Separator decreases the partial pressure of hydrogen gas dissolved in the water produced by fuel cells containing an alkaline electrolyte. The unit eliminates the hazards associated with the release of hydrogen from water solution when the hydrostatic pressure is rapidly decreased

Albright, C. F.

English

NASA Technical Reports Server

November 1969	 Brief 69-10635 
NASA TECH BRIEF	 1 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Device Separates Hydrogen from Solution in Water 
at Ambient Temperatures 
A separator has been devised to decrease the partial 
pressure of hydrogen gas dissolved in water under 
hydrostatic pressure. The separator is required to re-
move dissolved hydrogen from the water produced 
by fuel cells containing an alkaline electrolyte. It 
operates at room temperature (75'F) to decrease the 
partial pressure of the dissolved hydrogen from ap-
proAimately 60 psia to less than I psia in the effluent 
fuel cell water. The unit eliminates the hazards as-
sociated with the release of hydrogen gas from water 
solution when the hydrostatic pressure is rapidly 
decreased. 
The separator consists of closely spaced (1/8 in. or 
less) flat plates or 1/8 in.-diameter tubes made of a 
75 percent palladium-25 percent silver alloy coated on 
both sides with palladium black, which is tightly 
bonded to the alloy surfaces by a special process. The 
process involves the direct application of palladium 
chloride to the surfaces of the plates or tubes followed 
by hydrogen reduction of the chloride to palladium 
black. Nominal loadings of 2 milligrams of the palla-
dium black per square centimeter of alloy surface are 
achieved by this process. The surface area required 
to effect a specified decrease in hydrogen pressure is 
a function of water flow rate, temperature, and plate 
area or tube radius. The active area for hydrogen 
permeation can be minimized using closely spaced flat 
plates; but heavy backup plates would be required to 
enable the separator to withstand hydrostatic pres-
sures up to 75 psia. Small-diameter tubes (1/8 in. o.d., 
10 mil wall thickness) will withstand the hydrostatic 
pressures, but a greater active area than that of flat 
plates would be required to effect the same decrease
in hydrogen pressure. Tubes of larger diameter than 
1/8 in. would not be as efficient, whereas smaller-
diameter tubes cannot be properly coated internally 
with the palladium black. 
A separator that was fabricated consists of 18 tubes, 
each 20 inches long, arranged in parallel groups of 3, 
providing a series length of 10 feet, or an overall 
length of 30 feet. At 75' F, with a water flow of 10 mil 
per minute through the tubes, the unit will drop the 
partial pressure of dissolved hydrogen from 60 psia 
to less than 0.5 psia, without affecting the hydrostatic 
water pressure. At operating temperatures above 75°F 
even better efficiencies are possible. The separator will 
work equally well in air or vacuum, as in either case 
the partial pressure of hydrogen on the exterior of the 
tubes is essentially zero. A test unit has been operated 
for more than 5 months (3700 hours) without loss of 
efficiency. 
Notes: 
I. The rate of removal of hydrogen from water solu-
tion depends on the diffusion rate of hydrogen 
through water rather than through the tube wall; 
consequently practical designs can be achieved 
using relatively thick (10 mil) tubes. 
2. The permeability of hydrogen gas through palla-
dium or palladium-silver alloys at high pressures 
(400 psia) is well known and has been applied in a 
process for hydrogen purification. It is believed that 
the new separator design is the first instance of the 
practical use of these alloys for the separation of 
hydrogen from water solution at relatively low 
temperatures.
(continued overlenit 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000580 2020-03-16T18:30:12+00:00Z
3. The coated palladium-silver alloy can be used to 
pass hydrogen, either gaseous or dissolved, into or 
out of vessels containing gases or liquids. The alloy 
could have, application in electrochemical systems 
such as batteries (where the alloy can be an elec-
trode); in chemical processes for controlling the 
concentration of hydrogen, either as a reactant or 
product of reaction; and in hydrogen sensing de-
vices. 
4. Requests for further information may be directed 
to:
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058	 - 
Reference: B69-10635
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code GP, 
Washington, D.C. 20546. 
Source: Charles F. Albright of

The Garrett Corporation

under contract to

Manned Spacecraft Center

(MSC-13335)
. 
Brief 69-10635	 Category 03


Device separates hydrogen from solution in water at ambient temperatures

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