Note: Descriptions are shown in the official language in which they were submitted.
1
MEDICAL GAS PRODUCTION SYSTEM WITH GAS RECYCLING
FIELD OF THE INVENTION
The present invention relates to a medical gas production system and
method of use thereof to produce a gas composition from air in which the gas
composition has a concentration of oxygen greater than that of the supplied
air so that
the oxygen enriched gas composition can be transferred to an external holding
tank for
subsequent respiration by patients requiring oxygen enriched air for effective
breathing.
BACKGROUND
Oxygen concentrators are used in various environments to produce an
oxygen enriched gas mixture from atmospheric air that can be used as a medical
gas
for respiration by patients. A common principle relied upon in many oxygen
concentrators is known as pressure swing adsorption (PSA). Wikipedia defines
pressure swing adsorption as follows: "Pressure swing adsorption processes
utilize the
fact that under high pressure, gases tend to be attracted to solid surfaces,
or adsorbed.
The higher the pressure, the more gas is adsorbed. When the pressure is
reduced, the
gas is released, or desorbed. PSA processes can be used to separate gases in a
mixture because different gases tend to be attracted to different solid
surfaces more or
less strongly. If a gas mixture such as air is passed under pressure through a
vessel
containing an adsorbent bed of zeolite that attracts nitrogen more strongly
than oxygen,
part oral! of the nitrogen will stay in the bed, and the gas exiting the
vessel will be richer
in oxygen than the mixture entering. When the bed reaches the end of its
capacity to
adsorb nitrogen, it can be regenerated by reducing the pressure, thus
releasing the
adsorbed nitrogen. It is then ready for another cycle of producing oxygen-
enriched air."
A typical oxygen concentrator relies on pressure differential between a
series of tanks for moving air to be treated through the tanks. If the quality
of the
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resultant gas mixture is lacking due to an insufficient concentration of
oxygen or an
undesirable concentration of an impurity, it is known to discharge the treated
gas
mixture to atmosphere with a new cycle using fresh air from atmosphere being
required
to produce a replacement treated gas mixture. Discharging to atmosphere is
believed
to be the most efficient means of preventing usage of a gas mixture of
insufficient quality
due to the minimal pressure differential which may be available at the final
stage of
treatment and the desire to avoid additional pumps or compressors to redirect
the poor
quality gas mixture for further processing. Starting over the production of a
treated gas
mixture using the same source of air however can result in a continuing
quality problem.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a medical gas
production system for producing from air a gas composition having a
concentration of
oxygen greater than the air and delivering the gas composition to an external
holding
tank for subsequent respiration by patients, the system comprising:
a treatment tank containing an adsorbent bed for adsorbing gases from
the air to produce an oxygen concentrated gas mixture;
a receiver tank connected to the treatment tank by at least one transfer
line so as to enable transfer of the gas mixture from the treatment tank to
the receiver
tank;
an outlet line in communication with receiver tank so as to enable transfer
of the gas mixture from the receiver tank to the holding tank externally of
the system;
and
at least one transfer valve connected in series with the at least one
transfer line between the treatment tank and the receiver tank;
the at least one transfer valve being operable to allow backflow of the gas
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mixture from the receiver tank to the treatment tank if a measured quality of
the gas
mixture exiting the receiver tank falls below a prescribed threshold such that
further
gases may be adsorbed from the gas mixture in a second cycle within the
treatment
tank.
By enabling some backflow from the receiver tank to the treatment tank,
a second stage of absorption is permitted to take place on the same gas
mixture to
improve the quality thereof such that the resultant quality of the gas mixture
is more
likely to be improved as compared to starting over the production process with
the same
initial ambient air. By specifically controlling the timing of the backflow
communication
from the receiver tank to the treatment tank, very small pressure
differentials may be
used to drive the backflow without the addition of another pump or compressor
being
required.
Preferably said at least one transfer line comprises a single line
connected between the treatment tank and the receiver tank and said at least
one
transfer valve comprises a single valve connected in series with the single
line so as to
be operable between a closed position prevent communication of gases between
the
treatment tank and the receiver tank and an open position in which gases can
be
communicated in either one of two opposing directions between the treatment
tank and
the receiver tank.
