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 taking bicarbonate radical as a link, which mainly comprises the following steps: chemical absorbent is Na ₂CO ₃And K ₂CO ₃To fully absorb CO ₂NaHCO to form the corresponding bicarbonate ₃And KHCO ₃Used for mutagenizing a carbon source in the culture process of spirulina. Culture conditions in the experiment: the light intensity is 4000luxs, the illumination is carried out all day long, and the temperature is 30 ℃. Setting NaHCO ₃And KHCO ₃The concentrations of (A) were 0.1mol/L, 0.2mol/L and 0.3mol/L, respectively. After 18 days of culture, the spirulina platensis is induced to be cultured in 0.3mol/L NaHCO ₃The dry weight of the biomass in the system reaches 2.24g/L, and the carbon utilization efficiency is 26.71 percent, the maximum experimental solid carbon content is 230.36mg/L/d, and the KHCO content is 0.3mol/L ₃The dry weight of the biomass obtained in the system is 2.00g/L, the carbon utilization efficiency is 25.69%, and the maximum solid carbon amount is 153.41 mg/L/d. The chemical absorption and the microalgae conversion are coupled, so that the problems of high energy consumption and low microalgae carbon utilization efficiency in the desorption process of a chemical absorption method can be avoided.

Description

Method for developing efficient BECCS system with bicarbonate radical as ligament

The technical field is as follows:

the invention relates to the technical field of microalgae biological carbon sequestration, and relates to a method for trapping CO by chemical absorption ₂The carbon capture resource utilization combined with microalgae biological carbon sequestration is a method for developing a high-efficiency BECCS system taking bicarbonate radical as a link.

Background field:

by 2017, the energy storage in China has proved that the coal storage amount is up to 1.27 hundred million tons, which accounts for 13.4 percent of the total coal amount all over the world. The reserves of petroleum and natural gas respectively account for 1.5 percent and 2.8 percent of the reserves of the world and are far lower than the reserves of coal ^[1]. The current situations of rich coal, lack of oil and little gas determine that the energy structure in China mainly uses coal and uses petroleum and natural gas as auxiliary materials. Although the national government strives to adjust and optimize the energy system and expand the use of renewable and sustainable new energy, the consumption of new energy such as nuclear energy, wind energy, solar energy, biomass energy and the like only accounts for 11.7 percent due to the technical limit ^[2]. On the other hand, China is in a rapid development stage, and the demand for energy is increasing day by day, so that fossil fuel is always in the leading position of Chinese energy in a short period of time, and the combustion of the fossil fuel can generate CO ₂And the carbon emission in China is far higher than that in developed countries using novel energy sources. It is statistically estimated that there are about 33.4 million tons of CO per year ₂Discharge to the atmosphere of these CO ₂From power plants, oil refineries, biogas desulfurization and ethylene oxide, cement and steel production, with 40% CO ₂Produced by coal-fired power plants ^[3,4]A series of environmental problems such as global warming and sea level increase are caused.

Various tradesmen have been striving to alleviate the current situation of environmental degradation due to excessive carbon emissions, and in the past few years, the Chinese government has taken many policies and measures to reduceLess carbon emission and promotion of green transformation in various industries. Among them, carbon taxes are considered to be an effective prospective economic means of reducing carbon emissions in China ^[5]. The Chinese finishes the 'twelve-five' planning in 2015, and the 'thirteen-five' planning is compiled in order to achieve the carbon emission reduction target. The concept of establishing energy use right, carbon emission right, pollution discharge right trading market and promoting marketable energy-saving carbon emission reduction is provided, and ten specific, measurable, realizable, supervisoble and practical carbon emission reduction measures such as carbon recycling, scientific development of renewable energy sources, clean energy source substitution and the like are provided. In addition to controlling carbon emissions, fossil fuel combustion produces CO ₂Should also be the focus of the study.

