Method for fixing frequent peak regulation gas power plant flue gas carbon dioxide through chlorella

Abstract

The invention relates to a gas power plant flue gas treatment technology, and aims to provide a method for fixing frequent peak regulation gas power plant flue gas carbon dioxide through chlorella. The method comprises the steps that high-temperature flue gas of a gas power plant is cooled and filtered, obtained reaction gas is introduced into a chlorella carbon sequestration system, the chlorella carbon sequestration system is composed of a high-carbon grease algae powder area, a medium-carbon protein algae powder area and a low-carbon starch algae powder area, and each area comprises a photobioreactor containing chlorella liquid and a culture medium; sequentially connecting the photobioreactors of the three subareas so that the photobioreactors operate in a series connection manner; the change of the growth stage of chlorella is influenced by changing different nitrogen element content conditions and illumination conditions, so that the growth carbon sequestration metabolic pathway of chlorella is regulated and controlled in the face of CO2 with different concentrations. According to the invention, the growth habit adjustment of chlorella can be controlled by using different nitrogen environments and illumination conditions, so that the microalgae carbon sequestration system can adapt to the CO2 concentration change in a wider range.

Description

Technical Field

[0001] The invention relates to a flue gas treatment technology for a gas power plant, and in particular to a method for fixing carbon dioxide in flue gas of a gas power plant with frequent peak regulation using chlorella. Background Art

[0002] As global climate change issues have received increasing attention, greenhouse gas emissions, especially CO2 emissions, have become the focus of global environmental governance. As a clean energy power generation method, gas-fired power plants have low carbon dioxide emissions, but during frequent peak-shaving operations, flue gas emissions still have an impact on the environment. In existing technologies, gas-fired power plants usually use chemical absorption, physical adsorption or membrane separation to capture flue gas carbon dioxide. However, these methods often have problems such as high energy consumption, high equipment costs, complex operations or limited service life.

[0003] As a photosynthetic organism, Chlorella has the characteristics of high photosynthetic efficiency and rapid growth, and can effectively capture carbon dioxide from flue gas and convert it into biomass. Chlorella has strong adaptability to the environment, and its biomass is rich in protein and oil, which can be used as health products, food or feed, etc. The above characteristics make it a promising method for carbon dioxide capture and bioenergy production.

[0004] However, the peak emissions of gas-fired power plants can cause fluctuations in carbon dioxide concentrations. Traditional culture systems find it difficult to stably control the proliferation and accumulation of Chlorella in high- and low-carbon environments, resulting in low carbon source utilization and waste of resources.

[0005] The present invention aims to construct a Chlorella carbon fixation engineering system that can adapt to the flue gas of gas-fired power plants with frequent peak load regulation, and to adapt to the fluctuation of carbon concentration in the flue gas by flexible adjustment of three-zone operation to achieve efficient utilization of carbon sources. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for fixing carbon dioxide in flue gas of a gas-fired power plant with frequent peak-shaving by Chlorella. The method aims to solve the problem of unstable growth and carbon fixation efficiency of Chlorella due to large fluctuations in carbon dioxide concentration in flue gas during frequent peak-shaving of gas-fired power plants.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] A method for fixing carbon dioxide in flue gas of a frequently peaking gas-fired power plant using chlorella is provided, comprising:

[0009] (1) The high-temperature flue gas from the gas power plant is cooled by a heat exchanger and filtered by two-stage filters to obtain clean reaction gas at 20-50°C. The reaction gas is introduced into the carbon fixation system of Chlorella vulgaris, where the Chlorella vulgaris absorbs CO2 under light conditions to achieve cell reproduction and biomass accumulation. The tail gas after absorption and treatment is directly discharged to the outside.

