A molten iron heat-insulating agent and its preparation process

Abstract

This invention discloses a molten iron heat-insulating agent, which comprises the following components: 60-90 parts of carbonized straw, 20-30 parts of fly ash, and 1-13 parts of desulfurized gypsum powder. The preparation process of the molten iron heat-insulating agent includes: (1) mechanically mixing carbonized straw, fly ash, and desulfurized gypsum powder, adding water during the stirring process to make the mixture bind together; (2) drying or air-drying the mixture, and pulverizing it to an average particle size ≤3mm to obtain the molten iron heat-insulating agent. This invention uses carbonized straw instead of conventional carbonized rice husks, which greatly saves the preparation cost of the heat-insulating agent; secondly, this invention uses fly ash and desulfurized gypsum powder as raw materials for preparing the heat-insulating agent, which is a recycling and reuse of waste resources and promotes ecological and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical melt insulation technology, specifically relating to a molten iron insulation agent and its preparation process. Background Technology

[0002] The temperature of molten iron has a significant impact on steelmaking. According to the converter smelting process, the heat generated in converter smelting primarily comes from the physical and chemical heat of the molten iron. Under a given chemical heat, the physical heat of the molten iron is the key factor determining whether smelting can proceed smoothly. Low molten iron temperature leads to high converter blowdown losses, high consumption of steel feedstock, inconsistent steel quality, and reduced furnace life. Molten iron temperature is not only crucial for the steelmaking process but also affects molten iron transportation. If the temperature of the molten iron is too low during transportation, it will cause crusting and brittle formation on the molten iron ladle cars, directly impacting normal production operations. Conventional blast furnaces in my country produce nearly 10,000 tons of molten iron daily. This molten iron needs to be transported to steelmaking plants in ladles. Due to varying conditions at different plants and different transportation distances, the temperature of the molten iron will inevitably drop during transportation.

[0003] To minimize the temperature drop of molten iron during transport, insulating agents, also known as insulating coverings, are commonly used. These are important materials in steel production and their function is to maintain the temperature of molten iron during storage, transportation, and pouring, reducing temperature drop, while also isolating it from air and protecting it from secondary oxidation.

[0004] Traditional heat-insulating agents mainly use carbonized rice husks as raw materials, but the supply of carbonized rice husks is currently insufficient and the price is high, increasing the cost of steelmaking. Therefore, it is necessary to develop a low-cost, high-insulation-performance, and environmentally friendly heat-insulating agent for molten iron.

[0005] Patent document CN201710742766.0 discloses a molten iron heat preservation agent using dry quenching coke dust as raw material, wherein the molten iron heat preservation agent comprises the following components: 50g dry quenching coke dust. 100% water-quenched blast furnace slag 50%, expanded perlite 0 10%. Although the raw materials for the molten iron heat-preserving agent are derived from metallurgical enterprise waste and are inexpensive, the composition of dry quenching coke dust produced by different enterprises may vary significantly due to differences in raw materials and smelting environments. This undoubtedly leads to inconsistent performance of the final molten iron heat-preserving agent. Therefore, the above method of preparing molten iron heat-preserving agent using enterprise-produced dry quenching coke dust as the main raw material cannot be widely promoted.

[0006] Patent document 201510955655.9 discloses a molten iron heat-insulating agent, comprising the following raw materials in parts by weight: fly ash 50 60 portions, 10 pieces of dolomite 15 portions, vermiculite 8 15 portions, 3 portions of acidified graphite 5 portions, cement clinker 10 20 parts. The hot metal heat preservation agent is mainly made of fly ash, and also requires the addition of acidified graphite. Graphite is expensive to purchase, and the amount of hot metal heat preservation agent used is large. Therefore, the hot metal heat preservation agent will undoubtedly increase the cost of ironmaking.

