Fluidized bed suspension roasting system for preparing sulfidized zero-valent iron

Abstract

The application provides a fluidized bed suspension roasting system for preparing sulfidized zero-valent iron, which comprises a fluidized bed reaction device and a steam generating device, a gas supply device and a feeding device connected with the fluidized bed reaction device; the sulfidized zero-valent iron is obtained by modifying zero-valent iron powder in the fluidized bed reaction device by using steam generated by the steam generating device; and the zero-valent iron powder is in a suspended state under the joint action of steam and inert gas. Through the above mode, the sulfidized zero-valent iron which can be applied to the treatment of heavy metal wastewater, organic dye wastewater and the like is prepared by means of the advantages of the fluidized bed reactor, so that the zero-valent iron powder is modified efficiently and simply through sufficient contact between the sulfur steam and the zero-valent iron powder.

Description

Technical Field

[0001] This invention relates to the field of zero-valent iron sulfide preparation technology, and in particular to a fluidized bed suspension roasting system for preparing zero-valent iron sulfide. Background Technology

[0002] Zero-valent iron (ZVFe) is one of the most widely studied materials in the field of water environment remediation, but its practical application is limited by its tendency to agglomerate and oxidize, as well as its poor electron selectivity. To overcome these shortcomings, ZVFe can be sulfided to improve its dispersion, enhance its stability, and increase its electron selectivity. Existing methods for sulfidation modification of ZVFe include liquid-phase reduction, mechanical ball milling, and carbothermal reduction. However, these methods suffer from drawbacks such as expensive raw materials, high energy consumption during the preparation process, or demanding requirements for preparation equipment, making large-scale production difficult.

[0003] In the prior art, patent application number 202110211274.5, entitled "A Method for Preparing and Applying Zero-Valence Iron Sulfide," discloses a method for preparing zero-valent iron sulfide, comprising: 1) passing nitrogen gas through water to completely remove oxygen from the water, obtaining deoxygenated water; 2) adding zero-valent iron and a sulfur-containing reagent solution to an infusion bottle containing the deoxygenated water, and sealing it; 3) placing the sealed infusion bottle in a constant-temperature inverter, inverting it for a certain period of time beforehand, injecting a ferric salt solution into the infusion bottle, and continuing to invert it for a certain period of time; 4) filtering, freeze-drying, sieving, and collecting the product in a desiccator. This method is simpler to operate than the liquid-phase reduction method and does not use expensive chemical reagents, but it requires high-quality preparation conditions, is complex, and is difficult to scale up for production.

[0004] In addition, the invention patent application with application number 202010911917.2 entitled "A sulfide nano-zero valent iron and its preparation method and use" obtains sulfide zero valent iron by reducing a mixture of polysulfides and iron salt solutions with borohydride salt solution as a reducing agent. However, the above technical solution involves toxic borohydride salt solution and the preparation process is carried out in iron salt solution. The process of generating sulfide-modified zero valent iron is actually poorly controllable and therefore not suitable for green and efficient preparation of sulfide-modified zero valent iron.

[0005] In view of this, it is necessary to design an improved fluidized bed suspension roasting system for the preparation of zero-valent iron sulfide in order to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a fluidized bed suspension roasting system for preparing zero-valent iron sulfide.

[0007] To achieve the above-mentioned objectives, the present invention provides a fluidized bed suspension roasting system for preparing zero-valent iron sulfide, the fluidized bed suspension roasting system comprising a fluidized bed reactor, a steam generator, and a gas supply device;

[0008] The fluidized bed reactor includes a reaction chamber, a fluidized bed reactor disposed inside the reaction chamber, and a temperature control component for regulating the temperature of the fluidized bed reactor. The steam generator and the gas supply device are both connected to the fluidized bed reactor.

[0009] The fluidized bed reactor is also equipped with a feeding device for adding materials to the fluidized bed reactor.

[0010] Preferably, the fluidized bed suspension roasting system further includes a first pipe disposed outside the reaction chamber, both ends of the first pipe being connected to the fluidized bed reactor; a tail gas treatment device and a tail gas recirculation device are connected to the first pipe, a third valve is provided between the tail gas treatment device and the first pipe, the third valve being used to control the opening and closing of the tail gas treatment device, and a fourth valve is provided between the tail gas recirculation device and the first pipe, the fourth valve being used to control the opening and closing of the tail gas recirculation device.

