CO2 capture system and method for a sewage treatment plant

Abstract

The application provides a sewage treatment plant CO2 capture system and method, which comprises a biological reaction chamber, an adsorber and a cold / heat source pipeline, and the adsorber is filled with solid adsorbents; the air inlet of the biological reaction chamber is communicated with mixed gas, the air outlet of the biological reaction chamber is communicated with the air inlet of the adsorber, and the air outlet of the adsorber is connected with a CO2 product tank; the cold / heat source pipeline comprises a water source heat pump, the water source heat pump is communicated with regenerated water, and the water outlet of the water source heat pump, the adsorber and the water inlet of the water source heat pump are sequentially communicated through pipelines and valves to form a loop. The non-CO2 greenhouse gas is converted into CO2 through the biological reaction chamber, the adsorption is carried out through the adsorber, the CO2 is captured through the cold / heat source pipeline, the resource recycling is carried out, and the economic benefit rate is improved. The cold / heat source pipeline is connected with the regenerated water, the low-grade energy contained in the sewage is fully utilized, the low-temperature heat energy is transferred to high-temperature heat energy, the energy consumption is reduced, and the operation cost of the sewage treatment plant is reduced.

Description

Technical Field

[0001] This invention relates to the field of carbon capture technology in the wastewater treatment industry, specifically to a CO2 capture system and method for wastewater treatment plants. Background Technology

[0002] Climate change is a global strategic issue facing all countries. Separating and capturing CO2 in wastewater treatment plants, while simultaneously reducing emissions of non-CO2 greenhouse gases such as CH4 and N2O, can mitigate the problem of global warming.

[0003] Regarding reducing direct non-CO2 greenhouse gas emissions from wastewater treatment plants, most researchers emphasize achieving this through key measures such as optimizing wastewater treatment process design, refining operational parameters, and implementing sludge digestion and biogas recovery projects. However, there are few reports, both domestically and internationally, on the approach of capturing CO2 generated from wastewater treatment plants while simultaneously reducing emissions of non-CO2 greenhouse gases such as CH4, based on the resource utilization of wastewater.

[0004] CO2 capture technologies mainly employ absorption and adsorption separation methods. Absorption methods require large amounts of solvent, leading to problems such as solvent leakage, corrosion, and secondary pollution. Adsorption separation methods avoid these problems and offer advantages such as lower manufacturing costs of adsorbents and equipment, and less environmental pollution, making them promising for future development. However, temperature-swing adsorption, a type of adsorption separation, involves adsorption at low temperatures and desorption / regeneration at high temperatures. This requires significant energy to raise the temperature for desorption, limiting the application of temperature-swing adsorption technology.

[0005] Therefore, the inventors believe there is a need to provide a wastewater treatment plant CO2 capture system and method that can effectively utilize the low-grade energy contained in wastewater, transfer low-temperature heat energy to high-temperature energy, and capture CO2 for resource recovery and utilization. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a CO2 capture system and method for wastewater treatment plants.

[0007] According to the present invention, a CO2 capture system for a wastewater treatment plant includes: a biological reaction chamber, an adsorber, and a cold / heat source pipeline. The adsorber is filled with a solid adsorbent. The inlet of the biological reaction chamber is connected to a mixed gas, and the outlet of the biological reaction chamber is connected to the inlet of the adsorber. The outlet of the adsorber is connected to a CO2 product tank. The cold / heat source pipeline includes a water source heat pump, which is connected to reclaimed water. The outlet of the water source heat pump, the adsorber, and the inlet of the water source heat pump are sequentially connected through pipelines and valves to form a loop.

[0008] Preferably, the adsorber comprises one or more adsorbers arranged in parallel, and the bioreactor is connected to the adsorber via a fan.

[0009] Preferably, the water source heat pump includes one or more water source heat pumps connected in series.

[0010] Preferably, the air inlet of the adsorber is provided with an air inlet valve, and the air outlet of the adsorber is provided with an air outlet valve. The water inlet of the adsorber is provided with a water inlet valve, and the water outlet of the adsorber is provided with a water outlet valve.

[0011] Preferably, the water source heat pump includes a first water source heat pump and a second water source heat pump, the adsorber includes a first adsorber, a second adsorber, and a third adsorber, and the cold / heat source pipeline further includes a cold source three-way valve and a four-way reversing valve; the outlet of the first water source heat pump, the cold source three-way valve, the four-way reversing valve, the inlet valve, the adsorber, the outlet valve, and the inlet of the first water source heat pump are sequentially connected to form a loop; the outlet of the second water source heat pump, the four-way reversing valve, the inlet valve, the adsorber, the outlet valve, and the inlet of the second water source heat pump are sequentially connected to form a loop.

