Method for post-treatment of combustible solid waste and co-production of calcium-based absorbent, calcium-based absorbent and application of calcium-based absorbent

Abstract

The invention relates to a method for post-treatment of combustible solid waste and co-production of a calcium-based absorbent, the calcium-based absorbent and application of the calcium-based absorbent. The method for post-treatment of the combustible solid waste and co-production of the calcium-based absorbent comprises the following steps: step 1) carrying out hydro-thermal treatment on the combustible solid waste to obtain a solid treatment substance and a liquid-phase by-product at the same time; 2) mixing a calcium-based precursor with the liquid-phase by-product to obtain a mixture; 3) performing primary heat treatment on the mixture to obtain slurry; and 4) carrying out secondary heat treatment on the slurry to obtain the calcium-based absorbent. According to the method disclosed by the invention, the calcium-based absorbent with a porous structure and a high specific surface area is prepared by modifying the calcium-based absorbent with the hydrothermal conversion liquid-phase byproduct of the combustible solid waste, and the calcium-based absorbent can be applied to the process of capturing CO2 and SO2 in a power plant or a steel mill and the like, and has the advantages of low cost, good effect, good industrial implementation and the like.

Description

Technical Field

[0001] The invention relates to a method for post-processing combustible solid waste and co-producing a calcium-based absorbent, the calcium-based absorbent and use thereof, and belongs to the technical field of environmental pollution prevention and control and clean combustion. Background Art

[0002] Carbon dioxide (CO2) is one of the main components of greenhouse gases that cause global warming, and its contribution to the greenhouse effect is as high as 55%. Climate change caused by emissions such as CO2 has become a focus of worldwide attention. Carbon capture and storage technology (CCS technology) refers to a technology that captures and separates carbon dioxide from related concentrated emission combustion sources and stores it in various ways to avoid its emission into the atmosphere. It is one of the most effective technical paths to address climate change. Among them, compared with the compression, transportation and storage of CO2, the cost of capturing CO2 from flue gas from coal-fired power plants is the highest, accounting for more than 75% of the CCS cost. Therefore, how to capture CO2 on a large scale economically and effectively has become the focus and hot spot of research in scientific research institutions and enterprises today.

[0003] At the same time, coal-fired and biomass-fired boilers also produce a large amount of SO2 and other pollutants in the process of generating electricity. Among them, biomass-fired boilers generate electricity or produce steam, which has the advantages of being cleaner and more sustainable than coal-fired boilers. However, with the continuous increase in current environmental pressures, although the sulfur and ash content of biomass itself is low (compared to coal), considering the lower calorific value of biomass fuel, the converted sulfur and nitrogen emissions per unit calorific value do not have an advantage. Especially with the introduction of the concept of ultra-low emissions in China, sulfur and nitrogen emissions during the combustion of biomass fuels cannot be ignored.

[0004] The calcium cycle-based CO2 capture technology is considered to be one of the most promising post-combustion CO2 capture technologies, and it can be directly applied to conventional coal-fired power plants, cement plants, and steel plants. Based on the calcium cycle CO2 capture technology, the reaction formula is: in the carbonation reactor, CaO+CO2→CaCO3; in the calcination reactor, CaCO3→CaO+CO2. This technology has many advantages: 1. The absorbent precursor is abundant in nature and inexpensive; 2. It theoretically has superior chemical reaction kinetics; 3. It theoretically has a relatively high CO2 absorption capacity and can be recycled; 4. There is no need to reorganize the existing boiler unit; 5. The technology is low in cost and has good commercial application prospects; 6. This method is environmentally friendly and will not produce any secondary pollution.

[0005] In addition, calcium-based adsorbents (such as limestone) are also the most important desulfurizers, and their sulfation reaction characteristics have an important influence on fluidized bed combustion desulfurization. The calcium-based adsorbent reacts with SO2 in the boiler in the following direct sulfation reaction and indirect sulfation reaction.

