Method for operating a plant to provide carbon dioxide

Abstract

The present invention relates to a plant (1) for providing carbon dioxide (CO2), comprising a separation plant (2), which is fluidically connected to a gas mixture (4) consisting of flue gas and carbon dioxide (CO2), and which is designed to separate the carbon dioxide (CO2) and water vapor (H2O), hereinafter simply referred to as carbon dioxide, contained in the flue gas, in such a way that the water is not condensed by a stripper or a regenerator top condenser before entering a preheater (6), and in operation the separation plant (2) can be operated with steam from a steam line (7), and further comprises a first carbon dioxide line (5), which is fluidically connected to the separation plant (2) and from which the carbon dioxide (CO2) separated in the separation plant (2) flows in operation, and further comprises a preheater (6) through which the carbon dioxide line (5) is guided and through which the temperature of the carbon dioxide (CO2) is increased, and It further comprises a multi-stage compressor (13), which is fluidically connected on the inlet side with the carbon dioxide line (12) coming out of the preheater (6), and after a stage (30) the temperature and pressure of the carbon dioxide (CO2) are increased, after which the carbon dioxide (CO2) is guided through a line (14) to a steam generator (15), which in turn uses water (31) fed to the steam generator (15) to convert the thermal energy of the carbon dioxide (CO2) coming out of the compressor (13) after the stage (30). the carbon dioxide cooled in the steam generator (15) is returned to the compressor (13) for the next stage, the steam generated in the steam generator (15) is fluidically connected to a separation plant (2) via a steam line (7), and the carbon dioxide (CO2) leaving the compressor (13) after this stage flows through a separator (32) which is designed to separate the water (45) condensed in the final steam generator (15).

Description

[Technical Field]

[0001] The present invention relates to a plant and a method for operating a plant.

[0002] The present invention relates in particular to a plant and method for separating and processing carbon dioxide (CO2) for transportation in pipelines.

[0003] It is known that carbon dioxide (CO2) emissions from power plant operations and other processes need to be reduced, and in this case CO2 separation is seen as a key element in achieving the global goal of reducing CO2 emissions to the lowest possible levels.

[0004] The International Energy Agency (IEA) predicts that to meet climate targets, the amount of CO2 sequestered could increase from the current 50 million tonnes per year to 7.6 billion tonnes per year by 2050.

[0005] The only currently commercially available large-scale technology for separating carbon dioxide (CO2) from exhaust gases, such as flue gas, is the amine system. Amine systems require significant amounts of low-pressure steam, and therefore heat, for the process, which is very costly. This often makes CO2 separation economically unattractive to operators.

[0006] A further aspect is that after sequestration, carbon dioxide (CO2) often needs to be transported over long distances if there are no storage or recycling facilities nearby, for which pipeline transportation in the supercritical phase is often considered a good approach. To get carbon dioxide (CO2) into the supercritical phase, it needs to be compressed from near atmospheric pressure to supercritical pressure (above 73 bar and 31°C), typically 100-200 bar.

[0007] During compression, a significant amount of heat is released, which currently remains unused due to the low temperature levels.

[0008] Depending on how the amine system is used, there are a variety of potential heat sources. Some processes are exothermic, so that the waste heat stream can be utilized for low-pressure (LP) steam processing. However, if this is not the case and there is no alternative heat source, a fuel-fired or electric boiler must be installed. Often, natural gas boilers are used, which consume large amounts of gas and also generate additional carbon dioxide (CO2), which must also be separated, thus making the energy and investment requirements for the amine system even higher.

[0009] Regarding the heat of compression, it is effective to utilize it rationally and, in some cases, combine it with the LP steam processing required for the amine plant. However, it is first necessary to convert low-quality heat into high-quality heat. One possible approach is to use fewer intercoolers between compression stages, so that the carbon dioxide (CO2) is cooled only when it is above a temperature at which the heat can be used for LP steam processing. However, the carbon dioxide (CO2) is then cooled again to ambient temperature, so that the amount of steam that can be produced is relatively small and the heat is only partially utilized. If one expects to utilize 100% of the heat and maximize steam production, a high-temperature heat pump can be used. However, this involves significantly higher investment costs and space requirements.