[0011] Preferably, the feeding device includes a feeding bin and a feeding pipe connected to the bottom of the feeding bin. The feeding pipe is connected to the fluidized bed reactor, and a first valve and a second valve are sequentially provided on the feeding pipe.

[0012] Preferably, the bottom of the fluidized bed reactor is provided with a porous baffle.

[0013] Preferably, a second pipe is provided between the gas supply device and the reaction chamber, and a fifth valve and a first flow meter are provided on the second pipe; a third pipe is provided between the steam generator and the reaction chamber, and a sixth valve and a second flow meter are provided on the third pipe.

[0014] Furthermore, the present invention also provides a method for preparing zero-valent iron sulfide using the fluidized bed suspension roasting system, comprising the following steps:

[0015] S1. Turn on the temperature control component to heat the fluidized bed reactor to the preset temperature, and use the gas supply device to introduce inert gas into the fluidized bed reactor to discharge air.

[0016] S2. Place elemental sulfur powder into a steam generator, evacuate the vacuum, turn on the steam generator, and heat up to evaporate the elemental sulfur powder to form sulfur vapor.

[0017] S3. Zero-valent iron powder is added to the fluidized bed reactor through a feeding device. During the feeding process, inert gas is continuously introduced into the fluidized bed reactor, and the zero-valent iron powder is kept in a suspended state in the fluidized bed reactor by adjusting the inert gas flow rate.

[0018] S4. Sulfur vapor is introduced into the fluidized bed reactor, and an inert gas is introduced into the fluidized bed reactor at the same time. The sulfur vapor comes into contact with the zero-valent iron powder in the fluidized bed reactor to achieve the modification of the zero-valent iron powder by the sulfur vapor.

[0019] S5. After the reaction is complete, stop the flow of sulfur vapor and continue to flow the inert gas to remove excess sulfur vapor. The temperature control component stops operating. After the system temperature drops to room temperature, remove the zero-valent iron sulfide from the reaction chamber.

[0020] Preferably, in step S3, the particle size of the zero-valent iron powder is 5-100 μm, and the mass ratio of sulfur vapor to zero-valent iron powder introduced into the fluidized bed reactor is 1:20-1:2; in step S1, the preset temperature is 350-600℃; preferably, in step S5, the preset time is 2-20 min.

[0021] Preferably, in step S4, the total amount of gas in the fluidized bed reactor needs to be kept constant by controlling the total amount of the inert gas and the sulfur vapor.

[0022] Furthermore, the zero-valent iron sulfide prepared using the preparation method proposed in this invention can be used for dye degradation.

[0023] Specifically, the zero-valent iron sulfide prepared by the method of the present invention has an irregular shape and an overall core-shell structure. The outer layer of the zero-valent iron sulfide is composed of Fe. 1-x S, where x = 0 - 0.2.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention provides a fluidized bed suspension roasting system for preparing zero-valent iron sulfide. The fluidized bed suspension roasting system includes a fluidized bed reactor and a steam generator, a gas supply device, and a feeding device connected to the fluidized bed reactor. Zero-valent iron sulfide is obtained by modifying zero-valent iron powder in the fluidized bed reactor using steam generated by the steam generator. The zero-valent iron powder is in a suspended state under the combined action of steam and inert gas. Through this method, the advantages of the fluidized bed reactor itself can be utilized to ensure sufficient contact between sulfur vapor and zero-valent iron powder, efficiently and simply modifying the zero-valent iron powder, effectively overcoming the shortcomings of existing technologies in preparing zero-valent iron sulfide, such as harsh preparation conditions and poor controllability.

