Method for operating plant for providing carbon dioxide
By eliminating the top condenser of the desorption tower and combining with a multi-stage compressor and a steam generator, efficient separation and compression of carbon dioxide is achieved, and the problem of insufficient heat utilization in the prior art is solved, energy consumption and cost are reduced, and heat recovery efficiency is improved.
Patent Information
- Application Number
- CN202380082886.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-12-02
- Filing Date
- 2023-11-06
- Publication Date
- 2025-07-11
AI Technical Summary
In the prior art, there are problems of high energy consumption, cost-intensive and insufficient heat utilization during separation of carbon dioxide and long-distance transportation, especially in the absence of alternative heat sources, fuel combustion boilers or electric combustion boilers are required, resulting in additional carbon dioxide emissions and high investment demands.
By eliminating the top condenser of the desorption tower, using a mixture of carbon dioxide and water vapor from the amine system, a combination of multi-stage compressors and steam generators is used to maximize the recovery and utilization of heat, including the integration of preheaters, multi-stage compressors, steam generators and separators, ensuring that the carbon dioxide is not cooled to atmospheric temperature during the compression process until it enters the next compression stage.
It significantly reduces the energy demand and cooling water consumption of carbon dioxide compressors, reduces fuel consumption, reduces CAPEX, maximizes heat utilization and efficient steam production, and reduces carbon dioxide emissions.
Smart Images
Figure CN120303047A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a facility and a method for operating a facility.
[0002] The present invention particularly relates to a facility and a method for separating and processing carbon dioxide (CO2) for transportation in a pipeline. Background Art
[0003] It is known that carbon dioxide (CO2) emissions from the operation of power plants and other processes must be reduced. CO2 separation is regarded as an important factor in achieving the global goal of minimizing CO2 emissions as much as possible.
[0004] The International Energy Agency (IEA) predicts that the amount of CO2 separated could increase from the current 50 million tons per year to 7.6 billion tons per year by 2050 in order to achieve climate goals.
[0005] In order to separate carbon dioxide (CO2) from waste gases, such as in flue gas, the only technology that is currently commercially and widely available is the amine system. The amine system requires large amounts of low-pressure steam, thus requiring heat for the process, and is rather cost-intensive, which makes CO2 separation generally economically unattractive for operators.
[0006] On the other hand, after separation, when a storage or application is not nearby, carbon dioxide (CO2) usually has to be transported over long distances. For this purpose, pipeline transportation in the supercritical phase is generally regarded as a good option. In order to bring carbon dioxide into the supercritical phase, the carbon dioxide must be compressed from almost atmospheric pressure to the supercritical pressure (above 73 bar and 31 °C), typically between 100 bar and 200 bar.
[0007] A large amount of heat is released during compression, and currently, due to the low temperature level, this heat is not utilized.
[0008] According to the method using an amine system, there are different potential heat sources. Some processes are exothermic, such that waste heat streams can be used for low-pressure (ND) steam production. However, if this is not the case and there is no alternative heat source, a fuel-fired boiler or an electric boiler must be installed. Natural gas boilers, which typically consume large amounts of gas and additionally produce additional carbon dioxide (CO2), are usually used, and this carbon dioxide also has to be separated, thereby causing higher energy and investment requirements for the amine system.
[0009] For compression heat, the compression heat needs to be utilized reasonably and can be combined with the preparation of ND steam required by the amine facility. However, first of all, the low-value heat must be converted into high-value heat. A feasible solution is to use fewer intermediate coolers between the compression stages, so that carbon dioxide (CO2) is only cooled when it is above the temperature at which the heat can be used for the preparation of ND steam. However, the carbon dioxide (CO2) is then cooled again to the ambient temperature, so that the amount of steam that can be produced is relatively low and the heat is only partially utilized. If the heat should be utilized 100% and the steam production should be maximized, a high-temperature heat pump can be used. However, this requires significantly higher investment costs and space requirements.
