Carbon dioxide emission reduction method and system suitable for power plant

Abstract

The invention discloses a carbon dioxide emission reduction method and system suitable for a power plant, and the method comprises the steps: taking an alkaline industrial waste liquid as an adsorbent, and carrying out contact reaction on the alkaline industrial waste liquid and carbon dioxide-containing flue gas generated by coal combustion in the power plant to obtain a carbon-rich absorption liquid; the method comprises the following steps: mixing the dried and crushed biomass waste with biomass solid waste, carrying out a hydrothermal carbonization reaction in a high-pressure reaction kettle containing an inert atmosphere, and carrying out solid-liquid separation to obtain biochar and bio-oil, so that a power plant carries out blending combustion power generation based on the dried and crushed biochar. The alkaline industrial waste liquid is used as an adsorbent to capture carbon dioxide, the capture cost can be reduced, meanwhile, the carbon dioxide emission of a power plant is preliminarily reduced, biomass solid waste and carbon-rich absorption liquid obtained after carbon dioxide capture are mixed and separated to obtain biochar, the biochar can be used for combustion in the power plant, and the environment is protected. And the calculated amount of carbon dioxide emission generated by only using coal combustion is further reduced, so that low-cost carbon emission reduction of the power plant is finally realized.

Description

Technical Field

[0001] This application relates to the fields of energy and chemical technology and low-carbon technology, and in particular to a method and system for carbon dioxide emission reduction applicable to power plants. Background Technology

[0002] With the advancement of the "dual carbon" goals, the thermal power industry, as a major source of carbon emissions, faces enormous pressure to reduce emissions. Carbon capture, utilization, and storage (CCUS) technology is one of the key pathways to achieve deep emission reduction. However, existing CCUS technologies, especially the carbon dioxide capture stage, generally suffer from high costs and energy consumption. For example, commonly used amine absorbents are expensive and easily degraded. Summary of the Invention

[0003] In view of this, this application provides a carbon dioxide emission reduction method and system suitable for power plants, which can capture carbon dioxide while maximizing resource utilization, and use alkaline industrial waste liquid in conjunction with biomass solid waste to achieve efficient capture of flue gas carbon dioxide and co-production of high value-added products in a green cycle.

[0004] According to one aspect of this application, a method for reducing carbon dioxide emissions in power plants is provided, the method comprising: When a power plant burns coal and produces flue gas containing carbon dioxide, an alkaline industrial waste liquid is used as an adsorbent to react with the flue gas containing carbon dioxide, thereby capturing the carbon dioxide in the flue gas and obtaining a carbon-rich absorbent liquid. The alkaline industrial waste liquid includes alkaline papermaking black liquor, which is obtained from a paper mill. Biomass solid waste is obtained and crushed. The carbon-rich absorbent liquid is mixed with the crushed biomass solid waste and placed in a high-pressure reactor containing an inert atmosphere so that the carbon-rich absorbent liquid and the crushed biomass solid waste undergo a hydrothermal carbonization reaction under an inert atmosphere. The raw materials of the biomass solid waste include crop straw, and the crops include corn. The mixture formed after hydrothermal carbonization reaction is subjected to solid-liquid separation to obtain biochar as a solid product and bio-oil as a liquid product, wherein the bio-oil is enriched with phenolic compounds. Biochar is dried and pulverized so that power plants can co-fire the dried and pulverized biochar for power generation. In this process, crops absorb carbon dioxide through photosynthesis. When power plants burn biochar made from crop straw, the carbon dioxide produced by the burning of biochar is offset by the carbon dioxide absorbed by the crops through photosynthesis, so that when calculating carbon dioxide emissions, the carbon dioxide emissions produced by the burning of biochar are lower than the carbon dioxide emissions produced by the burning of coal.

[0005] According to another aspect of this application, a carbon dioxide emission reduction system suitable for power plants is provided, the system comprising: A black liquor storage tank is used to store alkaline industrial waste liquid, wherein the alkaline industrial waste liquid includes alkaline papermaking black liquor, which is obtained from a paper mill. Straw crushers are used to crush collected crop straw to obtain biomass solid waste, including corn. The reactor is used to react with carbon dioxide-containing flue gas by using alkaline industrial waste liquid as an adsorbent, thereby capturing carbon dioxide in the flue gas and obtaining a carbon-rich absorbent liquid. High-pressure reactors are used to carry out hydrothermal carbonization reactions of carbon-rich absorbent liquid and crushed biomass solid waste in an inert atmosphere. A solid-liquid separator is used to separate the solid and liquid components of a mixture formed after a hydrothermal carbonization reaction to obtain biochar as a solid product and bio-oil as a liquid product, wherein the bio-oil is enriched with phenolic compounds. A biochar drying and pulverizing system is used to dry and pulverize biochar so that power plants can generate electricity by co-firing the dried and pulverized biochar. In this system, crops absorb carbon dioxide through photosynthesis. When power plants use biochar made from crop straw for combustion, the carbon dioxide produced by biochar combustion is offset by the carbon dioxide absorbed by crop photosynthesis, so that when calculating carbon dioxide emissions, the carbon dioxide emissions produced by biochar combustion are lower than the carbon dioxide emissions produced by coal combustion. Bio-oil refining and purification system, used for refining and purifying bio-oils.

