A system and method for preparing iron-carbon materials using iron-rich municipal sludge

Abstract

This invention relates to the field of iron-carbon material preparation technology, specifically to a system and method for preparing iron-carbon materials using iron-rich municipal sludge. One method for preparing iron-carbon materials using iron-rich municipal sludge includes: pretreatment: drying and pulverizing the iron-rich municipal sludge to obtain pretreated sludge; iron-carbon material preparation: carbonizing the pretreated sludge using anoxic exhaust gas from a cement kiln tail to obtain iron-carbon materials. This invention couples iron-rich municipal sludge with anoxic exhaust gas from a cement kiln tail, solving the heat source supply problem in the traditional biomass and iron source preparation of iron-carbon materials. No additional heat source is required, nor is an external iron source needed, offline treatment, or secondary activation. The resulting iron-carbon material exhibits excellent catalytic degradation performance in the degradation of organic wastewater pollutants.

Description

Technical Field

[0001] This invention relates to the field of iron-carbon material preparation technology, and specifically to a system and method for preparing iron-carbon materials using iron-rich municipal sludge. Background Technology

[0002] Iron-carbon materials are materials obtained by uniformly loading zero-valent iron onto the surface of activated carbon. They have a high iron content and very small particle size, which results in a large number of active sites and excellent catalytic effect, making them suitable as catalysts for the catalytic treatment of wastewater.

[0003] Traditional iron-carbon materials are prepared using pure zero-valent iron and high-quality activated carbon as raw materials. However, in recent years, a process technology has emerged that utilizes organic biomass to produce biochar as a substitute for activated carbon. This process involves preparing iron-carbon materials from biomass, sludge, and other carbon-containing organic solid waste with iron sources such as elemental iron, magnetite, ferric oxide, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, and ferrous sulfide. While this reduces production costs to some extent, it still requires an external iron source and secondary activation of the biochar. This not only necessitates a separate high-humidity, oxygen-deficient activation environment (such as CO2 or water vapor) and additional heat consumption, but also requires offline processing of the primary activated material before secondary activation. The process is cumbersome, has low productivity, and the final iron-carbon material exhibits poor catalytic degradation performance. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of existing iron-carbon material preparation processes, which require offline processing and secondary activation, and the resulting iron-carbon materials have poor catalytic degradation performance. Thus, the present invention provides a system and method for preparing iron-carbon materials using iron-rich municipal sludge.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing iron-carbon materials using iron-rich municipal sewage sludge includes:

[0007] Pretreatment: The iron-rich municipal sludge is dried and crushed to obtain pretreated sludge;

[0008] Iron-carbon material preparation: Iron-carbon materials are prepared by carbonizing pretreated sludge using oxygen-deficient waste gas from cement kiln tail.

[0009] Preferably, the iron-rich municipal sludge is sludge that has undergone dewatering and sedimentation treatment using iron salt flocculants;

[0010] And / or, the mass percentage of iron in the iron-rich municipal sludge is 45-47%;

[0011] And / or, the temperature of the oxygen-deficient waste gas at the tail of the cement kiln is 450-1000℃, preferably 550-800℃.

[0012] Preferably, the moisture content of the iron-rich municipal sludge is reduced to below 30% after drying; preferably, the iron-rich municipal sludge is dried using the oxygen-deficient exhaust gas from the cement kiln tail after carbonization of the pretreated sludge.

[0013] And / or, the particle size of the iron-rich municipal sludge after crushing is 200-800 mesh;

[0014] And / or, the volume percentage of oxygen in the oxygen-deficient waste gas at the tail of the cement kiln is less than 10%.

[0015] Preferably, the pretreated sludge is carbonized in a vertical pneumatic bed; the pneumatic bed has a three-section carbonization chamber, which is divided into a first section, a second section, and a third section from top to bottom; the pretreated sludge is fed from top to bottom, and the oxygen-deficient exhaust gas from the cement kiln tail is fed from bottom to top;

[0016] Preferably, during the carbonization process, the pretreated sludge with small particle size is blown to the first stage by the oxygen-deficient exhaust gas at the tail of the cement kiln, while the pretreated sludge with large particle size sinks to the third stage.

