Carbon capture power station unit with a primary turbine and a secondary turbine
The carbon capture power station unit uses a primary and secondary turbine configuration to efficiently supply steam and electricity for amine-based solvent heating, addressing the challenges of variable demand and reducing operational disruption in existing power stations.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- DRAX POWER
- Filing Date
- 2025-12-12
- Publication Date
- 2026-07-30
AI Technical Summary
Existing carbon capture systems face challenges in efficiently providing steam and electricity to heat amine-based solvents for carbon capture without disrupting existing power station operations, particularly when dealing with variable steam demand and electrical generation loads.
A carbon capture power station unit is designed with a primary turbine to generate electricity and a secondary turbine to provide steam for heating the amine-based solvent, allowing for separate optimization of steam and electricity generation to meet the demands of the carbon capture system.
This configuration reduces operational disruption and infrastructure requirements by allowing the secondary turbine to supply steam and electricity efficiently, enabling cost-effective and adaptable carbon capture without relying on external power sources.
Smart Images
Figure GB2025052692_30072026_PF_FP_ABST
Abstract
Description
[0001] 64.173.174804 / 02
[0002] CARBON CAPTURE POWER STATION UNIT WITH A PRIMARY TURBINE AND A SECONDARY TURBINE TECHNICAL FIELD
[0003] This invention relates to carbon capture power station units, comprising a carbon capture system configured to use an amine-based solvent to extract carbon from flue gas. In particular, this invention relates to the use of a primary turbine to generate electricity, and the use of a secondary turbine to (i) generate electricity to power the carbon capture system, and (ii) provide steam for heating the amine-based solvent, after it has been used to capture carbon from the flue gas, so as to release the carbon (e.g. for storage).
[0004] BACKGROUND
[0005] Many power stations are designed to burn fuel to produce heat in order to create the steam used to drive a turbine to generate electricity. Flue gas is created as a by-product of burning various fuels, such as biomass. As flue gas contains carbon, it is desirable to capture at least some of the carbon from the flue gas before dispersion of the flue gas to the atmosphere so as to reduce carbon emissions.
[0006] Some carbon capture systems are configured to use an amine-based solvent to capture the carbon from the flue gas. This amine-based solvent can be heated, after capturing carbon from the flue gas, in order to release the carbon, e.g. for storage. The amine-based solvent can then be used to capture more carbon from flue gas. Carbon capture systems that are designed in this manner can be designed to transfer heat from a heat source to the amine-based solvent. In particular, some of these systems are configured to transfer heat from steam within a certain temperature and / or pressure range to the amine-based solvent using an amine-based solvent heater. In these examples, the amine-based solvent heater has a certain steam demand, based on the mass flow rate of the amine-based solvent, which in turn is based on the flow rate of the flue gas. This steam demand must be satisfied by the power station.
[0007] When designing a process to provide steam to heat the amine-based solvent, it is important to consider various criteria. One of these criteria is how to reduce the mass flow rate of additional fluid (e.g. water or steam) required to heat the amine-based solvent. Additional fluid in this context means fluid that is not already required by another part of the power station. It may be desirable to reduce the amount of fluid required to reduce operational costs and the amount of infrastructure required to accommodate the carbon capture system. In more general terms, it is often desirable to reduce the amount of additional (e.g. dedicated) infrastructure required to heat the amine-based solvent for the carbon capture system. The steam must be hot enough to heat the amine-based solvent to at least a minimum temperature for release of the captured carbon. It is often preferable to avoid heating steam to an appropriate temperature just for this purpose, as this may not be particularly efficient.
[0008] Additionally, when retrofitting a carbon capture system to a pre-existing power station unit, it is desirable to minimise disruption to the operation of the power station unit. Thus, it is desirable to design a process for heating the amine-based solvent that does not cause significant disruption to the existing power station processes. This may be particularlydifficult, as the steam demand varies based on the mass flow rate of flue gas being produced by the power station unit.
[0009] Another consideration is how to design a process that is adaptable to meet a variable steam demand of the amine-based solvent heater, which may vary dependent on the mass flow rate of flue gas, which itself varies depending on the electrical generation load of the power station unit. This introduces further complexity.
[0010] Carbon capture systems may also have a certain electricity demand that must be satisfied to power the carbon capture system. While the electricity could be purchased from the national grid or another source, it may be cheaper and / or more efficient for the power station to be able to generate at least some of this electricity independently. However, it may be very disruptive to try to provide electricity from an existing turbine to the carbon capture system. Thus, a solution for providing at least some of the electricity required by the carbon capture system may be desired.
[0011] SUMMARY
[0012] When viewed from a first aspect, the invention provides a carbon capture power station unit, comprising:
[0013] a furnace, configured to burn fuel to produce heat and flue gas;
[0014] a boiler, configured to use the heat from the furnace to heat steam;
[0015] a carbon capture system, configured to use an amine-based solvent to capture carbon from the flue gas; and
[0016] a steam path, configured to receive at least some of the steam from the boiler, the steam path comprising:
[0017] a primary turbine, comprising one or more stages, wherein the one or more stages of the primary turbine are configured to receive steam and use the received steam to generate electricity; and
[0018] a secondary turbine, comprising one or more stages, wherein the one or more stages of the secondary turbine are configured to receive steam and use the received stream to generate electricity;
[0019] wherein the secondary turbine is configured provide at least some of the electricity that it generates to power the carbon capture system;
[0020] wherein the steam path is configured to split into a first branch, comprising a stage of the primary turbine, and a second branch, comprising a stage of the secondary turbine;
[0021] wherein the steam path is configured to provide a first portion of steam to the first branch, and to provide a second portion of steam to the second branch;
[0022] wherein the second branch further comprises an amine-based solvent heater for the carbon capture system, arranged downstream of the stage of the secondary turbine; and
[0023] wherein the amine-based solvent heater is configured to receive at least some of the steam from the stage of the secondary turbine, and transfer heat from the received steam to the amine-based solvent so as to release the captured carbon.A carbon capture power station unit in accordance with the present invention is configured to use a secondary turbine to: (i) provide (e.g. at least some of) the power required by the carbon capture system; and (ii) provide (e.g. at least some of) the steam required to heat the amine-based solvent to release the captured carbon, e.g. for storage. This may allow re-use of the amine-based solvent to capture carbon from the flue gas.
