GB2491351A - A system for neutralising the residue of hydrogen production - Google Patents

Abstract

A system 1 is disclosed which includes a compression unit for generating hydrogen gas from water and a reaction material, resulting in generation of a residue, and for lowering the pH of the residue. The compression unit includes a reaction chamber 2 which is adapted to employ a chemical process to generate the hydrogen gas from water in an exothermic reaction with the reaction material. The reaction chamber is connected to a neutralisation unit, which contains carbon dioxide and supplies the residue in the reaction chamber with carbon dioxide to neutralise an alkali material therein. A control unit is connected to the neutralisation unit to control a quantity of carbon dioxide supplied to the reaction chamber to lower the pH of the residue material. Also disclosed is a system for lowering the pH of bauxite processing residue (red mud) by addition of carbon dioxide and a method for lowering the pH of alkaline materials by addition of carbon dioxide.

Description

HYDROGEN CLEAN UP SYSTEM AND METHOD OF ALKALINE RESIDUE

Technical field of invention

The present invention relates to a clean up system for cleaning up and safely disposing of alkaline residual material. Moreover, the invention relates to methods of using the aforesaid system to clean up alkaline residual material.

Background to the invention

There are several industries where there is a need to dispose of highly alkali material in a safe and environmentally friendly manner. One of these industries concerns, for example, the manufacture of Aluminium from bauxite, which generates an alkaline residual material. Similarly, there arises an alkaline residual material generated in other industries where hydrogen gas is generated.

As a well known energy vector, Hydrogen has many practical uses within 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 hydrocarbon fuels such as methane or via electrolysis of water. However, in certain processes, there is often an alkaline residue which requires treatment prior to disposal. Hydrogen generated from aforesaid one or more process steps can be utilized to fuel numerous applications: (i) for propelling vehicles; (ii) for fuelling micro energy system (for example battery replacements); and (iii) for emergency power supply systems.

With greater contemporary focus on environmental and sustainability issues, there are therefore problems to be addressed prior to disposal of any alkaline residual material in these applications involving use of Hydrogen.

In the case of portable applications, one or more additional process steps are required after Hydrogen generation, to enable satisfactory Hydrogen storage and transport. Hydrogen is the lightest know element and often requires extensive external equipment and energy input to achieve practical energy densities appropriate for use in transportation, or for the market for portable systems including Hydrogen units. Often bulky, high pressure storage tanks limit the application of Hydrogen in vehicle propulsion systems. This also makes it even less attractive to implement complicated systems of neutralizing any alkaline residue material with, for example, acids or similar techniques.

The alkaline residue is often a direct result of employing 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 the 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. However there are issues with the residue following the release of the Hydrogen gas, as it becomes alkaline with high pH > 9, which is dangerous to handle and damaging to the environment if not disposed of properly.

Similarly, in a United States patent no. US 6506360, there is described a system which utilizes the reaction of Aluminum with water in the presence of Sodium Hydroxide as a catalyst. The system uses pressure and the temperature of the reaction to control a degree of immersion of a fuel cartridge in water and consequently to control a vigour and duration of the reaction. Control of the temperature of the water and the degree of immersion of the fuel cartridge in the water can become complicated if utilization in any type of portable solution is intended. The method uses metallic Aluminium waste found in domestic settings and metal workshop to supposedly give an environmentally friendly solution to the problem of waste disposal. However it does not highlight the issue that the material residue following the Hydrogen gas release from the water is most likely to comprise a Sodium Aluminate/hydrated alumina composition, which is strongly alkaline and not environmentally friendly to handle at all.

In several other United States patent nos. US 4356163, US 5514353, US 3716416, there are problems with alkaline residues from controlled Hydrogen generators that employ alkali metals (or metal hydrides (United States patent no. US 5593640) or iron (United States patent no. US 5510201)) and water.

Additional United States patent nos. US 5143047, US 5494538, US 4600661, US 4072514, US 4064226, US 3985865, and US 3966895, have been issued for the 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 alkaline residues with high pH values and consequent difficulty associated with their disposal. In a Japanese patent no. JP 1061301 an Aluminium-ceramic composite has been proposed to initiate the 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 high 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. However, the residue is normally Aluminum 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. This still leaves the problem of how best to handle the alkaline residue that is left after these Hydrogen generation methods.

