1 Natural resource:
 The world production of sodium sulfate, mostly in the form of the
decahydrate amounts to approximately 5.5 to 6 million tons annually
(Mt/a). In 1985, production was 4.5 Mt/a, half from natural sources, and
half from chemical production. After 2000, at a stable level until 2006,
natural production had increased to 4 Mt/a, and chemical production
decreased to 1.5 to 2 Mt/a, with a total of 5.5 to 6 Mt/a.
 For all applications, naturally produced and chemically produced sodium
sulfate are practically interchangeable.
 Two thirds of the world's production of the dehydrate (Glauber's salt) is
from the natural mineral form mirabilite, for example as found in lake beds
in southern Saskatchewan. In 1990, Mexico and Spain were the world's
main producers of natural sodium sulfate (each around 500,000 tones),
with Russia, United States and Canada around 350,000 tons each. Natural
resources are estimated at over 1 billion tones.

2.4.2 Chemical industries:
 About one third of the world's sodium sulfate is produced as by-product of
other processes in chemical industry. Most of this production is chemically
inherent to the primary process, and only marginally economical. By effort
of the industry, therefore, sodium sulfate production as by-product is
declining.
 The most important chemical sodium sulfate production is during
hydrochloric acid production, either from sodium chloride (salt) and
sulfuric acid, in the Mannheim process, or from sulfur dioxide in the
Hargreaves process. The resulting sodium sulfate from these processes is
known as salt cake.
Mannheim: 2 NaCl + H2SO4 → 2 HCl + Na2SO4
Hargreaves: 4 NaCl + 2 SO2 + O2 + 2 H2O → 4 HCl + 2 Na2SO4
 The second major production of sodium sulfate are the processes where
surplus sulfuric acid is neutralized by sodium hydroxide, as applied on a
large scale in the production of rayon. This method is also a regularly
applied and convenient laboratory preparation.[4]
2 NaOH (aq.) + H2SO4 (aq.) → Na2SO4 (aq.) + 2 H2O (l)
 In the laboratory it can also be synthesized from the reaction between
sodium bicarbonate and magnesium sulfate.
2 NaHCO3 + MgSO4 → Na2SO4 + Mg (OH) 2 + 2CO2

CHAPTER:-3 Feeding of Multiple
Effect Evaporators
 An evaporator is essentially a heat exchanger in which a liquid is boiled to
give a vapor, so that it is also, simultaneously, a low pressure steam
generator.
 The single effect evaporator uses rather more than 1 kg of steam to evaporate
1 kg of water.
 It may be possible to make use of this, to treat an evaporator as a low pressure
boiler, and to make use of the steam thus produced for further heating in
another following evaporator called another effect.
 There are three types of feeding:-
3.1 FORWARD FEED:
 In the forward feed the liquid feed flows in the same direction as the vapor
flows.
 A simplified diagram of a forward-feed triple-effect evaporation system is
shown in Figure.
Figure 3- forward feed multiple effect evaporator
 If the feed to the first effect is near the boiling point at the pressure in the
first effect 1 kg of steam will evaporate almost 1 kg of water.
 The first effect operates at a high-enough temperature so that the evaporated
water serves as the heating medium to the second effect.
 Here, again, almost another kg of water is evaporated, which can be used as
the heating medium to the third effect.

 As a very rough approximation, almost 3 kg of water will be evaporated for
1 kg of steam for a three-effect evaporator. Hence, the steam economy,
which is kg vapor evaporated/kg steam used, is increased.
 This also approximately holds for a number of effects over three. However,
this increased steam economy of a multiple-effect evaporator is gained at
the expense of the original first cost of these evaporators.
 In this arrangement feed flows from high pressure to low pressure, hence
no pump is required in this system.
 In forward-feed operation as shown in Figure, the fresh feed is added to the
first effect and flows to the next in the same direction as the vapor flow.
 This method of operation is used when the feed is hot or when the final
concentrated product might be damaged at high temperatures.
 The boiling temperatures decrease from effect to effect. This means that if
the first effect is at P1= 1 atm abs pressure, the last effect will be under
vacuum at a pressure P3 .
3.2 BACKWARD FEED:
 In the backward-feed operation for a triple-effect evaporator, the fresh feed
enters the last and coldest effect and continues on until the concentrated
product leaves the first effect.
 This method of reverse feed is advantageous when the fresh feed is cold,
since a smaller amount of liquid must be heated to the higher temperatures
in the second and first effects. However, liquid pumps are used in each
effect, since the flow is from low to high pressure. This method is also used
when the concentrated product is highly viscous.
Figure -4 Backward feed multiple effect evaporation

