A comprehensive modification method for solid fuels based on flue gas micro-nano bubbles

Abstract

This application belongs to the field of solid fuel modification, and specifically discloses a comprehensive solid fuel modification method based on flue gas micro-nano bubbles. The method is to dissolve the solid fuel to be modified in a liquid solvent to obtain a mixed slurry; then introduce the un-desulfurized flue gas into the mixed slurry in the form of micro-nano bubbles; finally, perform solid-liquid separation and drying treatment on the modified mixed slurry to obtain the modified solid fuel. By introducing the un-desulfurized flue gas into the mixed slurry in the form of micro-nano bubbles and utilizing the combined action of the sulfur-containing flue gas and micro-nano bubbles, on the one hand, it can remove the minerals in the solid fuel, effectively improve the calorific value of the solid fuel, weaken the tendency of fouling and slagging during combustion, and reduce the emission of particulate matter. On the other hand, it can achieve the improvement of the physical characteristics and chemical properties of the solid fuel, such as carbon structure, pore structure, hydrophilicity / hydrophobicity, free radicals, etc., which is beneficial to the subsequent high-value utilization of the solid fuel, thereby realizing the comprehensive modification of the solid fuel.

Description

Technical Field

[0001] This application belongs to the field of solid fuel modification, and more specifically, relates to a comprehensive solid fuel modification method based on flue gas micro-nano bubbles. Background Art

[0002] China has rich coal resources, but the reserves of high-quality coal resources are limited, and the distribution is significantly "more in the west and less in the east, poorer in the south and richer in the north". The coal reserves are mainly concentrated in Shanxi, Shaanxi, Inner Mongolia and Xinjiang, accounting for more than 70% of the national coal reserves. There are problems such as uneven production and use of coal regions and mismatches between production and use of coal properties in terms of reserves, regional distribution and differences in coal quality requirements of various coal types, which greatly limit the comprehensive utilization efficiency of China's coal resources. At the same time, other solid fuels such as biomass and solid waste also have problems with poor direct utilization effects. Therefore, modifying solid fuels is of great significance for ensuring China's energy security and green development.

[0003] After modifying solid fuels by physical, chemical or biological methods, the relevant properties of solid fuels can be effectively improved to meet specific industrial application requirements, such as enhancing combustion / gasification / liquefaction efficiency, reducing pollutant emissions, improving coal quality grades, and preparing special materials. However, the solid fuel modification methods in the prior art have relatively single functions, can only meet specific industrial needs, cannot achieve comprehensive modification and quality improvement of solid fuels, and at the same time have problems of high cost and being unfavorable for industrial applications. Summary of the Invention

[0004] In view of the deficiencies of the prior art, this application provides a comprehensive solid fuel modification method based on flue gas micro-nano bubbles, aiming to solve the problems of single function and inability to achieve comprehensive modification of existing modification methods.

[0005] According to one aspect of this application, a comprehensive solid fuel modification method based on flue gas micro-nano bubbles is provided, specifically as follows:

[0006] S1 Dissolve the solid fuel to be modified in a liquid solvent to obtain a mixed slurry;

[0007] S2 Introduce the un-desulfurized flue gas into the mixed slurry in the form of micro-nano bubbles, so that under the combined action of the multi-free radicals generated by the micro-nano bubbles and the complex flue gas components, demineralization treatment of the solid fuel is carried out and improvements in the physical and chemical properties of the solid fuel are achieved, thereby realizing comprehensive modification of the solid fuel;

[0008] S3 Perform solid-liquid separation and drying treatment on the modified mixed slurry to obtain the modified solid fuel.

[0009] Through the above technical solution conceived by the present application, compared with the prior art, since the present application introduces micro-nano bubbles into the modification of solid fuel, and cooperates with the un-desulfurized flue gas to achieve physical modification and chemical modification while performing demineralization treatment, thus realizing the comprehensive modification of solid fuel.

[0010] As a further preference, in step S1, the liquid solvent is pure water, boiler drum water, domestic water or water after advanced treatment by a desulfurized wastewater treatment system.

[0011] As a further preference, in step S1, the particle size of the solid fuel to be modified is less than 200 μm.

[0012] As a further preference, in step S1, the solid-liquid ratio of the mixed slurry is 1:20 to 1:50.

[0013] As a further preference, in step S2, the size of the micro-nano bubbles is 100 nm to 10 μm.

[0014] As a further preference, in step S2, the treatment time is 30 min to 2 h, and the treatment temperature is 20 °C to 80 °C.