Similarly, in the manufacture of Aluminium from bauxite, raw bauxite is treated with strong Sodium Hydroxide solution. Bauxite is, essentially, hydrated Aluminium Oxide (alumina) contaminated by various amounts of Iron Oxide. The alumina dissolves in the caustic solution at elevated temperatures, and is filtered from the insoluble Iron Oxide. The alumina is then recovered from the solution thus obtained at the end of manufacture process. This residue from the fining process of alumina, so-called red mud, is often alkaline and needs careful handling and treatment to avoid damaging the environment on disposal.

There are many cases where the alkaline residue, for example such as hydroxides and other alkaline metals compositions from such cases as those described above, lies in the pH range of 9 to 14 and could be neutralized using acid. The possibility of removal of alkali by a non-acidic absorption method also remains, but this is further complicated by a possibility of reversibility, leading to long term leaching of the alkali.

A wide range of acids is potentially available to attempt to decrease the leaching.

For example, mineral acids such as sulphuric acid are cheap to manufacture and are readily available. However, the salts are freely soluble in water and would leach into the environment. Organic acids such as acetic acid and citric acid are also available, at greater cost, and while they, too, are freely soluble in water, there may be more scope for disposal since they are regarded as "organic" in the environmental meaning of the word. However, they are weak acids, and even when the excess alkali has been neutralized, the pH is still alkaline due to the hydrolytic effect and the incomplete ionization of a weak acid.

Summary of the invention

The present invention seeks to provide a treatment system, also called a "clean up system" in the following description, for lowering the pH of residue material.

According to a first aspect of the invention a clean up is performed through a treatment system including a compression unit for generating low-pressure Hydrogen gas (H2) from water and a reaction material, resulting in generation of a corresponding residue material, and for lowing a pH value of the residue material allowing environmentally friendly disposal and convenient, efficient handling.

The compression unit includes at least one reaction chamber which is adapted to employ an extracting chemical process to generate the low-pressure Hydrogen gas from water in an exothermic reaction with the reaction material in the at least one reaction chamber. Further at least one reaction chamber is connected to a neutralisation unit, which contains Carbon Dioxide (C02) and is operable to supply the residue material in the reaction chamber with Carbon Dioxide (C02) to neutralise the material therein. A control unit is connected to the neutralisation unit to control a quantity of Carbon Dioxide (C02) supplied to the at least one reaction chamber to lower a pH value of the residue material to less than 8.5 for allowing for its safe disposal.

The invention has the advantage that use of CO2 for neutralising alkali residue from the hydrogen generation process renders the final product suitable for landfill or disposal in domestic waste bins, once it has been removed from the hydrogen generation stage. Further it allows for neutralisation of an alkaline residual material in a space efficient way suitable for many hydrogen applications, such as vehicle propulsion and micro energy systems.

Optionally, the neutralisation unit is arranged so that when the hydrogen generator unit is connected to allow direct hydrogen injection with the fuel injection into an Internal Combustion Engine (ICE), the CO2 for the neutralisation unit can be taken from the engine exhaust. This allows for the hydrogen generator unit to be not only improving the engine emissions by ca 25%, through the hydrogen gas injection at ca 3-6% with diesel or petrol during combustion, but also the after treatment of the alkali residue having a further carbon reducing affect on the overall ICE system's emissions.

Further, optionally the neutralisation unit can be arranged in parallel or serially with the reaction chamber allowing for the alkali residue material to be removed from the reaction chamber to continue hydrogen production with a new batch of material in the reaction chamber. By having the reaction material in a cartridge would allow for safe and convenient handling on refuelling as well as transfer to the neutralisation chamber when containing alkaline material.

This system allows for safe disposal of the material treated by the Carbon Dioxide (C02) once the pH has been lowered to levels in the range of 5.5-8.5, which allows for disposal as normal domestic waste. Further there is low risk of leaching from the neutralised material into the ground after disposal as recovery is easily performed. I one preferred embodiment of the invention the resultant is sodium bicarbonate is the material left as a product following treatment and is conveniently recovered. In the unlikely event that the sodium bicarbonate is not recovered there is a small risk of the bicarbonate leaching away similarly to other soluble sodium salt and go into the environment. However, sodium bicarbonate is non-toxic and is used as a food stuff so would be less severe.

