Direct reduced iron production method by agglomerate self-heating air drying

Abstract

The present application relates to a kind of briquettes self-heating drying direct reduction iron production method, belongs to direct reduction iron production process field.Its characteristics are using self-heating ingredients or binder, the particle and powder under direct reduction iron sieve are returned to ingredients mixing machine after being finely ground, with raw material together after being mixed uniformly by adding water, into briquetting manufacturing process, after drying, briquettes enter reduction furnace to produce direct reduction iron.Direct reduction iron production raw material can be metallurgical dust mud or iron concentrate, metallurgical dust generally contains sodium chloride, potassium chloride, calcium oxide, carbon powder, etc., the interaction of pure iron in direct reduction iron powder with the above-mentioned substance and water in briquette occurs relatively rapid oxidation reaction, produces iron hydroxide, and releases heat, speeds up the drying speed of briquette, iron hydroxide gel fills in the pore of briquette, so that briquette is more dense, and strength improves.The production process saves the investment of briquette drying process and the consumption of a large amount of energy medium in drying process.

Description

Technical Field

[0001] This invention belongs to the field of direct reduced iron production technology and relates to a method for producing direct reduced iron by self-heating and drying of lumps. Background Technology

[0002] Globally, direct reduction (DR) processes mainly consist of three types: vertical shaft furnace, rotary kiln, and rotary hearth furnace. These processes almost all require the raw materials to be briquetteed, and the briquettes dried before being fed into the furnace. Using gas combustion to provide heat for drying the briquettes not only consumes a large amount of energy but also requires significant investment in the dryers. Natural air drying is affected by weather conditions; in rainy, snowy, or cold weather, the moisture in the pellets evaporates slowly, limiting the production cycle. Air drying also requires a large area and generates a significant amount of powder during the handling process.

[0003] Direct reduction processes, primarily using rotary hearth furnaces and rotary kilns, are also commonly used to treat dust and sludge from steel plants. This dust and sludge contains elements such as zinc and lead, which are harmful to the smooth operation and lifespan of blast furnaces. Therefore, most of the zinc and lead elements in the dust and sludge are removed through high-temperature direct reduction. The resulting direct reduced iron pellets are then returned to the blast furnace for use. The direct reduced iron pellet powder that is screened out enters the sintering unit to participate in the batching. However, because the content of residual harmful elements such as zinc and lead in the direct reduced iron pellet powder is still relatively high, almost twice that of the direct reduced iron pellets, the harmful elements will still accumulate in the blast furnace when such sintered ore is reintroduced, which will have an adverse effect on blast furnace production. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a direct reduced iron production method using agglomerated self-heating drying, which can not only solve the technical problem of slow self-heating drying time, but also reduce the adverse effects of harmful elements such as zinc and lead in the products of direct reduction processes using dust and sludge as raw materials on blast furnaces.

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

[0006] A method for producing direct reduced iron by self-heating drying of lumps includes the following steps:

[0007] S1 mixes raw materials, binder and coke powder with water, wherein the raw materials are metallurgical dust removal sludge or iron concentrate mixed with metallurgical dust removal sludge;

[0008] S2 presses the material mixed in S1 into blocks and dries them;

[0009] S3 reduces the dried raw material from S2 to produce direct reduced iron, and then screens it. Direct reduced iron that does not meet the particle size requirements is ground and returned to S1 for mixing.

[0010] The pure iron powder returned from S1 in S3 undergoes an oxidation reaction in S2 with sodium chloride, potassium chloride, calcium oxide, carbon, external coke powder, and water contained in the metallurgical dust collector, producing ferric hydroxide.

[0011] Optionally, in S3, the particle size of direct reduced iron that does not meet the particle size requirements is less than 6 mm.

[0012] Optionally, in S3, the direct reduced iron particles returned to S1 for mixing have a particle size of less than 1 mm.

[0013] Optionally, in S3, the finely ground direct reduced iron powder is temporarily stored in a silo, and then some or all of the direct reduced iron powder in the silo is taken back to S1 for mixing.

[0014] Optionally, the finely ground direct reduced iron powder is purged with nitrogen for protection after entering the silo.

[0015] Optionally, if the raw material contains calcium oxide and the calcium oxide content exceeds 5%, the dust containing calcium oxide shall be pre-dissolved and then mixed in S1.

[0016] Optionally, when the raw material is iron concentrate, the dust removal sludge added is metallurgical furnace flue gas dust removal sludge.

[0017] Optionally, the unqualified briquettes and powders from S2, as well as the unqualified powders after drying, are returned to S1 for mixing.