[0006] CaCO3+SO2→CaSO3+CO2(1)

[0007] CaO+SO2→CaSO3(2)

[0008] In the prior art, although the calcium-based adsorbents mainly based on limestone have large reserves in nature and are pollution-free, the low sulfation conversion rate of natural calcium-based adsorbents leads to an increase in solid waste content in practical applications. Therefore, there is an urgent need to develop highly active calcium-based adsorbent materials for desulfurization during combustion. The reactivity of natural calcium-based absorbents in the process of capturing carbon dioxide and sulfur dioxide is poor, and the conversion rate is low in actual use, which also causes a large energy consumption in the production process. In order to improve the reactivity of calcium-based absorbents, scholars have made a series of explorations, but materials with good performance often have high preparation costs, and simple modification treatments make it difficult to achieve high-efficiency capture of pollutants such as carbon dioxide / sulfur dioxide by materials.

[0009] Various modification methods in existing studies have different effects on improving the reaction activity and cyclic stability of calcium-based absorbents, but they all have certain problems and defects. For example, the cost of the absorbent has not been significantly reduced, or the preparation cycle of the absorbent is long, the process is complicated, and some even produce secondary pollution. Studies have pointed out that CaO prepared by advanced preparation methods such as sol-gel method and molecular self-assembly has better CO2 and SO2 capture conversion rate and reaction kinetics than CaO absorbents prepared from natural materials such as limestone. However, the CaO prepared by these advanced preparation methods is expensive and difficult to meet the actual needs of industry. Therefore, the development of high-performance, low-cost calcium-based adsorbent materials is of great significance for the capture of CO2 and SO2 in combustion flue gas.

[0010] With the acceleration of urbanization and the improvement of people's living standards, the output of solid waste has shown a continuous growth trend. Statistics show that more than 4 billion tons of solid waste are generated worldwide each year. Many of these solid wastes are rich in organic matter. This part of solid waste is called combustible solid waste, which is an important renewable energy source and its proportion in solid waste is increasing year by year. Urban domestic waste is an important source of combustible solid waste. According to the statistical data of the China Statistical Yearbook from 2014 to 2021, the amount of urban domestic waste collected and transported has generally shown an upward trend, reaching 235 million tons in 2020, and the disposal of waste is facing tremendous pressure. The existing harmless treatment methods are mainly landfill and incineration.

[0011] Landfill is the earliest method of solid waste treatment. The main advantages of this method are that the treatment process is convenient and has a wide range of applications. The landfill method also has great disadvantages. It will waste a lot of land resources. Since the land cost around central cities is very high, many landfills are difficult to accommodate the large amount of waste generated. In addition, the landfill treatment of organic matter such as sludge and kitchen waste will produce toxic leachate, which will pollute the soil and groundwater. Incineration is the traditional and most important thermochemical conversion technology. Compared with landfill treatment, this method has the most significant reduction effect and a higher degree of harmlessness. However, before incineration, a lot of energy is required to pre-dry the raw materials in order to achieve better treatment effects, which to a certain extent limits the energy efficiency of the entire process. In addition, solid waste will produce dioxins, polycyclic aromatic hydrocarbons, heavy metals and NO during the incineration process. x , SO2 and other pollutants, which are either emitted with flue gas or adsorbed in fly ash or bottom slag, causing secondary pollution to the environment. This is a controversial issue in the promotion of this technology.

[0012] Therefore, it is urgent to find a cleaner and more efficient method for treating combustible solid waste. In recent years, hydrothermal treatment of combustible solid waste has attracted much attention and is considered to be one of the most promising technologies for treating combustible solid waste. This technology uses sub-supercritical water as a reaction medium in a closed space to achieve efficient degradation of organic matter. Compared with traditional thermochemical technology, hydrothermal treatment has the characteristics of fast reaction speed, short processing time, and milder reaction conditions. This technology can achieve efficient utilization of organic matter and produce value-added products such as fuels or chemicals. The reaction is carried out in a compact and completely closed system, and toxic and harmful products are captured in the liquid and solid phases to avoid entering the external environment and causing pollution.

[0013] The solid phase product of hydrothermal treatment of combustible solid waste is mainly biochar, which can be used for soil remediation and improve soil quality by retaining soil moisture and nutrients. Due to the large surface area of ​​biochar, organic pollutants and heavy metals can be fixed by biochar adsorption. However, the liquid phase byproducts of hydrothermal treatment of combustible solid waste have not yet been utilized as resources. Experiments have shown that the composition of liquid phase byproducts changes with the raw materials and reaction conditions, and usually contains acetic acid, formic acid, formaldehyde, phenol, ethanol, methanol and ethylene glycol. The subsequent utilization of liquid phase products has become the main consideration in the design of hydrothermal processes.

