The main features of the new dry process cement kiln are: the inner lining and the high temperature contact surface are large, and the cement clinker phase is formed when the temperature exceeds 1450 °C. In the hottest part, the gas temperature in the kiln exceeds 1800 °C. Therefore, only alkaline refractories can withstand chemical reactions with cement clinker, fuel ash, kiln dust and various gases, and can withstand higher heat loads.

1. Kiln skin attachment and protection easiy

Magnesia spinel bricks can only be maintained at a temperature of about 600-800 °C. The thermal expansion coefficient of the hot surface layer is 0.6%-0.7%, and the refractory brick is relatively stable and is not easy to burst. If exposed to a flame above 1700 ° C, the internal temperature difference stress of the refractory material exceeds the strength of the brick itself when the temperature rises, and cracking and peeling cannot be avoided. Alkaline bricks are good for clinker reaction and kiln skin adhesion.

2. Good resistance to chemical erosion

At the high temperatures of the firing zone, the refractory material undergoes strong chemical erosion. When the material of the firing zone contains 28% of the liquid phase, the refractory material is easily eroded. Magnesia bricks and dolomite bricks are resistant to clinker erosion because they are all alkaline. The gas produced by the combustion and the sulfur, chlorine and alkali volatilized in the material have strong chemical erosion on various refractories.

3. Good thermal shock resistance

In the case of unstable kiln shutdown, open kiln and rotary kiln operation, rapid changes in temperature will lead to increased thermal shock damage. Under normal circumstances, the rotary kiln rotates less than 1 minute per revolution. Each turn of the kiln, the refractory material in the kiln (including the kiln skin of the firing zone) is exposed to the gas in the hot kiln, and the rest of the time is covered by the material. The surface temperature of the refractory material in the kiln will be subject to periodic fluctuations with a temperature difference of up to 400 °C. The interior of the refractory material is still at a lower temperature, and the temperature difference between the inside and the outside of the refractory material causes thermal stress inside, which causes damage.

4. High refractoriness and refractoriness under load

The refractory material used for the firing zone should have a refractoriness of at least 1730 ° C. Alkaline bricks commonly used in firing zones have a refractoriness of greater than 1750-1790 °C. The load softening temperature of the refractory brick refers to the temperature at which the refractory brick begins to soften under the pressure of 0.2 MPa. The load softening temperature of the magnesia brick is about 150 ° C higher than the clinker firing temperature. Higher load softening temperatures are not desirable because alkaline bricks will make the kiln skin difficult to form.

5. Moderate porosity

Rotary kiln linings are subject to strong chemical attack and penetration. Too much porosity results in the infiltration of flue gases and liquid phases and the deposition of harmful components, which can damage the kiln lining. However, the porosity is not as low as possible, and the apparent porosity is preferably maintained between 16% and 18%.