[0010] (2) The Chlorella carbon fixation system is composed of a high-carbon oil algae powder area, a medium-carbon protein algae powder area, and a low-carbon starch algae powder area, each of which includes at least two groups of photobioreactors, each of which is filled with a mixture of Chlorella liquid and culture medium; the photobioreactors of the three partitions are connected in sequence by pipelines, so that the Chlorella carbon fixation system operates in series;

[0011] (3) A CO2 concentration sensor is provided on the pipeline connecting the heat exchanger and the filter, and an electric control valve is provided on the pipeline connecting each reactor; the controller controls the corresponding valve action according to the real-time detected CO2 concentration value, thereby changing the series connection order of the three partitioned photobioreactors;

[0012] The series connection sequence of each reactor is determined according to the concentration change of CO2 in the reaction gas, as follows:

[0013] (a) When the volume fraction of CO2 in the reaction gas is 7-9% and not equal to 7%, the reaction gas is allowed to flow through the reactors of the high-carbon oil algae powder area, the medium-carbon protein algae powder area and the low-carbon starch algae powder area in sequence; the light conditions in the three zones are adjusted to 3000-5000 lux, 3000-5000 lux and 1000-2000 lux in sequence, the high-carbon oil algae powder area is induced to enter the lipid accumulation stage, the medium-carbon protein algae powder area is caused to accumulate protein, and the low-carbon starch algae powder area uses the remaining CO2 to maintain the activity of algal cells;

[0014] (b) When the volume fraction of CO2 in the reaction gas is 3-7% and not equal to 3%, the reaction gas is allowed to flow through the reactors of the medium-carbon protein algae powder area, the high-carbon oil algae powder area and the low-carbon starch algae powder area in sequence; the light conditions in the three partitions are adjusted to 3000-5000 lux, 3000-5000 lux and 500-1000 lux in sequence, inducing Chlorella to enter the protein accumulation stage in the medium-carbon protein algae powder area, causing the metabolism of Chlorella to shift to lipid accumulation in the high-carbon oil algae powder area, and using the remaining CO2 in the low-carbon starch algae powder area to maintain the activity of algal cells;

[0015] (c) When the volume fraction of CO2 in the reaction gas is in the range of 0.1-3%, the reaction gas is allowed to flow through the reactors of the low-carbon starch algae powder area, the medium-carbon protein algae powder area and the high-carbon oil algae powder area in sequence; the light conditions in the three zones are adjusted to 2000-3000 lux, 500-1000 lux and 500-1000 lux in sequence, so as to encourage Chlorella vulgaris to use limited carbon to form carbohydrates in the low-carbon starch algae powder area, and to slow down the photosynthesis rate in the medium-carbon protein algae powder area and the high-carbon oil algae powder area to maintain the activity of algal cells;

[0016] When preparing the culture medium, the nitrogen content of each zone is controlled by adding urea: 10-50 mg / L in the high-carbon oil algae powder zone, 100-150 mg / L in the low-carbon starch algae powder zone, and ≥250 mg / L in the medium-carbon protein algae powder zone.

[0017] As a preferred embodiment of the present invention, the preparation method of the culture medium is: adding the following amounts of components to 1 ton of water: 1 g of disodium ethylenediaminetetraacetate, 6 g of ammonium ferric citrate, 6 g of citric acid monohydrate, 36 g of calcium chloride dihydrate, 75 g of magnesium sulfate heptahydrate, 45 g of dipotassium hydrogen phosphate trihydrate, and 20 g of sodium carbonate;

[0018] For the culture medium in the high-carbon oil algae powder area, add an additional 0.02-0.11 g / L of urea; for the culture medium in the medium-carbon protein algae powder area, add an additional urea ≥0.54 g / L; for the culture medium in the low-carbon starch algae powder area, add an additional 0.22-0.32 g / L of urea.

[0019] As a preferred embodiment of the present invention, in the reactors of each partition, the mixing ratio of Chlorella liquid and culture medium is 1 / 2 to 1 / 4; the algae liquid culture conditions of each reactor are controlled at a temperature of 20 to 40°C and a pH of 6.0 to 8.0.

[0020] As a preferred embodiment of the present invention, the photobioreactors in each partition are all column-type photobioreactors, and each reactor is installed in a sun room; the indoor temperature and light conditions are automatically adjusted by combining natural light, artificial light, automatic skylights, fans and shielding devices.

[0021] As a preferred embodiment of the present invention, the heat exchanger is a finned heat exchanger, cooling water flows through the tube side, flue gas flows through the shell side, and the temperature range of the flue gas is 90-120°C.

[0022] As a preferred solution of the present invention, the two-stage filtration refers to arranging two filters in sequence, one of which is used to filter condensed water and the other is used to filter particulate matter.

