陶瓷膜过滤器内流场及热致损毁机理模拟分析

Simulation analysis of flow field and thermally induced damage mechanism in ceramic membrane filter

高温气体净化用陶瓷膜的热稳定性是陶瓷膜过滤器能否长期稳定运行的关键。基于标准k-ε湍流模型和多孔介质模型,对陶瓷膜过滤器内的气体流动进行了数值模拟,研究了稳态过滤阶段装置内气体速度场、压强场及温度场的分布特点,对比了非稳态脉冲清灰前后装置内的温度场变化,定量分析了脉冲清灰阶段热力耦合致陶瓷过滤材料损毁的机理。结果表明,模拟所建立的模型能较真实地反映气体在烟气过滤及脉冲清灰过程中的场分布特点。在稳态过滤阶段,气体在进/出气管处流速较高,在净气室和含尘室内流速较低,滤管内气体流速沿管体轴向向上逐渐增大,而气体压强逐渐减小,过滤器温度不随位置改变而变化。在非稳态脉冲清灰阶段,反吹入口附近的气体温度场形成低温区,在管轴向剖面上呈近椭圆形分布,沿轴向向下管内壁温度先降低后回升,而管内气体温度逐渐增大,含尘室内的温度几乎不变。在距离陶瓷膜过滤管顶部0.0664 m处,材料受到的热应力最大,为2.8 MPa。该处为陶瓷膜过滤管脉冲清灰过程中最易损毁的位置。

Thermal stability of ceramic membranes for high-temperature gas purification is the key to long-term stable operation of ceramic membrane filters. Based on the standard k-ε turbulence model and porous media model, the gas flow in the ceramic membrane filter was numerically simulated. The distribution characteristics of the gas velocity field, pressure field and temperature field in the device during the steady-state filtration phase were studied. The temperature field changes in the device before and after the non-steady-pulse cleaning were compared, and the mechanism of the ceramic filter material damage caused by thermal-mechanical coupling during pulse cleaning was studied by quantitative analyses. The results showed that the model established by the simulation can more realistically reflect the field distribution characteristics of the gas in the whole process of hot gas filtration and pulse cleaning. During the steady-state filtration stage of the hot gas, the gas velocity was higher at the inlet and outlet pipes compared to those in the dust-containing chamber and the clean air chamber. The gas velocity in the filter tube gradually increased along the axis of the tube, while the gas pressure gradually decreased. The filter temperature did not change with the change of position. During the non-steady-state pulse cleaning stage, the temperature field of the gas near the blowback inlet formed a low-temperature region, which was distributed in an almost elliptical shape in the axial section of the tube. It should be emphasized that the temperature at the inner wall of the tube first decreased and then rose along the axial direction. However, the temperature of the gas in the tube gradually increased and the temperature in dust-containing chamber was almost unchanged. At a distance of 0.0664 m from the top of the ceramic tube, the material was subjected to the greatest thermal stress of 2.8 MPa, which was the most vulnerable position during the pulse cleaning process.