Patent Description:
Carbon Capture and Storage (CCS) constitutes a range of technologies being developed to help mitigate the negative consequences of human made climate change by isolating CO<NUM> produced during fuel combustion (e.g., gas, liquid hydrocarbons, coal and biomass) and from CO<NUM> emitting industries (iron and steel, aluminium, silicon, ferrosilicon, cement, etc.). CO<NUM> capture can be obtained by three main methods; post-combustion, pre-combustion and combustion in almost pure oxygen. The separated CO<NUM> stream can be used and/or contained in geological formations. In a pre-combustion situation, hydrogen or hydrogen rich gases have historically led to combustion temperatures that are too high for conventional gas turbines.

However, recent technology development (premixing of fuel and air, development of burners for hydrogen rich fuels, development of higher temperature material system (base alloy/super alloys, bond coat and thermal barrier coatings)) has made pre-combustion CO<NUM> capture viable for the use in hydrogen-fuelled gas turbines.

Hydrogen-fuel can be made efficiently (in one process step) from cleaned, desulphurized syngas (of any origin) or natural gas and water by processes known as; Sorption Enhanced Water Gas Shift (SE-WGS) and/or Sorption Enhanced Steam Methane Reforming (SE-SMR), also called Sorption Enhanced Reforming (SER), characterized by using CaO as the CO<NUM>-absorbent (ref. <CIT> and U. Department of energy), also called Ca - looping (Dean at al. : <NUM>), when used in post-combustion cases (<CIT>).

The following reactions occur (depending on the fuel used);.

The temperature for all reactions is between <NUM> to <NUM>. These reactions are slightly exothermic and may have to be cooled by adding water or heat exchange. Reaction c) represents the sum of reactions a) and b). All reactions would lead to the same products (calcite and hydrogen), regardless of the proportions of the syngas and natural gas in the fuel mix introduced to the hydrogen production unit, if the amount of the CaO-CO<NUM> absorbent is high enough to accommodate all the carbon in the reaction.

Included in the hydrogen production unit is a CO<NUM> absorbent regenerator (calciner), where the solid calcium carbonate (CaCO<NUM>) from the hydrogen production process is regenerated according to the following reaction: CaCO<NUM> = CaO + CO<NUM>. If no hydrocarbon fuel (or fuel containing CO) is used to perform this highly endothermic process (about <NUM> to <NUM> is needed), the total amount of CO<NUM> is captured "<NUM>% pure" and can be used and/or stored.

It is very important to perform this endothermic regeneration process in a sustainable cost and energy efficient manner. This can be achieved by providing heat, or waste heat, that can be transferred in two different ways, i.e. directly or indirectly. Direct heat transfer involves an oxy-combustion of fuel; therefore, the use of an air separation unit (ASU) is required. Indirect heat exchange requires the integration of a high temperature heat exchanger in the regenerator. The heat could be taken from a high temperature fuel cell (SOFC) (as in <CIT>).

Another option would be to use a high temperature electrical power generating device to calcine the calcium carbonate as have been very briefly suggested in <CIT>. However, this publication is silent with regard to how such a calcination should be performed.

Other publications in this technical area worth mentioning are <CIT>,.

While conventional natural gas turbines may give too low temperatures for efficient performance of the regeneration reaction of the CaO-CO<NUM> absorbent, the challenging high temperature in the combustor end and the inlet of the turbine of a hydrogen-fuelled gas turbine, might on the other hand benefit from the cooling caused by an efficient heat exchange loop.

The objective of the present invention is to provide a cost and energy efficient hydrogen-fuelled gas turbine power plant able to operate under sustainable conditions. It is a derived object to alleviate the problem of excessive temperature at the end of the combustor and/or the inlet of the hydrogen-fuelled gas turbine.

It is further a derived object to provide a method for operation of such a power plant.

It is an inherent objective to provide such a power plant in which CO<NUM> is captured in a highly effective manner.

The above-mentioned objects are achieved by the present invention which according to a first aspect consists in a hydrogen-fuelled gas turbine power plant as defined by claim <NUM>.

According to another aspect the invention concerns a method as defined by claim <NUM>.

Preferred embodiments are disclosed by dependant claims.

