A coastal carbon capture method and capture system
By using micron-sized limestone and calcium hydroxide in a staged treatment method with seawater to treat ship exhaust, carbon dioxide is converted into bicarbonate in seawater. This solves the problems of high equipment investment and unstable carbon sequestration in existing technologies, and achieves efficient, stable carbon sequestration and low-cost carbon capture.
Patent Information
- Application Number
- CN202610737555.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-27
- Publication Date
- 2026-06-26
AI Technical Summary
Existing ship exhaust decarbonization technologies suffer from high equipment investment, high reagent costs, unstable carbon sequestration, and limited resource utilization, making them difficult to promote on a large scale in ship scenarios.
Micron-sized limestone and calcium hydroxide are mixed with seawater, and carbon dioxide is converted into bicarbonate ions in seawater through a staged treatment process to achieve stable storage. This includes a combination of microporous aeration, mechanical stirring, and in-tank pressurization. The carbon dioxide in the industrial exhaust gas is saturated and dissolved in seawater, and then chemically reacted in the primary and secondary reactors to ultimately convert the carbon dioxide into bicarbonate ions.
It achieves efficient and stable carbon sequestration, reduces operating costs, eliminates the need for carbon dioxide purification equipment, is suitable for direct treatment of raw industrial exhaust gas in places such as ships, and is compatible with any location where seawater can be used on-site.
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Figure CN122273288A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of low-carbon emission reduction technology, specifically to a coastal carbon capture method and capture system. Background Technology
[0002] With increasingly stringent carbon emission control requirements in the shipping industry, carbon dioxide capture and removal technologies for ship exhaust have become a key research focus. Currently, the mainstream carbon removal methods for marine ship exhaust fall into two main categories:
[0003] One type is chemical wet decarbonization, which uses a weakly alkaline carbon dioxide-loving chemical absorbent and relies on a cycle of low-temperature absorption and heating desorption to separate and recover carbon dioxide from the exhaust gas. This technology is relatively mature. However, this process has significant drawbacks. On the one hand, the equipment investment is large and the reagent cost is high. On the other hand, the subsequent storage of the captured carbon dioxide is severely constrained by site selection and storage capacity. Furthermore, the pathways for carbon dioxide resource reuse are limited, and the overall economic efficiency is poor, making it difficult to promote on a large scale in shipboard scenarios.
[0004] Another type is seawater carbon sequestration. This technology mostly involves direct carbon dissolution through discharge, generating bicarbonate which is then released into the ocean, relying on the marine ecosystem for carbon sequestration. However, this process has inherent drawbacks: low carbon dioxide dissolution, incomplete carbon sequestration, and a tendency to cause localized seawater acidification. This leads to the problem of reverse carbon dioxide release from bicarbonate-containing seawater discharged into shallow waters, making stable and long-term carbon sequestration impossible. In summary, both existing ship exhaust decarbonization technologies have significant technical bottlenecks and application limitations. There is an urgent need to develop a new carbon capture technology that is simple, provides stable carbon sequestration, requires no subsequent carbon dioxide storage and transportation, and is suitable for coastal and ship operating conditions. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a coastal carbon capture method and capture system that does not require carbon dioxide purification, but converts carbon dioxide into a stable bicarbonate form in seawater for permanent sequestration through graded treatment, and the treated seawater is compatible with natural seawater and can be directly and safely discharged into the sea.
[0006] To address the aforementioned technical problems, the present invention provides a coastal carbon capture method, comprising the following steps:
[0007] S10: In the first reaction device, industrial exhaust gas is mixed with seawater to make the seawater reach a state of CO2 saturation, thus obtaining saturated dissolved carbon seawater.
[0008] S20: Micron-sized limestone is added to the primary tubular reactor, and the saturated dissolved carbon seawater and residual tail gas from S10 are introduced into the primary tubular reactor to bring it to the set pressure. The following reaction occurs inside the primary tubular reactor:
[0009] CO2(g)→CO2(aq) (1)
[0010] (2);
[0011] S30: The mixture in the primary tubular reactor is filtered, and the purified tail gas is discharged. The filtered primary carbon-enriched seawater is sent to the secondary tubular reactor, where Ca(OH)2 is added. The following reaction occurs in the secondary tubular reactor:
[0012] (3);
[0013] S40: Filter the mixture in the two-stage tubular reactor and discharge the filtered secondary carbon-rich seawater into the natural sea area.
[0014] Furthermore, in step S10, industrial exhaust gas is mixed with seawater by a combination of microporous aeration, mechanical stirring, and in-tank pressurization.