 The high temperatures in the early effects reduce the viscosity and give
reasonable heat-transfer coefficients in this, the feed solution and the vapor
streams flows in the opposite direction.
 Fresh feed is admitted to the last effect and then pumped through other
effects.
 The steam is admitted to the steam chest of first effect and the vapors
produced are fed to the second effect and so on.
 In this kind of arrangement we require a pump as feed is pumped from high
pressure to the low pressure effect.
 This arrangement is generally preferred with viscous liquids.
 The pressure in the first effect is highest and it is lowest in the last effect.
3.3 Parallel-feed
 Parallel feed in multiple-effect evaporators involves the adding of fresh feed
and the withdrawal of concentrated product from each effect.
 The vapor from each effect is still used to heat the next effect. This method
of operation is mainly used when the feed is almost saturated and solid
crystals are the product, as in the evaporation of brine to make salt.
Figure -5 parallel feed multiple effect evaporator

3.4 Process Description:
 In our case we have taken 3- stage multiple effect evaporation system.
 The effluent streams are sent to the resin plants and after removal of
impurities it is fed to the multiple effect evaporator.
 It is first passed to de gassifier, where gases are removed from the streams.
 The 4 evaporator are arranged in series and forward feed is being used in
this operation.
 The feed after passing from is degassifier is pumped to the calendria, where
steam is passed from the outside to the calendria for heating.
 After this it is passed to the first evaporator where it gets evaporated and
vapours are generated.
 A vaccum draft is created at the end of last effect due to this the vapors
generated from first evaporator is passed to the calendria of second
evaporator for preheating of the feed from 1st
evaporator.
 The vapor generated from 2nd
evaporator is used to supply heat to the
calendria of 3rd
evaporator.
 The feed gets more and more concentrated as it passes from one effect to
the other effect
 The feed from 3rd
evaporator is sent to vapor liquid separator, and the vapor
generated from 3rd
effect is passed to calendria of VLS.
 The vapor generated from VLS is sent to a condenser where it is condensed
to the liquid.
 The feed in the VLS gets separated and slurry is formed in slow, which is
then passed to the drying equipment to form the by-product sodium sulfide.
(Na2SO4).

Chapter 4:- Process Modeling
 Two models are presented in this section. The first is the simplified
mathematical model, which gives a very efficient and simple tool for
system design and evaluation.
 The model is solved through a simple sequence of manual calculations.
Iterations are not exhaustive and do not require computer programming.
Also, the assumptions taken in model development do not sacrifice
process fundamentals, specifically, equal heat transfer area in all
effects.[6]
 The data generated by the model is limited to the following effect
properties:
 Thick liquor and distillate flow rates.
 Liquor concentration.
 Temperature.
 Heat transfer area.
 The model equations exclude the flash boxes and preheaters.
 The governing equation for the down condenser can be included and its
solution is made upon completion of the effect iterations.
 The following assumptions are made to develop the MEE-Forward Feed
simplified model:
i) Constant specific heat, Cp, for the Feed water at different temperature
and concentration.
ii)Constant thermodynamic losses in all effects.
iii)Constant heat transfer area in all effects.
iv) No vapor flashing takes place inside the effects.
v) Feed seawater is at the saturation temperature of the first effect.
vi) Equal thermal loads in all effects.
vii) The formed vapors are salt free.
viii) The driving force for heat transfer in the effect is equal to the difference
of the condensation and evaporation temperatures.
ix) Energy losses to the surroundings are negligible.
x) The feed water is modeled as a binary mixture of fresh water and salt.
 Taking these assumptions into consideration, the mathematical model is
developed below.
 The number of material and energy balance equations, which can be
written for each effect, is three.
 In addition, there are n equation for the heat transfer rate in each effect,
which relates the effect thermal load to the area, overall heat transfer
coefficient, and temperature driving force.