Sustainability is a keyword and a common denominator for the overall process illustrated by the fact that the present invention allows integrated CO<NUM> capture. The heat transfer loop, between - on one side - the end of the of the combustor and/or the inlet of the turbine of the hydrogen-fuelled gas turbine and - on the other side - the regenerator (calciner), comprises a hollow ring shaped compartment at the downstream end of the combustor or at the inlet of the turbine. The heat transfer medium can be different gases, such as for example; hydrogen, water vapour, CO<NUM>, air, helium, different gas mixtures or fluids such as mineral oils, hydrocarbons and different types of molten salts.

Thus, according to the present invention the high temperature required for the regeneration of the CaO-absorbent is ensured by a specifically designed heat exchange loop between the downstream (hot) end of the combustor or the upstream end of the turbine of a hydrogen-fuelled gas turbine, where the temperature may reach <NUM> to <NUM>, and the regenerator of the CaO absorbent.

It is worth mentioning that gas turbines, including hydrogen-fuelled gas turbines, encompasses a number of different configurations and overall designs, and that the present invention is adaptable to all these configurations and designs. For instance, with regard to the combustor chamber(s) of the gas turbines, it or they may in some embodiments be shaped as an annular chamber between the compressor and the turbine and having an axis common with the axis of the compressor and the turbine. In other embodiments the combustor chamber may be divided into two or more separate combustor chambers, each of which being positioned off-set the axis of the compressor and turbine. Thus, two, three or four separate can combustor chambers may be arranged in parallel around the axis connecting the compressor with the turbine.

Different embodiments of the invention are illustrated below with reference to the enclosed drawings, where;.

Now referring to <FIG>, the power system is generally comprised by a hydrogen-fuelled gas turbine <NUM> and a fuel supply device <NUM>. The fuel supply device <NUM> mainly consists of i) a reactor or reformer <NUM> arranged to receive water <NUM> and a base fuel which in the embodiment of <FIG> is methane or a methane rich gas <NUM> and ii) a regenerator <NUM>. The hydrogen-fuelled gas turbine <NUM> is comprised by the main parts i) a compressor <NUM>, ii) a combustor <NUM> (with a cylindrical compartment for heat exchange at the end) arranged to receive a flow of hydrogen <NUM> from the reactor <NUM> and compressed air <NUM> from the compressor <NUM>, and iii) a turbine <NUM> arranged to receive high-temperature combustion gases <NUM> from the combustor <NUM> and to thereby generate electricity <NUM>. In addition to generation of electrical energy, the turbine may also propel mechanical equipment for varying purposes.

Further to <FIG>, the fuel reformer <NUM> is based on the SE-SMR (or SER) method of hydrogen production, arranged in a CO<NUM> pre-combustion situation. A CaO containing CO<NUM> - absorbent regenerator <NUM> and an indirect heating transfer system <NUM> between the high temperature (downstream) end of the hydrogen-fuelled gas turbine combustor <NUM> and the CO<NUM> - absorbent regenerator <NUM> provides heat required for the release of CO<NUM> allowing a flow <NUM> of substantially pure CO<NUM> to be discharged from the regenerator <NUM>.

The heat transferred by the indirect heat transfer system <NUM> is collected by a ring-shaped member <NUM> at the downstream end of the combustor <NUM> and liberated in a heat exchanger in the regenerator <NUM>, and forms a closed heat exchange loop (<NUM>) between the regenerator (<NUM>) of the hydrogen gas producing reactor system (<NUM>) and at least one of the downstream end of the combustor (<NUM>) of the hydrogen-fuelled gas turbine (<NUM>) and the upstream end of the turbine (<NUM>) of said hydrogen-fuelled gas turbine.

A CH<NUM> fuel flow <NUM> is charged to a reactor <NUM> being part of the hydrogen-fuel supply system which is arranged to reform fuel and take care of CO<NUM> released in the reforming process, SE-SMR (or SER) by means of a CaO containing absorber. In the embodiment of <FIG>, the fuel is methane or a methane-rich gas, such as natural gas. A substantially pure hydrogen <NUM> gas leaves the reformer unit. In the reactor <NUM> the process of reforming involves a reaction between fuel (CH<NUM>), water (steam) and CaO in which the latter is converted to CaCO<NUM> in an exothermic reaction. The CaCO<NUM> made from the CO<NUM> in the reforming process, is subsequently regenerated to CaO in an endothermic process to be described. Water <NUM> in vaporized form is also charged to the reactor <NUM>.

