I. T. Cameron

Balancing curriculum processes and content in a project centred curriculum - In pursuit of graduate attributes

Chemical engineering education is challenged around the world by demands and rapid changes encompassing a wide range of technical and social drivers. Graduates must be prepared for practice in increasingly diverse workplace environments in which generic or transferable attributes such as communication and teamwork together with technical excellence are mandated by prospective employers and society at large. If academe is to successfully deliver on these graduate attributes, effective curriculum design needs to include appropriate educational processes as well as course content. Conventional teacher centred approaches, stand-alone courses and retro-fitted remedial modules have not delivered the desired outcomes. Development of the broader spectrum of attributes is more likely when students are engaged with realistic and relevant experiences that demand the integration and practice of these attributes in contexts that the students find meaningful. This paper describes and evaluates The University of Queenslands Project Centred Curriculum in Chemical Engineering (PCC), a programme-wide approach to meeting these requirements. PCC strategically integrates project-based learning with more traditional instruction. Data collected shows improved levels of student attainment of generic skills with institutional and nationally benchmarked indicators showing significant increases in student perceptions of teaching quality, and overall satisfaction with the undergraduate experience. Endorsements from Australian academic, professional and industry bodies also support the approach as more effectively aligning engineering education with professional practice requirements.

Review and future directions in the modelling and control of continuous drum granulation

Many granulation plants operate well below design capacity, suffering from high recycle rates and even periodic instabilities. This behaviour cannot be fully predicted using the present models. The main objective of the paper is to provide an overview of the current status of model development for granulation processes and suggest future directions for research and development. The end-use of the models is focused on the optimal design and control of granulation plants using the improved predictions of process dynamics. The development of novel models involving mechanistically based structural switching methods is proposed in the paper. A number of guidelines are proposed for the selection of control relevant model structures.

A new wavelet-based method for the solution of the population balance equation

A new wavelet-based method for solving population balance equations with simultaneous nucleation, growth and agglomeration is proposed, which uses wavelets to express the functions. The technique is very general, powerful and overcomes the crucial problems of numerical diffusion and stability that often characterize previous techniques in this area. It is also applicable to an arbitrary grid to control resolution and computational efficiency. The proposed technique has been tested for pure agglomeration, simultaneous nucleation and growth, and simultaneous growth and agglomeration. In all cases, the predicted and analytical particle size distributions are in excellent agreement. The presence of moving sharp fronts can be addressed without the prior investigation of the characteristics of the processes.

Modelling for dynamic simulation of chemical processes: the index problem

A set of ordinary differential equations (ODEs) and algebraic equations (AEs) can usually be employed to represent a class of models for dynamic simulation of processes. Together the set of ODEs and AEs is generally known as a differential-algebraic equation (DAE) system. It is customary to classify a DAE system in terms of its index, this being a non-negative integer. The index of a DAE system indicates the degree of difficulty associated with the numerical solution of the system. In the communication all DAE systems with index greater than unity are referred to as higher-index DAE systems. The objective of the work is to show through analysis of the model equations, and specific examples, how some of the causes of higher-index DAE systems can be identified and remedied

A survey of industrial process modelling across the product and process lifecycle

Abstract Modelling has become a central activity in most major corporations and SMEs. Modern processing and manufacturing is a “model centric” activity that pervades the whole product and process lifecycle. Within organizations there is a wide range of modelling practices that determine the efficacy of the modelling tasks in providing crucial information for decision making across the lifecycle. In order to inform modelling practitioners and developers of modelling and simulation systems, an international survey was carried out to ascertain the current state of play in process modelling practice in industry. The results presented here show some significant challenges exist for developers of modelling systems, but more importantly for internal organizational practices in corporations, to ensure that process modelling is efficient and derives maximum benefit for the organization.

