Settling Tanks Flashcards
what is the basic principle that settling tanks are created on?
terminal settling velocity
where are settling tanks used?
mining (slurries, large amount of liquid to filter)
Thickener
desired product is settled particles at bottom
Clarifier
desired product is clear liquid off the top
purpose of rake in settling tank
to push solids towards underflow exit
purpose of a well in settling tanks
prevents solids from flowing to the sides immediately, usually (1-2 m)
Can also be where add floculants which causes particles to agglomerate
Can also be used to remove surface charges (charged particles will repel each other causing increased settling time)
*tank depth usually 3-3.5m (so large portion of tank)
Solid exiting concentration
typically less than 10 wt% (too high concentration means increased settling area, and more costs)
Settling assumption
Stokes regime (particles moving slowly)
Methods of estimating settling velocity
empirical correlations for terminal velocity
batch testing (necessary for porous or agglomerating particles as empirical estimates are not good)