[0024] The provision of parallel stages of the primary and secondary turbines may enable them to be designed differently. For instance, the stage of the secondary turbine may be designed to provide steam at an appropriate temperature, pressure and / or mass flow rate for use by the amine-based solvent heater. Whereas, for example, the stage of the primary turbine may be designed to provide improved electricity generation from the first portion of steam.
[0025] The use of the stage of the secondary turbine to generate (e.g. at least some of) the electricity required by the carbon capture system may be cheaper than alternatives, such as buying the electricity from the national grid.
[0026] It will be appreciated that the amine-based solvent heater is configured to receive at least some of the steam from the stage of the secondary turbine after the steam has been used by the stage of the secondary turbine to generate electricity. It will also be appreciated that the amine-based solvent heater is configured to transfer heat from the received steam to the amine-based solvent after the amine-based solvent has been used to capture the carbon from the flue gas. The carbon capture system may be considered to comprise the amine-based solvent heater. The carbon capture system may be considered to comprise the secondary turbine.
[0027] The term boiler is used herein for the part of the carbon capture station unit that is configured to use the heat from the furnace to heat steam. It will be appreciated that this is a term in the art that originates from when furnaces were used to boil water so as to provide steam, and that many (e.g. modern) boilers no longer actually boil water to provide steam, and instead merely heat (e.g. superheat) steam. Thus, it will be appreciated that, in embodiments of the present invention, the boiler may not actually boil water and thus may be understood to be a steam heater or a steam superheater.
[0028] A power station may comprise one or more power station units. For instance, a power station may comprise a carbon capture power station unit and any of a solar energy power station unit, wind energy power station unit, geothermal power station unit, etc.. It will therefore be understood that the first aspect of the invention extends to a power station comprising the carbon capture power station unit.
[0029] The stage(s) of the primary and / or the secondary turbine(s) may be configured to generate electricity by expanding the received steam. Expanding the received steam may reduce the temperature and / or the pressure of the received steam.
[0030] In some embodiments, the stage of the primary turbine is an intermediate pressure stage, configured to receive the first portion of steam at an intermediate pressure, and expand the first portion of steam to a reduced (e.g. low) pressure to generate electricity. The stage of the primary turbine may be configured to provide the first portion of steam at the reduced pressure downstream of the stage of the primary turbine.
[0031] In some embodiments, the stage of the secondary turbine is an intermediate pressure stage, configured to receive the second portion of steam at an intermediate pressure, and expand the first portion of steam to a reduced (e.g. low) pressure to generate electricity. The stage of the secondary turbine may be configured to provide the second portion of steam at the reduced pressure downstream of the stage of the secondary turbine.The reduced pressure of the first portion of steam, after expansion through the stage of the primary turbine, may be different to the reduced pressure of the second portion of steam, after expansion through the stage of the secondary turbine.
[0032] In some embodiments, the carbon capture power station unit comprises a retrofitted carbon capture system and / or a retrofitted secondary turbine. In other words, the power station unit may have previously been operated without a carbon capture system and / or a secondary turbine. However, the carbon capture power station unit may now comprise a retrofitted carbon capture system and / or a retrofitted secondary turbine (retrofitted to the existing power station unit). The secondary turbine may be retrofitted so as to provide (e.g. at least some of) the steam and (e.g. at least some of) the power required by the retrofitted carbon capture system and the associated amine-based solvent heater. The present invention may be particularly useful for carbon capture power station units comprising a retrofitted carbon capture system and a retrofitted secondary turbine, as (e.g. at least some of) the steam demand and (e.g. at least some of) the electricity demand of the retrofitted carbon capture system can be satisfied by the carbon capture power station unit (e.g. by the retrofitted secondary turbine) with reduced disruption to pre-existing processes.
[0033] For instance, in some of these embodiments there may have been a pre-existing primary turbine, that was configured to use at least some of the steam from the boiler to generate electricity in one or more stages. In these embodiments, it is possible that none of the stages of the pre-existing primary turbine were designed to provide steam at an appropriate temperature, pressure and / or mass flow rate for use by the amine-based solvent heater. Additionally, even if the steam produced by one or more of the stages of the pre-existing primary turbine was suitable for use by the amine-based solvent heater, tapping off steam from one of these stages may cause disruption to pre-existing processes associated with the primary turbine. Thus, the use of a retrofitted secondary turbine which can be designed to provide steam at an appropriate temperature, pressure and / or mass flow rate for use by the amine-based solvent heater may reduce disruption to the pre-existing primary turbine and associated processes.
[0034] Furthermore, the carbon capture power station unit may not have had the infrastructure in place to provide electricity from the pre-existing primary turbine to the retrofitted carbon capture system. Thus, retrofitting of a secondary turbine that can be designed to provide (e.g. at least some of) the power required by the carbon capture process may enable (e.g. at least some of) the electricity required by the carbon capture system to be provided by the carbon capture power station unit, e.g. with reduced disruption to the pre-existing primary turbine and associated processes.
[0035] The amount of electricity produced by the (e.g. stage of the) secondary turbine may depend on the temperature and / or pressure of the steam provided to it. In some embodiments, steam may be provided to the (e.g. stage of the) secondary turbine directly from the boiler. However, this may result in the amount of electricity generated by the (e.g. stage of the) secondary turbine from the mass flow rate of steam required by the amine-based solvent heater to be significantly more than the amount of electricity required to power the carbon capture system. It may be desirable for the amount of electricity generated by the (e.g. stage of the) secondary turbine from the mass flow rate of steam required by the amine-based solvent heater to be similar to the amount of electricity required to power the carbon capture system. Thus, it may be preferable to provide steam at a reduced temperature and / or pressure to the (e.g. stage of the) secondary turbine instead.
