ROCK CIRCUIT FIBRE CIRCUIT DRY ROCK STORAGE os 9. She | als = > I ty o. VN a 1s 6. wt) o/s —— GROUP 4 7 GROUP 4 Ld : GROUP 3 RETURN LEGEND —— |. BELT CONVEYOR il ea a BAGGING 2. SCREEN 3 FIBRE STORAGE 3, CONE CRUSHER 4. FIBERIZER TAILINGS 5. CYCLONE 6. DEDUSTER O 7. FAN OPENER 8. BIN 9. FAN GROUP 5 10. DUST COLL. TYPICAL FLOW LINE ASBESTOS FIBRE FIGURE 6 — Typical flowsheet for asbestos fibre at Cassiar. claim tunnel, which runs the full length of the dry- rock storage. These drawpoints discharge onto vari- able-speed belt feeders, which feed the reclaim belt. . Milling Circuit (Fig. 6) The reclaim belt from dry-rock storage discharges into two rotary distributors, each of which feed three horizontal gyratory double-deck Hall screens. These primary mill screens are fitted with a two-mesh top deck screen and an 18-mesh screen on the bottom deck. The first fibre is lifted from the top deck at the dis- charge end by air through an aspirating hood (Fig. 7) and is conveyed through ducting to a 7-ft-diameter cyclone. This first aspiration is designed to pick up all of the released fibre, thus preventing damage by further crushing. To ensure aspiration of all the fibre, a certain amount of rock is necessarily lifted at the same time and this rock is eliminated in subsequent screening and aspiration stages. The cyclone collector is designed to separate the fibre from the air by means of centrifugal action. The fibre drops through the cone of the cyclone and is dis- charged through a six-bladed rotary airlock. The air and dust are vented through the central core of the cyclone to a_fan which discharges to a fabric dust filter. The cyclone is not designed to be highly effi- cient, as it also acts as a fibre cleaner, removing some of the finer dust, thus improving the fibre quality during the air-conveying cycle. The oversize rock from the primary screens is crushed in two 3-ft short-head cone crushers in paral- lel. The cone crusher product is elevated to four addi- tional screens in closed circuit with the crushers. These screens are also fitted with a two-mesh screen panel FIGURE 7—Primary mill screens with aspirating hoods. and the aspirated fibre from these screens is conveyed to similar cyclones in the initial fibre circuit. The fibre lifted from the two-mesh screen decks is directed to the group three or spinning fibre cleaning circuit. The middle size of both the primary and secondary screens discharges onto six screens fitted with a top screen deck of four mesh. Aspiration from these Ale