Manufacture and optimization of tubular ceramic membrane supports

Abstract

Inorganic membranes can be considered an alternative to organic membranes, due to their thermal, chemical and mechanical stability under harsh conditions. Ceramic membranes are used as support structures to increase permeability through composite inorganic membranes in separation processes. Tubular a-alumina membrane supports with smooth inner surfaces can be manufactured by means of the centrifugal casting technique.In this study, the effect of three different AKP powder sizes (0.25, 0.31 and 0.6lpm) and sintering temperatures (1000 to 1400°C) on the properties of the a-alumina supports were investigated in order to determine the optimum particle size and sintering temperature which would yield a porous support with an optimized permeability, while still retaining the smooth inner surface and adequate mechanical strength. A study concerning the possible replacement of the expensive AKP powder range with the less expensive Alcoa CT 3000 SG powder was also undertaken.The supports manufactured by centrifugal casting were characterized in terms of dimensions and by mercury porosimetry, water permeability and SEM. A novel strength testing apparatus was developed in order to determine the mechanical strength from the inside of the tubular structures.The effect of the polymer concentration, which is added to stabilize the colloidal suspension used in the centrifugal casting technique, as well as the influence of the sintering rate during polymer burn-off, was also investigated.A larger particle size resulted in an increased porosity, pore size and permeability, while a decrease in linear shrinkage and mechanical strength was observed. There was a decrease in porosity and permeability with increasing sintering temperature while the linear shrinkage and mechanical strength increased. The AKP-30 (0.31 pm) and AKP-1 S(O.61 pm) had a different particle packing than the AKP-50 (0.25pm) supports and consequently a decrease in pore size with increasing sintering temperature was observed for both the AKP-30 and AKP-15 supports, while the pore size remained constant for the AKP-50 supports. Increased polymer concentration Abstract resulted in an increase in permeability, pore size and porosity, while the mechanical strength of the support decreased. This was due to the evolution of "cracks" during sintering. The sintering rate had no profound influence on the properties of the membrane supports. The powder with the widest particle size distribution (AKP-15 powder) resulted in support structures with the widest pore size distribution. The aim of the study, i.e. the optimization of the supports, was attained when comparing the results in this study to our previous work as well as the available literature.Compared to our own previous study, the permeability increased from 28 to 41 ~.h.-'bar.-'m.-', the porosity from 36 to 37% and the pore radius from 99 to 167nm for the AKP-15 supports sintered at 1200°C.Structural cracking and warping during sintering of the powder compacts made from untreated Alcoa CT 3000 SG powder indicated tha...

Fabrication of Tubular Membrane Supports from Low Price Raw Materials, Using Both Centrifugal Casting and/or Extrusion Methods

“…14) and 52%, respectively. It is known that the particle size distribution (PSD) has an influence on the pore size distribution, as a narrow PSD results in a narrow pore size distribution, while a wide PSD would result in a wider pore size distribution (Bissett et al, 2008). The pore size indicates that this kind of membranes can be utilized in the microfiltration range (Masmoudi et al, 2005).…”

Composite ceramic membranes from natural aluminosilicates for microfiltration applications

“…Most of the supports are generally manufactured from compounds such as alumina (Al 2 O 3 ) [18][19][20][21][22][23][24][25][26][27][28], cordierite (2MgO Á 2Al 2 O 3 Á 5SiO 2 ) [29][30][31]) and mullite (3Al 2 O 3 Á 2SiO 2 ) [32][33]. These materials have relatively elevated prices which significantly contribute to the cost of membrane modules for industrial applications.…”

Shrinkage characteristics studies on conventional sintered zirconia toughened alumina using computed tomography imaging technique

“…The α-alumina of particle sizes 0.25, 0.31 and 0.61 μm was subjected to sintering studies. By varying the temperature from 1050°C to 1400°C it exhibits a low linear shrinkage at 1050°C as reported by Bisset et al [9]. The shrinkage is also varied during sintering by the addition of additives in the composites.…”