Method for collecting crystalline flake graphite separated out of molten iron

Abstract

The invention discloses a method for collecting crystalline flake graphite separated out from molten iron, and relates to the technical field of iron and steel smelting. Molten iron is transported to a steelmaking area through a molten iron tank car, a worker adopts a rapid thermocouple temperature measuring gun to conduct temperature measuring operation on the molten iron, and the molten iron temperature T is obtained; calculating the addition amount of the scrap steel according to the molten iron temperature T obtained by temperature measurement; when the scrap steel needs to be added, the crushed scrap steel is slowly and uniformly added into the molten iron tank according to the calculated weight by using an electromagnetic chuck; and conveying the molten iron tank filled with the molten iron to a crystalline flake graphite collecting area by using a special metallurgical crane. The collecting method has the beneficial effects that when the collecting method is used for collecting the crystalline flake graphite, a large amount of waste water cannot be generated, the collecting method is more environmentally friendly and economical, the content of the crystalline flake graphite in the dedusting powder recycled through the collecting method can be larger than or equal to 60%, the recycling amount is large, the follow-up purification cost is reduced, and the collecting method is more economical.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, specifically to a method for collecting flake graphite precipitated from molten iron. Background Technology

[0002] Flake graphite, also known as natural phanerocrystalline graphite, resembles fish scales in shape, belongs to the hexagonal crystal system, and has a layered structure. It possesses excellent properties such as high-temperature resistance, electrical conductivity, thermal conductivity, lubrication, plasticity, and resistance to acids and alkalis. It is a widely used strategic mineral resource, an essential basic mineral raw material for traditional industries and strategic emerging industries, an important strategic resource supporting the development of high technology, and another scarce resource after rare earth elements. Large flake graphite can only be extracted from raw graphite ore; current modern industrial technology cannot synthesize large flake graphite, and once the flakes are damaged, they cannot be restored. A large amount of flake graphite is produced as a byproduct in my country's iron and steel metallurgical industry. During blast furnace tapping, molten iron transfer, and molten iron pretreatment, the temperature changes in the molten iron cause carbon supersaturation, resulting in the precipitation of flake graphite. This type of flake graphite, after collection and purification, possesses the same properties as natural flake graphite.

[0003] Chinese patent CN114733287A discloses a device and method for collecting graphite precipitated during molten iron transfer. This patent uses devices such as fans, dust hoods, and spray boxes to capture graphite-containing fumes generated during the molten iron transfer and mixing process. However, this invention is not suitable for the "one-pot molten iron" process commonly used in steel plants, and the spray method for fume treatment generates a large amount of wastewater.

[0004] Chinese patent CN115321534B discloses a method for in-situ extraction of large flake graphite from desulfurization slag in molten iron pretreatment. This invention processes molten iron using the KR desulfurization process, then spreads the desulfurization slag flat on the ground, sprays it with water, and places it in a water tank. Large slag blocks are continuously stirred and broken up using a bucket, avoiding the damage to the flakes caused by traditional crushing and flotation processes, thus achieving in-situ extraction and recovery of large flake graphite. However, this method only yields 2%–3% flake graphite in the desulfurization slag, resulting in high purification costs.

[0005] Therefore, there is an urgent need for a method to collect flake graphite precipitated from molten iron. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings and defects of the existing technology by providing a method for collecting flake graphite precipitated from molten iron. When collecting flake graphite using this method, not only is a large amount of wastewater not generated, making it more environmentally friendly and economical, but the flake graphite content in the dust collected by this method can be ≥60%, resulting in a large recovery volume and thus reducing the subsequent purification cost, making it more economical.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for collecting flake graphite precipitated in molten iron, comprising the following steps: molten iron is transported to the steelmaking area via a molten iron ladle car; workers use a rapid thermocouple temperature gun to measure the temperature of the molten iron to obtain the molten iron temperature T; the amount of scrap steel to be added is calculated based on the measured molten iron temperature T; when scrap steel needs to be added, an electromagnetic chuck is used to slowly and evenly add crushed scrap steel to the molten iron ladle according to the calculated weight; a metallurgical crane is used to transport the molten iron ladle containing molten iron to the flake graphite collection area; after the molten iron ladle arrives at the designated location in the flake graphite collection area, the operator slowly lowers the dust removal hood to cover the mouth of the molten iron ladle, which can effectively reduce the intake of air and prevent the flake graphite from contacting oxygen in the air at high temperature and undergoing an oxidation reaction; at the same time, the bottom blowing nitrogen gas and the dust removal fan of the molten iron ladle are turned on; under the action of the bottom blowing nitrogen gas and the dust removal fan, the smoke and dust generated in the molten iron ladle enter the dry dust removal system through the suction port of the dust removal hood. After being processed by a dry dust removal system, the dust collected in the ash hopper is dust containing flake graphite.

