Recycling method of steelmaking magnesia carbon brick waste refractory

Abstract

The invention belongs to the technical field of converter steelmaking, and particularly relates to a steelmaking magnesia carbon brick waste refractory recycling method, which mainly recycles waste magnesia carbon bricks to prepare magnesium balls, and the magnesium balls are used for replacing light-burned dolomite under the high scrap ratio smelting condition of a converter, so that the steelmaking temperature drop can be reduced. The manufacturing method of the magnesium ball mainly comprises the following steps: (1) selecting magnesia carbon bricks from waste steel ladle refractory materials; (2) grinding the magnesia carbon bricks in a crushing and grinding machine into powder with the particle size of less than 5mm; (3) the magnesia carbon brick powder, iron powder and a binder are mixed according to the mass percentage and pressed into balls, and magnesium balls are formed; and (4) the prepared magnesium balls are added in the converter smelting process. The magnesium balls replace light-burned dolomite for slagging, temperature drop can be reduced, and the tapping temperature can be increased. The method is easy to operate and convenient to popularize and apply.

Description

Technical Field

[0001] The present invention belongs to the technical field of converter steelmaking, and in particular to a method for recycling waste refractory materials of steelmaking magnesia carbon bricks, and belongs to the technical field of metallurgy, and specifically relates to a method for preparing magnesium balls using waste refractory materials of steelmaking magnesia carbon bricks and the application of magnesium balls in high scrap steel ratio converter smelting. Background Art

[0002] The converter and ladle of the steelmaking system usually use magnesia carbon bricks as the lining, whose main components are MgO and carbon. A small amount of Al2O3 and SiO2 are also contained in the waste magnesia carbon bricks. MgO is an important component of converter slag. In the converter smelting process, MgO is generally provided by adding light-burned dolomite. However, light-burned dolomite is mainly composed of carbonates. When decomposed at high temperature, it will absorb a lot of heat, which is not conducive to high scrap steel ratio smelting.

[0003] Magnesium carbon bricks need to be exposed to high temperature, high oxidation and scrap steel impact production environment for a long time. In order to maintain the long life of the converter and ladle, magnesium carbon bricks are required to have antioxidant, high strength and corrosion resistance. This also makes it difficult to quickly melt the discarded magnesium carbon bricks, and it is relatively difficult to recycle the steelmaking system. Patent CN 103451373A "A magnesium ball for converter steelmaking and its production process" grinds the discarded magnesium carbon bricks and aluminum carbon bricks into powder, adds dolomite powder and water pressure to make magnesium balls, and adds lime and magnesium balls at the same time as the converter is blown or 30 seconds before the start of blowing, so as to achieve the purpose of replacing part of the light-burned dolomite with magnesium balls. Compared with the present invention, (1) only magnesium carbon bricks are used to press into balls, without aluminum carbon bricks, and the magnesium balls produced have higher magnesium oxide content and carbon content; (2) the magnesium balls also contain metallic iron, which can adjust the density of the magnesium balls and help control the position of the magnesium balls in the molten pool; (3) the magnesium balls are added within 1 to 2 minutes of converter blowing, and combined with the density of the magnesium balls, it is beneficial for the magnesium balls to quickly enter the impact zone of the oxygen stream in the molten pool, promote the direct reaction of carbon in the magnesium balls with oxygen, release heat, and use the high temperature in the impact zone to help the magnesium balls melt. The magnesium balls of the present invention are more suitable for converter high-scrap steel smelting process.

[0004] In view of the problems that light-burned dolomite is not conducive to high scrap steel ratio smelting and magnesia carbon bricks are difficult to melt quickly, the present invention optimizes the magnesia carbon brick recycling and processing method, and designs the composition and addition method of magnesium balls, which promotes its rapid melting while fully utilizing the heat generation capacity of carbon in magnesia carbon bricks to provide heat source for converter steelmaking, increase converter steel tapping temperature, and avoid the increase in scrap steel ratio leading to a decrease in molten pool temperature, which has an adverse effect on subsequent smelting production. Summary of the invention

[0005] The purpose of the present invention is to provide a method for recycling waste refractory materials of steelmaking magnesia carbon bricks, so as to solve the problem that magnesia carbon bricks are difficult to melt, and utilize the carbon in magnesia carbon bricks as a heating element to replace light-burned dolomite with a large temperature drop, which can further save heat and is beneficial to the smelting of high scrap steel ratio in converters.

