Numerical Estimation of Hearth Internal Geometry of an Industrial Blast Furnace

Abstract

Since the campaign of a modern blast furnace (BF) is usually restricted by its hearth integrity, monitoring the hearth internal geometry is of crucial importance for strategic operation planning. To provide an overall picture of the hearth inner geometry of a large‐scale BF in Chinese steelworks, a wear model based on the solution of an inverse heat conduction problem is developed. Using the wear model, the evolutions of erosion and skull lines in the hearth are tracked for the period from the blow‐in of the BF to its present state. The main findings are outlined herein, where a detailed analysis and discussion of some observations are made to gain a deep understanding of the internal state of the hearth. A correlation between the thickness of the estimated skull layer and taphole length is demonstrated. The results indicate that the skull layer in the bottom of the BF hearth is much thicker than that in the sidewall and that lining erosion of the hearth mainly occurs in the sidewall. In addition, a thicker skull layer preventing the sidewall from excessive lining erosion correlates well with a longer taphole.

Formation Mechanism of the Brittle Layer in Carbon Brick of Blast Furnace Hearth

“…These studies indicated that the peripheral flow of molten iron, dissolution of molten iron, attack of zinc and alkalis, thermal stress, and fluid‐induced shear stress are the reasons for the corrosion of carbon bricks. [ 3–5 ] It was found that a certain part of the hearth refractory was eroded, the molten iron would be enriched in the inner layer of this part, and a brittle layer appeared in the outer layer of the molten iron enrichment area. [ 6–8 ]…”

“…These studies indicated that the peripheral flow of molten iron, dissolution of molten iron, attack of zinc and alkalis, thermal stress, and fluid-induced shear stress are the reasons for the corrosion of carbon bricks. [3][4][5] It was found that a certain part of the hearth refractory was eroded, the molten iron would be enriched in the inner layer of this part, and a brittle layer appeared in the outer layer of the molten iron enrichment area. [6][7][8] At present, different scholars possess different views on the formation mechanism of the brittle layer, which is generally divided into the following four aspects: 1) erosion of alkali and zinc metal; 2) thermal stress; 3) infiltration of molten iron; and 4) oxidation.…”

Estimation of the Blast Furnace Hearth State Using an Inverse-Problem-Based Wear Model

“…Further, it influences the internal flow field of the liquids that may affect the state (e.g., carburization) of the hot metal. Over the years, numerous efforts have been made to develop wear models that can be used to offer an overall picture of the hearth internal geometry particularly with respect to lining and skull profiles [9][10][11][12][13][14][15]. Such wear models build on the solution of inverse heat conduction problems, where the deviations between thermocouple readings and temperatures estimated by a mathematical model at the same points are minimized by iteratively altering the location and shape of the inner profile.…”

“…A generic wear model optimized for fast computation, and thus industrial application has been presented in a previous paper [11], where special emphasis was put on outlining the underlying principles of the model and introducing the measures for yielding a wellconditioned numerical problem. Some examples of the estimated lining and skull profiles featuring three-dimensional (3D) representations were also presented.…”