Method for green and efficient production of DRI product

Abstract

The invention discloses a method for green and efficient production of a DRI product, which comprises the following steps: making iron-containing dust of an iron and steel plant into pellets, drying the pellets, then carrying out reduction roasting through a rotary hearth furnace to obtain the DRI product, separating the DRI pellets and DRI powder in the rotary hearth furnace through high-temperature screening, carrying out high-temperature pressing on screen underflow to improve the utilization value, and then carrying out product cooling and sensible heat recovery to obtain the DRI product. And the problems of high production energy consumption, high product pulverization rate and the like when the rotary hearth furnace is used for treating the iron and zinc-containing dust sludge in the steel plant are solved.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy and environmental protection, and in particular relates to a method for producing DRI products in a green and efficient manner. Background Art

[0002] The steel industry is an important part of the development of the national economy. Since the 21st century, my country's crude steel output has been ranked first in the world. The steel industry has made outstanding contributions to my country's economic development, but it also discharges a large amount of pollutants (wastewater, waste gas, waste slag, etc.) into the environment. The development of a circular economy is conducive to the green and sustainable development of the steel industry. Metallurgical dust and sludge is one of the most important solid waste emissions from iron and steel metallurgy. It is mainly produced by the dry or wet dust removal of atmospheric pollutants such as flue gas and dust or the treatment of wastewater generated in the metallurgical process. Compared with smelting slag, the treatment technology of metallurgical dust and sludge started late, but due to its large output, the high iron content of some dust and sludge, and the high added value of utilization, it has also become an important field for the utilization of metallurgical solid waste and the development of a circular economy.

[0003] The rotary hearth furnace process refers to the process of mixing iron-containing dust, reducing agent and binder, pressing them into balls, and then directly loading them into the rotary hearth furnace after drying. At a high temperature of 1150-1250℃, as the furnace bottom rotates, the charge passes through the preheating and reduction zones in sequence. The carbon-containing pellets are reduced to metallized pellets in the rotary hearth furnace, and the volatile metals such as ZnO in the pellets are reduced to metallic Zn. The metallic zinc volatilizes into the flue gas and is oxidized to form ZnO. The secondary dust rich in ZnO is obtained by collecting the flue dust. The produced metallized pellets can be used as raw materials for electric furnaces and converters. This process effectively recovers C, Fe, Zn and rare metals in the dust, and better solves the problem of the difficulty in utilizing zinc-containing dust in steel plants.

[0004] At present, the annual scale of iron-zinc dust and sludge disposal in China is about 4 to 5 million tons. However, due to the high production energy consumption and high product pulverization rate of the rotary hearth furnace in the treatment of iron-zinc dust and sludge in steel mills, the pulverization rate of DRI finished products produced by domestic rotary hearth furnaces is generally above 25%, and some even exceed 30%. This leads to low product value, difficulty in recycling, and high production costs, which seriously restricts the development of rotary hearth furnace technology in my country. In addition, the rotary hearth furnace technology started late, and there are few studies on the pretreatment technology of high-temperature finished ball powder of rotary hearth furnaces. Therefore, it is a key issue that urgently needs to be broken through to develop a green and efficient method for producing DRI products, improve the functionality and value of rotary hearth furnace products, recover the sensible heat in high-temperature pellets, and thus reduce the overall energy consumption of rotary hearth furnaces.

[0005] The prior art search and analysis for rotary hearth furnace production is as follows:

[0006] Chinese patent CN215628198U relates to a rotary hearth furnace metallized pellet hot pressing and hot delivery steelmaking system, which is used for hot delivery of the metallized pellets in the rotary hearth furnace for steelmaking, and comprises a spiral discharger connected to the output end of the rotary hearth furnace, and a hot briquetting machine for compressing the metallized pellets into blocks, a chute is also connected between the spiral discharger and the hot briquetting machine, and a transfer bucket is also provided at the discharge port of the hot briquetting machine, and the transfer bucket and the movable cover plate thereon are both insulated; the technology makes full use of the sensible heat of the metallized pellet product at a temperature of about 1000°C, and directly hot presses it and then delivers it to steelmaking, and the subsequent steelmaking process achieves energy conservation and emission reduction to the maximum extent, further reducing the operating cost, and the hot briquetting block has a compact structure, and the interior is not easily exposed to the air, which reduces reoxidation. However, this technology has the following disadvantages: 1) According to production practice, the proportion of oversize (particle size ≥ 3 mm) of the DRI product of the rotary hearth furnace exceeds 75%. This technology does not take into account the hot screening process, resulting in a large workload of hot pressing after discharging, and severe wear of the high-temperature roller briquetting machine, resulting in increased costs; 2) According to production practice, the metallization rate of the oversize (particle size ≥ 3 mm) of the DRI product of the rotary hearth furnace exceeds 90%, the dezincification rate exceeds 88%, and the residual zinc in the pellets is less than 0.5%, which has met the application performance and composition requirements of metallurgical furnaces such as iron-making blast furnaces, steel-making converters, and electric furnaces. There is no need to perform re-briquetting to avoid increasing production costs; 3) The transportation of hot briquette to the steel mill via the transfer bucket has problems such as difficulty in operation and severe heat loss, which is not conducive to the effective recovery of the sensible heat of the pellets.

[0007] Chinese patent CN215328298U discloses a new type of hot pressing production line for oxidized pellets, including: a vibrating screening device, which is used to screen the oxidized pellets after firing; a molding machine, which is arranged at the discharge side of the vibrating screening device, and is used to press the oxidized pellets after screening; a conveyor, which is arranged at the discharge side of the molding machine; this technology can make full use of the temperature of the pellets after firing, and directly put them into the hot pressing production line for pressing, and can be completed without additional heat. The pressed pellets are not only conducive to storage for a certain period of time, but also can use their own high temperature to reduce energy consumption and save costs. However, this patent: 1) The application field of the process of preparing oxidized pellets for blast furnaces from iron concentrate before ironmaking is different from this technology; 2) The mesh aperture of the vibrating screening equipment of this technology is 20mm, which exceeds the general size of DRI products produced by rotary hearth furnaces and is not universal; 3) The temperature of the hot pressed product is relatively high, but the sensible heat recovery device is not considered.

[0008] Chinese patent publication number CN115491505A provides a method and device for directly preparing hot briquettes from high-temperature kiln slag, the method comprising: step S1. The pressing plate moves toward the lower material port under the hydraulic push of the plate pusher; step S2. When the pressing plate moves to the blanking station, the kiln slag in the high-temperature kiln falls into the briquette hole on the briquetting plate, and the briquetting plate moves to the slag blocking station, and the kiln slag is flattened; step S3. When the pressing plate moves to the slag pressing station, the slag pressing machine presses down to obtain hot briquettes; step S4. When the pressing plate moves to the demoulding station, the hot briquettes are demoulded from the pressing plate. The method and device of this technology can quickly transform high-temperature sticky kiln slag into hot briquettes to realize resource utilization, and it has the advantages of simple process, high degree of equipment automation, low system investment and operating costs. However, this technology has the following disadvantages: 1) According to production practice, the proportion of screened material (particle size ≥ 3mm) in rotary kiln slag products exceeds 60%. This technology does not take into account the hot screening process, resulting in a large workload of hot pressing after discharging, and severe wear of the high-temperature roller pelletizing machine, resulting in increased costs; 2) The hot pressing process does not consider the recovery of sensible heat of the pellets, resulting in a waste of resources. Summary of the invention

[0009] In view of the problems of high production energy consumption and high product pulverization rate in the prior art of treating iron-zinc dust and sludge in steel mills with rotary hearth furnaces, the purpose of the present invention is to provide a green and efficient method for producing DRI products, in which the rotary hearth furnace DRI finished balls and DRI powder are separated at high temperature, and the screened material is hot-pressed into balls or blocks to improve its utilization value, and then the DRI finished balls are recycled by sensible heat recovery, which greatly reduces the energy consumption of the process.