[0017] And / or, after the pretreated sludge is carbonized, the small-particle-size pretreated sludge is carried by the oxygen-deficient exhaust gas at the tail of the cement kiln to a cyclone separator for separation, while the large-particle-size pretreated sludge is discharged from the bottom slag discharger.

[0018] Preferably, based on 500g of iron-rich municipal sludge, the amount of oxygen-deficient waste gas used at the cement kiln tail is 0.3-0.4m³. 3 ;

[0019] And / or, the flow velocity of the oxygen-deficient waste gas at the tail of the cement kiln in the third section is 0.5-1 m / s.

[0020] Preferably, the carbonization time is 45-85 minutes;

[0021] And / or, the carbonization is carried out simultaneously with activation. The iron element in the iron-rich municipal sludge of the present invention can act as an activator.

[0022] The present invention also provides a system for preparing iron-carbon materials using iron-rich municipal sludge, comprising a dryer, a pulverizer, a feeder and a pneumatic bed connected in sequence;

[0023] The pneumatic bed is connected to the oxygen-deficient waste gas outlet at the tail of the cement kiln.

[0024] Preferably, the pneumatic bed is a vertical structure with a carbonization chamber inside. The carbonization chamber is a three-section structure that is interconnected, and the three sections are, from top to bottom, the first section, the second section, and the third section.

[0025] Preferably, the second segment has a uniformly expanded diameter structure, with its large diameter end connected to the bottom of the first segment and its small diameter end connected to the top of the third segment.

[0026] And / or, a filter plate is provided at the lower part of the third section, and an air duct is provided at the bottom end of the third section, with the other end of the air duct connected to the oxygen-deficient exhaust gas outlet of the cement kiln tail; a bottom slag discharger is provided above the filter plate, with one end of the bottom slag discharger connected to the third section and the other end of the bottom slag discharger extending outward to the pneumatic bed; the function of the filter plate is to: allow oxygen-deficient exhaust gas to pass through, so as to ensure the fluidization, carbonization, and activation of iron-rich municipal sludge in the pneumatic bed; to uniformly distribute the oxygen-deficient exhaust gas, so as to improve the dispersion uniformity of the oxygen-deficient exhaust gas in the third section; and to play a good role in intercepting and supporting large-diameter solid particles in the third section.

[0027] And / or, a cyclone separator connected to the first segment is provided near the top.

[0028] Preferably, both the bottom slag discharger and the cyclone separator are connected to the product storage silo;

[0029] And / or, the bottom slag discharger is a slag discharge pipe that is inclined toward its bottom relative to the third section;

[0030] And / or, the ratio of the inner diameter of the first segment to the inner diameter of the third segment is (1.5-2):1.

[0031] In this invention, because the inner diameter of the first section is larger than that of the third section, the wind speed of the oxygen-deficient exhaust gas at the kiln tail in the first section is lower than that in the third section. This causes small solid particles to be blown to the first section, while large solid particles remain in the third section. The temperature of the oxygen-deficient exhaust gas at the kiln tail in the third section is higher, which can ensure better carbonization and activation of large solid particles. After carbonization and activation are completed, the oxygen-deficient exhaust gas at the kiln tail blows the small solid particles to the cyclone separator for gas-solid separation. After the small solid particles are discharged, the outlet of the first section is closed, and the valve of the bottom slag discharger is opened. The oxygen-deficient exhaust gas at the kiln tail carries the large solid particles out through the bottom slag discharger.

[0032] In this invention, in order to prevent the oxygen-deficient exhaust gas from the cement kiln tail from having too great an impact on the outside world, the flow rate of the oxygen-deficient exhaust gas from the cement kiln tail is reduced when large-diameter solid particles are discharged.