[0010] Carbon dioxide (CO2) from the amine system usually has a small amount of water vapor. This is achieved by configuring the amine system with a top condenser of the desorption column. In the top condenser of the desorption column, the water vapor contained in the carbon dioxide (CO2) is condensed. However, the latent heat of the water vapor is not utilized here. Summary of the Invention
[0011] The present invention now starts from the concept that the top condenser of the desorption column can be omitted. This means that the carbon dioxide (CO2) from the amine system has a relatively high proportion of water vapor. Typically, the mixture contains about 50 mol% water and 50 mol% carbon dioxide (CO2), and has a pressure between 1 bar and 4 bar and a temperature between 90 °C and 130 °C.
[0012] In this context, the object of the present invention is to provide a facility and method for providing carbon dioxide (CO2) in an optimal cost-effective manner.
[0013] Another object of the present invention is to maximize the heat recovery for the preparation of low-pressure (ND) steam with the smallest possible cost and space requirements.
[0014] The stated object is achieved by a facility for providing carbon dioxide (CO₂), the facility comprising a separation facility, wherein the separation facility is fluidly connected to a gas mixture stream consisting of flue gas and carbon dioxide (CO₂), wherein the separation facility is configured such that the carbon dioxide (CO₂) contained in the flue gas is separated, wherein during operation the separation facility can be operated with steam from a steam line, wherein a stripping column or a top condenser of a desorber is omitted in the separation facility (2); the facility further comprises a first carbon dioxide line, which is fluidly connected to the separation facility, and the carbon dioxide separated in the separation facility flows out of the first carbon dioxide line during operation; the facility further comprises a preheater, through which the carbon dioxide line is guided and which is configured such that the temperature of the carbon dioxide (CO₂) is increased; the facility further comprises a multi-stage compressor, which is fluidly connected to the carbon dioxide line emerging from the preheater on the inlet side, wherein after one stage, the temperature and pressure of the carbon dioxide (CO₂) are increased, wherein after this stage, the carbon dioxide (CO₂) is guided through a steam generator via a line, wherein the steam generator is configured such that water fed into the steam generator generates steam by means of an energy exchange with the thermal energy of the carbon dioxide (CO₂) emerging from the compressor after this stage, wherein the carbon dioxide cooled in the steam generator is guided back to the next stage in the compressor, wherein the steam generated in the steam generator is fluidly connected to the separation facility via a steam line, wherein the carbon dioxide (CO₂) flowing out of the compressor after this stage flows through a first separator, wherein the separator is configured to dehydrate the carbon dioxide (CO₂) emerging from the stage of the compressor.
[0015] The object of the method is achieved by the following steps:
[0016] - Transporting a gas mixture consisting of flue gas and carbon dioxide (CO₂) into the separation facility in a fluid-technical manner,
[0017] - Separating carbon dioxide (CO₂) and water vapor (H₂O) in the separation facility,
[0018] - Transporting the mixture consisting of carbon dioxide (CO₂) and water vapor (H₂O) to the preheater, wherein the mixture is heated in the preheater,
[0019] - Transferring the mixture heated in the preheater in the first stage of a multi-stage compressor, wherein the pressure and temperature of the mixture are increased in the first stage,
[0020] - Transferring the heated mixture to the steam generator after the first stage, wherein the thermal energy of the mixture is used to generate steam in the steam generator,
[0021] - Perform a reflux step, in which during the reflux step, the carbon dioxide (CO2) cooled in the steam generator is directed to a further stage of the compressor, where the temperature and pressure of the carbon dioxide (CO2) are increased in this further stage.
[0022] - After the further stage, transfer the heated carbon dioxide (CO2) to a further steam generator, where the thermal energy of the carbon dioxide (CO2) is used to generate steam in the further steam generator.
[0023] - Transfer the carbon dioxide (CO2) flowing out after the last stage through a preheater.
[0024] - Transfer the carbon dioxide (CO2) flowing out of the preheater to the output pipeline.
[0025] - Wherein the steam generated in the steam generator is fluidly connected to the separation facility via a steam pipeline.
