Mechanical Activation of Minerals by Grinding: Pulverizing and Morphology of Particles

A. Z. JUHASZ, Prof. D.Sc. Veszprem University of Chemical Engineering Veszprem, Hungary

and

L. OPOCZK Y, Prof. D.Sc. Central Research and Design Institute for Silicate lndustry Budapest. H ungary

ELLIS HORWQOD LIMITED Publishers · Chichester Halsted Press: a division of JOHN WILEY & SONS New York • Chichester · Brisbane ·Toronto

CONTENTS

Preface ............... ; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Chapter I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I I

l. General features of mechanical activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II

I. I. The scope of mechano-chemistry ............ , . . . . . . . . . . . . . . . . . . . . I I 1.2. Mechanical activation by fine grinding... .. . . . . . . . . . . . . . . . . . . . . . . . I2 1.3. Modes of mechanical activation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Symbols in Chapter I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 5 References . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 5

Chapter 2 ........... :............................................... I7

2. Characterisation and methods of examination of disperse systems . . . . . . . . I 7

2.1. Characterisation of the buik structure of solid disperse systems by the SPV system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 7

2.2. Study of disperse systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2. l. Determination of particle size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2.2. Particle size distribution ............ „ . . . . . . . . . . . . . . . . . . . . . . ·23 2.2.3. Specific surface area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.2.3.1. Methods for determining specific surface . . . . . . . . . . . . . . 28 2.2.3.2. Determining specific surface on the basis of permeability 30 2.2.3.3. Methods of measuring specific surface by adsorption . . . 33

2.2.4. Measurement of pore size and its distribution . . . . . . . . . . . . . . . . 36 2.2.5. Stability of buik and compaction work . . . . . . . . . . . . . . . . . . . . . . 38

2.3. Methodology of investigating mechano-chemical phenomena . . . . . . . . . 39 Symbols in Chapter 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . 40 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

•

6 Contents

Chapter 3 ................................ ·. . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3. Changes in the structure and in the chemical reactivity of solids due to deformation and fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.1. Macroscopic phenomena in solids induced by mechanical load . . . . . . . 44 3.1. l. Some basic phenomena of stress analysis. . . . . . . . . . . . . . . . . . . . . 44 3.1.2. Chemical phenomena accompanying deformation and fracture . . 49

3.2. Structural changes associated with deformation . . . . . . . . . . . . . . . . . . . . 52 3.2. l . Def~rmation of ideal crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 3.2.2. Deformation of real crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3.2.3. Deformation of polycrystalline materials . . . . . . . . . . . . . . . . . . . . . 65 3.2.4. Deformation of amorphous materials . . . . . . . . . . . . . . . . . . . . . . . 65

3.3. Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 3.4. Electrical and luminous phenomena triggered by mechanical activation 74 Symbols in Chapter 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 References ........................................................ 75

Chapter 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4. The process of fine grindi~g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . 77

4.1. Material characteristics relevant during comminution . . . . . . . . . . . . . . . · 77 4.1. l. Hardness (microhardness) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.1.2. A concept study of grindability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 4.1.3'. Physico-mechanical characteristics and grindability of clinker

minerals and cement clinkers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 4.2. The process of grinding and the interaction of particles . . . . . . . . . . . . . 88

4.2. l. Stages of grinding. Aggregation and agglomeration. . . . . . . . . . . . 89 4.2.2. Fine grinding and equilibrium states . . . . . . . . . . . . . . . . . . . . . . . . 101 4.2.3. Mechanism of particle interactions . . . . . . . . . . . . . . . . . . . . . . . . . . 105

4.3. Energy requirements during grinding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 4.4. The role of the medium in fine grinding . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

4.4. l. The etfect of the medium on the mechanical properties of solid bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

4.4.2. Etfect of medium on grinding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 4.4.3. Mechanism of action of grinding aids . . . . . . . . . . . . . . . . . . . . . . . 124

Symbols in Chapter 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 References .................. 1•••••••••••••••••••••••••••••••••••••• 140

Chapter 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

5. Structural changes and mechano-chemical reactions induced by fine grinding 147

5.1. Changes in the crystal structure............... ................... 151

Contents 7

5.2. Mechano-chemical reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 5.2. l. Homogeneous mechano-chemical reactions . . . . . . . . . . . . . . . . . . . 155 5.2.2. Mechano-chemical dissociation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 5.2.3. Mechano-chemicaldecomposition of organic and silicate polymers.

Surface activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 5.2.4. Mechano-chemic~l reactions between gases and solids . . . . . . . . . 163 5.2.5. Mechano-chemical reactions between liquids and solids . . . . . . . . 164 5.2.6. Mechano-chemical reactions between solids . . . . . . . . . . . . . . . . . . 165 5.2.7. Mechano-chemical reactions combined with capillary condensa-

tion ................ : ................................... 166 5.2.8. Chemi-hesion and the overlapping eftbct . . . . . . . . . . . . . . . . . . . . . 168

5.3. Effect of mechano-chemical activation on the physico-chemical and technological properties of silicates and other materials used in the silicate industry ...................................................... 170 5.3.1. Examples of changes in crystal structure . . . . . . . . . . . . . . . . . . . . . 170 5.3.2. Examples of solubility change& .. , . . . . . . . . . . . . . . . . . . . . . . . . . . 193 5.3.3. Examples of changeS. in high temperature reactions . . . . . . . . . . . 195 5.3.4. Examples of the modification of cation-.exchange capacity..... . 197 5.3.5. Improving the hydration capacity of ßC2S by fine grinding . . . . . 200 5.3.6. Enhancement of activity achieved by fine grinding hydraulites,

industrial wastes, and raw materials of the cement industry. . . . . 202 5.3.7. Changes in the dielectric properties . . . . . . . . . . . . . . . . . . . . . . . . . 203 5.3.8. Effect of grinding on clay-water systems . . . . . . . . . . . . . . . . . . . . . 204

Symbols in Chapter 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Chapter 6 ........................................................... 214

6. Equipment for fine grinding and the problem of mechanical activation .... 214

6.1. Ball mills ..... · .... ............................................ 214 6.2. Vibration mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 6.3. Jet mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 ' 6.4. The attritor mill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 6.5. Disintegrators ....................... ·. . . . . . . . . . . . . . . . . . . . . . . . . . 222 6.6. Planetary mills ................................................ 225 Symbols in Chapter 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

Subject index ........................................................ 229