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[an_iron_panda]

Hello...

 

I'm a student and I had exam to design plant (continuous),

and after following procedure to choose the possible equipment, i came up with 2 main equipment,

reactor and distillation column

 

and when i reach the distillation column im a bit confused about reflux

 

so the problem is

 

the reactor output come as the feed to the distillation column ( at round 58.000 kg/h )

my product is heavy component so it comes in the bottom ( according y x equil bottom mass flow round 8000 kg/h )

and the top component will be recycle to the reactor, ( according y x equil top mass flow round 50.000 kg/h )

 

i calculated the reflux value and return some of top component as reflux ( L round 29.000 kg/h, and D round 21.000 kg/h )

 

and the mass balance of the distillation will be

 F = B + D

 

because the L returned to the column, but the value wouldn't equal

 

so to equal the mass balance should i change the input component ( back to the reactor design )?

or i just did mistakes before this...

 

thank you cheresources

may the force be with you

 

 

[Pilesar]

The mass balance equation you gave is F = B + D. 

    The reflux L is not in that equation at all so does not mathematically affect it! If you draw a closed shape around any part of your flow diagram, you can develop a new material balance equation for that boundary. I suggest you draw a material balance boundary that crosses the reflux stream if you want the L in an equation. It is often convenient to enclose the condenser and reflux drum in a separate closed boundary, leaving the tower outside the boundary. The D stream (which you already calculated) will be another stream that crosses the boundary. See your material balance textbook which should have examples of this.

    You mention the feed will go into the bottom of the column. You will probably need some distillation stages below the feed to efficiently make your component separation. There are chemical engineering procedures to determine the optimum feed location and guessing at the feed location is not the same as learning chemical engineering.