| At present,there are many methods and methods for preparing ultrafine magnesium hydroxide powder,but there are still serious particle agglomeration,poor distribution,and more stay in the small test stage,rarely can conduct pilot research and industrial production,aimed at This situation,impinging stream technology is an important flow form in industrial applications.Its strong micro-mixing,high transfer coefficient,and effectively providing supersaturated state greatly shorten the mixing time.This is the preparation of ultrafine powder in the chemical industry Very large application prospects.In this paper,the self-designed impinging stream pilot and pilot units are used to prepare magnesium hydroxide ultrafine powders by immersion conditions,using magnesium chloride and sodium hydroxide as raw materials,and liquid phase precipitation.Taking the particle size of the experimental powder as the characterization index,using single factor and response surface test,the influence of different factors on the particle size was analyzed.The single factor test was used to examine the effects of concentration,flow rate,cyclic impact flow rate,cyclic impact time,temperature and stirring on the particle size of the magnesium hydroxide ultrafine powder.and found that magnesium chloride concentration,magnesium chloride / sodium hydroxide Flow rate and cyclic impact time have a greater impact on the particle size of the powder,and temperature,cyclic impact flow rate and stirring time have no significant effect on the particle size.When the cyclic impact flow rate is 600 L /h,the minimum particle size of magnesium hydroxide powder is 1.28 ?m;Takeing a response surface test to obtain the fitting function about the particle size,the interaction between different factors,the degree of influence on the particle size of the powder and the optimal parameter conditions according to the analysis results of the single factor.The normal probability distribution of the residuals is obviously linear,without abnormal data points,the residuals and the predicted values of the equations,the distribution is scattered,which proves that the model is reasonable and the function fit is high;the interaction relationship of magnesium chloride concentration,magnesium chloride/sodium hydroxide flow rate and cycle impact time Obviously;the three have a greater influence on the particle size of the powder,of which the cyclic impact time has the greatest influence on the particle size of the magnesium hydroxide powder,followed by the magnesium chloride concentration,and the smallest influence on the flow rate of magnesium chloride / sodium hydroxide;The concentration of magnesium chloride is 1.25 mol/L,the flow rate of magnesium chloride/sodium hydroxide is 300 L/h,and the cycle impact time is 60 min.Based on the single-factor test and response surface analysis to obtain the optimized process parameters for the preparation of ultrafine magnesium hydroxide powder,the magnesium chloride/sodium hydroxide flow rate was preliminarily enlarged to 1-3 times,and the magnesium hydroxide powder was prepared by the impact flow pilot plant In the body experiment,the minimum average particle size was measured to be 2.35 ?m.Compared with the traditional preparation method,under the same concentration of reactants,the minimum average particle size of magnesium hydroxide prepared by the stirred tank is 5.17 ?m,which is about 2.2 times the minimum average particle size of magnesium hydroxide prepared bythe pilot plant.It shows that the strong micro-mixing characteristics of impinging stream have great feasibility in the preparation of ultrafine powder.The powder was characterized by laser particle size analyzer,scanning electron microscope(SEM),X-ray diffraction(XRD),thermogravimetric analyzer(TG)and other measuring instruments.Strip shape,high purity,good thermal decomposition performance,no serious agglomeration and the quality is better than the traditional stirring kettle. |
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