Slides for the eLearning course Separation and purification processes in biorefineries (https://open-learn.xamk.fi) in IMPRESS project.
Section: Distillation
Subject: 1.1 Vapor Liquid Equilibrium
Reactive distillation
LeChatelier’s law
conventional process
mtbe production using Reactive distillation
various contact devices used for Reactive distillation
advantages of Reactive distillation
disadvantages of Reactive distillation
application of Reactive distillation
Slides for the eLearning course Separation and purification processes in biorefineries (https://open-learn.xamk.fi) in IMPRESS project (https://www.spire2030.eu/impress).
Section: Distillation
Subject: 1.2 Flash distillation.
Slides for the eLearning course Separation and purification processes in biorefineries (https://open-learn.xamk.fi) in IMPRESS project.
Section: Distillation
Subject: 1.1 Vapor Liquid Equilibrium
Reactive distillation
LeChatelier’s law
conventional process
mtbe production using Reactive distillation
various contact devices used for Reactive distillation
advantages of Reactive distillation
disadvantages of Reactive distillation
application of Reactive distillation
Slides for the eLearning course Separation and purification processes in biorefineries (https://open-learn.xamk.fi) in IMPRESS project (https://www.spire2030.eu/impress).
Section: Distillation
Subject: 1.2 Flash distillation.
This presentation is on shell and tube heat exchanger in which its design parameters and its troubleshooting conditions designed for better understanding and learning of all
An overview of distillation column design concepts and major design considerations. Explains distillation column design concepts, what you would provide to a professional distillation column designer, and what you can expect back from a distillation system design firm. To speak with an engineer about your distillation column project, call EPIC at 314-207-4250.
in this ppt i descussed about evaporator.evaporation,Evaporation is the process by which an element or compound transitions from its liquid state to its gaseous state below the temperature at which it boils.
types of Evaporators
Open kettle or pan
Horizontal tube natural circulation evaporator
Vertical tube natural circulation evaporator
Long tube vertical evaporator
Falling film evaporator
Forced circulation evaporator
Open-pan solar evaporator
This presentation is on shell and tube heat exchanger in which its design parameters and its troubleshooting conditions designed for better understanding and learning of all
An overview of distillation column design concepts and major design considerations. Explains distillation column design concepts, what you would provide to a professional distillation column designer, and what you can expect back from a distillation system design firm. To speak with an engineer about your distillation column project, call EPIC at 314-207-4250.
in this ppt i descussed about evaporator.evaporation,Evaporation is the process by which an element or compound transitions from its liquid state to its gaseous state below the temperature at which it boils.
types of Evaporators
Open kettle or pan
Horizontal tube natural circulation evaporator
Vertical tube natural circulation evaporator
Long tube vertical evaporator
Falling film evaporator
Forced circulation evaporator
Open-pan solar evaporator
Evaporation is a phase change process. Evaporation cause cooling. This slides will explain you all types of Evaporators. All types of Evaporators will explain in this slide.Difference from Drying, Distillation, Crystallization. Three principal elements are of concern in evaporator design:
heat transfer, vapor-liquid separation, and efficient energy consumption. Critical operational and product characteristics of the solution to be evaporated have a major effect on the selection of the evaporator type most suited for the application.
Heat sensitivity
Fouling.
i hope, it will helpful to the students and peoples in the search of topics mentioned
it is informative to study to even get passing marks or for revision
HEAT EXCHANGERS. Heat exchangers are devices that facilitate the exchange of heat between two fluids that are at different temperature while keeping them from mixing with each other.
2. Double Pipe Heat Exchangers
3. A typical double pipe heat exchanger basically consists of a tube or pipe fixed concentrically inside a larger pipe or tube They are used when flow rates of the fluids and the heat duty are small (less than 5 kW) These are simple to construct, but may require a lot of physical space to achieve the desired heat transfer area.
