Calcium-based desulfurizing agent and application thereof

Abstract

The invention provides a calcium-based desulfurizer. The calcium-based desulfurizer comprises CaO, fly ash and a waste refractory material. According to the desulfurizing agent provided by the invention, waste refractory materials and fly ash in a steel mill are utilized, so that the utilization of waste resources is realized. Wherein the added alumina-carbon refractory material and fly ash can form low-melting-point calcium aluminate salt and silicate with CaO in the desulfurized slag, the fluidity of the slag is improved, rolled iron and wrapped iron of the desulfurized slag are reduced, the consumption of steel and iron materials is reduced, in addition, the fly ash and the alumina-carbon refractory material also contain part of C element, the dissolution of the carbon element can recarburize semi-steel, more heat sources are provided, and the service life of the semi-steel is prolonged. And the addition amount of the scrap steel is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a calcium-based desulfurizing agent and application thereof. Background Art

[0002] At present, the main hot metal desulfurization processes are: KR (mechanical stirring) desulfurization and composite injection desulfurization. KR mainly uses CaO as a desulfurizer, and the composite injection desulfurizer is mainly CaO and passivated magnesium powder.

[0003] For example, a Chinese patent with application number 202010764157.7 discloses a KR molten iron desulfurization and coordinated resource utilization process of hazardous waste carbon slag from electrolytic aluminum. The carbon slag produced by electrolytic aluminum is processed to 150 mesh using a ball mill, and fly ash with a SiO2 content greater than 50% and aluminum ash with Al2O3>55% are purchased as additive materials for standby use. Magnesite with a MgCO3 content greater than 85% is purchased, and the above materials are pressed into spheres with a particle size of 3 to 5 mm using a dry powder briquette machine as a molten iron desulfurizer. There are three types: low-silicon molten iron desulfurizer, high-silicon molten iron desulfurizer, and conventional molten iron desulfurizer. The above desulfurizers are added with 5kg of lime and 1kg of desulfurizer per ton of molten iron. After the KR desulfurization process starts, add molten iron to desulfurize the molten iron. The desulfurizer used for molten iron with different silicon contents is selected from the three desulfurizers of the components described in step 4. However, the invention mainly utilizes the resources of the electrolytic aluminum plant to produce the desulfurizer, which will increase the cost when purchased from the aluminum plant, and does not utilize the internal Al2O3 resources.

[0004] In the steelmaking industry, aluminum-carbon refractories have good chemical and mechanical properties, such as high temperature strength and thermal shock resistance. During the steelmaking process, these refractories react with molten iron, resulting in physical and chemical corrosion due to chemical reactions and surface interactions. Due to damage, these used refractories are either recycled or landfilled. However, limited work has been done in the field of recycling refractories.

[0005] Therefore, providing a method for preparing a desulfurizing agent using waste refractory materials becomes a problem to be solved. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a calcium-based desulfurizer and its application. The present invention utilizes waste refractory materials to prepare the desulfurizer, thereby realizing the utilization of waste resources and achieving good desulfurization effect.

[0007] The invention provides a calcium-based desulfurizing agent, comprising CaO, fly ash and waste refractory materials.

[0008] Preferably, the calcium-based desulfurizing agent comprises:

[0009] 1% to 8% of waste refractory materials, 1% to 5% of fly ash and 88% to 97% of CaO.

[0010] Preferably, the waste refractory material comprises a long nozzle, an immersion nozzle and a stopper rod;

[0011] Preferably, the refractory material is an aluminum-carbon refractory material;

[0012] Preferably, in the refractory material, Al2O3≥50%, C≥7%.

[0013] Preferably, the purity of CaO is greater than 95%, the purity of SiO2 in fly ash is greater than 95%, and the purity of passivated magnesium powder is ≥95%.

[0014] The present invention also provides a KR desulfurization process, comprising the following steps:

[0015] The waste refractory material is crushed and ground, and then mixed with fly ash and CaO to obtain a mixed powder;

[0016] The mixed powder is pelletized to obtain a calcium-based desulfurizer;

[0017] The calcium-based desulfurizing agent is added into the metal liquid to be desulfurized for desulfurization.

[0018] Preferably, the particle size of the waste refractory material after crushing and grinding is less than 5 mm.

[0019] Preferably, the binder used in the pelletization is bentonite, and the pellet size of the pelletization is 20 to 50 mm.

