Economical material high-coal-ratio smelting method for blast furnace with small bosh angle

Abstract

The invention relates to the technical field of blast furnace ironmaking, in particular to a small bosh angle blast furnace economic material high-coal-ratio smelting method, which comprises the following steps: increasing the particle size of center coke, changing a sieve from 25mm to 28mm, increasing the nut coke ratio from 35kg / t to 40kg / t, reducing the pressure difference to improve the air permeability in the furnace, reducing the length of a tuyere small sleeve extending into the furnace from 500mm to 460mm, increasing the equivalent bosh angle from 68 degrees 4'to 69 degrees 9 ', and improving the yield of the blast furnace economic material high-coal-ratio smelting. The maximum angle of coke is larger than the maximum angle of ore by 2-3 degrees, the minimum angle of ore is smaller than the secondary center coke angle by 0.5-1 degree, center coke adding is carried out (the angle range is 6-13 degrees), the heat flow intensity is larger than 8000 kcal / (m < 2 >. H), enough air flow passes through the edge to guarantee smooth operation, and due to the fact that the edge coke is high in digestion speed, coke nuts are distributed to the edge, and the coke yield is increased. Tuyere coke replacement speed is increased, and air permeability is improved; and the oxygen enrichment of each ton of iron is increased to 100-120m < 3 >, and the theoretical combustion temperature is balanced. The method is suitable for a 1380-1780 m < 3 > blast furnace, the coal ratio can be stabilized at 175 kg / t or above for a long time through the technical method, and efficiency increase and cost reduction are achieved through coal extraction and tar reduction.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace ironmaking, in particular to a method for smelting economic materials with a high coal ratio in a small furnace belly angle blast furnace. Background Art

[0002] The current steel market situation is becoming increasingly severe. The steel market is saturated and demand has dropped significantly. If companies want to survive, they need to reduce costs. High coal ratio is an important way to make iron at low cost. Most of the domestic 1500m 3 The particle-grade blast furnace is equipped with more than 20% top-charged dry quenching coke to ensure stable gas flow. However, the market situation is poor. In order to reduce costs, some blast furnaces have begun to use full ramming coke. The price of ramming coke is about 150 yuan / ton lower than that of top-charged coke, which can effectively reduce fuel costs. Some design institutes design blast furnace belly angles of 76°20′, which is smaller than normal blast furnaces (78°-80°). Too small belly angles will cause the edges to become heavier and the furnace walls to become thicker. Using economic materials to reduce grade will result in large slag volume, high pressure difference, and high harmful elements. Under this condition, it is very difficult to increase the coal ratio and reduce the coke ratio. The coal ratio of most blast furnaces of the same type and with the same raw material conditions is 130-160kg / t. Therefore, a high-coal ratio smelting method for economic materials with small belly angle blast furnaces is proposed to address the above problems. Summary of the invention

[0003] The object of the present invention is to provide a method for smelting economic materials with high coal ratio in a small furnace belly angle blast furnace to solve the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] As an optional scheme of the small-furnace-angle blast furnace economic material high-coal ratio smelting method described in the present invention, wherein: a small-furnace-angle blast furnace economic material high-coal ratio smelting method comprises the following steps:

[0006] Step 1: Optimization of loading system and air supply system:

[0007] (1) Increase the gap of the central coke screen: When the blast furnace is in use, the central coke screen is changed from 25mm to 28mm, the central coke particle size is increased, and the coke under the screen is mixed with ore as coke cubes to reduce the pressure difference and improve the air permeability in the furnace; on the premise of ensuring a wind speed of more than 260m / s, low top pressure operation is performed, and the lower high-temperature coal gas is blown through the center;

[0008] (2) Material system: The maximum angle of coke is larger than the maximum angle of ore, and the minimum ore angle is smaller than the secondary center focal angle. The center focal angle range is 6-13°, achieving heat flux intensity > 8000 kcal / (m 2 h);