[0026] 2. The fluidized bed suspension roasting system provided by this invention, when used to prepare zero-valent iron sulfide, utilizes sulfur vapor to modify zero-valent iron powder in a suspended state, which can achieve modification while maintaining the surface morphology of zero-valent iron powder to the maximum extent. Secondly, the preparation method proposed in this invention can precisely control the degree of modification of zero-valent iron powder by adjusting the parameter conditions of the modification process (mass of sulfur vapor and zero-valent iron powder, temperature, and reaction time) to obtain zero-valent iron sulfide with better performance and more suitable for application. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the fluidized bed suspension calcination system provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is a SEM image of zero-valent iron sulfide obtained in Example 2 of the present invention;

[0029] Figure 3 SEM image of unmodified zero-valent iron powder;

[0030] Figure 4 SEM image of zero-valent iron sulfide prepared with excess sulfur vapor;

[0031] Figure 5 EDX plot of zero-valent iron sulfide prepared in Example 2 of the present invention and elemental content test results at corresponding positions;

[0032] Figure 6 EDX diagram of zero-valent iron sulfide prepared by excess sulfur vapor according to the present invention and the elemental content test results at the corresponding positions;

[0033] Figure 7 The diagram shows the degradation effect of zero-valent iron sulfide on methyl orange obtained in Examples 1 to 5 of the present invention.

[0034] The attached figures are labeled as follows:

[0035] 10. Fluidized bed reactor; 101. Control panel; 11. Fluidized bed reactor; 111. Porous baffle; 12. Feeding device; 121. First valve; 122. Second valve; 13. Temperature control component; 14. First pipeline; 141. Third valve; 142. Fourth valve; 20. Steam generator; 201. Third pipeline; 202. Sixth valve; 203. Second flow meter; 30. Gas supply device; 301. Second pipeline; 302. Fifth valve; 303. First flow meter. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0038] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] Please see Figure 1 As shown, this invention provides a fluidized bed suspension roasting system for preparing zero-valent iron sulfide. The system utilizes sulfur vapor generated in the fluidized bed suspension roasting system to modify zero-valent iron powder, thereby producing zero-valent iron sulfide. The fluidized bed suspension roasting system includes a fluidized bed reactor 10 and a steam generator 20 connected to the fluidized bed reactor 10, a tail gas circulation device, a tail gas treatment device, and a gas supply device 30 for introducing inert gas into the fluidized bed reactor 10. Under the combined action of the inert gas and steam, the zero-valent iron powder introduced into the fluidized bed reactor 10 is ensured to remain in a suspended state, facilitating contact between the sulfur vapor generated in the steam generator 20 and the zero-valent iron powder, thus achieving modification of the zero-valent iron powder.

[0040] Specifically, the fluidized bed reactor 10 includes a reaction chamber, a fluidized bed reactor 11 disposed inside the reaction chamber, and a temperature control component 13 for regulating the temperature of the fluidized bed reactor 11. The temperature control component 13 is equipped with a thermocouple or other device that can provide heat to provide energy for the reaction in the fluidized bed reactor 11. A porous baffle 111 is also provided at the bottom of the fluidized bed reactor 11. Further, the reaction chamber is provided with a feeding device 12 for adding zero-valent iron powder to the fluidized bed reactor 11. The feeding device 12 includes a feeding bin and a feeding pipe connected to the bottom of the feeding bin. The feeding pipe is connected to the reaction chamber through a sealing flange. A first valve 121 and a second valve 122 are sequentially provided on the feeding pipe. The arrangement of the first valve 121 and the second valve 122 facilitates the control of the connection state of the above-mentioned pipe. In some other embodiments, the fluidized bed suspension roasting system is also provided with a control panel 101 for controlling the working state of the fluidized bed reactor 10.

[0041] Furthermore, the exhaust gas recirculation device (not shown in the figure) and the exhaust gas treatment device (not shown in the figure) are used to treat the exhaust gas generated in the fluidized bed reactor 11. Specifically, a first pipe 14 is provided outside the reaction chamber, and both ends of the first pipe 14 are connected to the fluidized bed reactor 11. The exhaust gas recirculation device and the exhaust gas treatment device are connected in sequence on the first pipe 14. A third valve 141 is provided between the exhaust gas recirculation device and the first pipe 14. The third valve 141 is used to control the opening and closing of the exhaust gas treatment device. A fourth valve 142 is provided between the exhaust gas treatment device and the first pipe 14. The fourth valve 142 is used to control the opening and closing of the exhaust gas treatment device. In particular, in some embodiments, the first pipe 14 is also provided with an exhaust port (not shown in the figure) so as to exhaust the first pipe 14 intermittently to avoid safety accidents. With the above settings, during use, by closing the fourth valve 142 and opening the third valve 141, the exhaust gas treatment device can be connected to the reaction chamber, and the switch of the exhaust gas treatment device can be turned on to put it into operation, so as to purify the exhaust gas from inside the reaction chamber and avoid the gas generated during the operation of the system from polluting the environment. In addition, when it is necessary to recycle the exhaust gas in the reaction chamber, by closing the third valve 141 and opening the fourth valve 142, the exhaust gas recycling device can be connected to the reaction chamber, so that the exhaust gas from the reaction chamber can be treated by the exhaust gas recycling device and reintroduced into the fluidized bed reactor 11 of the reaction chamber.