 Therefore, a total of 4xn equations are used to obtain the profiles of the
flow rates, concentration, and temperature across the effects as well as the
heat transfer area. The unknown values are as follow:
Total
 Distillate flow rates, D1, D2, ..., Di, Dn (n unknown)
 Brine concentration, X1, X2, ... , Xi (n-1 unknown)
 Brine flow rate, B1, B2, ..., Bi, Bn (n unknown)
 Effect temperature, T1, T2, ..., Tn-I (n-1 unknown)
 Steam flow rate (1 unknown)
 Heat transfer area (1 unknown)
= (4 n) unknowns
Solution of the model equations to determine the variables, requires
specification of the following system parameters:
i) Temperature of the motive steam, Ts.
ii) Vapor temperature in effect n, Ti.
iii) Salt concentration in the brine stream leaving effect n, Xi.
iv) Salt concentration in the feed stream, Xf.
v) Total distillate flow rate, Md.
Fig. 6. Variables in evaporator, preheater, and flash box of effect i.

Calculations
4.1 FORWARD FLOW CALCULATIONS
Data Available:
Mass Flow Rate of feed = 14,400 kg/hr
= 4 kg/s
Feed inlet temperature = 30⁰C
Initial solid content = 10%
Final solid content = 40%
Saturated dry steam pressure = 2.05 bar
= 205kN/m2
Specific heat of feed = 4.184 kJ/kg K
Pressure of 3rd
effect evaporator = 13kN/m2
= 0.13 bar
From steam table at 0.13 boiling point of water = 325 K
Temperature of dry saturated steam at 205 kN/m2
= 394 K
Temperature Difference ∑∆T = (394-325)
= 69⁰K

Figure -7 Forward-feed arrangement for a triple-effect evaporator
Area= A1 = A2 = A3=65m2
Temperature difference across each evaporator
∆T1 = 18⁰K ∆T2 = 17⁰K ∆T3 = 34⁰K
Latent heat are given by ʎ0, ʎ1, ʎ2, ʎ3
For steam :
1. T0 = 394 k ʎ0 = 2200 kJ/kg
2. T1 = 376 k ʎ1 = 2249 kJ/kg
3 T2 = 359 k ʎ2 = 2293 kJ/kg
4 T3 = 325 k ʎ3 =2377 kJ/kg
Values obtained from Steam Table

Energy calculation:
Effect 1:
D0 ʎ0 = mf C p (T1-Tf) + D1 ʎ1
2200 D0 = 4 × 4.18 (376-303) + 2249 D1
D0= 0.5548 + 1.022 D1 …………………1
Effect 2:
D2 ʎ2 = d1 ʎ1 + (mf-d1) Cp (T1-T2)
D2 (2293) = 2249 D1 + (4-D1) 4.184 (376-354)
D2 (2293) = 2249 D1 + (4-D1) 71.128
D2 = 0.948 D1 + 0.124 …………………2
Effect 3:
D3 ʎ3 = D2 ʎ2 + (mf-D1-D2) 4.184 (359-325)
D3 (2377) = 2293 D2 + (4-D1-D2) 142.256
D3 = 0.0965 D2 + 0.0598 (4-D1-D2)
= 0.965 D2 + 0.240 - 0.0598 D1 - 0.0598 D2
D3 = 0.905 D2 - 0.0598 D1 + 0.240 …………………3
Material Balance over Evaporator:
So, Evaporation of Water = 3 kg
D1 + D2 + D3 = 3 kg/s
Substituting the values of D2 and D3
D1 + 0.948 D1 + 0.124 +0.80 D1 + 0.352 = 3
2.748 D1 = 2.524
Solid Liquor Total
Feed 0.4 3.6 4
Product 0.4 0.6 1

