Autoclave curing institution of aerated block production line
October 15, 2021
Autoclave curing system is a specific control measure related to temperature and time for full and effective curing of products. There are four stages: vacuum pumping, heating, constant temperature and cooling.
(1) Curing before entering the autoclave: curing before entering the autoclave after cutting. It can improve the state of the green body, reduce the temperature difference inside and outside the green body, and enhance the strength of the green body into the kettle and the ability to resist internal stress. After entering the kettle, the temperature rise can be faster.
(2) Vacuumizing: discharge the air in the kettle and part of the gas in the green body bubble to form a negative pressure state. Only when the saturated steam can quickly transfer the heat to the center of the green body and make the temperature of the whole green body rise rapidly. Shorten the heating time to make the temperature of each part of the green body basically the same. The temperature of each part in the kettle tends to be uniform to improve the thermal efficiency. The speed and degree of vacuum pumping depend on the air permeability and hardening of the green body. Good air permeability, high green body plastic strength when entering the kettle, faster vacuum pumping and higher vacuum degree. On the contrary, it should be pumped slowly and the vacuum degree should be appropriately lower to avoid damage to the green body. The speed of vacuum pumping should not be too fast. It usually takes 30 minutes, and the vacuum degree is -0.06 MPa.
(3) Temperature rise: after vacuum pumping, air shall be supplied immediately for temperature rise. During the heating process, there is a temperature difference between the inside and outside of the billet. The initial heating should be slow. With the gradual increase of the billet temperature, the internal and external temperature difference will gradually reduce. In the later heating stage, the heating speed can be accelerated. Generally, the heating time is 2.5-3 hours.
(4) Constant temperature: when the raw materials of aerated concrete are different, the formula is different, and the unit weight is different, the curing temperature of the green body and the curing time at this temperature are also different. Considering the characteristics of heat transfer in aerated concrete kettle. To ensure the strength and uniformity of products. And ensure better production efficiency. Constant temperature pressure is usually 1.3mpa; Constant temperature time is to enable the product to carry out sufficient hydration reaction and reach a certain crystallinity. The inner layer of the billet also achieves this effect. The constant temperature time shall be determined according to the specific situation on the basis of this principle. The constant temperature time is usually 6 ~ 8 hours. However, to ensure constant temperature, the constant temperature shall not fluctuate greatly with humidity.
(5) Cooling: at the beginning of cooling, the cooling speed shall be slow to avoid explosive damage to products due to internal and external temperature difference; The cooling can be fast in the medium term and slow in the later stage (when the gauge pressure is below 0.1MPa). On the one hand, the external pressure difference in the kettle is very small, and the steam exhaust power is weakened. On the other hand, the water of the product still needs to be evaporated, and the amount of steam is also large. Generally, the cooling is controlled within 2 hours.