System integrating microalgae carbon sequestration and desert ecological restoration

Abstract

The invention relates to a system for integrating microalgae carbon sequestration and desert ecological restoration. The system comprises a CO2 absorption area raceway pond reactor, a microalgae culture area raceway pond reactor, a sprinkling irrigation device and a control device. According to the system disclosed by the invention, efficient capture of CO2 and large-scale culture of microalgae are realized through a raceway pond partition design, floating ball filler circulation and an intelligent control technology. The harvested microalgae are prepared into algae liquid, desert soil is improved through a sprinkling irrigation system, the organic carbon content is remarkably increased, salinization is reduced, and vegetation recovery is promoted. The technology integrates carbon emission reduction and ecological restoration functions, and provides an innovative solution for industrial flue gas treatment and desertification control.

Description

Technical Field

[0001] This invention belongs to the field of environmental technology and relates to a system that integrates microalgae carbon fixation and desert ecological restoration. Background Technology

[0002] Currently, the fields of CO2 emission reduction from flue gas in thermal power plants and desert ecological restoration face three major technical bottlenecks: First, it is difficult to balance carbon capture efficiency and cost. Although traditional chemical absorption methods (such as MEA) achieve a capture rate of over 85%, the regeneration energy consumption reaches 2.3 GJ / t CO2, while open raceway microalgae ponds are difficult to industrialize due to uneven gas-liquid mixing and severe light attenuation. Second, the single resource utilization path of microalgae results in 78% of the harvest being used only for low-value-added biodiesel production, lacking targeted extraction technology for high-value components. Third, desert governance faces an efficiency contradiction: the application of chemical amendments leads to soil salinization within 2-3 years, while microbial remediation requires 5 years to achieve 20% vegetation coverage.

[0003] Microalgae carbon fixation technology enhances the liquid-phase CO2 conversion rate through a bicarbonate buffer system combined with immobilized carbonic anhydrase (CA). The applicant's experimental demonstration in the Kubuqi Desert of Inner Mongolia showed that 3-5 t / ha of microalgae biomass irrigation increased soil organic carbon by 1.8 times, sea buckthorn survival rate to 55%, and prevented secondary salinization, demonstrating its high photosynthetic efficiency and salt tolerance. While microalgae cultivation in raceway ponds can increase microalgae yield by 40%, it is limited by a stable carbon source supply. Therefore, there is an urgent need to construct a "carbon capture-microalgae proliferation-soil remediation" system to optimize the material and energy cycle and overcome the limitations of existing single technologies. Summary of the Invention

[0004] To address the lack of integrated systems combining microalgal carbon fixation and Shahmer remediation in existing technologies, this invention provides a system integrating microalgal carbon fixation and desert ecological restoration. Specifically, it includes: A system integrating microalgal carbon sequestration and desert ecological restoration includes: The CO2 absorption zone raceway reactor is used to bring the absorbent liquid into contact with CO2-containing gas to form a CO2-containing absorbent liquid. The bottom of the CO2 absorption zone is provided with an aeration disc, which is used to introduce CO2-containing gas into the CO2 absorption zone. The microalgae cultivation area raceway tank reactor is used to cultivate microalgae using a CO2-containing absorbent solution to form a microalgae culture medium. The bottom of the microalgae cultivation area is equipped with a gradient aeration device to introduce CO2-containing gas into the microalgae cultivation area for gradient aeration. The gradient aeration involves a gradual increase in aeration rate along the flow direction of the microalgae culture medium. The sprinkler system is used to spray microalgae culture solution onto the area to be repaired. A control device is used to control the parameters of the CO2 absorption zone raceway reactor and the microalgae cultivation zone raceway reactor.

[0005] Optionally, the CO2-containing gas is flue gas from a thermal power plant; Preferably, the CO2-containing gas contains 10% to 15% carbon dioxide by volume; preferably, the absorbent absorbs more than 2 kg / m³ of CO2. 3 ; Optionally, the absorption solution contains carbonic anhydrase at a concentration of 0.1-10.0 mg / L; The absorbent contains Na2CO3; the pH of the absorbent is 7.5-8.5. Preferably, the microalgae culture medium contains at least one of the following: skeletal-building algae, stress-resistance-enhancing algae, and rapid-developing algae; The scaffold-builder algae include at least one of the following: Microcolepidulae, Filamenta, and Oscillatoria. The stress-resistant algae include at least one algae from the genera *Pseudobranchia* and *Nostoc*. The fast-pioneer algae include at least one algae from the genera Chlorella, Chlamydomonas, and Scenedesmus.

