Preparation Of Asymmetric Cordierite Ceramic Membrane And Its Application In Separation Of Soot

As a new type of filter material,porous ceramic membrane has many advantages,such as: high temperature resistance,chemical resistance,easy cleaning,strong anti-aging ability,strong anti-microbial ability,long service life,etc.It has wide application prospects in many fields such as industrial wastewater treatment,seawater desalination,air purification,energy engineering,chemical and petrochemical,and biomedicine.Compared with other filter materials,porous cordierite ceramic films have more excellent thermal stability and chemical resistance,so their advantages will be more obvious in high temperature soot treatment.The existing methods for preparing cordierite ceramic membranes are mainly solid-phase reaction methods,but the performance of the prepared samples is often not stable enough,thereby hindering its widespread use in filter materials.In view of the above situation,in order to promote the application and research of cordierite ceramic membranes,the research topic is the preparation of asymmetric cordierite ceramic membranes and their application in the separation of soot.In this paper,we first synthesized cordierite granules with cordierite,and prepared the cordierite ceramic support with excellent performance through extrusion molding and sintering.The effect of the amount of reactants,the calcining temperature and the particle size of raw cordierite on the properties of the support were studied.Then,a phosphate-bonded cordierite is used to prepare a support with excellent properties by press molding and sintering.The influences of the amount of reactants,firing temperature and the particle size of raw cordierite on the properties of the support were systematically studied.Then,a stable slurry is prepared and an asymmetric cordierite ceramic film with better performance is prepared by dipping and pulling.On the one hand,the effects of the type of dispersant,the amount of dispersant and the solid content on the properties of the slurry were studied.On the other hand,the effect of the pore size and the number of layers of the support on the properties of the ceramic membrane was systematically studied.Finally,a membrane test device was prepared and the working performance of the membrane was studied.The main research content is as follows:(1)Preparation of Full Cordierite Ceramic SupportsCordierite powder and alumina powder,silica powder and magnesia powder were used as the main raw materials.Cordierite ceramic supports were prepared by extrusion molding and high temperature sintering.The influences of the amount of reactants,the firing temperature and the particle size of raw cordierite on the flexural strength,open porosity,pore size and distribution,and microstructure of the support were analyzed.The results show that with the decrease of the amount of reactants,the flexural strength of the prepared support first increases and remains basically unchanged,the opening rate first decreases,then remains basically unchanged,the pore size first increases and then decreases,the pores continuously becomes smaller and narrower.With the increase of sintering temperature,the flexural strength of the support gradually increases,and the open porosity gradually decreases.As the particle size of the raw cordierite increases,the pore diameter and the open porosity of the support gradually increase.Among them,V1 showed excellent performance at 1350°C,and its flexural strength,open porosity and pore size were 37.1 MPa,33.1%,and 1.79 μm.However,the porosity of V1 is still low,because the sintering temperature range of cordierite is narrow,there is no cordierite formation at low temperature,and the glass phase is formed after the temperature is raised,resulting in a decrease in porosity.Therefore,phosphate-bonded cordierite is used to reduce the firing temperature.(2)Preparation of phosphate bonded cordierite ceramic supportIn this paper,cordierite ceramic supports were prepared using a combination of aluminum phosphate and zirconium phosphate combined with cordierite.Cordierite powder and metal oxides,phosphoric acid as the main raw material,using pressure molding and high-temperature sintering method to prepare the supports.The influences of the amount of reactants,the firing temperature and the particle size of raw cordierite on the flexural strength,open porosity,pore size and distribution,surface and cross-section structure of the support were analyzed.The results show that with the decrease of the amount of reactants,the flexural strength of the support gradually decreases,the open porosity increases gradually,the pore size first increases and then decreases;with the increase of the firing temperature,the support collapses.The strength gradually increases,the hole opening rate gradually decreases,and the hole diameter first decreases and then increases;With the increase of the particle size of the raw cordierite,the flexural strength of the support gradually decreases,the open porosity increases gradually,and the pore diameter gradually increases.Among them,P2 shows excellent performance at 1100°C,and its mechanical strength,open porosity and pore size are 4.73 MPa,42.5% and 16.2 μm.(3)Preparation of membranesAsymmetric cordierite ceramic membranes were prepared by zirconium phosphate combined with cordierite by dipping and high temperature firing.The effects of the type of dispersant,the amount of dispersant and the solid content on the viscosity and settling properties of the slurry were analyzed.The effects of the support pore size and the number of membrane layers on the spalling strength,pore size and distribution,film thickness,surface and cross-sectional structure of the ceramic membrane were studied.The results showed that the dispersibility of sodium polyacrylate was the best.With the increase of the amount of dispersant,the stability of the slurry became better first and then became worse.With the increase of solid content,the stability of the ceramic slurry became better and worse.The dispersant was sodium polyacrylate,the amount of sodium polyacrylate was 1.5%,and the slurry had the best stability when the solid content was 15%.With the increase of the pore diameter of the support,the peeling resistance of the cordierite ceramic film becomes worse,the pore diameter becomes larger,the film thickness becomes larger,and the surface pores become larger;With the increase of the number of film layers,the pore diameter of cordierite ceramic film becomes larger,the pore size distribution gradually disperses and discontinuous holes may appear,the film thickness becomes larger,the surface pores become larger,and the number of surface pores decreases.(4)Preliminary study of membrane applicationMembrane test equipment was built to analyze the performance of membranes with different layers and pore sizes.The results show that with the increase of the number of membrane layers,the dust filtration efficiency becomes higher,the number of thermal shock resistance cycles increases,and the pressure loss rate increases.The double-layer membrane has high dust filtration efficiency,high pressure loss rate,and good thermal shock resistance.With the increase of membrane pore size,the dust filtration efficiency and pressure loss rate decrease.As the pore size distribution of the membrane becomes narrower,the number of thermal shock cycles increases;The membrane has no selective filtering effect on the gas.