[0014] In recent years, some scholars have pointed out that acetic acid modification can improve the cyclic CO2 capture capacity of calcium-based absorbents, but its SO2 capture characteristics are still unclear. In addition, the high preparation cost of acetic acid modification restricts the large-scale operation of this technology. Therefore, further research and improvement are urgently needed in this field to better play the advantages of solid adsorbent cyclic CO2 capture technology. Summary of the invention

[0015] Problem that the invention aims to solve

[0016] Therefore, based on the above industrial background, in order to solve the technical problems existing in the prior art, the present invention proposes a method for post-treatment of combustible solid waste and co-production of calcium-based absorbent, a calcium-based absorbent and its use, which not only makes resource utilization of the liquid by-products produced after hydrothermal treatment of combustible solid waste, but also can significantly modify the calcium-based precursor to obtain an economical and efficient calcium-based adsorbent, and use it for the capture and multiple-cycle absorption of flue gas CO2 and SO2.

[0017] Solutions for solving problems

[0018] [1] A method for post-processing combustible solid waste and co-producing calcium-based absorbent, characterized in that it comprises the following steps:

[0019] Step 1) The combustible solid waste is subjected to hydrothermal treatment to obtain a solid treated product and a liquid by-product;

[0020] Step 2) mixing a calcium-based precursor with the liquid by-product to obtain a mixture;

[0021] Step 3) subjecting the mixture to a heat treatment to obtain a slurry;

[0022] Step 4) subjecting the slurry to secondary heat treatment to obtain a calcium-based absorbent.

[0023] [2] The method according to [1], wherein in step 1), the combustible solid waste includes one or more of biomass raw materials, waste plastics, rubber, tires, leather, sponges, cloth, construction waste, feces or urban sludge.

[0024] [3] The method according to [1] or [2], wherein in step 1), the hydrothermal treatment is performed at a temperature of 250-500°C and for a time of 10-30 minutes.

[0025] [4] The method according to any one of [1] to [3], wherein in step 1), the pressure of the hydrothermal treatment is 5-35 MPa.

[0026] [5] The method according to any one of [1] to [4], wherein in step 1), the water-to-solid mass ratio of the hydrothermal treatment is 5-20.

[0027] [6] The method according to any one of [1] to [5], wherein in step 2), the calcium-based precursor is one or more of snow clam shell, limestone, quicklime, dolomite, eggshell, shell, marble, steel slag or carbide slag.

[0028] [7] The method according to any one of [1] to [6], wherein in step 3), the temperature of the primary heat treatment is 85-90°C, and the water-to-solid mass ratio of the primary heat treatment is 5-20.

[0029] [8] The method according to any one of [1] to [7], wherein in step 4), the temperature of the secondary heat treatment is 800-900°C.

[0030] [9] A calcium-based absorbent obtained by the method according to any one of [1] to [8].

[0031]

[10] Use of the calcium-based absorbent described in [9] for absorbing carbon dioxide or sulfur dioxide.

[0032] Effects of the Invention

[0033] The method for post-treatment of combustible solid waste and co-production of calcium-based absorbent of the present invention modifies the calcium-based absorbent with the liquid phase byproduct of hydrothermal conversion of combustible solid waste to prepare a calcium-based absorbent with a porous structure and a high specific surface area, which can be applied to the capture process of CO2 and SO2 in power plants or steel plants. The calcium-based absorbent of the present invention has a high circulation conversion rate and a stable pore structure, which is conducive to the adsorption of CO2 and SO2 and can promote the diffusion of reactants and products, and has the advantages of low cost, good effect, good industrial feasibility, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the process of using calcium-based absorbents to capture carbon dioxide.

