Elbows of the tertiary air duct (See the following figure for applied parts)
    In line with design requirements, many producers use alkali resistant castable as the refractory material for the tertiary air duct. Alkali resistant castable is cheap and easy to be applied. However, the wind temperature of the tertiary air duct is just 800~1000℃, which cannot realize sintering of castable. This makes it difficult for the material to meet design requirements of the strength; large cement kiln will cause more rapid wind speed in the tertiary air duct. As a result, the huge amount dust contained in chlor-alkali gas from the grate cooler will cause violent erosion and chlor-alkali corrosion to Y-shaped parts, elbows, and valves, resulting in loose and falling castable. Due to serious abrasion, castable of some producers can only be used for two months, causing frequent maintenance and other problems. Therefore, our company has designed special bricks for some severely damaged parts of the tertiary air duct (particularly elbows), which can ensure three service years when supporting with other materials.