Chemical Engineering Principles

Objectives and Syllabus

Provides a basis for non-chemical engineers to appreciate the chemical engineering aspects of subsequent modules.

Topics covered are - mass & energy balances; choice of datum, overall & component balances, simultaneous mass & energy balances, stoichiometry, combustion, recycle & purge streams: fluid flow; dimensionless groups, viscosity, streamline & turbulent flow, Reynolds number, roughness, energy losses: pumps; flow-head characteristics, sizing: heat transfer; conductivity, resistance, overall heat transfer coefficients, fouling factors, heat exchangers: unit operations; definition, categorisation, typical applications: flow sheets: safety & environmental aspects of plant design & operability.

The module includes a case study to familiarise students with the use of flow sheets. Practical work is in the form of tutorials covering a series of spreadsheet and flowsheet based exercises using the University’s computing facilities.

Aims

To provide a foundation in the principles of chemical engineering for persons whose first degree is otherwise.  The module explains how plant is designed and operated and covers those aspects of chemical engineering which are of particular relevance for building quantitative process models.

Objectives

• To introduce the concept of a process as a series of unit operations and to encourage a systems approach to plant design. 
• To become familiar with the principal features of design and principles of operation of a range of items of plant. 
• To develop a quantitative understanding of processes in terms of the relationships between their input and output streams. 
• To provide a thorough grounding in the application of heat and mass balances to a variety of items of plant and processes. 
• To develop a sufficient understanding of fluid flow and heat transfer for model building purposes.
  To become aware of safety and environmental aspects of plant design and operation.

Phasing

This is a stand-alone module and has no pre-requisites as such.

Study Modes

This module is of one week's full-time intensive study consisting of a variety of lectures, informal tutorials for problem solving and computer based lab sessions.  It is followed by an assignment to be carried out in the student’s own time.

Coursework

The time allocation for practical work provides for a series of spreadsheet based exercises.  These are structured to reinforce the material covered in the lectures and tutorials.

Assignment

Students are typically required to design a small section of plant with the emphasis on the specification and sizing of equipment.  The intent is that this should focus on fluid flow and heat transfer considerations rather than on the chemical or mechanical aspects of design.

Recommended Texts

• Coulson J M, Richardson J F, et al,  Chemical Engineering,  Volumes 1-6,  Various Chapters/Editions,  Pergamon Press.

Topics Included

Unit operations:  Concept of a unit operation.  Definitions of unit operation, process and plant.  Categorisation of unit operations.  Survey of the principle of operation of a wide range of unit operations.  Review of applications.  Summary of principal features of construction of major items of equipment and types of plant associated with common unit operations, eg distillation, filtration, liquid-liquid extraction, etc.  Familiarisation with flow sheets.  Case study based on flow sheet and/or P&I diagram of an appropriate plant.

Mass and energy balances:  Concept of a balance.  Input-output relationships.  Steady state considerations.  Black box approach.  Mass and energy balance diagrams and tables.  Mass balances for unit operations and items of plant.  Choice of basis/datum for balances.  Overall and component balances.  Tie components.  Balances for batch and continuous plant.  Simultaneous mass and energy balances.  Use of steam tables.  Sensible, latent and total heats.  Balances for condensing systems.  Use of steam traps.  Introduction to dynamic balances.  Co-current and counter-current operations.  Principles of stoichiometric combination.  Mass and energy balances for reacting systems.  Balances for combustion processes.  Limiting and excess reactants.  Balances for systems with recycle, purge and by-pass streams.  Efficiency and conversion.

Fluid flow:  Fluid statics, pressure distribution and head calculations.  Concept and use of dimensionless groups.  Rayleigh's method of indices.  Definition of viscosity.  Concept of Newtonian and non Newtonian flow.  Concepts of streamline and turbulent flow.  Reynolds number and its significance.  Flow profiles.  Concept of a boundary layer.  Simple analogies between electrical systems and fluid flow, heat transfer and mass transfer.  Flow/pressure drop relationship.  Friction factors and correlation with Reynolds number.  Roughness.  Sizing calculations for incompressible flow.  Systems with branches.  Energy losses across bends and fittings.  Entry and exit losses.  Siphon flow.  Principal features of positive displacement and centrifugal pumps.  Principles of operation.  Flow-head characteristics.  Effect of pipework.  Suction head and cavitation.  Sizing and specification.

Heat transfer:  Fourier's law and conductivity.  Concept of resistance.  Conduction through layers.  Concentric layers and log mean radius.  Insulation.  Conduction through a liquid.  Temperature and velocity profiles.  Concept of films.  Surface vs bulk properties.  Film and overall heat transfer coefficients.  Heat transfer through pipes, coils and jackets.  Fouling factors.  Principal features of construction of shell & tube and plate exchangers.  Survey of applications, eg. condensers, reboilers.  Temperature distribution characteristics of single pass exchangers.  Log mean temperature difference.  Calculation of thermal duty and/or surface area required.