Study of scull and lining in the hearth of blast furnace No. 2 of JSC EVRAZ ZSMK (Report 3)

Abstract

Modern blast furnaces have operation life of 15-20 years. Such a duration of their operation to a great extent reached due to the resistance of lining of hearth and hearth bottom. To study the processes, effecting the rate of its erosion, a study of composition and structure of the scull on the lining of walls of a blast furnace hearth and hearth bottom was accomplished. For the study the No. 2 blast furnace of EVRAZ ZSMK was chosen after its stoppage for overhaul. Results of visual examination of the state of the lining of lower part of the hearth and hearth bottom presented. Macro-structure of the picked out samples presented, general view of lump samples and polished section briquettes shown. Mineral composition of the samples and chemical composition of their separate mineral phases studied. It was determined, that the samples density, picked out lower the iron notch, was considerably higher. By authors opinion, it is stipulated by the increase of metal phase content in the scull along the hearth height in the direction from tuyere level to the hearth bottom, as well as considerable change of the scull porosity along both the horizontal section and the hearth height. The porosity of the samples, picked out lower the iron notch, was not high - at the level of 2.73-3.73%. The gases (oxygen, nitrogen, hydrogen) contained in the BF melts, lead to the forming of scull porous structure of insignificant thickness in the upper horizons of the hearth and in the notch channel. It was determined, that a building-up of zinc can be observed on the hearth bottom, as well as its alloys with iron and lead. The samples macro-structure was clear laminated. The zinc in the sample exists in the form of two mineral phases: an oxide phase (zinc oxide) and a metal phase, often with iron contaminant and rarely - with iron and lead. The results obtained, apart from the studies carried out earlier on the scull and BF hearth lining state, will be base of a theoretical analysis of scull forming mechanism and lining properties change, effecting the blast furnaces campaign duration.