Study On Thermo-damage Mechanism Of SiC Porous Ceramics For High Temperature Filtration

Porous ceramic membrane filtration technology is the most widely recognized technology in the world for efficient removal of particulate matter in high-temperature gas.Porous ceramic is the core component of this technology to achieve gas-solid separation,and it is the key to the long-term stable operation of high-temperature filtration devices.Silicon carbide porous ceramic materials are considered to be one of the most promising materials in high-temperature flue gas filtration.However,when the material is used,it will be subjected to the frequent thermal shock of a reverse pulse dust cleaning airflow at a relatively low temperature,which will cause greater thermal stress in the material.Under the effect of thermal-mechanical coupling,the mechanical properties of the material will decline,which will affect the normal operation of the high-temperature flue gas dust removal device in severe cases.To this end,this paper selects typical silicon carbide porous ceramic materials and studies their damage from two aspects,experimental and numerical simulation.The thermal shock resistance of the oxidation-bonded silicon carbide porous ceramic material was studied by thermal shock experiments.The effects of temperature difference,number of thermal shocks,and cooling medium on the flexural strength and fracture toughness of the silicon carbide porous ceramic materials were investigated using the three-point flexural method and the single-side notched beam method.It is found that the oxidation-bonded silicon carbide porous ceramics have the typical thermal shock temperature difference-strength characteristics of porous ceramics,and the flexural strength decreases with the increase of the temperature difference.When the number of thermal shocks is small,the strength of the material decreases from fast to slow.In addition,the factors that affect the thermal shock resistance of the material during the thermal shock heat exchange process were studied,and it was found that materials with a smaller heat transfer coefficient exhibited better thermal shock resistance.Experiments have verified that prefabricating certain cracks can enhance the fracture toughness of the material.The thermal stress-temperature difference relationship formula is obtained by fitting experimental data,which is in good agreement with the theoretical calculation results,and it can be used as a reference method to predict the thermal stress of SiC porous ceramics under different thermal shock temperature differences.Aiming at the ceramic membrane filtration experimental device for high-temperature flue gas purification,a three-dimensional model was established,and the Fluent software was used to solve the governing equations to calculate the distribution characteristics of the filter's velocity field,pressure field and temperature field during steady-state filtration.The mechanism of ceramic membrane filter material damage caused by thermal-mechanical coupling during the non-steady-state pulsed dust cleaning process was explored,and the most vulnerable position of the ceramic membrane filter tube was determined.The research work in this paper can provide theoretical guidance for the material optimization,structural design and purification device design of ceramic membrane filter materials.