The system preferably further comprises: (i) a gas analyser in
communication with the outlet line so as to be adapted to measure a
characteristic of
the gas mixture exiting the receiver tank; and (ii) a controller operatively
connected to
said at least one transfer valve so as to be adapted to operate the transfer
valve
automatically to allow backflow of the gas mixture from the receiver tank to
the
treatment tank if the characteristic of the gas mixture exiting the receiver
tank as
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measured by the gas analyser falls below a prescribed threshold stored on the
controller.
The system preferably also further comprises a controller operatively
connected to said at least one transfer valve so as to be adapted to operate
the valve.
In this instance, while the treatment tank is being filled with air and if the
measured
quality of the gas mixture exiting the receiver tank falls below the
prescribed threshold,
the controller is preferably adapted to automatically open said at least one
transfer valve
between the treatment tank and the receiver tank before a pressure within the
treatment
tank reaches a pressure within the receiver tank such that a pressure
differential
between the receiver tank and the treatment tank drives the backf low of the
gas mixture
from the receiver tank to the treatment tank.
The controller may be further adapted to maintain said at least one
transfer valve open while the treatment tank is being filled with air until
after flow
between the treatment tank and the receiver tank reverses and flows from the
treatment
tank to the receiver tank.
According to a second aspect of the present invention there is provided a
A medical gas production system for producing from air a gas composition
having a
concentration of oxygen greater than the air and delivering the gas
composition to an
external holding tank for subsequent respiration by patients, the system
comprising:
a treatment tank containing an adsorbent bed for adsorbing gases from
the air to produce an oxygen concentrated gas mixture;
a receiver tank connected to the treatment tank by at least one transfer
line so as to enable transfer of the gas mixture from the treatment tank to
the receiver
tank;
an outlet line in communication with receiver tank so as to enable transfer
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of the gas mixture from the receiver tank to the holding tank externally of
the system;
and
at least one transfer valve connected in series with the at least one
transfer line between the treatment tank and the receiver tank; and
a controller operatively connected to said at least one transfer valve so
as to be adapted to operate the valve;
the controller comprising a memory storing programming instructions
thereon and a processor adapted to execute the programming instructions such
that
while the treatment tank is being filled with air, the controller is adapted
to automatically
open said at least one transfer valve between the treatment tank and the
receiver tank
before a pressure within the treatment tank reaches a pressure within the
receiver tank
such that a pressure differential between the receiver tank and the treatment
tank drives
a backf low of the gas mixture from the receiver tank to the treatment tank.
Preferably the controller is further adapted to maintain said at least one
transfer valve open while the treatment tank is being filled with air until
after flow
between the treatment tank and the receiver tank reverses and flows from the
treatment
tank to the receiver tank.
According to a further aspect of the present invention there is provided a
medical gas production system for producing from air a gas composition having
a
concentration of oxygen greater than the air and delivering the gas
composition to an
external holding tank for subsequent respiration by patients, the system
comprising:
a receiver tank;
a first treatment tank containing an adsorbent bed for adsorbing gases
from the air to produce an oxygen concentrated gas mixture, the first
treatment tank
being connected to the receiver tank for a first transfer line containing a
first transfer
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valve in series therewith so as to control transfer of gases between the first
treatment
tank and the receiver tank;
a second treatment tank containing an adsorbent bed for adsorbing gases
from the air to produce an oxygen concentrated gas mixture, the second
treatment tank
being connected to the receiver tank by a second transfer line containing a
second
transfer valve in series therewith so as to control transfer of gases between
the second
treatment tank and the receiver tank;
a connecting line in communication between the first treatment tank and
the second treatment tank including a connecting valve in series therewith to
control
transfer of gases between the treatment tank and the second tank;
an outlet line in communication with receiver tank so as to enable transfer
of the gas mixture from the receiver tank to the holding tank externally of
the system;
a source of compressed air adapted to fill each of the first and second
treatment tanks with compressed air independently of one another;
a vacuum source adapted to apply a vacuum pressure to each of the first
and second treatment tanks independently of one another; and
a controller operatively connected to the valves so as to be adapted to
