CN110777091A - Method for developing efficient BECCS system with bicarbonate radical as ligament - Google Patents

Abstract

The invention discloses a method for developing a high-efficiency BECCS system with bicarbonate as a link. The main steps include: selecting Na ₂ CO ₃ and K ₂ CO ₃ as a chemical absorbent, and fully absorbing CO ₂ to form the corresponding NaHCO of bicarbonate. ₃ and KHCO ₃ were used to mutagenize the carbon source during the culture of Spirulina. Culture conditions in the experiment: light intensity=4000 luxs, all day light, temperature=30°C. Set the concentrations of NaHCO ₃ and KHCO ₃ to 0.1 mol/L, 0.2 mol/L and 0.3 mol/L, respectively. After 18 days of culture, the biomass dry weight of mutagenized Spirulina platensis in 0.3mol/L NaHCO ₃ system reached 2.24g/L, the carbon utilization efficiency was 26.71%, and the maximum carbon sequestration amount in the experiment was 230.36mg/L /d, the dry weight of biomass obtained in the KHCO ₃ system of 0.3 mol/L was 2.00 g/L, the carbon utilization efficiency was 25.69%, and the maximum carbon sequestration amount was 153.41 mg/L/d. Coupling chemical absorption with microalgae transformation can avoid the problem of high energy consumption and low carbon utilization efficiency of microalgae in the desorption process of chemical absorption method.

Description

A method for developing an efficient BECCS system linked by bicarbonate

Technical field:

The invention relates to the technical field of microalgae biological carbon sequestration, relates to a carbon capture resource utilization that combines chemical absorption and capture of _CO with microalgae biological carbon sequestration, in particular to the development of high-efficiency BECCS with bicarbonate as a link systematic approach.

Background fields:

As of 2017, my country's energy reserves have proven coal reserves of up to 127 million tons, accounting for 13.4% of the world's total coal. The reserves of oil and natural gas account for 1.5% and 2.8% of the world's reserves respectively, far lower than the reserves of coal ^[1] . The current situation of "rich coal, lack of oil, and little gas" determines that my country's energy structure is dominated by coal, supplemented by oil and natural gas. Although the national government is committed to adjusting and optimizing the energy system and expanding the use of renewable and sustainable new energy, the consumption of new energy such as nuclear energy, wind energy, solar energy and biomass energy only accounts for 11.7% due to technical limitations ^[2] . _On the other hand, China is in a stage of rapid development, and the demand for energy is also increasing, so in the short term, fossil fuels will always be in the leading position of China's energy. Developed countries using new energy sources. According to statistics, about 3.34 billion tons of CO ₂ are emitted into the atmosphere every year. These CO ₂ come from power plants, oil refineries, biogas desulfurization and the production of ethylene oxide, cement and steel, of which 40% of the CO ₂ is produced by combustion The generation of coal-fired power plants ^[3,4] has caused a series of environmental problems such as global warming and sea level rise.

People from all walks of life have been working hard to alleviate the status quo of environmental degradation caused by excessive carbon emissions. In the past few years, the Chinese government has adopted many policies and measures to reduce carbon emissions and promote the green transformation of various industries. Among them, carbon tax is considered to be an effective forward-looking economic means to reduce China's carbon emissions ^[5] . In 2015, China completed the "Twelfth Five-Year Plan" and formulated the "Thirteenth Five-Year Plan" in order to implement carbon emission reduction targets. The concept of "establishing energy use rights, carbon emission rights, pollution rights trading markets, and promoting market-oriented energy conservation and carbon emission reduction" was put forward, and ten clear and specific items such as carbon recycling, recycling, scientific development of renewable energy and clean energy replacement were proposed. , Measurable, implementable, supervised and effective carbon emission reduction measures. In addition to controlling carbon emissions, the capture and application of _CO2 from fossil fuel combustion should also be the focus of research.

Among many post-combustion capture technologies, chemical absorption method is the most widely used, because chemical absorption method has mature technical support and is a promising CO ₂ separation method. A typical decarburization system consists of two parts, an absorption tower and a desorption tower. The decarburization system is generally located after dust removal, desulfurization and denitrification. After cooling, the flue gas enters the tower from the bottom of the absorption tower, and is reversed to the sprayed chemical absorbent. contact, at which point the chemical absorbent undergoes a reversible chemical reaction with _CO2 . The absorbent rich liquid that has absorbed CO ₂ is pumped out of the absorption tower and exchanges heat with the absorbent lean liquid in the heat exchanger. After warming up at high temperature, it enters the desorption tower, where the chemical absorbent is regenerated at high temperature. The pure CO ₂ is separated, and the CO ₂ is stored or recycled through the processes of condensation, drying and compression ^[6] . Chemical absorption is widely used because of the advantages of fast reaction rate, good absorption effect and high degree of recovery. The disadvantages are high energy consumption, high investment cost, bubbles and entrainment in the solution.