[0006] Optionally, the aeration intensity in the CO2 absorption zone raceway reactor is 0.05-0.2 air flow rate per unit reactor volume per minute, and the gas-liquid contact time is 3-8 seconds. The gradient aeration rate is 0.05-0.15 m / s at the front end of the raceway reactor in the microalgae culture area, and gradually increases along the flow direction of the microalgae culture medium to 0.15-0.3 m / s at the end of the raceway reactor in the microalgae culture area. Preferably, both the CO2 absorption zone raceway reactor and the microalgae cultivation zone raceway reactor are equipped with guide walls, and the gas-liquid mass transfer coefficient in the CO2 absorption zone is ≥200s. - ¹.

[0007] Optionally, the microalgae culture medium contains floating ball packing material; carbonic anhydrase is immobilized on the floating ball packing material; Preferably, the float filler is made of nano-modified polypropylene with a particle size of 5-10 mm; the concentration of the float filler is 5.0 g / L to 0.05 g / L.

[0008] Preferably, the raceway reactor in the microalgae cultivation area is circulated with a culture medium solution, which is BG11 medium or BG110 medium.

[0009] Optionally, the system also includes a float packing circulation device for separating the float packing from the raceway reactor in the microalgae culture area and then circulating it back to the front end of the raceway reactor in the microalgae culture area.

[0010] Optionally, the area to be repaired is provided with a "tree-shrub-grass" grid or a "shrub-grass" grid; Preferably, the fresh weight concentration of algae in the sprayed microalgae culture medium is 0.2 g / L to 0.5 g / L, and the spraying rate per unit area is 2.5 L / m². 2 ~1.0 L / m 2 During non-rainy periods, within 7 to 21 days after spraying, spray water every 3 to 4 hours during the day, at a rate of 0.3 L / m³. 2 ~0.6 L / m 2 .

[0011] Optionally, the control device controls the parameters of the CO2 absorption zone raceway reactor and the microalgae cultivation zone raceway reactor, including: Monitor the pH, dissolved oxygen, and temperature of the raceway reactor in the CO2 absorption zone and the raceway reactor in the microalgae cultivation zone; adjust the amount of absorbent liquid added to the raceway reactor in the CO2 absorption zone and the amount of nutrient solution added to the raceway reactor in the microalgae cultivation zone; and adjust the aeration rate of the raceway reactor in the CO2 absorption zone and the raceway reactor in the microalgae cultivation zone.

[0012] A method integrating microalgal carbon sequestration and desert ecological restoration, employing the aforementioned system, includes the following steps: Step 1: In the CO2 absorption zone racetrack tank reactor, the absorbent is brought into contact with CO2-containing gas to form a CO2-containing absorbent. An aeration disc is provided at the bottom of the CO2 absorption zone, which is used to introduce CO2-containing gas into the CO2 absorption zone. Step 2: In the raceway tank reactor of the microalgae cultivation area, microalgae are cultivated using a CO2-containing absorbent solution to form a microalgae culture solution; the bottom of the microalgae cultivation area is equipped with a gradient aeration device to introduce CO2-containing gas into the microalgae cultivation area for gradient aeration; the gradient aeration means that the aeration volume gradually increases along the flow direction of the microalgae culture solution. Step 3: Spray the microalgae culture solution onto the area to be repaired using a sprinkler system.

[0013] Optionally, step one further includes adding float packing material to the microalgae culture medium through a float packing material circulation device and circulating the float packing material.

[0014] The technical solution of this invention has the following advantages: This invention proposes a synergistic system integrating microalgae carbon sequestration and desert ecological restoration, comprising a raceway reactor for CO2 absorption, a raceway reactor for microalgae cultivation, a sprinkler irrigation system, and a control system. First, the raceway reactor for microalgae cultivation, coupled with a CA enzyme catalytic reactor, enhances the CO2 absorption rate of flue gas from thermal power plants while reducing operating costs through gradient aeration. The sprinkler irrigation system utilizes microalgae biomass from the algal solution to increase the organic carbon content of desert soil and improve vegetation cover (using *Haloxylon ammodendron* and *Hippophae rhamnoides* as indicator species). The control system constructs an intelligent control platform that links flue gas pretreatment, microalgae cultivation, biomass processing, and sprinkler irrigation operations, forming a closed-loop system of "carbon reduction-resource utilization-ecological restoration," promoting sustainable energy-environment-ecological development.

