An efficient biological carbon sequestration system device based on coupling of flue gas and by-products after ammonia decarburization and cultivation of microalgae

Abstract

The utility model provides a kind of efficient biological carbon fixation system device based on ammonia method decarbonization after flue gas and byproduct coupling culture microalgae, utilize ammonia method decarbonization after flue gas as microalgae carbon source, utilize the ammonium sulfate obtained by ammonia method decarbonization as microalgae nitrogen source, utilize the ammonium bicarbonate obtained by ammonia method decarbonization as nitrogen source and auxiliary carbon source.Solution for ammonium sulfate is acidic, ammonium bicarbonate solution is alkaline, by adjusting the dosing ratio of ammonium bicarbonate and ammonium sulfate, can obtain the mixed culture medium solution of sufficient nitrogen content, pH value adjustable.Therefore, by real-time monitoring the pH value of culture medium, based on the deviation of this pH measurement value and preset target range, synergistic feedback control ammonia method decarbonization after flue gas flow and the dosing ratio of ammonium bicarbonate and ammonium sulfate, make culture system pH value stable maintain in preset target range, with efficient, controllable, stable, recycling etc.Advantages, can make the total cost of microalgae culture reduce more than 50%, cost advantage is very outstanding.

Description

Technical Field

[0001] This utility model relates to the fields of environmental engineering and microbial technology, specifically to a highly efficient biological carbon fixation system based on the coupled cultivation of microalgae from flue gas and byproducts after ammonia decarbonization. Background Technology

[0002] Microalgae, as a high-value biological resource, is rich in protein, unsaturated fatty acids, and bioactive substances, and has significant application potential in the food, pharmaceutical, and energy sectors. Research on algae applications has been conducted globally for over 200 years, and my country currently boasts the world's largest microalgae industry. Studies have shown that temperature control and lighting during microalgae cultivation require substantial energy consumption and CO2 supply, significantly increasing cultivation costs. This is the reason why microalgae cultivation has not been widely adopted, resulting in high prices for microalgae products that prevent them from reaching a large consumer base.

[0003] Currently, the clean flue gas from boilers, after undergoing denitrification, dust removal, desulfurization, and decarbonization, is free of impurities and toxic side effects according to laboratory tests. Among these, ammonia-based decarbonization technology is widely used in industry. Its basic principle is to utilize the absorption and desorption of CO2 by ammonia solution to achieve the absorption and separation of CO2 from the flue gas. During absorption, the ammonia solution reacts with CO2 in the flue gas to produce ammonium bicarbonate. This reaction is reversible and requires specific temperature and pressure conditions. During desorption, ammonium bicarbonate decomposes into ammonia and CO2. The CO2 is released, while the ammonia can be recycled. Generally, flue gas often contains sulfur dioxide. Ammonia-based decarbonization technology yields two main byproducts: ammonium bicarbonate and ammonium sulfate. Ammonium bicarbonate can serve as a nitrogen source and auxiliary carbon source for algae, while ammonium sulfate can serve as a nitrogen source for algae. After ammonia-based decarbonization, the CO2 concentration in the flue gas is between 10,000 and 50,000 ppm (1% to 5%), which can be used as a carbon source for algae.

[0004] However, such processes face a key challenge: drastic pH fluctuations. The introduction of CO2 from the flue gas acidifies the system, while microalgal photosynthesis consumes both CO2 and HCO3. - This can also lead to system alkalization. Traditional control methods typically suppress pH rise by simply introducing CO2 on and off, resulting in low control precision, large fluctuations, and difficulty in maintaining the pH within the narrow optimal range for microalgae growth. Furthermore, using only one ammonium salt (such as ammonium sulfate) as a nitrogen source cannot balance nitrogen source concentration and pH, further increasing the difficulty of pH control.

[0005] Currently, there is a lack of a solution that can simultaneously utilize the acidification of flue gas CO2 and the acid-base differences of the two ammonium salts, and achieve precise pH control through intelligent feedback. Utility Model Content

[0006] In view of the problems existing in the prior art, especially the existing technology for cultivating microalgae using flue gas and ammonia decarbonization byproducts, which suffers from unstable pH and difficulty in coordinating with nitrogen source control, this invention provides a highly efficient biological carbon fixation system based on the coupled cultivation of microalgae using flue gas and byproducts from ammonia decarbonization. The system utilizes the flue gas from ammonia decarbonization as the carbon source for microalgae, ammonium sulfate obtained from ammonia decarbonization as the nitrogen source, and ammonium bicarbonate obtained from ammonia decarbonization as both the nitrogen source and auxiliary carbon source. The ammonium sulfate solution is acidic, and the ammonium bicarbonate solution is alkaline. By adjusting the addition ratio of ammonium bicarbonate and ammonium sulfate, a mixed culture medium solution with sufficient nitrogen content and adjustable pH can be obtained. Therefore, by real-time monitoring of the pH value of the culture medium, and based on the deviation of the measured pH value from the preset target range, the flow rate of the flue gas from ammonia decarbonization and the addition ratio of ammonium bicarbonate and ammonium sulfate are coordinated and controlled to stably maintain the pH value of the culture system within the preset target range. This system has advantages such as high efficiency, controllability, stability, and recyclability, reducing the total cost of microalgae cultivation by more than 50%, demonstrating a significant cost advantage.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a highly efficient biological carbon fixation system based on the coupled cultivation of microalgae using flue gas and byproducts after ammonia decarbonization, comprising: a gas supply unit, a byproduct addition unit, a closed photobioreactor unit, a sensor feedback unit, and a biomass harvesting and recycling unit;

