Preparation methods of flue gas dephosphorizing agents, flue gas dephosphorizing agents and their applications

Abstract

The invention relates to the technical field of flue gas dephosphorization, discloses a preparation method of a flue gas dephosphorization agent, a flue gas dephosphorization agent and its application, and solves the technical problems of poor acid stability and low dephosphorization efficiency of the dephosphorization agent in the prior art. The preparation method of the flue gas dephosphorization agent comprises the following steps: heat-treating a mixture containing a biomass raw material, a pyridine nitrogen source, a pyrrole nitrogen source, and an oxidant solution, collecting solids after the heat treatment is completed to obtain a first precursor; annealing the first precursor under an inert atmosphere to obtain a second precursor; uniformly mixing the second precursor with a high entropy metal precursor powder to obtain a third precursor; mixing the third precursor, an activator, a binder, and a dispersant, and extruding to obtain a blank; carbonizing the blank under an inert atmosphere to obtain a carbonized body; activating the carbonized body under an activated gas atmosphere to obtain a dephosphorization agent.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas dephosphorization, and in particular to a preparation method of a flue gas dephosphorization agent, a flue gas dephosphorization agent and applications thereof. Background Art

[0002] In addition to CO, which accounts for 90% of the tail gas of yellow phosphorus produced by thermal process, it also contains a large amount of water vapor and impurities such as CH4, HF, CO2, O2, N2, AsH3, total sulfur, and total phosphorus. Long-term venting and combustion has caused serious waste of resources, large amounts of greenhouse gas emissions, and serious air pollution. Therefore, in the process of purifying yellow phosphorus tail gas to obtain high-purity carbonyl synthesis raw gas CO, the problem of complex composition and great difficulty in purification of yellow phosphorus tail gas is faced, among which the removal of total phosphorus is the most difficult.

[0003] At present, the removal of total phosphorus is mainly carried out by adsorption, which is divided into catalytic oxidation adsorption and temperature swing adsorption. Among them, catalytic oxidation adsorption is divided into liquid phase catalytic oxidation and solid phase catalytic oxidation. In the early days, foreign countries mainly used liquid phase catalytic oxidation for dephosphorization. However, liquid phase catalytic oxidation generally contains toxic heavy metals such as Cr and Hg, which will cause serious environmental pollution.

[0004] The solid-phase catalytic oxidation method has become a research hotspot in the later period because of its environmentally friendly characteristics. For example, Chinese invention patent CN101422737B discloses a technology of loading aluminum, iron, calcium and other metals on activated carbon by impregnation to make a special catalyst TP201 for dephosphorization. Chinese invention patent CN101695651B discloses a formula for preparing a composite dephosphorization agent by loading metal copper and iron by impregnation of conventional coal-based activated carbon. Chinese invention patent CN101590354B discloses that a metal salt and a promoter are impregnated or mixed in proportion with selected treated activated carbon, and a dephosphorization agent with good gas source adaptability is obtained by roasting. Chinese invention patent application CN101695653A discloses a method for preparing a modified activated carbon adsorbent that can handle low-concentration phosphine, which uses an activated carbon carrier after ultrasonic washing, and ultrasonically impregnates the active components copper and zinc, and adds promoters cerium and lanthanum.

[0005] In the above-mentioned dephosphorization agent preparation process, the metal active components are loaded on the finished activated carbon by the impregnation method, and then the phosphorus species are reacted with the metal active components on the activated carbon carrier and adsorbed on the activated carbon to achieve flue gas dephosphorization. Based on the adsorption-oxidation working principle of the dephosphorization agent, the phosphorus species need to be washed off from the activated carbon by water and converted into a phosphoric acid solution in the aqueous phase, so as to complete the dephosphorization activity recovery of the dephosphorization agent. However, the current method of simply combining the metal active components with the activated carbon carrier by the impregnation method will bring about the problem that the metal active components are not firmly combined with the activated carbon carrier. The metal active components are prone to fall off in the acidic regeneration liquid, thereby causing the gradual loss of the dephosphorization active center, and then leading to the final deactivation of the dephosphorization agent. Therefore, the dephosphorization agent prepared by the impregnation method faces the huge challenge of a significant decrease in adsorption capacity over time during the regeneration process. In addition, although the co-loading of different metal elements can synergistically improve the dephosphorization activity, it is difficult to obtain an ideal dephosphorization efficiency. Summary of the invention

