Study On Hydration Preparation Of Fire-retardant Level Magnesium Hydrate

Aiming at the existing state of magnesite resource, market potentiality and main problems exist in preparation of fire-retardant level Mg(0H)2, the subject has studied systematically hydration preparation of Mg(0H)2, discovered the causes of low purity of Mg(0H)₂, long reaction time, and size of hard control by studying synthesis mechanism of preparing Mg(OH)₂ via hydration, and then achieved the improved method.Optimum calcined conditions are determined through calcined condition tests: calcined temperature of 600℃, calcined time of 10 hours. On this condition, the resolution ratio of magnesite can get to 99%, and the achieved MgO is with good chemical activity, the adsorption to chloride ion is 36mol/kg, and hydrated reaction is prompt.By means of single factor tests under atmospheric pressure, optimum conditions of synthesis of fire-retardant level Mg(OH)₂ via hydration preparation are obtained as following: size of MgO is -200 mesh, hydration time is 4 hours, ratio of liquid to solid is 40:1, hydration temperature is 70℃, stirring speed of High Shearing Emulsor is 3200 r/min, and the consumption of mixed surfactant(titanate ester resin acceptor of 1g + polyethylene glycol of 0.5g + absolute ethyl alcohol of 10ml + carbon tetrachloride of 5ml) is 3%. In the products of grain and homogeneous size(d5o-2.8um) synthesized under above conditions, the purity of Mg(OH)₂ reaches 98%, the specific surface area is 18 m²/g, the gumming is higher, and the product qualifications almost meet the standard of fire-retardant level.Based research on preparation mechanism of Mg(OH)₂ via hydration method, the subject has found that it can accelerate reaction by increasing the activity of MgO to decrease the activation energy of hydrated reaction, and heightening hydrated reaction temperature or enlarging stirring speed to promote molecular energy. In the crystallization process of Mg(OH)₂, inhomogeneous nucleation mainly occurs, which lead to low purity and non-uniform size, but the influence of inhomogeneous nucleation can be reduced by introducing surface modifier or using High Shearing Emulsor.Taking use of magnesite as material, the subject has synthesized fire-retardant level...