Mass Transfer Operations (Introduction) PDF

Introduction to Mass Transfer Operations 1 Contents Definition of Mass Transfer Examples of Mass Transfer Mass Transfer Operations Basic Concepts: Concentrations:  Molar Concentration  Mass Concentration  Mole Fract...

Introduction to Mass Transfer Operations 1 Contents Definition of Mass Transfer Examples of Mass Transfer Mass Transfer Operations Basic Concepts: Concentrations:  Molar Concentration  Mass Concentration  Mole Fraction  Mass Fraction 2 Introduction Three fundamental transfer processes: i) Momentum transfer (∆P) ii) Heat transfer (∆T) iii) Mass transfer (∆C) 3  Definition of Mass Transfer The term mass transfer is used to denote the transference of a component in a mixture from a region where its concentration is high to a region where the concentration is lower. Mass transfer process can take place in a gas (vapor) or in a liquid, It can result from the random velocities of the molecules (molecular diffusion) or from the circulating or eddy currents present in a turbulent fluid (eddy diffusion). 4  Examples of Mass Transfer Consider a tank that is divided into two equal parts by a partition. Initially, the left half of the tank contains nitrogen N2 gas while the right half contains O2 at the same temperature and pressure. When the partition is removed the N2 molecules will start diffusing into the air while the O2 molecules diffuse into the N2. If we wait long enough, we will have a homogeneous mixture of N2 and O2 in the tank. 5 Examples of Mass Transfer 6 Mass Transfer Operations Salt Takes place easily according to 2nd law Salt water solution of thermodynamics of increasing entropy salt Difficult to take Salt place because it solution water needs external energy 7 RP P Separation R Separation process Stock process RP to purify P Feed Separation Output streams different stream Process in composition Separating matter and/or energy 8  Examples of Separation Processes  Separation of phases only G L L+G L+S (Flash Drums) (Filter or gravity settler) L S Transfer of some components from one stream to another V L most A + B Inert V Gas A + inert A + some A L (A +B) L Heat L L + most of A 9 most B + A  Classification of Separation Processes Evaporation: evaporation of a volatile solvent from a nonvolatile solute, e.g. water from nonvolatile solute (salt). Drying: removal of volatile liquids, e.g. water from solid materials. Distillation: components of a liquid mixture are separated by boiling due to differences in vapor pressure. Absorption: removal of a component from a gas stream by treatment with a liquid. Membrane separation: separation of a solute from a fluid by diffusion of the solute from a liquid or gas through a semi-permeable membrane barrier to the other fluid. Liquid-liquid extraction: removal of a solute from a liquid solution by contacting with another liquid solvent that is relatively immiscible with the solution. 10 Separation processes Adsorption: removal of a component (adsorbate) from a gas or liquid stream by adsorption on a solid material (adsorbent). Ion exchange: removal of certain ions in a solution from a liquid by an ion- exchange solid. Liquid-solid leaching: removal of a solute from a solid (containing the solute) by treating with a liquid that dissolves out the solute from the solid. Crystallization: removal of a solute, such as a salt from a solution, by precipitation the solute from the solution. Mechanical-physical separation: separation of solids, liquids, or gases by mechanical means. E.g. filtration, centrifugation, settling, and size reduction. 11 Concentrations 12 13 Relation Between Partial Pressure and Concentration 14 for gas 15 T h a n k Y o u 16