[0010] To achieve the above object, the present invention adopts the following technical solution:

[0011] The present invention provides a green and efficient method for producing a DRI product, comprising the following steps:

[0012] S1, high temperature reduction, mixing the iron-containing dust from the steel plant with industrial fresh water to obtain a mixture, then pressing the mixture through a medium-pressure roller briquetting machine or a briquetting plate to form pellets, and then drying the pellets and placing them in a rotary hearth furnace for reduction roasting to obtain DRI products;

[0013] S2, high temperature screening, after the DRI product is discharged by the high temperature discharging screw, high temperature screening is performed under nitrogen sealing to obtain high temperature DRI pellets and undersize;

[0014] S3, high temperature pressing, the screened material is pressed into a ball by high temperature hot pressing or stamping to obtain hot pressed pellets or hot pressed blocks;

[0015] S4, product cooling and sensible heat recovery, the high-temperature DRI pellets obtained in step S2 and the hot-pressed pellets or hot-pressed blocks obtained in step S3 are respectively cooled and sensible heat recovered by an inner membrane circulation cooler to obtain DRI products and high-temperature steam.

[0016] Preferably, in step S1:

[0017] The iron-containing dust in the steel plant is one or more of blast furnace gas mud or ash, blast furnace under-tank ash, blast furnace TRT ash, steelmaking LT ash, and cold rolling acid-alkali mud;

[0018] The moisture content of the mixture is 10-14%, and the carbon-oxygen ratio is 0.8-1.0.

[0019] Preferably, in step S1:

[0020] The drop strength of the pellets is ≥5 times / 0.5m;

[0021] The reduction roasting temperature is 1000-1300°C;

[0022] The temperature of the DRI product is 800-1000°C.

[0023] Preferably, in step S2: the vibrating screen used for high temperature screening is sealed and high temperature resistant, the normal operating temperature of the vibrating screen is ≥1000°C, and the mesh size is 3-5mm.

[0024] Preferably, in step S3:

[0025] The normal operating temperature of the high-temperature roller ball press or punch press is ≥700°C;

[0026] The compressive strength of the hot-pressed pellets or hot-pressed blocks is ≥2000N, and the particle size is ≥5mm.

[0027] Preferably, in step S4:

[0028] The high-temperature steam obtained by sensible heat recovery is used in the pellet drying process of step S1, and the temperature of the high-temperature steam is ≥110°C and the pressure is ≥0.1MPa;

[0029] The temperature of the DRI product is below 120°C.

[0030] Preferably, in step S4, the DRI product comprises:

[0031] DRI products with zinc content ≥ 0.5% are returned to the converter and electric furnace steelmaking process for reuse;

[0032] DRI products with zinc content less than 0.5% are returned to the blast furnace ironmaking process for reuse.

[0033] The green and efficient method for producing DRI products of the present invention also has the following beneficial effects:

[0034] 1. In view of the problems of high production energy consumption and high product pulverization rate in treating iron-zinc dust sludge in steel mills by rotary hearth furnace, the present invention mixes iron-zinc dust sludge in steel mills with water, and uses medium-pressure roller briquetting machine or ball-making disk to make pellets, which are dried by super-strong steel belt dryer and then placed in the furnace of rotary hearth furnace, and roasted at 1000-1300°C. After the high-temperature DRI product is discharged by the discharging screw, it is subjected to high-temperature screening under nitrogen sealing, and the obtained undersize material with smaller particle size is subjected to high-temperature roller briquetting or stamping, and then the obtained high-temperature DRI pellets are subjected to cooling treatment by inner membrane circulation cooler, and the sensible heat of the pellets is recovered, and the recovered heat is used in the drying process of raw pellets; finally, the cooled DRI pellets are respectively returned to steelmaking or ironmaking for reuse according to their specific chemical properties;

[0035] 2. The present invention separates the finished balls and powder of the rotary hearth furnace at high temperature, and hot presses the powder under the screen into balls or blocks, which expands its disposal path and improves its utilization value. Then, the finished balls are recycled for sensible heat through an efficient cooling device, which greatly reduces the energy consumption of the process;

