WO1998009001A1

WO1998009001A1 - Method and advice for generating hydrogen and oxygen

Info

Publication number: WO1998009001A1
Application number: PCT/SG1997/000035
Authority: WO
Inventors: Dusan Petrovic
Original assignee: Green Gas Generator Pte Ltd.
Priority date: 1996-08-28
Filing date: 1997-08-22
Publication date: 1998-03-05
Also published as: ZA977754B; AUPO199796A0; ID18195A

Abstract

A device (10) for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electrolyser (8) for containing the aqueous electrolyte and provided with electrodes (10) for application of electric current to the electrolyte, and electric supply means (1) for providing said electric current. The electric supply means (1) generates the electric current as a pulsating currrent.

Description

METHOD AND DEVICE FOR GENERATING HYDROGEN AND OXYGEN

This invention relates to a method and device for generating hydrogen and oxygen.

United States patent 4,081 ,656 for example describes a method and apparatus for generating a hydrogen and oxygen, by electrolytic dissociation of an aqueous electrolyte. Generating hydrogen and oxygen by this means for use as a combustible gas mixture has advantages over the use of bottled gases in that the generating apparatus may be made relatively portable, and the basic material for generating the gas mixture, namely water, is easily obtainable even at most sites. Widespread adoption of apparatus of this nature has not however occurred. For example, electrodes used for applying electric current to the water for effecting electrolysis may erode and cause metal slugs and other deposits to form which may cause damaging short-circuits to occur in the apparatus, so that the lifetime of the apparatus and operational reliability may not be satisfactory.

In one aspect, the invention provides a method of generating hydrogen and oxygen by electrolysis of an aqueous electrolyte wherein the electrolysis is effected by passing pulsating electric current through the electrolyte. The electrolyte may be formed from water. The method may be practised so as to avoid or at least limit sludge formation in the electrolyte. The current may be unidirectional. Preferably, the current is provided by application of a reduced voltage during start-up.

In another aspect the invention provides a method of electrolytic generation of hydrogen and oxygen from water which is sludge free using is a controlled pulse current source.

The invention also provides a device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte,

SUBSTITU^TE SHEET (RULE 26ι and electric supply means for providing said electric current, characterised in that the electric supply means comprises means for generating a pulsating current.

In another aspect, the invention provides a device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, wherein the electroiyser comprises a lengthwise extending series of chambers divided by transverse walls which are formed by spaced transversely extending electrodes, the electrodes having openings therethrough to permit flow of electrolyte through the chambers and to permit take-off of released hydrogen and oxygen when electric current is applied to electrolyte within the electroiyser. A tank may be provided for containing the electrolyte, which communicates with the interior of said chambers and which is arranged whereby released hydrogen and oxygen may enter the tank and cause influx of electrolyte from the tank into the chambers under influence of pressure of released hydrogen and oxygen in the tank.

In another aspect the invention provides a device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, the electroiyser including a tank for containing the electrolyte, which communicates with the interior of said chambers and which is arranged whereby released hydrogen and oxygen may enter the tank and cause influx of electrolyte from the tank into the chambers under influence of pressure of released hydrogen and oxygen in the tank, the electrolyte in the tank being in use pressurised to a low pressure such as to a pressure not more than 1.5 bar. This pressurisation may be controlled by setting a pressure switch at a maximum of, for example, 1.5 bar. This assists in efficient gas production by minimising the resistance of electricity flow between electrodes of the electroiyser.

In a still further aspect the invention provides a device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, the device having an outlet for the hydrogen and oxygen and a flashback arrester arranged such that released hydrogen and oxygen from the electroiyser flows in use through the flashback arrester to the outlet, wherein the flashback arrester includes a chamber having coolant therein and through which released hydrogen and oxygen passes in use to the outlet. The gas arrester may include valve means effective to close communication from the gas arrester to the outlet when flashback occurs therein. The valve means may comprise a nonreturn valve.

The invention also provides a method of preventing flashback in the electrolytic generation of hydrogen and oxygen by the use of a coolant and a non-return valve.

