Chemical and Biomolecular Engineering - Theses
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ItemDevelopment of an improved methodology for taphole development programs( 2004)Many industrial smelters are interested in improving their tapholes. At present, the key drivers for taphole development are to increase the throughput, improve the safety, streamline the operation and reduce the maintenance burden of tapholes. In the past, smelters have used a 'trial and error' approach to develop tapholes and in some cases hazardous and inoperable designs have been installed. To avoid this situation, some smelters have used heat transfer modelling as part of their taphole development programs, however the models that have been produced lack realistic boundary conditions, material properties and thorough validation. An improved methodology for the development of realistic taphole heat transfer models has been proposed and demonstrated in this work through a case study that was carried out on an industrial taphole. Boundary conditions including the tapping channel heat transfer coefficient were measured in the industrial taphole using a network of thermocouples. The thermocouples were installed during a regular maintenance shutdown and monitored continuously throughout an entire taphole campaign during which 23 taps occurred. The thermal conductivities of new and used samples of the taphole refractories were measured over the relevant range of operating temperatures using the laser flash technique. A 3D heat transfer model of the taphole was developed based on the measurements and the model was used to simulate the steady state and transient temperatures in the taphole over a complete tapping cycle. The model was validated against temperature data that was measured inside the taphole. Overall, the model was in good agreement with the measured data. For most areas of the taphole, the model predicted temperatures that were within 35°C of what was measured throughout the entire simulation. The validation in this work was more rigorous than the validation of any of the models presented in the available literature. The model demonstrated that realistic heat transfer models of industrial tapholes could be prepared when the relevant phenomena are understood and included in the model. The model assumed that the heat transfer coefficient measured in the tapping channel was uniform along the taphole. As a result, the model may have failed to capture a localised intense region of heat transfer in the tapping channel. It was recommended that further measurements be carried out in the taphole to investigate variations in the heat transfer coefficient along the tapping channel, and that the variations be subsequently incorporated into the model. A sensitivity analysis indicated that the model was most sensitive to the uncertainty in the contact resistances and the boundary conditions on the bath side of the model, which were not measured in this work. Further measurements were recommended to confirm the values used in the model. Further modelling was recommended to include phenomena that were relevant to taps other than the third tap that was the focus of the model. The phenomena were a worn tapping channel, aged taphole refractory, variations in the flow and freezing over. Further experiments and measurements were recommended to investigate the effect of flow variations and aged refractories on the heat transfer in the taphole.