Method for returning tailings of steelmaking steel slag to sinter

Abstract

The invention relates to a method for reusing tailings of steelmaking steel slag in sintered ore, and belongs to the technical field of primary treatment of metallurgical ore or waste materials. The method comprises the following steps: sequentially crushing and levigating the tailings of the steel slag, screening, carrying out magnetic separation to obtain a tailings magnetic separation material, adding the tailings magnetic separation material into a waste acid solution containing a small amount of hydrochloric acid and metal iron, carrying out acid pickling, filtering, conveying to a sintering ore raw material field, mixing with other iron-containing solid wastes, and feeding into a batching bin, the sintering ore raw materials are prepared according to the proportion, then primary uniform mixing is conducted, a solution formed by diluting steelmaking LT dedusting ash with water is added, a primary sintering mixture is formed, secondary uniform mixing granulation is conducted, a secondary sintering mixture is obtained, finally, the secondary sintering mixture is subjected to air draft sintering, and the finished product sintering ore is obtained. According to the method, when the tailings of the steel slag are returned to the sintering ore, the iron content is properly increased, the air permeability of the sintered pellets is improved, and meanwhile, material blockage caused in the process that the tailings are returned to the sintering ore is avoided.

Description

Technical Field

[0001] The invention relates to a method for returning the tailings remaining after screening converter steelmaking slag to be used for ironmaking sintered ore, belonging to the technical field of preliminary treatment of metallurgical ores or wastes. Background Art

[0002] The content of metallic iron in the steel slag from the steelmaking converter is generally 10-40%. The comprehensive utilization of steel slag is first to recover the iron metal in it. The beneficial components in the steel slag are recovered through crushing, screening and magnetic separation technology. The selected large-particle steel slag is returned to the steel plant for direct use, and the rest is tailings.

[0003] As for the tailings of steel slag, the tailings are currently returned to the production of sintered ore required for ironmaking. However, due to the complex composition of the tailings, there are more impurities and low iron content, and there are also problems: 1) Since the tailings contain free calcium oxide and magnesium oxide, it is easy to block the material outlet during the mixing process of sintering ingredients with tailings; 2) The pellets sintered with tailings have poor air permeability. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to properly increase the iron content of steel slag tailings and improve the air permeability of sintered pellets when the tailings are recycled into sintered ore, while avoiding blockage in the sintering process when the tailings are recycled.

[0005] The technical solution proposed by the present invention to solve the above technical problems is: a method for recycling tailings of steelmaking slag into sintered ore, comprising the steps performed in the following order: 1) The rod mill process is used to crush and grind the steel slag tailings; 2) Screening the crushed and ground tailings to obtain tailings with a particle size that meets the sintering requirements; 3) magnetically separating the tailings screened in the above step to obtain tailings magnetic separation material; 4) Put the tailings magnetic separation material into the molten pool, add the waste acid generated in the cold rolling production process for pickling, the waste acid contains a small amount of hydrochloric acid and metallic iron; then filter the tailings magnetic separation material after pickling in the molten pool; 5) The tailings magnetic separation material after pickling and filtration is transported to the raw material yard of sintering ore by car, and then the unloaded tailings magnetic separation material is mixed with other iron-containing solid waste in proportion in a mixer to form a tailings magnetic separation material mixture, which is then discharged from the mixer outlet and transported to the sintering batching bin by a belt; 6) Prepare the sintering raw materials according to the calculated proportions of each component required for sintering; 7) The sintered ore raw materials are loaded into a drum for primary mixing, and a binder solution is added to the primary mixing to form a primary sintered mixed material, wherein the binder solution is a solution obtained by diluting the steelmaking LT dust removal ash with water; the primary sintered mixed material is then transferred to a secondary mixing drum for mixing and granulation, and a secondary sintered mixed material is obtained after granulation; 8) The secondary sintered mixed material is transferred to the sintering trolley for exhaust sintering to obtain the finished sintered ore.

[0006] Furthermore, in the step 3), the iron content in the tailings magnetic separation material is required to be not less than 35%, the particle size range of the tailings magnetic separation material is 0-8 mm, and the tailings magnetic separation material larger than 8 mm is controlled to be ≤10%.

[0007] Furthermore, in the step 5), other iron-containing solid wastes are hot-rolled iron oxide scale and continuous casting iron mud, and the ratio of tailings magnetic separation material to other iron-containing solid wastes is 1:3.

