Integral casting method and structure for blast furnace hearth replacing cooling wall

Abstract

The invention discloses an integral pouring method and structure of a blast furnace hearth for replacing a cooling wall. A lining body formed by integrally pouring a high-thermal-conductivity amorphous refractory material is directly arranged on the inner side of a furnace shell; a plurality of hole channels are formed in the furnace shell, cooling elements are arranged in the hole channels, one end of each cooling element is embedded into and penetrates through the lining body and is in close contact with the lining body, a cooling wall is omitted, air gap thermal resistance is avoided, the cooling elements are in direct contact with a high-thermal-conductivity refractory material, heat can be quickly and directly transmitted to a cooling system, and the cooling efficiency is greatly improved; a protective slag iron shell is easily formed on the hot surface of the hearth; the overall pouring structure is free of brick joints, and permeation erosion of molten iron and alkali metal is avoided; the high thermal conductivity ensures that the temperature field of the hearth lining is uniformly distributed, the thermal stress is small, and the ring crack risk of a traditional structure is fundamentally eradicated; if abnormal erosion occurs in a local area, online repair can be performed by adopting a press-in technology, so that the maintenance cost is low, and the service life of the first-generation blast furnace is prolonged.

Description

Technical Field

[0001] This invention relates to the field of blast furnace ironmaking equipment design and manufacturing, and in particular to a method and structure for integral casting of the blast furnace hearth to replace the cooling wall. Background Technology

[0002] Blast furnace ironmaking is the core process of the modern steel industry. The blast furnace hearth, as the container for high-temperature molten iron and slag, directly determines the furnace's lifespan, production safety, and economic operating costs based on the longevity and stability of its structure. Achieving a longer blast furnace hearth lifespan is a key technological goal continuously pursued in the metallurgical field. Currently, the hearth structure commonly used in modern blast furnaces both domestically and internationally involves installing a cast iron or copper cooling wall inside the furnace shell, and then using carbon bricks (such as microporous carbon bricks or ultra-microporous carbon bricks) and ceramic cups (such as corundum mullite bricks or composite brown corundum bricks) for composite lining on the inner side of the cooling wall. This classic "cooling wall + carbon brick + ceramic cup" structure attempts to form a solidified slag-iron protective layer ("slag-iron shell") on the hot surface of the refractory material through forced cooling of the cooling wall, thus isolating it from the erosion of the high-temperature molten metal.

[0003] However, this traditional structure has revealed many inherent and insurmountable technical defects in practical applications, mainly including: The interfacial thermal resistance is a serious problem, resulting in low cooling efficiency: Assembly gaps and contact voids are unavoidable between the cooling wall and the furnace shell, and between the cooling wall and the carbon brick masonry. These gaps fill with gas at high temperatures, and gas is a poor conductor of heat, creating significant "contact thermal resistance" or "air gap thermal resistance." This severely hinders heat transfer from the refractory material to the cooling water, leading to an actual higher temperature on the hot surface of the masonry and making it difficult to effectively form a stable protective slag-iron shell. Although thermally conductive mortar is widely used to fill some of the gaps, 100% complete filling cannot be guaranteed, and the mortar sinters and pulverizes at high temperatures, its thermal conductivity being far lower than that of metallic materials, making the problem unsolvable.

[0004] The masonry structure has inherent weaknesses: carbon brick masonry consists of thousands of bricks with numerous joints. These joints are the weakest points in the hearth structure. Under high temperature and pressure, molten iron, alkali metals (potassium, sodium), zinc vapors, etc., can easily penetrate into the masonry through these joints, leading to abnormal dissolution of the carbon bricks, formation of an embrittled layer, and the generation of "ring-shaped cracks." The penetration of alkali metals also catalyzes the oxidation of the carbon bricks, further exacerbating the corrosion. Once a through-crack forms, the intruding molten iron will directly scour and burn the cooling walls, causing catastrophic consequences.