[0033] In this invention, during the pyrolysis of iron-rich municipal sludge, the iron element acts as a catalyst, contributing to improved pore structure and specific surface area of ​​the material. During pyrolysis, iron acts as a catalyst, promoting the pyrolysis reaction and influencing the microstructure and pore distribution of the material to a certain extent. First, iron catalyzes the pyrolysis of organic matter, helping to increase the porosity of the products. This is because iron promotes the decomposition of organic matter into smaller molecules, which can escape through gasification during pyrolysis, forming more pores. Second, at high temperatures, iron can form iron oxides in different valence states. These iron oxides can undergo reduction reactions during pyrolysis, deoxidizing and combining with carbon to generate gaseous oxides, further increasing the specific surface area of ​​the material.

[0034] The technical solution of this invention has the following advantages:

[0035] 1. A method for preparing iron-carbon materials using iron-rich municipal sludge, comprising: pretreatment: drying and pulverizing the iron-rich municipal sludge to obtain pretreated sludge; iron-carbon material preparation: carbonizing the pretreated sludge using anoxic exhaust gas from a cement kiln tail to prepare iron-carbon materials. This invention couples iron-rich municipal sludge with anoxic exhaust gas from a cement kiln tail, solving the heat source supply problem in the traditional biomass and iron source preparation of iron-carbon materials. No additional heat source is required, nor is an external iron source needed, offline treatment, or secondary activation. Furthermore, the final iron-carbon material exhibits excellent catalytic degradation performance in the degradation of organic wastewater pollutants.

[0036] 2. The present invention provides a method for preparing iron-carbon materials from iron-rich municipal sludge. The heat flow in the process conforms to energy cascade utilization. After carbonization of the iron-rich municipal sludge, the residual heat from the anoxic exhaust gas at the cement kiln tail can still be used for sludge drying. Furthermore, the anoxic exhaust gas from the cement kiln tail after carbonization of the iron-rich municipal sludge contains combustible organic matter, which can be fed back into the cement kiln pre-decomposition furnace for heat replenishment, thus improving energy utilization. The present invention utilizes pyrolysis to convert iron-rich municipal sludge into iron-carbon materials with certain economic value, while also avoiding the environmental risks associated with sludge treatment and disposal.

[0037] 3. The method of preparing iron-carbon materials using iron-rich municipal sludge of the present invention uses the oxygen-deficient exhaust gas from the tail of the cement kiln as both a low-oxygen gas source and a heat source, which can meet the activation conditions and punching requirements during the carbonization process. Thus, it is not necessary to create an additional high-humidity and oxygen-deficient environment for activation, thereby reducing energy consumption to a certain extent.

[0038] 4. The method of preparing iron-carbon materials using iron-rich municipal sludge of the present invention utilizes transition metals (such as Fe, Cu, Ni, etc.) present in iron-rich municipal sludge to enhance the activity of iron-carbon materials in activating persulfate and enhancing their ability to degrade organic wastewater. Furthermore, the iron element within the iron-rich municipal sludge exhibits enhanced catalytic effects under high-temperature pyrolysis conditions. This is because the Fe2O3 component in the iron-rich municipal sludge can react with organic components such as biochar in the sludge to generate pyrolysis products (CO, CO2, H2, CH4, etc.), thus promoting the conversion of biochar. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a connection sequence diagram of the system devices in embodiments 1-3 of the present invention;

[0041] Figure 2 This is a schematic diagram of part of the structure (pneumatic bed and rotary feeder) of the system in embodiments 1-3 of the present invention;

[0042] Figure 3 This is a process flow diagram of the system in Embodiments 1-3 of the present invention;

[0043] Figure 4 This is the XRD pattern of the iron-rich municipal sludge in Example 1 of the present invention after carbonization and activation in an air-driven bed at 650°C;

