U.S. patent number 3,755,128 [Application Number 05/072,250] was granted by the patent office on 1973-08-28 for electrolysis system and method.
This patent grant is currently assigned to Isotopes, Inc.. Invention is credited to Warren E. Herwig.
United States Patent |
3,755,128 |
Herwig |
August 28, 1973 |
ELECTROLYSIS SYSTEM AND METHOD
Abstract
An electrolysis apparatus and method including means for
decomposing an electrolyte into one or more gas products, and also
including means responsive to the pressure or flow condition of one
of the product gases for controlling the electrical input to the
electrolysis cell whereby to match the gas generation rate and the
gas demand rate in the electrolysis system. Electrical power cost
of the electrolysis process, a major operating expense, will be
reduced if the gas generation rate responds to the demand rate.
Inventors: |
Herwig; Warren E. (Greenfield,
WI) |
Assignee: |
Isotopes, Inc. (Westwood,
NJ)
|
Family
ID: |
22106466 |
Appl.
No.: |
05/072,250 |
Filed: |
September 15, 1970 |
Current U.S.
Class: |
204/228.3;
204/228.1; 204/228.5 |
Current CPC
Class: |
C25B
15/02 (20130101) |
Current International
Class: |
C25B
15/02 (20060101); C25B 15/00 (20060101); B01k
003/00 (); C01b 013/04 () |
Field of
Search: |
;204/228-230,129 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mack; John H.
Assistant Examiner: Valentine; D. R.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. An electrolysis system for decomposing an electrolyte into at
least one product gas, comprising an electrolysis cell having
terminals and adapted to have an electrolyte therein, said cell
being adapted to generate at least one product gas upon the
connection of direct current across the terminals of said cell, the
generation of said one product gas by said cell being a function of
the direct current input to said cell, means in circuit
relationship for supplying a variable direct current to said cell
terminals whereby said one product gas is generated by said cell,
means for sensing the flow rate of a product gas generated by said
cell, and feedback network means coupled directly between said
sensing means and said direct current supplying means for
controlling the variable direct current input to said cell as a
function of the condition sensed.
2. An electrolysis system as defined in claim 1 in which said
condition sensed is the flow rate from said cell of said one
product gas.
3. An electrolysis system as defined in claim 1 in which said means
for supplying direct current to said cell comprises at least one
thyratron type solid state device, and wherein said feedback
network produces an output electrical signal that controls the load
current conduction through said solid state device whereby to
control the electrical current input to said cell.
4. An electrolysis system for decomposing an electrolyte into at
least one product gas, comprising an electrolysis cell having
terminals and adapted to have an electrolyte therein, said cell
being adapted to generate at least one product gas upon the
connection of direct current across the terminals of said cell, the
generation of said one product gas by said cell being a function of
the direct current input to said cell, means in circuit
relationship for supplying a variable direct current to said cell
terminals whereby said one product gas is generated by said cell,
means for sensing a condition of a product gas generated by said
cell, feedback network means coupled directly between said sensing
means and said direct current supplying means for controlling the
variable direct current input to said cell as a function of the
condition sensed, and sensor means connected in current sensing
relation between said direct current supply means and said cell and
connected to said feedback network means for limiting the maximum
and minimum current supplied by said direct current supply means to
said cell to predetermined maximum and minimum values.
5. The method of controlling the rate of gas generation in an
electrolysis system of the type including an electrolysis cell in
which at least one product gas is generated by said cell upon the
connection of direct current to the terminals of said cell and in
which the generation of said one product gas by said cell is a
function of the direct current input to said cell, which comprises
the steps of sensing the flow rate from said cell of said one
product gas generated by said cell, and of controlling the direct
current input applied to said cell as a function of the flow rate
sensed whereby to control the rate of gas generation by said cell.
Description
The product gas demand function such as product gas pressure or
flow rate is converted into an electrical control signal which is
fed to a feedback network which controls the direct current output
of the power supply to the cell, to thereby cause a gas generation
rate equaling the demand rate. The gas demand function which is
measured compensates automatically for varying operating conditions
which affect gas generation rate such as ambient temperature, cell
electrolyte phenomena, and long term aging characteristics of the
electrolysis cell. Control signals representing various other
parameters of the electrolysis system such as high and low limits
for electrolysis current may also be fed into the feedback network
to control the current flow from the power supply to the cell.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electrolysis system, and more
particularly to an apparatus for and a method of matching the gas
generation rate in and the gas demand rate on an electrolysis
system.