[0010] Carbon dioxide (CO2) leaving an amine system generally contains a small amount of water vapor. This is achieved by designing the amine system with a desorber top condenser (German: Desorber-Top-Kondensator). In the desorber top condenser, the water vapor contained in the carbon dioxide (CO2) is condensed. However, the latent heat of the water vapor remains unused.

[0011] The present invention is based on the idea that the regeneration tower top condenser can be omitted. This means that the carbon dioxide (CO2) leaving the amine system has a relatively high proportion of water vapor. Typically, this mixture contains about 50 mol% water and 50 mol% carbon dioxide (CO2), has a pressure between 1 and 4 bar, and a temperature between 90 and 130°C. Summary of the Invention [Problem to be solved by the invention]

[0012] Against this background, the object of the present invention is to provide a plant and a method for the cost-optimal production of carbon dioxide (CO2).

[0013] A further object of the present invention is to maximize heat recovery for low pressure (LP) steam processing at the lowest possible cost and space requirements. [Means for solving the problem]

[0014] The object is to provide a plant for providing carbon dioxide (CO2), which comprises a separation plant, which is fluidically connected to a gas mixture consisting of flue gas and carbon dioxide (CO2), and which is designed so that the carbon dioxide (CO2) contained in the flue gas is separated, and in operation the separation plant can be operated with steam from a steam line, The stripper or regenerator top condenser in the separation plant (2) is omitted, and further comprises a first carbon dioxide line (5) which is fluidically connected to the separation plant and from which the carbon dioxide (CO2) separated in the separation plant flows during operation, and further comprises a preheater (6) through which the carbon dioxide line passes and which is designed to increase the temperature of the carbon dioxide (CO2), and further comprises a multi-stage compressor (13) which is fluidically connected on the inlet side to the carbon dioxide line coming out of the preheater and which increases the temperature and The problem is solved by a plant in which the water is cooled in the steam generator and the pressure is increased, after this stage the carbon dioxide (CO2) is guided through a line through a steam generator, the steam generator is designed in such a way that the water supplied to the steam generator generates steam by energy exchange with the thermal energy of the carbon dioxide (CO2) leaving the compressor after one stage, the carbon dioxide cooled in the steam generator is returned to the compressor for the next stage, the steam generated in the steam generator is fluidically connected to a separation plant via a steam line, the carbon dioxide (CO2) leaving the compressor after this stage flows through a first separator, the separator is designed in such a way that it dehydrates the carbon dioxide (CO2) leaving the compressor stage.

[0015] The problem with this method is solved by the following steps: - fluidically feeding a gas mixture consisting of flue gas and carbon dioxide (CO2) to a separation plant, - separating carbon dioxide (CO2) and water vapor (H2O) in a separation plant, - supplying a mixture of carbon dioxide (CO2) and water vapor (H2O) to a preheater and heating the mixture in the preheater; - further transferring the mixture heated in the preheater to a first stage of a multi-stage compressor, and increasing the pressure and temperature of the mixture in the first stage; - further transferring the heated mixture after the first stage to a steam generator and utilizing the thermal energy of the mixture to generate steam in the steam generator; - performing a return step, in which the carbon dioxide (CO2) cooled in the steam generator is sent to another stage of the compressor, in which the temperature and pressure of the carbon dioxide (CO2) are increased; - further transferring the heated carbon dioxide (CO2) after another stage to another steam generator and utilizing the thermal energy of the carbon dioxide (CO2) to generate steam in the other steam generator; - repeating the return steps until the final stage; - further transporting the carbon dioxide (CO2) exiting after the last stage through a preheater; - further transferring the carbon dioxide (CO2) exiting the preheater to an outlet line; - The steam generated in the steam generator is hydraulically connected to the separation plant via a steam line, Separator and dehydration units are arranged between the compressor stages, the separator being designed to separate the condensed water and the dehydration unit being designed to remove the residual water fraction in the carbon dioxide.