[0026] - Wherein a separator and a dehydration unit are arranged between the stages of the compressor, wherein the separator is configured to separate condensed water, and the dehydration unit is configured to remove the remaining water fraction in the carbon dioxide.
[0027] An important feature of the present invention is the compressor, which typically includes six to eight stages for compressing from atmospheric pressure to supercritical pressure. This means that the process of compression and steam preparation in the heat recovery steam generator (HRSG) actually runs multiple times depending on the final number of stages required to reach the discharge pressure.
[0028] The preheater and all other downstream components are only used once, regardless of the number of stages.
[0029] According to the present invention, the carbon dioxide (CO2) is only cooled to such an extent that the heat can still be used for steam preparation in the heat recovery steam generator. The temperature is typically 5°C to 10°C higher than the final temperature of the steam required by the amine system, but this depends on the final structure of the heat exchanger. However, this means that the carbon dioxide (CO2) is not cooled to atmospheric temperature before entering the next compressor stage. This enables steam preparation to be carried out with the same number of heat exchangers / HRSGs after each compression stage as in conventional operation.
[0030] However, in practice, the process can only start after the second stage or even after the third stage of the compressor, because carbon dioxide (CO2) must first be heated from the atmospheric discharge temperature after the amine system to an available temperature level. To further maximize steam production, the high temperature of the carbon dioxide (CO2) after the final HRSG can now be used to preheat the carbon dioxide (CO2) at the compressor inlet to an available temperature level, such that the entire compressor can operate at the steam production temperature level from suction to outlet, such that steam production can already start after the first compressor stage.
[0031] According to the invention, the high water content of the carbon dioxide (CO2) from the amine system is not reduced before entering the compressor. In typical current configurations, a so-called stripper or top condenser of a desorber is used for this purpose in order to condense out a significant amount of water already before the compressor. The premise of the invention is that the condenser is dispensed with. The condenser is typically part of the separation facility. Thereby, the latent heat of the condensed steam at an available temperature level inside the steam generator for steam production between the compressor stages can be detected. Condensation starts in the steam generator after the compression stage where the flow is compressed to greater than about 15 bar. The condensed water is separated in a separator downstream of the corresponding heat exchanger / HRSG.
[0032] Then, the flow transitions to the next process stage, in which, during cooling in the steam generator, additional water is condensed and separated before finally being dehydrated in a dehydration system to a final admissible water content (e.g., for pipelines) (typically triethylene glycol, but other techniques can also be applied).
[0033] Typically, the flow has to be cooled to near atmospheric temperature in order to enter the dehydrogenation system. Since the flow in the steam generator is only cooled to about 5 °C to 10 °C above the steam temperature, the steam downstream of the steam generator or the separator still contains a large amount of heat, which is used to preheat the steam at the compressor inlet in order to maximize steam production.
[0034] The dry carbon dioxide leaving the drying system is still always at the atmospheric temperature level. To also improve heat recovery in the final process stage, the carbon dioxide is heated to an available temperature level again by the flow leaving the compressor and having to be cooled back to atmospheric temperature.
[0035] This solution significantly reduces the energy requirement of the amine system, which results in fuel savings depending on the alternative heat source and also results in carbon dioxide (CO2) savings when using fossil fuels, and thus also results in CAPEX savings for the amine system in this regard, because less carbon dioxide (CO2) has to be separated, without the need for additional machines and only a little additional drive power.
[0036] Advantageous improvements are given in the dependent claims.
[0037] The advantages of the present invention are that the thermal utilization and recovery of the compression heat of carbon dioxide (CO₂) are maximized with almost no additional machine and space requirements.
[0038] Another advantage is the reduction of the external heat requirement for the preparation of ND steam for the amine system.
[0039] Another advantage is achieved by significantly saving the cooling water for the carbon dioxide (CO₂) compressor, since the feed water for the steam preparation of the amine system is used for intermediate cooling.