[0035] Figure 2 Performance test result diagram of calcium-based absorbent-1, calcium-based absorbent-2, calcium-based absorbent-3, calcium-based absorbent-4 and calcium-based absorbent-pair 1 obtained in Examples 1-4 and Comparative Example 1. DETAILED DESCRIPTION

[0036] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0037] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0038] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0039] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0040] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0041] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0042] The present invention provides a method for post-processing combustible solid waste and co-producing a calcium-based absorbent, which is characterized by comprising the following steps:

[0043] Step 1) The combustible solid waste is subjected to hydrothermal treatment to obtain a solid treated product and a liquid by-product;

[0044] Step 2) mixing a calcium-based precursor with the liquid by-product to obtain a mixture;

[0045] Step 3) subjecting the mixture to a heat treatment to obtain a slurry;

[0046] Step 4) subjecting the slurry to secondary heat treatment to obtain a calcium-based absorbent.

[0047] Combustible solid waste can be hydrothermally treated to obtain solid treated products, such as high-quality biomass activated carbon, and liquid by-products, which usually contain acetic acid, formic acid, glycolic acid, phenol, ethanol, methanol and ethylene glycol.

[0048] After the calcium-based precursor is mixed with the liquid by-product, the calcium-based precursor and the liquid by-product not only undergo an acid-base reaction but also a hydration reaction. The resulting calcium-based adsorbent will have a looser and more porous structure, better cyclic CO2 capture capability, and better SO2 adsorption activity.

[0049] According to the method of the present invention, in the step 1), the combustible solid waste includes one or more of biomass raw materials, waste plastics, rubber, tires, leather, sponges, cloth, construction waste materials, feces or urban sludge.

[0050] According to the method of the present invention, wherein, in the step 1), the temperature of the hydrothermal treatment is 250-500° C. and the time is 10-30 minutes.

[0051] The temperature of the hydrothermal treatment is preferably 250-500°C. The temperature of the hydrothermal treatment within the above range can, on the one hand, provide the activation energy required for the reaction, and on the other hand, the change in temperature directly affects the physical properties of the liquid by-products, thereby determining the effect of the hydrothermal treatment. Generally speaking, an increase in temperature leads to an increase in the amount of activated macromolecules and internal energy, which will accelerate the depolymerization of the raw materials, and the decomposition of the raw materials will be more thorough; however, if the temperature is too high, the solid coke yield of some combustible solid waste will decrease with the increase in temperature. Therefore, the temperature of the hydrothermal treatment is preferably 250-500°C.

[0052] The time of the hydrothermal treatment is preferably 10-30 minutes, more preferably 20-25 minutes. The reaction time will affect the effect of the hydrothermal treatment. For example, in a sub-supercritical water medium, the secondary and tertiary reactions of the product are always occurring, and these reactions will convert the intermediate with a higher molecular weight into a liquid and gas product with a smaller molecular weight, or cause polymerization to form a solid residue. Once the conversion of the raw material reaches the saturation point, the reaction time is further extended, and the possibility of an inflection point in the mass distribution of solid, liquid and gas phase products becomes greater. Therefore, the time of the hydrothermal treatment is preferably 10-30 minutes.

[0053] According to the method of the present invention, in the step 1), the pressure of the hydrothermal treatment is 5-35 MPa.

[0054] By maintaining the pressure of the hydrothermal treatment above the critical pressure of the medium, the rate of hydrolysis and raw material dissolution can be controlled. Pressure also increases the density of the solvent, allowing the relatively high-density medium to effectively penetrate into the molecules of the combustible solid waste components, thereby enhancing the decomposition and quality improvement of the solid waste. However, once supercritical conditions are reached, the effect of pressure on the yield of liquid oil or gas is small or negligible, so the pressure of the hydrothermal treatment is preferably 5-35MPa.

[0055] According to the method of the present invention, in the step 1), the water-to-solid mass ratio of the hydrothermal treatment is 5-20.