[0016] An essential feature of the present invention is a compressor that typically contains 6 to 8 stages for compression from atmospheric pressure to supercritical pressure, which means that the compression and steam treatment process in the waste heat boiler (HRSG) actually proceeds multiple times, depending on the final number of stages required to reach the outlet pressure.

[0017] The preheater and all further downstream connected components are used only once, regardless of the number of stages.

[0018] According to the present invention, the carbon dioxide (CO2) is only cooled to the extent that the heat can still be utilized for steam processing in the waste heat boiler. This temperature is typically 5-10°C higher than the final temperature of the steam required for the amine system, depending on the final design of the heat exchangers. However, this means that the carbon dioxide (CO2) is not cooled back down to ambient temperature before it reaches the next compressor stage. This allows for steam processing after each compression stage with the same number of heat exchangers / HRSGs as in conventional operation.

[0019] However, in practice, this process can only begin after the second or even third stage of the compressor, because the carbon dioxide (CO2) must first be heated from the atmospheric discharge temperature downstream of the amine system to a usable temperature level. Now, to further maximize steam processing, the high-temperature carbon dioxide (CO2) downstream of the last HRSG can be used to preheat the carbon dioxide (CO2) at the compressor inlet to a usable temperature level, so that the entire compressor from suction to outlet is operated at a temperature level capable of processing steam, and so that steam processing can begin already after the first compressor stage.

[0020] According to the present invention, the high water content of the carbon dioxide (CO2) leaving the amine system is not reduced before entering the compressor. To this end, in typical today's configurations, a so-called stripper or regenerator top condenser is used to condense out a large amount of water already before the compressor. The present invention envisions omitting this condenser. The condenser is typically part of a separation plant. This allows the latent heat of the condensing steam to be captured at a usable temperature level in the steam generator for steam processing between compressor stages. Condensation begins in the steam generator after the compression stage, which compresses the stream to above approximately 15 bar. The condensed water is separated in a separator after the corresponding heat exchanger / HRSG.

[0021] The stream then proceeds to the next process stage where, during cooling in a steam generator, further water is condensed and therefore separated, and it is then finally dehydrated in a dehydration system to a final acceptable water content (e.g. for pipelines) (typically triethylene glycol, but other technologies may be applicable).

[0022] Typically, the stream must be cooled again to near ambient temperature in order to enter the dehydration system. Because the stream in the steam generator can only be cooled to about 5-10°C above steam temperature, the stream after the steam generator or separator still contains significant heat, which is utilized to preheat the stream at the compressor inlet to maximize steam production.

[0023] The dried carbon dioxide leaving the drying system is still at ambient temperature level. To improve heat recovery also in the last process step, the carbon dioxide is reheated to a usable temperature level by the stream leaving the compressor which needs to be cooled again to ambient temperature.

[0024] This solution significantly reduces the energy requirements of the amine system, which results in fuel savings if fossil fuels are used, depending on the alternative heat source, and also in carbon dioxide (CO2) savings, and therefore in this regard also in capital investment savings for the amine system, since less carbon dioxide (CO2) needs to be separated, while no additional machinery is needed, and only some additional drive power is required.

[0025] Advantageous further configurations are set forth in the dependent claims.

[0026] An advantage of the present invention is that it maximizes the heat utilization and recovery of the heat of compression of carbon dioxide (CO2) with little additional machinery and additional space requirements.

[0027] An additional benefit is the reduction in external heat requirements for LP vapor processing for amine systems.

[0028] A further benefit comes from significant savings in cooling water for the carbon dioxide (CO2) compressor, since the feed water for the steam treatment of the amine system is used for intercooling.

[0029] A further benefit is gained from potential carbon dioxide (CO2) reductions when fossil fuels are used as the heat source for the boiler.