Optionally, the treatment system is arranged for treatment of alkali residue material, such as in a bauxite processing plant for the production of Aluminium. The treatment system decreases the pH of any alkali residue from the bauxite allowing safe disposal.

Optionally, there is also an ultrasonic treatment means arranged in connection with the neutralisation system to speed up the physical contact between residues and carbon dioxide. This allows for faster treatment and is especially suited for applications where large amounts of alkaline material is treated.

Further the use of elevated pressures also improves the efficacy of the reaction, which ideally could be implanted through the use of a small autoclave operating in connection with the neutralisation system at a few bar pressure.

In addition, the operating temperature of the neutralisation chamber can also be adjusted to an optimum temperature. This temperature will be as warm as possible to increase the rate of reaction, but must be below the thermal decomposition temperature of the final neutralised residue material, such as bicarbonates, otherwise we would get the final pH of e.g. sodium carbonate solution which would be above pH9. For example, the appropriate temperature for sodium bicarbonate will be in the range of about 40°C-70°C. The optimum temperature lies in the range of ca 50°C to ca 60°C. However, different metals will have different optimum temperatures for the neutralisation process with Carbon Dioxide (C02) according to the invention. This heat can be taken from the exothermic reaction to generate Hydrogen gas in one embodiment of the invention.

The advantage of using carbon dioxide (C02) is that it is so weakly acidic that it is impossible to make the residues excessively acid, and even in the situation whereby the neutralisation would go too far and the residue became more acidic, the carbon dioxide would quickly de-gas leaving the final pH closer to 7.

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 an illustration of a neutralisation system pursuant to the present invention; FIG. 2 is an illustration of a neutralisation system in a Hydrogen generator unit; FIG. 3A is a front view of a cartridge in a cartridge unit; FIG. 3B is an illustration of the cartridge in FIG. 3A on section AA; and FIG. 3C is an illustration of the cartridge in FIG. 3B on section BB.

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.

Description of embodiments of the invention

Referring to FIG. 1, a neutralisation system I is shown. The neutralisation system 1 is used in operation to lower the pH of an alkaline material 23 to about a range pH 5.5 to 8.5, so-called neutralizing the material 23 placed in a neutralisation chamber 2 of the neutralisation system 1. The neutralisation chamber 2 is connected through a gas connector 3 to a supply unit 4. The supply unit 4 has a pump 5 that supplies in operation the neutralization chamber 2 with Carbon Dioxide (C02). The neutralization chamber 2 has an exhaust valve 6 allowing exhaust from the system 1. A control unit 7 is connected to the supply unit 4 to control pumping of CO2 to the neutralisation chamber 2. The control unit 7 is further in communication with the neutralisation chamber 2 where a sensor is arranged to measure the pH of the alkaline material 23 to be neutralized.

To allow convenient handling of the alkaline material 23, in one preferred embodiment of the invention, the material 23 is placed in a cartridge unit 10 described further below. One or more cartridge units 10 can be placed in the neutralization chamber 2 at any one time depending on a capacity of the neutralization system 1. The neutralization system I is optionally used as a stand alone system where any alkaline reside material is placed inside the neutralization chamber 2 and the pH of the material is lowered using an addition of CO2 to the neutralization chamber 2. 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 1 to below neutral levels, namely pH c 7. The control unit 7 is normally configured so that a set time of exposure of the material 23 in the chamber 2 can be entered, thereby controlling a time period during which the CO2 is in contact with the material 23. Furthermore, the control unit 7 can also be arranged with a sensor which is in contact with the material 23, which sensor measures the pH and sends a corresponding pH-indicative signal to the control unit 7 once a preferred pH level is reached.

In applications for the transport industry (for example on land and at sea) and for stand alone fuel cells/generators, the neutralization system I will have a capacity of circa 1 to 50 kg of residue composite material 23 per operation cycle or more preferably circa 2 to 20 kg. At lower ranges of capacity, this allows for the neutralization system 1 to be onboard vehicles such as scooters, motorcycles, cars, vans, trucks, forklifts, speedboats or other.