[0023] As a preferred solution of the present invention, a Roots blower is provided between the two filters.

[0024] As a preferred embodiment of the present invention, the culture medium is arranged in a circulation tank and transported to the reactors in each partition through pipelines.

[0025] As a preferred embodiment of the present invention, there are at least two groups of photobioreactors in each partition, which are connected in parallel for backup. When the Chlorella in the running photobioreactor reaches the target biomass, it is switched to the backup reactor. Then, the Chlorella is harvested, and processed by centrifugation, concentration and drying in sequence to finally obtain the primary processed Chlorella product.

[0026] As a preferred embodiment of the present invention, the target biomass is 0.5-1.0 g / L.

[0027] Description of the invention principle:

[0028] 1. In the prior art, there have been many research results on the use of Chlorella to fix carbon in flue gas from coal-fired power plants, but there have been no research reports on the carbon fixation in flue gas from gas-fired power plants with frequent peak loads. Since the growth of Chlorella has strict requirements on the environment, the Chlorella carbon fixation system in the prior art has very high requirements for the smooth operation of the front-end operating conditions. If the CO2 concentration conditions carried by the reaction gas change too much, not only will the stable operation of Chlorella carbon fixation and biomass production fail to be achieved smoothly, it may even cause the death of Chlorella cells. Therefore, the general research idea of ​​scientific researchers at present is to find or cultivate microalgae species with higher tolerance so that their growth conditions can better adapt to the wide range of CO2 concentration changes. Obviously, this is very difficult.

[0029] 2. The present invention breaks through the inertial thinking of technicians in solving the above problems. When facing the different concentrations of CO2 in the flue gas of the frequently peaking gas power plant, the growth stage of Chlorella is affected by changing the nitrogen content and light conditions, thereby regulating its growth and carbon fixation metabolic pathway when facing different concentrations of CO2. The details are as follows:

[0030] For high-concentration CO2 flue gas, the flue gas is first introduced into the high-carbon oil algae powder area. A low-nitrogen environment is created for Chlorella in this area, and the light is adjusted to a higher range suitable for the growth of Chlorella. The high CO2 concentration provides more carbon sources, and Chlorella will allocate more carbon to lipid synthesis, inducing Chlorella to enter the lipid accumulation stage. Subsequently, the flue gas is introduced into the medium-carbon protein algae powder area; the CO2 content of the flue gas is reduced, the light is adjusted to an appropriate range, and the high-nitrogen growth environment limits lipid synthesis, prompting Chlorella in this area to accumulate protein. Finally, the flue gas enters the low-carbon starch algae powder area, the light intensity in this area is lowered, and Chlorella uses the remaining CO2 to grow slowly.

[0031] For medium-concentration CO2 flue gas, the flue gas is first introduced into the medium-carbon protein algae powder area. In this area, the light is adjusted to an appropriate range to provide a high-nitrogen environment for Chlorella and induce Chlorella to enter the protein accumulation stage. After that, the flue gas is introduced into the high-carbon oil algae powder area, and the light is adjusted to an appropriate range. Nitrogen source limitation will inhibit protein synthesis, and further use the remaining CO2 in the flue gas to shift the metabolic focus to lipid accumulation. Finally, it enters the low-carbon starch algae powder area, lowers the light intensity to reduce the growth metabolism of Chlorella, and uses the remaining CO2 in the flue gas to maintain the activity of algal cells.

[0032] For low-concentration CO2 flue gas, the flue gas is first introduced into the low-carbon starch algae powder area. In this area, the light is adjusted to a moderate range to provide a medium-nitrogen growth environment. Low carbon limits excessive lipid and protein synthesis, prompting Chlorella to use limited carbon to form carbohydrates such as starch for energy storage. Then, the flue gas is introduced into the medium-carbon protein algae powder area and the high-carbon oil algae powder area, and the light intensity of the two areas is lowered to slow down the photosynthesis rate, avoid excessive light energy supply to produce photoinhibition on cells, and maintain the activity of Chlorella in these two areas.

