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Porous inorganic siliceous-containing gas enriching material and process of manufacture and use
| Details |
Inventors: Hammel, Joseph J.;
Assignee: PPG Industries, Inc. (Pittsburgh, PA)
Primary Examiner: Spitzer; Robert
Assistant Examiner:
Attorney, Agent or Firm: Stachel; Kenneth J.
A hollow, porous, silica-rich fiber and a process for separating at least one gas from a gaseous mixture utilizing the hollow, porous, silica-rich fiber result in gas separations with good permeability and good selectivity. The hollow, porous, silica-rich fiber is non-crystalline and has pore sizes having a range of 1 to around 50 Angstroms in diameter and a mean pore size of around 5 to 50 Angstroms in diameter and a filament diameter in the range of 1 to around 250 microns and wall thickness in the range of around 1 to 50 microns. The hollow, porous, silica-rich fibers with a fine pore structure and thin walls are produced by forming hollow glass fibers by attenuation from melt at speeds in the range of 500 ft/min to around 30,000 ft/min and having a non-phase-separated glass composition selected from: a non-phase separable fiberizable glass composition, a phase separable borosilicate having one or more oxides of a metal from Group IVB of the Periodic Table, a phase-separable glass composition with an amount of boron oxide of around 5 weight percent up to around 60 weight percent, and alkali metal oxide silicate glass compositions. The non-heat treated glass fibers are leached to extract acid and/or water soluble components. At least one hollow, porous, silica-rich fiber is used in a device suitable to contain a gaseous mixture and the permeate is withdrawn from the glass fiber from the opposite side from that at which the gaseous mixture contacts the hollow, porous fiber. |
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DETAILED DESCRIPTION OF THE INVENTION In the following description and in the claims, the following terms have the described meanings.
The term "gas" includes permanent gases that means gases at less than extreme temperatures and pressures, and any condensible vapors, even the less-easily condensed vapors which are condensible at conditions other than those used in feed gas streams to be enriched or separated.
The term "perm selective" means permeable to different extents to different molecular species under equal driving force.
the term "ultrafiltered type" means transport is partially by a porous mechanism but membrane penetrant interactions are also important.
The term "gas separation" means separations ranging from 100 percent separation to enrichment of a gas in any concentration over and above that of the original gaseous mixture.
The term "permeability factor" represents the steady state rate of gas transmission through a membrane.
Values for permeability factors are not ordinarily normalized for membrane thickness.
For homogenous membranes, the permeability factor is inversely proportional to the sample thickness.
When the thickness of the active part of the membrane is not known, e.
g.
, in asymmetric membranes, the permeability factor is still a valid permeability characterization.
The permeability factor values determine the value-in-use of the membrane in permeation devices.
The derivation of the equation for permeability factor is as follows: the volume of gas transmitted through a membrane is directly proportional to the area, time and pressure of the permeation test as: Permeability factor=volume divided by area.
times.
time.
times.
pressure The units selected for volume, area, time and pressure are cm.
sup.
3 (STP), cm.
sup.
2, seconds and cm of mercury, respectively.
The term "separation factor" or "selectivity" for a membrane and for a given gaseous mixture including gases A, B, .
.
.
N is defined as the ratio of the permeability constant (P.
sub.
a) of the membrane for gas (A) to the permeability constant (P
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