[0006] By utilizing the above technical solutions, this application provides a carbon dioxide emission reduction method and system suitable for power plants. It uses alkaline papermaking black liquor to capture CO2 from coal-fired flue gas. The resulting carbon-rich absorbent is then subjected to a hydrothermal carbonization reaction with biomass solid waste (such as corn stalks), constructing a unique "alkali-acid" synergistic catalytic system. This system co-produces high-performance biochar with lignite-grade combustion characteristics and high-value-added phenolic bio-oil, achieving "waste-to-waste" treatment and synergistic processing of thermal power plant waste gas, papermaking waste liquor, and agricultural solid waste. The system is low-cost and highly efficient, providing a systematic solution for the low-carbon transformation of the thermal power industry and the recycling of agricultural and forestry waste.

[0007] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0008] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 A schematic flowchart of a carbon dioxide emission reduction method applicable to power plants provided in an embodiment of this application is shown. Figure 2 Thermogravimetric analysis (TGA) curve of a biochar prepared according to an embodiment of this application is shown: Figure 3 The following is a graph showing the effect of different NaOH concentrations on CO2 capture efficiency, provided in the embodiments of this application. Figure 4 A schematic diagram of a carbon dioxide emission reduction system suitable for power plants, provided in an embodiment of this application, is shown.

[0009] 201-Black liquor storage tank; 202-Straw crusher; 203-Reactor; 2031-Reactor gas inlet; 2032-Reactor liquid inlet; 2033-Reactor liquid outlet; 2034-Reactor gas outlet; 204-High-pressure reactor; 2041-High-pressure reactor feed inlet; 2042-High-pressure reactor discharge outlet; 205-Solid-liquid separator; 2051-Solid outlet of solid-liquid separator; 2052-Liquid outlet of solid-liquid separator; 206-Biochar drying and pulverizing system; 207-Bio-oil refining and purification system. Detailed Implementation

[0010] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0011] This embodiment provides a carbon dioxide emission reduction method suitable for power plants, the method comprising: Step 101: When the power plant burns coal to produce flue gas containing carbon dioxide, alkaline industrial waste liquid is used as an adsorbent to react with the flue gas containing carbon dioxide to capture the carbon dioxide in the flue gas and obtain carbon-rich absorbent liquid. The alkaline industrial waste liquid includes alkaline papermaking black liquor, which is obtained from a paper mill. Step 102: Obtain biomass solid waste and crush it. Mix the carbon-rich absorbent liquid with the crushed biomass solid waste and place it in a high-pressure reactor containing an inert atmosphere so that the carbon-rich absorbent liquid and the crushed biomass solid waste can undergo hydrothermal carbonization reaction under an inert atmosphere. The raw materials of the biomass solid waste include crop straw, and the crops include corn. Step 103: The mixture formed after the hydrothermal carbonization reaction is subjected to solid-liquid separation to obtain biochar as a solid product and bio-oil as a liquid product, wherein the bio-oil is enriched with phenolic compounds. Step 104: The biochar is dried and pulverized so that the power plant can generate electricity by co-firing the dried and pulverized biochar. In this process, crops absorb carbon dioxide through photosynthesis. When the power plant uses biochar made from crop straw for combustion, the carbon dioxide produced by the combustion of biochar is offset by the carbon dioxide absorbed by the crops through photosynthesis, so that when calculating carbon dioxide emissions, the carbon dioxide emissions produced by the combustion of biochar are lower than the carbon dioxide emissions produced by the combustion of coal.

