CN114480764B - Preparation method and system of blast furnace tuyere with heat insulation coating - Google Patents

Abstract

The invention discloses a preparation method of a blast furnace tuyere with a heat insulation coating, which comprises the following steps: fixing the tuyere body on a rotary table, preheating the tuyere body through an induction coil arranged at the periphery of the tuyere, and preheating the tuyere body to a temperature of more than 600 ℃; rotating the tuyere body at a constant speed, and simultaneously performing surfacing welding on the inner wall of the tuyere body by using a plasma welding gun; the welding gun is always positioned above the inner wall of the tuyere and is vertical to the inner wall of the tuyere in direction; the thickness of the heat insulation coating is controlled to be 2-3mm; after one circle of overlaying is finished, the plasma welding gun advances for a certain distance and then continues the next circle of overlaying. The invention aims to reduce the heat taken away by cooling water from hot air at the air port and improve the air temperature, thereby reducing the coke ratio, realizing energy conservation and reducing carbon emission.

Description

A preparation method and system for a blast furnace tuyere with a thermal insulation coating

technical field

The invention relates to blast furnace smelting, in particular to a blast furnace tuyere.

Background technique

With the deepening of people's understanding of global warming, the reduction of greenhouse gas emissions and low-carbon production have increasingly become the focus of social attention. As an industry with high energy consumption and high pollution, the iron and steel industry is one of the major emitters of greenhouse gases. The carbon emissions of my country's iron and steel industry account for about 16% of the total global carbon emissions, and blast furnace ironmaking is the process with the largest carbon emissions in the overall steel production process, accounting for 70% to 90% of the total emissions. Therefore, the development and application of blast furnace low-carbon smelting technology and the realization of energy saving and emission reduction in the blast furnace process are important tasks facing my country's iron and steel industry.

The heat of the blast furnace mainly comes from the combustion heat of coke and other fuels in the tuyere swirl area and the physical heat brought in by the hot air. Among them, the hot blast provides 15% to 20% of the total heat input of the blast furnace. The temperature of the hot blast not only affects the thermal system in the blast furnace, but also affects the consumption of raw materials. Studies have shown that every 100°C increase in blast temperature can reduce tons of iron coke Ratio of 2.8%, so increasing blast furnace air temperature is an important way to realize low-carbon production of blast furnace. The hot blast is produced from the hot blast stove, and then transported into the blast furnace through the blast furnace tuyere. However, the blast furnace tuyere is made of through-flow copper, and the water cooling strength is high. It will inevitably take away part of the heat of the hot blast and reduce the blast temperature, thereby improving the blast furnace. The amount of fuel coke used. Therefore, reducing the heat loss of the hot blast at the tuyere of the blast furnace is of great significance for increasing the blast furnace blast temperature and realizing energy saving and emission reduction.

Therefore, those skilled in the art are devoting themselves to developing a low-carbon and energy-saving blast furnace tuyere.

Contents of the invention

In view of the above-mentioned defects in the prior art, the present invention proposes a blast furnace tuyere with a heat-insulating coating, that is, a heat-insulating coating with a lower thermal conductivity than copper is coated on the inner wall of the tuyere, in order to reduce the hot air being cooled by the cooling water. The heat taken away increases the air temperature, thereby reducing the coke ratio, realizing energy saving and reducing carbon emissions. Coating methods can be various surface engineering techniques such as electroplating, spraying, and surfacing, and coating materials can be pure metals with lower thermal conductivity than copper, alloys composed of multiple elements, ceramic thermal barrier coatings, etc.

The following will be described in detail by taking plasma surfacing welding of Ni60A alloy coating on the inner wall of the tuyere as an example. Ni60A alloy is a nickel-based alloy whose chemical composition is Ni-15Cr-3.5B-4Si-8Fe-0.8C. The main component of this material is Ni, which can be infinitely miscible with Cu in the tuyere, and the melting point of the coating material is (1026°C) is also close to copper (1083°C), and can be melted together with copper during the surfacing process, which is conducive to the formation of metallurgical bonding and makes the coating not easy to peel off. During the surfacing process, ceramic phases such as Cr ₂₃ C ₆ and CrB will be formed in the coating, which will significantly reduce the thermal conductivity, which is about 15 W/(M K), which is far lower than the thermal conductivity of copper, which is 400W/(M K ). A numerically controlled plasma surfacing machine (PTA-400A) with low cost and high degree of automation is selected as the surfacing equipment. This Ni60A thermal barrier coating was deposited onto the inner wall of a blast furnace tuyere using a programmed surfacing procedure.

