A method for treating pollutants in steel sintering flue gas

Abstract

The present application relates to a kind of steel sintering flue gas pollutant processing method, belong to environmental pollution control field.The present application is prepared by modifying active coke loaded with cobalt as catalyst, better catalytic activation peroxymonosulfate to the pollutants generated in steel sintering flue gas is handled, effectively improve the catalytic effect of catalytic activation peroxymonosulfate to the pollutants generated in steel sintering flue gas;The modified active coke catalyst prepared in the present application is applied to the efficient synergistic removal of steel sintering flue gas, there is higher chlorobenzene removal rate and mineralization rate in the first 2h, by introducing steel sintering flue gas into PMS reaction solution, utilize the residence time of gas in reactor, realize the sufficient contact of PMS reaction solution and steel sintering flue gas pollutants, activate PMS to produce active species to promote the oxidation of pollutants, provide a simple, efficient, low-cost new type carbon catalyst preparation approach for the industrial practical application of steel sintering flue gas in advanced oxidation.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control and relates to a method for treating pollutants from sintering flue gas in steelmaking. Background Technology

[0002] Dioxins (also known as PCDD / Fs) are a class of highly toxic tricyclic aromatic organic compounds, classified as Group 1 carcinogens for humans by the World Health Organization. Therefore, the treatment of pollutants from steel sintering flue gas is of great significance. Currently, existing environmental protection equipment and technologies in the steel industry cannot fully meet the requirements of the latest ultra-low emission limits, necessitating the development of a technology capable of synergistically removing multiple pollutants from steel sintering flue gas.

[0003] Chlorobenzene is considered a suitable chemical model reagent because its aromatic ring is stable and difficult to oxidize. It can be used as a model pollutant for PCDD / Fs and can be used to evaluate the treatment effect of PCDD / Fs. Toluene, as a representative intermediate product after dioxin degradation and dechlorination, can also be used to evaluate the treatment effect of PCDD / Fs. Therefore, if chlorobenzene and toluene have good treatment effects, it can indicate to some extent that they also have good treatment effects on PCDD / Fs.

[0004] Currently, gas-solid processes are commonly used for elimination in actual industrial production, such as thermal combustion and catalytic combustion. However, these technologies are costly and it is difficult to completely oxidize pollutants into CO2, resulting in a large number of intermediate products being released into the air during the degradation process, causing secondary pollution.

[0005] In recent years, advanced oxidation processes (AOPs) have proven to be a promising method for further decomposition of sintering flue gas in steelmaking by introducing it into the liquid phase through wet scrubbing, due to their strong oxidizing power. AOPs generate free radicals through ultraviolet photolysis, heating, or metal activation of H2O2 or persulfates (such as PDS / PMS). Gaseous pollutants are then absorbed into the aqueous phase. Through addition, substitution, electron transfer, and bond breaking between free radicals and organic compounds, the large, recalcitrant gaseous pollutants absorbed by the aqueous phase are oxidized and degraded into low-toxicity / non-toxic small molecules, or even directly degraded into CO2 and H2O. This successfully avoids the release of toxic byproducts into the atmosphere and significantly reduces secondary air pollution. Persulfate (PMS) is a commonly used oxidant in AOPs, possessing advantages such as strong oxidizing power, low cost, and good water solubility. However, its O2O bond energy is relatively high, requiring a catalyst to break the O2O bonds during use to activate PMS and achieve pollutant degradation. The activation of PMS activity directly affects the effect of AOPs on the treatment of sintering flue gas in steelmaking. Therefore, catalysts play a very important role in the treatment of pollutants in sintering flue gas in steelmaking.

[0006] Therefore, it is necessary to select a highly efficient catalyst and provide a method for treating pollutants from steel sintering flue gas in order to improve the treatment effect of pollutants from steel sintering flue gas and further reduce the environmental pollution and threats to human health caused by pollutants from steel sintering flue gas. Summary of the Invention

[0007] To overcome the problems in the prior art, this invention proposes a method for treating flue gas from steel sintering. In the treatment process, modified activated coke loaded with cobalt is used as a catalyst to better activate PMS activity, which effectively improves the treatment effect of pollutants in steel sintering flue gas under the persulfate system in advanced oxidation processes.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: The processing method includes the following steps: S1: A certain amount of persulfate is added to the reactor, and the molar mass concentration of the persulfate aqueous solution is adjusted. After the persulfate and water are mixed evenly, a cobalt-loaded modified activated coke catalyst is added to activate the persulfate and degrade pollutants in the sintering flue gas. Since persulfate is soluble in water, it can also be sprayed out to treat the sintering flue gas.

