Perlmutter Solid-Liquid Filtration

Practical Guides in Chemical Engineering
1. Auflage 2015
ISBN: 978-0-12-803054-7
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 136 Seiten

Practical Guides in Chemical Engineering are a cluster of short texts that each provides a focused introductory view on a single subject. The full library spans the main topics in the chemical process industries that engineering professionals require a basic understanding of. They are 'pocket publications' that the professional engineer can easily carry with them or access electronically while working. Each text is highly practical and applied, and presents first principles for engineers who need to get up to speed in a new area fast. The focused facts provided in each guide will help you converse with experts in the field, attempt your own initial troubleshooting, check calculations, and solve rudimentary problems. Solid-Liquid Filtration covers the basic principles and mechanisms of filtration, filtration testing including filter aids and filter media, types of filtration systems, selection of filtration systems and typical operating and troubleshooting approaches. This guide also discusses general applications and tips for process filtration and can be utilized by process engineers as a framework for 'idea-generation when analyzing filtration for an operating bottleneck issue or a new process development problem. - Practical, short, concise information on the basics will help you get an answer or teach yourself a new topic quickly - Supported by industry examples to help you solve a real world problem - Single subject volumes provide key facts for professionals

Barry A. Perlmutter is President of Perlmutter & Idea Development LLC, P&ID. He has 40 years of technical engineering and business marketing experience in solid-liquid separation, filtration, centrifugation, and process drying. His skills focus on process solutions, innovation strategy and business development and market expansion. Barry has published and presented worldwide and is responsible for introducing many European technologies into the marketplace. He is an author of Elsevier's 'Solid-Liquid Filtration: Practical Guides in Chemical Engineering” and a new E-book 'Framework for Selecting Automated Filtration Technologies for Clarification Applications .” Barry began his career with the US Environmental Protection Agency and then entered the world of solid-liquid separation at Pall Corporation. For eleven years, he continued at Rosenmund Inc. as VP of Engineering and Sales including Comber and Guedu Dryers and Ferrum Centrifuges. From the process industries, Barry joined Process Efficiency Products, now part of Amiad USA, as a Director of Marketing and Sales for the manufacturing of filtration, separation and adsorption technologies for cooling tower and HVAC water, process fluids, and water and wastewater treatment. He then became President & Managing Director of BHS-Filtration Inc. (BHS-Sonthofen Inc.) where he grew the filtration, drying, mixing and recycling business of BHS for more than 20 years including the integration of AVA GmbH dryers. His current company, P&ID, allows Barry to provide consulting services for process and project development with operating companies and business development, marketing & sales strategies for process technology suppliers.He received a BS degree in Chemistry from Albany State (NY) University, MS degree from the School of Engineering at Washington University, St. Louis and an MBA from the University of Illinois, Chicago.

Autoren/Hrsg.

Perlmutter, Barry A.

