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Kinetics and mechanistic analysis of caustic magnesia hydration
Author(s) -
Rocha Sônia DF,
Mansur Marcelo B,
Ciminelli Virgínia ST
Publication year - 2004
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.1038
Subject(s) - magnesium , dissolution , slurry , particle size , precipitation , activation energy , particle (ecology) , kinetics , chemical engineering , materials science , chemistry , mineralogy , inorganic chemistry , metallurgy , composite material , geology , physics , oceanography , quantum mechanics , meteorology , engineering
The kinetics of magnesia hydration to produce magnesium hydroxide is crucial for process design and control, and for the production of an Mg(OH) 2 powder with desirable particle morphology. In this study, highly pure magnesia has been hydrated in a batch reactor. The effects of the following variables were evaluated experimentally: temperature (308–363 K), reaction time (0.5–5 h), initial slurry density (1–25%wt) and particle size in the ranges −212 + 75 µm and −45 + 38 µm. Experimental data indicate increasing magnesia hydration rates with increasing temperature, as expected. In addition, it has been observed that the hydration of magnesia increases significantly up to about 4–5%wt initial slurry density, stabilising afterwards. On the other hand, the reaction was almost unaffected when magnesia with different particle sizes were hydrated because of similar specific surface areas involved. A reaction mechanism to explain the oxide dissolution and the hydroxide precipitation has been proposed, assuming no significant change in the initial solids size and dissolution rate as the controlling step. The calculated activation energy value of 62.3 kJ mol −1 corroborates the mechanism proposed in this study and compares well with values previously reported in the literature. Copyright © 2004 Society of Chemical Industry