[0005] Thermal stress leads to structural damage: The carbon bricks, ceramic cups, cooling walls (cast iron or copper), and furnace shell steel plates all have significantly different coefficients of thermal expansion. During blast furnace intermittent shutdowns, restarts, or fluctuations in operating conditions, the hearth temperature changes drastically. The different expansion and contraction rates of these materials generate enormous shear stress at their contact interfaces. Prolonged exposure to this alternating thermal stress can easily cause the carbon bricks to loosen, warp, or even break. It is also a significant cause of fatigue damage at the cooling wall water pipe joints.

[0006] The cooling walls themselves are prone to failure and difficult to repair: cast iron cooling walls have poor toughness and are easily cracked under thermal stress; once the internal cooling water pipes are damaged and leak due to manufacturing defects, corrosion, or the aforementioned thermal stress, detection and location are extremely difficult. Leaks entering the furnace hearth can cause serious safety accidents such as explosions. Whether replacing a single cooling wall or carrying out large-scale repairs, the furnace must be shut down, resulting in long operation times and huge economic losses.

[0007] To address these issues, existing technologies have attempted some improvements, such as replacing cast iron cooling walls with copper cooling walls (which have better thermal conductivity); developing super-microporous carbon bricks with higher thermal conductivity and better permeability resistance; and optimizing the masonry process to reduce brick joints. However, these improvements are all optimizations within the traditional technical framework of "cooling wall + bricklaying," and have failed to fundamentally eliminate the two structural problems of air gap thermal resistance and brick joints.

[0008] Therefore, there is an urgent need in this field for a completely new hearth design concept and structural form that can completely eliminate cooling walls and bricklaying processes, solve the above-mentioned bottleneck problems in principle, and provide a breakthrough solution for achieving the next generation of long-life technology for blast furnace hearths. Summary of the Invention

[0009] To address the problems in the prior art, this invention provides a method and structure for integral casting of the blast furnace hearth, which abandons the traditional cooling wall and brick lining construction method and replaces the cooling wall, so as to achieve homogenization, high thermal conductivity, long service life and repairability of the hearth.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a blast furnace hearth lining structure, including a furnace shell, wherein a lining made of a high thermal conductivity amorphous refractory material is directly provided on the inner side of the furnace shell; the furnace shell is provided with a plurality of channels, and cooling elements are provided in the channels, one end of the cooling element being embedded in and penetrating the lining and in close contact with the lining.

[0011] Furthermore, the high thermal conductivity unshaped refractory material is a castable, ramming mix, or press-fit material, and its thermal conductivity is not less than 15 W / (m·K) at a hot surface of 800℃.

[0012] Furthermore, the high thermal conductivity amorphous refractory material comprises the following components by mass percentage: 40-60% fused alumina, 15-30% high-purity graphite, 5-15% silicon carbide, 2-5% metallic silicon powder, 1-3% antioxidant, and 4-10% ultrafine powder bonding system.

[0013] Furthermore, the cooling element is a copper water-cooled plate, a serpentine cooling pipe, or a heat pipe.

[0014] Furthermore, the cooling elements are arranged in multiple layers and rows within the liner, and their distribution density is designed in a gradient according to the heat load distribution along the height of the furnace hearth.

[0015] Furthermore, anchors for securing the liner are welded onto the inner wall of the furnace shell.

[0016] Furthermore, the material of the lining is designed in a gradient manner according to the heat load and erosion resistance requirements of different areas, with the hearth and bottom junction area and the taphole area using a material with stronger resistance to molten iron corrosion.

[0017] A construction method for a blast furnace hearth lining structure includes the following steps: S1: welding anchors inside the furnace shell; S2: installing cooling elements and temporarily fixing and sealing them; S3: setting up casting templates inside the furnace shell; S4: injecting highly thermally conductive monolithic refractory material; S5: curing and baking the cast lining.

[0018] Furthermore, the injected high thermal conductivity unshaped refractory material is poured using a pumping or self-leveling method, and a vibrator is used to compact it during the pouring process to ensure density.

[0019] Furthermore, the curing and baking of the cast lining follows a specific temperature rise curve, with the temperature rise rate controlled at 3-8℃ / h below 500℃.

