WO2011088515A1

WO2011088515A1 - Method and system for production of hydrogen

Info

Publication number: WO2011088515A1
Application number: PCT/AU2011/000064
Authority: WO
Inventors: Robert George Davis
Original assignee: Dysart Proprietary Limited
Priority date: 2010-01-22
Filing date: 2011-01-21
Publication date: 2011-07-28

Abstract

A method and system for the production of hydrogen is disclosed which includes distilling sea water by heat supplied by a furnace to produce steam and brine, the furnace also producing a furnace flue gas as a by-product which includes a plurality of constituent gases; electrolysing at least a portion of the steam to produce hydrogen; electrolysing the brine to produce hydrogen and chlorine gas and a sodium hydroxide solution; mixing at least a portion of the hydrogen gas produced from either or both of the electrolysis of the steam or brine and chlorine gas with water to form hydrochloric acid; applying the furnace flue gas and/or third party flue gases to the sodium hydroxide solution to create a sodium compounds solution of one or more of the constituent gases; applying the sodium compounds solution to the hydrochloric acid to regenerate the original gases constituent gases; and separating the gases produced when applying the sodium compounds to the hydrochloric acid. In addition, a method and system for carbon dioxide storage is disclosed including compressing the carbon dioxide; and applying the compressed carbon dioxide through apertures over which molten glass is supplied such that a glass foam is created.

Description

METHOD AND SYSTEM FOR PRODUCTION OF HYDROGEN

The present invention relates to a method and system for the production of hydrogen and, particularly, but not exclusively to a method and system for the production of hydrogen and capture of carbon dioxide from exhaust gases of fossil fuel power stations.

The Intergovernmental Panel on Climate Change stated in their Fourth Assessment Report (AR4), "Climate Change 2007", that:

• the amount of carbon dioxide in the atmosphere in 2005 (379 ppm) exceeds by far the natural range of the last 650,000 years (180 to 300 ppm); and

• the primary source of the increase in carbon dioxide is fossil fuel use.

The IPCC have further urged the world that by 2050, carbon dioxide emissions must be reduced by 90% from 2000 levels in order to halt the possible catastrophic destabilisation of the world's weather. Around 50% of the man-made emissions of carbon dioxide comes from power stations and the rest comes from transportation and industry, nearly all of which is a direct result of burning fossil fuels.

The reserves of fossil fuels will support the present consumption rates for a limited time only and are predicted as follows:-

• Oil 30 - 40 years

• Natural gas 60 - 80 years

• Coal 120 - 140 years

(source: www.bp.com)

At significant portion of fossil fuels are used for other essentials such as lubricating oils, fertilizers, various chemicals and plastics. It is of particular interest for future generations to preserve as much of these reserves as possible. Existing energy companies have large infrastructures which are reliant on the mining and use of fossil fuels. In addition they have a legal and moral responsibility to their shareholders and employees. Therefore, they cannot accept any proposal that capriciously devalues their assets and income. They need a stable pathway that allows a reasonable and rational transition to a new energy base. In addition, governments need viable options on which to base policies to encourage change.

Hydrogen is known as an energy source for internal combustion engines and turbines. Only minimal alteration to existing equipment is needed to transfer to the use of hydrogen from fossil fuels. Hydrogen is typically produced from hydrocarbons, such as natural gas, by a process known as steam reforming but may also be produced from water using electrolysis.

Carbon trading schemes have been introduced by governments around the world, with the most well known being the Kyoto Protocol. The Kyoto Protocol is a protocol to the United Nations Framework Convention on Climate Change (UNFCCC or FCCC), aimed at combating global warming and binds most developed nations to a cap-and-trade system (entities are given a cap to which they can emit up to and if they want to exceed that cap they must trade with an entity which has "excess" quota left) for the six major greenhouse gases (carbon dioxide, methane, nitrous oxide, sulphur hexafluoride and two groups of gases, hydrofluorocarbons and perfluorocarbons, produced by them).

Carbon dioxide capture and storage, or carbon capture and storage, is one method of decreasing the amount of carbon dioxide emitted by man-made sources, such as burning fossil fuels. Many different possibilities exist for the storage of carbon dioxide, including:

• Geological storage (also known as geo-sequestration) involving injecting carbon dioxide directly into underground geological formations;

• Ocean storage involving deep depositing of carbon dioxide so that it either forms a lake (due to being denser than water) or dissolving into the water; • Mineral storage involving reacting carbon dioxide with naturally occurring minerals to form carbonates; or

• Biological sequestration involving encouraging the extraction of carbon dioxide through plant materials, such as encouraging plankton blooms or growing algae.

As a result of the desire of the governments, and the global population in general, to slow down or decrease global warming, there is a need to mitigate the production of carbon dioxide through burning fossil fuels as well as to produce hydrogen as a cleaner burning fuel alternative.

According to a first aspect of the present invention there is provided a method for the production of hydrogen including:

distilling sea water by heat supplied by a furnace to produce steam and brine, the furnace also producing a furnace flue gas as a by-product which includes a plurality of constituent gases;

electrolysing at least a portion of the steam, either as steam or, by cooling, as desalinated water, to produce hydrogen;

electrolysing the brine to produce hydrogen and chlorine gas and a sodium hydroxide solution;

mixing at least a portion of the hydrogen gas produced from either or both of the electrolysis of the steam or brine and chlorine gas with water to form hydrochloric acid;

applying the furnace flue gas and/or third party flue gases to the sodium hydroxide solution to create a sodium compounds solution of one or more of the constituent gases;

applying the sodium compounds solution to the hydrochloric acid to regenerate the original gases constituent gases; and

separating the gases produced when applying the sodium compounds to the hydrochloric acid. Preferably, the hydrochloric acid is formed using desalinated water from the electrolysis of steam.

