Membrane Gas Separation

15 Evolution of Natural Gas Treatment with Membrane Systems 
313
Lloyd S. White
15.1 Introduction 
313
15.2 Market for Natural Gas Treatment 
315
15.3 Amine 
Treaters 
318
15.4 Contaminants and Membrane Performance 
319
15.5 Cellulose Acetate versus Polyimide 
320
15.6 Compaction 
in 
Gas 
Separations 
322
15.7 Experimental 
323
15.8 Laboratory Tests of Cellulose Acetate Membranes 
324
15.9 Field Trials of Cellulose Acetate Membranes 
326
15.10 Strategies for Reduced Size of Large-scale Membrane Systems 
327
15.11 Research Directions 
329
15.12 Summary 
330
Acknowledgements 
330
References 
331
16 The Effect of Sweep Uniformity on Gas Dehydration 
Module Performance 
333
Pingjiao Hao and G. Glenn Lipscomb
16.1 Introduction 
333
16.2 Theory 
336
16.2.1 Gaussian Distribution of Sweep 
336
16.2.2 Explicit 
Sweep 
Distribution 
Simulations 
338
16.3 Results 
and 
Discussion 
340
16.3.1 Module Performance with Ideal Sweep Distribution 
341
16.3.2 Effect of Sweep and ID Variation 
344
16.3.3 Effect of Sweep Distribution 
346
16.3.4 Effect of Fibre Packing Variation Along Case 
347
16.4 Conclusion 
350
List of Symbols 
351
References 
352
Index 
355

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 Preface
The International Congress on Membranes and Membrane Processes (ICOM) meetings 
are the most important events for the community of membrane science and technology. 
They are organized once every three years in the succession: Europe, Asia, America. The 
most recent ICOM2008 took place in Honolulu, Hawaii (USA). According to the opinion 
of the editors of this volume it was one the most interesting meetings ever attended. 
Probably the greatest interest was the subject of membrane gas separation. There were 
fi ve sessions devoted to this sub - fi eld of membrane science and technology, more than 
to any other area discussed at ICOM2008. After strong competition, 30 submitted papers 
were selected by the program committee as oral presentations. The material of these 
presentations was so interesting and relevant for the fi eld that it occurred to us while in 
Honolulu that it would be worthwhile to publish a volume based on the oral presentations 
of the gas separation sessions. This book is conceived to give a snapshot of the current 
situation in membrane gas separation and related fi elds as described by the speakers at 
ICOM2008. In this regard it differs from the volume published several years ago, also by 
John Wiley & Sons, Ltd [1] , which summarized the state of the art in this fi eld achieved 
during the last decade. 
The results presented in this book were obtained owing to the activity of really inter-
national group of teams from Australia, Czech Republic, France, Germany, Italy, Japan, 
Poland, Russia, Slovenia, United Kingdom and USA. The chapters submitted by the 
authors were partitioned among four Sections. Before considering the contents of these 
sections it should be emphasized that many chapters focus on the most relevant problems; 
without a solution to these problems further progress of membrane gas separation looks 
doubtful. 
Chapters 1 , 4 , 6 and 8 discuss the possible ways to prevent plasticization effects that 
result in signifi cant reduction in selectivity of separation of mixtures containing active 
(strongly sorbed) vapours. Recently it became clear that high permeability of certain 
polymer materials can be rationalized on the basis of the concept of inner porosity. 
In this regard, such polymers are similar to common porous inorganic media. In such 
polymers, mixed gas permeation is characterized by high selectivity, so the problem of 
plasticization is excluded. Transport behaviour of membranes with inner porosity is the 
subject of Chapters 2 , 3 and 5 . Another approach that permits overcoming the plasticiza-
tion problem is an application of perfl uorinated polymers that reveal a reduced solubility 
of hydrocarbon vapours. Different aspects of the use of such membrane materials are 
considered in Chapters 4 , 6 and 7 . Some of the contributions include interesting reviews 
of different problems of membrane gas separation (Chapters 1 , 10 , 14 and 15 ). 

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xiv
Preface
Section I (Novel Membrane Materials and Transport in Them) focuses on the most 
recent advances in development of new membrane materials and considers the transport 
parameters and free volume of polymeric and even inorganic membranes. Kanehashi
et al. (Chapter 1 ) present a detailed review of hyperbranched polyimides, which are 
compared with more common cross - linked polyimides. These polymers with unusual 
architecture were studied in the hope that they would show weaker tendency to plasticiza-
tion than conventional linear polymers. However, many representatives of this new 
class of polymers reveal relatively poor fi lm forming properties due to absence of chain 
entanglement. Nonetheless, some promising results obtained can show directions of 
further studies. 
The next two chapters deal with novel amorphous glassy polymers that are character-
ized by large free volume, high gas permeability and good combination of permeability 
and permselectivity. The polymer of intrinsic microporosity (PIM 
- 
1, Chapter
2 
) has 
attracted a great attention in membrane community, and at present several polymers 
structurally similar to PIM - 1 have been prepared and characterized. This polymer has 
‘ inner ’ surface area of about 700 m 
2
/g, higher than that of some sorts of carbon, and its 
gas and vapour solubility coeffi cients are the highest among all the polymers studied so 
far (even polytrimethylsilylpropyne). The subject of Chapter 3 is Si - containing addition -
type polynorbornene, also having relatively high gas permeability. The polymers of this 
class have been the subject of investigation during the last decade; however, only the 
introduction of Si(CH 
3
) 
3
groups into the monomer resulted in rather attractive properties 
of the polymer obtained. If somebody asked us 10 years ago which polymer structure 
would provide extra high permeability of the membrane materials, the answer would be: 
‘ Polyacetylenes and, maybe, some perfl uorinated polymers ’ . Now we see that much wider 
variation of polymer design can lead to large free volume and high permeability and dif-
fusivity. This result seems to be very optimistic for further activity of synthetic polymeric 
chemists aimed to create new membrane materials. 
The objects of the investigation by Jansen et al. (Chapter 4 ) were perfl uorinated copoly-
mers of Hyfl on AD. The authors reported novel data on free volume, presented the results 
of computer modelling and the gas permeation parameters. It should be stressed that such 
comprehensive study of a polymer becomes more and more popular today if one wants 
to understand transport and sorption parameters of a membrane material. This chapter 
will give much ‘ food ’ for future comparisons with other perfl uorinated polymers as well 
as conventional glassy polymers. 
The aim of Chapter 5 by Thornton et al. was to give systematic consideration to dif-
ferent types of transport in porous membranes. They developed a new model that allows 
one to predict the separation outcome for a variety of membranes in which the pore shape, 
size and composition are known, and conversely to predict pore characteristics with 
known permeation rates. 
An important event of recent years in membrane science was the discovery of a new 
phenomena observed when nano 
-