[0015] This invention's system achieves efficient CO2 capture and large-scale microalgae cultivation through a racetrack-like pool partition design, float-filled packing circulation, and intelligent control technology. The harvested microalgae are processed into an algal solution, which is then used in a sprinkler irrigation system to improve desert soil, significantly increasing organic carbon content, reducing salinization, and promoting vegetation restoration. This technology integrates carbon reduction and ecological restoration functions, providing an innovative solution for industrial flue gas treatment and desertification control. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the system in this invention. Detailed Implementation

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0019] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0020] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0021] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0022] This invention proposes a system integrating microalgal carbon fixation and desert ecological restoration, comprising: The CO2 absorption zone racetrack reactor is used to bring the absorbent liquid into contact with CO2-containing gas to form a CO2-containing absorbent liquid. The bottom of the CO2 absorption zone is equipped with an aeration disc (such as a micro-nano bubble generator), which is used to introduce CO2-containing gas into the CO2 absorption zone. A raceway tank reactor for microalgae cultivation is used to cultivate microalgae using a CO2-containing absorbent solution to form a microalgae culture medium. The bottom of the microalgae cultivation area is equipped with a gradient aeration device (such as a bubbler) to introduce CO2 gas into the microalgae cultivation area for gradient aeration; this replenishes the carbon dioxide in the culture medium and blows out the oxygen released by the microalgae. The gradient aeration involves a gradual increase in aeration rate along the flow direction of the microalgae culture medium to compensate for the decrease in carbon dioxide concentration in the culture medium due to microalgae utilization and carbon dioxide dissipation. The total CO2 carried in the CO2 aqueous dispersion is not less than 2 kg / m³. 3 .

[0023] The sprinkler system is used to spray microalgae culture solution onto the area to be repaired. A control device is provided to control the parameters of the raceway reactor in the CO2 absorption zone and the raceway reactor in the microalgae cultivation zone. The CO2 fixation rate of the system is 20~50 g / (m²). 2 ·d), the single-pass fixed CO2 efficiency is 40%~70%.

[0024] Furthermore, the algal species combination meets the principles of using native species and playing a complementary role, including scaffold builders, stress-resistant reinforcers, and rapid pioneers.

[0025] The scaffold builders selected species such as *Microcoleus vaginatus*, *Lyngbyaspp.*, and *Oscillatoria spp.* that can secrete polysaccharides, bind sand grains, and form an initial crust network.

[0026] For stress-resistant reinforcement, choose species such as *Scytonema javanicum* and *Nostocspp.* that can produce UV-resistant pigments, have nitrogen-fixing capabilities, and enhance crust stability and fertility.

[0027] For rapid pioneers, choose species such as Chlorella spp., Chlamydomonas spp., and Scenedesmus spp., which are highly adaptable, can grow quickly, and can cover bare sand.

[0028] Optionally, for most areas of mobile / semi-fixed sand dunes, especially for sand fixation projects that aim for stability, predictability, and large-scale promotion, to achieve the goal of quickly and reliably fixing shifting sand, a combination of *Micrococcus suis*, *Pseudobranchia javanica*, and *Hymenopterus hymenopterus* can be used. After cultivating each algae until their fresh weight reaches the same concentration (0.2 g / L~1.0 g / L), they can be mixed in a volume ratio of 4:3:3 to form a desert algae mixture.

[0029] Optionally, for areas with poor soil and low fertility, or for projects that are closely integrated with subsequent vegetation restoration projects and require rapid substrate improvement, to achieve sand fixation and simultaneous soil improvement to lay the foundation for plants, a combination of Micrococcus sheathingus, Pseudobranchia javanica, Nostoc commune, and Chlorella can be used. After each of these algae is cultured until its fresh weight reaches the same concentration (0.2 g / L~1.0 g / L), a desert algae mixture is prepared by mixing them in a volume ratio of 5:2:1.5:1.5.

[0030] Optionally, for extremely arid areas with very little rainfall, extremely high evaporation, and intense wind and sand activity, in order to achieve the goal of allowing life to survive in the driest places first, a combination of sheathed microalgae, local algae, and terrestrial green algae can be used. After cultivating them separately until the fresh weight of the algae reaches the same concentration (0.2 g / L~1.0 g / L), they can be mixed in a volume ratio of 5:3:2 to form a desert algae mixture.

