GB2518352A

GB2518352A - Energy generation process

Info

Publication number: GB2518352A
Application number: GB1313555.3A
Authority: GB
Inventors: Tim Kruger
Original assignee: Cogent Heat Energy Storage Systems Ltd
Current assignee: Origen Power Ltd
Priority date: 2013-07-30
Filing date: 2013-07-30
Publication date: 2015-03-25
Also published as: WO2015015162A1; GB201313555D0

Abstract

An energy generation process comprising the oxidation of carbon monoxide (CO) to carbon dioxide (CO2) in a fuel cell 10, the process comprising the step of producing the carbon monoxide from carbon dioxide and a carbon source, e.g. coke (reverse Boudouard reaction) or a hydrocarbon (e.g. methane, ethane, propane, butane and/or other C2 C12 hydrocarbons). The reaction with a hydrocarbon also produces hydrogen, which is also oxidised in the fuel cell. The oxidation is preferably carried out using oxygen, which migrates across the fuel cell from the cathode to the anode (fig 2). The carbon reactor 5 (e.g. a fluidised bed reactor) may be in fluid communication with the fuel cell, and the resulting CO2 may be sequestered. The fuel cell may be a solid oxide fuel cell (SOFC) or a molten carbonate fuel cell (MCFC). The apparatus may be portable and adapted for use in transportation, e.g. a ship, train, road vehicle or aeroplane.

Description

Energy Generation Process

Field

[0001] The invention relates to an energy generation process. in particular to energy generation using fuel cells, to an apparatus for energy generation and to the use of the apparatus.

Background

[0002] Despite an awareness of issues like global waiming, and finite natural resources, it remains the case that the human population places ever increasing demands on our surroundings. This is particularly the case with our demand for energy. in particular electricity. To compensate for this many "alternative" forms of electricity generation have been developed and commercialised in recent years.

[0003] It is often a secondary goal of these alternative forms of energy generation to provide "clean" energy. In particular, where the energy is being generated near to or in a population centre, which can be the case with some power stations, and is very often the case with power generation for transportation. For instance, traditional combustion engines cause pollution which can damage buildings, lead to poor health in the populous and which release green house gases (carbon dioxide and water in particular) into the atmosphere contnbuting to climate change.

[0004] It is therefore desirable to complement these solutions with other energy sources, such as battery technology which relies on the conversion of chemical energy to electricity, as does fuel cell technology. However, the problem with many methods of generating electricity from chemical energy is that they release haimful by-products as part of the chemical reaction. Such by-products include carbon dioxide (C02) a potent greenhouse gas and water (H20), which whilst offering a strong greenhouse effect, has lesser greenhouse effects due to environmental saturation with water vapour, it is therefore desirable to provide an alternative form of energy generation, which whilst harnessing chemical energy, produces by-products which are either environmentally benign, or in a form where they can be easily stored or reused. In addition, with regard to the problem of greenhouse gas emission, it would be desirable to provide a method of energy generation which is carbon neutral, in particular with regard to the emissions of carbon dioxide.

[0005] An additional proNem is that many alternative energy sources are only efficient on a large scale, and can therefore only be used for grid energy supply. It would be useful to provide new clean energy sources which are sufficiently small that they can be transported, and so used to supply energy in transportation, such as in ships, trains, aeroplanes or road transport vehicles. The existing "clean" technologies for transportation include rechargeable batteries and fuel cell technology. However, battery technologies are not yet sufficiently advanced that the cost benefit ratio favours their adoption. This is, in part, because batteries are often insufficiently powerful to allow for long distance travel without breaks to recharge, recharging often taking several hours. In addition, the cost of existing battery technologies is often so high relative to conventional petrochemical fuels, that it is effectively prohibitive except in circumstances where the need to provide clean energy is of particular importance.

[0006] Existing fud cell transportation technothgy, typically hydrogen fuel cells, is both costly, and lacking in a distribution infrastructure for the supply of the hydrogen fuel.

