Since 2003, when China Jiangnan Shipbuilding (Group) Co., Ltd. introduced China’s first high-speed pulse flame galvanizing furnace (Weistek®) to Dalian Xinyongshang Technology Co., Ltd., all structural galvanizing furnaces launched by Dalian Xinyongshang Technology Co., Ltd. to the world have been using heat-insulating and pressure-resistant non-sintered low-temperature castables as the bottom insulation material for the furnace bottom insulation structure for more than ten years.
In the hot-dip galvanizing industry in mainland China, whether it is a flat flame galvanizing furnace or a high-speed pulse galvanizing furnace, except for the furnace type launched by Dalian Xinyongshang Technology Co., Ltd. for the hot-dip galvanizing industry, as of the time of publication, all use heavy and lightweight refractory brick masonry structures.
Advantages of lightweight heat-insulating, pressure-resistant, non-sintered low-temperature castable insulation layer compared to traditional insulation layer
Comparison between “lightweight heat-insulating, pressure-resistant, non-sintered low-temperature castable” and “refractory brick masonry insulation layer”, the application advantages are obvious:
(1) “Refractory brick masonry insulation layer” is built with ordinary refractory bricks. When the galvanizing furnace needs to heat up, the refractory bricks absorb heat, resulting in a slow heating rate. However, when the furnace needs to cool down, the refractory bricks release heat to the outside, resulting in a very slow cooling rate, which affects work efficiency and wastes energy.
Ordinary refractory brick masonry insulation layer has many gaps in the masonry, and employees of hot-dip galvanizing companies cannot meet the precision requirements of thermal kiln masonry. The large number of gaps increases the penetration of heat to the foundation.
Since the zinc pot is placed on the insulation layer, if it is a refractory brick masonry, the zinc pot will expand during the heating process. Due to the strong friction between the pot bottom and the insulation layer masonry, the existing gaps in the refractory brick masonry will be pulled open, causing the gaps to expand further. During the cooling process of the zinc pot, the friction between the pot bottom and the refractory bricks is much smaller than the pressure friction between the refractory bricks. Therefore, the existing cracked masonry gaps cannot be restored. Therefore, the heating and stopping processes that often occur in hot-dip galvanizing production intensify the penetrating transfer of heat to the insulation layer at the bottom of the furnace. This causes a large amount of heat loss and reduces the thermal efficiency of the galvanizing furnace system.
(2) “Lightweight heat-insulating and pressure-resistant non-sintered low-temperature castable” is a refractory material made of refractory aggregates, powders, binders, and admixtures with a certain particle size distribution, also known as bulk refractory materials. It is used for the lining of thermal equipment and is directly baked without going through the firing process. Compared with refractory bricks, it has the characteristics of simple process (because the firing process is omitted), energy saving, low cost, and easy mechanized construction. It is used in the zinc pot base to meet the pressure requirements and has better thermal insulation performance than refractory bricks, reducing the heat dissipation of the galvanizing furnace foundation and significantly improving thermal efficiency.
Correct application of castables
For the correct application of castables, its characteristics must be mastered. The smaller the bulk density of the castable, the better its thermal insulation performance, but the decrease in bulk density will definitely reduce the compressive strength in the non-sintered state. For the galvanizing furnace system, when using castables, the compressive strength in the non-sintered state must be met first, and the thermal insulation protection of the furnace bottom heat must be met secondly. Therefore, the thermal insulation performance of the furnace bottom can only be improved by reducing the bulk density on the premise that the compressive strength meets the requirements.
The castable is constructed by one-time integral casting, and the micropores are enriched in the insulation layer of the base to form dense air pockets, so it has excellent thermal insulation performance. At the same time, the entire insulation layer has no gaps, which can ensure the integrated shrinkage of the entire insulation layer and reduce the heat transfer path to the earth. The heat is isolated and collected in the furnace combustion chamber to the maximum extent, thereby greatly improving the thermal efficiency.
The thermal insulation structure design of the zinc pot base adopts lightweight, heat-insulating, and compressive non-sintered low-temperature castables, which puts forward more requirements for the application of castables. The smaller the bulk density, the better the thermal insulation performance, but the decrease in bulk density will definitely greatly reduce the compressive strength in the non-sintered state. This will increase the thermal stability of the zinc pot after it is in place. In order to solve this contradiction, Tangshan Kaiping Xinde Hot-dip Galvanizing Technology Co., Ltd. has made gradual improvements in response to the development trend of thermal efficiency, energy saving and consumption reduction of the galvanizing furnace system. Relying on large state-owned enterprise groups and professional refractory research institutes, lightweight heat-insulating and compressive non-sintered low-temperature castables for zinc pot bases have been developed. This castable belongs to a new generation of high-grade amorphous heat-insulating refractory materials without beads.
Lightweight heat-insulating and compressive non-sintered low-temperature castables replace floating beads with “lightweight aggregates“. After the raw materials are burned and crushed, the third-grade aggregates are obtained. When manufacturing “lightweight aggregate + high-aluminum system” castables, multi-level (guaranteed to be above level three) particle grading and pre-mixed finished products are used for construction. Solved the technical problems of water drift and low strength in the construction of lightweight materials.
“Lightweight aggregate + high aluminum series” castables belong to alkaline refractory materials, which are used for heavy-load insulation structures of large tunnel kilns, roller kilns, shuttle kilns, anti-seepage insulation of aluminum electrolytic cells, and load insulation of galvanizing furnace bottoms. It solves the defects of water enrichment and cavitation segregation of floating beads. During the construction process, vibrating equipment can be used to accelerate the construction progress. Under natural air drying conditions, the process from initial setting to reaching the strength of the zinc-carrying pot is shortened to less than one week. The construction and galvanizing furnace renovation period is shortened, ensuring the timeliness of the production line to obtain economic benefits.
Conditions of use
1100℃, lightweight. Construction methods: pouring, coating and spraying. Low-temperature castable for hot surfaces.
Product features
(1) Aggregates are pre-sintered with special refractory materials to produce third-grade particles for secondary grading and pre-mixed finished product construction. This solves the technical problems of light material construction water drift and low strength.
(2) The material belongs to alkaline refractory materials, which are used for heavy-load insulation structures of large tunnel kilns, roller kilns, shuttle kilns, anti-seepage insulation of aluminum electrolytic cells, and load insulation of galvanized furnace bottoms.
(3) A new generation of beadless, high-grade, heat-insulating, and pressure-resistant non-sintered low-temperature castable developed by a professional refractory materials research institute.