[0009] The closed-loop photobioreactor unit includes a closed-loop connected closed-pipe photobioreactor and a circulation tank. The top of the circulation tank has an outlet, a liquid inlet, and a recycling inlet. The outlet of the gas supply unit is connected to the upstream inlet of the closed-pipe photobioreactor to supply flue gas after ammonia decarbonization. The outlet of the by-product addition unit is connected to the liquid inlet to replenish nutrient solution containing ammonium sulfate and ammonium bicarbonate. The biomass harvesting and recycling unit is used to harvest microalgal biomass and to recycle the harvested culture medium through the recycling inlet. The sensor feedback unit includes a pH sensor installed on the circulation tank to monitor the pH of the culture medium in real time. The control terminal of the sensor feedback unit coordinates the feedback to regulate the flow rate of the flue gas after ammonia decarbonization corresponding to the gas supply unit and the addition ratio of ammonium bicarbonate and ammonium sulfate corresponding to the by-product addition unit.

[0010] It should be noted that the closed-loop connection between the closed-pipeline photobioreactor and the circulation tank described in this technical solution refers to the fact that the outlet of the closed-pipeline photobioreactor is connected to another inlet of the circulation tank, and the outlet of the circulation tank is connected to the inlet of the closed-pipeline photobioreactor.

[0011] Preferably, the gas supply unit is used to provide flue gas after ammonia decarbonization with a CO2 concentration of 1~5% (preferably 2~3%) and a temperature of 25~35℃ (preferably 28~32℃). The gas source is boiler tail gas treated by chemical absorption method, which has the characteristics of suitable heat and stable composition, and directly enters the closed photobioreactor, which is conducive to microalgae absorption and utilization.

[0012] Preferably, the by-product addition unit uses ammonium sulfate (0.1~2.5 g / L), a by-product from the decarbonization process, as a nitrogen source for microalgae, and ammonium bicarbonate (0.1~2.5 g / L) as a nitrogen source and auxiliary carbon source. Based on the pH detection results, the ratio of ammonium bicarbonate to ammonium sulfate is automatically adjusted and added to the culture system, which not only optimizes the nutrient supply but also regulates the pH of the system, achieving comprehensive utilization of resources.

[0013] Preferably, the closed photobioreactor unit is a tubular reactor constructed of high-transmittance glass or polycarbonate material. The tubular reactor is equipped with a light source (such as external natural light or an internal LED lighting system), a gas-liquid mixing interface, and a cooling sidewall to ensure that CO2 fully contacts the microalgae cells, improve carbon fixation efficiency, and prevent thermal inhibition caused by excessive temperature.

[0014] Preferably, the sensor feedback unit includes a pH feedback gas supply module and a pH feedback dynamic adjustment by-product dosing unit. To address the issue of excessive pH fluctuations during cultivation, the system incorporates a pH sensor-linked solenoid valve control device to intelligently regulate CO2 supply and the dosing ratio of the two by-products. When biomass is low, the nitrogen consumption rate is low, and the pH feedback gas supply module is prioritized. This module is configured to dynamically adjust the flow rate of the decarbonized flue gas from the gas supply unit based on real-time pH measurements, maintaining the culture medium pH within the range of 6.8 to 7.4. When biomass is high, the nitrogen consumption rate is high, and the pH feedback dynamic adjustment by-product dosing unit is prioritized. This unit dynamically adjusts the by-product dosing ratio based on real-time pH measurements, thereby maintaining a suitable pH and sufficient nitrogen source. Furthermore, the system includes sensors for monitoring temperature, biomass, dissolved oxygen, and other parameters within the circulating tank, which are linked to the control system to achieve real-time monitoring and automatic adjustment of various parameters during cultivation.

[0015] Preferably, the biomass harvesting and recycling unit uses filtration to collect microalgal biomass periodically, and the filtrate is returned to the culture system after being supplemented with nutrients, which significantly reduces water consumption and culture medium costs and improves resource utilization.

[0016] Compared to existing technologies that use a gas distributor at the bottom of the circulating tank to introduce carbon source gas while the photobioreactor simply performs photosynthetic cultivation, this technology directly introduces the flue gas from ammonia decarbonization upstream of a closed-loop photobioreactor. In particular, the use of a closed-loop photobioreactor with good light transmittance coupled with a gas-liquid mixing system significantly improves CO2 mass transfer efficiency, allowing microalgae to achieve high biomass accumulation in a short time, thus increasing carbon capture efficiency per unit volume of culture medium. Various indicators of the culture medium are monitored within the circulating tank, especially with an intelligent pH feedback function. This allows for the adjustment of the flow rate of the flue gas from ammonia decarbonization and the dosage ratio of ammonium bicarbonate and ammonium sulfate by monitoring the pH of the culture medium in the circulating tank. This effectively avoids the algal growth inhibition problems caused by drastic pH fluctuations and insufficient nitrogen source in traditional reactors, improving the system's adaptive adjustment capability and ensuring long-term stable operation of the cultivation environment.

[0017] Preferably, the sensor feedback unit includes sensors for pH, biomass, dissolved oxygen, temperature, etc., installed on the circulation tank. By monitoring parameters such as pH of the culture medium in the circulation tank, the flow rate of the flue gas after ammonia decarbonization and the ratio of added ammonium bicarbonate to ammonium sulfate in the gas supply unit are adjusted.