[0009] (3) Stabilize the coke platform and widen the ore platform, with the maximum and minimum ore angles differing by 8-10°;

[0010] (4) Spread the coke cubes (8-28mm small coke) to the edge;

[0011] (5) The thickness of the coke layer at the furnace throat is 360-400 mm, and the thickness of the coke layer at the furnace waist is 140-170 mm;

[0012] (6) Shorten the length of the tuyere sleeve: the length of the tuyere sleeve extending into the furnace is reduced from 500 mm to 460 mm, and the equivalent furnace belly angle is increased from 68°4′ to 69°9′;

[0013] (7) Priority will be given to the storage space for fragile sintered ores, and the number of ore bins in blast furnaces will be increased. The storage space will be increased from 6 meters to 7 meters, and two ground-based ore bins will be prepared for each blast furnace.

[0014] Step 2: Prepare the furnace charge:

[0015] The comprehensive furnace grade is below 56.5%, the bituminous coal ratio is 30%, and the blast furnace coal ratio is 183kg / t;

[0016] Prepare the furnace charge as required, sintered ore 73-75%, pelletized ore 18-20%, lump ore 7-9%;

[0017] The coke composition M10 is 7-8%, the reactivity is 23-28%, the strength after reaction is 60-68%, the ash content is 12.5-13.5%, the volatile matter is 1-2%, and 10-15% of the secondary wet quenching coke is added;

[0018] Sintered ore low temperature reduction powder index RDI +3.15 At 63-68%, total iron content 53-54.5%, MgO content ≥ 2-3%;

[0019] The compressive strength of pellets is ≥2500N / piece, the total iron content is 61-63%, and the MgO content is ≤3-5%;

[0020] Step 3: Operation parameter selection:

[0021] Ore batch 42-44 tons, 1 ton of iron enriched with oxygen to 100-120m 3 , achieving oxygen-enriched production, hot air temperature 1220-1240℃, top pressure 220-230kPa, pressure difference 190-200kPa, slag basicity 1.20-1.25, MgO content in slag 8.4-8.7%, Al2O3 content 14.5-15.2%, magnesium-aluminum ratio 0.56-0.59.

[0022] As an optional scheme for the small-furnace-angle blast furnace economic material high-coal ratio smelting method described in the present invention, wherein: the coke diced ratio is increased from 35kg / t to 40kg / t.

[0023] As an optional solution of the method for smelting economic material and high coal ratio of a small furnace belly angle blast furnace described in the present invention, the flow rate of the soft water at the bottom of the furnace is 853m 3 / h controlled to 453m 3 / h, reducing the heat taken away by cooling water and ensuring the center temperature of the furnace.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention increases the gap of the central coke sieve, changes the sieve from 25mm to 28mm, increases the coke dicing ratio from 35kg / t to 40kg / t, increases the central coke particle size, reduces the pressure difference and improves the air permeability in the furnace. 3 / h controlled to 453m 3 / h, to ensure the center temperature of the furnace, adopt an open center distribution matrix, and move the angle outward to strengthen the center airflow. The above steps can solve the problem of poor air permeability and suppression of center airflow when using fully rammed coke columns;

[0026] By reducing the length of the tuyere sleeve extending into the furnace from 500mm to 460mm, the equivalent furnace belly angle is increased from 68°4′ to 69°9′. The coke-wrapped ore route is adopted to increase the edge airflow intensity and reduce the thickness of the furnace wall. The maximum angle of coke is 2-3° larger than the maximum angle of ore, and the minimum ore angle is 0.5°-1° smaller than the secondary center coke angle. The center is coked (angle range: 6-13°). Through the above means, the heat flux intensity is > 8000kcal / (m 2 h), sufficient airflow passes through the edge to ensure smooth flow. Because the coke at the edge is digested quickly, coke cubes (8-28mm small coke) are placed at the edge to speed up the replacement of coke at the tuyere and improve air permeability. The above steps can solve the problem of aggravated edges, thick furnace walls, and high pressure difference in blast furnaces caused by small bosh angles;

