Direct reduced iron and method for producing the same

Abstract

The application discloses direct reduced iron and a preparation method thereof, and relates to the technical field of metallurgical engineering. The by-product direct reduced iron (DRI) powder obtained through a rotary hearth furnace is directly used for preparing direct reduced iron, and part of iron-containing raw materials is replaced, so that the shortage of raw materials in the production of the rotary hearth furnace is effectively made up, additional purchase of raw materials is not needed, the procurement cost of raw materials is reduced, and the continuity and stability of the production of the rotary hearth furnace are improved. In addition, through reduction roasting of the rotary hearth furnace, deep reduction of iron in the DRI powder is realized, efficient recovery of iron metal in the DRI powder is realized, and valuable zinc elements in the DRI powder can also be recovered. In the application, the DRI powder with a certain particle size range is reused to the rotary hearth furnace, the raw materials are mixed and then formed into balls, a stable particle skeleton is formed, the structure of the dry-mixed material balls is compact after reduction, and the prepared DRI product has a reduced pulverization rate.

Description

Technical Field

[0001] This invention relates to the field of metallurgical engineering technology, and more specifically, to a direct reduced iron and its preparation method. Background Technology

[0002] Direct Reduced Iron (DRI) is a metallized iron product obtained by selectively reducing iron oxides in iron ore or iron-containing raw materials in a solid state using gaseous or solid reducing agents. It has a high metallization rate and features low phosphorus, low sulfur, and controllable impurity content, making it an important high-quality furnace charge for electric arc furnace steelmaking.

[0003] The mainstream industrial production process for DRI is the rotary hearth furnace direct reduction method. This process involves mixing iron-containing raw materials (such as iron ore powder, steel dust, etc.) with reducing agents and binders to form pellets, which are then roasted in a rotary hearth furnace to achieve deep reduction of iron and simultaneous removal of volatile elements such as zinc and lead.

[0004] However, during the actual operation of the rotary hearth furnace, the pulverization rate of DRI products remains high, affecting product quality. Furthermore, the small particle size of DRI powder makes it prone to pulverization, leading to incomplete reduction and causing dust pollution and equipment blockage within the furnace. Currently, the main methods for handling this are external sales or simple mixing and pelletizing. However, both of these methods result in a significant loss of iron from the DRI powder and waste of valuable zinc.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a direct reduced iron and its preparation method.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing direct reduced iron, comprising mixing direct reduced iron raw materials in a certain proportion and pressing them into pellets to obtain wet mixed pellets; drying the wet mixed pellets to obtain dry mixed pellets; and placing the dry mixed pellets in a rotary hearth furnace for reduction roasting.

[0008] The raw materials for direct reduced iron include iron-containing raw materials in a mass ratio of (60~97): (15~30): (2~6): (2~4), direct reduced iron powder, reducing agent, and binder.

[0009] The sources of direct reduced iron powder include: screening the direct reduced iron product obtained from a rotary hearth furnace to obtain direct reduced iron powder with a particle size of <3mm.

[0010] Secondly, the present invention provides a direct reduced iron, which is prepared by any of the methods described in the foregoing embodiments.

[0011] The present invention has the following beneficial effects: This invention provides a direct reduced iron (DRI) and its preparation method. By recycling DRI powder, a byproduct obtained from a rotary hearth furnace, into the production of DRI, it replaces part of the iron-containing raw materials, effectively filling the raw material gap in rotary hearth furnace production. This eliminates the need for additional raw material purchases, reducing raw material procurement costs and improving the continuity and stability of rotary hearth furnace production. Furthermore, the reduction roasting in the rotary hearth furnace achieves deep reduction of iron in the DRI powder, enabling efficient recovery of iron metal from the DRI powder, while also recovering valuable zinc from the DRI powder. This invention recycles DRI powder within a specific particle size range into the rotary hearth furnace. After mixing the raw materials, they are briquetting to form a stable particle skeleton. The dry-mixed briquettes have a dense structure after reduction, resulting in a reduced pulverization rate in the final DRI product. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0013] The inventors discovered that steel mills often face fluctuations and shortages in raw material supply during rotary hearth furnace production, leading to poor production continuity. Furthermore, traditional briquetting of iron-containing raw materials results in low-strength pellets due to the fine particle size and poor formability of the raw materials. These pellets are prone to pulverization after entering the furnace, reducing iron reduction efficiency, causing dust pollution and equipment blockage. Additionally, the high pulverization rate of DRI products negatively impacts product quality. Moreover, directly selling DRI powder or simply mixing it for pelletizing leads to significant loss of iron and zinc. Therefore, the inventors propose the following solution.