operate the valves;
the controller comprising a memory storing programming instructions
thereon and a processor adapted to execute the programming instructions such
that
the controller is adapted to:
(a) operate the source of compressed air to fill the second
treatment tank with compressed air until a pressure within the second
treatment tank
reaches a prescribed upper pressure value;
(b) operate the vacuum source to reduce a pressure within the first
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treatment tank until the pressure within the first treatment tank reaches a
prescribed
vacuum pressure;
(c) while the second treatment tank is being filled with compressed
air, (i) open the second transfer valve before the pressure within the second
treatment
tank reaches the pressure within the receiver tank such that a pressure
differential
between the receiver tank and the second treatment tank drives a backf low of
the gas
mixture from the receiver tank to the second treatment tank, and (ii) maintain
the second
transfer valve open until the gas mixture flows from the second treatment tank
to the
receiver tank and the pressure in both the receiver tank and the second
treatment tank
reaches the prescribed upper pressure value;
(d) subsequent to filling the second treatment tank with
compressed air, open the connecting valve to transfer some gases from the
second
treatment tank to the first treatment tank;
(e) operate the source of compressed air to fill the first treatment
tank with compressed air until the pressure within the first treatment tank
reaches the
prescribed upper pressure value;
(f) while the first treatment tank is being filled with air, (i) open the
first transfer valve between the first treatment tank and the receiver tank
before the
pressure within the first treatment tank reaches the pressure within the
receiver tank
such that a pressure differential between the receiver tank and the first
treatment tank
drives the backf low of the gas mixture from the receiver tank to the first
treatment tank,
and (ii) maintain the first transfer valve open until the gas mixture flows
from the first
treatment tank to the receiver tank and the pressure in both the receiver tank
and the
first treatment tank reaches the prescribed upper pressure value;
(g) operate the vacuum source to reduce the pressure within the
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second treatment tank until the pressure within the second treatment tank
reaches the
prescribed vacuum pressure;
(h) subsequent to filling the first treatment tank with compressed
air, open the connecting valve to transfer some gases from the first treatment
tank to
the second treatment tank; and
(i) repeat steps (a) through (h).
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is a schematic representation of the medical gas production
system;
Figure 2 illustrates schematic representations of a series of stages of a
normal mode of operation of the system according to Figure 1; and
Figure 3 illustrates schematic representations of a series of stages of an
optimized mode of operation of the system according to Figure 1.
In the drawings like characters of reference indicate corresponding parts
in the different figures.
DETAILED DESCRIPTION
Referring to the accompanying figures, there is illustrated a medical gas
production system generally indicated by reference numeral 10. The system 10
is
particularly suited for receiving ambient air, typically containing nitrogen,
oxygen and
other atmospheric gases, for treatment according to a pressure swing
adsorption
process to produce a resultant gas mixture having a higher concentration of
oxygen
than the incoming ambient air. The resultant gas mixture produced by the
system 10
is delivered to a holding tank 12 which is external of the system. The
resultant gas
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mixture within the external holding tank is a medical gas that is suitable for
respiration
by patients either alone or combined with ambient air so that the patient
breathes the
oxygen enriched gas mixture.
The pressure swing adsorption process exposes the gas mixture to be
treated under high pressure to an adsorbent bed comprising a molecular sieve
such as
zeolite. The nitrogen attracts more strongly to the absorbent bed than the
oxygen such
that part or all of the nitrogen will stay in the bed, and the gas exiting the
adsorbent bed
will be richer in oxygen than the mixture entering. When the adsorbent bed
reaches its
capacity to adsorb nitrogen, it can be regenerated by reducing the pressure,
thus
releasing the adsorbed nitrogen so as to be ready for another cycle of
producing oxygen
enriched air.
The system 10 according to the illustrated embodiment includes a first
treatment tank 14 and a second treatment tank 16, in which each of the
treatment tanks
contains an adsorbent bed of zeolite therein. When the treatment tanks are
filled with
pressurized air, the pores of the material in the adsorbent bed are more
likely to adsorb
nitrogen than oxygen. The gas mixture exiting the treatment tank while under
pressure
is thus enriched in oxygen relative to the incoming air. After removing the
oxygen
enriched gas mixture, subsequent depressurization, for example by the
application of
atmosphere to the treatment tanks, results in the adsorbed gases being
desorbed for
subsequent expulsion externally from the system 10, for example to vaccum.