[0036] 3. The present invention creatively develops a green and efficient method for producing DRI products, improves the technical and economic efficiency of the rotary hearth furnace in treating metallurgical dust and sludge, and contributes to the development of my country's metallurgical solid waste utilization and circular economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0038] Figure 1 A schematic flow chart of the green and efficient method for producing DRI products provided by the present invention. DETAILED DESCRIPTION

[0039] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0040] Combination Figure 1 As shown, the green and efficient method for producing DRI products provided by the present invention comprises the following steps:

[0041] S1, high temperature reduction, mixing the iron-containing dust from the steel plant with industrial fresh water to obtain a mixture, then pressing the mixture through a medium-pressure roller briquetting machine or a briquetting plate to form pellets, and then drying the pellets and placing them in a rotary hearth furnace for reduction roasting to obtain DRI products;

[0042] Specifically, the iron-zinc dust sludge of the steel plant is evenly mixed with industrial fresh water to obtain a mixture, and the moisture content of the mixture is controlled at 10-14%. When mixing the ingredients, the carbon-oxygen ratio of the iron-zinc dust sludge of the steel plant used in the mixture needs to be detected. If the carbon-oxygen ratio of the iron-zinc dust sludge of the steel plant is not within the range of 0.8-1.0, it can be adjusted by CDQ (dry coke quenching) or other reducing agents, and finally the carbon-oxygen ratio of the mixture is controlled within the range of 0.8-1.0. Then the mixture is placed in a medium-pressure double-roller briquetting machine or a briquetting plate to prepare pellets with a drop strength of ≥5 times / 0.5m, and then the pellets are dried by a super-strong steel belt dryer and placed in the furnace of a rotary hearth furnace, and reduction roasted at 1000-1300°C to obtain a DRI product with a temperature of 800-1000°C.

[0043] S2, high temperature screening, after the DRI product is discharged by the high temperature discharging screw, high temperature screening is performed under nitrogen sealing to obtain high temperature DRI pellets and undersize;

[0044] Specifically, after the DRI product obtained in step S1 is discharged by the high-temperature discharge screw, the temperature of the DRI product is 800-1000°C. In order to avoid product oxidation, high-temperature screening is performed under nitrogen sealing to obtain high-temperature DRI pellets and screened products; the screened products are mainly DRI powder and DRI pellets with smaller particle size. The vibrating screen used in the high-temperature screening process is sealed and high-temperature resistant. The normal working temperature of the vibrating screen is ≥1000°C, and the mesh size is 3-5mm.

[0045] S3, high temperature pressing, the screened material is pressed into a ball by high temperature hot pressing or stamping to obtain hot pressed pellets or hot pressed blocks;

[0046] Specifically, the finer particle size of the screened material obtained by high-temperature screening in step S2 is pressed into balls by high-temperature hot pressing (high-temperature roller ball press) or punching (high-temperature punching machine), thereby improving the strength and size of the product, expanding its application field, and thus enhancing the product value. The normal working temperature of the high-temperature roller ball press or punching machine is ≥700℃; the compressive strength of the hot-pressed pellets or hot-pressed blocks is ≥2000N, and the particle size is ≥5mm.

[0047] S4, product cooling and sensible heat recovery, the high-temperature DRI pellets obtained in step S2 and the hot-pressed pellets or hot-pressed blocks obtained in step S3 are respectively cooled and sensible heat recovered by an inner membrane circulation cooler to obtain DRI products and high-temperature steam.

[0048] The high-temperature steam obtained by sensible heat recovery is used for the pellet drying process in step S1, and the temperature of the high-temperature steam is ≥110°C and the pressure is ≥0.1MPa; the temperature of the DRI product after cooling is lower than 120°C.

[0049] The above DRI products have different application paths according to their different chemical compositions. DRI products with zinc content ≥ 0.5% are returned to the converter and electric furnace steelmaking process for reuse; DRI products with zinc content < 0.5% are returned to the blast furnace ironmaking process for reuse.

[0050] The green and efficient method for producing DRI products of the present invention is further introduced below with reference to specific examples.

