Iron and steel plant sludge ore blending sintered material, sintered pellet and manufacturing method and application of sintered pellet

Abstract

The invention discloses a steel plant sludge ore blending sintered material, sintered pellets and a manufacturing method and application thereof. The iron and steel plant sludge ore blending sintering material comprises a sintering raw material, iron and steel sludge and an SCR catalyst, and the adding amounts of the iron and steel sludge and the SCR catalyst respectively account for 1-3% and 0.1-0.4% of the total mass of the sintering raw material; the iron and steel plant sludge ore blending sintered pellets are prepared from the raw materials containing the sintered material, and the sintering raw materials and the iron and steel sludge are subjected to primary balling treatment to obtain mixed pellets; and then carrying out secondary balling treatment on the SCR catalyst and the mixed spherical particles, so that the SCR catalyst is dispersed and wrapped on the surfaces of the mixed spherical particles. By adopting the technical scheme of the invention, the influence of S, N and other elements in the steel plant sludge on the discharge amount of sintering flue gas pollutants can be effectively avoided, the resource utilization of the waste SCR catalyst can be realized, and the treatment cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology for steel sludge solid waste, and in particular to a steel plant sludge blending and sintering material, sintering pellets, their manufacturing method and application. Background Technology

[0002] Besides the main ironmaking and steelmaking processes, the steel production process also includes auxiliary processes. These processes play an important role in production but also generate a large amount of sludge and solid waste. For example, acid-base neutralization sludge is generated during the treatment of acidic or alkaline wastewater, biological sludge is formed in the biological treatment units of the wastewater treatment system, and other types of sludge include iron oxide sludge and continuous casting sludge. The sludge from steel plants has a high iron and carbon content, possessing certain recycling value and representing a potential resource. With the increasingly stringent requirements of the "Solid Waste Environmental Pollution Prevention and Control Law" regarding the reduction, resource utilization, and harmless disposal of industrial solid waste, more and more steel companies are adopting a "solid waste reuse, solid waste not leaving the factory" model. This involves treating and utilizing solid waste generated within the steel plant's internal production processes, thus aligning with the concept of sustainable development.

[0003] Steelmaking sludge is itself a metal resource with a certain calorific value, making it a potentially usable material. Sintered ore has a high yield and is subsequently used in blast furnace smelting. It also exhibits high tolerance to harmful elements, giving it a significant advantage in treating sludge with complex compositions. Therefore, existing technologies have already explored the application of steelmaking sludge in the sintering process.

[0004] In the prior art, patent application number CN202210073627.4 discloses a process for using stainless steel pickling sludge as a raw material for iron concentrate sintering. The process involves drying and grinding the stainless steel pickling sludge, then mixing it with dried iron concentrate, finely crushed limestone powder and quicklime, and crushed sintering fuel. The mixture is then granulated with water and laid on a sintering machine trolley. The sintering fuel in the material undergoes combustion and reduction, heating and sintering the mixture. The high-temperature sintered material is discharged from the sintering machine, crushed, and screened. Sintered ore with a particle size greater than 5mm is cooled and used as blast furnace feed. This invention uses stainless steel pickling sludge as a raw material for iron concentrate sintering without affecting the product quality of the sintered ore or the quality of the molten iron. It yields sintered ore with stable chemical composition, good physical properties, and a certain degree of permeability, achieving efficient utilization of valuable elements in the stainless steel pickling sludge within the steel enterprise.

[0005] Patent application number CN201611026585.X discloses a method for treating sludge using a metallurgical sintering process. The method includes the following steps: (A) Sludge pretreatment step: dewatering the sludge; (B1) Removal of non-free water step: mixing and reacting quicklime with the dewatered sludge to obtain a sludge mixture; (C1) Batching step: mixing the obtained sludge mixture with other raw materials until homogeneous to obtain a sintering mixture; (D) Mixing and granulation step: passing the sintering mixture through a mixer for primary and secondary mixing to obtain a homogeneous sintering material; (E) Sintering step: placing the homogeneous sintering material into a sintering machine trolley for sintering. This invention utilizes the effective chemical components in urban sludge and iron and steel metallurgical dust for metallurgical sintering, achieving resource utilization.