[0027] The thickness of the coke layer at the throat is 360-400mm, and the thickness of the coke layer at the waist is 140-170mm, which meets the air permeability requirements of the soft melting zone. The oxygen enrichment per ton of iron is 100-120m 3 , cooperate with high coal ratio to stabilize the theoretical combustion temperature before the tuyere. Stabilize the coke platform, widen the ore platform, and make the maximum and minimum ore angles differ by 8-10°. In terms of management, prevent the entry of circulating miscellaneous materials with high content of harmful elements into the furnace (steelmaking ash, sintering machine head ash, blast furnace bag ash, etc.), perform normalized zinc and alkali removal operations (low alkalinity 1.2-1.25, molten iron sulfur above 0.030%), reduce the impact of harmful element enrichment on furnace conditions, give priority to the storage of fragile sintered ore, and increase the blast furnace ore bin storage space from 6 meters to 7 meters. Prepare 2 ground ore bins for each blast furnace to reduce falling. The above steps can solve the problems of using low-grade economic materials, large slag volume, high pressure difference, and high harmful elements;

[0028] Treatment of pulverized coal: the fineness is increased from 82% to 83-84%, the proportion of bituminous coal is 25%-35%, to ensure the combustibility of pulverized coal and the heat-raising effect;

[0029] The present invention is applicable to 1380-1780m 3 For blast furnaces, the above technical methods can achieve a stable coal ratio of more than 175kg / t, increase coal and reduce coke to achieve increased efficiency and reduced costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the equivalent furnace belly angle and the modified equivalent furnace belly angle. DETAILED DESCRIPTION

[0031] Embodiment: The present invention provides a technical solution:

[0032] A high-coal ratio smelting method for economical materials in a small-furnace-angle blast furnace, wherein the comprehensive input grade is below 56.5%, the proportion of bituminous coal is 30%, and the blast furnace coal ratio is completed to 183kg / t.

[0033] Prepare the charge as required: 73-75% sintered ore, 18-20% pelletized ore, and 7-9% lump ore.

[0034] The coke composition M10 is 7-8%, the reactivity is 23-28%, the strength after reaction is 60-68%, the ash content is 12.5-13.5%, the volatile matter is 1-2%, and 10-15% of secondary wet quenching coke is added.

[0035] Sintered ore low temperature reduction pulverization index RD I +3.15 At 63-68%, total iron content 53-54.5%, MgO content ≥2-3%.

[0036] The compressive strength of the pellets is ≥2500N / piece, the total iron content is 61-63%, and the MgO content is ≤3-5%.

[0037] Ore batch 42-44 tons, 1 ton iron oxygen enrichment 100-120m 3 , hot air temperature 1220-1240℃, top pressure 220-230kPa, pressure difference 190-200kPa, slag basicity 1.20-1.25, MgO content in slag 8.4-8.7%, Al 2 O 3 The content is 14.5-15.2%, and the magnesium-aluminum ratio is 0.56-0.59.

[0038] A2 is the equivalent belly angle, A3 is the modified equivalent belly angle, and D is the length of the tuyere penetrating into the furnace.

[0039] Example 1

[0040] The overall grade of the blast furnace is 56.11%, and the blast furnace smelting charge includes 75% sintered ore, 18% pelletized ore, and 7% lump ore. The main chemical compositions of sintered ore and pelletized ore are shown in Table 1:

[0041] grade(%) Alkalinity Ferrous iron % CaO(%) MgO(%) <![CDATA[SiO 2 (%)]]> <![CDATA[Al 2 THE 3 (%)]]> S(％) 54.5 2.13 9.00 11.60 2.31 5.44 2.54 0.02 61.36 0.17 0.78 1.2 1.06 7.17 1.19 0.01

[0042] Sintered ore low temperature reduction pulverization index RD I +3.15 The pellet compressive strength is 2859N / piece; the coke ash content is 12.5%, the coke M10 is 7.6%, the coke reactivity is 27%, and the strength after reaction is 62%.