[0030] The above-mentioned characteristics, features and advantages of the present invention, as well as the manner in which they are accomplished, will be more clearly and more clearly understood in connection with the following description of the embodiments which are set forth in more detail in connection with the drawings.

[0031] Here, identical components or components having the same functions are denoted by the same reference numerals.

[0032] In the following, embodiments of the present invention will be described with reference to the drawings, which are not intended to represent the embodiments to scale; rather, the drawings, when used for illustration, are shown in a schematic and / or slightly distorted form. For supplementary teachings readily discernible in the drawings, reference is made to the relevant prior art. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows a schematic diagram of an embodiment of a plant according to the invention.

[0034] FIG. 1 shows a schematic diagram of an embodiment of a plant 1 according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] The plant 1 is designed to provide carbon dioxide (CO2) and includes a separation plant 2. The separation plant 2 is fluidically connected via a line 4 with a gas mixture 44 consisting of flue gas and carbon dioxide (CO2). The separation plant 2 is designed so that the carbon dioxide (CO2) contained in the flue gas 44 is separated. The separated carbon dioxide (CO2) flows from the separation plant 2 via a first carbon dioxide line 5 through a preheater 6. In the preheater 6, the temperature of the carbon dioxide (CO2) is increased.

[0036] The first carbon dioxide line 5 is fluidically connected to the separation plant 2, which is here designed as an amine plant. However, the carbon dioxide (CO2) leaving the separation plant is still mixed with a relatively large amount of water vapor. The ratio between the carbon dioxide (CO2) and the water vapor can be about 50 mol % water and 50 mol % CO2 here. The water vapor contained in the carbon dioxide (CO2) therefore still contains thermal energy, which is utilized according to the invention.

[0037] In operation, separation plant 2 is powered by steam from steam line 7. If fossil fuel is used, carbon dioxide (CO2) 46 generated in boiler 8 is also optionally supplied to separation plant 2 via line 10. Steam produced in boiler 8 is sent to separation plant 2 via line 11.

[0038] The carbon dioxide (CO2) heated downstream of the preheater 6 is fed via line 12 to a multistage compressor 13, which is fluidically connected on the inlet side to the carbon dioxide line 5 emerging from the preheater 6.

[0039] In the compressor 13, heated carbon dioxide (CO2) is fed to a first stage 30 where the temperature and pressure of the carbon dioxide (CO2) is increased.

[0040] After the first stage 30, the carbon dioxide (CO2) is fed via line 14 to a steam generator 15, which can be designed as a HRSG (Heat Recovery Steam Generator).

[0041] The steam generator 15 is designed so that the water 47 supplied to the steam generator 15 is converted into steam by energy exchange with the thermal energy of carbon dioxide (CO2) leaving the compressor 13 after stage 30.

[0042] The compressor 13 has 5 to 10, in particular 6 to 9, very in particular 7 or 8 stages.

[0043] The carbon dioxide (CO2) cooled in the steam generator 15 is returned to stage 30 via line 16 to the compressor 13. This is done multiple times, i.e. the carbon dioxide (CO2) is flowed through multiple stages in the process stage 30, after each stage the thermal energy of the carbon dioxide (CO2) is used to generate steam in the steam generator 15. For clarity, Figure 1 only shows the compressor stage 30, the steam generator 15, one line 14 to the steam generator 15, and one line 16 from the steam generator 15 to the compressor 13 and process stage 30. For clarity, the individual lines to the steam generator 15 and back to the compressor 13 have not been shown.

[0044] In the final steam generator 15, a significant amount of the water vapor contained in the carbon dioxide begins to condense. Before the carbon dioxide (CO2) flows through stage 34 of compressor 13, the carbon dioxide (CO2) flows through separator 32. In separator 32, water 45 is separated from the carbon dioxide (CO2) and discharged via line.

[0045] The steam generated in the steam generator 15 and in the further steam generator 36 is fluidically connected to the separation plant 2 via a steam line 7 .