[0006] Patent application CN201010502999.1 discloses a method for utilizing municipal sewage sludge as a raw material for sintering in the iron and steel industry, belonging to the technical field of harmless disposal and high-value-added utilization of municipal solid waste. The method involves mixing municipal sewage sludge with quicklime in a specific ratio, followed by drying and dehydration to obtain calcified sludge. This calcified sludge is then incorporated into sintering raw materials with adjusted compositions in a specific ratio and manner, and processed together with other sintering raw materials in the sintering process to ultimately produce sintered ore, which is used as a raw material for iron smelting. The advantages are: incorporating lime to calcify the municipal sewage sludge reduces sludge disposal costs and controls secondary pollution during sludge treatment; it achieves harmless treatment and resource utilization of sludge; the addition of calcified sludge effectively improves the vertical sintering speed, yield, and utilization coefficient during sintering, while also reducing the amount of flux and fuel added to the sintering raw materials, thus lowering raw material costs—a win-win situation.

[0007] The above-mentioned schemes all involve adding steel plant sludge to the ore blending and sintering process, thereby achieving the resource utilization of the sludge. However, steel plant sludge contains a relatively high amount of elements such as sulfur (S) and nitrogen (N), and existing studies have not considered the impact of these elements in the sludge. This leads to a significant increase in the emission concentrations of SO2 and NOx in the sintering flue gas when directly blending and sintering the ore, making it unsuitable for industrial-scale application. This is currently the main challenge limiting the resource utilization of steel plant sludge in ore blending and sintering.

[0008] Currently, sintering flue gas desulfurization technology is quite mature. Its main principle is to use adsorbents to absorb and capture SO2. When the SO2 concentration in the flue gas increases, the desulfurization efficiency can be improved by increasing the amount of adsorbent, resulting in relatively low emission reduction costs. However, the most mature technology for NOx emission reduction in sintering flue gas is selective catalytic reduction (SCR) denitrification technology. But this emission reduction technology has high investment and operating costs. The emission reduction system is designed with a limit on the NOx emission concentration. When the NOx emission concentration in the flue gas exceeds the design value, the emission reduction efficiency decreases, easily leading to the risk of NOx emission exceeding the standard.

[0009] SCR catalysts generally refer to catalysts used in SCR (selective catalytic reduction) denitrification systems in power plants. They are substances that promote the selective chemical reaction between the reducing agent and nitrogen oxides in the flue gas at a certain temperature during the SCR reaction. Currently, the most commonly used catalysts are the V₂O₅-WO₃(MoO₃) / TiO₂ series (with TiO₂ as the main support and V₂O₅ as the main active component). SCR catalysts are basically based on TiO₂, with V₂O₅ as the main active component, and WO₃ and MoO₃ as antioxidant and anti-poisoning auxiliary components.

[0010] In the prior art, patent application number CN202010209431.4 discloses a method for treating tail gas during sludge sintering using a Mn-based low-temperature SCR catalyst. The tail gas from the sludge sintering process is treated by selective catalytic reduction. The tail gas first passes through a dust collector for dust removal, then through a desulfurization system for desulfurization, and then enters a selective catalytic reduction reactor. The temperature of the tail gas entering the selective catalytic reduction reactor is below 200°C. The tail gas undergoes low-temperature selective catalytic reduction in the selective catalytic reduction reactor. At this time, the low-temperature selective catalytic reduction reaction is carried out in the presence of a catalyst, which includes an NH3 reducing agent and a MnEu / TiO2 catalyst.

[0011] In the existing steel sludge sintering process, the sintering flue gas has a high concentration of SO2 and NOx, which requires secondary treatment, resulting in high flue gas treatment costs.

[0012] Therefore, it is necessary to improve such a structure to overcome the aforementioned defects. Summary of the Invention

[0013] The purpose of this invention is to provide a steel plant sludge ore blending sintering material, sintering pellets, and their manufacturing method and application, which can solve the resource utilization of steel sludge in the sintering process and reduce flue gas treatment costs.

