발간논문

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Wu¨stite pellets were reduced to iron in H₂, CO, and CO·CO₂mixture under a total pressure of 765 mmHg at temperatures ranging from 650℃ to 1,050℃. The reduction rates were calculated by the decrease in weight of samples during reaction. The diffusion rates of iron through wu¨stite layer were observed by means of microscopic examination as well as chemical analysis. Relationship between solid state diffusion and overall reduction rates was examined to find out the rate controlling step. The mechanism and kinetics are discussed and activation energy are also calculated.

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To compare Brinell Hardness of irradiated rolled copper plate with unirradiated one, the copper plate is annealed for two hours at 150℃, 200℃, 350℃, 450℃, 600℃, and 800℃ respectively and irradiated in Reactor with total thermal neutron flux 7×10^(17) nvt and fast neutron flux 2.3×10^(17) nvt. Copper plate which was annealed above recrystallization temperature increase its hardness when irradiated with neutron. The increasing hardness ratio of irradiated copper plate which was annealed above 450℃ is, 6%, while annealed under recrystallization temperature shows softening. Such characters are explained by formation of defects and elimination of stress field by forming thermal spike in crystal structure. And by annealing for two hours above 200℃, the defects which cause radiation hardening are fully recovered.

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Pressure leaching of scheelite floatation tailings containing 6.55% of WO₃was done under various conditions. To obtain more than 90% extraction, four equivalents of soda ash as decomposer and two hours leaching at 190℃ was necessary. Soda ash was the best decomposing agent and the addition of caustic soda was effective to shorten the leaching time. Effect of pulp concentration and pH was briefly examined.

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The Sangdong Tungsten mine in Korea produces molybdenite and bismuthinite as by products. The flotation of the above minerals has been carried out after differential oxidation of bismuthinite and molybdenite surfaces by primary roasting, though there is no theoretical view points to the above process. In this experiment, the oxidation degrees of the ore surfaces were measured at the various temperatures by thermobalance, and the flotation was carried out with the samples which were roasted at the different conditions. During the roasting molybdenite surface was also oxidized as much as bismuthinite at low temperature. The flotation recovery of the molybdenite which was roasted above 250℃ was rapidly decreased. It seems to be difficult to say that depression of bismuthinite was caused by differential surface oxidation.

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The differenetial flotation test was carried out to the ore from Jeh-Sam-Uk mine which composed of mainly copper, lead, zinc, and iron sulfides and fluorite. The best results were obtained when copper and lead sulfides were floated prior to iron sulfide and fluorite being recovered in the scavenging. Flotation collectors used in the tests were xanthates for sulfides and oleic acid for fluorite collection. At a reasonable point of concentration, the grade of concentrates were 60.1% Pb of lead concentrate, 12.1% Cu of copper concentrate and 97.91% CaF₂of fluorite concentrate with recoveries of more than 80% in the lead and fluorite concentrates.

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For the combustion of slack Korean anthracite, the fluidization method is best suited with no requirement for briquetting or pulverization. Outstanding difficulties arising from low combustion reactivities, unreasonably high combustibles in the ash, and the stack loss by the carry over and the nuisance due to fly ash have being eliminated by preheating the combustion air and slack coal, modification of the furnace and removal of the ash through clinker formation. This method will probably solve the gasification problem of the Korean anthracite powders through further development work.

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The mineral characteristics of the three locals were similar and mainly composed of copper, lead, zinc, and iron sulfides. In order to facilitate treatment, the ores from the three locals were equally admined and flotation tests were performed. The best separation was achieved when copper and lead sulfides ware floated prior to zinc and iron sulfides. Iron sulfides were recovered in the scavenging. Flotation collectors used in the copper and lead circuit were Minerec B and Potassium ethyl xanthate, and amyl xanthate for zinc and iron sulfides. At a reasonable point of concentration the chemical analysis of the concentrates showed 23.3% Cu of copper concentrate, 68.7% Pb of lead concentrate, and, 47.8% Zn of zinc concentrates, with recoveries of about 70 to 80% in the copper, and, zinc concentrates.

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The artistic color texture of the Korean celadon is obtained by uniform reduction of 2-3% Fe₂O₃to FeO contained in the body and glaze material with strong and continuous reducing flame produced by the fire wood. Motley brown colors were evolved during unsuccessful firing from vagrance between oxidizing and reduction flame through the formation of color compounds with Fe₂O₃, Fe₃O₄and FeO color layers rather than from excessive reduction or concentration of the iron oxides in the raw material. Strong reducing flame obtained from the gasification combustion furnace using the Korean anthracite as the fuel served for the same purpose of satisfactory reduction of Fe₂O₃to FeO producing excellent celadon color.

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