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Selection, Masonry And Baking Of Refractory Bricks For Hot Air Ducts Of Top-fired Hot Blast Stoves
Jan 08, 2019

In recent years, due to the rapid expansion of China's aluminum smelting industry, high-quality aluminum-vanadium ore has been requisitioned and occupied by the aluminum smelting industry or local governments. The high-quality high-alumina bauxite resources for refractory materials have been nearly exhausted, and there are not many high-alumina vanadium. The clinker (including homogenized material) is high in price, and the production of low-creep and high-aluminum bricks is close to “no rice under the pot”. It is difficult to purchase genuine products when the price is low. In order to meet the design requirements, refractory manufacturers produce low-creep high-aluminum bricks mainly by adding a swelling agent. At the end of the reaction of mullite, the effect of offsetting shrinkage will be invalid, and the creep resistance is greatly reduced.


Compared with the same level of low creep high aluminum brick, andalusite high aluminum brick has more price advantage. It is recommended to use a crystal fiber blanket with a temperature resistance above 1400 °C for the filler at the expansion joint of the hot air duct, which avoids the stringage of the filler in a high temperature environment for a long time.


Hot air duct masonry


The quality of hot air pipeline construction will directly affect its service life. The construction of pipelines must be strictly in accordance with relevant national standards and drawings. The size and fullness of the grey joints must be strictly controlled. The hot air outlets and Sanchakou must be used for masonry. At the beginning of the hot damper interface and the corrugated compensator, it is strictly forbidden to close the door at these locations. Combination brick masonry is a heavy and difficult point. When building a masonry, you must abide by one principle, adhere to five strict and a strictly prohibited operation method. That is to say, the principle of masonry in accordance with the assembly plan of the assembled bricks is strictly followed; the elevation and level of the bottom of the composite brick are strictly guaranteed, the cross center line is strictly controlled, the ellipticity of the masonry is strictly controlled, the masonry bricks are strictly controlled, and the quality is strictly controlled. Inspection and handover work; it is strictly forbidden to process any bricks in the masonry process. Quality records are also required during the masonry process.


Hot air pipe baking


Phosphate mud is often used in the masonry of hot air ducts, and the hardening temperature of phosphate mud is ~350 °C. The thermal stress of refractory bricks increases with the increase of temperature difference. However, at temperatures above 1000 °C, refractory bricks lose their elasticity and become plastomers, and the stress disappears. Therefore, the stress generated when the expansion is limited below 1000 °C must be taken seriously. It is recommended that the hot air duct temperature be above 1000 °C.


The longevity of hot air duct is a systematic project. The reasonable pipeline design is the foundation. The excellent refractory quality is guaranteed, and the fine pipeline construction is the key. Thermodynamics, material mechanics and materials science should be used to analyze the pipelines, so that the pipelines can be expanded and expanded, the expansion can be controlled, the brick lining structure of the stress concentration parts can be optimized, the stress resistance of the brick lining can be enhanced, and the refractory materials can be reasonably selected. Make the pipeline "good quality and cheap".


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