EG2002 - Material Balances Lecture 1 Rev1 (1)

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