Inhaltsverzeichnis

1;Front Cover;1
2;Solid-Liquid Filtration;4
3;Copyright Page;5
4;Contents;6
5;List of Figures;8
6;List of Tables;10
7;About the Authors;12
8;Acknowledgments;14
9;1 Introduction;16
9.1;Filtration Overview;17
9.2;Filtration Equipment Categories;17
9.3;Principles and Mechanisms;18
9.3.1;Inertial Impaction;20
9.3.2;Diffusional Interception;20
9.3.3;Direct Interception;21
9.4;Filter Aids;23
9.4.1;Diatomite;23
9.4.2;Perlite;23
9.4.3;Cellulose and Other Organic Media;24
9.5;Filter Media;24
9.5.1;Media Synthetic Cloth;25
9.5.1.1;Plain, Square Weave;25
9.5.1.2;Twill Weave;26
9.5.1.3;Plain, Reverse Dutch (PRD);26
9.5.1.4;Double Layer Weave (DLW);26
9.5.2;Metal Media;27
9.5.2.1;Plain Weave;28
9.5.2.2;Twilled Weave;28
9.5.2.3;Plain Dutch Weave;28
9.5.2.4;The Twilled Dutch;30
9.6;Coagulants and Flocculants;30
9.7;Surface Charges;32
9.8;Filter Rating Systems;33
9.8.1;Nominal Rating;33
9.8.2;Absolute Rating;34
9.8.3;Beta Ratio;34
9.8.4;Air Permeability;34
10;2 Filtration Testing;36
10.1;Filtration Theory: Background and How to Use It in Practice;37
10.2;Slurry Characteristics;41
10.3;Particle Characteristics;43
10.4;Pressure Testing;46
10.5;Vacuum Testing;47
11;3 Types of Filtration Systems;50
11.1;Batch Systems;51
11.1.1;Plate and Frame Filter Press;51
11.1.2;Horizontal Pressure Leaf Filter;51
11.1.3;Membrane Press;52
11.1.4;Nutsche Filter—Agitated Nutsche Filter;52
11.1.5;Tubular Filter;52
11.1.6;Cartridge Filter;52
11.1.7;Bag Filter;53
11.1.8;Candle Filter;53
11.1.9;Pressure Plate Filter;56
11.1.10;Combination Filter Press-Membrane Press;56
11.1.11;Tower Press;57
11.2;Continuous Systems;57
11.2.1;Rotary Pressure Filter;57
11.2.2;Disc Filter;58
11.2.3;Rotary Drum Vacuum Filter;58
11.2.4;Pressurized Drum Filter (P-DF);58
11.2.5;Vacuum Belt Filters;59
11.2.6;Pan Filter;59
11.2.7;Screw Press;59
11.2.8;Belt Press;60
12;4 Combination Filtration;62
12.1;Testing for Combination Filtration;62
12.2;Thickening;63
12.2.1;Concentrating Candle Filters Followed by Batch Pressure Plate Filtration;63
12.2.2;Concentrating Candle Filters Followed by Continuous Vacuum Filtration;65
12.2.3;Candle Filtration Followed by Conventional Filter Press;66
12.3;Polishing;67
12.3.1;Continuous Vacuum Filtration Followed by Concentrating Candle Filtration;67
12.3.2;Continuous Rotary Pressure Filtration Followed by Candle Filtration;68
12.4;Process Segmentation;68
12.4.1;Continuous Vacuum Filtration Followed by Contained Filter Press Filtration;68
12.4.2;Continuous Vacuum Filtration with Reslurry Washing—Multiple Uses;69
13;5 Filtration Selection;72
13.1;Specifications;75
13.2;Upstream and Downstream Equipment;82
13.3;Integration and Controls;83
13.4;Applications;86
13.5;Centrifugal Alternatives to Pressure and Vacuum Solid-Liquid Filtration;87
13.5.1;Classification (Categories) of Centrifuges;87
13.5.2;When to Use a Centrifuge;87
13.5.3;Basic Process Steps;88
13.5.4;Selection Lab Testing;88
13.5.4.1;Static Settling Tests;89
13.5.4.2;Filtration Rate Tests;89
13.5.4.3;Spin Settling Rate Tests;89
13.6;Life Cycle Capital Equipment Costs;89
14;6 Commissioning and Operation;94
14.1;Commissioning Plan;94
14.2;Preventative Maintenance;95
14.3;Troubleshooting;96
14.4;Interesting Process Challenges After the Fact;98
14.4.1;Nutsche Filter;99
14.4.2;Continuous Rotary Pressure;99
14.4.3;Clarification Application with Candle Filters;100
14.4.4;Continuous Vacuum Belt Filter;101
14.4.5;Pressure Plate Filtration Systems;102
14.4.6;Replacing Candle Filters with Continuous-Indexing Vacuum Belt Filters;103
15;7 Conclusion;104
16;Appendix: Paint Filter Liquids Test;110
17;Glossary of Important Filtration Terms;114
18;Suggested Further Reading Online;132
19;References;134
20;Bibliography;136

Leseproben

Chapter 2

Filtration Testing

After cautioning process engineers to avoid jumping to conclusions, and be sure to take time to test and verify the best filtration solutions, this chapter addresses filtration theory background and practice. The chapter then addresses slurry characteristics (including viscosity, temperature, and pH) before discussing particle shape, size, concentration, and measurement as well as pressure and vacuum testing. Recognizing the role of each piece in the puzzle is critical to coming to the best answer when addressing a filtration question.

Keywords

Filtration theory; slurry characteristics; particle characteristics; pressure testing; vacuum testing

Testing plays an important role in filtration and is the key for selecting the most suitable filtration technology for the individual solid-liquid separation task. Although there are only limited theoretical backgrounds available, and even specialized engineering education at universities leaves many theoretical questions open, it is beneficial to have at least a minimal understanding of the theory of filtration itself. Identifying the role of each influencing part, the process engineer receives a potential tool to work with when it comes to understanding testing’s findings and developing a path forward.

This guide does not detail every step in preparing and conducting filtration tests. Every test should be individually designed on a case-by-case basis. Furthermore, it is generally assumed that the testing and engineering skills to follow the test procedure are mandatory, and standard operation procedures (SOPs) for the test equipment are available from the equipment’s manufacturer. However, as Sherlock Holmes often warns Watson not to jump to conclusions, this is also one of the biggest risks process engineers face during the testing process.

From experience and for the benefit of engineers, some overview observations are necessary:

• Don’t stop testing just because the first results suit your target.

• Don’t accept samples without verifying the parameters in the description.

• Never change more than one parameter at a time.

• One result is no result. Verification is a must.

• Take a break and check the conformity of the results before you call it a day.

That said, this chapter addresses filtration theory background and practice and slurry characteristics before discussing particle shape, size, concentration, and measurement as well as pressure and vacuum testing.

