Geoffrey Brooks

A new model of velocity distribution of a single-phase fluid flowing in packed beds

A new mathematical model of velocity distribution of single-phase fluid flow in packed beds was developed by assuming the flow characteristic is a combination of a continuous and a discontinuous systems of fluids between voids in the bed. The model can be applied for both compressible and incompressible fluids. The validity of the model has been checked using the measured data at inside and downstream of the bed. The agreement between measured data and the results predicted by the model is good. The model compares favourably with previous models in terms of accuracy and simplicity and does not require new empirical constants.

Thermal separation of arsenic and antimony oxides

Experiments were carried out to remove arsenic from antimony trioxide by two techniques: first, by selectively volatilizing the more volatile arsenic trioxide from a mixed oxide sample; and, second, by selectively condensing the less volatile antimony tetroxide at high temperatures, leaving arsenic trioxide to condense out at a lower temperature. Thermodynamic analysis of the As-Sb-O system indicated that if arsenic and antimony oxides behave like pure solid phases, then there is no limitation to producing pure antimony oxide by these proposed techniques. The selective volatilization experiments were carried out at 379 °C to 587 °C, using both nitrogen and air as carrier gases and an industrial antimony trioxide fume containing 13.8 wt pct As. The results showed it is difficult to achieve an arsenic content below 5.0 wt pct using either air or nitrogen, and formation of solid solutions between arsenic and antimony trioxides appears to be the main barrier to the removal of arsenic. Selective condensation experiments were carried out in which a mixed oxide vapor was progressively cooled through a series of condensers over a controlled temperature profile. Injection of oxygen into the vapor improved separation, and antimony tetroxide containing as low as 0.23 wt pct As was obtained. The recovery of antimony tetroxide in the experiments seems to have been limited by kinetic factors, and the results sug-gest that high conversions to antimony tetroxide are likely to be achieved only in antimony-rich vapors.

Solid-solution formation between arsenic and antimony oxides

An X-ray diffraction study of arsenic-trioxide and antimony-trioxide samples encapsulated under vacuum and then held at 395 °C for 24 hours revealed that cubic arsenic trioxide dissolves into cubic antimony trioxide up to a limit between 12.9 and 19.0 wt pct As. It was also found that arsenic trioxide does not dissolve as readily into antimony tetroxide, although the upper limit could not be determined by the technique used. These findings have implications in terms of their effect on proposed thermal techniques for separating arsenic and antimony oxides.

High Temperature behaviour of Directly Reduced Iron Fines

Abstract The objective of this work was to characterize the high temperature behaviour of direct reduced iron (DRI) fines because they could potentially be injected into liquid steel to reduce the nitrogen content of the steel. Physical and chemical analysis of samples of DRI fines were conducted including size analysis, chemical analysis, X-Ray Diffraction and simultaneous thermogravimetric and differential thermal analysis. The chemical changes during heating were also simulated using FACT thermodynamic analysis. It was found that the carbon and oxygen in the iron oxides reacted above 500 °C and were generally completed by 700 °C if the carbon-to-oxygen ratio was balanced. Samples with lower oxygen contents continued to react above this temperature due to the reduction of gangue oxides in the DRI.

Recent Developments in the Environment Process

Abstract The EnvIRONment process, invented by Prof. H.K. Worner, has been developed to treat metallurgical and organic wastes using pyrometallurgical technology. Developed at the University of Wollongong, the process successfully overcomes many of the technical challenges of processing ferruginous waste. Composite pellets of ferruginous, typically steelworks dust, and organic waste are bath smelted in a DC arc furnace, utilising a deep slag layer to produce iron, an innocuous slag, and a zinc enriched fume. Process viability has been demonstrated with over 4 years of trials in a purpose built 100 kg DC arc furnace. The suitability of bath smelting for processing of wastes, in particular metallurgical wastes, has been sufficiently encouraging that commercialisation of the EnvIRONment process is being pursued. Fundamental research being undertaken within the Department of Materials Engineering at the University of Wollongong is addressing unresolved aspects of the pyrometallurgical reactions operating within the process. The aim of the research is to quantify process kinetics while gaining a greater understanding of reduction mechanisms and the smelting behaviour of composite pellets. To date kinetic interpretation has been complex, however it is evident that the reaction of the composite pellets is influenced by several parameters including pellet chemistry and heating rate. Smelting of the composite pellets in slag was found to occur via dissolution of FeO and metallic iron at the slag-pellet interface.

Numerical modeling of three-phase slurry bubble column: Study of particle effects

In this study, a numerical investigation has been conducted to describe the pulp zone properties by predicting the local gas holdup and bubble size distribution accounting for the effect of bubble-particle aggregate on the flow dynamic of slurry bubble column. Modelling calculations have been conducted using Eulerian–Eulerian multiphase approach with k-e turbulence for the liquid phase. This work is carried out considering a finite volume method (FVM) tool using AVL FIRE, v.2014 coupled with the user defined subroutines especially for the change in the concentration number of different bubble sizes due to bubble break-up and coalescence. This code is validated comparing the experimental gas holdup with the numerically predicted data and a reasonable agreement has been found. In the current model, the effect of attachment and detachment process was included into the kinetic equation.by transferring the mass of attached particles to the gas bubble-particle aggregate. The results of this study show that the ...

Cold Modelling of Splashing Phenomena in Oxygen Steelmaking

In oxygen steelmaking, splashing and droplet formation play a key role in the kinetics of the process. Though splashing has been studied by previous investigators, there is only limited understanding of how different cavity modes affect splashing. Therefore, a cold model study (at various lance heights and gas flow rates) has been carried out focusing on the issue of cavity modes and how it affects splashing phenomenon. Analysis using Fast Fourier Transform (FFT) was carried out on cavity oscillation that showed that frequency and amplitude of oscillation was highest in penetrating mode. Measurements of splashing over a range of conditions showed splashing greatly reduced when cavities went from splashing to penetrating mode. The results were validated and compared with plant data and previous model investigations.