陶瓷膜孔道内尘粒沉积及脱附的模拟

Numerical simulation of the fouling and cleaning of a ceramic membrane

  • 摘要: 陶瓷膜是过滤高温含尘烟气最有效的材料之一,其过滤性能和再生性能与尘粒在陶瓷膜孔道内的沉积和脱附机制相关。本文建立了不同孔隙率的陶瓷膜物理模型,然后结合连续性方程、动量方程和能量方程,设定边界条件以及沉积条件,模拟了陶瓷膜过滤和脉冲反吹时,高温烟气的流动以及尘粒的沉积与脱附过程。结果表明,过滤速度较低和陶瓷膜孔隙率较高时,尘粒易于沉积在陶瓷膜孔道内;脉冲反吹时,增加反吹压力,延长反吹时间,尘粒易于从陶瓷膜孔道脱附。采用厚度为20 mm,长度为1.5 m,孔隙率为40%的陶瓷膜管过滤温度为1000 ℃,流速为1 m·min−1,压力为0.1 MPa的含尘烟气时,反吹气压力应不低于0.3 MPa,反吹时间不短于0.02 s,尘粒脱附时间在13 s,脉冲反吹时间间隔应高于452 s。

     

    Abstract: The main sources of fine particulate matter in the air are automobile exhaust and dust-containing hot flue gas emitted from combustion in the process of industrial manufacturing and municipal solid waste incineration, both of which are hard to clean at high temperatures. Ceramic membranes maintain high strength at high temperatures and an acid or alkaline atmosphere, and have a micron-scale and tortuous pores that block dust particles. The ceramic membrane is one of the most effective materials for successful hot flue gas cleaning as used in the integrated gasification combined cycle. Its filtration and regeneration performance are related to the deposition and desorption mechanism of dust particles in the channel of the membrane. In this study, a physical model of ceramic membranes of various porosities was established. Boundary and deposition conditions were then set up by combining continuity, momentum, and energy equations to simulate the flow of hot flue gas and the deposition and desorption process of dust particles during ceramic membrane filtration and pulse back-blowing. The results show that when the filtration velocity is low and porosity of the ceramic membrane is high, it is easy for dust particles to deposit in the membrane channel. Increasing back-blowing pressure prolongs back-blowing time during pulse back-blowing so that dust particles easily desorb from the channel of the ceramic membrane. When a ceramic membrane tube with a thickness of 20 mm, a length of 1.5 m, and a porosity of 40% is used to filtrate flue gas with a filtration temperature of 1000 °C, a flow rate of 1 m·min−1, and a pressure of 0.1 MPa, the blowback pressure should not be <0.3 MPa, blowback time should be longer than 0.02 s, and pulse blowback time interval should be more than 452 s.

     

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