2/10/2024 0 Comments Too casting copper cathodeIn the furnace, the copper sulphate becomes dehydrated and considerable quantities of it are blown out of the furnace, most of this being caught in the flues of the waste-heat boilers samples of flue dust collected beyond these boilers analyzed 16.5 per cent, of water-soluble sulphates. Crystallized copper sulphate can often be seen on the top edges, particularly around the loops of the cathodes, and even well washed cathodes will show from 0.002 to 0.004 per cent, of sulphur. The percentage of sulphates on the cathodes is variable, and depends on the care taken in washing the cathodes after removing them from the electrolytic tanks. The sulphur absorbed by copper during the melting period comes from two sources: (1) the sulphate left on the cathode sheets in the tank houses (2) the fuel. Sulphur has always been blamed by the furnace men as the reason why this refining process is necessary, yet the literature on the subject does not sufficiently emphasize how small a proportion of sulphur will ruin copper for practical purposes. ![]() While the copper first, cast will be good, as indicated by the set surface of the bars, it is impossible to hold it to the “tough pitch” condition, and long before the whole charge has been poured the copper will become “overpoled,”’ entailing numerous difficulties. Many experiments have been made to obviate the long periods of oxidation and subsequent reduction, with no success. Reduction period, otherwise known as “poling,” whereby the oxygen previously added is removed by covering the molten bath completely with coke or charcoal and introducing large poles of green wood this reduces the cuprous sub-oxide, bringing the copper to the “tough pitch” stage ready for casting.Oxidizing period-saturating the copper with cuprous sub-oxide and bringing the metal to the condition known as “set copper ” this is now done by blowing air into the molten bath of metal. ![]() Charging the cathodes into the furnace.The furnace operation, as now conducted, includes the following stages: Owing to the well known affinity of copper for sulphur, however, so much sulphur is absorbed by the copper during the operation that a long and expensive refining process is required to remove it, and the final product is inferior in purity and lower in electrical conductivity than the original cathode copper. The melting of cathode copper, usually containing 99.98+ per cent.
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