A four-layer gradient composite inner wall heat insulation protection process for brown jade pouring type furnace bottom

Abstract

The application discloses a four-layer gradient composite inner wall heat insulation protection process for a brown jade pouring electric arc furnace bottom, which comprises the following steps: step one, furnace bottom steel structure pretreatment; step two, elastic buffer bottom layer paving; step three, heavy load modified nano heat insulation layer high-pressure staggered joint construction; step four, anti-seepage special-shaped high-aluminum brick forced wet laying and integral pointing; step five, arc-shaped integrated anti-slag pouring working surface forming; step six, three-layer layered sealing construction at weak points of the furnace bottom; step seven, seven-day constant-temperature closed and moist curing; and step eight, exclusive segmented low-speed furnace drying, after the four-layer composite inner wall reconstruction is completed, the outer wall of the inner wall is stably controlled within 200 DEG C, the overall ambient temperature is lowered by 6-8 DEG C, high-temperature scalding and wall collapse safety risks are completely eliminated from the equipment body level, and a complete set of standardized construction processes of heavy load high-pressure staggered paving, full-area anti-seepage wet laying, three-layer layered sealing at the furnace bottom edges and corners, thick-layer wall exclusive constant-temperature curing and low-speed segmented furnace drying are matched.

Description

Technical Field

[0001] This invention relates to a four-layer gradient composite inner wall heat insulation and protection process for a brown corundum tilting furnace bottom, belonging to the field of brown corundum technology. Background Technology

[0002] Brown fused alumina is a core abrasive used in high-end precision casting, semiconductor polishing, military materials, and new energy grinding wheels. It is smelted in a 10000kVA tilting electric arc furnace at a high temperature of 2300℃. China accounts for over 85% of global brown fused alumina production capacity, producing high-purity... Products with a market growth rate of 8% and a significant premium are core profit-generating products for smelting enterprises.

[0003] The industry has long suffered from the bad habit of "emphasizing the furnace body while neglecting the furnace bottom" in technological upgrades: all R&D resources are tilted towards the upper vertical cylinder of the electric furnace, and the three-layer cylinder masonry process without static pressure adaptation design is directly transplanted to the furnace bottom, resulting in five major original structural defects: (1) The bottom layer has no elastic buffer. The repeated splashing and impact of the molten slag at a high temperature of 2300℃ caused the insulation bricks to pulverize and collapse within 1-2 months. The outer wall of the furnace is at a high temperature of 600-700℃ all year round. (2) The industry-standard dry-laying process does not have anti-seepage mortar. Molten bauxite seeps in along the brick joints. Every 2-3 years, production needs to be stopped for 30 days for overall dismantling and repair, resulting in high production capacity loss and high material and maintenance costs. (3) The structure of non-gradient thermal expansion matching generates a large number of through cracks due to thermal stress. The maximum vertical temperature difference of the molten pool is 142℃. 60% of product defects come from the bottom of the furnace, with black core, coarse grains and frequent alumina segregation. (4) The inner corner of the furnace bottom and the tapping port have no layered sealing structure, and the local peak temperature exceeds 725℃. The molten slag splash can easily cause burns to personnel and high-temperature corrosion of steel structures. (5) The price of imported refractory boards and complete processes is 10 times that of domestic ones. Due to patent blockade and mismatch of working conditions, it is impossible to promote them on a large scale in China. The existing domestic R&D focuses on the furnace body and lacks a complete four-layer composite protection standardized process and a complete industrial comparative test database that are suitable for the static pressure slag seepage working conditions of the furnace bottom. There are obvious technological gaps in the subdivided fields.

