Spherical Al2O3-coated mullite fibrous ceramic membrane and its applications to high-efficiency gas filtration

Porous ceramic membranes (PCMs) have been widely used in gas filtration to reduce the Particulate Matters (PMs) emission from industrial systems. Generally, the filter materials are composed of two parts: the support layer and filter layer. However, the typical PCMs prepared through accumulation of particles have existing problems like heavy self-weight, low porosity and high pressure drop, which limit their use in practical applications. In this paper, fibrous PCMs with three-dimensional structures were prepared and then coated with a layer of spherical alpha-Al2O3 membrane on the surface via spray-coating process. The effect of binder composition and sintering temperature on the porosity, phase composition, bulk density and mechanical strength of PCMs, as well as the effect of the coating thickness of spherical alpha-Al2O3 on PMs filtration efficiency and pressure drop were investigated. The results showed that samples with an added binder weight of 50 wt% and sintered at 1250 degrees C resulted to an optimal structure with material properties such as low bulk density (0.88 g/cm(3)), high porosity (70.36%), low linear shrinkage (0.40%), high mechanical strength (5.54 Mpa), and excellent corrosion resistance against both acid and alkali solutions. Furthermore, a spherical alpha-Al2O3 coating thickness of 150 mu m was found to effectively reduced the concentration of PMs from dust-laden air through the filtration tests, achieving enhanced dust removal efficiencies of almost 100% for 3-10 mu m, 99.2% for 1.0 mu m, 95.0% for 0.5 mu m and 91.6% for 0.3 mu m PMs with the pressure drop was only 280 Pa when the airflow linear velocity reached to 2.00 m min(-1). The membranes displayed a 10% increase efficiency in fine particles (d = 1.0-0.3 mu m) removal compared to those without alpha-Al2O3 coating layer.