A Distributed Parameter Approach to the Dynamics of Rotary Drying Processes

A nonequilibrium distributed parameter model for rotary drying and cooling processes described by a set of partial differential equations coupled with nonlinear algebraic constraints is developed in this work. These equations arise from the multi-phase heat and mass balances on a typical rotary dryer, A computational algorithm is developed by employing a polynomial approximation (orthogonal collocation) with a global spline technique leading to a differential-algebraic equation (DAE) system. The numerical solution is carried out by using a standard DAE solver. The two-phase-flow heat transfer coefficient is computed by introducing a correction factor to the commonly accepted correlations. Since interactions between the falling particles are considered in the correction factor, the results are more reliable than those computed by assuming that the heat transfer between a single falling particle and the drying air is unaffected by other particles. The heat transfer computations can be further justified via a study on the analogies between heat and mass transfer. The general model developed in this work is mathematically more rigorous yet more flexible than the lumped parameter models established by one of the authors (Douglas et al., (1993)). The three major assumptions of an equilibrium operation, perfect mixing and constant drying rate, are removed in the distributed parameter model. The simulation results are compared with the operational data from an industrial sugar dryer and predictions from earlier models. The model and algorithm successfully predict the steady state behaviour of rotary dryers and coolers. The generalized model can be applied to fertilizer drying processes in which the assumption of constant drying rate is no longer valid and the existing dynamic models are not applicable.

Analysis of dynamic process models for structural insight and model reduction—Part 1. Structural identification measures

An important consideration in the development of mathematical models for dynamic simulation, is the identification of the appropriate mathematical structure. By building models with an efficient structure which is devoid of redundancy, it is possible to create simple, accurate and functional models. This leads not only to efficient simulation, but to a deeper understanding of the important dynamic relationships within the process. In this paper, a method is proposed for systematic model development for startup and shutdown simulation which is based on the identification of the essential process structure. The key tool in this analysis is the method of nonlinear perturbations for structural identification and model reduction. Starting from a detailed mathematical process description both singular and regular structural perturbations are detected. These techniques are then used to give insight into the system structure and where appropriate to eliminate superfluous model equations or reduce them to other forms. This process retains the ability to interpret the reduced order model in terms of the physico-chemical phenomena. Using this model reduction technique it is possible to attribute observable dynamics to particular unit operations within the process. This relationship then highlights the unit operations which must be accurately modelled in order to develop a robust plant model. The technique generates detailed insight into the dynamic structure of the models providing a basis for system re-design and dynamic analysis. The technique is illustrated on the modelling for an evaporator startup. Copyright (C) 1996 Elsevier Science Ltd

A new approach to decentralised control design

A decentralised control design methodology, which is based on ideas from robust stabilisation using the normalised left coprime factorisation and the gap metric, is developed. Some indicators for decentralised control design are proposed. These indicators are useful as a guideline for screening alternative control structures. A sufficient stability condition is formulated by making use of these indicators. Unlike the Relative Gain Array (RGA), these indicators can guarantee the stability and achievable performance of the system under decentralised control for given design specifications. This methodology has been applied to two industrial case studies in which the systems are open-loop unstable and/or non-minimum phase.

A prototype expert system for hazard and operability studies

Abstract This paper describes the development of a prototype expert system for use in HAZard and OPerability (HAZOP) studies. The work is motivated by the fact that HAZOP studies are inherently logical exercises utilizing a process engineering knowledge base. The availability of an effective tool to aid engineers in design and operation would be of significant value. The knowledge domain required for HAZOP studies is wide. Hence the system must be built in modular form in order to be efficient. It must also be built in such a way that it is easy to incorporate additional knowledge into the system. The prototype developed in this work has been based on a PC version of Prolog. A basic inference engine, available in Prolog, has been enhanced and tailored into a user-friendly, interactive environment. Details of the knowledge organization and representation are discussed and an example session given. Further work is required to improve the system for serious industrial use through the addition of further knowledge modules, improved input—output facilities and optimization of the program.

A SIMPLE DYNAMIC MODEL FOR SOLID TRANSPORT IN ROTARY DRYERS

ABSTRACT The solid particle movement in a rotary drum plays an important role in drying processes. The solid distribution in the drum affects the amount of contact surface between the solid and the gas. The retention time of solids influences the time particles can stay in contact with the gas in order to transfer heat and mass. Any heat and mass transfer model for a solid particle dryer must be able to predict solid flowrate and solid hold-up. There have been several reports in the literature regarding the modelling aspects of solid transport in dryers. If the model is developed for model-based control, it must be simple and yet represent dynamics of the system accurately. This paper addresses solid motion modelling and the effects of different variables involved in solid transport phenomena. Sugar drying process is the case study in this work. A steady state semi-empirical model was modified to predict solid hold-up and flowrate in rotary dryers. This model was incorporated into a heat and mass transfer model ;o predict solid moisture and temperature for inferential and model-based control purposes. Results of several experiments that have been used to investigate dynamics of the system in terms of solid motion and to validate the model are also presented. The approach advocated in this paper is directly applicable to the transport of other solids in rotary drum equipment and can thus be regarded as a generalized model.