[0042] More specifically, both the gas supply device 30 and the steam generator 20 are connected to the reaction chamber via flanges. A second pipe 301 is provided between the gas supply device 30 and the reaction chamber. A fifth valve 302 is provided on the second pipe 301 to control the connection between the gas supply device 30 and the reaction chamber. To facilitate precise control of the amount and flow rate of gas entering the reaction chamber, a first flow meter 303 is also provided on the second pipe 301. A third pipe 201 is provided between the steam generator 20 and the reaction chamber. A sixth valve 202 is provided on the third pipe 201 to control the connection between the reaction chamber and the steam generator 20. In particular, a second flow meter 203 is also provided on the third pipe 201 to control the amount and flow rate of steam entering the reaction chamber. In this way, when it is necessary to introduce gas and steam into the fluidized bed reactor 11, the gas and steam flow rate can be adjusted by the first flow meter 303 and the second flow meter 203. Under the action of gas and steam, the zero-valent iron powder in the fluidized bed reactor 11 is always in a suspended state, so that the sulfur vapor can fully contact the zero-valent iron powder to obtain sulfided zero-valent iron.

[0043] In particular, the present invention also provides a method for preparing zero-valent iron sulfide using the above-mentioned fluidized bed suspension roasting system, which specifically includes the following steps:

[0044] S1. Turn on the temperature control component 13 to heat the fluidized bed reactor 11 to the preset temperature; open the fifth valve 302 and the third valve 141 to introduce inert gas into the fluidized bed reactor 11 and discharge air.

[0045] S2. Place a certain amount of elemental sulfur powder into the steam generator 20, evacuate the vacuum, turn on the steam generator 20, and heat up to evaporate the elemental sulfur powder to form sulfur vapor.

[0046] S3. Open the first valve 121 and the second valve 122 to add zero-valent iron powder into the fluidized bed reactor 11 through the feeding bin. After all the zero-valent iron powder has passed through the second valve 122, close the first valve 121 and the second valve 122 and continuously introduce inert gas into the fluidized bed reactor 11. Adjust the inert gas flow rate through the first flow meter 303 to keep the zero-valent iron powder in a suspended state in the fluidized bed reactor 11.

[0047] S4. Close the fifth valve 302, open the sixth valve 202 and the fourth valve 142, and introduce sulfur vapor into the fluidized bed reactor 11. At the same time, inert gas is introduced into the fluidized bed reactor 11. The sulfur vapor and zero-valent iron powder come into contact in the fluidized bed reactor 11, realizing the modification of zero-valent iron powder by sulfur vapor. Throughout the process, the total amount of inert gas and sulfur vapor is controlled by the first flow meter 303 and the second flow meter 203 to keep the total amount of gas in the fluidized bed reactor 11 basically constant.

[0048] S5. After the reaction is complete, close the sixth valve 202 and the fourth valve 142, open the third valve 141, stop the flow of sulfur vapor, continue to flow inert gas to discharge excess sulfur vapor, and stop the operation of the temperature control component 13. After the system temperature drops to room temperature, remove the feeding device 12 and take out the modified zero-valent iron sulfide from the reaction chamber.

[0049] Preferably, in step S1, the preset temperature is 350-600℃.

[0050] Preferably, in step S3, the particle size of the zero-valent iron powder is 5-100 μm, and the mass ratio of sulfur vapor to zero-valent iron powder introduced into the fluidized bed reactor 11 is 1:20-1:2. It should be noted that the mass of sulfur vapor here can be calculated based on the gas flow rate and reaction time displayed on the second flow meter 203.

[0051] Preferably, in step S5, the preset time is 2-20 minutes.

