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Željko Knez, Mojca Škerget STAGEWISE PROCESSES LABORATORY HANDBOOK (Collected material) Maribor, 2017 Full Prof. Dr. Željko Knez Faculty of Chemistry and Chemical Engineering, University of Maribor Laboratory for Separation Processes and Product Design Smetanova 17, 2000 Maribor Full Prof. Dr. Mojca Škerget Faculty of Chemistry and Chemical Engineering, University of Maribor Laboratory for Separation Processes and Product Design Smetanova 17, 2000 Maribor CIP – Catalogue record University of Maribor library 66.02/.09(075.8)(076) KNEZ, Željko Stagewise Processes, Laboratory handbook: (Collected material) / Željko Knez, Mojca Škerget. – Maribor: Faculty of Chemistry and Chemical Engineering, 2000 ISBN 86-435-0361-4 1. Škerget, Mojca COBISS-ID 45348609 It is not allowed to copy, reproduce, submit or translate this material without the approval of the authors Title of the publication: STAGEWISE PROCESSES, LABORATORY HANDBOOK Type of publication: Collected material Authors: Full Prof. Dr. Željko Knez, Full Prof. Dr. Mojca Škerget Proof-reader: Dr. Victor Kennedy Publisher: Faculty of Chemistry and Chemical Engineering, Maribor Printing: Printing office of the Technical Faculties Copies: 100 copies Year of publication: 2000 First reprint: 2009 Contents 1. THIN FILM EVAPORATION ................................................................................................ 1 1.1. THEORETICAL BACKGROUND ........................................................................................... 1 1.1.1. Theoretical thickness of the film ..................................................................................... 1 1.1.2. Retention time of the solution in the evaporator ........................................................... 1 1.1.3. Mass balance ................................................................................................................... 2 1.1.4. Heat balance .................................................................................................................... 5 1.2. TASK ................................................................................................................................. 6 1.3. TASK IMPLEMENTATION .................................................................................................. 6 1.4. PRESENTATION OF THE RESULTS IN THE LABORATORY NOTEBOOK ............................... 8 2. DIFFERENTIAL DISTILLATION ............................................................................................ 9 2.1. THEORETICAL BACKGROUND ........................................................................................... 9 2.2. TASK ............................................................................................................................... 11 2.3. TASK IMPLEMENTATION ................................................................................................ 11 2.4. PRESENTATION OF THE RESULTS IN THE LABORATORY NOTEBOOK ............................. 12 3. RECTIFICATION ............................................................................................................... 13 3.1. THEORETICAL BACKGROUND ......................................................................................... 13 3.1.1. Rectification apparatus .................................................................................................. 13 3.1.2. Mass balance ................................................................................................................. 14 3.1.3. Determining the theoretical number of plates with the McCabe-Thiele graphical method........................................................................................................................... 16 3.1.4. Reflux ratio ..................................................................................................................... 18 3.1.5. Pseudo-equilibrium curve .............................................................................................. 19 3.1.6. The average efficiency of the column ............................................................................ 20 3.1.7. Heat balance .................................................................................................................. 20 3.2. TASK ............................................................................................................................... 21 3.3. TASK IMPLEMENTATION ................................................................................................ 21 3.3.1. Apparatus ....................................................................................................................... 21 3.3.2. Execution: ...................................................................................................................... 23 3.4. PRESENTATION OF THE RESULTS IN THE LABORATORY NOTEBOOK ............................. 25 4. SOLID-LIQUID EXTRACTION ........................................................................................... 26 4.1. THEORETICAL BACKGROUND ......................................................................................... 26 4.1.1. Determining the theoretical number of stages for counterflow extraction ................. 28 4.1.2. Isolation of hypericin from St. John's wort (Hypericum perforatum) ........................... 32 4.2. TASK ............................................................................................................................... 34 4.3. TASK IMPLEMENTATION ................................................................................................ 34 I 4.3.1. Extraction ....................................................................................................................... 34 4.3.2. Using spectrophotometry to determine the concentration of hypericin in the extract (by DAC – Deutsche Arzneimittel Codex) ...................................................................... 36 4.3.3. Thin layer chromatography (TLC) .................................................................................. 36 4.3.4. Calculation ..................................................................................................................... 38 4.4. PRESENTATION OF THE RESULTS IN THE LABORATORY NOTEBOOK ............................. 39 5. ABSORPTION .................................................................................................................. 41 5.1. THEORETICAL BACKGROUND ......................................................................................... 41 5.2. TASK ............................................................................................................................... 46 5.3. TASK IMPLEMENTATION ................................................................................................ 47 5.4. PRESENTATION OF THE RESULTS IN THE LABORATORY NOTEBOOK ............................. 48 6. DRYING ........................................................................................................................... 49 6.1. THEORETICAL BACKGROUND ......................................................................................... 49 6.1.1. Drying solid materials .................................................................................................... 49 6.1.2. Basics of psychrometry .................................................................................................. 51 6.1.3. Drying rate ..................................................................................................................... 52 6.2. TASK ............................................................................................................................... 55 6.3. TASK IMPLEMENTATION ................................................................................................ 55 6.4. PRESENTATION OF THE RESULTS IN THE LABORATORY NOTEBOOK ............................. 57 Thin Film Evaporation 1 1. THIN FILM EVAPORATION 1.1. THEORETICAL BACKGROUND The main parameters that influencee evaporation in a thin film evaporator are the following: • The temperature of the heating medium, • The operating pressure in the evaporator and condenser, • The flow rate of the feed solution, • The speed of the rotor. 1.1.1. Theoretical thickness of the film The thickness of the film plays a major role in the evaporation process. It depends on the mass flow of the feed solution, its viscosity and the speed of the rotor. It is important to know the thickness of the film, in order to study the heat transfer in the thin film evaporator. The theoretical thickness of a falling film is calculated using the Hagen – Poiseuille equation: = Eq (1.1) 3 3ηF 2 δ �ρ gπd where: ρ – density (kg/m3), F – mass flow (kg/s), πd – internal diameter of the evaporator (m), η – dynamic viscosity (Ns/m2), δ – the thickness of the film entering the evaporator (m). 1.1.2. Retention time of the solution in the evaporator The retention time is the amount of time the feed solution is exposed to high temperature. The retention time is reduced by mechanically distributing the solution over the heating surface. It 2 Thin Film Evaporation depends on the flow rate of the feed solution through the evaporator, on the film thickness and on the thermal load. The retention time for the concentrated effluent is higher than that for the distillate, since the solution starts evaporating immediately after entering the evaporator. 1.1.3. Mass balance The mass balance calculations for a 2-component mixture are carried out considering a
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