Spirulina will use 1.83t of CO ₂ to produce 1t of dry biomass during the carbon fixation process of Spirulina ^[7] . The principle of spirulina's biological carbon fixation is divided into two parts, one part is light reaction, the other part is dark reaction. In the process of light reaction, Spirulina undergoes light energy absorption, light transfer, photochemical reaction, electron transfer process, and photosynthetic phosphorylation process to generate ATP and reduced coenzyme (NADPH) and decompose H ₂ O to generate O ₂ at the same time. The dark reaction stage mainly uses the ATP and NADPH generated in the light reaction stage to further complete the carbon metabolism process, and finally generate organic matter ^[8] . Spirulina lives in the aquatic environment, and the forms of inorganic carbon in water include CO ₂ (aq), CO ₃ ^2- , HCO ₃ ^- , H ₂ CO ₃ , etc. Not every type of inorganic carbon microalgae can absorb and utilize, The two forms of inorganic carbon that Spirulina can utilize are CO ₂ and HCO ₃ ^- . Compared with green algae, Spirulina has a strong carbonic anhydrase (CA) activity and a higher utilization efficiency of bicarbonate. But the efficiency of spirulina's biological carbon fixation is very low.

Active products such as saturated fatty acids and unsaturated fatty acids can be extracted from the biomass of Spirulina, which can be used as raw materials for industrial production of biodiesel, biogas, biohydrogen, bioethanol, and biobutanol. Biodiesel is a green and renewable fuel, usually prepared from biological raw materials. Spirulina biomass contains lipids, which can be converted into FAME (fatty acid methyl esters) through transesterification to produce biodiesel. Carbohydrates (mainly glucose, starch, cellulose, hemicellulose) can be converted into bioethanol by fermentation. The green residue after spirulina oil extraction can be used to produce biobutanol, because biobutanol has a higher energy density and is more suitable for use as biofuel than biomethanol or bioethanol, and biobutanol can be used in addition to biofuels solvent. Spirulina biological carbon sequestration and emission reduction of coal-fired flue gas CO ₂ is of great significance for alleviating the greenhouse effect, developing a low-carbon economy and pollution control of environmental protection industries. Spirulina is high in nutrients, but the process of spirulina cultivation consumes a lot of water and inorganic salt nutrients. It is necessary to propose a method that can reduce the cost in the production process of spirulina and promote the large-scale commercial utilization of spirulina.

Due to the burning of fossil fuels, a large amount of _CO2 is emitted into the air, and the emission shows a trend of increasing year by year. China is one of the largest carbon emitters, emitting 3.34 billion tons of _CO2 into the atmosphere every year. CO ₂ is the main greenhouse gas, and the environmental harm caused by emission into the atmosphere has attracted people's attention. At the same time, CO ₂ is also the most abundant carbon resource. How to effectively capture carbon and utilize carbon resources becomes the focus. In the traditional carbon capture process, chemical absorption is the most common, but there is a problem of high energy consumption. Biological carbon sequestration is the most environmentally friendly. Microalgae use _CO2 as a carbon source to synthesize biomass and other high-value additional products under photosynthesis, but the nutrient consumption during microalgae cultivation is large. In order to solve the problem of high energy consumption in the chemical absorption process and the cost of nutrients in the process of microalgae cultivation, a high-efficiency BECCS (Bioenergy coupled with carbon dioxide capture and storage) system with bicarbonate as a link was developed, that is, through bicarbonate. The chemical absorption carbon sequestration and the microalgae biological carbon sequestration are linked together to improve the microalgal biomass yield and promote the microalgae photosynthetic carbon sequestration on the basis of reducing the cost of nutrients.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the defects of the above-mentioned background technology, and to provide a method for coupling chemical absorption with microalgae carbon fixation.