[0046] The carbon dioxide (CO2) leaving the compressor 13 after stage 34 flows through the preheater 6 via line 17. Before the carbon dioxide (CO2) flows through the preheater 6, the carbon dioxide (CO2) flows through a second separator 37. In the second separator 37, water 45 is separated from the carbon dioxide (CO2) and discharged via line 45.

[0047] Downstream of the preheater 6, the carbon dioxide (CO2) flows through a dehydration unit 38, which is designed to dehydrate the carbon dioxide (CO2) emerging from the preheater 6. Here, water 45 separated in the dehydration unit 38 is discharged via a dehydration line.

[0048] The additional dehydration unit 38 is designed, for example, as a triethylene glycol (TEG) system.

[0049] The carbon dioxide (CO2) exiting downstream of the additional dehydration unit 38 flows through another preheater 39, where the temperature of the carbon dioxide (CO2) is increased. Downstream of the preheater 39, the carbon dioxide (CO2) flows through the next stage 40 of the compressor 13, where the temperature and pressure of the carbon dioxide (CO2) are increased.

[0050] The thermal energy of the carbon dioxide (CO2) is used in another steam generator 42 to generate steam for the separation plant 2.

[0051] Subsequently, the carbon dioxide (CO2) produced and provided in the plant 1 is processed for transportation, for example, in a pipeline 33. [Explanation of symbols]

[0052] 1...plant, 2...separation plant, 4...line, 5...first carbon dioxide line, 6...preheater, 7...steam line, 8...boiler, 10...line, 12...line, 13...multistage compressor, 14...line, 15...steam generator, 16...line, 17...line, 30...first stage, 33...pipeline, 34...stage, 37...second separator, 38...dehydration unit, 39...further preheater, 40...stage, 42...steam generator, 44...flue gas, 45...water, 46...carbon dioxide, 47...water

Claims

1. Carbon dioxide (CO ), including a separation plant (2). ２ ), wherein the separation plant (2) separates flue gas and carbon dioxide (CO ２ ) and the separation plant (2) is fluidically connected to a gas mixture (4) consisting of carbon dioxide (CO ２ ) and water vapor (H ２ O) is designed to be separated, In operation, the separation plant (2) can be operated with steam from a steam line (7), The system further includes a first carbon dioxide line (5), which is fluidically connected to the separation plant (2) and from which the carbon dioxide (CO 2 ) separated in the separation plant (2) is delivered. ２ ) flows out during operation, It further comprises a preheater (6) through which the carbon dioxide line (5) is guided and through which the carbon dioxide (CO ２ ) is designed to increase the temperature of It also includes a multi-stage compressor (13), which is fluidically connected at its inlet side to the carbon dioxide line (12) coming out of the preheater (6), After step (30), the carbon dioxide (CO ２ ) is increased in temperature and pressure, After the step (30), the carbon dioxide (CO ２ ) is guided through a line (14) through a steam generator (15), The steam generator (15) is adapted to convert the water (31) fed to the steam generator (15) into the carbon dioxide (CO 2 ) coming out of the compressor (13) after step (30). ２ ) to generate steam by energy exchange with the thermal energy of the The carbon dioxide cooled in the steam generator (15) is returned to the compressor (13) for further processing; the steam generated in the steam generator (15) is fluidically connected to the separation plant (2) via the steam line (7), The carbon dioxide (CO ) leaving the compressor (13) after the first process stage ２ ) flows through a first separator (32), which is designed to separate the water condensed in the final steam generator (15), Plant (1).

2. The carbon dioxide (CO ２ ) is being processed for transportation in a pipeline (33), A plant (1) according to claim 1.

3. the separation plant (2) is designed as an amine plant, A plant (1) according to claim 1 or 2.

4. the compressor (13) has 5 to 10, in particular 6 to 9, very in particular 7 or 8 stages, A plant (1) according to claim 1, 2 or 3.