The invention is further described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a diagram of a device for forming a combustible mixture of hydrogen and oxygen by electrolysis, in accordance with the invention;

Figure 1A is a diagram of an electronic controller forming part of the device of Figure 1 ;

Figure 2A is a side view of part of an electroiyser incorporated into the device of Figure 1 ;

Figure 2B is an underside view of the part shown in Figure 2A;

Figure 3 is an axial cross-section of a tank incorporated into the device of Figure 1 ;

Figure 4A is an axial cross-section of a dryer incorporated into the device of Figure 1 ; Figure 4B is a transverse sectional view of the dryer of Figure 4A;

Figure 5 is an axial cross-sectional view of a relief valve incorporated into the device of Figure 1 ;

Figure 6 is an axial cross-sectional view of a flashback arrester incorporated into the device of Figure 1;

Figure 7 is a diagram of an alternative device for forming a combustible mixture of hydrogen and oxygen by electrolysis in accordance with the invention;

Figure 8 is a plan view of an electrode incorporated into the device of Figure 7;

Figure 9 is a top view of a gasket incorporated in the device of Figure 7;

Figure 10 is a transverse cross-section of the gasket of Figure 9;

Figure 11 is an enlarged view of part of Figure 10; and

Figure 12 is a transverse cross-section of a central pipe incorporated into the device of Figure 7.

Referring to Figure 1 , the device 100 includes an electroiyser 8, for electrolysis of an aqueous electrolyte contained therewithin. A power supply 1 is connected to provide electric power to die electroiyser 8, and also to cooling fans 19 for cooling the electroiyser 8.

A tank 6 is fitted to the electroiyser. Combustible gas mixture generated by the electroiyser 8 passes to the tank 6 and thence, via a dryer 4 mounted on the tank and a flashback arrester 5, to a cutting torch 11 at which the gas mixture is burnt to generate a flame, for welding, cutting or the like.

SUBSTITUTE SHEE^* (RULE 26) The electroiyser 8 is made up of two electrode units 1 10 of which one is shown, in part, in more detail in Figures 2A and 2B. These units 1 10 are in the form of generally cylindrical assemblies of transversely extending electrodes 10. As shown in Figure 1, the units 110 are bolted in end-to-end relationship, to an intermediate pipe 32. Each unit 110 has two end flanges 16, with electrodes 10 in between these. The electrodes each having three aperture openings which are coupled to an intermediate pipe 32 (see Figure 3). The outermost ones of the electrodes in electroiyser 8 are unapertured and form closed opposite ends of the electroiyser.

Referring now to Figures 2A and 2B, the electrodes 10 forming the illustrated unit 110 are of generally planar octagonal configuration and arranged to extend transversely to the axis 110a of the unit. They are maintained in closely spaced parallel relationship by interposed annular gaskets 12 which are coaxially arranged with respect to the respective unit 110. The gaskets 12 are of relatively thin dimension (between 2.8-3.2mm) in the axial direction, so that the spacing between the electrodes is relatively small.

It was mentioned previously that each unit 110 has end flanges 16. Only one end flange 16 is shown in Figures 2A and 2B, but the end flanges 16 of each unit 110 are held in coaxially aligned relationship by elongate studs 18 (Figure 2A) which pass through the end flanges 16 and through generally planar bakelite insulators 14 which are interposed between the outermost electrodes 10 and the outermost flanges 16 only. While, not shown in the drawing, there may for example be between 100-190 electrodes and interposed gaskets 12 throughout the electrolytic chambers, depending on the quantity of gas production desired.

There is thus defined between the end plates of the two component units 110, a series of shallow cylindrical chambers 28, each being bounded in the radial direction by the inner periphery of a respective gasket 12, and bounded in the lengthwise axial direction of the assembly by opposed transverse surfaces of adjacent ones of the electrodes 10. As shown, the diameter of the gaskets 12 is somewhat less than the dimension of the electrodes 10 transverse to axes 110a, so that parts of the electrodes 10 extend outside die gaskets 12 and present cooling fins for facilitating cooling of the electroiyser 8, under action of the cooling fans 19 which are arranged to blow air across these.

