Distillation Column Design Guide

Distillation Column www.engineering-resource.com/Files/ distillation%20 column column1.ppt 

Distillation:  ““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 and removal of heat”

Distillation:  ““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 and removal of heat”

CHOIC !"#$ P% &" &$' !"#$ P%& P&C(' CO CO% %)* )*$ $  "he "he choice between use of tray column or a pac+ed column for a iven mass transfer operation should, theore theoretically, tically, be based on a detail cost analysis  for for the two types of contactors- However,  the the decision can be made on the basis of o f a qualitative analysis of relative advantaes and disadvantaes, eliminatin the need for a detailed cost comparison#hich are as follows

 

       

Liquid dispersion difculties Capable o handling wide ranges  liquid liquid rates Cleaning. Non-oaming systems Periodic cleaning weight o the column Design inormation nter stage cooling !emperature change Diameters

&s my system is non foamin  and and diameter calculated is larer than .-/0 m so I am oin to use !ray column. &lso as averae temperature calculated for my distillation column is hiher that is approximately equal to 12oc- 3o I prefer !ray column-

PL"!# C$N!"C!$%&: Cross 4ow plate  are are the most commonly used plate contactor in distillation- In which liquid 4ows downward and vapours 4ow upward- "he liquid move from plate to plate via down comer- & certain level of liquid is maintained on the plates by weir-

!hree basic types o cross 'ow trays used are

  

&ie(e Plate )Perorated Plate* +ubble Cap Plates ,al(e plates )'oating cap plates5

&election o  &election !rays:

I prefer &ie(e

because6 Plate  because6

Pressure drop  is is low as compared to bubble cap trays  "heir fundamentals are well established, entailin low ris+ "he trays are low in cost  relative relative to many other types of trays "hey can easily handle  wide wide variations in 4ow  ratesrates "hey are lihter in weiht - It is easier and cheaper to install *aintenance cost  is is reduced due to the ease of cleanin

&ie(e !ray

Label Diagram tray* Downcomer And Weir

)sie(e Man Way

Calming Zone

Major Beam

Plate Support Ring

"C!$%& "#C!N D&!LL"!$N C$L/0N $P#%"!$N &dverse vapour 4ow conditions can cause6      

+lowing Coning Dumping %aining 1eeping looding

FLOW SHEET

REFLUX DRUM

Condenser 

REFLUX DRUM (1) Methyl Iodide = 0.212 (2) Acetic Acid = 0.0005 ()Methyl Acet!te = 0.62 ( (4) "!te# = 0.167 FEED

FEED

  Pump

1) Methyl Iodide = 0.21 (2) Acetic Acid = 0.0005 ()Methyl Acet!te = 0.62 (4) "!te# = 0.17

(1) Methyl = 0.07 (1) Iodide Methyl Iodide = 0.074 (2) Acetic Acid = 0.65 (2) Acetic Acid = 0.65 ()MethylAcet!te=0.22 ()Methyl Acet!te =(4) 0.215 "!te# = 0.065

(4) "!te# = 0.065

  Reboiler  (1)Acetic Acid = 0.$$  (2)"!te# = 0.01

rom  ro m 0aterial 0aterial +alance:

 

2ea(y 3eyComponent4 3eyComponent4 "cetic"cid Light 3ey 3eyComponent Component 41ater 41ater

Component Component

  eed   raction 5 

)6*

  7.78

0ethyl

+ottom   raction 5b 7

!op   raction 5d   7.96

odide )9*

"cetic

7.;

 

7. ??????? :-;5 7 7 9 :-; 7

min

7 9 /-><

min

!heoretical no. o Plates:

illiland related the number o equilibrium stages and the minimum re'u5 ratio and the no. o equilibrium stages with a plot that was transormed by #dulEee into the relation@ 0.566    R −  Rmin    = 0.751 −     + 1  N  + 1 R       8rom which the theoretical no- of staes

 N  −  N min

to be,

N4 =<

Calculation o actual numbe o stages: $(erall !ray !ray #fciency:

 E o

     = 51 − 32.5log µ avg .α avg          

α avg =average relative volatility of light key component =1.75 μ avg = molar average li!i" vi#co#ity of fee" eval!ate" at average temperat!re of col!mn

&verae temperature of column 9=::2A0:5B> 9 1; oC 8eed viscosity at averae temperature 9 µav 9 .- 3o, o  9 9 ;/-/. 3o,  3o, No. o actual trays  9 9 8 Number o Plates below the eed tray 4 N+ 4 96

Determination o the Column Diameter: low Parameter: FLV

  L n = V   n

   ρ v         ρ L

0.5

       

8%D  9 9 %iquid Dapor 8actor 9 .-.;/

Capacity Parameter: "ssumed tray spacing 4 6 inch )7.; m*  "ssumed rom ig )6;-;* )6;-;* Plant Design and #conomics or Chemical #ngineering sie(e tray 'ooding capacity Csb  4 4 7.787 m@&ec &urace tension o   0i5ture 4  6.=; 6.=;   4 σ       ρ l  −4  ρ vG  &urace V nf   = C  sb       dynes@Cm  20      ρ v     0 .2

