Concepts of Chemical Engineering 4 Chemists - Hardcover

Hardcover

ISBN 10: 0854049517 ISBN 13: 9780854049516

Verlag: Royal Society of Chemistry, 2007

Inhaltsangabe

Concepts of Chemical Engineering 4 Chemists outlines the basic aspects of chemical engineering for chemistry professionals. It clarifies the terminology used and explains the systems methodology approach to process design and operation for chemists with limited chemical engineering knowledge. Offering practical insights into all areas of chemical engineering, including such aspects as pump design and the measurement of key process variables, the calculation of design parameters and reaction scale-up, as well as hazard analysis, project economics and process control. The books worked examples are ideal for those who either work alongside chemical engineers or who are embarking on chemical engineering-type projects.

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Über die Autorin bzw. den Autor

The Author Professor Simons is a Chartered Engineer and Fellow of the Institution of Chemical Engineers (IChemE) and is a member of the Executive Committee of the Standing Conference of Chemical Engineering Professors. He is also vice-chair of the committee of the IChemE's Particle Technology Subject Group and serves on the committee of the Royal Society of Chemistry's Process Technology Group, which initiated the short course on which this book is based. Professor Simons' expertise lies in particle technology, in general, and, more specifically, in the development of low carbon technologies in regards to the reduction of carbon dioxide emissions, particularly in carbon capture and storage, for which he was an expert reviewer of the Intergovernmental Panel on Climate Change's special report on this subject.

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Based on the popular course of the same title, Concepts of Chemical Engineering 4 Chemists outlines the basic aspects of chemical engineering for chemistry professionals. It clarifies the terminology used and explains the systems methodology approach to process design and operation for chemists with limited chemical engineering knowledge. The book provides practical insights into all areas of chemical engineering, including such aspects as pump design and the measurement of key process variables. The calculation of design parameters, such as heat and mass transfer coefficients, and reaction scale-up are also discussed, as well as hazard analysis, project economics and process control. Designed as a reference guide, it is fully illustrated and includes worked examples as well as extensive reference and bibliography sections. Concepts of Chemical Engineering 4 Chemists is ideal for those who either work alongside chemical engineers or who are embarking on chemical engineering-type projects.

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Concepts of Chemical Engineering 4 Chemists

By Stefaan J. R. Simons

The Royal Society of Chemistry

Copyright © 2007 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-0-85404-951-6

Contents

Chapter 1 Process Analysis – The Importance of Mass and Energy Balances Eric S. Fraga, 1, 
Chapter 2 Introduction to Chemical Reaction Engineering George Manos, 21, 
Chapter 3 Concepts of Fluid Flow Tim Elson, 55, 
Chapter 4 An Introduction to Heat Transfer Tim Elson and Paola Lettieri, 96, 
Chapter 5 An Introduction to Mass-Transfer Operations Eva Sorensen, 139, 
Chapter 6 Scale-Up in Chemical Engineering Tim Elson, 171, 
Chapter 7 An Introduction to Particle Systems Paola Lettieri, 203, 
Chapter 8 An Introduction to Process Control Eva Sorensen, 249, 
Chapter 9 Economic Appraisal of Large Projects Ken Sutherland, 272, 
Chapter 10 Hazard Studies and Risk Assessment Robert Thornton, 309, 
Subject Index, 342, 

CHAPTER 1

Process Analysis – The Importance of Mass and Energy Balances

ERIC S. FRAGA

1.1 INTRODUCTION

Process engineering includes the generation, study and analysis of process designs. All processes must obey some fundamental laws of conservation. We can group these into conservation of matter and conservation of energy. Given a set of operations, if we draw a box around this set, the amount of mass going in must equal the amount going out; the same applies to the energy. Mass and energy balance operations are fundamental operations in the analysis of any process. This chapter describes some of the basic principles of mass and energy balances.

1.1.1 Nomenclature and Units of Measurement

In carrying out any analysis, it is important to ensure that all units of measurement used are consistent. For example, mass may be given in kg (kilogrammes), in lb (pounds) or in any other units. If two quantities are given in different units, one quantity must be converted to the same unit as the other quantity. Any book on chemical engineering (or physics and chemistry) will have conversion tables for standard units.