[0014] The above-mentioned technical objective of this invention has been achieved by the following technical solutions:

[0015] A steel plant sludge sintering feedstock includes sintering raw materials, steel sludge, and a catalyst. The catalyst is an SCR catalyst. The amount of steel sludge added accounts for 1-3% of the total mass of the sintering raw materials, and the amount of SCR catalyst added accounts for 0.1-0.4% of the total mass of the sintering raw materials.

[0016] A further provision of the present invention is that the sintering raw materials include iron ore powder, return ore, flux, and sintering fuel.

[0017] A further provision of the present invention is that the mass percentages of the sintering raw material components are as follows: 60% blended ore, 15-17% recycled ore, 5-6% sintering powder, 4.5-5% dolomite, 2.5-3% limestone, 1.5-2% external dust, and 3.5-4% coke powder.

[0018] A further feature of the present invention is that the particle size of the SCR catalyst is 0.9-1.1 mm, and the SCR catalyst is a waste SCR catalyst (i.e., a waste SCR catalyst).

[0019] A type of sintering pellet made from sludge from a steel plant, wherein the raw material for the sintering pellet includes any one of the sintering materials described in claims 1-4.

[0020] A further feature of the present invention is that the inner layer of the sintered sphere is a sphere formed by mixing sintering raw materials and steel sludge, and the outer surface of the sintered sphere is coated with waste SCR catalyst particles.

[0021] A method for producing sintering pellets from sludge from a steel plant includes the following steps:

[0022] A1: Raw material mixing: The sintering raw materials are mixed with steel sludge and subjected to a first pelletizing process to obtain sintering pellets;

[0023] A2: Mixing and molding, adding waste SCR catalyst to sinter pellets, so that the catalyst and sinter pellets come into contact and mix, and then performing a second pelletizing treatment to coat the surface of the sinter pellets with waste SCR catalyst.

[0024] A3: Sintering and shaping involves igniting and sintering the sintered material pellets coated on the surface to obtain shaped sintered ore.

[0025] A further provision of the present invention includes the following steps;

[0026] B1: During the first pelletizing process in step A1, water is continuously supplied for 6-8 minutes. The amount of water added during this period accounts for 7.3-7.7% of the total mass of the mixture.

[0027] B2: During the second pelletizing process in step A2, the sintered pellets are mixed with the waste SCR catalyst for 50-70 seconds.

[0028] A further provision of the present invention is the application of sintering pellets made from sludge from steel plants, which includes the following steps: during sintering, a layer of sintered return ore is first laid as a base material, and then sintering pellets are laid on the base material.

[0029] In summary, the present invention has the following beneficial effects:

[0030] (1) This invention makes full use of the properties of sludge itself and utilizes the NH3 released by sludge. By adding waste SCR catalyst to the sintering raw materials, the NH3 released during the sintering process can be catalyzed to reduce NOx, thereby achieving NOx emission reduction in the process, effectively relieving the pressure of end-of-pipe flue gas emission reduction, reducing flue gas treatment costs, and further improving the utilization rate of sludge ore blending and sintering in steel plants.

[0031] (2) The present invention preferably uses waste SCR catalyst to reuse the waste SCR catalyst, give full play to the catalytic effect of the waste SCR catalyst at high temperature, and reduce NOx emissions generated during the sintering process. However, the waste SCR catalyst belongs to HW50 hazardous waste, and the cost of treating it according to the standard disposal method is very high. By sintering the waste SCR catalyst with ore, the hazardous waste can be disposed of while reducing NOx emissions.

[0032] (3) The present invention further optimizes the pelletizing process of sintered pellets, that is, adopts a two-stage pelletizing process, adding waste SCR catalyst after mixing and granulating the sintering material, which avoids most of the waste SCR catalyst being wrapped in the pellets by the sintering material, thereby creating favorable conditions for the waste SCR catalyst to catalyze NOx emission reduction and further improving the efficiency of reducing flue gas pollutants in the sintering process. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the present invention. Detailed Implementation

[0034] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to the figures and specific embodiments.

