Phosphorus pig iron carbonization desulfurization additive and production process

Abstract

The present application belongs to the technical field of aluminum electrolysis production, and provides a phosphorus pig iron recarburization and desulfurization additive and a production process. The additive raw material comprises graphite powder, passivated magnesium, calcium oxide, silicon iron powder, manganese iron powder, phosphorus iron powder, sodium carbonate and a binder. The additive has a four-layer structure, the passivated magnesium is wrapped inside the calcium oxide, and the graphite powder wraps the calcium oxide inside. When used, the graphite powder dissolves in the phosphorus pig iron water, the calcium oxide is gradually released to perform preliminary desulfurization, and after the calcium oxide reaction is completed, the passivated magnesium wrapped inside the calcium oxide is gradually released to perform further desulfurization. This gradual release method is beneficial to promoting the reaction while avoiding the one-time reaction of the passivated magnesium to release a large amount of heat to cause disturbance of the iron water and eliminate safety hazards. The additive has moderate particle size, good absorption effect when used, and simple production process, and can effectively meet the recarburization and desulfurization needs of the phosphorus pig iron.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum electrolysis production, and particularly relates to a phosphorus pig iron carbonization and desulfurization additive and a production process. BACKGROUND

[0002] In aluminum electrolysis production, the assembly of an aluminum electrolysis anode is to use phosphorus pig iron to cast and connect prebaked anode carbon blocks and steel claws together to form an electrolysis loop. After the anode carbon blocks are consumed, the residual carbon blocks and phosphorus pig iron are taken down together. The carbon blocks re-enter a forming system, and the phosphorus pig iron enters a smelting system to be reused after being smelted again. In this process, the carbon in the phosphorus pig iron is continuously burned out, and the carbon content gradually decreases. The carbon content reduction leads to the decrease of the fluidity of the phosphorus pig iron, the increase of the cold shrinkage of the phosphorus pig iron at room temperature, the decrease of the electrical conductivity of the phosphorus pig iron, and the increase of the Fe-C pressure drop of the phosphorus pig iron, thereby reducing the performance of the phosphorus pig iron.

[0003] In addition, in the recycling process of the phosphorus pig iron, the sulfur element in the phosphorus pig iron is continuously accumulated, and the sulfur content gradually increases. The sulfur has an anti-graphitization effect, which further reduces the carbon content in the phosphorus pig iron. In addition, the sulfur has thermal brittleness, and the increase of the sulfur content increases the possibility of thermal cracking of the phosphorus pig iron in the use process.

[0004] Therefore, how to carbonize and desulfurize the phosphorus pig iron is a technical problem to be solved by those skilled in the art. SUMMARY

[0005] The application provides a phosphorus pig iron carbonization and desulfurization additive and a production process, and aims to solve the above technical problems.

[0006] The application is implemented as follows. A phosphorus pig iron carbonization and desulfurization additive includes the following raw materials in percentage by weight: 64-70.12% of graphite powder, 0.1-0.5% of passivated magnesium, 24-28% of calcium oxide, 2.9-3.9% of ferrosilicon powder, 0.3-0.7% of manganese iron powder, 1.3-1.7% of phosphorus iron powder, 0.08-0.12% of sodium carbonate, and 0.8-1.2% of a binder.

[0007] Further, the particle size of the graphite powder is greater than 200 meshes, the fixed carbon content is greater than or equal to 98%, and the true density is 2.0-2.2 g / cm 3 .

[0008] Further, the particle size of the passivated magnesium is 1-2 mm.

[0009] Further, the binder is a mixture of polyvinyl alcohol and glycerol in a weight ratio of 3:1.

[0010] Furthermore, by weight percentage, the additive comprises the following raw materials: 66.4% graphite powder, 0.3% passivated magnesium, 26.8% calcium oxide, 3.4% ferrosilicon powder, 0.5% ferromanganese powder, 1.5% ferrophosphorus powder, 0.1% sodium carbonate, and 1% binder.

