Pneumatic Conveying Design Guide

David Mills

• Éditeur: Butterworth-Heinemann
• Année: 2015
• ISBN:
  9780081006689
• Édition: 3
• Sujet: Technology & Engineering
• Sous-sujet: Mechanical Engineering

Pneumatic Conveying Design Guide, 3rd Edition is divided into three essential parts, system and components, system design, and system operation, providing both essential foundational knowledge and practical information to help users understand, design, and build suitable systems.

All aspects of the pneumatic conveying system are covered, including the type of materials used, conveying distance, system constraints, including feeding and discharging, health and safety requirements, and the need for continuous or batch conveying.

This new edition also covers information on the other conveying systems available and compares them to this method. The existing content is brought up-to-date and the references are expanded and updated. This guide is an almost encyclopedic coverage of pneumatic conveying and as such is an essential text for both designers and users of pneumatic conveying systems. Each aspect of the subject is discussed from basic principles to support those new to, or learning about, this versatile technique.

• Highly practical with usable and unbiased information to enable you to choose, design and build suitable systems with a high degree of confidence
• New edition compares alternative conveying systems including pneumatic capsule conveying systems, and covers conveying of wet materials
• Contains updated information on by-pass systems, and will introduce you to simulation software

Appendix 1

The Determination of Relevant Material Properties

Abstract

A particular feature of the Design Guide has been the relationship between the properties of the material to be conveyed and the conveying capability of the material, and it has been emphasized that the name of the material alone is insufficient in assessing the capability of a material for pneumatic conveying. It has also been stressed that conveying trials should be undertaken for a new and untried material for the purpose of system design and that representative samples should be taken for future reference in case the performance changes. Tests that can be undertaken with bulk particulate materials appropriate to the requirements of pneumatic conveying are detailed. These can be used to determine the potential conveying capability of a material for pneumatic conveying in order to assess the type of system that might be appropriate. They can also be used to determine whether there have been any changes with regard to the material being conveyed after a period of time if there is a change in the conveying capability of the material.

Keywords

Deaeration constant; Elutriation; Laser diffraction; Particle shape; Permeameter; Pycnometer; Sedimentation; Shape factor; Specific surface; Voidage

Chapter Outline

Introduction 714

The Need for Characterization 715

Particle and Bulk Properties 715

Particle Size and Shape 716

Particle Size 716

Particle Size Distribution 716

Cumulative representation 717

Fractional representation 718

Methods of determining size 718

Particle Shape 720

Descriptive terms 720

Shape factors 720

Specific surface 721

Particle and Bulk Density 721

Particle Density 721

Reference values 722

Methods of determination 722

Bulk Density 722

Reference values 722

Applications 723

Voidage 724

Flow Properties 724

Factors Influencing Flowability 725

Particle size 725

Particle shape 725

Electrostatic charge 725

Moisture 725

Tests for Flowability 726

Angle of repose 726

Applications 727

Aeration Properties 727

Fluidization 727

Fluidized angle of repose 727

Applications 728

The Permeameter 728

Superficial air velocity 728

Permeability factor 729

The Fluidization Process 729

Minimum fluidizing velocity 730

Pneumatic transport 730

The Influence of Particle Size and Density 730

The Geldart classification 730

Air Retention 731

Deaeration constant 731

Specific Surface 734

British Standard procedure 734

Lea and Nurse method 734

The Blaine method 734

References 734

Introduction

It has been shown, in some detail, in many of the chapters of this Design Guide, that the properties of the materials to be conveyed are critical in terms of both designing a pneumatic conveying system and in understanding how it performs in service. In the extreme, where a system dramatically underperforms or ceases to operate, it will clearly be necessary to investigate the reasons in order to seek a solution. If it is not a fault with the feeding device or the air supply, it will generally be found to relate to the material being conveyed. If this occurs on commissioning, the situation may have to be resolved by litigation. If it occurs after a period of time, it may be caused by factors such as those discussed in Chapters 24 and 26 or it may result from a change in the material being conveyed. In either case it would always be recommended that a representative sample of the material should be kept in order to determine where the fault lies.

For the purpose of characterizing and defining materials, for which conveying data have been obtained, it would generally be recommended that various bench scale tests should be carried out on each material to obtain a number of measurable properties for reference. Such properties will allow comparison between the conveying capability of different materials to be made, and can enable correlations between material properties and pneumatic conveying characteristics to be determined, as considered in Chapter 13.

Details of a number of such tests that can be carried out to provide bulk and particle properties are presented in this appendix. Some property values are required for material identification purposes, such as mean particle size, size distribution and bulk, and particle density. Some material properties will be required in system design, such as particle hardness, friability, moisture content, and particle shape. Some of the bulk properties in which air and material interact are particularly useful in identifying conveying capability, such as air retention and permeability.

Such data were recorded for many of the materials tested in the various pneumatic conveying programs that are reported in this Design Guide. Data obtained are presented in Appendix 2, along with additional conveying characteristics for a variety of materials and pipelines.

The Need for Characterization

The need for characterization was highlighted in Chapter 2, by way of an introduction to the subject, and in particular with Figs. 2.19 to 2.21 at the end. In the first of these it was shown that the conveying capability of the material could change quite dramatically just as a consequence of the material being conveyed. For given identical conveying conditions, the material flow rate increased by more than 100% after it had been conveyed in a test facility a few times. In the second it was shown that for the material being conveyed, an increase in mean particle size from 60 μm to 100 μm, the material flow rate would be halved for exactly the same conveying conditions. Last it was shown that the material flow rate could be halved for a change fro...