Another application area where the invention can be used is in the alumina (Aluminium Oxide) refining process during, for example, alumina manufacturing.

When large plants produce alumina, the residue obtained from the alumina refining process, also known as red mud, is strongly alkaline and is very suitable for treatment in accordance with the present invention. The red mud consists in the main of hydrated Ferric Oxides, contaminated by any impurities in the original bauxite, and also by the residual caustic soda from a dissolution stage of the refining process.

This mud is highly toxic, not only due to the presence of heavy metals, but also due to a very high pH level. By exposing the red mud to 002, it is possible to reduce the pH of this residue to a level which would make it safer for disposal, provided that its heavy metals content is acceptably low. Therefore, the neutralization system 1 is susceptible to being implemented in large scale, such that its alumina refining process or similar employs an addition of 002 to the alkaline residue material manufactured.

The treatment employed in the bauxite process, shown below varies somewhat as bauxite is not a homogenous species and will vary somewhat from source to source.

In the treatment, soluble Sodium Aluminate is formed, and the solution is filtered from the red mud, which remains strongly alkaline because of its initial contact with strong caustic soda. Alumina is recovered from the Sodium Aluminate by dilution, which leads to precipitation of a hydrated Aluminium Oxide. This releases Sodium Hydroxide which is recycled back to the process. There is often some Sodium Hydroxide entrained with the red mud.

Bauxite is an inhomogeneous mixture containing e.g Gibbsite (Al(OH)3, Boehmite, y-AlO(OH), and Diaspore ct-AlO(OH) together with a range of impurities including, e.g Haematite Fe203, Goethite FeOOH, Anatase TiO2, and some siliceous minerals.

Taking Gibbsite as a typical but not exclusive example, the extraction of aluminium can be described using the following equations: NaOH + (Al(OH)3 NaAIO2 + H20 (elevated temperature) NaAIO2 + H20. NaOH + (Al(OH)3 (lower temperatures) The impurities are not dissolved during the digestion at high temperature, and are filtered from the strongly alkaline sodium aluminate solution. On cooling, or dilution, the aluminium is precipitated as a hydroxide or hydrated oxide, which is then converted to the metallic state using an electrolytic process. The toxic residues -10-necessarily contain substantial amounts of sodium hydroxide, and the pH renders this residue unsuitable for simple disposal.

Referring to FIG 2., a hydrogen generator unit 40 is shown with a neutralizing system 1. A cartridge unit 10 is placed in a reaction chamber 38, which reaction chamber 38 is attached to a base of a single cylinder displacement-type engine 12; optionally, the engine 12 is a Stirling-type engine of either beta or alpha configuration. Alpha and beta configurations for Stirling engines are elucidated in Wikipedia. The cartridge unit 10 contains a 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. The composite material 23 is preferably manufactured from Sodium but can also be manufactured from other metals such as Aluminium, Calcium, Magnesium, or Potassium. The following formulae provide examples of chemical processes, which are employed to generate Hydrogen and heat from an exothermic reaction with water: 2NaSi (s) + 5H20 (I) -÷ Na2Si2O5 (aq.) + 5H2 + Heat (-175 kJ/mol) Eq. 1 In this case, the reaction produces five moles of Hydrogen, in rapidity, from the reduction of five moles of water and only two moles of NaSi exothermically. As Sodium Silicide is pyrophoric, the cartridge unit 10 containing this fuel element/powder 23 is beneficially sealed with an air tight membrane prior to its use to prevent any incident of fire from contact with air. The Sodium Silicate thus produced is sensitive to aqueous hydrolysis, resulting in a highly alkaline effluent.

Ca (s) + 2H20 Ca(OH)2 + H2 (gas) Eq. 2 In the Hydrogen generator unit 40, there is a connection made between the cartridge unit 10 in the reaction chamber 38 and the engine 12 via a heat exchanger 35, which heat exchanger 35 allows heat generated from an exothermic chemical reaction in the cartridge unit 10 to be transferred from the cartridge unit 10 directly to the base of the engine 12. This heat exchange acts to initiate an engine cycle, such as a Stirling engine cycle, moving a displacement cylinder 14 and subsequently moving a piston connected to a flywheel 16.