[0015] As a further preference, in step S2, while introducing the flue gas, the mixed slurry is stirred, and the stirring rate is 200 r / min to 1500 r / min.

[0016] According to another aspect of the present application, there is provided a modified solid fuel prepared by the above method.

[0017] Generally speaking, compared with the prior art through the above technical solution conceived by the present application, the following technical advantages are mainly possessed:

[0018] 1. In the present application, by introducing un-desulfurized flue gas into the mixed slurry containing solid fuel in the form of micro-nano bubbles, and utilizing the combined action of sulfur-containing flue gas and micro-nano bubbles, on the one hand, minerals such as alkali metals and alkaline earth metals in the solid fuel can be removed, thereby effectively increasing the calorific value of the solid fuel, weakening the fouling and slagging tendency during the combustion process, and reducing the emission of particulate matter. On the other hand, the improvement of the physical characteristics and chemical properties of the solid fuel can be realized, such as carbon structure, pore structure, hydrophilicity / hydrophobicity, free radicals, etc., which is conducive to the subsequent high-value utilization of the solid fuel, thus realizing the comprehensive modification of the solid fuel, and having the advantages of simple operation, mild conditions, and low cost, and having a relatively broad application prospect;

[0019] 2. At the same time, in the present application, by optimizing the solid-liquid ratio and the size of the micro-nano bubbles, the content of ·OH and ·H free radicals in the aqueous solution can be increased, so as to obtain the best solid-liquid ratio under the most economical conditions. Description of the Drawings

[0020] Figure 1 is the flowchart of the comprehensive modification method for solid fuel based on flue gas micro-nano bubbles provided by the embodiments of the present application;

[0021] Figure 2 is the removal rate of minerals in the modified coal obtained in Example 1 and Comparative Examples 1-3 of the present application;

[0022] Figure 3 is the total content of acid-insoluble minerals in the modified coal obtained in Example 1 and Comparative Examples 1-3 of the present application;

[0023] Figure 4 are the microcrystalline structure parameters of the modified coal obtained in Example 1 and Comparative Examples 1-3 of the present application, where (a) is d002, (b) is La, (c) is Lc, and (d) is fa;

[0024] Figure 5 is the change in the carbon structure parameters of the modified coal obtained in Example 1 and Comparative Examples 1-3 of the present application;

[0025] Figure 6 are the S / N morphological distribution characteristics of the modified coal obtained in Example 1 and Comparative Examples 1-3 of the present application, where (a) is the morphological distribution characteristic of the S element in the modified coal, and (b) is the morphological distribution characteristic of the N element in the modified coal. Detailed implementation manners

[0026] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0027] As Figure 1 shown, according to one aspect of the present application, a comprehensive modification method for solid fuel based on flue gas micro-nano bubbles is provided, specifically as follows:

[0028] S1 Crush, grind and screen the solid fuel to be modified, and then dissolve it in a liquid solvent to obtain a mixed slurry;

[0029] S2 Introduce the un-desulfurized flue gas into the mixed slurry in the form of micro-nano bubbles, so that under the combined action of the multi-free radicals generated by the micro-nano bubbles and the complex flue gas components, demineralization treatment is carried out on the solid fuel and the physical and chemical properties of the solid fuel are improved, thereby realizing the comprehensive modification of the solid fuel. At the same time, it can also effectively reduce the contents of SO2, CO2 and NO x in the flue gas, achieving the effect of synergistic treatment of the flue gas;

[0030] S3 performs solid-liquid separation and drying treatment on the modified mixed slurry to obtain modified solid fuel, and a stream of high-temperature flue gas can be introduced for drying treatment through heat exchange, thereby further reducing production costs.

[0031] This application introduces micro-nano bubbles into the modification of solid fuel. Combined with the un-desulfurized flue gas, it can achieve physical modification and chemical modification while performing demineralization treatment, thereby realizing the comprehensive modification of solid fuel and effectively solving the problems of single function and poor effect in the existing modification methods. At the same time, this application uses the flue gas of the power plant itself to perform modification pretreatment on the solid fuel, which not only has a simple process and low cost, but also can synergistically remove SO2 in the flue gas, effectively improving the overall removal efficiency of SO2 in the flue gas, reducing the load of the desulfurization tower and the use of desulfurizer, thereby further reducing the operating cost of the power plant.

