Вплив попередньої обробки на температуру випалу вермикуліту

Abstract

UA: У статті розглянуто можливість зниження температури випалу для отримання спученого вермикуліту – наповнювача теплоізоляційних будівельних матеріалів. Показано, що попередня витримка у розчині нітрату калію зменшує більше ніж удвічі температуру випалу порівняно з необробленою сировиною при збереженні такої ж самої насипної щільності. Коефіцієнт теплопровідності після випалу обробленого вермикуліту теж удвічі менший, ніж у необробленого. Підібрано оптимальні режими попередньої обробки.

EN: Vermiculite feature is that it can be expanded up to 30 times its original volume when heated at 650–950 °C. Due to this property the expanded vermiculite possesses low thermal conductivity. The light concrete with vermiculite aggregate is used as the heat-protective enclosing structures in building and structure constructions. To reduce the burn temperature it has been proposed the vermiculite pretreatment by the potassium nitrite solution. The vermiculite samples have been saturated with the tri-molar potassium nitrite solution and held for different time periods. After keeping the samples have been burned under different temperatures. The bulk density and thermal conductivity coefficient were determined for all sample sets. The results show that the burn temperature halves and is equal to 400 °С versus 900 °C for non-treated vermiculite. The expanded vermiculite bulk density is equal to 0,105 g / cm3 . The thermal conductivity coefficient of expanded vermiculite is equal to 0,032 W/(m⋅K) that is almost three times less compared with non-treated vermiculite which have been burned under the same temperature 400 °С. Moreover, burning of the non-treated vermiculite under temperature 900 °С does not allow improving the thermal conductivity coefficient that is only equal to 0,063 W/(m⋅K). The experimental data indicate that the increase of the processing time does not affect the bloat possibility of vermiculite. Also the keeping the samples under temperature 95 °С for 144 hours does not result in the change of bulk density or thermal conductivity coefficient. The treatment with distilled water is not enough effective compared with potassium nitrite solution. The usage of burnt vermiculite under low temperature decreases the production cost of the building materials, reduces the energy consumption, and improves the heat insulation characteristics of building constructions. Calculated heat consumption for 300 kg per hour of expanded vermiculite at 900 °С and 400 °С demonstrates the economic feasibility of the proposed pretreatment.