These problems may take many years to address and are hindering the uptake of hydrogen fuel cell technology for transportation. As hydrogen is not naturally occurring and needs to be generated artificially. typically by steam reforming of methane or electrolysis, it is in effect an energy vector, rather than a fuel in itself. In addition, hydrogen has low energy volumetric energy density at ambient conditions and needs to either be compressed or incorporated within a solid or liquid compound, for example as a metal hydride, to increase its energy density sufficiently to allow its use in transportation appfications. If compressed, there are energy costs, transportation and safety issues. Formation of metal hydrides and recovery of hydrogen from them, whilst feasible requires the establishment of an infrastructure to recover the metal used in the metal hydride. For these reasons, hydrogen as a fuel is expensive and difficult to handle. It would be useful to be able to use carbon or hydrocarbons as fuel sources, which can be refined from existing natural resources at much lower energy cost than producing hydrogen, and which can (depending on which hydrocarbon is used) exist as liquids or solids at ambient conditions. Such sources have far higher volumetric energy density at ambient conditions, making them suitable for transportation applications.

[0007] The invention is intended to overcome or ameliorate at least some aspects of these problems. In particular, it is desirable to provide an energy generation process which is clean in terms of greenhouse gas emissions and which, if possiNe, can also be used as a power source in transportation.

Summary

[0008] Accordingly, in a first aspect of the invention there is provided an energy generation process comprising the oxidation of carbon monoxide 1C0) to carbon dioxide in a fuel cell. Typically, in accordance with the following reaction: 2C0 + 02 -* 2C02 The process comprises the step of producing the carbon monoxide from carbon dioxide and a carbon source.

[0009] For many fuel cells, carbon monoxide acts as a poison', preventing the fuel cell from operating. However, some types of fuel cells, namely Solid Oxide Fuel Cells (SOFCs) and Molten Carbonate Fuel Cells (MCFCs) are not poisoned by carbon monoxide and can utilise carbon monoxide as a fuel. Currently. however SOECs and MCFCs are not designed to run exclusively or primarily on carbon monoxide and the fuel cell used in the invention is typica'ly specifically adapted to run exclusively or primarily on carbon monoxide.

[0010] The oxidation of carbon monoxide to carbon dioxide is an exothermic reaction, releasing 283 kJ of energy per mol of CO reacted; this energy typically being released as heat. In this invention, much of the energy will typically be converted into electricity, with the remainder being converted into high grade heat, which can be used to drive the endothermic reaction of carbon dioxide and carbon source.

[0011] Often the carbon source will be selected from coke and/or a hydrocarbon.

Typically, the hydrocarbon is selected from straight and branched chain C1 to C12 alkanes, straight and branched chain C2 to C1 alkenes, saturated and unsaturated cyclic hydrocarbons, and combinations thereof. In many cases, the C1 to C12 alkane is selected from methane, ethane, propane, butane and combinations thereof.

[0012] The process could be said to comprise the steps of: a) reacting carbon dioxide with a carbon source to form carbon monoxide; and b) oxidising the carbon monoxide to carbon dioxide.

[0013] It will often be the case that the carbon monoxide will be produced from carbon dioxide and carbon. This is a reverse Boudouard reaction, as shown: C02+C-*2C0 As such, the process may include the step of forming carbon monoxide from carbon dioxide and carbon in a reverse Boudouard reaction. The two step reaction process could then be depicted as: a) CO,+C-*2C0 b) 2C0 +02 2C02 [0014] The reverse Boudouard reaction is a reversible endothermic reaction, requiring 172.5 kJmof' to drive the reaction to form carbon monoxide. This heat may be generated using energy sourced from the oxidation of carbon monoxide to carbon dioxide described above. Where this is the case, the energy may be released as heat from the fuel cell, or converted to electricity which is then used to heat the reaction. If the temperature of reaction drops, the equilibrium shifts to the left, and the carbon monoxide reverts to carbon dioxide. For this reason, it is desirable to maintain high operating temperatures (which favour the forward reaction as shown) where the reverse Boudouard reaction is being used.

[0015] It shou'd be noted that as used herein references to the energies required to drive the reaction, or which are released from the reactions, as cited in kJmoi1 are the enthalpy calculations at standard temperature and pressure.

