Membrane technology is a rapidly developing area, with key growth accross the process sector, including biotech separation and biomedical applications (e.g. haemodialysis, artificial lungs), through to large scale industrial applications in the water and waste-water processing and the food and drink industries. As processes mature, and the cost of membranes continues to dramatically reduce, so their applications and use are set to expand. Process engineers need access to the latest information in this area to assist with their daily work and to help to develop and apply new and ever more efficient liquid processing solutions.
This book covers the latest technologies and applications, with contributions from leading figures in the field. Throughout, the emphasis is on delivering solutions to practitioners. Real world case studies and data from leading organizations -- including Cargill, Lilly, Microbach, ITT -- mean this book delivers the latest solutions as well as a critical working reference to filtration and separation professionals.
Covers the latest technologies and applications in this fast moving bioprocessing sector
Presents a wide range of case studies that ensure readers benefit from the hard-won experience of others, saving time, money and effort
World class author team headed up by the Chair of Chemical Engineering at Oxford University, UK and the VP of Plant Operations and Process Technology at Cargill Corp, the food services company and largest privately owned company in the US
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Yes, you can access Membrane Technology by Z F Cui,H S Muralidhara in PDF and/or ePUB format, as well as other popular books in Design & Industriedesign. We have over one million books available in our catalogue for you to explore.
Fundamentals of Pressure-Driven Membrane Separation Processes
Z.F. Cui, Y. Jiang and R.W. Field
Department of Engineering Science, Oxford University, Oxford, UK
Table of Contents
1.1 Introduction
1.2 Processes
1.2.1 Process Classification
1.2.2 Definitions
1.3 Membranes
1.3.1 Membrane Structures
1.3.2 Membrane Materials
1.3.3 Membrane Modules
1.4 Operation
1.4.1 Concentration Polarization
1.4.2 Membrane Fouling
1.5 Prediction and Enhancement of Permeate Flux
1.5.1 Flux Prediction Models
1.5.2 Flux Enhancement and Fouling Control
1.6 Summary
Further Readings
1.1 Introduction
Membrane processes are one of the fastest growing and fascinating fields in separation technology. Even though membrane processes are a relatively new type of separation technology, several membrane processes, particularly pressure-driven membrane processes including reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF), are already applied on an industrial scale to food and bioproduct processing.
The concept of membrane processes is relatively simple but nevertheless often unknown. Membranes (lat.: membrana = thin skin) might be described as conventional filters (like a coffee filter) but with much finer mesh or much smaller pores to enable the separation of tiny particles, even molecules! In general, one can divide membranes into two groups: porous and nonporous. The former group is similar to classical filtration with pressure as the driving force; the separation of a mixture is achieved by the rejection of at least one component by the membrane and passing of the other components through the membrane (see Fig. 1.1). However, it is important to note that nonporous membranes do not operate on a size exclusion mechanism. It should be pointed out that this chapter focuses on pressure-driven membrane processes using porous membranes for its close relevance to food and bioproduct processing.
Figure 1.1 Basic principle of porous membrane processes. (Above is idealized; complete separation is not achieved in practice.)
Membrane separation processes can be used for a wide range of applications and can often offer significant advantages over conventional separation such as distillation and adsorption since the separation is based on a physical mechanism. Compared to conventional processes, therefore, no chemical, biological, or thermal change of the component is involved for most membrane processes. Hence membrane separation is particularly attractive to the processing of food, beverage, and bioproducts where the processed products can be sensitive to temperature (vs. distillation) and solvents (vs. extraction).
1.2 Processes
1.2.1 Process Classification
There are four major pressure-driven membrane processes that can be divided by the pore sizes of membranes and the required transmembrane pressure (TMP): MF (0.1–5 μm, 1–10 bar), UF (500–100,000 Da, 1–100 nm, 1–10 bar), NF (100–500 Da, 0.5–10 nm, 10–30 bar), and RO (<0.5 nm, 35–100 bar). Figure 1.2 presents a classification on the applicability of different membrane separation processes based on particle or molecular sizes. RO process is often used for desalination and pure water production, but it is the UF and MF that are widely used in food and bioprocessing.
Figure 1.2 The applicability ranges of different separation processes based on sizes.
While MF membranes target on the microorganism removal, and hence are given the absolute rating, namely, the diameter of the largest pore on the membrane surface, UF/NF membranes are characterized by the nominal rating due to their early applications of purifying biological solutions. The nominal rating is defined as the molecular weight cut-off (MWCO) that is the smallest molecular weight of species, of which the membrane has more than 90% rejection (see later for definitions). The separation mechanism in MF/UF/NF is mainly the size exclusion, which is indicated in the nominal ratings of the membranes. The other separation mechanism includes the electrostatic interactions between solutes and membranes, which depends on the surface and physiochemical properties of solutes and membranes.
1.2.2 Definitions
In contrast to Figure 1.1, real membrane separations split the feed mixture stream into two streams with different compositions as shown in Figure 1.3.
Figure 1.3 A realistic membrane separation process.
The feed stream
to a membrane module is split into (i) the retentate stream
, which is the stream that has been retained by the membrane containing both the material that has been rejected by the membrane and a quantity of material that would not be rejected by the membrane but has yet not been given the opportunity to pass through the membrane; and (ii) the permeate stream
, the stream that has passed through the membrane, containing much less or no bigger molecules or particles than the pores.
Like any separation processes, the membrane separation processes can be evaluated by two important parameters, efficiency and productivity. The productivity is characterized by the parameter permeate flux, which indicates the rate of mass transport across the membrane. In general terms, the local mass transport of a component i through a membrane element is related to its concentration on the feed side CRi and the permeate side CPi (see Fig. 1.3). The flow of a component i through a membrane element can be referred to as its flux Ji. This flux is a velocity and is commonly expressed in [kg/(m² s)] or [kmol/(m² s)]. When n components are permeating through the membrane a total flux Jtot can be defined as:
(1.1)
The retention factor Ri of a component i can be defined and used as a measure of performance.
(1.2a)
where CP and CR are the concentration of component i in the permeate and the retentate.
Actually pressure-driven membrane processes can be operated in two different modes: dead-end and cross-flow operations. In the dead-end mode, one stream of the feed enters the membrane module and flows vertically toward the membrane surface, and only one stream leaves the membrane module. In the cross-flow mode, one stream of the feed flows tangentially to the...
Table of contents
Cover image
Title page
Table of Contents
Copyright
Preface
About the Editors
About the Contributors
Chapter 1. Fundamentals of Pressure-Driven Membrane Separation Processes
Chapter 2. Challenges of Membrane Technology in the XXI Century
Chapter 3. Membrane Processes in Fruit Juice Processing
Chapter 4. Membrane Application in Soy Sauce Processing
Chapter 5. Application of Membrane Technology in Vegetable Oil Processing
Chapter 6. Membrane Applications in Monoclonal Antibody Production
Chapter 7. Membrane Processes for the Production of Bulk Fermentation Products
Chapter 8. Membrane Technologies for Food Processing Waste Treatment
Chapter 9. Practical Aspects of Membrane System Design in Food and Bioprocessing Applications
Chapter 10. Membrane Fouling and Cleaning in Food and Bioprocessing
Chapter 11. US Regulatory Approval of Membrane Technology