[0032] In terms of removing minerals, this application has a high demineralization efficiency, can effectively increase the calorific value of solid fuel, while reducing the tendency of fouling and slagging during combustion and reducing the emission of particulate matter. During the modification process, the generation of flue gas micro-nano bubbles can enhance the solubility of acidic gases in the flue gas in water, significantly reduce the pH of the mixed slurry, and effectively remove alkali metals and alkaline earth metals (AAEMs) existing in the form of ion-exchange state and acid-soluble state in solid fuel. At the same time, due to the existence of flue gas micro-nano bubbles, more ·OH free radicals, ·O free radicals, etc. will be generated. Compared with the ·H free radicals provided by the acid solution in acid pickling modification, these free radicals have stronger electron energy, which can break the Al—O bond or Si—O bond in the AAEMs silicate / aluminum silicate lattice structure, thereby promoting the transformation of acid-insoluble AAEMs into other forms and overall improving the removal efficiency of AAEMs. This application can also simultaneously remove some trace elements in solid fuel, reduce the enrichment of toxic elements in solid fuel, and reduce the toxicity of particulate matter. In addition, this application uses the action of flue gas acidic gases (SO2, CO2, HCl, etc.) in the form of micro-nano bubbles with water, and the formed mixed acidic solutions such as H2SO3, H2SO4, H2CO3, HCl, etc., to achieve the strengthening and efficient removal of inorganic impurities in solid fuel.

[0033] In terms of physical modification, this application can achieve the following effects:

[0034] (1) Change the carbon structure: Flue gas micro-nano bubbles will generate strongly oxidizing free radicals such as ·OH and ·O in water. These free radicals can effectively destroy the complex organic structure in solid fuel, destroy the aromatic ring structure in solid fuel, reduce the aromaticity of solid fuel, thereby improving the thermal utilization (pyrolysis, combustion, gasification, etc.) efficiency of solid fuel, and can also promote the breakage of side chains and bridge chains in solid fuel, reduce the molecular weight of solid fuel, and thus can improve the liquefaction efficiency of solid fuel.

[0035] (2) Changing pores: Due to the strong oxidizing free radicals such as ·OH and ·O, the complex organic structure in solid fuel is destroyed, the degree of aromatization and molecular weight are reduced, and the pores inside the solid fuel can be more effectively opened to form a pore-rich structure. At the same time, the specific surface area of solid fuel particles can be increased synchronously, further improving the thermal utilization efficiency of solid fuel. Meanwhile, if the solid fuel is subsequently processed into activated carbon, the large specific surface area and pore structure can effectively increase the adsorption capacity of activated carbon.

[0036] (3) Hydrophilicity and hydrophobicity: During the continuous generation of flue gas micro-nano bubbles, a large number of ·OH free radicals will be generated. During the reaction of ·OH free radicals with solid fuel, the -OH functional groups in solid fuel particles will be increased, thereby increasing the hydrophilic property of solid fuel, which helps to improve the dispersibility and stability of solid fuel in water. For the preparation of coal water slurry, the increase in hydrophilicity can reduce the aggregation between coal particles, improve the fluidity of coal water slurry, and thus improve its overall performance. At the same time, the increase in the hydrophilic property of coal will also increase the viscosity of coal, so it can become a high-viscosity coal to replace coking coal.

[0037] If it is necessary to change the hydrophilicity and hydrophobicity of coal, the flue gas micro-nano bubble generating device can be subsequently closed, and only flue gas components are continuously introduced into the water. The ·H free radicals, water molecules, etc. generated by the dissolution of gases such as O2 and SO2 in the flue gas components in water can react with the functional groups on the surface of solid fuel, thereby reducing the content of -OH functional groups and lowering the hydrophilic property of solid fuel. Some will replace the -OH functional groups to generate straight-chain or branched-chain alkyl hydrocarbons, alkyl phenols and other hydrophobic groups, and even make the solid fuel become a hydrophobic solid fuel.

[0038] In terms of chemical modification, sulfur-containing molecular structures such as thiophene / sulfone / sulfoxide and nitrogen-containing molecular structures such as pyridine / pyrrole in coal have relatively high thermal stability. Desulfurization and denitrification require relatively high temperatures. Flue gas micro-nano bubbles generate strong oxidizing free radicals such as ·OH and ·O in water, which can effectively destroy these stable sulfur- and nitrogen-containing organic molecular structures to form sulfur free radicals such as ·SH and RS· and nitrogen free radicals such as ·NH2, ·NR2, and ·NO2. The thermal stability of these free radicals is very low and they are relatively easy to remove, which can help for the high-value utilization of subsequent solid fuel.

