Regular Article

Corrosion mechanism of carbon brick in the blast furnace hearth by potassium

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 100083 Beijing, PR China
² State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 100083 Beijing, PR China
³ Department of Materials Engineering, KU Leuven, 44 Kasteelpark Arenberg, 3001 Leuven, Belgium

^* Email: jiaokexin_ustb@126.com

Received: 1 November 2016
Accepted: 20 July 2017

Abstract

Alkali plays a significant role in the formation of brittle layer of carbon brick in the blast furnace hearth. The brittle layer in a commercial blast furnace hearth was investigated. Large amounts of potassium compounds were found in the brittle layer. Subsequently, the carbon bricks which reacted with potassium in the simulation of blast furnace hearth under different contents of potassium in the brick (0.25, 0.5, 1.0 and 2.0 wt.%) during various reaction times (0.5, 1, 2 and 4 h) were experimentally studied. Finally, the formation mechanism of the brittle layer in carbon brick was clarified. The investigation results show that a large number of cracks are present in the brittle layer. The average potassium content in the brittle layer is 1 wt.%. According to the experimental results, cracks in the carbon brick can be formed by the attack of potassium. The reason for the formation of the brittle layer in the carbon brick is that the liquid potassium permeates into the carbon brick through the pores and cracks, and then reacts with SiO₂ and Al₂O₃ in CO atmosphere. The generated potassium compounds nepheline and leucite lead to the volume expansion and the damage of the carbon brick.