[0004] Existing improvement solutions such as shallow thickening of bricks and local repairs can only alleviate surface damage in the short term and cannot simultaneously solve the four major damage contradictions of static pressure extrusion, melt penetration, high-temperature aging, and short-term collapse. At the same time, the traditional high-temperature outer wall of the furnace bottom does not meet the requirements for carbon peaking and safety production supervision. There is an urgent need for the brown jade tilting furnace bottom inner wall heat insulation and protection technology to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a heat insulation and protection process for the inner wall of a brown jade tilting furnace bottom, thereby solving the problems mentioned in the background technology. This invention provides a four-layer gradient composite inner wall heat insulation and protection process for a brown jade tilting furnace bottom, which includes eight standardized construction procedures. The core is the construction of a four-layer gradient composite protection system, along with integrated technologies for modified refractory materials, specialized construction, sealing, curing, and furnace drying.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a four-layer gradient composite inner wall thermal insulation and protection process for a brown jade tilting furnace bottom, comprising the following construction steps: S1. Pretreatment of furnace bottom steel structure: Remove the old refractory layer and slag attachments from the furnace bottom steel shell, polish the steel shell to the metal substrate, correct the welding deformation area and apply high temperature and corrosion resistant coating, and control the flatness error of the steel shell wall to ±3mm / m. S2. Elastic buffer bottom layer: Cut 5mm thick aluminum silicate fiber felt as a buffer layer, and lay it on the inner wall of the steel shell from bottom to top with staggered joints. All splicing seams of the panels are covered with high-temperature resistant sealing tape and fixed with clamps under pressure. S3. Heavy-duty modified nano-insulation layer high-pressure staggered joint construction: Utilizing nano-insulation boards modified with 15% mullite short fibers and 5% high-temperature silica powder, the boards have a compressive strength of 0.8 MPa and a thermal conductivity of ≤0.035 W / m² at 1000℃. Layered staggered laying, with the joints of adjacent boards staggered by 1 / 2 board length, gaps filled with nano-sealing powder and compacted, high-pressure clamps applied evenly throughout the process for fixation, and the insulation layer has a uniform thickness of 30mm. S4. Forced wet laying and integral grouting of waterproof, irregularly shaped high-alumina bricks: Selected Heavy-duty special-shaped high-alumina bricks with ≥75% refractoriness and a refractoriness of 1790℃ are used. The bricks are laid wet throughout using self-mixed anti-slag mortar, with standard brick joints controlled at 0.8-1.2mm. Custom-made special-shaped bricks are used for the inner corners of the furnace bottom and the joints between the furnace body. After the brickwork is completed, the entire surface is grouted for waterproofing. S5. Arc-shaped integrated anti-slag casting working surface forming: A special arc-shaped steel mold is set up at the furnace bottom. The casting material is composed of fused corundum aggregate, 2% impermeable microsilica powder, and extended explosion-proof fiber. It is layered and vibrated at low speed, and cast in one piece to cover the high-alumina brick layer. The casting material has a room temperature compressive strength of ≥65MPa. S6. Three-layer sealing construction for weak points of the furnace bottom: For the inner corner of the furnace bottom and the steel outlet, perform inner-middle-outer three-layer sealing: the inner layer is filled with ultra-fine nano sealing powder, the middle layer is laid with thickened ceramic fiber felt, and the outer layer is coated with high-temperature resistant sealant. The steel outlet is equipped with a prefabricated corundum sleeve. S7. Seven-day constant temperature and humidity curing: After all pouring and sealing processes are completed, the plastic film is fully covered and sealed for curing. The curing environment is kept at a stable temperature of 10-30℃ for seven consecutive days. Premature demolding and heating are prohibited. S8, Exclusive Segmented Low-Speed ​​Oven: After the curing is completed, a stepped low-speed oven curve is adopted, with four-stage heating and segmented long-term heat preservation to gradually remove free water and crystal water from the wall and avoid thermal shock that causes the wall to delaminate and crack.

[0007] Furthermore, the four-layer gradient composite protection system consists of the following layers from the steel shell outwards: an elastic buffer bottom layer, a heavy-duty modified nano-insulation layer, a seepage-proof high-alumina brick support layer, and an integrated anti-molten slag casting working surface. The four-layer structure is compatible with the static pressure of thousands of tons of molten slag at the furnace bottom, the scouring of molten material at 2300℃, and the daily hot and cold alternating pouring conditions. The upper cylinder masonry structure of an electric furnace without an elastic buffer bottom layer cannot be directly applied to the furnace bottom.

