[Measurement of Mass Flow Rate of Pneumatically Conveyed Solid]

By

ACKNOWLEDGEMENT

I would take this opportunity to thank my research supervisor, family and friends for their support and guidance without which this research would not have been possible.

DECLARATION

I, [type your full first names and surname here], declare that the contents of this dissertation/thesis represent my own unaided work, and that the dissertation/thesis has not previously been submitted for academic examination towards any qualification. Furthermore, it represents my own opinions and not necessarily those of the University.

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ABSTRACT

Many industrial processes such as coal pulverising, flour making, cement production, and fertiliser processing involve moving bulk solids by means of pneumatic conveying. Almost all particles become electrically charged during pneumatic transportation, which can be hazardous in industrial environment. The primary sources of electrification are frictional contact charging between particles, between particles and the conducting facility, charge transfer or sharing from one particle to another and charge induction. Contact charging occurs at their common boundary when two dissimilar substances are brought into contact. On separation, each surface will carry an equal amount of charge with opposite polarity. Triboelectrification can be regarded as a complicated form of contact electrification in which there is transverse motion when two substances impinge or are rubbed together. The transverse motion can in turn accentuate the charge transfer. Contact electrification occurs not only in pneumatic conveying, but also in milling, grinding, sieving and screw feeding. Another source of electrostatic charge is induction. Charges will be induced on a conductor in an electrostatic field generated by charged particles. This conductor in turn changes the field distribution. If a conductor is insulated from the earth, its potential depends on the amount of charges, the permittivity of particles and their locations relative to the conductor . The charge due to induction disappears when the charged particle moves away from the vicinity or sensing volume of the conductor as in pneumatic conveyance. Charges can be shared by two particles when they collide to each other, or when one particle is settled on another. Charge sharing is more obvious between conductive particles. Electrostatic charge can be recombined, for example via the earth or by contact with an object holding opposite charge. However charge on non-conductive particles can be retained and the relaxation time depends on the volume resistivity of bulk solids. If the volume resistivity is high, the charge could be retained even if the solids are in an earthed container. For particles suspended in pure gases as in pneumatic conveying, particles can remain charged for a long period of time irrespective of the particle material's conductivity.

TABLE OF CONTENTS

ACKNOWLEDGEMENTII

DECLARATIONIII

ABSTRACTIV

CHAPTER 1: INTRODUCTION1

Project Aims And Objectives3

CHAPTER 2: LITERATURE REVIEW4

CHAPTER 3: TEST DESIGN AND IMPLEMENTATION37

CHAPTER 4: EXPERIMENTAL TESTS AND RESULTS43

CHAPTER 5: DISCUSSIONS61

Solids fraction measurement61

Velocity Measurement62

Mass Flow Rate Calculations62

Direct Measurements65

Mass Flow Rate Measurement of Solids Based On Corio Lis Force Methods65

CHAPTER 5: CONCLUSIONS70

REFERENCES74

CHAPTER 1: INTRODUCTION

The philosophy for calibration of electrostatic fieldmeters is to use a pair of plane parallel conducting surfaces to define the electric field E in the central ...