D1 = 0.918 kg/s
D2 = 0.948 D1 + 0.124
= 0.994
D3 = 0.9052 (0.9048 D1 + 0.124) - 0.05981 D1+ 0.240
= 0.798 D1 + 0.352
D3 = 1.0877
D0 = 0.5548 + 1.022 D1
D0 = 0.5548 + 1.022 * 0.918
D0 = 1.50
Steam Economy = kg vaporized / kg steam input
E = 3 / 1.5
= 2
The heat transfer coefficient are then:
U1 = D0 λ0 / A1 ∆T1
= (1.5 * 2200) / (65 * 18)
= 2.82 kJ/m2
s K
U2 = D1 λ1 / A2 ∆T2
= (0.918 * 2249) / (65 * 17)
= 1.86 kJ/m2
s K
U3 =D2 λ2 / A3 ∆T3
= (0.994 * 2293) / (65 * 34)
=1.03 kJ/m2
s K

4.2 BACKWARD FLOW CALCULAIONS
Data Available:
Mass Flow Rate of feed = 14,400 kg/hr
= 4 kg/s
Feed inlet temperature = 30⁰C
Initial solid content = 10%
Final solid content = 40%
Saturated dry steam pressure = 2.05 bar
= 205 kN/m2
Specific heat of feed = 4.184 kJ/kg K
Pressure of 3rd
effect evaporator = 13 kN/m2
= 0.13 bar
From steam table at 0.13 boiling point of water = 325 K
Temperature of dry saturated steam at 205 kN/m2
= 394 K
Temperature Difference ∑∆T = (394-325)
=69⁰K
Figure 8 Backward-feed arrangement for a triple-effect evaporator
Area = A1 = A2 = A3 = 65 m2
Taking:

∆T1 = 18 K, ∆T2 = 21 K, ∆T3 = 30 K
The temperatures in the effect and the corresponding latent heats are:
T0 =394 K and λ0 =2200 kJ/kg
T1 =376 K and λ1 =2255 kJ/kg
T2 =355 K and λ2 =2302.9 kJ/kg
T3 =325 K and λ3 =2377 kJ/kg
The heat balance equations are then:
Effect 3:
D2 λ2 = MF Cp (T3 − Tf) + D3 λ3
2302 D2 = 4 × 4.18 (325−303) +2377 D3
D2 = 0.1597 + 1.032 D3
Effect 2:
D1 λ1 = (MF − D3) Cp (T2 −T3) + D2 λ2
2255 D1 = (4 − D3) 4.18 (355 − 325) + 2302.9 D2
D1 = 0.998 D3 + 0.3854
Effect 1:
D0 λ0 = (Mf − D3 − D2) Cp (T1 − T2) +D1 λ1
2200 D0 = (4 − D3 −D2) 4.18 (374−355) + 2255 D1
D0 = 0.0551 (4 – D3 – D2) + 1.025 D1
We Know That,
(D1 + D2 + D3) = 3 kg/s
0.3854 + 0.998 D3 + 1.032 D3 + 0.1597 + D3 = 3
D1 = 1.1938
D2 = 0.9957
D3 = 0.8101

Substituting the values of D1, D2, & D3 Gives
D0 = 1.31
Steam Economy = kg vaporized / kg steam input
E = 3 / 1.31
= 2.29
The heat transfer coefficient are then:
U1 = D0 λ0 / A1 ∆T1
= (1.31 * 2200) / (65 * 18)
= 2.46 kJ/m2
s K
U2 = D1 λ1 / A2 ∆T2
= (1.1938 * 2255) / (65 * 21)
= 1.97 kJ/m2
s K
U3 =D2 λ2 / A3 ∆T3
= (0.9957 * 2302) / (65 * 30)
=1.17 kJ/m2
s K
4.3 Effect of feed system on economy
 In the case of forward feed systems, all the liquor has to be heated from Tf
to T1 by steam although, in the case of backward feed, the heating of the
feed in the last effect is done with steam that has already evaporated (N −1)
times its own mass of water, assuming ideal conditions.
 The feed temperature must therefore be regarded as a major feature in this
class of problem.
 The effect of feed temperature on the economy and the evaporation in each
effect, for the case of a liquor fed at the rate of 12.5 kg/s to a triple-effect
evaporator in which a concentrated product was obtained at a ﬂowrate of
8.75 kg/s.
 Neglecting boiling-point rise and working with a ﬁxed vacuum on the third
effect, the curves shown in Figures 14.8 and 14.9 for the three methods of
forward, backward and parallel feed were prepared.