[0012] Preferably, the adsorber has a spiral structure inside.

[0013] Preferably, the air intake direction of the adsorber is from bottom to top.

[0014] Preferably, the solid adsorbent includes activated carbon, molecular sieve, and composite porous media.

[0015] Preferably, the bioreactor chamber is provided with a carrier packing material, which is used to convert the mixed gas, the mixed gas including components such as CH4, N2O, and CO2.

[0016] According to the present invention, a CO2 capture method for a wastewater treatment plant, employing the aforementioned CO2 capture system for a wastewater treatment plant, includes the following steps:

[0017] Step S1: The mixed gas is introduced into the bioreactor chamber, where the bioreactor chamber converts non-CO2 greenhouse gases.

[0018] In step S2, the gas enters the adsorber in the adsorption state from the outlet of the bioreactor chamber for low-temperature CO2 adsorption, and the unadsorbed gas is discharged into the external environment.

[0019] Step S3: After the adsorption state ends, the adsorber, which has entered the desorption state, is connected to the water source heat pump, which serves as a heat source, to desorb CO2. The precipitated CO2 enters the CO2 product tank.

[0020] Step S4: After the desorption state is completed, the adsorber, which has entered the cooling state, is connected to the water source heat pump, which serves as the cold source, for cooling, in preparation for entering the adsorption state.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention converts non-CO2 greenhouse gases into CO2 through a bioreactor, adsorbs them through an adsorber, and captures the CO2 through a cold / heat source pipeline for resource recovery and utilization. This helps to reduce the greenhouse effect, alleviate environmental pressure, and improve economic efficiency. The cold / heat source pipeline is also connected to reclaimed water, making full use of the low-grade energy contained in the sewage, realizing the transfer of low-temperature heat energy to high-temperature energy, which helps to alleviate energy consumption pressure, reduce energy consumption, and reduce the operating costs of sewage treatment plants.

[0023] 2. This invention uses multiple adsorbers, each switching between adsorption, desorption, and cooling states in a cyclical manner, to continuously adsorb CO2 from wastewater treatment plant emissions. Furthermore, by using multiple water source heat pumps as different cold and heat sources to heat or cool the adsorbers in different states, the system's efficiency is improved.

[0024] 3. The adsorber of the present invention has a spiral structure inside, and the air inlet direction of the adsorber is from bottom to top, which helps to promote full contact between the adsorbent and the gas, enhance the heat transfer between the adsorbent and the water source heat pump, and has the functions of high flow rate and high energy efficiency, which can greatly reduce the size of the adsorber. Attached Figure Description

[0025] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0026] Figure 1 This is a schematic diagram of the overall structure of the CO2 capture system in a wastewater treatment plant, which is the main feature of this invention. The solid lines in the diagram represent CO2 recovery pipelines, and the dashed lines represent cold / heat source pipelines.

[0027] Figure 2 This is a schematic diagram illustrating the CO2 capture method in the wastewater treatment plant in Embodiment 2 of the present invention. In the diagram, the solid lines represent CO2 recovery pipelines, the dashed lines represent cold / heat source pipelines, the black solid valves represent open valves, and the white solid valves represent closed valves.

[0028] As shown in the figure:

[0029] Bioreactor 1, Fan 2, First Adsorber 3

[0030] Second adsorber 4, Third adsorber 5, First inlet valve 6

[0031] Second air intake valve 7, Third air intake valve 8, First water outlet valve 9

[0032] Second outlet valve 10, Third outlet valve 11, First inlet valve 12

[0033] Second inlet valve 13, Third inlet valve 14, First vent valve 15

[0034] Second exhaust valve 16, Third exhaust valve 17, Four-way reversing valve 18

[0035] 19 Cold source three-way valve 20 First water source heat pump 21 Second water source heat pump

[0036] CO2 product container 22 Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0038] like Figure 1 As shown, a CO2 capture system for a wastewater treatment plant according to the present invention includes: a biological reaction chamber 1, an adsorber, and a cold / heat source pipeline. The adsorber is filled with a solid adsorbent. The air inlet of the biological reaction chamber 1 is connected to a mixed gas, and the air outlet of the biological reaction chamber 1 is connected to the air inlet of the adsorber. The air outlet of the adsorber is connected to a CO2 product tank 22. The cold / heat source pipeline includes a water source heat pump, which is connected to reclaimed water. The water source heat pump outlet, the adsorber, and the water source heat pump inlet are sequentially connected through pipelines and valves to form a loop.