There are seven fundamental quantities that are typically used to describe chemical processes, mass, length, volume, force, pressure, energy and power, although some of these can be described in terms of others in the list. For example, volume is length raised to the power 3; power is energy per unit time, pressure is force per area or force per length squared, and so on.

Chemical engineering uses some standard notation for many of the quantities we will encounter in process analysis. These are summarised in Table 1 where T is time, M is mass and L is length.

In describing processes, the variables that describe the condition of a process fall into two categories:

(i) extensive variables, which depend on (are proportional to) the size of the system, such as mass and volume, and

(ii) intensive variables, which do not depend on the size of the system, such as temperature, pressure, density and specific volume, and mass and mole fractions of individual system components.

The number of intensive variables that can be specified independently for a system at equilibrium is known as the degrees of freedom of the system.

Finally, it is important to note that the precision of quantities is often not arbitrary. Measuring tools have limits on the precision of measurement. Such measures will have a particular number of significant figures. Calculations with measurements may not result in an increase in the number of significant figures. There are two rules to follow to determine the number of significant figures in the result of calculations:

(i) When two or more quantities are combined by multiplication and/or division, the number of significant figures in the result should equal the lowest number of significant figures of any of the multiplicands or divisors. In the following example, one multiplicand has three significant figures and the other, four. Therefore, the result must have no more than three significant figures regardless of the number of figures that are generated by the calculation:

3:57 x 4:286 = 15:30102 [??] 15:3

(ii) When two or more numbers are either added or subtracted, the positions of the last significant figure of each number relative to the decimal point should be compared. Of these positions, the one farthest to the left is the position of the last permissible significant figure of the sum or difference. It is important to make sure that all the numbers are represented with the same exponent if scientific notation is used:

1:53 x 103 - 2:56 = (1:53 x 103) - (0:00256 x 103)

= (1:53 - 0:00256) x 103

= 1:52744 x 103

= 1:53 x 103

1.2 MASS BALANCES

Chemical processes may be classified as batch, continuous or semi-batch and as either steady-state or transient. Although the procedure required for performing mass, or material, balances depends on the type of process, most of the concepts translate directly to all types.

The general rule for mass balance in a system box (a box drawn around the complete process or the part of the process of interest) is:

input + generation - output - consumption = accumulation (1)

where,

(i) input is the material entering through the system box. This will include feed and makeup streams;

(ii) generation is the material produced within the system, such as the reaction products in a reactor;

(iii) output is the material that leaves through the system boundaries. These will typically be the product streams of the process;

(iv) consumption is the material consumed within the system, such as the reactants in a reactor;

(v) accumulation is the amount of material that builds up within the system.

In a steady-state continuous process, the accumulation should always be zero, which leads to a more simple mass balance equation:

input + generation = output + consumption (2)

In the case of systems with no reaction, where mass is neither generated nor consumed, the result is even simpler:

input = output (3)

1.2.1 Process Analysis Procedure

The analysis of the mass balance of a process typically follows a number of steps:

(i) Draw and label a diagram for the process, clearly indicating the information given by the problem definition and the values that have been requested.

(ii) Choose a basis of calculation if required. If no extensive variables (e.g. amount or flow rate of a stream) have been defined, a basis of calculation is required and this must be an extensive variable.

(iii) Write down appropriate equations until zero degrees of freedom are achieved. In other words, write down enough equations so that the number of equations equals the number of unknown variables and such that all the unknown variables are referred to in the equations. Possible sources of equations include the following:

(a) Mass balances. For a system with n species, n mass balance equations may be written down. These mass balance equations may be drawn from a total mass balance and from individual species mass balances.

(b) Process specifications and conditions such as, for example, the separation achieved by a distillation unit or the conversion in a reactor.

(c) Definitions such as the relationship between density, mass and volume or the relationship between mole fraction and total...

Details zur Ausgabe

• Verlag: Royal Society of Chemistry
• Erscheinungsdatum: 2007
• Sprache: Englisch
• ISBN 10: 0854049517
• ISBN 13: 9780854049516
• Einband: Gebundene Ausgabe
• Anzahl der Seiten: 372
• Herausgeber: Simons Stefaan
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: gpsr@libri.de; gpsr@libri.de; ; Friedensallee 273; Hamburg; 22763; Deutschland