[0039] In other aspects, the method provided in this application can be carried out under normal temperature and pressure, with simple operation mode and mild operation conditions. At the same time, the gas source used in this application is power plant flue gas, with low cost and easy availability. If the flue gas also contains a relatively high concentration of Cl or NO x content, the modification effect of solid fuel will be further improved.

[0040] In addition, after the flue gas is modified by micro-nano bubbles, the SO2 content in the flue gas will be effectively reduced. If there is still a high concentration of Cl or NO x content in the flue gas, it can be reduced together during the modification process of the flue gas micro-nano bubbles. Subsequently, the flue gas enters the desulfurization tower, which can effectively reduce the operating load of the desulfurization tower, reduce the dosage of desulfurizing agent, save costs, and also reduce the content of harmful gases discharged into the atmosphere. If multiple solid fuel modification devices are connected in series, the function of the desulfurization tower can even be replaced. The coal washing wastewater obtained after the solid-liquid separation of the modified mixed slurry can be connected to the desulfurization wastewater treatment unit without the need to additionally equip a coal washing wastewater treatment system.

[0041] Furthermore, in step S1, the liquid solvent is preferably pure water, and it can also be boiler drum water, domestic water or water after deep treatment by a desulfurization wastewater treatment system (water treated by technologies such as reverse osmosis, mechanical vapor recompression or multi-effect evaporation of the clear water in the upper part of the clarifier), thereby effectively reducing the modification cost.

[0042] Furthermore, in step S1, the particle size of the solid fuel to be modified should not be too large, less than 200μm is sufficient. The optimal particle size ranges of different types of solid fuels are different. The particle size of coal used in power plants is generally below 100μm, which meets the requirements.

[0043] Furthermore, in step S1, the solid-liquid ratio of the mixed slurry is 1:20 to 1:50. By optimizing the solid-liquid ratio of the mixed slurry, the modification effect and the water consumption can be balanced to achieve the optimal modification effect under the best solid-liquid ratio. If the solid-liquid ratio is too high, the ion concentration of AAEMs in the aqueous solution will reach the saturation state too quickly. If the solid-liquid ratio is too low, although the modification effect can be achieved quickly, after exceeding the threshold range of the best solid-liquid ratio, it will cause great waste of water.

[0044] Furthermore, in step S2, the un-desulfurized flue gas can be led out after the power plant dust collector and before the desulfurization tower. Its composition is relatively complex, mainly composed of CO2, SO2 and O2, and contains a small amount of escaped NO x , and the un-desulfurized flue gas can be passed into the micro-nano bubble generating device, and then the micro-nano bubble generating device passes the un-desulfurized flue gas into the mixed slurry in the form of micro-nano bubbles.

[0045] Furthermore, in step S2, the size of the micro-nano bubbles is 100nm to 10μm. By optimizing the size of the micro-nano bubbles, the content of ·OH and ·H free radicals in the aqueous solution can be increased, so as to obtain the best solid-liquid ratio under the most economical conditions.

[0046] Furthermore, in step S2, the treatment time is 30min to 2h, and the treatment temperature is 20℃ to 80℃.

[0047] Further, in step S2, while introducing the flue gas, the mixed slurry is stirred to promote the solid-liquid contact, and the stirring rate is 200 r / min to 1500 r / min.

[0048] According to another aspect of the present application, there is provided a modified solid fuel prepared by the above method.

[0049] The technical solutions provided by the present application will be further described below according to specific embodiments.

[0050] Example 1

[0051] S1 Dissolve the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:20;

[0052] S2 Use 3000 ppm SO2 + 5% O2 + 15% CO2 mixed with balance gas N2 to simulate the un-desulfurized flue gas, and introduce it into the mixed slurry in the form of micro-nano bubbles. The size of the micro-nano bubbles is 1 μm, the treatment time is 30 min, the treatment temperature is 25 °C, and the stirring rate is 800 r / min, so as to achieve the comprehensive modification of the solid fuel;

[0053] S3 Perform solid-liquid separation and drying treatment on the modified mixed slurry to obtain the modified coal.

[0054] Example 2

[0055] S1 Dissolve the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:50;

[0056] S2 Use 3000 ppm SO2 + 5% O2 + 15% CO2 mixed with balance gas N2 to simulate the un-desulfurized flue gas, and introduce it into the mixed slurry in the form of micro-nano bubbles. The size of the micro-nano bubbles is 500 nm, the treatment time is 1 h, the treatment temperature is 30 °C, and the stirring rate is 200 r / min, so as to achieve the comprehensive modification of the solid fuel;

[0057] S3 Perform solid-liquid separation and drying treatment on the modified mixed slurry to obtain the modified coal.

