Extractive Metallurgy Division - Control of Oxygen in Copper During Refining (TN)

FOR many years basic control of refinery operations depended on visual observation of small chill specimens poured at various intervals during processing. The oseto of these samples was related to the physical and chemical properties of the metal. Since the =setn is dependent on many factors other than oxygen content, this method, while giving a general indication of the condition of the copper, does not accurately measure the oxygen content. For the last 3 years a modified vacuum fusion procedure which enables the operator to determine the oxygen content of the copper within 1 5 min of sampling has been in use at the Westinghouse Copper Mill. For use with this apparatus a sampling technique has been developed which gives oxygen values representative of the oxygen content of the wire bar. The sampling technique is based on a statistical study, which compared the oxygen content of the laboratory sample of copper poured at the same time a wire bar was being poured, with the oxygen content of the wire bar. The apparatus used for the determination of oxygen in copper is shown in Fig. 1 and is essentially the same as previously described but with one important modification. A very porous fritted glass disc has been inserted in the tubing between the manom- eter and 40/50 ground glass joint. The fritted disc retains the copper vapor and copper particles in the furnace section and prevents contamination of the mercury in the manometer. Without the disc the manometer became difficult to read after a few weeks of operation. In earlier work1 it had been established that the simplified vacuum fusion apparatus used at the Copper Mill gave essentially the same results as a con-vential vacuum fusion apparatus. However, for this study it was necessary to determine the difference, if any, between the oxygen content of the wire bar and the oxygen content of the small chill sample used for the oxygen analysis. This correlation was established by taking a chill sample at the same time wire bars were being poured. The wire bar being poured at the time the chill sample was taken was marked and removed for further analysis. The copper is sampled at various times during refining and cast into laboratory size samples with the mold shown in Fig. 2. The mold is made of cold rolled steel and is 2 in. high and 2 1/2 in. in diam. The large upper portion of the cast sample is used for measurement of the conductivity of the copper, The lower portion which is a rod about 1/4 in. diam by 3/4 in. long is used for determination of the oxygen content. This portion of the sample weighs about 5 g which is approximately the size sample used for the analysis. The only preparation neces-