Projcet Dr Riyah

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Ministry of Higher Education and

Scientific ResearchUniversity of Technology

Chemical Engineering Department

PROJECT

Fourth Year

By

Dr Riyadh Sadeq Al Muktar


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Reference

1. Sinnott R. and Towler C; 2009 " chemical Engineering Design"

5

th

edition Butterworth-Heinemann2. Coke,A.K ;2007"Ludwig s Applied Process Design of Chemical

and petrochemical Plant" vol. 1 4th

edition Gulf professional

Publisher

3.Branan C. 2005 " rules of Thumbs for Chemical

Engi neer s"4t h edi t i on Gul f professional

Publisher

4.Couper ,J.;Penny, W R ;Fair J and Walas 2010

"Chemical Process Equipment" 2ndedition

5.Peters,M; timmerhause k.D;and West R. 2003 "

plant Design and economics for Chemical

Engineers '5thedition McGraw-Hill

6.Perry R and Green D; 1997 " Perry s Chemical

Engineers Handbook " 7th

edition MaGraw hill


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Design Information and Data

Information on manufacturing processes, equipment parameters, materials of

construction, costs and the physical properties of process materials are

needed at all stages of design; from the initial screening of possibleprocesses, to the plant start-up and production

When a project is largely a repeat of a previous project, the data and

information required for the design will be available in the Company's

process files, if proper detailed records are kept. For a new project or

process, the design data will have to be obtained from the literature, or by

experiment (research laboratory and pilot plant), or purchased from other

companies. The information on manufacturing processes available in the

general literature can be of use in the initial stages of process design, for

screening potential process; but is usually mainly descriptive, and toosuperficial to be of much use for detailed design and evaluation.

SOURCES OF INFORMATION ON MANUFACTURING PROCESSES

The chemical process industries are competitive, and the information that is

published on commercial processes is restricted. The articles on particular

processes published in the technical literature and in textbooks invariably

give only a superficial account of the chemistry and unit operations used.

They lack the detailed information needed on reaction kinetics, process

conditions, equipment parameters, and physical properties needed for

process design. The information that can be found in the general literature is,

however, useful in the early stages of a project, when searching for possible

process routes. It is often sufficient for a flow-sheet of the process to be

drawn up and a rough estimate of the capital and production costs made.

The most comprehensive collection of information on manufacturing

processes is probably the Encyclopedia of Chemical Technology edited by

Kirk and Othmer (1978, 1991 If), which covers the whole range of chemical

and associated products. Another encyclopedia covering manufacturing

processes is that edited by McKetta (1977). Several books have also beenpublished which give brief summaries of the production processes used for

the commercial chemicals and chemical products. The most well known of

these is probably Shreve's book on the chemical process industries, now

updated by Austin, Austin (1984). Others worth consulting are those by

Faith et al, (1965), Groggins (1958),


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Stephenson (1966) and Weissermal and Arpe (1978). Cornyns (1993) lists

named chemical manufacturing processes, with references. The extensive

German reference work on industrial processes, Ullman's Encyclopedia

of Industrial Technology, is now available in an English translation, Ullman

(1984). Specialised texts have been published on some of the more

important bulk industrial chemicals, such as that by Miller (1969) on

ethylene and its derivatives; these are too numerous to list but should be

available in the larger reference libraries and can be found by reference to

the library catalogue

Books quickly become outdated, and many of the processes described are

obsolete, or at best obsolescent. More up-to-date descriptions of the

processes in current use can be found in the technical journals. The journal

Hydrocarbon Processing publishes an annual review of petrochemical

processes, which was entitled Petrochemical Developments and is nowcalled Petrochemicals Notebook', this gives flow-diagrams and brief process

descriptions of new process developments. Patents are a useful source of

information; but it should be remembered that the patentee will try to write

the patent in a way that protects his invention, whilst disclosing the least

amount of useful information to his competitors. The examples given in a

patent to support the claims often give an indication of the process

conditions used; though they are frequently examples of laboratory

preparations, rather than of the full-scale manufacturing processes. Several

short guides have been written to help engineers understand the use of

patents for the protection of inventions, and as sources of information; such

as those by Capsey (1963), Lieberry (1972) and HMSO (1970, 1971).

