A methodology to investigate the wear of blast furnace hearth carbon refractory lining

Abstract

In this work it is presented a methodology applied by Companhia Siderúrgica Nacional (CSN, Brazil) in order to assess its blast furnace 3 carbon refractory hearth lining conditions. The aim of the investigation was the gathering of critical data base for blast furnace refractories life cycle follow up and eventual repair decision taking.The sample drilling locations were chosen around the tap holes and hearth bottom areas. The advancing drilling depths were based on local temperature profiles. The isotherm limit of 500 °C was elected as a control parameter to assess the critical carbon refractory condition. The guidelines for sampling and testing as well as the results obtained through the physical and chemical characterizations of the cored samples are presented. The condition of the refractory lining is discussed under the light of the different known wear mechanisms of blast furnace hearth carbon refractories.

Analysis of Blast Furnace Hearth Sidewall Erosion and Protective Layer Formation

“…A number of studies have investigated the hearth erosion of the BF, but the information on the composition and the microstructure of lumped skull lining material are still very limited. [7][8][9][10][11][12][13][14][15][16] An improved understanding of the skull formation and the wear…”

Assessment of Hearth Refractory Wear in Operating Blast Furnaces

“…The blast furnace hearth experiences high temperatures, erosion due to fluid flow, thermal stress, chemical attack, and steam oxidation. The hearth performance is key to the overall blast furnacecampaign life [1].Therefore, understanding theextent of refractory damageis importantto avoid expensive repairs and to optimize production and extend the campaign life.This paper describes the combination of two non-destructive techniques: stress wave analysis (Acousto Ultrasonic-Echo technology, AU-E) [2] and heat transfer analysis using refractory thermocouple and cooling system measurements. This combined thermal assessment using AU-E measurements and thermal data is used to more accurately predict the wear profile of the hearth while in operation.…”

“…Inverse geometry heat transfer modelingis often usedfor assessing refractory wear.Assuming 1D heat transfer between a group of linearly aligned thermocouples, the thickness of the remaining refractory is extrapolated based on the thermal properties of the system. The thickness of the protective skull can also be estimated using the 1D heat transfer analysis considering thermocouple history [1].…”

Blast Furnace Hearth Lining: Post Mortem Analysis

“…The wear mechanisms for carbon hearth lining of blast furnaces were reported in the lecture, but it is mainly present as isolated variables. It occurs in function of the high complex real process of hot metal in blast furnaces 2,3 . In this way, post mortem analyses are an important tool to bring a new over view of the real complex wear process that is responsible for total lifetime of this refractory system.…”

“…During the furnace campaign, the refractory lining suffers mechanical and chemical stress such as: oxidation, corrosion by alkalis, disintegration by CO, erosion and dissolution by intense flux of hot metal and slag, liquid penetration (hot metal and slag), infiltration of gaseous phase (alkali vapor and/or carbon monoxide) and thermal stress 2,3,4 . Both the liquid penetration and the hot gaseous infiltration are allowed through the open porosity this refractory material 5,6,7 .…”