[0006] The main purpose of the present invention is to provide a preparation method of a flue gas dephosphorization agent, a flue gas dephosphorization agent and application thereof, so as to solve the technical problems of poor acid stability and low dephosphorization efficiency of the dephosphorization agent in the prior art.

[0007] In order to achieve the above object, according to the first aspect of the present invention, a method for preparing a flue gas dephosphorization agent is provided, and the technical scheme is as follows:

[0008] The preparation method of the flue gas dephosphorization agent comprises the following steps:

[0009] Heat-treating a mixture containing a biomass raw material, a pyridinic nitrogen source, a pyrrolic nitrogen source, and an oxidant solution, and collecting a solid after the heat treatment is completed to obtain a first precursor;

[0010] annealing the first precursor under an inert atmosphere to obtain a second precursor;

[0011] The second precursor and the high entropy metal precursor powder are uniformly mixed to obtain a third precursor;

[0012] The third precursor, the activator, the binder and the dispersant are mixed and then extruded to obtain a green body;

[0013] Carrying out carbonization treatment on the green body in an inert atmosphere to obtain a carbonized body;

[0014] The carbonized body is activated in an activated gas atmosphere to obtain a dephosphorization agent.

[0015] As a further improvement of the preparation method of the above-mentioned flue gas dephosphorization agent:

[0016] The biomass raw material is fresh bamboo dried at 90-110° C. for 6-10 hours;

[0017] The mixture also contains at least one of PVP, CTAB, SDS, PEG, PAA, sodium citrate, and sodium gluconate;

[0018] The pyridinic nitrogen source is at least one of melamine, pyridine, aniline and pyrazine;

[0019] The pyrrolic nitrogen source is at least one of urea, melamine and polypyrrole;

[0020] The oxidant is at least one of potassium permanganate, potassium ferrate and hydrogen peroxide;

[0021] The adhesive is at least one of starch, cellulose and molasses; the starch is corn starch and / or cassava starch; the cellulose is sodium carboxymethyl cellulose and / or hydroxypropyl methyl cellulose; the molasses is cane molasses and / or beet molasses;

[0022] The dispersant is water.

[0023] As a further improvement of the preparation method of the above-mentioned flue gas dephosphorization agent: the heat treatment is heating at 160-200° C. for 8-24 hours.

[0024] As a further improvement of the preparation method of the above-mentioned flue gas dephosphorization agent: the annealing treatment is annealing at 700-900° C. for 1-3 hours.

[0025] As a further improvement of the preparation method of the above-mentioned flue gas dephosphorization agent: the high entropy metal precursor powder includes salts of at least four metals of iron, copper, magnesium, zinc, cobalt, nickel, cerium, aluminum, chromium and molybdenum.

[0026] As a further improvement of the above-mentioned method for preparing the flue gas dephosphorization agent: the mixing process of the second precursor and the high entropy metal precursor powder comprises the following steps:

[0027] dissolving the salts of the at least four metals in water, and then freeze-drying them to form a high entropy metal precursor powder;

[0028] The second precursor is mixed with the high entropy metal precursor powder by ball milling to obtain a third precursor.

[0029] As a further improvement of the preparation method of the above-mentioned flue gas dephosphorization agent: the carbonization treatment is carbonization at 500-700° C. for 1-3 hours.

[0030] As a further improvement of the preparation method of the flue gas dephosphorization agent mentioned above: the activation treatment is activation at 850-1000° C. for 1-3 hours, and the activation gas atmosphere is water vapor.

