The Synthesis Of Nanometer Alumina Hydrate And Alumina Particles By Rotating Bed With Helix Channels

Aluminum hydroxide,what is called alumina hydrate in industry,istypical sexes compound,Which has physics chemical properties of goodchemical stability , nonpoisonous and tasteless , unvolatilizing ,etc., sothere is extensive application in such aspects as chemistry , medicines ,plastics , refractory material and electronic product as catalyst ,fire-retardant pharmaceutical , abrasive and coating ,etc.. Nanometeractive aluminum hydroxide is one of nonhalid fire-retardant compositivematerials with three major functions of fire-retardant, eliminating smoke ,packing and there is no secondary pollution while burning.nano-pseudoboehmite is widely applied to such fields as the catalysis ,accurate ceramics , refractory material ,etc.because of its fine dissolvingand characteristic of sex change of gel. At present , there are many kindsof preparation for aluminum hydroxide ,which are inconvenient onindustrialization because of high costs and equipment expecting much.The carbonation method from sodium aluminates solution and carbondioxide waste gas in a Rotating Bed with Helix Channels,which canaccord with actual conditions in a aluminum mill,is the lowest cost ofcraft route.Rotating Bed with Helix Channels(RBHC)is a novelmass-transfer and reaction equipment with high-effective and intensifiedby centrifugal field. Special features of RBHC are small size, low profile,low weight, short contact time, great operation intensity and highervolumetric mass-transfer and reaction coefficient compared withconventional equipment. Synthesis of nano-meter particles by the RBHChigh-gravity reactive precipitation utilize high-gravity field much morethan gravity in earth, and the method can intensified mass-transfer andreaction process, and control efficiency chemical reaction andcrystallization process in molecular size. So nano-meter particles withsmaller size and uniform distribution could be achieved by thismethod.The dissertation has done some works as follows.The synthesis of nano-meter pseudoboehmite and aluminum hydroxideparticles was studied through experiments.Mechamism and technicalconditions of the synthesis of pseudoboehmite and aluminum hydroxidewas discussed. The influence of aging,adding surfacemodifier,concentration of reactant and ratio of gas/liquid flow rate andtemperature of carbonization on pseudoboehmite particle size in thepreparation was investigated. concentration of NaAlO2suspension,Rotational speed ,gas-liquid ratio and temperature oncarbonization reaction time were investigated systematically in theprocess of synthesis of aluminum hydroxide. Contrasive experimentsbetween Stirred Tank Reactor and RBHC High-gravity reactor wasperformed. The product was characterized by TEM and XRD.Theprepared particles are pseudoboehmite nano-fibers and spheric aluminumhydroxide particles with average diameter about 10nm. The ultra-fine alumina has a special use in such aspects as catalysis ,fire- retardant , sound insulation , insulating , meticulous pottery,therefore the preparation of the nanometer alumina particles is significant.The synthesis of nanometer γ-Al₂O₃ by calcining nanometerpseudoboehmite particles under certain temperature and nanometerα-Al2O3 by calcining aluminum hydroxide under the high temperature wasinvestigated in the disseration. The dissertation proposes a new method of preparation of nanosized-alumina hydrate and alumina. This method with low costs of rawmaterials, simple production technology , pollution-free and its productsare of good performance, So it has good ecnomic and environmentalbenefits,which puts forward a new direction for the development ofproduction of Al₂O₃ in our country.