The substantially pure hydrogen gas <NUM> leaves the reformer to be charged to the combustor <NUM> (or combustor area) of the hydrogen-fuelled gas turbine. Compressed air <NUM> from the compressor <NUM> of the hydrogen-fuelled gas turbine <NUM> is also charged to the combustor <NUM>. The hydrogen gas <NUM> and the compressed air <NUM> may be premixed (not shown) before being charged to the combustor <NUM>. The mixture is burned at high temperatures, typically at about <NUM> to <NUM>.

The high temperature, high-pressure gas stream <NUM> that enters the turbine <NUM> expands though the turbine to produce electricity.

As indicated above, the CaCO<NUM> <NUM> generated in the reformer unit needs to be regenerated to CaO <NUM> for reuse as CO<NUM> capturing agent in the reactor <NUM>. This takes place in regenerator <NUM> forming a second part of the hydrogen-fuel supply device <NUM>.

The regeneration of CaCO<NUM> needs a temperature of about <NUM> to <NUM> to operate efficiently. This is an endothermic process consuming energy. At normal pressure, the process runs at temperatures of about <NUM> and above. This is thus a preferred embodiment. The necessary energy, or heat, for this process is according to the present invention provided by the combustor <NUM> of the hydrogen-fuelled gas turbine. A closed heat loop, using for instance hydrogen as heat transfer medium, circulating between the high temperature end of the combustor <NUM> and the energy demanding regenerator <NUM> of the fuel supply device system has two functions;.

The closed loop heat exchange medium can be any medium able to handle temperatures experienced at the combustor <NUM> and should preferably be able to handle temperatures of about <NUM> to <NUM>.

The total CO<NUM> amount from this pre-combustion CO<NUM> capture process, is released from the regenerator, captured, stored, and/or used.

The high-quality exhaust gas <NUM> (N<NUM>, H<NUM>O and O<NUM>) leaving the turbine <NUM> at temperatures of more than <NUM>, can optionally be used for a range of purposes. The heat <NUM> from the exothermic SE-SMR reaction would similarly have optional use. The heat <NUM> may for instance be used in a gasification plant to convert solid carbonaceous material to more readily exploitable gases such as syngas or natural gas, or it may be used to preheat the air from the compressor <NUM>.

Attention is now directed to <FIG>, showing a power production plant, where a hydrogen-fuelled gas turbine is combined with a fuel reformer based on syngas, i.e. a SE-WGS method of hydrogen production, arranged in a CO<NUM> pre-combustion situation. A CaO containing CO<NUM> -absorbent regenerator <NUM> and an indirect heating exchange system <NUM> between the hydrogen-fuelled gas turbine combustor <NUM> and the CO<NUM> - absorbent regenerator <NUM> provides heat for the absorbent regeneration and releases CO<NUM> <NUM> for CO<NUM> capture, storage, and/or usage.

Most of the components of <FIG> are the same as the ones in <FIG>. A difference between <FIG> and <FIG> is mainly that the fuel <NUM>' supplied to the hydrogen gas fuel supply device is syngas. Furthermore, the ring-shaped member <NUM>' of the heat transfer system <NUM> is somewhat wider than the ring-shaped member <NUM> shown in <FIG>, providing a broader contact surface area with the hot combustion gas <NUM> leaving the combustor <NUM>, thereby allowing a higher rate of heat transfer.

<FIG> shows essentially the same as <FIG>, the difference being that the ring-shaped member <NUM>" of the heat transfer system covers - or constitutes - partly a downstream area of the combustor <NUM>, partly an upstream end of the turbine <NUM>, thereby further increasing its contact surface area with the hot combustion gas <NUM>.

It should be understood, that, while shown for the embodiment in which syngas is the fuel, the different embodiments of the ring-shaped member <NUM>, <NUM>' and <NUM>" work equally well with natural gas as fuel or a combination of the two types of fuel.

Attention is now drawn to <FIG> showing a power production plant, where hydrogen in a pre-combustion situation is produced by the SE-SMR hydrogen production method for use in a hydrogen-fuelled gas turbine. The heat from the hot exhaust gas leaving the turbine is in this embodiment recovered for high-pressure steam generation for production of additional power/electricity <NUM>' by a steam turbine <NUM>.