Chemical absorption is most widely used in a plurality of post-combustion capture technologies, and the chemical absorption method has mature technical support and is promising CO ₂The method of (1). The typical decarbonization system consists of two parts, namely an absorption tower and a desorption tower, and is generally positioned after dust removal, desulfurization and denitrification, flue gas enters the absorption tower from the bottom of the absorption tower after being cooled and is in reverse contact with a sprayed chemical absorbent, and at the moment, the chemical absorbent and CO are in reverse contact ₂A reversible chemical reaction occurs. Absorb CO ₂The rich absorbent solution is pumped out of the absorption tower and exchanges heat with the poor absorbent solution in the heat exchanger, the rich absorbent solution enters the desorption tower after being heated at high temperature, the high-temperature regeneration of the chemical absorbent is realized in the desorption tower, and pure CO is separated ₂Condensing, drying and compressing CO ₂Sealed or recycled ^[6]. Chemical absorption is widely used due to the advantages of high reaction rate, good absorption effect, high recovery degree and the like, and has the defects of high energy consumption, high investment cost and easy occurrence of bubbles and entrainment in solution.

1.83t of CO can be utilized in the course of carbon sequestration of spirulina organisms ₂To produce 1t dry weight of biomass ^[7]. The principle of carbon sequestration of spirulina organisms is divided into two parts, one part is a light reaction, and the other part is a dark reaction. In the course of photoreaction, the spirulina undergoes light energy absorption, light transmission, photochemical reaction, electron transmission, and photosynthetic phosphorylationProcess for decomposing H while generating ATP and reduced coenzyme (NADPH) ₂O to O ₂. The dark reaction stage mainly utilizes ATP and NADPH generated in the light reaction stage to further complete the carbon metabolism process, and finally generates organic matters ^[8]. Spirulina living in aquatic environment, and inorganic carbon in water has CO ₂(aq)、CO ₃ ^2-、HCO ₃ ^-、H ₂CO ₃Etc. not every kind of inorganic carbon microalgae can be absorbed and utilized, but two kinds of inorganic carbon that spirulina can utilize are CO ₂And HCO ₃ ^-Spirulina Carbonic Anhydrase (CA) activity was very strong and bicarbonate utilization efficiency was higher compared to green algae. But the efficiency of carbon sequestration by spirulina organisms is low.

Active products such as saturated fatty acid and unsaturated fatty acid can be extracted from biomass of spirulina, and can be used as raw materials for industrially producing biodiesel, biogas, biological hydrogen production, bioethanol and biobutanol. Biodiesel is a green renewable fuel, usually produced from biological feedstocks, and spirulina biomass contains lipids that can be converted to FAME (fatty acid methyl esters) by transesterification to produce biodiesel. Carbohydrates (mainly glucose, starch, cellulose, hemicellulose) can be converted into bioethanol by fermentation. The green residue after the extraction of spirulina oil can be used for producing biobutanol which is more suitable for biofuel than biomethanol or bioethanol because of its higher energy density, and can be used as a solvent in addition to biofuel. Carbon sequestration and emission reduction coal-fired flue gas CO of spirulina organisms ₂Has important significance for alleviating greenhouse effect, developing pollution control of low-carbon economy and environmental protection industries. The spirulina contains high nutrient content, but the spirulina culture process consumes a large amount of water and inorganic salt nutrient substances. There is a need to provide a method for reducing the cost of spirulina production and promoting the commercial utilization of spirulina on a large scale.

Due to combustion of fossil fuels, large amounts of CO ₂The amount of emissions is discharged into the air, and the amount of emissions tends to increase year by year. China is one of the carbon-emitting countries and emits to the atmosphere every yearCO in ₂Up to 33.4 million tons. CO 2 ₂Is a main greenhouse gas, and the environmental hazard brought by the emission into the atmosphere draws attention of people, and simultaneously CO ₂Is also the most abundant carbon resource, and how to effectively capture carbon and utilize the carbon resource becomes the key point. In the traditional carbon capture process, chemical absorption is the most common, but the problem of high energy consumption exists. The biological carbon fixation is most environment-friendly, and the microalgae uses CO under the photosynthesis ₂Is a carbon source, synthesizes biomass and other high-value additional products, but has large consumption of nutritive salt in the process of culturing microalgae. In order to solve the problems of high energy consumption in the chemical absorption process and the cost of nutrient salts in the microalgae culture process, a high-efficiency BECCS (bioenergy spent with carbon dioxide capture and storage) system taking bicarbonate radical as a link is developed, namely, chemical absorption carbon fixation and microalgae biosolid carbon fixation are connected together through bicarbonate, the yield of microalgae biomass is improved on the basis of reducing the cost of nutrient salts, and the photosynthetic carbon fixation of microalgae is promoted.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a method for carbon fixation by coupling chemical absorption with microalgae carbon fixation.