[0031] Furthermore, the absorption solution contains carbonic anhydrase (CA), and the concentration of the immobilized carbonic anhydrase is between 0.1 and 10.0 mg / L, with an optimal range of 0.5-5 mg / L. A CA preparation with an activity ≥2000 WAU / mg protein should be selected.

[0032] Preferably, the absorption solution contains 20 mg / L Na2CO3 (sodium carbonate); the pH of the microalgae culture medium is 7.5-8.5; Furthermore, the microalgae are cultured in BG11 medium, wherein algae with nitrogen-fixing functions, such as Java pseudoclade algae and common noctiluca, are cultured in BG110 medium without sodium nitrate (NaNO3).

[0033] Preferably, in the CO2 absorption zone, the added solution 1 is 20 mg / L Na2CO3 (sodium carbonate); the added solution 2 at the front end of the microalgae cultivation zone is a solution with twice the concentration of BG11 or BG110 medium (but the concentration of sodium carbonate is still 20 mg / L); after the CO2 absorption zone and before the microalgae cultivation zone, a pipe mixer is used to mix solutions 1 and 2 in an equal volume ratio, so that the concentration and composition of the solution entering the microalgae cultivation zone meet the requirements of BG11 or BG110 medium.

[0034] Furthermore, the aeration intensity in the CO2 absorption zone is 0.05-0.2 air flow rate per unit reactor volume per minute, and the gas-liquid contact time is 3-8 seconds. The gradient aeration rate is 0.05-0.15 m / s at the front end of the microalgae cultivation zone, and gradually increases along the flow direction of the microalgae culture medium to 0.15-0.3 m / s at the end of the microalgae cultivation zone. Preferably, both the CO2 absorption zone and the microalgae cultivation zone are equipped with flow guide walls, and the gas-liquid mass transfer coefficient in the CO2 absorption zone is ≥200s. - ¹.

[0035] Furthermore, the microalgae culture medium contains floating ball packing material; carbonic anhydrase is immobilized on the floating ball packing material; Preferably, the concentration of the float packing is 5.0 g / L to 0.05 g / L, with an optimal range of 0.25 g / L to 2.5 g / L. Preferably, the float filler is made of nano-modified polypropylene with a particle size of 5-10 mm; Furthermore, the system also includes a float packing circulation device for separating the float packing from the end of the microalgae culture medium and then circulating it to the front of the raceway pool.

[0036] Furthermore, the sprinkler irrigation device directly connects the mixed algal solution to the sprinkler irrigation system for desert ecological restoration, and sprays the algal solution directly onto the existing grass checkerboard and "tree-shrub-grass" system or grass checkerboard and "shrub-grass" system through the sprinkler irrigation system. Spraying should be done on cloudy or rainy days between May and October when the wind is below level 3 and the sunlight is weak.

[0037] The fresh weight concentration of algae in the spray solution is 0.2 g / L~0.5 g / L, and the spraying rate per unit area is 2.5 L / m². 2 ~1.0 L / m 2 .

[0038] During non-rainy periods, within 7 to 21 days after algae spraying, spray water every 3 to 4 hours during the day, at a rate of 0.3 L / m³. 2 ~0.6 L / m 2 .

[0039] The effectiveness of desert algae soil crusting should be evaluated in the second year after spraying. Areas that do not meet the minimum soil crusting requirements (crust coverage less than 20%, crust biomass greater than 1.0 mg / kg, and crust thickness greater than 1 mm) should be sprayed again until all areas meet the minimum soil crusting requirements.

[0040] Furthermore, the process by which the control device controls the microalgae culture parameters of the microalgae culture medium includes: Monitor the pH, dissolved oxygen, and temperature of the microalgae culture medium and the microalgae cultivation area; regulate the amount of Na2CO3 solution added to the CO2 absorption area and the amount of nutrient solution added to the microalgae cultivation area; regulate the aeration rate of flue gas in the CO2 absorption area and the microalgae cultivation area.