[0031] In order to achieve the above object, according to the second aspect of the present invention, a flue gas dephosphorization agent is provided, and the technical scheme is as follows:

[0032] The flue gas dephosphorization agent is prepared by the preparation method described in the first aspect above.

[0033] In order to achieve the above object, according to the third aspect of the present invention, a flue gas dephosphorization method is provided, and the technical scheme is as follows:

[0034] The flue gas dephosphorization method comprises the steps of: using the flue gas dephosphorization agent prepared by the preparation method described in the first aspect to perform solid-phase catalytic oxidation dephosphorization treatment on the flue gas, or using the flue gas dephosphorization agent described in the second aspect to perform solid-phase catalytic oxidation treatment on the flue gas.

[0035] The preparation method of the flue gas dephosphorization agent, the flue gas dephosphorization agent and the application thereof of the present invention have the following advantages:

[0036] (1) Biomass raw materials such as bamboo have a high lignin content, and lignin is more stable than cellulose and hemicellulose. In the weakly alkaline or alkaline environment provided by the nitrogen source, the present invention uses an oxidant at a relatively low temperature (160-200°C) to destroy the stubborn lignin. Since lignin has a three-dimensional cross-linked structure, it is decomposed by the oxidant to form interconnected mesopores, thereby increasing the mesopore content. At the same time, the oxidant can promote the oxidative depolymerization of hemicellulose and cellulose to generate by-products such as organic acids, furfural, and catechol. The by-products can further undergo violent decomposition reactions with the oxidant, releasing a large amount of gases such as oxygen and water vapor, which react with the carbon skeleton at high temperature to form micropores and mesopores. The formation of rich pores helps to fully contact with the high entropy metal precursor powder in the subsequent process, thereby increasing the loading amount of the metal active component.

[0037] (2) Since the electronegativity of nitrogen atoms is higher than that of carbon atoms, the lone pair of electrons of carbon atoms are easily captured by nitrogen atoms, resulting in the nitrogen atoms being negatively charged, while the carbon atoms adjacent to the nitrogen atoms are positively charged, which helps to adsorb negatively charged phosphorus species such as phosphate ions (PO4 3- The negatively charged nitrogen atoms interact with the positively charged hydrogen atoms of water or phosphine, promoting the formation of alkaline conditions and the adsorption of phosphine. The alkaline conditions formed can not only further promote the dissociation of phosphine into PH2 - and PH - , and helps the oxidant to react with the benzoquinone structure of lignin. The positively charged carbon atoms adsorb oxygen with additional lone pairs of electrons, promoting the chemical adsorption of oxygen. The chemically adsorbed oxygen is then activated into superoxide radicals (·O2 - ), O2 - PH2 that can be oxidatively dissociated - and PH -Therefore, the present invention changes the charge distribution of activated carbon by nitrogen doping, increases the surface active sites of the material, improves the alkalinity of the activated carbon surface and the activity of activated oxygen, enhances its adsorption capacity for phosphorus species, thereby enhancing the dephosphorization activity of activated carbon and improving the dephosphorization efficiency.

[0038] In addition to changing the charge distribution on the surface of activated carbon, nitrogen doping can promote the catalytic redox reaction between metal active components and phosphorus species, which helps to oxidize or convert phosphorus species in the gas phase into easily adsorbed forms, thereby improving the dephosphorization efficiency. In addition, nitrogen doping can improve the thermal and chemical stability of activated carbon, allowing it to maintain a high dephosphorization performance in high temperature or corrosive atmospheres. At the same time, nitrogen doping can also form a synergistic effect with metal doping. For example, the nitrogen groups on the surface of nitrogen-doped activated carbon can form coordination bonds with metals, thereby improving the dispersibility and catalytic activity of the metal, which helps to enhance the removal efficiency of phosphorus species in exhaust gas.

