The Environmental Optimisation of the Iron Ore Sintering Process
Authors:   , Wilcox Matthew 
Published: April 2024

Iron ore sintering is an established thermal agglomeration process where fine iron ores are fused together to produce a coarser product which is a suitable burden material for blast furnaces. Due to the scale of blast furnace demands, a typical steelworks sinter plant can produce thousands of tonnes of sinter every day which in turn results in the formation of significant quantities of dusts. The majority of these dusts will be captured and reused in the process due to their iron content. However, dusts released to atmosphere can create environmental concerns and they can also be problematic to the sintering process itself. This thesis considers two major aspects related to the optimisation of environmental emissions from blast furnace sinter production; namely sinter dusts and the addition of recycled steelmaking material by-products (reverts) back into the sintering process. Firstly, considering sinter dusts, these are removed from the exhaust stream using processes including electrostatic precipitators (ESPs). But the dusts must be removed from ESP plates to maintain dust removal efficiency. The dusts consist of sinter sub-components and metal chlorides. Although an established method for removing chlorides from the dusts, following an industrial scale trial carried out by Tata Steel UK, in this thesis, experiments have been carried out to optimise the water washing process of sinter plant waste dust. This involved varying parameters such as washing time, agitation speed and liquid to solid ratios. Initial tests confirmed that > 95 % of soluble chlorides within the dusts can be mobilised by water washing with only one wash under standard operating conditions. Experiments were then carried out to assess whether the washing solution could be effectively recycled to wash more dusts. Results showed that the washing solution could still mobilise chloride from the dust for up to ten cycles, although there was decline in effectiveness at later cycles. One issue noted during these experiments was the hydrophobicity of ESP dust, making it harder to work with during washing and even allowing some dust to apparently remain dry after washing. To combat this, more dust washing experiments were then carried out which featured the inclusion of surfactants, the aim being for the surfactants to mitigate the hydrophobic effects. Three surfactants were tested, each of varying properties, and all showed positive impacts to the processing of the dust, TX-100 being the most effective. More detailed analysis of the surfactants outside of a dust washing setting was also undertaken and confirmed that TX-100 was more effective at tackling the dusts hydrophobicity. Upon completion of dust washing experiments, tests were undertaken using a pilot-scale sinter pot to better establish the impacts of sintering before and after washing the dusts. These results showed impacts on sinter strength and dust production when including both dust types, although utilising the washed dust appeared to result in higher dust emissions. Furthermore, both dusts were then micro-pelletised and sintered alongside sinter blends with the same dust content, to establish if reducing the fines content in the sinter blend could allow their use at higher rates. These showed that pelletising the dusts greatly improved the sinter bed permeability, aided sinter strength and reduced dust emissions. Overall, this thesis considers the environmental optimisation of raw material sintering for steel manufacturing, focusing on the remediation and recycling of input materials. Investigating how these processes can be improved and identifying any impacts on process quality, product quality and dust emissions.