| 摘要 |
By this method, the fluid to be filtered is led through a filter bed formed of particulate filter particles, such as sand, which filter bed is retained in an upstanding annular space. The fluid is introduced to the interior part 15 of the annular space and is led transversely to the movement the filter bed, through it and away. The filter bed is provided on the inner wall of annular space with a microfilter, such as sieve grid 16, with a mesh size of 10 to 200 microns, whereby the heavy and flocculated dirt particles settling upon the microfilter are led down and away and are drawn off together with the particulate filter particles 32. To avoid stoppages of the microfilter, it is flowingly hydraulically cleaned from the inner space. Additionally, by introduction of water in the take-off space 11 there is produced a vortex bed, whereby at this space the withdrawal of the particulate filter medium is effected with a mammoth pump 17 known per se. The compressed air for the operation of the mammoth pump 17 is supplied not steadily but pulsatingly. Thus, there are provided in the vortex bed in combination with the water supply thereto some hydraulic pulses which serve to hinder the development of bridges in and above it.
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