Low-carbon short-process method for preparing high-purity industrial pure iron

Abstract

The invention discloses a low-carbon short-process method for preparing high-purity industrial pure iron. The method comprises the following steps: proportioning and pelletizing iron fine powder, drying by a chain grate, preheating and pre-oxidizing green pellets, deeply oxidizing, solidifying and desulfurizing the preheated pellets in an oxidation rotary kiln, selectively reducing the solidified pellets by adopting an electric heating rotary kiln, feeding the reduced pellets into a melting furnace in a hot state, melting, separating slag and iron, and the like, so that the smelting process can be greatly shortened; sulfur removal is completed through oxidation in a solid state, and iron oxide is selectively reduced in the smelting process, so that iron slag separation is good in the melting separation process, the content of carbon, sulfur, silicon, manganese and the like in iron is extremely low, the complicated procedures of converter decarbonization, desulfurization, deoxidation, dephosphorization, impurity reduction and the like are avoided, and meanwhile the production requirement of high-purity iron can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and mineral engineering, and specifically relates to a method for preparing high-purity industrial pure iron with a low-carbon short process. Background Art

[0002] Industrial pure iron is a metal material with a very low carbon content. The iron content is generally above 99.5%. The lower the content of other elements except Fe, the better. Industrial pure iron is an important raw material used for smelting precision alloys, high-temperature alloys, ultra-low carbon stainless steel, electric heating alloys, etc. The long-process production method of blast furnace + converter can smelt industrial pure iron with a carbon content that meets the use requirements, but the process is long. The blast furnace smelting process relies on "iron, burning, coke" and other processes, with large carbon emissions and high energy consumption indicators. In the converter smelting, oxygen decarburization, aluminum deoxidation, slag desulfurization, dephosphorization, manganese reduction and other impurity elements are required. The process is complicated, and its purity is still not high. In addition, the sulfur, phosphorus and manganese content is high, and only industrial pure iron of general quality can be produced. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing high-purity industrial pure iron in a low-carbon, short-process manner, which can greatly shorten the smelting process. Hydrogen selective reduction and clean melting are used in the smelting process, avoiding complicated decarbonization, desulfurization, deoxidation, dephosphorization, impurity reduction and other processes, while meeting the production requirements of high-purity iron.

[0004] To achieve the above object, the present invention adopts the following technical solution: A method for preparing high-purity industrial pure iron by a low-carbon short process comprises the following steps: 1) Mix the iron concentrate with an iron content of 65% or more and a particle size of -200 mesh accounting for 85-95% with bentonite in a mass ratio of 100:(1.5-2.5), add water and use a ball-making disk to prepare wet pellets of 13-18 mm, the moisture content is controlled at 7%-9%, and the half-meter drop times are 3 times or more; 2) Prepare qualified wet pellets and send them to the chain grate by belt conveyor, and use the waste heat of 900~1000℃ flue gas from the next stage oxidation consolidation rotary kiln to dry, preheat and pre-oxidize them for 25~30min. After leaving the chain grate, the pellet temperature is 800~900℃, containing FeO: 9~15%, and the compressive strength is greater than 300N / ball; 3) The preheated and preoxidized pellets are sent to the oxidation rotary kiln, using the 1000~1100℃ flue gas waste heat and 1500~2000Nm 3 / ton of pellets are fully oxidized, consolidated and desulfurized with compressed air. After oxidation and consolidation, the pellet compressive strength is 800N / ball or above, and the sulfur content in the pellets is removed to below 0.01%; 4) The pellets that have completed oxidation consolidation are sent to the reduction rotary kiln and reduced with low-rank lignite containing hydrogen. The particle size of the low-rank lignite is 10-30 mm, the amount added is 20%-27% of the iron content of the pellets, the reduction temperature is 1000-1100°C, and the metallization rate of the produced metallized pellets is 95% or above; 5) The metallized pellets produced by the reduction rotary kiln are directly hot-transferred to the smelting furnace and heated to 1450~1550℃ for iron slag separation, so as to produce high-purity industrial pure iron: Fe>99.9%, C<0.002%, Si<0.002%, Mn<0.005%, S<0.01%, P<0.01%, Al<0.001%, Cr<0.001%, V<0.001%, Ti<0.001%.

[0005] The present invention has the following beneficial effects: 1. The present invention integrates the pelletizing equipment, chain grate, oxidation consolidation rotary kiln, reduction rotary kiln, smelting furnace, desulfurization equipment and auxiliary facilities, so that the iron ore concentrate pelletizing equipment makes pellets, the raw pellets are dried and preheated and pre-oxidized by the chain grate, the preheated pellets are oxidized and consolidated and desulfurized by the rotary kiln, the consolidated pellets are selectively reduced by the electric heating rotary kiln, and the reduced pellets are hot. The smelting furnace is used for smelting, slag and iron separation, and other processes are seamlessly connected. The processes involved in the process use heat step by step, avoiding heat loss and waste caused by the alternating hot and cold transportation of materials in each link, and greatly reducing energy consumption indicators.