[0056] The water in the hydrothermal system is not only a solvent as a reaction medium, but also acts as a hydrogen donor and nucleophilic agent, directly participates in the reaction, and attacks the polymer main chain. Due to the role of water in the depolymerization reaction, the lower amount of water leads to a decrease in the solubility of small molecule products or intermediates in water, inhibits the formation of oil phase products, and also slows down the rate of depolymerization of solid phase raw materials; and the increase in the amount of water is beneficial to improving the conversion rate of raw materials and the yield of crude oil. However, if the amount of water is too much (the material concentration is too low), the volumetric efficiency and productivity of the reaction will be seriously affected, requiring more energy, and causing an increase in downstream wastewater treatment costs, thereby reducing the economy of the reaction process. Therefore, in the step 1), the water-to-solid mass ratio of the hydrothermal treatment is preferably 5-20. At this water-to-solid mass ratio, it can be expected to achieve the best yield of hydrothermal activated carbon, and the carboxylic acid in the liquid phase product also has a good effect of modified calcium-based adsorbent.

[0057] According to the method of the present invention, in the step 2), the calcium-based precursor is one or more of snow clam shell, limestone, quicklime, dolomite, eggshell, shell, marble, steel slag or carbide slag.

[0058] Preferably, the calcium-based precursor is subjected to calcination to obtain a raw material containing calcium oxide, and the raw material containing calcium oxide is used as the calcium-based precursor.

[0059] According to the method of the present invention, in the step 3), the temperature of the primary heat treatment is preferably 85-90°C, and the water-to-solid mass ratio of the primary heat treatment is 5-20. At this temperature, the reaction of the calcium-based precursor with the organic acid in the liquid by-product can be better accelerated, and at this temperature, the oil phase components in some liquid by-products can be dissolved and fully reacted with the calcium-based precursor. In addition, this temperature range can also ensure the reaction time of the calcium-based precursor with the liquid by-product, thereby preparing a calcium-based adsorbent with uniform structure.

[0060] Since both acid-base reactions and hydration reactions are violent exothermic reactions, if the content of liquid by-products is too little, it may cause overburning of calcium oxide, and the content of organic acids contained in the liquid by-products is not enough to successfully modify all the calcium-based adsorbents, thereby affecting the activity of the calcium-based absorbent; if the content of liquid by-products is too much, the drying cycle is long, which is not conducive to industrial production.

[0061] Preferably, the time for one heat treatment is 3-5 hours, more preferably 4 hours.

[0062] According to the method of the present invention, in the step 3), the temperature of the secondary heat treatment is 800-900° C. Too low a temperature of the secondary heat treatment often leads to incomplete decomposition of the intermediate after the liquid by-product modification, or the decomposition rate is too slow, resulting in a long production cycle; while too high a temperature of the secondary heat treatment will cause the material to sinter, thereby affecting the CO2 capture capacity of the calcium-based absorbent.

[0063] Preferably, the secondary heat treatment time is 1-3 hours, more preferably 2 hours.

[0064] The method according to the present invention further comprises the following steps:

[0065] Step 5) granulating the calcium-based absorbent into powder to obtain calcium-based absorbent particles.

[0066] The present invention also provides a calcium-based absorbent, which is the calcium-based absorbent obtained by the method according to the present invention.

[0067] The present invention also provides a use of the calcium-based absorbent according to the present invention for absorbing carbon dioxide or sulfur dioxide.

[0068] For example, Figure 1 As shown, flue gas containing 15-40% CO2 concentration can be introduced into the carbonation reactor, and the above-mentioned calcium-based absorbent absorbs CO2 at 650°C, and then the CO2-free flue gas is directly discharged into the atmosphere, and the generated carbonation product is transported to the regeneration reactor through the return device 1, and calcined at 900°C to release carbon dioxide, so that the calcium-based absorbent is regenerated and a high concentration of CO2 is obtained at the same time. The high concentration of CO2 can be used in chemical industry or compressed, transported, and sealed; and the regenerated calcium-based absorbent is transported back to the carbonation reactor through the return device 2 to capture the flue gas CO2.

[0069] Example

[0070] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0071] Example 1

[0072] The cellulose is hydrothermally treated in a hydrothermal treatment kettle to obtain a solid treated material 1 and a liquid by-product 1; the snow clam shell is mixed with the liquid by-product 1 to obtain a mixture 1; the mixture 1 is subjected to a primary heat treatment to obtain a slurry; the slurry is subjected to a secondary heat treatment to obtain a calcium-based absorbent-1.

[0073] The temperature, water-to-solid ratio, time and pressure of the hydrothermal treatment are shown in Table 1, and the temperature and time of the primary heat treatment and the secondary heat treatment are shown in Table 2.