[0018] The beneficial effects of this invention are as follows:

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is the process route diagram for Example 1;

[0022] Figure 2 This is the process route diagram for Example 2. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and 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, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0026] Example 1

[0027] Please see Figure 1 This embodiment includes the following steps:

[0028] 1) Iron dust, coke powder or coal powder and binder from steel enterprises are fed into the batching silo, and then fed into the high-strength mixer through the quantitative feeding device under the silo. The final mixed material is then conveyed to the briquetting machine by belt.

[0029] 2) After the briquetting machine presses out unqualified lumps and powders, the unqualified powders are dried and then conveyed into the return silo by a belt conveyor. The powders are then fed into the mixer by a quantitative feeding device under the silo.

[0030] 3) After the qualified lumps are dried, they are sent to the reduction furnace for reduction roasting. The produced direct reduced iron lumps are screened. The lumps smaller than 6mm are sent to the rod mill for grinding. The ground direct reduced iron lumps smaller than 1mm are sent to the high-intensity mixer. The lumps larger than 1mm are sent back to the mill for grinding.

[0031] 4) Dust collector ash, coke powder / coal powder, binder, agglomerated return material, and direct reduction pellet powder are rapidly mixed in a high-intensity mixer. Water is added to the mixer until the mixed material contains 5% to 10% water. After mixing, the material is sent to a briquetting machine to briquette. The briquette is then transported to the stockyard for drying via a swinging spreader or a loader. During the drying process, the oxidation of metallic iron in the direct reduction pellet powder releases heat, accelerating the drying speed of the pellets.

[0032] Example 2

[0033] Please see Figure 2 This embodiment includes the following steps:

[0034] 1) Iron concentrate, metallurgical furnace flue gas dust, and binder are fed into the batching silo, and then fed into a high-intensity mixer via a quantitative feeding device under the silo to mix them, controlling the proportion of flue gas dust in the above raw materials to be less than 20%. The materials in the mixer enter a disc pelletizer for pelletizing.

[0035] 2) The unqualified pellets and powder produced by the disc pelletizer are dried and then transported by belt conveyor into the return silo, and fed into the mixer by the quantitative feeding device under the silo.

[0036] 3) After the qualified pellets are dried, they are sent to a rotary kiln for reduction roasting. The produced direct reduced iron pellets are screened. Pellets smaller than 6mm are sent to a ball mill for grinding. The ground direct reduced iron pellets with a particle size of less than 0.5mm are sent to a high-intensity mixer. Particles larger than 0.5mm are sent back to the mill for further grinding.

[0037] 4) Iron concentrate, flue gas dust, binder, substandard pellet return material, and direct reduction pellet powder are rapidly mixed in a high-intensity mixer. Water is added to the mixer until the mixed material contains 6%–12% moisture. The mixed material is then conveyed by belt to a disc pelletizer. After mixing, the material is sent to the disc pelletizer for pelletizing. The rolled green pellets are then transported to the stockpile for drying via a oscillating spreader or a loader. During the drying process, the oxidation of metallic iron in the direct reduction pellet powder releases heat, accelerating the drying speed of the pellets.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for producing direct reduced iron by self-heating drying of briquettes, characterized by, The method comprises the following steps: S1: uniformly mixing raw materials, a binder and coke powder with water, wherein the raw materials are metallurgical dust mud or iron concentrate with added metallurgical dust; S2: briquetting and air-drying the uniformly mixed materials in S1; S3: producing direct reduced iron by reducing the air-dried materials in S2, and screening the direct reduced iron, wherein the direct reduced iron that does not meet the particle size requirement is ground and returned to S1 for mixing, the particle size of the direct reduced iron that does not meet the particle size requirement is less than 6 mm, and the particle size of the direct reduced iron that is ground and returned to S1 for mixing is less than 1 mm; The pure iron powder returned to S1 in S3 is oxidized to produce iron hydroxide under the interaction of sodium chloride, potassium chloride, calcium oxide, carbon and additional coke powder and water contained in the metallurgical dust in S2; the ground direct reduced iron powder is temporarily stored in a bin, and then part or all of the direct reduced iron powder in the bin is returned to S1 for mixing; When the raw materials contain calcium oxide and the content of calcium oxide exceeds 5%, the dust containing calcium oxide is digested in advance, and then mixed in S1.

2. The method of briquet self-heat drying direct reduced iron production according to claim 1, characterized in that, The ground direct reduced iron powder is protected by nitrogen after entering the bin.

3. The method of agglomerate self-warming air drying direct reduced iron production according to claim 1, characterized by, When the raw materials are iron concentrate, the added dust mud is metallurgical flue gas dust mud.

4. The method of agglomerate self-warming air drying direct reduced iron production according to claim 1, characterized by, The unqualified briquetting materials and powder in S2 and the unqualified powder after air-drying are returned to S1 for mixing.

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