Madoc Sheehan

Microwave modification of sugar cane to enhance juice extraction during milling.

Abstract Sugar extraction from cane requires shredding and crushing, both of which are energy intensive activities. Cane shredders account for almost 30% of the total power requirements for the juice extraction train in a sugar mill with four mills. Shredder hammers also wear quickly during the crushing season and need to be regularly maintained or replaced. Microwave pre-treatment of other plant based materials has resulted in significant reductions in total processing energy. This paper briefly reviews the underlying structure of sugar cane and how microwave pre-treatment may interact with sugar cane. Microwave treatment reduced the strength of sugar cane samples to 20 % of its untreated value. This strength reduction makes it easier to crush the cane and leads to a 320 % increase in juice yield compared with untreated cane when cane samples were crushed in a press. There was also a 68 % increase in Brix %, a 58 % increase in total dissolved solids, a 58 % reduction in diffusion time, a 39 % increase in Pol %, and a 7 % increase in juice purity compared with the control samples after 60 minutes of diffusion in distilled water.

Assessment of microalga biofilms for simultaneous remediation and biofuel generation in mine tailings water

Microalgae crops can generate a biochemical profile of high energy density and may be used for remediation of contaminated waste waters. This manuscript presents a laboratory-scale investigation into the potential for growing endemic microalgae biofilms in phosphorus-enriched nickel refinery tailings water, with an emphasis on product potential and the remediation of heavy metals. The dominant species of the consortia was a Chlorella-like microalga. The growth was monitored over time, with a productivity (0.77±0.07gAFDW.m-2.day-1) showing promising potential. The biochemical profile of biomass had a high total carbohydrate yield (40.0%), and a potential for increased lipid yields (6.7-19.5%). Biofilms showed a significant potential for the removal of heavy metals (Ni, Co, Mn, Sr) from the waste water with 24.8%, 10.5%, 24.8% and 26.4% reduction in Ni, Co, Mn and Sr, respectively. Results highlight significant potential for large-scale biofilm biomass production using metal-laden nickel refinery waste waters.

Implementing a systematic process for rapidly embedding sustainability within chemical engineering education: a case study of James Cook University, Australia

Sustainability has emerged as a primary context for engineering education in the 21st Century, particularly the sub-discipline of chemical engineering. However, there is confusion over how to go about integrating sustainability knowledge and skills systemically within bachelor degrees. This paper addresses this challenge, using a case study of an Australian chemical engineering degree to highlight important practical considerations for embedding sustainability at the core of the curriculum. The paper begins with context for considering a systematic process for rapid curriculum renewal. The authors then summarise a 2-year federally funded project, which comprised piloting a model for rapid curriculum renewal led by the chemical engineering staff. Model elements contributing to the renewal of this engineering degree and described in this paper include: industry outreach; staff professional development; attribute identification and alignment; program mapping; and curriculum and teaching resource development. Personal reflections on the progress and process of rapid curriculum renewal in sustainability by the authors and participating engineering staff will be presented as a means to discuss and identify methodological improvements, as well as highlight barriers to project implementation. It is hoped that this paper will provide an example of a formalised methodology on which program reform and curriculum renewal for sustainability can be built upon in other higher education institutions.

Modelling the dynamics of solids transport in flighted rotary dryers

This paper proposes a simple dynamic solids transport model for flighted rotary dryers, which results by discretising the dryer in the axial direction into a series of equivolume elements. Each resultant element is partitioned into two zones; one active and the other passive. Solids interchange between the active and passive zones is included, leading to a tanks-in-series/parallel approach, traditionally used by reaction engineers. Modelling solids transport in this manner allows the residence time distribution (RTD) characteristics of the rotary dryer to be elucidated. In this work gPROMS is used to simulate the proposed rotary dryer model. Data from a 100 tonne per hour raw sugar dryer is reconciled against the dynamic solids transport model, by estimating overall solids transport coefficients.

