Further Experimental Investigation of Freeze-Lining/Bath Interface at Steady-State Conditions

Fallah-Mehrjardi, Ata; Hayes, Peter C.; Jak, Evgueni

doi:10.1007/s11663-014-0149-1

Cited by 11 publications

(12 citation statements)

References 21 publications

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“…In most of the previous predictions for thermal steady state conditions, the assumption has been made that the temperature at the bath-freeze lining interface equals the liquidus temperature of the bulk slag, and that the primary phase forms a dense sealing layer at this deposit/liquid interface. As a result of recent research on these systems, there is now extensive experimental evidence [51,57,58,60,63,91] to demonstrate that the interface temperature can be below the liquidus and that the primary phase is not necessarily present at the deposit/liquid interface at thermal steady state conditions (see sections 2.3 and 2.4).…”

Section: Discussionmentioning

confidence: 99%

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Fundamental studies on the chemical aspects of freeze linings

Crivits¹

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The application of freeze lining technologies has been shown to be highly effective in extending the working lives of pyrometallurgical furnaces operating under aggressive process conditions and corrosive liquid melts. Freeze linings are obtained by cooling the outer furnace walls, resulting in the formation of solid protective deposits on the inner walls of the furnace linings. Of particular interest to process operators are the freeze lining thickness and the heat loss through the furnace walls, both of which are directly related to the bath-freeze lining interface temperature.In most of the predictions for thermal steady state conditions, the assumption has been made that the temperature at the freeze lining/liquid interface is equal to the liquidus temperature of the bulk slag, and that the primary phase forms a dense sealing layer at this deposit/liquid interface. As a result of recent research on these systems, there is now extensive experimental evidence to demonstrate that the interface temperature can be below the liquidus and that the primary phase is not necessarily present at the deposit/liquid interface at thermal steady state conditions. These observations clearly indicate that other factors, in addition to thermal parameters of the system, need to be taken into account in the design of freeze lining systems.In the present study, heat and mass transfer and elementary reaction steps, and the associated thermal, physical, and chemical factors that can influence freeze lining behaviour are identified.From experiments undertaken using CaCl2-H2O solutions, accurate measurements have been made of deposit growth and microstructural changes taking place in the deposit over time were directly observed. These experiments have demonstrated the importance of nucleation rate of the primary phase and the thermal history of the freeze lining.High-temperature experiments in the 'Cu2O'-'Fe2O3'-MgO-SiO2 system in equilibrium with metallic copper have clearly demonstrated that at thermal steady state, bath/freeze lining interface temperatures are lower than the liquidus temperatures, and the possibility of operating processes at subliquidus bath temperatures. These experiments also indicated that an increase in bath temperatures results in an increase of the steady state interface temperature.High-temperature experiments in the Al2O3-CaO-SiO2 system were designed to study the effect of slag viscosity. Differences in the characteristics of the deposit/liquid interface were observed, however, it was unclear whether the observed differences in freeze lining behaviour were caused by the changes in viscosity, or the differences in morphology of the primary phase. The spontaneous decrepitation of freeze linings containing the dicalcium silicate phase on cooling clearly illustrated iv the need for caution when designing freeze lining systems that may form compounds undergoing significant changes in volume due to polymorphic transformations.The research supports the view that deposit/liquid interface temperatures in ...

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Section: Discussionmentioning

confidence: 99%

“…Fallah-Mehrjardi et al [9,51,57,58,60,63,91] studied freeze linings in the Al2O3-'Cu2O'-'Fe2O3'-SiO2, calcium ferrite, cryolite and industrial lead slag systems. Depending on the system, the interface temperature ranged from the solidus temperature to the liquidus temperature.…”