2. Description of the Prior Art
Electrolysis systems are known in the prior art in which a direct
current is applied across a pair of electrodes in contact with an
electrolyte to cause decomposition of the electrolyte into one or
more product gases. One such system, involving an aqueous
electrolyte and hydrogen and oxygen product gases, is shown in U.S.
Pat. No. 3,410,770, granted to Lester W. Buechler on Nov. 12, 1968.
The system of the Buechler patent just mentioned consists
essentially of six parts: (1) an electrolysis module (a stack of
cells); (2) a recirculating electrolyte loop; (3) water addition
equipment; (4) oxygen manifolding; (5) hydrogen manifolding; and
(6) a direct current power supply. The system of the aforementioned
Buechler patent as well as other known electrolysis systems
encounter operating problems when the operating requirements are
increased from those of a continuous steady state operation to a
variable demand with minimum operator attendance. In prior art
electrolysis systems, operator attendance is required for
adjustment of the electrolysis current due to: (1) changes in gas
demand; (2) changes in ambient conditions affecting the rate of gas
production; (3) changes in the system parameters affecting the rate
of gas production; and (4) cell aging characteristics affecting
rate of gas production.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
electrolysis system and apparatus which includes means for
automatically matching the gas generation rate and the gas demand
rate, whereby to operate the system at optimum efficiency and to
effect economy in the operation of the system.
It is another object of the invention to provide an electrolysis
system, apparatus and method in accordance with which the
electrolysis current is applied to the electrolysis cell or module
as a function of the gas demand rate whereby to cause the gas
generation rate of the system to equal the gas demand rate.
It is a further object of the invention to provide an electrolysis
system and apparatus which is substantially automatic in its
operation and which does not require operator attendance for
adjusting the gas generation rate.
It is a further object of the invention to provide an aqueous
electrolysis system, apparatus and method in accordance with which
the electrolysis current is automatically adjusted to compensate
for changes in gas demand, for changes in ambient conditions
affecting the rate of gas production, for changes in system
parameters such as electrolyte temperature affecting the rate of
gas production, and to compensate for cell aging characteristics
affecting the rate of gas production.
In achievement of these objectives there is provided in accordance
with this invention an electrolysis apparatus and method including
means for decomposing an electrolyte into one or more gas products,
and also including means responsive to the pressure or flow
condition of one of the product gases for controlling the
electrical input to the electrolysis cell whereby to match the gas
generation rate and the gas demand rate in the electrolysis system.
Electrical power cost of the electrolysis process, a major
operating expense, will be reduced if the gas generation rate
responds to the demand rate.
The product gas demand function such as product gas pressure or
flow rate is converted into an electrical control signal which is
fed to a feedback network which controls the direct current output
of the power supply to the cell, to thereby cause gas generation
rate equaling the demand rate. The gas demand function which is
measured compensates automatically for varying operating conditions
which affect gas generation rate such as ambient temperature, cell
electrolyte phenomena, and long term aging characteristics of the
electrolysis cell. Control signals representing various other
parameters of the electrolysis system such as high and low limits
for electrolysis current may also be fed into the feedback network
to control the current flow from the power supply to the cell.
Further objects and advantages of the invention will become
apparent from the following description taken in conjunction with
accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an electrolysis apparatus and system
embodying the automatic control features of the invention;
FIG. 2 is a schematic diagram of control circuitry which may be
incorporated in the system and apparatus of the present invention
to control the gas generation rate as a function of the gas demand
rate and also as a function of other factors;
FIG. 3 is a schematic diagram of another control circuit which may
be used to control the gas generation rate as a function of the gas
demand rate also as a function of other factors; and
FIG. 4 is a vector diagram showing the various electrical
relationships in the circuit of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is shown an electrolysis system and
apparatus which except for the automatic control system to be
hereinafter described, is substantially similar to the electrolysis
system shown in the aforementioned U.S. Pat. No. 3,410,770, granted
to Lester W. Buechler, on Nov. 12, 1968, the teachings of which
patent are hereby incorporated by reference into this
application.