[0012] Currently, after carbon dioxide capture, there is a lack of large-scale, economically viable resource utilization pathways for the captured carbon dioxide, severely restricting the commercialization of CCUS technology. Meanwhile, my country generates a large amount of biomass solid waste (such as crop straw) and industrial organic wastewater (such as black liquor from papermaking) annually. Improper treatment of these wastes can cause environmental pollution and resource waste. Black liquor from papermaking is typically highly alkaline, and traditional treatment methods are costly. However, its alkaline properties can theoretically be used to capture acidic gases (such as CO2). Therefore, how to synergistically integrate carbon dioxide emission reduction with the resource utilization of the aforementioned wastes to form a circular economy model of "treating waste with waste and turning waste into treasure" has become an urgent technical challenge.

[0013] In the above embodiments of this application, such as Figure 1 As shown, this technology can combine carbon dioxide emission reduction, industrial wastewater treatment, and biomass solid waste resource utilization to form a low-cost, high-efficiency integrated carbon emission reduction technology. Specifically, alkaline industrial waste liquids, such as alkaline papermaking black liquor, can be selected. Alkaline papermaking black liquor contains alkaline substances such as NaOH and Na2CO3, which can undergo an acid-base reaction with CO2.

[0014] Flue gas can be introduced into countercurrent contact with alkaline papermaking black liquor through an absorption tower or a bubbling reactor, where dissolved CO2 is converted into carbonates / bicarbonates to generate carbon-rich absorbent (e.g., a mixture containing Na2CO3 / NaHCO3).

[0015] Next, biomass such as corn stalks can be crushed into particles smaller than 5mm to increase the reaction contact area.

[0016] The mixed biomass solid waste and carbon-rich absorbent liquid, with a solid-liquid mass ratio between 1:6 and 1:10, are placed in a high-pressure reactor and purged with an inert atmosphere, such as N2 (oxygen content can be <0.1%), and reacted at 240°C to 280°C for 20 to 40 minutes. Specifically, the hydrothermal carbonization reaction temperature is preferably 260°C, and the reaction time is preferably 30 minutes. When the hydrothermal carbonization reaction is carried out in a high-pressure reactor, the air inside the reactor must be purged before introducing the inert gas.

[0017] The alkaline substances in black liquor can accelerate biomass hydrolysis and promote dehydration / decarboxylation reactions. CO2-derived carbonates react with cellulose / lignin in the biomass, increasing the solid carbon retention rate, ultimately yielding biochar and bio-oil. The biochar can be dried and pulverized for co-firing in power plants, while the bio-oil can undergo liquid-phase extraction / distillation to separate and purify phenolic compounds, forming fuel oil or chemical feedstock. Thermogravimetric analysis of the obtained biochar is shown in the following figure. Figure 2 ,Depend on Figure 2 It can be seen that the relative content of phenolic compounds is significantly higher than that of bio-oil obtained by traditional hydrothermal carbonization process.

[0018] In particular, crops such as corn absorb atmospheric CO2 through photosynthesis during their growth. Therefore, when biochar made from straw releases CO2 during combustion, it only returns the carbon absorbed during the growth period, resulting in net carbon emissions of approximately 0.

[0019] Therefore, replacing chemical adsorbents with waste liquid can reduce emissions and save costs, while also benefiting industrial wastewater treatment. The hydrothermal carbonization process catalyzes biomass conversion in the carbon-rich absorbent, increasing biochar yield and synergistically fixing carbon. Biochar co-firing for power generation enables a closed-loop carbon cycle in biomass, achieving near-zero carbon emissions for auxiliary energy supply. That is, through the coupling of material recycling (waste liquid—CO2 adsorbent, straw—energy) and carbon recycling (photosynthetic carbon fixation—biochar combustion carbon release), the goal of "treating waste with waste and turning carbon into resources" can be achieved, realizing a circular economy and carbon neutrality pathway.

[0020] Optionally, the pH value of the alkaline industrial waste liquid is not less than 11, sodium hydroxide is added to the alkaline industrial waste liquid as a reinforcing agent, the mass concentration of sodium hydroxide in the absorbent is between 1% and 4%, and the liquid-to-gas ratio of the absorbent to the flue gas is between 0.2 and 0.4 L / m³.

[0021] In the above embodiments of this application, the volume concentration of carbon dioxide can be between 10% and 20%, and the final carbon dioxide capture efficiency is not less than 90%. The pH value of the alkaline industrial waste liquid is not less than 11. Adding 1%-4% sodium hydroxide by mass concentration as a reinforcing agent can enhance the alkalinity of the waste liquid and improve its chemical absorption capacity for carbon dioxide. The liquid-to-gas ratio is between 0.2 and 0.4 L / m³, which can ensure sufficient contact and reaction between the waste liquid and the flue gas. Under these conditions, facing a carbon dioxide concentration of 10%-20% by volume, a capture efficiency of not less than 90% can be achieved, effectively reducing carbon dioxide emissions from power plant flue gas. At the same time, the waste liquid is utilized to reduce treatment costs, achieving synergistic effects between industrial wastewater treatment and carbon emission reduction.