Chapter 5: Practical works
5.1 Boiling Point Elevation Experiment
AIM: To determine the boiling point elevation of sodium sulfate.
APPARATUS: Cylindrical flask, plate heater, digital thermometer.
CHEMICALS: sodium sulfate powder, water.
THEORY:
 The vapor pressure of aqueous solution is less than that of water at the same
temperature.
 Consequently for a given pressure the boiling point of solutions is higher
than that of pure water. The increase in boiling point over that of water is
known as boiling point elevation (BPE).
 It is small for dilute solutions and for solutions organic colloids but may be
large as 80C for concentrated solutions of inorganic salts.
 For strong solutions the BPE is the best found from duhring’s rule, which
states that boiling point of given solution is plotted against that of water at
the same pressure.
 Thus if the boiling point of solution is plotted against that of water at the
same pressure.
PROCEDURE:
(1)Prepare sodium sulfate solutions of different concentrations in water.
(2)Make 10% of sodium sulfate solutions by adding 90ml of water in 10
grams of sodium sulfate.
(3)Mix the solution properly.
(4)Now keep the mixture on plate heater and switch on the heater.
(5)Increase the temperature of the heater.
(6)Measure the temperature at which the liquid in the flask will start boiling.
(7)Measure the temperature of the solution by using digital thermometer.
(8)Repeat the same procedure for 20%, 30%, & 40% sodium sulfate
solution.

Figure:-
OBSERVATION TABLE:
SR.NO CONCENTRATION OF
SOLUTION
BUBBLE POINT
TEMPERATURE
1. 10% 100.3C
2. 20% 101.2C
3. 30% 102.5C
4. 40% 103.0C
Graph :-Temperature vs concentration
Graph-1 temperature vs concentration graph
Figure-9 Boiling point elevation apparatus
0%
10%
20%
30%
40%
50%
100 100.5 101 101.5 102 102.5 103 103.5

CONCLUSION:
 Form the above experiment we can conclude that the boiling point
elevation for different concentrations of sodium sulfate solution is
negligible.
 Hence the boiling point elevation can be considered as zero.
5.2 Heat Flux Experiment
Aim: To determine the critical heat flux.
Equipment: Critical Heat Flux Apparatus.
Chemicals: Sodium sulfate, Distilled water
Procedure:
1. Task specified amount of distilled water in contain.
2. See that the both water are completely submerged.
3. Connect the water RI & test water wire across the states & move
necessary electrical connection.
4. Switch on the water R-I-C let variable be at opposition
5. Keep it until you get required bulk time of water in the container e.g. 50
˚C, 60˚C, 70˚C temperature.
6. Keep it till you set required bulk time & switch OFF the water R.
7. Very gradually inner water voltage across the test heater by slowly
changing variable position & stop while at each position to absence
boiling phenomenon on wire.
8. On increasing the voltage till breaks then carefully note voltage & current
at time point.
9. Repeat the experiment by altering bulk temperature of water.

Figure:-
Figure -10 Critical heat flux apparatus
Precautions:
 Keep the variable to be zero voltage position before starting so that both
heaters can completely immersed.
 The sufficient amount of distilled water in the container so that both
heaters can be completely immersed.
 Connect the test heater wire across the study.
 Do not touch the water or terminal point when main switch ON.
 Operate the various studies in steps & sufficient time in between,.
 After attachment at critical heat flux decrease slowly voltage & boils it in
zero position.
Note:-
 The instrument did not worked properly so the readings could not be
obtained and we found it from the theoretical data that the maximum
allowable temperature drop can be 30C.
 The boiling point elevation on the basis of different concentration is also
found by the experiment.
 There is the formation of scale in evaporator so we propose the following
descaling agents with their general description.