[0018] It should be noted that the sensor feedback unit mainly includes a pH feedback gas supply module and a pH feedback dynamic adjustment by-product dosing unit, comprising a pH sensor, a solenoid valve system, and a by-product nitrogen source dosing unit installed on the circulation tank. The monitoring end of the pH feedback gas supply module is electrically connected to the pH sensor on the circulation tank, and the control end of the pH feedback gas supply module is electrically connected to the flow solenoid valve on the gas inlet. The pH feedback gas supply module is configured to dynamically adjust the flow rate of the flue gas after ammonia decarbonization in the gas supply unit based on real-time pH measurements, so as to maintain the pH value of the culture medium in the circulation tank within the range of 6.8 to 7.4. The monitoring end of the pH feedback dynamic adjustment by-product dosing unit is electrically connected to the pH sensor on the circulation tank, and the control end of the pH feedback dynamic adjustment by-product nitrogen source module is electrically connected to the metering pump on the by-product dosing pipeline. The pH feedback dynamic adjustment by-product dosing unit is configured to dynamically adjust the ratio of ammonium bicarbonate to ammonium sulfate supplied by the by-product dosing pipeline based on real-time pH measurement values, so as to maintain sufficient nitrogen source in the culture medium in the circulation tank while adjusting the pH value to be maintained within the range of 6.8 to 7.4.

[0019] Preferably, a gas-liquid mixing interface is provided at the upstream inlet of the closed-pipe photobioreactor; the gas inlet of the gas-liquid mixing interface serves as the gas inlet of the closed-pipe photobioreactor, and is used to introduce the flue gas after ammonia decarbonization, that is, the flue gas CO2 is directly introduced into the closed photobioreactor, instead of into the circulation tank; the liquid inlet of the gas-liquid mixing interface is used to connect to the liquid outlet of the circulation tank.

[0020] Preferably, flue gas after ammonia decarbonization is introduced through a flue gas duct, and along the flow direction, a variable frequency induced draft fan, a flue gas check valve, a flue gas filter, and an inlet CO2 sensor are sequentially installed on the flue gas duct.

[0021] Preferably, the sensor feedback unit further includes a temperature sensor, a biomass sensor, and a dissolved oxygen sensor installed on the circulating tank, used to monitor the process parameters of the culture medium in the circulating tank, and to coordinate the control of the flue gas supply module, the by-product feeding module, and the biomass harvesting and recycling unit.

[0022] Preferably, the reactor material of the closed-pipe photobioreactor is transparent glass or transparent polycarbonate, and LED lights and a sidewall cooling system are installed on the sidewall of the pipe to ensure that CO2 fully contacts the microalgae cells, improve carbon fixation efficiency and prevent thermal inhibition caused by excessive temperature.

[0023] Preferably, the biomass harvesting and recycling unit includes a flocculation system and a centrifugation system connected in series; the outlet of the recycling tank is connected to the inlet of the flocculation system, the upper outlet of the flocculation system is connected to the recycling inlet, and the lower outlet of the flocculation system is connected to the inlet of the centrifugation system; the liquid outlet of the centrifugation system is connected to the recycling inlet, and the solid outlet of the centrifugation system is used to harvest microalgae biomass.

[0024] Preferably, the upper outlet of the flocculation system is also connected to a waste liquid treatment system for periodically removing a portion of the bottom liquid.

[0025] Preferably, the liquid outlet of the centrifuge system is also connected to a waste liquid treatment system for periodically removing a portion of the bottom liquid.

[0026] The above-mentioned high-efficiency biological carbon fixation system based on the coupled cultivation of microalgae using flue gas and byproducts from ammonia decarbonization can be used to carry out a high-efficiency biological carbon fixation method based on the coupled cultivation of microalgae using flue gas and byproducts from ammonia decarbonization, including the following:

[0027] Prepare flue gas after ammonia decarbonization at a temperature of 25-35 °C and a CO2 concentration of 1-5%. Prepare ammonium sulfate and ammonium bicarbonate obtained from ammonia decarbonization and use them to prepare a culture medium. Inoculate microalgae into the prepared culture medium and directly introduce the flue gas after ammonia decarbonization for photosynthetic cultivation. By monitoring the pH value of the culture medium in real time, coordinate feedback to regulate the flow rate of the flue gas after ammonia decarbonization and the addition ratio of ammonium bicarbonate and ammonium sulfate, so that the pH value of the culture medium is stably maintained within the preset target range, thereby achieving efficient biological carbon fixation.

[0028] This technical solution directly utilizes the flue gas obtained from ammonia decarbonization as a carbon source for microalgae, the ammonium sulfate obtained from ammonia decarbonization as a nitrogen source for microalgae, and the ammonium bicarbonate obtained from ammonia decarbonization as both a nitrogen source and an auxiliary carbon source. By coupling and synergistically optimizing microalgae cultivation conditions, it achieves the resource-based synergistic utilization of CO2 and by-products in the flue gas obtained from ammonia decarbonization. The flue gas parameters after ammonia decarbonization are suitable and can be directly utilized, while the by-products can be used as a nutrient source and pH regulator. This technical solution breaks through the bottleneck of high energy consumption and a large proportion of carbon source and nutrient costs in traditional microalgae cultivation, and can reduce the total cost of microalgae cultivation by more than 50%. It has the characteristics of low cost, high efficiency, and environmental friendliness, and is suitable for large-scale microalgae carbon fixation and biomass production.