Through ANSYS numerical simulation, it is calculated that the temperature of the cooling water at the outlet of the tuyere with Ni60A coating on the inner wall is lower than that of the common tuyere without surfacing, and the heat taken away by the cooling water is obviously reduced, that is, It is said that the new low-carbon energy-saving tuyere effectively reduces the heat loss of hot air at the tuyere.

Based on the above numerical simulation results, the energy-saving effect and the effect of reducing carbon emissions of the tuyere with Ni60A thermal insulation coating were calculated:

The specific heat capacity C _p of circulating water is 4.1868kJ/(kg·℃), assuming that the cooling water m of each tuyere is 28 tons/hour, and the temperature drop ΔT of the outlet of the tuyere is 3℃, then each tuyere reduces the amount of water taken away per hour. The heat of the hot air is: Q=C _p m·ΔT=4.1868×28×1000×3=351691.2KJ.

Assuming that the tuyere works 365 days a year, the annual heat loss of each tuyere is: Q _total = 351691.2×24×365=3.08×10 ⁹ KJ.

The heat value per kilogram of standard coal stipulated in China is 7000 kcal, that is, 7000×4.18585=29300.95KJ, and the annual heat loss reduction of each tuyere is equivalent to 3.08×10 ⁹ /29300.95=1.05×10 ⁵ Kg of standard coal.

Taking a 3200m ³ blast furnace equipped with 32 tuyeres as an example, each blast furnace can save 1.05×10 ⁵ × 32 = 3.36×10 ⁶ Kg of standard coal per year, converted into coke savings of 3.63×10 ⁶ ×0.9714 = 3.263904×10 ⁶ Kg = 3264 tons.

In addition, based on the calculation of 2.5 tons of carbon dioxide emitted by one ton of coke, the tuyere welded with Ni60A thermal insulation coating can reduce the carbon dioxide emission of the blast furnace by 8160 tons per year.

Specifically, the present invention firstly provides a method for preparing a blast furnace tuyere with a thermal insulation coating, comprising the steps of:

Fix the tuyere body on the turntable, preheat the tuyere body by setting the induction coil around the tuyere, and preheat the tuyere body to above 600°C;

Rotate the tuyere body at a constant speed, and use the plasma welding torch to surfacing the inner wall of the tuyere body; the welding torch is always positioned above the inner wall of the tuyere, and the direction is perpendicular to the inner wall of the tuyere; the thickness of the heat-insulating coating is controlled at 2-3mm;

After completing one lap of surfacing, make the plasma welding torch advance for a certain distance and continue the next lap of surfacing.

Furthermore, the induction coil uses an 8mm copper tube with an insulating sleeve, and the number of turns is based on the standard that can preheat the tuyere body to above 600°C.

Further, a square linear slide rail is arranged on the center line of the tuyere, a square slide block is arranged on the square linear slide rail, and the welding torch is fixed on the lower end surface of the square slide block.

Further, the square slider is a linear motor.

Further, a height-adjustable scraping tool is set on the upper surface of the square slider, and the thickness of the coating can be controlled by adjusting the height of the scraping tool; during work, with the rotation of the tuyere body, the square slider The welding torch at one end performs surfacing welding of the protective coating on the inner wall of the tuyere body, while the scraping tool at the other end of the square slider scrapes and grinds the protective coating to ensure the uniformity and surface smoothness of the coating.

Further, a blowing fan is provided at the front end of the linear guide rail for blowing away coating debris generated by scraping and grinding.