The technical scheme of the invention is that the method for developing the high-efficiency BECCS system taking the bicarbonate radical as the ligament comprises the following steps:

1) selection of chemical absorbent: the traditional typical chemical absorbent is divided into ammonia water absorbent, alcohol amine absorbent, amino acid salt absorbent and potassium carbonate absorbent. However, some chemical absorbents absorb CO ₂The substances generated later are corrosive or toxic, and are not beneficial to the culture of the subsequent spirulina. Selection of Na ₂CO ₃And K ₂CO ₃To fully absorb CO ₂After generation of NaHCO ₃And KHCO ₃And three different concentrations of 0.1mol/L, 0.2mol/L and 0.3mol/L are respectively set.

2) And mutagenizing spirulina and spirulina: the spirulina was pre-cultured in a common zarrouk medium at 30 deg.C under 4000luxs light intensity, and 5% CO was introduced at 0.1vvm ₂Mixed gas (5% CO) ₂+95％N ₂) Or air, the microalgae enters the pre-culture stage. After 5 days of ventilation, the mutagenized spirulina grows to the logarithmic phase, the pre-culture stage is finished, and the cultured spirulina seeds are used as the inoculation mother liquor of the formal experiment. Controlling the inoculation amount to OD in formal inoculation experiment ₅₆₀＝0.2

3) And formal culture experiment: using a zarrouk culture medium without a carbon source as a basal medium, and respectively adding NaHCO with different concentrations ₃And KHCO ₃(0.1mol/L, 0.2mol/L and 0.3mol/L) as a carbon source. The culture medium has a volume of 200ml, and is sterilized at 121 deg.C for 30min with NaHCO ₃And KHCO ₃Filtering with 0.45 μm filter membrane for sterilization, and inoculating algae with OD ₅₆₀0.2 of induced Spirulina platensis.

Culturing under the conditions of light intensity of 4000luxs and temperature of 30 +/-1 deg.C for 18 days.

The induced blunt-ended spirulina in the step 2) is induced blunt-ended spirulina subjected to nuclear radiation.

Compared with the prior art, the invention has the advantages that:

1) the invention researches a BECCS system taking bicarbonate radical as a link, and induces the spirulina platensis to be NaHCO of 0.3mol/L through 18 days of culture ₃The highest biomass dry weight obtained in the system is 2.29g/L, KHCO at 0.3mol/L ₃2.00g/L of microalgae biomass dry weight is obtained in the system. In NaHCO ₃The utilization efficiency of carbon in the system is higher than KHCO ₃Systematic, highest carbon utilization efficiency is 0.3mol/L NaHCO ₃26.71% was obtained in the system. The maximum carbon fixing amount of the induced blunt-top spirulina is 23036mg/L/d, which is higher than the carbon fixing amount of the ordinary microalgae organisms.

2) The invention fixes CO by chemical absorption ₂Coupled with microalgae biological carbon sequestration, the problem of high energy consumption in the desorption process of a chemical absorbent is avoided, and simultaneously, carbonate absorbs CO ₂The generated bicarbonate is used as a carbon source in the process of culturing the spirulina, so that the cost problem in the process of culturing the microalgae is reduced, and the microalgae can extract high-value added-value products such as grease, polysaccharide, protein and the like.

Description of the drawings:

FIG. 1 is a schematic representation of biomass dry weight of induced Spirulina platensis in bicarbonate system

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

FIG. 3 is a graph showing the carbon fixation of mutagenized blunt-tipped helices in a bicarbonate system

FIG. 4 shows the change in chlorophyll content of mutagenized spirulina in bicarbonate system

FIG. 5 is a graph showing the oil content of mutagenized spirulina in a bicarbonate system

The specific implementation mode is as follows:

the invention is further illustrated by the following specific examples and the accompanying drawings. The examples are intended to better enable those skilled in the art to better understand the present invention and are not intended to limit the present invention in any way.