[0040] Another advantage is achieved by the potential carbon dioxide (CO₂) savings when fossil fuels are used as the heat source for the boiler.
[0041] The characteristics, features, and advantages of the present invention described above, as well as the ways and means of achieving these characteristics, features, and advantages, become clearer and easier to understand in conjunction with the following description of the embodiments, which are elaborated in detail with reference to the accompanying drawings.
[0042] Here, components with the same function or the same components are provided with the same reference numerals.
[0043] The embodiments of the present invention will be described below with reference to the accompanying drawings. The accompanying drawings should not show the embodiments to scale. Rather, when it helps to explain, the drawings are given in a schematic and / or slightly distorted manner. In aspects supplementary to the teachings directly visible from the drawings, reference is made to the relevant prior art. Description of the Drawings
[0044] The drawings show:
[0045] Figure 1 A schematic diagram showing an embodiment of a facility according to the present invention. Detailed Description of the Embodiments
[0046] Figure 1 A schematic diagram showing an embodiment of a facility 1 according to the present invention.
[0047] Facility 1 is configured to provide carbon dioxide (CO₂) and includes a separation facility 2. The separation facility 2 is fluidly connected via a pipeline 4 to a gas mixture 44 composed of flue gas and carbon dioxide (CO₂). The separation facility 2 is configured such that the carbon dioxide (CO₂) contained in the flue gas 44 is separated. The separated carbon dioxide (CO₂) flows from the separation facility 2 through a preheater 6 via a first carbon dioxide pipeline 5. The temperature of the carbon dioxide (CO₂) is increased in the preheater 6.
[0048] The first carbon dioxide pipeline 5 is fluidly connected to the separation facility 2. The separation facility 2 is configured here as an amine facility. However, the carbon dioxide (CO2) coming out of the separation facility is still mixed with a relatively large amount of water vapor here. The ratio between the carbon dioxide (CO2) and the water vapor can be approximately 50 mol% water and 50 mol% CO2 here. Therefore, the water vapor contained in the carbon dioxide (CO2) also contains the thermal energy utilized according to the present invention.
[0049] During operation, the separation facility 2 is operated with steam from the steam pipeline 7. When using fossil fuels, the carbon dioxide (CO2) 46 generated in the boiler 8 can also optionally be conveyed into the separation facility 2 via the pipeline 10. The steam generated in the boiler 8 is guided into the separation facility 2 via the pipeline 11.
[0050] The carbon dioxide (CO2) heated after the preheater 6 is conveyed via the pipeline 12 to the multi-stage compressor 13. The multi-stage compressor 13 is fluidly connected on the inlet side to the carbon dioxide pipeline 5 coming out of the preheater 6.
[0051] In the compressor 13, the heated carbon dioxide (CO2) is conveyed to the first stage 30, where the temperature and pressure of the carbon dioxide (CO2) are increased.
[0052] After the first stage 30, the carbon dioxide (CO2) is conveyed via the pipeline 14 to the steam generator 15, which can be configured as a HRSG (heat recovery steam generator).
[0053] The steam generator 15 is configured such that the water 47 conveyed into the steam generator 15 is converted into steam by means of an energy exchange with the thermal energy of the carbon dioxide (CO2) coming out of the compressor 13 after the stage 30.
[0054] The compressor 13 has five to ten stages, in particular six to nine stages, and more particularly seven or eight stages.
[0055] The carbon dioxide (CO2) cooled in the steam generator 15 is guided via the pipeline 16 back into the stage 30 in the compressor 13. This occurs multiple times, i.e., the carbon dioxide flows through multiple stages in the process stage 30, where after each stage, the thermal energy of the carbon dioxide (CO2) is used to generate steam in the steam generator 15. In Figure 1 For clarity, only the compressor stage 30, the steam generator 15, the pipeline 14 leading to the steam generator 15, and the pipeline 16 leading from the steam generator 15 to the compressor 13 and to the process stage 30 are shown. For clarity, the individual pipelines leading to the steam generator 15 and back to the compressor 13 are omitted.