[0043] Control blast furnace parameters:

[0044] (1) Charging system: 42 tons of ore, 8 tons of coke, 26000m3 of oxygen 3 / h or more, hourly material speed 7.5 batches, material line 1.5m,

[0045] Material: p:34 / 32 / 30 / 28 / 25 2 / 3 / 3 / 2 / 1

[0046] k:36 / 33 / 31 / 28.5 / 25.5 / 13 3 / 3 / 2 / 2 / 2 / 3

[0047] Gradually increase the load so that the coke window thickness matches the widened ore platform, dredge the central airflow, and stabilize the edge airflow. The coke layer thickness at the furnace throat is 360-400mm, and the coke layer thickness at the furnace waist is 140-170mm, meeting the permeability requirements of the soft melting zone.

[0048] (2) Air supply system: hot air pressure 430 kPa, top pressure set to 220 kPa constant, wind speed 262 m / s.

[0049] (3) Thermal system and slag making system: The silicon content of pig iron is 0.30%-0.45%, the physical heat is greater than 1490℃, and the slag basicity is controlled at 1.22-1.25.

[0050] Reduce the length of the tuyere extending into the furnace to 460mm, and correct the furnace belly angle to 69.9° to avoid edge thickening. Prevent steelmaking dust, sintering machine head ash, and blast furnace bag ash with high zinc content from being added to sintering and pelletizing. In terms of operation, release sulfur with low alkalinity, strengthen the central airflow to discharge zinc and alkali, activate the center, and reduce the enrichment of harmful elements. Increase the gap of the central coke sieve to 28mm, improve the central coke particle size, reduce the blast furnace pressure difference, and improve the permeability of the material column. Coke is spread to the edge to promote coke replacement and activate the furnace.

[0051] Coke management: Establish a record of coke categories and load materials in different stacks and bins. Add 10-15% of secondary wet quenching coke to the coke structure to reduce coke costs. Timely stacking reduces coke rolling and coke fragmentation. The deviation of accurate material distribution circles does not exceed 0.1 circle.

[0052] Through the above measures, the coal ratio of the blast furnace reached 183kg / t, achieving the goal of increasing coal and reducing coke.

[0053] Cost reduction per ton of iron = 0.42 yuan / ton * (183-150) kg / t = 13.86 yuan / ton.

[0054] Example 2

[0055] The overall furnace grade is 56.04%, and the blast furnace smelting charge includes 74.5% sintered ore, 20.5% pelletized ore, and 5% lump ore. The main chemical compositions of sintered ore and pelletized ore are shown in Table 1.

[0056] grade Alkalinity Ferrous iron % CaO(%) MgO(%) SiO2(%) Al2O3(%) S(％) 54.35 2.11 8.68 11.59 2.347 5.51 2.55 0.02 61.02 0.15 0.79 1.1 1.21 7.67 1.19 0.01

[0057] Sintered ore low temperature reduction pulverization index RD I +3.15 is 64%; the compressive strength of the pellets is 2920.45N / piece; the coke ash content is 12.6%, the coke M10 is 7.2%, the coke reactivity is 27.5%, and the strength after reaction is 63.2%.

[0058] Control blast furnace parameters:

[0059] (1) Charging system: 44 tons of ore, 8.5 tons of coke, 25500m3 of oxygen 3 / h or more, hourly material speed is 7 batches, material line is 1.5m.

[0060] Material: p:34 / 32 / 29.5 / 27 / 23 2 / 3 / 3 / 2 / 2

[0061] k:36.5 / 34 / 31 / 27.5 / 24 / 9 3 / 3 / 2 / 2 / 2 / 4

[0062] (2) Air supply system: hot air pressure 428 kPa, top pressure set to 218 kPa unchanged, wind speed 265 m / s.

[0063] (3) Thermal system and slag making system: The silicon content of pig iron is 0.30%-0.45%, the physical heat is greater than 1490℃, and the slag basicity is controlled at 1.2-1.25.

