Characterization and formation mechanism of clinkers and ring deposits in rotary kiln furnace during calcination of spodumene lithium ore

Abstract

The lithium extraction process from spodumene, which contains the highest lithium content among ores (3.73 wt% Li), begins with the calcination of α-spodumene in a rotary kiln (RK) to transform it into β-spodumene, from which lithium is more easily extracted using acid. However, during this calcination process, deposits, commonly called a ring, can form on the RK walls, reducing productivity. Clinkers also are formed during the calcination process. In the current study, the clinker and deposits formed during calcination were characterized to determine their formation mechanisms. The bulk analysis of raw material was carried out by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). Rietveld analysis of the XRD pattern was conducted to measure the amount of gangue minerals, the most abundant of which were muscovite and hornblende. The XRD pattern showed β-spodumene and quartz as crystalline phases. SEM-EDS analysis revealed that clinkers and deposits contained solid particles agglomerated as glass phases, formed through breakdown of muscovite and hornblende. The glass phases promoted the agglomeration of solid particles, resulting in the formation of clinkers and deposits, which can negatively impact the spodumene calcination process by reducing its efficiency. © 2025 Elsevier Ltd