[0006] The specific method steps and control method parameters are as follows: A method for recycling waste refractory materials of steelmaking magnesia carbon bricks, characterized in that it comprises the following steps: (1) Select magnesia carbon bricks from the waste ladle refractory materials; (2) Grind the magnesia carbon brick into powder less than 5 mm in a crushing and grinding machine; (3) Mixing magnesia carbon brick powder, iron powder and binder in a mass ratio of 86-90:7-10:2-3 and pressing them into balls to form magnesium balls; (4) Add the prepared magnesium balls into the converter smelting process.

[0007] Further, as a preferred embodiment, the composition of the magnesium ball is MgO: 65-75%, C: 10-15%, SiO2: 2-10, Al2O3: 2-10%, Fe: 5-10%, and some inevitable impurities in terms of weight percentage; the particle size is 20-50 mm; the density is 5.5-7.5 g / cm 3 , strength is 800~1200N.

[0008] Furthermore, as a preferred embodiment, the method for adding magnesium balls is as follows: in the converter smelting process, 1 kg / t magnesium balls can replace 2.3 kg / ton of light-burned dolomite, and the magnesium balls are added within 5% to 15% of the oxygen blowing, and the addition amount is controlled at 3 to 8 kg / t.

[0009] Further, the converter smelting process is specifically as follows: (1) Raw materials: scrap steel and molten iron, with scrap steel accounting for 25-35% by weight; the composition of molten iron is C: 4.0-5.0%, Si: 0.1-1.0%, Mn: 0.1-0.5%, P: 0.10-0.16%, S: 0.002-0.05%, and the rest are iron and some residual elements; the temperature of molten iron entering the furnace is 1250-1450℃.

[0010] (2) Oxygen supply: The top blowing flow rate during the smelting process is controlled at 35000Nm 3 / h; oxygen supply 0~35%, gun position 1.65m, oxygen supply 35~90%, gun position 1.8~2.2m; oxygen supply 90~100%, gun position 1.3~1.5m; actual oxygen lance position control can be adjusted appropriately according to the slagging situation.

[0011] (3) Adding materials: Add magnesium balls when blowing 8% oxygen; add lime and magnesium balls at one time when blowing 15% oxygen; add 600 kg of lime in two batches when blowing 40-80% oxygen; after blowing 85% oxygen, do not add any slag.

[0012] Furthermore, in the converter high scrap ratio smelting, magnesium balls are used instead of light-burned dolomite to ensure that the converter tapping temperature is 15~40℃ higher than the tapping temperature of light-burned dolomite smelting.

[0013] The advantages of the present invention mainly include the following aspects: (1) The method of selecting magnesia carbon bricks is adopted to select magnesia carbon bricks from the waste refractory materials, thereby increasing the amount of MgO, while minimizing the mixing of other substances and ensuring the stability of the composition.

[0014] (2) Magnesium balls are added within 1-2 minutes of converter blowing. At this time, the oxygen stream has formed an impact crater, and the density of magnesium balls is 5.5-7.5 g / cm due to the addition of iron powder. 3 It can ensure that the magnesium ball penetrates the slag layer smoothly and reaches the oxygen flow impact pit, so that the carbon in the magnesium ball can burn and generate heat quickly. At the same time, the carbon in the magnesium ball can be oxidized in large quantities to reduce the melting point of the magnesium carbon brick. Combined with the temperature of more than 2000℃ in the impact pit, MgO can be melted quickly, which can further promote the melting of the magnesium carbon brick.

[0015] (3) First grind the magnesia carbon brick into powder, and then press it into balls. The strength of the magnesium balls is controlled at 800~1200N, which can ensure that they will not break when feeding, and can also ensure that they can be quickly broken in the molten pool; the magnesium balls are added to the converter and expand and break into powder at high temperature, which can improve the melting performance of the magnesia carbon brick and accelerate the melting. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below in conjunction with Examples and Comparative Examples.