[0008] Furthermore, the modified nano-insulation board preparation method in step S3 is as follows: using silica aerogel as the substrate, 15% mullite short fibers + 5% high-temperature silica micro powder are mixed and molded, and high-temperature sintering is carried out to form a three-dimensional compressive skeleton structure, which solves the defects of board powdering, slippage and collapse under long-term static pressure.

[0009] Furthermore, the anti-slag masonry mortar mentioned in step S4 is a special mortar compounded by the enterprise itself. The mortar fullness during the masonry process is ≥98%, completely abandoning the industry's common dry masonry construction method, and comprehensively blocking the infiltration of molten bauxite along the brick joints.

[0010] Furthermore, the three-layer sealing structure described in step S6 is independent of the furnace door and electrode hole sealing process, and is only suitable for the inner corner of the furnace bottom and the stress concentration leakage points at the steel tapping port. It can reduce the local peak temperature of 725℃ to below 200℃ and eliminate the safety hazards of molten slag splashing.

[0011] Furthermore, the constant temperature curing and low-speed segmented baking curves in steps S7 and S8 are exclusive temperature control standards for thick four-layer composite walls, which are completely different from the conventional baking system for the upper cylinder of the electric furnace. They are used to solve the problems of delamination at the interface of multi-layer refractory materials and water loss and cracking of the cast surface layer.

[0012] Furthermore, the process is adapted to the construction of new load-bearing inner walls of 7500kVA and 10000kVA tilting brown fused alumina electric arc furnaces and the waterproofing and life-extending renovation of old walls; after fine-tuning the thickness of each layer of paving, it can be extended to the protection of the inner walls of the bottom of brown fused alumina and silicon carbide tilting electric furnaces and small non-ferrous metal static smelting furnaces.

[0013] Furthermore, the industrial verification standard is as follows: continuous full-load smelting operation for 90 days, average temperature of the outer wall of the furnace bottom ≤200℃, maximum vertical temperature difference of the bottom of the molten pool ≤50℃, surface melt erosion depth ≤5mm, no through wall cracks, no loosening or falling off of high-alumina bricks, and bottom discharge defect rate ≤7%.

[0014] The beneficial effects of this invention are: (1) Advantages of structural protection and durability: The addition of an elastic buffer bottom layer, which is not available in the industry's furnace body process, and the four-layer composite structure work together to offset static pressure, high temperature and melt erosion; no through cracks or brick falling off were found in the 90-day industrial test, and the melt erosion depth was only 4.2mm, which is 75% less than the traditional two-layer inner wall erosion, greatly extending the furnace bottom overhaul cycle and reducing downtime maintenance losses, refractory material and labor costs.

[0015] (2) Advantages of heat insulation, cooling and quality improvement: The steady-state temperature of the outer wall of the furnace body was reduced from 670℃ to 191℃, and the vertical temperature difference of the molten pool was reduced from 142℃ to 48℃; the defective rate of bottom discharge was reduced from 28% to 7%. The proportion of high-end products (≥96%) increased from 16% to 20%, significantly improving the gross profit of high-end orders for enterprises.

[0016] (3) Advantages in safe production and living environment: The temperature of the furnace bottom work area drops by 6-8℃, completely eliminating the hidden dangers of molten slag splashing at 700℃, brick falling and causing injury or burn, reducing the probability of occupational diseases and safety accidents caused by high temperature, and meeting the safety supervision requirements of the Ministry of Industry and Information Technology and the Emergency Management Department for high temperature equipment.

[0017] (4) Advantages of localization and promotion: All refractory raw materials are produced domestically, and the procurement cost is much lower than that of imported materials from overseas; the construction process is standardized and can be replicated in batches for the transformation of 7500 / 10000kVA brown fused alumina smelting furnaces nationwide; the thickness can be finely adjusted to adapt to the bottom protection of white fused alumina, silicon carbide and non-ferrous metal smelting furnaces across industries.