[0009] S2: Adjust the volumetric flow rate of sintering flue gas at a stable concentration per unit time, and introduce the sintering flue gas into the reactor from the bottom. The added cobalt-supported modified activated coke catalyst can rapidly activate persulfate in water to form hydroxyl radicals, sulfate radicals, or singlet oxygen formed in the catalyst / PMS coupled aqueous solution system. 1 Active species such as O2 can purify and remove iron and steel sintering flue gas as it rises in the liquid. Preferably, the modified activated coke catalyst in step S1 is prepared through the following steps: (1) Take activated coke, wash and dry it, and then grind and screen it using a ball mill to obtain activated coke particles as a carrier; (2) Dissolve cobalt nitrate hexahydrate in deionized water and mix it uniformly by ultrasonication to obtain an aqueous solution of cobalt nitrate; (3) The activated coke particles obtained in step (1) are impregnated in the cobalt nitrate aqueous solution obtained in step (2) and stirred evenly. Then the mixture is ultrasonically impregnated and the impregnated activated coke particles are left to stand in a container for a period of time. (4) The activated coke particles that have been left to stand in step (3) are placed in an oven to dry, and then calcined in a tube furnace under a nitrogen atmosphere.

[0010] Preferably, in step (1), ultrapure water and ethanol are used to wash the activated coke, the drying temperature is 60~110 ℃, and the particle size of the activated coke particles is 60~80 mesh.

[0011] Preferably, in step (2), the molar volume concentration of the cobalt nitrate aqueous solution is 0.23 mol / L to 2.83 mol / L.

[0012] Preferably, in step (3), the stirring time is 1~6 min, the ultrasonic impregnation time is 1~3 h, and the standing time is 12~24 h.

[0013] Preferably, in step (4), the drying temperature is 60~110 ℃, the drying time is 6~24 h, the calcination temperature is 400~600 ℃, and the calcination time is 5~7 h.

[0014] Preferably, the mass fraction of cobalt supported on the modified activated coke catalyst in step S1 is 2-20%.

[0015] Preferably, in step S1, the concentration of persulfate is 5-20 mM / L, and the amount of modified activated coke catalyst added is 1.6-8.1% of the mass of persulfate.

[0016] Preferably, in step S2, the volumetric flow rate of the sintering flue gas is 0.4 to 0.7 times the volume of the persulfate reaction liquid.

[0017] Modified activated carbon is used to activate persulfate in the liquid phase to continuously generate hydroxyl radicals (•OH) and sulfate radicals (SO4•). - ) and superoxide radicals (O2• - The aforementioned free radicals have been shown to have higher redox potentials than oxidants, thus enabling them to rapidly degrade organic matter; or they may accelerate the decomposition of persulfate via non-free radical pathways. 1 O2 can catalytically oxidize persulfate to eliminate VOCs (chlorobenzene, toluene) and Hg. 0 It efficiently degrades VOCs into small molecules of CO2 and H2O, while simultaneously reducing Hg. 0 Oxidation into more controllable Hg 2+ .

[0018] The beneficial effects of this invention are: 1. This invention utilizes the fact that after the sintering flue gas from steel is introduced into the bottom of the reactor and dispersed into small bubbles, the modified activated coke fully contacts the PMS solution and can fully react with the active substances produced by the catalytic activation of PMS, and be degraded to generate CO2 and a small amount of intermediate products. Some of the CO2 gas and a small amount of intermediate products can be dissolved in water, reducing the amount of CO2 emitted into the air, which helps to reduce the greenhouse effect and avoids secondary pollution caused by the emission of intermediate products.

[0019] 2. This invention improves the activation effect of the catalyst on PMS by using a modified activated cobalt catalyst with supported cobalt, thereby enabling the PMS coupled aqueous solution system to have a better treatment effect on pollutants in iron and steel sintering flue gas.