[0016] Often the source of carbon will be coke, as this is generally the most cost effective source of carbon avaflable, although other carbon sources may also be used. The coke will often be heated to a temperature in the range 800 -1400K, on many occasions in the range 950 -1250K, or in the range 1000 -1250K. At these temperatures the equilibrium for the reaction is to the right, strongly favouring the formation of carbon monoxide.

[0017] Alternatively, the carbon monoxide may be generated through the reaction of carbon dioxide with one or more hydrocarbons, as described above. Often these will be saturated hydrocarbons such as alkanes, although alkenes and alkynes may also be used.

Often, where a hydrocarbon is used, this will be a C1-C4 hydrocarbon, often C1-C4 aThane.

Often, methane or ethane will be selected as these compounds are readily avaflable and transportable and easy to obtain in a relatively pure form. In such cases, the reaction would become, for instance with methane: CO2 + CH4 -, 2C0 + 2H2 For other hydrocarbons, the reaction products will remain the same, but reaction stoichiornetries will change. The two step reaction process could then be depicted as: a) CO,+CI-14-*2C0+21-I, b) 2C0+09-*2C02 [0018] In such cases, step a) of the process also produces hydrogen. The use of hydrocarbons has the advantage that more energy is released per mole of carbon dioxide reacted than where carbon itself is used. It can also be difficult to source sufficiently pure carbon for reaction with the carbon dioxide, a problem avoided through the use of hydrocarbons which are readily available in pure form, Further, coke, or other pure carbon sources are often difficult to transport. whereas many of the common hydrocarbons are either gaseous or liquid at ambient temperatures, and can therefore be stored and transported easily, making them useful fuels for use in transportation systems. In addition, the presence of hydrogen, or if this has reacted to form water, steam, in the system can help to prevent the build up of carbon within the fuel cell, reducing maintenance costs and system down-time. Finally, whilst the carbon monoxide and hydrogen may be separated. a step which would increase costs, the hydrogen produced has the potential to act as a further energy source, which can be burned to form water and energy, perhaps in a secondary fuel cell. In such cases, no separation would be required and the reaction b) could be depicted as: CO-i-H2+02-*CO,-i-H20 [0019] It is envisaged, that if hydrogen is produced, it wUl either be converted to water or stored for later conversion. If water is produced this could be stored for release to the environment in liquid rather than gaseous form, used to drive other reactions, or to generate energy as the water produced will be in the form of steam and can be passed through turbines, or if the energy is being generated in transportation. it may be used by the transportation device. For instance, if the energy generation process is being used to power a train, the water produced could be used as a coolant, and in the washrooms of the train among other things.

[0020] The carbon dioxide may be obtained from any source, including metal carbonates, such as magnesium carbonate or calcium carbonate. As such, and the process

S

may include the additional step of producing the carbon dioxide from the calcination of a metal carbonate, such as calcium carbonate. This reaction follows the foimula: CaCO3 -CaO + CO2 [0021] Where an alternative metal carbonate is used, the reaction of will simply liberate an alternative metal oxide, although stoichiornetries may, of course, vary. The calcination reaction is endothermic, for calcium carbonate requiring 178 kJmof' to dnve the reaction, and for this reason, it may be that an alternative, less energy absorbing method of carbon dioxide generation is used. As with the reverse Boudouard reaction above, this heat may be generated using energy sourced from the oxidation of carbon monoxide to carbon dioxide using the methods described above.

[0022] As such, the overall process of the invention cou'd comprise three steps: a) calcining a metal carbonate, typically calcium carbonate, to produce calcium oxide and carbon dioxide; b) reacting the carbon dioxide with a carbon source to produce carbon monoxide; and c) oxidising the carbon monoxide to carbon dioxide in a fud cell.

Where each of steps a) to c) are present, steps a) and b) may be carried out in a single reaction vessel, the carbon monoxide being transferred from this vessel to a fuel cell for the oxidation step c). Advantages of using only a single reaction vessel for steps a) and b) is that only a single vessel must be heated, and that the carbon dioxide produced in step a) can react with the carbon or hydrocarbon without delay. Alternatively, two vessels may be used, where the gas recycling within the apparatus is such that system efficiency is improved; however, this adds bulk to the system.