Each treatment tank further includes an inlet 18 at the bottom end thereof
and an outlet 20 at the top end thereof. Although each inlet primarily
receives an
incoming flow into the treatment tank and the outlet primarily discharges flow
from the
outlet tank, both the inlet and the outlet are capable of bidirectional flows
into or out of
the tank at various stages of the production process as described in further
detail below.
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The system 10 further includes an air compressor 22 which functions as
a supply of compressed air and which communicates with a main supply line 24
which
delivers the compressed air to the system. The main supply line 24 is
connected to a
main tee connector 26 which feeds (i) a first supply line 28 in communication
from the
.. main supply line 24 to the inlet of the first treatment tank 14 and (ii) a
second supply
line 30 in communication from the main supply line 24 to the inlet of the
second
treatment tank 16.
A first supply valve 32 is connected in series with the first supply line 28
and a second supply valve 34 is connected in series with the second supply
line 30.
Each of the supply valves is operable between an open condition in which flow
of
compressed air is permitted from the main supply line 24 into the inlet of the
respective
treatment tank and a closed position in which communication between the main
supply
line and the respective treatment tank is interrupted and prevented.
To enable gases to be discharged from the treatment tanks to a location
external of the system, for example during the desorbing cycle of the
adsorbent bed, a
first atmospheric discharge line 36 and a first vacuum discharge line 48 are
both in open
communication with the first supply line 28 at an intermediate location
between the first
supply valve and the inlet of the first treatment tank. Similarly, a second
atmospheric
discharge line 38 and a second vacuum discharge line 46 are both in open
communication with the second supply line 30 at an intermediate location
between the
second supply valve and the inlet of the second treatment tank. A suitable tee
connector
is provided at the junction of the discharge lines with the respective supply
line.
Both of the atmospheric discharge lines 36 and 38 are coupled by a
common tee connector to a common discharge vent 50. The discharge vent 50 is
.. equipped with a noise muffler in series therewith which discharges to
atmosphere.
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To control when gases are discharged through the atmospheric discharge
lines 36 and 38 to the discharge vent 50, a first atmospheric discharge valve
40 is
provided in series with the first atmospheric discharge line 36 and a second
atmospheric discharge valve 42 is provided in series with the second
atmospheric
discharge line 38. Each of the atmospheric discharge valves is operated
between an
open condition allowing gases to readily pass through the valve from the
respective
treatment tank to vent the respective line externally of the system to
atmosphere and a
closed position in which any discharge flow is prevented through the
respective line.
Both of the vacuum discharge lines 48 and 46 are coupled by a common
tee connector to a common vacuum line that is connected to a vacuum pump 54.
The
vacuum pump is operated to provide suction on the vacuum line for selectively
applying
a vacuum pressure to the treatment tanks through the vacuum discharge lines 48
and
46 when desired.
To control when gases are drawn from the treatment tanks through the
vacuum discharge lines 48 and 46 using a vacuum pressure from the vacuum pump,
a
first vacuum discharge valve 56 is provided in series with the first vacuum
discharge
line 48 and a second vacuum discharge valve 52 is provided in series with the
second
vacuum discharge line46. Each of the vacuum discharge valves is operated
between
an open condition allowing gases to readily pass through the valve from the
respective
treatment tank to apply vacuum pressure to expel gasses externally of the
system to
atmosphere and a closed position in which any discharge flow is prevented
through the
respective line.
By selectively opening the first atmospheric discharge valve 40, the
second atmospheric discharge valve 42, the first vacuum discharge valve 56,
and the
second vacuum discharge valve 52 independently of one another, either one of
the first
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br second treatment tanks can be discharged to either one of the atmospheric
discharge
vent 50 or the suction line of the vacuum pump 54 as required by the system
for
expelling adsorbed gases from the adsorption beds.
During the production process, treated or oxygen-enriched air, that is a
gas mixture having a higher concentration of oxygen than the source ambient
air, is
collected from the outlets of the first and second treatment tanks for
subsequent transfer
to a receiver tank 58 where the gas mixtures from the two treatment tanks are
mixed
together prior to discharging to the external holding tank 12. The receiver
tank 58 has
an inlet 60 at the top end thereof and an outlet 62 at the bottom end thereof.
Similarly
to the inlet and outlets of the treatment tanks, each of the inlet and outlet
of the receiver
tank may receive a bi-directional flow therethrough.
