Study on the Quenching Hydration of Calcined Hydromagnesite and the Dissolving Properties of the Hydrated Products

The hydration of magnesium-bearing minerals following calcination is a critical step in the manufacturing of magnesium hydroxide. However, the sensible heat of calcined minerals is not adequately exploited in the traditional procedure. It is worth investigating the hydration of hot calcined minerals directly, i.e., by quenching hydration, especially in hydration agent solutions. In this paper, calcined hydromagnesite was subjected to a series of quenching hydration experiments in a glycine solution. Several kinetic models were employed to describe the hydration process. The samples were characterized by XRD, SEM, and a laser diffraction analyzer. A pH-stat method was employed to determine the dissolution property of the hydrated products. The study found that quenching treatment had a pronounced positive effect on the hydration degree at 25°C, but that this effect diminished with increasing temperature. Chemical reactions govern the hydration of calcined hydromagnesite, with the quenching item having a lower activation energy than the control. The characterization results highlight the effect of quenching treatment at low temperature on the formation of hydrated Mg(OH)₂ with poor crystallinity and irregular morphology, which in turn promotes the dissolution property. At pH 6.5, 97% of the quenching hydration product obtained at 25°C dissolved within 150 min.