countercurrent multistage extraction (using supercritical fluids) what for? separation of compounds,...

COUNTERCURRENT MULTISTAGE EXTRACTION

(using supercritical fluids)What for?

Separation of compounds,mostly liquid,

of similar volatility

Why supercritical fluids?

Low temperatureSolvent free products

Multistage countercurrent separationBetter and new products

Chapter 5

Example:

Separation of n-3 Fatty acids derived from fish oil

EPA C20 with 5 double bondsDHA C22 with 6 double bondsDPA C22 with 5 double bonds

EPA: Eicosapentanoic acid DPA: Docosapentanoic acid DHA: Docosahexanoic acid

COUNTERCURRENT MULTISTAGE EXTRACTION

Linoleic acid C17H31COOH, MW: 280,44

Linolenic acid C17H29COOH, MW: 278,42

Arachidonic acid C19H31COOH, MW: 304,46

Some Fatty Acids

Fatty acids in weight-percent Spezies -Linolenic acid EPA DPA DHA

C18:3 C20:5 C22:5 C22:6

Plants Flax 50 --- --- ---Soya 8 --- --- ---Thistle 9 --- --- ---

Algae Amphidinium carterri 0,1 7,4 0,6 25,4Dunaliella primolecta 10,4 9,7 3,9 ---Cryptomonas sp. 7,0 16,0 --- 10,0

Fish Mackerel 1,48 14,16 2,82 10,26Codfish 0,92 6,00 2,4 7,62Sardine --- 18,08 2,16 10,25Thuna fish --- 4,9 1,2 27,7Herring 1,15 4,28 0,74 4,06

Fatty Acid Content of Some Natural Materials

Component Feed Gas phase Liquid phase Ki Pseudo-

component[A-%] [A -%] [A -%] [-]

C14:0 7,22 12,21 6,91 1,770,13 0,22 0,12 1,830,19 0,31 0,19 1,630,48 0,70 0,47 1,49 C14

C16:4n-1 2,89 3,84 2,83 1,361,73 2,28 1,69 1,35

C16:1n-7 9,17 11,82 8,98 1,32C16:3n-3 1,12 1,45 1,10 1,32

0,38 0,48 0,38 1,26C16:0 16,13 19,81 15,85 1,25

0,41 0,49 0,41 1,200,21 0,24 0,20 1,200,17 0,19 0,17 1,120,41 0,43 0,40 1,08 C160,13 0,12 0,12 1,000,33 0,33 0,33 1,00

C18:4n-3 3,12 3,09 3,11 0,991,44 1,39 1,44 0,97

Analysis and Pseudo Components of Fish Oil FA I

C18:1n-9 10,12 9,62 10,11 0,95 3,05 2,86 3,05 0,940,44 0,40 0,43 0,930,12 0,10 0,12 0,83

C18-0 3,17 2,81 3,17 0,89 C18C20:4n-6 1,00 0,73 1,02 0,72C20:5n-3 18,07 13,51 18,30 0,74

0,24 0,13 0,23 0,57C20:4n-3 1,01 0,69 1,03 0,67

0,27 0,17 0,26 0,65C20:1n-11 0,69 0,46 0,69 0,67

0,30 0,20 0,31 0,650,23 0,15 0,17 0,88

C20:0 0,22 0,14 0,23 0,61C21:5n-3 0,74 0,49 0,76 0,64 C20

0,37 0,18 0,40 0,45C22:6n-3 10,26 5,81 10,52 0,55C22:4n-6 0,12 0,14C22:5n-3 2,17 1,19 2,23 0,53C22:1n-11 0,36 0,15 0,38 0,39C22:0 0,09 0,09C24:1 0,38 0,12 0,40 0,30 C22

99,08 99,31 98,74

Analysis and Pseudo Components of Fish Oil FA II

Triglycerides

P = Palmitic acid

O = Oleic acid

S = Stearic acid

Fatty Acids Glycerol Triglycerides

Triglycerides

s

Hydrolysis, Saponification

Glycerolysis

Methanolysis

Interesteri-

fication

Reduction

Transformation of Triglycerides

Countercurrent multistage processing

Characteristics:

Binary separation

Reflux

Enriching section

Stripping section

Supercritical solvent cycle

COMPOSITION OF PRODUCTS YIELD

FEED QUANTITY

COMPOSITION OF FEED

PHASE EQUILIBRIA: (EXPERIMENT; CORRELATING)

SEPARATION FACTORS

Definition of the separation problem

COUNTERCURRENT MULTISTAGE EXTRACTION

Determine: Number of theoretical stages (or number of transfer units).

Height (Size) of a separation device Separation performance (Mass Transfer)

Capacity of a separation device Throughput -----> diameter

Definition of Task

Maximum concentration in a

countercurrent process

Limiting Phase Equilibrium

Phase equilibrium: PUFA - CO2

Separation PUFA - CO2-Propane

Se

pa

rati

on

fa

cto

r

Ethyl ester in gas [wt.-%]

14 MPa

333 K

Separation factor for FAEE in sc CO2

P,x - Diagramm PUFA- Feed - CO2

% C20:

EE1: 3.3

EE10: 91.6

EE 13: 9.5 +

90.5 % C 22

Density of Coexisting Phases

Equilibrium Calculations: Fundamental Equation

.lndR

R

1ln

,,

zVV

T

n

P

T

V

nVTii

ij

.

