Chemical Systems

AIMS

This subject introduces students to aspects of reactor system design. Chemical reactors are at the heart of any major chemical process design. Chemical reaction engineering is concerned with the exploitation of chemical reactions on a commercial scale. Chemical reaction engineering aims at studying and optimizing chemical reactions in order to define the best reactor design. Hence, the interactions of flow phenomena, mass transfer, heat transfer, and reaction kinetics are of prime importance in order to relate reactor performance to feed composition and operating conditions.

This subject is one of the key parts of the chemical and biochemical engineering curriculum upon which a lot of later year material is built.

INDICATIVE CONTENT

1. Kinetics of homogeneous reactions
2. Design of single ideal reactors
3. Multiple reactor systems
4. Other design reactors (recycle reactors and temperature effects)
5. Basics of non-ideal flow
6. Models for reactors
7. Mixed flow in model reactors.

AIMS

This subject aims to extend the fundamental concepts of heat transfer from that covered in CHEN20009 Transport Processes to include natural and forced convection and two phase systems. Mass transfer concepts are extended to unsteady state mass transfer and Fick's Second Law, prediction of diffusivity and of mass transfer coefficients. These fundamental concepts are then applied to the design of processes and equipment including shell and tube, air-cooled and plate heat exchangers, evaporator systems, membrane devices, binary distillation systems, gas absorbers and cooling towers. Experience in the use of appropriate simulation packages such as HYSYS for exchanger and distillation column design are included. This simulation work builds on the skills developed in CHEN20011 Chemical Process Analysis .

INDICATIVE CONTENT

• Forced Convection: Use of heat transfer correlations to predict coefficients
• Heat Exchange: concept of an overall heat transfer coefficient, fouling factors; determination of the area required for a given heat duty, Heat exchanger design. Use of simulation packages such as HYSYS and ASPEN
• Free convection: discussion and application of Grashof Number and other dimensionless groups
• Condensation and Boiling: Fundamentals. Evaporation: various evaporator types and their advantages and disadvantages (forced circulation, film types); multiple and single effects; backward and forward feed; boiling point elevation; mechanical recompression; evaporator energy balances
• Mass Transfer: Unsteady state mass transfer and Fick's Second Law; prediction of diffusivity; dimensional analysis and equations of change for mass transfer
• Distillation: single-stage separations, equilibrium flash, differential distillation; multistage separations, operating lines, reflux; binary distillation, varying reflux ratio, minimum reflux, total reflux, optimum reflux, feed plate location, side streams, open steam; tray efficiency via overall and Murphree efficiencies. Use of simulation packages such as HYSYS
• Gas absorption: basic mass transfer mechanism; material balances, co-current and countercurrent flow, limiting L/G ratio; multistage absorption and the absorption factor method; continuous contact, transfer units, height of a transfer unit, calculation of number of transfer units. Humidification and cooling tower height calculation
• Membrane Systems: Microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Gas separation systems. Robeson’s bound. Electrodialysis and pervaporation. Membrane selection.

This subject provides an introduction to process work in process engineering, focusing specifically on process safety and sustainability. Material taught in other chemical engineering subjects will be reinforced via a series of assignments in which ill-defined and open-ended process engineering problems will be tackled. Both hypothetical and real case studies from the process engineering field are used throughout the subject.

Several assessment tasks combine to form a capstone project. Within this project students, in teams of three or four, perform design tasks related to the development of a Chemical Process Engineering facility. This capstone project culminates in an Environmental Effects Statement assignment. Several industry speakers, from the process engineering and environmental areas, talk and provide content to aid with this assignment.

AIMS

This subject concerns the fundamental science of fluid flow relevant to a range of engineering applications, and is essential for specialisations relating to Chemical, Civil and Environmental Engineering.

INDICATIVE CONTENT

Topics covered include - Fluid statics, manometry, derivation of the continuity equation, mechanical energy balance, friction losses in a straight pipe, Newton’s law of viscosity, treatment of pipe roughness, valves and fittings; simple pipe network problems; principles of open channel flow; compressible flow, propagation of pressure wave, isothermal and adiabatic flow equations in a pipe, choked flow. Pumps – pump characteristics, centrifugal pumps, derivation of theoretical head, head losses leading to the actual pump head curve, calculating system head, determining the operating point of a pumping system, throttling for flow control, cavitation and NPSH, affinity laws and pump scale-up, introduction to positive displacement pumps; stirred tanks- radial, axial and tangential flow, type of agitators, vortex elimination, the standard tank configuration, power number and power curve, dynamic and geometric similarity in scale-up; Newtonian and non-Newtonian fluids, Multi-dimensional fluid flow-momentum flux, development of multi-dimensional equations of continuity and for momentum transfer, Navier-Stokes equations, application to tube flow, Couette flow, Stokes flow.