[0058] Example 3

[0059] S1 Dissolve the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:30;

[0060] S2 Use 3000 ppm SO2 + 5% O2 + 15% CO2 mixed with balance gas N2 to simulate the un-desulfurized flue gas, and introduce it into the mixed slurry in the form of micro-nano bubbles. The size of the micro-nano bubbles is 100 nm, the treatment time is 50 min, the treatment temperature is 20 °C, and the stirring rate is 1500 r / min, so as to achieve the comprehensive modification of the solid fuel;

[0061] S3 performs solid-liquid separation and drying on the modified mixed slurry to obtain modified coal.

[0062] Example 4

[0063] S1 dissolves the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:35;

[0064] S2 uses 3000 ppm SO2 + 5% O2 + 15% CO2 mixed with balance gas N2 to simulate un-desulfurized flue gas, and introduces it into the mixed slurry in the form of micro-nano bubbles. The size of the micro-nano bubbles is 10 μm, the treatment time is 2 h, the treatment temperature is 50 °C, and the stirring rate is 300 r / min, so as to achieve comprehensive modification of solid fuel;

[0065] S3 performs solid-liquid separation and drying on the modified mixed slurry to obtain modified coal.

[0066] Example 5

[0067] S1 dissolves the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:25;

[0068] S2 uses 3000 ppm SO2 + 5% O2 + 15% CO2 mixed with balance gas N2 to simulate un-desulfurized flue gas, and introduces it into the mixed slurry in the form of micro-nano bubbles. The size of the micro-nano bubbles is 5 μm, the treatment time is 1.5 h, the treatment temperature is 80 °C, and the stirring rate is 500 r / min, so as to achieve comprehensive modification of solid fuel;

[0069] S3 performs solid-liquid separation and drying on the modified mixed slurry to obtain modified coal.

[0070] Comparative Example 1

[0071] S1 dissolves the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:20. Stir the mixed slurry to achieve comprehensive modification of solid fuel. The treatment time is 30 min, the treatment temperature is 25 °C, and the stirring rate is 800 r / min;

[0072] S2 performs solid-liquid separation and drying on the modified mixed slurry to obtain modified coal.

[0073] Comparative Example 2

[0074] S1 dissolves the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:20;

[0075] S2 Pass H2SO4 into the mixed slurry. Since the pH of the mixed slurry stabilizes at 2.5 after continuously introducing the un-desulfurized flue gas, it is necessary to ensure that the pH of the mixed slurry remains stable at 2.5. After reacting for a period of time, comprehensive modification of the solid fuel is achieved. The treatment time is 30 min, the treatment temperature is 25 °C, and the stirring rate is 800 r / min;

[0076] S3 Perform solid-liquid separation and drying on the modified mixed slurry to obtain modified coal.

[0077] Comparative Example 3

[0078] S1 Dissolve the coal to be modified in deionized water to obtain a mixed slurry, and the solid-liquid ratio of the mixed slurry is 1:20;

[0079] S2 Use 3000 ppm SO2 + 5% O2 + 15% CO2 mixed with balance gas N2 to simulate un-desulfurized flue gas and directly pass it into the mixed slurry. The treatment time is 30 min, the treatment temperature is 25 °C, and the stirring rate is 800 r / min, so as to achieve comprehensive modification of the solid fuel;

[0080] S3 Perform solid-liquid separation and drying on the modified mixed slurry to obtain modified coal.

[0081] Perform demineralization performance detection, crystal structure detection, pore structure detection, and surface chemical composition and element content detection on the modified coal obtained in Example 1 and Comparative Examples 1-3 respectively. The results are as Figures 2 to 6 shown. In the figure, the flue gas micro-nano bubbles are the modified coal obtained in Example 1, deionized water is the modified coal obtained in Comparative Example 1, H2SO4 is the modified coal obtained in Comparative Example 2, and the flue gas is the modified coal obtained in Comparative Example 3.

[0082] (1) Demineralization performance detection

[0083] Table 1 shows the content and occurrence form of inorganic elements in the coal to be modified used in Example 1 and Comparative Examples 1-3.