4. Double-pipe exchangers is the generic term covering a range of jacketed 'U' tube exchangers normally operating in countercurrent flow of two types which is true double pipes and multitubular hairpins. One fluid flows through the smaller pipe while the other fluid flows through the annular space between the two pipes. Two types of flow arrangement: Parallel flow Counter flow
5. • The fluids may be separated by a plane wall but more commonly by a concentric tube (double pipe) arrangement shown in fig. If both the fluids move in the same direction, the arrangement is called a parallel flow type. In the counter flow arrangement the fluids move in parallel but opposite directions. In a double pipe heat exchanger, either the hot or cold fluid occupies the annular space and the other fluid moves through the inner pipe. The method of solving the problem using logarithmic mean temperature difference is typical and more iteration must be done. So it takes more time for the problem to solve. Therefore another method is practiced for solving this type of problems. This method is known as Effectiveness and Number of Transfer Units or simply ε-NTU method.“Effectiveness of heat exchangers is defined as actual heat transfer rate by maximum possible heat transfer rate”.The LMTD method may be applied to design problems for which the fluid flow rates and inlet temperatures, as well as a desired outlet temperature, are prescribed.
6. Application of Double Pipe Heat Exchanger Pasteurization or sterilization of food and bioproducts Condensers and evaporators of air conditioners Radiators for internal combustion engines Charge air coolers and intercoolers for cooling supercharged engine intake air of diesel engines.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
2. 28.10.2020 2
Evaporation
• Evaporation is the
conversion of a liquid to a
vapor.
• Evaporation is the removal
of volatile solvent from a
solution or relatively
dilutes slurry by vaporizing
the solvent.
Evaporators are used for
this process.
3. 28.10.2020 3
Evaporators
• Evaporators are used to separate materials based
on differences in their boiling temperatures.
• Its purpose is to concentrate nonvolatile solutes
such as organic compounds, inorganic salts, acids
or bases.
• Typical solutes include phosphoric acid, caustic
soda, sodium chloride, sodium sulfate, gelatin,
syrups and urea.
5. 28.10.2020 5
LONG-TUBE VERTICAL (LTV)
EVAPORATORS
• These types of evaporators are used more than all
other types combined for evaporation because of
low cost per unit capacity
simplicity of construction
heat transfer performance
• The LTV-type evaporator cannot handle crystallizing
solutions but excellent for foaming solution.
• There are two main types of LTV evaporators:
a) Climbing (Rising) film evaporators
b)Falling film evaporators
6. 28.10.2020 6
Climbing (Rising) Film Evaporators
• LTV rising-film evaporator is
used primarily to concentrate
non-salting liquors.
• Climbing film evaporators are
used mainly in the paper
industry, food industry to
condense milk.
8. 28.10.2020
Falling Film Evaporators
• LTV falling film evaporator can
be used to concentrate the
non-salting liquids and more
viscous liquors.
• Principal applications have
been for citrus juices.
• They are also used to
concentrate heat-sensitive
materials and corrosive
solutions.
10. 28.10.2020 10
SHORT-TUBE (CALANDRIA) VERTICAL
EVAPORATORS (STV)
• The short tube evaporators were
the first developed commercially
and still represent probably the
largest number of unit in
operation.
• Used in sugar factory.
• Used for noncorrosive materials.
11. 28.10.2020 11
Advantages
Inexpensive
Efficient heat transfer at high temperature
Easy to descale
Disadvantages
× Poor heat transfer at low temperature
differences or with viscous liquids
× Require a great deal of floor space
12. 28.10.2020 12
HORIZONTAL TUBE EVAPORATORS
• Horizontal tube evaporators use a tube and spray
method of heat transfer.
• The tubes are arranged so as to maximize the heat
transfer area between the steam and the liquor.
C = condensate
F = feed
N = noncondensibles’ vent
P = product or concentrate
S = steam
V = vapor
13. 28.10.2020 13
• The major use is for making distilled water for
boiler feed. Horizontal tube evaporators are
used in the pharmaceutical industry, pulp and
paper industry.
• They are relatively low cost. They have very
low headroom. Horizontal tube evaporators
are not suitable for salting or scaling liquids,
and they have smaller capacity than other
evaporators.
15. 28.10.2020 15
The liquor in a forced-circulation evaporator is
pumped through the tubes to minimize tube
scaling or salting when precipitates are
formed during evaporation.
Submerged-tube type is the most common
type forced circulation evaporator.
Forced circulation evaporators are used in the
mining industry, and also they are used to
evaporate corrosive or highly viscous
solutions.
Forced circulation evaporators are efficient
the transfers heat from steam to liquid,
continuous liquid flow, low amount of salting,
scaling and fouling.
They are expensive and need power for
circulating pump.