The aqueous electrolysis system and apparatus of FIG.1 comprises a
cell 10 having a pair of gas permeable electrodes, namely, cathode
11 and anode 12, in direct contact with the opposite surfaces of
the electrolyte matrix 13 which is saturated with an aqueous
electrolyte. Electrodes 11 and 12 are connected by leads 15 and 16
to a source of direct current generally indicated at 14 to be
described more fully hereinafter. The quantity of gas produced is
directly proportional to the number of electrolysis cells and to
the current flow through each cell. Electrolyte matrix 13 is a
porous diaphragm of asbestos fibers or other material which is
resistant to attack by caustic alkali solution or other
electrolyte. The thickness of the electrodes 11, 12 and the matrix
13, as shown in FIG. 1, have been exaggerated for purposes of
clarity in description. The electrodes 11 and 12 and the
electrolyte matrix 13 are supported in housing 17 which forms a gas
chamber 18 with the cathode 11 and an electrolyte chamber 19 with
the anode 12. The aqueous electrolyte 20 is contained in the
electrolyte chamber 19.
The electrolyte matrix 13, saturated with the aqueous electrolyte,
serves a dual function. The matrix 13 maintains intimate contact
between the interface of the electrolyte and the gas permeable
electrodes 11 and 12 and also serves as a gas impervious barrier to
prevent mixing of the gas products.
Electrolyte is supplied to the cell by the circulation of
electrolyte solution from separator 22 to electrolyte chamber 19 by
means of pump 23 through conduits 24, 25 and 26. The gas generated
at the electrode 12 adjacent the electrolyte chamber 19 is removed
from the electrolyte chamber entrained in the circulating
electrolyte solution.
During the operation of the cell, the aqueous electrolyte 20,
impelled by the driving force of the gas bubbles present in it, is
forced from the electrolyte chamber 19 through conduit means 24 and
passes to electrolyte separator 22 where the gas produced at the
electrode 12 and entrained in the aqueous electrolyte 20 is
extracted and separated from the circulating electrolyte solution.
Design details for the separator 22 are not shown as separators of
this type are well known in the art. Water consumed in electrolysis
is replaced by means of water storage means 30 from which water is
fed in controlled amounts to separator 22 via conduit 31 to
maintain the electrolyte at optimum concentration. Valve 32
regulates the addition of water to the electrolyte solution in
separator 22 at a rate determined to replace the water consumed by
electrolysis.
The oxygen gas produced at anode electrode 12 is withdrawn overhead
from the separator 22 via conduit 33, through differential pressure
regulator or control valve 58, and through connected conduit 59.
Oxygen not required for maintaining system pressure is discharged
through conduit or "plumbing" 59. The degassed electrolyte passes
out of the separator 22 via conduit means 25 to pump 23 wherein it
is directed via conduit means 26 back to the electrolyte chamber
19.
The hydrogen gas produced at cathode electrode 11 is evolved into
gas chamber 18 and the chamber 18 is maintained under pressure by
regulating the passage of gas out of the chamber. The gas that is
removed from gas chamber 18 is passed by conduit 50 through valve
60 and thence externally of the system through conduit 61. Demand
for hydrogen gas is generated by valve 60 or by a system of valves
and control devices in response to the variable demand requirements
of a gas demanding load external of the system. Hydrogen demand is
discharged by conduit or "plumbing" 61. Valve 60 and conduit 61 are
both located external to the electrolysis and control system but
interface with the electrolysis and control system at 62.
When a direct current is initially applied to the apparatus at
cathode 11 and anode 12, as will be described hereinafter, gas
generated at electrode 11 is collected in the chamber 18 until the
pressure of the gas in the chamber 18 exceeds the pressure of the
gas generated at electrode 12. This occurs in a relatively short
time interval and if any electrolyte is present in chamber 18 it
will be forced through the capillary matrix to chamber 19. The
differential pressure control valve 58 in oxygen conduit 33
maintains a preset pressure differential between the hydrogen gas
pressure in gas chamber 18 and the pressure of the oxygen gas in
conduit 33 leading from separator 22. The hydrogen gas pressure in
conduit 50 is monitored to valve 58 by conduit 72 connected between
conduit 50 and differential pressure control valve 58.
