Method for reducing fuel ratio in high ball ratio blast furnace ironmaking

Abstract

The present application relates to the field of blast furnace smelting technology, and discloses a method for reducing fuel ratio in blast furnace iron smelting with high ball ratio, which combines the "central coke adding" technology and "mineral coke mixed loading" technology, maintains the central coal gas flow through central coke adding, suppresses the pipeline travel and coal gas flow fluctuation, improves the dispersibility and mixing property through mineral coke mixed loading, and suppresses the reaction degradation of lump coke. The method provided by the present application can directly reduce fuel consumption, improve the air permeability and reducibility, realize the blast furnace smelting with low fuel ratio and high ball ratio, reduce the fuel ratio and production cost in blast furnace iron smelting, and realize the efficient utilization of resources.

Description

Technical Field

[0001] This invention relates to the field of blast furnace smelting technology, and specifically to a method for reducing the fuel ratio in high ball ratio blast furnace ironmaking. Background Technology

[0002] Blast furnace ironmaking is a core ironmaking technology that involves layering iron ore (sintered ore, pellets, lump ore, etc.), fuel (coke, pulverized coal, etc.), and flux (such as limestone) into a blast furnace to continuously produce pig iron through a high-temperature reduction reaction. In blast furnace ironmaking, reducing the fuel ratio is an important research direction for lowering the cost of molten iron.

[0003] In traditional blast furnace ironmaking, the ratio of sinter, pellets, and lump ore is approximately 7:2:1, with sinter making up the majority. From an energy consumption and pollutant emission perspective, the pelletizing process is significantly lower than the sintering process. Replacing a high proportion of sinter with a high proportion of pellets would provide a new solution for green metallurgy. However, pellets have a smaller particle size, and their metallurgical properties differ greatly from sinter. Therefore, they have a greater impact on blast furnace permeability than sinter, and using large amounts of pellets increases permeability resistance. Coke plays a crucial role in maintaining permeability, and a decrease in the coke ratio is accompanied by an increase in permeability resistance. Therefore, for blast furnace ironmaking with a high pellet ratio, operating with a low coke ratio becomes extremely difficult. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for reducing the fuel ratio in high ball ratio blast furnace ironmaking, thereby achieving low fuel ratio and high ball ratio blast furnace smelting by improving blast furnace permeability and reducing ironmaking costs.

[0005] To achieve the above objectives, the present invention provides a method for reducing the fuel ratio in high-ball-ratio blast furnace ironmaking, comprising: (1) The coke is screened into coke lumps and coke pieces, wherein the coke lumps have a particle size > 30 mm and the coke pieces have a particle size of 8-30 mm; (2) The coke blocks are added to the blast furnace using a center-adding coke feeding method; (3) Under the condition of pulverized coal injection, the coke is mixed with iron ore and flux and then added to the blast furnace for ironmaking; the iron ore is composed of 30-40wt% sinter and 60-70wt% pellets, and the flux is selected from a combination of active lime and quicklime.

[0006] Furthermore, a bell-less furnace top device is used for material distribution.

[0007] Furthermore, the amount of coke lumps used is 250-300 kg / ton of iron, and the amount of coke briquettes used is 80-150 kg / ton of iron.

[0008] Furthermore, the amount of pulverized coal used is 120-140 kg / ton of iron.

[0009] Furthermore, the iron ore has a particle size of 8-30 mm.

[0010] Furthermore, the pellets consist of 80-85 wt% alkaline pellets and 15-20 wt% acidic pellets.

[0011] Furthermore, the alkaline pellets are prepared from 75 wt% iron concentrate, 2 wt% bentonite, 10 wt% limestone, 6 wt% hydrated lime and 7 wt% dolomite.

[0012] Furthermore, the alkaline pellets are prepared using a chain grate-rotary kiln.

[0013] To improve the permeability of blast furnaces under high pellet ratio smelting, this invention combines "center coking" and "ore-coke mixed charging" technologies. This improves the permeability of the charge column, optimizes the reduction process, and reduces the fuel ratio. The coke lumps are added to the blast furnace using a center coking charging method, which creates a coke column in the central region. Even with the addition of more pellets, it can suppress the flow of ore into the center, maintaining good permeability in the central area. This creates a low-permeability resistance zone in the center, stably maintaining the central gas flow. Even with high permeability resistance due to a low coke ratio, this also suppresses pipe travel and gas flow fluctuations. However, excessively strong central gas flow can lead to insufficient peripheral gas flow, affecting ore preheating and reduction, and ultimately increasing fuel consumption. Therefore, this application combines the "mineral-coke mixed loading" technology, adding coke particles of the same size as the ore, which improves the mixability with the ore, increases the reaction area of ​​the coke, improves the dispersibility, and promotes the gasification reaction of the mixed coke. As the ore reduction rate increases, the mixed coke reacts preferentially, inhibiting the reaction deterioration of lump coke.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The method provided by this invention can directly reduce fuel consumption, improve permeability and reducibility, achieve blast furnace smelting with low fuel ratio and high ball ratio, reduce the fuel ratio and production cost of blast furnace ironmaking, and achieve efficient utilization of resources. Specific implementation methods To better understand the present invention, the present invention will be further described below with reference to the embodiments. However, the content of the present invention is not limited to the following embodiments. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the protection scope of the present invention.