[0052] Preferably, the inert gas used in the above process is one or more of the following inert gases: argon, nitrogen, helium, neon, krypton, xenon, and radon.

[0053] Preferably, the zero-valent iron sulfide has an irregular shape and an overall core-shell structure, with the outer layer composed of Fe. 1-x S, where x = 0-0.2, the core structure is mainly composed of Fe. 0 It contains a small amount of sulfur, and the sulfur content is lower closer to the core. The zero-valent iron sulfide prepared by this invention can be applied to the treatment of heavy metal wastewater, organic dye wastewater and other fields.

[0054] The fluidized bed suspension roasting system for preparing zero-valent iron sulfide according to the present invention will be further described below with reference to specific embodiments:

[0055] Example 1

[0056] Please see Figure 1 As shown, this embodiment provides a fluidized bed suspension roasting system, including a fluidized bed reactor 10, a steam generator 20 connected to the fluidized bed reactor 10, a tail gas circulation device, a tail gas treatment device, and a control panel 101 for controlling the working state of the fluidized bed reactor 10. The fluidized bed reactor 10 is also connected to a gas supply device 30 for introducing inert gas into the fluidized bed reactor 10 and a feeding device 12 for adding materials to the fluidized bed reactor 10.

[0057] Specifically, the fluidized bed reactor 10 includes a reaction chamber, a fluidized bed reactor 11 disposed inside the reaction chamber, and a temperature control component 13 for regulating the temperature of the fluidized bed reactor 11. The fluidized bed reactor 11 is housed inside the fluidized bed reactor 11. The temperature control component 13 includes devices such as thermocouples that can provide heat to supply energy for the calcination reaction in the fluidized bed reactor 11. A porous baffle 111 is also provided at the bottom of the fluidized bed reactor 11. Further, the reaction chamber is equipped with a feeding device 12 for adding zero-valent iron powder to the fluidized bed reactor 11. The feeding device 12 includes a feeding bin and a feeding pipe connected to the bottom of the feeding bin. The feeding pipe is connected to the reaction chamber via a sealing flange. A first valve 121 and a second valve 122 are sequentially provided on the feeding pipe. The arrangement of the first valve 121 and the second valve 122 facilitates control of the connectivity of the aforementioned pipe.

[0058] Furthermore, the tail gas recirculation device and the tail gas treatment device are used to treat the tail gas generated in the fluidized bed reactor 11. Specifically, a first pipe 14 is provided outside the reaction chamber, and both ends of the first pipe 14 are connected to the fluidized bed reactor 11. The tail gas recirculation device and the tail gas treatment device are connected in sequence on the first pipe 14. A third valve 141 is provided between the tail gas recirculation device and the first pipe 14. The third valve 141 is used to control the opening and closing of the tail gas treatment device. A fourth valve 142 is provided between the tail gas treatment device and the first pipe 14. The fourth valve 142 is used to control the opening and closing of the tail gas treatment device. In particular, the first pipe 14 is also provided with an exhaust port so as to exhaust the first pipe 14 intermittently to prevent safety accidents.

[0059] Furthermore, both the gas supply device 30 and the steam generator 20 are connected to the reaction chamber via flanges. A second pipe 301 is provided between the gas supply device 30 and the reaction chamber. A fifth valve 302 is installed on the second pipe 301 to control the connection between the gas supply device 30 and the reaction chamber. To facilitate precise control of the amount and flow rate of gas entering the reaction chamber, a first flow meter 303 is also installed on the second pipe 301. A third pipe 201 is provided between the steam generator 20 and the reaction chamber. A sixth valve 202 is installed on the third pipe 201 to control the connection between the reaction chamber and the steam generator 20. In particular, a second flow meter 203 is also installed on the third pipe 201 to control the amount and flow rate of steam entering the reaction chamber. It should be noted that in this embodiment, the first flow meter 303 is a glass rotor flow meter, and the second flow meter 203 is a vortex flow meter. In other embodiments, other flow meters can be selected as needed, as long as they can achieve gas flow rate control.

[0060] Example 2

[0061] This embodiment uses the fluidized bed suspension roasting system provided in Example 1 to further prepare zero-valent iron sulfide. The preparation process includes the following steps:

[0062] S1. Turn on the temperature control component 13 to heat the fluidized bed reactor 11 to 450°C; open the fifth valve 302 and the third valve 141 to introduce inert gas into the fluidized bed reactor 11 and discharge air.

