Note: Descriptions are shown in the official language in which they were submitted.
PORTABLE OXYGEN GENERATOR ~ 13 12 6 6
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
This invention relates to a portable oxygen generator and, in particular, a
portable oxygen generator which pro~uces gaseous oxygen by a process of
decomposition of aqueous hydrogen peroxide using a catalyst of embossed
metallic lead strips.
2. DESCRIPTION OF THE PRIOR ART
Oxygen gas is used in scientific, medical and industrial procedures and
there is a need for a relatively light and portable generating system. The
development of a portable system has been disclosed in U.S. patent
4,792,435, entitled OXYGEN GENERATING SYSTEM which issued
December 20, 1988 to Nakajima Dokosho Company Limited of Tokyo, Japan
in respect of an invention made by Nakajima, Masahiko, of Tokyo, Japan.
As described in the abstract of this patent, the invention disclosed is an
oxygen generating system for continuously generating oxygen gas by the
catalytic decomposition of an aqueous hydrogen peroxide that includes
a catalyst having a platinum group catalyst component carried on a highly
porous sintered ceramic support of a large pore size and a reaction chamber
for accommodating the catalyst. The system further includes a control device
for controlling the operation of the hydrogen peroxide supplying based on a
detection signal from a pressure sensor for detecting the pressure of the
generated oxygen gas. The oxygen generating system is compact and
re~uced in weight due to the catalytic decomposition of hydrogen peroxide at
high concentration, which can be carried out effectively and safely under an
increased temperature.
Other relevant prior art includes U.S. patents:
3,887,696 6/1975 Bernard et al.
3,917,461 11/1975 Kuhl et al.
~312~6
4,315,732 2/1982 Rowbottam et al.
4,466,556 8/1984 Sochting
4,488,951 12/1984 Nolan et al.
4,601,884 7/1986 Coeckelsberghs et al.
and Japanese patents:
42155 10/1977
26445 7/1978
49843 11/1981
and United Kingdom patent 2056310 dated 3/1981.
Aqueous hydrogen peroxide is produces a large amount of oxygen per unit
volume and is know as a means of reducing the size and the weight of an
oxygen generator as compared, for example, to a high pressure oxygen gas
cylinder. Japanese Utility Model Publication No. 26445/1980 discloses an
oxygen gas generating system adapted to catalytically decompose aqueous
hydrogen peroxide by using a manganese compound as a catalyst. This
has been pointed out by Nakajima that the decomposing reaction proceeds
explosively if the concentration of hydrogen peroxide exceeds about 5 w/w
%. However, higher concentrations are necess~ry to achieve practical utility
in a portable supply of aqueous hydrogen peroxide.
A platinum type catalyst for decomposing aqueous hydrogen peroxide at a
higher concentrations was disclosed in Japanese Patent Publication No.
42155/1977. However, Nakajima teaches that this catalyst is not satisfactory
given the required reaction area and defoliation problems and that prior to
his patent that no effective practical means were available. Thus, he
teaches that the catalyst layer on the support tends to be deteriorated with
the increase of the gas pressure inside the support and to be washed out by
the aqueous hydrogen peroxide.
It is also known to have a system of controlling the flow rate of hydrogen
3 21312fi6
peroxide by adjusting a valve for supplying aqueous hydrogen peroxide
depending on the pressure of the generated oxygen gas by means of a
mechanical link. (See Japanese Patent Publication No. 49843/1981).
Nakajima discloses a pressure sensor for detecting the pressure of the
oxygen gas and a water level sensor for detecting the water level in the
gas/water separator attached to the separator. The sensors ~isclosed are
semiconductor sensors or mechanical diaphragm sensors. A control unit
controls a pump depending on the signal from the pressure sensor.
SUMMARY OF THE INVENTION
The present invention provides an improved construction of a portable
oxygen generator employing the principle of the decomposition of hydrogen
peroxide in the presence of a catalyst in a reactor. The system comprises a
feed tank having an intake mouth to receive liquid hydrogen peroxide prior to
operation, a cap to seal the mouth during operation and an outlet pipe; an
on\off valve to permit an operator to control discharge from the feed tank; a
regulator valve to stop discharge from the feed tank when pressure in the
system is equal to a precletermined pressure and to permit discharge when
pressure in the system is less than said predetermined pressure; a reactor in
which hydrogen peroxide is decomposed in the presence of a catalyst to
oxygen and water, said reactor being in communication with said feed tank
through said discharge pipe, said on\off valve and said regulator; a cooling
coil in communication with said reactor to condense the water to a liquid and
cool the oxygen from the reactor; a separator tank in communication with
said cooling coil to receive an hold the liquid water and oxygen from the
cooling coil and being in communication with the feed tank to balance
pressure in the feed tank with the pressure in the separator tank; a drain
leading from a bottom portion of said separator tank to discharge liquid water
and having a drain valve to open or close said drain as may be desired from
time to time; a product line leading from a portion of the separator tank
above the anticipated level of liquid water to supply oxygen for use by an
operator of the system.