[0020] 3. The PMS coupled aqueous solution system of this invention can simultaneously treat PCDD / Fs and Hg in steel sintering flue gas. 0 It also enables rapid and efficient treatment of toluene, a representative product of chlorobenzene dechlorination, achieving a removal rate of over 90% for chlorobenzene and toluene within 3 hours, and removing Hg. 0 The removal rate is close to 100%.

[0021] 4. This invention is simple to operate, requires no surfactant, and the catalyst-activated PMS process does not require the introduction of additional energy sources such as light and heat, which helps to reduce energy consumption and thus reduce costs.

[0022] 5. This invention can be used to treat gas concentrations of 80 ppm to 470 ppm Hg in steel sintering flue gas. 0 Concentration of 100 ug / m 3 It effectively removes pollutants, achieving effective removal of low-concentration pollutants at room temperature. It is highly sensitive to pollutants in steel sintering flue gas and has a good treatment effect.

[0023] 6. Since the PMS activated by catalysis in this invention has excellent removal effect on toluene, this invention can also be applied to industries that mainly produce toluene, such as chemical manufacturing, coal processing, rubber products manufacturing, and coking. Attached Figure Description

[0024] Figure 1 The images show the effect of modified activated coke catalytic activation of PMS for removing gaseous chlorobenzene prepared in Examples 1-8 of this invention.

[0025] Figure 2 The images show the effect of modified activated coke catalytic activation of PMS for removing gaseous chlorobenzene, as prepared in Examples 9-10 of this invention.

[0026] Figure 3 The effect of modified activated coke catalytic activation of PMS to remove gaseous chlorobenzene is shown in the figure.

[0027] Figure 4 The effect of catalytic activation of PMS to remove gaseous chlorobenzene using activated coke catalysts loaded with different elements.

[0028] Figure 5 The graph shows the effect of cobalt oxide catalytic activation of PMS and the catalyst of this invention catalytic activation of PMS in removing gaseous chlorobenzene.

[0029] Figure 6 The graph shows the effect of the catalyst of this invention on the catalytic activation of PMS and the effect of cobalt oxide catalytic activation of PMS on the removal of gaseous chlorobenzene and the CO2 yield.

[0030] Figure 7 The images show the effect of the catalysts prepared in Examples 1, 4, 6, and 8 of this invention on the catalytic activation of PMS to remove gaseous toluene.

[0031] Figure 8 The catalyst prepared in Example 5 of this invention catalyzes the activation of PMS to remove heavy metal Hg. 0 Renderings.

[0032] Figure 9 The catalyst prepared in Example 5 of this invention catalyzes the activation of PMS to simultaneously remove chlorobenzene, toluene, and the heavy metal Hg. 0 The rendered image. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments.

[0034] The persulfate used in the examples and comparative examples is potassium permonosulfate (PMS).

[0035] The composition of the activated char in the examples and comparative examples is shown in Table 1.

[0036] Table 1 Example 1 First, the modified activated coke catalyst was prepared: Take activated coke, wash it repeatedly with ultrapure water and ethanol, and dry it in an oven at 60 ℃. Then grind the activated coke and sieve it to obtain 60-80 mesh granular activated coke for later use.

[0037] Dissolve 0.2015 g of cobalt nitrate hexahydrate (Co(NO3)2•6H2O) in 3 mL of deionized water and mix thoroughly by ultrasonication to form a cobalt nitrate aqueous solution with a concentration of 0.23 mol / L.

[0038] Take 2g of 60-80 mesh activated coke particles and immerse them in a cobalt nitrate aqueous solution. Stir rapidly with a glass rod for 1 minute to ensure that the activated coke is quickly wetted by the cobalt nitrate solution. Place the activated coke that has been wetted by the cobalt nitrate solution in an ultrasonic cleaner and ultrasonically immerse it for 3 hours. Then, remove the ultrasonically immersed activated coke and let it stand for 12 hours.

[0039] The activated coke, after being allowed to stand, was dried in a 60 °C oven for 6 h. Then, the dried, impregnated activated coke was calcined at 600 °C for 7 h under a nitrogen atmosphere at a heating rate of 3 °C / min. The resulting cobalt-loaded modified activated coke catalyst was labeled 2Co-AC(I), indicating that the mass fraction of cobalt loaded in the cobalt-loaded modified activated coke prepared in this example was 2%.

