GB2510805A - Composite material for hydrogen generation - Google Patents

Abstract

A composite material is used for hydrogen gas generation from water in an exothermic reaction. The composite material is a mixture of a powder form of a metal and sodium oxide or sodium hydroxide. The composite material powder is exposed to an acidic gas, such as carbon dioxide, hydrogen chloride or sulphur dioxide. The acidic gas allows the alkali component of the composite material powder to be coated with a layer of salt, which salt is inert to the metal powder and soluble in water. Once the composite material is exposed to water and the soluble layer of salt is dissolved, the exothermic reaction between the composite material and the water allows for the generation of hydrogen gas at ambient pressure. After the exothermic reaction to produce hydrogen gas, the residual composite material is treated with an acidic gas to lower its pH. In another aspect, a hydrogen generator unit (40, Fig. 2) includes at least one reaction chamber adapted to receive a cartridge (1, Fig. 2) with the composite material, wherein the unit employs an extracting chemical process to generate low-pressure hydrogen. A method of manufacturing the composite material is also claimed.

Description

COMPOSITE MATERIAL FOR HYDROGEN GENERATION

Field of the invention

The present invention relates to a composite material for use in Hydrogen generator units, for example to Hydrogen generator units suitable for use in Hydrogen fuelling systems for fuel cells and internal combustion engine standalone energy systems.

Moreover, the invention relates to methods of using the aforesaid composite material for generating Hydrogen gas and the manufacture of the composite material.

Background of the invention

Hydrogen is a well known energy vector which has many practical uses within the chemical and energy industrial sectors. These practical uses require Hydrogen to be generated from chemically rich compounds containing Hydrogen via one or more process steps, for example steam reformation of methane and other hydrocarbon fuels or via electrolysis of water. Hydrogen generated from aforesaid one or more process steps can be utilized to fuel numerous applications: (i) for vehicle propulsion; (H) for fuel for micro energy system (battery replacements); and (Hi) for emergency power supply systems.

In portable applications, one or more additional process steps are required after Hydrogen generation in respect of Hydrogen storage and transport. As the lightest know element, Hydrogen often requires extensive external equipment and energy input to achieve practical energy densities appropriate for use in transportation or portable systems market for Hydrogen units. Often bulky, high pressure tanks limit the application of Hydrogen in vehicle propulsion systems.

In an alternative approach for achieving high densities of Hydrogen storage, Hydrogen is often stored within a metal hydride wherein Hydrogen molecules are disassociated into individual hydrogen atoms that are able to absorb or dissolve into a metal phase. It is also often required to add heat to recover all of the stored hydrogen. In a yet further approach, Hydrogen is stored cryogenically as liquid Hydrogen, or at a high pressure in gaseous form, for example in vehicle applications.

Further liquid hydrogen needs to be maintained at temperatures not exceeding - 253°C (20.28K) to prevent boiling.

In the case of contemporary fuel cell or Hydrogen internal combustion powered vehicles, Hydrogen is commonly stored at pressures of up to 7OMPA, for example within specially prepared composite Aluminium and Carbon fibre tanks. High pressure storage is required primarily to give comparable energy densities to that of existing hydrocarbon liquid or gaseous fuels.

It is known to employ metallic composite materials to generate Hydrogen through reaction with water. In a United States patent no. US3957483 issued on 18 May 1976 to M. Suzuki, it is disclosed how a Magnesium composition is utilized for producing Hydrogen. This document elucidates that the presence of one or more compounds selected from the group consisting of Sodium Chloride (NaCI), Potassium Chloride (KCI) and various similar metal salts leads to an increase in a quantity of Hydrogen gas generated. This type of solution allows for somewhat more convenient handling of the composite prior to use in a reaction to generate Hydrogen gas.

Similarly, in a United States patent no. US 6506360, there is described a system which utilizes a reaction of Aluminum with water in the presence of Sodium Hydroxide as a catalyst. The system uses a pressure and a temperature of the reaction to control a degree of immersion of a fuel cartridge in water and consequently to control a vigor and a duration of the reaction. The fuel cartridge exemplified has a volume of about 1 liter, contains about 500 ml of Magnesium composition, and is submersed in 10 liters of water for allowing for 2 hours of Hydrogen gas generation which is sufficient for cooking food on a burner plate. A control of the temperature of the water and a degree of immersion of the fuel cartridge in the water can become complicated if utilization in any type of portable solution is intended. The disclosed approach requires complex handling and is costly as temperatures and environments need to be controlled.