The chambers 28 in each of the units 110, are in communication with each other via 5 respective sets of openings 22, 24, 26 in each of the electrodes 10. Of these, openings 22, 26 are adjacent the inner periphery of the respective gasket 12, and opening 24 is axially positioned. The innermost end plates have openings similar to these openings to permit communication of electrolyte in the units 110 from and to pipe 32. In use of the device 100, the electroiyser 8 is positioned to extend horizontally and so that openings 22 are arranged 10 at vertically uppermost locations and openings 26 at vertically lowermost locations. At inner ends of the units 110, the chambers 28 within the assemblies communicate to the pipe 32 via the aforementioned openings at the innermost ends of the units 110 and via the openings 22, 24, 26 in the electrodes 10.

15 Referring now to Figure 3, the tank 6 is supported from pipe 32, which in use of the device extends generally horizontally, by an upright pipe 120. Pipe 120 is open to the interior of pipe 32, but closed at its upper end by a lower wall of the tank, to which the pipe is secured as by welding.

20 Two tubes are is coaxially arranged within pipe 120 and extend vertically through an opening in the base of the tank 6 extending above a full water level marker from the bottom of the tank. The bottom end of tube 36 extends downwardly to terminate just below the bottom of the tank within the pipe 32. A pipe 39 extends upwardly from within pipe 32 to pass into tank 6. This pipe enables the aqueous solution to flow from pipe 32 through holes

25 40 in the pipe 39 to enter tank 6 and also to be subsequently recycled to the electrolytic chamber by reverse flow. Except for an outlet opening 47 at the lid 122, through which gas generated by the device 100 is taken from the tank, the tank is substantially sealed in use.

The power supply 1 is shown in more detail in Figure 1A as comprising control 30 electronics 9, contactor 17, a bridge rectifier 25 and two electronically controlled switches

SUBSTITUTE SHEET iFULE 26) 21. The power supply 1 is operated from a three-phase AC supply having active lines L,, L^ and l→- and a neutral line N. Contactor 17 is placed in the lines L₍ and L-> is operated under control of the control electronics 9 to selectively couple these lines to the input of the bridge rectifier 25. Switches 21 couple at one side thereof respectively to the neutral line N and to one output of the bridge rectifier 25 and are connected together at the other sides and both to one of the outermost electrode 10 of the electroiyser 8. The other outermost electrode 10 of the electroiyser 8 is coupled to the other output of the rectifier 25.

To use the device 100, the tank 6 is partly filled with electrolyte as is the electroiyser 8. The electrolyte may be any suitable aqueous solution, such as distilled or potable water with addition of NaOH or KOH as catalyst.

Thus electroiyser 8 is substantially filled with electrolyte and the tank 6 partially filled with electrolyte. Then, operation is commenced by so switching the contactor 17 so that lines 1-_! and L*. are connected to the bridge rectifier 25 so that the rectified DC voltage derived from the bridge rectifier 25 and neutral N is applied through a current sensor 30 to the outermost electrodes 10 of the electroiyser and thus to all the electrodes 10 via the electrolyte in the electroiyser, in a fashion which is controlled by the switch 21 in the neutral line N. In accordance with the invention, this switch 21 is controlled from the control electronics 9 to provide unidirectional pulsating voltage to the electroiyser with corresponding generation of unidirectional pulsating electric current through the electroiyser.

After a predetermined time, which may for example be of the order of 1 to 2 sec, the switch 21 in the neutral line N is opened and one connected to the rectifier closed so that the AC line-to-line voltage from the electric supply is applied to the bridge rectifier. Such voltage may for example be 380 volts or 415 volts. Then, the switch 21 is controlled to cause pulsating voltage DC at this higher value to be applied through the current sensor 30 to the electroiyser, so that corresponding unidirectional current of higher value is passed through the electroiyser. The operation then continues under application of this higher voltage. It has been found that the application of pulsating current to the electroiyser limits electrode wear-out by preventing metal formation which otherwise commonly occurs with electrolytic devices and which, over time, tends to build up and cause short circuits between electrodes, thus reducing the life of the apparatus.

