Measurements of Some Thermal Properties of Steel-Refractory Systems and Heat Losses from Steelmaking Furnaces

Abstract

Experimental procedures have been developed to measure heat losses and temperature in a laboratory scale, high temperature furnace under different conditions and thereby, to estimate various thermal properties of steelrefractory system such as emissivity, thermal conductivity and thermal contact resistance between refractory and steel plates etc. To these ends, a large number of experiments were carried out in an in-house designed resistance furnace with the help of pyrometers, contact thermocouples and heat flux transducer etc. Prior to detailed experimental work, calibrations of different measuring devices viz. thermocouple, pyrometer, heat flux transducers was carried out and measurements evaluated against available data bases, well established theoretical frameworks as well as against a computational procedure developed in-house. It is shown that while thermo-physical properties tend to depend on specific composition of material chosen, present estimates are not largely different from values reported for similar material in the literature. Thermal properties of the materials and contact resistances thus determined were finally embodied in a mathematical model, to calculate (i) transient thermal profile in a steel ladle lining during pre-heating operation and (ii) in situ wear (or thinning) of refractory lining in an industrial scale steelmaking furnace.

Inner Wall Temperature Distribution Measurement of The Ladle Based on Cavity Effective Emissivity Correction

“…The temperature distribution of the ladle is mainly measured by single-point infrared radiation pyrometer and thermal imager. I. Jain, G. Dietmar, V. A. Kononov et al [12][13][14][15][16] adopted a single-point infrared radiation pyrometer to obtain the temperature of the ladle shell and verify the simulation results of the temperature field of the ladle insulation layer. On the basis of single-point temperature measurement, In actual application, the thermometry sets the emissivity of the measured object to a constant value [17][18][19][20] , however, the emissivity of the measured points surface of the ladle is uncertainty, it brings great error to the measurement.…”

Thermal measurement and degradation quantification of teeming ladle refractories and the effects on the process

“…The results from Bauer's studies suggest that the refractories have an emissivity close to 1, the theoretical maximum, as shown in Figure 8, Figure 9 and Figure 10. The idea that a refractory without carbon would have a spectral emissivity so close to the theoretical maximum is unlikely, especially when compared to the findings in more recent studies (24,51). This casts doubt on the values calculated in these studies.…”

“…Jain makes reference to this in the body of the paper stating "emissivity of the magnesia-carbon refractory material, as it appears, decreases with increase in temperature due to continuous oxidation of carbon and the resultant increase in the porosity of the refractory surface due to prolonged heating." (51). This…”

“…The materials are also heated to 2300°K and the emissivity is assumed to be independent of temperature at this point (53). This is not shown to be the case in both Glaser's (2011) and Jain's (2015) studies and consequently this method is not applicable to the measurements required for accurate teeming ladle measurements (24,51). Elich (1995) presents a study of the refractories used in a glass melting furnace and measures the reflectivity of these refractories using the integrated sphere method, which is then used to calculate the emissivity (54).…”

“…Jain's (2015) study uses a similar testing method to Glaser's but the furnace used to heat the samples has been adapted so the door represents the refractory build of a teeming ladle (51). The sample size in Jain's study is 50mm x 30mm x 10mm and the pyrometer used is a Chino IR-AHS which has a spectral response of 0.96µm (60).…”