[0023] Often the oxidation will be oxidation with oxygen gas. This will often be sourced from air. Air may be used, as only the oxygen in the air will migrate across the fuel cell, allowing easy separation of the oxygen, the other components being released as a separate flue gas. As such, the oxygen used in the oxidation reaction is of a good level of punty, and the carbon dioxide produced is correspondingly pure. As used herein, the term "pure", regardless of the substance to which it is applied, may mean that the substance has in the range 0% to 1% impurities, at most 1%, often in the range 0.0001% to 1%, or 0.001% to 0.5% impurities.

[0024] In some instances, there may be unreacted carbon monoxide exiting the fuel cell with the carbon dioxide. In such cases, the carbon monoxide can be separated from the carbon dioxide so that the carbon dioxide passed for sequestration is pure. There may therefore be the additional step of separating carbon dioxide from carbon monoxide after oxidation. The separated carbon monoxide can be recycled through the fuel cell, for a second pass at oxidation, or diverted and used elsewhere either in the system or externally.

For instance, the unreacted carbon monoxide may be oxidised in an after-burner. As with the fuel cell reaction, this second oxidation step will typically be with pure oxygen, however, as the fuel cell will not be used to extract the oxygen from air, an alternative source of pre-purified oxygen is typically used. This prevents nitrogen from interfering with the reaction, and removes the need to separate nitrogen from the carbon dioxide produced. Further, the oxidation will occur at a higher flame temperature, and this heat can be used to boost the reaction temperature of the endothermic reactions. In addition, the occlusion of nitrogen from the combustion process will avoid the formation of various NO exhaust gases which are both hazardous to human health and powerful greenhouse gases in their own right. As additional equipment is necessary to oxidise the carbon monoxide outside the fuel cell, it may be that the carbon monoxide will generally be recycled, to reduce weight and volume of the apparatus. However, where weight and volume are not important, for instance in static systems, an after burner will often be present, and in such cases it may be that the fuel cell is engineered to run at sub-optimal efficiency with respect to the conversion of carbon monoxide to carbon dioxide, such that a proportion, perhaps in the range 5% -30%, perhaps in the range 10% -25%, perhaps in the range iS -20% is passed through the fuel cdl unreacted. The subsequent oxidation of the unreacted carbon monoxide can then be used to promote the endothermic reactions of steps b) and c), by producing additional heat. The oxygen could be derived from a cryogenic air separation unit, if undertaken at large scale, or from electrolysis is undertaken at a smaller scale.

[0025] As explained, because a fuel cell is used, the oxidation of carbon monoxide to carbon dioxide is a clean reaction, in the sense that the carbon dioxide produced is pure.

Where a hydrocarbon is employed as the carbon source, water vapour will be present with the carbon dioxide in the exhaust gas from the fuel cell. It is a relatively simple procedure to generate a pure CO2 stream from a water vapour and CO2 mixture, as it only requires the cooling of the mixture to below 100°C, at which point the water vapour precipitates out as water. This makes it very easy to sequester the carbon dioxide, or store it for use or resale. A further benefit of producing pure carbon dioxide is that there is no energy penalty resulting from the need to purify or concentrate the carbon dioxide prior to storage as would be the case for carbon dioxide released from conventional flue gases from petrochemical combustion. As such, the process claimed may comprise the additional step of sequestering the carbon dioxide. The sequestration techniques used will generally be conventional and well known to those skilled in the art. Often sequestration will be geological sequestration, although mineral carbonisation or other methods may be used.

[0026] An advantage of the process of the invention is therefore that it provides clean, non-polluting energy, as the carbon dioxide is suitable for direct sequestration upon exit from the fuel cell, or storage for alternative use. As there is no rdease of this greenhouse gas to the environment, the invention provides an energy generation system which is carbon neutral, and therefore of huge potential in helping to address the need for clean energy generation.

[0027] Further, if a metal oxide is produced, for instance in a calcination reaction, the recarbonation of the metal oxide, either as part of the process, or at some point in the future where it's final use involves recarbonating, the process becomes carbon negative.