The described method of start-up by applying a lower voltage first also contributes to improving reliability of the apparatus. It has been found that pulsating voltage or current of frequency in the range 50Hz to 300 Hz such as 100 Hz is satisfactory. The pulse/break ratio may be between ^XA and ¹/β, for example.

As a result of the current flow through the electroiyser, electrolytic dissociation of the water component of the electrolyte therein occurs, with the production of stoichiometric quantities of oxygen and hydrogen which are together intermingled (in this case). The resultant gas passes from the chambers 28, via the upper openings 22 in the electrodes 10, into the pipe 32 from whence it can flow via tube 39 and then via tube 36 into the upper part of the tank 6 below the roof and released outward via the gas dryer 4. Since the tank is, as mentioned, substantially closed, there is a resultant pressure rise of gas in the tank which forces electrolyte downwardly to flow into the chambers 28 via the openings 40.

In addition to the downwards circulation of the electrolyte as described, upward circulation of electrolyte also occurs. Since the gas generated in chambers 28 tends to form a gas/electrolyte emulsion so that the gas flows in this emulsion up the tube 36, so carrying some electrolyte with it. Thus, as operation continues, the gas and electrolyte will at times flow upwardly into the tank and at other times will flow down from the tank into the pipe 32 and thus into the chambers 28. These two flows tend to occur cyclically so as to, in general, provide an efficient circulation of electrolyte through the electroiyser. The electric supply may be applied as desired such as at outer ones of the electrodes 10 in the units 110.

Opening 47 in the top of tank 6 communicates with the dryer 4. The dryer 4 is shown in more detail in Figures 4A and 4B as comprising a cylindrical substantially closed vessel

SUBSTITUTE HEET (RULE 26) 142 having a lower opening 60 which communicates with the interior of the tank 6 and with the interior of a tube 144 which extends vertically upwardly from a top wall 146 of the tank. A cylindrical piston 148 has an elongate cylindrical bore 150 which extends axially thereof from one end of the piston to terminate a short distance from the other end. The piston 148 5 is mounted on die tube 144 so that the tube extends within the bore 150 of the piston. In the absence of gas pressure, the inner end of the bore 150 rests upon and substantially closes off the upper end of the tube 144.

There is a clearance between the interior surface of the bore 150 in the piston 148 and

10 the exterior surface of the tube 144, and the piston 148 has side openings 62 which extend from the outer surface thereof generally radially inwardly to communicate with the bore 148.

Released gas in the tank 6 passes upwardly through the opening 47 and into tube 144 so as to bear against the upper end of the piston bore, to press the piston upwardly so that gas

15 can pass out the upper end of the tube and into the bore 150 in the piston and thence outwardly through the openings 62 into the interior of the chamber 72. The gas then passes around an interior wall 70 which is positioned within the chamber 146 and in front of a side outlet 66 of the dryer. Wall 70 assists in preventing liquid passing through outlet 66, so that only gas passes therethrough. The gas then exits the dryer via the outlet 66. Moisture

20 entraιngd^~irrthe gas as it enters the tube 144 is caused to condense out in the dryer under influence of the relatively high velocity of gas flow in the relativeljTconfined annular space between the outer periphery of the tube 144 and the inner periphery of bore 150 between the upper end of tube 60 and outlets 62.

25 Outlet 66 from dryer 4 communicates with the inlet of the flashback arrester 5, which is shown in Figure 6. In particular,, the flashback arrester is in the form of a elongate upright hollow cylindrical structure 160 closed at each end by end walls 162, 164 and divided by transverse partition walls 152, 154, and 156 into an upper chamber 108, a lower chamber 78 and two intermediate chambers 98, 102 positioned one above the other and between chambers

30 108 and 78. Chamber 78 is filled with liquid coolant and chamber 86 is partly so filled. Gas

SUBSTITUTE SHEET (RULE 26! is admitted to the arrester 5 via an inlet pipe 80, at the base of the flashback arrester, to enter into chamber 78 through a check valve 82. The gas then passes through openings 84 in the partition wall 152 between chambers 78 and 102 into the coolant 86 in chamber 102, thence to the upper part of chamber 102. The gas then passes to the upper part of chamber 102 and 5 then enters chamber 98 via openings 88 in the partition wall 154. From chamber 98, gas passes through a valve 90 into chamber 108 from whence it leaves the flashback arrester via an outlet pipe 96 which leads to the torch 11.