[0044] Figure 5 This is a thermogravimetric analysis (TGA) of iron-rich municipal sludge in Embodiment 1 of the present invention at 50-1000℃;

[0045] Figure 6 This is an electron microscope image of the iron-rich municipal sludge in Example 1 of the present invention after carbonization at 600°C;

[0046] Figure 7 These are infrared transmission images of the iron-carbon materials in Examples 1-3 and Comparative Example 1 of the present invention;

[0047] Figure 8 These are test results of the catalytic degradation performance of the iron-carbon materials prepared in Example 1 and Comparative Example 1;

[0048] 1-Dryer, 2-Pulverizer, 3-Raw material storage bin, 4-Feeder, 5-Pneumatic bed; 6-Oxygen-deficient exhaust gas pipeline, 7-Cyclone separator, 8-Bottom slag discharger, 9-Product storage bin, 10-Mixing and feeding motor. Detailed Implementation

[0049] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0050] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0051] Example 1

[0052] This embodiment provides a system for preparing iron-carbon materials using iron-rich municipal sludge, comprising a dryer, a pulverizer, a feeder, and a pneumatic bed connected in sequence; the connection sequence of the system used in this embodiment is as follows: Figure 1 As shown, the structure of the pneumatic bed and feeder in the system is as follows: Figure 2 As shown, the pneumatic bed has a vertical structure with a carbonization chamber inside. The carbonization chamber is a three-section structure that is interconnected. From top to bottom, the three sections are the first section, the second section, and the third section. The second section is a uniformly expanded diameter structure, with its large diameter end connected to the bottom of the first section and its small diameter end connected to the top of the third section. A filter plate is installed at the bottom of the third section, and an air duct is installed at the bottom end of the third section. The other end of the air duct is connected to the oxygen-deficient exhaust gas outlet of the cement kiln tail. A bottom slag discharger is installed above the filter plate. One end of the bottom slag discharger is connected to the third section, and the other end of the bottom slag discharger extends outward from the pneumatic bed. A cyclone separator is installed near the top of the first section and is connected to it. Both the bottom slag discharger and the cyclone separator are connected to the product storage bin. The bottom slag discharger is a slag discharge pipe that is inclined towards the bottom of the third section. The inner diameter ratio of the first section to the third section is 1.7:1. The industrial analysis parameters, elemental analysis parameters, XRF analysis parameters, and ICP heavy metal test parameters of iron-rich municipal sludge powder are shown in Table 1.

[0053] Table 1

[0054]

[0055] This embodiment uses the aforementioned system for preparing iron-carbon materials from iron-rich municipal sludge to prepare iron-carbon materials. The process flow is as follows: Figure 3As shown, the specific process includes: a pretreatment section for iron-rich municipal sludge and a carbonization section for oxygen-deficient waste gas at the tail of a cement kiln; wherein, the pretreatment section for iron-rich municipal sludge is as follows: the iron-rich municipal sludge obtained from the sewage treatment plant first enters the dryer 1 for drying and dehydration treatment, and the dried iron-rich municipal sludge enters the pulverizer 2 for pulverization and grinding treatment. The pulverized iron-rich municipal sludge reaches the carbonization conditions and is placed in the raw material storage silo 3 for storage.

[0056] The carbonization and activation section of the cement kiln tail anoxic exhaust gas is as follows: the iron-rich municipal sludge, after being crushed and treated in the raw material storage silo 3, is added into the pneumatic bed 5 through the rotary feeder 4 to participate in the carbonization and activation process. The heat source and atmosphere of the pneumatic bed 5 are transported through the cement kiln tail anoxic exhaust gas pipeline 6. After the iron-rich municipal sludge is carbonized and activated in the pneumatic bed 5 by the cement kiln tail anoxic exhaust gas, small iron-carbon materials are collected by the cyclone separator 7, and larger iron-carbon materials are collected by the bottom slag discharger 8. Finally, they are all placed in the product storage silo 9 for storage.