[0040] Secondly, the prepared cobalt-loaded modified activated coke was used to catalyze the activation of PMS for the treatment of pollutants in steel sintering flue gas. After being balanced with nitrogen and oxygen, the sintering flue gas of steel with a chlorobenzene concentration of 80±4 ppm is introduced into the reactor from the bottom. The volumetric flow rate of the sintering flue gas per unit time is adjusted to 0.4 times the volume of the PMS reaction liquid. The sand core plate in the reactor disperses the sintering flue gas into small bubbles, which rise in the water.

[0041] PMS was added to the reactor until the molar concentration of the PMS solution reached 20 mM / L. After uniform mixing, the modified activated coke catalyst with a cobalt-supported mass fraction of 2% was added to the reactor. The amount of modified activated coke catalyst added was 8.1% of the mass of persulfate. At this point, the catalyst rapidly activated the persulfate in the water to form active substances (such as hydroxyl radicals, sulfate radicals, or singlet oxygen formed by the catalyst / PMS coupled aqueous solution system). 1 (O2, etc.). As small bubbles rise in the water, they can fully react with the active substances produced by the catalyst activation and be oxidized to generate CO2 and other related intermediate products. Some of the water-insoluble CO2 gas is discharged from the reactor, while the intermediate products remain in the reaction solution in liquid form. Persulfate and catalyst are then added to further treat the reaction solution until it meets the standards before being discharged.

[0042] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0043] Example 2 First, the modified activated coke catalyst was prepared: Take activated coke, wash it repeatedly with ultrapure water and ethanol, and dry it in an oven at 80 ℃. Then grind the activated coke and sieve it to obtain 60-80 mesh granular activated coke for later use.

[0044] Dissolve 0.4115 g of cobalt nitrate hexahydrate (Co(NO3)2•6H2O) in 3 mL of deionized water, and mix thoroughly by ultrasonication to form a cobalt nitrate aqueous solution with a concentration of 0.47 mol / L.

[0045] Take 2g of 60-80 mesh activated coke particles and immerse them in a cobalt nitrate aqueous solution. Stir rapidly with a glass rod for 3 minutes to ensure that the activated coke is quickly wetted by the cobalt nitrate solution. Place the activated coke that has been wetted by the cobalt nitrate solution in an ultrasonic cleaner and ultrasonically immerse it for 2 hours. Then, remove the ultrasonically immersed activated coke and let it stand for 18 hours.

[0046] The activated coke, after being allowed to stand, was dried in an oven at 80 °C for 12 h. Then, the dried, impregnated activated coke was calcined at 500 °C for 6 h under a nitrogen atmosphere at a heating rate of 3 °C / min. The resulting cobalt-loaded modified activated coke catalyst was labeled 4Co-AC(I), indicating that the mass fraction of cobalt loaded in the cobalt-loaded modified activated coke prepared in this example was 4%.

[0047] Secondly, the prepared cobalt-loaded modified activated coke was used to catalyze the activation of PMS for the treatment of pollutants in steel sintering flue gas. After being balanced with nitrogen and oxygen, the sintering flue gas of steel with a chlorobenzene concentration of 80±4 ppm is introduced into the reactor from the bottom. The volumetric flow rate of the sintering flue gas per unit time is adjusted to 0.5 times the volume of the PMS reaction liquid. The sand core plate in the reactor disperses the sintering flue gas into small bubbles, which rise in the water.

[0048] PMS was added to the reactor until the molar mass concentration of the PMS solution was 5 mM / L. After uniform mixing, the modified activated coke catalyst with a mass fraction of 4% cobalt was added to the reactor. The amount of modified activated coke catalyst added was 8.1% of the mass of persulfate.

[0049] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0050] Example 3 First, the modified activated coke catalyst was prepared: Take activated coke, wash it repeatedly with ultrapure water and ethanol, and dry it in an oven at 110 ℃. Then grind the activated coke and sieve it to obtain 60-80 mesh granular activated coke for later use.

[0051] Dissolve 0.6304 g of cobalt nitrate hexahydrate (Co(NO3)2•6H2O) in 3 mL of deionized water, and mix thoroughly by ultrasonication to form a cobalt nitrate aqueous solution with a concentration of 0.72 mol / L.

