Process for purifying natural graphite by using alkali-acid method

The invention relates to a process for purifying natural graphite by using an alkali-acid method. The process comprises the following steps: 1. mixing natural graphite or microcrystalline graphite with a NaOH solution, and stirring to form a mixture; 2, feeding the mixture into a rotary heating cylinder of an alkali melting furnace by means of a feeding mechanism; 3, calcining the mixture by usingthe heating cylinder, wherein the heating cylinder comprises a nickel plate lining and a plurality of nickel plate lifting boards, the heating way of the calcination is direct heating or indirect heating, the temperature is maintained to be 300-500 DEG C, the time is 20-60min; during calcinations, enabling the heating cylinder to rotate along a longitudinal center line, and continuously raising the mixture by using all the nickel plate lifting boards so as to enable the mixture to be in a suspending state; maintaining the interior of the heating cylinder to be in a reducing atmosphere and under a micro-positive press