How bad is the fire mouth? Taking the cement rotary kiln as an example, the burner not only has to withstand the impact of high-temperature flames above 1700°C, but also the chemical erosion of clinker slag and the thermal shock test of rapid cooling and rapid heating. Ordinary refractory materials may crack, peel or even burn through in a few months under such working conditions, but high-quality burner castables can extend the service life by 2-3 times.