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Cryogenic Mixed Refrigerant Processes
international journal of refrigeration 33 (2010) 648–649
available at www.sciencedirect.com
w w w . i i fi i r . o r g
journal homepage: www.elsevier.com/locate/ijrefrig
Book Review G. Venkatarathnam, Cryogenic Mixed Refrigerant Processes, Dept. of Mech. Engineering, Indian Institute of Technology Madras. in: K.D. Timmerhaus, Carlo Rizzuto (Eds.), The International Cryogenics Monograph Series, Springer ScienceDBusiness Media, LLC, (2008), e-ISBN: 978-0-387-78514-1, 262 pp., Hardcover, ISBN 978-0-387-78513-4. One of the most rapidly growing branches of process industry in the second half of the 20th and beginning of 21st century is liquefaction of natural gas, which allowed transferring enormous quantities of energy from distant gas fields to energy demanding regions with a concentrated population and industry. Most history of natural gas liquefaction is based on the use of cascade liquefiers. This basic process was developed very soon to a qualitatively new level with the invention of the mixed refrigerant process. It makes possible the minimization of liquefaction energy consumption, thus bringing maximum positive effects for the environment. Many varieties of mixed refrigerant liquefaction processes have been developed for decades of its application. It is a real challenge to classify them, to understand the real sense of particular elements of the flow schemes and to compare the processes from the point of energy efficiency. The author of the book, Professor of Mechanical Engineering at the Indian Institute of Technology in Madras, accepted the challenge and dedicated 15 years of his work to systematic study, classification and evaluation of this branch of refrigeration technology. In his book, the author is guiding the reader from elements of liquefaction technology thermodynamics to fundamentals of process simulation theory and practice, to explanation of the function of mixed refrigerants and optimization of their composition to description and optimized heat–mass balances of individual cycles used in industry or proposed for possible future usage, with their process balance data. The content of the book is structured into seven main chapters: 1. 2. 3. 4. 5. 6. 7.
Fundamental principles and processes Simulation of cryogenic processes Need for refrigerant mixtures Constant-temperature refrigeration processes Optimum mixture composition Natural gas liquefaction processes Cooling and liquefaction of air and its constituents.
The strength of the book is a unified system of formal tools, flow schemes, graphics and tables, which enables understanding and comparison of individual processes even at brief reading as well as in-depth study and understanding finesses
of each process. The concept of the exergy efficiency is used as a universal tool of the energetic comparison. For each process, the reader can find an optimized heat–mass balance in a form of tables with component concentrations, temperature, pressure, vapor fraction and flow rate. Optimization was done for fixed external data like ambient temperature, inlet gas composition and pressure, compressor efficiency and minimum temperature difference at heat exchangers, which were not varied further as the extend of the book would have to be enormous and the general concept would be lost. However, the publication of the optimized composition of the refrigerant mixtures, determined for each process or its particular stages, is one of the most useable benefits for process engineers as a starting point for their own process design and optimization with respect to their specific external data and their variations. Exergy usage and losses are expressed in a form of segment diagrams, where loss of exergy is quantified for every machine, heat exchanger or expansion valve. Q–T diagrams help to understand how successful the thermal design of each process is from the point of minimum DT, and allow for intuitive understanding of the course of the Q–T curve of each stream depending on its composition. The most valuable part of the book is Chapter 6, where analyses of the most frequent variants of the cycles, suitable for small to large, peak shaving to base load liquefiers are presented. Starting with single stage mixed refrigerant process without or with separator and precooled mixed refrigerant process, the author presents the most frequently used propane precooled mixed refrigerant process (C3-MR) and mixed refrigerant precooled process (DMR). The same attention is paid to the Kleemenko mixed refrigerant process with two separators, pioneered in 1959 but still used at small peak shaving plants. The cascade liquefaction process with three separate circuits with mixed refrigerants, the main components of each circuit are methane, ethane and propane respectively, is the most complex example analyzed in the book. Liquefaction cycles based on expansion turbines working with nitrogen or nitrogen methane refrigerant and one or two turbines close this chapter. Chapter 7 is dedicated to mixed refrigerant cycles for liquefaction of nitrogen, possibly air, for its separation, or other air separation products, oxygen and argon. Although these cycles have not found their application in industry yet, because of various limitations, one of them being the general safety avoiding use of hydrocarbons in the same equipment where oxygen or liquid air takes place, the other being relative complexity of handling mixed refrigerant, when they are not recoverable from the main raw gas, the author did an important work by proposing and optimizing the cycles, based mostly on Kapitza and Kleemenko cycle bases.