[0017] Embodiment 1: 1. Preparation of magnesium balls: (1) Magnesium carbon bricks are selected from converter bricks and ladle bricks off the production line. Magnesium carbon bricks are manually selected based on the color difference of waste materials; (2) Magnesium carbon bricks are ground into powder less than 5 mm in a crushing and grinding machine; (3) Magnesium carbon brick powder, iron powder and binder (binder is pregelatinized starch) are mixed in a mass ratio of 86~90:7~10:2~3 and pressed into balls to form magnesium balls; (4) Magnesium balls: The mass percentage of the prepared magnesium balls is MgO: 70.5%, C: 12.6%, SiO2: 3.6%, Al2O3: 3.8%, Fe: 8.2%, and some inevitable impurities; the particle size is 20~50 mm; the density is 6.0 g / cm 3 , strength is 1100N.

[0018] 2. Converter smelting: 120-ton converter smelting; (1) Raw materials: 36.4 tons of scrap steel, 93.6 tons of molten iron, scrap steel ratio 28%; molten iron composition: C: 4.5%, Si: 0.25%, Mn: 0.34%, P: 0.114%, S: 0.024%, and the rest are iron and some residual elements; the temperature of the molten iron entering the furnace is 1330℃.

[0019] (2) Oxygen supply: The top blowing flow rate during the smelting process is controlled at 35000Nm 3 / h; oxygen supply 0~35%, gun position 1.65m, oxygen supply 35~90%, gun position 1.8~2.2m; oxygen supply 90~100%, gun position 1.3~1.5m; actual oxygen lance position control can be adjusted appropriately according to the slagging situation.

[0020] (3) Adding materials: When blowing oxygen at 8%, add 520 kg of magnesium balls; when blowing oxygen at 15%, add 1800 kg of lime and 260 kg of magnesium balls at one time; when blowing oxygen at 40-80%, add 600 kg of lime in two batches; after blowing oxygen at 85%, do not add any slag.

[0021] Smelting by the above method, the final converter temperature is: 1612℃, final carbon: 0.065%, final phosphorus: 0.013%, final slag basicity is 2.86, MgO: 8.2%, TFe: 14.6%, the steel output is 120.3 tons; the slag pouring time before steel tapping is 1.5 minutes.

[0022] In the converter smelting process, 780 kg of the magnesium balls of the present invention are used to completely replace light-burned dolomite, which can reduce the temperature drop by about 27°C, and when the scrap steel ratio in the converter reaches 28%, the converter terminal temperature is above 1610°C, and the scrap steel is completely melted, which does not affect the converter slag splashing and furnace protection and the normal smelting of the next process (refining furnace). In addition, the added magnesium balls can be completely melted during the smelting process, and the slag can be poured smoothly before steel tapping, which does not affect the converter production rhythm.

[0023] Embodiment 2: 1. Preparation of magnesium balls: (1) Select magnesium carbon bricks from converter bricks and ladle bricks off the production line; (2) Grind the magnesium carbon bricks into powder less than 5 mm in a crushing and grinding machine; (3) Mix the magnesium carbon brick powder, iron powder and binder in a weight percentage of 86~90:7~10:2~3 and press them into balls to form magnesium balls; (4) Magnesium balls: The composition of the prepared magnesium balls is MgO: 69.3%, C: 11.7%, SiO2: 4.1%, Al2O3: 4.3%, Fe: 8.1%, and some inevitable impurities; the particle size is 20~50mm; the density is 5.9g / cm 3 , strength is 1080N.

[0024] 2. Converter smelting: 120-ton converter smelting; (1) Raw materials: 36.6 tons of scrap steel, 93.4 tons of molten iron, scrap steel ratio 28.2%; molten iron composition: C: 4.6%, Si: 0.32%, Mn: 0.33%, P: 0.121%, S: 0.022%, and the rest are iron and some residual elements; the temperature of the molten iron entering the furnace is 1360℃.

[0025] (2) Oxygen supply: The top blowing flow rate during the smelting process is controlled at 35000Nm 3 / h; oxygen supply 0~35%, gun position 1.65m, oxygen supply 35~90%, gun position 1.8~2.2m; oxygen supply 90~100%, gun position 1.3~1.5m; actual oxygen lance position control can be adjusted appropriately according to the slagging situation.