[0056] In the final steam generator 15, a large amount of water vapor contained in the carbon dioxide begins to condense. Before the carbon dioxide (CO2) flows through stage 34 of the compressor 13, the carbon dioxide flows through the separator 32. In the separator 32, water 45 is separated from the carbon dioxide (CO2) and is led out via a pipeline.
[0057] The steam generated in the steam generator 15 and the additional steam generator 36 is fluidly connected to the separation facility 2 via a steam pipeline 7.
[0058] The carbon dioxide (CO2) flowing out of the compressor 13 after stage 34 flows through the preheater 6 via a pipeline 17. Before the carbon dioxide (CO2) flows through the preheater 6, the carbon dioxide flows through the second separator 37. In the second separator 37, water 45 is separated from the carbon dioxide (CO2) and is led out via a pipeline.
[0059] After the preheater 6, the carbon dioxide (CO2) flows through the dehydration unit 38, where the dehydration unit 38 is configured to dehydrate the carbon dioxide (CO2) exiting the preheater 6. Here, the water 45 separated in the dehydration unit 38 is led out via a dehydration pipeline.
[0060] The additional dehydration unit 38 is configured, for example, as a triethylene glycol (TEG) system.
[0061] The carbon dioxide (CO2) flowing out after the additional dehydration unit 38 flows through another preheater 39, where the temperature of the carbon dioxide (CO2) is increased. After 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.
[0062] The thermal energy of the carbon dioxide (CO2) is used to generate steam for the separation facility 2 in another steam generator 42.
[0063] The carbon dioxide (CO2) generated and provided in the facility 1 is subsequently processed, for example, for transportation in the pipeline 33.
Claims
1. A facility (1) for providing carbon dioxide (CO₂), said facility comprising a separation facility (2), wherein the separation facility (2) is in fluid connection with a gas mixture (4) consisting of flue gas and carbon dioxide (CO₂), and wherein the separation facility (2) is configured such that the carbon dioxide (CO₂) and water vapor (H₂O) contained in the flue gas are separated. Wherein, in operation, the separation facility (2) can be operated with steam from a steam line (7). The facility further comprises a first carbon dioxide line (5), which is in fluid connection with the separation facility (2), and the carbon dioxide (CO₂) separated in the separation facility (2) flows out of the first carbon dioxide line during operation. The facility further comprises a preheater (6), through which the carbon dioxide line (5) is guided and which is configured to increase the temperature of the carbon dioxide (CO₂). The facility further comprises a multi-stage compressor (13), which is in fluid connection on the inlet side with a carbon dioxide line (12) emerging from the preheater (6). Wherein, after a stage (30), the temperature and pressure of the carbon dioxide (CO₂) are increased, and after the stage (30), the carbon dioxide (CO₂) is guided through a steam generator (15) via a line (14). Wherein the steam generator (15) is configured such that the water (31) fed into the steam generator (15) generates steam by means of an energy exchange with the thermal energy of the carbon dioxide (CO₂) emerging from the compressor (13) after the stage (30), and the carbon dioxide cooled in the steam generator (15) is guided back to the next stage in the compressor (13). Wherein the steam generated in the steam generator (15) is in fluid connection with the separation facility (2) via the steam line (7). Wherein the carbon dioxide (CO₂) flowing out of the compressor (13) after the first process stage flows through a first separator (32), and the separator (32) is configured to separate the water condensed in the last steam generator (15).
2. The facility (1) according to claim 1. Wherein the carbon dioxide (CO₂) generated in the facility (1) is processed for transportation in a pipeline (33).
3. The facility (1) according to claim 1 or 2. Wherein the separation facility (2) is configured as an amine facility.
4. The facility (1) according to claim 1, 2 or 3. Wherein the compressor (13) has five to ten stages, in particular six to nine stages, and more particularly seven or eight stages.