[0008] S9 periodically discharges the dust from the ash hopper for subsequent storage, transportation, and further processing.

[0009] Furthermore, the calculation of the amount of scrap steel added is as follows: when the molten iron temperature T > 1280℃, according to the experiment, 50kg of crushed scrap steel is added for every 10℃ increase in molten iron temperature T; while when the molten iron temperature T ≤ 1280℃, no scrap steel is added.

[0010] Furthermore, the specific steps for activating the bottom-blowing nitrogen in the molten iron ladle are: a bottom-blowing nitrogen flow rate of 1000 Nm³. 3 / h not only ensures the stirring effect, but also blows up the flake graphite that precipitates on the surface of the molten iron.

[0011] Furthermore, the specific method for activating the dust removal fan is as follows: the dust removal fan adopts frequency conversion technology, and the dust removal fan can control the slight negative pressure between the dust removal hood and the molten iron ladle opening, ensuring the dust removal effect while reducing the intake of air.

[0012] Furthermore, the dry dust collection system includes gravity dust collection and baghouse dust collection. Specifically, the flue gas first enters the gravity dust collection stage. In the gravity dust collector, larger dust particles naturally settle to the bottom of the collector under gravity, thus achieving initial dust separation. After gravity dust collection, the flue gas then enters the baghouse dust collection stage. The baghouse dust collector contains a large number of filter bags. When the flue gas passes through the filter bags, the dust is trapped, while clean air is discharged through the filter bags. Over time, a certain thickness of dust layer accumulates on the filter bags. When a certain resistance is reached, a cleaning operation is required.

[0013] After adopting the above technical solution, the beneficial effects of the present invention are as follows: when collecting flake graphite using this collection method, not only will a large amount of wastewater not be generated, making it more environmentally friendly and economical, but the flake graphite content in the dust collected by this collection method can be ≥60%, and the recovery amount is large, thereby reducing the subsequent purification cost and making it more economical. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a flowchart illustrating the present invention.

[0016] Figure 2 This refers to the C saturation content of molten iron at different temperatures in this invention.

[0017] Figure 3 This is a schematic diagram of the device structure of the present invention.

[0018] Figure 4 This is a schematic diagram of the purified flake graphite in this invention. Detailed Implementation Example

[0019] See Figure 1 and Figure 3 As shown, the technical solution adopted in this specific embodiment is as follows: It includes the following methods: S1, molten iron is transported to the steelmaking area via molten iron ladle cars. Workers use rapid thermocouple temperature guns to measure the temperature of the molten iron and obtain the temperature T. S2. Calculate the amount of scrap steel to be added based on the measured molten iron temperature T. The specific calculation method is as follows: when the molten iron temperature T > 1280℃, according to the experiment, add 50kg of crushed scrap steel for every 10℃ increase in molten iron temperature T; and when the molten iron temperature T ≤ 1280℃, no scrap steel is added.