A first transfer line 64 is provided in communication from the outlet of the
first treatment tank to the inlet of the receiver tank for transferring gases
therethrough
between the tanks. A first transfer valve 66 is connected in series with the
first transfer
line so as to be operable between an open position permitting gases to be
transferred
in either direction from the receiver tank to the first treatment tank, or
alternatively from
the first treatment tank to the receiver tank, and a closed position in which
flow of gases
through the first transfer line is prevented.
Similarly, a second transfer line 68 is provided in communication from the
outlet of the second treatment tank to the inlet of the receiver tank for
transferring gases
therethrough between the tanks. A second transfer valve 70 is connected in
series with
the second transfer line so as to be operable between an open position
permitting gases
to be transferred in either direction from the receiver tank to the second
treatment tank
or alternatively from the second treatment tank to the receiver tank, and a
closed
.. position in which the flow of gases through the second transfer line is
prevented.
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A connecting line 72 is also provided which is connected between the
outlet of the first transfer tank and the outlet of the second transfer tank.
The connecting
line is connected to each of the outlets by connection to the first and second
transfer
lines using respective tee connectors in each of the transfer lines
respectively. A
connecting valve 74 is connected in series with the connecting line 72 so as
to be
operable between an open position permitting gases to be transferred in either
direction
between the two treatment tanks and a closed position in which the flow of
gases
through the connecting line is prevented.
An outlet line 76 is in communication with the outlet 62 at the bottom of
the receiver tank for communicating from the receiver tank to the external
holding tank
12. A pair of outlet valves 78 are connected in series with one another within
the outlet
line 76 such that each outlet valve is able to interrupt flow through the
outlet line from
the receiver tank to the holding tank. The redundancy of the outlet valves
provides
added precaution to ensure no flow exits the system.
A gas analyser 80 is in communication with the outlet line at an
intermediate location therealong between the outlet of the receiver tank and
the external
holding tank. The analyser 80 comprises a variety of sensors capable of
analysing the
contents of the gas mixture flowing through the outlet line. In this manner
the analyser
is capable of measuring the concentration of oxygen within the gas mixture
exiting the
receiver tank as well as being capable of measuring the concentration of one
or more
impurities within the gas mixture such as undesirable gases or toxins for
instance.
A suitable controller 82 of the system is provided in the form of a computer
in electrical communication with the sensors of the analyser 80 as well as
being in
communication with each of the valves. All of the valves described herein
comprise
solenoid actuated valves which can be controlled between open and closed
states upon
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receipt of the appropriate signals from the computer controller 82. The
controller 82
further includes a memory storing programming instructions thereon as well as
a
processor capable of executing the programming instructions to effect the
various
functions of the system as described in the following.
In a general manner of operation, the various valves of the system are
operated to treat a batch of air within each of the treatment tanks in an
alternating
manner with the resultant oxygen enriched gas being transferred from the
treatment
tanks to the receiver tank in an alternating manner. The controller typically
operates the
system in either one of a normal mode or an optimized mode of operation. In
the normal
mode, a given quantity of gas is treated in a single pass through a respective
one of
the treatment tanks prior to being transferred to the receiver tank for mixing
with other
batches of treated gas. In the optimized mode of operation, some gas in the
receiver
tank is permitted to backf low into one or both of the treatment tanks to
undergo a second
adsorption cycle to further enrich the oxygen concentration within the gas
mixture prior
to returning the gas mixture to the receiver tank. The concentration of oxygen
within the
receiver tank can be increased while simultaneously reducing the concentration
of other
undesirable gases within the gas mixture in the receiver tank.
The controller typically automatically determines that the system should
be operated in the optimized mode if a measurement of the quality of the gas
by the
analyser is deemed to fall below a prescribed threshold stored on the
controller. In one
instance, the quality of the gas mixture is determined by the concentration of
oxygen
such that the quality is below the prescribed threshold if the oxygen
concentration falls
below a prescribed minimum threshold. Alternatively, the quality of the gas
mixture at
the outlet of the receiver tank may be considered below threshold quality if
the
concentration of an impurity or undesirable gas within the gas mixture exceeds
a
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maximum threshold. The controller continues to monitor the quality of the gas
mixture
in the outlet line or at the outlet of the receiver tank so as to continue to
operate in the
optimized mode as long as the measured quality remains below the prescribed
threshold. Once the measured quality is determined to exceed the prescribed
threshold,
the controller will then resume operation in the normal mode.