[0014] In a first aspect, the present invention provides a method for preparing direct reduced iron, comprising mixing direct reduced iron raw materials in a certain proportion and pressing them into pellets to obtain wet mixed pellets; drying the wet mixed pellets to obtain dry mixed pellets; and placing the dry mixed pellets in a rotary hearth furnace for reduction roasting.

[0015] The raw materials for direct reduced iron include iron-containing raw materials in a mass ratio of (60~97): (15~30): (2~6): (2~4), direct reduced iron powder, reducing agent, and binder.

[0016] The sources of direct reduced iron powder include: screening the direct reduced iron product obtained from a rotary hearth furnace to obtain direct reduced iron powder with a particle size of <3mm.

[0017] This invention uses DRI powder produced in the rotary hearth furnace as a feedstock to replace some iron-containing raw materials, effectively making up for the raw material shortage in rotary hearth furnace production. It eliminates the need for additional external raw material purchases, reduces raw material procurement costs, and improves the continuity and stability of rotary hearth furnace production.

[0018] Furthermore, DRI powder, due to its small particle size, is easily pulverized and its reduction in the rotary hearth furnace is insufficient, resulting in a high content of iron and zinc elements. This invention achieves efficient recovery of iron and zinc elements from DRI powder by returning it to the furnace for reuse, eliminating the need to sell DRI powder or simply prepare it into pellets. This avoids the loss of iron and zinc metals and improves resource utilization.

[0019] Furthermore, since the iron-containing raw materials have a fine particle size, the resulting pellets have low strength during pelletizing. This invention solves the technical problem of poor pelletizing properties and low strength of fine iron-containing raw materials by screening DRI powder with a suitable particle size, whose larger particle size serves as a natural skeleton for pelletizing, thereby increasing the 1M drop strength of carbon-containing pellets to more than 5 times. This also avoids the pellets from pulverizing and clogging the equipment after entering the furnace.

[0020] The addition of DRI powder results in a stable granular skeleton in the pellets during pelletizing, which increases the pellet strength. After reduction, the pellets have a dense structure, resulting in a lower pulverization rate, more uniform particle size, and higher metallization rate in the DRI products, thus enhancing the industrial application value of DRI products.

[0021] The method provided by this invention can solve the problem of insufficient raw materials in rotary hearth furnaces and improve production continuity. Simultaneously, it can efficiently recover valuable metals from DRI powder, improving resource utilization. Furthermore, DRI powder can enhance the strength of pellets formed through briquetting, reduce the pulverization rate during DRI product production, and lower the risk of pellet clogging the furnace after pulverization. This method is simple, highly compatible with existing rotary hearth furnace production processes in steel enterprises, requires no additional large-scale equipment, and is suitable for large-scale industrial application in steel companies. By co-processing two types of metallurgical solid waste—rotary hearth furnace DRI powder and iron-containing raw materials from steel enterprises—it achieves the reduction, resource recovery, and harmlessness of solid waste, reducing environmental pollution caused by solid waste stockpiling, and meeting the green, low-carbon, and circular development requirements of the modern steel industry.

[0022] In an optional embodiment, the present invention provides a method for preparing directly reduced iron, the specific steps of which are as follows: S01, Mixing The raw materials for direct reduced iron are mixed in a certain proportion to obtain a homogenized mixture.

