1. The preheater tubes are not easily broken enamel surface, no crack, acid and alkali resistance, resistance to gas erosion, smooth and high, gas flow resistance, easy Fouling; 2. As the flue gas across tube, the flue gas side of the heat capacity of exile to strengthen, under the same heat transfer coefficient (enamel thickness ratio of thermal conductivity with very small, about 0.0002, the calculation is negligible), wall temperature vertical preheater than ordinary steel increased 10-30 Degree Celsius, the overall heat transfer coefficient of about 20.3-24.2W;