The present invention also provides a preparation system for a blast furnace tuyere with a heat-insulating coating, which includes a turntable for fixing the tuyere body, an induction coil wound around the periphery of the tuyere body for preheating, and a square set on the center line of the tuyere. type linear slide rail, a square slide block arranged on the square linear slide rail, a welding torch fixed on the lower end face of the square slide block, and a height-adjustable scraping cutter arranged on the upper end face of the square slide block.

Further, the square slider is a linear motor.

Further, it also includes a blowing fan arranged at the front end of the linear guide rail.

Furthermore, the induction coil uses an 8mm copper tube with an insulating sleeve, and the number of turns is based on the standard that the tuyere can be preheated to above 600°C.

The present invention can reduce the heat loss of the hot air at the tuyeres after adding the Ni60A thermal insulation coating with low thermal conductivity on the inner wall of the tuyeres, and save energy consumption; at the same time, after the air temperature of the hot air is increased, the amount of coke required for blast furnace smelting will be significantly reduced , save smelting costs, and also reduce carbon emissions caused by coke combustion.

The idea, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention.

Description of drawings

Fig. 1 is a schematic diagram of the process of preheating blast furnace tuyeres with induction coils in a preferred embodiment of the present invention;

Fig. 2 is the schematic diagram that carries out plasma welding to blast furnace tuyere in Fig. 1;

Fig. 3 is a schematic diagram of the winding method of the induction coil in Fig. 1;

Fig. 4 is a schematic diagram of overlay welding on the inner wall of the tuyere in Fig. 1;

Fig. 5 is a schematic diagram with scraping and grinding of the coating during the surfacing process in another embodiment of the present invention;

Figure 6 is an axial view of the embodiment of Figure 5;

Figure 7 is a cloud map of the temperature field distribution of the water inlet and water outlet of a common blast furnace tuyere;

Fig. 8 is a cloud map of the temperature field distribution of the blast furnace tuyere water inlet and water outlet with thermal insulation coating.

In the figure: 1-tuyere body, 2-induction coil for preheating, 3-plasma torch support rod, 4-plasma torch, 5-heat insulation coating, 6-tuyere center line, 7-water inlet, 8- Water outlet, 9-square linear guide, 10-square slider, 11-scraping cutter, 12-purge fan.

Detailed ways

The following describes several preferred embodiments of the present invention with reference to the accompanying drawings, so as to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned herein.

According to the preparation steps of the blast furnace tuyere with heat-insulating coating of the present invention: as shown in Figures 1 and 3, the tuyere body 1 first needs to be fixed on the turntable. Preheat to reduce the heat loss of the plasma arc and prevent the occurrence of incomplete penetration. The preheating adopts the induction preheating method, and the induction coil 2 is wound around the periphery of the tuyere for surfacing welding on the inner wall of the tuyere body 1, as shown in Figs. 2 and 4 . The induction coil uses an 8mm copper tube with an insulating sleeve. The number of turns is based on the ability to preheat the tuyere to above 600°C, and it also needs to match the power of the induction heating equipment.

During the surfacing process, the plasma welding torch 4 needs to extend into the deep part of the inner wall of the tuyere body 1, so it is necessary to customize the length of the plasma torch support rod and the size of the welding torch itself according to the actual size of the tuyere and the position to be surfacing, so as to ensure that the overlay welding process can run smoothly. For example, the total length of the tuyere body 1 is 600mm, the minimum diameter of the inner hole of the tuyere is 130mm, the total range of the surfacing layer to be prepared is 400mm, the total length of the support rod 3 is not less than 500mm, and the height of the welding torch 4 (the distance from the nozzle to the top of the torch) is not less than 500mm. Greater than 100mm.

The surfacing welding mode of the tuyere is: the induction coil is fixed, the welding torch 4 is always located above the inner wall of the tuyere, the direction is perpendicular to the inner wall of the tuyere, and the tuyere is in a state of constant speed rotation, as shown in Figure 4, the thickness of the heat insulation coating 5 is generally controlled at 2-3mm Left and right, the thickness of the coating can be controlled by controlling the powder feeding amount in the plasma surfacing equipment. Appropriately increasing the thickness is beneficial to reduce the heat loss of hot air, but too large thickness may be detrimental to the anti-melt loss performance of the tuyeres, which needs to be determined according to the actual situation.

