Construction of refractory castables
We have shared the construction methods of refractory castables in many articles in the past, including blast furnaces, circulating fluidized bed boilers, etc. Today, taking the second-stage converter in the petrochemical industry as an example, we will briefly share the construction of refractory castables for converters. The construction of refractory castables for the second-stage converter must be carried out after a series of construction preparations such as equipment preparation, material and tool preparation, and steel formwork installation have been completed. The focus of its construction is on the mixing, pouring and maintenance of refractory castables. The details are as follows:
01 Mixing of refractory castables
(1) The mixer uses a large forced mixer for mixing. The mixing procedure and water addition are strictly in accordance with the construction instructions provided by the material manufacturer;
(2) The mixing water should be clean and potable water. The water temperature and discharge temperature should be controlled within 10~25℃. The mixing time after adding water should not exceed 2min;
(3) In order to prevent the castable from condensing in the mixer and the string barrel, the mixer and the string barrel should be cleaned frequently.
02 Refractory Castable Pouring
(1) Before pouring the cylinder, fill the ball arch support ring with water to clean the castables that are poured into the cylinder;
(2) When pouring, the string cylinder should be moved symmetrically at 180°, and the material should be evenly poured along the circumference. The string cylinder should not be fixed in one place to pour the material;
(3) The pouring speed should be equal, and the height of 350mm per hour is appropriate;
(4) When vibrating the castable with an inserted vibrator, the vibration time should be strictly controlled. When there are no bubbles escaping around the vibrator, stop vibrating immediately to avoid stratification. While vibrating, tap the formwork gently with a mallet;
(5) The vibrating of the castable should be carried out in layers, with a thickness of 150mm being appropriate. When vibrating, the vibrating rod should be inserted into the lower castable by 50mm to ensure that the new and old castables are tightly combined. Pure calcium aluminate cement refractory castable should be poured continuously, with each interval not exceeding 30 minutes;
(6) The free fall height of the castable should be within 1.3m during pouring. Too high a height will cause the particles of the castable to separate. When using a string barrel, 800mm is the best;
(7) Stop pouring when the castable is poured to 100mm above the formwork, and continue pouring after the lower formwork is installed;
(8) The ambient temperature for castable construction should be between 5-35℃;
(9) The thickness of the lining The thickness control top block is used for control. The thickness deviation of the castable lining is ±5mm.
03 Curing
(1) After the castable is poured, it is cured according to the design requirements. Since the lining of the second-stage converter is continuously poured by supporting the formwork, the start time of curing can only be determined based on the initial setting time of the castable. Generally, the method of pouring water on the formwork to cool down and maintain it for no less than 24 hours after the construction is completed until the castable releases heat. During the curing period, all pipe openings are closed to reduce air convection and avoid water evaporation.
(2) After curing for 24 hours, the formwork can be removed. After natural curing, a hammer inspection is carried out. A crisp sound indicates that the structure is dense and there are no cracks on the lining surface. After the furnace is baked, the quality of the entire furnace lining is inspected. Small mesh cracks are allowed, but no through cracks are allowed.
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