[0011] This invention also provides a production process for a phosphorus pig iron carbon-enhancing and desulfurization additive, comprising the following steps:

[0012] S1: Add polyvinyl alcohol to glycerol and stir evenly to obtain an adhesive. Divide the passivated magnesium into four parts, spray each part evenly with the adhesive, and pour calcium oxide into the fluidized bed.

[0013] S2: Take a portion of passivated magnesium for spraying adhesive and evenly sprinkle it into fluidized calcium oxide so that the calcium oxide evenly coats the passivated magnesium to obtain passivated magnesium / calcium oxide composite particles.

[0014] Step S2 was repeated three more times. By controlling the fluidization time, the coating thickness of calcium oxide was increased, resulting in four passivated magnesium / calcium oxide composite particles with particle sizes of 3 mm, 4 mm, 5 mm, and 6 mm.

[0015] S3: Spray four portions of passivated magnesium / calcium oxide composite particles evenly with adhesive, and pour graphite powder into the fluidized bed;

[0016] S4: Take a portion of the passivated magnesium / calcium oxide composite particles coated with adhesive and evenly sprinkle them into the fluidized graphite powder so that the graphite powder evenly coats the passivated magnesium / calcium oxide composite particles to obtain passivated magnesium / calcium oxide / graphite composite particles.

[0017] Repeat step S4 three more times, and increase the coating thickness of graphite powder by controlling the fluidization time to obtain four passivated magnesium / calcium oxide / graphite composite particles with a particle size of 8 mm.

[0018] S5: Spray the four parts of passivated magnesium / calcium oxide / graphite composite particles evenly with the adhesive, take ferrosilicon powder, ferromanganese powder, ferrophosphorus powder and sodium carbonate, mix and stir evenly to obtain a mixed powder, and pour the mixed powder into the fluidized bed;

[0019] S6: Take a portion of passivated magnesium / calcium oxide / graphite composite particles with spray adhesive and evenly sprinkle them into the fluidized mixed powder so that the mixed powder evenly coats the composite particles to obtain phosphorus pig iron carbon-enhancing and desulfurization additive.

[0020] Repeat step S6 three more times to obtain four portions of phosphorus pig iron carbon-enhancing desulfurizing agent with the same particle size;

[0021] Four parts of phosphorus pig iron carbon-enhancing and desulfurizing agent were compounded to obtain phosphorus pig iron carbon-enhancing and desulfurizing additive.

[0022] The phosphorus pig iron carbon-enhancing and desulfurizing additive and its production process provided by this invention consist of four parts of phosphorus pig iron carbon-enhancing and desulfurizing agent with the same content of passivated magnesium but different contents of calcium oxide and graphite powder. These can be compounded according to the different standards for sulfur and carbon set by different manufacturers. In the production process, a binder made from a mixture of polyvinyl alcohol and glycerol is used to bind the graphite powder, passivated magnesium, and calcium oxide together. Additionally, silicon, manganese, and phosphorus are added as elemental raw materials, enabling it to simultaneously perform carbon enhancement, desulfurization, and balance the chemical composition of the phosphorus pig iron during application. The carbon-enhancing desulfurization additive has a four-layer structure. The thickness of calcium oxide and graphite varies in each component. Passivated magnesium is encapsulated within the calcium oxide, and graphite powder further encapsulates the calcium oxide. During use, as the graphite powder dissolves in the molten pig iron, the calcium oxide from the four components of the carbon-enhancing desulfurization additive is gradually released to contact the pig iron for initial desulfurization. After the calcium oxide reaction is complete, the passivated magnesium, encapsulated within the calcium oxide, is then gradually released to contact the pig iron for further desulfurization. This gradual release method facilitates the reaction while preventing the passivated magnesium from releasing a large amount of heat during a single reaction, thus avoiding disturbance to the molten iron and eliminating safety hazards. This additive has a suitable particle size, good absorption during use, and a simple production process, effectively meeting the carbon-enhancing and desulfurization requirements of pig iron. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] The raw materials and equipment used in the examples were all commercially available, and the equipment operation methods were performed according to the manufacturer's recommendations. The graphite powder used in the examples had a particle size of 200 mesh or larger, a fixed carbon content of ≥98%, and a true density of 2.0–2.2 g / cm³. 3 The passivated magnesium has a particle size of 1-2 mm, and the binder is a mixture of polyvinyl alcohol and glycerol in a weight ratio of 3:1. The elemental content requirements for pig iron phosphate and the elemental content of the pig iron phosphate raw materials used in the examples are shown in the table below:

