(628m) High Flux and Selective Air Separation Membrane for Oxy-Fired Combustion
AIChE Annual Meeting
2011
2011 Annual Meeting
Separations Division
Poster Session : Membranes
Wednesday, October 19, 2011 - 6:00pm to 8:00pm
For past two decades, zeolite membranes have been drawing significant attention from the researchers because of their great potential for gas separation. Zeolite membranes are robust (high thermal and chemical stability) and possess small intracrystalline pores of molecular dimensions. These properties make zeolite membranes highly promising for the size selective separation of oxygen (0.346 nm) from nitrogen (0.364 nm) for oxy-fired coal combustion.
Oxy-fired coal combustion uses almost N2-free oxygen to produce concentrated flue gas (>80% CO2)and thereby eliminating the need of separate carbon capture process. Moreover, it also reduces the emission of NOx. All these features make oxy-fired coal combustion a very attractive process by making it more economical, less energy-intense and environmental friendly.
In this study, we explored seeded synthesis of silicalite-1 membranes on disk-shaped supports to make air separation membranes for oxy-fired coal combustion. Non-steady state permeation tests were carried out to characterize the membranes. Scanning electronic microscope was used to study the morphology of the membrane surface and cross section of the membrane. H2, N2, O2, and SF6 permeances through membranes were calculated from the permeation tests data.
H2 permeance ranged from 4.37×10-9 to 8.07×10-7 mol.m-2.s-1.Pa-1 where as, N2 permeance was between 9.96×10-10 to 3.28×10-7 mol.m-2.s-1.Pa-1. O2 permeance was rather similar to that of N2, which fell in the range from 2.06×10-9 to 3.28×10-7 mol.m-2.s-1.Pa-1. SF6 permeance had a bigger range (1.63×10-10 mol.m-2.s-1.Pa-1 to 5.03×10-7 mol.m-2.s-1.Pa-1). Permselectivities of H2/N2, H2/SF6, and O2/N2 were calculated.The lowest and highest permselectivities of H2/N2 were 2.44 and 4.4 respectively. The permselectivity of O2/ N2 ranged from 0.97 to 1.5 and that of H2/SF6 ranged from 5 to 50.
Low O2/ N2 permselectivity was due to the large intracrystalline pore size of silicalite-1. Furthermore, thermal treatment created defects on the membrane surface that minimized the O2/ N2 permselectivity. Membranes were required to undergo modification in order to increase the O2/N2 permselectivity. We further employed chemical vapor deposition (CVD) and atomic layer deposition (ALD) to modify the membrane surface to obtain a high O2/N2 permselectivity. These results are also presented and discussed in this submission.