[0029] This technical solution directly utilizes flue gas from ammonia decarbonization at a temperature of 25-35 ℃ and a CO2 concentration of 1-5%. The gas source is boiler tail gas treated by chemical absorption, possessing characteristics such as suitable heat and stable composition, which is conducive to microalgae absorption and utilization. This technical solution directly utilizes ammonium sulfate, a byproduct of ammonia decarbonization, as a nitrogen source for microalgae, and ammonium bicarbonate as a nitrogen source and auxiliary carbon source. This not only optimizes nutrient supply but also adjusts the pH of the system, achieving comprehensive resource utilization.

[0030] This technical solution achieves high-precision and stable control of the cultivation environment by real-time feedback of pH value and coordinated regulation of the flow rate of flue gas after ammonia decarbonization and the nutrient salt addition ratio of ammonium bicarbonate and ammonium sulfate. This solution enables the direct and synergistic utilization of CO2 and byproducts in the flue gas after ammonia decarbonization, and is suitable for large-scale microalgae carbon fixation and biomass production.

[0031] In this technical solution, the temperature of the flue gas after ammonia decarbonization is 25~35 ℃, such as 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃, 30 ℃, 31 ℃, 32 ℃, 33 ℃, 34 ℃ or 35 ℃, etc.

[0032] In this technical solution, the CO2 concentration of the flue gas after ammonia decarbonization is 1~5%, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc.

[0033] It should be noted that in this technical solution, after inoculation of microalgae, the flue gas from ammonia decarbonization and the nutrient solution containing ammonium sulfate and ammonium bicarbonate are continuously supplied. The only difference is that the harvesting of microalgae biomass can be periodic, for example, harvesting microalgae biomass after 4-10 days of photosynthetic cultivation, with real-time monitoring of various parameters during this period; or it can be continuous harvesting. The filtrate after harvesting the microalgae biomass is recycled after replenishing the nutrient solution containing ammonium sulfate and ammonium bicarbonate. This relevant content is existing technology and will not be elaborated upon here.

[0034] In this technical solution, the temperature of the flue gas after ammonia decarbonization is 28~32 ℃, such as 28 ℃, 28.5 ℃, 29 ℃, 29.5 ℃, 30 ℃, 30.5 ℃, 31 ℃, 31.5 ℃ or 32 ℃, etc.

[0035] In this technical solution, the CO2 concentration of the flue gas after ammonia decarbonization is 2~3%, such as 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3%, etc.

[0036] In this technical solution, the concentration of ammonium sulfate in the prepared culture medium is 0.1~2.5 g / L, for example, 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.8 g / L, 1.0 g / L, 1.2 g / L, 1.5 g / L, 1.7 g / L, 2.0 g / L or 2.5 g / L.

[0037] In this technical solution, the concentration of ammonium bicarbonate in the prepared culture medium is 0.1~2.5 g / L, for example, 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.8 g / L, 1.0 g / L, 1.2 g / L, 1.5 g / L, 1.7 g / L, 2.0 g / L or 2.5 g / L, etc.

[0038] In this technical solution, the ratio of ammonium bicarbonate to ammonium sulfate in the prepared culture medium is dynamically adjusted according to the monitored pH results. The concentration range of ammonium bicarbonate to ammonium sulfate is (0.1~2.5 g / L) / (0.1~2.5 g / L). By adjusting the ratio of ammonium bicarbonate to ammonium sulfate, acidic or alkaline culture media can be obtained, which can dynamically regulate the pH of the culture system and provide a sufficient nitrogen source.

[0039] It should be noted that existing technologies suffer from problems such as the toxicity of ammonium sulfate and ammonium bicarbonate, pH dysregulation, and nitrogen loss or deficiency. Particularly when using a single ammonium salt as a nitrogen source, in the technical scheme of controlling the pH of microalgae cultivation by feedback regulation of the flue gas flow rate after ammonia decarbonization, a pH that is too low can easily cause acid stress to the microalgae, while a pH that is too high can easily cause ammonium poisoning. Simultaneously, to maintain pH stability, solely controlling the flue gas flow rate or the content of a single ammonium salt through feedback regulation can lead to excessive or insufficient carbon dioxide, or excessive or insufficient nitrogen source. This makes it impossible to achieve coordination between nitrogen source, carbon dioxide, and pH, and is therefore unsuitable for large-scale microalgae cultivation. However, this technical scheme, through experiments, demonstrates that by dynamically and collaboratively controlling the addition ratio of ammonium sulfate and ammonium bicarbonate, and the flue gas flow rate after ammonia decarbonization, it is possible to directly utilize ammonium sulfate obtained from ammonia decarbonization as a nitrogen source for microalgae, and directly utilize ammonium bicarbonate obtained from ammonia decarbonization as both a nitrogen source and an auxiliary carbon source. This results in a stable pH in the cultivation system, sufficient nitrogen source, and avoids ammonium poisoning, acid stress, and waste or deficiency of carbon dioxide.

[0040] In this technical solution, the microalgae is Chlorella sp., which is tolerant to low concentrations of CO2, and is preferably Chlorella vulgaris.

