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Periodyczna filtracja wirowa zawiesiny zrzutowej po wirówkach BIRD'a, zawierającej dodatek flokulantu Magnaflog

Palica M., Pęczek K., Kurowski Ł., Niemirowski J.

Rocznik Ochrona Środowiska

2008

Tom 10

275-288

A course of centrifugal filtration of dump suspension with and without Magnaflog 336 flocculant of concentration 1 g/m3 susp. was compared in the paper. In both cases the filter cloth PT 912 selected in batch filtration tests was used. Similarly, a flocculant dosage was chosen in additional tests in which an influence of the flocculant amount on pressure filtration was checked. It was proved that practically justifiable dosage should be slightly smaller than abovementioned (1.7 g/m3 susp.). On basis of 42 tests for suspension without flocculant and 42 tests for suspension containing flocculant, two dependencies describing dewatering intensity (final moisture content in cake) as a function of the acceleration simplex and centrifugation time were found. They are as follows w exp [A (a g)B C ] D pl = ? + where constants and exponents are given in Tab.2. The dependencies are valid with good accuracy. For most common values of (a/g) and ? used in experiments, and suspension with and without flocculant, the final moisture content of cake was in the range wpl = 37.2 - 37.6 %. Also, what was very important, filtrate was quite clear and could be turned backward to a process line. Additional experiments, such as PSD analysis and sedimentation tests, proved that the deposition of suspension and addition of flocculant favour agglomeration thus facilitating (accelerating) phase separation. Selected data of PSD analyses performed in the particle size analyser Analysette 22 of Fritsch are gathered in Tab.3. The sedimentation tests proved a decrease of the turbidity zone after 2 hours to such extent that it is possible to reduce the amount of suspension at least 5 times. Roughly calculations indicated that solid phase fraction in post-sedimentation sludge increased from about uz = 0.045 to uz = 0.173. Therefore, such sludge can be easier separated, and moreover (very important), its amount is many times smaller than the amount of inlet suspension. This implies that the initial separation of inlet suspension is strongly advisable. On the other hand, no significant differences between sedimentation with and without addition of Magnaflog 336 flocculant were observed. It seems that the turn-back of clarified liquid to circulation and a supply of sludge from a settling tank to inlet suspension, or alternatively the filtration of sludge after a settling tank should be the relatively cheaper and advisable method of dewatering