The invention develops a BECCS system taking bicarbonate as a bond, which comprises the following steps:

1) selection of chemical absorbent: the economic absorbent is selected, the market price of ammonia water is the cheapest, but the tolerance of the spirulina to ammonia nitrogen is not good, and the high-concentration ammonia nitrogen can generate toxic action on the photosynthetic system of the spirulina. And the carbon source form which the spirulina can utilize is HCO ₃ ^-And CO ₂Based on the method, the chemical absorbent adopts carbonate to absorb CO ₂The bicarbonate produced is then used to culture microalgae. Na having a high absorption rate is preferable ₂CO ₃And K ₂CO ₃。

2) Pre-culturing induced spirulina platensis: the induced blunt-tipped spirulina was inoculated under aseptic conditions and cultured in 200mL autoclaved zarrouk medium in a 250mL Erlenmeyer flask while passing air at a flow rate of 0.1 vvm.

The composition of SE medium is given in the following table:

TABLE 1 nutrient component ratios in Zarrouk medium

TABLE 2 A ₅、B ₆Composition of solution

Culture conditions for inducing Spirulina platensis: the light intensity is 4000luxs, the illumination is carried out all day long, the temperature is 30 +/-1 ℃, and the culture period is intermittently shaken;

3) in the formal experiment, in the experimental process, a Zarrouk culture medium without adding a carbon source is adopted to inoculate OD ₅₆₀The two types of bicarbonate were used as carbon sources at concentrations of 0.1mol/L, 0.2mol/L, and 0.3mol/L, respectively, with no aeration during the main culture.

The culture conditions include day-to-day illumination, light intensity of 6000luxs, and temperature of 30 + -1 deg.C

A. Biomass detection:

collecting 2mL of algae suspension, measuring the biomass of the mutagenized spirulina, measuring a spectrophotometric value at a wavelength of 560nm, and substituting the spectrophotometric value into a dry weight standard curve to convert the dry weight of the biomass. Each sample was run in triplicate, and blank samples were also treated in the same manner, with samples containing no algae as controls.

The biomass dry weight standard curve of the spirulina is measured by a drying method. Diluting high concentration Spirulina solution with deionized water to OD ₅₆₀100ml of algal solution was measured out when the concentration was 0.2, 0.4, 0.6, 0.8 and 1.0, respectively. Before filtering the algae liquid, drying the filter membrane with the aperture of 0.45 mu m in an oven at 150 ℃ for 2h to remove the interference of water, weighing the filter membrane after the filter membrane is dried to constant weight and cooled down, and recording the weight of the filter membrane before filtering. And then 100ml of the algae liquid is filtered by a membrane, the filtered filter membrane is put into an oven at 150 ℃ again to be dried to constant weight, and the filter membrane after the microalgae filtration is weighed after cooling. The difference value of the two previous filter membrane weighing processes is the biomass dry weight of the spirulina.

A schematic representation of the spirulina biomass after 18 days of culture is shown in FIG. 1.

Analysis of FIG. 1, induced Spirulina platensis grow differently in two different species, different bicarbonate concentration systemsThe highest dry weight of biomass was obtained in the system with a concentration of 0.3 mol/L. NaHCO 2 ₃2.29g/L of KHCO is obtained in the system ₃The dry weight of biomass in the system was 2.00 g/L. The three concentrations of bicarbonate did not produce a toxic effect on spirulina, but spirulina growth retardation occurred in the high concentration bicarbonate system.

B. Detection of inorganic carbon

Taking a certain amount of solution in the system, filtering the solution by a filter membrane of 0.45 mu m, collecting supernatant, and determining the inorganic carbon value in the solution in a liquid-phase TOC detector.

As shown in the second figure, the Spirulina platensis was induced to have NaHCO content of 0.3mol/L ₃The inorganic carbon utilization efficiency in the system is highest, mainly because the high-concentration bicarbonate system has higher buffer capacity, the carbon utilization efficiency is improved.