[0022] Optionally, when alkaline industrial waste liquid is used as an adsorbent and reacts with flue gas containing carbon dioxide, the alkaline substances in the adsorbent and the captured carbon dioxide together form an alkaline-acid synergistic catalytic system. During the hydrothermal carbonization reaction of the carbon-rich absorbent liquid and the crushed biomass solid waste under an inert atmosphere, the method further includes: Step 105: Promote the conversion of biomass in biomass solid waste into biochar through an alkaline-acid synergistic catalytic system.

[0023] In the above embodiments of this application, in the alkali-acid synergistic catalytic system, the alkaline substance can accelerate the hydrolysis of biomass and destroy its complex structure, while the acidic environment formed by the captured carbon dioxide can promote decarboxylation, dehydration, and other reactions. The synergistic effect of these two factors creates more suitable chemical conditions for biomass conversion, effectively reducing the reaction activation energy and making the reaction easier to proceed. This not only improves the yield of biochar but also optimizes the pore structure and surface properties of biochar, enhancing its adsorption performance and combustion stability. This provides a strong guarantee for the efficient use of biochar in power plants to assist in power generation and achieve carbon emission reduction targets.

[0024] Optionally, step 105 promotes the conversion of biomass in biomass solid waste into biochar through an alkaline-acid synergistic catalytic system, including: Step 1051: In the initial stage of hydrothermal carbonization reaction, the alkaline environment of the carbon-rich absorbent liquid promotes the initial alkaline decomposition of water in cellulose and hemicellulose, as well as lignin, in biomass solid waste. Step 1052: In the later stage of the hydrothermal carbonization reaction, the carbonic acid formed by carbon dioxide dissolving in water and the organic acids generated by the hydrothermal carbonization reaction cause the pH value of the alkaline-acid synergistic catalytic system to decrease, forming an acidic environment. The acidic environment catalyzes the cleavage of the β-O-4 ether bond in lignin, thus obtaining biochar.

[0025] In the above embodiments of this application, during the initial stage of the hydrothermal carbonization reaction, the alkaline environment promotes the hydrolysis of cellulose and hemicellulose and the preliminary alkaline decomposition of lignin. The carbon-rich absorbent solution has an alkaline environment, containing a large number of hydroxide ions (OH-). Cellulose and hemicellulose are high-molecular-weight polysaccharides composed of monosaccharides such as glucose linked by glycosidic bonds. Under the high temperature and pressure conditions at the initial stage of hydrothermal carbonization, OH- in the alkaline environment... It can attack the glycosidic bonds in cellulose and hemicellulose molecules.

[0026] glycosidic bond in OH Under the attack of alkaline substances, the long-chain cellulose and hemicellulose molecules break down, gradually depolymerizing to form smaller oligosaccharides and even monosaccharide molecules. For example, the β-1,4-glycosidic bonds in cellulose molecules are easily broken under alkaline conditions, releasing glucose units. These small-molecule sugars further participate in subsequent dehydration, cyclization, and other reactions, providing precursors for biochar formation.

[0027] Lignin is a complex aromatic polymer containing numerous phenylpropane units linked together by ether and carbon-carbon bonds. In alkaline environments, some ether bonds in lignin molecules, especially α-ether bonds, are sensitive to alkali.

[0028] OH The alkaline environment can attack the oxygen atoms in these ether bonds, causing them to break and leading to the gradual disintegration of the lignin molecule. Simultaneously, the alkaline environment can cause the lignin molecules to swell, increasing their contact area with the reaction medium and further promoting lignin decomposition. The lignin fragments after initial alkaline hydrolysis participate in subsequent polymerization and carbonization reactions, ultimately forming part of the biochar.

[0029] In the later stages of the hydrothermal carbonization reaction, the acidic environment catalyzes the breaking of the β-O-4 ether bond in lignin. As the hydrothermal carbonization reaction proceeds, carbon dioxide continuously dissolves in water to form carbonic acid, which partially ionizes to produce hydrogen ions (H+). + This process gradually increases the acidity of the solution. Furthermore, during hydrothermal carbonization, biomass undergoes a series of complex chemical reactions, producing organic acids such as formic acid and acetic acid. These organic acids also release H₂O. + This further lowers the pH of the solution, creating an acidic environment.

[0030] The β-O-4 ether bond in lignin molecules is a relatively stable chemical bond. However, under acidic conditions, H+ can attack the oxygen atom in the β-O-4 ether bond, causing it to become positively charged, thus making the ether bond unstable.