[0023] The raw materials for direct reduced iron include iron-containing raw materials in a mass ratio of (60~97): (15~30): (2~6): (2~4), DRI powder, reducing agent, and binder.

[0024] The sources of DRI powder include: screening the direct reduced iron product obtained from a rotary hearth furnace to obtain DRI powder with a particle size of <3mm. DRI powder within this particle size range has good particle support and can be used as a skeleton for pelletizing, improving the strength of the pellets.

[0025] Preferably, the DRI powder is further humidified before mixing, and the moisture content of the DRI powder after humidification is 12~18 wt%. That is, after humidification, the moisture content of the DRI powder accounts for 12~18% of the total mass of the wet material.

[0026] Preferably, the DRI powder has a TFe content ≥ 50 wt% and a Zn content of 0.5~3.5 wt%.

[0027] Preferably, the iron-containing raw material is iron-containing dust and sludge with a small particle size, typically <100 mesh. The iron-containing raw material is selected from at least one of steelmaking sludge, blast furnace bag ash, and steelmaking LT ash.

[0028] Preferably, the reducing agent includes at least one of coking dust and pulverized coal.

[0029] Preferably, the reducing agent has a carbon content ≥70% (mass content) and a particle size <100 mesh, providing a sufficient carbon source for the reduction of iron.

[0030] Preferably, the binder includes at least one of starch-based organic binders and composite binders. Selecting the above-mentioned binder can improve the formability and pellet strength of the homogenized mixture.

[0031] Preferably, the parameters of the mixing process include: mixing speed of 150~200 r / min and mixing time of 10~15 min.

[0032] In an optional embodiment, the homogenized carbon content of the homogenized mixture is 9~11wt%; preferably 10±0.5wt%.

[0033] When there is a significant raw material shortage in the rotary hearth furnace, the mass percentage of DRI powder can be increased to 30%, while ensuring that the homogenized carbon content in the homogenized mixture is 9-11%. In this case, the proportion of iron-containing raw materials can be reduced accordingly to meet the raw material supply requirements of the rotary hearth furnace.

[0034] S02, Ball pressing molding The homogenized mixture provided in step S01 is pressed into balls to obtain wet-mixed balls.

[0035] In an optional embodiment, the particle size of the wet-mixed pellets is 15~32mm.

[0036] Preferably, the process parameters for briquetting include: briquetting machine pressure of 105~115 bar and briquetting temperature of 30~60℃.

[0037] Preferably, the briquetting process can be carried out using a double-roll briquetting machine, that is, the homogenized mixture provided in step S01 is fed into the double-roll briquetting machine, and the process parameters of the double-roll briquetting machine are controlled within the above range to obtain wet mixed briquettes of 15~32mm.

[0038] This invention utilizes the particle characteristics of DRI powder to form the molding skeleton of wet-mixed spheres, solving the problem of low sphere strength of fine iron-containing raw materials.

[0039] S03, drying The wet mixed pellets obtained in step S02 are dried to obtain dry mixed pellets.

[0040] Preferably, the drying process parameters include: drying temperature 110~320℃, drying time 20~35min.

[0041] Preferably, the drying can be carried out using a chain grate dryer, that is, the wet mixed balls obtained in step S02 are fed into the chain grate dryer, and the drying process parameters are controlled within the above range to obtain dry mixed balls.

[0042] In an optional implementation, the moisture content of the dry-mixed pellets is ≤2% to avoid cracking of the dry-mixed pellets due to moisture evaporation during reduction roasting.

[0043] Preferably, the drop strength of the dry-mixed pellets is ≥5 times (1m free fall to the steel plate), which meets the strength requirements for conveyor belt transfer into the furnace for feeding and reduction.

[0044] S04, Reduction Calcination The dry-mixed pellets obtained in step S03 are placed in a rotary hearth furnace for reduction roasting.