[0008] Further, in the step 6), the mass percentage of each component of the sintered ore raw material is: 72% to 78% of hematite rich ore powder, 1% to 3% of tailings magnetic separation material mixture, 5% to 10% of sintered return ore, 10% to 12% of sintering flux, and 4% to 5% of solid fuel, and the sum of the mass percentages of each component is 100%; at the same time, the binary basicity R2 of the sintered ore raw material is controlled to be 1.80-1.90, the mass percentage of SiO2 in the sintered ore raw material is controlled to be 4.2-4.8% and the mass percentage of MgO is controlled to be 1.10-1.49%; the solid fuel for sintering is any one of coke powder, anthracite powder or a mixture of coke powder and anthracite powder, the mass percentage of carbon in the solid fuel is controlled to be 77-85%, and the solid fuel with a particle size of ≤3.0 mm accounts for ≥90% of the total mass of the solid fuel; the sintering flux is a mixture of dolomite, quicklime and limestone.

[0009] Furthermore, in the step 7), the mass percentage of the steelmaking LT dust removal ash in the binder solution is 6.5-7.0%.

[0010] The invention has the following beneficial effects: 1) since the tailings of steel slag are firstly ground by a rod mill process and then magnetically separated, steel slag magnetic separation materials with high iron content and fine particle size more suitable for sintering can be selected; 2) since the tailings magnetic separation materials after magnetic separation are pickled, free calcium oxide and magnesium oxide in the tailings magnetic separation materials can be removed, and the formation of carbonate solids (calcium carbonate and magnesium carbonate) by hydration of calcium oxide and magnesium oxide with carbon dioxide in the air can be avoided, thereby reducing the formation of excessive carbonate solids in the tailings magnetic separation materials, and further avoiding the blockage caused by carbonate solids in the stirring discharge port and the mixing drum; 3) since the solution diluted with water of steelmaking LT dust removal ash is used as a binder for one-time mixing, compared with the existing method of adding water, it is beneficial to improve the air permeability of the mixed balls after sintering; 4) the cold rolling waste acid liquid and steelmaking LT dust removal ash are fully recycled and utilized, the production cost is reduced, and the economic benefits of the enterprise are improved. Implementation Example

[0011] The method of recycling tailings of steelmaking slag into sintered ore in this embodiment comprises the steps performed in the following order: 1) Use rod mill process to crush and grind the tailings of steel slag; you can choose the rod mill (model MBY0918) produced by Xinhai Mining Company.

[0012] 2) Screening the crushed and ground tailings to obtain tailings with a particle size that meets the sintering requirements; 3) Magnetic separation is performed on the tailings screened in the above step to obtain tailings magnetic separation materials, and the following requirements are met: the iron content in the tailings magnetic separation materials is not less than 35%, the particle size range of the tailings magnetic separation materials is 0-8mm, and the proportion of tailings magnetic separation materials larger than 8mm in all tailings magnetic separation materials is controlled to be ≤10%; 4) Put the tailings magnetic separation material into the molten pool, add the waste acid generated in the cold rolling production process for pickling, the waste acid contains a small amount of hydrochloric acid and metallic iron; then filter all the materials in the molten pool; This step realizes that calcium oxide and magnesium oxide in the tailings magnetic separation material use acid to produce calcium ions (Ca 2+ ) and magnesium ions (Mg 2+ ), dissolve it in the waste acid solution, and finally filter all the materials in the molten pool to obtain tailings magnetic separation material without free calcium oxide and magnesium oxide, and then proceed to the next step of ore blending.

[0013] The waste acid liquid is the waste acid liquid produced in the cold rolling production of the steel plant. The waste acid liquid contains trace amounts of hydrochloric acid and metallic iron, with a hydrochloric acid content of 0.01-0.1%. The principle of removing calcium oxide and magnesium oxide contained in the tailings magnetic separation material is that free calcium oxide and magnesium oxide are easily hydrated during the batching process, and then form carbonate solids with carbon dioxide in the air. The chemical reaction formula involved is as follows: CaO+H2O=Ca(OH)2, MgO+H2O=Mg(OH)2, Ca(OH)2+CO2=CaCO3+H2O, Mg(OH)2+CO2=MgCO3+H2O.