[0035] like Figure 1 As shown, the present invention proposes a steel plant sludge sintering material, which includes sintering raw materials, steel sludge and catalyst, wherein the catalyst is an SCR catalyst.

[0036] The sintering raw materials include iron ore powder, sintering return ore, flux, and sintering fuel. The mass percentages of the sintering raw material components are as follows: blended ore 60%, return ore 15-17%, sintering powder 5-6%, dolomite 4.5-5%, limestone 2.5-3%, external dust 1.5-2%, and coke powder 3.5-4%. The above components are for illustrative purposes only. The types of iron ore powder, sintering return ore, flux, and sintering fuel are not limited, and existing types and compositions of sintering raw materials can be used directly.

[0037] The amount of steel sludge added accounts for 1-3% of the total mass of the sintering material, and the amount of SCR catalyst added accounts for 0.1-0.4% of the total sintering material. The SCR catalyst is waste SCR catalyst with a particle diameter of 0.9-1.1 mm.

[0038] The working principle of this application is as follows: During the sintering process, the contact temperature between NH3 released from the combustion of raw materials and NO is below 400℃. Under non-catalytic conditions, NH3 cannot react with NOx. Therefore, this invention proposes adding spent SCR catalyst to the sintering material to reduce NOx emissions during the sintering process by catalytically reducing NOx with NH3. The expression is as follows:

[0039]

[0040] Steel plant sludge contains high levels of nitrogen (N) and sulfur (S), leading to a significant increase in pollutant emissions from sintering flue gas and consequently increasing subsequent flue gas treatment costs. During pyrolysis experiments on steel plant sludge, this application found that at pyrolysis temperatures of 400-500℃, the sludge releases NH3 at a rate of 1.55 mg / g. -1 ;

[0041] In the SCR catalyst, TiO2 reacts with CaO in the sintering raw materials to form a perovskite structure, which increases the proportion of secondary hematite in the sinter phase, thereby reducing the RDI of the sinter. +3.15 Performance indicators. Therefore, the amount of waste SCR catalyst added must be precisely controlled. Preferably, the amount of SCR catalyst added is controlled to be 0.1-0.4% of the total mass of the sintering raw materials.

[0042] Preferably, the SCR catalyst is a spent SCR catalyst, which facilitates the recycling of the spent SCR catalyst and reduces production costs. More preferably, the spent SCR catalyst is crushed, which fully exposes the internal active sites, allowing NH3 and NOx to easily adsorb and contact the catalyst and undergo redox reactions at the active sites, thereby catalyzing the efficient reduction of NOx by NH3.

[0043] Finer catalyst particle size promotes NOx reduction, but it also accelerates the reaction of TiO2 with CaO in the sintering raw materials, forming a perovskite structure. Therefore, this invention optimizes and controls the catalyst particle size to effectively ensure NOx reduction while preventing excessive reaction of TiO2 with CaO to form a perovskite structure. Preferably, the particle diameter of the spent SCR catalyst is 0.9-1.1 mm.

[0044] In the sintering cup experiment, taking the addition of 2% steel sludge as an example, the theoretical release of NH3 during the sintering process was 49.5 mg·m³. -3 Based on the above, this application adds the waste SCR catalyst to the sintering raw materials. Under the catalysis of the waste SCR catalyst, the NH3 released by the sludge is used to catalyze the reduction of NOx emissions during the sintering process, thereby effectively reducing NOx emissions, reducing the risk of NOx emissions exceeding the standard during the sintering process with sludge addition, reducing the cost of flue gas treatment, and also achieving the harmless treatment of the waste SCR catalyst.

[0045] A type of sintering pellet made from sludge from a steel plant is described. The sintering raw material and steel sludge are used as the base raw material. The two raw materials are mixed and waste SCR catalyst particles are added to the raw material. The raw material with the added catalyst is then sintered to obtain sintering pellets. The inner layer of the sintering pellets is a mixture of sintering raw material and steel sludge pellets, and the waste SCR catalyst particles are wrapped around the outer surface of the mixed pellets.

