**Mauricio Roche \*, Mikko Helle and Henrik Saxén**

Thermal and Flow Engineering Lab, Åbo Akademi University, 20500 Turku, Finland **\*** Correspondence: mroche@abo.fi

Received: 4 July 2019; Accepted: 5 August 2019; Published: 7 August 2019

**Abstract:** Monitoring and control of the blast furnace hearth is critical to achieve the required production levels and adequate process operation, as well as to extend the campaign length. Because of the complexity of the draining, the outflows of iron and slag may progress in different ways during tapping in large blast furnaces. To categorize the hearth draining behavior, principal component analysis (PCA) was applied to two extensive sets of process data from an operating blast furnace with three tapholes in order to develop an interpretation of the outflow patterns. Representing the complex outflow patterns in low dimensions made it possible to study and illustrate the time evolution of the drainage, as well as to detect similarities and differences in the performance of the tapholes. The model was used to explain the observations of other variables and factors that are known to be affected by, or affect, the state of the hearth, such as stoppages, liquid levels, and tap duration.

**Keywords:** hearth; drainage; PCA; analysis tool; pattern; tapholes