Hydrogen gas generated by the reaction in the cartridge unit 10 is allowed to enter into a diaphragm of a pump 17 via a separate pipe connection 16 from an outlet of the cartridge unit 10. A rotational motion of the flywheel 16 moves the diaphragm pump 17 to create a partial vacuum which extracts any Hydrogen gas from the cartridge 10. Hydrogen then enters a chamber of the diaphragm pump 17 until continued movement of the flywheel 16 moves the diaphragm to close an inlet valve of the diaphragm pump 17. 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 18. The capacity of the diaphragm pump 17 is chosen to incorporate a factor of safety to avoid over pressurization of the fuel cell 18 and is of sufficient capacity to safely pressurize Hydrogen generated from the cartridge unit 10.

The heat therefore applied to a base of the Stirling engine 12 acts to compresses the Hydrogen gas released from the cartridge unit 10 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 18 (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 16, 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 19 which uses external cooling water required in the normal operation of a PEM fuel cell 18 (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 14. This cooling element 19 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 -12-displacement 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. 1 also illustrates a water collection unit 30 which extracts water generated by the fuel cell 18 and recycles this water into a separate water storage tank 31. Prior to starting the reaction, it is necessary to remove air in the cartridge unit 10 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 of the fuel cell 18. The pumping of the water to the fuel cell 18 is designed to create a back pressure in the cartridge unit 10. The effect of back pressure is to create a partial vacuum. The difference in pressure between the cartridge unit 10 and water storage tank 31 allows water to be feed into the cartridge unit 10 without the pumping once a valve 33 is opened. For applications of using the Hydrogen generator unit in rural and remote areas even polluted water used to generate the Hydrogen gas in reaction with the composite material 23 in the cartridge unit 10. This would allow the added benefit of using the Hydrogen generator unit for cleaning or purifying water.

After a plurality of cycles of operation (optionally determined to release a maximum amount of Hydrogen from the composite material 23 inside the cartridge unit 10), the cartridge unit 10 is rejected/ejected. Continued operation is achieved either by loading a new cartridge unit 10 into position for the Hydrogen reaction to take place through, for example, a spring loaded mechanism 34. This cartridge unit 10 reloading mechanism is illustrated further in FIG. 3.

The utilization of the cartridge unit 10 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 -13-cartridge units 10 is often of an 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, but the cartridge system and neutralization system 1 can be designed to totally address this drawback.

When the used cartridge unit 10 is rejected/ejected from the reaction chamber 38, it can be moved into the neutralization chamber 2 of the neutralization system 1. The supply unit 4 then allows for CO2 to be pumped into the neutralization chamber 2 and therefrom into the one or more cartridge units 10. The reaction of the alkaline material and the CO2 to lower the pH of the material 23 is described in more detail below. Once the material 23 has been exposed to the CO2 for long enough and the pH has come down to a value of about pH 7, the cartridge unit 10 can be removed from the neutralization system 1. The cartridge unit 10 can then be opened and the material 23 therein can be disposed of as normal household waste without any risk to the environment. Beneficially, the cartridge unit 10 is capable of being cleaned and refilled, therefore rendering recycling possible.

Example of a cleaning process: i) Neutralization of cartridge residue A preferred embodiment of the present invention for treating the alkali material 23 using of carbon dioxide (C02) involves a neutralization step. Considering an example whereby the concentration of Sodium Hydroxide after use is 0.1 molar, this would result in a pH of about 13 in the Hydrogen generation examples elucidated in the foregoing. Reaction of this solution with a molar equivalent of Carbon Dioxide, would result in conversion of the Hydroxide into Sodium Carbonate, Na2CO3, namely washing soda. A 0.1 molar solution of Sodium Carbonate has a pH value of around 9.3. This is still too high for ready discharge into landfill or other cheap manners of disposal. However, reaction with a further molar equivalent would result in the formation of Sodium Bicarbonate, NaHCO3, namely baking powder. A molar solution of Sodium Bicarbonate has a pH value of around 8.3 which is generally acceptable since Sodium Bbicarbonate is not only non-toxic, but is also used as a food additive.

