Filtration Flashcards
1
Q
What are the potential driving forces for filtration?
A
- gravity
- vacuum
- pressure
- centrifugal force
(only last 3 are used on an industrial scale)
2
Q
Filter Press
A
- 2 plates squeeze together to form a filter cake
- slurry distributed between 2 plates and the plate compression removes liquid
- often operated in parallel so that one can be cleaned while other is used
- uses vibration to remove cake
3
Q
Belt Press
A
- completely continuous
- belt is a filter material, so liquid from slurry falls through belt (slight vacuum (0.8-0.5 atm) under belt or gravity used to pull liquid from system)
- cannot get very dry filter cake, but can handle very large flowrates.
4
Q
Rotary Drum
A
- drum rotates with rotating material being the filter
- slurry is fed at the basin (slight vacuum at centre of drum which pulls liquid into it)
- can handle very large flowrates, but expensive
5
Q
Filter theory 2 types of filters:
A
- Surface filter (particles collected at surface as size of solids > pore size of filter) (used for solid concentration greater than 1% by volume)
- depth filter (small particles can penetrate into filter media)
- want solid concentration less than 1% by volume (otherwise can be very expensive to replace)
6
Q
Necessary properties of a filter media
A
- must remove solids with certain size (to give clear filtrate)
- pores should not become plugged enough that filtration becomes too slow
- must be strong enough not to tear
- must be chemically resistant (not react with slurry)
7
Q
What are the 2 properties that may be kept constant when filtering
A
1.constant pressure
- reduce rpm of pump to get lower flowrate
- constant flowrate
- increase rpm of pump to get higher pressure
8
Q
Cycle Time
A
- the total time for filtration to occur (time to cycle, time to filter and dead time - wash time, disassembly/assembly time)
- is cyclical