[0052] Take 2g of 60-80 mesh activated coke particles and immerse them in a cobalt nitrate aqueous solution. Stir rapidly with a glass rod for 6 minutes to ensure that the activated coke is quickly wetted by the cobalt nitrate solution. Place the activated coke that has been wetted by the cobalt nitrate solution in an ultrasonic cleaner and ultrasonically immerse it for 1 hour. Then, remove the ultrasonically immersed activated coke and let it stand for 24 hours.

[0053] The activated coke, after being allowed to stand, was dried in an oven at 110 °C for 24 h. Then, the dried, impregnated activated coke was calcined at 400 °C for 5 h under a nitrogen atmosphere at a heating rate of 3 °C / min. The resulting cobalt-loaded modified activated coke catalyst, labeled 6Co-AC(I), indicates that the mass fraction of cobalt loaded in the cobalt-loaded modified activated coke prepared in this example was 6%.

[0054] Secondly, the prepared cobalt-loaded modified activated coke was used to catalyze the activation of PMS for the treatment of pollutants in steel sintering flue gas. After being balanced with nitrogen and oxygen, the sintering flue gas of steel with a chlorobenzene concentration of 80±4 ppm is introduced into the reactor from the bottom. The volumetric flow rate of the sintering flue gas per unit time is adjusted to 0.7 times the volume of the PMS reaction liquid. The sand core plate in the reactor disperses the sintering flue gas into small bubbles, which rise in the water.

[0055] PMS was added to the reactor until the molar mass concentration of the PMS solution was 10 mM / L. After uniform mixing, the modified activated coke catalyst with a mass fraction of 6% cobalt was added to the reactor. The amount of modified activated coke catalyst added was 8.1% of the mass of persulfate.

[0056] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0057] Example 4 The experimental method in this embodiment is the same as that in Example 3, except that: in this embodiment, after ultrasonic uniform mixing, a cobalt nitrate aqueous solution with a concentration of 0.98 mol / L is formed. In this embodiment, the cobalt-loaded modified activated coke catalyst is labeled as 8Co-AC(I), which indicates that the mass fraction of cobalt-loaded modified activated coke prepared in this embodiment is 8%.

[0058] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0059] Example 5 The experimental method in this embodiment is the same as that in Example 3, except that: in this embodiment, after ultrasonic uniform mixing, a cobalt nitrate aqueous solution with a concentration of 1.26 mol / L is formed. In this embodiment, the cobalt-loaded modified activated coke catalyst is labeled as 10Co-AC(I), which indicates that the mass fraction of cobalt-loaded modified activated coke prepared in this embodiment is 10%.

[0060] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0061] Example 6 The experimental method in this embodiment is the same as that in Example 3, except that: in this embodiment, after ultrasonic uniform mixing, a cobalt nitrate aqueous solution with a concentration of 1.54 mol / L is formed. In this embodiment, the cobalt-loaded modified activated coke catalyst is labeled as 12Co-AC(I), which indicates that the mass fraction of cobalt-loaded modified activated coke prepared in this embodiment is 12%.

[0062] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0063] Example 7 The experimental method in this embodiment is the same as that in Example 3, except that: in this embodiment, after ultrasonic uniform mixing, a cobalt nitrate aqueous solution with a concentration of 2.00 mol / L is formed. In this embodiment, the cobalt-loaded modified activated coke catalyst is labeled as 15Co-AC(I), which indicates that the mass fraction of cobalt-loaded modified activated coke prepared in this embodiment is 15%.

[0064] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0065] Example 8 The experimental method in this embodiment is the same as that in Example 3, except that: in this embodiment, after ultrasonic uniform mixing, a cobalt nitrate aqueous solution with a concentration of 2.83 mol / L is formed. In this embodiment, the cobalt-loaded modified activated coke catalyst is labeled as 20Co-AC(I), which indicates that the mass fraction of cobalt-loaded modified activated coke prepared in this embodiment is 20%.

[0066] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 1 As shown.

[0067] like Figure 1As shown, the removal rate of chlorobenzene from PMS by Co-AC(I) catalytic activation remained above 90% within three hours of reaction, indicating that the modified activated coke catalyst prepared by this method has certain practical applicability in the activation and removal of chlorobenzene from liquid-phase PMS.