[0007] Patent document 201210543783.9 discloses a low-cost molten iron heat-insulating agent, comprising 60 70% high-carbon fly ash, 25 35% water-quenched blast furnace slag, 3 5% fluorite powder. The patent requires that the high-carbon fly ash have a particle size of less than 1 mm, preferably more than 80% of the high-carbon fly ash have a particle size of less than 75 μm, and the hot metal heat-preserving agent is simply obtained by mixing and packaging the raw materials. The hot metal heat-preserving agent prepared by the above method will generate a large amount of dust during use, which will not only damage the environment of the ironmaking workshop, but may also cause safety accidents.

[0008] To overcome the shortcomings of the prior art, the present invention provides a molten iron heat preservation agent. The heat preservation agent uses carbonized straw as the main raw material to replace the currently expensive carbonized rice husk, supplemented with fly ash, and then adds desulfurized gypsum to prepare the molten iron heat preservation agent, which has a very good heat preservation effect on molten iron during transportation. Summary of the Invention

[0009] Fly ash is a fine ash collected from the flue gas after coal combustion. It is a major solid waste discharged from coal-fired power plants and is one of the largest industrial waste residues discharged in my country. Desulfurization gypsum is an industrial by-product obtained from coal-fired enterprises after treating sulfur dioxide in flue gas. Like fly ash, it needs to be further developed and utilized. This invention utilizes fly ash and desulfurization gypsum as raw materials for molten iron insulation. The biggest advantage is the recycling and reuse of waste resources, promoting ecological and environmental protection. In addition, it reduces the mining of other mineral resources such as gypsum, thus conserving resources.

[0010] The purpose of this invention is to provide a molten iron heat preservation agent and a preparation process for the molten iron heat preservation agent. The molten iron heat preservation agent provided by this invention not only fully complies with the sustainable development concept of protecting the environment and conserving resources, but also avoids dust during use, providing a good working environment for ironmaking plants.

[0011] The objective of this invention is achieved through the following technical solutions.

[0012] In a first aspect, the present invention provides a molten iron heat-preserving agent, the molten iron heat-preserving agent comprising the following components: carbonized straw 60 90 portions, fly ash 20 30 parts, desulfurized gypsum powder 1 13 copies.

[0013] Preferably, the fly ash and desulfurized gypsum powder have a particle size of 100. 200 mesh.

[0014] Preferably, the components of the molten iron heat-insulating agent include: carbonized straw 80 90 parts, fly ash 30 parts, desulfurized gypsum powder 5 parts 13 copies.

[0015] More preferably, the hot metal heat-insulating agent comprises: 90 parts carbonized straw, 30 parts fly ash, and 5 parts desulfurized gypsum powder. 8 copies.

[0016] In the most preferred embodiment of the present invention, the desulfurized gypsum component of the molten iron heat preservation agent is 8 parts.

[0017] The amount of the molten iron heat-preserving agent added is 0.3-1.0 kg / ton of molten iron, and the temperature drop rate of the molten iron is 0.3-0.7℃ / min.

[0018] Secondly, the present invention provides a process for preparing a molten iron heat-preserving agent, the method comprising the following steps: (1) Mechanically mix carbonized straw, fly ash and desulfurized gypsum powder, and add water during the mixing process to make the mixture stick together; (2) Dry the mixture by drying or air drying, and crush it to an average particle size of ≤3mm to obtain molten iron heat preservation agent.

[0019] Preferably, the amount of water added in step (1) is 6-15% of the mass of the mixture, and the mixture is best when it can be pressed into a ball and is not sticky.

[0020] Preferably, the average particle size of the molten iron heat-insulating agent in step (2) is 1-1.5 mm.

[0021] Desulfurized gypsum has good binding properties. When an appropriate amount of water is added during the mixing of carbonized straw, fly ash, and desulfurized gypsum powder, the desulfurized gypsum powder will bind the three materials together. Essentially, the molten iron insulation agent provided by this invention is a product of mixing carbonized straw, fly ash, and desulfurized gypsum powder, then solidifying and pulverizing it. The three materials are tightly bound, and the particle size after pulverization is controlled to ≤3mm, completely avoiding dust generation in actual operation.

