Investigation of the Freeze-Lining Formed in an Industrial Copper Converting Calcium Ferrite Slag

Fallah-Mehrjardi, Ata; Jansson, J.; Taskinen, Pekka; Hayes, Peter C.; Jak, Evgueni

doi:10.1007/s11663-013-9987-5

Cited by 18 publications

(9 citation statements)

References 16 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 (Fallah-Mehrjardi 2013;Fallah-Mehrjardi et al 2013a, 2013b, 2013c, 2014a, 2014b, 2014c 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 to explain freeze lining behaviour, other factors, in addition to thermal parameters of the system, need to be considered.…”

Section: Freeze Liningsmentioning

confidence: 99%

“…While most slag systems formed freeze linings consisting of several (partially) crystalline layers, the slag system containing the highest concentration of silica was found to form a glassy freeze lining, containing only a few microcrystals. (Fallah-Mehrjardi 2013;Fallah-Mehrjardi et al 2013a, 2013b, 2013c, 2014a, 2014b, 2014c) studied freeze linings in the Al 2-O 3 -'Cu 2 O'-'Fe 2 O 3 '-SiO 2 , 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: Mass Transfermentioning

confidence: 99%

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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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Section: Freeze Liningsmentioning

confidence: 99%

Section: Mass Transfermentioning

confidence: 99%

An investigation of factors influencing freeze lining behaviour

Crivits

Hayes

Jak

2017

Mineral Processing and Extractive Metallurgy

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“…The majority of these studies have focused on the phase assemblages and microstructures formed during the growth of the deposits. [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] EXPERIMENTAL RESULTS…”

Section: Modelsmentioning

confidence: 99%

“…Recent work has been undertaken by the authors [49][50][51][52][53][54]57,58 to determine the influence of process parameters, such as cooling gas flow rate, melt convective flow induced by rotation of the crucible, bulk bath temperature and process time, on the deposits formed from copper-containing silicate slag. The synthetic slag used in the experiments was prepared from high-purity (99.9 wt.%) oxide powders; the bulk slag composition is 6.5 wt.% An example of the temperature distribution across the deposit section for a given set of process conditions at steady state, for a bulk bath temperature (T bath ) of 1165°C, is given in Fig.…”

Section: Temperature Profilementioning

confidence: 99%

“…The key parameters used in heattransfer calculations include superheat (difference between bath and liquidus temperatures), thermal conductivity of the frozen deposit (mainly related to the bulk composition of the freeze lining), convective heat-transfer coefficient (a function of fluid flow in the bath), and cooling capacity of the wall (geometry of the cooling medium, input temperature, and flow rate of the coolant). 13,15,31,[33][34][35][36][37] Recent experimental studies [49][50][51][52][53][54]57,58 under carefully controlled conditions in a diverse range of systems and process conditions, including hightemperature melts and aqueous solutions, have shown that the interface temperature can be between T liquidus and T solidus . The studies have shown that the key freeze-lining characteristics at steadystate conditions, including deposit thickness, temperature of the stagnant deposit interface, and heat transfer across the freeze lining, are all dependent on the dynamic equilibrium involving the deposition and removal of solids from the deposit.…”

Section: Implications For Modeling and Industrial Practicementioning

confidence: 99%

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Understanding Slag Freeze Linings

Fallah-Mehrjardi

Hayes

Jak

2014

JOM

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Slag freeze linings, the formation of protective deposit layers on the inner walls of furnaces and reactors, are increasingly used in industrial pyrometallurgical processes to ensure that furnace integrity is maintained in these aggressive, high-temperature environments. Most previous studies of freezelinings have analyzed the formation of slag deposits based solely on heat transfer considerations. These thermal models have assumed that the interface between the stationary frozen layer and the agitated molten bath at steady-state deposit thickness consists of the primary phase, which stays in contact with the bulk liquid at the liquidus temperature. Recent experimental studies, however, have clearly demonstrated that the temperature of the deposit/liquid bath interface can be lower than the liquidus temperature of the bulk liquid. A conceptual framework has been proposed to explain the observations and the factors influencing the microstructure and the temperature of the interface at steady-state conditions. The observations are consistent with a dynamic steady state that is a balance between (I) the rate of nucleation and growth of solids on detached crystals in a subliquidus layer as this fluid material moves toward the stagnant deposit interface and (II) the dissolution of these detached crystals as they are transported away from the interface by turbulent eddies. It is argued that the assumption that the interface temperature is the liquidus of the bulk material represents only a limiting condition, and that the interface temperature can be between T liquidus and T solidus depending on the process conditions and bath chemistry. These findings have implications for the modeling approach and boundary conditions required to accurately describe these systems. They also indicate the opportunity to integrate considerations of heat and mass flows with the selection of melt chemistries in the design of future high temperature industrial reactors.

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