[0041] Example 1 like Figure 1 As shown, this embodiment provides a system integrating microalgae carbon sequestration and desert ecological restoration, including: The CO2 absorption zone raceway reactor 1 is used to make the absorbent liquid and CO2-containing gas (flue gas) cross-flow into contact to form a CO2-containing absorbent liquid. The bottom of the CO2 absorption zone is provided with an aeration disc 11, which is used to introduce CO2-containing gas into the CO2 absorption zone. The aeration intensity in the CO2 absorption zone is 0.1 per minute of air flow per unit reactor volume, and the gas-liquid contact time is 5 seconds.

[0042] The raceway reactor 2 in the microalgae cultivation area is used to cultivate microalgae using a CO2-containing absorbent solution to form a microalgae culture medium. The CO2-containing absorbent solution and nutrient solution are mixed in a mixer 21 and then enter the raceway reactor 2 in the microalgae cultivation area. A gradient aeration device 22 is provided at the bottom of the microalgae cultivation area to introduce CO2 gas into the microalgae cultivation area for gradient aeration. The gradient aeration involves a gradual increase in aeration rate along the flow direction of the microalgae culture medium. The gradient aeration rate is 0.1 m / s at the front of the microalgae cultivation area, gradually increasing to 0.2 m / s at the end of the microalgae cultivation area along the flow direction of the microalgae culture medium.

[0043] The microalgae culture medium contains float packing material 24; carbonic anhydrase is immobilized on the float packing material 24; the float packing material is made of nano-modified polypropylene with a particle size of 5-10 mm; the concentration of the float packing material is 2.5 g / L. The system also includes a float packing material circulation device for separating the float packing material from the end of the microalgae culture medium and circulating it to the front end of the raceway pool through the microsphere circulation pipe 23.

[0044] The sprinkler system 3 is used to spray the microalgae culture medium onto the area to be repaired 4. A control device is used to control the parameters of the CO2 absorption zone raceway reactor and the microalgae cultivation zone raceway reactor.

[0045] A combination of Micrococcus sheathingus, Pseudobranchia javanica, and Bryophytica hygrophytes was cultured separately until the fresh weight of the algae reached the same concentration (0.2 g / L~1.0 g / L), and then mixed in a volume ratio of 4:3:3 to form a desert algae mixture.

[0046] The absorption solution (solution 1) contains carbonic anhydrase (CA) at a concentration of 5.0 mg / L. The absorption solution also contains 20 mg / L of Na₂CO₃ (sodium carbonate).

[0047] like Figure 1 As shown, in the raceway reactor of the microalgae cultivation area, a pipeline mixer is used after the CO2 absorption zone and before the microalgae cultivation zone to achieve equal volume ratio mixing of the carbon dioxide-containing absorbent and nutrient solution, so that the concentration and composition of the solution entering the microalgae cultivation zone meet the requirements of BG11 or BG110 culture medium.

[0048] Both the CO2 absorption zone and the microalgae cultivation zone are equipped with flow guide walls, and the gas-liquid mass transfer coefficient in the CO2 absorption zone is ≥200s. - ¹.

[0049] The sprinkler irrigation device directly connects the mixed algal solution to the sprinkler irrigation system for desert ecological restoration, and sprays the algal solution directly onto the existing grass checkerboard and "tree-shrub-grass" system or grass checkerboard and "shrub-grass" system.

[0050] The system can be coupled with photovoltaic power generation to provide electrical energy to the system.

[0051] This system enhances CO2 absorption through an absorption zone, where bottom aeration and enzyme catalysis work synergistically, increasing CO2 dissolution efficiency by 3-5 times. The microalgae cultivation zone enables targeted microalgae culture, achieving a biomass density of 2-5 g / L through gradient aeration combined with nutrient regulation (N / P=16:1). The sprinkler irrigation device increases the proportion of soil aggregates (>0.25mm particles by 23%) and reduces EC value by 30% using microalgae organic fertilizer. This invention employs a zoned synergistic design. The absorption zone focuses on efficient CO2 dissolution, the cultivation zone optimizes microalgae metabolism, and the circulation system achieves dynamic carbon source balance. This invention utilizes float-type packing to immobilize CA enzymes, with a lifespan of >50 cycles, and reduces catalyst costs by 40%. Eco-energy synergy: Integrating solar power (reducing energy consumption by 30%) with bio-fertilizers to improve restoration efficiency.