Finally, if water is produced, this can be released in liquid form, or reused, therefore avoiding any issues with the greenhouse properties of water vapour being present in the environment. This can be done with minimal cost as the water produced from the fuel cell is sufficiently pure that no harm would be caused to the aquatic or marine environment through direct release into the water courses. Further, it is often advantageous to have water present, as the conversion of this to steam can help to facilitate the transfer of heat within the system, and can be used to directly generate electricity if passed through steam turbines.

[0028] A further advantage of the invention is the absence of catalysts, which reduces operating costs, and removes the need to dispose of the generally toxic catalyst when they become poisoned. There is therefore provided a process for the oxidation of carbon monoxide to carbon dioxide in the absence of a catalyst. The reverse Boudouard reaction can also occur in the absence of a catalyst.

[0029] In a second aspect of the invention there is provided an apparatus for energy generation comprising a carbon reactor in fluid communication with a fuel cell. The combination of a carbon reactor and fuel cell allows for the apparatus to carry out the process of the first aspect of the invention. It can be of use if the carbon reactor is in thermal communication with the fuel cell, such that heat generated by the oxidation reaction (carbon monoxide to carbon dioxide) can be used to drive the carbon monoxide generation reaction. This thermal communication may be via conducting metals, heat exchangers, through communication of the hot flue gases exiting the fuel cell with the carbon reactor, the heat from the flue gases being used to heat the carbon reactor, and produce the carbon monoxide and in some cases the metal oxide. It is generally the case that heat exchangers or direct communication of flue gases with the carbon reactor will be used.

[0030] It is often the case that the fuel cell is a high temperature fuel cell, such as a solid oxide fuel cell 1SOFC), although other high temperature fuel cells may also be used, including molten carbonate fuel cells (MCFC). The fuel cells used with the apparatus of the invention will generally be adapted so that carbon monoxide is the primary source of fuel. Carbon monoxide may be the only source of fuel.

[0031] The fuel cells may be arranged to multiply their energy production using typical methods such as the formation of fuel cell stacks or placing multiple fuel cells in series, as would be known to the person skilled in the art.

[0032] As used herein, the term "high temperature fuel cell" is intended to mean fuel cells with operating temperatures in the range 900 -1200K, often in the range 950 - 1150K. In general usage, this term would often include operational temperatures as low as 700K, however, it is generally the case that where the reverse Boudouard reaction is being used, in order to maintain the equilibrium to the right, favouring the production of carbon monoxide, higher temperatures will be used in the fuel cells used in the apparatus and process of the invention. Often SOFC's will be used as these are resilient to carbon monoxide poisoning. Where the typical operating temperature of the fuel cell selected for use in the process of the invention is lower than 900K, the temperature can be increased.

This may be through combustion of some of the carbon monoxide produced in the reverse Boudouard reaction, or through the use of a heat pump, for instance some of the energy produced by the fuel cell reaction (c) could be used to heat the cell itself.

[0033] It may be the case that an afterburner is present in the apparatus, to oxidise (after separation) unreacted carbon monoxide and unreacted hydrogen, if the carbon source is a hydrocarbon, exiting the fuel cell with the carbon dioxide. As with the fuel cell reaction, the oxidation will typically be with pure oxygen, however, as described above, the source of the oxygen is typically not air. Instead, the oxygen will often be derived from a cryogenic air separation unit, if undertaken at large scale, or from electrolysis if undertaken at a smaller scale. The heat generated by the afterburner can be used to drive either the reaction of carbon dioxide with the carbon source to form carbon monoxide, if additional energy is required. If the carbon dioxide is derived from calcination, this heat could also be used to dnve this reaction.

[0034] The carbon reactor generally comprises a fluidised bed, although any heating lO vessel may be used, including shaft furnaces, rotary kilns, and multiple hearth furnaces.

[0035] If necessary. some or all of the gases released from the fuel cell after the oxidation reaction may be recycled, to ensure complete conversion of carbon monoxide to carbon dioxide. To avoid recycling of the carbon dioxide generated, this may be separated from any unreacted carbon monoxide and oxygen, so that only the starting materials are returned to the fuel cell.

