COAL BREAKAGE CHARACTERISTICS IN VARIOUS FORMS OF COMMINUTION EQUIPMENT. Report

Directorate-General For Energy

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• Publié par: DIRECTORATE-GENERAL-FOR-ENERGY
• Nombre de lectures: 58
• Langue: English
• Poids de l'ouvrage: 6 Mo

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Commission of the European Communities
technical coal research
COAL BREAKAGE CHARACTERISTICS
IN VARIOUS FORMS
OF COMMINUTION EQUIPMENT
Report
EUR 12362 EN
Blow-up from microfiche original Commission of the European Communities
technical coal research
COAL BREAKAGE CHARACTERISTICS
IN VARIOUS FORMS
OF COMMINUTION EQUIPMENT
BRITISH COAL CORPORATION
Coal Research Establishment
Stoke Orchard
UK-Cheltenham, Glos. GL52 4RZ
Contract No. 7220-EA/813
FINAL REPORT
Directorate-General Energy
1990 EUR 12362 EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunication«, Information Industries and Innovation
L-2920 LUXEMBOURG
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting on behalf
of then is responsible for the use which might be made of the following
information
Catalogue number: CD-NA-12362-EN-C
© ECSC — EEC — EAEC, Brussels - Luxembourg, 1990 III
COAL BREAKAGE CHARACTERISTICS IN VARIOUS FORMS OF COMMINUTION EQUIPMENT
SUMMARY
The report describes work carried out since June 1986, aimed at
exploiting the use of fine coal (pulverised and microfine) as a substitute
for oil and gas in industrial processes, by evaluating coal breakage
behaviour both in laboratory-scale fundamental studies and in commercially
available comminution equipment. Particular emphasis has been placed on
specific energy requirements for breakage and product particle size
characteristics for a range of coal types. In addition, several novel
mills have been assessed for their potential in direct-fired combustion
systems. Wet milling trials have also been included in order to augment
coal water mixture (CWM) studies.
Laboratory tests were carried out under well-defined, controlled
stress conditions, i.e. compression and impact. These tests showed that
(i) the amount of fines (-300 um) produced by compression and impact
depends on the energy per unit mass applied, (ii) initial particle size had
little, if any, effect on the amount of fines produced for a given energy
per unit mass, (iii) the ranking order with respect to the fines produced
for a given energy per unit mass is the same for compression and impact,
(iv) for impact milling, the amount of fines produced depends only on the
cumulative energy per unit mass, not on the energy per unit mass supplied
in individual impacts, and (v) approximately 25 - 30% more energy is needed
to produce fines by impact than by compression.
Milling trials on a range of commercially available equipment were
carried out at manufacturers' sites, using reference coals selected on the
basis of Hardgrove Index (HGI) and coal rank. Particular emphasis has been
placed on specific energy requirements for breakage and product particle
size characteristics.
Comparison of the conventional mills tested showed that vertical
spindle mills (in particular a pendulum mill) gave the best overall
performance (fine product size, low specific energy) for both pulverised
and microfine products. The performance of impact mills varied
considerably, mainly as a result of the wide variety of design geometries
tested. The best performance was given by impact mills of relatively
simple design.
In general the performance of a mill in pulverised coal milling is an
indicator of thee of that mill in microfine milling, except
possibly in the case of an impact classifier mill which showed enhanced
performance in milling to a microfine product size.
Multi-rotor impact mills have been evaluated in depth because of their
relative novelty, compactness and potential for low-cost manufacture. Two
of these mills were tested as part of a combined mill/combustion system.
After modifications to design and operation, both mills were shown to be
suitable for use in direct-fired combustion of microfine coal.
Wet milling trials showed that two novel mills (a planetary roller and
centrifugal ball mill) were capable of producing high solids loadings (63
and 74% solids respectively) after one pass through the mill, making them
suitable for on-line production of CWM. IV
Ultra-fine grinding was studied, using fluid energy mills (dry
