Research On The Key Technology Of Preparing Flame Retardant Magnesium Hydroxide By Hydrate Pyrolysis Method

Firstly,highly active magnesium oxide was prepared by dynamic pyrolysis.And then,using brine as raw materials prepared magnesium hydroxide.This process need not to add the precipitant and would not bring impurities compared with other preparation method.Also,the technical route was novel,the process was simpleand low cost and had industrial application of high promotion value.What's more,the pross was pollution-free and had high social and economic benefit.Thus,this was a production technology of broad prospects for development.The subject has studied hydration dynamics and crystallization kinetics of magnesium hydroxide,built mathematical model by coupling reactions,crystallization processes and provide the basis for controling process and designing mould.The effects of reaction temperature,reaction time,stirring rate and solid-liquid ratio on the hydration of magnesium oxide were investigated by means of single factor test to find the best hydration conditions.The experiment results showed that the optimal condition of magnesium oxide hydration as follows:temperature was 80?,time was 48 h,solid-liquid ratio of water and magnesium oxide is 20:1,the stirring rate is 600 r/min.The kinetics of magnesium oxide was studied in the same solid-liquid ratio and stirring rate and got the hydration curves of different temperature.Based on first-order reaction kinetics model,calculated that the reaction rate constants of 20?,40?,60?,80? were 0.1372,0.2943,0.6084 and 1.1848.Then accorded to the Arrhenius equation could calculat that the activity energy of magnesium oxide was about 30.94 KJ/mol which belonged to the chemical reaction speed control mechanism.The effects of the concentration of hydrated agent on magnesium hydroxide's crystalmorphology were studied and obtained that magnesium chloride as a hydrating agent can improve the hydration of magnesia at low temperature.The product was flaky in hydrothermal condition for the concentration of MgCl2 was less than 1.00 mol/L.The product was strip in hydrothermal condition for the concentration of MgCl2 was more than 1.50 mol/L.Flaky Mg(OH)2 can be producted at high temperature in hydrothermal condition for each concentration of MgCl2 and the product was regularly.The surface polarity and micro-stress of magnesium hydroxide crystals reduced and structure was more stable at high temperature which leaded to obvious changes in the macroscopic properties of the crystal,and reunion trended weakened.In this paper,crystallization kinetics of magnesium hydroxide was studied by moment method and obtained that the equations of nucleation rate and growth rate,then,built crystal Dynamics mathematical model.