[0036] In some embodiments, the steam path further comprises a preceding stage of the primary turbine, upstream of a position where the steam path splits into the first branch and thesecond branch. Thus, it will be understood that the second portion of steam may be tapped off from this preceding primary turbine stage for use by the (e.g. stage of the) secondary turbine. The steam from the preceding stage of the primary turbine may be at a reduced temperature and / or pressure when compared with the steam directly from the boiler.
[0037] Therefore, the amount of electricity generated by the (e.g. stage of the) secondary turbine from the mass flow rate of steam required by the amine-based solvent heater when provided with steam at this temperature and / or pressure may be similar to the amount of electricity required to power the carbon capture system. As previously mentioned, this may be desirable.
[0038] In some embodiments, the preceding stage of the primary turbine is a high pressure stage, configured to receive steam at a high pressure, and expand the received steam to a reduced (e.g. intermediate) pressure to generate electricity.
[0039] The carbon capture power stage may comprise a second boiler. The second boiler may be arranged downstream of the high pressure stage of the primary turbine (e.g. between the high pressure stage and the intermediate pressure stage of the primary turbine). The preceding stage of the primary turbine may be configured to provide (e.g. at least some of) the steam at the reduced (e.g. intermediate) pressure to the second boiler. The reduced (e.g. intermediate) pressure of the steam may still be sufficiently high for it to be used to generate more electricity (e.g. without requiring the pressure of the steam to be increased). While the reduced (e.g. intermediate) pressure of the steam may be sufficiently high for it to be used to generate more electricity, re-heating of the steam may increase the amount of electricity that it can be used to generate.
[0040] In some embodiments, the steam path (e.g. the first branch of the steam path) further comprises a subsequent stage of the primary turbine, downstream of the stage of the primary turbine.
[0041] In some embodiments, the subsequent stage of the primary turbine is a low pressure stage, configured to receive steam at a low pressure, and expand the received steam to a reduced pressure (e.g. a very low pressure) to generate electricity.
[0042] Thus, the primary turbine may comprise an intermediate pressure stage configured to expand the first portion of steam from an intermediate pressure to a low pressure and a low pressure stage configured to expand the steam from a low pressure to a very low pressure. It may be difficult to design a single stage of the primary turbine that can provided improved generation of electricity as the first portion of steam is expanded from an intermediate pressure to a very low pressure. On the other hand, if two primary turbine stages are used to expand the first portion of steam from the intermediate pressure to the very low pressure, each these stages can be designed to provide improved generation of electricity as the first portion of steam is expanded through a smaller pressure range. Thus, efficiency of electricity generation from the first portion of steam may be improved.
[0043] In some embodiments, the steam path further comprises a second boiler, upstream of the stage of the secondary turbine, configured to use the heat from the furnace to re-heat at least the first portion of steam. The second boiler may be configured to re-heat both the first portion and the second portion of steam. For instance, the second boiler may be configured to re-heat the first portion of the steam from the first stage of the primary turbine before it is used by a second stage of the primary turbine to generate electricity. The second boiler may be arranged upstream of the position where the steam path splits into the first branch and the second branch. The second boiler may be arranged downstream of the preceding stage of the primary turbine.Re-heating of the first portion of steam before it is provided to the (e.g. stage of the) secondary turbine may provide steam at an appropriate temperature and / or pressure for the amount of electricity generated by the (e.g. stage of the) secondary turbine from the mass flow rate of steam required by the amine-based solvent heater to be similar to the amount of electricity required to power the carbon capture system. As previously mentioned, this may be desirable.
[0044] In a carbon capture power station unit comprising a retrofitted carbon capture system, tapping off steam upstream of a pre-existing second boiler for use by the (e.g. stage of the) secondary turbine may reduce the mass flow rate of steam through the pre-existing second boiler. Therefore, this may reduce the pre-existing second boiler’s heat demand. Thus, tapping off steam for the (e.g. stage of the) secondary turbine downstream of the second boiler may reduce disruption to pre-existing processes associated with operation of the preexisting second boiler and / or the furnace.
[0045] In some embodiments, the second branch of the steam path is configured to split downstream of the stage of the secondary turbine into a continuation of the second branch, comprising the amine-based solvent heater, and a third branch. The second branch of the steam path may be configured to provide a third portion of the steam from the (e.g. stage of the) secondary turbine to the third branch of the steam path. The second branch of the steam path may be configured to provide a fourth portion of the steam from the (e.g. stage of the) secondary turbine to the amine-based solvent heater (e.g. to the continuation of the second branch). The third and fourth portions of the steam from the (e.g. stage of the) secondary turbine may be considered to be sub-portions of the second portion of steam. Splitting the steam path downstream of the (e.g. stage of the) secondary turbine may allow more steam to be provided to the (e.g. stage of the) secondary turbine than is required by the amine-based solvent heater. In some embodiments, more steam is required by the (e.g. stage of the) secondary turbine to generate enough electricity to power the carbon capture system than the mass flow rate of steam required by the amine-based solvent heater. Thus, providing more steam to the (e.g. stage of the) secondary turbine than is required by the amine-based solvent heater may enable the secondary turbine to generate enough electricity to power the carbon capture system. In such embodiments, the steam path may be configured to tap off only the mass flow rate of steam that is required for use by the amine-based solvent heater (e.g. the fourth portion of steam) from the outlet of the (e.g. stage of the) secondary turbine, while the rest of the steam (e.g. the third portion) is provided to the third branch of the steam path.