[0033] Based on the above description, it can be seen that the present invention divides the microalgae carbon fixation system into three partitions and adaptively adjusts the series order thereof, and can utilize different nitrogen environments and light conditions to control the growth habit regulation of microalgae, so that the microalgae carbon fixation system can adapt to a wider range of CO2 concentration changes. This technical solution breaks through the technical imagination in the prior art and can achieve unexpected and significant technical effects.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention improves the adaptability of the Chlorella growth system to environmental changes through multi-region division and dynamic regulation, and utilizes different continuous operation sequences of three zones, so that the Chlorella in the carbon fixation engineering system can maintain growth under different CO2 concentration conditions.

[0036] 2. The three-zone adjustable operation scheme of the present invention enhances the flexibility and scalability of the system. The regional settings and cultivation parameters in the carbon fixation engineering system can be adjusted in real time according to changes in the production load of the gas power plant to adapt to changes in different flue gas emission conditions.

[0037] 3. The present invention can effectively cope with the production pressure on the carbon fixation engineering system when the gas-fired power plant frequently peaks. Even if the CO2 concentration in the flue gas changes drastically, it can always be absorbed and utilized by Chlorella. While avoiding the emission of flue gas to the outside, a large amount of high-value biomass products are produced, providing a solution for gas-fired power plants that is both environmentally friendly and economically beneficial. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1This is an equipment flow chart of the Chlorella carbon fixation system in the present invention.

[0039] Figure 2 The present invention is a flow chart of the control method.

[0040] Figure 1 The figure marks in the figure are: 100-gas flue gas; 101-heat exchanger; 102-CO2 sensor; 103-primary filter; 104-Roots blower; 105-secondary filter; 201-high carbon oil algae powder area; 202-medium carbon protein algae powder area; 203-low carbon starch algae powder area; 301-centrifuge; 302-concentrator; 303-drying box. DETAILED DESCRIPTION

[0041] The specific implementation scheme of the present invention is described in detail below.

[0042] Part I Implementation of the Invention

[0043] 1. If Figure 1 As shown, the present invention first provides a method for fixing carbon dioxide in flue gas of a frequently peaking gas power plant by using Chlorella, the system comprising: a heat exchanger 101, a two-stage filter and a Chlorella carbon fixation system arranged in sequence through pipelines; the Chlorella carbon fixation system is composed of a high-carbon oil algae powder area 201, a medium-carbon protein algae powder area 202, and a low-carbon starch algae powder area 203, each partition including at least two groups of photobioreactors, in which a mixture of Chlorella liquid and culture medium is contained; the photobioreactors of the three partitions are connected in series by pipelines, so that the Chlorella carbon fixation system operates in series. The two-stage filter filtration refers to the sequential arrangement of a primary filter 103 and a secondary filter 105, the former is mainly used to filter condensed water, and the latter is mainly used to filter particulate matter, and a Roots blower 104 is provided between the two filters. A CO2 concentration sensor 102 is provided on the pipeline connecting the heat exchanger 101 and the primary filter 103, and an electrically controlled valve is provided on the pipeline connecting each reactor; the controller can control the corresponding valve action according to the real-time detected CO2 concentration value, thereby changing the series connection order of the three partitioned photobioreactors.

[0044] As an optional example, the photobioreactors are all column-type photobioreactors; the reactors are installed in a sun room, and the indoor temperature and light conditions are automatically adjusted by combining natural light, artificial light, automatic skylights, fans and shielding devices. The heat exchanger 101 is a finned heat exchanger, with cooling water passing through the tube side and flue gas passing through the shell side.

[0045] The culture medium is arranged in the circulation tank and transported to the reactors in each partition through the pipeline. In the reactors in each partition, the mixing ratio of Chlorella liquid and culture medium is 1 / 2 to 1 / 4; the algae liquid culture conditions of each reactor are controlled at a temperature of 20 to 40°C and a pH of 6.0 to 8.0.