[0039] Furthermore, the present invention selectively introduces pyridinic nitrogen and pyrrolic nitrogen with high chemical activity through pyridinic nitrogen source and pyrrolic nitrogen source, and the nitrogen element has diversity, so that the surface of activated carbon has different adsorption sites at the same time, and the adsorption capacity of phosphorus species is enhanced. In the presence of an oxidant, it can promote the reaction of oxygen-containing functional groups with nitrogen-containing species to generate nitrogen-containing functional groups, thereby improving the nitrogen doping efficiency; and, adding an activator (potassium carbonate and / or potassium hydroxide) to the blank can reduce the activation temperature, thereby avoiding the conversion of nitrogen-containing species into inactive graphite nitrogen, and promoting the generation of pyridinic nitrogen and pyrrolic nitrogen. Therefore, the present invention, through the joint action of an oxidant and an activator, allows nitrogen-containing species to be converted into pyridinic nitrogen and pyrrolic nitrogen with higher activity as much as possible, thereby improving the dephosphorization activity of activated carbon.

[0040] (3) The multi-stage heat treatment designed by the present invention (including heat treatment, annealing, carbonization and activation treatment) allows the internal pore structure of the activated carbon to be fully developed while ensuring the stability of the carbon skeleton. These steps not only increase the specific surface area and structural stability of the activated carbon, but also optimize the pore size distribution, so that it has better selective adsorption capacity for gas molecules of different sizes. Among them, the annealing process is different from the traditional single carbonization process (500-600°C, 1-3 hours). Its function is not only to fix nitrogen at a higher temperature, but also to help repair defects in the carbon skeleton, so that the mechanical strength and chemical stability of the activated carbon during use can be improved.

[0041] (4) By introducing high entropy metal precursor powders including a variety of metal salts such as iron, copper, magnesium, zinc, cobalt, nickel, cerium, aluminum, chromium and molybdenum, a multi-metal high entropy alloy can be formed. The synergistic effect between the metal elements can significantly improve the catalytic activity and chemical stability of the dephosphorization agent, adjust the electronic structure of the material, and improve the chemical reaction efficiency between the dephosphorization agent and the phosphorus species. The complementarity of different metals can optimize the pore structure and surface area of ​​the material, thereby further improving the dephosphorization effect. In addition, the present invention loads the nitrogen source and the metal salt onto the precursor before the carbonization treatment, ensuring that these elements can be evenly distributed and penetrate into the material during the carbonization and activation process, avoiding the active components from falling off in the acidic regeneration liquid, and extending the dephosphorization service life. The nitrogen element and the metal salt can also interact under high temperature treatment to form metal nitrides or carbides with specific structures. These compounds have excellent catalytic properties and help improve the dephosphorization ability of the dephosphorization agent.

[0042] In summary, the preparation method of the flue gas dephosphorization agent of the present invention breaks the traditional nitrogen doping process and metal impregnation doping process, and is combined with the existing biomass activated carbon preparation process (primary carbonization-molding-secondary carbonization-activation), providing a new simple method for preparing a dephosphorization agent. The prepared nitrogen-multi-metal co-doped activated carbon has excellent physical and chemical properties and excellent dephosphorization performance, and is extremely practical in the technical field of flue gas dephosphorization treatment.

[0043] The following is a further description of the embodiments of the invention provided in this specification in conjunction with the accompanying drawings and specific implementation methods. Additional aspects and advantages of the embodiments of the invention provided in this specification will be partially given in the following description, and partially will become apparent from the following description, or will be understood through the practice of the embodiments of the invention provided in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings that constitute part of the embodiments of the inventions provided in this specification are used to assist in understanding the embodiments of the inventions provided in this specification. The contents provided in the drawings and their related descriptions in the embodiments of the inventions provided in this specification can be used to explain the embodiments of the inventions provided in this specification, but do not constitute improper limitations on the embodiments of the inventions provided in this specification.

[0045] Figure 1 This is the XRD spectrum of the dephosphorization agent of Example 1 of the present invention.

[0046] Figure 2 This is a SEM photograph of the dephosphorization agent of Example 1 of the present invention.