[0057] In this embodiment, the iron-rich municipal sludge obtained from the wastewater treatment plant is first dried and dewatered to reduce the moisture content to below 30%. Then, the iron-rich municipal sludge is pulverized to achieve a particle size between 200 and 800 mesh. The treated iron-rich municipal sludge powder meets the carbonization requirements and is stored in a dry storage silo to avoid a humid environment. In the anoxic waste gas carbonization activation section at the cement kiln tail, the iron-rich municipal sludge is added via a feeder with stirring (500g of iron-rich municipal sludge powder is mixed with 0.32m³ of feed). 3 (Gas-source carbonization) In the third stage, the flow velocity of the anoxic waste gas from the cement kiln tail is 0.76 m / s, preventing the accumulation of powdery sludge. The sludge then enters the pneumatic bed to participate in the carbonization and activation process. Anoxic waste gas (600℃; oxygen content less than 10%) is transported from the cement kiln tail through a pipeline. Under the high-temperature anoxic atmosphere in the pneumatic bed, the iron-rich municipal sludge undergoes carbonization (carbonization takes only 20 minutes at 600℃ due to its small particle size and rapid heat exchange) and activation (45 minutes). Small iron-carbon particles are collected by a cyclone separator, while larger particles are collected by a bottom slag discharger. Finally, the sludge is stored in a product storage silo. The XRD pattern of the iron-rich municipal sludge after carbonization and activation in the pneumatic bed at 600℃ is shown below. Figure 4 As shown, the thermogravimetric analysis (TGA) of the iron-rich municipal sludge at 50-1000℃ is as follows. Figure 5 As shown in the figure, the electron microscope image of the iron-rich municipal sludge after carbonization at 600℃ is as follows. Figure 6 As shown, the infrared transmission image of iron-rich municipal sludge after carbonization at 600℃ is as follows. Figure 7 As shown.

[0058] according to Figure 4Analysis revealed that the Fe in the iron-rich municipal sludge after carbonization and activation was in the forms of Fe(II) and FeO. This is because the reducing substances (CO, H2, CH4) produced during the carbonization and activation process may react with the Fe2O3 contained in the iron-rich sludge to form low-valent iron species. Although some Fe2O3 phase was present, this is because the iron-rich municipal sludge was cooled in air after carbonization and activation before testing, during which some low-valent iron was oxidized to Fe2O3.

[0059] according to Figure 5 Analysis revealed that in the first and second stages, the iron-rich municipal sludge experienced significant weight loss between the dehydration and organic matter volatilization phases, with the organic matter completely volatilizing before the temperature reached 511℃. Although the samples were dried before the TG experiment, significant changes in water loss still occurred. The results indicate that the moisture content of iron-rich municipal sludge comprises not only external moisture but also interstitial water and compound-bound water within the large molecules of the iron-rich sludge. The pyrolysis process of iron-rich municipal sludge in the second and third stages is relatively complex. When the temperature reaches approximately 200℃, the iron-rich municipal sludge (SS) begins to decompose into coke, tar, moisture, and complex light hydrocarbon gases. Simultaneously, with increasing temperature, a series of cross-interactions occur among the pyrolysis-related products, such as initial tar cracking, steam gasification, and methane reforming. In the intermediate stage, the bonds of heat-resistant organic compounds are broken and fractured. Later stages involve secondary pyrolysis, carbonization, and degradation of structurally stable organic components. Importantly, the presence of endogenous Fe2O3 promotes high-temperature catalytic pyrolysis. Fe2O3 can catalyze tar cracking, generating more reducing gases. When the temperature exceeds 700℃, entering the third stage, inorganic and recombinant minerals decompose, including reducing gases from the pyrolysis of iron-rich municipal sludge (SS) reacting with iron-containing compounds. In a reducing atmosphere, this may lead to the reduction of Fe2O3 and Fe3O4 to FeO, resulting in mass loss. As the reaction temperature increases, sulfur in SS may be released as gas (SO2) at approximately 750℃. Due to the rapid heating rate in the TG experiment, thermal hysteresis may exist; therefore, sulfur content may be released as SO2 at around 800-850℃.

