Thermal purification of natural graphite by means of high-speed heating

Abstract

The thermal method for the cleaning of carbon materials in an electrothermal fluidized bed belongs to the «green» technologies for producing graphite for the manufacture of anodes of lithium-ion batteries. The technology involves a rapid heating of the feedstock particles to the specified processing temperatures. The aim of the work was to simulate the thermal cleaning of carbon materials in electrothermal fluidized bed and choose such modes for the treatment of natural graphite that will ensure carbon content in the finished product of at least 99.95%. To achieve the goal, a 5 kW laboratory resistive furnace was developed. While processing carbon samples weighing up to 30 g, the reactor simulates the operating conditions that arise during fast heating to 3000°C in a fluidized bed in an inert gas atmosphere. A typical multistage purification cycle in laboratory conditions included the heating of the material during 0.5-1 min and holding it at a constant temperature for 5-15 min. The production mode was controlled based on the dependences of the operating temperature on the power consumption obtained by the «witness» method. The laboratory study of the thermal purification of natural graphite from the Zavallevsky deposit was carried out. The composition of the processed samples was determined by elemental analysis using a spectrometer and by measuring the ash after combustion of the samples. As a result of the study, acceptable parameters of the operating modes were determined, in particular, the temperature of 2900-3100°C and the processing time of 15 min, which ensure the manufacture of high-quality product with a carbon content of at least 99.95%.