[0031] The positively charged oxygen atom attracts electrons from the adjacent carbon atom, reducing the electron cloud density of the carbon-oxygen bond, weakening the bond energy, and ultimately causing the β-O-4 ether bond to break. The breaking of the β-O-4 ether bond releases a large amount of phenolic compounds and other small-molecule aromatic substances.

[0032] These small molecules undergo further dehydration and polymerization reactions in an acidic environment, gradually forming biochar with aromatic ring structures. As the reaction continues, these aromatic ring structures accumulate and carbonize, eventually yielding biochar with a certain porosity and stability.

[0033] By utilizing an alkaline environment in the early stages of hydrothermal carbonization to promote the hydrolysis of cellulose and hemicellulose and the initial alkaline hydrolysis of lignin, and by utilizing an acidic environment in the later stages of the reaction to catalyze the breaking of β-O-4 ether bonds in lignin, the alkaline-acid synergistic catalytic system can effectively promote the conversion of biomass solid waste into biochar, thereby improving the yield and quality of biochar.

[0034] Optionally, in step 102, after mixing the carbon-rich absorbent liquid with the crushed biomass solid waste and placing it in a high-pressure reactor containing an inert atmosphere, the method further includes: Step 106: Heat the high-pressure reactor to a preset temperature range, wherein the preset temperature range includes 240°C to 280°C; Accordingly, in step 102, the carbon-rich absorbent and the crushed biomass solid waste undergo a hydrothermal carbonization reaction under an inert atmosphere, including: Step 1021: The carbon-rich absorbent liquid and the crushed biomass solid waste are placed within a preset temperature range and subjected to a hydrothermal carbonization reaction under an inert atmosphere for a preset reaction time, wherein the preset reaction time is within a preset reaction time range, which includes 20 min to 40 min.

[0035] In the above embodiments of this application, the high-pressure reactor is heated to a preset temperature range of 240℃-280℃, and the carbon-rich absorbent liquid and crushed biomass solid waste are reacted at this temperature and under an inert atmosphere for 20-40 minutes. The temperature range of 240℃-280℃ provides sufficient energy to accelerate the hydrolysis of cellulose and hemicellulose and the decomposition of lignin in the biomass, promote the function of the alkali-acid synergistic catalytic system, and improve the biochar yield. At the same time, a suitable combination of temperature and time can optimize the biochar structure, giving it richer pores and a larger specific surface area, thus enhancing its adsorption performance. Moreover, precise control of temperature and time can avoid over-reaction or under-reaction, improve reaction efficiency, reduce energy consumption, and provide high-quality raw materials for subsequent applications of biochar in power plant auxiliary power generation, thus contributing to carbon emission reduction.

[0036] Optionally, the obtained biochar has a high heating value of not less than 17 MJ / kg and an ignition temperature of not less than 390℃.

[0037] In the embodiments described above, the biochar has a high calorific value of not less than 17 MJ / kg, which provides sufficient energy for co-firing in power plants, improves energy utilization efficiency, and reduces coal consumption. Its ignition temperature is not less than 390℃, making it safer and more stable during storage and transportation, and reducing the risk of spontaneous combustion. The combination of these two factors ensures both the efficient utilization of biochar as an energy source and enhances its safety, helping power plants achieve low-carbon and safe operation.

[0038] Optionally, the solid-liquid mass ratio of biomass solid waste to carbon-rich absorbent liquid is between 1:6 and 1:10.

[0039] In the above embodiments of this application, the solid-liquid mass ratio of biomass solid waste to carbon-rich absorbent is controlled between 1:6 and 1:10. This ensures that the carbon-rich absorbent fully wets the biomass solid waste, promotes the uniformity of the alkali-acid synergistic catalytic reaction, and improves the yield and quality of biochar. Simultaneously, it avoids waste due to excessive absorbent or incomplete reaction due to insufficient absorbent. While ensuring good carbon emission reduction and resource utilization efficiency, it also reduces treatment costs, achieving a win-win situation for both economic and environmental benefits.

[0040] By applying the technical solution of this embodiment, the following beneficial effects are achieved: 1. Waste treatment with waste, significantly reducing costs: Using alkaline wastewater such as black liquor from papermaking as a CO2 absorbent replaces expensive traditional absorbents, realizing the resource utilization of wastewater and significantly reducing the raw material cost of carbon capture.