[0015] Furthermore, in step S20, micron-sized limestone is mixed with seawater to form a suspension, which is then introduced into a primary tubular reactor.
[0016] Furthermore, in step S20, if the remaining tail gas in S10 is insufficient to bring the primary tubular reactor to the set pressure, then industrial tail gas continues to be introduced into the primary tubular reactor.
[0017] Furthermore, in step S30, micron-sized Ca(OH)2 is mixed with seawater to form a suspension slurry, which is then fed into a two-stage tubular reactor.
[0018] Furthermore, carbon dioxide analysis is performed on the discharged purified exhaust gas. If the carbon dioxide content in the purified exhaust gas is below the threshold, the primary carbon-enriched seawater is directly discharged into the natural sea area; if the carbon dioxide content in the purified exhaust gas is above the threshold, the primary carbon-enriched seawater is sent into a secondary tubular reactor.
[0019] A capture system employing the above-mentioned coastal carbon capture method includes:
[0020] The first reaction device is connected to an industrial exhaust gas collector at its air inlet and a seawater transfer pump at its liquid inlet. Both the air outlet and the liquid outlet of the first reaction device are connected to the first-stage tubular reactor.
[0021] The primary tubular reactor is provided with an exhaust port and a first discharge port. The exhaust port is connected to the atmosphere, and the first discharge port is connected to the secondary tubular reactor.
[0022] The two-stage tubular reactor is provided with a second discharge port, which is connected to a natural sea area;
[0023] Both the first and second discharge ports are equipped with permeable membranes.
[0024] Furthermore, the first reaction device is a sealed carbon dissolving tank, the liquid inlet is located at the top of the sealed carbon dissolving tank, a microporous aeration disc is provided at the bottom of the sealed carbon dissolving tank, the air inlet is connected to the aeration disc, and a stirring mechanism is installed at the top inside the sealed carbon dissolving tank.
[0025] Furthermore, a carbon dioxide analyzer is installed on the exhaust port.
[0026] The beneficial effects of the carbon capture method and capture system of the present invention are as follows:
[0027] Physical saturation followed by chemical fixation maximizes the carbon carrying capacity of seawater.
[0028] Two-stage gradient treatment: inexpensive calcium carbonate is used in the main reaction first, and calcium hydroxide is used in the deep treatment as a backup, reducing operating costs;
[0029] The final product is mainly bicarbonate, which is consistent with the carbon system of natural seawater. It does not cause secondary pollution and can be directly discharged into the sea.
[0030] The capture system is simple to operate, requires no CO2 purification equipment, and can directly process raw industrial exhaust gas. It is suitable for any location where seawater can be obtained locally and where industrial exhaust gas is emitted. Attached Figure Description
[0031] Figure 1 This is a flowchart of an embodiment of the carbon capture method of the present invention;
[0032] Figure 2 This is a flowchart of Embodiment 2 of the carbon capture method of the present invention. Detailed Implementation
[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.
[0034] Reference Figure 1 The diagram shown is a flowchart of a coastal carbon capture method provided by the present invention. In this embodiment, the method includes the following steps:
[0035] S10: Carbon dioxide saturated dissolved in seawater.
[0036] Seawater from natural sea areas is transported to the first reaction unit until the seawater level reaches a set value. Industrial waste gas from offshore oil and gas platforms, ships, coastal steel mills, power plants, and other locations where seawater can be sourced locally and industrial waste gas emissions are collected and introduced into the first reaction unit. Microporous aeration is used within the first reaction unit to break the industrial waste gas into micron-sized microbubbles, which are then evenly dispersed and rise to fully contact the seawater. Further mechanical stirring creates turbulent water flow, disrupting the gas-liquid interface film and accelerating carbon dioxide dissolution. Industrial waste gas is continued to be introduced into the first reaction unit to maintain a slightly pressurized state. Under this state, the first reaction unit is sealed, allowing the carbon dioxide to fully dissolve within it. Under these multiple enhancements, carbon dioxide rapidly transitions from the gas phase to the liquid phase of the seawater, physically dissolving in the seawater in molecular form (CO2(g) → CO2(aq)) until the seawater reaches carbon dioxide saturation, producing saturated carbon-dissolved seawater. At this point, the saturated carbon-dissolved seawater coexists with the remaining, incompletely dissolved waste gas within the first reaction unit.
[0037] S20: Calcium carbonate weathering reaction in a single-stage tubular reactor.
