METHOD OF PURIFICATION OF NATURAL GRAPHITE Russian patent published in 1999 - IPC

FIELD: preparation of construction materials in atomic power engineering and heat technology. SUBSTANCE: natural graphite is mixed with aqueous alkali solution, e.g. 40- 80% NaOH solution, sintered in furnace under stirring at 850 C for 3 hours. Product is placed into pulsation column. Dilute acid, e. g. 5.0-7.0% HNO₃, is fed upwards at rate of 1.7-3.0 m/h. Specific acid consumption is 5 1/kg of graphite. Pulse frequency is 25-35 pulses per minute. On completion of acid washing, graphite is washed with water in the same pulsating mode. Precipitate is separated on nutch filter, dried at 200 C. Graphite ash content is reduced from 7% to 0.04-0.48. Process power capacity becomes lower. EFFECT: more efficient purification method. 5 cl, 1 ex, 1 tbl