| 摘要 |
A wash-box for separating materials of different densities (e.g. coal and shale) comprises a stratification compartment (8), a perforate grid plate (12) extending across an upper part of the stratification compartment, and means (20, 22) by which water is admitted to the wash-box. The wash-box comprises a compression chamber (10) in underwater communication with the stratification compartment, and pressure applying means (14, 16, 18, 19) operative alternately to pressurise and de-pressurise the compression chamber (10), to cause repeated rising and falling of movement of water in the stratification compartment, to stratify raw material on the grid plate (12). The wash-box comprises a control device (24), comprising a pressure transducer (26) operative to measure the pressure pertaining in the compression chamber (10), in particular the average pressure pertaining in the compression chamber over a complete cycle of rising and falling movement of the water in the stratification compartment, and to produce a control signal dependent upon such measurement. The control signal is compared with a preset value, and the difference between the control signal and said preset value is utilised to determine the rate of admission of water to the wash-box, by actuation of a valve (22). |