[0025] Phosphorus pig iron C S Si Mn P Content requirement ≥3.0 ≤0.22 2.0~2.5 0.6~0.9 0.8~1.5 Actual content 1.92 0.54 1.91 0.65 1.02

[0026] Example 1

[0027] This invention provides a phosphorus pig iron carbon-enhancing and desulfurization additive, wherein every 100kg of the additive comprises the following raw materials: 66.4kg graphite powder, 0.3kg passivated magnesium, 26.8kg calcium oxide, 3.4kg ferrosilicon powder, 0.5kg ferromanganese powder, 1.5kg phosphorus iron powder, 0.1kg sodium carbonate, and 1kg binder.

[0028] The production process of the above-mentioned phosphorus pig iron carbon-enhancing and desulfurization additive includes the following steps:

[0029] S1: Add polyvinyl alcohol to glycerol and stir evenly to obtain an adhesive. Divide the passivated magnesium into four parts, spray the adhesive evenly onto each part, and pour calcium oxide into the fluidized bed.

[0030] S2: Take a portion of the passivated magnesium for spraying adhesive and evenly sprinkle it into the fluidized calcium oxide to make the calcium oxide evenly coat the passivated magnesium, thus obtaining passivated magnesium / calcium oxide composite particles.

[0031] Step S2 was repeated three more times. By controlling the fluidization time, the coating thickness of calcium oxide was increased, resulting in four passivated magnesium / calcium oxide composite particles with particle sizes of 3 mm, 4 mm, 5 mm, and 6 mm.

[0032] S3: Spray four portions of passivated magnesium / calcium oxide composite particles evenly with adhesive, and pour graphite powder into the fluidized bed.

[0033] S4: Take a portion of the passivated magnesium / calcium oxide composite particles with the spray adhesive and evenly sprinkle them into the fluidized graphite powder so that the graphite powder evenly coats the passivated magnesium / calcium oxide composite particles to obtain passivated magnesium / calcium oxide / graphite composite particles.

[0034] Step S4 was repeated three more times. By controlling the fluidization time, the coating thickness of the graphite powder was increased, resulting in four passivated magnesium / calcium oxide / graphite composite particles with a particle size of 8 mm.

[0035] S5: Spray the four parts of passivated magnesium / calcium oxide / graphite composite particles evenly with the adhesive, take ferrosilicon powder, ferromanganese powder, ferrophosphorus powder and sodium carbonate, mix and stir evenly to obtain a mixed powder, and pour the mixed powder into the fluidized bed.

[0036] S6: Take a portion of the passivated magnesium / calcium oxide / graphite composite particles for spraying adhesive and evenly sprinkle them into the fluidized mixed powder so that the mixed powder evenly coats the composite particles to obtain the phosphorus pig iron carbon-enhancing and desulfurization additive.

[0037] Repeat step S6 three more times to obtain four portions of phosphorus pig iron carbon-enhancing desulfurizing agent with the same particle size.

[0038] Four parts of phosphorus pig iron carbon-enhancing and desulfurizing agent were compounded in equal proportions to obtain phosphorus pig iron carbon-enhancing and desulfurizing additive.

[0039] In the above production process, since calcium oxide, graphite powder and mixed powder cannot be completely coated on the surface of the particles, the amount of calcium oxide, graphite powder and mixed powder used for coating is greater than the amount in the formula. By controlling the fluidization treatment time, the raw materials in the granular phosphorus pig iron carbon-enhancing and desulfurizing additive obtained after coating reach the preset ratio.