[0045] In an optional embodiment, reduction roasting includes sintering the dry-mixed pellets in a rotary hearth furnace, passing them sequentially through a heating zone, a reduction zone, and a cooling zone.

[0046] The roasting parameters in the heating zone include: roasting temperature of 1000~1150℃ and residence time of 3~5min. The dry-mixed pellets undergo preheating and temperature rise in the heating zone to remove residual moisture, while simultaneously achieving the initial pyrolysis of the reducing agent.

[0047] The calcination parameters in the reduction zone include: calcination temperature of 1150~1270℃ and residence time of 20~25min.

[0048] Preferably, the heat source for heating the reduction zone includes mixed gas or converter gas.

[0049] In the reduction zone, the dry-mixed pellets use mixed coal gas or converter gas as a heat source to achieve deep reduction of iron oxides in the homogenized mixture under a high-temperature reducing atmosphere, reducing FeO and Fe2O3 to metallic iron. At the same time, zinc in DRI powder and iron-containing raw materials volatilizes. Zinc enters the flue gas in the form of zinc oxide and is collected by the waste heat boiler and dust collector, realizing the resource recovery of zinc.

[0050] The calcination parameters in the cooling zone include: calcination temperature ≤1100℃, residence time 3~5min. The reduced dry-mix pellets are preliminarily cooled to prevent them from cracking upon direct cooling after being removed from the furnace at high temperatures.

[0051] Preferably, the thickness of the dry-mixed material balls in the rotary hearth furnace is 20~60mm.

[0052] Preferably, the rotation speed of the rotary hearth furnace is 30 min / revolution.

[0053] Preferably, the dry-mixed pellets are evenly distributed into the annular bottom of the rotary hearth furnace by a vibrating feeder to ensure uniform reaction during the reduction roasting process and stable product quality.

[0054] S05, DRI Product Collection The direct reduced iron (DRI) product obtained in step S04 is discharged from the rotary hearth furnace via a screw conveyor and cooled by a cylindrical cooler (internal or external cooling) to obtain the DRI product. This product can be used directly as a raw material for electric arc furnace steelmaking.

[0055] The zinc-containing flue gas generated by the rotary hearth furnace reduction roasting enters the waste heat boiler and bag filter dust collection system through the flue. The zinc powder in the flue gas is collected by the waste heat boiler and dust collector, realizing the resource recovery of zinc. The recovered flue gas is treated by the bag filter dust collection system to meet emission standards, realizing the comprehensive utilization of flue gas.

[0056] Secondly, the present invention provides a direct reduced iron, which is prepared by any of the methods described in the foregoing embodiments.

[0057] In an optional implementation, the metallization rate of direct reduced iron is ≥70%, and the dezincification rate is ≥85%.

[0058] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0059] Example 1 This embodiment provides a method for preparing direct reduced iron, including the following steps: S01, Mixing The direct reduced iron product obtained from the rotary hearth furnace was screened, and DRI powder with a particle size of <3mm was collected. The TFe content of the DRI powder was 55.96wt% and the Zn content was 3.01wt%.

[0060] The DRI powder is humidified, and the moisture content of the humidified DRI powder accounts for 15% of the total mass of the wet material.

[0061] By mass percentage, 55% steelmaking sludge, 17% blast furnace bag ash, 20% DRI powder, 5% coking dust and 3% starch-based organic binder are mixed at 180 r / min for 12 min to obtain a homogenized mixture. The homogenized carbon content in the homogenized mixture is 10.03 wt%.

[0062] The carbon content in steelmaking sludge is 2.54% by mass; the carbon content in blast furnace bag ash is 25.90% by mass; the carbon content in DRI powder is 2.43% by mass; and the carbon content in coking dust is 75% by mass, with a particle size of <100 mesh.

[0063] S02, Ball pressing molding The homogenized mixture provided in step S01 is fed into a double-roller briquetting machine. The process parameters of the double-roller briquetting machine are controlled as follows: briquetting machine pressure 110 bar, forming temperature 43℃ for briquetting to obtain wet mixed balls with a size of 15 mm * 25 mm * 32 mm.