[0051] Example 1

[0052] This embodiment takes the rotary hearth furnace production base of A Steel Plant, which disposes 250,000 tons of iron-zinc dust and sludge annually, as an example. The raw materials of this base are formed by a double-roll ball forming process.

[0053] This embodiment adopts the green and efficient method of producing DRI products of the present invention as follows:

[0054] (1) First, blast furnace gas ash, blast furnace ash, steelmaking LT ash, cold rolling acid-alkali mud are digested, dried and pre-treated, and the CDQ ratio is adjusted to a carbon-oxygen ratio of 1.0, and then added to a mixer and fully mixed. Industrial new water is added during the process to obtain a mixture, and the moisture content of the mixture is controlled to be 13wt%;

[0055] (2) The mixed material is then pressed into pellets by a roller pelletizer and dried in a dryer, wherein the energy medium of the dryer can be high-temperature DRI pellet sensible heat recovery by-product steam, the steam temperature is about 150°C and the pressure is about 0.2 MPa;

[0056] (3) The dried pellets enter a rotary hearth furnace for reduction roasting to obtain DRI products. The high-temperature DRI product is discharged through a spiral discharging machine. At this time, the DRI product temperature is 950°C. It enters a high-temperature resistant vibrating screen for high-temperature screening. The mesh size is 3mm. The obtained DRI pellets on the screen enter an inner membrane circulating cooler for product cooling and sensible heat recovery. The discharge temperature of the DRI pellets is 90°C. The obtained underscreen material enters a high-temperature double-roller pelletizing machine for pelletizing. The pellet size is about 25*35*15mm. The above process is nitrogen sealed throughout the entire process.

[0057] (4) The DRI undersize material is then hot-pressed and pelletized into pellets that enter an inner membrane circulation cooler for product cooling and sensible heat recovery, with the discharge temperature being approximately 90°C.

[0058] After the above process:

[0059] 1) The pulverization rate of DRI products in the rotary hearth furnace of Plant A was reduced from 25% to 3%, and the strength of the obtained DRI product pellets exceeded 2200N, meeting the strength requirements for entering metallurgical furnaces such as blast furnaces, converters, and electric furnaces;

[0060] 2) Due to the use of advanced sensible heat recovery technology, the total energy consumption of the rotary hearth furnace of Plant A has been reduced from 195kgce / tDRI to 179kgce / tDRI, with a significant reduction in energy consumption.

[0061] Example 2

[0062] This embodiment takes the rotary hearth furnace production base of B Steel Plant, which disposes 300,000 tons of iron-zinc dust and sludge annually, as an example. The raw materials of this base are pelletized, and the raw material pretreatment is not equipped with drying, grinding and other processes. Before the application of the invention, the powderization rate of the finished product was high, exceeding 30%.

[0063] This embodiment adopts the green and efficient method of producing DRI products of the present invention as follows:

[0064] (1) The raw materials disposed by Plant B are mainly blast furnace bag ash, steelmaking OG mud, electric furnace ash, iron-making field ash, blast furnace trough ash, etc. The CDQ ratio is adjusted to a carbon-oxygen ratio of 0.95, and then added to the mixer for thorough mixing. Due to the high moisture content in the raw materials, no water is added or a small amount of water is added during the mixing process to obtain a mixture, and the moisture content of the mixture is controlled to be 12%;

[0065] (2) The mixed material is then pelletized on a pelletizing plate with a diameter of 13.5 m. The pellets are screened and then sent to a dryer for drying. The energy medium of the dryer is the byproduct steam of the high-temperature DRI pellet sensible heat recovery. The steam temperature is about 140°C and the pressure is about 0.2 MPa.

[0066] (3) The dried pellets enter a rotary hearth furnace for reduction roasting to obtain DRI products. The high-temperature DRI product is discharged through a spiral discharging machine. At this time, the DRI product temperature is 980°C, and enters a high-temperature resistant vibrating screen for high-temperature screening. The mesh size is 5mm. The obtained DRI pellets on the screen enter an inner membrane circulating cooler for product cooling and sensible heat recovery. The discharge temperature of the DRI pellets is 100°C; the undersize material enters a high-temperature double-roller pelletizing machine for pelletizing. The pellet size is about 25*30*15mm. The above process is nitrogen sealed throughout the entire process.

