The normal desiccant air dryer is manufactured with the inlet air temperature of 45℃. However, this large scale heat of compression desiccant dryer allows the maximum inlet air temperature as high as 170℃. Meanwhile, it enables zero purge loss for it avails itself of the circulating compressed air to dry. This range of compressed air purification equipment serves in a large steel mill in China. It is maintained regularly every year with good service performance.