World Wide WebIt is worthwhile searching the Internet for information on processes,

equipment and products. Many manufacturers and government departments

maintain web sites. In particular, up-to-date information can be obtained on

the health and environmental effects of products.

GENERAL SOURCES OF PHYSICAL PROPERTIES

International Critical Tables (1933) is still probably the most

comprehensive compilation of physical properties, and is available in most

reference libraries. Though it was first published in 1933, physical properties

do not change, except in as much as experimental techniques improve, and


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ICT is still a useful source of engineering data. Tables and graphs of

physical properties are given in many handbooks and textbooks on Chemical

Engineering and related subjects. Many of the data given are duplicated

from book to book, but the various handbooks do provide quick, easy access

to data on the more commonly used substances.

An extensive compilation of thermophysical data has been published by

Plenum Press, Touloukian (1970-77). This multiple-volume work covers

conductivity, specific heat, thermal expansion, viscosity and radiative

properties (emittance, reflectance, absorptance and transmittance),

Elsevier have published a series of volumes on physical property and

thermodynamic data. The Engineering Sciences Data Unit (ESDU) was set

up to provide authenticated data for engineering design. Its publications

include some physical property data, and other design data and methods of

interest to chemical engineering designers. They also cover data and

methods of use in the mechanical design of equipment.Caution should be exercised when taking data from the literature, as

typographical errors often occur. If a value looks doubtful it should be cross-

checked in an independent reference, or by estimation.

The values of some properties will be dependent on the method of

measurement; for example, surface tension and flash point, and the method

used should be checked, by reference to the original paper if necessary, if an

accurate value is required.

The results of research work on physical properties are reported in the

general engineering and scientific literature. The Journal of Chemical

Engineering Dataspecialises in publishing physical property data for use in

chemical engineering design. A quick search of the literature for data can be

made by using the abstracting journals; such as Chemical Abstracts

(American Chemical Society) and Engineering Index (Engineering Index

Inc., New York). Computerised physical property data banks have been set

up by various organizations to provide a service to the design engineer. They

can be incorporated into computer aided design programs and are

increasingly being used to provide reliable, authenticated, design data. An

example of such a data bank is the Physical Property Data Service (PPDS)

available from the National Engineering Laboratory (NEL).


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ACCURACY REQUIRED OF ENGINEERING DATA

The accuracy needed depends on the use to which the data will be put.

Before spending time and money searching for the most accurate value, or

arranging for special measurements to be made, the designer must decide

what accuracy is required; this will depend on several factors:

1. The level of design; less accuracy is obviously needed for rough scouting

calculations, made to sort out possible alternative designs, than in the final

stages of design; when money will be committed to purchase equipment, and

for construction,

2. The reliability of the design methods; if there is some uncertainty in the

techniques to be used, it is clearly a waste of time to search out highly

accurate physical property data that will add little or nothing to the reliability

of the final design.

3. The sensitivity to the particular property: how much will a small error inthe property affect the design calculation. For example, it was shown in

Chapter 4 that the estimation of the optimum pipe diameter is insensitive to

viscosity. The sensitivity of a design method to errors in physical properties,

and other data, can be checked by repeating the calculation using slightly

altered values.


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PREDICTION OF PHYSICAL PROPERTIES

Whenever possible, experimentally determined values of physical properties

should be used. If reliable values cannot be found in the literature and if

time, or facilities, are not available for their determination, then in order to

proceed with the design the designer must resort to estimation. Techniques

are available for the prediction of most physical properties with sufficient

accuracy for use in process and equipment design.