[0041] In this technical solution, the inoculation density of the microalgae is 0.15~0.25 g / L, such as 0.15 g / L, 0.16 g / L, 0.17 g / L, 0.18 g / L, 0.19 g / L, 0.20 g / L, 0.21 g / L, 0.22 g / L, 0.23 g / L, 0.24 g / L, or 0.25 g / L.

[0042] In this technical solution, the photosynthetic culture is carried out in a closed tubular photobioreactor. A gas inlet is set at the upstream inlet of the closed tubular photobioreactor, and a circulation tank is connected to the downstream outlet of the closed tubular photobioreactor. The flue gas after ammonia decarbonization enters through the gas inlet, and the nutrient solution containing ammonium sulfate and ammonium bicarbonate is replenished by entering the circulation tank through independent dosing pipelines.

[0043] In this technical solution, the flow rate of the flue gas after ammonia decarbonization and the ratio of added ammonium sulfate and ammonium bicarbonate are further controlled by monitoring the pH, biomass, and dissolved oxygen content of the culture medium in the circulating tank.

[0044] In this technical solution, the strategy of coordinated feedback control is as follows: when the pH value of the culture medium is detected to be higher than the upper limit of the preset target range, the flow rate of the flue gas after ammonia decarbonization is increased, and / or the proportion of ammonium sulfate added is increased; when the pH value of the culture medium is detected to be lower than the lower limit of the preset target range, the flow rate of the flue gas after ammonia decarbonization is decreased, and / or the proportion of ammonium bicarbonate added is increased.

[0045] In this technical solution, the preset target range for the pH value of the culture medium in the circulation tank is 6.8~7.4.

[0046] It should be noted that this technical solution is equipped with an intelligent pH dynamic feedback function, which dynamically adjusts the flow rate of flue gas after ammonia decarbonization and the addition ratio of ammonium sulfate and ammonium bicarbonate based on real-time pH measurement values, so as to maintain the pH value of the culture medium in the range of 6.8 to 7.4 and ensure sufficient nitrogen and carbon sources, thereby maintaining a suitable microalgae growth environment.

[0047] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0048] This invention provides a highly efficient biological carbon fixation system based on the coupled cultivation of microalgae using flue gas and byproducts after ammonia decarbonization. For the first time, it realizes the direct utilization of flue gas (low concentration CO2) and byproducts (ammonium sulfate and ammonium bicarbonate) after ammonia decarbonization, coupled with the cultivation of microalgae, achieving the synergistic utilization of CO2 resources and the high-value utilization of byproducts, and significantly improving the overall utilization rate of carbon and nitrogen resources. Attached Figure Description

[0049] Figure 1 This is a highly efficient biological carbon fixation system based on the coupled cultivation of microalgae using flue gas and byproducts from ammonia decarbonization, as described in a specific embodiment of this utility model. In the figure: 1: Flue gas after ammonia decarbonization; 2: Byproduct addition unit; 3: Flue gas pipeline; 4: Byproduct addition pipeline; 5: Variable frequency induced draft fan; 6: Flue gas check valve; 7: Closed-loop photobioreactor; 8: Circulation bottom pipe; 9: Circulation top pipe; 10: Circulation tank; 11: Circulation pump; 12: Harvesting and flocculation pipeline; 13: Harvesting pump; 14: Flocculation system; 15: Centrifugation system inlet pump; 16: Flocculation return pipeline. 17: Centrifuge system inlet pipeline; 18: Centrifuge system; 19: Centrifuge system return pump; 20: Centrifuge return pipeline; 21: Return filter; 22: Flue gas filter; 23: Temperature sensor; 24: pH sensor; 25: Biomass sensor; 26: Dissolved oxygen sensor; 27: Circulation tank outlet CO2 sensor; 28: Inlet flue gas CO2 sensor; 29: Circulation tank outlet pipe; 30: Outlet filter; 31: Waste liquid pipeline; 32: Waste liquid treatment system; 33: Water replenishment system; 34: Flocculation system return pump; 35: Microalgae biomass. Detailed Implementation

[0050] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0051] like Figure 1 As shown, the high-efficiency biological carbon fixation system device based on the coupled cultivation of microalgae using flue gas and by-products after ammonia decarbonization in a specific embodiment of this utility model includes: a gas supply unit, a by-product addition unit 2, a closed photobioreactor unit, a sensor feedback unit, and a biomass harvesting and recycling unit.

[0052] The closed-loop photobioreactor unit includes a closed-loop tubular photobioreactor 7 and a circulation tank 10. The top of the circulation tank 10 has a circulation tank outlet, a liquid inlet, and a recycling inlet. The liquid outlet of the closed-loop tubular photobioreactor 7 is connected to another liquid inlet of the circulation tank 10 via a circulation top pipe 9. The outlet of the circulation tank 10 is connected to the liquid inlet of the closed-loop tubular photobioreactor 7 via a circulation bottom pipe 8. A circulation tank outlet pipe 29, equipped with an outlet filter 30 and a circulation tank outlet CO2 sensor 27, is provided corresponding to the circulation tank outlet. The outlet of the gas supply unit is connected to... The upstream inlet of the closed-loop photobioreactor 7 is connected to supply flue gas 1 after ammonia decarbonization; the outlet of the by-product addition unit 2 is connected to the liquid inlet via the by-product addition pipe 4 to replenish the nutrient solution containing ammonium sulfate and ammonium bicarbonate; the biomass harvesting and recycling unit is used to harvest microalgal biomass and to recycle the harvested culture medium through the recycling inlet; the sensor feedback unit is used to monitor the process parameters of the culture medium in the recycling tank and to control the gas supply unit, the by-product addition unit 2, and the biomass harvesting and recycling unit.

