Optimising Carbon Type Differentiation Techniques to Reduce Dust Emissions in Blast Furnace Ironmaking

Abstract

The manufacturing process of iron, using the blast furnace (BF) generates dust as a byproduct, which is recycled, however, the generation of the dust in excess is undesirable.A comprehensive review of the dust has determined that each of the raw materials for blast furnace ironmaking contributes to its formation, including several forms of carbon thus addressing the hypothesis 'The raw materials that feed the blast furnace are expelled into the gas stream and all influence the blast furnace dust.' The current technique for quantifying coal originating carbon type mostly in the form of coal char, referred to as the nominal term Low Order Carbon (LOC) within BF dust consists of thermogravimetric analysis (TGA) however, this technique does not allow for samples of dust to be analysed in a timely manner, in line with the ever-changing conditions of the blast furnace. In this work, the TGA method has been trialled for use with BF dust, with improvements offered to the heating profile, allowing for faster analysis.Moreover, alternative techniques have been trialled, in combination with various characterisation methods such as X-ray diffraction, Scanning Electron Microscopy, total carbon and Optical Emission Spectroscopy. The 'Winkler Method' which was originally designed to quantify charcoal in soil sediment has been successfully adapted and optimised to suit LOC quantification in BF dust, showing a good correlation with the original benchmark technique. This answered the hypothesis, 'Thermal techniques can be used to differentiate carbon sources in dust generated in blast furnaces that use granulated coal injection.' The techniques for LOC quantification were applied to dust samples spanning a 9 month period. to determine the process parameters that influence the LOC presence within the dust. It was found that the resolution of sampling is key to identify relationships between process parameters and LOC within the dust. A novel technique to continuously monitor the dust output of the furnace found that the dust output and the LOC within the dust are related, where the increasing dust output leads to increasing concentrations of LOC within the carbon profile of the dust itself. Process parameters including blast pressure, blast volume, and production rate were considered to increase the dust output from the furnace based on the work of the dust probe, thus answering the hypothesis 'Coal combustion in the raceway can be impacted by process parameters and the evidence can be found in the fingerprint of blast furnace dust.' A node mapping exercise was used to model an ideal set of process conditions for low dust operations. The foundations to make macro advances in carbon and dust output reduction in blast furnace ironmaking are laid out in this thesis. iii Acknowledgements The academic guidance provided by Dr Hollie Cockings has been totally faultless, her enthusiasm for the subject has kept me motivated throughout this thesis and her direction has been second to none. My gratitude to the staff of the Materials and Manuf...