Distillation Control Flashcards
(18 cards)
What are the 2 most critical CVs in distillation control?
1) Pressure
2) Composition
What are the feed sources in a distillation tower?
1) Upstream process
2) Tank storage
3) Recycled downstream product
4) Pipeline
What is the order of the start-up procedure in a distillation column?
1) Cooling water
2) Steam
3) Introduce the feed
4) Reflux
5) Monitor distillate/bottoms/tops
What is external reflux?
Product being pumped into the column
What is internal reflux?
Product flowing down the column
What is the reflux ratio?
External reflux flow/ distillate flow
What section of a distillation tower is the rectifying section?
Section that is above the feed tray
What section of a distillation tower is the stripping section?
Section below the feed tray
What is a sign of high differential pressure across the distillation tower and what creates that condition?
Flooded trays cause by too much feed or reflux flow
What is a sign of low differential pressure across the distillation tower and what creates that condition?
Dry trays caused by too much steam
If an operator changes the steam flow from 100 kg/hr to 160 kg/hr what will be the effect on the tops pressure, tops composition, and bottoms composition?
Tops pressure: increases and settles out below the SP of the steam
Tops composition: increases and settles out below the SP
Bottoms composition: drops below the SP
If an operator changes the reflux flow from 50 kg/hr to 110 kg/hr what will be the effect on the tops pressure, tops composition, and bottoms composition?
Tops pressure: stays roughly the same
Tops composition: increases rapidly
Bottoms composition:
increases but shows a deadtime as the bottoms will not be affected right away
A ____________ is where only a liquid stream is taken from the Accumulator.
Total condenser
In __________________ the column pressure is controlled by manipulating the cooling water flow
rate. Long residence times will ultimately lead to a larger lag time for the system which in turn leads to a reduced condensing rate.
Water throttling
The _____________________ ensures the cooling water flow rate is kept constant. The pressure is controlled by varying the area used in the condenser. This is done by controlling the flow out of the condenser.
Partially flooded condenser
In ________________ method the column pressure is controlled by manipulating the overhead flow rate which gives excellent pressure control.
Overhead throttling
In _____________ liquid and vapour are taken off the accumulator.
Partial condenser
What can happen if incondensibles are not removed from the accumulator?
They will block the condenser therefore blocking the distillation process