Most of the components of <FIG> are the same as the ones in <FIG>. The difference between <FIG> and <FIG> is mainly that additional electric power is generated by a steam turbine <NUM>, a configuration called a combined cycle. For this purpose, the hot exhaust gas leaving the turbine <NUM> is used to generate steam in a steam generator <NUM> and the steam generated is charged to the steam turbine <NUM>.

Attention is now directed to <FIG> showing a power production plant, where hydrogen in a pre-combustion situation is produced from syngas, in a SE-WGS hydrogen production method, for use in a hydrogen-fuelled gas turbine as previously discussed. The heat from the hot exhaust gas <NUM> leaving the turbine <NUM> is in this embodiment recovered for high-pressure steam generation for production of additional power/electricity by a steam turbine.

Most of the components of <FIG> are the same as the ones in <FIG> and <FIG>. The difference between <FIG> and <FIG> is mainly that additional electric power <NUM>' is generated by a steam generator <NUM> in combination with a steam turbine <NUM>, a configuration called a combined cycle, as already discussed with reference to <FIG>.

It should be emphasized that all embodiments described herein could encompass the additional step of power generation described with reference to <FIG> and <FIG>.

Attention is then directed to <FIG> showing a power production plant, where hydrogen in a pre-combustion situation can be produced alternatively from a source of natural gas (or methane) by the SE-SMR hydrogen production method, or from a source of syngas by the SE-WGS hydrogen production method, or from any combination of such sources for use in a hydrogen-fuelled gas turbine. The CaO containing CO<NUM> - absorbent regenerator <NUM> and an indirect heating transfer system <NUM> between the hydrogen-fuelled gas turbine combustor <NUM> and the CO<NUM> - absorbent regenerator <NUM> provides heat for the CaO regeneration and release of CO<NUM> for capture, storage, and/or use as discussed with reference to previous embodiments. The system for CO2-capture is the same as described in all previous embodiments.

In <FIG>, a common reactor/reformer <NUM> is indicated to receive the two types of source gases. This means that the SE-SMR reforming and the SE-WGS reaction are performed simultaneously in the same reactor and under the same conditions. This has been found not to constitute a problem. As an alternative, separate reactors/ reformers may be used for each source gas, CH<NUM> and syngas. In a such a case, the two reactors may be connected to a common regenerator or to separate regenerators. The simplest configuration is, however the one shown.

<FIG> also shows a separate flow <NUM> of H<NUM> for external use, and illustrates the fact that the present method and device allows simultaneous production of energy in the forms of electricity, heat and high quality hydrogen.

The CaO containing absorber may simply be based on CaO from natural rocks/ minerals, but it may also be a synthetically manufactured CaO containing absorber, e.g. of the kind described by <CIT>. The advantage of such a synthetic absorber is that it endures a high number of cycles of regeneration without losing significant absorption ability.

<FIG> shows two alternate configurations of the ring-shaped member <NUM>' shown in <FIG> and <FIG>. In the configuration shown in <FIG>, the inlet to <NUM> and the outlet from <NUM> the ring-shaped member <NUM>'a are adjacent to one another and the heat transfer fluid flows in one nearly full circle in one and the same direction throughout the void inside the ring-shaped member. The inside of the ring-shaped member <NUM>'a may or may not be provided with ribs <NUM> that serves to increase the surface area that the hot combustion gas <NUM> contacts on its way from the combustor <NUM> to the turbine <NUM>. In the direction of the gas flow through the compressor and the turbine, such ribs may have an extension that corresponds to - or is smaller than -the extension of the ring shaped member. The size and profile of the ribs <NUM>, if present, will be adapted to the space available. Their radial extension may vary along their length as may their thickness, to optimize not only their size but also their aerodynamic properties. Optionally, the ribs may also be slightly curved along their length in order to increase the contact with the passing gas flow. At least parts of the ribs may be located in a longitudinal area of the turbine in which no vanes are present to take up part of its cross-section.

In <FIG>, the inlet <NUM> to and outlet <NUM> from the ring-shaped member <NUM>'b are located at opposite sides thereof, and the heat transfer fluid entering the void in the ring-shaped member <NUM>'b at its inlet, is split in two partial flows that each flows a half-circle to the outlet at the opposite side of the ring-shaped member <NUM>'b.