2131~6~
The oxygen generating system preferably has a reactor pipe having a round
cross section. The catalyst preferably comprises lead strips and each lead
strip preferably has a rectangular cross section and a length approximately
equal to the length of the reactor. The lead strips are laid longitudinally
within the reactor and packed in juxtaposition across the cross section of the
reactor to leave gaps between the lead strips for the flow of hydrogen
peroxide and water and oxygen through the reactor.
DESCRIPTION OF FIGURES
In the figures which illustrate a preferred embodiment of this invention:
Figure 1 is a process flow diagram of the oxygen generator of this invention;
Figure 2 illustrates a front sectional view of the oxygen generator;
Figure 3 illustrates a left side sectional view of the oxygen generator;
Figure 4 illustrates a right side sectional view of the oxygen generator;
Figure 5 illustrates a top sectional view of the oxygen generator;
Figure 6 illustrates a lead strip used in a reactor of this invention; and
Figure 7 illustrates a cross section of the reactor illustrating the packing of the
lead strips within the reactor.
2 o DESCRIPTION OF THE PRc~tHRED EMBODIMENT
The flow diagram of Figure 1 may be referred to for understanding the general
structure and operation of the invention. A feed tank (1) is filled with an
aqueous hydrogen peroxide at a high concentration of about 35 % by weight.
The hydrogen peroxide is fed by gravity through a pipe (3), a feed valve (5) anda regulator (7) to a reactor (9). The decomposition of the peroxide occurs in
the reactor (9) so that water vapour and oxygen pass out of the reactor (9)
through pipe (11) to the cooling coils (13). The cooling coils (13) condense thewater to a liquid and the oxygen and water pass through pipe (15) into a
separator or expansion tank (17). The liquid water collects in the base of the
tank (17) and the oxygen fills the atmosphere of the tank (17). A return pile
(19) permits the oxygen to recirculate to the feed tank (1) to pressurize the
system. A draw off pipe (20) with an on\off valve (21) is provided to remove
~1~126G
water from the system. A product pipe (22) with an on\off valve (23) is
provided to draw off the oxygen for use. A pressure gauge (25) is provided on
the product pipe (22) to measure the pressure of the oxygen being supplied to
a user. Relief valves (27) and (29) are provided to protect against over
pressuring of the system.
It will be understood by persons skilled in the art that all parts exposed to
hydrogen peroxide will be constructed and passivated in a known manner to
withstand pressures generated by the system and to avoid the corrosion.
The construction and layout of portable unit of this invention is shown in Figures
2-5. The operating equipment is contained in a housing (2) erected over a
base (4). The base (4) supports all the equipment by means of conventional
support structures generally depicted as (6) which are not described further.
A handle (8) is pivotally attached over the housing (2) to f~cilit~te transportation
of the unit.
Since the unit is intended to operate as a portable unit it is not designed to
operate from a continuous supply of hydrogen peroxide although a person
skilled in the art would be able to adapt the invention to a continuous supply.
Consequently, the feed tank (1 ) has a wide mouth (10) so that liquid hydrogen
peroxide may be poured into the tank (1) while the on\off valve (5) is closed.
A screw cap (12) seals the mouth (10) of the feed tank (1) prior to operation.
Further the product valve (23) and the drain valve (21 ) should be closed at thecommencement of operation.
Once the on\off valve (5) is opened the peroxide is fed by gravity through pipe
(3) and regulator (7) to the reactor (9) to decompose the peroxide to oxygen
and water. As the water vapour and oxygen pass through the cooling coils
(13), into the separator tank (17) and back along pipe (19) the pressure in the
system begins to rise. The regul~tor valve (7) is preset to shut off the flow ofhydrogen peroxide through pipe (3) to the reactor (9) at a predetermined
6 ~ 2 ~ 6
operating pressure. Once flow is interrupted, the decomposition reaction stops
and the system reaches equilibrium at the desired operating pressure.
The reactor (9) used in the preferred embodiment is a schedule 40 gauge pipe
containing a catalyst of lead strips (30) (see Figure 6 and 7). Each end of the
reactor (9) has a screw cap (14 and 16) to permit the reactor to be opened and
closed to replace the lead strips (30). Each cap seals a reactor end about its
respective connecting pipe when the system is operational. A screen (32) is
provided within each cap to prevent the lead strips from sliding out of the
reactor. As illusl,~led in Figure 6 the lead strips (30) are rectangular in cross
section and about as long as the interior of the reactor (9). As shown in Figure7 the strips (30) are packed longitudinally within the reactor (9) to fill its interior
cross section insofar as rectangular strips may fill a round pipe. The gaps (34)between the strips (30) allow the peroxide to pass between them to effect
decomposition in the presence of the lead catalyst. It may be determined when
the strips are ready for replacement by the monitoring the reaction time of the
system, i.e. how long it takes to reach operating pressure at startup.
This invention is useful in medical, scientific and industrial applications where
2 o a portable source of oxygen is required.
It will be appreci~ted by those skilled in the art that the description of the
preferred embodiment is intended to be illustrative, rather than limiting of theconstruction and operation of this invention. Modifications and adaptations of
this invention including the selection of materials and the layout of componentsmay be determined by such skilled persons.