[0038] Micron-sized limestone powder was selected and mixed with natural seawater to prepare a uniform limestone suspension. The saturated carbonized seawater and residual tail gas from the first reaction device were introduced into a primary tubular reactor. The dissolved CO2 in the saturated carbonized seawater first reacted with the limestone as follows:
[0039] (2)
[0040] The reaction produces calcium ions and bicarbonate ions, realizing the conversion of free carbon dioxide into a stable carbon form. As the dissolved CO2 in seawater decreases, the CO2 in the remaining tail gas entering the single-stage tubular reactor continues to dissolve in seawater, undergoing the following reaction:
[0041] CO2(g)→CO2(aq) (1)
[0042] The dissolved carbon dioxide then reacts with limestone (2) to achieve large-scale sequestration of carbon dioxide in industrial exhaust gas.
[0043] It can be seen that there are two reactions in the first-stage tubular reactor. The presence of saturated dissolved carbon seawater shortens the start time of reaction (2), and reaction (1) extends the duration of reaction (2), greatly increasing the recovery rate of carbon dioxide in industrial tail gas.
[0044] Reaction (2) requires a certain residence time and reaction pressure. If the remaining tail gas in the first reaction device cannot reach the reaction pressure after being introduced into the first-stage tubular reactor, the industrial tail gas can be directly introduced into the first-stage tubular reactor to improve the carbon dioxide treatment efficiency.
[0045] After the reaction is completed, the primary tubular reactor contains a large amount of purified tail gas after decarbonization, primary carbon-rich seawater containing bicarbonate ions, and possibly unconsumed limestone solids.
[0046] S30: Deep reaction in a two-stage tubular reactor.
[0047] For the materials in the primary tubular reactor, the purified exhaust gas can be directly discharged into the atmosphere. However, free carbon dioxide may still be present in the primary carbon-enriched seawater, so secondary treatment is necessary. Specifically, the limestone solids suspended in the primary carbon-enriched seawater are filtered out. The filtered primary carbon-enriched seawater is then fed into the secondary tubular reactor. Ca(OH)₂ is introduced into the secondary tubular reactor, specifically by mixing micron-sized Ca(OH)₂ with seawater to form a suspension slurry before feeding it into the secondary tubular reactor. The following reaction occurs within the secondary tubular reactor:
[0048] (3)
[0049] The remaining carbon dioxide in the primary carbon-enriched seawater is further converted into bicarbonate ions, completely eliminating free carbon dioxide and improving overall carbon capture efficiency. Since only a small amount of carbon dioxide remains in the primary carbon-enriched seawater entering the secondary tubular reactor, there will inevitably be some calcium hydroxide slurry remaining in the secondary tubular reactor, which can be reused multiple times.
[0050] S40: Compliant with discharge standards into the sea.
[0051] Solid-liquid separation is performed on the mixture in the two-stage tubular reactor to retain unreacted calcium hydroxide solid particles. The filtered secondary carbon-enriched seawater is rich in high concentrations of bicarbonate ions. The pH and mineral composition of the water are consistent with those of natural seawater. There is no free carbon dioxide or solid impurities. It is directly discharged into the natural sea area. The bicarbonate ions are integrated into the marine carbon pool to achieve permanent sequestration on a scale of tens of thousands of years, completing the entire process of coastal carbon capture operation.
[0052] Reference Figure 2 As shown, in Embodiment 2 of the present invention, if it is determined that the carbon in the primary carbon-rich seawater has been completely decarbonized, then there is no need to perform a deep carbon fixation reaction on the primary carbon-rich seawater. The specific steps are as follows:
[0053] S10: Carbon dioxide saturated dissolved in seawater.
[0054] Seawater from natural sea areas and industrial exhaust gas are transported to the first reaction device, where carbon dioxide is saturated and dissolved to obtain saturated carbon-dissolved seawater.
[0055] S20: Calcium carbonate weathering reaction in a single-stage tubular reactor.
[0056] The saturated dissolved carbon seawater and the remaining tail gas from the first reaction unit are introduced into the first-stage tubular reactor, where they come into contact with the limestone suspension in the first reaction unit. The dissolved CO2 in the saturated dissolved carbon seawater first reacts with the limestone as follows:
[0057] (2)
[0058] This process converts free carbon dioxide into a stable carbon form, while the CO2 in the remaining tail gas entering the primary tubular reactor continues to dissolve in seawater, thus improving the solidification and recovery rate of carbon dioxide in industrial tail gas.
