Effect of the nature of the process binder and the carbonaceous material on the burn-off of carbon from periclase carbonaceous mixtures

Abstract

Periclase carbonaceous refractories are currently used in those regions where there is extra wear on the linings of the superheating zone and of the slag wells of steel-smelting aggregates [1][2][3][4][5]. These refractories are gradually replacing the periclase-chromite and fusecast refractories used to date.In order to determine the physicochemical processes which occur in the molding of periclase carbonaceous articles, we studied the effect of the forms of binder and the carboncontaining materials on the degree of burn-off of the carbon in micrograin mixtures consisting of slntered periclase powder and carbon.Taking into account the technicoeconomic information and the fact that the properties , of the refractories must satisfy high user standards, we used a sintered periclase powder PPE-88 which meets GOST 24862--81 and different forms of carbon-containing materials (Table i).As the binding materials (10 parts by wt. added to 100 parts of the mass of dry batch) We used technical sodium polyphosphate (NaPO3)n toGOST20291--80 with a density of 1.45 g/cm3; wate~ glass grade B, Na20,SiO2-mH~O with a density of 1.35 g/cmS; and ethyl silicate E'TS-32 and ETS-40 to TU 6-02-641-76 and TU 6-02-895-78, respectively.The batches for pressing were made using a method involving the simultaneous milling of the periclase powder and carbon-containing material in a 60:40 ratio in a vibromill before passing at least 90% through a 0.06-mm mesh sieve. The specimens of cylindrical shape, 25-mm diameter and height, were pressed at 100 MPa and heat-treated at 1000~ with a 2-h dwell in a furnace with sillite heaters.After the firing we made an approximate calculation of the relative (Amre I) and absolute (dmabs) degree of burn-off of carbon in accordance with the formulas:C where mz is the mass of the specimen before firing, g; m2, mass of the specimen after firing, O g; n, mass fraction of carbon-free material:; Amrel, relative loss of mass of the carbon-free material, %; and C, mass fraction of carbon in the batch, %.The results showed (Table 2) that the greatest degree of burn-off is found in the natural crystalline graphite from the Zaval'evsk Deposits (batch 2-P).It was established that the use of sodium polyphosphate is preferable to that of water glass for reducing the burn-off of carbon.A complex thermal analysis (CTA)* of specimens was carried out in 0D-102 and 0D-103 derivatographs in air over the 20-1000~ temperature range. The rate of increase in the temperature:reference material was aluminum oxide. The portions weighed 0.3-1.0 g. The results of the thermographic studies (Tables 3 and 4) showed that the degree of burn-off of the carbon-containing materials from masses containing water glass is greater than from those *The study was carried out by E. I. Kelareva (Eastern Institute of Refractories). L. I. Brezhnev Dnepropetrovsk Metallurgical Institute. Eastern Institute of Refractories~

Effect of the structure of the phosphorus-containing anion in the phosphate binder on the inhibition of thermal oxidation of graphite powders

“…The bodies of the high-alumina and corundum compositions can contain orthophosphoric acid as a binder and the bodies of the periclase composition can contain commercial-grade sodium polyphosphate binder [1][2][3].The inhibiting effect of the phosphate binders on the thermal oxidation of the graphite powders introduced into the ramming bodies was demonstrated recently [4]. This paper establishes the relationship between the inhibiting effect and the structure of the phosphorus-containing anion of the binder.…”

“…Calculation of the constants appearing in Hiss' equation that are required for calculating the equilibrium phase composition in the five-component CaO-nMgO-Fe20~-Al203-SiO 2 system covering a large number of materials of refractory technology was carried out [2] (Hiss' equation is known to be valid for systems with any number of components). Berezhnoi [3] suggested a simple and effective method for calculating the equilibrium phase composition of forsterite refractories and the minimum quantity of the additives to be introduced into the raw materials for obtaining a refractory material and for establishing several correlations between the composition and the properties of the raw materials and the refractories. Perepelitsyn et al [4] described a method for calculating the required MgO additive on the basis of the data concerning the content and the composition of the glass phase.…”

“…The bodies of the high-alumina and corundum compositions can contain orthophosphoric acid as a binder and the bodies of the periclase composition can contain commercial-grade sodium polyphosphate binder [1][2][3].…”

Investigation of Taimyrsk graphites for producing periclase-carbon ladle refractories

“…In these conditions the use of traditional refractories such as chamotte, and siliceous refractories, is ineffective. Basic refractories are used for these purposes, of which periclase-carbon is the most prospective.Amorphous, cryptocrystalline, and crystalline graphite [1-6] may be used as the carbon component in periclase-carbon refractories.The highest resistance in service is shown by periclase-carbon with crystalline graphite [2,3]. It is possible to use cryptocrystalline graphite [6,7].…”