international journal of refrigeration 33 (2010) 648–649
What some reader may miss in the book is a table of properties of components of mixed refrigerants, possibly their diagrams of state. Although they can be relatively easily found in other literature or recovered from widely used mass properties programs, having them at hand when reading the book would be practical for better understanding of concentration effects at mixed refrigerants. This book is an important source of knowledge for postgraduate students, process engineers working on equipment projects for gas liquefaction industry as well as those, operating liquefaction plants, or for feasibility studies analysts, as well as for newcomers in this branch of technology. Reading of the book doesn’t require any previous specific knowledge except of basic course of thermodynamics on university level. All readers will certainly appreciate the work done by the author on optimization of all the cycles. It may save a lot of
649
research and engineering work of those working on projects. Possibly, it can also help to achieve more optimized solutions. Special thanks should also be expressed to editors of The International Cryogenic Monograph Series for their support to publishing the book, namely to Prof. K.D. Timmerhaus, mentioned by the author as the reviewer of the book. Vaclav Chrz Chart Ferox, a.s., Ustecka 30, 405 30 Decin, Czech Republic Tel.: þ420 412 507 628; fax: þ420 412 507 435. E-mail address: [email protected] Available online 27 January 2010 0140-7007/$ – see front matter doi:10.1016/j.ijrefrig.2009.11.013
available at www.sciencedirect.com
w w w . i i fi i r . o r g
journal homepage: www.elsevier.com/locate/ijrefrig
Book Review G. Venkatarathnam, Cryogenic Mixed Refrigerant Processes, Dept. of Mech. Engineering, Indian Institute of Technology Madras. in: K.D. Timmerhaus, Carlo Rizzuto (Eds.), The International Cryogenics Monograph Series, Springer ScienceDBusiness Media, LLC, (2008), e-ISBN: 978-0-387-78514-1, 262 pp., Hardcover, ISBN 978-0-387-78513-4. One of the most rapidly growing branches of process industry in the second half of the 20th and beginning of 21st century is liquefaction of natural gas, which allowed transferring enormous quantities of energy from distant gas fields to energy demanding regions with a concentrated population and industry. Most history of natural gas liquefaction is based on the use of cascade liquefiers. This basic process was developed very soon to a qualitatively new level with the invention of the mixed refrigerant process. It makes possible the minimization of liquefaction energy consumption, thus bringing maximum positive effects for the environment. Many varieties of mixed refrigerant liquefaction processes have been developed for decades of its application. It is a real challenge to classify them, to understand the real sense of particular elements of the flow schemes and to compare the processes from the point of energy efficiency. The author of the book, Professor of Mechanical Engineering at the Indian Institute of Technology in Madras, accepted the challenge and dedicated 15 years of his work to systematic study, classification and evaluation of this branch of refrigeration technology. In his book, the author is guiding the reader from elements of liquefaction technology thermodynamics to fundamentals of process simulation theory and practice, to explanation of the function of mixed refrigerants and optimization of their composition to description and optimized heat–mass balances of individual cycles used in industry or proposed for possible future usage, with their process balance data. The content of the book is structured into seven main chapters: 1. 2. 3. 4. 5. 6. 7.