In the event that flame should return from the torch and enter the arrester 5 via pipe 10 96, any such gas which ignites in the chambers 98, 108, 102 is extinguished in the coolant 86.

Valve 90 is normally open, but is arranged to close under the condition of increased pressure in chamber 98 which arises on gas ignition, to prevent water flow into the pipe 96. 15 The flashback arrester enables drying and cleaning of the pipe leading from the arrester to the torch 11 without disturbance. It also prevents flame from returning into the tank 6 in the event that due to error the operator fails to fill coolant into the arrester, causing flashback in the tank 6.

0 The tank 6 has a silencer 2 shown in Figure 5. This comprises an upright hollow cylindrical outer casing 160 and a coaxial cylindrical inner casing 162 contained therewithin, the inner casing having its outer surface spaced somewhat from the inner surface of casing 160. The casings are closed at each end by transverse walls 165, 166. An inverted cup- shaped element 164 is secured to the wall 166 at the upper end of the silencer by a bolt 114 5 which passes through a central opening in a transverse wall 164b of element 164, through an annular spacer 168, and into a tapped central hole in the wall 166. Element 164 has a depending cylindrical skirt portion 164a which depends downwardly from wall 164b in spaced relationship around the upper part of the casing 160.

0 A safety valve 104 is positioned coaxially within casing 162 and secured to the lower wall 165. The silencer is fitted to the top of tank 6 and arranged such that the valve 104 is subjected to gas pressure within the tank via a lower opening 112 in wall 165. When there is a high pressure within the tank 6, due for example to flashback, the valve 104 opens to permit gas outflow through side openings 106 in casing 162 and through openings 170 in the wall 166. The element 164 prevents outward dispersion of electrolyte which may leave the tank via the silencer under these conditions. In particular, because the flow outwardly from the wall 166 via openings 170 is upwards, the outflowing electrolyte is diverted downwardly along d e outer side wall of the casing 160 by the inverted cup-shaped element 164.

The stoichiometric mixture of hydrogen and oxygen which is produced by device 100 is particularly effective for welding or for cutting torches, as mentioned in the aforementioned United States Patent 4,081 ,656.

The device can be controlled as desired from the control 9 (Figure 1A). The control electronics incorporated into control 9 may provide a complete user interface, gas generator monitoring and controls. Thus control electronics may perform sensory functions such as electric supply condition, current, temperature, tank water level, gas pressure in the tank, and control functions including on or off switching of any or all parts of the apparatus, and controlling fans 19 and an alarm 27.

The control electronics may effect regulation which makes continuous current pulse level adjustments to a specified value as well, as effecting the described gradual current increase up to a specified value, to effect the described "soft start" when the electrolyzer is switched on.

The alarm 27 may be arranged to provide an indication of an emergency situation such as "faulty electronics", "no current", "over current", "over temperature", and "low water level" . It may automatically switch off the device under any of the above-mentioned circumstances.

STITUTE SHEET (RULE 26) The electronics provides an adequate pulse/break ratio in order to achieve efficient apparatus operation.

The described arrangement has the advantage that the electrolyte is circulated more or less continuously through the electroiyser in a fashion which minimises any tendency to overheating and limits the extent of crystallisation at the electrodes 10. The continuous bathing and wetting of the electrodes prevents deposit of non-conductive crystal segments onto the surface of the electrodes. Such crystals would otherwise in time cause wearing-off of the electrode and the production of metal sludge. In that regard, the minimisation of sludge build-up is an important advantage deriving from the described construction.

The device described is operated with a low above atmospheric pressure of gas in the tank 6, such as of not more than 1.5 bar, and this assists in causing efficient gas production, as it minimises the resistance of electricity flow between the electrodes. Higher pressure above 1.5 bar will create more gas bubbles between the electrodes and this causes resistance of current flow. This pressure is controlled by a pressure switch cutting off at 1.5 bar. When that pressure is reached, the switches 21 are opened to stop current flow to the electroiyser.