,n 46.8 m@sec 46.8 m@sec "ssume ;6= m Column Cross-sectional "rea)" c*4 6.; m9 Down comer area Ad  4 7.6;"c  4 4 7.9; m9 Net "rea )"n* 4 "c  -- "d  46.>6 46.>6 m9 "cti(e area  " 4 6.6 m9 "a4"c-9"d  4 2ole area Ah  taFe taFe 67H Aa  4 4 7.6  6.6 47.7>9 m9 1eir length  1eir "d @ "c 4 7.9> @ 6.;> 4 7.6; 7.6;

rom Kgure 66.=6 Coulson M

%ichardson th (olume =rd edition Lw @ dc 4 7.7 Lw 4 6.>;9O7.7 =  7.8== 7.8== m 1eir length should be 7 to ;H o column diameter which is satisactory !aFe weir height hw4 ;7 mm 2ole diameter dh 4 ; mm  4 Plate thicFness 4 ; mm

ChecF 1eeping: 

U ( min ) =

(

 K 2 − 0.9 25.4 − d h

( ρ v )

)

1/ 2

where /min  is is the minimum design (apor (elocity. !he (apor (elocity at weeping point is the minimum (elocity or the stable operation. n order to ha(e 3 9  (alue (alue rom Kg66.=7 Coulson M %ichardson th (olume we ha(e to 6st Knd =rd edition  we how)depth o the crest o liquid o(er the weir*

how48;7?)Lm@lwO*9@=A 0a5imum liquid rate QL mR4 >.8 Fg@sec 0inimum Liquid %ate "t 87H turn down ratio 4 =.=3g@sec "t 0a5imum rate ) how*4  97 97 mm Liquid "t 0inimum rate )how*  4 4 6 mm Liquid hw  I I how  4 4 ;7 I 6 4  mm Liquid rom Kg 66.=7 Coulson and %ichardson ,ol. 3 9  4 4 =7.;7 &o

/

)min*

4 < m@sec  4

Now ma5imum (olumetric 'ow rate )(apors* +ase 4 9.69 m=@sec !op 4 6.6> m=@sec "t 87H turn down ratio  "t "ctual minimum (apor (elocity  "ctual 4minimum (apor rate @ " h 4 69.6 m@sec &o minimum (apor rate will be well abo(e the weep point.

Plate Pressure Drop )P.D*:

Consist o dry plate P.D  )oriKce )oriKce loss* P.D due to static head o liquid  and and residual P.D  )bubbles )bubbles ormation result in energy loss* Dry Plate Drop: 0a5. ,apor (elocity through holes )/h* 4 0a5imum ,olumetric low %ate @  2ole 2ole "rea 4 6.=7 m@sec Perorated area "p )acti(e area* 46.6 m9

rom Kg. 66.=> )Coulson M %ichardson th (olume =rd edition* or plate thicFness@hole diameter  4 4 6.77 1e get Co  4 4 7.> 2

U  h   ρ V  hd  = 51  C o   ρ  L   !his equation is deri(ed or oriKce meter pressure drop. hd4 > mm Liquid %esidual 2ead )hr*: hr 4 )69.;O67=  @@ L* 4 6=.= mm Liquid

&o ht 

=

hd 

+

" hw

+

how !

+

hr 

!otal pressure drop 4>I);7I97*I6=.=9 ht  4 4 6=6.=; mm liquid !otal column pressure drop  Pa Pa )N@m9* 4 ) 9 .-....> m> &rea of $  Holes Holes 9 .-::;2 m> 3o,

Number $ 2oles 4 ; m &o 2eight o column  4 4 )-6*O7.;7I 6I7.=> 4 =; meters

ho)=Weir cr!#t

Plate Specifications

1.$5m height=%5m

Hole "iameter=5mm

hap=$( mm &o. of hole#=5'((

h W=5( mm

Specification Sheet Of *i#tillation +ol!mn,

-"entification, Item *i#tillation col!mn No. required 1 Tray type Sieve tray F!nction, Separation of cetic ci" from io"o methane and Reaction /y pro"!ct#. Operation, +ontin!o!#

0aterial han"le",

eed   "mount Compositio n   of &cetic &cid

 "emp-

!op

E0;; (Bhr

.-/E

::1oC

  +ottom

:1/2 (Bhr

 

.-..;

0:oC

>02/ (Bhr

 

.-11

::2oC

*e#ign "ata, $o- of tray9 /2  $o  Pressure Pressure 9 :.:-; (pa   Heiht Heiht of column 9 (pa  "ray  "ray thic+ness thic+ness 9 ; mm 

&ctive holes 9 ;1..  &ctive   #eir #eir heiht 9 ;. mm   #eir #eir lenth 9 : m   7e4ux 7e4ux ratio 9 /-><  "ray  "ray spacin spacin 9.-; m   &ctive &ctive area 9 :-:/ m >   Percent Percent 8loodin 91.   ntrainment ntrainment 9 .-.0; 

%eerences 

Coulson  7ichardson /th volume