Tadao Ishikawa

Production of High Purity Artificial Graphite

The most effective treatment to remove V from raw coke was to treat the coke with 5% of NH4Cl and heat at 2000 deg C for 3 hr. A graphitization furnace was used to attain the temperature of 2000 deg C. Satisfactory results were also obtained by the same purification and graphitization process by adding the necessary amount of NH4Cl or NaCl to the raw mixture. For molded graphite products, impregnation with saturated soiutions ofNH4Cl or NaCl and treatment with Cl2 during heating were tried. The methods were also applicable to the purification of graphite of low purity. The degree of graphitization of purified graphite was slightiy higher than that of unpurified graphite. The elimination of B from graphite must be attained in order for it to meet the requirement for use in atomic reactors. It was shown that the treatment of graphite with Cl2 containing HF mist at 2000 deg C for 3 hr is effective for the purpose of decreasing B content to less than 1 ppm. The formation of (CF)n must be avoided by use of the Cl2-HF mixture at high temperature, because (CF)n is formed below 700 deg C. (H.H.D.)

黒鉛電極に関する研究 (第4報):硫酸塩水溶液電解においての人造黒鉛陽極の膨潤および崩潰について

We have investigated on a rapid method of estimating the life of anode graphite at the amalgam process chlorine-caustic cell, by electrolysis of sodium sulphate solution and by electrolysis of sodium chloride solution containing sulphate.This method is based on our researches about the mechanism of corrosion of anode graphite described in the previous papers.That is to say, the corrosion in electrolysis of sodium sulphate solution under conditions of above 40°C, acidity of below 1N, and anode current density of above 5amp/dm2, and that at the amalgam process chlorine-caustic cell were of just the same mechanism, namely, the pure chemical oxidation consumption from surface of graphite crystal.The following methods were found preferable:(1) The sodium sulphate solution electrolysis method for the domestic anode graphite:The corrosion rates in mg/Ah unit of anode graphites treated for 3 hours under electrolytic conditions of sulphate concentration of Na2SO4·10H2O 100g/l, 60°C, anode current density of 10amp/dm2 are compared with each other.This method was found to be better than the other method for the domestic anode graphite.(2) The rapid method, combining electrolysis of sodium sulphate solution with electrolysis of sodium chloride solution containing sulphate, for domestic and A chesons anode graphites:The anode graphites were treated preliminarily by the above-mentioned sulphate solution electrolysis, and then treated intermediately for 2 hours under conditions of 60°C, acidity of pH 2 to 3, and anodic current density of 50amp/dm2 with sodium chloride solution of concentration of NaCl 260g/l contained sulphate of Na2SO4 25g is one liter of brine.In the last formal electrolysis, the samples are treated for 4 hours under the same condition as intermediate treatment, and the corrosion rates which were measured as difference of weight in this formal electrolysis are compared with each other.This method resulted in the best coincidence with the order obtained in long time test by amalgam process chlorine-caustic cell as for the domestic and Achesons anode graphites.

Studies on the Graphite Electrode, 1

The degree of graphitization of artificial graphites was estimated by the anodic swelling in electrolysis of sulphuric acid and Brodies wet-oxidation. Moreover, the mechanism of the corrosion of graphite was discussed.The results obtained are as follows;1. Swelling test:Swelled graphite by anodic treatment with sulphuric acid evolved oxygen when it was digested in alkaline solution, and the volume of oxygen suggested the degree of graphitization.2. Wet-oxidation test:Generally, lower graphitized carbon (amorphous carbon) consumed more than higer one (graphite).In artificial graphite, however, contrary to our expectations, higher graphitized graphite consumed more than lower one.The above facts availed for the estimation of the degree of graphitization.