Mechanism of Periclase-Chromite Refractory Breakdown Under Acid Slag Action
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Vol. 61, No. 3, September, 2020
REFRACTORIES IN HEATING UNITS MECHANISM OF PERICLASE-CHROMITE REFRACTORY BREAKDOWN UNDER ACID SLAG ACTION K. G. Zemlyanoi1,3 and L. V. Serova2 Translated from Novye Ogneupory, No. 5, pp. 5 – 11, May, 2020.
Original article submitted February 10, 2020. Periclase-chromite refractories are studied after operation under action of acid slags. The refractory microstructure and corrosion mechanism in fayalite melts are demonstrated. Ways of improving refractory stability are proposed. Keywords: periclase-chromite refractories lining, fayalite slags, porous structure, corrosion mechanism.
Refractories in the periclase-chromite (chromite ore) system are used extensively in lining ferrous metal heating units during melting alloyed and special steels, nonferrous metallurgy (reverberatory furnace, copper production converter), and also lining heating furnaces for rolled product, rotary furnaces for cement production, and polymetal manufacture [1 – 4]. A common factor governing the selection of periclasechromite refractories in different branches of industry is the acid nature of melts and primarily slag having a direct effect on the heating unit lining working layer. Therefore, a study of the breakdown of periclase-chromite refractories in acid slag is an important task making it possible to improve refractory quality and correspondingly lining life.
range 3.00 – 60.00°, scanning pitch 0.02°) Rikagu – Carl Zeiss (Japan) diffractometer with a rotating anode, with programmed control MiniFlex Guidance data collection and a PDXL Basic data processing package. Identification of diffraction maxima was performed using the JSPDS data bank, semiquantitative evaluation of phase content, i.e., using corundum number RIR (Reference Intensity Ratio) by the Chung method [5]. Apparent density, open porosity, and water absorption (for kerosene) were determined according to GOST 2409–2014 “Refractories. Methods for determining apparent density, overall porosity, water absorption.” Petrographic study of refractory objects was conducted in reflected light of an Olympus microscope at 200-fold magnification; a “Siams” system was used during treatment of photographs. A study was made of the breakdown of Combinat Magnezit refractory grade PCS based on melting powders of periclase and chromite ore (chrome spinelid) under action of an acid slag of fayalite composition (Table 1). Apart from periclase the refractory contains solid solutions of spinelids with the generalized formula (Mg,Fe)O·(Fe,Cr,Al)2O3, silicates in the form of olivine, forsterite, and monticellite, and they exhibit a concreted microcrack structure [6]. A refractory specimen was selected from a lining after operation for 4 months under action of molten fayalite slag, a gas atmosphere with a high amount of CO, CO2, SO3, and water vapor, and also sharp temperature drops in the range 1000 – 1400°C. A refractory specimen after operation is shown in Fig. 1. It is seen that three zones are separated from
RESEARCH METHODS Test material chemical composition
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