[0036] Often the apparatus will be portable. As used herein the term "portable' is intended to mean capable of transport without substantial disassembly. This does not require a human, or small number of humans to be able to carry the apparatus. although this may be of use, but only that through the use of mechanical lifters such as cranes, or fork lift trucks, and transport vehicles inc'uding trains or lornes, that the apparatus be movable from one place to another without requinng disassembly and reassembly on arrival.

[0037] It is desirable that the portable apparatus be capable of use during transport. such that it is adapted for use as a source of power in transportation. The heat generated by the reactions of the apparatus may be used in direct transfer to power a transportation vehicle, or may be converted to electricity to provide power for the vehicle. Vehicles which may be powered in this way include trains. trams, aeroplanes, ships. and road vehicles such as heavy goods vehicles (lorries or trucks) and cars.

[0038] It may be the case that the apparatus further comprises a carbon dioxide storage vessel. This would allow for retention of the carbon dioxide generated prior to sequestration, and coirld be of particular use where the apparatus is for use in transportation, and so the carbon dioxide should be stored dunng transit. In such cases, the storage vessel can be emptied when full, and sequestered. Facilities for emptying the carbon dioxide storage vessel may be provided at vehicle destinations and/or way-points.

For instance where the apparatus is being used to power a ship, at docks; a train at train depots andlor stations; an aeroplane, at airports; a road vehicle at depots for large vehicles or for smaller vehicles the service station network could be used.

[0039] In a third aspect of the invention there is provided a use of the apparatus of the second aspect of the invention in energy generation. in particular in energy generation for transportation, such that the apparatus of the second aspect of the invention is adapted for use as a source of power in transportation.[0040] The overall reaction enthalpy for the lO reaction of carbon dioxide with a carbon source to produce carbon monoxide; and subsequent oxidation to carbon dioxide in a fuel cdl is exothermic and the energy released in the oxidation step can be used to drive the reaction of carbon dioxide with the carbon source. The remaining energy generally being converted to electricity. In some examples, roughly 50% of the heat generated by the oxidation of carbon monoxide to carbon dioxide may be converted into electricity, the remaining 50% being used to drive the endothermic step of generating carbon monoxide. The exact percentages would depend upon the carbon source used. This would result in a roughly 70% efficiency of conversion of the chemical energy in the carbon source to electricity. The invention therefore provides a process, apparatus and use in which the foflowing steps can be included: a) reacting carbon dioxide with a hydrocarbon to produce carbon monoxide; b) oxidising the carbon monoxide to carbon dioxide in a fuel cell; c) storing the carbon dioxide; and d) sequestering the carbon dioxide.

Step a) will generally be carried out on a fluidising bed, the resulting carbon monoxide being transferred to a SOFC for reaction with oxygen from the air and conversion to carbon dioxide. The heat energy available from the hot flue gases exiting the fuel cell can be used to drive the reaction of step a), and the remaining energy can be converted to electricity.

[0040] The carbon dioxide can be stored prior to sequestration, to produce a carbon neutral energy generation process.

[0041] Unless otherwise stated each of the integers described in the invention may be used in combination with any other integer as would be understood by the person skilled in the art. Further, although all aspects of the invention preferably "comprise" the features descnbed in relation to that aspect, it is specifically envisaged that they may "consist" or "consist essentially" of those features outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art.

[0042] Further, in the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, is to be construed as an implied statement that each intermediate value of said parameter, lying between the smaller and greater of the alternatives, is itself also disclosed as a possible value for the parameter.

[0043] In addition, unless otherwise stated, all numerical values appearing in this application are to be understood as being modified by the term "about".

Brief Description of the Drawings

[0044] In order that the present invention may be more readily understood, it will be described thrther with reference to the figures and to the specific examples hereinafter.

[0045] Figure 1 is a schematic representation of the process.