Additional United States patent nos. US 5143047, US 5494538, US 4600661, US4072514, US 4064226, US 3985865, and generation of Hydrogen gas in an uncontrolled manner in systems comprising mixtures of alkali or alkali earth metals and/or Aluminum and water or aqueous salt solutions. These processes all experience a common problem of highly reactive systems and solutions, as well as alkaline residues with high pH values and consequent difficulty associated with their disposal. In a Japanese patent no. JF 1061301 an Aluminium-ceramic composite has been proposed to initiate th water splitting reaction, the ceramic comprises calcined dolomite, namely Calcium/Magnesium oxide. Once contacted with water, these oxides cause a very substantial increase in the pH, which stimulates corrosion of Aluminium with accompanying release of Hydrogen. The system has all the disadvantages of the water splitting reaction using alkaline metals, namely very highly reactive materials alkalinity and difficult recyclability of generated reaction products. In a United States patent no. US 4072514, Magnesium and Aluminium are mechanically ground together to form a composite material which is then exposed to water to generate Hydrogen gas. In a French patent no. 2465683, a continuous removal of the passivation layer on Aluminum by mechanical means, in order to sustain an Aluminum-assisted water splitting reaction, has been disclosed.

The United States patent no. US 6440385, which refers to most of the patents and drawbacks outlined above, describes a method of automatic gas production by reaction of an alkaline solution reactant with a metal, wherein the method includes continuously feeding without interruption the reactant in conjunction with continuous cleaning of a surface of the metal, for producing Hydrogen for a given energy need.

The patent describes a process of generating Hydrogen gas from water at a pH close to neutral, in the pH range 4 to 9. Hydroxide with a high pH value due to the presence of alkali. It is mentioned how the Aluminum Hydroxide could be recyclable back to Aluminum metal through the well-known electrolysis process, but this is not always possible and is costly. There are still drawbacks with the approach as there is a need for close control of reaction environment to allow easy use.

In patent application, EP1749796A1, (a hydrogen generation process is described where aluminium is mixed with one or more reaction materials such as calcium hydroxide, potasium hydroxide, sodium hydroxide or a mixture thereof in the presence of an aquas liquid. This technology produces hydrogen under the right reaction conditions and the reaction products is less than about pH of 11.75. In one embodiment the reaction was heated up to about 600 and the yield of the hydrogen genration was 85%. The residual reaction products in the aquous solution is still highly alkaline and has drawbacks mentioned earlier of save and environmentally friendly disposal. With greater contemporary focus on environmental and sustainable ussues, there are therefore problems to be addressed pror to disposal of alkaline residual reaction product in these uses for generating Hydrogen.

In a published international POT patent application no. WO 0174710, there is described a manner in which a Hydrogen generation system employs a wicking material to control a contact between a mixture of fuel contained in a fuel tank and a hydrolysing catalyst supply of Hydrogen. The system is portable but requires a complex feedback mechanism for automatically maintaining a constant pressure for Hydrogen-generating reactions.

In addition, Hydrogen and fuel cell systems have also been developed for use on electric vehicles for range extension purposes. Such systems provide a way of charging batteries during vehicle operation, thus extending the range of such vehicles. The storage of Hydrogen in such application therefore requires extensive ancillary equipment which increases vehicle weights in cases of vehicle applications.

Summary of the invention

The present invention seeks to provide an improved composite material for generation of Hydrogen gas on demand in accordance with claim 1. The added benefit of more reliable, stable, and user friendly composite material and final environmentally friendly disposal of any residue product after the Hydrogen gas generation are clear benefits of the invention.

According to a first aspect of the present invention, there is provided a composite material for Hydrogen gas generation from water in an exothermic reaction, wherein the composite material is a mixture of powder form of a metal and sodium oxide or sodium hydroxide, characterized in that the composite material powder is exposed to an acidic gas allowing the alkali component of the composite material powder to be coated with a layer of salt, which salt is inert to the metal powder and soluble in water; the composite material is placed in a cartridge system and exposed to water; an exothermic reaction between the composite material and the water occurs once the soluble layer of salt is dissolved to generate hydrogen gas at ambient pressure; and the residual material of the composite material post Hydrogen gas reaction is alkaline and treated with an acidc gas to lower the pH of the residual material.

The benefit of the stabilization of the composite powder makes it much more user friendly and not so reactive with water moisture or water. Transportation and storage of the composite material can be costly as it needs to be done in a controlled environment where there is no risk of any water getting in contact with the composite powder material.