[0006] 2. The present invention uses oxidation to consolidate. Under the condition of ensuring that the hot air is supplied at 1050°C, the heat released by the ferrous oxide in the pellets during oxidation can meet the heat source demand in the oxidation kiln, without external heat supply. After oxidation consolidation, the pellets have a certain compressive strength, and the integrity of the pellets can be maintained during the entire reduction process in the reduction kiln, thereby improving the heat transfer of the material layer and increasing the heat utilization efficiency. In addition, the sulfur carried by the raw pellets is removed as much as possible, so that the sulfur content in the subsequent reduction of the metallized pellets in the preparation of industrial pure iron by smelting iron slag separation is in a trace amount, below 0.01%, and no further desulfurization is required.

[0007] 3. The present invention can make full use of local green electricity resources such as wind, light, and water. The entire process system uses green electricity for heating, and low-grade lignite containing hydrogen during metallurgical reduction can give full play to the high efficiency, energy conservation and emission reduction of hydrogen metallurgy, thereby realizing low-carbon green metallurgy.

[0008] 4. The present invention adopts a green electricity externally heated reduction type rotary kiln, uses hydrogen-containing low-rank lignite for hydrogen metallurgy, controls the internal temperature at about 1050°C, and avoids the formation of rotary kiln rings caused by the soft melting of materials due to the local flame temperature being too high during the reduction process, which makes the process impossible to proceed smoothly; at the same time, it also avoids carburization or excessive reduction of other substances caused by excessive temperature, thereby making the preparation of industrial pure iron with higher purity and simpler process when melting. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0010] The process of the present invention will be further explained below in conjunction with the accompanying drawings.

[0011] like Figure 1 As shown, the method for preparing industrial pure iron with a low carbon short process of the present invention is as follows: 1) Mix the iron ore concentrate and bentonite in a ratio of 100:2, add water and use a pelletizing plate to prepare wet pellets of 13-18 mm. The unqualified wet pellets classified by roller screening are returned for crushing and re-pelletizing.

[0012] 2) Prepare qualified wet pellets and send them to the chain grate by belt conveyor, and use the waste heat of 950℃ flue gas from the next stage oxidation consolidation rotary kiln to dry, preheat and pre-oxidize them for 30 minutes. After leaving the chain grate, the pellet temperature is 860℃, containing FeO: 12.5%, and the compressive strength is 400N / ball; 3) The preheated and preoxidized pellets are sent to the oxidation rotary kiln, and the waste heat of the 1050℃ flue gas and 1800Nm 3 / ton of pellets are fully oxidized, consolidated and desulfurized with compressed air. After oxidation and consolidation, the compressive strength of the pellets is 960N / ball, and the sulfur content in the pellets is removed to below 0.01%; 4) The pellets that have completed oxidation consolidation are sent to the reduction rotary kiln and reduced with low-rank lignite containing hydrogen. The particle size of the low-rank lignite is 10-30 mm, the amount added is 25% of the iron content of the pellets, the reduction temperature is 1100°C, and the metallization rate of the produced metallized pellets is 96%; 5) The metallized pellets produced by the reduction rotary kiln are directly hot-transferred to the smelting furnace and heated to 1550℃ for iron slag separation, so as to produce high-purity industrial pure iron: Fe>99.9%, C<0.002%, Si<0.002%, Mn<0.005%, S<0.01%, P<0.01%, Al<0.001%, Cr<0.001%, V<0.001%, Ti<0.001%.

Claims

1. A method for preparing high-purity industrial pure iron by a low-carbon short process, characterized in that: The following steps are involved: 1) Mix the iron concentrate with an iron content of 65% or more and a particle size of -200 mesh accounting for 85-95% with bentonite in a mass ratio of 100:(1.5-2.5), add water and use a ball-making disk to prepare wet pellets of 13-18 mm, the moisture content is controlled at 7%-9%, and the half-meter drop times are 3 times or more; 2) Prepare qualified wet pellets and send them to the chain grate by belt conveyor, and use the waste heat of 900~1000℃ flue gas from the next stage oxidation consolidation rotary kiln to dry, preheat and pre-oxidize them for 25~30min. After leaving the chain grate, the pellet temperature is 800~900℃, containing FeO: 9~15%, and the compressive strength is greater than 300N / ball; 3) The preheated and preoxidized pellets are sent to the oxidation rotary kiln, using the 1000~1100℃ flue gas waste heat and 1500~2000Nm 3 / ton of pellets are fully oxidized, consolidated and desulfurized with compressed air. After oxidation and consolidation, the pellet compressive strength is 800N / ball or above, and the sulfur content in the pellets is removed to below 0.01%; 4) The pellets that have completed oxidation consolidation are sent to the reduction rotary kiln and reduced with low-rank lignite containing hydrogen. The particle size of the low-rank lignite is 10-30 mm, the amount added is 20%-27% of the iron content of the pellets, the reduction temperature is 1000-1100°C, and the metallization rate of the produced metallized pellets is 95% or above; 5) The metallized pellets produced by the reduction rotary kiln are directly hot-transferred to the smelting furnace and heated to 1450~1550℃ for iron slag separation, so as to produce high-purity industrial pure iron: Fe>99.9%, C<0.002%, Si<0.002%, Mn<0.005%, S<0.01%, P<0.01%, Al<0.001%, Cr<0.001%, V<0.001%, Ti<0.001%.

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