Chapter 6: Descaling agents
6.1 General description
 Descaling Liquid is a liquid acid containing descaling accelerators,
corrosion-inhibitors and wetting agents.
 A descaling agent or chemical descaler is a chemical substance used to
remove lime scale or carbonates from metal surfaces in contact with hot
water, such as in boilers, water heaters, evaporators and kettles.
 Descaling agents are typically acidic compounds such as hydrochloric
acid that react with the alkaline carbonate compounds present in the scale,
producing carbon dioxide gas and a soluble salt.
 Strongly acidic descaling agents are often corrosive to the eyes and skin.
 Notable descaling agents include citric acid, formic acid, glycolic
acid, hydrochloric acid, phosphoric acid, sulfamic acid and acetic acid.[7]
6.2 Purpose of chemical cleaning:
 The primary reasons for chemical cleaning of boilers/ heat exchangers are
to prevent tube failures & improve unit availability.
 Tube failures in low pressure boilers/heat exchangers are normally the
results of creep which occurs when internal deposits produce excessive
metal temperature. A relatively smaller quantity of deposit creates
difficulties in high pressure boilers.
 Caustic corrosion & hydrogen damage, which occur only in the presence
of deposits, may cause tube failures at temperatures well below the creep
limit.
 Deposits originating both from fabrication & during operation should be
considered potential problems.
 After a boiler / heat exchanger placed into service, numerous solid
constituents may enter the units with the feed water & some portion of
the insoluble can be expected to deposit on surfaces.
 If not removed these deposits accumulated over a period of time can
minimize the quantity of these materials; however, complete freedom
from deposition is not possible in a high pressure system.

 The need for occasional chemical cleaning during the life of the
equipment has become a recognized fact & should be accepted as a
routine maintenance practice.
 A frequency of service cleaning of every 3 to 4 months is recommended.
This frequency should be increased if individual unit operating history
dictates.[8]
6.3 Features
 Acid based product contains inhibitors against attack on ferrous metals
 Unlimited shelf life
 Easy to rinse off
 Fast and effective scale remover
 Removes scale and rust from condensers, evaporators, heat exchangers,
etc.
 Removes water scale from boilers
 Descaling Liquid should not be used on aluminium, zinc, tin, stainless
steel or any galvanized surfaces for which a special grade cleaner should
be used.
6.4 Notes regarding safety in descaling
operations:
 Descaling liquid contains strong acids. Handle with care and pay special
attention to Material Safety Data Sheet and / or Product Label. Use
personal protection equipment as recommended.
 Reaction products from acid components in descaling products may
include gasses like carbon dioxide and hydrogen.
 Formation of hydrogen gas can be monitored with gas detection
equipment on the vents.
 To avoid suffocation and potentially explosive atmosphere, gasses should
be removed safely by purging system with water after draining the
cleaning solution.
 Vent of system during descaling operations must be provided for same
reason. Always use gas detection equipment to check that the atmosphere
is safe before entering confined spaces for inspection after descaling
operations.
 When circulating the descaling solution, always circulate with inlet at the
bottom to avoid air pockets and potential entrapment of gaseous reaction
products.

Chapter 7: Simulation by using Excel
7.1 Introduction to Simulation
 In a multiple effect evaporator problem the feed conditions and flow rate
(F) are given. The overall heat transfer coefficients (Ui) are assumed to be
known. The desired final concentration (xs) is specified as well as the
pressure of the saturated steam used as the heat source (Ps).
 Additionally, the pressure in one effect (usually the last) is specified (P3).
 The task of the students is to find the amount of steam that must be fed to
the first effect (D), the unknown liquid and vapor flow rates (D1,D2,D3,
L1, L2, L3), the pressures in the other effects (P1, P2), and heat transfer
area of each effect (A).
 Generally the heat transfer areas for all effects are assumed equal.
The governing equations are
 a total mass balance on each evaporator in the evaporation train,
 a solute balance on each effect,
 an energy balance on each effect, and
 The heat transfer rate equation for each effect.
 Several approaches can be used to solve the typical multiple effect
evaporator problem. All textbooks that cover evaporation present a pencil-
and-paper iterative approach.
 Although this method works and requires no expensive software, it has a
number of limitations. The calculations are quite tedious, especially for
larger problems.
A second approach would be to use a commercial simulator.
 These include general purpose simulators such as ASPEN, Unisys,
HYSYS, or ChemCAD, specialty simulators such as Simprosys or
Proces SimO that are specifically for modeling evaporation and drying,
or ERI SYM, a desalinization simulator.
 In theory, these simulators merge two capabilities: the successive
iterative calculations to close material and/or heat balance equations
with a set of thermodynamic equilibrium correlations and data that
successfully model the physical chemistry of the process.
 Programs (e.g., a spreadsheet like Excel) can easily provide the same
capabilities for bookkeeping of material and energy balance
equations—especially through the trial and error calculations.