[0018] (5) Industrial autonomy and low-carbon advantages: The entire process is independently developed and finalized by enterprises, breaking away from the monopoly of overseas refractory materials and construction patents; the furnace wall is significantly cooled to reduce heat loss of equipment, reduce the carbon footprint of smelting, and enhance the global competitiveness of domestic abrasives; at the same time, it drives the development of local refractory new materials and technical transformation construction supporting industries, creating jobs.

[0019] (6) Technological value-added advantages: The complete process can provide external companies with value-added services such as furnace bottom technical renovation general contracting, special refractory raw material supply, on-site construction guidance, and wall loss detection, helping smelting enterprises to transform from a single production type to a composite industry of "production + technical services". Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0021] Example 1: Complete Renovation of the Inner Wall of a 10000kVA Tilting Electric Furnace Bottom Step S1: Pre-treatment of the furnace bottom steel structure. Empty all old refractory bricks and solidified slag from the furnace bottom. Grind the inner wall of the steel shell with a steel wire shot blasting machine until the metal substrate is intact. Correct welding deformation and crack positions, and repair welds to make them smooth. Apply high-temperature resistant inorganic anti-corrosion coating to the entire area. Use a 2m straightedge to check the flatness of the wall surface, and control the error to ≤3mm / m. Clean dust and debris for later use. Step S2: Lay the elastic buffer bottom layer in a staggered pattern. Cut 5mm thick aluminum silicate buffer fiber felt and lay it in a staggered pattern from the lowest point of the furnace bottom upwards, with an overlap width of 50mm between adjacent felt pieces. Cover all splicing gaps with high-temperature resistant aluminum foil sealing tape. Use steel clamps to press and fix the material at multiple points evenly to prevent the plate from slipping during subsequent heating and to completely cover the entire steel shell area of ​​the furnace bottom. Step S3: High-pressure staggered joint construction of heavy-duty modified nano-insulation layer (1) Modified nanoplate prefabrication: 15% mullite short fibers + 5% high-temperature silica powder were added to the silica aerogel substrate, and the mixture was pressed into a 30mm thick plate with a thermal conductivity of 0.032W / m³ at 1000℃. The compressive strength at room temperature is 0.8 MPa; (2) Layered installation: The boards are arranged in a staggered manner, and the joints of the upper and lower layers are staggered by 1 / 2 board length; the gaps between the boards are filled with nano sealant powder, and the board is compacted and smoothed with a scraper; a customized hydraulic high-pressure clamp is used to apply pressure evenly along the surface of the board to fix it, preventing the boards from bulging or loosening, and ensuring seamless full coverage of the entire layer; Step S4: Forced wet laying and grouting of anti-seepage irregular-shaped high-alumina bricks, using... =76%, refractoriness 1790℃ heavy-duty special-shaped high-alumina bricks; self-mixed anti-slag mortar is used for wet masonry throughout the process, the mortar joint is controlled by calipers to 0.8-1.2mm, and the mortar fullness is ≥98%; L-shaped prefabricated special-shaped bricks are used at the right angle of the furnace bottom and the ring joint of the furnace body, with no straight gaps; after all masonry is completed, the surface is grouted to prevent seepage and seal the tiny seepage channels in the brick joints. Step S5: Integral arc-shaped anti-slag casting surface layer, erect a custom arc-shaped steel template and attach it to the outer surface of the high-alumina brick masonry layer; Casting material ratio: 98% fused corundum aggregate + 2% impermeable microsilica powder, plus 0.3% extended explosion-proof fiber; Layered casting, low-speed vibration compaction, one-time integral molding, no segmented construction interface; Remove the external support template after natural initial setting; Step S6: Three-layer sealing of the inner corner of the furnace bottom and the tap hole. (1) Inner corner of the furnace bottom: the inner layer of ultra-fine nano sealing powder fills the micro gaps, the middle layer is laid with 10mm thick ceramic fiber felt to absorb thermal expansion deformation, and the outer layer is coated with high temperature resistant sealant for full coverage; (2) Steel outlet: a pre-installed corundum sleeve buffers the molten material flow, and the gap between the sleeve and the wall is simultaneously sealed with a three-layer sealing structure; after sealing, the surface is compacted and smoothed. Step S7: Seven-day constant temperature, airtight, and moisturizing curing. After all construction is completed, double-layer thickened plastic film is used to completely cover the inner wall of the furnace bottom for airtight curing. The workshop temperature control equipment maintains a constant temperature of 18~25℃. Moisturizing is carried out by spraying the inside of the film at regular intervals for seven consecutive days. It is strictly forbidden to remove the mold or raise the temperature in advance.