[0026] (3) Adding materials: When blowing oxygen at 8%, add 550 kg of magnesium balls; when blowing oxygen at 15%, add 2000 kg of lime and 520 kg of light-burned dolomite at one time; when blowing oxygen at 40-80%, add 700 kg of lime in two batches; after blowing oxygen at 85%, do not add any slag.

[0027] Smelting by the above method, the final converter temperature is: 1620℃, final carbon: 0.072%, final phosphorus: 0.014%, final slag basicity is 2.88, MgO: 8.3%, TFe: 15.1%, the steel output is 120.4 tons; the slag pouring time before steel tapping is 1.3 minutes.

[0028] This furnace smelting uses 550kg of the magnesium balls of the present invention to replace 1.2 tons of light-burned dolomite, which can reduce the temperature drop by about 18°C. When the scrap steel ratio in the converter reaches 28.2% with appropriate molten iron conditions, the converter terminal temperature is 1620°C, and the scrap steel is completely melted, which does not affect the slag splashing protection of the converter and the normal smelting of the next process (refining furnace). In addition, the added magnesium balls can be completely melted during the smelting process, and the slag can be poured smoothly before steel tapping, which does not affect the production rhythm of the converter.

[0029] Comparative Example 1: The waste refractory materials of magnesia carbon bricks have not been deliberately selected, resulting in a large number of other impurities and a low magnesium oxide content in the magnesium balls.

[0030] 1. Preparation of magnesium balls: (1) Grind the converter bricks and ladle bricks off the production line into powders with a size of less than 5 mm in a crushing and grinding machine; (2) Mix the brick powder, iron powder and binder in a weight percentage of 86-90:7-10:2-3 and press them into balls to form magnesium balls; (3) Magnesium balls: The composition of the prepared magnesium balls is MgO: 47.2%, C: 5.6%, SiO2: 15.6%, Al2O3: 20.3%, Fe: 8.2%, and some inevitable impurities; the particle size is 20-50 mm; the density is 6.1 g / cm 3 , strength is 1100N.

[0031] The magnesium ball has a low magnesium oxide content and high silicon dioxide and aluminum oxide content, which is not suitable for converter slag making and cannot replace light-burned dolomite for converter smelting.

[0032] Comparative Example 2: The smelting process is the same as that of Example 1, except that magnesium balls are not added and conventional lime and light-burned dolomite are used.

[0033] Converter smelting: 120-ton converter smelting; (1) Raw materials: 36.4 tons of scrap steel, 93.6 tons of molten iron, scrap steel ratio 28%; molten iron composition: C: 4.5%, Si: 0.26%, Mn: 0.33%, P: 0.115%, S: 0.023%, the rest are iron and some residual elements; the temperature of the molten iron entering the furnace is 1331℃.

[0034] (2) Oxygen supply: The top blowing flow rate during the smelting process is controlled at 35000Nm 3 / h; oxygen supply 0~35%, gun position 1.65m, oxygen supply 35~90%, gun position 1.8~2.2m; oxygen supply 90~100%, gun position 1.3~1.5m; actual oxygen lance position control can be adjusted appropriately according to the slagging situation.

[0035] (3) Adding materials: When blowing oxygen at 15%, add 1800 kg of lime and 1800 kg of light-burned dolomite at one time; when blowing oxygen at 40-80%, add 600 kg of lime in two batches; after blowing oxygen at 85%, do not add any slag.

[0036] The above method was used for smelting. The final converter temperature was 1585℃, the final carbon was 0.063%, the final phosphorus was 0.012%, the final slag basicity was 2.85, MgO was 8.1%, TFe was 14.8%, and the steel output was 120.3 tons. The slag pouring time before steel tapping was 1.5 minutes. Due to insufficient temperature, the situation in the converter after steel tapping was observed and unmelted scrap steel was found. The subsequent problems are as follows: (1) The final converter temperature is low, resulting in the scrap steel not being completely melted. There is a risk of scrap steel getting stuck at the steel tapping port during the steel tapping process. In addition, the scrap steel is not completely melted, which will affect the slag splashing furnace protection effect. (2) The final converter temperature is low. After steel tapping, the temperature of the molten steel is low when it reaches the refining, and the refining power-on time is extended.