The circulation of electrolyte and gas is influenced by the ratio between the electrode size as exposed within each chamber 28 and the dimensions of the holes 22, 24, 26. It is thus possible to select the desired circulation rate by the simple expedient of varying the sizes of the holes. In a practical form of the invention operated from a 240 volt three-phase supply, the exposed area of each electrode in a chamber 28 was of 164 mm in diameter with the three holes which are vertically arranged being spaced as follows: (a) distance between upper hole 22 and central hole 24: 77 mm; and

(b) distance between central hole 24 and lower hole 22: 78 mm.

The diameters of these holes were as follows: hole 22: 10mm; hole 24:8mm; and hole 26:8mm.

The spacing between the electrodes, corresponding to the thickness of the gaskets 12 may be in the range 2.6 to 3.2 mm. The electrodes may, for example, be formed from stainless steel or nickel-plated mild steel and the gaskets from PTFE (Teflon) insulation material.

In an exemplary construction, the current flow through the electroiyser varied from 10 ampere to 35 ampere (average value) under control from the control 9 to vary the required gas output. The electroiyser contained a total of 190 electrodes. Generally it the number of electrodes may be between 100 and 190, depending on the volume of gas output desired.

In general devices is constructed in accordance with the invention may offer some or all of the following advantages: - cost savings ease of handling wide range of industrial applications continuous gas generation portability - fully automatic operation use of easily available potable water non-pollutive nature of the hydrogen/oxygen mixture which contributes to environmental protection lighter specific gravity generated gas, which renders it relatively non-explosive and safer to use.

The modified device 200 shown in Figure 7 is similar to the device 100 previously described. The following description is confined to the differences between the two embodiments. In the device of Figure 7, the two component units 222 of the electroiyser 208 are formed from assemblies of transversely extending electrodes 210 (Figure 8) and coaxially arranged interposed annular gaskets 212 (Figures 9, 10, and 11). The electrodes 210 are of somewhat octagonal configuration and are provided with openings 222, 224, 226 to facilitate 5 liquid and gas flow as previously described in relation to openings 22, 24, 26. Further openings 88 are provided in the electrodes 210, these being arranged to interfit with buttons 212A integrally formed on the interposed gaskets 212. As shown in Figures 9, 10, and 11, there are four of these buttons on each face of each gasket. Buttons 212A and openings 88 facilitate the assembly process and secure the electroiyser structure firmly to prevent spillage.

10

Also in the device of Figure 7, the tank 206 is separated from the electroiyser 208 using electrically non-conducting pipes 235, 236, 237. Pipe 237 is an electrolyte inlet pipe which communicates from the bottom of the electroiyser tank 206 through a circulating pump 202 to join with intermediate pipe 95 to which the two units 210 are secured in the same

15 manner as the securement of the units 110 to the pipe 32 in the embodiment of Figure 1. The pipe 237 thus communicates with the interior of pipe 95 via the inlet 103 shown in Figure 12, inlet 103 being somewhat below the axis of the pipe 95, and above the lowermost part thereof. Pipe 235 communicates via a gas outlet 101 at the top of pipe 95 and with interior of the tank 206, at an upper level thereof. This permits outflow of gas from pipe 95 to tank

20 206. Electrolyte is taken from the pipe 95, at a location somewhat above the central axis thereof, via the outlet 102. Outlet 102 communicates with pipe 236 which forms cooling coils 218 and which joins to the tank 206 at an upper location thereof. The cooling fan 219 shown is arranged to pass air over cooling fins attached to the cooling coils 218 for cooling the electrolyte.

25

As shown in Figure 12, the interior of the pipe 95 is divided by a divider wall 204 extending there across at a slight angle to the horizontal and below the axis of the pipe. It has been found that this facilitate sufficient circulation through the electrolyte cells defined by the units 210.