Preferably, the constituent gases include carbon, sulphur and nitrogen from the gases carbon dioxide, sulphur dioxide, nitrogen monoxide or nitrogen dioxide.

Preferably, the method further includes the method of storing carbon dioxide according to the second aspect of the present invention. Preferably, the method further includes generating electricity and, further preferably, generating electricity from the heat of the furnace and, more preferably, from steam generated by the furnace.

Preferably, the furnace uses burning a hydrocarbon based fuel as a heat source. Preferably, the furnace uses burning fossil fuels as a heat source. Alternatively, the furnace uses burning bio-fuels as a heat source.

Preferably, the brine is produced at a concentration of 20% to 30% by weight of salt and, further preferably, 25%.

Preferably, the furnace flue gas and/or third party flue gases are cooled in a closed circuit cooling tower. Further preferably, the method includes removing particulates, including mercury oxide, from the flue gases prior to entry to the cooling tower.

Preferably, heat retrieved from the cooling tower is used to heat the sea water prior to the sea water being distilled.

Preferably, applying the furnace flue gas and/or third party flue gases to the sodium hydroxide solution takes place between 70°C and 80°C, and, more preferably, at 75°C. Preferably, heat from the exothermic reactions caused by applying the furnace flue gas and/or third party flue gases to the sodium hydroxide solution is used to heat sea water prior to the sea water bring distilled. Preferably, the furnace flue gas and/or third party flue gases are aerated under pressure through the sodium hydroxide solution.

Preferably, the furnace flue gas and/or third party flue gases is applied to the first of a plurality of vats connected in series, un-reacted flue gases from an earlier vat being passed to a later vat and sodium hydroxide solution is applied to the last of the vats in the series and travels through the vats in the opposite direction to the flue gases.

Preferably, there are at least three vats connected in series.

According to a second aspect of the present invention there is provided a method of storing carbon dioxide including:

compressing the carbon dioxide;

creating molten glass;

applying the carbon dioxide through a plurality of apertures over which the molten glass is arranged such that a glass foam is created; and

cooling the glass foam such that carbon dioxide is trapped within the glass foam. Preferably, the method further includes coating the glass foam with a layer of glass. Further preferably, the layer of glass is a layer of malleable glass rather than molten glass.

Preferably, the glass foam is formed into spheres by a forming apparatus.

Preferably, the layer of glass is formed around the spheres of glass foam. Preferably, the method is performed under pressure and, further preferably, at a pressure of around 150 Bar.

Preferably the carbon dioxide is compressed prior to application through the apertures and, further preferably, compressed to between 150 and 200 Bar and, ideally, 170 Bar.

According to a third aspect of the present invention there is provided a hydrogen production system including:

distillation means for distilling sea water by heat from a furnace to produce steam and brine, the furnace also producing a furnace flue gas as a by-product which includes a plurality of constituent gases;

electrolysis means for electrolysing at least a portion of the steam to produce hydrogen;

electrolysis means for electrolysing the brine to produce hydrogen and chlorine gas and a sodium hydroxide solution;

mixing means for mixing at least a portion of the hydrogen gas produced from either or both of the electrolysis of the steam or brine and chlorine gas with water to form hydrochloric acid;

a first vat enabled to receive the furnace flue gas and/or third party flue gases and the sodium hydroxide solution such that the flue gases and solution react to create a solution of sodium compounds of one or more of the constituent gases;

a second vat enabled to receive the solution of sodium compounds and the hydrochloric acid to regenerate the original gases constituent gases; and

gas distillation means for distilling the constituent gases produced from the reaction of the sodium compounds and the hydrochloric acid. Preferably, the system further includes the carbon dioxide storage system according to the fourth aspect of the present invention. According to a fourth aspect of the present invention there is provided a carbon dioxide storage system including:

compression means for compressing the carbon dioxide;

a glass furnace for creating molten or malleable glass;

gas supply means for supplying the carbon dioxide through a plurality of apertures over which the molten glass is supplied such that a glass foam is created; and

cooling means for cooling the glass foam such that carbon dioxide is trapped within the glass foam.

Preferably, system includes a coating apparatus for coating the glass foam with a layer of glass. Further preferably, the layer of glass is a layer of malleable glass rather than molten glass. Preferably, the system includes a forming apparatus which forms the glass foam into spheres.

Preferably, the layer of glass is formed around the spheres of glass foam. Aspects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following drawings in which:

Figure 1 shows a schematic diagram of an example of method for the production of hydrogen including carbon dioxide capture;

Figure 2 shows a cooling tower for cooling of flue gases and removal and collection of particulates;

Figure 3 shows an electrolysis apparatus;

Figure 4 shows a vat which mixes flue gases and sodium hydroxide;

Figure 5 shows multiple vats of the type shown in Figure 4 connected in series;

Figure 6 shows an alternative arrangement of multiple vats with sodium hydroxide configured to remove carbon dioxide from air;

Figure 7 shows furnace for creating molten glass; Figure 8 shows a side view of an apparatus for creating glass spheres to encapsulate carbon dioxide or any other unwanted gas;

Figure 9 shows a partial top view of the apparatus of Fig. 8; and

Figure 10 shows a high to low pressure transfer chamber for the glass spheres.

