COUNTERCURRENT MULTISTAGE EXTRACTION Chapter 5 COUNTERCURRENT MULTISTAGE EXTRACTION (using supercritical fluids) What for? Separation of compounds, mostly liquid, of similar volatility Why supercritical fluids? Low temperature Solvent free products Multistage countercurrent separation Better and new products

COUNTERCURRENT MULTISTAGE EXTRACTION Separation of n-3 Fatty acids Example: Separation of n-3 Fatty acids derived from fish oil EPA C20 with 5 double bonds DHA C22 with 6 double bonds DPA C22 with 5 double bonds EPA: Eicosapentanoic acid DPA: Docosapentanoic acid DHA: Docosahexanoic acid

Some Fatty Acids Linoleic acid C17H31COOH, MW: 280,44 Linolenic acid C17H29COOH, MW: 278,42 Arachidonic acid C19H31COOH, MW: 304,46

Fatty Acid Content of Some Natural Materials 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 25,4 Dunaliella primolecta 10,4 9,7 3,9 --- Cryptomonas sp. 7,0 16,0 --- 10,0 Fish Mackerel 1,48 14,16 2,82 10,26 Codfish 0,92 6,00 2,4 7,62 Sardine --- 18,08 2,16 10,25 Thuna fish --- 4,9 1,2 27,7 Herring 1,15 4,28 0,74 4,06

Analysis and Pseudo Components of Fish Oil FA I Component Feed Gas phase Liquid phase Ki Pseudo- component [A-%] [A -%] [A -%] [-] C14:0 7,22 12,21 6,91 1,77 0,13 0,22 0,12 1,83 0,19 0,31 0,19 1,63 0,48 0,70 0,47 1,49 C14 C16:4n-1 2,89 3,84 2,83 1,36 1,73 2,28 1,69 1,35 C16:1n-7 9,17 11,82 8,98 1,32 C16:3n-3 1,12 1,45 1,10 1,32 0,38 0,48 0,38 1,26 C16:0 16,13 19,81 15,85 1,25 0,41 0,49 0,41 1,20 0,21 0,24 0,20 1,20 0,17 0,19 0,17 1,12 0,41 0,43 0,40 1,08 C16 0,13 0,12 0,12 1,00 0,33 0,33 0,33 1,00 C18:4n-3 3,12 3,09 3,11 0,99 1,44 1,39 1,44 0,97

Analysis and Pseudo Components of Fish Oil FA II C18:1n-9 10,12 9,62 10,11 0,95 3,05 2,86 3,05 0,94 0,44 0,40 0,43 0,93 0,12 0,10 0,12 0,83 C18-0 3,17 2,81 3,17 0,89 C18 C20:4n-6 1,00 0,73 1,02 0,72 C20:5n-3 18,07 13,51 18,30 0,74 0,24 0,13 0,23 0,57 C20:4n-3 1,01 0,69 1,03 0,67 0,27 0,17 0,26 0,65 C20:1n-11 0,69 0,46 0,69 0,67 0,30 0,20 0,31 0,65 0,23 0,15 0,17 0,88 C20:0 0,22 0,14 0,23 0,61 C21:5n-3 0,74 0,49 0,76 0,64 C20 0,37 0,18 0,40 0,45 C22:6n-3 10,26 5,81 10,52 0,55 C22:4n-6 0,12 0,14 C22:5n-3 2,17 1,19 2,23 0,53 C22:1n-11 0,36 0,15 0,38 0,39 C22:0 0,09 0,09 C24:1 0,38 0,12 0,40 0,30 C22 99,08 99,31 98,74

Triglycerides P = Palmitic acid O = Oleic acid S = Stearic acid

Fatty Acids Glycerol Triglycerides

Transformation of Triglycerides Hydrolysis, Saponification Glycerolysis Methanolysis Interesteri- fication Reduction

Countercurrent multistage processing Characteristics: Binary separation Reflux Enriching section Stripping section Supercritical solvent cycle

COMPOSITION OF PRODUCTS YIELD FEED QUANTITY COMPOSITION OF FEED Definition of the separation problem COMPOSITION OF PRODUCTS YIELD FEED QUANTITY COMPOSITION OF FEED PHASE EQUILIBRIA: (EXPERIMENT; CORRELATING) SEPARATION FACTORS

COUNTERCURRENT MULTISTAGE EXTRACTION Definition of Task 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

Maximum concentration in a countercurrent process Limiting Phase Equilibrium Maximum concentration in a countercurrent process

Phase equilibrium: PUFA - CO2

Separation PUFA - CO2-Propane

Separation factor for FAEE in sc CO2 14 MPa 333 K Separation factor  Ethyl ester in gas [wt.-%]

P,x - Diagramm PUFA- Feed - CO2

Density of Coexisting Phases EE1: 3.3 EE10: 91.6 EE 13: 9.5 + 90.5 % C 22

Equilibrium Calculations: Fundamental Equation

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

Equilibrium Calculations: Mixing Rule b,

Separation factor: Concentration Dependence FA-ethyl esters - CO2 Riha 1996

McCabe-Thiele Analysis Design Methods For Number of Theoretical Stages McCabe-Thiele Analysis Ponchon-Savarit in a Jänecke-Diagram Simulation

CC-GE: Basic Equations Mass balances: Enthalpy balances: Equilibrium relations: Rate equations for mass transfer:

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.

Mc- Cabe-Thiele Analysis Equilibrium

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.

Scheme of Stage Calculations

Experimental Verfication in a Laboratory Plant

PUFA - Separation: C16 - C18 Van Gaver

PUFA- Separation: C18: sat. / unsaturated Van Gaver

HETP, HTU FA-ethyl esters - CO2 Riha 1996

Kolonnenschaltung zur Gewinnung einer PUFA-Fraktion

Separation routes for n3 fatty acids (as esters) Feed AgNO3 Urea Distillation SFE-Countercurrent Extraction EPA 92 wt.-% DHA 90 wt.-% EPA 44 wt.-% DHA 42 wt.-% EPA 73 wt.-% DHA 85 wt.-% Chromatographic Separation Processes, SFC EPA > 95 wt.-% DPA > 95 wt.-% DHA > 95 wt.-%

Solexol - Process with near critical propane IEC 41:280, 1949

Multistage cc separation of n3- FAEE Krukonis 1988

Multistage cc separation of n3- FAEE THEORY Krukonis 1988

Multistage cc separation of n3- FAEE THEORY Krukonis 1988

SOLVING A MULTICOMPONENT SEPARATION IN CC-GE Define the mixture: Summary and Design Procedure 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 ) or number of transfer units (NTU)

Determine efficiency of mass transfer equipment: 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