For all embodiments shown, the ring shaped member <NUM>, <NUM>' and <NUM>" may have inlet and outlet in either of the configurations shown and even in other configurations. Furthermore, the ring-shaped member may be designed and configured in a manner making it replaceable when worn out, e.g. by being connectable to the combustor <NUM> and the turbine <NUM> by threads or the like.

The ring-shaped member <NUM>, <NUM>', <NUM>", when assembled to the hydrogen-fuelled gas turbine, becomes a part thereof and may be seen as the downstream end of the combustor <NUM>, the upstream end of the turbine <NUM> or a connection member between the two.

The material for the ring-shaped member <NUM>, <NUM>', <NUM>" is selected among materials having an acceptable heat conductivity in combination with an acceptable tolerance for high temperatures. The materials generally chosen for the wall of a combustor or turbine as described above are promising candidates therefore.

<FIG> shows an embodiment of the present invention that differs from the previous embodiments with regard to the combustor which in the embodiment of <FIG> is comprised by two separate combustor chambers 24a, 24b which are off-set from the axis between the compressor <NUM> and the turbine <NUM>. Also the heat exchange element previously represented as feature <NUM>, <NUM>' and <NUM>" is replaced by a heat exchanger <NUM> which is also off-set the axis between the compressor and the turbine. The arrangement of the heat exchanger <NUM> off-set from said axis implies that it does not contribute to an increase of the length dimension of the turbine, and it allows use of various types and sizes of heat exchange elements, thus greatly improving the versatility of the system. This combination makes it easier to design the system in a manner allowing fine tuning of the heat to be transferred to the regenerator <NUM>. In <FIG>, hot gas 25a is directed from the combustors 24a to the heat exchanger <NUM>, and the same gases is discharged from the heat exchanger <NUM> at a somewhat lower temperature as gas flow 25b which in turn is directed into the turbine <NUM>. Naturally, the flow path from the combustors 24a, 24b to and through the heat exchanger <NUM> and further on to the turbine26, must be shaped and dimensioned to accommodate an efficient gas flow at a high rate with an acceptably low pressure drop.

With all versions of the present invention, additional heat exchange elements to those discussed, shown and/ or claimed may be installed e.g. to cool hot parts more than what is achieved by the elements <NUM>, <NUM>', <NUM>" or78.

Inherent in turbine design is safety measures that is not discussed herein and mainly will be in accordance with the standard in this technology field, such as measures for immediate fuel cut off in case of load-shedding or during emergency shut-downs, in order to prevent the turbine from over-speeding. Due to the presence of significant amounts of energy accumulated in the heat exchanger during normal operation, additional safety measures may be made to prevent the turbine from over-speeding in such situations.

Claim 1:
Hydrogen-fuelled gas turbine power system with pre-combustion CO2 capture, the main parts of which being comprised by a compressor (<NUM>), a combustor (<NUM>), a turbine (<NUM>) and a fuel supply device (<NUM>) for supplying the fuel to the hydrogen-fuelled gas turbine (<NUM>),
- the turbine (<NUM>) being adapted for connection to auxiliary means for power generation in the form of electrical energy;
- the fuel supply device (<NUM>) having the form of a hydrogen gas producing reactor system with at least one reactor (<NUM>) selected from the group consisting of i) a reactor capable of supporting sorption enhanced steam methane reforming (SE-SMR) of methane and ii) a reactor capable of supporting sorption enhanced water gas shift (SE-WGS) of syngas, or a combination of the two;
- the reactor (<NUM>) being connected in a closed loop with a regenerator (<NUM>) for circulating and regenerating a CaO containing CO<NUM> absorber between the reactor (<NUM>) and the regenerator (<NUM>),
characterized in the presence of a closed heat exchange loop (<NUM>) between the regenerator (<NUM>) of the hydrogen gas producing reactor system (<NUM>) and at least one of the downstream end of the combustor (<NUM>) of the hydrogen-fuelled gas turbine (<NUM>) and the upstream end of the turbine (<NUM>) of said hydrogen-fuelled gas turbine, enabling the function of raising the temperature in the regenerator (<NUM>) at <NUM> while simultaneously lowering the temperature in the upstream end of the turbine (<NUM>) of the hydrogen-fuelled gas turbine (<NUM>) and cooling relevant turbine(<NUM>) parts to a level acceptable for long term stable use of the hydrogen-fuelled gas turbine and reducing the need for dilution air to the turbine.