Referring firstly to Fig. 1 , a process diagram for a method for the production of hydrogen is shown. Fig. 1 shows an overview of the one example of the entire process. Individual components of the process are discussed in greater detail below the overall discussion of Fig. 1 . Air 10 and coal 12 is provided to a furnace 14, which as a by-product produces flue gases 42. The furnace 14 can then be used to generate steam 16 to drive a generator 18 for creating electricity. This arrangement is typical of a power station and although coal is used as the example for fuel, any other appropriate fossil fuel could be substituted.

The impurities in the flue gases 42 are identified as:- carbon dioxide (C0₂), sulphur dioxide (S0₂), nitrogen oxide (NO), nitrogen dioxide (N0₂), mercury oxide (HgO) and ash. The steam 16 is obtained from distillation of sea water 20 in a distillatory apparatus 22, which is heated by the furnace 14. A portion of the steam 16 is directed to an electrolysis apparatus 24 which is supplied by electricity from the generator 1 8. Electrolysis of the steam 16 creates hydrogen gas 26 and oxygen gas 28.

As a result of the distillation of sea water in the distillatory apparatus 22, a concentrated brine solution 30 is created. The brine solution 30 should be concentrated to between 20% and 30% by weight of salt and, ideally, 25% by weight of salt.

The brine solution 30 is directed to a brine electrolysis apparatus 32 which, again, is supplied by electricity from the generator 18. Electrolysis of the brine solution 30 creates hydrogen gas 34, chlorine gas 36 and sodium hydroxide solution 38.

The sodium hydroxide solution 38 is then passed to a vat 40, although there may be multiple vats, in to which flue gases 42 are also supplied. Prior to supplying the flue gases 42 to the vat 40, the flue gases 42 are removed of particulate matter including mercury oxide and then passed to a cooling tower.

The mercury oxide (HgO) is in the form of a vapour mixed with ash in the flue gas. Both the mercury oxide and ash require to be removed, using known processes, prior to the flue gases passing through the cooling tower. Mainly because the ash is easier to handle if kept dry and the mercury oxide solidifies into particles, which are insoluble in water, at lower temperatures. The flue gases 42 are then mostly made up of carbon dioxide (C0₂), sulphur dioxide (S0₂) and nitrogen oxides (nitrogen monoxide (NO) and nitrogen dioxide (N0₂)). Upon mixing with the sodium hydroxide solution 38, carbon dioxide forms sodium carbonate (Na₂C0₃), although some sodium bicarbonate (NaHC0₃) may also form, sulphur dioxide forms sodium sulphite (Na₂S0₃) and nitrogen oxides form sodium nitrite (NaN0₂) and sodium nitrate (NaN0₃). Other gases present in the flue gases 42 will tend to pass through the sodium hydroxide solution 38 without reacting, allowing these specific gases to be captured. In this manner, these gases can be extracted from the flue gases for subsequent processing.

A reacted solution 44 containing the various compounds mentioned above is then drawn from the vat 40.

The hydrogen gas 34 and chlorine gas 36 formed during electrolysis of the brine solution 30, or at least part of the gases, are mixed with water to form hydrochloric acid 46. The reacted solution 44 is then mixed with the hydrochloric acid 46 in vats 48, which converts the various compounds back to the original gases and leaves a brine solution 30, which can be fed back to the brine electrolysis apparatus 32.

At this point the vat 48 provides carbon dioxide, sulphur dioxide and nitrogen oxides gases. These gases require to be separated and therefore a gas distillation process is carried out to separate out the individual gases.

Separated carbon dioxide 50 is output to a carbon dioxide capture process. In the example of Fig. 1 , this process involves a second furnace 52 again supplied with air 10 and coal 12. The second furnace 52 supplies heat for a glass furnace 54 supplied by silicate 56 and sodium hydroxide from the electrolysis of brine plus other additives as required and outputs molten glass 58.

The molten glass 58 is then supplied to a glass sphere apparatus 60. Carbon dioxide 50 is supplied to the glass sphere apparatus 60 which creates a foam of molten glass with the carbon dioxide before shaping to a sphere and coating with an outer layer of glass. In this manner, glass spheres 62 are created containing carbon dioxide, ideally under pressure. The hot glass spheres are cooled in cooling apparatus 64 before being stored in an appropriate location, either on land or at sea. For example, the glass spheres could be stored at depth in the ocean and recovered by suction pipe or other method, should there ever be the need. The following description described in more detail the individual components of the overall process.

Furnaces Furnaces 14, 52 are, in this example, standard construction as used for burning pulverised coal, with the attendant delivery and pulverising infrastructure. It is also foreseeable that the furnaces may burn other materials, such as biofuels, and, particularly, other fossil fuels such as gas or oil. Accordingly, location of the system for carrying out the described method would preferably be close to existing power stations so that some of the required infrastructure is already in place. Although two furnaces have been described above, it is also possible to operate a single furnace and draw the required heat for producing steam and for creating molten glass from the same source.

The flue gases from the furnace or furnaces will ultimately be directed to the carbon dioxide (as well as other flue gases) capturing process, but before going through that process it is preferable for the flue gases to be cooled and the particulates or ash to be removed.