[0040] The phosphorus pig iron recarburization desulfurization method using the phosphorus pig iron recarburization desulfurization additive of example 1 comprises: weighing 1.6% of the additive according to the weight of the phosphorus pig iron raw material, taking 1000 kg of phosphorus pig iron and 16 kg of the additive, dividing the phosphorus pig iron into four equal parts, and dividing the additive into four parts according to the mass ratio of 4:2:1:1, i.e., 8 kg, 4 kg, 2 kg and 2 kg, laying 8 kg of the additive, 250 kg of the phosphorus pig iron, 4 kg of the additive, 250 kg of the phosphorus pig iron, 2 kg of the additive, 250 kg of the phosphorus pig iron, 2 kg of the additive and 250 kg of the phosphorus pig iron from bottom to top in the intermediate frequency furnace in layers, respectively, and remelting, wherein the melting temperature is controlled at 1500 DEG C, the molten phosphorus pig iron is continuously stirred during the melting process, and the molten phosphorus pig iron is slagged 4 times, and the sample is detected after the 4 times of slagging, and the detection results are shown in the following table:

[0041] Phosphorus pig iron C S Si Mn P Before treatment 1.92 0.54 1.91 0.65 1.02 After treatment 3.36 0.09 2.21 0.71 1.24

[0042] As can be seen from the table, after using the additive, the carbon content in the phosphorus pig iron is increased by 75%, at the same time, the sulfur content is obviously decreased, the content of other elements is also increased, the recarburization desulfurization effect is remarkable, and the element content of the treated phosphorus pig iron meets the content requirement.

[0043] Example 2

[0044] The phosphorus pig iron recarburization desulfurization additive provided by the embodiment of the application comprises the following raw materials per 100 kg of the additive: 64.28 kg of graphite powder, 0.5 kg of passivated magnesium, 28 kg of calcium oxide, 3.9 kg of ferrosilicon powder, 0.7 kg of manganese iron powder, 1.7 kg of phosphorus iron powder, 0.12 kg of sodium carbonate and 0.8 kg of a binder.

[0045] The production process of the phosphorus pig iron recarburization desulfurization additive is the same as that of example 1, and four parts of the phosphorus pig iron recarburization desulfurization agent are compounded according to the same proportion to obtain the phosphorus pig iron recarburization desulfurization additive.

[0046] The recarburization desulfurization method of the phosphorus pig iron using the phosphorus pig iron recarburization desulfurization additive of example 2 is the same as that of example 1, and the detection results are shown in the following table:

[0047] Phosphorus pig iron C S Si Mn P Before treatment 1.92 0.54 1.91 0.65 1.02 After treatment 3.25 0.06 2.28 0.72 1.35

[0048] As can be seen from the table, after using the additive, the carbon content in the phosphorus pig iron is increased by 69.27%, at the same time, the sulfur content is obviously decreased, the content of other elements is also increased, the recarburization desulfurization effect is remarkable, and the element content of the treated phosphorus pig iron meets the content requirement.

[0049] Example 3

[0050] The phosphorus pig iron carbonization desulfurization additive provided by the embodiment of the present application comprises the following raw materials per 100 kg of the additive: 70.12 kg of graphite powder, 0.1 kg of passivated magnesium, 24 kg of calcium oxide, 2.9 kg of ferrosilicon powder, 0.3 kg of manganese iron powder, 1.3 kg of phosphorus iron powder, 0.08 kg of sodium carbonate, and 1.2 kg of a binder.

[0051] The production process of the phosphorus pig iron carbonization desulfurization additive is the same as that in Embodiment 1, and four portions of the phosphorus pig iron carbonization desulfurization additive are obtained by compounding the phosphorus pig iron carbonization desulfurization agent in an equal proportion.

[0052] The method for carbonizing and desulfurizing the phosphorus pig iron by using the phosphorus pig iron carbonization desulfurization additive in Embodiment 3 is the same as that in Embodiment 1, and the detection results are shown in the following table:

[0053] Phosphorus pig iron C S Si Mn P Before treatment 1.92 0.54 1.91 0.65 1.02 After treatment Phosphorus pig iron Si Mn Before treatment After treatment 3.55 0.22 2.13 0.67 1.18

[0054] As can be seen from the table, after the additive is used, the carbon content in the phosphorus pig iron is increased by 84.89%, and at the same time, the sulfur content is significantly decreased to meet the content requirement, and the content of other elements is also increased, the carbonization and desulfurization effect is remarkable, and the element content of the treated phosphorus pig iron meets the content requirement.