[0046] The preparation method of the culture medium is as follows: add the following components to 1 ton of water: 1g disodium ethylenediaminetetraacetic acid, 6g ammonium ferric citrate, 6g citric acid monohydrate, 36g calcium chloride dihydrate, 75g magnesium sulfate heptahydrate, 45g dipotassium hydrogen phosphate trihydrate, 20g sodium carbonate; for the culture medium of the high carbon oil algae powder area, add 0.02-0.11g / L of urea; for the culture medium of the medium carbon protein algae powder area, add urea ≥0.54g / L; for the culture medium of the low carbon starch algae powder area, add 0.22-0.32g / L of urea. Make the nitrogen content in each culture medium: 10-50mg / L in the high carbon oil algae powder area, 100-150mg / L in the low carbon starch algae powder area, and ≥250mg / L in the medium carbon protein algae powder area.

[0047] 2. If Figure 2 As shown, based on the above carbon fixation system, the method provided by the present invention for fixing carbon dioxide from flue gas of a frequently peaking gas power plant using Chlorella includes the following contents:

[0048] (1) The high-temperature flue gas (90-120°C) of the gas power plant is cooled by the heat exchanger 101 and filtered by two-stage filters to obtain clean reaction gas at 20-50°C; the reaction gas is introduced into the carbon fixation system of Chlorella vulgaris, and the Chlorella vulgaris absorbs CO2 under light conditions to achieve cell reproduction and biomass accumulation; the tail gas after absorption and treatment is directly discharged to the outside;

[0049] The series connection sequence of each reactor is determined according to the concentration change of CO2 in the reaction gas, as follows:

[0050] (a) When the volume fraction of CO2 in the reaction gas is 7-9% and not equal to 7%, the reaction gas is allowed to flow through the reactors of the high-carbon oil algae powder area, the medium-carbon protein algae powder area and the low-carbon starch algae powder area in sequence; the light conditions in the three zones are adjusted to 3000-5000 lux, 3000-5000 lux and 1000-2000 lux in sequence, the high-carbon oil algae powder area is induced to enter the lipid accumulation stage, the medium-carbon protein algae powder area is caused to accumulate protein, and the low-carbon starch algae powder area uses the remaining CO2 to maintain the activity of algal cells;

[0051] (b) When the volume fraction of CO2 in the reaction gas is 3-7% and not equal to 3%, the reaction gas is allowed to flow through the reactors of the medium-carbon protein algae powder area, the high-carbon oil algae powder area and the low-carbon starch algae powder area in sequence; the light conditions in the three partitions are adjusted to 3000-5000 lux, 3000-5000 lux and 500-1000 lux in sequence, inducing Chlorella to enter the protein accumulation stage in the medium-carbon protein algae powder area, causing the metabolism of Chlorella to shift to lipid accumulation in the high-carbon oil algae powder area, and using the remaining CO2 in the low-carbon starch algae powder area to maintain the activity of algal cells;

[0052] (c) When the volume fraction of CO2 in the reaction gas is in the range of 0.1-3%, the reaction gas is allowed to flow through the reactors of the low-carbon starch algae powder area, the medium-carbon protein algae powder area and the high-carbon oil algae powder area in sequence; the light conditions in the three zones are adjusted to 2000-3000 lux, 500-1000 lux and 500-1000 lux in sequence, so as to encourage Chlorella vulgaris to use limited carbon to form carbohydrates in the low-carbon starch algae powder area, and to slow down the photosynthesis rate in the medium-carbon protein algae powder area and the high-carbon oil algae powder area to maintain the activity of algal cells;

[0053] There are at least two groups of photobioreactors in each partition, and they are connected in parallel for backup. When the Chlorella in the running photobioreactor reaches the target biomass, it is switched to the backup reactor. Then the Chlorella is harvested, and successively subjected to centrifugal treatment in the centrifuge 301, concentrating treatment in the concentrator 302, and drying treatment in the dryer 303, to finally obtain the primary processed Chlorella product.

[0054] In the flue gas of a gas-fired power plant, the CO2 concentration usually does not exceed 9%, so the maximum value of the monitored concentration in the present invention is also set to 9%.

[0055] Part II Application Examples of the Invention

[0056] In the present invention, there are multiple varieties of Chlorella for carbon fixation, for example, the following varieties can be directly purchased from the freshwater algae species bank of the National Aquatic Biological Germplasm Resource Bank: Chlorella (Chlorella sp.), numbered FACHB-32; Chlorella (Chlorella vulgaris), numbered FACHB-1068; Chlorella (Chlorella pyrenoidosa), numbered FACHB-9; Chlorella (Chlorella vugaris Bey), numbered FACHB-31; Chlorella (Chlorella ellipsoideaGern, numbered FACHB-40.

