35 research outputs found
Wear Mechanisms of Carbon-Based Refractory Materials in Silicomanganese Tap Holes—Part I: Equilibrium Calculations and Slag and Refractory Characterization
Silicomanganese (SiMn) as an alloy supplies silicon and manganese to the steelmaking industry.
It is produced through carbothermic reduction in a submerged arc furnace. The slag and metal
are typically tapped through a single-level tap hole at 50 K (50 C) below the process temperature
of 1873 K to 1923 K (1600 C to 1650 C). In one tapblock refractory design configuration,
the tap hole is installed as a carbon tapblock and rebuilt during the life of the lining
using carbon-based cold ramming paste. The carbon tapblock lasts for a number of years and
ramming paste only for months. The purpose of the study presented here was to determine to
what extent chemical reactions between carbon-based refractory and slag or metal in the tap
hole of a SiMn furnace can contribute to wear of tap-hole refractory. The results of the study
are reported in two parts. In Part I, the results of thermodynamic calculations of the potential
for chemical reaction between carbon-based refractory material and slag or metal are reported.
The results were tested experimentally using pure graphite and synthetic SiMn slag (produced
from pure oxides). The paper also reports the composition, microstructure, and phases of
industrial SiMn slag, and commercially available carbon block and cold ramming paste
refractory materials. These compositions were used in predicted equilibria of refractory–slag
reactions. Thermodynamic calculations suggest that reaction between SiMn slag and carbonbased
tap-hole refractory is possible, and experiments with nominally pure materials support
this. However, practical refractory materials are by no means pure materials, and contain
secondary phases and porosity which can be expected to affect reaction with slag. Such reactions
are examined in Part II.National Research Foundation of South Africa (Grant TP2011070800005).http://link.springer.com/journal/116632016-04-30hb201
Thermal conductivity of solidified manganese- bearing slags-A preliminary investigation
Abstract -The thermal conductivity of slag is an important parameter in the design of furnace-containment systems based on freeze-lining technology. Literature indicates that the crystal content of a slag has a significant influence on its thermal conductivity. Industrial, rich, manganese-bearing slag was cooled at different rates to create samples with different microstructures. The coefficients of thermal conductivity of these samples were measured in a nitrogen atmosphere from room temperature to 990°C at 100°C intervals. The laser-flash measurement technique was used for this purpose. Follow-up investigations included XRF and XRD and modelling in FACTSage
Wear Mechanisms of Carbon-Based Refractory Materials in SiMn Tap-Holes—Part II: In Situ Observation of Chemical Reactions
The purpose of the study presented here is to determine to what extent chemical reactions
between carbon-based refractory and slag or metal in the tap-hole of a SiMn furnace can
contribute to wear of tap-hole refractory. The results of the study are reported in two parts. In
Part I, thermodynamic calculations suggested that reaction between silicomanganese slag and
carbon-based tap-hole refractory is possible, and experiments with nominally pure materials
support this. However, practical refractory materials are by no means pure materials and
contain secondary phases and porosity which can be expected to affect reaction with slag. In
Part II, such reactions are examined experimentally, in cup and wettability tests, using commercially
available carbon block and cold-ramming paste refractory materials and mainly
industrial SiMn slag. Clear evidence was found of chemical reaction at approximately 1870 K
(approximately 1600 C), forming SiC and, it appears, metal droplets. Both carbon block and
ramming paste refractory reacted with slag, with preferential attack on and penetration into the
binder phase rather than aggregate particles. The two types of carbon-based refractory materials
showed similar extents of chemical reaction observed as wetting and penetration in the laboratory
tests. The differences in refractory life observed practically in industrial furnaces should
therefore be attributed to wear mechanisms other than pure chemical wear as studied in this
work.National Research Foundation of South Africa (Grant TP2011070800005).http://link.springer.com/journal/116632016-04-30hb201
Passivation Threshold for the Oxidation of Liquid Silicon and Thermodynamic Non-equilibrium in the Gas Phase
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