Optionally, the metal in the composite material is one of Aluminium, Boron alloys, Silicon alloys, Zinc, or Gallium. The composite material is used in a Hydrogen generator where it is placed in a reaction chamber and exposed to water.

The benefit of the stabilization of the composite powder makes it much more user friendly and not so reactive with water moisture or water. Transportation and storage of the composite material can be costly as it needs to be done in a controlled environment where there is no risk of any water getting in contact with the composite powder material.

Optionally, an acidic gas is one or more of the following i) hydrogen chloride, H) sulphur dioxide and/or iii) carbonic acid, and it is exposed transiently to the metal component of the alkali composite material creating a very fine, e.g. monolayer, layer of the salt on the composite powders particles. This prevents the premature reaction of the metal component with the alkali allowing for safer and more user friendly handling of the composite material.

Once the water has dissolved the stabilizing salt layer of the composite material the generation of low pressure hydrogen takes place in the reaction chamber. The invention is of advantage in that use and handling of the composite material is made much more convenient and safe.

Optionally, the Hydrogen generator unit is implemented so that the fuel cell is operable to generate clean water by way of a chemical reaction within the fuel cell, wherein said generator unit is adapted so that said water is recirculated for use in the extraction chemical process for generating low-pressure Hydrogen.

Optionally, the alkali residual material left after the Hydrogen has been generated is neutralized through the use of Carbon Dioxide (C02) to lower the pH of the residue from 9-12 to below about 8.5 and preferably to ca. 7. The reaction is performed at a temperature of 40-70C, and more preferrably 50-60C for the best results.

According to a second aspect of the invention, there is provided a method of manufacturing a composite material, wherein that said method includes melting a metal and injecting the molten metal stream into an atomisation chamber. Injecting at least one inert gas at higher pressure to create metal droplets and control the environment in the chamber to avoid ignition. Then spraying the molten metal droplets onto a cooling plate where condensation and cooling takes place allowing for collection of the metal in powdered form post the cooling plate. The mixing of the powdered metal and the Sodium hydroxide then takes place to generate a well uniform and blended material. This mixture of blended material is then exposed to an acidic gas at a reaction temperature in the range of 40-70C and more preferably 50- 60C allowing a thin layer of a water soluble salt to form on the blended material and forming a stabilized composite material. The manufacturing approach of spray forming and the stabilization process allows for a very cost efficient and user friendly end product for future transportation and use by end users.

According to a third aspect of the invention a salt of a strong base and weack acid, such as Sodium carbonate which is mixed with the powdered metal to create a stable composite material. The advantage of the use of Sodium carbonate is that the need for creating the salt layer on the composite material to keep it stable. The use of the cartridge system hence provides a user friendly and environmental solution for the hydrogen generation steps of the invention. Further the clean up or so called scrubbing of the alkaline residual material is neurtrliased using carbon dioxide aliwoing for further carbon capture and a safely treated residual material that can be disposed of.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein: FIG. 1 is a flow diagram of the process when manufacturing a composite material; FIG. 2 is an illustration of the use of a composite material in an operational cycle of a Hydrogen generator unit with a neutralization system; and FIG. 3 is an illustration of a neutralisation system for 002 clean up fo alkaline material pursuant to the present invention.

In the accompanying diagrams, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing. An arrow in the drawings can also be used to indicate the positioning of some element within another part.

Description of embodiments of the invention

Referring to FIG. 1, shows a flow diagram of the manufacture of a composite material 23 (shown as 23 in FIG. 2), also referred to as a fuel element in this description. The metal is preferably selected from the group of metals such as Aluminium, Calcium, Magnesium, Sodium, or Potassium, Boron alloys, Silicon alloys, Zinc, Gallium.. In one preferred embodiment the metal in the composite material 23 is Aluminium in a microstructure form. The manufacturing process to generate the powdered composite material is advantageously a form of Spray forming with gas atomisation and spray microstructure forming. There are certain considerations needed in the manufacturing process depending on what type of metal and state of such metal that is being used which would be apparent to the person skilled in the art due to residue and impurities in the different versions of the metal.

The Aluminium used for the manufacture of the composite material 23 can be of varied grade. The price per tonne of the aluminium varies with the most expensive being pure Aluminium, with a 30% drop in price for Aluminium cuttings, again a further drop in price by 30% for Aluminium turnings, and finally a cost of about 1/20 for Aluminium foil per tonne compared to the pure Aluminium.