[0046] The third branch of the steam path may comprise a second stage of the secondary turbine. The (e.g. first) stage of the secondary turbine may be required to provide steam at an appropriate temperature and / or pressure for use by the amine-based solvent heater. Thus, the steam at the outlet of the (e.g. first) stage of the secondary turbine may still be at a high enough pressure and / or temperature for it to be used to generate electricity. If only a portion (the fourth portion) of the steam is provided to the amine-based solvent heater, the remaining steam (e.g. the third portion) can be used to generate more electricity. In some embodiments, the electricity demand of the carbon capture system may be satisfied by the combination of the electricity generated by the first and second stages of the secondary turbine.
[0047] In some embodiments, the carbon capture power station unit is configured to control a mass flow rate of the fourth portion of steam, provided to the amine-based solvent heater, based on a steam demand of the amine-based solvent heater.The steam demand of the amine-based solvent heater may vary based on the mass flow rate of the flue gas. The mass flow rate of the flue gas may be increased when more fuel is provided to the furnace. It may be desirable to increase the amount of fuel provided to the furnace when it is desirable to produce more electricity (e.g. when the electricity price is high). Conversely, it may be desirable to decrease the amount of fuel provided to the furnace when it is desirable to produce less electricity (e.g. when the electricity price is low). In some embodiments, the carbon capture power station unit may be configured to control the mass flow rate of the fourth portion of the steam based on: (i) an amount of fuel burned by the furnace and / or (ii) an electricity demand to be satisfied by the carbon capture power station unit.
[0048] In some embodiments, the carbon capture power station unit is configured to control a mass flow rate of the third portion of steam, provided to the third branch of the steam path, based on an electricity demand of the carbon capture system.
[0049] The electricity demand of the carbon capture system may vary based on the mass flow rate of the flue gas. In some embodiments, the carbon capture power station unit may be configured to control the mass flow rate of the third portion of the steam based on: (i) an amount of fuel burned by the furnace and / or (ii) an electricity demand to be satisfied by the carbon capture power station unit.
[0050] In some embodiments, the carbon capture power station unit is configured to control a mass flow rate of the second portion of steam based on at least one of: an electricity demand of the carbon capture system; and a steam demand of the amine-based solvent heater. The carbon capture power station unit may be configured to control a mass flow rate of the second portion of steam so as to ensure that enough steam is provided to the (e.g. first) stage of the secondary turbine to provide the required mass flow rate of steam to the amine-based solvent heater. The carbon capture power station unit may be configured to control a mass flow rate of the second portion of steam so as to ensure that enough steam is provided to the (e.g. stage of the) secondary turbine to generate enough electricity to power the carbon capture system. In some embodiments, the carbon capture power station unit may be configured to control the mass flow rate of the second portion of the steam based on: (i) an amount of fuel burned by the furnace and / or (ii) an electricity demand to be satisfied by the carbon capture power station unit.
[0051] In some embodiments, the carbon capture system is configured to be powered exclusively using electricity generated by the secondary turbine. Thus, the carbon capture system’s electricity requirement may be met without requiring electricity from any other sources. In some embodiments, the secondary turbine is configured to provide all of the electricity that it generates to power the carbon capture system (although this is not necessarily limited to embodiments in which the carbon capture system is powered exclusively using electricity generated by the secondary turbine). In such embodiments, there may be a reduced requirement (or in certain embodiments, no requirement at all) to provide additional capability to store, use or dissipate the electricity generated by the secondary turbine.
[0052] In some embodiments, (e.g. the stage of) the secondary turbine is configured to provide all of the steam used by the amine-based solvent heater to transfer heat to the amine-based solvent. Thus, it may not be necessary to provide any other sources of steam for the amine-based solvent heater. It will be understood that this arrangement is not necessarily limited to embodiments in which all of the steam from the (e.g. stage of the) secondary turbine is provided to the amine-based solvent heater. For instance, the (e.g. stage of the) secondary turbine may output more steam than is required by the amine-based solvent heater.The carbon capture power station unit may comprise a return path, configured to return the steam from one or more of the branches of the steam path to the boiler. This may allow the steam to be re-heated and re-used as part of a steam cycle.
[0053] In some embodiments, the furnace is configured to burn biomass to produce heat and flue gas. The production of biomass captures carbon from the atmosphere, and the carbon capture system is configured to capture carbon from the flue gas produced by burning biomass. Thus, embodiments of the carbon capture power station unit that are configured to burn biomass may be used to (i) generate electricity; and (ii) extract carbon from the atmosphere (e.g. so as to provide carbon negative electricity generation).
[0054] When viewed from a second aspect, the invention provides a biomass carbon capture power station unit, comprising:
[0055] a furnace, configured to burn biomass to produce heat and flue gas;
[0056] a boiler, configured to use the heat from the furnace to heat steam;
[0057] a carbon capture system, configured to use an amine-based solvent to capture carbon from the flue gas; and
[0058] a steam path, configured to receive at least some of the steam from the boiler, the steam path comprising:
[0059] a primary turbine, comprising one or more stages, wherein the one or more stages of the primary turbine are configured to receive steam and use the received steam to generate electricity; and
[0060] a secondary turbine, comprising one or more stages, wherein the one or more stages of the secondary turbine are configured to receive steam and use the received stream to generate electricity;
[0061] wherein the secondary turbine is configured provide at least some of the electricity that it generates to power the carbon capture system;
[0062] wherein the steam path is configured to split into a first branch, comprising a stage of the primary turbine, and a second branch, comprising a stage of the secondary turbine;
[0063] wherein the steam path is configured to provide a first portion of steam to the first branch, and to provide a second portion of steam to the second branch;
[0064] wherein the second branch further comprises an amine-based solvent heater for the carbon capture system, arranged downstream of the stage of the secondary turbine; and
[0065] wherein the amine-based solvent heater is configured to receive at least some of the steam from the stage of the secondary turbine, and transfer heat from the received steam to the amine-based solvent so as to release the captured carbon. A biomass carbon capture power station unit in accordance with the present invention is configured to use a secondary turbine to: (i) provide (e.g. at least some of) the power required by the carbon capture system; and (ii) provide (e.g. at least some of) the steam required to heat the amine-based solvent to release the captured carbon for storage (e.g. so as to allow re-use of the amine-based solvent to capture carbon from the flue gas).Furthermore, a biomass carbon capture power station unit according to the present invention may be used to (i) generate electricity; and (ii) extract carbon from the atmosphere (e.g. so as to provide carbon negative electricity generation).
