MASS TRANSFER II DISTILLATION

INTRODUCTION Distillation is the process of separating the components or substances from a liquid mixture by selective boiling and condensation. Distillation may result in essentially complete separation (nearly pure components), or it may be a partial separation that increases the concentration of selected components of the mixture.

RAOULT’S LAW DALTON’S LAW It states that the partial vapor pressure of each component of an ideal mixture  of liquids is equal to the vapour pressure of the pure component multiplied by its mole fraction in the mixture. pi= pi*xi Where  pi is the partial pressure of the component  pi* -vapor pressure of the pure component   xi -mole fraction of the component  in the mixture (in the solution). DALTON’S LAW Dalton's law states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. Ptotal = P1 +P2……………Pn where p1, p2, ..., pn represent the partial pressures of each component.

Relative volatility Relative volatility is a measure comparing the vapor pressures of the components in a liquid mixture of chemicals. This quantity is widely used in designing large industrial distillation processes.In effect, it indicates the ease or difficulty of using distillation to separate the more volatile components from the less volatile components in a mixture. It denoted byα. α = y(1-x) /x(1-y) Where y= Mole fraction of vapor X= Mole fraction of Liquid

Vapor–liquid equilibrium In  chemical engineering, the vapor–liquid equilibrium (VLE) describes the distribution of a chemical species between the vapor phase and a liquid phase. It measure with help of degree of freedom(DOF) DOF=C-P+2 Where C is component, P is phase DOF=2-2+2 DOF = 2 There are total 4 variable : Temperature, Pressure, Vapor phase composition, Liquid phase composition

Boiling-point diagrams

METHOD OF DISTILLATION Distillation is carried out in two ways: Reflux Without Reflux In without Reflux two common distillation is used: Simple Distillation Flash Distillation In Reflux one common distillation is used: Fractionational distillation

SIMPLE DISTILLATION In this known quatity of liquid is charged. Coil is provided for the heating. In early stage leaving vapor is rich in high volatile Compostion of less volatile increase in the still hence boiling point increase. High volatile product collect from the condenser after the condensation.

FLASH DISTIILATION In this feed is heated in the Heat Exchanger After increasing the temperature of feed, feed insert into the pressure reducing valve. Due to decrease in the pressure heated feed start convert into the vapor. In the Separating column liquid and vapor are separated.

FRACTIONATING COLUMN It consist of: (i) cylindrical shell (ii)Reboiler (iii) Condenser In this Cylinderical shell is divided into two parts: (i) Rectification Section (ii) Stripping Section

Mccabe Thiele Method The McCabe–Thiele method is considered to be the simplest and method for the analysis of binary distillation. It uses the fact that the composition at each theoretical tray (or equilibrium stage) is completely determined by the mole fraction of one of the two components

REFLUX RATIO Total reflux : Not a practical method To know the minimum no. of plates 2. Minimum Reflux Ratio: To know the maximum no. of plates 3. Optimum Reflux Ratio: It lies b/w Total reflux ratio & Minimum reflux ratio

Azeotropic distillation Interactions between the components of the solution create properties unique to the solution, as most processes entail nonideal mixtures, where Raoult's law does not hold. Such interactions can result in a constant-boiling azeotrope which behaves as if it were a pure compound (i.e., boils at a single temperature instead of a range). At an azeotrope, the solution contains the given component in the same proportion as the vapor,

Flooding: Excessive liquid buildup inside the column leads to column flooding condition. The nature of flooding depends on the column operating pressure and the liquid to vapor flow ratio. The column flooding conditions sets the upper limit of vapor velocity for steady operation. weeping: Weeping occurs at low vapor/gas flow rates. The upward vapor flow through the plate perforations prevents the liquid from leaking through the tray perforation. At low vapor flow rates, liquid start to leak/rain through the perforation (called weeping).

MASS TRANSFER II EXTRACTION

INTRODUCTION The technique of removing one component from a solid or liquid by mean of liquid solvent

MIXER SETTLER It operate in batchwise manner. Feed is charge from the top and discharge from the bottom. Required amount of solvent is added. After the process raffinate and extract collect from bottom.

PERFORATED PLATE EXTRACTION TOWER It is multistage countercureent process. In this axial mixing take place. The perforation in the plate about 1.5-4.5mm in diameter. The principal interface is maintained at the top, light liquid is removed from the top and heavy liquid from the bottom.

SPRAY TOWER In this tower is packed with packing. It provide the large interfacial area for the phase contacting. It is mostly used in petroleum industry. It is suitable to handle dirt liquid, suspension or high viscosity liquid.

LEACHING It is an operation in which a solid mixture is contact with a liquid solvent for the removal of one or more constituents of solid mixture. Example of leaching: Extraction of sugar from sugar beats Extraction of perfume from flower Extraction of tea and coffee

MASS TRANSFER II ADSORPTION

INTRODUCTION When a solid surface exposed to a fluid phase, the molecule from the bulk of fluid phase have tendency to accumulate or concentrate at the surface of a solid. The phenomena of the concentration of the chemical substance of solid is called adsorption.

TYPE OF ADSORPTION Physical Adsorption : It is result of intermolecular force of attraction b/w molecule of adsorbent and adsorbate. Chemical Adsorption : It is result of chemical bonding b/w molecule of adsorbent and adsorbate.