[0074] Example 2

[0075] The same method as in Example 1 was adopted, only the specific conditions of the hydrothermal treatment were changed, to obtain a liquid by-product 2 and a calcium-based absorbent-2.

[0076] The specific conditions of the temperature, water-to-solid ratio, time and pressure of the hydrothermal treatment are shown in Table 1, and the temperature and time of the primary heat treatment and the secondary heat treatment are shown in Table 2.

[0077] Example 3

[0078] The same method as in Example 1 was adopted, only the specific conditions of the hydrothermal treatment were changed, to obtain a liquid by-product 3 and prepare a calcium-based absorbent-3.

[0079] The specific conditions of the temperature, water-to-solid ratio, time and pressure of the hydrothermal treatment are shown in Table 1, and the temperature and time of the primary heat treatment and the secondary heat treatment are shown in Table 2.

[0080] Example 4

[0081] The same method as in Example 1 was adopted, only the specific conditions of the hydrothermal treatment were changed, to obtain a liquid by-product 4 and a calcium-based absorbent-4.

[0082] The specific conditions of the temperature, water-to-solid ratio, time and pressure of the hydrothermal treatment are shown in Table 1, and the temperature and time of the primary heat treatment and the secondary heat treatment are shown in Table 2.

[0083] Table 1

[0084] Example Temperature / ℃ Water-to-solid ratio (mass) Time / min Pressure / MPa 1 280 5 20 8 2 300 5 20 16 3 400 10 20 25 4 500 10 20 35

[0085] Table 2

[0086]

[0087] Comparative Example 1

[0088] The snow clam shells were mixed with water, and subjected to primary and secondary heat treatments to obtain a calcium-based absorbent-pair 1, wherein the temperature and time settings of the primary and secondary heat treatments were the same as those in Example 1.

[0089] Performance Testing

[0090] The performance of calcium-based absorbent-1, calcium-based absorbent-2, calcium-based absorbent-3, calcium-based absorbent-4 and calcium-based absorbent-pair 1 was tested. The calcium cycle adsorption process of 650℃ adsorbing carbon dioxide and 900℃ releasing carbon dioxide was used to conduct thermogravimetric test cycles for thirty cycles. The results are as follows: Figure 2 shown.

Claims

1. A method for post-processing combustible solid waste and co-producing calcium-based absorbent, characterized in that: The following steps are involved: Step 1) The combustible solid waste is subjected to hydrothermal treatment to obtain a solid treated product and a liquid by-product; Step 2) mixing a calcium-based precursor with the liquid by-product to obtain a mixture; Step 3) subjecting the mixture to a heat treatment to obtain a slurry; Step 4) subjecting the slurry to secondary heat treatment to obtain a calcium-based absorbent.

2. The method according to claim 1, wherein: In step 1), the combustible solid waste includes one or more of biomass raw materials, waste plastics, rubber, tires, leather, sponges, cloth, construction waste materials, excrement or urban sludge.

3. The method according to claim 1 or 2, wherein: In the step 1), the temperature of the hydrothermal treatment is 250-500° C. and the time is 10-30 minutes.

4. The method according to any one of claims 1 to 3, wherein: In the step 1), the pressure of the hydrothermal treatment is 5-35 MPa.

5. The method according to any one of claims 1 to 4, wherein: In the step 1), the water-to-solid mass ratio of the hydrothermal treatment is 5-20.

6. The method according to any one of claims 1 to 5, wherein: In the step 2), the calcium-based precursor is one or more of snow clam shell, limestone, quicklime, dolomite, eggshell, shell, marble, steel slag or carbide slag.

7. The method according to any one of claims 1 to 6, wherein: In the step 3), the temperature of the first heat treatment is 85-90° C., and the water-to-solid mass ratio of the first heat treatment is 5-20.

8. The method according to any one of claims 1 to 7, wherein: In the step 4), the temperature of the secondary heat treatment is 800-900°C.

9. A calcium-based absorbent obtained by the method according to any one of claims 1 to 8.

10. Use of the calcium-based absorbent according to claim 9 for absorbing carbon dioxide or sulfur dioxide.

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