[0037] Comparative Example 3: 1. Preparation of magnesium balls: (1) Select magnesium carbon bricks from converter bricks and ladle bricks off the production line; (2) Grind the magnesium carbon bricks into powder less than 5 mm in a crushing and grinding machine; (3) Mix the magnesium carbon brick powder, iron powder and binder in a weight percentage of 97:3 and press them into balls to form magnesium balls; (4) Magnesium balls: The composition of the prepared magnesium balls is MgO: 77.6%, C: 13.9%, SiO2: 4.0%, Al2O3: 4.2%, Fe: 0, and some inevitable impurities; the particle size is 20~50mm; the density is 3.2g / cm 3 , strength is 1100N.

[0038] 2. Converter smelting: 120-ton converter smelting; (1) Raw materials: 36.4 tons of scrap steel, 93.6 tons of molten iron, scrap steel ratio 28%; molten iron composition: C: 4.5%, Si: 0.24%, Mn: 0.35%, P: 0.123%, S: 0.020%, and the rest are iron and some residual elements; the temperature of the molten iron entering the furnace is 1332℃.

[0039] (2) Oxygen supply: The top blowing flow rate during the smelting process is controlled at 35000Nm 3 / h; oxygen supply 0~35%, gun position 1.65m, oxygen supply 35~90%, gun position 1.8~2.2m; oxygen supply 90~100%, gun position 1.3~1.5m; actual oxygen lance position control can be adjusted appropriately according to the slagging situation.

[0040] (3) Adding materials: When blowing oxygen at 8%, add 520 kg of magnesium balls; when blowing oxygen at 15%, add 1800 kg of lime and 600 kg of light-burned dolomite at one time; when blowing oxygen at 40-80%, add 600 kg of lime in two batches; after blowing oxygen at 85%, do not add any slag.

[0041] The smelting method described above resulted in a converter terminal temperature of 1611°C, terminal carbon of 0.062%, terminal phosphorus of 0.013%, final slag basicity of 2.88, MgO of 7.2%, TFe of 14.8%, and a steel output of 120.3 tons. In addition, when pouring slag before steel tapping, it was found that the slag was too bubbly and difficult to pour, and the pouring time was extended to 3.5 minutes, indicating that the carbon in the magnesium balls still reacted with the ferrous oxide in the slag to generate CO gas, resulting in excessive bubbling of the slag.

[0042] Compared with Example 1, the magnesium ball does not contain iron powder and the density of the magnesium ball is 3.2 g / cm 3 , the magnesium balls are not fully melted, and the magnesium oxide in the slag becomes lower; in addition, since the carbon in the magnesium balls cannot be fully burned during the smelting process, the magnesium balls still react with the slag when pouring the slag before tapping, resulting in slag bubbles and slightly lower terminal temperature.

[0043] Comparative Example 4: 1. Preparation of magnesium balls: same as in Example 1; 2. Converter smelting: 120-ton converter smelting; (1) Raw materials: 36.4 tons of scrap steel, 93.6 tons of molten iron, scrap steel ratio 28%; molten iron composition: C: 4.52%, Si: 0.26%, Mn: 0.33%, P: 0.118%, S: 0.025%, and the rest are iron and some residual elements; the temperature of the molten iron entering the furnace is 1333℃.

[0044] (2) Oxygen supply: The top blowing flow rate during the smelting process is controlled at 35000Nm 3 / h; oxygen supply 0~35%, gun position 1.65m, oxygen supply 35~90%, gun position 1.8~2.2m; oxygen supply 90~100%, gun position 1.3~1.5m; actual oxygen lance position control can be adjusted appropriately according to the slagging situation.

[0045] (3) Adding materials: When blowing 2% oxygen, add 520kg of magnesium balls; when blowing 15% oxygen, add 1800kg of lime and 260kg of magnesium balls at one time; when blowing 40-80% oxygen, add 600kg of lime in two batches; after blowing 85% oxygen, do not add any slag.