[0020] The present invention also provides a composite injection desulfurization process, comprising the following steps:

[0021] The waste refractory material is crushed, ground and mixed with fly ash and CaO to obtain a calcium-based desulfurizer;

[0022] The calcium-based desulfurizer and purified magnesium powder are respectively sprayed into the metal liquid to be desulfurized for desulfurization, and the calcium-magnesium mass ratio of calcium oxide in the calcium-based desulfurizer to the purified magnesium powder is 3.0-5.5:1.

[0023] Preferably, the particle size of the waste refractory material after crushing and grinding is less than 5 mm.

[0024] Preferably, the molten metal to be desulfurized is semi-steel.

[0025] Compared with the prior art, the present invention provides a calcium-based desulfurizer, including: CaO, fly ash and waste refractory materials. The desulfurizer provided by the present invention utilizes waste refractory materials and fly ash inside the steel plant, realizing the utilization of waste resources. Among them, the addition of aluminum-carbon refractory materials and fly ash can form low-melting-point calcium aluminate salts and silicates with CaO in the desulfurization slag, improve the fluidity of the slag, reduce the iron curling and iron wrapping of the desulfurization slag, and reduce the consumption of steel materials. In addition, fly ash and aluminum-carbon refractory materials also contain some C elements. The dissolution of carbon elements can increase the carbon content of semi-steel, provide more heat sources, and increase the amount of scrap steel added. DETAILED DESCRIPTION

[0026] The invention provides a calcium-based desulfurizing agent, comprising CaO, fly ash and waste refractory materials.

[0027] In some preferred embodiments of the present invention, the calcium-based desulfurizing agent comprises:

[0028] 1% to 8% of waste refractory materials, 1% to 5% of fly ash and 88% to 97% of CaO.

[0029] The calcium-based desulfurizer provided by the present invention comprises 1% to 8% of waste refractory materials, which may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or any value between 1% and 8%. In the present invention, the waste refractory materials include a long nozzle, an immersion nozzle and a stopper rod; preferably, the refractory materials are aluminum-carbon refractory materials. In the present invention, in the refractory materials, Al2O3≥50%, C≥7%.

[0030] The Al2O3 in the aluminum-carbon refractory can form low-melting-point calcium aluminate salt with the CaO in the desulfurization slag, which can improve the fluidity of the slag, reduce the iron curling and iron wrapping of the desulfurization slag, and reduce the consumption of steel materials. In addition, the aluminum-carbon refractory also contains some C elements. The dissolution of carbon elements can increase the carbon content of semi-steel, provide more heat sources, and increase the amount of scrap steel added.

[0031] The calcium-based desulfurizer provided by the present invention also includes 1% to 5% fly ash, which can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value between 1% and 5%.

[0032] The calcium-based desulfurizer provided by the present invention also includes 88% to 97% CaO, which can be 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or any value between 88% and 97%. In the present invention, the CaO purity is greater than 95%.

[0033] The present invention also provides a KR desulfurization process, comprising the following steps:

[0034] The waste refractory material is crushed and ground, and then mixed with fly ash and CaO to obtain a mixed powder;

[0035] The mixed powder is pelletized to obtain a calcium-based desulfurizer;

[0036] The calcium-based desulfurizing agent is added into the metal liquid to be desulfurized for desulfurization.

[0037] Specifically, the present invention crushes and collects the waste refractory materials, and then uses a ball mill to grind them into particles with a diameter of less than 5 mm.

[0038] Then the ground waste refractory material is mixed with fly ash and CaO to obtain a mixed powder.

[0039] Next, the mixed powder is pelletized to obtain a calcium-based desulfurizer.

[0040] The binder used in the pelletization is bentonite, and the binder accounts for 1% to 5% of the mixed powder by mass, and can be 1%, 2%, 3%, 4%, 5%, or any value between 1% and 5%. The pellet size of the pelletization is 20 to 50 mm, and can be 20, 25, 30, 35, 40, 45, 50, or any value between 20 and 50 mm.

[0041] Finally, the calcium-based desulfurizer is added into the molten metal to be desulfurized for desulfurization. The molten metal to be desulfurized is semi-steel, and the dosage of the calcium-based desulfurizer is calculated according to the S content in the molten iron.