[0053] The sensor feedback unit includes a pH sensor 24 installed on the circulation tank 10. By monitoring the pH value of the culture medium in the circulation tank 10, the flow rate of the flue gas 1 after ammonia decarbonization in the gas supply unit is adjusted, and the ratio of ammonium bicarbonate and ammonium sulfate added by the by-product addition unit 2 is also adjusted. The sensor feedback unit also includes a temperature sensor 23, a biomass sensor 25, and a dissolved oxygen sensor 26 installed on the circulation tank 10, which are used to monitor the process parameters of the culture medium in the circulation tank 10 and coordinate the control of the by-product addition unit 2 and the biomass harvesting and recycling unit.

[0054] A gas-liquid mixing interface is provided at the upstream inlet (located in the bottom circulation pipe 8) of the closed-pipe photobioreactor 7; the gas inlet of the gas-liquid mixing interface serves as the gas inlet of the closed-pipe photobioreactor 7, used to introduce the flue gas 1 after ammonia decarbonization; the liquid inlet of the gas-liquid mixing interface is used to connect to the liquid outlet of the circulation tank 10, and the material flow is realized through the circulation pump 11; the flue gas 1 after ammonia decarbonization is introduced through the flue gas pipe 3, and along the flow direction, a variable frequency induced draft fan 5, a flue gas check valve 6, a flue gas filter 22, and a flue gas CO2 sensor 28 are sequentially installed on the flue gas pipe 3; the reactor material of the closed-pipe photobioreactor 7 is transparent glass or transparent polycarbonate, and LED lights and a side wall cooling system are installed on the side wall of the pipe;

[0055] The biomass harvesting and recycling unit includes a flocculation system 14 and a centrifugal system 18 connected in series. The outlet of the recycling tank 10 is connected to the inlet of the flocculation system 14 via a harvesting flocculation pipe 12, and material flow is achieved through a harvesting pump 13. A water replenishment system 33 is connected to the harvesting flocculation pipe 12. The upper outlet of the flocculation system 14 is connected to the recycling inlet via a flocculation return liquid pipe 16, and material flow is achieved through a flocculation system return liquid pump 34. The upper outlet of the flocculation system 14 is also connected to a waste liquid treatment system 32 via a waste liquid pipe 31 for periodically removing a portion of the bottom liquid. The flocculation system 14... The lower outlet of the centrifuge system is connected to the inlet of the centrifuge system 18 via the centrifuge system inlet pipe 17, and the material flow is achieved through the centrifuge system inlet pump 15. The liquid outlet of the centrifuge system 18 is connected to the recycling inlet via the centrifuge return liquid pipe 20, and the material flow is achieved through the centrifuge system return liquid pump 19. The liquid outlet of the centrifuge system 18 is also connected to the waste liquid treatment system 32 via the waste liquid pipe for periodically treating part of the centrifuge liquid. The solid outlet of the centrifuge system 18 is used to harvest microalgae biomass 35. A return liquid filter 21 is installed on the main pipe entering the recycling inlet to filter solid impurities.

[0056] To verify the stability and applicability of the proposed high-efficiency biological carbon fixation system based on the coupled cultivation of microalgae using flue gas and byproducts from ammonia decarbonization, three groups of microalgae photosynthetic cultivation experiments under different conditions were designed, and five comparative groups were set up for comparison. The microalgae used in the experiments was *Chlorella vulgaris*, which has been proven in multiple studies to have good CO2 tolerance and biomass accumulation capacity, and is widely used in CO2 biological fixation and water purification processes. All experiments were conducted under actual boiler flue gas conditions, with the gas source being flue gas from ammonia decarbonization, CO2 concentration controlled at 1-5%, and temperature maintained at 30±5℃.

[0057] Example 1

[0058] Initially, 0.5 g / L ammonium sulfate and 1.7 g / L ammonium bicarbonate were added to the culture medium as a nitrogen source and auxiliary carbon source, respectively. The initial inoculation density of the algal solution was 0.20 g / L. During the first two days of cultivation, the biomass was consistently below 1 g / L, and the pH feedback gas supply module was used for regulation, maintaining the pH between 6.8 and 7.4 throughout the cultivation process. By the third day of cultivation, the microalgal biomass concentration began to reach 1 g / L, at which point nitrogen consumption was rapid. The pH feedback dynamic adjustment by the byproduct addition unit was then used to regulate the pH by adjusting the addition ratio of ammonium sulfate and ammonium bicarbonate, while the pH feedback gas supply module assisted in regulation. This effectively avoided the adverse effects of drastic pH fluctuations and insufficient nitrogen on algal cell growth during photosynthesis. After 7 days of cultivation, the microalgal biomass concentration significantly increased to 5.42 g / L. The extremely high photosynthetic efficiency easily led to a rise in pH and a large consumption of nitrogen. At this point, the ammonium sulfate addition ratio was increased, and the flue gas CO2 flow rate was also increased, resulting in a CO2 biological fixation efficiency of 78.3%. Compared with experimental results in similar conditions in the comparative literature without the use of feedback control, such as the peak biomass of Chlorella being only 0.96 g / L under 2% CO2 culture conditions, this system effectively improved the carbon capture efficiency and yield of microalgae while maintaining pH stability.