[0046] The smelting method described above has the following results: the final converter temperature is 1603℃, the final carbon is 0.064%, the final phosphorus is 0.013%, the final slag basicity is 2.82, MgO is 6.8%, TFe is 14.8%, and the steel output is 120.2 tons. In addition, during the slag pouring process before steel tapping, the slag is quite bubbling, and the slag can only be poured slowly, with a pouring time of 3.2 minutes. This indicates that the magnesium balls are not fully melted, and the magnesium oxide in the slag becomes lower; in addition, since the carbon in the magnesium balls cannot be fully burned during the smelting process, the magnesium balls still react with the slag when pouring the slag before steel tapping, resulting in slag bubbles and a decrease in the final temperature.

[0047] Comparative Example 5: 1. Preparation of magnesium balls: same as in Example 1; 2. Converter smelting: 120-ton converter smelting; (1) Raw materials: 36.4 tons of scrap steel, 93.6 tons of molten iron, scrap steel ratio 28%; molten iron composition: C: 4.5%, Si: 0.24%, Mn: 0.35%, P: 0.115%, S: 0.025%, the rest are iron and some residual elements; the temperature of the molten iron entering the furnace is 1332℃.

[0048] (2) Oxygen supply: The top blowing flow rate during the smelting process is controlled at 35000Nm 3 / h; oxygen supply 0~35%, gun position 1.65m, oxygen supply 35~90%, gun position 1.8~2.2m; oxygen supply 90~100%, gun position 1.3~1.5m; actual oxygen lance position control can be adjusted appropriately according to the slagging situation.

[0049] (3) Adding materials: When blowing oxygen at 15%, add 1800 kg of lime and 260 kg of magnesium balls at one time; when blowing oxygen at 30%, add 520 kg of magnesium balls; when blowing oxygen at 40-80%, add 600 kg of lime in two batches; after blowing oxygen at 85%, do not add any slag.

[0050] The above method was used for smelting, and the final converter temperature was 1605℃, the final carbon was 0.065%, the final phosphorus was 0.013%, the final slag basicity was 2.88, MgO was 7.0%, TFe was 14.8%, and the steel output was 120.3 tons; the slag pouring time before steel was 3.0 minutes. The magnesium balls were added late, and the smelting process was not fully melted, resulting in slag bubbles when pouring slag before steel was tapped, and the slag pouring time was extended.

[0051] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0052] The present invention is not limited to the following specific embodiments. A person skilled in the art can implement the present invention in various other specific embodiments according to the contents disclosed in the present invention, or any simple changes or modifications made to the design structure and ideas of the present invention fall within the protection scope of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

Claims

1. A method for recycling waste refractory materials of steelmaking magnesia carbon bricks, characterized by: The method comprises the following steps: preparing magnesium balls from magnesium carbon bricks after recycling, specifically: mixing magnesium carbon brick powder, iron powder and a binder according to mass percentage and pressing them into balls to form magnesium balls; using the obtained magnesium balls in a converter smelting process; The components of magnesium ball are as follows by weight: MgO: 65~75%, C: 10~15%, SiO2: 2~10, Al2O3: 2~10%, Fe: 5~10%, and some inevitable impurities.

2. The method for recycling waste refractory materials of steelmaking magnesia carbon bricks according to claim 1, characterized in that: The particle size of the magnesium ball is 20-50 mm; the density is 5.5-7.5 g / cm 3 , strength is 800~1200N.

3. The method for recycling waste refractory materials of steelmaking magnesia carbon bricks according to claim 1, characterized in that: In the converter smelting process, 1kg / t magnesium balls can replace 2.3kg / ton light-burned dolomite.

4. The method for recycling waste refractory materials of steelmaking magnesia carbon bricks according to claim 1, characterized in that: In converter smelting, magnesium balls are added within 5%~15% of the oxygen blowing volume, and the addition amount is controlled at 3~8kg / t.

5. The method for recycling waste refractory materials of steelmaking magnesia carbon bricks according to claim 1, characterized in that: Specifically, converter smelting includes: converter high scrap steel ratio smelting, in which the mass proportion of scrap steel is 25~35%.

6. The method for recycling waste refractory materials of steelmaking magnesia carbon bricks according to claim 4, characterized in that: In the converter high scrap ratio smelting, magnesium balls are used instead of light-burned dolomite to ensure that the converter tapping temperature is 15~40℃ higher than the tapping temperature of light-burned dolomite smelting.