Mechanical Research Of The Semi-crystalline Calcium Silicate Separation And Moleculer Migration In Mesoscopic Flow

With the development of mineral and coal mining industry,different kinds of semi-calcium silicates have been synthesized.The crystalline state and structure will be affected by the extract process of silicate resource and reaction process of calcium silicate.Then the filtration process will be changed.We track the filtration with three different levels: macroscopic level,mesoscopic level for filter cake and molecular level for crystalline state.Combined with the migration theory and simulation method,the dewatering theory can be researched,thus the thesis has significant meaning.Due to the special structure of the high aluminum fly ash,which have the basic structures of mullite and corundum with the amorphous silicate on the surface,the two temperature steps of desilicate process has been proposed with making full use of the industrial waste heat.This process can increase the ratio of aluminum and silicate from 1.92 to 2.51.The desilication fly ash suspension is difficult to be filtered because the filter cake is tight and hard.The results can be shown like this,when the addition of cetyltrimethylammonium is 0.6‰,the filtration flux can be increased twice and the moisture content of the filter cake can be decreased by 13%.The filtration efficiency has been improved by the theory of division and capillary action.Then the silicate can be used to produce silicate calcium with different crystalline degree.The reaction process has been tracked and a model has be set up to describe the crystallize process for the crystal whisker.Then the aluminum has been added into the reaction and works as the Nucleation promoter.The highest crystalline degree is aournd 95% with the promoter.The filtration properties of the semi-silicate calcium are quite different.We track the filtration with three different levels: macroscopic level,mesoscopic level and molecular level and find that the semi-silicate calcium has the best filtration properties.At this time,the filtration process has relationship with the molecular structure,interlayer water,the specific area and the water state.According to the above results,we find that the mesoscopic level can be treated as the bridge between the macro problems and the micro problems,and can be used to solve the molucaler flow problems in the porous medium.The mesoscopic flow field is quite different with the normal flow field,due the the effect of capillarity,the force between the molurclue,and the surface tensor.Thus,the research points out the rule of the molecule migration in the mesoscopic flow field.A new dimensionless parameter has been defined in the work and was named as gradient number Gr,which describe the relationship between molecule size and the velocity gradient.Based on the two fluid theory and dilute fluid theory,we use the perturbation method and Taylor expansion to get the mass transfor eqution,mometum eqution and constitutive eqution.And then we get the stress tensor and concentration results with lower Wi,Pe and Gr.In the Taylor Votex flow,we compare these results with Brownian Dynamic simulation research,and get a good agreement.Perturbation method can be used when Gr is lower than 0.208,Wi is lower than 0.012 and Pe is lower than 10.Finally,we compare two mesoscopic simulation methods: Brownian Dynamic method and Stocastic Rotation Dynamic method in the micro orifice flow field with electricity.When the Peclet number is lower than 500 and the h* is lower than 0.6,BD silumation is the best choice,or not the SRD which is much more expensive for calculation time can be used.The research provides the synthesis method for calcium silicate and theory for filtration process.The perturbation method for molecular migration can be used as a rule to get the fluid flow state.The work has significant meaning for the filtration process for silicate and particle routes in the flow field.