Further dissolution of Carbon Dioxide, either atmospheric or deliberately added, would have the effect of reducing the pH value even further, the limit probably lying -14-within a range of pH of 5 to 7. Aqueous Carbonic acid has a pH value of 5.3. This is illustrated by the equations shown below: 2NaOH + CO2 Na2CO3 H20 + CO2 H2C03 Na2CO3 + CO2 2NaHCO3 There are several advantages to this approach. Carbon dioxide is cheap and plentiful as it is a waste product from many processes; Carbon Dioxide sequestration from Carbon capture and storage apparatus for complying with international climate change legislation is potentially a copious source of Carbon Dioxide. Secondly, it would be impossible to overshoot and make the residues excessively acid because Carbonic acid is exceedingly weak, Carbon Dioxide has limited solubility in water and any excess Carbonic acid dissociates rapidly back to Carbon Dioxide and water.

Finally, energy generation by the use of the Hydrogen-containing powder, such as the composite material 23, and Carbon Dioxide treatment in accordance with the present invention of the residue could be regarded not only as Carbon-neutral approach, but even as a Carbon negative one.

The above embodiment uses Sodium Hydroxide as a model alkali compound.

However, the chemistry is also true for all other alkaline compounds such as lime or other alkali metal hydroxides. For example, Ammonium Carbonate has a pH value of around 9.0, while Ammonium Bicarbonate solution has a pH value of 7.8.

Further, the applications of the Hydrogen generator unit 40 and the engine 12 encompass from in an order of 1 W to 500 W output systems for portable electronic devices, to in an order of 500 W to 10 kW output for bigger systems. Further, the cartridge unit 10 loaded with 1 kg (the typical size of a single cartridge) of fuel element/composite material 23, for example NaSi (s) as described in Equation 1 (Eq.

1) above, is capable of producing 1500 litres of Hydrogen or 134 g of Hydrogen.

Moreover, 10 kg (10 nominal cartridges) of the composite material 23 therefore will generate 1.34 kg of hydrogen, equating to 45 kWhr of energy. Converted to electricity -15-through the fuel cell 18 this hydrogen (assuming an industry standard Fuel Cell operating at an energy efficiency of 50%) is capable of producing 22.5 kWhr of electrical energy. The elementlcomposite therefore would be comparable to an industry standard 24 kWhr Lithium Ion battery pack. Such a pack when used to power an electric vehicle would provide the vehicle with a travelling range of approximately 180 km per recharge and therefore is highly desired by the motor industry. Simple manual cartridge replacements loaded into a magazine arrangement feed from a separate on board water supply would therefore provide an additional km travelling range. Most electric vehicles in the market today provide a travelling range of less than 180 km per recharge, hence requiring recharging over night or part charging of battery pack at charging stations, which today are uncommon and disposed spatial far apart. A major advantage of the system pursuant to the present invention is that it replaces part or most of a 24 kWhr (for example as pertinent for a Nissan Leaf electric vehicle) battery pack which makes up a substantial part of the vehicle cost and has to be replaced every five years. The Hydrogen and clean up solution as described in this embodiment of the present invention would hence remove the cost half of the battery pack. A drawback of the residue material 23 being alkaline is then further addressed by the utilization of the CO2 cleaning as aforementioned, namely for lowering the pH. Such an approach pursuant to the present invention is capable of providing a hybrid Electrical and Hydrogen vehicle to be a realized which provides in operation a negative Carbon solution in respect of anthropogenically-induced climate change.