[0046] A method for producing sintering pellets from sludge from a steel plant includes the following steps;

[0047] A1: Raw material mixing: The sintering raw materials are mixed with steel sludge and subjected to a first pelletizing process to obtain sintering pellets;

[0048] A2: Mixing and molding, adding waste SCR catalyst to sinter pellets, so that the catalyst and sinter pellets come into contact and mix, and then performing a second pelletizing treatment to coat the surface of the sinter pellets with waste SCR catalyst.

[0049] A3: Sintering and shaping involves igniting and sintering the sintered material pellets coated on the surface to obtain shaped sintered ore.

[0050] If a one-time pelletizing process is used, where waste SCR catalyst particles are directly mixed with steel sludge and sintering raw materials for pelletizing, the excellent pelletizing properties of the sintering raw materials will encapsulate the waste SCR catalyst inside the sintering pellets, severely hindering the contact between NH3 and NOx and the waste SCR catalyst, resulting in a reduced catalytic emission reduction effect. To address the above problem, this application adopts a two-time pelletizing process, which disperses and encapsulates the waste SCR catalyst on the surface of the sintering pellets, thereby ensuring sufficient contact between NH3 and NOx and the waste SCR catalyst.

[0051] The method for manufacturing sintered microspheres also includes the following steps;

[0052] B1: During the first pelletizing process in step A1, water is continuously supplied for 6-8 minutes. The amount of water added during this period accounts for 7.3-7.7% of the total mass of the mixture.

[0053] B2: During the second pelletizing process in step A2, the sintered pellets are mixed with the waste SCR catalyst for 50-70 seconds.

[0054] The application of sintering pellets made from sludge from a steel plant in the sintering process includes the following steps: in the sintering forming process of step A3, a layer of sintered return ore is first laid as the base material, and then the sintering pellets are laid on the base material.

[0055] Example 1

[0056] Step 1: Separate the spent SCR catalyst particles;

[0057] Expired SCR catalysts that have reached the end of their service life in industrial flue gas denitrification processes were obtained. These were V2O5-WO3 / TiO2 type honeycomb catalysts that needed replacement after 24,000 hours of operation due to deactivation. The spent catalyst consisted of two parts: a honeycomb catalyst body and metallurgical dust clogging the catalyst pores. Strong airflow was used to remove the dust clogging the catalyst pores. The remaining catalyst body was then crushed to obtain catalyst particles with a particle size of 0.9-1.1 mm.

[0058] Step 2: Mixing and granulating the sintering raw materials;

[0059] Sintering raw materials were prepared by mixing ore (62.7%), recycled ore (16%), sintering powder (5.8%), dolomite (4.8%), limestone (2.8%), quicklime (2.7%), external dust (1.7%), and coke powder (3.5%). In an external mixing manner, 2% by mass of steel plant sludge was added to the sintering raw materials and mixed with them in a cylindrical mixer for granulation. The first mixing time was 2 minutes, and the second mixing time was 7 minutes after adding water, with the moisture content of the mixture controlled at 7.5%. The chemical composition of the steel plant sludge in this embodiment is shown in Table 1 below.

[0060]

[0061] Step 3: Add spent SCR catalyst;

[0062] Continue to take 0.2% of the waste SCR catalyst particles by mass of the sintering raw material and pour them into the cylindrical mixer, and mix them with the sintering material pellets for 60 seconds.

[0063] Step 4: Ignition and sintering;

[0064] Two kg of sintered return ore with a particle size of 10-16 mm was laid at the bottom of the sintering cup as a base material, and then the mixture was loaded into the sintering cup. Ignition was carried out using liquefied petroleum gas at a temperature of 1100℃ and a negative pressure of 6 kPa for 1.5 minutes. Afterwards, the gas supply was turned off, and the negative pressure of the exhaust fan was adjusted to 15 kPa for evacuation sintering. The NOx emission concentration in the flue gas was recorded during the sintering process. The sintering time started from ignition and continued until the flue gas temperature reached its maximum value.