As the pressure of the gas produced at the electrode 12 is raised
or lowered, the valve 58 opens or closes in response to this
pressure to provide a decrease or increase in the oxygen gas
pressure in oxygen conduit 33 so as to maintain an appropriate
differential pressure across the cell 10 and avoid leakage of
electrolyte solution through the matrix 13 to chamber 18. In this
manner, the electrolyte in the capillary matrix 13 adjacent
electrode 11 is constantly replenished with electrolyte solution.
Since the gas produced at electrode 11 is not entrained in the
electrolyte, the need for a separator unit to disentrain gas
produced at electrode 11 from the electrolyte is eliminated.
The hydrogen manifold pressure in conduit 50 is the independent or
reference pressure for the differential pressure valve 58 and the
oxygen manifold 33 pressure is the dependent or following pressure.
Oxygen not required for maintaining manifold 33 pressure is
discharged through conduit or "plumbing" 59.
It will also be understood that in the pressure differential
control system, the valve 58 could be placed in conduit 50 instead
of in conduit 33 as shown, in which case the oxygen pressure in
conduit or manifold 33 would be used as the reference pressure.
Also, while in the system illustrated in FIG. 1, the demand
function transducer device 51 senses a gas flow or pressure
condition in hydrogen manifold 50, the transducer device 51 could
instead sense a gas flow or pressure condition in oxygen manifold
33.
If the differential pressure valve 58 is located in hydrogen
manifold 50 and the pressure in oxygen manifold 33 is used as the
reference pressure for the differential pressure system, then the
demand function transducer device 51 should also be located in
oxygen manifold 33.
As is obvious to one skilled in the art, a multicellular apparatus
comprising a plurality of the unit cells may be connected in series
and clamped into a compressed face-to-face relationship along a
common axis to form a module or stack of cells. In commercial
applications such assemblies are preferred for efficient,
quantitative production of hydrogen and oxygen.
In the illustrated embodiment of FIG. 1, the polarity connections
of the direct current input power to the cell electrodes 11 and 12
are such that electrode 12 is the anode at which oxygen is evolved.
The reason for this, as explained in the aforementioned U.S. Pat.
No. 3,410,770 to Lester W. Buechler, is that the volume of oxygen
produced at the anode is one half that of the hydrogen produced at
the cathode and consequently a smaller separator 22 is required to
disentrain the O.sub.2 from the circulating electrolyte. However,
it will be understood that instead of the preferred arrangement
just referred to, the polarity connections of the power supply to
the electrolysis cell could be the reverse of those just described,
so that electrode 11 is the anode at which oxygen is evolved and
electrode 12 is the cathode at which hydrogen is evolved.
It will be noted in the schematic diagram of FIG. 1 that the power
supply generally indicated at 14 has its electrical output
connected by conductors or cables 15 and 16 to the electrodes 11
and 12 of the cell 10. An electrical transducer device 51 which may
sense either gas pressure or gas flow conditions in the hydrogen
manifold 50, depending upon the particular type of transducer
device 51 which is used, is electrically connected by conductor
means schematically indicated at 75, to the input of the feedback
network 53.
As will be explained in more detail hereinafter, the feedback
network 53 in response to a control signal or signals applied
thereto controls the power supply 14 via conductor means 73 to
provide a variable electrolysis current to the electrolysis cell 10
via cables 15 and 16. The electrolysis current is therefore a
function of the gas pressure or of the gas flow condition sensed by
transducer 51, depending upon whether transducer device 51 is of a
type which senses gas pressure or gas flow. In this manner a given
pressure or flow rate of the hydrogen can be maintained.
If the transducer device 51 is of a type which senses pressure, a
transducer device which may be used is manufactured by
Robinson-Halpern of 5 Union Hill Road, West Conshohocken,
Pennsylvania 19428, under the designation "Variable Set Point
Pressure Transducer Model 107A". This pressure transducer senses
pressure variations or departures from a reference set point
pressure and provides an output voltage or error signal which is
proportional to the deviation of the pressure from the set point.
Thus, for example, if transducer 51 detects a pressure drop in
hydrogen manifold 50 which is indicative of increased demand for
hydrogen, it will transmit a proportional signal to feedback
network 53 which will cause feedback network 53 to cause an
increase in the direct current flow to cell 10 from power supply 14
sufficient to increase the gas generation rate of cell 10 until the
pressure in hydrogen manifold 50 is returned to the set point.
Conversely, if transducer 51 detects a pressure increase in
hydrogen manifold 50 which is indicative of decreased demand for
hydrogen, it will transmit a proportional signal to feedback
network 53 which will cause feedback network 53 to cause a
reduction in the direct current output of power supply 14 to the
electrodes 11 and 12 of cell 10 to thereby decrease the gas
generation rate of cell 10 until the pressure in hydrogen manifold
50 is returned to the set point.
The thermal and mass flow considerations require that the maximum
and minimum electrolysis currents be limited to preselected values.
A sensor 55 connected in current sensing relation to cable 16 (or
15) leading from power supply 14 to one of the electrodes of cell
10 is used to quantitatively sense the electrolysis current and to
feed a signal via conductor means 77 into the feedback network 53
to limit the maximum and minimum current supplied by power supply
to electrolysis cell 10 to maximum and minimum values.
The feedback network and associated power supply may be of the type
shown and described, for example, in U.S. Pat. No. 3,333,178
granted to Roland L. Van Allen and Charles E. Hardies on July 25,
1967, and the teachings of U.S. Pat. No. 3,333,178 to Van Allen and
Hardies are hereby incorporated by reference into the present
application. Thus, for example, the feedback network 53 and power
supply 14 may assume the form shown in FIG. 4 of the aforementioned
Van Allen et al. patent which is substantially embodied in FIG. 2
of the present application. There is shown in FIG. 2 of the present
application a feedback network and thyristor power supply utilizing
solid state devices generally indicated at 100 and 100' of the type
having thyratron characteristics. A number of solid state devices
of this character are now available to the industry. General
Electric Company offers devices identified as "Silicon Controlled
Rectifiers" (SCRs) and Westinghouse Electric Corporation produces
devices of this type identified by the name "Trinistors."
The solid state devices of the type indicated at 100 and 100' in
FIG. 2 include three terminals, two which (102, 108) may be
considered as main current carrying terminals and the third (120)
as a gate or control terminal. These devices are so characterized
that with respect to the main current carrying terminals the device
at all times presents a high impedance to current flow in one
direction, that is a high reverse impedance, and in this respect,
the device exhibits the characteristics of a rectifier, while the
device presents a high impedance to the flow of current between the
main terminals in the opposite direction that is, a high forward
impedance, until the device is energized or fired upon application
of a control signal to the gate or control terminal. When the
device is fired, the forward impedance with respect to the main
current carrying terminals abruptly drops to an extremely low
value, and the flow of current through the device between the main
current carrying terminals is independent of and does not require
application of a control or energizing signal to the gate terminal
and will continue so long as a potential is maintained across the
main current carrying electrodes. When the potential across the
main current carrying electrodes is extinguished, the device
returns to its normal or unenergized condition, presenting a high
forward impedance, and will not pass current although a potential
is applied across the main current carrying electrodes, providing a
breakdown potential is not reached, until a control signal is
applied to the gate terminal to again energize the device.
It is apparent from the foregoing that this class of solid state
devices possess certain operational characteristics of a thyratron
and may therefore be described as "solid state thyratrons" or
"solid state devices possessing thyratron characteristics." The
latter terms are used throughout this description and in the
appended claims to define solid state devices of the class
described hereinbefore. Furthermore, as a descriptive aid, the main
current-carrying terminals of the solid state devices of the class
described hereinbefore are referred to herein and in the appended
claims as "anode terminal" and herein and in the appended claims as
"anode terminal" and "cathode terminal" although the terms "anode"
and "cathode" are not generally employed in connection with solid
state devices, and probably would not be used to designate the
components of these solid state devices to which the main current
carrying terminals are connected.
Referring now more specifically to FIG. 2, the combined feedback
network and power supply shown in FIG. 2 comprises a pair of solid
state devices having thyratron characteristics 100 and 100', each
including an anode terminal 102, 102' which are respectively
connected to opposite terminals 104, 104' of a center tapped
transformer secondary generally indicated at 106. The circuit of
FIG. 2 is analogous to a full-wave center tap rectifier and
provides a controlled flow of load output current to the input
electrical terminals of the electrolysis cell during each half
cycle of the applied voltage across transformer secondary 106, the
current conduction period during each half cycle depending upon the
cumulative effect of the control signals applied to the feedback
network 53, as will be explained more fully hereinafter. The solid
state devices 100, 100' also each respectively include a cathode
terminal 108, 108', respectively, which are connected to each other
and also to the output or load terminal 116 which is connected to
cable 16 leading to electrode 12 of the electrolysis cell. The
other cable 15 leading to the electrolysis cell is connected to the
center tap 118 of the transformer secondary 106.
The solid state devices 100 and 100' each include a gate or control
terminal 120, 120', respectively. The apparatus further includes a
pair of saturable magnetic cores 122 and 122', respectively,
preferably constructed of a material presenting a substantially
rectangular hysteresis characteristic. Two control windings 124,
126 are provided for the saturable magnetic cores 122 and 122',
each of the two windings 124, 126 being common to both of the
saturable magnetic cores 122 and 122'. Windings 124, 126 are
adapted to be energized with direct current control voltages to
control the degree of saturation of saturable magnetic cores 122,
122'. The control voltage across control winding 124 may be
derived, for example, from the output voltage signal of transducer
device 51 which monitors either the gas pressure or the gas flow in
the hydrogen manifold 50, depending on the type of transducer
device 51 which is used. The control voltage across control winding
126 for example, may be a signal derived from the current sensing
device 55, FIG. 1, and diagrammatically shown as being connected by
conductor means 77 to the feedback network to limit the direct
current supplied by the power supply 14 to electrolysis cell 10 to
maximum and minimum values. The minimum input current to cell 10 is
set at a value which provides a minimum gas product rate sufficient
to provide dilution of gas from leaks or gas migration from cavity
20 across the capillary matrix 13 to cavity 18. In this way, a
maximum gas purity in cavity 18 is maintained.
Upon conditions of low hydrogen gas demand, the gas generation rate
may exceed the demand rate. This condition results in an increased
hydrogen pressure which is relieved by regulator valve 79 connected
to hydrogen manifold line 50, regulator valve 79 permitting the
escape of hydrogen gas through relief conduit 81.
Connected in circuit with each of the solid state thyratron devices
100 and 100' is a gate winding 130, 130'. One end of each gate
winding 130, 130' is connected to the terminal 104 or 104' of the
secondary winding 106 and to anode terminal 102, 102' in series
with a solid state rectifier 132, 132'. The opposite end of each
gate winding 130, 130' is connected through a resistor 134, 134',
to the gate or control element terminal 120, 120' of the solid
state thyratron device 100, 100'. Each of the respective gate
windings 130, 130' is mounted on or in magnetic association with
one of the respective saturable cores 122, 122', respectively.
The control windings 124, 126 and the gate windings 130, 130' each
are shown with a dot which indicates winding sense or polarity
relationship.
In the operation of the apparatus of FIG. 2, assume that the
alternating current power supply at transformer secondary winding
terminals 104 and 104' has passed through zero potential and is
beginning a half cycle which is positive relative to the anode
terminal 102 of solid state device 100 and negative with respect to
the anode terminal 102' of solid state device 100'. Under this
condition, the solid state device 100 presents a high forward
impedance since the control element 120 of solid state device 100
is nonenergized, and the solid state device 100' presents a high
reverse impedance. Rectifier 132' blocks current flow through gate
winding 130' of saturable core 122'. Gate winding 130 in the
circuit of solid state device 100 presents a high impedance, since
core 122 is not saturated at this instant and no power is applied
across the load output terminals 115 and 116. Current, however,
will flow through the gate circuit of coil 130, i.e., through coil
130, resistor 134, gate terminal 120, through a portion of solid
state device 100, cathode terminal 108, and across load terminals
115, 116, back to center tap 118 of transformer secondary 106, to
thereby carry the magnetic material of core 130 toward one level of
saturation, the parameters of the gate circuit being selected to
insure adequate current flow to effect this performance.
Core 122 will be driven to saturation at some point during the half
cycle of the alternating current supply source which is positive
relative to the anode terminal 102 of solid state device 100, as
determined by the combined effect of the vectorial sum of the
control signals applied to the windings 124 and 126.
At the instant core 122 saturates, the impedance of gate winding
130 abruptly drops with a concomitant increase in current through
gate winding 130. The abrupt current variation through gate winding
130 is applied as a control signal through resistor 134 to gate
terminal 120 of solid state device 100 to energize or fire the
device 100 within a microsecond or less following saturation of
core 122. When fired, the forward impedance of solid state device
100 abruptly drops very close to zero and the power supply is
connected across load terminals 115, 116 through the remaining
portion of the half cycle. The solid state device 100 when fired
presents a substantially complete short circuit across gate winding
130 and thereby terminates the control signal from gate winding 130
to gate terminal 120 of the solid state device 100. Thus, the
arrangement for producing and applying a control signal to the gate
terminal of the solid state device provides an automatic clipping
or limiting operation which prevents application of a control
signal of a magnitude which exceeds the design limitations of the
solid state device.
Upon the next half cycle of applied alternating current voltage,
when the input power of transformer secondary winding 106 is
positive with respect to the anode terminal 102' of solid state
device 100' and negative with respect to the anode terminal 102 of
solid state device 100, the respective solid state devices 100 and
100' and the circuits associated therewith reverse their respective
relationships from those described for the first half cycle of
applied voltage. That is, the solid state device 100' now presents
a high forward impedance and the solid state device 100 presents a
high reverse impedance. The solid state device 100' becomes
conductive or fires at a predetermined angular condition in the
second half cycle of applied voltage in the same manner as
described in connection with the solid state device 100 during the
first half cycle of applied voltage. When fired, the forward
impedance of the solid state device 100' abruptly drops very close
to zero and the power supply is connected across the load terminals
115, 116, through the remaining portion of the second half cycle.
During the second half cycle, current flow in gate winding 130'
induces voltage in gate winding 130 through the control circuit,
and this induced voltage together with the combined effect of the
control signals applied to control windings 124, 126 acts to effect
resetting of core 122 to the initial saturation level for response
to the next half cycle. A corresponding action takes place during
alternate half cycles to reset core 122'.
Other control systems which may be used instead of the phase angle
shifting system of the U.S. Pat. No. 3,333,178 to Van Allen et al,
hereinbefore described, are set forth in Sprague Technical Paper
No. 63-9, published by Sprague Electric Company, North Adams,
Massachusetts, entitled "The Silicon Controlled Rectifier in
Proportional Power Control," the teachings of which technical paper
are hereby incorporated by reference into the present patent
application. One phase angle control circuit substantially as
disclosed in the aforementioned technical paper is shown in FIG. 3
of the present application and the voltage vector diagram for the
circuit of FIG. 3 is shown in FIG. 4 of the present
application.
Referring now to FIG. 3, there is shown what is known as the
"Silicontrol gate drive" which is a special patented form of wide
angle phase-shifting circuit controlled by a saturable reactor.
This special form offers a full 180.degree. range of linear phase
shift using a small (4 millwatt) direct current control signal and
provides a steeply rising gate pulse which triggers the firing of
the thyratron type solid state device. This Silicontrol gate drive
is manufactured and sold by Sprague Electric Company of North
Adams, Massachusetts. Referring now to FIG. 3, there is shown an
input transformer generally indicated at 150 including a primary
winding 152 to which is applied, for example, 115 volt, 60 cycles
per second alternating current electric power. Transformer 150
includes a secondary winding 154. Across the terminals B and X of
the transformer secondary winding 154 is connected a fixed
phaseshift network RC.sub.1 which establishes a "base line" voltage
E.sub.R across resistor R as shown in the vector diagram of FIG. 4.
Connected across resistor R is a series resonant circuit consisting
of inductor L and capacitor C. The voltages across L and C are
represented in the vector diagram of FIG. 4 by vectors A'P' and
P'B', separated by small angle .phi. (the loss angle of the
inductor). In the vector diagram of FIG. 4, the primed letters such
as A'P', etc., correspond to the same unprimed letters of the
circuit diagram of FIG. 3.
When the inductance of L is altered slightly, the relative lengths
of vectors A'P', P'B' are effectively varied and if the angle .phi.
is made to stay constant, by careful design, the point P', will in
effect, move around the dotted circle of the vector diagram of FIG.
4. A pulse forming network generally indicated in block diagram
form at 156 in FIG. 3 is connected across the center tap terminal O
of the transformer secondary 154 and also across the terminal P
which is the junction point between the inductance L and the
capacitance C in the series resonant network across the resistance
R.
By careful design, the circular locus is made to pass through the
input potential point X' on the vector diagram, and since angle X'
A' B' is a right angle, the vector X'B' is a diameter of the circle
and the input center tap O' is at the center of the circle.
The vector O'P' then represents an output that can be taken from
the network, varying in phase angle by approximately 300.degree.
while remaining constant in amplitude.
Two silicon controlled rectifiers SCR No. 1 and SCR No. 2 (not
shown) may be connected to provide rectified direct current to the
electrodes 11, 12 of cell 10, the magnitude of the current flow to
cell 10 being controlled during both half cycles of alternating
current across transformer 150 by the circuit of FIG. 3.
The inductor L takes the form of a specially designed saturable
reactor 155 whose inductance is varied by saturating its core to a
greater or less degree by passing varying amounts of direct current
through the control windings 1-2, 3-4. The output voltage across
the terminals O, P, are formed into pulse spikes by the pulse
forming network 156 which drives the coupling transformer generally
indicated at 158. Due to the blocking action of the two output
diodes 162A, 162B, the pulse spikes are delivered on alternate half
cycles from terminals G.sub.1 and G.sub.2, which are each
respectively connected to the gate or control terminal of one of a
pair solid state thyratron devices (not shown) which in this case
are the pair of silicon controlled rectifiers SCR No. 1 and SCR No.
2, the terminals K.sub.1, K.sub.2 of the circuit of FIG. 3 being
connected to the cathode terminals of the respective solid state
devices.
The control windings 1-2, 3-4, which control the degree of
saturation of the saturable core reactor 155 and hence control the
value of the inductance L in the phase shift circuit, derive their
signal voltages from the sources as set forth in the example of
FIGS. 1 and 2. For example, the voltage signal across control
winding 1-2 of FIG. 3 may be the signal from the transducer device
51 indicating the gas pressure or flow condition in the hydrogen
manifold 50. The voltage signal across control winding 3-4 may be
derived from the current transducer device 55 in current sensing
relation to conductor or cable 16 between the thyristor power
supply 14 and the electrode 12, to indicate the direct current flow
to cell 10.
It will be understood that the feedback and power supply systems
shown in FIGS. 2 and 3 are by way of example only and that other
suitable types of feedback and power supply systems may be
substituted therefor.
It can be seen from the foregoing that there is provided in
accordance with the invention an apparatus for and method of
matching the gas generation rate with the gas demand rate in an
electrolysis system by measuring a demand function such as gas
pressure or gas flow, and adjusting the input direct current to the
electrodes of the electrolysis cell in accordance with the sensed
demand function whereby to match the gas generation and demand
rates. This matching of gas generation rate with gas demand rate
results in important savings in the cost of electrical current
input to the electrolysis cell.
It will also be noted that a very important advantage of the
apparatus and method is that in sensing the gas pressure or gas
flow and controlling the input current to the electrolysis cell as
a function of the sensed gas pressure or gas flow as taught by the
present invention, not only is the gas output of the cell varied in
accordance with the varying gas demand rate of the external gas
demanding load, but also automatic and inherent compensation is
simultaneously made without further adjustment for such varying
operating conditions as ambient temperature, module electrolyte
phenomena, and long term aging characteristics of the electrolysis
cell.
While there have been shown and described particular embodiments of
the invention, it will be obvious to those skilled in the art that
various changes and modifications may be made therein without
departing from the invention and, therefore, it is aimed to cover
all such changes and modifications as fall within the true spirit
and scope of the invention.
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