[0014] Since the carbonate in the tailings magnetic separation material will adhere more and more to the discharge port and material wall of the subsequent car, mixer and mixing drum, it is easy to cause blockage in the subsequent transmission process of the tailings magnetic separation material. By acid washing to remove the free calcium oxide and magnesium oxide in the slag magnetic separation material, this problem is solved, making the subsequent operation of the tailings magnetic separation material smooth.

[0015] 5) The tailings magnetic separation material after pickling is transported to the raw material yard of sintering ore by car. In order to prevent dust during transportation, it is sprayed in advance; then the unloaded tailings magnetic separation material is mixed with other iron-containing solid waste (hot rolling scale and continuous casting iron mud) in a certain ratio of 1:3 in a mixer to form a tailings magnetic separation material mixture, which is then discharged from the mixer outlet and transported to the sintering batching bin by a belt. Hot rolling scale refers to the scale obtained in hot rolling production, and continuous casting iron mud refers to the iron mud obtained in continuous casting production.

[0016] 6) Calculate the mass percentage of each component of the sintered ore raw material according to the technical quality index of the sintered ore, and prepare the sintered ore raw material according to the calculated proportion of each component required for the sintered ore; the mass percentage content of each component of the sintered ore raw material is: hematite rich ore powder 72%-78%, tailings magnetic separation material mixture 1%-3%, sintering return ore 5%-10%, sintering flux 10-12%, solid fuel 4-5%, and the sum of the mass percentage content of each component is 100%. Sintering return ore refers to the ore that is screened out and returned for re-sintering when the blast furnace enters the sintered ore. In this embodiment, the binary basicity R2 of the sintered ore raw material is controlled to be 1.80-1.90, and the mass percentage content of SiO2 in the sintered ore raw material is controlled to be 4.2-4.8% and the mass percentage content of MgO is controlled to be 1.10-1.49%. The solid fuel for sintering in this embodiment is any one of coke powder, anthracite powder or a mixture of coke powder and anthracite powder, the mass percentage of carbon in the solid fuel is controlled to be 77-85%, and the solid fuel with a particle size of ≤3.0 mm accounts for ≥90% of the total mass of the solid fuel. The flux for sintering in this embodiment is a mixture of dolomite, quicklime and limestone, accounting for 10-12% of the mass of the sintering ore raw materials.

[0017] 7) The sintered ore raw material is loaded into a primary mixing drum for primary mixing, and a binder solution is added to the primary mixing to form a primary sintered mixed material, wherein the binder solution is a solution obtained by diluting the steelmaking LT dust removal ash with water, and the mass percentage of the steelmaking LT dust removal ash in the binder solution is 6.5-7.0%; the primary sintered mixed material is then transferred to a secondary mixing drum for mixing and granulation, and a secondary sintered mixed material (i.e., sintered pellets) is obtained after granulation.

[0018] The steelmaking LT dust removal ash has a fine particle size (less than 0.074mm, the proportion reaches more than 90%), and the viscosity after dilution with water is relatively large. The steelmaking LT dust removal ash solution diluted with water is sprayed into the primary mixing drum for use as a binder. In the conventional process, only water is added during the primary mixing, so the air permeability of the sintered pellets is poor. The air permeability of the pellets made by adding the steelmaking LT dust removal ash solution during the primary mixing in this embodiment is significantly improved after sintering.

[0019] 8) The sintering mixture is subjected to exhaust sintering, and the secondary sintering mixture is transferred to the sintering trolley for exhaust sintering. The exhaust negative pressure during the sintering process is controlled to be 14-17 KPa, and the ignition temperature is 1145-1210°C. After the sintering is completed, the finished sintered ore is obtained.

[0020] In step 6) of this embodiment, several groups of sintered ore raw materials with specific proportions are given in Table 1 below. The production indicators of the several groups of sintered ore raw materials prepared according to Table 1 after final sintering are shown in Table 2 below.