[0063] S2. Place 5g of elemental sulfur powder into the steam generator 20, evacuate the vacuum, turn on the steam generator 20, and heat up to evaporate the elemental sulfur powder to form sulfur vapor.

[0064] S3. Open the first valve 121 and the second valve 122, and add 10g of zero-valent iron powder to the fluidized bed reactor 11 through the feeding bin. After all the zero-valent iron powder has passed through the second valve 122, close the first valve 121 and the second valve 122, and continuously introduce inert gas into the fluidized bed reactor 11. Adjust the inert gas flow rate through the glass rotor flow meter to keep the zero-valent iron powder in a suspended state in the fluidized bed reactor 11.

[0065] S4. Close the fifth valve 302, open the sixth valve 202 and the fourth valve 142, and introduce sulfur vapor into the fluidized bed reactor 11. At the same time, inert gas is introduced into the fluidized bed reactor 11. The sulfur vapor and zero-valent iron powder come into contact in the fluidized bed reactor 11, realizing the modification of zero-valent iron powder by sulfur vapor. Throughout the process, the total amount of inert gas and sulfur vapor is controlled by glass rotor flowmeter and vortex flowmeter to keep the total amount of gas in the fluidized bed reactor 11 basically constant.

[0066] S5. After the reaction is complete, close the sixth valve 202 and the fourth valve 142, open the third valve 141, stop the flow of sulfur vapor, continue to flow inert gas to discharge excess sulfur vapor, and stop the temperature control component 13 from operating; after the system temperature drops to room temperature, remove the feeding device 12 and take out the modified zero-valent iron sulfide from the reaction chamber. In this embodiment, nitrogen is used as the inert gas; in other embodiments, other inert gases may be used, and this is not a limitation.

[0067] The SEM image of the zero-valent iron sulfide prepared in this embodiment is shown below. Figure 2 As shown, compare it with Figure 3 The SEM images of the unmodified zero-valent iron powder were compared, and the results showed that there were slight differences in the morphology of the edge and core of the sulfided zero-valent iron prepared in this embodiment. This is because during the modification process, the outer layer of zero-valent iron mainly came into contact with sulfur, and the interior of some iron particles was eroded.

[0068] Examples 3 to 5

[0069] The only difference between Examples 3 to 5 and Example 1 is that the mass ratio of sulfur vapor to zero-valent iron powder introduced into the fluidized bed reactor is different from that in Example 1. The other steps are basically the same and will not be repeated here. Table 1 shows the mass ratio of sulfur vapor to zero-valent iron powder in Examples 1 to 5 and the molar mass ratio of S and Fe in the zero-valent iron sulfide prepared under the corresponding conditions.

[0070] Table 1 Mass ratios of Examples 1 to 5

[0071]

[0072] To investigate the degradation effect of the zero-valent iron sulfide prepared in Examples 1 to 5 on dyes, methyl orange was used as the experimental subject to test the degradation properties of the zero-valent iron sulfide prepared in the examples. The degradation effect is shown in the figure below. Figure 7 As shown, the results indicate that the zero-valent iron sulfide prepared in Example 1 has the best performance. The study shows that the Fe on the surface of the zero-valent iron sulfide... 1-x The thickness of the S layer affects the electron transfer capability of the material, and the surface roughness affects the specific surface area of ​​the material. In other words, the degradation of zero-valent iron sulfide varies with different sulfur-iron mass ratios. In Example 2, with a sulfur-iron mass ratio of 1 / 4, zero-valent iron sulfide showed the best degradation effect on the dye. This may be because the zero-valent iron sulfide prepared under these conditions has a stronger electron transfer capability, a larger specific surface area, and the best overall performance.