 In practice, most simulators require a substantial amount of data entry
of thermodynamic parameters to provide any results. For many of the
general purpose simulators support for inorganics and/or Biological
/agricultural components.
The third solution approach is to write the governing equations in matrix form
and use a matrix algebra solver to obtain the solution. This approach has the
advantage of presenting evaporation as a “stage-wise” operation and is
numerically stable and computationally efficient.
 The first drawback of this approach is that the solution is slow because the
student still has to look up enthalpies from the steam table for each
iteration.
 Secondly, according to the authors, a significant investment of time is
needed to train students to be able to rewrite the problem into the matrix
format the solvers can handle.
We present a solution method for multiple effect evaporators that directly solves
the nonlinear equations. The method builds on our sophomore materials and
energy balances course where we teach students to perform a degree of freedom
analysis and to use a spreadsheet to solve flow sheet problems. Since the students
are already comfortable using a spreadsheet to solve a flow sheet problem, using
a spreadsheet for a multiple effect evaporator problem is easy.
In general for N effects there will be 3N unknowns and 3N equations – namely a
mass balance, energy balance, and heat transfer rate equation for each effect. In
principle, these equations should be relatively easy to solve. However, the
coefficients in the equations depend on the unknowns through thermodynamic
relationships.

7.2 PROCEDURE FOR SOLVING PROBLEM OF
FORWARD FEED BY USING EXCEL:
1. Input the data which are shown in yellow box in the fig.
Figure -11 Input data to be inserted by user
2. Material balance is carried out on the basis of input data and total liquid
evaporated is found out.
Figure-12 Material balance of evaporator
3. Assume suitable values of Ui and fix the Area (Ai) of each effect of evaporator.
4. On the basis of values of steam pressure and the pressure in the last effect
values of temperature and latent heat of vaporization are inserted from steam
table.
Temperature in each effect is found by using the formula which is given
below:-
Ti = T i-1 - ΔΤi U1/Ui
5. Total temperature drop ΔΤ is found out.
a) Temperature drop in each effect can be obtained by applying the relation
in between total temperature drop and heat transfer coefficient.

b) On the basis of the values of Ui that are assumed values of ΔΤ for each
effect are found out.
Figure-13 Parameters values obtained from calculations
6. Temp in each effect is found by subtracting the values of ΔΤi and latent heat
values and pressure values are inserted from steam tables.
Figure-14 values of Temperature and latent heat from steam table
7. By applying this values and energy balance equations we get values of live
steam required and amount of vapour that we get from each effect.
8. Assuming the values of D1 which is always less than 1 iterations are carried
out until value of D1+D2+D3 = D.

Figure-15 Iterations
9. Steam Economy is found out on the basis of the values of D0 and D obtained.