[0047] Figure 3 It is a schematic structural diagram of the dephosphorization performance evaluation device of the present invention. DETAILED DESCRIPTION

[0048] The following is a clear and complete description of the embodiments of the inventions provided in this specification in conjunction with the accompanying drawings. A person of ordinary skill in the art will be able to implement the embodiments of the inventions provided in this specification based on these descriptions. Before describing the embodiments of the inventions provided in this specification in conjunction with the accompanying drawings, it should be particularly noted that:

[0049] The technical solutions and technical features provided in each part of the embodiments of the invention provided in this specification, including the following description, may be combined with each other if there is no conflict.

[0050] In addition, the embodiments of the embodiments of the inventions provided in this specification involved in the following description are generally only a partial embodiment of the embodiments of the inventions provided in this specification rather than all the embodiments. Therefore, based on the embodiments of the embodiments of the inventions provided in this specification, all other embodiments obtained by ordinary technicians in this field without making any creative work should fall within the scope of protection of the embodiments of the inventions provided in this specification.

[0051] Regarding the terms and units in the embodiments of the inventions provided in this specification: The terms "including", "comprising", "having" and any variations thereof in the descriptions and claims of the embodiments of the inventions provided in this specification and in the related parts are intended to cover non-exclusive inclusions. In addition, other relevant terms and units in the embodiments of the inventions provided in this specification can be reasonably interpreted based on the relevant contents of the embodiments of the inventions provided in this specification.

[0052] Embodiment 1: The preparation method of the flue gas dephosphorization agent of this embodiment comprises the following steps:

[0053] (1) heating a mixture containing a biomass raw material, a pyridinic nitrogen source, a pyrrolic nitrogen source, and a hydrogen peroxide solution (mass fraction of 30%) at 190° C. for 12 hours, collecting a solid after the heat treatment is completed, and obtaining a first precursor;

[0054] The biomass raw material is fresh bamboo dried at 100° C. for 8 hours; the pyridine nitrogen source and the pyrrole nitrogen source are both melamine; and the mass ratio of hydrogen peroxide to the biomass raw material is 0.6.

[0055] (2) Annealing the first precursor at 800° C. for 2 hours in an inert atmosphere to obtain a second precursor.

[0056] (3) uniformly mixing the second precursor and the high entropy metal precursor powder to obtain a third precursor;

[0057] The high entropy metal precursor powder includes equal masses of molybdenum nitrate, nickel nitrate, cobalt nitrate, iron nitrate and copper nitrate; the mixing process includes the steps of: dissolving the salts of the five metals in water (heating can be used to promote dissolution), and then freeze-drying to form a high entropy metal precursor powder; ball-milling the second precursor and the high entropy metal precursor powder at a mass ratio of 300:1 to obtain a third precursor.

[0058] (4) The third precursor, potassium carbonate, a binder and a dispersant are mixed and extruded to obtain a green body; the mass ratio of potassium carbonate to the second precursor is 0.5; the binder is sugar cane molasses, and the mass ratio of sugar cane molasses to the third precursor is 0.4; the dispersant is water, and 30 mL of water is added for every 100 g of the third precursor.

[0059] (5) The green body was carbonized at 600°C for 2 hours under an inert atmosphere to obtain a carbonized body.

[0060] (6) The carbonized body was activated at 900°C for 2 hours in a water vapor atmosphere to obtain a dephosphorization agent.

[0061] Example 2: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this example is different in that: the mixture also contains a PVP solution (mass fraction is 2%), and the mass ratio of PVP to biomass raw material is 0.01.

[0062] Example 3: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this example is different in that the pyridinic nitrogen source is pyridine, the pyrrolic nitrogen source is urea, and the mass ratio of pyridine to urea is 1:1.

[0063] Example 4: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this example is different in that the oxidant is potassium permanganate solution, the activator is potassium hydroxide, and the phosphorus-containing precursor is ammonium dihydrogen phosphate.

[0064] Example 5: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this example is different in that the high entropy metal precursor powder includes equal masses of molybdenum chloride, nickel chloride, cobalt chloride, iron chloride, and copper chloride.