Technical scheme of the present invention: develop the method for the efficient BECCS system with bicarbonate as a link, comprising the steps:

1) Selection of chemical absorbents: Traditional typical chemical absorbents are divided into ammonia water absorbents, alcohol amine absorbents, amino acid salt absorbents, and potassium carbonate absorbents. However, the substances generated by some chemical absorbents after absorbing CO ₂ will be corrosive or toxic, which is not conducive to the subsequent cultivation of spirulina. Select Na ₂ CO ₃ and K ₂ CO ₃ to generate NaHCO ₃ and KHCO ₃ after fully absorbing CO ₂ , and set three different concentrations of 0.1mol/L, 0.2mol/L and 0.3mol/L respectively.

2), Mutagenic Spirulina Spirulina treatment: Spirulina was pre-cultured in ordinary zarrouk medium, the temperature was set to 30 ° C, the light intensity was 4000 luxs, and 5% CO ₂ mixed gas (5% CO 2 was introduced at a flow rate of 0.1 vvm) ₂ +95% _N2 ) or air, the microalgae enter the pre-cultivation stage. After 5 days of aeration, the mutagenized spirulina grows to the logarithmic growth phase, and the pre-cultivation phase ends. In the formal inoculation experiment, the control inoculum amount is OD ₅₆₀ =0.2

3), formal culture experiment: use zarrouk medium without carbon source as basal medium, add different concentrations of NaHCO ₃ and KHCO ₃ (0.1mol/L, 0.2mol/L and 0.3mol/L) respectively as carbon source . The medium volume was 200ml, sterilized by high temperature at 121°C for 30min, NaHCO ₃ and KHCO ₃ were filtered and sterilized through a 0.45μm filter membrane, and then inserted into the mutagenized Spirulina platensis with algae amount OD ₅₆₀ =0.2.

The culture was carried out for 18 days under the condition of light intensity=4000luxs, temperature=30±1℃, all day light.

In the step 2), the mutagenized Spirulina platensis is the mutagenized Spirulina platensis that has undergone nuclear radiation.

Compared with the prior art, the present invention has the following advantages:

1) the present invention studies the BECCS system with bicarbonate as a link, through 18 days of cultivation, the highest biomass dry weight obtained by mutagenesis of Spirulina platensis in 0.3mol/L NaHCO system is _2.29g /L, Microalgal biomass dry weight of 2.00 g/L was obtained in a 0.3 mol/L KHCO ₃ system. The carbon utilization efficiency in NaHCO ₃ system is higher than that in KHCO ₃ system, and the highest carbon utilization efficiency is 26.71% in 0.3mol/L NaHCO ₃ system. The maximum carbon sequestration capacity of mutagenized Spirulina platensis was 23036mg/L/d, which was higher than that of ordinary microalgae.

2) The present invention couples chemical absorption and fixation of CO ₂ with microalgae biological carbon fixation, avoiding the problem of high energy consumption in the desorption process of chemical absorbents, and at the same time, the bicarbonate generated by carbonate absorption of CO ₂ is used as the source of the spirulina cultivation process. The carbon source reduces the cost of the microalgae cultivation process, and the microalgae can extract high-value value-added products such as oil, polysaccharide, and protein.

Description of drawings:

Fig. 1 is a schematic diagram of the dry weight of biomass of mutagenized Spirulina platensis in bicarbonate system

Fig. 2 is a schematic diagram showing the change of solution inorganic carbon content and carbon utilization efficiency in bicarbonate system

Figure 3 is a schematic diagram of the amount of carbon sequestered by a mutagenized blunt-topped helix in a bicarbonate system

Figure 4 is the change of chlorophyll content of mutagenized spirulina in bicarbonate system

Figure 5 is a schematic diagram of the oil content of mutagenized spirulina in bicarbonate system

Detailed ways:

The present invention will be further described below through specific embodiments and accompanying drawings. The embodiments of the present invention are for better understanding of the present invention by those skilled in the art, and do not limit the present invention.

The present invention develops a kind of BECCS system with bicarbonate as a link, comprising the steps:

1) Selection of chemical absorbents: Choose economical absorbents. Ammonia water is the cheapest in the market, but Spirulina has poor tolerance to ammonia nitrogen, and high concentrations of ammonia nitrogen will have toxic effects on the photosynthetic system of Spirulina. Moreover, the carbon sources that Spirulina can utilize are HCO ₃ ^- and CO _2. Based on this, carbonate is used as a chemical absorbent, and the bicarbonate generated after absorbing CO ₂ is used to cultivate microalgae. Na ₂ CO ₃ and K ₂ CO ₃ which have a faster absorption rate are preferred.