Filtration Theory: Background and How to Use It in Practice

With a little basic filtration theory, the process engineer can make great strides in selecting the best processes for each unique situation. Although the process engineer might have good reasons to select a continuous or batch process, in the initial view due to the overall process (including the upstream and downstream technologies) the product’s slurry characteristics very often do not match the engineer’s first choice. Filtration testing is a method to identify slurry characteristics. As these characteristics can only be influenced within limits, but have a great impact on overall process, identifying them as early as possible in the planning phase is beneficial.

The filtration technology differs among three major cases for solid-liquid filtration only: (i) cake building, (ii) non-cake-building filtration as dynamic filtration, and (iii) deep-bed filtration (Schubert & Rippberger, 2003).

Cake-building filtration is defined as removing solids from a suspension by the use of a filter media through which the filtrate is passing. The filter media is starting the cake-building process. Once initiated, the cake itself functions as a solids trap for the remaining filtration process. No separation in the filter media takes place; the solids are either collected in the cake or they pass into the filtrate. The built cake will later be removed from the filter cloth (and therefore needs to have a minimum height of at least several millimeters).

Suspensions that do not allow building a practicable cake height within an economical time typically have only a low solid content and/or are very fine dispersed. For these slurries a dynamic filtration (i.e., cross-flow filtration) can be a solution. In this filtration principle, the solids are also separated at the surface of a filter media, but as soon as a cake is built, it is taken away by a high-speed cross flow (of slurry), maybe supported by a back pulse. With this method, it is possible to generate a clear (solid-free) filtrate, but only a thickened sludge of solids, not a cake.

As a third alternative, deep-bed filtration is used. This method captures the solids of the suspension within the filter media, such that no cake is built on top of the media. The principle of deep-bed cake filtration occurs with large particles that form a very permeable cake such that as the cake builds up to over several inches, the flow of mother liquor remains high and/or constant. Another possibility occurs using a filter aid such that the filter aid forms a precoat and the particles are amorphous such that they are removed within the depth of the precoat layer.

Many parameters have an influence on the filtration process. These include, but are not limited to:

• form and size of particles

• particle size distribution (PSD)

• agglomerate building behavior

• deformability

• compressibility

• viscosity

• solid content

• zeta potential

• pressure

While all of the above may not be known for all filtration applications, the final target is always to find a theoretical approach together with a practical method of testing.

The filtration theory upon which cake building and deep-bed filtration is based is Darcy’s law. The law describes the flow of fluids through porous materials (Darcy, 1836). Dynamic or cross-flow filtration is not part of this guide and therefore is not discussed. In the VDI-Guideline 2762 for filtration, the theoretical development is more detailed; however, the main focus for this guide is the testing results and how the engineer can use testing data to make correct process decisions.

Formulated by Henry Darcy, based on the results of experiments on water’s flow through sand beds, Darcy’s law forms the scientific basis of fluid permeability. A practical equation was developed from Darcy’s law based upon the following assumptions:

• The built cake is not compressible.

• The pressure during the cake building is constant.

• The filtrate is clear and all solids from the suspension do end up in the cake.

• The resistance created by the filter media is negligible compared with the cake resistance.

Experiences have shown, in many cases, considering the previous assumptions, that a single equation can be used (Nicolau, 2003) (Figure 2.1).

Figure 2.1 Darcy equation.

Most cases of everyday filtration testing can be described with Darcy’s equation. The first focus of the relationship is on the definitions of the various parameters:

1. All parameters on the right side are only a square rooted relation to the sizes on the left side (under proportional relationship).

2. The pressure and time are increasing values (more pressure leads to more capacity).

3. All others (viscosity, solid content, etc.) are decreasing values (more solid content leads to less capacity).

4. Alpha is a sum of all “unknowns” such as PSD, porosity, solid’s shape and size, etc.

As the filtration tests for a specific slurry are usually made with the same slurry sample, a secondary assumption is that the viscosity and solid concentration can be taken as consistent for this testing. This results in another step of simplification and finally ends in (assuming that all test parameters are kept constant mainly pressure, temperature, and sample preparation) the equations demonstrated in Figures 2.2 and 2.3. The two most simplified equations (Figure 2.2) describe the relationship of the specific filtration flow (/) to the filtration time (vF) as a square rooted relationship.

Figure 2.2 Simplified Darcy equation showing the relationship between filtration flow and time.

Figure 2.3 Simplified Darcy equation showing the relationship between filtration flow and cake height.

Figure 2.3 describes the relationship of the build cake height () in relation to the filtration flow (/). To allow for practical use, the entire unknowns are summed up in the two factors and . For everyday test work these two factors can be determined for each individual case by several bench top tests. With this in mind, the process engineer now can make theoretical assumptions by altering the parameters without needing all details at hand.

Let’s take an example to get a better idea of what is behind the theoretical approach:

The first test has given a filtration time of 60 s, 20 mm of cake height and a...