[0022] In addition, compared with carbonized rice husks, carbonized straw is not only cheaper, but also has a higher fixed carbon content and a lower ash content. Carbonized straw has a honeycomb-like microstructure, which makes the molten iron insulation agent prepared with carbonized straw as the main raw material have a better heat insulation effect, and it is also lighter in weight. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Preparation of molten iron heat-insulating agent Example 1 Add 60 parts of carbonized straw, 20 parts of fly ash and 1 part of desulfurized gypsum powder to a mixer and mix well. Add 10 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 3 mm to obtain the molten iron heat preservation agent.

[0025] Example 2 Add 80 parts of carbonized straw, 30 parts of fly ash and 5 parts of desulfurized gypsum powder to a mixer and mix well. Add 11 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 2 mm to obtain the molten iron heat preservation agent.

[0026] Example 3 Add 90 parts of carbonized straw, 30 parts of fly ash and 5 parts of desulfurized gypsum powder to a mixer and mix well. Add 12 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 1.5 mm to obtain the molten iron heat preservation agent.

[0027] Example 4 Add 90 parts of carbonized straw, 30 parts of fly ash and 6 parts of desulfurized gypsum powder to a mixer and mix well. Add 12 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 1.5 mm to obtain the molten iron heat preservation agent.

[0028] Example 5 Add 90 parts of carbonized straw, 30 parts of fly ash and 7 parts of desulfurized gypsum powder to a mixer and mix well. Add 12 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 1.5 mm to obtain the molten iron heat preservation agent.

[0029] Example 6 Add 90 parts of carbonized straw, 30 parts of fly ash and 8 parts of desulfurized gypsum powder to a mixer and mix well. Add 12 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 1 mm to obtain the molten iron heat preservation agent.

[0030] Example 7 Add 90 parts of carbonized straw, 30 parts of fly ash and 10 parts of desulfurized gypsum powder to a mixer and mix well. Add 12 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 1 mm to obtain the molten iron heat preservation agent.

[0031] Comparative Example 1 Add 90 parts of carbonized rice husk, 30 parts of fly ash, and 8 parts of desulfurized gypsum powder to a mixer and mix well. Add 12 parts of water during the mixing process and mix thoroughly until the mixture can be easily kneaded into a ball. Dry the mixture and crush it to an average particle size of 1 mm to obtain the molten iron heat preservation agent.

[0032] Comparative Example 2 Add 90 parts of carbonized straw and 30 parts of fly ash to a mixer and mix well. Add 12 parts of water during the mixing process. Dry the mixture and crush it to an average particle size of 1 mm to obtain a molten iron heat preservation agent.

[0033] Application example: molten iron heat-insulating agent used in molten iron transportation. Experimental objective: To test the heat preservation effect of the molten iron heat preservation agent prepared in this invention on the transportation of molten iron.

[0034] Experimental Method: Molten iron obtained from blast furnace smelting was loaded into a standard 200-ton capacity ladle. When the amount of molten iron in the ladle reached 50 tons, a heat-insulating agent was added at a rate of 0.8 kg / ton of molten iron. Dust generation was observed during the addition process. After tapping, the temperature of the molten iron in the ladle was measured, and data T1 was obtained. Timing was started simultaneously until the ladle arrived at the steel plant, at which point the temperature of the molten iron in the ladle was measured again, and data T2 was obtained. The transportation time was recorded.

[0035] Experimental Results: Statistical analysis was conducted on the dust generation of various molten iron heat-insulating agents during actual operation, as well as the cooling rate of molten iron after the addition of the heat-insulating agent. Since the molten iron heat-insulating agent prepared in this invention contains desulfurized gypsum, the sulfur content of the heat-insulating agent is also a key monitoring indicator; as long as the sulfur content is ≤1.2%, it meets the production requirements. Specific results are shown in the table below.