[0065] Example 6: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this example is different in that the high entropy metal precursor powder includes equal masses of molybdenum sulfate, nickel sulfate, cobalt sulfate, iron sulfate, and copper sulfate.

[0066] Example 7: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this example is different in that the high entropy metal precursor powder includes equal masses of molybdenum acetate, nickel acetate, cobalt acetate, iron acetate, and copper acetate.

[0067] Example 8: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this example is different in that the high entropy metal precursor powder includes equal masses of molybdenum nitrate, nickel nitrate, cobalt nitrate, and iron nitrate.

[0068] Comparative Example 1: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that only pyridine is used as the nitrogen source.

[0069] Comparative Example 2: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that only urea is used as the nitrogen source.

[0070] Comparative Example 3: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that only diphenylamine is used as the nitrogen source.

[0071] Comparative Example 4: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that no oxidant is used.

[0072] Comparative Example 5: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that no activator is used.

[0073] Comparative Example 6: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that the carbonized body is activated at 800°C for 2 hours under a water vapor atmosphere to obtain the dephosphorization agent.

[0074] Comparative Example 7: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that the carbonized body is activated at 1050°C for 2 hours under a water vapor atmosphere to obtain the dephosphorization agent.

[0075] Comparative Example 8: Compared with Example 1, the preparation method of the flue gas dephosphorization agent in this comparative example is different in that the high entropy metal precursor powder includes equal masses of molybdenum nitrate, nickel nitrate, and cobalt nitrate.

[0076] Then, the dephosphorization performance of the dephosphorization agents of Examples 1-8 and Comparative Examples 1-8 was tested, and the test results are shown in Table 1. Among them, the removal efficiency represents the percentage of the adsorbed phosphine to the initial inlet phosphine concentration, and a removal efficiency of 99.9% means that only 0.1% of the phosphine is not adsorbed by the catalyst and passes through the catalyst, and the catalyst can still process the remaining 99.9% of the phosphine, that is, only 0.1% of the phosphine outlet concentration is detected at the tail gas outlet; the phosphorus capacity represents how many milligrams of phosphine is adsorbed per gram of the dephosphorization agent; and the regeneration efficiency represents the percentage of the regenerated phosphorus capacity to the phosphorus capacity of the fresh dephosphorization agent.

[0077] Table 1

[0078]

[0079] As can be seen from Table 1, the various indicators of Examples 1-8 are excellent. The total nitrogen content of the dephosphorizing agent of Example 1 was 7.15% as measured by X-ray photoelectron spectroscopy (XPS), of which the contents of pyridinic nitrogen, pyrrolic nitrogen, and graphitic nitrogen were 63.1%, 28.4%, and 8.5%, respectively. The total nitrogen content of the dephosphorizing agent of Example 2 was 7.65%, of which the contents of pyridinic nitrogen, pyrrolic nitrogen, and graphitic nitrogen were 64.2%, 29.1%, and 6.7%, respectively, indicating that the nitrogen element mainly exists in the form of pyridinic nitrogen and pyrrolic nitrogen, which helps to show high dephosphorization activity. Among them, the various indicators of Example 2 are better than those of Example 1, indicating that adding a small amount of PVP to the mixture can promote the introduction of nitrogen elements and the formation of pyridinic nitrogen and pyrrolic nitrogen.

[0080] In addition, the specific surface area, total pore volume and average pore diameter of the dephosphorization agent of Example 1 were 1164 m 2 / g, 0.638cm 3 / g, 2.19nm, the specific surface area, total pore volume and average pore diameter of the dephosphorization agent in Example 2 are 1328m 2 / g, 0.708cm 3 / g, 2.13nm.

