The Application of Infrared Spectrophotometry to Analysis of Dehydration Process of Inorganic Hydroxides and Evaluation of Monolithic Refractories

Inorganic oxides are widely used as raw materials and formed as byproducts in iron and steelmaking processes. Some inorganic oxides such as CaO and MgO absorb water to form inorganic hydrates. When hydrates form, they expand. On the other hand, hydrates often dehydrate on heating to form oxides. To analyze hydrates in oxides is therefore important in order to examine hydration and dehydration processes.This paper concerns with the analysis of dehydration processes of Mg(OH)2, Ca(OH)2 and Al(OH)3 in which high temperature infrared spectrophotometry and thermogravimetry (TG) were used to elucidate the expansion behavior of monolithic refractories. Two monolithic refractories, which contained the same amount of MgO, were investigated with hydration. Mg(OH)2 was observed in the samples that expanded after pressed. No Mg(OH)2 was observed in the sample that did not expand after pressed. In addition, infrared spectrums give the amount of Mg(OH)2. Infrared spectrophotometry can be used for the quantitative analysis of the small amount of inorganic hydrates in oxides.