[0015] Example 1: This embodiment provides a method for high pellet ratio blast furnace ironmaking, which includes the following steps: Step 1: Preparation of sintered ore: Mix 70 parts by weight of vanadium-titanium magnetite concentrate, 30 parts by weight of iron-manganese ore, 20 parts by weight of chromite, 6 parts by weight of coke powder, 2 parts by weight of coal powder, 10 parts by weight of active lime, and 5 parts by weight of quicklime. Add water to form a mixture with a moisture content of 8%. Add this mixture to a belt sintering machine for gas ignition and sintering. Control the material layer height at 600 mm. 800mm. After sintering, the sintered ore is screened to obtain a particle size of 8-30mm.

[0016] Step 2: Preparation of acidic ore pellets: Mix 90 parts by weight of vanadium-titanium magnetite concentrate with 5 parts by weight of bentonite, add 6 parts by weight of water, pelletize, and then dry, preheat, roast, and sieve the pellets to obtain acidic ore pellets with a particle size of 8-30 mm. Preferably, the process is prepared using a "chain grate machine-rotary kiln-annular cooler".

[0017] Step 3: Preparation of alkaline pellets: 75 parts by weight of vanadium-titanium magnetite concentrate is mixed with 2 parts by weight of bentonite, 10 parts by weight of limestone, 6 parts by weight of hydrated lime, and 7 parts by weight of dolomite. 6 parts by weight of water is added, and the mixture is pelletized. The pellets are then dried, preheated, roasted, and sieved to obtain alkaline pellets with a particle size of 8-30 mm. Preferably, the process is a "chain grate machine-rotary kiln-annular cooler".

[0018] Step 4: Screen the coke into coke lumps and coke pieces, wherein the coke lumps have a particle size > 30 mm and the coke pieces have a particle size of 8-30 mm.

[0019] Step 5, Charging: A bell-less top charging system is used for ring-shaped charging, adding coke and iron ore in a predetermined order. Coke lumps are added to the blast furnace using a center-addition method, while coke nuts are added after being mixed with iron ore and flux. The iron ore consists of 30 wt% sinter and 70 wt% pellets, with the pellets comprising 80 wt% alkaline pellets and 20 wt% acidic pellets. The flux is a 1:1 mixture of quicklime and active lime. The coke lump dosage is 250 kg / ton of iron, and the coke nut dosage is 150 kg / ton of iron. Step 6, Smelting: Inject 120 kg of pulverized coal per ton of iron into the blast furnace, control the blast temperature at 1230℃, and achieve an oxygen enrichment rate of 7% to obtain molten iron and slag.

[0020] Example 2: Similar to Example 1, except that the iron ore consists of 40 wt% sinter and 60 wt% pellets, the pellets consist of 85 wt% alkaline pellets and 15 wt% acidic pellets, the amount of coke lumps is 300 kg / ton of iron, the amount of coke briquettes is 80 kg / ton of iron, and the amount of pulverized coal is 140 kg / ton of iron.

[0021] In this embodiment, the blast furnace coke ratio is 380-400 kg / ton of iron, and the pulverized coal injection ratio is 120-140 kg / ton of iron. Compared with the traditional high-ball ratio blast furnace ironmaking method, the fuel ratio is reduced, thereby achieving low fuel ratio and high ball ratio blast furnace smelting, which reduces ironmaking costs.

[0022] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, any improvements and modifications made based on the core ideas of the present invention without departing from the spirit and scope of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for reducing the fuel ratio in high-ball-ratio blast furnace ironmaking, characterized in that: include: (1) The coke is screened into coke lumps and coke pieces, wherein the particle size of the coke lumps is >30mm and the particle size of the coke pieces is 8-30mm; (2) The coke blocks are added to the blast furnace using a center-adding coke feeding method; (3) Under the condition of pulverized coal injection, the coke is mixed with iron ore and flux and then added to the blast furnace for ironmaking; the iron ore is composed of 30-40wt% sinter and 60-70wt% pellets, and the flux is selected from a combination of active lime and quicklime.

2. The method according to claim 1, characterized in that: The material is distributed using a bellless furnace top device.

3. The method according to claim 1, characterized in that: The amount of coke lumps used is 250-300 kg / ton of iron, and the amount of coke briquettes used is 80-150 kg / ton of iron.

4. The method according to claim 1, characterized in that: The amount of pulverized coal used is 120-140 kg / ton of iron.

5. The method according to claim 1, characterized in that: The iron ore has a particle size of 8-30 mm.

6. The method according to claim 1, characterized in that: The pellets consist of 80-85 wt% alkaline pellets and 15-20 wt% acidic pellets.

7. The method according to claim 6, characterized in that: The alkaline pellets were prepared from 75 wt% iron concentrate, 2 wt% bentonite, 10 wt% limestone, 6 wt% hydrated lime and 7 wt% dolomite.

8. The method according to claim 6 or 7, characterized in that: The alkaline pellets are prepared using a chain grate-rotary kiln.