Detailed Description

[0046] In one example of the process of the invention a hydrocarbon fuel source is fed into carbon reactor 5 together with carbon dioxide and oxygen wherein the hydrocarbon is oxidised to produce carbon monoxide and svngas. This is passed to a fuel stack 10 together with air (as shown in Figure 2) in order to oxidise the carbon monoxide and syngas to steam and carbon dioxide and produce electricity. Any unreacted carbon monoxide and syngas may be recycled, the steam and carbon dioxide being passed through condenser 15 to allow separation of the steam from the carbon dioxide prior to removal of the carbon dioxide from the system and sequestration. This creates a carbon neutral energy generation system. Some of the carbon dioxide may be returned to the carbon reactor 5 for use as a feedstock in the reduction reaction producing carbon monoxide and syngas. Hot oxygen depleted air from the fuel cell 10 is passed through heat exchanger 20 prior to rdease to the atmosphere. The heat extracted from this air is, in this examp'e, used to heat the water from the condenser 15, converting this thto steam which is used to drive turbines and generate electricity, extracting as much energy as possible from the process ensuring that no heat is wasted. Fans 30 are used to move gases around the system. The example provides a highly efficient energy process which is carbon neutral.

Examples

Energy Calculations [0047] The energy calcubtions for the process of the invention are as follows: 1.] C02+C-i2CO L\H= +172.SkJmoL' 1.2 CO2 + CH4 -2C0 + 2H2 A/J= +468 kfmoL' 2.] 2C0+02-7'2C02 IS AH= -283 ki ofenergypermo/ofCO.

2.2 2C0 + 2H2 + 202 92C09 + 2H90 AH= -596 ki of energy per mol of CO.

[0048] As the electrical efficiency of a solid oxide fuel cell is generally around 50%, the fuel cell generates: 50% x 283k] x 2 mol = 283kJ electricity As the chemical energy stored in the carbon is 393.SkJmoF' the overall electrical efficiency of the system is 70% (2). This unusually high efficiency is derived from the heat energy investcd in step 1 which boosts the overall chemical energy available.

The heat produced from the fuel cell is used to drive these reactions.

100491 It should be appreciated that the processes and apparatus of the invention are capable of being incorporated in the form of a variety of embodiments, only a few of which have been illustrated and described above.

Claims

Claims 1. An energy generation process comprising the oxidation of carbon monoxide to carbon dioxide in a fuel cell, the process comprising the step of producing the carbon monoxide from carbon dioxide and a carbon source.

2. A process according to daim 1, wherein the carbon source is selected from coke andlor a hydrocarbon.

3. A process according to claim 2, wherein the hydrocarbon is selected from straight and branched chain C1 to C12 alkanes, straight and branched chain C2 to C12 aficenes, saturated and unsaturated cyclic hydrocarbons, and combinations thereof.

4. A process according to claim 3, wherein the Ci to C12 alkane is selected from IS methane, ethane, propane, butane and combinations thereof.S. A process according to any preceding claim, compnsing the steps of: a) reacting carbon dioxide with a carbon source to form carbon monoxide; and b) oxidising the carbon monoxide to carbon dioxide.

I

6. A process according to claim 5. wherein step a) is a reverse Boudouard reaction.

7. A process according to claim S. wherein step a) also produces hydrogen.

8. A process according to any preceding claim, wherein oxidation comprises oxidation with oxygen gas.

9. A process according to claim 8, wherein the oxygen gas comprises oxygen separated from air by migration across the fuel cell.

10. A process according to any preceding claim, comprising the additional step of sequestering the carbon dioxide.ii. An apparatus for energy generation comprising a carbon reactor in fluid communication with a fuel cell.12. An apparatus according to claim II, wherein the fuel cell is a solid oxide fuel cell.13. An apparatus according to claim 11 or claim 12, wherein the carbon reactor comprises a fluidised bed.14. An apparatus according to any of claims ii to 13, adapted for use as a source of power in transportation.15. An apparatus according to any of claims 11 to 14, which is portable.16. An apparatus according to any of claims II to 15, further comprising a carbon dioxide storage vessel.17. Use of the apparatus of any of claims 11 to 16. in energy generation for transportation.18. Use according to claim 17, wherein the transportation is selected from a ship, train, road vehicle or aeroplane.19. A process or apparatus substantially as descnbed herein with reference to the drawings.