[0064] S03, drying The wet mixed balls obtained in step S02 are fed into a chain grate dryer and dried at 280°C for 30 minutes to obtain dry mixed balls with a moisture content of 0.8% and a drop strength of 7 times.

[0065] S04, Reduction Calcination The dry mixed balls obtained in step S03 are evenly distributed into the annular bottom of the rotary hearth furnace using a vibrating material distributor. The material thickness is 30 mm, and the furnace bottom rotation speed is 30 min / revolution r / min.

[0066] The dry-mixed pellets are sintered in a rotary hearth furnace, passing sequentially through a heating zone, a reduction zone, and a cooling zone. The heating zone has a roasting temperature of 1000℃ and a residence time of 3 minutes; the reduction zone has a roasting temperature of 1250℃ and a residence time of 22 minutes, and is heated by mixed gas; the cooling zone has a roasting temperature of 1100℃ and a residence time of 3 minutes.

[0067] S05, DRI Product Collection The direct reduced iron (DRI) product obtained in step S04 is discharged from the rotary hearth furnace via a screw conveyor and cooled by a cylindrical cooler to obtain DRI balls. The zinc-containing flue gas generated during the reduction roasting in the rotary hearth furnace is treated with dust removal to recover zinc powder.

[0068] The DRI balls produced by the method provided in this embodiment have a compressive strength of 1350N, a metallization rate of 65.13%, a pulverization rate of 26.50%, and a dezincification rate of 85.15%, which effectively makes up for the 20% raw material shortage in the rotary hearth furnace and improves production continuity.

[0069] Example 2 This embodiment provides a method for preparing direct reduced iron, including the following steps: S01, Mixing The direct reduced iron product obtained from the rotary hearth furnace was screened, and DRI powder with a particle size of <3mm was collected. The TFe content of the DRI powder was 55.96wt% and the Zn content was 3.05wt%.

[0070] The DRI powder is humidified, and the moisture content of the humidified DRI powder accounts for 15% of the total mass of the wet material.

[0071] By mass percentage, 45% steelmaking sludge, 17% blast furnace bag ash, 30% DRI powder, 5% coking dust and 3% starch-based organic binder are mixed at 180 r / min for 12 min to obtain a homogenized mixture. The homogenized carbon content in the homogenized mixture is 10.02 wt%.

[0072] The carbon content in steelmaking sludge is 2.54% by mass; the carbon content in blast furnace bag ash is 25.90% by mass; the carbon content in DRI powder is 2.43% by mass; and the carbon content in coking dust is 75% by mass, with a particle size of ≤100 mesh.

[0073] S02, Ball pressing molding The homogenized mixture provided in step S01 is fed into a double-roller briquetting machine. The process parameters of the double-roller briquetting machine are controlled as follows: briquetting machine pressure 110 bar, forming temperature 60℃ for briquetting to obtain wet mixed balls with a size of 15 mm * 25 mm * 32 mm.

[0074] S03, drying The wet mixed balls obtained in step S02 are fed into a chain grate dryer and dried at 300°C for 30 minutes to obtain dry mixed balls with a moisture content of 0.5% and a drop strength of 9 times.

[0075] S04, Reduction Calcination The dry mixed balls obtained in step S03 are evenly distributed into the annular bottom of the rotary hearth furnace using a vibrating material distributor. The material thickness is 30 mm, and the furnace bottom rotation speed is 30 min / revolution.

[0076] The dry-mixed pellets are sintered in a rotary hearth furnace, passing sequentially through a heating zone, a reduction zone, and a cooling zone. The heating zone has a roasting temperature of 1000℃ and a residence time of 3 minutes; the reduction zone has a roasting temperature of 1250℃ and a residence time of 22 minutes, and is heated by mixed gas; the cooling zone has a roasting temperature of 1100℃ and a residence time of 3 minutes.