[0020] S3. When scrap steel needs to be added, use an electromagnetic chuck to slowly and evenly add the crushed scrap steel into the molten iron ladle according to the calculated weight. S4, using a metallurgical crane to transport molten iron ladles to the flake graphite collection area. S5. After the molten iron ladle reaches the designated location in the flake graphite collection area, the operator slowly lowers the dust cover to cover the mouth of the molten iron ladle. This effectively reduces the intake of air and prevents the flake graphite from oxidizing due to contact with oxygen in the air at high temperatures. S6, simultaneously start the nitrogen blowing and dust removal fan at the bottom of the molten iron ladle: The specific steps for starting the bottom blowing nitrogen in the molten iron ladle are as follows: bottom blowing nitrogen flow rate 1000 Nm. 3 / h not only ensures the stirring effect, but also blows up the flake graphite precipitated on the surface of the molten iron. The dust removal fan is operated by using frequency conversion technology. It can control the slight negative pressure between the dust removal hood and the molten iron ladle opening, ensuring the dust removal effect while reducing air intake.

[0021] S7, under the action of bottom-blown nitrogen and induced draft fan, the smoke and dust generated in the molten iron ladle (containing precipitated flake graphite) enters the dry dust removal system through the suction port of the dust removal hood.

[0022] S8, after being processed by a dry dust collection system (comprising gravity dust collection and bag filter dust collection), the dust collected in the ash hopper is dust containing flake graphite. The dry dust collection system includes gravity dust collection and bag filter dust collection, specifically: 1) The smoke and dust first enter the gravity dust removal stage. In the gravity dust collector, the larger dust particles in the smoke and dust will naturally settle to the bottom of the dust collector under the action of gravity, thus achieving preliminary dust separation. 2) After gravity dust removal, the flue gas enters the baghouse dust collector. The baghouse dust collector contains numerous filter bags. As the flue gas passes through the filter bags, the dust is trapped, while clean air is discharged. Over time, a certain thickness of dust layer accumulates on the filter bags. When a certain resistance is reached, a cleaning operation is required. Cleaning methods such as pulse-jet cleaning are used to shake the dust off the filter bags into the ash hopper at the bottom of the dust collector. S9 periodically discharges the dust from the ash hopper for subsequent storage, transportation, and further processing. Example

[0023] During a blast furnace tapping operation, a temperature sample taken from the trough showed a temperature of 1490℃ and a carbon content of 5.52%. When transported to the steel plant, the molten iron reached a temperature of 1350℃, with a carbon content of 4.78%, and flake graphite had begun to precipitate. A graph showing the relationship between molten iron temperature and carbon content can be found here. Figure 2As shown, since T > 1280℃, and T is 1350 - 1280 = 70℃ higher than 1280℃, according to the rule of adding 50kg of crushed scrap steel for every 10℃ increase, the amount of scrap steel to be added this time is (70 ÷ 10) × 50 = 350kg. The staff used an electromagnetic chuck to slowly and evenly add the crushed scrap steel into the molten iron ladle according to the calculated weight of 350kg. The molten iron ladle was then transported to the graphite recovery station. The dust hood was lowered, and simultaneously, bottom-blowing nitrogen and the dust-collecting induced draft fan were activated. The bottom-blowing nitrogen flow rate was 1000 Nm³ / h, and the dust-collecting induced draft fan employed variable frequency technology. This fan controlled the slight negative pressure between the dust hood and the ladle opening, ensuring effective dust collection while minimizing air intake. Under the combined action of the bottom-blowing nitrogen and the dust-collecting induced draft fan, the flake graphite precipitated from the molten iron and the dust generated by iron oxidation were collected by the dust hood and subjected to dry dust removal. The resulting dust ash mainly contained flake graphite and iron oxide, weighing 832 kg. The flake graphite content was 62.4%, with a small amount of powdered graphite, and the remainder consisting of iron oxide and other impurities. After graphite collection, the molten iron temperature was 1275℃, and the carbon content was 4.59%, meeting the requirements for steelmaking. The purified flake graphite can be found in [reference needed]. Figure 4 As shown. Example