[0022] Comparative example: Traditional two-layer simple furnace bottom inner wall construction Another 10000kVA electric furnace of the same specifications, load and raw material ratio was selected and the industry-standard process was adopted: dry-laid bottom layer of ordinary aluminosilicate insulating bricks + surface layer of ordinary high alumina castable, without buffer layer, modified nano heat insulation layer, seepage-proof wet masonry, layered sealing structure, no special curing and baking process, and the rest of the smelting and production conditions were completely consistent with the example.

[0023] Summary of 90-day industrial-scale control test results

[0024] Test results prove that the four-layer gradient composite thermal insulation protection process of this invention can comprehensively solve all the pain points of the industry, such as high temperature, seepage, structural damage, finished product defects, and safety hazards of traditional furnace bottom inner walls, and the technical improvement effect is significant.

[0025] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A four-layer gradient composite inner wall heat insulation and protection process for a brown jade tilting furnace bottom, characterized in that, The following construction procedures are included: S1. Pretreatment of furnace bottom steel structure: Remove the old refractory layer and slag attachments from the furnace bottom steel shell, polish the steel shell to the metal substrate, correct the welding deformation area and apply high temperature and corrosion resistant coating, and control the flatness error of the steel shell wall to ±3mm / m. S2. Elastic buffer bottom layer: Cut 5mm thick aluminum silicate fiber felt as a buffer layer, and lay it on the inner wall of the steel shell from bottom to top with staggered joints. All splicing seams of the panels are covered with high-temperature resistant sealing tape and fixed with clamps under pressure. S3. Heavy-duty modified nano-insulation layer high-pressure staggered joint construction: Utilizing nano-insulation boards modified with 15% mullite short fibers and 5% high-temperature silica powder, the boards have a compressive strength of 0.8 MPa and a thermal conductivity of ≤0.035 W / m² at 1000℃. Layered staggered laying, with the joints of adjacent boards staggered by 1 / 2 board length, gaps filled with nano-sealing powder and compacted, high-pressure clamps applied evenly throughout the process for fixation, and the insulation layer has a uniform thickness of 30mm. S4. Forced wet laying and integral grouting of waterproof, irregularly shaped high-alumina bricks: Selected Heavy-duty special-shaped high-alumina bricks with ≥75% refractoriness and a refractoriness of 1790℃ are used. The bricks are laid wet throughout using self-mixed anti-slag mortar, with standard brick joints controlled at 0.8-1.2mm. Custom-made special-shaped bricks are used for the inner corners of the furnace bottom and the joints between the furnace body. After the brickwork is completed, the entire surface is grouted for waterproofing. S5. Arc-shaped integrated anti-slag casting working surface forming: A special arc-shaped steel mold is set up at the furnace bottom. The casting material is composed of fused corundum aggregate, 2% impermeable microsilica powder, and extended explosion-proof fiber. It is layered and vibrated at low speed, and cast in one piece to cover the high-alumina brick layer. The casting material has a room temperature compressive strength of ≥65MPa. S6. Three-layer sealing construction for weak points of the furnace bottom: For the inner corner of the furnace bottom and the steel outlet, perform inner-middle-outer three-layer sealing: the inner layer is filled with ultra-fine nano sealing powder, the middle layer is laid with thickened ceramic fiber felt, and the outer layer is coated with high-temperature resistant sealant. The steel outlet is equipped with a prefabricated corundum sleeve. S7. Seven-day constant temperature and humidity curing: After all pouring and sealing processes are completed, the plastic film is fully covered and sealed for curing. The curing environment is kept at a stable temperature of 10-30℃ for seven consecutive days. Premature demolding and heating are prohibited. S8, Exclusive Segmented Low-Speed ​​Oven: After the curing is completed, a stepped low-speed oven curve is adopted, with four-stage heating and segmented long-term heat preservation to gradually remove free water and crystal water from the wall and avoid thermal shock that causes the wall to delaminate and crack.