[0084] Table 1 Content and occurrence form of inorganic elements in the coal to be modified

[0085]

[0086] Figure 2 is the removal rate of minerals in the modified coal obtained in Example 1 and Comparative Examples 1-3, Figure 3 is the total content of acid-insoluble minerals in the modified coal obtained in Example 1 and Comparative Examples 1-3, where:

[0087] Removal rate = Content of Na / Ca / / Mg / Fe in modified coal / Content of Na / Ca / / Mg / Fe in raw coal; Comprehensive removal rate = Content of (Na + Ca + Mg + Fe) in modified coal / Content of (Na + Ca + Mg + Fe) in raw coal.

[0088] It can be seen from Figure 2 that, compared with deionized water washed coal, both acid washing and flue gas washing can effectively improve the mineral removal rate in coal. The removal rates of various elements by flue gas washing are roughly equivalent to those by H2SO4 washing, while flue gas micro-nano bubble washing can further improve the mineral removal rate in coal. At the same time, it can be seen from Figure 3 that the additional minerals removed are mainly acid-insoluble minerals (mainly silicates and aluminosilicates), which indicates that flue gas micro-nano bubbles can react with acid-insoluble minerals, destroy the lattice structure, promote the transformation of acid-insoluble minerals, and thus improve the mineral removal rate.

[0089] (2) Crystal structure

[0090] XRD tests and Raman tests were respectively carried out on the modified coals obtained in Example 1 and Comparative Examples 1-3 to obtain the structural evolution behavior of the modified coals. The XRD results and Raman results were subjected to peak fitting to obtain the following relevant parameters:

[0091] In terms of XRD: After peak fitting of the 002 peak, the aromatization degree of coal was obtained, and the calculation formula is as follows:

[0092]

[0093] In the formula, d002 is the distance between the single layers of the aromatic layer of the coke microcrystalline structure; Lc is the stacking height of the microcrystals perpendicular to the aromatic layer; La is the size of the microcrystals parallel to the aromatic layer; θ002 and θ100 are the diffraction angles corresponding to the 002 peak and the 100 peak respectively; β002 and β100 correspond to the half-height widths of the 002 peak and the 100 peak; λ is the wavelength of the incident light, generally taking λ = 0.15406nm; k1 and k2 are waveform factors, generally taking k1 = 0.89; k2 = 1.84.

[0094] The graphitization degree was characterized by the aromatization degree fa. The integrated intensities (areas) of the 002 peak and the γ peak obtained by XRD peak fitting can respectively represent the number of aromatic carbon atoms (Car) and the number of aliphatic carbon atoms (Cal).

[0095]

[0096] Figure 4 are the changes in the microcrystalline structure parameters of the modified coals obtained in Example 1 and Comparative Examples 1-3. It can be seen from Figure 4It can be seen that deionized water washing has no effect on the microcrystalline structure of coal. H2SO4 and flue gas washing have almost the same effect on the microcrystalline structure of coal. This is mainly because the acid formed after the flue gas dissolves in water also produces H ions, which is the same as the core essence of H2SO4. H ions will promote the breakage of side chains or bridge chains in the coal structure, so it will promote the increase of the interlayer spacing (increase of d002) and stacking height (increase of Lc) of the microcrystalline structure, turning the macromolecular structure into a small molecular weight structure (decrease of La). As the bridge chains and side chains break, what remains are structures that exist in a stable form, such as benzene rings, so the degree of aromatization increases (increase of fa). After micro-nano bubble washing of coal, since the generated free radicals such as ·OH and ·O have higher electron energy compared to ·H and can also break the benzene ring or heterocyclic organic structure, it will further promote the increase of the interlayer spacing and the formation of a smaller molecular weight organic structure. The internal organic links between different aromatic layers will also be damaged, resulting in a decrease in the stacking height. The destruction of organic structures such as benzene rings leads to a significant decrease in the degree of aromatization of coal.