[0042] The present invention also provides a composite injection desulfurization process, comprising the following steps:

[0043] The waste refractory material is crushed, ground and mixed with fly ash and CaO to obtain a calcium-based desulfurizer;

[0044] The calcium-based desulfurizer and purified magnesium powder are respectively sprayed into the metal liquid to be desulfurized for desulfurization, and the calcium-magnesium mass ratio of calcium oxide in the calcium-based desulfurizer to the purified magnesium powder is 3.0-5.5:1.

[0045] Specifically, the present invention crushes and collects the waste refractory materials, and then uses a ball mill to grind them into particles with a diameter of less than 5 mm.

[0046] The ground waste refractory material is then mixed with fly ash and CaO to obtain a calcium-based desulfurizer.

[0047] Next, the calcium-based desulfurizer is directly sprayed into the metal liquid to be desulfurized with the passivated magnesium powder in a composite injection process according to a calcium-magnesium mass ratio of 3.0 to 5.5:1 for desulfurization. The calcium-magnesium mass ratio of the calcium oxide in the calcium-based desulfurizer to the purified magnesium powder can be 3.0:1, 3.5:1, 4.0:1, 4.5:1, 5.0:1, 5.5:1, or any value between 3.0 and 5.5:1. In the present invention, the purity of the passivated magnesium powder is ≥95%. The metal liquid to be desulfurized is semi-steel.

[0048] The dosage of the calcium-based desulfurizer and purified magnesium powder is calculated according to the S content of molten iron.

[0049] The desulfurizer provided by the present invention can utilize waste refractory materials in steel mills, thereby improving the comprehensive utilization rate of refractory materials, reducing steel material consumption and the amount of carburizer added, improving economic benefits, and reducing the amount of carburizer added, saving costs. In addition, the addition of Al2O3 in the waste refractory materials can improve the desulfurization rate and reduce the desulfurization slag TFe, reducing steel material consumption, and having a significant effect of reducing costs and increasing efficiency.

[0050] The desulfurizer provided by the present invention utilizes waste refractory materials and fly ash in the steel plant, realizing the utilization of waste resources. The addition of aluminum-carbon refractory materials and fly ash can form low-melting-point calcium aluminate salts and silicates with CaO in the desulfurized slag, improve the fluidity of the slag, reduce the iron curling and iron wrapping of the desulfurized slag, and reduce the consumption of steel materials. In addition, fly ash and aluminum-carbon refractory materials also contain some C elements. The dissolution of carbon elements can increase the carbon content of semi-steel, provide more heat sources, and increase the amount of scrap steel added.

[0051] In order to further understand the present invention, the calcium-based desulfurizing agent provided by the present invention and its application are described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0052] Comparative Example 1:

[0053] During the vanadium extraction and steelmaking process, about 200 kg of recarburizer is added to keep the carbon content of the semi-steel greater than 3.3%. After adding the recarburizer, ultra-low sulfur steel is smelted. The S and C contents of the semi-steel before desulfurization are 0.095% and 3.41% respectively, and the S and C contents after desulfurization are 0.0048% and 3.43% respectively. The TFe content in the desulfurized slag is 70%, and the desulfurization rate is 94.9%.

[0054] Embodiment 1:

[0055] The used aluminum-carbon refractory materials were collected and crushed, and then rolled to a particle size of less than 5mm using a ball mill. After crushing and grinding, the Al2O3 content was measured to be 63% and the C content was 7%. The waste refractory materials were mixed with passivation lime powder at a ratio of 5% and fly ash at a ratio of 3%. After mixing, the composite injection process was directly used to spray the passivation magnesium powder into the semi-steel for desulfurization according to the calcium-magnesium mass ratio of 3.5. Before desulfurization of the semi-steel, the S and C contents were 0.096% and 3.21% respectively, and after desulfurization, the S and C contents were 0.0035% and 3.55% respectively. The TFe content in the desulfurized slag was 65.5%, and the desulfurization rate was 96.4%.