[0057] A specific embodiment:

[0058] according to Figure 2The equipment connection method shown is to set up a Chlorella carbon fixation system in the flue gas emission device of a gas-fired power plant in Guangdong Province. Two groups of photobioreactors are set in each partition, and they are connected in parallel for mutual backup. The configuration of the culture medium, the temperature and light control conditions, and the culture conditions of the reactor are implemented as mentioned above.

[0059] The Chlorella species used in this embodiment is Chlorella PY-ZU1, which is publicly recorded in the following document: "Enhancing lipid production in microalgaeChlorella PY-ZU1 with phosphorus excess and nitrogen starvation under 15% CO2 in a continuous two-step cultivation process", published on 2019-11-1.

[0060] 1. High-temperature flue gas from a gas-fired power plant was introduced for 5 consecutive days, and the cultivation and control strategies of Chlorella in each area were dynamically adjusted according to the fluctuation of the carbon dioxide concentration in the flue gas. According to statistics, the time when CO2 in the flue gas was monitored to be low concentration (when the volume fraction of CO2 was 0.1-3%) was 26 hours in total, the time when the volume fraction of CO2 was 3-7% and not equal to 3%) was 48 hours in total, and the time when the volume fraction of CO2 was 7-9% and not equal to 7%) was 46 hours in total. The CO2 concentration sensor installed in the tail gas emission pipeline of the carbon fixation system was used to collect data. After the data was sorted out, it was confirmed that the maximum residual CO2 concentration in the tail gas during the entire 5-day experiment did not exceed 0.2%, and the cumulative time exceeding 0.1% concentration did not exceed 4 hours. In five days, a total of 125.27 kg of Chlorella biomass was harvested.

[0061] 2. Parallel experiments were conducted using the same reactor, Chlorella species, and culture medium. The CO2 input was maintained at a concentration of 0.1-9% for 5 consecutive days, 0.22-0.32 g / L of urea was added, the light was maintained at 2000-3000 lux, and the temperature was maintained at 20-40°C. After 5 days, a total of 124.60 kg of biomass was harvested.

[0062] Based on the above embodiments, it can be seen that the technical solution of the present invention can well meet the carbon fixation requirements of Chlorella in the flue gas CO2 of gas-fired power plants with frequent peak-shaving, and will not cause excessive CO2 concentration in tail gas emissions or a decrease in Chlorella biomass production capacity due to frequent changes in CO2 concentration.