[0041] 2. Synergistic effect and high product value: By co-hydrothermally carbonizing carbon-rich black liquor with biomass solid waste, a unique "alkali-acid" synergistic catalytic system is constructed. The initial alkaline environment promotes biomass hydrolysis, while the subsequent acidic environment formed by CO2 specifically catalyzes the depolymerization of lignin to generate high-value-added phenolic compounds, while simultaneously obtaining high-calorific-value (up to 18 MJ / kg) biochar, realizing the targeted conversion of CO2 and biomass solid waste into high-value products.

[0042] 3. System Integration for a Win-Win Environmental and Economic Benefit: Integrating carbon capture, wastewater treatment, and solid waste resource utilization into a complete technology chain. This not only effectively reduces CO2 emissions but also solves the pollution problem of industrial and agricultural waste, and produces energy products (biochar) and chemical raw materials (bio-oil) with market potential, achieving significant environmental and economic benefits.

[0043] 4. Providing a new path for the low-carbon transformation of the thermal power industry: The produced biochar has the combustion characteristics of lignite and can be directly used for co-firing in power plants, partially replacing fossil fuels and forming a small cycle of "capture-conversion-reuse" within the plant, providing a feasible carbon recycling solution for the power industry.

[0044] In one specific embodiment, carbon dioxide emission reduction in power plants can be achieved, for example, through the following steps: 1. Raw material input: Coal-fired flue gas, alkaline papermaking black liquor, and corn stalks are three types of waste materials to be treated, which are suitable for carbon dioxide emission reduction systems in power plants. 2. CO2 capture steps: Using alkaline papermaking black liquor as an absorbent, carbon dioxide in coal-fired flue gas is captured in a bubbling absorption device to obtain carbon-rich absorbent. 3. Hydrothermal carbonization step: The carbon-rich absorbent solution is mixed with corn stalks and subjected to hydrothermal carbonization in a high-pressure reactor. During this process, the alkaline substances in the absorbent and the captured CO2 together construct an "alkali-acid" synergistic catalytic system, which directionally promotes the conversion of biomass into high-value products (biochar and bio-oil). 4. Product separation step: The mixture formed after the hydrothermal carbonization reaction is subjected to solid-liquid separation; 5. Product output: The final co-production yields high-performance biochar (solid product) and bio-oil rich in phenolic compounds (liquid product).

[0045] Therefore, through the above steps, it is possible to achieve carbon dioxide emission reduction, resource utilization of papermaking black liquor, and high-value utilization of agricultural straw.

[0046] In another, more specific embodiment, simulated coal-fired flue gas (CO2 volume fraction 16%, N2 equilibrium) can be prepared. Black liquor from corn stalk pulping (pH≈12) is used as the base absorbent, with NaOH added at mass concentrations of 1%, 2%, and 4% respectively as enhancing agents. The absorbent volume is 200 mL. Absorption experiments are conducted in a bubbling reactor at room temperature, with the flue gas flow rate controlled at 0.5 L / min. The results are as follows... Figure 3 As shown, when the NaOH concentration is 2%, the CO2 capture efficiency can be stably reached above 90%, realizing low-cost and high-efficiency carbon capture based on waste liquid.

[0047] Next, the carbon-rich absorbent obtained from the black liquor enhanced with 2% NaOH for capturing simulated flue gas was mixed with crushed corn stalks at a solid-liquid ratio of 1:8 and placed in a high-pressure reactor. After purging the air by introducing N2, the mixture was reacted at 260°C for 30 minutes. After the reaction was completed, the mixture was cooled, depressurized, and filtered to separate the solid and liquid.

[0048] The resulting solid, after drying, becomes biochar with a yield of 60.80% and a higher calorific value of 17.57 MJ / kg (approximately 4190 kcal / kg). Thermogravimetric analysis shows that its ignition temperature is 395℃ and its burnout temperature is 628℃. Its comprehensive combustion characteristics are comparable to those of lignite, indicating its potential for direct co-firing with coal.

[0049] The resulting liquid is bio-oil. GC-MS analysis showed that the relative content of phenolic compounds (such as phenol, cresol, and guaiacol) was significantly higher than that of traditional hydrothermal carbonization processes, confirming the significant promoting effect of the "alkali-acid" synergistic catalytic environment formed by CO2 introduction on the formation of phenolic products. Extraction and separation of this bio-oil can enrich high-value-added phenolic chemicals.