[0059] After the reaction is completed, the primary tubular reactor contains a large amount of purified tail gas after decarbonization, primary carbon-rich seawater containing bicarbonate ions, and possibly unconsumed limestone solids.
[0060] S30: Deep reaction in a two-stage tubular reactor.
[0061] For the material in the primary tubular reactor, the carbon dioxide content in the purified exhaust gas is analyzed. If the carbon dioxide content in the purified exhaust gas is lower than the set threshold, it indicates that the primary limestone reaction has fully removed the carbon dioxide, and the carbon components in the seawater have reached the stable storage standard, so there is no need to carry out the secondary calcium hydroxide reaction. The primary carbon-enriched seawater after solid-liquid separation and filtration can be directly discharged into the natural sea area, bypassing the secondary tubular reactor, simplifying the process and saving calcium hydroxide reagent consumption and equipment operating energy consumption.
[0062] If the analysis results show that the carbon dioxide content in the purified exhaust gas is higher than the set threshold, it is determined that the decarbonization in the primary tubular reactor is incomplete. Following the process of Example 1, primary carbon-rich seawater is sent into the secondary tubular reactor, and calcium hydroxide suspension slurry is added to carry out a deep carbon fixation reaction.
[0063] S40: Compliant with discharge standards into the sea.
[0064] After solid-liquid separation and filtration of the mixture in the two-stage tubular reactor, it is directly discharged into the natural sea area, completing the entire process of coastal carbon capture operation.
[0065] This embodiment achieves adaptive process control through online detection, balancing carbon capture efficiency with operational economy, and is adaptable to flexible applications with different gas source concentrations and environmental protection requirements.
[0066] The capture system of the coastal carbon capture method of the present invention includes:
[0067] The first reaction device is connected to an industrial exhaust gas collector at its air inlet and a seawater transfer pump at its liquid inlet. Both the air outlet and liquid outlet of the first reaction device are connected to a primary tubular reactor.
[0068] The primary tubular reactor is equipped with an exhaust port and a first discharge port. The exhaust port is connected to the atmosphere, and the first discharge port is connected to the secondary tubular reactor.
[0069] The two-stage tubular reactor is equipped with a second discharge port, which is connected to a natural sea area;
[0070] Both the first and second discharge ports are equipped with permeable membranes.
[0071] During operation, a seawater transfer pump is activated to deliver seawater from natural sea areas to the first reaction unit, the sealed carbon dissolving tank, maintaining a set liquid level within the tank. Industrial exhaust gases emitted from offshore oil and gas platforms, ships, and coastal steel mills / power plants—anywhere seawater can be used locally—are collected via an industrial exhaust gas collector. These exhaust gases primarily consist of carbon dioxide, nitrogen, and small amounts of soot and impurities. The exhaust gases are then introduced into a microporous aeration disc at the bottom of the sealed carbon dissolving tank. A combined approach of microporous aeration, mechanical stirring, and in-tank pressurization is employed. The microporous aeration disc breaks the exhaust gases into micron-sized microbubbles, which are then evenly dispersed and rise to fully contact the seawater. The agitator at the top of the tank is activated, creating turbulent water flow that disrupts the liquid film at the gas-liquid interface. The sealed tank maintains a slightly pressurized state, increasing the partial pressure of the carbon dioxide gas phase. Under these multiple enhancements, carbon dioxide rapidly transitions from the gas phase to the seawater liquid phase, physically dissolving in molecular form until the seawater reaches carbon dioxide saturation, thus preparing saturated carbon-dissolved seawater.
[0072] Micron-sized limestone powder was selected and mixed with natural seawater to prepare a uniform limestone suspension. Saturated dissolved seawater from a sealed carbon dissolving tank and residual tail gas were introduced into a primary tubular reactor, simultaneously feeding the limestone suspension into the reactor. The internal pressure of the primary tubular reactor was adjusted; if the residual tail gas flow was insufficient to reach the set reaction pressure, industrial tail gas was added to maintain stable reactor pressure. During the isothermal static reaction in the tubular reactor, dissolved carbon dioxide reacted with limestone to generate calcium ions and bicarbonate ions, achieving the conversion of free carbon dioxide into a stable carbon form. At this time, the dissolved carbon dioxide content in the seawater decreased, allowing gaseous carbon dioxide in the primary tubular reactor to continue dissolving into the liquid phase of the seawater. Sufficient carbon dioxide extended the reaction time with limestone, improving the carbon dioxide conversion and recovery rate.