[0059] Example 2

[0060] Initially, 0.5 g / L ammonium sulfate was added to the culture medium as a nitrogen source, and 1.7 g / L ammonium bicarbonate was added as both a nitrogen source and an auxiliary carbon source. The initial inoculation density of the algal solution was 0.20 g / L, similar to the cultivation in Example 1. After 7 days of cultivation, the microalgae grew rapidly and the system stabilized. However, in this example, after the seventh day of cultivation, continuous rainy weather occurred, resulting in insufficient light and low photosynthetic efficiency, with the pH value reaching 6.5. At this point, the proportion of ammonium bicarbonate added was increased, while the CO2 flow rate of the flue gas was reduced. During the rainy weather, the system pH was maintained between 6.8 and 7.4. By the tenth day of cultivation, the rainy weather ended, photosynthetic efficiency improved, and the pH value gradually increased. At this time, the proportion of ammonium sulfate added as a byproduct was increased, and the CO2 flow rate of the flue gas was increased to ensure system pH stability and sufficient nitrogen source.

[0061] Example 3

[0062] The aim was to verify the stability and resource recycling efficiency of the system under continuous operation. The experiment employed a "batch harvesting, replenishment and circulation" strategy, with one-third of the culture medium being harvested daily and the filtrate replenished (1 g / L ammonium sulfate, 2 g / L ammonium bicarbonate) before being added back to the reactor. Over 10 days of continuous operation, the microalgal biomass in the reactor fluctuated between 6.2 and 6.4 g / L, and the average CO2 absorption efficiency remained at 77.9%. After simple filtration and nutrient replenishment, no algal degradation, contamination, or metabolic disorders were observed in the filtrate, indicating that the system possesses strong closed-loop operation capabilities and the potential for long-term operation.

[0063] Comparative Example 1

[0064] Following the traditional cultivation technique of a closed-loop photobioreactor, decarbonized flue gas with a CO2 concentration of 2.5% was directly introduced, but no byproducts were added; only pH feedback was used for flue gas regulation, and the nutrient source was conventional NaNO3 (1.0 g / L). Under the same light and temperature conditions, after 7 days, the biomass concentration of microalgae was only 2.73 g / L, the CO2 absorption efficiency was 52.4%, and the pH of the reaction solution fluctuated significantly (6.6–7.8), which significantly affected the metabolic stability of microalgae and the CO2 absorption efficiency. Furthermore, because no byproducts were used as a nutrient source, the nitrogen utilization rate was only 54.8%, resulting in high cultivation costs and low resource utilization. These phenomena indicate that in traditional systems without feedback control and byproduct synergistic regulation, the carbon fixation efficiency of microalgae is significantly limited, making it difficult to meet the stability requirements for continuous operation.

[0065] Comparative Example 2

[0066] Compared to Example 1, using only 1.0 g / L ammonium sulfate as the nitrogen source, the culture medium itself is acidic, and CO2 can only be introduced intermittently to ensure that the pH does not drop further. This results in a significant decrease in microalgal biomass concentration after 7 days of cultivation, to only 1.43 g / L, with a CO2 biological fixation efficiency of 34.4%.

[0067] Comparative Example 3

[0068] Compared to Example 1, which uses only 1.0 g / L ammonium bicarbonate as a nitrogen source, the culture medium itself is alkaline, requiring a large amount of CO2 to be introduced to maintain the culture system within the range of 6.8-7.4. This results in a situation where, after 7 days of culture, although the microalgal biomass concentration is slightly higher than that of Comparative Example 2 at 3.25 g / L, the CO2 biological fixation efficiency drops sharply to 19.2%, and a large amount of CO2 is wasted.

[0069] Comparative Example 4

[0070] Compared to Example 1, by keeping the byproduct addition ratio fixed at 0.5 g / L ammonium sulfate and 1.7 g / L ammonium bicarbonate, and maintaining system pH stability solely through pH feedback control of flue gas CO2, after 7 days of cultivation, the microalgal biomass concentration significantly decreased to only 2.93 g / L. The pH feedback control exhibited a certain lag, resulting in pH fluctuations ranging from 6.7 to 7.5, exceeding the target range. The CO2 biofixation efficiency reached 56.1%.

[0071] Comparative Example 5

[0072] Compared to Example 1, maintaining system pH stability solely through dynamic adjustment of byproducts while fixing flue gas CO2 flow rate resulted in a significant decrease in microalgal biomass concentration to only 2.96 g / L after 7 days of cultivation, with CO2 biofixation efficiency reaching 51.3%. In the early stages of cultivation, CO2 was significantly excessive, while in the later stages, it was significantly insufficient.

[0073] The comparative analysis of the above embodiments and comparative examples shows that the microalgae carbon fixation system of this invention performs excellently in several key performance indicators. The pH feedback gas supply module can monitor the changes in the acidity and alkalinity of the culture medium in real time and adjust the CO2 supply in a timely manner to maintain a suitable growth environment; the pH feedback dynamic adjustment by-product addition unit realizes the resource-efficient utilization of by-products from ammonia decarbonization, maintaining pH while providing sufficient nitrogen source, reducing nutrient costs and improving nitrogen and carbon utilization efficiency; the closed photobioreactor has good mass transfer conditions and light efficiency, effectively improving CO2 absorption and microalgae photosynthetic rate; and the recycling system ensures multiple uses of the nutrient solution, further reducing operating costs.

