Particle Technology

hindered settling

Problems 6.9

Question 1.14


Height of the settling interface against time graph. Batch settling curve
We chose one characteristic and followed it upwards, having decided what the longest period of time is that we can allow the suspension to settle. We know that the characteristic and the resulting design (0.82 m high tank, settled for 24 hours and sediment height of 32 cm) will work, but it is still a poor design: the tank is too short and too wide. If it was to be made circular an area of 1650 m2 requires a diameter of 46 metres. We could follow other characteristics from the origin upwards, but we would have to check that they provide a suitable design in terms of recycling 85% of the water. A better design, given the high flow rate and low settling velocity, would be to run the tank continuously: as a continuous thickener. This is the subject of the next question.

 

 

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