[0067] (4) The DRI undersize material is then hot-pressed and pelletized into pellets that enter an inner membrane circulation cooler for product cooling and sensible heat recovery, with the discharge temperature being approximately 100°C.

[0068] After the above process:

[0069] 1) The pulverization rate of DRI products in the rotary hearth furnace of Plant A was reduced from 35% to 5%, and the strength of the obtained DRI product pellets exceeded 2000N, meeting the strength requirements for entering the furnaces of metallurgical furnaces such as blast furnaces, converters, and electric furnaces;

[0070] 2) Due to the use of advanced sensible heat recovery technology, the total energy consumption of the rotary hearth furnace of Plant B was reduced from 205kgce / tDRI to 185kgce / tDRI, with a significant reduction in energy consumption.

[0071] Example 3

[0072] This embodiment takes the rotary hearth furnace production base of C Steel Plant, which disposes 200,000 tons of iron-zinc dust and sludge annually, as an example. The raw materials of this base are formed by a double-roller pelletizing process, and the raw material pretreatment is not equipped with drying, digestion and other processes. Before the application of the invention, the powderization rate of the finished product was high, exceeding 30%.

[0073] This embodiment adopts the green and efficient method of producing DRI products of the present invention as follows:

[0074] (1) The raw materials disposed by Plant C are mainly blast furnace gravity ash, blast furnace bag ash, steelmaking sludge, electric furnace ash, etc. Due to the high carbon content in the raw materials, the carbon content of the mixture will exceed 10% and the carbon-oxygen ratio will be 0.9, so CDQ or other reducing agents are not added. The above materials are added to the mixer and mixed thoroughly. Due to the high moisture content in the raw materials, no water is added or a small amount of water is added during the mixing process to obtain a mixture, and the moisture content of the mixture is controlled to be 15%;

[0075] (2) The mixed material is then pressed into balls by a medium-pressure roller press, and the balls are screened and then sent to a dryer for drying. The energy medium of the dryer is the byproduct steam recovered from the sensible heat of the high-temperature DRI balls, with a steam temperature of about 130°C and a pressure of about 0.1 MPa.

[0076] (3) The dried pellets are then reduced and roasted in a rotary hearth furnace to obtain DRI products. The high-temperature DRI product is discharged through a spiral discharging machine, at which point the product temperature is 980°C, and enters a high-temperature resistant vibrating screen for high-temperature screening, with a mesh size of 3mm. The resulting DRI pellets on the screen enter an inner membrane circulating cooler for product cooling and sensible heat recovery, with a DRI pellet discharge temperature of 110°C; the underscreen material enters a high-temperature double-roller pelletizing machine for pelletizing, with a pellet size of approximately 25*25*15mm. The entire process is nitrogen sealed;

[0077] (4) The DRI undersize material is then hot-pressed and pelletized into pellets that enter an inner membrane circulation cooler for product cooling and sensible heat recovery, with a discharge temperature of approximately 110°C.

[0078] After the above process:

[0079] 1) The pulverization rate of DRI products in the rotary hearth furnace of Plant C was reduced from 32% to 2%, and the strength of the obtained DRI product pellets exceeded 2500N, meeting the strength requirements for entering metallurgical furnaces such as blast furnaces, converters, and electric furnaces;

[0080] 2) Due to the use of advanced sensible heat recovery technology, the total energy consumption of the rotary hearth furnace in Plant C has been reduced from 150kgce / tDRI to 125kgce / tDRI, with a significant reduction in energy consumption.