As shown in FIG.1 the Aluminium in stage A) melted in e.g. a bottom pour induction unit with a temperature at ca. 50-150°C above the metal liquidus temperature. The molten metal stream is then in stage B) sprayed into a spray chamber where inert gas such as Ar or N2 is used to avoid destabilisation of the molten stream of metal. A first set of inert gas jets operate at 2-4 bar while a secondary set of gas jets at higher pressure ca 6-10 bar spray into the molten Aluminium stream to cause atomisation.

The particle size, droplet diameter and structure can be controlled by varied by altering the atomisation gas mass flow rate as well as the molten metal mass flow rate. In stage C) the molten metal droplets in the stream impact on an impact surface of a cooling plate that cools and condenses the particles which are collected as an Aluminium powder in a controlled, enclosed environment to avoid any ignition of the powder. The particle size will follow a normal bell curve and powder diameters up to ca 750-850 pm with a median diameter of about 180-200 pm.

The powdered Aluminium is then in stage D) placed in a mixing chamber where it is mixed in spray clouds of the powdered metal and precipitated with for example Sodium hydroxide, Sodium oxide, andlor Carbonic acid,. The mixing takes place under controlled conditions allowing a blend of the composite material to be achieved. In one embodiment the Sodium hydroxide is used and is present in the composite material blend of the powders to act as a catalyst when the blend comes into contact with water and the exothermic reaction of generating low pressure Hydrogen gas is initiated.

As this composite material 23, or fuel element 23 as also referred to, is highly reactive and hygroscopic it requires controlled environments and supervision during any handling and/or transportation. Therefore the composite material 23 is put through stabilization phase in stage E) where it is placed in a stabilization unit and exposed to an acidic gas, such as carbon dioxide, hydrogen chloride or sulphur dioxide. The exposure to the acidic gas is done transiently to the composite material.

This creates a very fine, e.g. monolayer, layer of the salt on the composite powder particles. This prevents the premature reaction of the metal component with the alkali allowing for safer and more user friendly handling of the composite material, which is in a stabilized form. The resulting composite material has the benefit of being a robust fuel element, and can be handled in most traditional transport, shipping and commercial environments without the need to avoid the slightest contact with moisture or even high humidity environments. In addition it increases the storage life of the composite material, which can be of critical importance in applications where it is used to generate energy and power in remote locations e.g. off grid properties, forward operating military bases, or as emergency range extenders for vehicles. The stablization phase would be less necessary for a composite material using carboinc acid in comparison to the use of Sodium hydroxide or Sodium oxide, which greatly benefit from the acid gas stabilization process.

In another embodiment the stabilization phase of the manufacturing process can be performed during the mixing phase, stage D), of the Aluminium and Sodium Hydroxide by exposing the mixing phase to e.g. the sulphur dioxide. This needs to be done in a controlled manner create a uniform coating throughout the composite material and generate a suitable layer of salt on the powdered composite material, which will allow for easy removal during the hydrogen generation process but still be sufficient to remove the hygroscopic properties of the mixture when in atmospheric or semi to fully open conditions with e.g. high air moisture percentage.

In a further embodiment the stabilization phase of the manufacturing process can be performed during the spray forming process where the metal component of the composite material is exposed to the acidic gas either just before, during or after the cooling step, stage C). This would allow for a more rapid manufacturing process as long as the process can remain safe and efficient.

In an alternative embodiment of the invention the manufacturing of the composite material 23 is performed through the process of milling down, or even grinding down, the metal used in a closely monitored environment to avoid ignition. Further the smaller the particle size in question the more stringent the milling process environment would need to be. The advantage of this process is that it does not require any specialist machinery and can be performed using equipment that is readily available. This milling process would replace stages A), B) , and C) above in the spray forming process. The mixing stage D) of metal e.g. Aluminium and catalyst e.g. Sodium hydroxide or Sodium oxide, can either be performed before or after the stabilization stage E) depending on the process. Preferably the stabilization is performed last allowing for uniform coating of the composite material 23 ready for distribution without major drawbacks of needing to vigilantly be aware of any moisture content during transportation, storage or use prior to the generation of low pressure Hydrogen gas.

