Distillation is the most common separation technique that involves evaporating and condensing components of a liquid mixture to separate them based on differences in their boiling points. It consumes large amounts of energy for heating and cooling. Fractional distillation uses a fractionating column and refluxing to improve separation efficiency compared to simple distillation. Various parameters like reflux ratio, pressure, temperature controls are optimized to achieve desired purities and specifications of fractions in a distillation column. Stripping steam is also used to help separate lighter components from heavier fractions.

1. Distillation
By

2. Introduction
B
• The most common separation
technique
C • Consumes enormous amounts of
energy, both in terms of cooling and
A
heating requirements
• Contribute to more than 50% of plant
operating costs
D
E
• Definition: a process in which a liquid or vapour mixture of two or more
substances is separated into its component fractions of desired purity,by the
application (evaporation) and removal(condensation) of heat.

3. Simple Distillation set up
A

4. Fractional Distillation
Fractionation
Furnace
Stripping
Reflux ratio??

5. Influence of Pressure
• Boiling points varies with pressure : keep it constant
• Lower the partial pressure; lower the boiling pt.
• Lighter components difficult to condense at low P; operates at higher P(10-12
bar)
• Heavier components will have to be heated up to 400 degC for distillation to
occur, hence HC bonds will start to break.
• For heavier comps, distillation carried under vacuum condition to avoid the
carbon chain from cracking

6. Crude Distiller –1 Configuration

7. Crude Distiller 2 - Configuration

8. Separation
• IBP, FBP
• Gap
• Overlap
• Aim for:
 overlap Naphtha < 10 degC < Tops
 no gap & overlap between Naphtha and Kero
 overlap LGO < 10 degC < Kero
 overlap HGO < 10 degC < LGO
Separation efficiency is due to reflux ratio

9. Column Control For Product Spec
• Control FBP of product by controlling the top temp of the column, higher top
temp, heavier comps boils over, higher FBP, more product on overheads( at fixed pressure)
• How to change production? for better separation, create more reflux,
• How to  top temp?(1) reduce/increase amount of heat removed from column @ (2)
reduce/increase amount of heat supplied to column
• Heat removed by reflux flow. reflux, remove more heat, top temperature 
• Heat supplied via (1) feed temperature & (2) bottom reboiler

10. Stripping Steam
• Component A and B
Ptotal = PA + PB
• Introduce steam with same Ptotal
Ptotal = PA new + PB new + Psteam
• PA new < PA and PB new < PB
• Hence enable comp A and B to vaporise at lower P and T (if low enough, no
heat addition required)
• Known as to lower the partial pressure of the component, applied in
removing the light ends from fractions

11. Multi cut splitter and strippers
• 2 cut splitter only gets 2 product, have to feed
into another 2 columns to further separate
• For instance to separate into 3 fractions, side
stripper can be used
Furnace

12. Crude Distiller –1 Configuration

13. Crude Distiller 2 - Configuration