2) Pre-culture of mutagenized Spirulina platensis: inoculate the mutagenized Spirulina platensis under sterile conditions, and culture the Spirulina with 200mL autoclaved zarrouk medium in a 250mL conical flask, during Air was introduced at a flow rate of 0.1 vvm.

The composition of SE medium is as follows:

Table 1 Proportion of nutrients in Zarrouk medium

Table ₂ A5, _B6 solution composition

Cultivation conditions for mutagenized Spirulina platensis: light intensity=4000 luxs, all-day light, temperature=30±1°C, and intermittent shaking during cultivation;

3), formal experiment: in the experiment process, adopt the Zarrouk substratum that does not add carbon source, inoculate the algae amount of OD ₅₆₀ =0.2, two kinds of bicarbonate are respectively used as carbon source, and the concentration is respectively 0.1mol/L, 0.2mol/ L and 0.3mol/L, no aeration during the formal culture.

Culture conditions: All day light, light intensity=6000luxs, temperature=30±1℃

A. Biomass detection:

Collect 2 mL of algal suspension to measure the biomass of mutagenized Spirulina, measure the spectrophotometric value at a wavelength of 560 nm, and substitute the spectrophotometric value into the dry weight standard curve to convert it into biomass dry weight. Each sample was replicated in triplicate, blank samples were also treated in the same way, and samples without algae served as controls.

The biomass dry weight standard curve of Spirulina was determined by drying method. Dilute the high-concentration spirulina liquid with deionized water to OD ₅₆₀ =0.2, 0.4, 0.6, 0.8, and 1.0, respectively, and measure 100 ml of the algal liquid. Before the filter membrane of algae liquid, the filter membrane with a pore size of 0.45 μm was dried in an oven at 150 ° C for 2 hours to remove the interference of moisture. After the filter membrane was dried to a constant weight and cooled down, the filter membrane was weighed. Record the weight of the filter membrane before filtration. Then 100ml of algae liquid was suction filtered through the membrane, and the filtered membrane was put into a drying oven at 150°C and dried to constant weight. After cooling, the filter membrane after filtering the microalgae was weighed. The difference between the two filter membrane weighing before and after is the dry weight of spirulina biomass.

The schematic diagram of Spirulina biomass cultured for 18 days is shown in Figure 1.

Analysis of Figure 1 shows that the growth of mutagenized Spirulina platens in two different species and different concentrations of bicarbonate systems is different, and the highest biomass dry weight is obtained in the system with a concentration of 0.3mol/L. The dry weight of biomass was 2.29 g/L in NaHCO ₃ system and 2.00 g/L in KHCO ₃ system. The three concentrations of bicarbonate did not have toxic effects on Spirulina, but the growth retardation of Spirulina occurred in the high concentration of bicarbonate system.

B. Detection of Inorganic Carbon

Take a certain amount of the solution in the system, filter it through a 0.45 μm filter membrane, collect the supernatant, and measure the inorganic carbon value in the solution in a liquid TOC detector.

It can be seen from Figure 2 that the utilization efficiency of inorganic carbon was the highest in the 0.3mol/L NaHCO ₃ system of mutagenized Spirulina platensis, mainly due to the higher buffering capacity of the high-concentration bicarbonate system, which promoted the improvement of carbon utilization efficiency.

C. Calculation of carbon sequestration

After the end of the experiment period, take out all the algae liquid, dry the algae and then take 20mg of microalgae for elemental analysis in an elemental analyzer to obtain the proportion of C element, multiply the dry weight of the spirulina biomass by the C element in the algal powder, The formula for calculating the amount converted to fixed carbon dioxide is as follows:

----螺旋藻生物固碳量，mg/L/d；

---- Spirulina biological carbon fixation, mg/L/d;

P _biomass ---- Spirulina biomass yield, g/L/d;

_Calgae ---- the proportion of C content in spirulina powder, %;

----CO₂相对分子质量；

----CO ₂ relative molecular mass;

M _C ---- C relative atomic mass.

D. Determination of chlorophyll content

Take 5ml of Spirulina algae liquid, centrifuge at 5000rpm for 20min, pour off the supernatant, add 5ml of methanol to the precipitate, ultrasonically vibrate for 15min in the dark, put it in a refrigerator at 4°C, and extract for 12h. Centrifuge again, collect the supernatant, measure the absorbance at wavelengths of 666 nm, 653 nm, and 470 nm, and set zero with methanol as the blank.