[0081] In summary, the present invention aims at the problems of high production energy consumption and high product powderization rate in treating iron-zinc dust and sludge in steel mills by rotary hearth furnace. After mixing iron-zinc dust and sludge in steel mills with industrial fresh water, the mixture is made into pellets by medium-pressure roller briquetting machine or pelletizing disk, dried by super-strong steel belt dryer and placed into the furnace of rotary hearth furnace, and roasted at 1000-1300°C. After the high-temperature DRI product is discharged by the discharging screw, it is subjected to high-temperature screening under nitrogen sealing. The obtained undersize product with smaller particle size is subjected to high-temperature roller briquetting or stamping, and then the obtained high-temperature DRI pellets are subjected to cooling treatment by inner membrane circulation cooling machine, and the sensible heat of the pellets is recovered, and the recovered heat is used in the drying process of raw pellets. Finally, the cooled DRI pellets are respectively returned to steelmaking or ironmaking for reuse according to their specific chemical properties. The present invention separates the finished balls and powder of the rotary hearth furnace at high temperature, and hot presses the powder under the screen into balls or blocks, which expands its disposal path and improves its utilization value. The finished balls are then recycled and reused by high-efficiency cooling devices, which greatly reduces the energy consumption of the process. The present invention creatively develops a green and efficient method for producing DRI products, improves the technical and economic efficiency of the rotary hearth furnace in treating metallurgical dust and sludge, and promotes the development of my country's metallurgical solid waste utilization and circular economy.

[0082] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A green and efficient method for producing DRI products, characterized in that: The following steps are involved: S1, high temperature reduction, mixing the iron-containing dust from the steel plant with industrial fresh water to obtain a mixture, then pressing the mixture through a medium-pressure roller briquetting machine or a briquetting plate to form pellets, then drying the pellets and placing them in a rotary hearth furnace for reduction roasting to obtain DRI products; S2, high temperature screening, after the DRI product is discharged by the high temperature discharging screw, high temperature screening is performed under nitrogen sealing to obtain high temperature DRI pellets and screened material; S3, high temperature pressing, the screened material is pressed into a ball by high temperature hot pressing or stamping to obtain hot pressed pellets or hot pressed blocks; S4, product cooling and sensible heat recovery, the high-temperature DRI pellets obtained in step S2 and the hot-pressed pellets or hot-pressed blocks obtained in step S3 are respectively cooled and sensible heat recovered by an inner membrane circulation cooler to obtain DRI products and high-temperature steam.

2. The green and efficient method for producing DRI products according to claim 1, characterized in that: In step S1: The iron-containing dust in the steel plant is one or more of blast furnace gas mud or ash, blast furnace undertank ash, blast furnace TRT ash, steelmaking LT ash, and cold rolling acid-alkali mud; The moisture content of the mixture is 10-14%, and the carbon-oxygen ratio is 0.8-1.

0.

3. The green and efficient method for producing DRI products according to claim 1, characterized in that: In step S1: The drop strength of the pellets is ≥5 times / 0.5m; The reduction roasting temperature is 1000-1300°C; The temperature of the DRI product is 800-1000°C.

4. The green and efficient method for producing DRI products according to claim 1, characterized in that: In the step S2: the vibrating screen used for high temperature screening is sealed and high temperature resistant, the normal operating temperature of the vibrating screen is ≥1000°C, and the mesh size is 3-5mm.

5. The green and efficient method for producing DRI products according to claim 1, characterized in that: In step S3: The normal operating temperature of the high-temperature roller ball press or punching machine used for the high-temperature hot pressing or punching is ≥700°C; The compressive strength of the hot-pressed pellets or hot-pressed blocks is ≥2000N, and the particle size is ≥5mm.

6. The green and efficient method for producing DRI products according to claim 1, characterized in that: In step S4: The high-temperature steam obtained by sensible heat recovery is used in the pellet drying process of step S1, and the temperature of the high-temperature steam is ≥110°C and the pressure is ≥0.1MPa; The temperature of the DRI product is below 120°C.

7. The green and efficient method for producing DRI products according to claim 1, characterized in that: In the step S4, in the DRI product: DRI products with zinc content ≥ 0.5% are returned to the converter and electric furnace steelmaking process for reuse; DRI products with zinc content less than 0.5% are returned to the blast furnace ironmaking process for reuse.

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