Turning now to figure 2, the normal mode of operation will now be
described in further detail.
In a first stage of the normal mode, the second treatment tank 16 is initially
filled using the air compressor to supply compressed air through the second
supply line
by opening the second supply valve. Simultaneously, the first treatment tank
14 begins
undergoing a desorbing cycle by opening the first atmospheric discharge valve
40 for
discharging to atmosphere through a suitable muffler. The second treatment
tank may
be pressurized from 50 to 85 psi for example while the first treatment tank is
discharged
from 50 to 0 psi for example.
In the second step of the normal mode, the desorbing cycle in the first
treatment tank continues by closing the first atmospheric discharge valve 40
and
opening the first vacuum discharge valve 56 so that the vacuum pump applies a
vacuum pressure to the first treatment tank. Simultaneously, the second
treatment tank
is continued to be filled with pressurized air from the air compressor. When
the pressure
within the second treatment tank exceeds a prescribed amount, for example
exceeds
85 psi, the second transfer valve is opened such that excess pressure can be
communicated from the second treatment tank to the receiver tank 58 by
transferring
treated gas from the treatment tank to the receiver tank. Compressed air is
continued
to be pumped into the second treatment tank so that pressure in both the
second
treatment tank and the receiver tank elevate together to an upper limit, for
example 100
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psi.
At step three of the normal mode, all of the valves are closed and the
connecting valve in the connecting line 72 is opened so that gas can be
transferred
from the second treatment tank to the first treatment tank which has the
effect of
reducing pressure in the second treatment tank from an upper limit to a lower
limit, for
example from 100 down to 50 psi while pressure within the first treatment tank
increases from a negative vacuum pressure, for example -30 psi up to 50 psi.
The first
supply valve remains open so that compressed air can be supplied to the inlet
of the
first treatment tank to continue to increase the pressure in the first
treatment tank.
In step four of the normal mode, the valves are reconfigured for
discharging the second treatment tank through the muffler to reduce pressure
from 50
psi to zero psi for example while continuing to supply compressed air to the
inlet of the
first treatment tank to continue to increase the pressure in the first
treatment tank, for
example from 50 psi to 85 psi. More particularly, the second atmospheric
discharge
valve 42 is opened for discharging the second treatment tank, while only the
first supply
valve is opened for pressurizing the first treatment tank from the air
compressor.
At step five of the normal mode, the valves are reconfigured so that the
second vacuum discharge valve 52 is opened for continuing the desorbing cycle
of the
second treatment tank by applying a vacuum pressure to the second treatment
tank,
while the first supply valve remains open to continue pressurizing the first
treatment
tank. When pressure within the first treatment tank exceeds a prescribed
amount, for
example exceeds 85 psi, the first transfer valve is opened such that the
excess pressure
can be communicated from the first treatment tank to the receiver tank 58 by
transferring treated gas from the treatment tank to the receiver tank.
Compressed air is
continued to be pumped into the first treatment tank so that pressure in both
the first
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treatment tank and the receiver tank elevate together to an upper limit for
example 100
psi.
At step six of the normal mode, the controller reconfigures the valves
again similarly to step three in which the connecting line 72 is opened so
that gas can
be transferred from the first treatment tank to the second treatment tank
which has the
effect of reducing pressure in the first treatment tank from an upper limit to
a lower limit,
for example from 100 down to 50 psi, while pressure within the second
treatment tank
increases from a negative vacuum pressure, for example -30 psi up to 50 psi.
The
second supply valve remains opened so that compressed air can be supplied to
the
inlet of the second treatment tank to continue to increase the pressure in the
second
treatment tank.
The process of the normal mode then resumes back to step one to follow
through the various steps once again by continuing to pressurize the second
treatment
tank up to an upper limit, for example from 50 psi to 85 psi, while the first
treatment tank
again undergoes the beginning of a desorbing cycle by opening the first
atmospheric
discharge valve 40 for discharging to atmosphere.
Turning now to figure 3, the optimized mode of operation will now be
described in further detail.