In FIG. 3A, FIG. 3B and FIG. 3C, details of inner workings of the cartridge unit 10 are illustrated, also with reference to FIG. 2. FIG. 3A is an illustration of a front view of the cartridge unit 10 and two partial cross sections of the views of the cartridge 10 detailed on sections AA as FIG. 3B and sections BB as FIG. 3C. The cartridge unit is constructed in two parts, namely a lower unit 21 containing fuel elements 23 arranged to be operated in a vertical position along a longitudinal (horizontal) direction of the lower unit 21, and an upper unit 22 containing a reaction chamber to separate Hydrogen gas when generated in operation. The reaction chamber consists of an inner stainless steel or Hydrogen-resistant material mesh 24 arranged to function as both a heat exchanger and a separator for separating the Hydrogen produced from water through a chemical process as shown. -16-

The lower unit 21 is designed such that it is slightly larger than the upper unit 22, SO that these units 21, 22 can be easily mutually fixed or clamped together to provide an air tight seal therebetween to define the reaction chamber. Once sealed, the air in the chamber is extracted via a pump connected to the upper chamber creating a negative pressure in an arrangement acting to further clamp the cartridge 10 together. Water is then added via a separate valve filling the area around the fuel elements 23. The fuel elements 23 are separated from the heat exchanger element via the mesh 24 and are prevented from entering an upper area of the upper unit 22 by virtue of a membrane 26. Water reacts with the fuel elements 23, also called composite material, 23 which has a surface that is porous to increase the surface area for reaction and thus a corresponding rate of reaction.

The Hydrogen reaction cleaves Hydrogen atoms from corresponding water molecules, wherein the Hydrogen atoms are buoyant and of a sufficiently small size to enable them to pass through the membrane to the upper unit 22 of the cartridge 10. On account of the reaction between the water and the fuel elements 23 being exothermic, the temperature of the surrounding medium is raised, and this temperature rise is transferred through the mesh 24 to heat exchanger element 25, this being fabricated from a material exhibiting a high thermal conductivity. The heat element 25 is connected to a temperature base plate 28 which is connected to the base of the engine, for example implemented as a Stirling engine in one preferred embodiment of the present invention.

Operation of the engine cycle as illustrated in FIG. 2 extracts Hydrogen from the cartridge 10 (namely the upper unit 22) via a pipe 27 as indicated. As Hydrogen is extracted, a pressure difference is created between the upper and lower chambers resulting in water refilling the reaction chamber through the capillary effect, thereby continuing the reaction. After a plurality of cycles of the engine cycle, all of the reaction fuel element 23 will be spent and the lower unit 21 is then optionally replaced with a new corresponding unit containing fuel. The external water connection 29 and pump connection 30 are preferably located on the upper unit 22 allowing for rapid replacement of a new fuel unit. -17-

Once the cartridge unit 10 has been replaced/ejected from the reaction chamber 38, it is inserted into the neutralization chamber 2 of the neutralization system 1. In the neutralization chamber 2, the connection 29, which previously was used for adding water, is now connected to the supply unit 4 allowing 002 to be introduced into the cartridge unit 10 and into contact with the alkaline residue material 23. The CO2 can either be pumped into the cartridge unit 10 by operation of the pump unit 5 or a back pressure can be created via the pump connection 30, as previously done to introduce water into the cartridge unit 10. The pump connection 30 would be connected to a pump that extracts any existing air or other gas in the cartridge allowing the CO2 to enter into contact with the material 23 to be cleaned up.

In a further embodiment of the invention, the reaction chamber 38 and the cartridge unit 10 are combined as a unitary component. Such a unitary component allows for a compact system where the cartridge is replaced and connected to the hydrogen generator unit before operation starts again. Further the clean up process using 002 could also be performed in the cartridge before the cartridge unit is replaced. For example, in a hybrid vehicle, there could be a switch to the alternative power supply (for exmaple battery packs) while the residue material in the cartridge is cleaned with 002 before a new cartridge is put in place and Hydrogen generation is resumed. In this later embodiment, the cartridge unit 10 has both a compartment acting as a reaction chamber and neutralization chamber 2 at different stages of the process of Hydrogen generation and clean-up of the residue material 23. As described previously, the cartridge could also have more than one chamber allowing for a continued Hydrogen generation to take place while previously used and now alkaline material 23 is being cleaned with 002 in another chamber.