Chlorophyll can be used as an indicator for evaluating the photosynthesis of Spirulina. The higher the concentration of chlorophyll, the stronger the photosynthesis of microalgae, and the higher the biomass accumulation. It can be seen that the highest chlorophyll value is in the 0.3mol/L NaHCO ₃ system on the 9th day of culture. get.

E. Determination of oil content

The Nile red fluorescence staining method was used to determine the oil content. Take 2.55ml of algae solution and add 450μL of dimethyl sulfoxide and 24μL of Nile red solution; let stand for 10min in a dark room at 30°C, and select 580nm as the excitation fluorescence detection wavelength. Determination.

The oil can be used as a value-added product in the later stage of spirulina cultivation, and can be further used in the production and preparation of biodiesel, which can be used in energy.

It should be understood that the embodiments and examples discussed here are only for illustration, and for those skilled in the art, improvements or changes may be made, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Related literature:

[1] Ministry of Land and Resources of the People's Republic of China. China Mining Assets Report 2018 [C]. Beijing, 2018.

[2] General Institute of Hydropower and Water Conservancy Planning and Design. China Renewable Energy Development Report 2017 [C]. 2018, International Energy Transformation Forum.

[3] Cheng J, Zhu Y, Zhang Z, et al. Modification and improvement of microalgae strains for strengthening CO ₂ fixation from coal-fired flue gas inpower plants [J]. Bioresource Technology, 2019, 291: 121850.

[4] Singh H M, Kothari R, Gupta R, et al.Bio-fixation of flue gas from thermal power plants with algal biomass:Overview and research perspectives[J].Journal of Environmental Management,2019,245:519–539.dioxide ,nitrogenoxide and sulfur dioxide from flue gas using Chlorella sp.cultures.Bioresour.Technol.102,9135-9142.

[5] Lin B, Xu M. Exploring the green total factor productivity of China’s metallurgical industry under carbon tax: A perspective on factorsubstitution [J]. Journal of Cleaner Production, 2019, 233: 1322–1333.

[6] Fang Mengxiang, Zhou Xuping, Wang Tao, et al. CO ₂ chemical absorbent [J]. Progress in Chemistry, 2015, 27(12): [7]

Chisti Y.Biodiesel from microalgae[J].Biotechnology Advances,2007,25(3):294–306.

[8] Li Yongfu. A novel flat-panel photobioreactor with built-in LED light source for efficient CO ₂ fixation by microalgae [D]. Qingdao: Ocean University of China, 2014.808-1814.

Claims (2)

1. a kind of method of developing the efficient BECCS system with bicarbonate as a link, is characterized in that, comprises the steps: 1), the choice of chemical absorbent: select Na ₂ CO ₃ and K ₂ CO ₃ , fully absorb CO ₂ to generate NaHCO ₃ and KHCO ₃ , and set three different concentrations of 0.1mol/L, 0.2mol/L and 0.3mol/L; 2), mutagenic spirulina spirulina treatment: Spirulina was pre-cultured in ordinary zarrouk medium, the temperature was set to 30°C, the light intensity was 4000 luxs, and a 5% CO ₂ mixture (5% CO ₂ +95% N ₂ ) or air was introduced at a flow rate of 0.1vvm The algae enter the pre-cultivation stage; After aeration, mutagenized Spirulina grows to the logarithmic growth phase, and the pre-cultivation phase ends, and the cultivated algal species is used as the inoculation mother solution for the formal experiment; In the formal inoculation experiment, the control inoculum amount was OD ₅₆₀ =0.2; 3) Formal training experiment: Use the zarrouk medium without carbon source as basal medium, respectively add NaHCO and KHCO ₍ 0.1mol/ _L , 0.2mol/L and 0.3mol/L) of different concentrations as carbon source; The medium volume was 200ml, sterilized by high temperature at 121°C for 30min, NaHCO ₃ and KHCO ₃ were filtered and sterilized through a 0.45 μm filter membrane, and then inserted into the mutagenized Spirulina platensis with algae amount OD ₅₆₀ =0.2; The culture was carried out for 18 days under the condition of light intensity=4000luxs, temperature=30±1℃, all day light. 2. development according to claim 1 is the method for the efficient BECCS system of linking with bicarbonate, it is characterized in that, in described step 2), mutagenized Spirulina platensis is the mutagenized Spirulina platensis through nuclear radiation .

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