[0052] Example 2 The system of Example 1 was used. Microalgae culture medium was introduced into the raceway tank zonal reactor, and the microalgae culture medium circulated in the raceway tank zonal reactor. The aeration disc was used to introduce CO2-containing gas into the CO2 absorption zone. A gradient aeration device was used to perform gradient aeration in the microalgae cultivation zone. The gradient aeration was performed by gradually decreasing the aeration rate along the flow direction of the microalgae culture medium. Float ball packing was added to the microalgae culture medium through a float ball packing circulation device, and the float ball packing was circulated. The control device monitors the pH, dissolved oxygen, CO2 concentration, and temperature of the microalgae culture medium; introduces NaHCO3 solution and immobilized carbonic anhydrase into the CO2 absorption zone; adjusts the aeration rate of the CO2 absorption zone and the microalgae cultivation zone; adds CaCO3, nutrients, and float packing to the microalgae cultivation zone; and encapsulates CA enzyme (activity 500 U / g) in PVA, with a cycle of 4 hours.

[0053] The absorption solution (solution 1) contains carbonic anhydrase (CA) at a concentration of 5.0 mg / L. The absorption solution also contains 20 mg / L of Na₂CO₃ (sodium carbonate).

[0054] In the raceway reactor of the microalgae cultivation zone, a pipeline mixer is used after the CO2 absorption zone and before the microalgae cultivation zone to achieve equal volume ratio mixing of the carbon dioxide-containing absorbent and the nutrient salt solution, so that the concentration and composition of the solution entering the microalgae cultivation zone meet the requirements of BG11 or BG110 culture medium.

[0055] Spraying should be done on cloudy or rainy days between May and October when the wind is below level 3 and the sunlight is weak.

[0056] The fresh weight concentration of algae in the spray solution is 0.2 g / L~0.5 g / L, and the spraying rate per unit area is 2.5 L / m². 2 ~1.0 L / m 2 .

[0057] During non-rainy periods, within 7 to 21 days after algae spraying, spray water every 3 to 4 hours during the day, at a rate of 0.3 L / m³. 2 ~0.6 L / m 2 .

[0058] result: CO2 absorption rate was 89%, microalgal biomass was 3.2 g / L; soil organic carbon increased from 0.3% to 0.8%, and vegetation coverage (statistics based on Haloxylon ammodendron and Hippophae rhamnoides as indicator species) increased by 275%.

[0059] Example 3 Adaptability test in saline-alkali desert Adjustments were made to the system in Example 2: Salt-tolerant microalgae (Dunaliella salina) were selected, and NaHCO3 (0.8 mol / L) was added.

[0060] Results: Soil EC value decreased from 4.2 dS / m to 3.1 dS / m, while the abundance of nitrogen-fixing bacteria increased 15 times.

[0061] Example 4: Long-term operational stability verification Running data: After continuous operation for one year according to the method in Example 2, the packing material loss rate was <3% and the enzyme activity retention rate was 82%. The CO2 fixation rate of microalgae remained stable at over 85%, and the soil improvement effect continued to increase.

[0062] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A system integrating microalgae carbon sequestration and desert ecological restoration, characterized in that, include: The CO2 absorption zone raceway reactor is used to bring the absorbent liquid into contact with CO2-containing gas to form a CO2-containing absorbent liquid. The bottom of the CO2 absorption zone is provided with an aeration disc, which is used to introduce CO2-containing gas into the CO2 absorption zone. The microalgae cultivation area raceway tank reactor is used to cultivate microalgae using a CO2-containing absorbent solution to form a microalgae culture medium. The bottom of the microalgae cultivation area is equipped with a gradient aeration device to introduce CO2-containing gas into the microalgae cultivation area for gradient aeration. The gradient aeration involves a gradual increase in aeration rate along the flow direction of the microalgae culture medium. The sprinkler system is used to spray microalgae culture solution onto the area to be repaired. A control device is used to control the parameters of the CO2 absorption zone raceway reactor and the microalgae cultivation zone raceway reactor.

2. The system integrating microalgae carbon fixation and desert ecological restoration according to claim 1, characterized in that, The CO2-containing gas is flue gas from a thermal power plant. Preferably, the volume percentage of carbon dioxide in the CO2-containing gas is 10% to 15%. Preferably, the absorbent liquid absorbs more than 2 kg / m³ of CO2. 3 .

3. The system integrating microalgae carbon fixation and desert ecological restoration according to claim 1, characterized in that, The absorption solution contains carbonic anhydrase at a concentration of 0.1 - 10.0 mg / L; The absorbent contains Na2CO3; the pH of the absorbent is 7.5-8.