[0065] Step 5: Testing of sintered ore quality indicators and metallurgical properties

[0066] After sintering, the sintered ore is crushed and screened. The drum strength of the sintered ore is measured. According to the international standard ISO-3271-1975, 7.5 kg of sintered ore with three particle sizes of 25-40 mm, 16-25 mm, and 10-16 mm are weighed according to the weight ratio and placed into the drum. The drum is started and rotated 200 times. Then, the sintered ore is screened. The sintered ore is oscillated back and forth 20 times. The sintered ore after screening is taken out, and the weight of sintered ore with a particle size > 6.3 mm is weighed. The drum strength is obtained by dividing the mass of sintered ore with a particle size > 6.3 mm by the total weight of 7.5 kg.

[0067] According to the national standard GB / T13242-91, the low-temperature reduction pulverization performance (RDI+3.15) of sinter was tested. Samples with a certain particle size range (10–12.5 mm) were statically reduced in a fixed bed at 500℃ using a reducing gas composed of CO, CO2, and N2. After 60 min of constant-temperature reduction, the samples were cooled, placed in a rotating drum (Φ130×200 mm), rotated 300 times, and then removed. The samples were then classified using square-hole sieves of 6.3 mm, 3.15 mm, and 0.5 mm, and weighed. The mass percentage of each particle size was calculated, and the mass percentage of the particle size >3.15 mm was recorded as RDI. +3.15 , with RDI +3.15 The performance evaluation index for low-temperature reduction and pulverization of sintered ore.

[0068] Example 2

[0069] The basic process of this embodiment is the same as that of Embodiment 1, except that the proportion of waste SCR catalyst added in the mixture with the sintering pellets is 0.1%.

[0070] Example 3

[0071] The basic process of this embodiment is the same as that of embodiment 1, except that the proportion of waste SCR catalyst added in the mixture with the feed pellets is 0.4%.

[0072] Example 4

[0073] The basic process of this embodiment is the same as that of embodiment 1, except that the proportion of waste SCR catalyst added in the mixture with the sintering pellets is 0.5%.

[0074] Comparative Example 1

[0075] This comparative example serves as a baseline experiment. Its basic procedure is the same as that of Example 1, except that no steel plant sludge or waste SCR catalyst is added to the sintering raw materials. The sintering pellets are directly loaded into the sintering cup for sintering. The experimental results are shown in Table 2.

[0076] Comparative Example 2

[0077] This comparative example does not add waste SCR catalyst during the sintering of steel plant sludge. Its basic process is the same as in Example 1, except that the sintering raw materials are only mixed and granulated with steel plant sludge, without adding waste SCR catalyst, and the sintering pellets are directly loaded into the sintering cup for sintering.

[0078] Comparative Example 3

[0079] This comparative example uses a different method for adding spent SCR catalyst. Instead of granulating the sintered material first and then mixing the spent SCR catalyst, the spent SCR catalyst particles, steel plant sludge, and sintering raw materials together in a cylindrical mixer, the mixture is poured into a sintering cup for sintering.

[0080] Comparative Example 4

[0081] This comparative example uses spent SCR catalyst powder. The basic process is the same as in Example 1, except that the spent SCR catalyst bulk is crushed into powder with a particle size of less than 200 mesh. The sintering pellets are then mixed with the spent SCR catalyst powder. The mixture is poured into a sintering cup for sintering.

[0082] The metallurgical properties of sinter and the NOx emission concentration in flue gas under different experimental conditions are shown in the table below.

[0083]

[0084]

[0085] According to the data in the table, it can be seen that: (1) As can be seen from Comparative Example 1, when no sludge from steel plants is added to the iron ore sintering raw material, the NOx emission concentration in the flue gas is 235 mg·m³. -3 In Comparative Example 2, the addition of 2% steel plant sludge to the sintering raw materials increased the NOx emission concentration in the sintering flue gas to 279 mg·m³. -3 This indicates that adding steel plant sludge to the sintering raw materials will significantly increase the NOx emission concentration in the flue gas.