[0056] Embodiment 2:

[0057] The used aluminum-carbon refractory materials were collected and crushed, and then rolled to a particle size of less than 5 mm using a ball mill. After crushing and grinding, the Al2O3 content was measured to be 65% and the C content was 8%. The waste refractory materials were mixed with passivated lime powder at a ratio of 5% and 3% of fly ash to obtain a mixed powder. Bentonite was used to mix and make balls (the diameter of the balls was 35.5 mm, and the mass ratio of bentonite to the mixed powder was 2.5%). After that, the KR method was used for deep desulfurization. The addition method was to directly add it to the surface of the molten steel. Before the semi-steel desulfurization, the S and C contents were 0.093% and 3.31% respectively. After desulfurization, the S and C contents were 0.0032% and 3.62% respectively. The TFe content in the desulfurized slag was 64.6%, and the desulfurization rate was 96.6%.

[0058] Embodiment 3:

[0059] The used aluminum-carbon refractory materials were collected and crushed, and then rolled to a particle size of less than 5mm using a ball mill. After crushing and grinding, the Al2O3 content was measured to be 66% and the C content was 6%. The waste refractory materials were mixed with passivation lime powder at a ratio of 5% and fly ash at a ratio of 3%. After mixing, the composite injection process was directly used to spray the passivation magnesium powder into the semi-steel according to the calcium-magnesium mass ratio of 4.0 for deep desulfurization. Before desulfurization of the semi-steel, the S and C contents were 0.098% and 3.25% respectively. After desulfurization, the S and C contents were 0.0045% and 3.45% respectively. The TFe content in the desulfurized slag was 66.5%, and the desulfurization rate was 95.4%.

[0060] Embodiment 4:

[0061] The used aluminum-carbon refractory materials were collected and crushed, and then rolled to a particle size of less than 5mm using a ball mill. After crushing and grinding, the Al2O3 content was measured to be 67% and the C content was 7%. The waste refractory materials were mixed with passivated lime powder at a ratio of 5% and 3% of fly ash to obtain a mixed powder. Bentonite was used to mix and make balls (the diameter of the balls was 34.5mm, and the mass ratio of bentonite to the mixed powder was 2%). After that, the KR method was used for deep desulfurization. The addition method was to directly add it to the surface of the molten steel. Before the semi-steel desulfurization, the S and C contents were 0.097% and 3.26% respectively. After desulfurization, the S and C contents were 0.0044% and 3.53% respectively. The TFe content in the desulfurized slag was 66.6%, and the desulfurization rate was 95.5%.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A calcium-based desulfurizer, characterized in that: include: CaO, fly ash and waste refractory materials.

2. The calcium-based desulfurizer according to claim 1, characterized in that: The calcium-based desulfurizer comprises: 1% to 8% of waste refractory materials, 1% to 5% of fly ash and 88% to 97% of CaO.

3. The calcium-based desulfurizer according to any one of claims 1 to 2, characterized in that: The waste refractory materials include a long nozzle, an immersed nozzle and a stopper rod; Preferably, the refractory material is an aluminum-carbon refractory material; Preferably, in the refractory material, Al2O3≥50%, C≥7%.

4. The calcium-based desulfurizer according to any one of claims 1 to 2, characterized in that: The purity of CaO is greater than 95%, the purity of SiO2 in fly ash is greater than 95%, and the purity of passivated magnesium powder is ≥95%.

5. A KR desulfurization process, characterized in that: The following steps are involved: The waste refractory material is crushed and ground, and then mixed with fly ash and CaO to obtain a mixed powder; The mixed powder is pelletized to obtain a calcium-based desulfurizer; The calcium-based desulfurizing agent is added into the metal liquid to be desulfurized for desulfurization.

6. The process according to claim 5, characterized in that The particle size of the waste refractory material after crushing and grinding is less than 5mm.

7. The process according to claim 5, characterized in that The binder used in the pelletizing is bentonite, and the pellet size of the pelletizing is 20 to 50 mm.

8. A composite injection desulfurization process, characterized in that: The following steps are involved: The waste refractory material is crushed, ground and mixed with fly ash and CaO to obtain a calcium-based desulfurizer; The calcium-based desulfurizer and purified magnesium powder are respectively sprayed into the metal liquid to be desulfurized for desulfurization, and the calcium-magnesium mass ratio of calcium oxide in the calcium-based desulfurizer to the purified magnesium powder is 3.0-5.5:

1.

9. The process according to claim 8, characterized in that The particle size of the waste refractory material after crushing and grinding is less than 5mm.

10. The process according to any one of claims 5 to 9, characterized in that: The molten metal to be desulfurized is semi-steel.