[0081] Figure 1 It is the XRD spectrum of the dephosphorization agent of Example 1. Figure 1 As shown, no single metal peak was found, indicating that a solid solution phase high entropy structure was formed; at the same time, the diffraction peaks were assigned and it was found that the diffraction peaks were shifted to high angles compared with the composite metal oxide standard card. This is because the atoms of different components differ in properties such as size, electronegativity and chemical bonds. When occupying lattice positions, the lattice will expand or contract. Relative to the main atoms in the composite metal oxide, other atoms with smaller atomic radius are doped into the high entropy structure, which means a reduction in lattice parameters and the effect of high entropy alloy phases. The metals combine with each other to improve the structural stability.

[0082] Figure 2 : is a SEM photo of the dephosphorization agent of Example 1. Figure 2 As shown, the dephosphorization agent has more micropores and macropores, and mesopores and micropores extend from the macropores. Most of these pores have needle-shaped characteristics. Therefore, the dephosphorization agent also presents an open and dense structure and can withstand higher pressure.

[0083] The various indicators of Control Examples 1-3 are significantly weaker than those of Example 1, indicating that not only nitrogen doping can significantly improve the dephosphorization activity of the dephosphorization agent, but also a suitable nitrogen source is particularly important for the dephosphorization performance; among them, Control Example 3 selected a neutral nitrogen source, which caused various indicators to decrease significantly, indicating that the dephosphorization agent prepared under alkaline conditions has better dephosphorization activity.

[0084] The control example 4 did not use an oxidant. XPS analysis showed that the dephosphorization agent of the control example 4 did not contain pyrrolic nitrogen, and the content of graphite nitrogen was as high as 65.8%, which resulted in a significant decrease in the dephosphorization performance.

[0085] The control example 5 did not use an activator. The specific surface area, total pore volume and average pore diameter of the dephosphorization agent of the control example 5 were 780 m 2 / g, 0.363cm 3 / g, 1.86nm, the specific surface area and total pore volume are significantly reduced, which leads to a significant decrease in the dephosphorization performance.

[0086] Comparative Examples 6-7 show the effect of activation temperature on the dephosphorization performance of the dephosphorization agent. Among them, when the activation temperature is too low (800°C), the metal solid solution is not completely decomposed, and the metal still exists in the form of metal salts, which basically has no catalytic oxidation ability for phosphorus species. When the activation temperature is too high (1050°C), the dephosphorization performance shows a downward trend due to the appearance of an impurity peak of a single metal oxide. The appearance of this single metal oxide indicates that an excessively high activation temperature will cause some metal components to precipitate from the high entropy structure, thereby affecting the dephosphorization performance.

[0087] The dephosphorization performance of Control Example 8 is not ideal due to the small number of metal active components.

[0088] The specific implementation of the flue gas dephosphorization method of the present invention is to use the above-mentioned preparation method to prepare the flue gas dephosphorization agent to perform solid-phase catalytic oxidation dephosphorization treatment on the flue gas. The flue gas is the tail gas of yellow phosphorus production, and the total phosphorus therein mainly includes the following phosphorus species:

[0089] Phosphine (PH4): This is a common gaseous phosphide in yellow phosphorus tail gas, which is toxic and flammable.

[0090] Gaseous phosphorus oxides (such as P4O 10 ): These are oxidized phosphorus compounds formed during the oxidation of yellow phosphorus and may exist in the form of gaseous or solid particles.

[0091] Yellow phosphorus (P4) vapor: Since yellow phosphorus has a certain volatility at high temperatures, part of the yellow phosphorus may exist in the exhaust gas in the form of vapor.

[0092] Other gaseous phosphides: including some low-level phosphides, such as diphosphine (P2H4) or other possible gaseous phosphides, which are usually intermediate products generated by the decomposition or reaction of phosphorus under specific conditions.

[0093] The schematic diagram of the structure of the device used for the above dephosphorization performance evaluation is as follows Figure 3As shown, nitrogen, oxygen and phosphine are mixed in a gas mixing bottle and then flow into a reactor (1.5 mm in inner diameter) loaded with a dephosphorizing agent. The concentration of PH3 in the outlet gas is continuously detected by a HF-901 gas chromatograph (Shandong Huifen Instrument Co., Ltd.). Measurement conditions: bed temperature 80 °C, test space velocity 6000 h -1 , PH3 concentration is 2500ppm, oxygen concentration is 1vol%, and the rest is nitrogen.

