The full-electric glass melting furnace basically has no pollution to the environment, and has important guidance and practical significance for the development of the glass industry and the reduction of environmental pollution. Now many glass factories have adopted the full-electric melting process. Because of the cold top (50~150 °C) or semi-cold top melting of the electric melting kiln, it needs to withstand the high temperature of 1050~1200 °C during the baking stage, so that the material selection and structure of the melting pool roof brick are different. In hot top tank kilns, the current mainstream materials used in China are sintered clay bricks(hereinafter referred to as clay bricks) and lightweight mullite bricks.
This article compares the status quo of the use of two kinds of bricks in electric melting kilns, analyzes the advantages of light-weight mullite bricks, and briefly analyzes the application status and development trends of light-weight mullite brick dome roofs in the general state electric melting kilns.
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Common types of glass electric melting furnace roof
The roof of the electric melting furnace and the breast wall of the melting pool not only provide sealing and heat preservation for the furnace during the baking, but also prevent the dust from flying and reduce the loss of raw materials during the normal production of the cold roof. Therefore, whether it is the pre-baking or normal production, The dome is an indispensable part of the electric furnace. There are various shapes of the melting pool of the electric melting furnace, which results in the diversity of the dome structure. The common dome structures are introduced one by one below.
1.1 Arch Dome
Because of its light weight and stable structure, arch dome is widely used in industrial furnaces, especially suitable for rectangular tank kilns. The melting area of electric melting kilns is much smaller than that of tank kilns due to current technology limitations, and the current daily output of 30 to 80 t electric melting kilns are mostly hexagonal, dodecagonal, and circular structures, so the dome is used in medium and large electric melting kilns the above has not been widely used. The dome is the most commonly used type in electric melting kilns with a daily output of less than 10 tons and rectangular melting kilns.
The material of the dome brick is mostly clay brick to meet the demand. Figure 1 shows the dome structure of a 4t /day electric melting kiln.
1.2 Hexagonal dome
Due to the discharge characteristics of the electric melting furnace, the melting pool is mostly hexagonal, and the hexagonal dome that meets this characteristic was born. Figure 2 shows the structure of the hexagonal dome of a 6 t electric melting furnace. The advantages of the hexagonal dome are shown in the figure. It fits perfectly with the hexagonal electric melting kiln, which can effectively save the space occupied by the breast wall and the dome. The hexagonal dome bricks are made of 8 pieces of clay bricks and cut at a certain angle. In order to ensure that the dome bricks will not fall during use, the production angle and masonry requirements of the dome bricks are strict.
Hexagonal domes have stricter requirements on the angle of the lower dome bricks when the length of one side is longer. Considering the difficulty of construction and structural stability, they are generally no longer used in electric melting kilns with a daily output of more than 20 tons.
Figure 1 . Arch dome
Figure 2. Hexagonal dome
1.3 Hemisphere dome
Electric melting furnaces with a daily production capacity of more than 20 t no longer use hexagonal kilns, so hemispherical kilns have been used on regular polygonal or circular kilns. The advantages of hemispherical domes are convenient reinforcement, low cost, and clay bricks are generally used as materials. There are many types of hemispherical dome bricks, and they have high requirements for production and masonry precision, and they have been gradually eliminated.
1.4 Hanging dome
The difference between electric melting kiln hanging mortar and other mortars is that its load-bearing method is suspended load-bearing on the top steel structure. There are two types of materials: clay bricks and light mullite bricks. Clay bricks are not commonly used because of their heavy weight. They are most commonly used. Is a lightweight mullite brick with a density of 1.0 g/Cm3. Figure 4 is a picture of a 6-ton electric melting kiln in China. The hanging wall is composed of a single block of pre-divided size. Each block contains 1 stainless steel hanging piece to ensure that each brick is Have independent load-bearing support.
Figure 3. Hemisphere dome
Figure 4. Hang dome
Lightweight mullite hanging troughs have the following advantages when used in electric melting kilns:
(1) Light weight and good insulation effect. The density of 1.0g/cm3 reduces the dead weight of the trellis body and also reduces the load of the load-bearing steel beam. At the same time, the good insulation effect during the kiln debugging helps to reduce energy loss and obtain higher The initial charging temperature.
(2) High temperature resistance. The operating temperature can reach 1400~1500 °C, which can fully meet the demand compared with the maximum operating temperature of the electric furnace dome top not exceeding 1300 °C.
(3) The shape is not limited, and the shape of the hanging chute can be designed at will according to the kiln type, which can meet the sealing requirements of all shapes of electric melting kilns.
(4) The installation and operation are simple. After the steel structure is installed, it can be continuously hung and mud masonry according to the brick number.
(5) Reusable. The hanging hangings and the steel structure can be hoisted and moved as a whole. At present, most hanging hangings designed by our company can be hoisted as a whole, which can be reused after major repairs.
However, the cost of hanging domes is slightly higher than other types of domes, and there is a cost of hoisting, so it has not been widely used in small electric furnaces.
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1.5 Other types
According to different customer needs, there are other forms of special-shaped chrysalis, but they are used less, so this article will not elaborate
2 Application of Lightweight Mullite Hanging Wall in Electric Furnace
Lightweight mullite hanging turrets have an absolute advantage in performance. At present, our company has basically adopted it as the roof structure of electric melting furnaces designed and built with a melting area of more than 8m2. The following analyzes the future development direction of hanging chute from two aspects of small electric melting furnace and large electric melting furnace.
2.1 The application of hanging chute in small electric melting kiln
Small electric melting furnaces (melting area 1 ~ 8m2, less than 1m2 are beyond the scope of this article) can use hanging structure. The main factor limiting its promotion is cost. At present, some domestic manufacturers have used it, but it has not been fully popularized. With the reduction of material costs and people's emphasis on resource reuse, it is believed that there will be more space for hanging slings to be used in small electric melting kilns.
2.2 Application of Hanging Hanger in Large Electric Furnace
With the gradual development of electric melting furnaces in the direction of large melting areas (melting areas greater than 20m2) in recent years, new challenges have also been raised for the design of hanging dome. Large hanging dome area means weight increase.In order to ensure that the hanging dome can be reused, our company has created a split hanging structure. Figure 5 is a schematic diagram of the splitting of the 21m2 electric melting furnace hanging dome designed by our company for a domestic manufacturer. The dome body is divided into 3 parts, each part is independent of load-bearing, and can be separated and hoisted separately during loading and unloading.
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Figure 5. Split dome
3. Concluding remarks
The light-weight mullite hanging dome signed by our company has been used in many projects, and its advantages have been fully verified. What needs to be promoted vigorously at present is its use in small electric melting kilns. With market demand, ultra-large electric melting furnaces will also be available, and the span of the load-bearing steel structure of the dome will pose new challenges to the design.
