Simulation and analysis of pressure drop in high temperature twin-candle ceramic filter system

Abstract

The ceramic candle filter presents an interesting alternative to collect aerosol particles smaller than 2.5[micrometer] (MP2.5) because of its high resistance to high temperature, high pressure, chemicals and corrosion. As cake builds up on the outside surface of the ceramic candle filter, pressure drop, one of the important characteristics of filtration, would be increased rapidly. Meanwhile, the collection efficiency and energy consumption also increased in tandem. So, a pulse jet is injected periodically to shake down the accumulated dust cake, thereby reducing the pressure drop in the system. One technique frequently used to indirectly predict cake formation rate applies computational fluid dynamics (CFD) since it offers low cost, low risk and ease of use. However, nearly all previous CFD investigations focused on single filters. In this research, the cake formation rate on twin ceramic candle filters in a prototype system was modeled and its pressure drops validated with experimental data obtained by Hosokawa Powder Technology Research Institute (HPTRI). A suitable CFD model provided by commercial software code FLUENT was selected and employed to simulate the 3D fluid flow inside the twin-candle unit. The calculated flow field was used to estimate the local flow velocities. Due to the reasonable assumption of 100% collection efficiency and submicrometer aerosol size, the particles would move along the gas streamline with uniform distribution. Thus we could predict the differences in cake formation rate on each part or element of the candle filter from the local face velocity and calculate the cake resistance properties. In addition, the CFD technique was used to investigate the effects of such major parameters as filtration velocity, temperature, dust concentration and inlet feed location, to be varied. It was found that the filtration velocity was the most important parameter affecting the pressure drop of the system.