[0094] XPS test was performed using an X-ray photoelectron spectrometer (Thermo ESCALAB 250XI). Specific surface area and pore structure were measured using a high-performance specific surface and micropore analyzer (BSD-PM2). The specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method, and the total pore volume and pore size distribution were analyzed using the density functional theory (DFT) model. XRD spectra were characterized using a DX-2700 X-ray diffractometer produced by Haoyuan Instruments. SEM images were taken using a field emission electron scanning microscope (JSM 7800F Prime, Japan Electron Co., Ltd.).

[0095] The above is a description of the relevant contents of the embodiments of the inventions provided in this specification. Based on these descriptions, a person of ordinary skill in the art will be able to implement the embodiments of the inventions provided in this specification. Based on the above contents of the embodiments of the inventions provided in this specification, all other preferred implementations and embodiments obtained by a person of ordinary skill in the art without making any creative work shall fall within the scope of protection of the embodiments of the inventions provided in this specification.

Claims

1. A method for preparing a flue gas dephosphorization agent, characterized in that: The following steps are involved: Heat-treating a mixture containing a biomass raw material, a pyridine nitrogen source, a pyrrole nitrogen source, and an oxidant solution, and collecting a solid after the heat treatment is completed to obtain a first precursor; the heat treatment is heating at 160 to 200° C. for 8 to 24 hours; annealing the first precursor under an inert atmosphere to obtain a second precursor; The second precursor is mixed with high entropy metal precursor powder to obtain a third precursor; the high entropy metal precursor powder includes salts of at least four metals of iron, copper, magnesium, zinc, cobalt, nickel, cerium, aluminum, chromium, and molybdenum; The third precursor, the activator, the binder and the dispersant are mixed and then extruded to obtain a green body; the activator is potassium carbonate and / or potassium hydroxide; Carrying out carbonization treatment on the green body in an inert atmosphere to obtain a carbonized body; The carbonized body is activated in an activation gas atmosphere to obtain a dephosphorization agent; the activation treatment is performed at 850-1000°C for 1-3 hours, and the activation gas atmosphere is water vapor.

2. The method for preparing a flue gas dephosphorization agent according to claim 1, characterized in that: The biomass raw material is fresh bamboo dried at 90-110° C. for 6-10 hours; The mixture also contains at least one of PVP, CTAB, SDS, PEG, PAA, sodium citrate, and sodium gluconate; The pyridinic nitrogen source is at least one of melamine, pyridine, aniline and pyrazine; The pyrrolic nitrogen source is at least one of urea, melamine and polypyrrole; The oxidant is at least one of potassium permanganate, potassium ferrate and hydrogen peroxide; The adhesive is at least one of starch, cellulose and molasses; The dispersant is water.

3. The method for preparing a flue gas dephosphorization agent according to claim 2, characterized in that: The annealing treatment is performed at 700-900° C. for 1-3 hours.

4. The method for preparing a flue gas dephosphorization agent according to claim 1, characterized in that: The mixing process of the second precursor and the high entropy metal precursor powder includes the steps of: dissolving the salts of the at least four metals in water, and then freeze-drying them to form a high entropy metal precursor powder; The second precursor is mixed with the high entropy metal precursor powder by ball milling to obtain a third precursor.

5. The method for preparing a flue gas dephosphorization agent according to claim 1, characterized in that: The carbonization treatment is carried out at 500-700° C. for 1-3 hours.

6. Flue gas dephosphorization agent, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 5.

7. A flue gas dephosphorization method, characterized in that: The method comprises the following steps: using the flue gas dephosphorization agent prepared by the preparation method according to any one of claims 1 to 5 to carry out solid-phase catalytic oxidation dephosphorization treatment on the flue gas, or using the flue gas dephosphorization agent according to claim 6 to carry out solid-phase catalytic oxidation dephosphorization treatment on the flue gas.

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