[0020] Compared with the prior art, the beneficial effects that this invention can achieve are: 1. Excellent thermal conductivity: The elimination of cooling walls avoids air gap thermal resistance, and the cooling elements are in direct contact with highly thermally conductive refractory materials. Heat can be quickly and directly transferred to the cooling system, which greatly improves cooling efficiency and makes it easy to form a protective slag-iron shell on the hot surface of the hearth. 2. Ultra-long structural life: The integral cast-in-place structure has no brick joints, avoiding the penetration and erosion of molten iron and alkali metals; the high thermal conductivity ensures a uniform temperature field distribution in the furnace lining, with low thermal stress, fundamentally eliminating the risk of ring cracking in traditional structures. 3. Good repairability: If abnormal erosion occurs in local areas, online repair can be carried out using the press-in technology, which has low maintenance costs and extends the service life of the first generation of blast furnaces; 4. Convenient construction: It simplifies the furnace hearth construction process, shortens the construction cycle, and reduces the reliance on highly skilled masonry workers. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of the integral casting structure of the blast furnace hearth according to the present invention; Figure 2 This is a supplementary cross-sectional structural diagram of the integral casting structure of the blast furnace hearth of the present invention. Figure 3 This is a schematic diagram of the construction method for the integral casting structure of the blast furnace hearth according to the present invention.

[0022] The components include: furnace shell 1; lining 2; cooling elements 3; and anchors 4. Detailed Implementation

[0023] To make the technical means, creative features, and achieved objectives and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0024] Example: Combination Figure 1 and Figure 2 As shown, this invention provides an integrally cast blast furnace hearth structure, including a furnace shell 1, a lining 2, and cooling elements 3. Multiple cooling elements 3 are provided. The lining 2 is a monolithic lining 2, formed by integrally casting a highly thermally conductive monolithic refractory material inside the furnace shell 1. The cooling elements 3 penetrate the furnace shell 1 and are embedded inside the monolithic lining 2. At least a portion of the cooling elements 3 is in direct contact with the monolithic lining 2 for heat exchange. The highly thermally conductive monolithic refractory material is a castable refractory with a thermal conductivity of not less than 15 W / (m·K) at 800℃. The highly thermally conductive monolithic refractory material comprises the following components by mass percentage: The furnace contains 50-75% fused alumina aggregate and fine powder, 15-25% flake graphite, 5-12% silicon carbide, 2-5% metallic silicon powder, 1-3% antioxidant, and 4-10% binder. The binder is pure calcium aluminate cement; the antioxidant is boron carbide (B4C) or metallic aluminum powder (Al). Cooling elements 3 are copper water-cooled plates, copper serpentine tubes, or heat pipes. The cooling elements 3 are distributed in a multi-layered, multi-row, three-dimensional grid pattern within the monolithic lining 2. The distribution density of the cooling elements 3 is differentiated according to the heat load of different areas of the blast furnace hearth, with a higher density in the hearth taphole area and the area where the furnace bottom meets the hearth than in other areas. Anchors 4, Y-shaped or V-shaped metal parts, are installed on the inner wall of the furnace shell 1 to enhance the anchoring strength of the monolithic lining 2. Monolithic liner 2 is a functionally graded liner, in which different regions are integrally cast from highly thermally conductive monolithic refractory materials with different thermal conductivity and / or erosion resistance.

[0025] Secondly, combining Figure 3 As shown, a construction method for an integrally cast blast furnace hearth structure includes the following steps: Step S1, pre-treating the furnace shell and welding anchors to its inner wall; Step S2, opening mounting holes in the furnace shell, inserting cooling elements into the mounting holes from the outside and fixing and sealing them, the fixing and sealing being achieved by welding to seal the cooling elements to the mounting holes in the furnace shell; Step S3, setting up a casting template inside the furnace shell; Step S4, casting high thermal conductivity unshaped refractory material into the cavity between the template and the furnace shell, the casting being carried out continuously by pumping, and during the casting process, using an immersion vibrator for layered vibration, forming a compacted structure after vibration. Monolithic lining for anchors and cooling elements; Step S5, curing and baking the monolithic lining, the baking process follows a preset temperature rise curve, the temperature rise rate is controlled at 3-10℃ / h below 500℃, the temperature rise rate is 3-6℃ / h in the temperature range of 0-150℃, and the temperature is held at 150℃ for 15-25 hours; the temperature rise rate is 5-8℃ / h in the temperature range of 150-350℃, and the temperature is held at 350℃ for 25-35 hours; the temperature rise rate is 8-12℃ / h in the temperature range of 350-600℃, and the temperature is held at 600℃ for 35-45 hours.