[0055] In summary, the production process of the phosphorus pig iron carbonization desulfurization additive provided by the embodiment of the present application is simple, the carbonization and desulfurization effect is good, and the carbonization and desulfurization requirements of the phosphorus pig iron can be effectively met.

[0056] In addition, the content of each portion of the phosphorus pig iron carbonization desulfurization agent in the phosphorus pig iron carbonization desulfurization additive provided by the embodiment of the present application can be adjusted according to the actual carbonization and desulfurization requirements, for example, when carbonization is mainly required and desulfurization is secondarily required, the proportion of the phosphorus pig iron carbonization desulfurization agent containing passivated magnesium / calcium oxide composite particles with a particle size of 3 mm and 4 mm is increased during compounding, the content of calcium oxide is relatively low, and the content of graphite powder is relatively high; when desulfurization is mainly required and carbonization is secondarily required, the proportion of the phosphorus pig iron carbonization desulfurization agent containing passivated magnesium / calcium oxide composite particles with a particle size of 5 mm and 6 mm is increased during compounding, the content of calcium oxide is relatively high, and the content of graphite powder is relatively low.

[0057] The above merely describes preferred embodiments of the present application but should not be taken in a limiting sense but rather in an illustrative sense. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A production process for a phosphorus pig iron carbon-enhancing and desulfurization additive, characterized in that, The additives, by weight percentage, comprise the following raw materials: 64-70.12% graphite powder, 0.1-0.5% passivated magnesium, 24-28% calcium oxide, 2.9-3.9% ferrosilicon powder, 0.3-0.7% ferromanganese powder, 1.3-1.7% ferrophosphorus powder, 0.08-0.12% sodium carbonate, and 0.8-1.2% binder; The production process includes the following steps: S1: Add polyvinyl alcohol to glycerol and stir evenly to obtain an adhesive. Divide the passivated magnesium into four parts, spray each part evenly with the adhesive, and pour calcium oxide into the fluidized bed. S2: Take a portion of passivated magnesium for spraying adhesive and evenly sprinkle it into fluidized calcium oxide so that the calcium oxide evenly coats the passivated magnesium to obtain passivated magnesium / calcium oxide composite particles. Step S2 was repeated three more times. By controlling the fluidization time, the coating thickness of calcium oxide was increased, resulting in four passivated magnesium / calcium oxide composite particles with particle sizes of 3 mm, 4 mm, 5 mm, and 6 mm. S3: Spray four portions of passivated magnesium / calcium oxide composite particles evenly with adhesive, and pour graphite powder into the fluidized bed; S4: Take a portion of the passivated magnesium / calcium oxide composite particles coated with adhesive and evenly sprinkle them into the fluidized graphite powder so that the graphite powder evenly coats the passivated magnesium / calcium oxide composite particles to obtain passivated magnesium / calcium oxide / graphite composite particles. Repeat step S4 three more times, and increase the coating thickness of graphite powder by controlling the fluidization time to obtain four passivated magnesium / calcium oxide / graphite composite particles with a particle size of 8 mm. S5: Spray the four parts of passivated magnesium / calcium oxide / graphite composite particles evenly with the adhesive, take ferrosilicon powder, ferromanganese powder, ferrophosphorus powder and sodium carbonate, mix and stir evenly to obtain a mixed powder, and pour the mixed powder into the fluidized bed; S6: Take a portion of passivated magnesium / calcium oxide / graphite composite particles coated with adhesive and evenly sprinkle them into the fluidized mixed powder so that the mixed powder evenly coats the composite particles to obtain phosphorus pig iron carbon-enhancing desulfurizer. Repeat step S6 three more times to obtain four portions of phosphorus pig iron carbon-enhancing desulfurizing agent with the same particle size; Four parts of phosphorus pig iron carbon-enhancing and desulfurizing agent were compounded to obtain phosphorus pig iron carbon-enhancing and desulfurizing additive.