[0036] Table 1. Thermal insulation effect of molten iron insulation agent

[0037] According to the standard that the sulfur content in the thermal insulation agent is not greater than 1.2%, Example 1 of the present invention All the prepared thermal insulation agents in Example 6 met this standard. However, in Example 7, the sulfur content in the prepared thermal insulation agent exceeded the standard due to the high amount of desulfurized gypsum added. Therefore, the method in Example 7 is not applicable, and this unqualified product will not be subject to further application testing. The sulfur content in the thermal insulation agent is directly related to the amount of desulfurized gypsum added. In order to maximize the use of desulfurized gypsum, the inventors believe that the preparation process in Example 6 is the optimal method.

[0038] The dust generation records during the operation of the hot metal heat preservation agent show that the hot metal heat preservation agent containing desulfurized gypsum powder in its raw materials does not generate dust during operation, and even when the average particle size of the heat preservation agent is 1 mm, no dust is generated. In contrast, in Example 2, which does not contain desulfurized gypsum powder, the carbonized straw and fly ash do not have a good binding state, and are essentially just simply mixed, resulting in dust generation during actual application.

[0039] According to the cooling rate statistics in the table above, the heat preservation agent prepared in Example 6 has the best heat preservation effect, with a cooling rate of 0.3℃ / min. The cooling rates of the heat preservation agents prepared in the embodiments of this invention are between 0.3-1.0℃ / min. Among them, the heat preservation agent prepared in Example 1 has a relatively poor heat preservation effect compared to the other groups. The reason for this may be that the particle size of the heat preservation agent is larger, or that the content of desulfurized gypsum powder in the components is too low, resulting in weak adhesion between the components. During transportation, the components disperse, thus weakening the heat preservation effect. In addition, the heat preservation agent prepared in Comparative Example 1, whose main component is carbonized rice husk, has a lower heat preservation effect compared to Example 6, whose main component is carbonized straw. This shows that carbonized straw has a better heat preservation effect than carbonized rice husk. The raw material components of Comparative Example 2 do not contain desulfurized gypsum powder, and the components have no binding effect. It is a conventional mixing process, which will not only generate a lot of dust in practical applications, but also result in poor heat preservation effect. Therefore, it can be proven that using desulfurized gypsum powder as a binder to bind the components and then crushing them results in a molten iron heat preservation agent with uniform particle size and better heat preservation effect.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A molten iron heat-preserving agent, characterized in that, The hot iron insulation agent comprises: carbonized straw 80 90 parts, fly ash 30 parts, desulfurized gypsum powder 5 parts 8 parts; the particle size of the fly ash and desulfurized gypsum powder is 100. 200 mesh; The preparation process of the molten iron heat-preserving agent includes the following steps: (1) Mechanically mix carbonized straw, fly ash and desulfurized gypsum powder, and add water during the mixing process to make the mixture stick together; (2) Dry the mixture by drying or air drying, and crush it to an average particle size of ≤3mm to obtain molten iron heat preservation agent.

2. The molten iron heat-preserving agent according to claim 1, characterized in that, The hot metal heat-insulating agent comprises: 90 parts carbonized straw, 30 parts fly ash, and 5 parts desulfurized gypsum powder. 8 copies.

3. The molten iron heat-preserving agent according to claim 2, characterized in that, The desulfurized gypsum component of the molten iron insulation agent is 8 parts.

4. According to claim 1 3. The molten iron heat-preserving agent described in any one of the above is characterized in that, The amount of the molten iron heat-insulating agent added is 0.

3. 1.0 kg / ton of molten iron.

5. The molten iron heat-preserving agent according to claim 1, characterized in that, In step (1), the amount of water added is 6% of the mass of the mixture. 15%.

6. The molten iron heat-preserving agent according to claim 1, characterized in that, In step (1), the amount of water added is 8% of the mass of the mixture. 10%.

7. The molten iron heat-preserving agent according to claim 1, characterized in that, The average particle size of the molten iron insulation agent in step (2) is 1. 1.5mm.

Images