A detailed review of all the different methods available is beyond the scope

of this book; selected methods are given for the more commonly needed

properties. The criterion used for selecting a particular method for

presentation in this chapter was to choose the most easily used,

simplest, method that had sufficient accuracy for general use. If highly

accurate values are required, then specialised texts on physical property

estimation should be consulted; such as those by: Reid et al (1987),Bretsznajder (1971) and Sterbacek et al. (1979), and AIChemE (1983)

(1985).

DENSITYLiquids

Values for the density of pure liquids can usually be found in the handbooks.

It should be noted that the density of most organic liquids, other than those

containing a halogen or other "heavy atom", usually lies between 800 and

1000 kg/m3 An approximate estimate of the density at the normal boilingpoint can be obtained from the molar volume

where, = density, kg/m3,

M = molecular mass,

Vm = molar volume, m3/kmol.

For mixtures, it is usually sufficient to take the specific volume of the

components as additive; even for non-ideal solutions,


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Gas and vapour density (specific volume)For general engineering purposes it is often sufficient to consider that real

gases, and vapours, behave ideally, and to use the gas law:

PV=nRT


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VISCOSITY

Viscosity values will be needed for any design calculations involving the

transport of fluids or heat. Values for pure substances can usually be found

in the literature.. Methods for the estimation of viscosity are given below.

Liquids

A rough estimate of the viscosity of a pure liquid at its boiling point can be

obtained from the modified Arrhenius equation:

Where viscosity, mNs/,

pb density at boiling point, kg/m3.

A more accurate value can be obtained if reliable values of density are

available, or can be estimated with sufficient accuracy, from Souders'

equation, Souders (1938):


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GasesReliable methods for the prediction of gas viscosities, and the effect of

temperature and pressure, are given by Bretsznajder (1971) and Reid et al.

(1987). Where an estimate of the viscosity is needed to calculate Prandtl

numbers (see Volume 1, Chapter 1) the methods developed for the direct

estimation of Prandtl numbers should be used.For gases at low pressure Bromley (1952) has suggested the following

values:

Prandtl number

Monatomic gases (e.g. Ar, He) 0.67 5 per cent

Non-polar, linear molecules (e.g. C>2, C^) 0.73 15 per cent

Non-polar, non-linear molecules (e.g. CH4, CeHe) 0.79 15 per cent

Strongly polar molecules (e.g. CH3OH, SO2, HC1) 0.86 8 per cent

The Prandtl number for gases varies only slightly with temperature.


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THERMAL CONDUCTIVITY

The experimental methods used for the determination of thermal

conductivity are described by Tsederberg (1965), who also lists values for

many substances. Ho et al.(1972) give values for the thermal conductivity

of the elements.

Solids

The thermal conductivity of a solid is determined by its form and structure,

as well as composition. Values for the commonly used engineering materials

are given in various handbooks.

8.8.2. LiquidsThe data available in the literature up to 1973 have been reviewed by

Jamieson et al, (1975). The Weber equation (Weber, 1880) can be used to

make a rough estimate of thethermal conductivity of organic liquids, for usein heat-transfer calculations.

GasesApproximate values for the thermal conductivity of pure gases, up to

moderate pressures, can be estimated from values of the gas viscosity, using

Eucken's equation, Eucken (1911):


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SPECIFIC HEAT CAPACITYThe specific heats of the most common organic and inorganic materials can

usually be found in the handbooks.

. Solids and liquidsApproximate values can be calculated for solids, and liquids, by using a

modified form of Kopp's law, which is given by Werner (1941). The heat

capacity of a compound is taken as the sum of the heat capacities of the

individual elements of which it is composed. The values attributed to each

element, for liquids and solids, at room temperature,


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Gases

For a gas in the ideal state the specific heat capacity at constant pressure

is given by:

Cp = a + bT + cT2 + dT3 (equation 3.19)

Values for the constants in this equation for the more common gases can be

found in the handbooks.

Several group contribution methods have been developed for the estimation

of the constants, such as that by Rihani and Doraiswamy (1965) for organic

compounds. Their values for each molecular group are given in Table 8.4,


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