The composite material 23 is preferably manufactured from Aluminium, but can also be manufactured from other compounds such as Sodium, Calcium, Magnesium, or Potassium, Zinc, Gallium, or any metal that forms amphoteric oxides. Without prejudice to the invention we believe that the following formulae details examples of the chemical processes when stabilisation of Aluminium and Sodium, which are then employed to generate Hydrogen and heat from an exothermic reaction with water: Aluminium is a very reactive metal however its apparent lack of activity is due to a very thin, but coherent oxide film covering the surface of the metal which prevents further oxidation or hydrolysis. When Aluminium reacts with acid or alkali, the first stage is dissolution of the oxide file to expose the reactive metal surface, which then undergoes further reactions as shown: A1203 + 6HCI -> 2A1C13 + 3H20 25 A1203 + 2NaOH -> 2NaAIO2 + H20 These two reactions expose the surface of the Aluminium to allow further reaction: 2A1 + 6HCI -> 2A1C13 + 3H2 2A1 + 2NaOH + 2H20 -> 2NaAIO2 + 3H2 Thus aqueous acid or aqueous sodium hydroxide will react with Aluminium metal to produce hydrogen despite the presence of the oxide film.

Sodium oxide and hydroxide are very hygroscopic and will absorb water vapour from the atmosphere so that a mixture comprising Aluminium metal and either of these two sodium compounds would be very unstable, and have a tendency to liberate hydrogen on storage due to absorption of adventitious water. Following exposure of the sodium compounds to an acidic gas the sodium compounds are coated with a salt which is itself inert to the Aluminium metal, thus increasing the stability of the composite material 23. However, Carbon dioxide could be used as an alternative, as sodium carbonate/bicarbonate would be formed on the surface of the sodium compound, particularly in the presence of trace amounts of water.

Na20 + C02 -> Na2CO3 Na2CO3 + H20 + C02 -> 2NaHCO3 As carbon dioxide is only slightly soluble in water and carbonic acid, H2C03, is only very weakly ionised, with a pKa value of about 6.4, the reaction to stabilise the composite material 23 would be slow. The alternative would be to use a more 20 strongly acidic gas at very low concentration under inert conditions. Suitable gases include hydrogen chloride and sulphur dioxide: Na20 + 2HCI -> 2NACI + H20 NaOH + S02 -> NaHSO3 These two salts, sodium chloride and sodium bisulphite are easily soluble in water and when the mixture of the stabilised composite material 23 with Aluminium powder is immersed in water, the salt dissolves thus allowing immediate access of the Aluminium metal to the sodium hydroxide solution, thus allowing facile generation of hydrogen as seen above.

In a further third emobidment of the invention the compostie material consists of aluminium metal powder and sodium carbonate powder mixed together. Without prejudice to the invention, the process of chemical reactions would then be illustrated by the following equations: Na2CO3 + H20 -> H2C03 + 2NaOH 2NaOH -> 2Na+ + 20H-Sodium hydroxide is fully ionised in solution, and is termed a strong base.

H2C03 c-> 2H+ + C03-The carbonic acid is only slightly ionised in solution and is termed a weak acid. Thus in a solution of sodium carbonate in water, there is an excess of hydroxide ions and the solution is strongly alkaline, with a pH likely to be in excess of 10. This is sufficetly alkaline to permit the oxidative hydrolysis of aluminium metal to produce very readily the facile production of hydrogen gas in accordance with known chemistry.

A alternaitve embodicment of the invention is not limited to sodium carbonate, as alternative salts of a strong base and a weak acid produces a similar reaction.

Examples of weak acids includes acids, such as carboinc acid, acetic acid, aqueous hydrogen sulphide, phosphorous acid and tartaric acid. Examples of metals which from strong bases includes metals, such as sodium, potassium, rubidium and barium.

Sodium carbonate is one of the preferred salts as it is readily available, cost effective, and is relativley benign, as it is commonly used as washing soda.

In a further embodiment the compostie material is manufactured through the use of traditional mixing equipment, such as mixing equipment used in the FMCG or Pharmaceutical industry. In a preferred solution the Aluminium is in a powder form with a size in the range of normally 15 -400 microns, preferrably of the range of 75- 250 microns, and most preferrably ca 125 micrns maximum particle size. The powdered Aluminum coud be produced by grinding or other methods know the to the person skilled in the art. The salt used in this embodiment is example Sodium Carbonate. The Sodium carbonate is introduced into the mixing chamber of the blender also called mixing equipment. The mixing chamber is a controlled, dry environment to avoid any reaction with the sodium carbonate. The Aluminium powder is then mixed with the salt at a speed of 15-1 50 rpm. The quantities of the Aluminium to the sodium carbonate are in the proportion of 1:1. Once the Aluminium powder is added to the mixing chamber a uniform composite material with very stable properties is achieved, as there is no reaction of the Aluminium powder and the Sodium carbonate in the event of small amounts of humidity.