[0021] Table 1 category Mass percentage of hematite rich ore powder Sintering return ore mass percentage Dolomite mass percentage Quicklime mass percentage Limestone mass percentage Solid fuel mass percentage Tailings magnetic separation material mass percentage Ingredients 1 72.25 10 4.5 5 2.5 5 1 Ingredients 2 74 9 4.3 5 2.5 5 1 Ingredients 3 78 7.5 3.7 5 1.5 4 2 Ingredients 4 78 5 4.5 5 2.5 4.95 2. Ingredients 5 78 5 4.5 5 2.5 5 3 Table 2 category <![CDATA[Utilization factor t / m 2 •h]]> Yield % Solid fuel consumption kg / t Drum strength% Low temperature reduction powderization rate% Sintering quality requirements Not less than 1.20 No less than 79 Not more than 51 No less than 78 No higher than 61 Ingredients 1 1.29 80.12 49.53 80.95 60.98 Ingredients 2 1.29 80.58 49.52 80.50 60.67 Ingredients 3 1.31 81.25 48.12 79.67 59.81 Ingredients 4 1.31 81,99 48.23 79.01 59.12 Ingredients 5 1.31 81,97 48.27 79.00 59.11 It can be seen from Table 2 that the final sintering according to the method of the embodiment of the present invention meets the sintering quality requirements.

[0022] The above description is only a preferred embodiment of the present invention, but the present invention is not limited thereto. All equivalent replacements or equivalent changes of the concepts and technical solutions according to the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling tailings of steelmaking slag into sintered ore, characterized in that It includes the following steps, performed in the following order: 1) The rod mill process is used to crush and grind the steel slag tailings; 2) Screening the crushed and ground tailings to obtain tailings with a particle size that meets the sintering requirements; 3) magnetically separating the tailings screened in the above step to obtain tailings magnetic separation material; 4) Put the tailings magnetic separation material into the molten pool, add the waste acid generated in the cold rolling production process for pickling, the waste acid contains a small amount of hydrochloric acid and metallic iron; then filter the tailings magnetic separation material after pickling in the molten pool; 5) The tailings magnetic separation material after pickling and filtration is transported to the raw material yard of sintering ore by car, and then the unloaded tailings magnetic separation material is mixed with other iron-containing solid waste in proportion in a mixer to form a tailings magnetic separation material mixture, which is then discharged from the mixer outlet and transported to the sintering batching bin by a belt; 6) Prepare the sintering raw materials according to the calculated proportions of each component required for sintering; 7) The sintered ore raw materials are loaded into a drum for primary mixing, and a binder solution is added to the primary mixing to form a primary sintered mixed material, wherein the binder solution is a solution obtained by diluting the steelmaking LT dust removal ash with water; the primary sintered mixed material is then transferred to a secondary mixing drum for mixing and granulation, and a secondary sintered mixed material is obtained after granulation; 8) The secondary sintered mixed material is transferred to the sintering trolley for exhaust sintering to obtain the finished sintered ore.

2. The method for recycling tailings of steelmaking slag into sintered ore according to claim 1, characterized in that: In the step 3), the iron content in the tailings magnetic separation material is required to be not less than 35%, the particle size range of the tailings magnetic separation material is 0-8mm, and the tailings magnetic separation material larger than 8mm is controlled to be ≤10%.

3. The method for recycling tailings of steelmaking slag into sintered ore according to claim 1, characterized in that: In the step 5), other iron-containing solid wastes are hot-rolled iron oxide scale and continuous casting iron mud, and the ratio of tailings magnetic separation material to other iron-containing solid wastes is 1:

3.

4. The method for recycling tailings of steelmaking slag into sintered ore according to claim 1, characterized in that: In the step 6), the mass percentage of each component of the sintering raw material is: 72% to 78% of hematite rich ore powder, 1% to 3% of tailings magnetic separation material mixture, 5% to 10% of sintering return ore, 10% to 12% of sintering flux, and 4% to 5% of solid fuel, and the sum of the mass percentages of each component is 100%; at the same time, the binary basicity R2 of the sintering raw material is controlled to be 1.80-1.90, the mass percentage of SiO2 in the sintering raw material is controlled to be 4.2-4.8% and the mass percentage of MgO is controlled to be 1.10-1.49%; the solid fuel for sintering is any one of coke powder, anthracite powder or a mixture of coke powder and anthracite powder, the mass percentage of carbon in the solid fuel is controlled to be 77-85%, and the solid fuel with a particle size of ≤3.0 mm accounts for ≥90% of the total mass of the solid fuel; the sintering flux is a mixture of dolomite, quicklime and limestone.

5. The method for recycling tailings of steelmaking slag into sintered ore according to claim 1, characterized in that: In the step 7), the mass percentage of the steelmaking LT dust removal ash in the binder solution is 6.5-7.0%.