[0039] The bioreactor 1 is equipped with a carrier packing material used to convert a mixed gas containing components such as CH4, N2O, and CO2. Solid adsorbents include activated carbon, molecular sieves, and composite porous media. When the mixed gas from the wastewater treatment plant enters the bioreactor 1, non-CO2 greenhouse gases such as CH4 and N2O are converted into other substances through adsorption, absorption, and oxidation by microorganisms attached to the carrier. Typically, sulfides are converted into sulfates, nitrogen oxides such as N2O are converted into nitrates and nitrogen, and carbides such as CH4 are decomposed into water and CO2. The bioreactor 1 effectively reduces non-CO2 greenhouse gases in the wastewater treatment plant's emissions while increasing the CO2 concentration entering the temperature-switching adsorber.

[0040] The adsorber operates in three states: adsorption, desorption, and cooling. The adsorber comprises one or more adsorbers connected in parallel. Preferably, multiple adsorbers are used to continuously adsorb CO2 from wastewater treatment plant emissions, with each adsorber cycling through adsorption, desorption, and cooling states. The water source heat pump comprises one or more water source heat pumps connected in series. Preferably, multiple water source heat pumps are used as different cold and heat sources to heat or cool the adsorbers in different states.

[0041] The bioreactor 1 is connected to the adsorber via a fan 2. The adsorber has an internal spiral structure, and the air intake direction is from bottom to top. This structure promotes full contact between the adsorbent and the gas, enhances the heat transfer between the adsorbent and the water source heat pump, and features high flow rate and high energy efficiency, while significantly reducing the size of the adsorber.

[0042] The adsorber has an air inlet valve at its air inlet and an air outlet valve at its air outlet. It also has a water inlet valve at its water inlet and an water outlet valve at its water outlet.

[0043] In this embodiment, two water source heat pumps and three adsorbers are used as an example. The water source heat pumps include a first water source heat pump 20 as a cold source and a second water source heat pump 21 as a heat source. The adsorbers include a first adsorber 3, a second adsorber 4, and a third adsorber 5. The cold / heat source pipeline also includes a cold source three-way valve 19 and a four-way reversing valve 18. The outlet of the first water source heat pump 20, the cold source three-way valve 19, the four-way reversing valve 18, the inlet valve, the adsorbers, the outlet valve, and the inlet of the first water source heat pump 20 are connected in sequence to form a loop. The outlet of the second water source heat pump 21, the four-way reversing valve 18, the inlet valve, the adsorbers, the outlet valve, and the inlet of the second water source heat pump 21 are connected in sequence to form a loop.

[0044] The bioreactor 1 is connected to the first inlet valve 6, the second inlet valve 7, and the third inlet valve 8 via a fan 2, and to the first adsorbent 3, the second adsorbent 4, and the third adsorbent 5 respectively. The first adsorbent 3, the second adsorbent 4, and the third adsorbent 5 are connected to the CO2 product tank 22 via the first outlet valve 15, the second outlet valve 16, and the third outlet valve 17. The interior of the first adsorbent 3, the second adsorbent 4, and the third adsorbent 5 is equipped with a spiral structure and filled with solid adsorbents such as activated carbon, molecular sieves, and composite porous media.

[0045] The first water source heat pump 20 and the second water source heat pump 21 are connected in series. The outlet of the first water source heat pump 21 is connected in sequence to the cold source three-way valve 19 and the four-way reversing valve 18. The four-way reversing valve 18 is connected to the first inlet valve 12, the second inlet valve 13, and the third inlet valve 14. The first inlet valve 12, the second inlet valve 13, and the third inlet valve 14 are connected to the first adsorber 3, the second adsorber 4, and the third adsorber 5, respectively. The first adsorber 3, the second adsorber 4, and the third adsorber 5 are connected to the first outlet valve 9, the second outlet valve 10, and the third outlet valve 11, respectively. The first outlet valve 9, the second outlet valve 10, and the third outlet valve 11 are connected to the inlet of the first water source heat pump 20, forming a loop. The outlet of the second water source heat pump 21 is first connected to the four-way reversing valve 18, and then connected to the first inlet valve 12, the second inlet valve 13, and the third inlet valve 14 respectively. The first inlet valve 12, the second inlet valve 13, and the third inlet valve 14 are connected to the first adsorber 3, the second adsorber 4, and the third adsorber 5 respectively. The first adsorber 3, the second adsorber 4, and the third adsorber 5 are connected to the first outlet valve 9, the second outlet valve 10, and the third outlet valve 11 respectively. The first outlet valve 9, the second outlet valve 10, and the third outlet valve 11 are connected to the inlet of the second water source heat pump 21, forming a loop.