[0066] It will be appreciated that any of the (e.g. optional) features of the first aspect of the present invention can be applied equally to the second aspect. Similarly, any of the benefits of the first aspect of the present invention may apply equally to the second aspect.
[0067] The second aspect of the invention extends to a power station comprising the biomass carbon capture power station unit.
[0068] BRIEF DESCRIPTION OF DRAWINGS
[0069] One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which:
[0070] Figure 1 shows a schematic diagram of a power station which has a carbon capture power station unit and another power station unit ;
[0071] Figure 2 shows a schematic diagram of a part of the carbon capture power station unit; and
[0072] Figure 3 shows a schematic diagram of an overview of the carbon capture power station unit.
[0073] DETAILED DESCRIPTION
[0074] Figure 1 shows a schematic diagram of a power station 100 which has a carbon capture power station unit 200 and another power station unit 300. In this example, the power station unit 300 is a biomass power station unit which is not (or not yet) fitted with a carbon capture system. However, in other examples it may be a different type of power station unit. For instance, the power station unit 300 may be a wind power station unit, a solar power station unit, etc.. The power station 100 may of course include further power station units (not shown), such as one or more further carbon capture power station units.
[0075] In this example, the carbon capture power station unit 200 is configured to generate electricity by burning biomass to heat steam, and using the heated steam to drive a primary turbine. While this carbon capture power station unit is designed to burn biomass, other types of carbon capture power station units may be designed to burn another type of fuel, e.g. natural gas or the like. In further examples, the power station 100 may only comprise a single power station unit, e.g. the carbon capture power station unit 200.
[0076] Figure 2 shows a schematic diagram of part of the carbon capture power station unit 200. In Figure 2, the flow of steam is represented as a solid line, and the flow of flue gas is represented as a dotted line.
[0077] The carbon capture power station unit 200 includes a primary turbine 210. The primary turbine 210 is a three-stage turbine, which has a high pressure turbine stage, an intermediate pressure turbine stage 212 and a low pressure turbine stage. Only the intermediate pressure turbine stage 212 is shown in Figure 2.Upstream of the intermediate pressure turbine stage 212 of the primary turbine 210, a path that the heated steam from the boiler follows (i.e. the steam path) splits to form a first branch 215 and a second branch 216. A first portion of steam is provided to the first branch 215, and a second portion of steam to the second branch 216. The first branch 215 of the steam path includes the intermediate pressure stage 212 of the primary turbine 210, and the second branch 216 of the steam path comprises a secondary turbine 220.
[0078] The intermediate pressure stage 212 of the primary turbine 210 is configured to receive the first portion of steam and expand the steam so as generate electricity. When the steam is expanded through the intermediate pressure turbine stage 212, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to a low pressure. The secondary turbine 220 is a two-stage turbine, which has an intermediate pressure turbine stage 221 and a low pressure turbine stage 222. The intermediate pressure stage 221 of the secondary turbine 220 is configured to receive the second portion of steam and expand the steam so as generate electricity. When the steam is expanded through the intermediate pressure turbine stage 212, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to a low pressure.
[0079] Downstream of the intermediate pressure stage 221 of the secondary turbine 220, the steam path splits again to form a continuation of the second branch 217, which comprises that low pressure stage 222 of the secondary turbine 220, and a third branch 218, which comprises an amine-based solvent heater 231.
[0080] The intermediate pressure stage 221 of the secondary turbine 220 is configured to provide a (third) portion of steam to the third branch 218 of the steam path (e.g. to the amine based-solvent heater 231), and a (fourth) portion of steam to the continuation of the second branch 217 (e.g. to the low pressure stage 222 of the secondary turbine 220). The third portion of steam and the fourth portion of steam are sub-portions of the (second portion) of steam provided to the intermediate pressure stage 221 of the secondary turbine 220 by the second boiler 203.
[0081] The low pressure stage 222 of the secondary turbine 220 is configured to receive the (fourth portion) of low pressure steam from the intermediate pressure stage 221 of the secondary turbine 220 and expand the steam so as generate electricity. When the steam is expanded through the low pressure turbine stage 222, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to a very low pressure.
[0082] The carbon capture power station unit 200 has a carbon capture system 230, which includes the secondary turbine 220 and an amine-based solvent heater 231. The carbon capture system 230 is configured to use an amine-based solvent to capture carbon from the flue gas produced by the furnace. Once the carbon has been captured by the amine-based solvent, the flue gas can be dispersed. This approach reduces carbon emissions from the power station unit 200.
[0083] After the carbon has been captured by the amine-based solvent, it is possible to release the captured carbon (e.g. for storage) by heating the amine-based solvent. The amine-based solvent heater 231 is configured to receive the (third) portion of steam from the intermediate pressure stage 221 of the secondary turbine 220, and transfer heat from the received (third portion of) steam to the amine-based solvent so as to release the captured carbon (e.g. for storage). Thus, the amine-based solvent can be re-used to capture more carbon from the flue gas.Figure 3 shows a schematic diagram of the carbon capture power station unit 200. The carbon capture power station unit 200 includes a furnace 201 , which is configured to burn biomass to produce heat and flue gas.
[0084] The carbon capture power station unit 200 includes a boiler 202, which is arranged at least partially within the furnace. The boiler 202 is configured to receive steam and use heat produced by the furnace 201 to heat the received steam to a higher temperature.