This manufactuing techinque of blending the powerderd metal, such as aluminium with the e.g. sodium hydroxide or sodium oxide is also possible. In such an event a further improved approach is used to introduce the salt layer in the composite material by the mixing chamber containing an acidic gas for the coating of a salt layer of the salt in the composite material. In a preferred setup the acidic gas is carbon dioxide and it prevents any water vapur from being in the mixing chamber as deliquesent. Once the sale e.g. sodium carbonate is entered into the mixing chamber there is a mono-layer coating the salt crystals. Once the composite material is put into contact wtih an aquas solution preferrably water the monolayer is disolved and the sodium carbonate can start its reaction with the water and Aluminium to generate hydrogen at low pressures and with conrolled release.

Referring to FIG. 2, an illustration of how the composite material 23 in its stabilized form can be utilized in a hydrogen generator unit 40 as shown. A cartridge unit 1 is attached to a base of a single cylinder displacer-type engine 2; optionally, the engine 2 is a Stirling-type engine of either beta or alpha configuration. Alpha and beta configurations or Stirling engines are elucidated in Wikipedia. The cartridge unit 1 contains the composite material 23 used as a source to generate Hydrogen gas when in contact with water, which water acts as a Hydrogen source during an associated reaction.

In the hydrogen generator unit 40 there is further a connection made between the cartridge unit 1 and the engine 2 via a heat exchanger 15, which heat exchanger 15 allows heat generated from an exothermic chemical reaction in the cartridge unit 1 to be transferred from the cartridge unit 1 directly to the base of the engine 2. This heat exchange acts to initiate an engine cycle, such as a Stirling Engine cycle, moving a displacement cylinder 4 and subsequently moving a piston 5 connected to a flywheel 6.

Hydrogen gas generated by the reaction in the cartridge unit 1 is allowed to enter into a diaphragm of a pump 7 via a separate pipe connection 16 from an outlet of the cartridge unit 1. A rotational motion of the flywheel 6 moves the diaphragm pump 7 to create a partial vacuum which extracts any Hydrogen gas from the cartridge 1.

Hydrogen then enters a chamber of the diaphragm pump 7 until continued movement of the flywheel 6 moves the diaphragm to close an inlet valve of the diaphragm pump 7. As the diaphragm continues to move, it compresses the Hydrogen gas and then releases the compressed Hydrogen gas through the outlet valve to the input a fuel cell 8. The capacity of the diaphragm pump 7 is chosen to incorporate a factor of safety to avoid over pressurization of the fuel cell 8 and is of sufficient capacity to safely pressurize Hydrogen generated from the cartridge unit 1.

The heat therefore applied to a base of the Stirling engine 2 acts to compresses the Hydrogen released from the cartridge unit 1 to a pressure greater than atmospheric pressure. The compressed Hydrogen gas is matched to a required input of an external energy conversion device, for example a high temperature proton exchanged membrane (PEM) fuel cell 8 (or other suitable fuel cell operating at a temperature in excess of 60°C). To facilitate a steady stream of Hydrogen gas, the input of the external energy conversion device optionally incorporates a small buffer tank to hold an amount of Hydrogen gas to ensure a constant supply for operation of the device. The flywheel 6, or in the case of a beta type Stirling engine the gear arrangement, facilitates the movement of the piston back to its starting position to facilitate a start of a second cycle of operation. The cooling element of the Stirling cycle in this example is aided by utilizing a heat exchanger 9 which uses external cooling water required in the normal operation of a PEM fuel cell 8 (or in the case of an internal combustion engine energy conversion technology the input to the engine cooling facility) to cool the gas around the displacement cylinder 4. This cooling element 9 completes the cycle which is repeated until either all the Hydrogen is released or a stop single is generated by the energy conversion device (fuel cell or internal combustion engine). For example, a Stirling engine setup (with a displacer or beta type Stirling engine or other suitable heat engine cycle), provides a small light weight apparatus for further compression and controlled injection into either a direct injection internal combustion engine or saturated Hydrogen suitable for use within a fuel cell energy system. The injection of Hydrogen gas into an internal combustion engine cleans up the emissions from the engine by more than 25% compared to conventional ICEs; considerable output soot reduction and NOX reduction is potentially feasible to achieve by employing the present invention.

FIG. 2 also illustrates a water collection unit 10 which extracts water generated by the fuel cell 8 and recycles this into a separate water storage tank 11. Prior to starting the reaction, it is necessary to remove air in the cartridge unit 1 to avoid explosive mixtures of Hydrogen and air arising. This is achieved by using either a separate pump or incorporating a back pressure of the cooling water pump 12 of the fuel cell 8. The pumping of the water to the fuel cell 8 is designed to create a back pressure in the cartridge unit 1. The effect of back pressure is to create a partial vacuum. The difference in pressure between the cartridge unit 1 and water storage tank 11 allows water to be feed into the cartridge unit 1 without the pumping once valve 13 needing to be opened. The water entering the cartridge unit 1 initially dissolves the stabilizing salt layer around the composite material 23 before the Hydrogen gas generation process is initiated.