[0068] Example 9 The experimental method in this embodiment is the same as that in Example 5, except that the amount of modified activated coke catalyst added in this embodiment is 4.9% of the mass of persulfate.

[0069] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 2 As shown.

[0070] like Figure 2 As shown, when the amount of 10Co-AC(I) added is further reduced, the removal rate of chlorobenzene in catalytically activated PMS decreases to a certain extent. Therefore, it can be concluded that the amount of catalyst is one of the key factors in activating PMS to produce active substances.

[0071] Example 10 The experimental method in this embodiment is the same as that in Example 5, except that the amount of modified activated coke catalyst added in this embodiment is 1.6% of the mass of persulfate.

[0072] In this embodiment, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 2 As shown.

[0073] like Figure 2 As shown, when the amount of 10Co-AC(I) added was further reduced compared to Example 9, the removal rate of chlorobenzene in catalytically activated PMS decreased significantly. Therefore, it can be concluded that the amount of catalyst used is one of the key factors in activating PMS to produce active substances.

[0074] Comparative Example 1 In this comparative example, cobalt-loaded modified activated coke was prepared using a co-precipitation method. The prepared cobalt-loaded modified activated coke catalyst was labeled 10Co-AC(C), indicating that the mass fraction of cobalt loaded in the cobalt-loaded modified activated coke prepared in this comparative example was 10%. This comparative example used the same method as in Example 3 to treat pollutants from steel sintering flue gas.

[0075] In this comparative example, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 3 As shown.

[0076] pass Figure 3It can be seen that the removal rate of p-chlorobenzene in this comparative example decreased significantly after 3 hours of reaction compared with Example 5. This is because the 10Co-AC(C) catalyst prepared by the co-precipitation method failed to efficiently activate PMS to generate more active substances to oxidize chlorobenzene. Furthermore, the catalyst began to deactivate to some extent as the reaction time increased. In addition, the pH value needs to be adjusted with ammonia water during the preparation of the modified activated coke catalyst by the co-precipitation method, which is more troublesome than the method of this invention.

[0077] Comparative Example 2 In this comparative example, a hydrothermal method was used to prepare cobalt-loaded modified activated coke. The prepared cobalt-loaded modified activated coke catalyst was labeled 10Co-AC(H), indicating that the mass fraction of cobalt loaded in the cobalt-loaded modified activated coke prepared in this comparative example was 10%. This comparative example used the same method as Example 3 to treat pollutants from steel sintering flue gas.

[0078] In this comparative example, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 3 As shown.

[0079] pass Figure 3 It can be seen that the removal rate of p-chlorobenzene in this comparative example is significantly lower than that in Example 5. This is because the 10Co-AC(H) catalyst prepared by hydrothermal method failed to efficiently activate PMS to generate more active substances to oxidize chlorobenzene. Furthermore, the catalyst began to deactivate to some extent as the reaction time increased. In addition, ethylene glycol and sodium hydroxide need to be introduced during the preparation of modified activated coke catalyst by hydrothermal method, which increases the types of raw materials used. Moreover, the reaction still needs to be carried out at a high temperature of 180 °C for 24 hours, which leads to an increase in the preparation cost of the catalyst.

[0080] Comparative Example 3 In this comparative example, unmodified activated coke was used to catalytically activate PMS. This comparative example used the same method as Example 1 to treat pollutants from steel sintering flue gas.

[0081] In this comparative example, the effect of removing chlorobenzene by catalytic activation of PMS with unmodified activated carbon is as follows: Figure 3 As shown.

[0082] pass Figure 3 As can be seen, in this comparative example, PMS cannot be activated by the unmodified activated carbon to produce active substances, thereby promoting the deep oxidation of chlorobenzene. Therefore, "PMS + unmodified activated carbon" has almost no removal effect on chlorobenzene.

[0083] Comparative Example 4 In this comparative example, PMS was used alone to treat pollutants in the flue gas from steel sintering. This comparative example used the same method as Example 3 to treat the pollutants in the flue gas from steel sintering.

[0084] In this comparative example, the effect of using PMS alone to remove chlorobenzene is as follows: Figure 3 As shown.

[0085] pass Figure 2 As can be seen, PMS had no effect on removing chlorobenzene in this comparative example because it was not activated to produce active substances.