.;

.

Vi

Li

i

ii

i

LiL

ii

ViV

i

j

iij

x

yK

Px

f

Py

f

K

K

PT

V b

a T

V V bm

m

m

R ( )

( ),

.

or

1

,

5.0

5.0

5.0

1 1

ji

iijijjjiiij

ijjjiiij

N N

ijjim

xx

xkkaaa

kaaa

axxTa

Equilibrium Calculations: Cubic EOS (RK-type), Mixing Rule a

.15.0

with

1 1

ijjjiiij

N

i

N

jijjim

lbbb

bxxb

.min

,1

1

2calcexp2calcexp

N

iiiii yyxx

N

Equilibrium Calculations: Mixing Rule b,

0,0 0,2 0,4 0,6 0,8 1,01,0

1,1

1,2

1,3

1,4

1,5

1,6

1,7

1,8

1,9

2,0

T = 60 °C p = 12 MPa p = 14 MPa p = 16 MPa

[-

]

x (C14..C18) [wt.-fraction]

FA-ethyl esters - CO2

Riha 1996

Separation factor: Concentration Dependence

Design Methods For Number of Theoretical Stages

McCabe-Thiele Analysis

Ponchon-Savarit in a Jänecke-Diagram

Simulation

Mass balances:

Enthalpy balances:

Equilibrium relations:

Rate equations for mass transfer:

,0d

d

d

d

z

V

z

L ii ., VVLL ii

.0

d

d

d

d q

z

VH

z

LH Vi

.ii

i LL

VKV

,d

d iiiGi VVV

Pak

z

V

CC-GE: Basic Equations

with:z = axial coordinate in the separation device;Li, Vi = flow of component i in the liquid and gaseous

phase;L, V = total flow of liquid and gaseous phase;HV, HL = enthalpy of gaseous and liquid phase;kGi = mass transfer coefficient of component i, related

to the gaseous phase;a = mass transfer area per volume of transfer device;P = total pressure;Ki = equilibrium partition coefficient of component i between gaseous and liquid phase;Vi* = equilibrium concentration of component i in the gaseous phase.

.f 11 xy

.11 112

1121 x

xy

.// 111111 pRnnnpppp VxRyVxVLyn

.// 111101111 0

pSppppVxLySxVLy

.111 FFF xFxLyV

Equilibrium

Mc- Cabe-Thiele Analysis

Minimum number of stages / mimimum reflux ratio

Limiting conditions

PUFA - separation: n-min, v-min

Jänecke - diagram for sc solvent

Countercurrent- Extraction in a Jänecke - Diagram

PUFA - separation: Jänecke analysis

Separation Analysis

Simulation of the separation

Select method: nth or NTU

Determine min. reflux, min. nth or NTU

Vary reflux-ratio;

Calculate separation as function of nth or NTU

Calculate nth or NTU as function of separation

Determine concentration profiles.

.ipp

pipip L

L

VKV

,01,1, ippipiipip FVLVL

.andi

pippi

ip VVLL

,011 11

pFpVpLpVpLp qHFHVHLHVHLppppp

./ iii xyK

.,,,,,f jijii yyxxTPK

Scheme of Stage Calculations

Experimental Verfication in a Laboratory Plant

Van Gaver

PUFA - Separation: C16 - C18

Van Gaver

PUFA- Separation: C18: sat. / unsaturated

thnhHETP /

.

,d

,

Fak

VHTU

yy

yNTU

NTUHTUh

v

y

y

o

i

FA-ethyl esters - CO2

Riha 1996

HETP, HTU

C14..C18

Rücklauf

Fischöl-

esterfeed

C20 +C22

C24 + Rest

C20..C24 + Rest

CO2-Kreislauf

Rücklauf

Kolonnenschaltung zur Gewinnung einer PUFA-Fraktion

Feed

Distillation SFE-Countercurrent Extraction

AgNO3 Urea

EPA 44 wt.-%

DHA 42 wt.-%

EPA 73 wt.-%

DHA 85 wt.-%

EPA 92 wt.-%

DHA 90 wt.-%

Chromatographic Separation Processes, SFC

EPA > 95 wt.-% DPA > 95 wt.-% DHA > 95 wt.-%

Separation routes for n3 fatty acids (as esters)

Solexol - Process with near critical propane

IEC 41:280, 1949

Multistage cc separation of n3- FAEE

Krukonis 1988

Multistage cc separation of n3- FAEE

Krukonis 1988

THEORY

Krukonis 1988

THEORY

Multistage cc separation of n3- FAEE

SOLVING A MULTICOMPONENT SEPARATION IN CC-GE

Define the mixture: components or pseudo-components

Define the separation: identify key components, purity and recovery rate

Determine separation performance: (as a function of reflux ratio):

number of theoretical stages (n ) ornumber of transfer units (NTU)

Summary and Design Procedure

Determine efficiency of mass transfer equipment:tray efficiency, or HETP, or HTU

Determine limits for mass flow of countercurrent streams:

maximum flow (entrainment, flooding)minimum flow (for effective mass transfer)

Decide for a certain reflux ratio

Calculate separation performance size of a column

for the chosen equipment and operating conditions

Summary and Design Procedure