30 The arrangement of Figure 7 provides that the electroiyser 208 is physically more isolated from the tank 206 than is the case with the electroiyser 8 and tank 6 in the arrangement of Figure 1. This has been found to facilitate the production and assembly process, and allows the provision of the described pump and cooling coils in order to improve circulation and cooling. Also, particularly where, as is desirable, the pipes 235, 236, 237 are formed of electrically insulating material, the tank may be connected at a safe voltage potential such as a null voltage potential with reference to the mains supply, or could be connected to earth.

In use, the device of Figure 7 functions in the same way as the device of Figure 1.

Outlet is taken from the tank 206 via a pipe 240 which may for example have cooling fins 242 as shown, in any event such that gas is passed to a gas dryer 204 and a flash back arrestor 205 to the cutting torch 211 , in similar fashion to that described in relation to Figure 1. Also, the tank may be fitted with a relief valve 202 and pressure switch 203 like the relief valve 2 and pressure switch 3 described with reference to Figure 1.

The described device has been advanced merely by way of explanation and many modifications and variations may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

CLAIMS :-

1. A method of generating hydrogen and oxygen by electrolysis of an aqueous electrolyte wherein the electrolysis is effected by passing pulsating electric current through the electrolyte.

2. A method as claimed in claim 1 wherein the electrolyte is formed from water.

3. A method as claimed in claim 1 or claim 2 wherein said current is unidirectional.

4. A method as claimed in any preceding claim wherein said current is provided by application of a reduced voltage during start-up.

5. A method as claimed in any preceding claim wherein the current is controlled so as to avoid or at least limit sludge formation in the electrolyte.

6. A method of electrolytic generation of hydrogen and oxygen from water which is sludge free using a controlled pulse current source.

7. ^{^""}A device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electrolyte for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, and electric supply means for providing said electric current, characterised in that the electric supply means comprises means for generating a pulsating current.

8. A device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, wherein the electroiyser comprises a lengthwise extending series of chambers divided by transverse walls which are formed by spaced transversely extending electrodes, the electrodes having openings

SUBSTITUTE SHEET fRULE 26/ therethrough to permit flow of electrolyte through the chambers and to permit take-off of released hydrogen and oxygen when electric current is applied to electrolyte within the electroiyser.

5 9 A device as claimed in claim 8 having a tank for containing the electrolyte, which communicates with the interior of said chambers and which is arranged whereby released hydrogen and oxygen may enter the tank and cause influx of electrolyte from the tank into the chambers under influence of pressure of released hydrogen and oxygen in the tank.

10 10. A device as claimed in claim 9 wherein a device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, the electroiyser including a tank for containing the electrolyte, which communicates with the interior of said chambers and which is arranged whereby released

15 hydrogen and oxygen may enter the tank and cause influx of electrolyte from the tank into the chambers under influence of pressure of released hydrogen and oxygen in the tank, the electrolyte in the tank being in use pressurised to a low pressure.

11. A device for generating hydrogen and oxygen by electrolysis of an aqueous 0 electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, the electroiyser including a tank for containing the electrolyte, which communicates with the interior of said chambers and which is arranged whereby released hydrogen and oxygen may enter the tank and cause influx of electrolyte from the tank into the chambers under influence of pressure of released 5 hydrogen and oxygen in the tank, the electrolyte in the tank being in use pressurised to a low pressure.

12. A device as claimed in claim 10 or claims 11 wherein said maximum pressure is substantially 1.5 bar. 0

13. A device as claimed in claim 12 wherein said pressurisation is controlled by setting a pressure switch at a maximum pressure.

14. A device for generating hydrogen and oxygen by electrolysis of an aqueous electrolyte, comprising an electroiyser for containing the aqueous electrolyte and provided with electrodes for application of electric current to the electrolyte, the device having an outlet for the hydrogen and oxygen and a flashback arrester arranged such that released hydrogen and oxygen from the electroiyser flows in use through the flashback arrester to the outlet, wherein the flashback arrester includes a chamber having coolant therein and through which released hydrogen and oxygen passes in use to the outlet.

15. A device as claimed in claim 14 wherein the gas arrester includes valve means effective to close communication from the gas arrester to the outlet when flashback occurs therein.

16. A device as claimed in claim 15 wherein the valve means comprises a non-return valve.