7.3 PROCEDURE FOR SOLVING PROBLEM OF
BACKWARD FEED BY USING EXCEL:
1. Input the data which are shown in yellow box in the fig or the data will be
directly inserted on the basis of the data inserted in the forward feed.
Figure -16 Input data to be inserted by user or obtained from forward feed
2) Material balance is carried out on the basis of input data and total liquid
evaporated is found out.
Figure- 17 Material balance of evaporator
3) Assume suitable values of Ui and fix the Area (Ai) of heat transfer for each
effect.
4) On the basis of values of steam pressure and the pressure in the last effect
values of temperature and latent heat of vaporization are inserted from steam
table.
Temperature in each effect is found by using the formula which is given
below:-
Ti = T i-1 - ΔΤi U1/Ui

5) Total temperature drop ΔΤ is found out.
a) Temperature drop in each effect can be obtained by applying the relation
in between total temperature drop and heat transfer coefficient.
b) On the basis of the values of Ui that are assumed values of ΔΤ for each
effect are found out.
Figure-18 Parameters values obtained from calculations
6) Temp in each effect is found by subtracting the values of ΔΤi and latent heat
values and pressure values are inserted from steam tables.
Figure-19 values of Temperature and latent heat from steam table
7) By applying this values and energy balance equations we get values of live
steam required and amount of vapor that we get from each effect.
8) Assuming the values of D1 which is always less than 1 iterations are carried
out until value of D1+D2+D3 = D.

Figure-20 Iterations
9. Steam Economy is found out on the basis of the values of D0 and D obtained.
Comparing the steam economy for both forward and backward feed we can say
that backward feed is better than forward feed.
7.4 Uses of using our excel iteration method:
1. This approach is useful as user has not to look up the value of latent heat
of vaporization as well as temperature and pressure from steam table.
2. It is user friendly as the user has to input the initial condition and final
solid concentration required and calculation are made automatically.

Conclusion
 The steam consumption for the forward feeding scheme is more than that
of backward feeding scheme i.e. the steam economy of the backward feed
is more than forward feed it is proved by using mathematical model that is
theoretical calculation and excel simulation.
 There is elevation in boiling point of the liquor in each effect which is every
negligible so it can be ignored.
 Scale formation problem is also faced which can be solved by using
descaling agents such as sulfamic acid, sulphuric acid, citric acid, formic
acid, glycolic acid, hydrochloric acid, phosphoric acid and acetic acid.

REFERENCES:-
1. Mass Transfer. From Fundamentals to Modern Industrial Applications.
Koichi Asano Copyright 2006 WILEY-VCH Verlag GmbH & Co.
KGaA,Weinheim
2. Design and simulation of a multiple-effect evaporator using vapor bleeding
by MonalishaNayak -2012
3. http://facstaff.cbu.edu/~rprice/lectures/evap1.html
4. Handbook on sodium sulfate
5. McCabe, W.L., Smith J.C., Harriot P., 1993, Unit Operations of Chemical
Engineering, 5th Ed., McGraw Hill,USA.
6. Plant process simulation by B.V. Babu
7. http://wssproducts.wilhelmsen.com/marine-chemicals/cleaning-and-
maintenance-1/cleaning-and-maintenance/descaling-liquid-25-l/
8. http://www.chemicleanengrs.com/descaling-chemicals.htm
9. Richardson, J.F., Harker J.H., Backhurst J.R., 2002, Particle Technology
and Separation Processes, 5th Ed., 2Vol. Linacre House, Jordan Hill,
Oxford.
10.Thakore S.B. & Bhatt B.I., 2007, “Introduction to Process Engineering and
Design”, Tata McGraw Hill Publishing Co. Ltd., New Delhi.
11.Bhatt, B.I. & Vora S.M., 2004, “Stoichiometry”, 4th
Ed., Tata McGraw-
Hill Publishing Co. Ltd., New Delhi.
12.Kern, D.Q., 1950, Process Heat Transfer, McGraw-Hill, USA.
13.Kaya D. & Sarac HI., 2007, Mathematical modeling of multiple-effect
evaporators and energy economy. Energy 32, Pages 1536–1542.
14.Perry R.H. & Green D., 1984, Perry’s Chemical Engineer’s Handbook, 6th
Ed., McGraw Hill, USA
15.Joshi M.V. and Mahajani V.V. Process Equipment Design, McMillan
Publishers India Ltd., 3rd ed., 1996, New Delhi
16.Dutta B.K. ‘Heat Transfer-Principles and Applications’, PHI Pvt. Ltd.,
New Delhi, 1st Ed. (2006), pp. 361-420.

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