[0046] The gas passing through bioreactor 1 enters the adsorber in the adsorption state for low-temperature CO2 adsorption. Unadsorbed exhaust gas is discharged into the atmosphere through a regulating three-way valve. After adsorption, the adsorber in the desorption state utilizes heat from a two-stage booster provided by the first water source heat pump 20 and the second water source heat pump 21 for CO2 desorption. The precipitated CO2 enters the CO2 collection tank 22 through a regulating three-way valve. After desorption, the adsorber in the cooling state utilizes the effluent from the first water source heat pump 20 as a cold source for cooling, preparing it for the adsorption state.

[0047] Example 2

[0048] According to the present invention, a method for CO2 capture in a wastewater treatment plant, based on the CO2 capture system of Example 1, includes the following steps:

[0049] Step S1: The mixed gas is introduced into the bioreactor 1, and the bioreactor 1 converts non-CO2 greenhouse gases.

[0050] In step S2, the gas enters the adsorber in the adsorption state from the gas outlet of the bioreactor 1 for low-temperature CO2 adsorption, and the unadsorbed gas is discharged into the external environment.

[0051] Step S3: After the adsorption state ends, the adsorber that has entered the desorption state is connected to the water source heat pump, which serves as the heat source, to desorb CO2. The precipitated CO2 enters the CO2 product tank 22.

[0052] Step S4: After the desorption state is completed, the adsorber, which has entered the cooling state, is connected to the water source heat pump, which serves as the cold source, for cooling, in preparation for entering the adsorption state.

[0053] like Figure 2 As shown, the first inlet valve 6 is open, the first outlet valve 15 opens the atmospheric discharge port, and the first water inlet valve 12 and the first water outlet valve 9 are both closed. The first adsorber 3 is in the adsorption state, and the solid adsorbent that fixes the CO2 in the gas onto the carrier completes the low-temperature adsorption. The unadsorbed tail gas is then discharged into the atmosphere through the regulating three-way valve. The cold source three-way valve 19 opens the cold source channel, the four-way reversing valve 18 is in the first state, the second inlet valve 7 is open, the second outlet valve 16 is closed, the second water inlet valve 13 is open, and the second water outlet valve 10 opens the cold source discharge port. The second adsorber 4 is in the cooling state, using the water output from the first water source heat pump 20 as a cold source for cooling, thus setting the temperature conditions for the next step of low-temperature adsorption. The four-way reversing valve 18 is in the first state, the third inlet valve 8 is closed, the third outlet valve 17 is open, the third water inlet valve 14 is open, the third water outlet valve 11 opens the heat source discharge port, and the third adsorber 5 is in the desorption state. The water from the second water source heat pump 21 is used as a heat source to raise the temperature, causing selectively fixed CO2 to precipitate from the solid adsorbent and enter the CO2 product tank 22 through the third outlet valve 17. The first adsorber 3, second adsorber 4, and third adsorber 5 are configured to continuously adsorb CO2 from the wastewater treatment plant's exhaust gas. The first adsorber 3, second adsorber 4, and third adsorber 5 cycle through adsorption, desorption, and cooling states, respectively.

[0054] A first water source heat pump 20, connected in series with a second water source heat pump 21, extracts low-grade energy from reclaimed water or wastewater from a sewage treatment plant with a relatively constant temperature and stable flow rate. This energy serves as a cold / heat source for the first adsorber 3, the second adsorber 4, and the third adsorber 5. The cold water from the first water source heat pump 20 enters the second adsorber 4 in a cooling state through a three-way valve 19 and a four-way reversing valve 18, thus cooling the adsorber. The cold water from the first water source heat pump 20 exits the second adsorber 4 through the second outlet valve 10 and mixes with the inlet water of the first water source heat pump 20, increasing the inlet water temperature and thus increasing the heating capacity of the water source heat pump, thereby regulating the outlet heat source temperature of the second water source heat pump 21. The heat water from the second water source heat pump 21 enters the third adsorber 5 in a desorption state through the four-way reversing valve 18, thus heating the third adsorber 5 and desorbing CO2. The heat water from the second water source heat pump 21 exits the third adsorber 5 through the third outlet valve 11 and enters the inlet water of the second water source heat pump 21.

[0055] The temperature of reclaimed water or wastewater from wastewater treatment plants ranges from 12-30℃, with winter temperatures around 12-13℃ and summer temperatures around 26-28℃. The desorption process in CO2 temperature-switching adsorption requires a significant amount of energy, while wastewater contains substantial residual heat energy, accounting for 40% of total urban waste heat emissions. By fully utilizing the characteristics of wastewater—small annual temperature variations and stable flow—residual heat energy can be extracted from wastewater using water source heat pump technology and converted into high-grade heat energy for the CO2 desorption process.

