Liquid-Liquid Extraction Course

Lesson 1 • Thermodynamic Basis of Extraction

Covers Gibbs free energy, chemical potential, and activity coefficients as drivers of solute transfer between phases. Links thermodynamic theory to practical distribution behaviour.

Lesson 2 • Solvent Selection Principles

Presents criteria for choosing an extraction solvent including selectivity, immiscibility, recoverability, and safety. Guides students toward systematic solvent screening decisions.

Lesson 3 • Introduction to Separation Processes

Positions LLE within the broader landscape of separation technologies and defines its industrial relevance. Establishes vocabulary used throughout the course.

Lesson 4 • Ternary Phase Diagrams

Teaches construction and interpretation of ternary diagrams including binodal curves, tie lines, and plait points. Provides the graphical tool used in equilibrium stage calculations.

Lesson 1 • Kremser Equation and Analytical Methods

Presents the Kremser equation for systems with constant distribution coefficients and compares it to graphical results. Enables rapid hand calculations for preliminary design.

Lesson 2 • Stage Efficiency and Real Stages

Distinguishes theoretical from actual stages using Murphree and overall stage efficiencies. Converts theoretical stage counts to real equipment requirements.

Lesson 3 • Crosscurrent Multistage Extraction

Analyses repeated single-stage contacts with fresh solvent and computes cumulative recovery. Demonstrates diminishing returns and optimal solvent splitting strategies.

Lesson 4 • Single-Stage Extraction Calculations

Derives mass balances for a single equilibrium contact and solves for extract and raffinate compositions. Establishes the calculation framework extended to multistage systems.

Lesson 1 • Diffusion and Convection in Drops

Covers molecular diffusion, internal circulation, and oscillation effects on intra-drop mass transfer. Explains why drop hydrodynamics strongly influence extraction rates.

Lesson 2 • Height of a Transfer Unit Approach

Introduces the NTU-HTU method as an alternative to stage counting for differential contactors. Connects mass transfer coefficients to column height calculations.

Lesson 3 • Drop Formation and Breakup

Analyses how dispersed-phase drops form, break, and coalesce and how these phenomena control interfacial area. Links drop size distribution to mass transfer performance.

Lesson 4 • Interfacial Mass Transfer Theory

Explains the two-film theory and the concept of overall mass transfer coefficients for liquid-liquid systems. Provides the theoretical basis for equipment sizing in later chapters.

Lesson 1 • Pulsed and Reciprocating Plate Columns

Analyses how mechanical pulsation improves drop dispersion and mass transfer in plate columns. Covers pulse frequency and amplitude as key operating variables.

Lesson 2 • Centrifugal Extractors

Explains centrifugal force enhancement of phase separation in Podbielniak and annular centrifugal extractors. Highlights applications requiring short residence time or small footprint.

Lesson 3 • Spray and Packed Columns

Covers spray columns and random or structured packing as simple differential contactors. Explains axial mixing as the primary performance limitation.

Lesson 4 • Rotating Disc and Agitated Columns

Presents rotating disc contactors and other mechanically agitated columns that enhance mass transfer through controlled turbulence. Compares agitation intensity to separation performance.

Lesson 1 • Design Verification and Sensitivity Analysis

Tests the design against variations in feed composition, flow rate, and physical properties to confirm robustness. Identifies the most critical design parameters for process control.

Lesson 2 • Column Height Determination

Calculates required column height from the number of transfer units and the height of a transfer unit. Integrates stage efficiency or HTU data with column diameter results.

Lesson 3 • Internals Design and Specification

Specifies distributor, packing support, and interface control hardware for the designed column. Ensures uniform phase distribution and stable interface position.

Lesson 4 • Design Basis and Process Specifications

Translates a separation objective into quantitative design inputs including feed composition, flow rates, and recovery targets. Establishes the design basis document used throughout the sizing procedure.

Lesson 1 • Back-Extraction and Stripping

Covers re-extraction of solute from the loaded solvent using pH shift, temperature change, or a stripping solvent. Connects back-extraction design to the forward extraction stage count.

Lesson 2 • Raffinate Treatment and Solvent Removal

Addresses residual solvent in the raffinate phase through steam stripping, air stripping, or adsorption. Ensures product and waste streams meet quality specifications.

Lesson 3 • Importance of Solvent Recovery

Quantifies the economic and environmental impact of solvent losses and establishes recovery targets. Motivates the design of efficient back-extraction and stripping systems.

Lesson 4 • Distillation-Based Solvent Recovery

Designs distillation columns for separating solvent from extract and raffinate streams. Addresses azeotrope formation and its impact on recovery scheme selection.

Lesson 1 • Dynamic Simulation and Control Studies

Extends steady-state models to dynamic simulation for evaluating startup, shutdown, and disturbance responses. Supports control system design covered in the next chapter.

Lesson 2 • Sensitivity and Optimisation Studies

Runs parametric sensitivity studies and optimisation routines to identify the best operating conditions. Connects simulation outputs to economic objective functions.

Lesson 3 • Model Validation Against Experimental Data

Validates simulation predictions against laboratory or pilot plant data using statistical metrics. Identifies sources of model error and applies correction strategies.

Lesson 4 • Thermodynamic Model Selection for LLE

Compares NRTL, UNIQUAC, UNIFAC, and other activity coefficient models for liquid-liquid equilibrium prediction. Guides model selection based on available data and system complexity.

Lesson 1 • Startup, Shutdown, and Steady-State Procedures

Provides step-by-step procedures for bringing an extraction unit to steady state and safely shutting it down. Emphasises phase establishment and interface stabilisation sequences.

Lesson 2 • Interface Level Control Strategies

Designs control loops for maintaining stable liquid-liquid interface position in settlers and columns. Covers cascade, split-range, and model-based control approaches.

Lesson 3 • Troubleshooting Common Operational Problems

Diagnoses and resolves flooding, emulsification, phase inversion, and poor separation in operating units. Builds a systematic fault-finding methodology applicable to any LLE system.

Lesson 4 • Key Process Variables and Instrumentation

Identifies the critical measured variables in an LLE unit including interface level, flow rates, and phase compositions. Specifies appropriate sensors and analyzer types for each variable.