5. Downstream of the first separator (32) is a next stage (34) of the compressor (13), in which the carbon dioxide (CO ２ ) is increased in temperature and pressure, Downstream of the next stage (34), the carbon dioxide (CO ２ ) is guided through a line (35) through another steam generator (36), The further steam generator (36) is configured to convert the water supplied to the further steam generator (36) into the carbon dioxide (CO 2 ) coming out of the compressor (13) after the next stage (34). ２ ) to generate steam by energy exchange with the thermal energy of the The carbon dioxide cooled in the steam generator (36) is returned to the compressor (13). A plant (1) according to any one of claims 1 to 4.

6. the carbon dioxide (CO2) leaving the compressor (13) after the next stage (34) flows through a second separator (37) designed to separate the water condensed in the steam generator (36); A plant (1) according to claim 5.

7. an additional dehydration unit (38) fluidically coupled to the preheater (6), A plant (1) according to any one of claims 1 to 6.

8. the additional dehydration unit (38) is designed as a triethylene glycol (TEG) system; A plant (1) according to claim 7.

9. a further preheater (39) fluidically coupled to said additional dehydration unit (38), A plant (1) according to claim 7 or 8.

10. the compressor (13) has an additional stage (40) fluidically coupled to the further preheater (39), in which the temperature and pressure of the carbon dioxide (CO2) are increased; A plant (1) according to claim 9.

11. After the additional step (40), the carbon dioxide (CO ２ ) is guided through a line (41) through a steam generator (42), The steam generator (42) is configured to convert the water (43) supplied to the steam generator (42) into the carbon dioxide (CO 2 ) coming out of the compressor (13) after the additional step (40). ２ ) to generate steam by energy exchange with the heat energy of the The carbon dioxide cooled in the steam generator (42) is then returned to the compressor (13) in a next step. A plant (1) according to claim 10.

12. Carbon dioxide (CO ２ 1. A method for providing a Steps below: - Flue gas and carbon dioxide (CO ２ ) and a gas mixture (44) hydraulically feeding the gas mixture (44) to a separation plant (2), - the carbon dioxide (CO ２ ) and water vapor (HO) in said separation plant (2), - the carbon dioxide (CO ２ ) is supplied to a preheater (6), and the carbon dioxide (CO ２ ) in said preheater (6), the carbon dioxide (CO ２ ) is further transferred to the first stage (30) of a multi-stage compressor (13), and said carbon dioxide (CO ２ ) in said first stage (30), - the heated carbon dioxide (CO ２ ) after said first stage (30) is further transferred to a steam generator (15), and said carbon dioxide (CO ２ Utilizing the thermal energy of the steam generator (15) to generate steam in the steam generator (15); - carrying out a return step, in which the carbon dioxide (CO 2 ) cooled in the steam generator (15) is returned; ２ ) to another stage (34) of the compressor (13), where the carbon dioxide (CO ２ increasing the temperature and pressure of the - the heated carbon dioxide (CO ２ ) after said further stage (34) is further transferred to another steam generator (36), and said carbon dioxide (CO ２ Utilizing the thermal energy of the steam generator (36) to generate steam in the steam generator (36); - repeating the returning step until the last stage; the carbon dioxide (CO ２ ) further transporting the mixture through said preheater (6), the carbon dioxide (CO ２ ) further transferred to an outlet line; and the steam generated in the steam generator (15, 36, 42) is fluidically connected via the steam line (7) with the separation plant (2), - a separator (32, 37) and a dehydration unit (38) are arranged between the stages (30, 34, 40) of the compressor (13), the separator (32, 37) being designed to separate the condensed water (45) and the dehydration unit (38) being designed to remove the residual water proportion (45) in the carbon dioxide.

13. An additional dehydration unit (38) is arranged downstream of the preheater (6). The method of claim 12.

14. the additional dehydration unit (38) is designed as a triethylene glycol (TEG) system; A plant (1) according to claim 13.

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