The removal of mercury and mercuric oxides, as well as ash, will also take place before the cooling process using known processes. Cooling of flue gases

The flue gases are passed through a cooling tower to lower their temperature before being pumped into the vats 40 of sodium hydroxide. The reactions which take place in the vats 40 operate more efficiently at a temperature of around 75°C. The reactions can take place below that temperature but it is more likely to result in the formation of sodium bicarbonate. Sodium bicarbonate's decomposition at subsequent higher temperatures can result in the formation of carbonic acid, which readily decomposes into C0₂ and water, but adds a further step in the process. At higher temperatures the solution would heat up during the exothermic reactions and start to boil, which is not desirable. Therefore, the solution must be kept at a reasonably even temperature with heat exchangers, but preferably above 75°C.

Referring to Fig. 2, a closed circuit cooling tower 200 is shown. Unlike normal cooling towers the flue gases will not pass out into the atmosphere at this stage. The cooling towers have a multiple function of cooling, collecting any remaining particulates and condensing the steam which has been produced when the water first contacted the flue gases. The steam will not be suitable elsewhere in the complex because it will be mixed with the flue gases.

The flue gases 202 pass upwards through a very thick mist of fine spray of water 204 which rapidly absorbs heat from the flue gases 202 and the fine spray of water 204 is converted into steam. Subsequent water sprays 206, 208, 210, 21 2 are coarser and more of a swamping deluge aimed at condensing the steam and also further cooling the flue gasses 202 to an acceptable level of approximately 70°C. These water sprays 206, 208, 210, 212 will also wash out any remaining particulates and salt, if sea water is being used, left by the initial evaporation of the fine spray 204. Collection trays 214 collect the cooling water and particulates from the flue gas which is collected in drains 21 6.

The coolant will be desalinated water which will be cooled via heat exchangers and then recycled to the cooling tower. Some of the flue gases will be absorbed into the coolant but, because it is being recycled, they will reach a saturation level and not be of any consequence.

Distillation

The prime requirements of the distillation process are to produce the steam required to drive the generation of the electricity, the production of brine for the flue gas capture process and, as a by-product, produce desalinated water. Some of desalinated water can be used for the production of hydrogen, some may be used for the production of hydrochloric acid and some may be used for the cooling tower, as discussed above. It is also envisaged that a proportion will be available for sale and distribution. A standard boiler is required for distillation, but with a refinement to continuously draw off brine at the correct concentration. As mentioned above, the concentration is preferably between 20% and 30% by weight of salt and, ideally, 25% by weight of salt. The sea water feeding in to the boiler will be substantially preheated via heat exchangers located at other parts of the complex, taking advantage of other processes which require cooling or are exothermic, thus minimising the additional heating needed to produce the steam. The final heat of the steam is anticipated to be about 500°C to 600°C to make the generation of electricity more effective.

Some brine production will be surplus and therefore may be drawn from the system for other purposes such as into evaporation pits to enable salt to be sold.

Electricity generation

Given that the unwanted impurities in flue gases will be removed at a later stage in the process, and that the flue gases will be cooled before being exhausted into the atmosphere, the heat of the furnaces and the subsequent steam production can be very hot. Therefore, the choice of method of electricity production within the proposition can made on the basis of which method will be the most efficient and economic both in terms of running costs and original capital outlay.

For example, electricity production could be by:-

• thermoelectric - this appealing because there are no moving parts, but some inefficiencies are inherent and to overcome these the capital costs may be too high;

• external combustion, the Stirling engine; or

• steam turbine

The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa. A thermoelectric generator creates a voltage when there is a different temperature on each side of a material which has a thermoelectric effect. Thermoelectric generation in the method for the production of hydrogen as discussed with reference to Fig. 1 is possible at all locations in which there are high temperature fluids operating, especially where those fluids must be cooled.

For example, hot steam is used in the electrolysis apparatus 24 and can be passed over one side of thermoelectric "pn" junction plates (a junction formed by joining P-type and N-type semiconductors) and cold fluid, such as sea water, on the other side. The junction plates can be organised in series with the plates used to carry out the electrolysis. The very hot steam, on which the electrolysis is applied, can pass through two central chambers. These chambers can then be divided by the anode where the hydrogen is collected. The outer layers are the thermocouple junction array which is protected by stainless steel sheeting, annealed or fixed to the array. The hot steam passes over the hot side of the array and the cold coolant passes over the cold side. In this manner, electricity can be generated to supplement or drive other aspects of the system.

A standard arrangement, such as the commonly used steam turbine is preferable for continuing maintenance reasons. However, a thermoelectric arrangement is useful because of the large differences in temperature available and the resultant efficiency improvement of the system as a whole

Electrolysis of brine

Referring now to Fig. 3, the brine solution 30, containing around 25% by weight of salt, is passed to an electrolysis apparatus 300, which corresponds to the electrolysis apparatus 32 of Fig.1 . The brine solution 30 may come from either the distillatory apparatus 22 or as a by-product of the vats 48, which react hydrochloric acid and sodium compounds. When fully operational, it is envisaged that the main source of brine will be from the vats 48 due to the closed loop nature of the particular system. But, fresh brine will be introduced on a continuing basis to maintain a correct concentration prior to electrolysis and to refresh the recirculating solution while also removing some of the old solution which will by now include some contaminants. The electrolysis apparatus 300 includes positive electrodes 302 and negative electrodes 304 separated by a liquid permeable membrane 306. When an electrical voltage is applied across the positive and negative terminals, chlorine gas is formed at the positive electrodes 302 and hydrogen gas is formed at the negative electrodes 304. The brine solution 30 is supplied to the positive electrodes 302 and the liquid permeable membrane 306 allows liquid to be in communication between each side of the terminals. Sodium hydroxide solution 38 can then be drawn off from the side of the negative terminals. The liquid permeable membrane 306 prevents the gases from mixing above the level of the solution and allows the hydrogen gas 34 and chlorine gas 36 to be drawn from the electrolysis apparatus 300 by pipes 308.

