Raceway and hearth conditions relative process conditions in the LKAB exper- imental BF

The experimental BF (EBF) offers unique possibility to analyse the hearth conditions after each campaign, usually twice a year. Core drilling in to the coke bed of raceway and hearth has been carried out during short stoppages and after a finalised trial campaign, respectively. Based on results from previous drilling exercises indicating that raceway combustion significantly influences the hearth conditions an extended number of cores were drilled out to cover the hearth area and depth. 14 cores were drilled in order to cover the whole hearth and positions of centre, beneath all three raceways, between raceways and close to the taphole. Sub-samples of each core were characterized using e.g. physical methods, chemical analyses and XRD for historical temperature estimation including calibration curve stated by laboratory treatment of charged coke. Differences in tuyere slag formation found in cores drilled out from raceway during all coke and PCI operation are discussed and analysed in thermodynamic calculations. The development of coke properties relative depth and radial position are described. Characterisation results from solid samples and relation to EBF process conditions and collected process data are discussed. Investigation involves operation conventional BF operation with PCI, ULCOS version 4 with hot recycling gas injection at tuyere and shaft level and ULCOS version 1 with cold recycled gas at tuyere level and hot recycled gas in shaft level. The results correlate well with previous findings regarding the effect of raceway conditions on hearth state.