[0086] Comparative Example 5 This comparative example uses the same method as Example 3 for the removal of pollutants from sintering flue gas in steelmaking. The difference is that a modified activated coke catalyst supported on cerium is used to activate and catalyze PMS in this comparative example. The modified activated coke catalyst in this comparative example is labeled as 10Ce-AC(C).

[0087] In this comparative example, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 4 As shown.

[0088] pass Figure 4 It can be seen that the removal rate of p-chlorobenzene in this comparative example basically decreased to 0 within three hours of reaction. Therefore, it can be concluded that it is difficult to activate PMS in the liquid phase to form active species for degrading chlorobenzene by using rare earth element cerium (Ce) modified activated coke catalyst.

[0089] Comparative Example 6 This comparative example uses the same method as Example 3 for the removal of pollutants from sintering flue gas in steelmaking. The difference is that a modified activated coke catalyst loaded with molybdenum is used to activate and catalyze PMS in this comparative example. The modified activated coke catalyst in this comparative example is labeled as 10Mo-AC(C).

[0090] In this comparative example, the effect of catalytic activation of PMS by modified catalyst in removing chlorobenzene is as follows: Figure 4 As shown.

[0091] pass Figure 4 It can be seen that the removal rate of p-chlorobenzene in this comparative example basically decreased to 0 within three hours of reaction. Therefore, it can be concluded that it is difficult to activate PMS in the liquid phase to form active species for degrading chlorobenzene using molybdenum-modified activated coke catalyst.

[0092] Comparative Example 7 This comparative example uses the same method as Example 3 to remove pollutants from sintering flue gas in steelmaking. The difference is that a Co3O4 catalyst is used to activate and catalyze PMS in this comparative example. The catalyst in this comparative example is labeled as D-Co3O4.

[0093] In this comparative example, the effect of PMS removal of chlorobenzene by catalytic activation with Co3O4 catalyst is as follows: Figure 5 As shown.

[0094] pass Figure 5It can be seen that the removal rate of p-chlorobenzene in this comparative example is significantly lower than that in Example 5. This is because D-Co3O4 failed to efficiently activate PMS to generate more active substances to oxidize chlorobenzene, and the catalyst began to deactivate to some extent as the reaction time increased.

[0095] Comparative Example 8 This comparative example uses the same method as Example 3 to remove pollutants from sintering flue gas in steelmaking. The difference is that in this comparative example, C and Co3O4 composite nanoparticles are used as a catalyst to activate PMS. The catalyst in this comparative example is labeled as C-Co3O4.

[0096] In this comparative example, the effect of PMS catalytic activation by C and Co3O4 composite nanoparticle catalyst on the removal of chlorobenzene and the CO2 yield during the removal process are as follows: Figure 6 As shown.

[0097] pass Figure 6 It can be seen that although the chlorobenzene removal rate in this comparative example is similar to that in Example 5 of the present invention, the CO2 yield in this comparative example is significantly lower than that in Example 5 of the present invention within the first 2 hours. This indicates that more CO2 is generated during the removal process of the present invention, resulting in fewer intermediate products. Furthermore, no intermediate products were detected in the exhaust gas of the present invention. The Co-modified activated char has higher adsorption performance for chlorobenzene and can catalyze and activate more PMS within the first 2 hours, promoting the deep oxidation of chlorobenzene and thus promoting CO2 generation. Therefore, the present invention still has a better removal effect.

[0098] Comparative Example 9 This comparative example uses the catalysts from Examples 1, 4, 6, and 8 to catalytically activate PMS and treat iron and steel sintering flue gas with a toluene content of 470 ± 10 ppm. The treatment results are as follows: Figure 7 As shown.

[0099] pass Figure 7 It can be seen that the present invention can maintain a relatively high level of treatment effect on high concentrations of toluene. This is mainly because both chlorobenzene and toluene are VOCs containing benzene rings, and toluene, because it does not contain chlorine atoms, is less likely to cause chlorine poisoning of the catalyst. The prepared 10Co-AC(I) can efficiently activate PMS to generate more active substances to oxidize toluene.

