The submerged arc furnace is the main equipment for ferroalloy smelting. With the rapid development of my country's ferroalloy industry and the macro-control of high-energy-consuming enterprises by the state, as well as the development of large-scale submerged arc furnace capacity in recent years, the furnace lining is an important part of the furnace body. In the smelting process, it is subjected to high temperature and high heat, as well as mechanical erosion and physical and chemical erosion of the charge and slag. Therefore, reasonable design, excellent material selection, and careful masonry are the keys to prolonging the life of the submerged arc furnace.
1. The working environment of the furnace lining and the selection of furnace building materials
The quality of the furnace lining directly affects the length of the furnace age. The furnace lining should have a certain strength and good thermal insulation performance, not only to withstand the mechanical erosion of the charge, high temperature furnace gas, molten iron and physical and chemical erosion of the slag, but also to ensure good thermal shock Stability, if the material is improperly selected or the quality of the masonry is not up to standard, the furnace lining will accelerate melting, erosion and even cracking, which will lead to leakage of iron through the furnace and directly affect the normal progress of the smelting process.
Therefore, in the construction of furnace lining, the reasonable selection of refractory materials should be carried out according to the temperature difference and adverse factors of each part to achieve the purpose of improving the comprehensive performance and service life of the furnace lining, which is the basic principle of furnace lining masonry. The main materials used are: asbestos board, high-alumina aggregate, high-alumina fine powder, high-alumina brick, carbon brick, clay brick, rough seam paste, refractory clay, castable, carbon cement, etc. Masonry material standards: high refractoriness, certain strength (especially high temperature strength), small volume expansion coefficient, high thermal shock resistance; good resistance to physical and chemical erosion; good thermal insulation and heat storage performance; processing High precision, the shape conforms to the national standard; all materials should be kept clean, and must not be mixed with soil, dust and other sundries to prevent moisture and damage.
2. Masonry level and material selection of submerged arc furnace
Reasonable design drawings before masonry, as shown in the figure. Organize professional furnace-laying teams and tools, and purchase various materials as required. At present, the masonry method of large submerged arc furnace lining usually adopts water-cooled furnace wall and heat preservation furnace lining. The masonry method of this 31.5MVA manganese silicon alloy submerged arc furnace lining adopts heat preservation furnace lining.
1) Insulation layer.
The asbestos board with better insulation effect is adopted, with a thickness of 10mm and a total of two layers. The same goes for the furnace walls.
2) Elastic layer.
A 60-80mm thick high-aluminum aggregate is laid on the insulating layer, and a 100mm-wide gap is reserved between the furnace wall insulating layer and the refractory brick layer, and high-alumina aggregate is filled with high-alumina aggregate size ranging from 3 to 12mm.
3) The furnace bottom and furnace wall are surrounded by carbon refractory brick layers.
The large-scale submerged arc furnace adopts no less than 10 layers of furnace bottom, and this electric furnace adopts 12 layers of furnace bottom, which is made of three different grades of high-alumina bricks, and the thickness of the refractory brick layer at the bottom of the furnace is about 900mm. The furnace wall ring carbon refractory bricks are built with double rings, the thickness of each ring is 230mm, and the total thickness is 460mm.
4) Working layer - carbon brick layer.
There are three layers of carbon bricks at the bottom of the furnace, from bottom to top, each layer is pre-baked carbon bricks and two layers of semi-graphite carbon bricks, with a total thickness of about 1 200mm, and the furnace wall ring carbon bricks are semi-graphite carbon bricks, with a thickness of 400mm . Carbon bricks should take anti-oxidation measures. The thickness of the submerged arc furnace shell is 30mm, the inner diameter is 12200mm, the depth of the furnace after the completion of the furnace lining is 3685mm, and the diameter of the furnace is 10200mm. The thickness of the iron layer left in the tap hole furnace is 200mm. The electric furnace has 2 tap holes in total. The length of the short chute at the tap hole is 1000mm, and the angle of the tap hole is 150°. The 7th floor of the furnace bottom refractory bricks pre-embeds 4 temperature measuring thermocouples (1 in the center of the furnace bottom, 1 directly under the three electrode pole centers), and 6 pre-embedded temperature measuring thermocouples around the furnace wall (the ring-laid refractory bricks There are 3 horizontally distributed on the 16th layer, facing three electrodes respectively, and 3 horizontally distributed on the 23rd layer, which are vertically displaced by about 2m from the 3rd on the 16th layer).
The masonry of the entire electric furnace should ensure the tightness of the refractory material and the integrity of the furnace lining, and a sufficient elastic layer can ensure the thermal expansion and contraction of the furnace lining. The thickness of the furnace bottom and furnace wall and the evenly distributed temperature measuring thermocouples can reduce the probability of iron leakage through the furnace, improve the thermal insulation and heat storage capacity of the furnace lining, and ensure the thermal stability of the furnace lining when the furnace is shut down or under heavy load. smelting.
Furnace lining
Before masonry, thoroughly clean and dehumidify the bottom of the furnace, open 6 small exhaust holes in the bottom of the furnace, calculate and mark each layer at the corresponding position of the furnace shell according to the drawings, especially the position of the furnace mouth.
1) Furnace bottom refractory brick masonry
From bottom to top, there are two insulating layers of asbestos boards, which play the role of insulation and heat insulation. On the insulating layer, high-alumina aggregate with a thickness of 80mm is laid as an elastic layer. After the elastic layer at the bottom of the furnace is tamped and leveled, the center line of the furnace body is determined. The 31.5MVA manganese-silicon alloy submerged arc furnace adopts 12 layers of refractory bricks at the bottom of the furnace. The order of masonry from bottom to top is: 7 layers of LZ-55 high-alumina bricks, 2 layers of LZ-65 high-alumina bricks Layer, LZ-75 high alumina brick 3 layers. The brick type adopts G-2 type (dimensions: 345mm×150mm×75mm), the masonry method is dry-laying method, the brick layers are cross-shaped, and each layer is staggered by 300~45. Press the brick seam. The brick joints are less than or equal to 2mm, and each layer of brick joints is filled with high-alumina fine powder. A 100mm wide gap is reserved for the refractory brick layer of the furnace bottom and the insulation layer of the furnace wall as an elastic layer and filled with high-alumina aggregate. The dry lining method has less moisture, which is beneficial to the oven, but the filler porosity is large and the lining is loose, which is not conducive to ensuring the integrity of the lining. In contrast, the wet masonry method uses refractory mud to build brick joints, which is beneficial to improve the integrity of the furnace lining, but due to excessive moisture, more heat is consumed during the oven, which is not conducive to temperature stability.
2) Furnace wall refractory brick ring
The refractory bricks of the furnace wall are built by the heat preservation method, and the inner wall of the furnace shell is covered with two layers of asbestos boards, which are pasted with high-alumina phosphate refractory mud. The elastic layer of the reserved gap of about 80mm is filled with high-alumina aggregate. The ring-laying bricks are wet-laid with high-alumina phosphate fire mud. The inner and outer rings are made of LZ-65 high-alumina bricks. The ratio of 2:1 is the base masonry matching radian (G-1 brick size: 230mm×150mm×75mm; G-3 brick size: 230mm×150mm/135mm×75mm)). There are 33 layers of ring-laying bricks in total. When the refractory-brick layer of ring-laying bricks reaches a certain height, the furnace bottom carbon bricks are ready to be laid