After a plurality of cycles of operation (optionally determined to release a maximum amount of Hydrogen from the cartridge unit 1), the cartridge unit 1 is rejected/ejected.

Continued operation is achieved either by loading a new cartridge unit 1 into position for the Hydrogen reaction to take place through, for example, a spring loaded mechanism 14.

Referring to FIG. 3, a neutralisation system 100 is shown. The neutralisation system 100 is used to lower the pH of the alkaline material 23 to about pH 5.5-8.5, so called neutralizing the material placed in a neutralisation chamber 200 of the system 100.

The neutralisation chamber 200 is connected through a gas connector 300 to a supply unit 400. The supply unit 400 has a pump 500 that supplies the neutralization chamber 200 with carbon dioxide (Ca2). The neutralization chamber 200 has an exhaust valve 600 allowing exhaust from the system 100. A control unit 700 is connected to the supply unit 400 to control the pumping of CO2 to the neutralisation chamber 200. The control unit 700 is further in communication with the neutralisation chamber 200 where a sensor is arranged to measure the pH of the material 23 being neutralized.

To allow convenient handling of the alkaline material 23 it is in one preferred embodiment of the invention placed in a cartridge unit 1 described previously. One or more cartridge units 1 can be placed in the neutralization chamber 200 at any one time depending on the capacity of the neutralization system 100. The neutralization system 100 can be used as a stand alone system where any alkaline reside material is placed inside the neutralization chamber and the pH of the material is lowered using the addition of CO2 to the neutralization chamber 200. It will also be apparent to the person skilled in the art that a different embodiment of the invention also allows for lowering of the pH of material in the system 100 to below neutral levels i.e. pH c 700. The control unit 700 is normally configured so that a set time of exposure of the material 23 in the chamber 200 can be entered hence controlling the time that the CO2 is in contact with the material 23. Further the control unit 700 can also be arranged with a sensor which is in contact with the material 23, which sensor measures the pH and sends a signal to the control unit 700 once the preferred pH level is reached.

In applications for the transport industry (e.g. on land and at sea) and for stand alone fuel cells/generators the neutralization system 100 will have a capacity of ca 1-50kg of residue composite material 23 per operation cycle or more preferably ca 2-20kg.

At the lower ranges this allows for the neutralization system 100 to be onboard vehicles such as scooters, motorcycles, cars, vans, trucks, forklifts, speedboats, refrigeration units or other.

The utilization of the cartridge unit 1 setup allows for a very compact and user friendly solution for numerous applications such as portable units, vehicle Hydrogen generation units, or even for stationary units which need a safe and easy disposal of the residual waste from the Hydrogen reaction in the cartridges. The residue in the cartridges is often of alkaline nature with a pH value in the range of 8 to 14, but most often with a pH value in a range of 9 to 12. This waste product is today a major drawback for Hydrogen generator systems using metallic powder systems.

As described in FIG. 3, exposing the alkali residue material left in the cartridge unit 1 to Carbon Dioxide, which in this instance is used to lower the pH of the residue, is a way of reducing the pH to about 7, which makes it user friendly to handle. This is illustrated by the equations without prejudice to the invention we believe: 2NaOH + C02 -> Na2CO3 + H20 H20 + C02 -> H2C03 Na2CO3 + C02 -> 2NaHCO3 The cartridge system can be designed to supply the unit 1 with a right amount of composite material for implementing improved handling of the composite material 23.

It allows for safe disposal or return of the cartridge for safe disposal or treatment by e.g. acids or other pH lowering methods like the Carbon Dioxide mentioned above.

Beneficially, the cartridge 1 is capable of being cleaned and refilled, therefore rendering recycling possible.

Further, the applications of the Hydrogen generator unit 40 and the engine 2 encompass from in an order of 1W to 500W output systems for portable electronic devices, to in an order of 500W to 10kW output for bigger systems. Further, the cartridge unit 1 loaded with 1 kg (the typical size of a single cartridge) of fuel element/composite material 23, e.g. NaSi (s) as seen below, is capable of producing 1500 litres of hydrogen or 134g of hydrogen.