[0086] Compared to Example 1, in Comparative Example 2, when steel plant sludge was added to the sintering raw materials, by adding waste SCR catalyst to the sintering bed, the NH3 generated during the heating process of the steel plant sludge reacted with NO under the action of the waste SCR catalyst. Ultimately, the NOx emission concentration in the sintering flue gas of Example 1 was reduced to 220 mg·m³. -3 Therefore, it can be proven that the solution of the present invention can effectively utilize the reaction between NH3 and NOx generated during the heating process of sludge in steel plants, thereby achieving NOx emission reduction in sintering flue gas.

[0087] (2) Comparison of Example 3 and Example 1 shows that by optimizing the pelletizing process, specifically by employing a two-stage pelletizing process to coat the surface of the sintered pellets with the spent catalyst, the NOx emission reduction effect in the sintering flue gas can be effectively guaranteed. However, if the spent SCR catalyst is added before the sintering material is mixed and granulated, the NO emission concentration in the sintering flue gas increases to 263 mg·m³. -3 Its ability to reduce emissions of pollutants from flue gas is limited.

[0088] (3) Compared with Example 1, Comparative Example 4 used waste SCR catalyst with a particle size of less than 200 mesh, and the NOx emission concentration in the sintering flue gas was reduced to 216 mg·m³. -3 The results show that finer particle size of spent SCR catalyst leads to better NOx reduction. However, since the main component of spent SCR catalyst is TiO2, it can cause RDI of the sintered ore. +3.15 The performance is severely reduced, mainly because TiO2 reacts with CaO in the sintering raw materials to form a perovskite structure, which increases the proportion of secondary hematite in the sinter phase, thereby reducing the RDI of the sinter. +3.15 Performance metrics.

[0089] In summary, by utilizing the characteristic of NH3 release from steel plant sludge at high temperatures, adding waste SCR catalyst to sintering raw materials, and controlling the addition method, particle size, and proportion of the waste SCR catalyst, favorable conditions can be created for catalytic reduction of NO by NH3, while meeting the quality indicators and metallurgical performance requirements of sintered minerals. This will achieve emission reduction of flue gas pollutants during the sintering process and effectively alleviate the pressure of reducing emissions of end-of-pipe flue gas pollutants.

[0090] When excessive amounts of spent SCR catalyst are added, the spent SCR catalyst severely affects the RDI of sinter. +3.15 Performance indicators are crucial; therefore, the addition amount of spent SCR catalyst needs to be controlled within the range of 0.1-0.4%. If the particle size of the spent SCR catalyst is too small, although it can be more dispersed during sintering, which is beneficial for the catalytic reduction of NO by NH3, the TiO2 in the dispersed spent SCR catalyst powder will combine with CaO to form a perovskite structure, causing the low-temperature reduction pulverization index (RDI) of the sintered ore to decrease. +3.5The effect is significantly reduced. If the particle size of the spent SCR catalyst is too large, it is difficult for the large particles of spent SCR catalyst to be evenly distributed on the surface of the sintered pellets, thus limiting the catalytic effect of NH3 reducing NO. Therefore, the suitable particle size of spent SCR catalyst should be controlled between 0.9-1.1 mm, and the addition amount should be controlled between 0.1-0.4%.

[0091] This application has the following advantages compared with the prior art:

[0092] NOx emission reduction: By adding waste SCR catalyst to the sintering material, NOx is catalytically reduced by utilizing NH3 released during the pyrolysis of steel sludge, which significantly reduces the NOx emission concentration in sintering flue gas.

[0093] Resource utilization of spent SCR catalysts: This enables the recycling of spent SCR catalysts, reduces waste treatment costs, and decreases the demand for new catalysts.

[0094] Reduced flue gas treatment costs: Reduced NOx emissions during sintering lower the load and cost of subsequent flue gas treatment systems.

[0095] Improving the environmental friendliness of the sintering process: Reducing pollutant emissions during the sintering process and improving the environmental protection level of the steel production process.

[0096] The specific principle is as follows:

[0097] Catalytic reduction: Using spent SCR catalyst as a catalyst, the redox reaction between NH3 and NOx is promoted to generate harmless N2 and H2O, thereby reducing NOx emissions.