[0097] In terms of Raman: The first-order peak (800 - 2000 cm -1 ) of Raman is deconvoluted into D1 peak, D2 peak, D3 peak, D4 peak and G peak. Among them, the D1 peak is at 1350 cm -1 peak, usually called the defect band, which corresponds to the graphite lattice vibration mode with A1g symmetry and is attributed to in-plane defects, such as defects and heteroatoms; the D2 peak is at 1620 cm -1 peak, which always exists with the presence of the G1 peak, and its intensity weakens with the increase of the carbon order degree; the D3 peak is usually a very broad band near 1500 - 1550 cm-1 and is considered to be the manifestation of sp2 bonds in amorphous carbon, such as organic molecules, molecular fragments or functional groups in substances with a low degree of carbon order. The D3 peak may be related to the reaction sites, thus affecting the reactivity of coke; the D4 peak is at 1150 cm-1 and only appears in substances with a low degree of carbon order, such as bituminous coal and coal char. The D4 peak may be attributed to the sp3—sp2 hybrid sites at the microcrystalline edge or the stretching vibration of polyene C—C and C=C, or it may also be due to the reaction sites; the G peak is at 1580 cm -1 peak, corresponding to the stretching vibration peak with E2g symmetry in the aromatic layer of the graphite crystal. The characteristics of Raman spectroscopy have been proven to have a good correlation with the degree of carbon structure order. Therefore, Raman spectroscopy can be used to analyze the influence of the heat treatment process on the structural evolution of coke. The following three band area ratios are mainly calculated: I D1 / I G , I D3 / I G and I G / I ALL , where I D1 / I G is the relative content of the unstable structure, I D3 / I G is the loudness content of the amorphous structure, I G / I ALL is the relative content of the graphite structure.

[0098] As Figure 5 shown, after washing coal with deionized water, ID1 / IG, ID3 / IG and IG / IALL are almost the same as those of raw coal, indicating that washing coal with deionized water will not change the structure and content of defective carbon, amorphous carbon and graphite carbon in coal. However, after washing coal with H2SO4 and flue gas, ID1 / IG and ID3 / IG decrease rapidly, and IG / IALL increases sharply, indicating that H+ ions in the solution during the washing process of H2SO4 and flue gas will promote the elimination of defective carbon and amorphous carbon, reduce the content of defective carbon and amorphous carbon in coal, thereby increasing the relative content of graphite carbon, manifested as an increase in the degree of graphitization. After washing coal with flue gas micro-nano bubbles, ID1 / IG and ID3 / IG show an increasing trend, while IG / IALL decreases sharply. This is mainly because free radicals such as ·OH and ·O generated by flue gas micro-nano bubbles have high reaction activities and can destroy the graphite carbon structure (such as benzene ring or heterocyclic organic structure), turning it into amorphous carbon and defective carbon. Generally, the relative content of defective carbon and amorphous carbon is more compared with that of H2SO4 and flue gas washing coal, which fully indicates that washing coal with flue gas micro-nano bubbles will promote the decomposition of the graphite carbon structure and reduce the aromatization degree of coal.

[0099] (3) Pore structure

[0100] An adsorption tester was used to analyze the modified coal obtained in Example 1 and Comparative Examples 1-3. The BET model was used to measure the total specific surface area, and the BJH model was used to determine the pore size distribution of coke.

[0101] Table 2 Pore structure parameters of the modified coal in Example 1 and Comparative Examples 1-3

[0102]

[0103] Table 2 shows the measured pore structure parameters of the modified coal. Washing with deionized water has little effect on the specific surface area and pore volume of coal. Due to the bond-breaking effect of ·H free radicals, washing coal with H2SO4 and flue gas will synchronously increase the micropore area, external surface area, total specific surface area and pore volume of coal to a certain extent. After washing coal with flue gas micro-nano bubbles, due to the destructive effect of strong oxidizing free radicals such as ·OH and ·O, the molecular weight of the coal matrix decreases, the aromatization degree decreases, effectively opening the pores inside the coal to form a pore-rich structure, further increasing the micropore area, external surface area, total specific surface area and pore volume of coal.

[0104] (4) Surface chemical composition and element content

[0105] The modified coals obtained in Example 1 and Comparative Examples 1-3 were subjected to XPS testing to obtain the surface chemical composition and elemental content of the modified coals. The S2p and N1s spectra of the XPS results were deconvoluted, and the electron binding energies corresponding to different structures were as follows:

[0106] S2p:

[0107] Pyrite (158 - 159.6 eV)

[0108] Sulfide (161.2 - 163.6 eV)

[0109] Thiophene (164 - 164.4 eV),

[0110] Sulfoxide (165 - 166 eV)

[0111] Sulfone (167 - 168.3 eV)

[0112] Sulfate (168.4 - 175 eV)

[0113] N1s:

[0114] Pyridinic N, N-6: The binding energy is located at 398.7 eV ± 0.3 eV. This nitrogen atom is usually connected to a carbon atom and a hydrogen atom to form a five-membered ring structure.

[0115] Amino, imine, amide nitrogen (N-H): The binding energy is located at 399.8 eV ± 0.2 eV. These nitrogen atoms can form bonds with hydrogen, carbon, and / or other elements.