17. 28.10.2020 17
AGITATED THIN (WIPED-FILM) FILM
EVAPORATORS
Agitated film evaporators use mechanical to promote heat transfer.
They employ a single large diameter straight or tapered tube as the heating surface, in which
a set of the blades is rotated. The cost of these evaporators is very high and the capacity
relatively low.
These evaporators are used highly viscous liquids or liquids requiring very low
residence times. These evaporators exhibit poor heat transfer performance
on low viscosity fluids.
Their maintenance are difficult because of internal moving parts.
Symbols:
C = condensate
F = feed
N = noncondensibles’ vent
P = product or concentrate
S = steam
V = vapor
Agitated Thin Film Evaporator
18. Classification of liquors
• Those which can be heated to high temperatures
without decomposition, and
– those that can be heated only to a temperature of about
330 K.
• Those which yield solids on concentration, in which
case crystal size and shape may be important, and
– those which do not
• Those which, at a given pressure, boil at about the
same temperature as water, and
– those which have a much higher boiling point.
19. Heat transfer in evaporators
The rate equation for heat transfer
Q is the heat transferred per unit time
U is the overall coefficient of heat transfer
A is the heat transfer surface
T is the temperature difference between the
two streams
Boiling point rise (BPR): The difference between the boiling point of a solution
and that of water is the BPR
Example
At atmospheric pressure (101.3 kN/m2), a 25% solution of sodium chloride boils at
381 K and shows a BPR of 8 deg K. If steam at 389 K were used to concentrate the
salt solution, the overall temperature difference would not be (389 − 373) = 16 deg K,
but (389 − 381) = 8 deg K
Such solutions usually require more heat to vaporise unit mass of water, so that the
reduction in capacity of a unit may be considerable
20. Duhring’s rule
If the boiling point of the
solution is plotted against
that of water at the same
pressure, then a straight
line is obtained
If the pressure is fixed, the
boiling point of water is
found from steam tables,
and the boiling point of the
solution from the Duhring’s
diagram
21. The heat transfer processes occurring in evaporation equipment
Boiling at a submerged surface
Basic heat transfer process
is assumed to be nucleate
boiling with convection
induced predominantly by
the growing and departing
vapour bubbles
Two-phase forced-
convection boiling processes
occurring in closed conduits,
where convection is induced
by the flow which results
from natural or forced
circulation effects.
Burnout
or
DNB point
Or
Max heat flux
22. In the design of evaporators, a method of predicting the heat transfer coefficient in
nucleate boiling hb, and the maximum heat flux which might be expected before hb begins
to decrease, is of extreme importance.
McNelly equation
inclusion of the characteristic dimension d is necessary dimensionally, though its
value does not affect the result obtained for hb.
For single tube the maximum heat flux is given by Zuber’s equation
qmax is the maximum heat flux,
λ is the latent heat of vaporisation
ρL is the density of liquid
ρv is the density of vapour
σ is the interfacial tension
g is the acceleration due to gravity
23. The heat transfer processes occurring in evaporation equipment
Forced convection boiling
25. The liquid coefficient hL is given by
Parameter for two-phase turbulent flow developed by Lockhart and Martinelli
26. Vacuum operation
With a number of heat sensitive liquids it is necessary to work at low
temperatures, and this is effected by boiling under a vacuum
Operation under a vacuum increases the temperature difference between
the steam and boiling liquid as shown below
In practice, the advantages are not as great as this since operation at a lower
boiling point reduces the value of the heat transfer coefficient and additional
energy is required to achieve and maintain the vacuum.
27. • Single-effect evaporators are used
– when the throughput is low
– when a cheap supply of steam is available
– when expensive materials of construction must be used as
is the case with corrosive feedstocks and
– when the vapour is so contaminated so that it cannot be
reused
• Single effect units may be operated in
– batch
– semi-batch
– continuous batch
– continuously
Single-Effect Evaporators
28. Problem
A single-effect evaporator is used to concentrate 7 kg/s of a
solution from 10 to 50 per cent solids.
Steam is available at 205 kN/m2 and evaporation takes place at
13.5 kN/m2.
If the overall coefficient of heat transfer is 3 kW/m2 deg K,
estimate the heating surface required and the amount of steam
used if the feed to the evaporator is at 294 K and the condensate
leaves the heating space at 352.7 K.
The specific heats of 10 and 50 per cent solutions are 3.76 and
3.14 kJ/kg deg K respectively.