[0024] During a blast furnace tapping operation, a temperature sample taken from the trough was 1450℃ with a carbon content of 5.32%. Upon transport to the steel plant, the molten iron reached a temperature of 1278℃, and testing revealed a carbon content of 4.60%, with flake graphite already precipitated. A graph showing the relationship between molten iron temperature and carbon content can be found [link to graph]. Figure 2 As shown, since T < 1280℃, no scrap steel is added. The molten iron ladle is then transported to the graphite recycling station, the dust hood is lowered, and simultaneously, bottom-blowing nitrogen and the dust-collecting induced draft fan are turned on. The bottom-blowing nitrogen flow rate is 1000 Nm³ / h, and the dust-collecting induced draft fan uses variable frequency technology. The dust-collecting induced draft fan can control the slight negative pressure between the dust hood and the ladle opening, ensuring dust collection efficiency while reducing air intake. Under the combined action of the bottom-blowing nitrogen and the dust-collecting induced draft fan, the flake graphite precipitated from the molten iron and the dust generated by the oxidation of the molten iron are collected by the dust hood and subjected to dry dust removal, yielding dust mainly containing flake graphite and iron oxide. The dust weighs 786 kg, with a flake graphite content of 63.7%, a small amount of powdered graphite, and the remainder being iron oxide and other impurities. After graphite collection, the molten iron temperature is 1262℃, and the C content is 4.53%, meeting the requirements for steelmaking. The purified flake graphite can be found in [reference needed]. Figure 4 As shown.

[0025] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for collecting flake graphite precipitated from molten iron, characterized in that: It includes the following methods: S1, molten iron is transported to the steelmaking area by molten iron ladle cars. Workers use rapid thermocouple temperature guns to measure the temperature of the molten iron and obtain the temperature T of the molten iron. S2, calculate the amount of scrap steel to be added based on the measured temperature T of the molten iron; S3. When scrap steel needs to be added, use an electromagnetic chuck to slowly and evenly add the crushed scrap steel into the molten iron ladle according to the calculated weight. S4, using a metallurgical crane to transport molten iron ladles to the flake graphite collection area. S5. After the molten iron ladle reaches the designated location in the flake graphite collection area, the operator slowly lowers the dust cover to cover the mouth of the molten iron ladle. This effectively reduces the intake of air and prevents the flake graphite from oxidizing due to contact with oxygen in the air at high temperatures. S6, simultaneously turn on the bottom blowing nitrogen gas and dust removal fan of the molten iron ladle; S7, under the action of bottom-blown nitrogen and induced draft fan, the smoke and dust generated in the molten iron ladle enter the dry dust removal system through the suction port of the dust removal hood; S8, after being processed by the dry dust removal system, the dust collected in the ash hopper is dust containing flake graphite. S9 periodically discharges the dust from the ash hopper for subsequent storage, transportation, and further processing.

2. The method for collecting flake graphite precipitated in molten iron according to claim 1, characterized in that: Specifically, S2 means that when the molten iron temperature T > 1280℃, according to the experiment, 50kg of crushed scrap steel is added for every 10℃ increase in molten iron temperature T; while when the molten iron temperature T ≤ 1280℃, no scrap steel is added.

3. The method for collecting flake graphite precipitated in molten iron according to claim 1, characterized in that: The specific steps for starting the bottom blowing nitrogen gas in S6 are as follows: bottom blowing nitrogen gas flow rate 1000 Nm. 3 / h not only ensures the stirring effect, but also blows up the flake graphite that precipitates on the surface of the molten iron.

4. The method for collecting flake graphite precipitated in molten iron according to claim 1, characterized in that: The specific steps for starting the dust removal fan in S6 are as follows: The dust removal fan adopts frequency conversion technology, which can control the slight negative pressure between the dust removal hood and the molten iron ladle opening, ensuring the dust removal effect while reducing air intake.

5. The method for collecting flake graphite precipitated in molten iron according to claim 1, characterized in that: The dry dust collection system in S8 includes gravity dust collection and bag filter dust collection, specifically: 1) The smoke and dust first enter the gravity dust removal stage. In the gravity dust collector, the larger dust particles in the smoke and dust will naturally settle to the bottom of the dust collector under the action of gravity, thus achieving preliminary dust separation. 2) After gravity dust removal, the flue gas enters the bag filter stage. The bag filter is equipped with a large number of filter bags. When the flue gas passes through the filter bags, the dust is trapped by the filter bags, while the clean air is discharged through the filter bags. Over time, a certain thickness of dust layer will accumulate on the filter bags. When a certain resistance is reached, a dust cleaning operation is required.

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