1. PROCESS AND PROCESS VARIABLE
LECTURE
PROCESS AND PROCESS VARIABLE

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

3. 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.

4. 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.

5. 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.

6. 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

7. 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

8. 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 = g/cm3

9. 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

10. 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

11. 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

12. 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