5. The facility (1) according to any one of the above claims. Wherein the next stage (34) of the compressor (13) is provided downstream of the first separator (32), and in the next stage (34), the temperature and pressure of the carbon dioxide (CO₂) are increased. After the said lower stage (34), the carbon dioxide (CO2) is guided via a pipeline (35) through a further steam generator (36). The said further steam generator (36) is configured such that the water fed into the said further steam generator (36) generates steam by means of an energy exchange with the thermal energy of the carbon dioxide (CO2) emerging from the compressor (13) after the said lower stage (34). The carbon dioxide cooled in the said steam generator (36) is guided back into the compressor (13).
6. The installation (1) according to claim 5, wherein the carbon dioxide (CO2) flowing out of the compressor (13) after the said lower stage (34) flows through a second separator (37), and the said second separator (37) is configured to separate the water condensed in the steam generator (36).
7. The installation (1) according to any one of the above claims, the said installation having an additional dehydration unit (38), which is fluidically coupled to the preheater (6).
8. The installation (1) according to claim 7, wherein the said additional dehydration unit (38) is configured as a triethylene glycol (TEG) system.
9. The installation (1) according to claim 7 or 8, the said installation having a further preheater (39), which is fluidically coupled to the said additional dehydration unit (38).
10. The installation (1) according to claim 9, wherein the compressor (13) has an additional stage (40), which is fluidically coupled to the said further preheater (39), and wherein the temperature and pressure of the carbon dioxide (CO2) are increased in the said additional stage (40).
11. The installation according to claim 10, wherein after the said additional stage (40), the carbon dioxide (CO2) is guided via a pipeline (41) through a steam generator (42), wherein the said steam generator (42) is configured such that the water (43) fed into the said steam generator (42) generates steam by means of an energy exchange with the thermal energy of the carbon dioxide (CO2) emerging from the compressor (13) after the said additional stage (40). The carbon dioxide cooled in the said steam generator (42) is guided back to the next lower stage in the compressor (13).
12. A method for providing carbon dioxide (CO2), the said method having the following steps: - fluid-technically conveying a gas mixture (44) composed of flue gas and carbon dioxide (CO2) into a separation facility (2), - separating the carbon dioxide (CO2) and water vapor (H2O) in the said separation facility (2), - conveying the carbon dioxide (CO2) to a preheater (6), wherein the carbon dioxide (CO2) is heated in the said preheater (6). - Transfer the carbon dioxide (CO2) heated in the preheater (6) into the first stage (30) of a multi-stage compressor (13), where the pressure and temperature of the carbon dioxide (CO2) are increased in the first stage (30). - Transfer the heated carbon dioxide (CO2) into a steam generator (15) after the first stage (30), where the thermal energy of the carbon dioxide (CO2) is used to generate steam in the steam generator (15). - Perform a reflux step, where in the reflux step, the carbon dioxide (CO2) cooled in the steam generator (15) is guided into another stage (34) of the compressor (13), where the temperature and pressure of the carbon dioxide (CO2) are increased in the another stage (34). - Guide the heated carbon dioxide (CO2) into another steam generator (36) after the another stage (34), where the thermal energy of the carbon dioxide (CO2) is used to generate steam in the another steam generator (36). - Repeat the reflux step until the last stage. - Transfer the carbon dioxide (CO2) flowing out after the last stage through the preheater (6). - Transfer the carbon dioxide (CO2) flowing out from the preheater (6) into an output pipeline. - Wherein the steam generated in the steam generators (15, 36, 42) is fluidly connected to the separation facility (2) via the steam pipeline (7). - Wherein separators (32, 37) and a dehydration unit (38) are provided between the stages (30, 34, 40) of the compressor (13), wherein the separators (32, 37) are configured to separate condensed water (45) and the dehydration unit (38) is configured to remove the remaining water fraction (45) in the carbon dioxide.
13. The method according to claim 12, wherein an additional dehydration unit (38) is provided downstream of the preheater (6).
14. The method according to claim 13, wherein the additional dehydration unit (38) is configured as a triethylene glycol (TEG) system.