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. The words Aluminium and Aluminum are the UK and US way of naming the same material and are hence -18-interchangeable throughout this patent application. 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. -19-

Claims (17)

1. CLAIMS1. A treatment system including a compression unit for generating low-pressure Hydrogen gas (H2) from water and a reaction material, resulting in generation of a corresponding residue material, and for lowering a pH value of the residue material, characterized in that the compression unit includes at least one reaction chamber which is adapted to employ an extracting chemical process to generate the low-pressure Hydrogen gas from water in an exothermic reaction with the reaction material in the at least one reaction chamber, wherein the at least one reaction chamber is connected to a neutralisation unit, which contains Carbon Dioxide (C02) and is operable to supply the residue material in the reaction chamber with Carbon Dioxide (C02) to neutralise the material therein, and wherein, a control unit is connected to the neutralisation unit to control a quantity of Carbon Dioxide (C02) supplied to the at least one reaction chamber to lower a pH value of the residue material to less than 8.5 for allowing for its safe disposal.
2. 2. A treatment system as claimed in claim 1, wherein an Internal Combustion Engine (ICE) is included and implemented to supply the Carbon Dioxide (C02) from the engine exhaust to the neutralisation unit.
3. 3. A treatment system as claimed in claim 1, wherein a thermal engine is included and implemented as a Stirling engine employing an alpha-type displacement configuration or a beta-type configuration to utilize the low pressure Hydrogen (H2) generated in operation.
4. 4. A treatment system as claimed in claim 3, wherein the Stirling engine has associated therewith a chain multiple compression chamber to compress the generated Hydrogen (H2) in a continuous cycle.

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5. 5. A treatment system as claimed in claim 1, 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.
6. 6. A treatment system as claimed in claim 1, wherein a fuel cell is operable to generate clean water by way of a chemical reaction occurring within the fuel cell when in operation, 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 treatment system as claimed in any one of the preceding claims, wherein the Hydrogen generator unit is adapted to function as an auxiliary heating unit for use within vehicles.
8. 8. A treatment system as claimed in any one of the previous claims, wherein said compression unit is adapted to function as a portable chilling unit.
9. 9. A treatment system as claimed in any one of the previous claims, wherein said control unit is provided with a sensor for determining when a pH value of the material being cleaned up is less than 8.5.
10. 10. A treatment system as claimed in any one of the preceding claims, wherein the treatment system is operable to employ a cartridge system having one or more neutralization chambers as separate sections for storing an energy material used to extract Hydrogen gas from water as well as introducing Carbon Dioxide (C02) to any alkaline residue material associated with the energy material.
11. 11. A treatment system as claimed in claim 10, wherein the replaceable material for treatment includes reactants comprising at least one of: Aluminium Oxide, Calcium, Magnesium, Sodium, Borides, or Potassium.
12. 12. A treatment system for receiving an alkali residual material therein, a neutralisation chamber connected to a clean up unit, and a control unit regulating a clean up process implemented by the system, characterized in that -21 -the neutralisation chamber contains Carbon Dioxide (C02) when in operation; the control unit is operable to allow the Carbon Dioxide (C02) from the neutralisation unit to come into contact with an alkali residue material in the clean up unit, and that the amount of Carbon Dioxide (C02) is such that a pH value of the alkali residue material is sufficient to allow safe and environmentally friendly disposal of the material.
13. 13. A treatment system as claimed in claim 12, wherein the residual material for treatment is bauxite processing residue, and the treated material becomes Sodium Bicarbonate.
14. 14. A treatment system as claimed in any one of the preceding claims, wherein an ultrasonic treatment means is arranged in connection with the neutralisation unit to improve the physical contact between the residual material.
15. 15. A treatment system as claimed in any one of the preceding claims, wherein the treatment system operates at an elevated pressure through an autoclave unit connected to the neutralisation unit to increase the pressure to above 2 Bar.
16. 16. A treatment system as claimed in any one of the preceding claims, wherein the neutralisation unit operates at an elevated temperature of about 40°C-70°C, and more preferably about 50°C.
17. 17. A method of lowering a pH value of a residual, alkaline material, which method comprises steps of: (i) placing the alkaline material into a reaction chamber of a neutralisation unit; (ii) closing the reaction chamber and introducing Carbon Dioxide (C02) into the reaction chamber; (iii) monitoring the pH value of the residual material; (iv) continuing steps (ii) and (iii) until the pH value of the residual material is less than substantially 8.5, more preferably substantially 7; and (v) removing the treated residual material from the reaction chamber.