1. PROCESS AND PROCESS VARIABLE
LECTURE
PROCESS AND PROCESS VARIABLE

2. 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.

3. PROCESS
Process
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.

4. 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.

5. 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

6. 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

7. 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

8. 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

9. EXAMPLE
Given,
m (hexane) = 6.59 g/s , r =0.659 g/cm3
so, V = m/r = g cm3 = 10 cm3/s
0.659 s g
V (CCl4) = 100 cm3/min, r =1.595 g/cm3
so, m = Vr = 100 ×
= g/min

10. EXAMPLE 100 liter 1 min 1m3 1000 liter 1000 kg 1 m3 100 kg/min
Calculate the volumetric and mass flowrate if a volume of 500 liters of water is collected for a period of 5 minutes. Given the density of water is 1000 kg/m3.
i. Volumetric flowrate = 500/5= 100 liters/min
ii. Mass flowrate
100 liter
1 min
1m3
1000 liter
1000 kg
1 m3
100 kg/min

11. PROCESS VARIABLES Molecular Weight
molecular weight = sum of atomic weights
basis: atomic weight of 12C = 12 (exactly)
atomic weight of naturally occurring C = (back cover of text)
e.g. atomic oxygen, O, MW = 16
molecular oxygen, O2, MW = 32
1 mol = x 1023 molecules (Avogadro’s number)
ECB3013: Material and Energy Balances
Ir. Abdul Aziz Omar

12. PROCESS VARIABLES Mole and Mass Fraction
mole fraction = (moles of a species)/(total moles)
mass fraction = (mass of a species)/(total mass) = weight fraction
ECB3013: Material and Energy Balances
Ir. Abdul Aziz Omar

13. EXAMPLE
Component
No. Mole
Mol Fraction, yi N2 55
0.579 O2 25
0.263
CO2 15
0.158
Total 95
1.0

14. Average molecular weight = 31.6
PROCESS VARIABLES
average molecular weight =
Component
Mol Fraction, yi Mi N2
0.579 28 O2
0.263 32
CO2
0.158 44
Total
1.0
Mav=31.6
Average molecular weight = 31.6
ECB3013: Material and Energy Balances
Ir. Abdul Aziz Omar

15. PROCESS VARIABLES
CONCENTRATION
molar concentration = moles of component per unit volume of solution
mass concentration = mass of component per unit volume of solution
parts per million = moles (or mass) of component per million moles (or mass units) of mixture

16. a fluid exerts a pressure on the wall of its container
PROCESS VARIABLES
PRESSURE
force per unit area
a fluid exerts a pressure on the wall of its container
due to molecules bouncing off the wall
measured by determining force and area
Note: This is often written with a gc in the denominator

17. PROCESS VARIABLES
Hydrostatic Pressure -- pressure difference between bottom and top of a column of fluid of height h -- based on Newton's law of gravity
barometer = an instrument for measuring atmospheric pressure
1 atm = mmHg(0 oC, std. go)
Pressure may be measured as:
Atmospheric pressure
Absolute Pressure
Gauge Pressure

18. PROCESS VARIABLES
Atmospheric Pressure
Pressure measured at sea-level or at base level
760 mmHg
1 atm
1.013 bar
101.3 kPa
14.7 psi (lb/sq.in.)
Absolute Pressure
sum of atmospheric pressure and gauge pressure
Pabs = Pgauge + Patm

19. Gauge Pressure
Reading from the gauge
Relative to atmospheric pressure
zero means abs pressure = atmospheric pressure
from: Pabs = Pgauge + Patm
Pgauge = Pabs- Patm

20. PROCESS VARIABLES
TEMPERATURE
temperature is a property that tells us if two systems are in thermal equilibrium
measuring devices are systems that can be brought to thermal equilibrium with the system of interest (hopefully without disturbing this system) examples are liquid in glass thermometers, thermocouples, resistance thermometers, bimetallic thermometers, radiation pyrometers, etc.

21. PROCESS VARIABLES
The unit temperature is given in oC, oF, oR or K and related to each other using the following equations.
T(K) = T(oC)
T(oR) = T(oF)
T(oR) = 1.8T(K)
T(oF) = 1.8T(oC) + 32
ECB3013: Material and Energy Balances
Ir. Abdul Aziz Omar