It is envisaged that the electrodes will be made of a stainless steel sheet bonded, or adhered so that there is good conductivity, to a solid copper core. This allows as high current flow as possible, at the appropriate voltage, over a large surface area.

The hydrogen and chlorine may be mixed together in pure water to form hydrochloric acid for use in other processes. It also possible to draw off some of the chlorine produced for sale to industry. In this case the balance of hydrogen remaining can be transferred to the main hydrogen store.

As far as possible this will be a continuous process. The brine enters one end and the sodium hydroxide is drawn off at the other end and passed through to the next process.

The power required for this may be supplied by the internal generation process. The power input can also be supplemented by surplus electricity produced by renewable sources such as wind and solar during periods where it is not needed through the main grid.

Electrolysis of steam or hot water for Hydrogen production The hydrogen will be produced via electrolysis in a chamber similar to the electrolysis of brine.

The electrolysis will be applied to pure water laced with a very dilute addition of sodium hydroxide. This creates ions which will enhance and speed up the electrolysis. Both hydrogen and oxygen will be produced and both gases will be drawn off and dried ready for transference to storage.

It is envisaged that both hydrogen and oxygen may be piped, separately, to an adjacent power station for burning in the steam furnaces. The stoichiometric reaction results in a very hot flame but the only by-product is hot steam. Because there is no need to maintain a cooler burn in order to minimise the production of nitrogen oxide gases, the hydrogen and oxygen combustion temp can be much hotter and the input steam to the generators can be much higher. This will result in considerably greater efficiency of the steam turbines which will offset some of the costs of sequestering carbon dioxide.

The power input can also be supplemented by surplus electricity produced by renewable sources such as wind and solar during periods where it is not needed through the main grid.

Capture of flue gases Referring to Fig. 4, a vat 400, which corresponds to the vat 40 as described in relation to Fig. 1 , an flue gas inlet 402 carries flue gases 42 from one or more furnaces (such as furnaces 14 and 54 of Fig. 1 ) into the vat 400 through a plurality of nozzles 404. The flue gases 42 are preferably under high pressure, allowing better dispersion through the nozzles 404, by actively aerating the gases through the solution, in to the vat 400. The sodium hydroxide solution 38 enters through a solution inlet 406 into the vat 400. As discussed above, the sodium hydroxide solution reacts with carbon dioxide, sulphur dioxide and nitrogen oxides (nitrogen monoxide and nitrogen dioxide) to form sodium carbonate (Na₂C0₃), although some sodium bicarbonate (NaHC0₃) may also form, sodium sulphite (Na₂S0₃), sodium nitrite (NaN0₂) and sodium nitrate (NaN0₃). The chemical reactions are:-

2NaOH + C02→ Na2C03 + H20

2NaOH + S02→ Na2S03 + H20

2NaOH + 2N02→ NaN02 + NaN03 + H20

The resulting solution, a sodium compound solution, 408 then exits through vat outlet 410. Un-reacted gases 41 2 are able to exit the vat 40 through gas outlet 414 at the top of the vat 40. The flue gases need only to be actively aerated through the sodium hydroxide solution and it is not necessary to have wet filters. Exact amounts of reactants are not required because residual amounts of previous reactants will not disrupt the current reaction. No other special or catalytic reactants are introduced and therefore there does not need to be any elaborate system of retrieval of any special reactant.

Other processes that use amines or ammonia to do the same task do not integrate into the method as a whole and have an inherent danger in the toxicity of the products used and the possibility of leakages.

The preferred temperature for the reactions in the vat 400 to take place is approximately 75°C. The reactions are exothermic and, therefore, some cooling of the process is needed to maintain this temperature. Heat exchange pipes 416 are immersed into the solution and the coolant (which may be the sea water 20 from Fig. 1 ) in the pipes will withdraw excess heat.

Now referring to Fig. 5, to ensure the capture of all contaminants, a series of three vats 400a, 400b, 400c, being vats of the same type as Fig. 4, are arranged so that the first vat 400a that the gases enter contains an sodium solution which has already passed through the other two vats as shown in Fig. 5. In this manner, any remaining un-reacted flue gases which reach the last of the vats in the series (400c) receives the most concentrated solution of sodium hydroxide. The resulting solution, a sodium compound solution 408 (44 in Fig. 1 ), then exits the first vat 400a after passing through the other vats 400b, 400c. At this point it may be necessary to add more sodium hydroxide solution to react with the remaining dissolved nitrogen oxides, sulphur dioxide and carbon dioxide The cooled flue gases 42 are drawn through the successive vats 400a,

400b, 400c in the opposite direction to the sodium hydroxide solution 38 to ensure that the flue gases are substantially fully reacted with the sodium hydroxide solution 38. On the other hand when the gases have been drawn through all vats to the last one (400c), the fresh sodium hydroxide solution 38 will take up the final remaining flue gases to be reacted. The remaining flue gas, which is now essentially clean air, can then be cooled further and released back to the atmosphere.

The resultant sodium compound solution 408 is then extracted for further processing.

