COALTECH 2020 Task 4.8.1 Dewatering and drying of fine coal to a saleable product by P.E. Hand, Isandla Coal Consulting cc. March 2000 Copyright COALTECH 2020 This document is for the use of COALTECH 2020 only, and may not be transmitted to any other party, in whole or in part, in any form without the written permission of COALTECH. Table of contents Index ........................................................................................................................................ 2 1 Foreword ........................................................................................................................... 8 2 Introduction ...................................................................................................................... 9 2.1 Definitions .................................................................................................................. 9 2.2 Problem statement ................................................................................................... 10 2.3 Basic Economics ...................................................................................................... 11 2.3.1 Arising Slimes .................................................................................................. 13 2.3.2 Existing Slimes ................................................................................................ 13 2.4 Purpose .................................................................................................................... 14 2.4.1 Clean coal......................................................................................................... 14 2.4.2 Discard ............................................................................................................. 15 2.5 Plant Moisture Balance ........................................................................................... 17 3 Survey of Dewatering and Drying Equipment ............................................................ 20 3.1 Mechanical ............................................................................................................... 21 3.1.1 Stockpiles (Solar drying) ................................................................................. 21 3.1.2 Screens ............................................................................................................. 21 3.1.2.1 Dewatering ................................................................................................... 21 3.1.2.2 Linear Screen ............................................................................................... 23 3.1.2.3 Pan Sep Screens ........................................................................................... 24 3.1.3 Thickening ....................................................................................................... 25 3.1.4 Centrifuges ....................................................................................................... 26 3.1.4.1 Screenbowl Centrifuge................................................................................. 26 3.1.4.2 Solidbowl Centrifuge ................................................................................... 29 3.1.4.3 Scroll Type Centrifuges ............................................................................... 30 3.1.4.4 Pusher Centrifuge......................................................................................... 32 3.1.4.5 Air Purged Basket Centrifuges .................................................................... 32 3.1.5 Filtration ........................................................................................................... 32 2 3.1.5.1 Filter cloth .................................................................................................... 32 3.1.5.2 Continuous Filters ........................................................................................ 33 3.1.5.2.1 Vacuum Drum Filter .............................................................................. 33 3.1.5.2.2 Vacuum Disc Filter ................................................................................ 34 3.1.5.2.3 Parnaby Type Belt Filter Press .............................................................. 35 3.1.5.2.4 Ceramec Filter ........................................................................................ 36 3.1.5.2.5 Horizontal Belt Filter ............................................................................. 37 3.1.5.2.6 Hyperbaric.............................................................................................. 39 3.1.5.3 Batch Filters ................................................................................................. 42 3.1.5.3.1 Filter Presses .......................................................................................... 42 3.1.5.3.2 Larox Filter ............................................................................................ 47 3.1.5.3.3 Bethlehem Tower Press ......................................................................... 49 3.1.5.3.4 Tube Press Filter .................................................................................... 50 3.2 Thermal Drying ........................................................................................................ 51 3.2.1 Direct................................................................................................................ 51 3.2.1.1 Rotary Driers ................................................................................................ 51 3.2.1.2 Fluidised Bed ............................................................................................... 53 3.2.1.3 Flash Dryer................................................................................................... 54 3.2.1.4 Pneumodrier ................................................................................................. 55 3.2.2 Indirect ............................................................................................................. 57 3.2.2.1 Holoflite ....................................................................................................... 57 3.2.2.2 Torus Disc .................................................................................................... 58 3.3 Other types ............................................................................................................... 59 3.3.1 Centridry .......................................................................................................... 59 3.3.2 EA Process ....................................................................................................... 61 3.3.3 Microwave ....................................................................................................... 61 3.3.4 Chemicals ......................................................................................................... 62 3.3.4.1 Super Absorbent Polymers .......................................................................... 62 3.3.4.2 Dewatering Chemicals ................................................................................. 62 3.3.4.3 Oil Agglomeration ....................................................................................... 63 3.3.5 Other Aspects ................................................................................................... 63 3.3.6 Summary of Costs ............................................................................................ 64 3.3.6.1 Mechanical Dewatering Cost Summary ...................................................... 64 3 3.3.6.2 Thermal Drying Cost Summary ................................................................... 65 4 South African Practice .................................................................................................. 66 4.1 Fine Coal Treatment ................................................................................................ 66 4.2 Ultrafine Treatment ................................................................................................. 67 4.2.1 Ingwe................................................................................................................ 67 4.2.1.1 Middelburg South ........................................................................................ 67 4.2.1.2 Rietspruit Colliery ........................................................................................ 68 4.2.1.3 Koornfontein Colliery .................................................................................. 68 4.2.2 Anglo Coal ....................................................................................................... 69 4.2.2.1 New Vaal Colliery ....................................................................................... 69 4.2.2.2 Kleinkopje .................................................................................................... 69 4.2.3 Sasol ................................................................................................................. 69 4.2.3.1 SSF Plants .................................................................................................... 69 4.2.3.2 Twistdraai .................................................................................................... 69 4.2.4 Duiker .............................................................................................................. 70 4.2.4.1 Atcom ........................................................................................................... 70 4.2.4.2