EG2002 : Process Engineering
EG2002
• Concepts/Theory
• Examples - try them your self!
• Further reading
• Problems (Tutorial questions)
Course Notes
Lectures
• Attendance optional
• Introduce and discuss key concepts
• Provide Context
• Alternative Perspectives
• Answer questions
• Please make notes
• I will not be posting my slides in MyAberdeen
Text Books
Overview
Session 1 - Introduction
Session 2 - Change of composition
Session 3 - Multiple processes
Session 4 – Chemical reaction
Session 5 - Recycles and purges
Session 6 – Complex material balances
SIX sessions = NINE lectures ?????
Learning Outcomes
At the end of this first session you should…….
• Understand what a material balance is and why they are so important
• Be able to write down the general equation for conservation of mass.
Decision time
What do you need to know? • What? Where? How much? What else?
Process in UK
Co-products ? te/hr
Xylene 50 te/hr
Toluene ? te/hr
Technology: ExxonMobil
Process: Toluene Dis-Proportionation (TDP)
Fuel ? te/hr Steam ? te/hr Electricity ?te/hr
By-products ? te/hr
Cooling water ? te/hr Additives ? te/hr
Effluents ? te/hr
CAPEX
OPEX
Profit
Working Capital
Material & Energy Balances can help!
• Feasibility studies
• Economic Evaluations
• Design (process, mechanical, civil or electrical)
• EHS Systems
• Production monitoring systems
• Troubleshooting
Mass & Energy
E = mc2
Nuclear fusion : Two protons stuck together have less mass than two protons on their own
Mass & Energy
Material and Energy Balances are always performed separately
(with exception of the nuclear industry)
Material, Mass & Weight
• Material is anything made of matter
• Mass is a property of matter
• Weight is the force exerted by a mass on earth as a consequence of it mass and the acceleration due to gravity.
Material, Mass & Weight
• Material balances include Mass balances but also Molar balances
• Mass and Weight balances in effect the same.
• The terms material, mass and weight balances are used interchangeably in industry
The material balance
System Boundary
System Boundary
System Boundary(s)
This Lecture Theatre System Boundary
3 D drawn
2 D
Flowsheet
System Boundary
IN OUT
We are concerned only with material crossing the system boundary
Material Balance levels
Overall
Component
Molecular
Atomic
Nucleonic
Sub-Atomic
(all mass)
e.g. Students, Staff, Air
e.g. Oxygen, Carbon Dioxide
e.g. Carbon, Oxygen atoms
e.g. Quarks, Leptons
e.g. Protons, Neutrons
Material Balance @ Component level
IN OUT
Balance on students
Students Out = Students In ???????
Only if totally lecture theatre full or
numbers being controlled at certain level
This is known as Steady State
Material Balance @ Component level
IN OUT
Balance on students
Students Out = Students In - Accumulation ????
Only if there are no vampires or necromongers!
Students who choose to stay
Material Balance @ Component level
IN OUT
Balance on students
Students Out = Students In - Accumulation + Generation - Consumption
Students converted from vampires
Students converted to vampires
You could also do a component balance on vampires of course
Material Balance
IN OUT
Material Balance @ component level
Mass Out = Mass In - Accumulation + Generation - Consumption
Material Balance @ overall level
Mass Out = Mass In - Accumulation
Differential Balances
• Indicate what is happening at an instant of time
• Each term of the balance equation has a rate
e.g. kg/hr.
• Usually applied to continuous processes.
• Useful for design
Integral Balances
• Indicates what happens between two instants
in time
• Each term of the balance equation is some given
quantity per batch, day, hour etc
• Flow throughout the period may well not
be uniform
• Usually applied to batch processes
• Useful also for economic evaluations