29. Assuming that the steam is dry and saturated at 205 kN/m2, then from the Steam
Tables, the steam temperature = 394 K at which the total enthalpy = 2530 kJ/kg.
At 13.5 kN/m2, water boils at 325 K and, in the absence of data on the boiling point
elevation, this will be taken as the temperature of evaporation, assuming an
aqueous solution.
The total enthalpy of steam at 325 K is 2594 kJ/kg.
Thus the feed, containing 10 per cent solids, has to be heated from 294 to 325 K at
which temperature the evaporation takes place.
In the feed, mass of dry solids = (7 × 10)/100 = 0.7 kg/s
and, for x kg/s of water in the product: (0.7 × 100)/(0.7 + x) = 50
from which: x = 0.7 kg/s
Thus: water to be evaporated = (7.0 − 0.7) − 0.7 = 5.6 kg/s
Summarising:
Solution
30. Using a datum of 273 K:
Heat entering with the feed = (7.0 × 3.76)(294 − 273) = 552.7 kW
Heat leaving with the product = (1.4 × 3.14)(325 − 273) = 228.6 kW
Heat leaving with the evaporated water = (5.6 × 2594) = 14, 526 kW
Thus:
Heat transferred from the steam = (14526 + 228.6) − 552.7 = 14, 202 kW
The enthalpy of the condensed steam leaving at 352.7 K = 4.18(352.7 − 273) = 333.2
kJ/kg
The heat transferred from 1 kg steam = (2530 − 333.2) = 2196.8 kJ/kg
and hence:
Steam required = (14, 202/2196.8) = 6.47 kg/s
As the preheating of the solution and the sub-cooling of the condensate represent
but a small proportion of the heat load, the temperature driving force may be taken
as the difference between the temperatures of the condensing steam and the
evaporating water,
or: T = (394 − 325) = 69 deg K
Thus: Heat transfer area, A = Q/UΔT (equation 14.1)
= 14, 202/(3 × 69) = 68.6 m2
31. Multiple-effect Evaporators
• Three methods have been introduced which
enable the performance to be improved,
– either by direct reduction in the steam consumption
– or by improved energy efficiency of the whole unit
• Multiple effect operation
• Recompression of the vapour rising from the
evaporator
• Evaporation at low temperatures using a heat
pump cycle.
32. Forward-feed arrangement for a triple-
effect evaporator
For three evaporators the temperatures and pressures are T1, T2, T3, and P1, P2, P3, respectively,
in each unit, if the liquor has no boiling point rise
33. Effect 1 Q1 = U1A1 Δ T1 where Δ T1 = (T0 − T1)
Effect 2 Q2 = U2A2 Δ T2 where Δ T2 = (T1 − T2)
Effect 3 Q3 = U3A3 Δ T3 where Δ T3 = (T2 − T3)
Neglecting the heat required to heat the feed from Tf to T1, the heat Q1
transferred across where A1 appears as latent heat in the vapour D1 and is used
as steam in the second effect Q1 = Q2 = Q3
So that: U1A1 Δ T1 = U2A2 Δ T2 = U3A3 ΔT3
On this analysis, the difference in temperature across each effect is inversely
proportional to the heat transfer coefficient.
(a) the heat required to heat the feed from Tf to T1 has been neglected, and
(b) the liquor passing from stages 1 to 2 carries heat into the second effect, and
this is responsible for some evaporation. This is also the case in the third effect.
34. The latent heat required to evaporate 1 kg of water in 1, is approximately equal to
the heat obtained in condensing 1 kg of steam at T0.
Thus 1 kg of steam fed to 1 evaporates 1 kg of water in 1.
Again the 1 kg of steam from 1 evaporates about 1 kg of steam in 2.
Thus, in a system of N effects, 1 kg of steam fed to the first effect will evaporate in
all about N kg of liquid.
The economy of the system, measured by the kilograms of water vaporised per
kilogram of steam condensed, increases with the number of effects
The water evaporated in each effect is proportional to Q, since the latent heat is
approximately constant.
35. Thus the total capacity is:
If an average value of the coefficients Uav is taken, then
Thus, it is seen that the capacity of a multiple-effect system is the same as that of
a single effect, operating with the same total temperature difference and having
an area A equal to that of one of the multiple-effect units.