Section: Chemical Compositionmentioning

confidence: 99%

Fundamental studies on the chemical aspects of freeze linings

Crivits¹

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“…The technology involves extracting heat through the lining by cooling of one face of the lining. The freeze lining approach has been applied to the design of lances and to fixed walls in particularly aggressive environments to enable the processes to be successfully undertaken at an industrial scale (Marx et al 2010;Fallah-Mehrjardi et al 2014a, 2014b, 2014cBlancher et al 2015). In these systems, the heat is transferred from the bulk slag to the deposit liquid interface, then through the thickness of the freeze lining and the outer wall of the reactor.…”

Section: Freeze Liningsmentioning

confidence: 99%

“…Equations ( 1) and (3) show that both the steady state thickness of the lining and the heat loss through the lining are dependent on T bath,FL . A number of approaches have been used to predict the growth and steady state thickness of freeze linings (Taylor and Welch 1987;Pistorius 2004;Zietsman 2004;Verscheure et al 2006;Irons 2011a, 2011b;Fallah-Mehrjardi et al 2014a, 2014b, 2014c. In most of the previous predictions for thermal steady state conditions, the assumption has been made that the temperature at the bath/freeze lining interface equals the liquidus temperature of the bulk slag, and that the primary phase forms a dense sealing layer at this deposit/liquid interface.…”

Section: Freeze Liningsmentioning

confidence: 99%

An investigation of factors influencing freeze lining behaviour

Crivits

Hayes

Jak

2017

Mineral Processing and Extractive Metallurgy

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Recent studies have indicated that the steady state thicknesses and interface temperatures of freeze linings can be influenced by factors other than the thermal parameters of the systems. To explore these possibilities further cold modelling of freeze linings was undertaken in the CaCl 2 -H 2 O system using an experimental apparatus that enabled the variation of both the bath temperature and the fluid flow rate. Through in situ experimental observations, it was shown that the phases formed, the deposit/liquid interface temperature and the freeze lining thicknesses depend strongly on chemical parameters and elementary reaction steps, which are not considered by the conventional thermal treatment of freeze linings. These results indicate the need for further systematic investigation of various process parameters that influence the elementary reaction steps that may be active in these systems under dynamic steady state conditions.

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“…Attention has been given to the physical aspects of freeze lining growth through the use of a cold probe technique. Fallah-Mehrjardi, Hayes, and Jak (2014) studied the effect of bath chemistry on the freeze lining microstructure of a copper smelting slag at the laboratory scale using the cold probe technique and found that the freeze lining formed depended on the viscosity of the slag bath. Kalliala et al (2015) also used the cold probe technique in a refractory sleeve to show that the freeze lining composition depends on the cooling rate of the freeze lining during formation.…”

Section: Introductionmentioning

confidence: 99%

Elastic damage characterization of an ilmenite smelter freeze lining

Mabentsela

2023

J. S. Afr. Inst. Min. Metall.

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A furnace freeze lining is necessary for safety and economic reasons in several smelting operations. The integrity of the freeze lining is put at risk by furnace power imbalances. Although numerous models have been derived to model the growth and depletion of the freeze lining due to power imbalances, no model exists for thermomechanical damage to the freeze lining. This study provides an initial pathway for modelling thermomechanical damage to the freeze lining in an ilmenite smelting furnace using information from the literature and experimental work. A methodology under the framework of continuum damage mechanics is proposed to model mechanical damage to the freeze lining due to phase changes, thermophysical changes, and constrained thermal expansion. Drill cores of solidified slag ingots were used to represent the freeze lining. The modified power law proved to be the best predictor of the softening response of the drill cores. Damage driving parameters were extracted from the raw data, and governing equations of the parameters with respect to temperature were derived for use in a finite element method (FEM) code.

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Further Experimental Investigation of Freeze-Lining/Bath Interface at Steady-State Conditions

Cited by 11 publications

References 21 publications

Fundamental studies on the chemical aspects of freeze linings

Fundamental studies on the chemical aspects of freeze linings

An investigation of factors influencing freeze lining behaviour

Elastic damage characterization of an ilmenite smelter freeze lining

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