Fundamental principles and processes Simulation of cryogenic processes Need for refrigerant mixtures Constant-temperature refrigeration processes Optimum mixture composition Natural gas liquefaction processes Cooling and liquefaction of air and its constituents.
The strength of the book is a unified system of formal tools, flow schemes, graphics and tables, which enables understanding and comparison of individual processes even at brief reading as well as in-depth study and understanding finesses
of each process. The concept of the exergy efficiency is used as a universal tool of the energetic comparison. For each process, the reader can find an optimized heat–mass balance in a form of tables with component concentrations, temperature, pressure, vapor fraction and flow rate. Optimization was done for fixed external data like ambient temperature, inlet gas composition and pressure, compressor efficiency and minimum temperature difference at heat exchangers, which were not varied further as the extend of the book would have to be enormous and the general concept would be lost. However, the publication of the optimized composition of the refrigerant mixtures, determined for each process or its particular stages, is one of the most useable benefits for process engineers as a starting point for their own process design and optimization with respect to their specific external data and their variations. Exergy usage and losses are expressed in a form of segment diagrams, where loss of exergy is quantified for every machine, heat exchanger or expansion valve. Q–T diagrams help to understand how successful the thermal design of each process is from the point of minimum DT, and allow for intuitive understanding of the course of the Q–T curve of each stream depending on its composition. The most valuable part of the book is Chapter 6, where analyses of the most frequent variants of the cycles, suitable for small to large, peak shaving to base load liquefiers are presented. Starting with single stage mixed refrigerant process without or with separator and precooled mixed refrigerant process, the author presents the most frequently used propane precooled mixed refrigerant process (C3-MR) and mixed refrigerant precooled process (DMR). The same attention is paid to the Kleemenko mixed refrigerant process with two separators, pioneered in 1959 but still used at small peak shaving plants. The cascade liquefaction process with three separate circuits with mixed refrigerants, the main components of each circuit are methane, ethane and propane respectively, is the most complex example analyzed in the book. Liquefaction cycles based on expansion turbines working with nitrogen or nitrogen methane refrigerant and one or two turbines close this chapter. Chapter 7 is dedicated to mixed refrigerant cycles for liquefaction of nitrogen, possibly air, for its separation, or other air separation products, oxygen and argon. Although these cycles have not found their application in industry yet, because of various limitations, one of them being the general safety avoiding use of hydrocarbons in the same equipment where oxygen or liquid air takes place, the other being relative complexity of handling mixed refrigerant, when they are not recoverable from the main raw gas, the author did an important work by proposing and optimizing the cycles, based mostly on Kapitza and Kleemenko cycle bases.
international journal of refrigeration 33 (2010) 648–649
What some reader may miss in the book is a table of properties of components of mixed refrigerants, possibly their diagrams of state. Although they can be relatively easily found in other literature or recovered from widely used mass properties programs, having them at hand when reading the book would be practical for better understanding of concentration effects at mixed refrigerants. This book is an important source of knowledge for postgraduate students, process engineers working on equipment projects for gas liquefaction industry as well as those, operating liquefaction plants, or for feasibility studies analysts, as well as for newcomers in this branch of technology. Reading of the book doesn’t require any previous specific knowledge except of basic course of thermodynamics on university level. All readers will certainly appreciate the work done by the author on optimization of all the cycles. It may save a lot of
649
research and engineering work of those working on projects. Possibly, it can also help to achieve more optimized solutions. Special thanks should also be expressed to editors of The International Cryogenic Monograph Series for their support to publishing the book, namely to Prof. K.D. Timmerhaus, mentioned by the author as the reviewer of the book. Vaclav Chrz Chart Ferox, a.s., Ustecka 30, 405 30 Decin, Czech Republic Tel.: þ420 412 507 628; fax: þ420 412 507 435. E-mail address: [email protected] Available online 27 January 2010 0140-7007/$ – see front matter doi:10.1016/j.ijrefrig.2009.11.013