The value of the multiple-effect system is that better use is made of steam
although, in order to achieve this, a much higher capital outlay is required for the
increased number of units and accessories.
36. Problem
4 kg/s (14.4 tonne/hour) of a liquor containing 10 per cent solids is fed at 294 K to
the first effect of a triple-effect unit. Liquor with 50 per cent solids is to be
withdrawn from the third effect, which is at a pressure of 13 kN/m2 (∼0.13 bar).
The liquor may be assumed to have a specific heat of 4.18 kJ/kg K and to have no
boiling point rise. Saturated dry steam at 205 kN/m2 is fed to the heating element
of the first effect, and the condensate is removed at the steam temperature in
each effect as shown in Figure. If the three units are to have equal areas, estimate
the area, the temperature differences and the steam consumption. Heat transfer
coefficients of 3.1, 2.0 and 1.1 kW/m2 K for the first, second, and third effects
respectively, may be assumed.
37. Solution 1
A precise theoretical solution is neither necessary nor possible, since during the
operation of the evaporator, variations of the liquor levels, for example, will
alter the heat transfer coefficients and hence the temperature distribution. It is
necessary to assume values of heat transfer coefficients, although, as noted
previously, these will only be approximate and will be based on practical
experience with similar liquors in similar types of evaporators.
Temperature of dry saturated steam at 205 kN/m2 = 394 K.
At a pressure of 13 kN/m2 (0.13 bar), the boiling point of water is 325 K, so that
the total temperature difference ΣΔT = (394 − 325) = 69 deg K.
38. First Approximation.
Assuming that: U1 Δ T1 = U2 ΔT2 = U3 ΔT3 (equation 14.8)
then substituting the values of U1, U2 and U3 and ΣΔT = 69 deg K gives:
T1 = 13 deg K
T2 = 20 deg K
T3 = 36 deg K
Since the feed is cold, it will be necessary to have a greater value of T1 than given
by this analysis. It will be assumed that T1 = 18 deg K, T2 = 17 deg K, T3 = 34 deg K.
If the latent heats are given by λ0, λ1, λ2 and λ3, then from the Steam Tables in the
Appendix:
For steam to 1: T0 = 394 K and λ0 = 2200 kJ/kg
For steam to 2: T1 = 376 K and λ1 = 2249 kJ/kg
For steam to 3: T2 = 359 K and λ2 = 2293 kJ/kg
T3 = 325 K and λ3 = 2377 kJ/kg
Assuming that the condensate leaves at the steam temperature, then heat
balances across each effect may be made as follows:
39. Assuming that the condensate leaves at the steam temperature, then heat
balances across each effect may be made as follows:
40. Making use of the previous equations and the fact that (D1 + D2 + D3) = 3.2 kg/s, the
evaporation in each unit is, D1 ≈ 0.991, D2 ≈ 1.065, D3 ≈ 1.144, D0 ≈ 1.635 kg/s. The
area of the surface of each calandria necessary to transmit the necessary heat under
the given temperature difference may then be obtained as:
These three calculated areas are approximately equal, so that the temperature
differences assumed may be taken as nearly correct. In practice, T1 would have to be a
little larger since A1 is the smallest area. It may be noted that, on the basis of these
calculations, the economy is given by e = (3.2/1.635) = 2.0. Thus, a triple effect unit
working under these conditions gives a reduction in steam utilisation compared with
a single effect, though not as large an economy as might be expected.
41. Alternate Solution 2
From Figure 14.5 it may be seen that for a feed GF to the first effect, vapour D1 and
liquor (GF − D1) are fed forward to the second effect.
In the first effect, steam is condensed partly in order to raise the feed to its boiling
point and partly to effect evaporation.
In the second effect, further vapour is produced mainly as a result of condensation
of the vapour from the first effect and to a smaller extent by flash vaporisation of
the concentrated liquor which is fed forward.
As the amount of vapour produced by the latter means is generally only
comparatively small, this may be estimated only approximately.
Similarly, the vapour produced by flash evaporation in the third effect will be a
small proportion of the total and only an approximate evaluation is required.
42. Improving the Economy of Evaporators
Poor evaporator economy results from wasting heat present in
the vapors
Some of the techniques used to reclaim heat from the vapors
include use of multiple effects such that
1. Vapors from the first effect are used to heat the succeeding
effects
2. Use of vapors to preheat the feed
3. Vapor recompression