Capture of C02 direct from the atmosphere

Obviously, drawing any gaseous mixture containing carbon dioxide, sulphur dioxide or nitrogen oxides, amongst other gases, through the sodium hydroxide solution will also capture these gases. As carbon dioxide is seen as the biggest risk in terms of green house gases, it is possible for that gaseous mixture to simply be air. However, because the concentration of carbon dioxide in the atmosphere is so low, at approximately 350 - 400 ppm, an enormous amount of air needs to be passed through the solution to draw off the carbon dioxide. For example, to capture one tonne of carbon dioxide will require approximately 3,000 tonnes of air to be drawn through the solution. Therefore, although possible, it is not practical to use a powered pump to draw the air through the solution. Accordingly, an arrangement to capture carbon dioxide from the atmosphere is shown in Fig. 6. A vat 600, which is a very large flat bottomed containment similar to flat evaporation pans used to gather salt from sea water, contains a sodium hydroxide solution 602. The solution 602 can be as deep as practical, for example, one metre, and is covered with a plastic cover 604 through which entry vents 606 and venturi vents 608 are arranged to draw the air 610 through the solution 602. That is, the pressure differential at the venturi vents 608 acts to draw air down the entry vents 606 and through the solution 602. To allow the venturi vents 608 to continually suck air from the vat 600, floats or spacers 61 2 are provided to maintain a gap between the solution 602 and the cover 604.

The solution can be gradually, but continuously withdrawn and recharged with fresh sodium hydroxide solution. The converted solution can then be processed as described below.

Release of captured gases from sodium compounds solution.

The solution 408 from the flue gas capture process is now a concentrated solution of sodium carbonate, sodium bicarbonate, sodium sulphite, sodium nitrite, and sodium nitrate plus some residual sodium hydroxide solution.

The sodium compound solution 408 is mixed in a further vat or vats (48 of Fig. 1 ) with hydrochloric acid 46, which is preferably supplied from the hydrogen and chlorine gas created through the electrolysis of brine (as described above) mixed with water. As a result of reacting with the hydrochloric acid, the sodium compound solution is broken down to the original gases of carbon dioxide, sulphur dioxide and nitrogen oxides and leaving a solution of brine. The main chemical reactions are:-

(The carbonates, Na₂C0₃ and NaHC0₃ ):

Na₂C0₃ + HCI → NaCI + H₂0 + C0₂

NaHC0₃ + HCI → NaCI + H₂C0₃ The carbonic acid formed by this reaction readily decomposes to C0₂ and water:

H₂C0₃ → H₂0 + C0₂ (Sodium sulphite Na₂S0₃ ):

Na₂S0₃ + 2HCI → 2NaCI + S0₂ + H₂0

(Sodium nitrite NaN0₂ and sodium nitrate NaN0₃ ):

NaN0₂ + HCI → HN0₂ + NaCI

At the higher temperature the Nitrous acid is unstable and breaks down: HN0₂ → NO + N0₂ + H₂0

NaN0₃ + HCI → HNO + NaCI + 0₂

The Nitroxyl (HNO) is very reactive toward nucleophiles which are present in the solution and it quickly dimerizes to Hyponitrous acid H₂N₂0₂ which then dehydrates to Nitrous oxide.

2HNO → H₂N₂0₂

H₂N₂0₂ → N₂0 + H₂0

Each of these sets of reactions can take place simultaneously in the same solutions. The impurities (carbon dioxide, sulphur dioxide and nitrogen oxides) are now concentrated in one non-reactive mix to be distilled and separated into each pure component (as described below). The components will be: C0₂, S0₂, N0₂, NO and N₂0. The addition of Oxygen to the mix will transform NO to N0₂.

These chemical reactions are temperature dependent, particularly for the separation of the nitrogen oxides. It may be necessary to add more hydrochloric acid than is required for a stoichiometric reaction so that as close to 100% as possible of the impurity gases are removed from the solution. The remaining solution is heated up to near boiling point to ensure that all the gases are expelled and in particular the NO_x gases have completed their transition from the nitric and nitrous acids. The reactions are exothermic but this is an advantage as the resulting sodium chloride solution (brine) can be used in the brine electrolysis process, where a warmer temperature helps promote a more effective electrolysis. Some cooling may be necessary via heat exchangers. Any residual sodium hydroxide in the solution reacts with hydrochloric acid to also form salt (NaCI) and water.

The resulting gas is preferably dried, possibly by passing over a desiccant such as powdered water glass.

Distillation of impurity gas mix

As mentioned above, the gases released from mixing the sodium compounds solution with hydrochloric acid are carbon dioxide, sulphur dioxide and nitrogen oxides. To be able to deal with these gases individually, they must be separated.

Firstly, oxygen is added to the warm gas mix to force the change of any NO to N02. The oxygen can be drawn from the electrolysis of water process (24 in Fig. 1 ) which produces both hydrogen and oxygen.

Next, the gas mix is cooled by, for example, a standard compression expansion technique, but using pure oxygen as the refrigerant. Oxygen can be obtained, initially, from the electrolysis of steam or distilled water, as discussed above. Once the full process is underway the pure oxygen can be drawn from the previous run through of the distillation process.

A number of cycles of compression will take place and there will be a series of chambers maintained at specific temperatures. The distillation temperatures of the relevant gases are as follows:

N0₂ +21 .1 °C

S0₂ -10°C

C0₂ -57°C at a pressure of 5.185 bar N₂0 -88.48°C

NO -150.8°C

As such, each of the series of chambers can be cooled to below the distillation temperature of a particular gas, but above that of the next gas in the series, so that the particular gas can be extracted as a liquid.

