J. Torrkulla’s research while affiliated with Åbo Akademi University and other places

The hearth is a crucial region of the blast furnace, since the life of its refractory may be decisive for the campaign length of the furnace. Excessive growth of skull on the hearth wall and bottom, in turn, reduces the inner volume of the hearth, causes drainage and other problems that limit productivity, and has a negative effect on hot metal temperature and chemistry. A set of indicators that reflect the internal state of the hearth has been developed. The motivation for the indicators is outlined and their application to hearth state detection is illustrated with several examples from the operation of two Finnish blast furnaces.

In the operation of the ironmaking blast furnace, the function of the hearth is crucial, both to ensure a long campaign and a high production rate of hot metal of high quality. In order be able to take appropriate actions in controlling the state of the furnace hearth, the behavior of it has to be understood. The work reported in this paper has been carried out to study the general behavior of the molten phases in the furnace hearth during tapping. The influence exerted by the state of the hearth coke — the dead man — on the flow patterns has been investigated by CFD modeling. The results of the study agree well with findings reported in the literature as well as with practical observations in the operation of the blast furnace.

A model for estimation of erosion and skull profiles of the blast furnace hearth is presented. The model, which is based on thermocouple measurements in the hearth bottom and wall lining, estimates the most severe erosion of the lining experienced during the campaign and also the present thickness of the skull material. The model is illustrated on process data from two Finnish blast furnaces. Complementary measurements and calculations are used to verify the results. Based on the findings, conclusions are drawn about the internal state of the blast furnace hearth, for instance whether the dead man floats or sits at the bottom. Finally, some suggestions on how to control the state of the furnace hearth are given.

A two-dimensional mathematical model of steelmaking ladles is presented. The model can be used as a design tool, by which a number of variables such as holding time, material choice, and refractory layer thicknesses can be studied with regard to their influence on the steel temperature evolution during casting. In addition, the model can act as a decision support and as a basis for automation of temperature control. Temperature measurements from an operational steelmaking ladle are compared to simulation results obtained with the model, demonstrating its feasibility and applicability to steelmaking.

A mathematical model suitable as a tool for improving temperature control in the steel plant is presented. With this tool, a number of variables such as holding time, material choice and refractory layer thicknesses can be studied with regard to their influence on the steel temperature evolution during casting. In addition, the model can be used as a decision support and forms a basis for automation of temperature control.