[0073] Under the conditions of Examples 1-5, the present invention also investigated the structure of zero-valent iron sulfide obtained when sulfur vapor was in excess (i.e., the mass ratio of sulfur vapor to zero-valent iron powder was greater than 1:2). The SEM image of zero-valent iron sulfide obtained when the mass ratio of sulfur vapor to zero-valent iron powder was 2:1 is shown below. Figure 4 As shown, compare it with Figure 2 and Figure 3 Comparative analysis showed that when sulfur vapor was in excess, all iron particles were not only sulfided externally but also significantly corroded internally, exhibiting a marked change in morphology compared to the unsulfided zero-valent iron particles. The EDX image of the sulfided zero-valent iron obtained in Example 1 and the elemental content test results at corresponding positions are shown below. Figure 5 As shown, the EDS diagram and elemental content test results at corresponding positions of the zero-valent iron sulfide prepared when the mass ratio of sulfur vapor to zero-valent iron powder is 2:1 are as follows. Figure 6 As shown, this result further verifies that during the modification of zero-valent iron powder with sulfur vapor, the main process is the sulfidation of the outer layer of the zero-valent iron powder, and the sulfur content in the modified sulfidated zero-valent iron gradually increases from the center of the iron powder particles towards the edge. It should be noted that... Figure 5 and Figure 6 In the diagram, 1-3 all represent the locations of the measurement points, where... Figure 5 In the diagram, 1 represents the sulfidated zero-valent iron core, and 2 represents the sulfidated zero-valent iron edge or shell. Figure 6 In the diagram, 1 indicates the location where the zero-valent iron core is sulfided, 2 indicates the location where the core is not sulfided, and 3 indicates the location of the edge or shell.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing zero-valent iron sulfide using a fluidized bed suspension roasting system, characterized in that, Includes the following steps: S1. Turn on the temperature control component to heat the fluidized bed reactor to the preset temperature, and use the gas supply device to introduce inert gas into the fluidized bed reactor to discharge air. The preset temperature is 350-600℃. S2. Place elemental sulfur powder into a steam generator, evacuate the vacuum, turn on the steam generator, and heat up to evaporate the elemental sulfur powder to form sulfur vapor. S3. Zero-valent iron powder is added to the fluidized bed reactor through a feeding device. During the feeding process, inert gas is continuously introduced into the fluidized bed reactor. By adjusting the flow rate of the inert gas, the zero-valent iron powder is kept in a suspended state in the fluidized bed reactor. The particle size of the zero-valent iron powder is 5-100μm, and the mass ratio of sulfur vapor to zero-valent iron powder introduced into the fluidized bed reactor is 1:20-1:

2. S4. Sulfur vapor and inert gas are simultaneously introduced into the fluidized bed reactor. The sulfur vapor contacts the zero-valent iron powder in the fluidized bed reactor to modify the zero-valent iron powder. The reaction time is 2-20 minutes. In this step, the total amount of gas in the fluidized bed reactor needs to be maintained constant by controlling the total amount of gas in the inert gas and sulfur vapor. S5. After the reaction is complete, stop the flow of sulfur vapor and continue to flow the inert gas to remove excess sulfur vapor. The temperature control component stops operating. After the system temperature drops to room temperature, remove the zero-valent iron sulfide from the reaction chamber. The fluidized bed suspension roasting system includes a fluidized bed reactor, a steam generator, and a gas supply device; The fluidized bed reactor includes a reaction chamber, a fluidized bed reactor disposed inside the reaction chamber, and a temperature control component for regulating the temperature of the fluidized bed reactor. The steam generator and the gas supply device are both connected to the fluidized bed reactor. The fluidized bed suspension roasting system further includes a first pipe disposed outside the reaction chamber, both ends of which are connected to the fluidized bed reactor; a tail gas treatment device and a tail gas circulation device are connected to the first pipe, a third valve is provided between the tail gas treatment device and the first pipe, the third valve is used to control the opening and closing of the tail gas treatment device, and a fourth valve is provided between the tail gas circulation device and the first pipe, the fourth valve is used to control the opening and closing of the tail gas circulation device; the feeding device includes a feeding bin and a feeding pipe connected to the bottom of the feeding bin, the feeding pipe is connected to the fluidized bed reactor, and a first valve and a second valve are sequentially provided on the feeding pipe; a porous baffle is provided at the bottom of the fluidized bed reactor; A second pipe is provided between the gas supply device and the reaction chamber, and a fifth valve and a first flow meter are provided on the second pipe; a third pipe is provided between the steam generator and the reaction chamber, and a sixth valve and a second flow meter are provided on the third pipe; The fluidized bed reactor is also equipped with a feeding device for adding materials to the fluidized bed reactor.

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