[0060] according to Figure 6 Analysis shows that the biochar produced after carbonization of iron-rich municipal sludge is porous and loose. This is due to the pore structure or voids created by the gasification and escape of endogenous organic matter. In addition, the presence of Fe results in the observation of many C-Fe particles on the surface of the sludge biochar; these particles are iron or iron oxide.

[0061] according to Figure 7 Analysis shows that 3430cm -1 The peak value at 1630 cm⁻¹ is related to the OH group. -1The peak value at 1043 cm⁻¹ is caused by vibrations at C=O. -1 The peak at 460 cm⁻¹ is considered to be the stretching of the C-OH group. -1 The peak value at that point represents the Fe-O vibration.

[0062] Example 2

[0063] The difference between this embodiment and Embodiment 1 is that 500g of iron-rich municipal sludge powder is mixed with 0.3m 3 For gas source carbonization, the flow velocity of the oxygen-deficient waste gas at the tail of the cement kiln in the third section is 0.72 m / s, the temperature of the oxygen-deficient waste gas at the tail of the cement kiln is 800℃, the carbonization time is 15 min, the activation time is 30 min, and other conditions are the same as in Example 1.

[0064] Example 3

[0065] The difference between this embodiment and Embodiment 1 is that 500g of iron-rich municipal sludge powder is carbonized with 0.4m3 of gas source, the flow velocity of the anoxic waste gas at the tail of the cement kiln in the third section is 0.95m / s, the temperature of the anoxic waste gas at the tail of the cement kiln is 550℃, the carbonization time is 25min, the activation time is 60min, and other conditions are the same as in Embodiment 1.

[0066] Comparative Example 1

[0067] This comparative example provides a method for preparing iron-carbon materials, comprising the following steps:

[0068] 1) Place ordinary municipal sludge in an electric heating drying oven and dry it at a constant temperature of 105℃ for 24 hours;

[0069] 2) Cool the dried sludge from step 1) to room temperature, then grind it in a mortar until it has a particle size of 2-3 mm;

[0070] 3) Weigh out the ordinary municipal sludge and nano zero-valent iron ground in step 2) at a mass ratio of 500:1, place them in a crucible, mix and stir evenly, and then put them into a muffle furnace for calcination. During the calcination process, the temperature is raised to 600℃ at a rate of 6℃ / min, and then calcined at 600℃ for 60min. After calcination, cool to room temperature, and put the product obtained by pyrolysis into a grinder to grind into powder to obtain iron-carbon material.

[0071] Test Example 1

[0072] The catalytic degradation performance of the iron-carbon materials in Example 1 and Comparative Example 1 was tested under the following conditions:

[0073] 1) Preparation of COD simulated water: Dissolve suitable organic matter (e.g., glucose) in deionized water to obtain simulated organic wastewater with 5 ppm COD. For the accurate concentration of COD, it can be corrected using COD measurement methods (photometry).

[0074] 2) Degradation experiment: The iron-carbon materials of Example 1 and Comparative Example 1 were added to the prepared COD simulated water, respectively. Under normal circumstances, an appropriate ratio can be selected (e.g., 1g iron-carbon material / 1L simulated water), and then the reaction was carried out at the same temperature, time and pH value.

[0075] 3) COD determination: After the reaction is completed, the COD concentration in the simulated water needs to be determined using standard COD determination methods (such as secondary oxidation method or photometric method).

[0076] Test results are as follows Figure 8 As shown, compared with the iron-carbon material prepared in Comparative Example 1, the iron-carbon material prepared in Example 1 of this invention has a superior COD degradation effect.