[0073] The mixture from the first-stage tubular reactor flows out through the first discharge port and undergoes solid-liquid separation through an internal permeable membrane. The membrane intercepts micron-sized limestone particles, allowing only the liquid phase to pass through. The separated gas is discharged through the exhaust port, and the carbon dioxide content in the exhaust gas is monitored in real time by a carbon dioxide analyzer. If the test results show that the carbon dioxide content in the purified exhaust gas is below a set threshold, the primary carbon-enriched seawater is directly discharged into the natural sea area. If the test results show that the carbon dioxide content in the purified exhaust gas is above the set threshold, it is determined that the first-stage decarbonization is incomplete. The primary carbon-enriched seawater filtered through the permeable membrane is then sent to the second-stage tubular reactor. The residual dissolved carbon dioxide in the primary carbon-enriched seawater fully contacts and reacts with the calcium hydroxide suspension slurry, further converting the remaining carbon dioxide into calcium ions and bicarbonate ions, thus completely eliminating free carbon dioxide.
[0074] After the reaction in the two-stage tubular reactor, the mixture flows out through the second discharge port and undergoes solid-liquid separation again through the built-in permeable membrane. The filtered secondary carbon-rich seawater is then directly discharged into the natural sea area.
[0075] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.
Claims
1. A coastal carbon capture method, characterized in that, Includes the following steps: S10: In the first reaction device, industrial exhaust gas is mixed with seawater to make the seawater reach a state of CO2 saturation, thus obtaining saturated dissolved carbon seawater. S20: Micron-sized limestone is added to the primary tubular reactor, and the saturated dissolved carbon seawater and residual tail gas from S10 are introduced into the primary tubular reactor to bring it to the set pressure. The following reaction occurs inside the primary tubular reactor: CO2(g)→CO2(aq) (1) （2）； S30: The mixture in the primary tubular reactor is filtered, and the purified tail gas is discharged. The filtered primary carbon-enriched seawater is sent to the secondary tubular reactor, where Ca(OH)2 is added. The following reaction occurs in the secondary tubular reactor: （3）； S40: Filter the mixture in the two-stage tubular reactor and discharge the filtered secondary carbon-rich seawater into the natural sea area.
2. The coastal carbon capture method as described in claim 1, characterized in that, In step S10, industrial exhaust gas is mixed with seawater by a combination of microporous aeration, mechanical stirring, and in-tank pressurization.
3. The coastal carbon capture method as described in claim 1, characterized in that, In step S20, micron-sized limestone is mixed with seawater to form a suspension, which is then fed into a primary tubular reactor.
4. The coastal carbon capture method as described in claim 1, characterized in that, In step S20, if the remaining tail gas in S10 is insufficient to bring the primary tubular reactor to the set pressure, then industrial tail gas continues to be introduced into the primary tubular reactor.
5. A coastal carbon capture method as described in claim 1, characterized in that, In step S30, micron-sized Ca(OH)2 is mixed with seawater to form a suspension slurry, which is then fed into a two-stage tubular reactor.
6. A coastal carbon capture method as described in claim 1, characterized in that, In step S30, carbon dioxide analysis is performed on the discharged purified exhaust gas. If the carbon dioxide content in the purified exhaust gas is lower than the threshold, the primary carbon-enriched seawater is directly discharged into the natural sea area; if the carbon dioxide content in the purified exhaust gas is higher than the threshold, the primary carbon-enriched seawater is sent into a secondary tubular reactor.
7. A capture system employing the coastal carbon capture method according to any one of claims 1-6, characterized in that, include: The first reaction device is connected to an industrial exhaust gas collector at its air inlet and a seawater transfer pump at its liquid inlet. Both the air outlet and the liquid outlet of the first reaction device are connected to the first-stage tubular reactor. The primary tubular reactor is provided with an exhaust port and a first discharge port. The exhaust port is connected to the atmosphere, and the first discharge port is connected to the secondary tubular reactor. The two-stage tubular reactor is provided with a second discharge port, which is connected to a natural sea area; Both the first and second discharge ports are equipped with permeable membranes.
8. A coastal carbon capture system as described in claim 7, characterized in that, The first reaction device is a sealed carbon dissolving tank. The liquid inlet is located at the top of the sealed carbon dissolving tank, and a microporous aeration disc is provided at the bottom of the sealed carbon dissolving tank. The air inlet is connected to the aeration disc, and a stirring mechanism is installed at the top inside the sealed carbon dissolving tank.
9. A coastal carbon capture system as described in claim 7, characterized in that, A carbon dioxide analyzer is installed on the exhaust port.