2NaSi (s) + 5H20 (I) -Na2Si2O5 (aq.) + 5H2 + Heat (-175 kJ/mol).

Therefore 10kg (10 nominal cartridges) of the composite material 23 therefore will generate 1.34kg of hydrogen, equating to 45kWhr of power. Converted to electricity through the fuel cell 8 this hydrogen (assuming an industry standard Fuel Cell operating at an energy efficiency of 50%) is capable of producing 22.SkWhr of electricity. The element/composite therefore would be comparable to an industry standard 24kWhr Lithium Ion battery pack. Such a pack when used to power an electric vehicle would give a range of lOOmiles and therefore is highly desired by within the motor industry. Simple manual cartridge replacement loaded into a magazine arrangement feed from a separate on board water supply would therefore provide an additional 100 miles of range. Most electric vehicles in the market today has a range below 100 miles, hence requires recharging over night or pad charging of battery pack at charging stations, which today are few and far apart. A real advantage of the system is that a 24kWhr (e.g. Nissan Leaf) battery pack normally makes up a substantial amount of the total car costs and has to be replaced every five years. The use of the described hydrogen system according to the invention would substantially reduce the cost of a vehicle utilizing battery packs.

Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "consisting of", "have", "is" used to describe and claim the present invention are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

Claims (10)

1. CLAIMS1. A composite material for Hydrogen gas generation from water in an exothermic reaction, wherein the composite material is a mixture of powder form of a metal and sodium oxide or sodium hydroxide, characterized in that the composite material powder is exposed to an acidic gas allowing the alkali component of the composite material powder to be coated with a layer of salt, which salt is inert to the metal powder and soluble in water; an exothermic reaction between the composite material and the water occurs once the soluble layer of salt is dissolved to generate Hydrogen gas at ambient pressure; and the residual material of the composite material post Hydrogen gas reaction is alkaline and treated with an acidic gas to lower the pH of the residual mateiral.
2. 2. A composite material as claimed in claim 1, wherein the metal of the composite material is at least one of: Aluminium, Calcium, Magnesium, Sodium, Potassium, Zinc or Gallium.
3. 3. A composite material as claimed in claim 1 or 2, wherein the acidic gas is one or more of carbon dioxide, hydrogen chloride or sulphur dioxide and it is exposed transiently to the salt component of the composite material creating a very fine layer of the salt on the composite material particles.
4. 4. A Hydrogen generator unit for generating low-pressure Hydrogen from water, characterized in that the generator unit includes at least one reaction chamber which is adapted to recieve a cartridge system with the composite material and employ an extracting chemical process to generate low-pressure Hydrogen from an exothermic reaction between a composite material and water, wherein the composite material has a water soluble salt layer which needs to dissolve prior to the exothermic hydrogen gas generating reaction is initiated.
5. 5. A Hydrogen generator unit as in claim 4, wherein a thermal engine is adapted to be used as a part of a refrigeration cycle to generate cooling and electricity for providing associated refrigeration.

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6. 6. A Hydrogen generator unit as claimed in claim 4, wherein a fuel cell is operable to generate clean water by way of a chemical reaction within the fuel cell, wherein said generator unit is adapted so that said water is recirculated for use in the extraction chemical process for generating low-pressure Hydrogen.
7. 7. A Hydrogen generator unit as claimed in claim 4, wherein a cartridge-based system, which contains the composite material, is operable to receive replaceable cartridges for providing reactants for the extraction chemical process.
8. 8. A method of manufacturing a composite material, wherein that said method includes the steps of: melting a metal and injecting the molten metal stream into an atomisation chamber; injecting at least one inert gas at higher pressure to create metal droplets and control the environment in the chamber to avoid ignition; spraying the molten metal droplets onto a cooling plate where condensation and cooling takes place; collecting the meal in powdered form post the cooling plate; mixing the powdered metal with Sodium hydroxide to generate a blended material; and exposing the blended material to an acidic gas at a temperature of 40-70C allowing a thin layer of a water soluble salt to form on the blended material and forming a stabilized composite material.
9. 9. A method of manufacturing a composite material according to claim 8, wherein that said salt is sodium hydroxide, the acidic gas is carbon dioxide and the powdered metal is Aluminium, and the monolayer is a water soluable protective layer that forms around the sodium carbonate during the blending process.
10. 10. A method of generating hydrogen from a composite material according to claims 8 or 9, wherein the composite material generates Hydrogen gas when in contact with water resulting in a residual alkaline material post reaction, and the residueal alkaline material is neturalised by exposing it to carbon dioxide which lowers the pH.