Geoff Barton

Process synthesis and optimisation tools for environmental design: methodology and structure

Abstract Process design requires the simultaneous satisfaction of environmental, economic and social goals. This invariably requires some trade off between these objectives. The challenge for process design engineers is to develop synthesis and analysis tools, which support this requirement. Process System Engineering (PSE) techniques for multiple objective optimisation have to date focused typically on the optimisation of cost versus the potential for waste minimisation, with the recent inclusion of operability issues. The incorporation of environmental sensitivity into PSE approaches has been less than satisfactory. Much of this stems from the (seeming) difficulty in translating process information to environmental objectives. It is our argument that life cycle assessment (LCA), a methodology for quantifying the full ‘cradle-to-grave’ impact of industrial processes, can be used to assist in developing environmental objectives for process design and analysis. In this paper, we resrict our analysis to the multiple objective optimisation of environmental and economic objectives. Our approach is demonstrated for the case study of a nitric acid plant, modeled using Hysys

Interaction between process design and process control: economic analysis of process dynamics

Abstract A method is presented to assess the impact of disturbances on plant economic performance. The method is suitable for use during process design, and can be used to help evaluate alternative process structures or alternative control schemes for a given process. Non-linear steady-state optimization is performed to determine the best operating point in the absence of disturbances. Frequency response analysis of a linearized plant dynamic model is used to estimate the effects of plant disturbances on this ideal performance under a variety of control strategies. The method is illustrated on a case study involving minerals flotation circuit design.

Recent progress in microstructured polymer optical fibre fabrication and characterisation

Recent progress in microstructured polymer optical fibre fabrication and characterisation will be presented. A wide range of different optical functionalities can now be obtained by modifications of the microstructure, as is demonstrated by the fibres presented here. Microstructured fibres that are single-mode, highly birefringent or show twin-core coupling are described, in addition to graded-index microstructured fibres and hollow core fibres, the latter case being where light is guided in an air core. Microstructured polymer optical fibres are an exciting new development, offering opportunities to develop fibres for a wide range of applications in telecommunications and optical sensing.

Quantum dot and silica nanoparticle doped polymer optical fibers.

A novel and highly versatile doping method has been developed to allow active dopants, including materials incompatible with the polymer matrix, to be incorporated into microstructured polymer optical fibers through the use of nanoparticles. The incorporation of quantum dots and silica nanoparticles containing Rhodamine isothiocyanate is demonstrated.

Benefits from process control: results of a joint industry-university study

Abstract A key component of any process control upgrade project is the initial benefits analysis. This analysis defines the correct scope of the project based on the plants economics, production requirements and capacity, and equipment capacity. The scope must be defined to correctly determine the process units and controls included in the project, design the control strategies, specify the equipment required, plan the engineering aspects and develop a realistic schedule. As a result of the importance of this topic, a major study was undertaken by the Warren Centre for Advanced Engineering (University of Sydney) to establish a general method to be made available to Australian industry. The study was performed by a team of over 40 professionals from industry, government and academe and lasted over 1 year. The resulting method for control benefits analysis is described in this paper. The method addresses the organizational aspects of personnel interviews and data collection. It also addresses technical issues such as the calculations and plant tests required to predict control benefits. None of this material is new in itself, but the selection and integration provides a coherent method not available elsewhere. In addition to the method, this paper describes seven industrial case studies. Substantial benefits, ranging from 1.4 to 6% of operating costs, were identified in the case studies. The success of these studies indicates that the benefits method can be adapted to a wide range of processing plants.

Robust parameter estimation in on-line optimization—part I. methodology and simulated case study

Abstract This paper describes a two-step method for the design of a robust parameter estimation scheme that may be used to update the process model employed in on-line optimization. The first step involves determining the “key” model parameters (i.e. those having a significant effect on the calculated optimum). The second step involves finding the “best” set of measurements to estimate these key parameters. This is done by passing all possible measurements through a series of “sieves” (comprising structural analysis, singular value analysis and calculation of parameter confidence regions), with only the more promising measurements passing on to the next stage. The Williams-Otto (simulated) plant was used to assess the proposed methodology. For this purpose, it was found that the parameter estimation scheme was robust to both the presence of measurement noise and uncertainties in the non-key parameters.

An Improved Drying Achedole for Australian Ironbark Timber: Optimisation and Experimental Validation

ABSTRACT A continuous schedule for the drying of Australian ironbark timber has been optimised using non-linear model-predictive control techniques. Initially, an experimental study was carried out using a conventional schedule to dry nine 600 mm long × 250 mm wide × 25 mm thick boards in order to obtain information on the drying behaviour and the extent of timber cracking. A diffusion model accurately fitted the average moisture contents observed when using this conventional drying schedule. The fitted coefficients in the diffusion model were used to optimise the drying schedule with the aim being to keep the strain below 0.02 mm/mm and the surface moisture above 7%. The resulting optimised schedule set gentler conditions at the start of drying and more aggressive ones towards the end than the conventional schedule. The new schedule was tested in an experiment using the same number of boards from the same tree, and was found to reduce the number of small and medium-sized cracks to less than 25% of the nu...

A validated mathematical model for a zinc electrowinning cell

A set of (95) equations forming a dynamic, nonlinear model of an industrial pilot-plant scale zinc electrowinning cell fed with high purity electrolyte is presented. Only the solution of the steady-state model is considered in this paper. Values for unknown model parameters have either been obtained from the literature or else estimated using experimental data taken from the pilot-plant cell. Sensitivity studies showed that uncertainties in the temperature dependency of the zinc and hydrogen reaction exchange current densities and the exchange coefficient for the hydrogen reaction have a major effect on the model predictions. Excellent agreement between predicted and experimental results was obtained, provided that cathodic mass transfer effects were included in the model. Both parameter estimation and solution of the steady-state model were carried out using the SPEEDUP flowsheeting package.

Experimental determination of the factors affecting zinc electrowinning efficiency

AbstractA series of experiments were conducted to investigate the factors affecting the efficiency of zinc electrowinning. The experiments were conducted in 10-1 cells using a high purity industrial zinc sulphate solution. The lowest specific energy consumption achieved in the cells was 2637 kWh t−1 Zn under the following conditions: