WO1995032321A1

WO1995032321A1 - Electrolytic cell control method and apparatus

Info

Publication number: WO1995032321A1
Application number: PCT/NZ1995/000042
Authority: WO
Inventors: Daniel Christian John
Original assignee: Aquagas New Zealand Limited
Priority date: 1994-05-24
Filing date: 1995-05-24
Publication date: 1995-11-30
Also published as: AU2539795A

Abstract

A method and apparatus for the control of an electrolytic cell comprising controlling the input current to the cell based on the sensed pressure and temperature variations in the cell, the current being in the form of variable pulses.

Description

ELECTROLYTIC C CONTROL METHOD AMD APPARATUS

BACKGROUND

This invention relates to the control of an electrolytic cell and, in particular, the control of an electrolytic cell for the production of gas for use in a variety of equipment such as gas welding equipment.

One of the problems with the production of gas by use of an electrolytic cell is in the efficient control of the electrolytic cell so that electricity is not wasted. Gas produced by electrolytic cells can economically provide gas for a variety of uses including gas welding apparatus.

The output from an electrolytic cell is a function of the input current to the cell. With all other variables such as temperature, pressure, viscosity and electrolytic concentration remaining constant, the output of the cell as a function of the current rises steeply to a point at which the input of further current produces only a minimal increase in output. Furthermore, the change from a steadily increasing output is a function of current and a much reduced output for each further increment of current occurs over a short range of current values being the optimum current values for the operation of the cell. In field conditions, the other operating parameters such as temperature, pressure, viscosity and concentration may change. This is particularly the case with both temperature and pressure which may vary markedly from the commencement of current through the cell throughout operation over a reasonable period of time. As a result, the most efficient input current for the production of gas from the cell changes with time as a result of the changing temperature and pressure conditions.

OBJECT OF THE INVENTION

Therefore, it is an object of the present invention to provide an electrolytic cell control method and apparatus which accounts for this variation in the ideal input current as a result of changing temperature or pressure conditions. Alternatively, it is an object to overcome some of the disadvantages of the prior art or at least provide the public with a useful choice.

SUMMARY OF THE INVENTION

Accordingly in a first aspect, the invention may broadly be said to consist in an electrolytic cell control apparatus comprising: pressure sensing means to sense the pressure within said electrolytic cell during operation; temperature sensing means to sense the temperature within said electrolytic cell during operation; and a control means to control the electrical signal provided to said electrolytic cell such that said signal provided to said electrolytic cell is a signal comprised of pulses and of substantially constant frequency and voltage and of variable current, said variations in current arising from variations in the sensed pressure or temperature.

Accordingly, in a second aspect, the invention may broadly be said to consist in an electrolytic cell control apparatus comprising: pressure sensing means to sense the pressure within said electrolytic cell during operation; temperature sensing means to sense the temperature within said electrolytic cell during operation; a signal generator to receive an incoming alternating current and to output a signal which is variable in accordance with variations in a received input from said pressure and temperature sensing means; and; a control means to control the electrical signal provided to said electrolytic cell and wherein said signal provided to said electrolytic cell is a signal comprised of pulses and of substantially constant frequency and voltage and of variable current. Accordingly, in a third aspect, the invention may broadly be said to consist in a method of controlling an electrolytic cell comprising the steps of: sensing the pressure within said electrolytic cell; sensing the temperature within said electrolytic cell; and controlling an electrical input to said electrolytic cell being a pulsating input of substantially constant voltage and frequency and of variable current and wherein said variations and current are in response to variations in the sensed pressure or temperature within said cell.

Accordingly, in a fourth aspect, the invention may broadly be said to consist in a method of controlling an electrolytic cell comprising the steps of: sensing the pressure within said electrolytic cell; sensing the temperature within said electrolytic cell; generating a signal which is variable upon variations in said pressure or temperature levels; and controlling an electrical input to said electrolytic cell being a pulsating input of substantially constant voltage and frequency and of variable current related to said generated signal. BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects of the invention may become apparent from the following description which will now be described with reference to the following drawings in which:

Figure 1: comprises a stenotic diagram of at least one embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This invention concerns control apparatus and methods for the control of electrolytic cells used in the production of gas. The gas itself may have a variety of uses including use in welding, etc.

Such electrolytic cells generally contain a series of plates within a pressure cell which are immersed in an electrolyte. The passing of current through such plates will create the production of gas on the surface of the plates suitable for use in welding and other such apparatus. However, the most efficient operating parameters for such an electrolytic cell will change during operation of the cell. In particular, temperature and pressure are likely to be variable within the electrolytic cell.

In a preferred form, the cell may contain a plurality of concentric cylindrical plates in accordance with known apparatus. The invention itself comprises a control apparatus as shown in Figure 1 having a series of sensors such as a pressure sensing means 1 and a temperature sensing means 3. Other sensors may also be provided for a variety of different uses such as a modifier sensor 5 to sense the levels of introduction of a modifier to the gas produced by the electrolytic cell. In some uses it is desirable to add a modifier such as an alcohol to the hydrogen and oxygen mixture produced by the cylinders. This modifier and the quantity of the modifier supplied to the gas may also require monitoring to both ensure the correct quantity of modifier is introduced into the gas as well as any changes in characteristics in the production of the gas required as a result of the addition of this modifier.

In the preferred example shown in Figure 1, two pressure sensing means 1 and 2 are provided. Each pressure sensing means is essentially the same and are provided as a pair of pressure sensors so that one may fail and a second pressure sensor will still be in operation.

In addition to the temperature sensor 3 and modifier sensor 5 as previously discussed, a water level sensor 4 may also be provided as an indicator of a minimum water level with the electrolytic cell so that water may be added as required. Each of these sensors 1 through 5 may be operatively connected to an intermediate processing unit

6 to control the operation of the sensors and to activate a suitable signalling means such as signalling means 7, 9, 10, 11 or 12 upon receipt of signals from the sensors which are outside the operating parameters of the apparatus.

In the present example, not only may the intermediate processor 6 assemble a variety of inputs from the sensors 1 through 5 to provide a suitable output for later use but also activate a warning buzzer

7 or indicator lights 9 through 12 upon receipt of signals indicating a pressure outside the normal operating pressure, a temperature outside normal operating temperature, too low a water level or any problem with the modifier. Of course, in addition to the signalling of a problem, the intermediate processor 6 may also activate a safety device such as a contactor control 14 to remove power from the apparatus. The contactor control 14 may be activated if any one of the conditions indicated by the sensors is unsatisfactory or may only be activated in cases in which the type of hazard is such as to render the apparatus unsafe. In this preferred embodiment where two pressure sensors 1 and 2 are provided, it may not be necessary to remove power from the apparatus merely through the failure of a single pressure sensor if the pressure limits indicated by the second sensor are still satisfactory.

The signal from the sensors 1 through 5 or at least from the pressure and temperature sensors, whether modified by an intermediate processor 6 as in this preferred example or not, may be directed to a signal generator 18. The signal generator 18 may receive and input being an alternating current input for the electrolytic cell or, in the preferred version, a signal representative of that input current. In most circumstances, it is more desirable to modify signals in accordance with the information received by the sensors upon a much smaller current than that used in actually driving the apparatus and to use this signal as an input to a circuit to modify the larger currents preceding to the apparatus itself.

In this example, the signal generator 18 receives a signal representative of the input electrical signal being a signal of three components.

The components of the signal being 15, 16 and 17 are representative of the synchronocity, voltage and current respectively. The synchronocity signal 15 provides the signal generator 18 with information on the phase of the oscillating signal. The signal generator 18 may take the information on the incoming oscillating electrical signal and the information provided by the sensors to provide an output which varies with accordance to variations in the sensed pressure and temperature within the electrolytic cell.

The output from the signal generator may proceed through a driver circuit 19 to a pulse width modulation control system 20. Ultimately, regardless of the particular arrangement used, the signal generated by the signal generator 18 will vary the electrical signal provided to the electrolytic cell. The present invention provides an input signal of substantially constant voltage and frequency and the width of the pulse provided varying the current provided to the apparatus. It has been found that this pulsating signal provides a more efficient control of the electrolytic cell.