[0064] Strengthen the screening of wet quenching coke, control the screening rate to less than 45kg / s, reduce the amount of powder entering the furnace, and ensure the air permeability of the material column. The wet quenching coke is placed in the center of the furnace throat radius to reduce the impact on the two airflows. The center coke is 4 circles, and the center airflow is gradually strengthened to solve the problems of furnace wall temperature fluctuation and high pressure difference.

[0065] Through the above measures, the furnace hearth can be kept in good working condition, creating conditions for a high coal ratio.

[0066] Cost reduction per ton of iron = 0.42 yuan / ton * (176-150) kg / t = 10.92 yuan / ton.

[0067] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. The above is only a preferred implementation of the present invention. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the protection scope of the present invention.

Claims

1. A method for smelting economic materials and high coal ratio in a small furnace belly angle blast furnace, characterized in that: The usage steps include the following: Step 1: Optimization of loading system and air supply system: (1) Increase the gap of the central coke screen: When the blast furnace is in use, the central coke screen is changed from 25mm to 28mm, the central coke particle size is increased, and the coke under the screen is mixed with ore as coke cubes to reduce the pressure difference and improve the air permeability in the furnace; on the premise of ensuring a wind speed of more than 260m / s, low top pressure operation is performed, and the lower high-temperature coal gas is blown through the center; (2) Material system: The maximum angle of coke is larger than the maximum angle of ore, and the minimum ore angle is smaller than the secondary center focal angle. The center focal angle range is 6-13°, achieving heat flux intensity > 8000kcal / (m 2 h); (3) Stabilize the coke platform and widen the ore platform, with the maximum and minimum ore angles differing by 8-10°; (4) Spread the coke cubes (8-28mm small coke) to the edge; (5) The thickness of the coke layer at the furnace throat is 360-400 mm, and the thickness of the coke layer at the furnace waist is 140-170 mm; (6) Shorten the length of the tuyere sleeve: the length of the tuyere sleeve extending into the furnace is reduced from 500 mm to 460 mm, and the equivalent furnace belly angle is increased from 68°4′ to 69°9′; (7) Prioritize the storage space for fragile sintered ore, increase the number of ore bins in blast furnaces, increase the storage space from 6 meters to 7 meters, and prepare 2 ground-level ore bins for each blast furnace; Step 2: Prepare the furnace charge: The comprehensive furnace grade is below 56.5%, the bituminous coal ratio is 30%, and the blast furnace coal ratio is 183kg / t; Prepare the furnace charge as required, sintered ore 73-75%, pelletized ore 18-20%, lump ore 7-9%; The coke composition M10 is 7-8%, the reactivity is 23-28%, the strength after reaction is 60-68%, the ash content is 12-13%, the volatile matter is 1-2%, and 10-15% of the secondary wet quenching coke is added; Sintered ore low temperature reduction powder index RDI +3.15 At 63-68%, total iron content 53-54.5%, MgO content ≥ 2-3%; The compressive strength of pellets is ≥2500N / piece, the total iron content is 61-63%, and the MgO content is ≤3-5%; Step 3: Operation parameter selection: Ore batch 42-44 tons, 1 ton iron oxygen enrichment 100-120m 3 , hot air temperature is 1220-1240℃, top pressure is 220-230kPa, pressure difference is 190-200kPa, slag basicity is 1.20-1.25, MgO content in slag is 8.4-8.7%, Al2O3 content is 14.5-15.2%, and magnesium-aluminum ratio is 0.56-0.

59.

2. The method for smelting economic material and high coal ratio of a small furnace belly angle blast furnace according to claim 1, characterized in that: The diced coke ratio is increased from 35kg / t to 40kg / t.

3. The method for smelting economic material and high coal ratio of a small furnace belly angle blast furnace according to claim 1, characterized in that: The furnace bottom soft water flow rate is 853m 3 / h controlled to 453m 3 / h, reducing central heat loss.

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