Claims

1. A method for fixing carbon dioxide from flue gas of a frequently peaking gas-fired power plant using Chlorella vulgaris, characterized in that: include: (1) The high-temperature flue gas from the gas power plant is cooled by a heat exchanger and filtered by two-stage filters to obtain clean reaction gas at 20-50°C; The reaction gas is introduced into the carbon fixation system of Chlorella, and under light conditions, Chlorella absorbs CO2 to achieve cell reproduction and biomass accumulation; the tail gas after absorption and treatment is directly discharged to the outside; (2) The Chlorella carbon fixation system is composed of a high-carbon oil algae powder area, a medium-carbon protein algae powder area, and a low-carbon starch algae powder area, each of which includes at least two groups of photobioreactors, each of which is filled with a mixture of Chlorella liquid and culture medium; the photobioreactors of the three partitions are connected in sequence by pipelines, so that the Chlorella carbon fixation system operates in series; (3) A CO2 concentration sensor is provided on the pipeline connecting the heat exchanger and the filter, and an electric control valve is provided on the pipeline connecting each reactor; the controller controls the corresponding valve action according to the real-time detected CO2 concentration value, thereby changing the series connection order of the three partitioned photobioreactors; The series connection sequence of each reactor is determined according to the concentration change of CO2 in the reaction gas, as follows: (a) When the volume fraction of CO2 in the reaction gas is 7-9% and not equal to 7%, the reaction gas is allowed to flow through the reactors of the high-carbon oil algae powder area, the medium-carbon protein algae powder area and the low-carbon starch algae powder area in sequence; the light conditions in the three zones are adjusted to 3000-5000 lux, 3000-5000 lux and 1000-2000 lux in sequence, the high-carbon oil algae powder area is induced to enter the lipid accumulation stage, the medium-carbon protein algae powder area is caused to accumulate protein, and the low-carbon starch algae powder area uses the remaining CO2 to maintain the activity of algal cells; (b) When the volume fraction of CO2 in the reaction gas is 3-7% and not equal to 3%, the reaction gas is allowed to flow through the reactors of the medium-carbon protein algae powder area, the high-carbon oil algae powder area and the low-carbon starch algae powder area in sequence; the light conditions in the three partitions are adjusted to 3000-5000 lux, 3000-5000 lux and 500-1000 lux in sequence, inducing Chlorella to enter the protein accumulation stage in the medium-carbon protein algae powder area, causing the metabolism of Chlorella to shift to lipid accumulation in the high-carbon oil algae powder area, and using the remaining CO2 in the low-carbon starch algae powder area to maintain the activity of algal cells; (c) When the volume fraction of CO2 in the reaction gas is in the range of 0.1-3%, the reaction gas is allowed to flow through the reactors of the low-carbon starch algae powder area, the medium-carbon protein algae powder area and the high-carbon oil algae powder area in sequence; the light conditions in the three zones are adjusted to 2000-3000 lux, 500-1000 lux and 500-1000 lux in sequence, so as to encourage Chlorella vulgaris to use limited carbon to form carbohydrates in the low-carbon starch algae powder area, and to slow down the photosynthesis rate in the medium-carbon protein algae powder area and the high-carbon oil algae powder area to maintain the activity of algal cells; When preparing the culture medium, the nitrogen content of each zone is controlled by adding urea: 10-50 mg / L in the high-carbon oil algae powder zone, 100-150 mg / L in the low-carbon starch algae powder zone, and ≥250 mg / L in the medium-carbon protein algae powder zone.

2. The method according to claim 1, characterized in that: The preparation method of the culture medium is as follows: add the following components in 1 ton of water: 1 g of disodium ethylenediaminetetraacetate, 6 g of ammonium ferric citrate, 6 g of citric acid monohydrate, 36 g of calcium chloride dihydrate, 75 g of magnesium sulfate heptahydrate, 45 g of dipotassium hydrogen phosphate trihydrate, and 20 g of sodium carbonate; For the culture medium in the high-carbon oil algae powder area, add an additional 0.02-0.11 g / L of urea; for the culture medium in the medium-carbon protein algae powder area, add an additional urea ≥0.54 g / L; for the culture medium in the low-carbon starch algae powder area, add an additional 0.22-0.32 g / L of urea.

3. The method according to claim 1, characterized in that In the reactors of each partition, the mixing ratio of Chlorella liquid and culture medium is 1 / 2 to 1 / 4; the algae liquid culture conditions of each reactor are controlled at a temperature of 20 to 40° C. and a pH of 6.0 to 8.

0.

4. The method according to claim 1, characterized in that: The photobioreactors in each partition are all column-type photobioreactors, and each reactor is installed in a sun room; the indoor temperature and light conditions are automatically adjusted by combining natural light, artificial light, automatic skylights, fans and shielding devices.

5. The method according to claim 1, characterized in that: The heat exchanger is a finned heat exchanger, cooling water flows through the tube side, and flue gas flows through the shell side, and the temperature range of the flue gas is 90-120°C.

6. The method according to claim 1, characterized in that The two-stage filtration refers to arranging two filters in sequence, one of which is used to filter condensed water and the other is used to filter particulate matter.

7. The method according to claim 1, characterized in that Between the two filters, there is a Roots blower.

8. The method according to claim 1, characterized in that: The culture medium is arranged in a circulation tank and transported to the reactors in each partition through pipelines.

9. The method according to claim 1, characterized in that: There are at least two groups of photobioreactors in each partition, and they are connected in parallel to serve as backup for each other. When the Chlorella in the running photobioreactor reaches the target biomass, it is switched to the backup reactor. Then the Chlorella is harvested and processed by centrifugation, concentration and drying in sequence to finally obtain the primary processed Chlorella product.

10. The method according to claim 9, characterized in that The target biomass is 0.5-1.0 g / L.

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