[0098] Promoting the utilization of steel sludge: By using steel sludge as part of the sintering raw material, not only is the resource utilization of waste realized, but also the NH3 released during the pyrolysis process is utilized, which further promotes the reduction of NOx emissions.

[0099] The specific application process is as follows: Sintering raw materials such as iron ore powder, sintering return ore, flux, and sintering fuel are mixed in a certain proportion; steel sludge is added to the sintering raw materials in a certain proportion (e.g., 1-3%); the waste SCR catalyst is crushed to obtain catalyst particles with a particle size of 0.9-1.1 mm; the sintering raw materials and steel sludge are mixed evenly and subjected to a first pelletizing process to obtain sintering pellets; waste SCR catalyst particles are added to the sintering pellets and subjected to a second pelletizing process to coat the surface of the sintering pellets; a layer of sintering return ore is laid at the bottom of the sintering equipment as a base material; the sintering pellets coated with waste SCR catalyst are laid on the base material; ignition and sintering are carried out, controlling the sintering temperature and the negative pressure of the exhaust until sintering is completed; after sintering, the sintered ore is crushed, screened, and tested, including indicators such as drum strength and low-temperature reduction pulverization performance; the NOx emission concentration in the flue gas during the sintering process is monitored to evaluate the emission reduction effect. Through the above process, NOx emissions in sintering flue gas can be effectively reduced while ensuring the quality and metallurgical performance of sintered ore, achieving a win-win situation for both environmental protection and economic benefits in the steel production process.

[0100] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. These terms are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connect" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0101] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A sintering material for steel plant sludge, characterized in that, It includes sintering raw materials, steel sludge, and catalysts. The catalyst used is an SCR catalyst. The amount of steel sludge added accounts for 1-3% of the total mass of the sintering raw materials, and the amount of SCR catalyst added accounts for 0.1-0.4% of the total mass of the sintering raw materials.

2. The sintering material for steel plant sludge as described in claim 1, characterized in that, Sintering raw materials include iron ore powder, recycled ore, flux, and sintering fuel.

3. The sintering material for steel plant sludge as described in claim 2, characterized in that, The mass percentages of the sintering raw material components are as follows: 60% blended ore, 15-17% recycled ore, 5-6% sintering powder, 4.5-5% dolomite, 2.5-3% limestone, 1.5-2% external dust, and 3.5-4% coke powder.

4. The sintering material for steel plant sludge as described in claim 1, characterized in that, The SCR catalyst has a particle size of 0.9-1.1 mm and uses spent SCR catalyst.

5. A type of sintering pellets made from sludge from a steel plant, characterized in that, The raw material for the sintered pellets includes the sintering material as described in any one of claims 1-4.

6. The steel plant sludge blending and sintering pellets according to claim 5, characterized in that, The inner layer of the sintered sphere is a sphere made of a mixture of sintering raw materials and steel sludge, and the outer surface of the sintered sphere is covered with waste SCR catalyst particles.

7. A method for producing sintered pellets from sludge from a steel plant, characterized in that, Includes the following steps: A1: Raw material mixing: The sintering raw materials are mixed with steel sludge and subjected to a first pelletizing process to obtain sintering pellets; A2: Mixing and molding, adding waste SCR catalyst to sinter pellets, so that the catalyst comes into contact with and mixes with the sinter pellets, and then performing a second pelletizing treatment to coat the surface of the sinter pellets with waste SCR catalyst. A3: Sintering and shaping involves igniting and sintering the sintered material pellets coated on the surface to obtain shaped sintered ore.

8. The method for producing sintered pellets of sludge from a steel plant according to claim 7, characterized in that, It also includes the following steps; B1: During the first pelletizing process in step A1, water is continuously supplied for 6-8 minutes. The amount of water added during this period accounts for 7.3-7.7% of the total mass of the mixture. B2: During the second pelletizing process in step A2, the sintered pellets are mixed with the waste SCR catalyst for 50-70 seconds.

9. The application of the steel plant sludge blending and sintering pellets according to claim 5 or claim 6, characterized in that, The process includes the following steps: during sintering, a layer of sintered return ore is first laid as the base material, and then sintered pellets are laid on the base material.

Images