Pressure Driven Membrane Processes

Pressure Driven Membrane Processes Table of contents Introduction 4 2. 2.1 2.2 2.3 Osmotic pressure difference Introduction to osmosis Osmotic pressure model Calculation of the osmotic pressure 10 10 12 13 3. 3.1 3.2 3.3 Resistance towards mass transport Concentration polarization Gel layer model Membrane fouling 15 15 18 19 4. Summary 22 Please click the advert 1. Download free books at BookBooN.com 2 Pressure Driven Membrane Processes Pressure Driven Membrane Processes – 2nd edition This text is written to all chemical engineering students who are participating in courses about membrane processes and membrane technology. You are supposed to have the basic skills in mathematics and chemistry in general. Thus, this text is for students who have completed the basic engineering introduction courses. This text gives an introduction to principles behind pressure driven membrane processes. Relevant theory and models will be presented together with terms widely used in the world of membrane technology. May 2007 Søren Prip Beier Download free books at BookBooN.com 3 Introduction Pressure Driven Membrane Processes 1 Introduction Pressure driven membrane processes are widely used in almost all kinds of chemical, pharmaceutical, food and dairy industries. A membrane process is capable of performing a certain separation by use of a membrane. The core in every membrane process is, thus, the membrane that allows certain components to pass trough and retain other components. Initially, some of the most important terms used in membrane technology are shown in Figure 1. Figure 1: Membrane process Sketch of a membrane process. The core is the membrane it self, through which a driving force induces a flux from the bulk to the permeate side. The feed side is often referred to as the bulk solution. The components in the bulk solution that are retained can also be referred to at the retentate after it has been in contact with the membrane. When a driving force is established across the membrane, a flux will go through the membrane from the bulk solution to the permeate side. The flux is referred to with the letter “J” and is often given in the units of liter pr. m2 pr. hour [L/(m2·h)]. The liquid going through the membrane is called the permeate. A particular separation is accomplished by use of a membrane with the ability of transporting one component more readily than another. In other words, the membrane is more permeable to certain Download free books at BookBooN.com 4 Introduction Pressure Driven Membrane Processes components than other components because of differences in physical or chemical properties between the membrane and the components that are transported through the membrane. Difference in size: In many membrane processes (microfiltration and ultrafiltration for example) porous membranes with a given pore size distribution are used. Because of the given pore size, some components will be retained by the membrane because of their size and some components are small enough to pass through to pores in