[0026] First, the old blast furnace lining and cooling walls were removed, leaving only the furnace shell 1. The inner wall of furnace shell 1 underwent a comprehensive inspection and treatment, including sandblasting to remove rust and rounding to ensure a smooth, crack-free surface and conformity to design specifications. All original cooling wall mounting holes were sealed and welded. "Y"-shaped anchors made of heat-resistant stainless steel were used. The anchors were uniformly welded in a rectangular array on the inner wall of the furnace shell using welding rods, with a spacing of 150mm (axial) × 150mm (circumferential) and a welding height of 50mm to ensure sufficient mechanical interlocking force with the subsequently poured refractory material.

[0027] Based on the pre-designed three-dimensional layout of the cooling water channels, through holes are precisely positioned and drilled on the furnace shell. The drilling is performed using CNC plasma cutting to ensure that the hole diameter matches the outer diameter of the cooling element's sleeve (usually with a 2-3mm gap).

[0028] In this embodiment, a serpentine cooling tube made of T2 grade high-conductivity pure copper is selected as the cooling element. It is inserted from the outside of the furnace shell through a through hole and temporarily fixed and precisely positioned by scaffolding and special clamps erected inside the furnace to ensure that its embedment depth and tube spacing meet the design requirements (in this example, the design is: axial spacing 400mm, circumferential spacing 300mm, forming a three-dimensional grid-like heat dissipation system).

[0029] After the cooling element 3 is in place, it is welded to the outside of the furnace shell 1 using argon arc welding to ensure airtightness and watertightness. All inlets and outlets of the cooling element 3 are reliably connected to the external water supply ring pipe.

[0030] Based on the internal contour of the blast furnace hearth, high-strength composite steel formwork is installed inside the furnace shell 1. A layer of release agent (usually grease or a special water-based release agent) is evenly applied to the surface of the formwork to facilitate later demolding and ensure a smooth lining surface. The formwork must be firmly supported and able to withstand the lateral pressure of the refractory material during the casting process.

[0031] Material proportions: This example uses a high thermal conductivity ultra-low cement content castable, with the following specific mass proportions: fused dense corundum aggregate (8-5mm): 20%, fused dense corundum aggregate (5-3mm): 15%, fused dense corundum aggregate (3-1mm): 15%, fused corundum fine powder (≤0.088mm): 15%, high-purity flake graphite (99% fixed carbon): 18%, black silicon carbide (SiC 98%): 8%, metallic silicon powder (Si 98%): 3%, boron carbide (B4C) as an antioxidant: 2%, pure calcium aluminate cement (Ca-70) as a binder: 4%, and added composite dispersant (water-reducing agent): 0.2%.

[0032] The materials are mixed using a forced mixer. First, dry mix all the raw materials in the mixer for 2-3 minutes to ensure they are evenly mixed. Then, add 4.8%-5.2% clean room temperature mixing water and wet mix for 5-8 minutes until the slurry is uniform and has suitable fluidity and thixotropy.

[0033] The mixed castable refractory is continuously pumped into the cavity between the formwork and the furnace shell 1 using a concrete pump. The pouring process is carried out in layers, with each layer not exceeding 600mm in thickness. Immediately after each layer is poured, a high-frequency immersion vibrator is used for thorough compaction, with vibration points spaced no more than 300mm apart, until the surface is covered with slurry and no large number of air bubbles emerge. During vibration, avoid contact with the cooling element 3 and the formwork to ensure their position remains unchanged. The entire pouring process must be completed continuously without interruption.