The method embodied by the apparatus involves the sensing of at least the pressure and temperature of the electrolytic cell and controlling the electrical input to the electrolytic cell to provide pulsed electrical input to said cell of substantially constant voltage and frequency and of variable current. The current varies in accordance with the sensed operating conditions of the cell itself. This is achieved by varying the width of the pulse in the signal provided to the electrolytic cell. In the preferred form, this control includes the production of a signal modified by the output from the sensors which in turn controls the electrical input to the cell.

The control of extreme limits and the operation of warning signals upon any parameters forming outside those of normal operation can be incorporated in the preferred form of the invention. This may also include a safety device which in operation disconnects the electrical supply to the apparatus upon receipt of signals from the sensors outside those for safe operation.

Thus it can be seen that the apparatus and method provide some improvement over existing control of electrolytic cells and in particular, allow for the efficient operation of the electrolytic cell despite variations in the pressure and temperature within the cell. This is achieved by varying the current applied to the cell in accordance with the sensed parameters.

Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth. Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope or spirit of the invention as defined in the appended claims.

Claims

CT.ΛTMS

1. An electrolytic cell control apparatus comprising: pressure sensing means to sense the pressure within said electrolytic cell during operation; temperature sensing means to sense the temperature within said electrolytic cell during operation; and a control means to control the electrical signal provided to said electrolytic cell such that said signal provided to said electrolytic cell is a signal comprised of pulses and of substantially constant frequency and voltage and of variable current, said variations in current arising from variations in the sensed pressure or temperature.

2. An electrolytic cell control apparatus comprising: pressure sensing means to sense the pressure within said electrolytic cell during operation; temperature sensing means to sense the temperature within said electrolytic cell during operation; a signal generator to receive an incoming alternating current and to output a signal which is variable in accordance with variations in a received input from said pressure and temperature sensing means; and; a control means to control the electrical signal provided to said electrolytic cell and wherein said signal provided to said electrolytic cell is a signal comprised of pulses and of substantially constant frequency and voltage and of variable current.

3. An electrolytic cell control apparatus as claimed in claim 2 wherein an output from said pressure and temperature sensing means is processed by an intermediate processor prior to input to said signal generator.

4. An electrolytic cell control apparatus as claimed in claim 3 wherein said intermediate processor also controls signal means and activates said signal means upon receiving an input from any one or more of said sensing means which is outside predetermined limits for operation of said electrolytic cell.

5. An electrolytic cell control apparatus as claimed in claim 4 wherein a modifier sensing means is provided to sense the quantity of any modifier provided to the gas output from the electrolytic cell and an output from said modifier sensing means is also provided to said signal generator.

6. An electrolytic cell control apparatus as cla ed in claim 5 wherein said modifier sensing means senses the quantity of alcohol added to the gas outputted from said electrolytic cell to control the nature of that gas.

7. An electrolytic cell control apparatus as claimed in claim 6 wherein said output from said modifier sensing means is also provided to said intermediate processor for processing prior to input to said signal generator.

8. An electrolytic cell control apparatus as claimed in any one of claims 2 to 7 wherein a driver circuit is provided intermediate of said output from said signal generator and said control circuit for the control of the input to said electrolytic cell.

9. A method of controlling an electrolytic cell comprising the steps of: sensing the pressure within said electrolytic cell; sensing the temperature within said electrolytic cell; and controlling an electrical input to said electrolytic cell being a pulsating input of substantially constant voltage and frequency and of variable current and wherein said variations and current are in response to variations in the sensed pressure or temperature within said cell.

10. A method of controlling an electrolytic cell comprising the steps of: sensing the pressure within said electrolytic cell; sensing the temperature within said electrolytic cell; generating a signal which is variable upon variations in said pressure or temperature levels; and controlling an electrical input to said electrolytic cell being a pulsating input of substantially constant voltage and frequency and of variable current related to said generated signal.

11. A method of controlling an electrolytic cell as claimed in claim 10 wherein said generated signal is generated from an inputted signal representative of an electrical input controlled by said control means prior to said electrolytic cell.

12. A method of controlling an electrolytic cell as claimed in claim 11 wherein said method includes the steps of sensing a quantity of modifier supplied to a gas produced by said electrolytic cell and adjusting the generated signal in accordance with the levels of said modifier.

13. An electrolytic cell control apparatus substantially as hereinbefore described with reference to the accompanying drawing.

14. A method of controlling an electrolytic cell substantially as hereinbefore described with reference to the accompanying drawing.