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SKG16.3 > Distillation & Separation > Flashcards

Distillation & Separation Flashcards

1
Q

Separation Processes

A

A process in which a mixture is separated into individual components or group of components

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2
Q

Why?

Separation Processes

A
  • Product specification
  • Recovery
  • Purification
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3
Q

Methods

SEPARATION

A

DISTILLATION
SIEVE
ABSORPTION
EXTRACTION
ADSORBTION
CRYSTALLIZATION

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4
Q

Distillation

A

It involves a volatile vapor phase and a liquid phase that vaporizes

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5
Q

Absorption

A

A solute or solutes are absorbed from the gas phase into a liquid phase in absorption.

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6
Q

Adsorption

A

One or more liquid or gas stream are adsorbed on the surface or in the pores of a solid adsorbent.

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7
Q

Crystallization

A

Solute components soluble in a solution is removed from the solution by adjusting the conditions

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8
Q

Liquid-liquid Extraction

A

When a solute or solutes are removed from a liquid phase to another liquid phase

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9
Q

Leaching

A

Fluid is used to extract a solute from a solid.

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10
Q

Membrane separation

A

Separation of molecules by the use of membranes that control the rate of
movement of molecules between two phases.

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11
Q

Types of Mixture

Homogeneous

A

Create another phase
or Add another phase

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12
Q

Types of Mixture

Heterogeneous

A

Exploit the existing phase difference

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13
Q

Separation of Heterogeneous Mixtures

A
  • Filtration
  • Centrifuge
  • Floatation by gas bubble
  • Settling by Gravity
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14
Q

Phase creation

General Separation Technique

A

Separation by phase creation
- distillation
- crystallization
- evaporation

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15
Q

Addition

General Separation Technique

A

Separation by phase addition
e.g. absorption, extraction

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16
Q

barrier

General Separation Technique

A

Separation by barrier
e.g. reverse osmosis,
gas permeation

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17
Q

solid agent

General Separation Technique

A

Separation by solid agent.
e.g. adsorption, ion exchange

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18
Q

force field or gradient

General Separation Technique

A

Separation by force field or gradient.
e.g. electrolysis, centrifugation

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19
Q

Types of Separation Processes

A
  • Equilibrium
    Governed
  • Rate
    Governed
20
Q

Equilibrium
Governed

A
  • Flash
    Vaporization
  • Distillation
  • Absorption
21
Q

Rate
Governed

A
  • Membrane
  • Crystallization
  • Electrolysis
22
Q

Concept Of Distillation

A

a process of physically separating mixtures into two or more products that have different boiling points, by preferentially boiling the more volatile components out of the mixtures.

23
Q

Why Distillation?

A
  • Continuous
  • Relatively cheap
  • High capacity
  • Efficient
  • Easy to scale-up
  • No moving parts
24
Q

Distillation Not suitable for :

A
  • Small volatility difference,
  • Small quantity of high boiling component to be recovered from the feed,
  • A compound is thermally unstable even under vacuum conditions,
  • Mixture is extremely corrosive
25
Q

Equilibrium Stage Concept

A

A distillation column may be
considered as a series of equilibrium flashes with two feeds and two products

26
Q

Bubble Point Temperature

A

The temp. at which the first vapor bubble is formed when liquid is
heated slowly at constant pressure.

27
Q

Dew Point Temperature

A

The temp. at which the first liquid droplets is formed when a vapor
is cooled slowly at constant pressure

28
Q

Bubble Point Pressure

A

The pressure at which the first bubble is formed when a liquid is
expanded slowly at constant temp

29
Q

Rectifying section

A

Section of tower above the feed point. Heavy components are condensed out of the vapor in
this section

30
Q

Stripping section

A

Section of tower below the feed point. Light components are stripped out of the liquid in this section

31
Q

Reflux

A

Liquid from the overhead condenser that is returned to the top of the tower. The reflux ratio is the reflux rate divided by the overhead product rate

32
Q

Rules of Thumb

More Separation

A
  • More Reflux
  • More Trays
  • Lower Pressure
33
Q

Typical distillation contains several major components

A

– a vertical shell where the separation of liquid components is carried out
– column internals such as trays/plates and/or packings which are used to enhance component separations
– a reboiler to provide the necessary
vaporisation for the distillation process
– a condenser to cool and condense the vapour leaving the top of the column
– a reflux drum to hold the condensed vapour from the top of the column so that liquid (reflux) can be recycled back to the column

34
Q

FEED

A

– liquid mixture that is to be
processed.
– introduced usually somewhere near the middle of the column to a tray
known as the feed tray.
– feed tray divides the column
into a top (enriching or rectification) section and a bottom (stripping) section.

35
Q

REBOILER

A

– Heat is supplied to the reboiler
to generate vapour.
– Source of heat input can be
any suitable fluid, although in
most chemical plants this is normally steam. In refineries, the heating source may be the output streams of other columns.
– Vapour raised in the reboiler is
re-introduced into the unit at the bottom of the column.
– Liquid removed from the reboiler is known as the bottoms product or simply, bottoms.

36
Q

CONDENSER

A

– Vapour moves up the column,
and as it exits the top of the unit, it is cooled by a condenser.
– Condensed liquid is stored in a holding vessel known as the reflux drum.
– Some of this liquid is recycled back to the top of the column and this is called the reflux.
– The condensed liquid that is removed from the system is known as the distillate or top product

37
Q

Draw Tray – Total Draw

A

– All liquid is drawn from the tray.
– No net liquid flow internally down to the section below.
– No vapor-liquid contact on the tray

38
Q

Purpose

Pumpback

A
  • Good control of desired product spec
  • Keep the trays/packing in the pumpback section completely wet all the times
39
Q

Pumparound

A

– Sub-cooled liquid recycle in a column
– Removes heat from the column
– Reduces vapour traffic
– Condenses liquid product

40
Q

Advantages

Pumparound

A
  • Efficient recovery of heat at high temperature (used for preheat, reboiling)
  • Higher capacity or smaller tower diameter above p/a section
  • Unload overhead condensing system
41
Q

Multi-component Separation

A

The number and type of fractionators required depend on the number of products to be made and the feed composition

42
Q

Naphtha minus separation

A

From Naphta minus, go through Debutanizer to produce LPG & Full Range Naphta. LPG go through De-Ethanizer to produce Gas & LPG. Full Range Naphta go through Naphta Splitter to produce Full Range Tops & Naphta

43
Q

Function of process control systems

A

to maintainyields and product quality by holding certain operating variables at the desired values, or by returning to those values after an upset.

44
Q

Common Problem Faced In Distillation

A
  • Flooding
  • Dry trays
  • Foaming
  • Mis-operation
  • Controls
  • Feed Quality Variation
  • Utility Problem
  • Non-condensibles
  • Water in feed
45
Q

Multi-Component Separation

The number and type of fractionators required
depend on

A

the number of products to be made and
the feed composition

46
Q

Contacting Device Selection

A
  • Reduce investment cost
  • Debottleneck throughput or improve product specification
  • Save energy via lower pressure drop or higher efficiency
  • Improve flexibility or turndown
  • Provide reliable construction / easy maintenance

SKG16.3 (12 decks)

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