PURPOSE: To precoat filter aid to uniform thickness by controlling the flow rate of upward flow of slurry contg. filter aid when the filter aid is precoated on a filter element by feeding the slurry contg. the filter aid fed as an upward flow from a bottom end area of each filter element to the intermediate area of each filter element.
CONSTITUTION: Slurry 39 contg. a specified concn. of filter aid is fed with a precoating pump 51 from a slurry tank 50 to a slurry feeding pipe 15. The slurry flowing upward through each intermediate area of filter element 30 is led to a guiding device at the top of the filter element so as to make the flow rate of upward flow from each intermediate area uniform and is flowed into ducts 72, 73 to flow down and return to the slurry tank 50. The flow rate of the returned slurry corresponds to the flow rate where the flow rate at the top area of the element 30 coincides with the settling speed of the filter aid. By continuing the above described precoating procedure, the concn. of the filter aid in the slurry tank 50 decreases gradually. The precoating is finished when the filter aid is depleted.
ADACHI TETSUROU
EBARA KATSUYA
SHINDOU KIICHI
NUMAZAKI SEIICHI
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