This invention relates to a method of and means for producing hydrogen in an enclosed environment such as a submarine vessel.

To avoid the risk of explosion associated with storage of large supplies of hydrogen in bulk it is known to produce hydrogen as it is required by reforming a suitable hydrocarbon such as methanol. However, hitherto it has not been fully satisfactory in all respects to produce hydrogen, by reforming a hydrocarbon, in an enclosed environment such as in a submarine vessel without much complexity.

An object of the invention is to provide a new and improved method of and means for producing hydrogen which is suitable for use in an enclosed environment.

According to one aspect of the present invention we provide a method of producing hydrogen in an enclosed environment comprising reforming a hydrocarbon fuel by a process including heating the fuel (and any needed water), to produce a gaseous product comprising a plurality of constituents, one of which is hydrogen, separating a majority of the hydrogen constituent from the gaseous products, combusting the remainder of the gaseous products to remove the residual hydrogen therefrom, removing carbon dioxide from the products of said combustion, discharging the remainder of the products of combustion from the enclosed environment or recycling the remainder of the products of combustion to be combusted and used for heating the fuel (and any needed water) prior to and during reformation with said products of combustion.

The fuel and any needed water may be heated by combustion of said remainder of the gaseous products prior to and during reformation of the fuel.

Supplementary hydrogen supplied separately from said remainder of the gaseous products may be combusted with said gaseous products.

The supplementary hydrogen may be supplied during start-up from a reservoir of hydrogen.

The reservoir may be replenished from said majority of the hydrogen.

If desired, the supplementary hydrogen may be supplied from said majority of the hydrogen separated from the gaseous products.

According to another aspect of the present invention we provide means for producing hydrogen in an enclosed environment comprising a reformer having a heat source for reforming a hydrocarbon fuel (plus any needed water), to produce a gaseous product comprising a plurality of constituents, one of which is hydrogen, means for separating a majority of the hydrogen constituent from the gaseous product and means for feeding the remainder of the gaseous product to a combustion means to combust the remainder of the gaseous product to remove the residual hydrogen therefrom and product products of combustion comprising mainly carbon dioxide, means to remove carbon dioxide from the products of combustion and means to feed the remainder of the products of combustion either to be discharged from the enclosed environment or to be recycled back to the combustion means and wherein said combustion means provides said heat source for the reformer.

The reformer may comprise a duct in which the fuel (and any needed water) are heated and vaporised and then passed over a catalyst to reform the fuel to hydrogen and other constituents.

The means for separating the majority of the hydrogen from the gaseous products of the reformer may comprise diffusion separating means such as a palladium based alloy membrane which permits passage only of hydrogen.

The means to remove carbon dioxide may comprise an absorber to absorb carbon dioxide into water.

The water may be transferred between source of water which is at a first, higher, pressure and the absorber which is at a second, lower, pressure by an apparatus comprising: a vessel,

a dividing member in the vessel, the vessel and the dividing member being relatively movable to divide the vessel into separate variable volume chambers, a first pair of valves, one of which controls passage of liquid between a first of said chambers and said source of water, the other of which controls passage of liquid between a second of said chambers and said source of water, a second pair of valves, one of which controls passage of liquid between said first chamber and said absorber, the other of which controls passage of liquid between said second chamber and said absorber, absorbs carbon dioxide into water, operating means repeatedly to perform the following cycle of operations; close the valves of one of said pairs and open the valves of the other of said pairs; then move the dividing member to cause the volume of said first chamber to increase and the volume of said second chamber to decrease, then close the valves of the other of said pairs and open the valves of said one pair, and then move the dividing member to cause the volume of said first chamber to decrease and the volume of said second chamber to increase.

The water may be sea water.

Means may be provided to feed the hydrogen separated from the gaseous products of the reformer to provide hydrogen fuel of an electricity generating fuel cell.

The fuel cell may be adapted to generate electricity to power an electric motor of a submarine vessel.

An example of the invention will now be described with reference to the accompanying drawing, which is a diagrammatic illustration of a reformer/fuel cell installation in a submarine vessel.

Referring to the Figure, a submarine vessel has a pressure wall P in which is disposed an electricity generating fuel cell 10 of conventional type, the electrical output of which is utilised to power the submarine vessel both for motive power and for services. All these power requirements are illustrated diagrammatically by a load 11. The fuel cell 10 is supplied with oxygen from a reservoir 12, with which the submarine vessel is provided, and with hydrogen along a line 13 as a result of reformation of methanol.

The submarine vessel is provided with a tank 14 for methanol or methanol and water from which methanol or methanol and water is pumped by a pump 15 to a reformer and hydrogen separating means 16. The reformer comprises a duct 17 in which methanol or methanol and water mixture is heated by a heat exchanger 18 until the mixture is vaporised (with minimal segregation of components) after which it enters a section of the duct 17 where a catalyst of metallic form or of "deposited on ceramic" form is heated and catalyses reactions which reform the methanol to carbon monoxide and hydrogen, followed by a "shift reaction" which changes carbon monoxide plus water to carbon dioxide plus more hydrogen. A degree of surplus water is used to move the shift reaction equilibrium to minimum carbon monoxide. The reactions may take place at around 400°C, or higher, but the latter needs a larger heat exchanger.

