PROCESS AND PROCESS VARIABLE LECTURE PROCESS AND PROCESS VARIABLE

LEARNING OBJECTIVES By the end of this topic, you should be able to: Understand the process and process variables

PROCESS A process is any operation or series of operations by which a particular objective is accomplished. The operations cause a physical or chemical change in a substance or mixture of substances. The material that enters a process is referred as the INPUT or FEED, and that which leaves is the OUTPUT or PRODUCT. It is common for processes to consist of multiple steps, each of which is carried out in a process unit, and each process unit has associated with it a set of INPUT and OUTPUT process streams.

PROCESS Generally, the INPUTs and OUTPUTs Unit INPUT or FEED OUTPUT or PRODUCT Process Unit 1 Process Unit 2 INPUT 1 OUTPUT 1 or INPUT 2 OUTPUT 2 Generally, the INPUTs and OUTPUTs are known as process streams.

PROCESS UNIT There are a number of process unit. Each of the process unit is selected based on the individual function. Most of the process units are used for the physical separation particularly, Distillation-separation of mixture liquids based on boiling point Absorption-separation of mixture of gases based on gas solubility in liquid solvent Adsorption-separation of mixture of liquids or gases based on affinity into solid adsorbent Heat Exchanger-particularly for condenser, separation of mixture of gases by removing heat at lower temperature Crystallization- separation of mixture of liquids by vaporizing the liquid component and remaining the dissolved solid component to form crystal. Extraction- separation of mixture of liquid based on liquid affinity into liquid solvent. Membrane-separation of mixture of liquids or gases or mixture solids & gases based on molecular sizes. Dryer- separation of mixture of solid & liquid by removing the liquid component by heating.

EXAMPLE 1 PRODUCT 1, V1 (rich with Ethanol at T, P) Distillation (heating at 80oC) The quality of PRODUCT 1 depends on the efficiency of the distillation unit. FEED, L1 kg/h 50 wt % Water 50 wt % Ethanol at T, P PRODUCT 2, L2 (rich with Water at T, P) Given: Bp of water = 100oC Bp of ethanol = 80oC

EXAMPLE 2 FEED 2, L1 kmol/h PRODUCT 1, G2 kmol/h (G) Pure amine solvent at T, P PRODUCT 1, G2 kmol/h (G) 1 mol % CO2 99 mol % CH4 at T, P Absorption The gas stream is in contact with the liquid stream through various packings, and due to the high solubility CO2 into amine, it dissolves into the liquid stream remaining CH4 in gas stream. FEED 1, G1 kmol/h 10 mol % CO2 90 mol % CH4 at T, P PRODUCT 2, L2 kmol/h containing CO2 at T, P

PROCESS VARIABLES MASS & VOLUME Density, ρ = mass / volume units: g/cm3, kg/m3, lbm/ft3 Specific Gravity, SG, is ratio of density of a substance to density of a reference: SG = ρ/ ρ ref ρ ref , usually water at 4oC = 1.000 g/cm3

PROCESS VARIABLES FLOW RATE - Fluid movement from a point to another Mass Flow Rate m - mass (lbm, kg, g) per time (h, s, min) Volumetric Flow Rate V - volume (ft3, cm3, m3, liter) per time Molar Flow Rate n - molar (mol, kmol, lb-mol) per time In industries, rotameter and orifice are used to measure the volumetric flowrate for any process stream, for gas and liquid process streams. In addition, mass flowmeter is used to measure the mass flowrate of any procees stream. Density is used to convert between mass and volumetric flow rates, = m/v = m/V

CLASS ACTIVITY 2 Fill in the blanks with the correct dimensions and units Quantity Dimension Unit (SI) Volume Density Force ML/T2 Pressure N/m2 Power watt

CLASS ACTIVITY 2 Quantity Dimension Unit (SI) Volume L3 m3 Density M/L3 kg/m3 Force ML/T2 N or kg.m/s2 Pressure M/LT2 N/m2 or kg/m.s2 Power M.L2/s3 J/s or watt

TAKE HOME ACTIVITY 1 Working in a group of two, solve the following problems. Compare your answer with other groups. Quantity Dimension Unit (SI) Concentration kg/m3 Enthalpy J/mol.K Viscosity kg/m.s Thermal conductivity W/m.K Entropy Heat of reaction J/mol