[0077] S05, DRI Product Collection The direct reduced iron (DRI) product obtained in step S04 is discharged from the rotary hearth furnace via a screw conveyor and cooled by a cylindrical cooler to obtain DRI balls. The zinc-containing flue gas generated during the reduction roasting in the rotary hearth furnace is treated with dust removal to recover zinc powder.

[0078] The DRI balls produced by the method provided in this embodiment have a compressive strength of 1820N, a metallization rate of 65.68%, a pulverization rate of 24.45%, and a dezincification rate of 90.8%, which effectively makes up for the 30% raw material shortage in the rotary hearth furnace and improves production continuity.

[0079] Comparative Example 1 This comparative example provides a method for preparing direct reduced iron, with the same specific steps as in Example 1, except that DRI powder is not added and steelmaking sludge is used to make up the balance.

[0080] That is, the raw materials for direct reduced iron provided in this comparative example, by mass percentage, include 75% steelmaking sludge, 17% blast furnace bag ash, 5% coking dust and 3% starch-based organic binder, and the homogenized carbon content in the mixture is 10.06 wt%.

[0081] The DRI balls prepared by the method provided in this comparative example have a compressive strength of 1150 N, a metallization rate of 54.45%, a pulverization rate of 28.75%, and a dezincification rate of 83.15%.

[0082] This comparative example uses steelmaking sludge and bag filter ash to prepare direct reduced iron products. Due to the characteristics of the raw materials, the carbon-containing pellets obtained by mixing generally have insufficient mechanical strength after drying. The pellets are very easy to break during transportation, transfer and furnace feeding, generating a large amount of powder. After a large amount of powder enters the rotary hearth furnace with the material, it will damage the material layer structure in the furnace and reduce the permeability of the material layer. This not only hinders the normal progress of the reduction reaction and causes the overall reduction effect to deteriorate, but also further aggravates the pulverization of the material, resulting in a high pulverization rate of the finished product.

[0083] Comparative Example 2 This comparative example provides a method for preparing direct reduced iron. The specific steps are the same as in Example 1, except that DRI powder is not added and blast furnace bag ash is used to make up the balance.

[0084] In other words, the raw materials for direct reduced iron provided in this comparative example, by mass percentage, include 64% steelmaking sludge, 33% blast furnace bag ash, and 3% starch-based organic binder. The homogenized carbon content in the mixture is 10.17 wt%. Considering that the carbon content is sufficient (requiring a carbon content of 9~10%), no reducing agent is added.

[0085] The DRI balls prepared by the method provided in this comparative example have a compressive strength of 1098 N, a metallization rate of 53.33%, a pulverization rate of 30.15%, and a dezincification rate of 81.15%. This comparative example uses a high proportion of blast furnace bag ash to prepare direct reduced iron products, resulting in DRI balls with even lower compressive strength and a decline in all quality indicators.

[0086] Comparative Example 3 This comparative example provides a method for preparing direct reduced iron, with the same specific steps as in Example 1, except that: DRI powder with a particle size ≥3mmd is added, and the content of homogenized carbon in the mixture is 10.03wt%.

[0087] The DRI balls produced by the method provided in this comparative example have a compressive strength of 1320 N, a metallization rate of 49.58%, a pulverization rate of 26.35%, and a dezincification rate of 79.82%. This comparative example uses ≥3% DRI powder in the production process. Due to the large particle size of the DRI powder, the material mixing is uneven, resulting in poor carbon distribution in the pellets. Although the product strength and pulverization rate are improved, the product quality is significantly reduced.

[0088] Comparative Example 4 This comparative example provides a method for preparing direct reduced iron. The specific steps are the same as in Example 1, except that: DRI powder with a particle size of less than 3 mm is added and added at 5% (the remainder is made up with steelmaking sludge), and the content of homogenized carbon in the mixture is 10.5 wt%.

[0089] The DRI balls prepared by the method provided in this comparative example have a compressive strength of 1260 N, a metallization rate of 56.15%, a pulverization rate of 27.86%, and a dezincification rate of 83.84%.