[0100] Comparative Example 10 This comparative example uses the catalyst from Example 5 to catalytically activate PMS for Hg. 0 The content is 100±3 ug / m 3 The sintering flue gas of steel was treated, and the treatment results were as follows: Figure 8 As shown.

[0101] pass Figure 8 It can be seen that the present invention is effective against Hg. 0 The treatment effect was good, basically maintained at 100%. The prepared 10Co-AC(I) can efficiently activate PMS to generate more active substances to oxidize heavy metal Hg. 0 Transformed into easily controllable Hg 2 .

[0102] Comparative Example 11 This comparative example uses the catalyst from Example 5 to catalytically activate PMS for simultaneous treatment of steel sintering flue gas. The treatment results are as follows: Figure 9 As shown.

[0103] pass Figure 9 It can be seen that the present invention has a good comprehensive removal rate of pollutants in steel sintering flue gas. In normal production process, the pollutants in steel sintering flue gas are usually mixed rather than single. Therefore, the present invention has excellent treatment effect on steel sintering flue gas.

[0104] In summary, the examples listed above are merely illustrative of the embodiments of the present invention and are not intended to limit the implementation of the invention. For those skilled in the art, various modifications, equivalent substitutions, and even further improvements can be made without departing from the technical solution of the present invention. All such modifications within the principles of the present invention fall within the scope of protection of the claims.

Claims

1. A method for treating pollutants from sintering flue gas in iron and steel production, characterized in that: The processing method includes the following steps: S1: Add a certain amount of persulfate to the reactor and adjust the molar mass concentration of the persulfate aqueous solution. After the persulfate and water are mixed evenly, add a cobalt-loaded modified activated coke catalyst to activate the persulfate and degrade the pollutants in the flue gas from steel sintering. S2: Adjust the volumetric flow rate of the sintering flue gas of steel with a stable concentration per unit time, and introduce the sintering flue gas of steel into the reactor from the bottom of the reactor; The modified activated coke catalyst in step S1 is prepared through the following steps: (1) Take activated coke, wash and dry it, and then grind and screen it using a ball mill to obtain activated coke particles as a carrier; (2) Dissolve cobalt nitrate hexahydrate in deionized water and mix it uniformly by ultrasonication to obtain an aqueous solution of cobalt nitrate; (3) The activated coke particles obtained in step (1) are impregnated in the cobalt nitrate aqueous solution obtained in step (2) and stirred evenly. Then the mixture is ultrasonically impregnated and the impregnated activated coke particles are left to stand in a container for a period of time. (4) The activated coke particles that have been left to stand in step (3) are placed in an oven to dry, and then calcined in a tube furnace under a nitrogen atmosphere.

2. The method for treating pollutants from sintering flue gas in iron and steel production according to claim 1, characterized in that: In step (1), the activated coke is washed with ultrapure water and ethanol, and the drying temperature is 60~110 ℃. The particle size of the activated coke is 60~80 mesh.

3. The method for treating pollutants from sintering flue gas in iron and steel production according to claim 1, characterized in that: In step (2), the molar volume concentration of the cobalt nitrate aqueous solution is 0.23 mol / L to 2.83 mol / L.

4. The method for treating pollutants from sintering flue gas in iron and steel production according to claim 1, characterized in that: In step (3), the stirring time is 1~6 min, the ultrasonic impregnation time is 1~3 h, and the standing time is 12~24 h.

5. The method for treating pollutants from sintering flue gas in iron and steel production according to claim 1, characterized in that: In step (4), the drying temperature is 60~110 ℃, the drying time is 6~24 h, the calcination temperature is 400~600 ℃, and the calcination time is 5~7 h.

6. The method for treating pollutants from sintering flue gas in iron and steel production according to claim 1, characterized in that: In step S1, the mass fraction of cobalt supported on the modified activated coke catalyst is 2-20%.

7. The method for treating pollutants from sintering flue gas in iron and steel production according to claim 1, characterized in that: In step S1, the concentration of persulfate is 5-20 mM / L, and the amount of modified activated coke catalyst added is 1.6-8.1% of the mass of persulfate.

8. The method for treating pollutants from sintering flue gas in iron and steel production according to claim 1, characterized in that: In step S2, the volumetric flow rate of the sintering flue gas in steelmaking per unit time is 0.4 to 0.7 times the volume of the persulfate reaction liquid.

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