Filters and Filtration Handbook

Trevor Sparks, George Chase

• Publisher: Butterworth-Heinemann
• Year: 2013
• ISBN:
  9780080994000
• Edition: 6
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

Filters are used in most industries, especially the water, sewage, oil, gas, food and beverage, and pharmaceutical industries. The new edition of Filters and Filtration Handbook is an all-encompassing practical account of standard filtration equipment and its applications. Completely revised and rewritten, it is an essential book for the engineer working in a plant situation, who requires guidance and information on what's available and whether it's suitable for the job. Co-published with the Institution of Chemical Engineers.

• An up-to-date and comprehensive reference covering essential theory of filters and filtration, and including types of filter, media, filtration, equipment, techniques and systems.
• Helps you decide the best filtration methods and materials for the task at hand
• Includes new material on basic principles, filter media and the application of filtration within production systems

Section 1

Filtration – Introduction, Physical Principles and Ratings

Abstract

We rely upon the separation of particles from fluids to provide us with the essentials of life – clean air and water. Furthermore, almost every foodstuff, medicine or manufactured article in your home, car or workplace relied upon a separation process somewhere in its production. Without the ability to separate particles from fluids, no part of your life would be the same.

This section provides an introduction to filtration, and separation as an engineering discipline, exploring the importance of filtration to everyday life and industry. The business of filtration, as well as its history, is discussed. The physical principles of filtration, as well as filter ratings and testing, are reviewed.

Keywords

Filtration and separation; physical principles of filtration; filter rating and testing

Contents

1.1 Introduction – Filtration and Separation 2

1.1.1 Types of filtration process – the functions that they fulfil 6

1.1.1.1 Filtration as a part of an overall separation process 6

1.1.2 Air quality 7

1.1.3 Drinking water 8

1.1.4 Climate change 10

1.1.5 The filtration business 11

1.1.5.1 Industry drivers and trends 11

1.1.6 History of filtration 13

1.2 Physical Principles of Filtration 15

1.2.1 Particles 17

1.2.1.1 Solid–fluid suspension 18

1.2.1.2 Capture mechanisms 20

1.2.1.3 Filter medium 21

1.2.1.4 Surface, cake and depth filtration 22

1.2.1.5 Cross-flow versus dead-end filtration processes 30

1.2.1.6 Compressible cake 31

1.2.1.7 Pre-coat and body feed 32

1.2.1.8 Solid–liquid cake filtration and other de-watering mechanism 32

1.2.1.9 Solid–liquid cake filtration, filter cake washing and other process steps 33

1.3 Filter Ratings 39

1.3.1 Absolute ratings 40

1.3.2 Nominal rating 42

1.3.3 Mean filter rating 42

1.3.3.1 Filter efficiency 43

1.3.4 Beta ratio 43

1.3.4.1 Microbial rating 44

1.3.5 Filter permeability (flow curves) 45

1.3.6 Effect of pulsating flow 49

1.4 Filter Tests 49

1.4.1 Bead challenge test 50

1.4.2 Multi-pass test 50

1.4.3 Single-pass test 51

1.4.4 Bubble point test 51

1.4.5 Dirt-capacity test 53

1.4.6 Media migration test 53

1.4.7 Fatigue tests 54

1.1 Introduction – Filtration and Separation

We rely upon the separation of particles from fluids to provide us with the essentials of life – clean air and water. Furthermore, almost every foodstuff, medicine or manufactured article in your home, car or workplace relied upon a separation process somewhere in its production. Without the ability to separate particles from fluids, no part of your life would be the same:

• Engines and power stations would choke from particulate contamination in fuels, incoming air and lubricating fluids. Their emissions would be far more environmentally damaging.

• All metals, plastics, foods and medicines would be less pure, less wholesome, less effective or, probably, at least an order of magnitude more expensive.

The global population continues to grow, and with this comes ever-higher demands for clean water (and the treatment of municipal and industrial wastewater), a safe environment (Figure 1.1) and food. At the same time, everyone strives for a higher standard of living; this can simply mean the provision of safer water in some developing parts of the world. In more developed economies, urbanization, car ownership and all that these entails in terms of manufacturing and operating are coming to societies which, a few decades ago, existed as rural farming communities. This places an increased burden on local environments, as well as increased demand for materials (ceramics, plastics, metals), chemicals and other outputs from industry (Figure 1.2).

Figure 1.1 A waterscape.

Figure 1.2 Industrial emissions.

In short, without separation, our world would be less clean, less colourful, less sustainable and almost everything that you consume or use would be more expensive. This handbook explores these issues in more detail and provides information on current technologies and techniques in use. In particular, Section 5 describes a number of examples that illustrate many of the important principles of separation through filtration.

These filtration needs are met by a large and highly diverse global industry. Many tens of thousands of people around the world spend their entire working lives engaged solely in the provision of filtration equipment, media or services; equally, there are people who spend their whole time using filtration as practitioners, perhaps running the filtration step in a chemical process or on a mineral concentration plant. A further many thousand people are actively working in research and development, looking for new technologies or theories that will improve our knowledge and application of filtration, leading to improvements in effectiveness and efficiency that, in turn, improve lives. In addition to these people, for many people, filtration fills a portion of their time, they may be developing new processes to deliver sustainable sources of fuel and filtration is necessary, or they may be responsible for optimizing mineral processing on a large mine, in which filtration plays an essential part, albeit alongside other essential processes. One purpose of this handbook is to provide a reference guide for experienced practitioners as well as those who need to dip into the subject for a particular purpose. Inevitably, we are dealing with filtration as an engineering subject, one that fits into chemistry, chemical engineering, mining, metallurgy, civil engineering and many other disciplines.

The word ‘filter’ can mean many things (even if we set aside its meaning in photography, electronics, computer science, online shopping, etc.).¹ In the context of particle–fluid separation, a filter can be a small disc of paper that a laboratory chemist fits to a syringe, or it can be a machine (in this example, a filter press) weighing more than 150 tonnes that removes water from a slurry of ore on an iron processing plant. The cost of these example filters spans a few pennies to many millions of Euros.

The phrase ‘filtration and separation’ contains a certain amount of redundancy. As the previous edition of this handbook discusses, the phrase is shorthand for ‘filtration and other related forms of separation’. The safe separation of iron particles in engine oil away from sensitive parts can be achieved using a filter, but equally using a simple magnetic device, other physical fields, such as gravity, can equally deliver a form of separation. Separation need not require filtration, but, for our purposes, filtration actually implies separation.

A related physical process, classification or the grading of solid particles according to their size can be achieved using filtration – a fraction above a certain size can be retained on a vibrating sieve, while particles below that size can pass through the sieve. However, the classification of similarly sized particles according to another physical differences, say density or magnetic properties, requires a physical force field – in these examples, particles differing in density can be graded in an accelerating field (say a cyclone) and, clearly, a simple magnet, or device incorporation magnets, will classify in the latter.

Thus, in the context of this handbook, filtration specifically, and separation generally, refers to the act of separating one or more distinct phases of matter from another using physic...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Acknowledgement
• Section 1. Filtration – Introduction, Physical Principles and Ratings
• Section 2. Filter Media
• Section 3. Air and Gas Filtration
• Section 4. Solid–Liquid Filtration
• Section 5. Solid–Liquid Filtration – Examples of Processes
• Section 6. Other Separation Processes and Equipment
• Section 7. Filter Selection, Process Design, Testing, Optimization and Troubleshooting Guidelines
• Glossary
• Index