[0085] The carbon capture power station unit 200 includes a primary turbine 210. The primary turbine 210 is a three-stage turbine, which has a high pressure turbine stage 211 , an intermediate pressure turbine stage 212 and a low pressure turbine stage 213. The high pressure turbine stage 211 is configured to receive steam at a high temperature and a high pressure from the boiler and expand the steam so as generate electricity. When the steam is expanded through the high pressure turbine stage 211, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to an intermediate pressure. The carbon capture power station has a second boiler 203 (e.g. a re-boiler) which is arranged at least partially within the furnace. The second boiler 203 is configured to receive the intermediate pressure steam from the high pressure turbine stage 211, and use heat produced by the furnace 201 to heat the received steam to a higher temperature. This reheated intermediate pressure steam can be referred to as hot re-heat steam.
[0086] Downstream of the second boiler 203, a path that the steam follows (i.e. the steam path) splits to form a first branch 215 and a second branch 216. The second boiler 203 is configured to provide a first portion of steam to the first branch 215, and a second portion of steam to the second branch 216. The first branch 215 of the steam path includes the intermediate pressure stage 212 and the low pressure stage 213 of the primary turbine 210. The second branch 216 of the steam path comprises a secondary turbine 220.
[0087] The intermediate pressure stage 212 of the primary turbine 210 is configured to receive the first portion of the intermediate pressure, high temperature, steam from the second boiler 203 and expand the steam so as generate electricity. When the steam is expanded through the intermediate pressure turbine stage 212, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to a low pressure.
[0088] The low pressure stage 213 of the primary turbine 210 is configured to receive the low pressure steam from the intermediate pressure stage 212 of the primary turbine 210 and expand the steam so as generate electricity. When the steam is expanded through the low pressure turbine stage 213, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to a very low pressure.
[0089] The very low pressure steam from the low pressure stage 213 is returned to the boiler 202 so as to be re-used in the steam cycle. The return path, that the steam follows from the turbine back to the boiler 202, may include one or more condensation, heat exchange and / or evaporation stages so as to return the steam to the boiler 202 at an appropriate temperature and / or pressure for re-use.
[0090] As previously mentioned, the second branch of the steam path comprises a secondary turbine 220. The secondary turbine 220 is a two-stage turbine, which has an intermediate pressure turbine stage 221 and a low pressure turbine stage 222. The intermediate pressure stage 221 of the secondary turbine 220 is configured to receive the second portion of the intermediate pressure, high temperature, steam from the second boiler 203 and expand the steam so as generate electricity. When the steam is expanded through the intermediatepressure turbine stage 212, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to a low pressure.
[0091] Downstream of the intermediate pressure stage 221 of the secondary turbine 220, the steam path splits again to form a continuation of the second branch 217, which comprises that low pressure stage 222 of the secondary turbine, and a third branch 218, which comprises an amine-based solvent heater 231.
[0092] The intermediate pressure stage 221 of the secondary turbine 220 is configured to provide a (third) portion of steam to the third branch 218 of the steam path (e.g. to the amine based-solvent heater 231), and a (fourth) portion of steam to the continuation of the second branch 217 (e.g. to the low pressure stage 222 of the secondary turbine 220). The third portion of steam and the fourth portion of steam are sub-portions of the (second portion) of steam provided to the intermediate pressure stage 221 of the secondary turbine 220 by the second boiler 203.
[0093] The low pressure stage 222 of the secondary turbine 220 is configured to receive the (fourth portion) of low pressure steam from the intermediate pressure stage 221 of the secondary turbine 220 and expand the steam so as generate electricity. When the steam is expanded through the low pressure turbine stage 222, the temperature and the pressure of the steam is reduced. The pressure of the steam is reduced to a very low pressure.
[0094] The very low pressure steam from the low pressure stage 222 of the secondary turbine 220 is provided to the return path so as to be returned to the boiler 202 for re-use in the steam cycle.
[0095] The carbon capture power station unit 200 has a carbon capture system 230, which includes the secondary turbine 220 and an amine-based solvent heater 231. The carbon capture system 230 is configured to use an amine-based solvent to capture carbon from the flue gas produced by the furnace 201. Once the carbon has been captured by the amine-based solvent, the flue gas can be dispersed. This approach reduces carbon emissions from the power station unit 200.
[0096] After the carbon has been captured by the amine-based solvent, it is possible to release the captured carbon (e.g. for storage) by heating the amine-based solvent. The amine-based solvent heater 231 is configured to receive a (third) portion of steam from the intermediate pressure stage 221 of the secondary turbine 220, and transfer heat from the received (third portion of) steam to the amine-based solvent so as to release the captured carbon. Thus, the amine-based solvent can be re-used to capture more carbon from the flue gas.
[0097] The amine-based solvent heater 231 is configured to provide the (third portion of) steam to the return path after heat has been transferred from the (third portion of) steam to the amine-based solvent. The return path is configured to return the third portion of steam to the boiler 202 for re-use in the steam cycle.
[0098] The pressure of the steam from the intermediate pressure stage 221 of the secondary turbine 220 is different to the pressure of the steam from the intermediate pressure stage 212 of the primary turbine 210. The temperatures of the steam from the intermediate pressure stage 221 of the secondary turbine 220 may also be different to the temperature of the steam from the intermediate pressure stage 212 of the primary turbine 210.
[0099] The secondary turbine 220 has been designed such that the intermediate pressure stage 221 of the secondary turbine 220 is appropriate for use by the amine-based solvent heater 231 in order to provide the steam required to heat the amine-based solvent.The secondary turbine 220 has been designed to provide the electricity that it generates to the carbon capture system 230 in order to satisfy the carbon capture system’s electricity demand.