For example, the first chamber is cooled to approximately 0°C so that the nitrogen dioxide precipitates out as a liquid. At this point it is possible to withdraw the liquid and nitrogen dioxide and mix it with a sodium hydroxide solution (produced in another part of the plant) thus producing sodium nitrate which has many commercial uses including a fertilizer.

A second chamber is cooled to approximately -20°C so that the sulphur dioxide precipitates out as a liquid. Once again, sulphur dioxide can be stored and sold as a commercial product, such as a preservative for foods.

A third chamber is cooled to approximately -70°C and at a pressure of approximately 6 bar. The carbon dioxide will precipitate out as a liquid to be drawn off and further compressed to go through an encapsulation process.

A fourth chamber is cooled to approximately -100°C and so that the nitrous oxide precipitates out as a liquid and a fifth chamber is cooled to approximately - 160°C so that any remaining nitrogen monoxide precipitates out as a liquid.

The remaining gas will be oxygen which can be returned to a collection area where it can be combined with additional pure oxygen to be added to the gases as above to convert nitrogen oxide to nitrogen dioxide and to act as the refrigerant.

Encapsulation of C0₂ Sequestration of carbon dioxide is one method of preventing carbon dioxide contributing as a "green house" gas. The one overwhelming fact is the huge world wide quantity of carbon dioxide that has to be disposed of, a staggering 42 billion tonnes per annum and rising. Sequestration by injection into the earth at selected sites has possibilities, but 55 cubic kilometres has to be found each year for many years. There is also the danger of leakage from these sites which is still being evaluated. Promoting the growth of algae using carbon dioxide is a form of bio-sequestration and also has good potential but the problem of disposing of large volumes of product may be overwhelming and is not a permanent storage solution. If bio-sequestration through algae were the only way of sequestering carbon dioxide, the output of algae would be at least 80 billion tonnes per annum. However, using it for bio-fuels, stockfeed and other food substitutes will eventually take up a significant portion of the waste carbon dioxide. In fact, it may be possible to use the algae as a bio-fuel to power the furnaces as part of the method of producing hydrogen.

Chemical capture of carbon dioxide is also being considered but finding and preparing sufficient chemical reactants such as serpentine is logistically difficult. In addition, there is a possibility that some by-products are dangerous in their own right. It is also noteworthy that, at best, the weight of material created would be at least double the weight of carbon dioxide sequestered also it has to be stored safely without affecting ground water.

Storing huge quantities of carbon dioxide in metal containers for the long term is implausible because of the amount of metal needed and the long term problems of corrosion of the tanks.

It is reasonable to expect that most of these processes will be usable to some extent for specific purposes, even so, in the short term there will still be a significant remainder of carbon dioxide which needs to be sequestered immediately within the next 5 - 1 0 years. A form of storage sequestration is proposed in detail below which mitigates some of the issues mentioned above. In general, carbon dioxide is foamed in glass and then sealed to provide a storage medium. Preferably, glass spheres of about 100mm in diameter are used. The glass spheres are made up of glass foamed with carbon dioxide and then covered in a thin skin of tempered glass. This combination will safely contain carbon dioxide under a very high pressure of 150 bar. The shape and size of the spheres means that they can be handled easily and safely by conventional equipment.

It is envisaged that the safest place to store the glass spheres is in the sea, just off the continental shelf in deep water, but no more than 1000m. The spheres will sink and the high pressure of the deep ocean will counteract any tendency of the high pressure within the spheres to break them open if flaws are present. If needed sometime in the future, they can be retrieved with suction or other similar methods. Alternatively, if the deep sea option is not available, the spheres can be stored on land.

The fear of leakages of the carbon dioxide into the atmosphere or the ocean is greatly minimized by the strengthened glass. Because the capsules are small, any breakages will only release a minimal amount of carbon dioxide. It is estimated that around half the weight of the spheres will be carbon dioxide.

The basic ingredient of glass is silicate (sand) and this is readily available in huge quantities throughout the world. The other requirement is sodium hydroxide and this will be readily available from the electrolysis of brine, as described earlier. Only small quantities of other additives will be required to enhance the strength of the glass. Glass furnace

A glass furnace 700 is shown in Fig. 7 and is supplied with heat 702, from any suitable heat source but most likely from burning of hydrocarbons, and silicate 704, as well as other additives as required for glass manufacture. The furnace 700 produces flue gases 706, which are captured for processing as described above. Glass is drawn from the furnace for use in subsequent processes. As far as possible, the production of glass is a continuous process.

Glass foam and skin

Referring now to Fig. 8 and 9, glass sphere apparatus 800 receives hot molten glass from the glass furnace 700 which is forced through nozzles 804 which force the glass over a screen of jets 806. Compressed carbon dioxide 808, still liquid but at a temperature of approximately -70°C, is forced through the jets 806 so that glass foam is produced 81 0. At the same time it will rapidly cool the glass from about 1 100°C to about 600°C. From here the foam quickly passes through two opposed roller dies 812 which pre-form the foam glass into spheres 814.

As they emerge from this, blasts of very cold carbon dioxide will be blown over the spheres to cool them further before they are passed through the next set of roller dies 816. Malleable glass 818 is supplied to coat the foam spheres prior to passing through the roller dies 816. The spheres then have a covering of a thin sheet of malleable glass 820, forming a complete glass sphere 822 with encapsulated carbon dioxide. From here the spheres pass through another rapid cooling area and then into ponds of circulated cold water until their residual temperature is about 100°C or much less if possible.