5. Preferably, the microalgae culture medium contains at least one of the following: skeletal-building algae, stress-resistance-enhancing algae, and rapid-developing algae; The scaffold-builder algae include at least one of the following: Microcolepidulae, Filamenta, and Oscillatoria. The stress-resistant algae include at least one algae from the genera *Pseudobranchia* and *Nostoc*. The fast-pioneer algae include at least one algae from the genera Chlorella, Chlamydomonas, and Scenedesmus.

4. The system integrating microalgae carbon fixation and desert ecological restoration according to claim 1, characterized in that, The aeration intensity in the CO2 absorption zone raceway reactor is 0.05-0.2 liters per minute per unit reactor volume, and the gas-liquid contact time is 3-8 seconds. The gradient aeration rate is 0.05-0.15 m / s at the front end of the raceway reactor in the microalgae culture area, and gradually increases along the flow direction of the microalgae culture medium to 0.15-0.3 m / s at the end of the raceway reactor in the microalgae culture area. Preferably, both the CO2 absorption zone raceway reactor and the microalgae cultivation zone raceway reactor are equipped with guide walls, and the gas-liquid mass transfer coefficient in the CO2 absorption zone is ≥200s. - ¹.

5. The system integrating microalgae carbon fixation and desert ecological restoration according to claim 1, characterized in that, The microalgae culture medium contains floating ball packing material; carbonic anhydrase is immobilized on the floating ball packing material; Preferably, the float filler is made of nano-modified polypropylene with a particle size of 5-10 mm; the concentration of the float filler is 5.0 g / L to 0.05 g / L. Preferably, the raceway reactor in the microalgae cultivation area is circulated with a culture medium solution, which is BG11 medium or BG110 medium.

6. The system integrating microalgae carbon fixation and desert ecological restoration according to claim 1, characterized in that, The system also includes a float packing circulation device, which is used to separate the float packing from the raceway reactor in the microalgae culture area and then circulate it back to the front end of the raceway reactor in the microalgae culture area.

7. The system integrating microalgae carbon fixation and desert ecological restoration according to claim 1, characterized in that, The area to be repaired is marked with either a "tree-shrub-grass" grid or a "shrub-grass" grid. Preferably, the fresh weight concentration of algae in the microalgae culture medium sprayed by the sprinkler irrigation device is 0.2 g / L to 0.5 g / L, and the spraying rate per unit area is 2.5 L / m². 2 ~1.0 L / m 2 During non-rainy periods, within 7 to 21 days after spraying, spray water every 3 to 4 hours during the day, at a rate of 0.3 L / m³. 2 ~0.6 L / m 2 .

8. The system integrating microalgae carbon fixation and desert ecological restoration according to claim 1, characterized in that, The control device controls the parameters of the CO2 absorption zone raceway reactor and the microalgae cultivation zone raceway reactor, including: Monitor the pH, dissolved oxygen, and temperature of the raceway reactor in the CO2 absorption zone and the raceway reactor in the microalgae cultivation zone; adjust the amount of absorbent liquid added to the raceway reactor in the CO2 absorption zone and the amount of nutrient solution added to the raceway reactor in the microalgae cultivation zone; and adjust the aeration rate of the raceway reactor in the CO2 absorption zone and the raceway reactor in the microalgae cultivation zone.

9. A method integrating microalgal carbon sequestration and desert ecological restoration, characterized in that, The system according to any one of claims 1 to 8 comprises the following steps: Step 1: In the CO2 absorption zone racetrack tank reactor, the absorbent is brought into contact with CO2-containing gas to form a CO2-containing absorbent. An aeration disc is provided at the bottom of the CO2 absorption zone, which is used to introduce CO2-containing gas into the CO2 absorption zone. Step 2: In the raceway tank reactor of the microalgae cultivation area, microalgae are cultivated using a CO2-containing absorbent solution to form a microalgae culture solution; the bottom of the microalgae cultivation area is equipped with a gradient aeration device to introduce CO2-containing gas into the microalgae cultivation area for gradient aeration; the gradient aeration means that the aeration volume gradually increases along the flow direction of the microalgae culture solution. Step 3: Spray the microalgae culture solution onto the area to be repaired using a sprinkler system.

10. The method for integrating microalgae carbon sequestration and desert ecological restoration according to claim 9, characterized in that, Step one also includes adding float packing material into the microalgae culture medium through a float packing material circulation device and circulating the float packing material.

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