In the first step of the optimized mode, the valves are controlled similarly
to the normal process such that the second treatment tank 16 is initially
filled using the
air compressor to supply compressed air through the second supply line by
opening
the second supply valve. Simultaneously, the first treatment tank 14 begins
undergoing
a desorbing cycle by opening the first atmospheric discharge valve 40 for
discharging
to atmosphere through a suitable muffler. The second treatment tank may be
pressurized from 50 to 85 psi for example while the first treatment tank is
discharged
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from 50 to 0 psi for example.
In the second step of the optimized mode, the desorbing cycle in the first
treatment tank continues by closing the first atmospheric discharge valve 40
and
opening the first vacuum discharge valve 56 so that the vacuum pump applies a
vacuum pressure to the first treatment tank. Simultaneously, the second
treatment tank
is continued to be filled with pressurized air from the air compressor. When
the pressure
within the second treatment tank exceeds an intermediate pressure level which
is less
than the pressure of the receiver tank 58, the second transfer valve is
opened. For
example, the second transfer valve can be opened when the pressure in the
receiver
tank 58 is at 80 psi but the pressure in the second treatment tank is only at
75 psi such
that a previously treated gas mixture within the receiver tank 58 backf lows
through the
second transfer line into the second treatment tank until the receiver tank
and the
second treatment tank stabilize at a balanced pressure, for example at 77 psi.
Throughout this process, the air compressor can remain activated with the
second
supply valve being opened to supply compressed air through the second supply
line
into the second treatment tank. The second transfer valve 70 remains open such
that
pressure within both the second treatment tank and the receiver tank elevate
together
from 77 psi up to 100 psi with gases from the second treatment tank continuing
to flow
from the second treatment tank into the receiver tank through this later part
of the
second stage of the optimized process.
At step three of the optimized mode, the second transfer valve 70 that
was open in step two initially remains open while the connecting valve 74 in
the
connecting line 72 is opened. The second transfer valve remains open until the
receiver
tank drops to approximately 80 psi as some of the gas in the receiver tank
flows back
through the transfer valve and subsequently through the connecting line 72
into the first
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treatment tank 14. The connecting valve 74 remains open subsequent to closing
of the
second transfer valve 70 so that gas is continued to be transferred from the
second
treatment tank to the first treatment tank which has the effect of reducing
pressure in
the second treatment tank from an upper limit to a lower limit, for example
from 100
down to 50 psi while pressure within the first treatment tank increases from a
negative
vacuum pressure, for example -30 psi up to 50 psi. The first supply valve 32
also
remains opened throughout step three so that compressed air can be supplied to
the
inlet of the first treatment tank to continue to increase the pressure in the
first treatment
tank.
In step four of the optimized mode, the valves are reconfigured for
discharging the second treatment tank through the muffler of the discharge
line to
reduce pressure from 50 psi to zero psi for example while continuing to supply
compressed air to the inlet of the first treatment tank to continue to
increase the
pressure in the first treatment tank, for example from 50 psi to 75 psi. More
particularly,
only the second atmospheric discharge valve 42 is opened for discharging the
second
treatment tank, while only the first supply valve 32 is opened for
pressurizing the first
treatment tank from the air compressor.
In step five of the optimized mode, the process is similar to step two of
the optimized process but with flow of gases being exchanged between the first
treatment tank and the receiver tank instead of between the second treatment
tank and
the receiver tank according to step two. More particularly, in step five of
the optimized
mode, the desorbing cycle in the second treatment tank continues by closing
the
second atmospheric discharge valve 42 and opening the second vacuum discharge
valve 52 so that the vacuum pump applies a vacuum pressure to the second
treatment
tank. Simultaneously the first treatment tank is continued to be filled with
pressurized
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air from the air compressor. When the pressure within the first treatment tank
exceeds
an intermediate pressure level which is less than the pressure of the receiver
tank 58,
the first transfer valve is opened. For example, the first transfer valve can
be opened
when the pressure in the receiver tank is at 80 psi but the pressure in the
first treatment
tank is only at 75 psi such that a previously treated gas mixture within the
receiver tank
58 backf lows through the first transfer line into the first treatment tank
until the receiver
tank and the first treatment tank stabilize at a balanced pressure, for
example at 77 psi.