milling) and stirred bead mills (wet milling).
Comparison of the effect of coal type on breakage performance showed
that (i) at optimum running conditions, breakage behaviour of bituminous
coals is dependent on HGI, (ii) in ultrafine milling tests using anthracite
(where particle-particle attrition is involved) resistance to grinding is
significantly greater than predicted by HGI as a result of high
microhardness of anthracite vitrinite, (iii) slurryability of coals in
wet-milling trials is a rank-dependent property.
The report includes a brief discussion on wear of mills, in terms of
measured abrasion parameters.
Coal Research Establishment
British Coal
Stoke Orchard
Cheltenham
Glos
GL52 4RZ
UK CONTENTS
Page No.
1. INTRODUCTION 1
2. THEORY OF COMMINUTION 2
2.1 Breakage Characteristics 2
2 2.2 Particle Size Distribution
3
2.3 Energy Consumption
5
3. REFERENCE COALS
6
4. FUNDAMENTAL STUDIES OF COAL BREAKAGE
6
4.1 Introduction 6
4.2 Experimental
6 4.2.1 Compression tests
4.2.2 Impact tests 7
7 4.2.3 Size analysis
4.3 Results and Discussion
4.3.1 Compression tests 7
8
4.3.2 Impact tests
9
4.4 Implications of the Results
11
5. MILL TYPES AND TRIAL RESULTS
11
5.1 Tumbling Mills
11
5.1.1 General features
12
5.1.2 Modes of action 13
5.1.3 Liners 13
5.1.4 Ball-loaded mills 15
5.1.5 Rod-loadeds 15
5.1.6 Wet vs dry milling 16
5.1.7 Open and closed circuit milling 17
5.1.8 Mill trials
5.1.8.1 British Rema batch ball mill 18
5.1.8.1.1 Test conditions 18 2 Results 18
5.1.8.1.3 Discussion 18
5.1.8.2 NEI Hardinge ball mill 19
5.1.8.2.1 Description 19 2 Test conditions (dry milling) 19
5.1.8.2.3 Results 19 4 Discussion 20
20 5.1.8.2.5 Test conditions (wet milling)
20 6 Results
21 5.1.8.2.7 Discussion
22 8 Comparison of wet and dry milling VI
Page No.
5.2 Vertical Spindle Mills 22
5.2.1 General features
5.2.2 Ball and race mills - specific features 25
5.2.3 Roller mills - specific features
5.2.3.1 Ring-roller mills
5.2.3.2 Table-roller mills6
5.2.4 Mill trials 2
5.2.4.1 FCB Compac ball and race mill 2
5.2.4.1.1 Description2 Test conditions 27
5.2.4.1.3 Results4 Discussion
5.2.4.2 NEI Raymond pendulum mill8
5.2.4.2.1 Description2 Test conditions
5.2.4.2.3 Results 29 4 Discussion
5.2.4.3 Williams pendulum mill
5.2.4.3.1 Description2 Test conditions 30
5.2.4.3.3 Results4 Discussion1
5.2.4.4 NEI Lopulco table-roller mill
5.2.4.4.1 Description 32 Test conditions2
5.2.4.4.3 Results4 Discussion
5.2.4.5 Comparison of results3
5.3 Impact Mills 35
5.3.1 General features
5.3.2 Rotary impact mills with rigid grinding elements 37
5.3.2.1 Atritor dryer-pulveriser 37
5.3.2.1.1 Description2 Test conditions8
5.3.2.1.3 Results 34 Discussion9 VII
Page No.
5.3.2.2 KEK-Gardner Universal (pin) mill 39
5.3.2.2.1 Description 32 Test conditions 40
5.3.2.2.3 Results4 Discussion
5.3.2.3 Alpine UPZ fine impact mill1
5.3.2.3.1 Description 42 Test conditions Al 3 As-received crushed feedstock 42
5.3.2.3.3.1 Results2 Discussion2
5.3.2.3.4 Twice-crushed feedstock 4
5.3.2.3.4.1 Results 42 Discussion3
5.3.2.3.5 Comparison of single- and two-stage
milling
5.3.3 Impact mills with swing hammers4
5.3.3.1 NEI Impax mill 4
5.3.3.1.1 Description2 Test conditions
5.3.3.1.3 Results5 4 Discussion6 5 Wear assessment 4
5.3.3.2 Sardón Saxifrage mill7
5.3.3.2.1 Description2 Test conditions
5.3.3.2.3 Results 48 4 Discussion
5.3.4 Impact mills with externally controlled
classifiers9
5.3.4.1 Alpine ZPS mill
5.3.4.1.1 Description 42 Test conditions 50
5.3.4.1.3 Results4 Discussion1
5.3.4.2 Hosokawa Mikropul air classifier mill 5VIII
Page No.
5.3.4.2.1 Description 51
5.3.4.2.2 Test conditions2 3 Results
5.3.4.2.4 Discussion3
5.3.4.3 British Rema Prema CLM mill
5.3.4.3.1 Description
5.3.4.3.2 Test conditions 53 Results4
5.3.4.3.4 Discussion
5.3.4.4 Comparison of results
5.3.4.5 Wear assessment 55
5.3.5 Multi-rotor mills
5.3.5.1 Tas mill2 Septu ultrafine mill6
5.3.5.2.1 Product fineness7 2 Energy consumption 58
5.3.5.2.3 Coal type
5.3.5.3 Altenburger Ultra-Rotor mill
5.3.5.4 Discussion 59
5.4 Stirred Bead Mills
5.4.1 General features
5.4.2 Mill trials 61
5.4.2.1 Eiger Kotormill
5.4.2.1.1 Description2 Test conditions 6
5.4.2.1.3 Results2 4 Discussion
5.4.2.2 Netzsch Mastermix (LMJ) agitator mill 63
5.4.2.2.1 Description2 Test conditions
5.4.2.2.3 Results 64
5.4.2.3 Comparison of results
5.5 Fluid Energy Mills5
5.5.1 General features
5.5.2 Spiral jet mills7
5.5.2.1 British Rema jet mill 6