In order to control the thickness and uniformity of the coating 5 more precisely, and at the same time improve the smoothness of the surface of the coating 5, so as to minimize the wind resistance to the high-speed hot air in the tuyere, as shown in Figure 5-6, set the square on the center line of the tuyere. Type linear slide rail 9, square slide block 10 is arranged on square linear slide rail 9. In a further embodiment, the slider 10 can also be set as a linear motor of the square linear slide rail 9 . The welding torch 4 is fixed on the lower end surface of the square slide block 10, and a highly adjustable scraping cutter 10 is set on the upper end surface of the square slide block 10 at the same time. By adjusting the height of the scraping cutter 10, the thickness of the coating 5 can be controlled. thickness. When working, along with the rotation of the tuyere body 1, the welding torch 4 at one end of the square slider 10 carries out overlay welding of the protective coating 5 to the inner wall of the tuyere body 1, while the scraping tool 10 at the other end of the square slider 10 pairs The protective coating 5 is scratched to ensure the uniformity and surface smoothness of the coating 5 . Scratch the tool 10 behind the welding torch 4 in the direction of the centerline by a distance of one circle. After one lap of surfacing, control the square slider 10 to advance a set distance, and start the next lap of surfacing and scraping. At the front end of the linear guide rail 9, a fan 12 is arranged to blow away the coating debris generated by scraping and grinding, so as not to affect the surfacing.

Figure 7 and Figure 8 respectively show the temperature field distribution of the water inlet 7 and water outlet 8 of the tuyere before and after surfacing 3 mm of Ni60A thermal insulation coating on the inner wall, and the temperature of the cooling water at the water outlet is reduced by about 3 °C , it can be seen that the heat taken away by the cooling water is significantly reduced, indicating that the blast furnace tuyere with heat-insulating coating can effectively reduce the heat loss of the hot air at the tuyere.

In fact, increasing the thickness of the thermal insulation coating, or using other coating materials with lower thermal conductivity, is expected to further reduce the temperature difference between the water inlet and the water outlet, that is, to further reduce the heat loss of the hot air. At the same time, the energy-saving effect of the corresponding tuyere and the effect of reducing carbon emissions can also be estimated according to the actual temperature difference and the calculation method mentioned in the summary of the invention.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (3)

1. A preparation method of a blast furnace tuyere with a heat insulation coating is characterized by comprising the following steps:

fixing the tuyere body on a rotary table, preheating the tuyere body by an induction coil arranged at the periphery of the tuyere, and preheating the tuyere body to above 600 ℃;

rotating the tuyere body at a constant speed, and simultaneously performing surfacing welding on the inner wall of the tuyere body by using a plasma welding gun; the welding gun is always positioned above the inner wall of the tuyere and is vertical to the inner wall of the tuyere in direction; the thickness of the heat insulation coating is controlled to be 2-3mm;

after one circle of overlaying is finished, the plasma welding gun is made to advance for a certain distance and then the next circle of overlaying is continued;

wherein, a square linear slide rail is arranged on the center line of the tuyere, a square slide block is arranged on the square linear slide rail, and a welding gun is fixed on the lower end surface of the square slide block; the square sliding block is a linear motor; the upper end surface of the square sliding block is provided with a scraping cutter with adjustable height, and the thickness of the coating can be controlled by adjusting the height of the scraping cutter; when the tuyere device works, the welding gun at one end of the square sliding block carries out overlaying welding on the protective coating on the inner wall of the tuyere body along with the rotation of the tuyere body, and the scraping cutter at the other end of the square sliding block scrapes the protective coating so as to ensure the uniformity and surface smoothness of the coating.

2. The method for manufacturing a tuyere for a blast furnace having a thermal insulation coating according to claim 1, wherein the induction coil uses a 8mm copper tube with an insulation sleeve, and the number of turns is based on the criterion that the tuyere body can be preheated to 600 ℃ or more.

3. The method for manufacturing a blast furnace tuyere with a thermal barrier coating according to claim 1, wherein a blowing fan for blowing coating chips generated by scraping is provided at a front end of the linear guide.

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