Study On Cordierite Plate Ceramic Membrane Microbubble Generator

The bubble generator is a key component of the flotation column,which directly affects the size and number density of the bubbles,thus affecting the flotation efficiency.At present,the conventional bubble generator has the disadvantages that the micropores are easy to block,the foaming is uneven,the operation process is complicated,and the energy consumption is high,which once limits the development of the bubble generator.The use of porous ceramic membrane foaming is not only simple in operation,low in energy consumption,but also its large specific surface area is favorable for the generation of a large number of microbubbles.Cordierite is a kind of porous ceramic membrane preparation material with excellent performance because of its low raw material price,good corrosion resistance,large specific surface area and high mechanical strength.Therefore,this paper prepares a new type of ceramic membrane bubble generator with excellent comprehensive performance by using cheap industrial grade cordierite powder as raw material and adopting"step-by-step preparation,integral assembly and primary sintering".By changing the structure of the bubble generator,the problem of uneven foaming and easy clogging of micropores is alleviated to some extent.The preparation parameters of the green body,the assembly method of the bubble generator,the pore former?type/content/particle size?,sintering temperature,holding time and operating conditions were discussed.The cross-sectional morphology,phase composition,pore structure,pore size distribution and bubble size distribution of the bubble generator were characterized by XRD,SEM,mercury intrusion testing and digital microscopy.The specific research work is as follows:?1?Exploring the influence of preparation conditions such as molding process,joint assembly scheme,pore former and sintering process on the performance of the foamer.The single factor experiment results of molding conditions such as water addition and drying time indicate that when the water addition amount is 40%,the drying temperature is 100?,the drying time is 12 h,and the mold release is performed at 2-3 hours of drying,a structurally intact green component can be obtained.By comparing the three assembly schemes,it was found that the green component was separately prepared,and then bonded and assembled by the ceramic slurry,and finally,the overall sintering method was used to obtain a bubble generator with excellent performance and good airtightness.Comparing the comprehensive performance of bubble generators withdifferent types and contents of pore formers,the results show that adding carbon powder is prone to incomplete combustion;adding starch,a large number of closed pores are easily formed inside the sample;and PS microspheres are added and a uniform microporous structure can be formed inside the material when the addition amount is 10%.The bubble size is small and the bubble number density is high.The mechanical properties and foaming properties of bubble generatorsprepared at different sintering temperatures and holding times were investigated.The results show that the sintering temperature has a significant effect on the crystal phase structure of the material.With the increase of sintering temperature,the diffraction peak of the cordierite phase first increases and then decreases and reaches the maximum at 1300?.Increasing the sintering temperature and extending the holding time can increase the mechanical strength of the material,but at the same time reduce the number of micropores inside the material,resulting in a decrease in the number of microbubbles.When the sintering temperature is 1300?and the holding time is 1 h,the comprehensive performance of bubble generation is optimal.?2?The effect of single particle size and composite particle size PS microspheres on the performance of bubble generator was studied,and the influence mechanism of two particle size types of pore former on the opening rate of bubble generator was investigated.The results show that the sample with single particle size PS microspheres increases the porosity of the material with the increase of the pore size of the pore former.However,when the particle size of the PS microsphere exceeds 10?m,more large pores appear inside the material.As a result,the compressive strength and the alkali corrosion resistance of the material are greatly reduced,the average diameter of the generated bubbles is increased,and the uniformity of the bubble distribution is deteriorated.The inside of the composite particle size PS microsphere sample was added,and more microscopic pores were distributed on the pore edge.These microscopic pores were the main reason for the porosity of the material being higher than that of the single particle size PS microsphere sample.In addition,the air permeation rate of the composite particle size PS microsphere sample is also increased,and the material is less resistant to foaming during foaming,so that the foaming performance is better.However,as the particle size of the composite PS microspheres increases,the compressive strength of the sample decreases,the alkali corrosion resistance deteriorates,the pore size distribution becomes wider,the average size of the microbubbles becomes larger,and the distribution uniformity deteriorates.When PS microspheres with a particle size of 5/10?m were added,the open porosity of the sample was 54.87%,the air permeation rate was 8.43 m³·h^-1·Pa^-1·m^-2,and the compressive strength was 8.05 MPa.The alkali corrosion resistance rate is 99.95%,and at this time,the pore distribution inside the material is uniform,the pore diameter is small,the average bubble size is small,and the comprehensive performance of the bubble generator is best.?3?The effects of three operating conditions on the size and number density of bubbles generated by the bubble generator were studied.The results show that with the increase of pressure difference,the average particle size of bubbles decreases and the density of bubbles increases.With the increase of gas-liquid ratio,the average particle size of bubbles increases,and the density of bubbles increases.As the volume increases,the average particle size decreases,and the bubble number density also decreases.When the pressure difference is between 0.02 MPa and 0.06 Mpa,the gas-liquid ratio is between 1:2 and 1:4,and the flow rate is between 0.6 m³/h and 1.0m³/h the bubble of the cordierite ceramic membrane occurs.The average bubble diameter produced by the device is between 23.54?m and 36.43?m,and the bubble number density is between 1.93×10³ and 1.97×10⁴ counts per mm³,which can meet the requirements of air flotation.