[0100] The electricity demand and the steam demand of the carbon capture system 230 vary based on the mass flow rate of flue gas produced by the furnace 201. In turn, the mass flow rate of flue gas produced by the furnace 201 is based on the amount of fuel, which in this example is biomass, burned by the furnace 201. However, the amount of fuel burned by the furnace is based on a desired amount of electricity to be produced by the carbon capture power station unit 200. Thus, ultimately, the electricity and steam demand of the carbon capture system 230 vary based on a desired amount of electricity to be produced by the carbon capture power station unit 200 as a whole.
[0101] Operation of the carbon capture power station 200 will now be explained in greater detail, with continued reference to Figure 3.
[0102] The carbon capture power station unit 200 is configured to control a mass flow rate of the second portion of steam from the second boiler 203 to the secondary turbine 220 based on the electricity demand of the carbon capture system 230 and the steam demand of the amine-based solvent heater 231. The total amount of steam is controlled to be sufficient to satisfy both the steam demand and electricity demand of the carbon capture system 230, both of which vary as the mass flow rate of flue gas varies.
[0103] The carbon capture power station unit 200 is configured to control a mass flow rate of the third portion of steam, provided to the amine-based solvent heater 231 , to satisfy the amine-based solvent heater’s steam demand. The remaining (fourth portion) of steam from the intermediate pressure stage 221 of the secondary turbine is provided to the low pressure stage 222 of the secondary turbine 220 to satisfy the remaining electricity demand (that has not already been met by the intermediate pressure stage 221). The electricity demand of the carbon capture system 230 can be satisfied by the combination of the electricity generated in the intermediate pressure stage 221 and the low pressure stage 222 of the secondary turbine 220.
[0104] The electricity demand and the steam demand of the carbon capture system 230 both vary based on the mass flow rate of flue gas produced by the furnace 201. However, the steam demand reduces more than the electricity demand as the mass flow rate of flue gas is reduced. Therefore, it is advantageous to control the mass flow rate of the second portion of steam and the third portion of steam independently so that the electricity and steam provided by the secondary turbine 220 can be matched to the electricity and steam demands of the carbon capture system 230, even as the demands change at different rates.
[0105] In this example, the two-stage secondary turbine 220 is controlled so as to provide only as much steam as is required to the amine-based solvent heater 231, and to generate only as much electricity is required by the carbon capture system 230.
[0106] In this example, the carbon capture system 230 is retrofitted to an existing power station unit 200. The pre-existing power station unit 200 had a pre-existing primary turbine 210, and the infrastructure was not in place to provide electricity directly from the primary turbine 210 to the carbon capture system 230. Thus, the provision of the secondary turbine 220 enables the carbon capture power station unit 200 to self-generate the electricity required by the carbon capture system 230 with limited disruption to the pre-existing primary turbine 210. Similarly, none of the steam from the pre-existing primary turbine 210 was suitable for use by the amine-based solvent heater 231. Thus, the intermediate pressure stage 221 of thesecondary turbine 220 is designed to provide steam at a suitable pressure and temperature for use by the amine-based solvent heater 231 , with limited disruption to the pre-existing power station unit 200.
[0107] There are various options for tapping off steam from the existing steam cycle to provide steam for the carbon capture system 230. These include: (i) tapping off high pressure steam directly from the boiler 202; (ii) tapping off relatively cold intermediate pressure steam at the outlet of high pressure turbine stage 211 of the primary turbine 210; (iii) tapping off steam from the second boiler 203 (which is the approach used in this example); and (iv) tapping of low pressure steam at the outlet of the intermediate pressure stage 212 of the primary turbine 210.
[0108] However, in this example, the steam at the outlet of the intermediate pressure stage 212 of the primary turbine 210 is not at a high enough pressure to meet the steam and electricity requirements of the carbon capture system 230 across the load range. The steam at the output of the high pressure turbine stage 211 is not at a high enough temperature to meet the carbon capture process steam and electricity demand across the whole load range. Furthermore, tapping off steam upstream of the pre-existing second boiler 203 would change the heat demand of the furnace 201, which would cause increased disruption to operation of the pre-existing power station unit 200 when the carbon capture system 230 is retrofitted. While steam taken directly from the boiler 202 would have enough energy to meet the carbon capture system’s steam and electrical requirements, tapping off steam at this point would also change the heat demand of the furnace 201 , as the mass flow rate of steam to the second boiler 203 would be reduced. Additionally, expanding the mass flow rate of steam required by the amine-based heater 231 directly from the boiler 202 to the temperature and pressure range required by the amine-based solvent heater 231 would generate significantly more electricity than the carbon capture system 230 requires.
[0109] Therefore, this approach would require the secondary turbine 220 to be configured to dissipate the excess energy or provide it elsewhere (e.g. to the national grid or to be stored). This would increase the complexity (and thus the cost) of the secondary turbine 220.
[0110] It will be appreciated that tapping off hot re-heat steam from the second boiler 203 avoids several of the disadvantages of tapping off steam from other places in the existing steam cycle.
[0111] By leveraging the existing steam cycle to provide the steam for driving the secondary turbine 220, the amount of new infrastructure required to meet the retrofitted carbon capture system’s 230 steam demand and electricity demand is reduced.
[0112] While this approach may result in less steam passing through the existing intermediate pressure stage 212 and low pressure stage 213 of the primary turbine 210, the proportion of the steam tapped off from the second boiler 203 in this example is small enough to avoid adverse impacts on downstream processes in the existing steam cycle.
[0113] A condenser is provided at the output of the low pressure stage 222 of the secondary turbine 220 to condense the steam at the output so as to provide a condensate that is suitable for return to the pre-existing steam / condensate cycle (e.g. a point along the return path). The temperature and the pressure of this condensate matches the temperature and the pressure of condensate at a certain point in the pre-existing return path closely enough that it can be re-integrated into the existing steam cycle at this point.