[0056] This application can effectively reduce the emission of greenhouse gases such as CH4 into the atmosphere, mitigate the greenhouse effect, and alleviate environmental pressure. Furthermore, it can capture CO2 for resource recovery and utilization, which can greatly improve economic efficiency.

[0057] This application utilizes the low-grade energy contained in sewage by inputting a small amount of high-grade electrical energy to transfer low-temperature heat energy to high-temperature energy. This not only alleviates the pressure of energy consumption but also reduces energy consumption and lowers the operating costs of sewage treatment plants.

[0058] In summary, the CO2 capture system and method for wastewater treatment plants provided in this application play an important role in promoting energy conservation and carbon reduction in wastewater treatment plants.

[0059] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0060] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A CO2 capture system for a wastewater treatment plant, characterized in that, include: The bioreactor (1), the adsorber and the cold / heat source pipeline, wherein the adsorber is filled with a solid adsorbent; The inlet of the bioreactor (1) is connected to the mixed gas, the outlet of the bioreactor (1) is connected to the inlet of the adsorber, and the outlet of the adsorber is connected to a CO2 product tank (22). The cold / heat source pipeline includes a water source heat pump, which is connected to reclaimed water. The outlet of the water source heat pump, the adsorber, and the inlet of the water source heat pump are connected in sequence through pipelines and valves to form a loop. Non-CO2 greenhouse gases are converted into CO2 through a bioreactor, adsorbed by an adsorber, and captured through cold / heat source pipelines for resource recovery and utilization. The adsorber has a spiral structure inside.

2. The CO2 capture system for a wastewater treatment plant as described in claim 1, characterized in that, The adsorber includes one or more adsorbers arranged in parallel, and the bioreactor (1) is connected to the adsorber via a fan (2).

3. The CO2 capture system for a wastewater treatment plant as described in claim 1, characterized in that, The water source heat pump includes one or more water source heat pumps connected in series.

4. The CO2 capture system for a wastewater treatment plant as described in claim 1, characterized in that, The air inlet of the adsorber is equipped with an air inlet valve, and the air outlet of the adsorber is equipped with an air outlet valve. The water inlet of the adsorber is equipped with a water inlet valve, and the water outlet of the adsorber is equipped with a water outlet valve.

5. The CO2 capture system for a wastewater treatment plant as described in claim 4, characterized in that, The water source heat pump includes a first water source heat pump (20) and a second water source heat pump (21). The adsorber includes a first adsorber (3), a second adsorber (4), and a third adsorber (5). The cold / heat source pipeline also includes a cold source three-way valve (19) and a four-way reversing valve (18). The outlet of the first water source heat pump (20), the cold source three-way valve (19), the four-way reversing valve (18), the inlet valve, the adsorber, the outlet valve and the inlet of the first water source heat pump (20) are connected in sequence to form a loop; The outlet of the second water source heat pump (21), the four-way reversing valve (18), the inlet valve, the adsorber, the outlet valve and the inlet of the second water source heat pump (21) are connected in sequence to form a loop.

6. The CO2 capture system for a wastewater treatment plant as described in claim 1, characterized in that, The air intake direction of the adsorber is from bottom to top.

7. The CO2 capture system for a wastewater treatment plant as described in claim 1, characterized in that, The solid adsorbent includes activated carbon, molecular sieves, and composite porous media.

8. The CO2 capture system for a wastewater treatment plant as described in claim 1, characterized in that, The bioreactor (1) is equipped with a carrier packing material, which is used to convert the mixed gas, including CH4, N2O and CO2.

9. A method for CO2 capture in a wastewater treatment plant, characterized in that, The wastewater treatment plant CO2 capture system according to any one of claims 1-8 includes the following steps: Step S1: The mixed gas is introduced into the bioreactor (1), and the bioreactor (1) converts non-CO2 greenhouse gases. In step S2, the gas enters the adsorber in the adsorption state from the outlet of the bioreactor (1) for low-temperature CO2 adsorption, and the unadsorbed gas is discharged into the external environment. Step S3: After the adsorption state ends, the adsorber that enters the desorption state is connected to the water source heat pump, which serves as a heat source, to desorb CO2. The precipitated CO2 enters the CO2 product tank (22). Step S4: After the desorption state is completed, the adsorber, which has entered the cooling state, is connected to the water source heat pump, which serves as the cold source, for cooling, in preparation for entering the adsorption state.

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