[0034] Immediately after pouring, cover the lining surface with plastic film and maintain it in a moist environment at ambient temperature (20-30℃) for at least 48 hours. After curing, carefully remove all formwork. After demolding, inspect the lining surface; it should be dense, flat, and free of visible cracks and holes. Immediately after removing the formwork, subject the integrally poured furnace hearth to hot air baking to remove physical and chemically bound water from the lining. The baking process must strictly follow the preset temperature rise curve to prevent rapid evaporation of water that could cause the lining to crack. The baking regime used in this example is as follows: 0℃→150℃: heating rate 5℃ / h, hold at 150℃ for 20 hours.

[0035] 150℃→350℃: Heating rate 8℃ / h, hold at 350℃ for 30 hours.

[0036] 350℃→600℃: heating rate 10℃ / h, hold at 600℃ for 40 hours.

[0037] 600℃ → Room temperature: Cool naturally with the furnace.

[0038] The entire baking process takes approximately 10-12 days. After baking, a final inspection of the lining is conducted. Once it is confirmed that there are no cracks or other defects, the blast furnace can be put into use.

[0039] After the blast furnace was put into operation, monitoring was conducted using thermocouples installed on the furnace shell 1. Data showed that the overall temperature field distribution of the furnace shell was uniform, with temperature differences between regions less than 15℃, indicating that heat was efficiently and evenly dissipated, successfully forming a stable slag-iron protective layer on the hot surface of the hearth. Compared with traditional structures, the heat dissipation efficiency of the hearth is improved by approximately 30%, and it is expected to extend the service life of the hearth from the traditional 12-15 years to over 20 years.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A blast furnace hearth lining structure, comprising a furnace shell (1), characterized in that: The inner side of the furnace shell (1) is directly provided with a lining (2) integrally cast from a highly thermally conductive amorphous refractory material; the furnace shell (1) is provided with several channels, and a cooling element (3) is provided in the channel. One end of the cooling element (3) is embedded in and passes through the lining (2) and is in close contact with the lining (2).

2. The blast furnace hearth lining structure according to claim 1, characterized in that: The high thermal conductivity unshaped refractory material is a castable, rammed earth, or press-fit material, and its thermal conductivity is not less than 15 W / (m·K) at a hot surface of 800℃.

3. The blast furnace hearth lining structure according to claim 2, characterized in that: The high thermal conductivity unshaped refractory material comprises the following components by mass percentage: 40-60% fused alumina, 15-30% high-purity graphite, 5-15% silicon carbide, 2-5% metallic silicon powder, 1-3% antioxidant, and 4-10% ultrafine powder bonding system.

4. The blast furnace hearth lining structure according to claim 1, characterized in that: The cooling element (3) is a copper water-cooled plate, a serpentine cooling pipe, or a heat pipe.

5. The blast furnace hearth lining structure according to claim 1 or 4, characterized in that: The cooling element (3) is arranged in multiple layers and rows in the liner (2), and its distribution density is designed in a gradient according to the heat load distribution along the height of the furnace hearth.

6. The blast furnace hearth lining structure according to claim 1, characterized in that: Anchors (4) for anchoring the liner (2) are welded to the inner wall of the furnace shell (1).

7. The blast furnace hearth lining structure according to claim 1, characterized in that: The material of the lining (2) is designed in a gradient manner according to the heat load and anti-corrosion requirements of different areas. The material with stronger resistance to molten iron corrosion is used in the junction area of ​​the hearth and bottom and the taphole area.

8. A construction method for the blast furnace hearth lining structure according to any one of claims 1-7, characterized in that, The process includes the following steps: S1: Welding anchors inside the furnace shell; S2: Installing cooling elements and temporarily fixing and sealing them; S3: Setting up casting templates inside the furnace shell; S4: Injecting highly thermally conductive monolithic refractory material; S5: Curing and baking the cast lining.

9. The construction method for the blast furnace hearth masonry structure according to claim 8, characterized in that: The high thermal conductivity unshaped refractory material is injected and poured using a pump or self-leveling method. During the pouring process, a vibrator is used to compact the material to ensure density.

10. The construction method for the blast furnace hearth masonry structure according to claim 8, characterized in that: The curing and baking of the cast lining follows a specific temperature rise curve, with the temperature rise rate controlled at 3-8℃ / h below 500℃.

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