[0090] This comparative example reduces the amount of DRI powder added. Although the quality of the DRI balls is comparable to that of the example, based on the annual processing capacity of 225,000 tons of a 250,000-ton rotary hearth furnace, the product output is 165,000 tons, and the pulverization rate is 30%, the annual output of DRI powder is 49,200 tons. The DRI undersize powder cannot be fully recycled for production, resulting in the loss of TFe and Zn metals from the remaining 37,900 tons of DRI undersize powder.

[0091] The direct reduced iron and its preparation method provided in this invention have at least the following advantages: This method successfully solves several technical challenges in rotary hearth furnace production in steel enterprises, such as insufficient raw materials, low DRI powder recovery rate, and difficulty in solid waste treatment. It also achieves efficient recovery of iron and zinc elements and improves the quality of DRI products. The method is simple, low-cost, and compatible with existing equipment, showing broad prospects for industrial application in steel enterprises using rotary hearth furnace technology, and can create significant economic, environmental, and social benefits.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing direct reduced iron, characterized in that, The process includes mixing raw materials for direct reduced iron in a certain proportion and pressing them into pellets to obtain wet mixed pellets; drying the wet mixed pellets to obtain dry mixed pellets; and placing the dry mixed pellets in a rotary hearth furnace for reduction roasting. The raw materials for the direct reduced iron include iron-containing raw materials, direct reduced iron powder, reducing agent and binder in a mass ratio of (60~97): (15~30): (2~6): (2~4); The sources of the direct reduced iron powder include: screening the direct reduced iron product obtained from the rotary hearth furnace to obtain direct reduced iron powder with a particle size of <3mm.

2. The method according to claim 1, characterized in that, The reduction calcination includes sintering the dry mixed pellets in the rotary hearth furnace by sequentially passing them through a heating zone, a reduction zone, and a cooling zone. The calcination parameters of the heating zone include: calcination temperature of 1000~1150℃ and residence time of 3~5min; The calcination parameters of the reduction zone include: calcination temperature of 1150~1270℃ and residence time of 20~25min; The calcination parameters of the cooling zone include: calcination temperature ≤1100℃, residence time 3~5min; Preferably, the thickness of the dry-mixed material balls in the rotary hearth furnace is 20~60mm; Preferably, the rotational speed of the rotary hearth furnace is 20-30 min / revolution; Preferably, the heat source for heating the reduction zone includes mixed coal gas or converter gas.

3. The method according to claim 1, characterized in that, The moisture content of the dry-mixed pellets is ≤2%; Preferably, the drying process parameters include: drying temperature 110~320℃, drying time 20~35min.

4. The method according to claim 1, characterized in that, The particle size of the wet-mixed pellets is 15~32mm; Preferably, the process parameters for briquetting include: briquetting machine pressure of 105~115 bar and briquetting temperature of 30~60℃.

5. The method according to claim 1, characterized in that, The raw materials for direct reduced iron are mixed to obtain a homogenized mixture, wherein the homogenized carbon content of the homogenized mixture is 9-11 wt%; preferably 9.5-10.5 wt%. Preferably, the parameters of the raw material mixing process for direct reduced iron include: mixing speed of 150~200 r / min and mixing time of 10~15 min.

6. The method according to claim 1, characterized in that, The direct reduced iron powder has a TFe content ≥ 50 wt% and a Zn content of 0.5~3.5 wt%.

7. The method according to claim 1, characterized in that, The reducing agent has a carbon content ≥70% and a particle size ≤1mm; Preferably, the reducing agent includes at least one of coking dust and pulverized coal.

8. The method according to claim 1, characterized in that, The adhesive includes at least one of starch-based organic adhesives and composite adhesives.

9. A direct reduced iron, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The direct reduced iron according to claim 9, characterized in that, The metallization rate of the direct reduced iron is ≥70%, and the dezincification rate is ≥85%.