Throughout this process, the air compressor can remain activated with the
first supply
valve being opened to supply compressed air through the first supply line into
the first
treatment tank. The first transfer valve 66 remains open such that the
pressure within
both the first treatment tank and the receiver tank elevate together from 77
psi up to
100 psi with gases from the first treatment tank continuing to flow from the
first treatment
tank into the receiver tank through this later part of the fifth stage of the
optimized
process.
At step six of the optimized mode, the first transfer valve 66 that was open
in step five initially remains open while the connecting valve 74 in the
connecting line
72 is opened. The first transfer valve 66 reamins open until the receiver tank
drops to
aapproximately 80 psi as some of the gas in the received tank flows back
through the
transfer valve and subsequently through the connecting line 72 into the second
treatment tank 16. The connecting valve 74 remains open subsequent to closing
the
first transfer valve 66 so that gas is continued to be transferred from the
first treatment
tank to the second treatment tank which has the effect of reducing pressure in
the
second treatment tank from an upper limit to a lower limit, for example from
100 down
to 50 psi, while pressure within the second treatment tank increases from a
negative
vacuum pressure, for example -30 psi up to 50 psi. The second supply valve 34
remains
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opened throughout step five so that compressed air can be supplied to the
inlet of the
second treatment tank to continue to increase the pressure in the second
treatment
tank.
As described herein, in the normal cycle the treatment tanks fill the
receiver tank. This one-way flow will keep the receiver tank full and it will
feed the
external holding tank.
In the optimized cycle the timing of the valving will open the transfer valve
to the receiver tank early and the receiver tank will drain some of the stored
pressure
into the treatment tank that is pressurizing to get filtered twice and by
keeping the
transfer valve open it will fill back into the receiver tank. The valve
between the receiver
tank and the pressurizing treatment tank will open when the treatment tank is
at 75ps1.
Due to the discharge valves being closed the receiver tank pressure is about
80 psi
when the receiver tank valve opens to the pressurizing treatment tank. About 5
psi of
the receiver tank will dump into the treatment tank. They will typically
equalize at about
77 psi. The valve stays open and the treatment tank and the receiver tank will
fill to
100 psi. The same process is repeated every treatment tank fill where 5 psi of
the
receiver tank gets re-filtered by the pressurizing treatment tank. By leaving
the transfer
valve open for additional time, about 20p51 of gas in the receiver tank will
be transferred
to the pressurizing treatment tank droping the pressure in te receiver tank to
80psi and
be refilled back to 100 psi by the same treatment tank.
By recycling some of the gas from receiver tank back into one or both
treatment tanks for a second cycle of treatment within the adsorbent bed, the
quality of
the gas is improved. The analyzers will monitor the quality and when the
quality of the
gas is confirmed to be OK, the optimized cycle is over and the gas will flow
from the
receiver tank to the external holding tank. The flow then proceeds only in a
direction
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from the treatment tanks to the receiver tank since the quality in the
receiver tank does
not need to be filtered twice.
The opening and closing of the various valves is determined by the
controller using a controller which measures a duration of each step in the
process and
reconfigures the valves to the next step configuration upon expiration of the
prescribed
duration for that step. The prescribed duration of each step to cause the
tanks to be
filled and discharged at the prescribed pressures noted above is determined
during
initial calibration of the system for a given configuration of tanks and
connection lines
having prescribed volumes and flow transfer rates. Once the prescribed
duration for
each step is determined during initial calibration of a prescribed system
configuration,
the same durations can be used by controllers of all other systems with the
same
system configuration of tanks and flow lines.
In alternative embodiments, pressure sensors may be operatively
conntected to each of the tanks for measuring the pressure in the tank and
communicating the pressure back to the controller as a sensor signal so that
the valves
can be opened and closed when the measured pressure reaches the desired
pressure
value instead of operating the valves at each step according to a prescribed
duration
associated with each step that is stored on the controller. The use of
pressure sensors
increases the cost and complexity of the system and is typically not required
if using a
system configuration of tank sizes and flow lines which has been calibrated to
determine the prescribed duration for each step of the normal and optimized
processes
noted above.
Since various modifications can be made in my invention as herein above
described, and many apparently widely different embodiments of same made, it
is
intended that all matter contained in the accompanying specification shall be
interpreted
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as illustrative only and not in a limiting sense.
CA 3029511 2019-01-09