[0116] Pyrrolic and Pyridonic N, N-5: The binding energy is located at 400.3 eV ± 0.2 eV. These nitrogen atoms usually participate in forming five- or six-membered heterocyclic structures.

[0117] Quaternary Nitrogen, N-Q: The binding energy is located at 401.4 eV ± 0.3 eV. This nitrogen atom acts as a substituent in the aromatic graphene structure and is connected to four carbon atoms.

[0118] Pyridine-N-oxide or Ammonia, N-O: The binding energy is located at 402.8 eV. This nitrogen atom can be part of a pyridine ring where the nitrogen atom is oxidized, or the nitrogen in an ammonia molecule.

[0119] Chemisorbed Nitrogen Oxides (N-OX): The binding energy is located at 405.0 eV ± 0.5 eV. These nitrogen atoms usually form bonds with oxygen atoms and may be connected to other elements such as carbon or hydrogen.

[0120] Figure 6 are the S / N morphological distribution characteristics of the modified coals obtained in Example 1 and Comparative Examples 1-3. For S, from Figure 6 it can be seen that water washing does not change the distribution of S forms in coal. H2SO4 and flue gas coal washing will remove some inorganic sulfur such as pyrite, water-soluble sulfides and sulfates in coal, and will not damage the organic sulfur structure existing in the form of thiophene, sulfoxide and sulfone. Flue gas micro-nano bubble coal washing will promote the decomposition of some thiophene in coal and convert it into sulfoxide and sulfone. At the same time, it will also promote the decomposition of some sulfoxide and sulfone and convert them into sulfides and sulfates, ultimately reducing the content of organic sulfur in coal overall.

[0121] For N, from Figure 6 it can be seen that water washing does not change the distribution of N forms in coal. H2SO4 and flue gas coal washing will remove the decomposition of some N-H (amino, imine, amide nitrogen), N-Q (quaternary ammonium nitrogen), N-O (pyridine oxide nitrogen or ammonia nitrogen), N-OX (chemisorbed nitrogen oxides) in coal, and will not damage the organic nitrogen structure existing in the form of pyridine nitrogen and pyrrole nitrogen. While flue gas micro-nano bubble coal washing will promote the decomposition of some pyridine nitrogen and pyrrole nitrogen in coal and convert them into N-H (amino, imine, amide nitrogen), N-Q (quaternary ammonium nitrogen), N-O (pyridine oxide nitrogen or ammonia nitrogen), N-OX (chemisorbed nitrogen oxides).

[0122] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included within the protection scope of the present application.

Claims

1. A comprehensive modification method of solid fuel based on flue gas micro-nano bubbles, characterized in that: The solid fuel comprehensive modification method is specifically: S1 dissolving a solid fuel to be modified in a liquid solvent to obtain a mixed slurry, wherein the solid fuel is coal; S2 introduces the undesulfurized flue gas into the mixed slurry in the form of micro-nano bubbles. The flue gas micro-nano bubbles will generate ·OH free radicals and ·O free radicals in the water. Under the joint action of the multi-radicals generated by the micro-nano bubbles and the complex flue gas components, the solid fuel is demineralized and the physical and chemical properties of the solid fuel are improved, thereby achieving comprehensive modification of the solid fuel and synergistically removing SO2 from the flue gas. S3 performs solid-liquid separation and drying on the modified mixed slurry to obtain modified solid fuel.

2. The solid fuel comprehensive modification method according to claim 1, characterized in that: In step S1, the liquid solvent is pure water, boiler drum water, domestic water or water after deep treatment in a desulfurization wastewater treatment system.

3. The comprehensive modification method of solid fuel according to claim 1, characterized in that: In step S1, the particle size of the solid fuel to be modified is less than 200 μm.

4. The comprehensive modification method of solid fuel according to claim 1, characterized in that: In step S1, the solid-liquid ratio of the mixed slurry is 1:20 to 1:

50.

5. The comprehensive modification method of solid fuel according to claim 1, characterized in that: In step S2, the size of the micro-nano bubbles is 100 nm to 10 μm.

6. The comprehensive modification method of solid fuel according to claim 1, characterized in that: In step S2, the treatment time is 30 minutes to 2 hours, and the treatment temperature is 20°C to 80°C.

7. The comprehensive modification method for solid fuel according to any one of claims 1 to 6, characterized in that: In step S2, the slurry is stirred while the flue gas is introduced, and the stirring rate is 200 r / min to 1500 r / min.

8. Modified solid fuel obtained by the comprehensive modification method of solid fuel as described in any one of claims 1 to 7.

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