C. Calculation of the amount of solid carbon

After the experiment period is finished, taking out all algae liquid, drying the algae, then taking 20mg of microalgae for element analysis in an element analyzer to obtain the C element ratio, multiplying the dry weight of the biomass of the spirulina by the C element in the algae powder, and converting the amount of the spirulina into the fixed carbon dioxide according to the following calculation formula:

-the amount of carbon fixed by the spirulina organisms, mg/L/d;

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

C _algae-spirulina powder C content in% >;

----CO ₂relative molecular mass;

M _C- -C relative to atomic mass.

D. Chlorophyll content determination

Centrifuging 5ml of Spirulina solution at 5000rpm for 20min, pouring out supernatant, adding 5ml of methanol into the precipitate, ultrasonically oscillating for 15min in dark condition, placing in a refrigerator at 4 deg.C, extracting for 12 hr, centrifuging again, collecting supernatant, measuring absorbance values at wavelengths of 666nm, 653nm and 470nm, and adjusting to zero with methanol as blank.

Chlorophyll can be used as an index for evaluating the photosynthesis of spirulina, the higher the chlorophyll concentration is, the stronger the photosynthesis of the spirulina is, the higher the biomass accumulation is, and the highest chlorophyll value can be seen in the culture day 9, 0.3mol/L NaHCO ₃And (4) obtaining in the system.

E. Determination of oil content

Measuring the oil content by adopting a Nile red fluorescent staining method, taking 2.55ml of algae solution, and adding 450 mu L of dimethyl sulfoxide and 24 mu L of Nile red solution; standing in a dark room at 30 deg.C for 10min, and selecting 580nm as fluorescence excitation detection wavelength for determination.

The grease can be used as an added-value product in the later stage of spirulina culture, can be further used for producing and preparing biodiesel, and is applied to the aspect of energy.

It should be understood that the embodiments and examples discussed herein are illustrative only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.

The related documents are:

[1] china Ministry of civil republic of China, national resources department, China mining assets report 2018[ C ]. Beijing, 2018.

[2] China renewable energy development report 2017[ C ].2018, International energy revolution forum.

[3]Cheng J,Zhu Y,Zhang Z,et al.Modification and improvement ofmicroalgae strains for strengthening CO ₂fixation 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 fromthermal 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 Meng, Zhou Xu Duan, Wang, etc. CO ₂Chemical absorbent [ J]Chemical progression, 2015, 27 (12): [7]

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

[8]Novel flat plate type photobioreactor with Nengfu and built-in LED light source for efficiently fixing CO by microalgae ₂[D]The Qingdao: china ocean university, 2014.808-1814.

Claims (2)

1. A method for developing a bicarbonate-based efficient BECCS system, comprising the steps of:

1) selection of chemical absorbent: selection of Na ₂CO ₃And K ₂CO ₃To fully absorb CO ₂After generation of NaHCO ₃And KHCO ₃Three different concentrations of 0.1mol/L, 0.2mol/L and 0.3mol/L are respectively set;

2) and mutagenizing spirulina and spirulina:

the spirulina was pre-cultured in a common zarrouk medium at 30 deg.C under 4000luxs light intensity, and 5% CO was introduced at 0.1vvm ₂Mixed gas (5% CO) ₂+95％N ₂) Or air, the microalgae enters a pre-culture stage;

inducing the growth of the spirulina to logarithmic growth phase after ventilation, ending the pre-culture stage, and taking the cultured algae seeds as inoculation mother liquor of a formal experiment;

controlling the inoculation amount to OD in formal inoculation experiment ₅₆₀＝0.2；

3) And formal culture experiment:

using a zarrouk culture medium without a carbon source as a basal medium, and respectively adding NaHCO with different concentrations ₃And KHCO ₃(0.1mol/L, 0.2mol/L and 0.3mol/L) as a carbon source;

the culture medium has a volume of 200ml, and is sterilized at 121 deg.C for 30min with NaHCO ₃And KHCO ₃Filtering with 0.45 μm filter membrane for sterilization, and inoculating algae with OD ₅₆₀0.2 of induced Spirulina platensis;

culturing under the conditions of light intensity of 4000luxs and temperature of 30 +/-1 deg.C for 18 days.

2. The method for developing a bicarbonate-bound high-efficiency BECCS system according to claim 1, wherein the induced spirulina platensis of step 2) is nuclear-irradiated induced spirulina platensis.

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