[0114] After heating the amines, the steam provided to the amine-based solvent heater 231 is also re-integrated into the existing steam / condensate cycle at a point along the return path. Asecond condenser is provided to condense the steam, and the condensate is re-integrated at a certain point in the existing steam / condensate cycle on the return path where the temperature and pressure of the condensate closely matches the temperature and the pressure of condensate in the pre-existing steam / condensate cycle.
[0115] By tapping off hot steam from the existing steam / condensate cycle after it has been heated by the furnace 201, and by re-integrating the condensate into the existing steam / condensate cycle before it is re-heated by the furnace 201 , the thermal demand of the furnace 201 is unchanged. This helps to minimise disruption to the combustion process, as the heat demand is unchanged.
[0116] The steam from the intermediate pressure stage 221 of the secondary turbine 220 is controlled by an adaptive steam turbine stage. This adaptive stage not only controls the steam flow, but also controls the pressure at the steam extraction point from which the steam for the amine-based solvent heater 231 is extracted.
[0117] It will be appreciated by those skilled in the art that this disclosure has been illustrated by describing one or more specific examples thereof, but is not limited to these examples; many variations and modifications are possible, within the scope of the accompanying claims.
Claims
CLAIMS1. A carbon capture power station unit, comprising:a furnace, configured to burn fuel to produce heat and flue gas;a boiler, configured to use the heat from the furnace to heat steam;a carbon capture system, configured to use an amine-based solvent to capture carbon from the flue gas; anda steam path, configured to receive at least some of the steam from the boiler, the steam path comprising:a primary turbine, comprising one or more stages, wherein the one or more stages of the primary turbine are configured to receive steam and use the received steam to generate electricity; anda secondary turbine, comprising one or more stages, wherein the one or more stages of the secondary turbine are configured to receive steam and use the received steam to generate electricity;wherein the secondary turbine is configured to provide at least some of the electricity that it generates to power the carbon capture system;wherein the steam path is configured to split into a first branch, comprising a stage of the primary turbine, and a second branch, comprising a stage of the secondary turbine;wherein the steam path is configured to provide a first portion of steam to the first branch, and to provide a second portion of steam to the second branch;wherein the second branch further comprises an amine-based solvent heater for the carbon capture system, arranged downstream of the stage of the secondary turbine; andwherein the amine-based solvent heater is configured to receive at least some of the steam from the stage of the secondary turbine, and transfer heat from the received steam to the amine-based solvent so as to release the captured carbon.
2. The carbon capture power station unit of claim 1 , wherein the steam path further comprises a preceding stage of the primary turbine, upstream of a position where the steam path splits into the first brand and the second branch.
3. The carbon capture power station unit of claim 1 or claim 2, wherein the steam path further comprising a second boiler, upstream of the stage of the secondary turbine, configured to use the heat from the furnace to re-heat at least the first portion of steam.
4. The carbon capture power station unit of any preceding claim, wherein the second branch of the steam path is configured to split downstream of the stage of the secondary turbine to provide a continuation of the second branch, comprising the amine-based solvent heater, and a third branch;wherein the second branch of the steam path is configured to:provide a third portion of the steam from the stage of the secondary turbine to the third branch of the steam path; andprovide a fourth portion of the steam from the stage of the secondary turbine to the amine-based solvent heater;wherein the third portion of steam and the fourth portion of steam are subportions of the second portion of steam.
5. The carbon capture power station unit of claim 4, wherein the third branch of the steam path comprises a second stage of the secondary turbine.
6. The carbon capture power station unit of any of claim 4 or claim 5, wherein the carbon capture power station unit is configured to control a mass flow rate of the fourth portion of steam, provided to the amine-based solvent heater, based on a steam demand of the amine-based solvent heater.
7. The carbon capture power station unit of any preceding claim, wherein the carbon capture power station unit is configured to control a mass flow rate of the second portion of steam based on at least one of:an electricity demand of the carbon capture system; anda steam demand of the amine-based solvent heater.
8. The carbon capture power station unit of any preceding claim, wherein the carbon capture system is configured to be powered exclusively using electricity generated by the secondary turbine.
9. The carbon capture power station unit of any preceding claim, wherein the secondary turbine is configured to provide all of the electricity that it generates to power the carbon capture system.
10. The carbon capture power station unit of any preceding claim, wherein the secondary turbine is configured to provide all of the steam used by the amine-based solvent heater to transfer heat to the amine-based solvent.
11. The carbon capture power of any preceding claim, further comprising a return path, configured to return the steam from one or more of the branches of the steam path to the boiler.
12. The carbon capture power station unit of any preceding claim, wherein the furnace is configured to burn biomass to produce heat and flue gas.
13. A biomass carbon capture power station unit, comprising:a furnace, configured to burn biomass to produce heat and flue gas;a boiler, configured to use the heat from the furnace to heat steam;a carbon capture system, configured to use an amine-based solvent to capture carbon from the flue gas; anda steam path, configured to receive at least some of the steam from the boiler, the steam path comprising:a primary turbine, comprising one or more stages, wherein the one or more stages of the primary turbine are configured to receive steam and use the received steam generate electricity; anda secondary turbine, comprising one or more stages, wherein the one or more stages of the secondary turbine are configured to receive steam and use the received steam to generate electricity;wherein the secondary turbine is configured to provide at least some of the electricity that it generates to power the carbon capture system;wherein the steam path is configured to split into a first branch, comprising a stage of the primary turbine, and a second branch, comprising a stage of the secondary turbine;wherein the steam path is configured to provide a first portion of steam to the first branch, and to provide a second portion of steam to the second branch;wherein the second branch further comprises an amine-based solvent heater for the carbon capture system, arranged downstream of the stage of the secondary turbine; andwherein the amine-based solvent heater is configured to receive at least some of the steam from the stage of the secondary turbine, and transfer heat from the received steam to the amine-based solvent so as to release the captured carbon.