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Process flowsheeting
Process flowsheeting A W Westerberg, H P Hutchison, R L Motard and P Winter Cambridge University Press, Cambridge, UK (1979) 251 pp £12 The book is aimed at a limited audience; those who wish to know more about designing process flowsheeting systems, rather than those who wish to know about using them. It could perhaps be useful to one engaged in comparing a number of commercially available systems, and certainly would be an ideal text for a graduate-level course even though there are no set problems for homework assignments. The book is presented in a comfortable style with frequent but, discrete use of the first person plural and Winter's useful introduction sets the scene by placing the task of flowsheeting into its design context. A brief history of process flowsheeting shows how various factors have directed development into three approaches each of which merit a whole chapter in the second half of the book: the sequential modular, equation solving and linearization approaches. Some of the mathematical techniques needed are made more complicated by the large numbers of variables involved. Recognizing this, the authors have included a whole chapter to explain and discuss those techniques. In particular, the descriptions of methods which handle large, sparse matrices is clear and compre-
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patience can lead to early attempb at a fully detailed process simulation. The model may then be used to help take simple, preliminary decisions (at hensive as too is the section on direct great cost) which should have been linearization methods. settled before deciding on the exact Physical property generation is process to be simulated. If the perstressed as an important ingredient in formance characteristics of the units good design, but coverage is poor. in a proposed flowsheet can easily be This anomaly is explained in the estimated or are known beforehand introduction: a companion volume (as they will be in a repeated design) entirely devoted to this topic is to then a fast, inexpensive linear simufollow. lation is possible and can be used to Many process simulation difficulties examine preliminary questions such as arise because of poorly planned proprocess configuration and feedstock blem specification which results from blending. a weak appreciation of the significance In the second of these two excellent of the degrees of freedom of a flowsheet. chapters, it is shown how the linear Knowing that such a weakness renders method can be extended into an futile the learning of elegant solution iteractive quasi-linear method in which methods, the authors have included a a matrix is established using linear discussion of this topic. They show in equations where possible and otherwise turn how the degrees of freedom are putting in linear approximations. The established for a single process stream, sparse set of equations is solved to for a few process units and then for give a trial solution which is then used a simple flowsheet which comprises to update the linear approximations and those units. thus close the loop that will be iterated Descriptions of the three flowto reach convergence. Many examples sheeting methods (named above) follow of the application of the quasi-linear a well tried, proven pattern: general method to a wide range of problems description, breakdown of the software into tasks (with an explanation of each), are given. The book will be a most usefuI a simple example and mention of addition to the shelves of those responspecial cases which deserve extra sible for computer-aided process design. attention. The last two chapters are excellent M E Leesley and were, for me, the best in the book. To my knowledge it is the only In the January issue of CAD it was material in the book which has not stated that a softback version of been published before in this form. Engineering Software was available. The first of these is a chapter on This was in fact only printed for simulation by linear methods. Imdelegates of the conference.
computer-aided design
214
patience can lead to early attempb at a fully detailed process simulation. The model may then be used to help take simple, preliminary decisions (at hensive as too is the section on direct great cost) which should have been linearization methods. settled before deciding on the exact Physical property generation is process to be simulated. If the perstressed as an important ingredient in formance characteristics of the units good design, but coverage is poor. in a proposed flowsheet can easily be This anomaly is explained in the estimated or are known beforehand introduction: a companion volume (as they will be in a repeated design) entirely devoted to this topic is to then a fast, inexpensive linear simufollow. lation is possible and can be used to Many process simulation difficulties examine preliminary questions such as arise because of poorly planned proprocess configuration and feedstock blem specification which results from blending. a weak appreciation of the significance In the second of these two excellent of the degrees of freedom of a flowsheet. chapters, it is shown how the linear Knowing that such a weakness renders method can be extended into an futile the learning of elegant solution iteractive quasi-linear method in which methods, the authors have included a a matrix is established using linear discussion of this topic. They show in equations where possible and otherwise turn how the degrees of freedom are putting in linear approximations. The established for a single process stream, sparse set of equations is solved to for a few process units and then for give a trial solution which is then used a simple flowsheet which comprises to update the linear approximations and those units. thus close the loop that will be iterated Descriptions of the three flowto reach convergence. Many examples sheeting methods (named above) follow of the application of the quasi-linear a well tried, proven pattern: general method to a wide range of problems description, breakdown of the software into tasks (with an explanation of each), are given. The book will be a most usefuI a simple example and mention of addition to the shelves of those responspecial cases which deserve extra sible for computer-aided process design. attention. The last two chapters are excellent M E Leesley and were, for me, the best in the book. To my knowledge it is the only In the January issue of CAD it was material in the book which has not stated that a softback version of been published before in this form. Engineering Software was available. The first of these is a chapter on This was in fact only printed for simulation by linear methods. Imdelegates of the conference.
computer-aided design