The catalyst reforms the methanol to produce gaseous products of reformation having a plurality of constituents which comprise hydrogen, carbon dioxide, carbon monoxide and some water vapour. These gaseous products of reformation are then passed over a palladium-silver alloy (26%) membrane 19 which permits passage only of hydrogen. If desired other diffusion or other hydrogen separating means may be provided. As a result, a majority of the hydrogen constituent of the gaseous products of reformation pass through the

membrane are available for supply as very pure hydrogen to the fuel cell 10 through the line 13.

The reformer 16, comprising the duct 17, heat exchanger 18 and membrane barrier 19 are disposed in a thermally insulated casing C suitable for maximum pressure excursions. The remainder of the gaseous products of reformation comprising carbon dioxide, carbon monoxide, the residual hydrogen of the total hydrogen constituent and water vapour are then fed to a burner 20 via a line 19a. A set of non return valves 19b is provided in the line 19a, so that any possible pressure surges in the combustion region cannot get back into the "fuel cell" area. The design of the reformer and its casing is such that any ignition in this region can only produce modest pressure rises. It is to be noted that there is a considerable volume reservoir in the absorber.

Oxygen is also fed to the burner 20 via line 12a. from the reservoir 12. The combustion of the hydrogen and carbon monoxide removes these from the gaseous products of reformation so that the products of combustion of the burner 20 comprise nearly all carbon dioxide and water vapour. The amount of hydrogen in the remainder of the gaseous products of reformation is such that a temperature of, for example, 2000°C, is achieved by the burner 20. The direct products of combustion of the burner 20 are generated at about 2000°C, but are diluted by recirculation of (relatively) cool gas from the exit of the heat exchanger, by the pump 23 (so the gas flow through the heat exchanger may be 3 or 4 times the nett output of burner flow). All or substantially all of the hydrogen in the remainder of the gaseous products will be burnt at the burner 20 and no more hydrogen is normally needed. However, if in any particular circumstances supplementary hydrogen is required it may be fed to the burner 20 from line 13 via lines 13a. and 13c,

Whilst in the illustrated example the fuel (and any needed water) are heated by the heat exchanger 18 prior to and during the reformation the apparatus may be arranged so that heat produced by combustion of the products of reformation is applied to the fuel (and any needed water) only prior to

reformation, the necessary temperature being maintained during reformation by suitable design of the apparatus, for example, by providing suitable heat insulation.

Of course, until reformation has started no hydrogen is produced. Therefore, to enable start -up from cold, an appropriate amount of hydrogen is supplied via the line 13a from a small reservoir 13b. so that the burner 20 heats the heat exchanger to the temperature necessary for the reformation process to start. By providing suitable controls and, if desired, dilution with effective inert gas, risk of explosion is avoided.

Some of the gaseous products of combustion are partially recycled to the enclosure of the reformer/separator 16 via a circuit 22 and pump 23 whilst the remainder of the products of combustion are fed via line 24 to a cooler 25 and a line 26 to an absorber 27. The products of combustion in the line 26 comprise approximately 98 per cent carbon dioxide and the residue being mainly water vapour. The carbon dioxide is brought into intimate contact with sea water in the absorber 27 and so is absorbed in the sea water. The sea water is supplied to the absorber 27 via line 28 from a water management system 29 which draws in sea water from the exterior of the pressure hull P via line 30. Sea water containing carbon dioxide from the absorber 27 is fed via line 31 and pump 32 back to the water management system 29 from which it is discharged to the exterior of the pressure hull P via line 33.

The water management system 29 comprises: a vessel, a dividing member in the vessel, the vessel and the dividing member being relatively movable to divide the vessel into separate variable volume chambers, a first pair of valves, one of which controls passage of liquid between a first of said chambers and the line 30, the other of which controls passage of liquid between a second of said chambers and the line 33, and a second pair of valves, one of which controls passage of liquid between said first chamber and the line 28, the other of which controls passage of liquid between said second chamber and the line 31.

The water management system 29 also has an operating means repeatedly to perform the following cycle of operations; close the valves of one of said pairs and open the valves of the other of said pairs; then move the dividing member to cause the volume of said first chamber to increase and the volume of said second chamber to decrease, then close the valves of the other of said pairs and open the valves of said one pair, and then move the dividing member to cause the volume of said first chamber to decrease and the volume of said second chamber to increase and then to repeat the above described cycle of operation.

A more detailed description of the water management system is contained in GB-B-2158889 the content of which is incorporated herein by reference.

Not all of the products of combustion are absorbed in the absorber 27. There is a small amount of residual exhaust gas which is fed by the absorber via line 34 either to be passed via non-return valve 35 to be compressed by pump 36 and discharged to the exterior of pressure wall P, which normally takes place only during start-up or, and preferably, during normal operation, is recycled by line 37 back to the burner 20.

By feeding the remainder of the products of reformation to the burner 20 the residual hydrogen is disposed of by combustion and the burner provides the necessary heat source for the reformer 17 thereby providing a safe and economical system.

Although the reformer/fuel cell system has been described hereinbefore in a submarine vessel for use in the sea, the invention may be applied to other enclosed environments such as a mine, particularly a mine where the workings are submerged.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in

terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.