[0050] In addition, a pilot-scale device (suitable for carbon dioxide emission reduction systems in power plants) can be constructed, in which flue gas from the power plant is introduced into a carbon dioxide capture unit (reactor) and contacted with alkaline black liquor from a paper mill (pre-added with 2% NaOH) to capture CO2. The carbon-rich absorbent is mixed with crushed corn stalks and then pumped into a hydrothermal carbonization unit for reaction. After separation, the solid product is processed into biochar, while the liquid product is sent to a refining unit to extract phenolic chemicals. Pilot-scale operation results show that this technical route is continuous, stable, and feasible, and all technical indicators are consistent with laboratory results, verifying its feasibility for engineering scale-up.

[0051] Furthermore, as Figure 1 In terms of specific implementation, this application provides a carbon dioxide emission reduction system suitable for power plants, such as... Figure 4 As shown, the system includes: Black liquor storage tank 201 is used to store alkaline industrial waste liquor and add NaOH fortifying agent, wherein the alkaline industrial waste liquor includes alkaline papermaking black liquor, which is obtained from a paper mill; Straw crusher 202 is used to crush collected crop straw to obtain biomass solid waste, including corn; Reactor 203 is used to react with flue gas containing carbon dioxide using alkaline industrial waste liquid as an adsorbent, thereby capturing carbon dioxide in the flue gas and obtaining carbon-rich absorbent liquid. High-pressure reactor 204 is used to carry out hydrothermal carbonization reaction of carbon-rich absorbent liquid and crushed biomass solid waste under an inert atmosphere. Solid-liquid separator 205 is used to separate the solid and liquid components of the mixture formed after hydrothermal carbonization reaction to obtain biochar as a solid product and bio-oil as a liquid product, wherein the bio-oil is enriched with phenolic compounds. The biochar drying and pulverizing system 206 is used to dry and pulverize biochar so that the power plant can generate electricity by co-firing the dried and pulverized biochar. In this process, crops absorb carbon dioxide through photosynthesis. When the power plant uses biochar made from crop straw for combustion, the carbon dioxide produced by the combustion of biochar is offset by the carbon dioxide absorbed by the crops through photosynthesis, so that when calculating carbon dioxide emissions, the carbon dioxide emissions produced by the combustion of biochar are lower than the carbon dioxide emissions produced by the combustion of coal. Bio-oil refining and purification system 207 is used for refining and purifying bio-oil.

[0052] It should be noted that other corresponding descriptions of the functional units involved in the carbon dioxide emission reduction system applicable to power plants provided in this application embodiment can be found in the following references. Figure 1 The corresponding descriptions in the method will not be repeated here.

[0053] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application. Those skilled in the art will understand that the modules in the system of the embodiment scenario can be distributed throughout the system of the embodiment scenario as described, or they can be modified to reside in one or more systems different from this embodiment scenario. The modules of the above-described embodiment scenario can be combined into one module, or further divided into multiple sub-modules.

[0054] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any modifications that can be made by those skilled in the art should fall within the protection scope of this application.

Claims

1. A method for reducing carbon dioxide emission suitable for use in a power plant, characterized by, The method comprises: When the power plant burns coal to produce flue gas containing carbon dioxide, the carbon dioxide in the flue gas is captured by contacting the flue gas containing carbon dioxide with an absorbent, and a carbon-rich absorbent is obtained, wherein the absorbent is an alkaline industrial waste liquid, and the alkaline industrial waste liquid comprises an alkaline papermaking black liquor obtained from a paper mill; Biomass solid waste is obtained and crushed, and the carbon-rich absorbent is mixed with the crushed biomass solid waste and placed in a high-pressure reactor containing an inert atmosphere, so that the carbon-rich absorbent and the crushed biomass solid waste undergo a hydrothermal carbonization reaction under the inert atmosphere, wherein the raw material of the biomass solid waste comprises crop straw, and the crops include corn; The mixture formed after the hydrothermal carbonization reaction is subjected to solid-liquid separation to obtain biochar as a solid product and bio-oil as a liquid product, wherein the bio-oil is rich in phenolic compounds; The biochar is dried and crushed, and the power plant burns the dried and crushed biochar for power generation, wherein the crops absorb carbon dioxide through photosynthesis, and when the power plant burns the biochar made of crop straw, the carbon dioxide produced by the burning of the biochar offsets the carbon dioxide absorbed by the crops through photosynthesis, so that the carbon dioxide emission amount of the biochar burning is lower than that of the coal burning when calculating the carbon dioxide emission amount.

2. The method of claim 1, wherein, The pH value of the alkaline industrial waste liquid is not less than 11, and sodium hydroxide is added to the alkaline industrial waste liquid as a reinforcing agent, and the mass concentration of sodium hydroxide in the absorbent is between 1% and 4%, and the liquid-gas ratio of the absorbent to the flue gas is between 0.2 and 0.4 L / m³.