Using CFD to derive reduced order models for heat transfer in particle curtains

3–D Eulerian–Eulerian CFD is used to simulate convective heat transfer in free falling particle curtains. Total heat loss for curtaining particles is compared to heat loss for isolated single particles. Spherical silica particles with density of 2,634 kg/m³ at 400 K (200 µm, 400 µm and 600 µm) flow at approximately 0.041 kg/s to 0.2 kg/s through a narrow slot in a rectangular box (0.45 m × 0.9 m × 0.225 m) filled with ambient air. The slot sizes through which the particles enter the rectangular box were 10 to 80 mm wide. Modifying the slot size at 0.041 kg/s for 400 µm particles can lead to 13% increases in rates of convective heat transfer per unit mass. A reduced order model was developed to predict the centreline temperatures of particles in the falling curtains. The drag coefficient in the ROM was varied to suit a range of particle sizes and mass flow rates.

Hydrodynamic Modeling of Copper Electrodeposition at a Vertical Rotating Cylinder Electrode

The hydrodynamics of a rotating cylinder electrode were modeled to predict tertiary current distributions during electrodeposition of copper from acidic sulfate media, and to evaluate the effects of the resulting density gradients close to the electrode. Assuming no such density variations, then predictions of transport-limited current densities were in good agreement with Mizushina’s empirical law and with Leveque’s theoretical description, but not with measured values. Assuming a linear density variation with copper concentration, predictions of concentration profiles agreed to within 3 % of experimentally measured limiting current densities at the rotating cylinder electrode. For solution compositions relevant to copper electrowinning, a diffusion coefficient for cupric ions of 1.2×10 -9 m 2 /s at 45 o C, was inferred by solving the continuity, Navier-Stokes and mass balance equations with Fluent® computational fluid dynamics software.

Development of a competency mapping tool for undergraduate professional degree programmes, using mechanical engineering as a case study

ABSTRACT Mapping the curriculum of a professional degree to the associated competency standard ensures graduates have the competence to perform as professionals. Existing approaches to competence mapping vary greatly in depth, complexity, and effectiveness, and a standardised approach remains elusive. This paper describes a new mapping software tool that streamlines and standardises the competency mapping process. The available analytics facilitate ongoing programme review, management, and accreditation. The complete mapping and analysis of an Australian mechanical engineering degree programme is described as a case study. Each subject is mapped by evaluating the amount and depth of competence development present. Combining subject results then enables highly detailed programme level analysis. The mapping process is designed to be administratively light, with aspects of professional development embedded in the software. The effective competence mapping described in this paper enables quantification of learning within a professional degree programme, and provides a mechanism for holistic programme improvement.

Experimental and simulation approaches: effect of microwave energy on mechanical strength in sugarcane

Sugarcane processing produces cane sugar (sucrose) from freshly harvested sugarcane through mechanical milling processes such as shredding and crushing. To make sugarcane more processable, we employed heat treatment of sugarcane using microwave energy to soften sugarcane prior to its mechanical processing. In this paper, we report our first simulation and experimental investigation of the influence of microwave heating on the mechanical properties of sugarcane stalk internodes. Finite-difference time-domain simulations were used to understand the microwave field distribution in the microwave-heated sugarcane specimens. Microwave-heating induced sugarcane property changes in Youngs modulus, yield strength and ultimate strength were measured using compressive testing. The results show that microwave heat treatment significantly reduces mechanical strength and stiffness of sugarcane so that treated sugarcane stalks become more processable in mechanical milling processes. This work provides preliminary data with which the sugar industry could reduce shredding and crushing forces, torques, and energy. Potential savings in energy consumption, and operation and maintenance costs would be expected.

Predicting solvent effects on reactions and liquid-liquid equilibrium by computer simulation

This paper reviews the application of molecular modelling techniques for the prediction of solvent effects on fundamental engineering processes. In particular, the prediction of the effects of solvents on reaction kinetics and liquid-liquid phase equilibrium are discussed. The product selectivity for a solvent sensitive Diels-Alder reaction between cyclopentadiene and methylacrylate is modelled in two solvents using molecular dynamics techniques. The relevant post-reaction phase separations are also modelled. Although accurate quantitative predictions were not made, the example illustrates the potential benefits and problems of molecular modelling for engineering applications.

CFD and experimental study of convectional heat transfer in free falling particle curtains

The convection heat transfer in particle curtains was studied using a combination of experiments and CFD simulations. The Eulerian-Eulerian approach of CFD has been used to simulate particle curtains. Experiments were conducted with glass beads (290 and 400 μm in mean diameter) flowing through a 20×150mm slot at different mass flow rates (0.06-0.135kg/s). The centreline temperature of particle curtains was determined experimentally using infrared photography. Effects of mass flow rate and particle size on heat transfer have been investigated.