[0074] In summary, based on domestic and international literature and the implementation results of this utility model, it is evident that this system effectively integrates multiple technologies, including flue gas resource utilization after ammonia decarbonization, comprehensive utilization of by-products, and efficient microalgae cultivation. This significantly improves CO2 fixation efficiency, resource utilization efficiency, and system operational stability, demonstrating strong innovation and industrialization potential. This utility model overcomes the bottlenecks in current microalgae carbon fixation technologies, such as low CO2 utilization, high operating costs, and difficult by-product disposal.

[0075] In summary, this invention provides a highly efficient microalgae carbon fixation system that combines the optimization of flue gas resources and by-product nutrients after ammonia decarbonization, overcoming key technical challenges such as low gas utilization, pH dysregulation, and resource waste in traditional microalgae cultivation processes.

[0076] The above description is only a specific embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model fall within the protection and disclosure scope of the present utility model.

Claims

1. An efficient biological carbon sequestration system device based on coupling microalgae cultivation with flue gas and by-products after ammonia-based decarbonization, characterized in that, include: Gas supply unit, by-product addition unit, closed photobioreactor unit, sensor feedback unit, biomass harvesting and recycling unit; The closed-loop photobioreactor unit includes a closed-loop connected closed-pipe photobioreactor and a circulation tank. The top of the circulation tank has a circulation tank outlet, a liquid inlet, and a recycling inlet. The outlet of the gas supply unit is connected to the upstream inlet of the closed-pipe photobioreactor to supply flue gas after ammonia decarbonization. The outlet of the by-product addition unit is connected to the liquid inlet for replenishing nutrient solution containing ammonium sulfate and ammonium bicarbonate. The biomass harvesting and recycling unit is used to harvest microalgal biomass and to recycle the harvested culture medium through the recycling inlet. The sensor feedback unit includes a pH sensor, which is installed on the circulation tank to monitor the pH of the culture medium in real time. The control terminal of the sensor feedback unit enables coordinated feedback control of the flow rate of the flue gas after ammonia decarbonization corresponding to the gas supply unit and the addition ratio of ammonium bicarbonate and ammonium sulfate corresponding to the by-product addition unit.

2. The high-efficiency biological carbon sequestration system device based on the coupling culture of microalgae by using the decarbonized flue gas and by-products of ammonia process according to claim 1, characterized in that, The sensor feedback unit is mainly equipped with a pH feedback gas supply module and a pH feedback dynamic adjustment by-product dosing unit, including a pH sensor, a solenoid valve system, and a by-product nitrogen source dosing unit installed on the circulation tank.

3. The high-efficiency biological carbon sequestration system device based on the coupling culture of microalgae with the flue gas and by-products after ammonia decarburization according to claim 1 or 2, characterized in that, A gas-liquid mixing interface is provided at the upstream inlet of the closed-pipe photobioreactor; the gas inlet of the gas-liquid mixing interface serves as the gas inlet of the closed-pipe photobioreactor for introducing flue gas after ammonia decarbonization; the liquid inlet of the gas-liquid mixing interface is used to connect to the liquid outlet of the circulation tank.

4. The high-efficiency biological carbon fixation system based on the coupled cultivation of microalgae using flue gas and byproducts after ammonia decarbonization, as described in claim 1 or 2, is characterized in that... After ammonia decarbonization, the flue gas is introduced through a flue gas duct. Along the flow direction, a variable frequency induced draft fan, a flue gas check valve, a flue gas filter, and an inlet CO2 monitor are sequentially installed on the flue gas duct.

5. The high-efficiency biological carbon sequestration system device based on the coupling culture of microalgae with the flue gas and by-products after ammonia decarburization according to claim 1 or 2, characterized in that, The sensor feedback unit also includes a temperature sensor, a biomass sensor, and a dissolved oxygen sensor installed on the circulating tank, used to monitor the process parameters of the culture medium in the circulating tank and to coordinate the control of the gas supply unit, the by-product addition unit, and the biomass harvesting and recycling unit.

6. The high-efficiency biological carbon sequestration system device based on the coupling culture of microalgae with the flue gas and by-products after ammonia decarburization according to claim 1 or 2, characterized in that, The closed-loop photobioreactor is made of transparent glass or transparent polycarbonate, and LED lights and a sidewall cooling system are installed on the sidewall of the pipeline.

7. The high-efficiency biological carbon sequestration system device based on the coupling culture of microalgae with the flue gas and by-products after ammonia decarburization according to claim 1 or 2, characterized in that, The biomass harvesting and recycling unit includes a flocculation system and a centrifugation system connected in series. The outlet of the recycling tank is connected to the inlet of the flocculation system, the upper outlet of the flocculation system is connected to the recycling inlet, and the lower outlet of the flocculation system is connected to the inlet of the centrifugation system. The liquid outlet of the centrifugation system is connected to the recycling inlet, and the solid outlet of the centrifugation system is used to harvest microalgae biomass.

8. The high-efficiency biological carbon sequestration system device based on the coupling culture of microalgae by using the decarbonized flue gas and by-products of ammonia process according to claim 7, characterized in that, The upper outlet of the flocculation system is also connected to the waste liquid treatment system for periodically removing a portion of the bottom liquid. 9.The high-efficiency biological carbon sequestration system device based on the coupling culture of microalgae with the decarbonized flue gas and by-products according to claim 7, characterized in that, The liquid outlet of the centrifuge system is also connected to the waste liquid treatment system.

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