Structural and functional analysis of a blast furnace using muon tomography

The blast furnace (BF) is the fundamental tool used in the manufacture of iron. Due to the difficulty of accessing direct measurements of the phenomena within it, we have sought to determine the density distribution of its internal volume in the hope of improving its productivity as much as possible. To do this, we use muon tomography, also known as muography. This is an imaging technique based on the differential absorption of a flux of incident particles, muons, by the target under study, similar to clinical X-ray imaging. Muons are elementary particles that have the property of passing through dense materials, up to several metres away (2 m of steel for a 3 GeV muon). Their relative absorption allows the generation of density distribution images of an object by tracking the number of muons received by a detector, before and after passing through a structure. The incident direction of the detected muons is reconstructed by means of a detector composed of 3 scintillator panels [164], [154] that we moved to 3 positions around the BF. With this technique, we obtained a 3D image of the internal structure of an BF using a Markov Chain Monte Carlo (MCMC) inverse problem solving algorithm on muon flux data. We were also able to perform a time tracking of the BF and some of its operating parameters. We distinguished the position and shape of the melting zone, a key element in the productivity of a furnace. In this way, we were able to validate this innovative measurement concept in the application to an BF and open the field to a series of future experiments to gain both spatial and temporal resolution. These improvements also require a better knowledge of the flux of muons incident on their targets. We have used the CORSIKA simulation software [124], a Monte Carlo driven nucleo-hadronic interaction model, to study the effects of many parameters on the muon flux, such as atmospheric conditions (pressure, temperature), geomagnetic field, detector altitude, etc. We qualified these developments by comparing the results with commonly used analytical models and laboratory measurements. By applying these fluxes to the 3D BF reconstruction, we studied the impact of the input flux in the estimation of the opacity (amount of material traversed along a trajectory). The first numerical results suggest that the opacity estimation is strongly affected by the muon flux model choice in directions close to the horizontal and in particular for low opacity targets. (author)