3. The method of claim 1, wherein, When the alkaline industrial waste liquid is used as an absorbent to contact with the flue gas containing carbon dioxide, the alkaline substances in the absorbent and the captured carbon dioxide form an alkali-acid synergistic catalysis system, and during the hydrothermal carbonization reaction of the carbon-rich absorbent and the crushed biomass solid waste under the inert atmosphere, the method further comprises: The alkali-acid synergistic catalysis system promotes the conversion of biomass in the biomass solid waste into biochar.

4. The method of claim 3, wherein, The method of promoting the conversion of biomass in the biomass solid waste into biochar by the alkali-acid synergistic catalysis system comprises: In the early stage of the hydrothermal carbonization reaction, the alkaline environment of the carbon-rich absorbent promotes the initial alkaline hydrolysis of cellulose and hemicellulose in the biomass solid waste and lignin; In the later stage of the hydrothermal carbonization reaction, the carbonic acid formed by dissolving carbon dioxide in water and the organic acid generated by the hydrothermal carbonization reaction cause the pH value of the alkali-acid synergistic catalysis system to decrease to form an acidic environment, which catalyzes the breakage of the β-O-4 ether bond in lignin to obtain biochar.

5. The method of claim 1, wherein, After the carbon-rich absorbent and the crushed biomass solid waste are mixed and placed in a high-pressure reactor containing an inert atmosphere, the method further comprises: The high-pressure reactor is heated to a preset temperature range, wherein the preset temperature range includes 240°C to 280°C; Correspondingly, the hydrothermal carbonization reaction of the carbon-rich absorbent and the crushed biomass solid waste under the inert atmosphere comprises: The carbon-rich absorption liquid and the broken biomass solid waste are in a preset temperature range and are subjected to a hydrothermal carbonization reaction under an inert atmosphere for a preset reaction time, wherein the preset reaction time is in a preset reaction time range, and the preset reaction time range includes 20 min to 40 min.

6. The method according to any one of claims 1 to 5, characterized in that, The obtained biochar has a high calorific value of not less than 17 MJ / kg and an ignition temperature of not less than 390 ℃.

7. The method of claim 6, wherein, The solid-liquid mass ratio of the biomass solid waste to the carbon-rich absorption liquid is between 1:6 and 1:

10.

8. A carbon dioxide abatement system suitable for use in a power plant, characterized in that, The system comprises: a black liquor tank for storing an alkaline industrial waste liquid and adding a NaOH intensifier, wherein the alkaline industrial waste liquid comprises alkaline papermaking black liquor obtained by a paper mill; a straw crusher for crushing the collected crop straw to obtain biomass solid waste, wherein the crop comprises corn; a reactor for capturing carbon dioxide in flue gas by contacting the flue gas containing carbon dioxide with the alkaline industrial waste liquid as an adsorbent to obtain a carbon-rich absorption liquid; a high-pressure reaction kettle for allowing the carbon-rich absorption liquid and the broken biomass solid waste to be subjected to a hydrothermal carbonization reaction under an inert atmosphere; a solid-liquid separator for performing solid-liquid separation on a mixture formed after the hydrothermal carbonization reaction to obtain biochar as a solid product and bio-oil as a liquid product, wherein the bio-oil is rich in phenolic compounds; a biochar drying and crushing system for drying and crushing the biochar to enable a power plant to generate power by blending and burning the dried and crushed biochar, wherein the crop absorbs carbon dioxide through photosynthesis, and when the power plant burns the biochar made of crop straw, the carbon dioxide generated by the burning of the biochar offsets the carbon dioxide absorbed by the crop through photosynthesis, so that the carbon dioxide emission amount generated by the burning of the biochar is lower than the carbon dioxide emission amount generated by the burning of coal when calculating the carbon dioxide emission amount. a bio-oil refining and purification system for refining and purifying the bio-oil.

9. The system of claim 8, wherein, The system further comprises: the reactor is further used for forming an alkali-acid synergistic catalysis system based on the alkaline substance in the adsorbent and the captured carbon dioxide.

10. The system of claim 8, wherein The system further comprises: the high-pressure reaction kettle is further used for promoting the initial alkaline hydrolysis of cellulose and hemicellulose and lignin in the biomass solid waste through the alkaline environment of the carbon-rich absorption liquid in the early stage of the hydrothermal carbonization reaction, and promoting the catalysis of the rupture of β-O-4 ether bonds in the lignin through the acidic environment formed by the decrease in the pH value of the alkali-acid synergistic catalysis system in the middle and late stages of the hydrothermal carbonization reaction to obtain biochar.

Images