2. The brown jade tilting furnace bottom four-layer gradient composite inner wall heat insulation and protection process according to claim 1, characterized in that, The four-layer gradient composite protection system consists of the following layers from the steel shell outwards: an elastic buffer bottom layer, a heavy-duty modified nano-insulation layer, a seepage-proof high-alumina brick support layer, and an integrated anti-slag casting working surface. The four-layer structure is compatible with the repeated scouring of the furnace bottom by the high-temperature 2300℃ melt and the daily hot and cold alternating tilting conditions. The upper cylinder masonry structure of the electric furnace without an elastic buffer bottom layer cannot be directly applied to the furnace bottom.

3. The brown jade tilting furnace bottom four-layer gradient composite inner wall heat insulation and protection process according to claim 1, characterized in that, The modified nano-insulation board in step S3 is prepared by mixing 15% mullite short fibers and 5% high-temperature silicon micro powder, followed by high-temperature sintering to form a three-dimensional compressive skeleton structure, which solves the defects of board powdering, slippage and collapse under long-term static pressure.

4. The brown jade tilting furnace bottom four-layer gradient composite inner wall heat insulation and protection process according to claim 1, characterized in that, The anti-slag masonry mortar mentioned in step S4 is a special mortar compounded by the enterprise. The mortar fullness during the masonry process is ≥98%, completely abandoning the industry's common dry masonry construction method, and comprehensively blocking the infiltration of molten bauxite along the brick joints.

5. The brown jade tilting furnace bottom four-layer gradient composite inner wall heat insulation and protection process according to claim 1, characterized in that, The three-layer sealing structure described in step S6 is independent of the furnace door and electrode hole sealing process. It is only suitable for the inner corner of the furnace bottom and the stress concentration leakage points at the steel tapping port. It can reduce the local peak temperature of 725℃ to below 200℃ and eliminate the safety hazards of molten slag splashing.

6. The brown jade tilting furnace bottom four-layer gradient composite inner wall heat insulation and protection process according to claim 1, characterized in that, The constant temperature curing and low-speed segmented baking curves in steps S7 and S8 are exclusive temperature control standards for thick four-layer composite walls, which are completely different from the conventional baking system for the upper cylinder of the electric furnace. They are used to solve the problems of delamination at the interface of multi-layer refractory materials and water loss and cracking of the cast surface layer.

7. The brown jade tilting furnace bottom four-layer gradient composite inner wall heat insulation and protection process according to claim 1, characterized in that, The process is suitable for the construction of new load-bearing inner walls of 7500kVA and 10000kVA tilting brown fused alumina electric arc furnaces and the waterproofing and life extension renovation of old walls; after fine-tuning the thickness of each layer of paving, it can be extended to the protection of the inner walls of the bottom of brown fused alumina and silicon carbide tilting electric furnaces and small non-ferrous metal static smelting furnaces.

8. The brown jade tilting furnace bottom four-layer gradient composite inner wall heat insulation and protection process according to claim 1, characterized in that, The industrial verification standard is as follows: continuous full-load smelting operation for 90 days, average temperature of the outer wall of the furnace bottom ≤200℃, maximum vertical temperature difference of the bottom of the molten pool ≤50℃, surface melt erosion depth ≤5mm, no through wall cracks, no loosening or falling points of high alumina bricks, and bottom discharge defect rate ≤7%.

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