Preferably, the pressure of the carbon dioxide injection will be between 175 and 225 bar and most preferably at 200 bar. The whole apparatus 800 will operate within a closed sealed environment maintained at a pressure of around 150 bar. At a pressure of 150 bar, carbon dioxide weighs approximately 850 grams per litre (at 20°C), enabling a greater amount of carbon dioxide to be stored in each glass sphere. To enable the glass spheres to exit the pressurised closed sealed environment, a sealed release chamber 1000 is provided, as shown in Fig. 10. The chamber 1 000 has a high pressure side 1002 and a low pressure side 1004. Between the high pressure and low pressure sides is a rotating pressure seal 1006. The paddles 1008 on the seal are spaced such that the glass spheres 822 can pass between them whilst the paddles maintain the pressure seal with the outside wall 1010 of the chamber. To aid the glass spheres 822 passage through the rotating pressure seal 1006, a guide 1012 is provided. In addition both the high pressure and low pressure side is, at least partially, filled with a liquid to aid passage of the glass spheres and to improve the seal between the high pressure and low pressure sides.

Associated processes Additional to the production of hydrogen and capture of carbon dioxide, there is the very real benefit of being able to produce desalinated water through the distillation of sea water.

Further modifications and improvements may be made without departing from the scope of the present invention.

Claims

CLAIMS:

1 . A method for the production of hydrogen including:

electrolysing at least a portion of the steam to produce hydrogen;

separating the gases produced when applying the sodium compounds to the hydrochloric acid.

2. A method as claimed in claim 1 , wherein the constituent gases include carbon, sulphur and nitrogen from the gases carbon dioxide, sulphur dioxide, nitrogen monoxide or nitrogen dioxide.

3. A method as claimed in claim 1 or claim 2, including generating electricity and, further preferably, generating electricity from the heat of the furnace and, more preferably, from steam generated by the furnace.

4. A method as claimed in any one of the preceding claims, wherein the furnace uses burning a hydrocarbon based fuel as a heat source.

5. A method as claimed in claim 4, wherein the hydrocarbon based fuel is a fossil fuel.

6. A method as claimed in claim 4, wherein the hydrocarbon based fuel is a bio- fuel.

7. A method as claimed in any one of the preceding claims, wherein the brine is produced at a concentration of 20% to 30% by weight of salt and, further preferably, 25%.

8. A method as claimed in any one of the preceding claims, wherein the furnace flue gas and/or third party flue gases are cooled in a closed circuit cooling tower.

9. A method as claimed in any one of the preceding claims, wherein applying the furnace flue gas and/or third party flue gases to the sodium hydroxide solution takes place between 70°C and 80°C, and, more preferably, at 75°C.

10. A method as claimed in any one of the preceding claims, wherein heat from the cooling tower and heat from the exothermic reactions caused by applying the furnace flue gas and/or third party flue gases to the sodium hydroxide solution is used to heat sea water prior to the sea water bring distilled.

1 1 . A method as claimed in any one of the preceding claims, wherein the furnace flue gas and/or third party flue gases are aerated under pressure through the sodium hydroxide solution.

12. A method as claimed in any one of the preceding claims, wherein the furnace flue gas and/or third party flue gases is applied to the first of a plurality of vats connected in series, un-reacted flue gases from an earlier vat being passed to a later vat and sodium hydroxide solution is applied to the last of the vats in the series and travels through the vats in the opposite direction to the flue gases.

13. A method as claimed in claim 12, wherein there are at least three vats connected in series.

14. A method as claimed in any one of the preceding claims, wherein the hydrochloric acid is formed using desalinated water from the electrolysis of steam.

15. A method of storing carbon dioxide including:

compressing the carbon dioxide;

creating molten glass;

cooling the glass foam such that carbon dioxide is trapped within the glass foam.

16. A method as claimed in claim 15, wherein the method further includes coating the glass foam with a layer of glass.

17. A method as claimed in claim 15, wherein the layer of glass is a layer of malleable glass rather than molten glass.

18. A method as claimed in any one claims 1 5 to 17, wherein the glass foam is formed into spheres by a forming apparatus.

19. A method as claimed in claim 18, wherein the layer of glass is formed around the spheres of glass foam.

20. A method as claimed in any one claims 15 to 1 9, wherein the method is performed under pressure and, further preferably, at a pressure of around 150 Bar.

21 . A method as claimed in any one claims 15 to 20, wherein the carbon dioxide is compressed and, further preferably, compressed to between 1 50 and 200 Bar and, ideally, 175 Bar.

22. A hydrogen production system including:

gas distillation means for distilling the constituent gases produced from the reaction of the sodium compounds and the hydrochloric acid.

23. A carbon dioxide storage system including:

compression means for compressing the carbon dioxide;

a glass furnace for creating molten or malleable glass;

gas supply means for supplying the carbon dioxide through a plurality of apertures over which the molten glass is supplied such that a glass foam is created; and cooling means for cooling the glass foam such that carbon dioxide is trapped within the glass foam.

24. A system as claimed in claim 23, wherein system includes a coating apparatus for coating the glass foam with a layer of glass.

25. A system as claimed in claim 23 or claim 24, wherein the system includes a forming apparatus which forms the glass foam into spheres.

26. A system as claimed in claim 25, the layer of glass is formed around the spheres of glass foam.

27. A method for the production of hydrogen according to any one of claims 1 to

13 including a method of storing carbon dioxide according to any one of claims 15 to 21 .

28. A hydrogen production system according to claim 22 including a carbon dioxide storage system according to any one of claims 23 to 26.