[0077] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing iron-carbon materials using iron-rich municipal sewage sludge, characterized in that, include: Pretreatment: The iron-rich municipal sludge is dried and crushed to obtain pretreated sludge; Iron-carbon material preparation: Iron-carbon material is prepared by carbonizing pretreated sludge using anoxic exhaust gas from cement kiln tail; the temperature of the anoxic exhaust gas from cement kiln tail is 450-1000℃, and the volume percentage of oxygen in the anoxic exhaust gas from cement kiln tail is less than 10%; Based on a mass of 500 g of iron-rich municipal sludge, the amount of oxygen-deficient waste gas used at the cement kiln tail is 0.3-0.4 m³. 3 .

2. The method according to claim 1, characterized in that, The iron-rich municipal sludge is sludge that has been dewatered and settled using iron salt flocculant. And / or, the mass percentage of iron in the iron-rich municipal sludge is 45-47%; And / or, the temperature of the oxygen-deficient waste gas at the tail of the cement kiln is 550-800℃.

3. The method according to claim 1 or 2, characterized in that, The moisture content of the iron-rich municipal sludge is reduced to below 30% after drying; the iron-rich municipal sludge is dried using the oxygen-deficient exhaust gas from the cement kiln tail after carbonization of the pretreated sludge. And / or, the particle size of the iron-rich municipal sludge after crushing is 200-800 mesh.

4. The method according to claim 1 or 2, characterized in that, The pretreated sludge is carbonized in a vertical pneumatic bed; the pneumatic bed has a three-section carbonization chamber, which is divided into a first section, a second section and a third section from top to bottom; The pretreated sludge is fed from top to bottom, and the oxygen-deficient exhaust gas from the cement kiln tail is fed from bottom to top; During the carbonization process, the pretreated sludge with small particle size is blown to the first stage by the oxygen-deficient exhaust gas at the tail of the cement kiln, while the pretreated sludge with large particle size sinks to the third stage. And / or, after the pretreated sludge is carbonized, the small-particle-size pretreated sludge is carried by the oxygen-deficient exhaust gas at the tail of the cement kiln to a cyclone separator for separation, while the large-particle-size pretreated sludge is discharged from the bottom slag discharger.

5. The method according to claim 1 or 2, characterized in that, And / or, the flow velocity of the oxygen-deficient waste gas at the tail of the cement kiln in the third section is 0.5-1 m / s.

6. The method according to claim 1 or 2, characterized in that, The carbonization time is 45-85 minutes.

7. A system for preparing iron-carbon materials using iron-rich municipal sewage sludge, characterized in that, It includes a dryer, a crusher, a feeder, and a pneumatic bed connected in sequence; The pneumatic bed is connected to the oxygen-deficient waste gas outlet at the tail of the cement kiln.

8. The system according to claim 7, characterized in that, The pneumatic bed has a vertical structure and a carbonization chamber inside. The carbonization chamber is a three-section structure that is interconnected. The three sections are, from top to bottom, the first section, the second section, and the third section.

9. The system according to claim 8, characterized in that, The second section is a uniformly expanded diameter structure, with its large diameter end connected to the bottom of the first section and its small diameter end connected to the top of the third section. And / or, a filter plate is provided at the lower part of the third section, and an air duct is provided at the bottom end of the third section, with the other end of the air duct connected to the oxygen-deficient exhaust gas outlet of the cement kiln tail; a bottom slag discharger is provided above the filter plate, with one end of the bottom slag discharger connected to the third section, and the other end of the bottom slag discharger extending outward to form an air bed. And / or, a cyclone separator connected to the first segment is provided near the top.

10. The system according to claim 9, characterized in that, Both the bottom slag discharger and the cyclone separator are connected to the product storage silo; And / or, the bottom slag discharger is a slag discharge pipe that is inclined toward its bottom relative to the third section; And / or, the ratio of the inner diameter of the first segment to the inner diameter of the third segment is (1.5-2):1.

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