lall Rlldmall SAIMM（拉尔RlldmallSAIMM）.pdf

THE COAL PLANT OF THE 21ST CENTURY- A CONTRACTORS VIEW lall Rlldmall I.TA PROCESS ENGINEERING urn The Coal Plant of the 21st Century A Contractors View I R Rudman ABSTRACT Technological advances in the design of dense medium separating devices are quite rare occurrences. Two advances in recent years are the use of large diameter dense medium cyclones and Larcodems. A plant module of 500tph or even more can now be built having a single washing device, replacing a previous large coal bath circuit combined with a small diameter cyclone circuit. The use of these high capacity devices coupled with developments in screening and magnetic separation technology could enable a reduced capital and operating cost plant to be built Operating results from some of South Africa s plants, that are almost there are discussed. LARGE DIAMETER DENSE MEDIUM CYCLONES Dense medium cyclones are presently utilised in all of South Africas dense medium coal washing plants where small coal is washed. (There may still be one DWP plant in operation somewhere) The top size of coal being washed is normally between lOmm and- 20mrn, while the bottom size is usually O.5mm. The most popular dense medium cyclones in older plants are the 500mm, 600rnrn and 660mm diameter units . The larger plants having either two or three cyclones operated in parallel in a single module. All dense medium cyclones on the larger mines were gravity fed at a static head of 9D (The minimum recommended by DSM for coal washing), it was only the small operators that practised pump feeding of dense medium cyclones . S