The physical adsorption desiccant mainly includes silica gel, alumina gel, molecular sieve, activated carbon, bone charcoal, charcoal, mineral desiccant, or activated clay, etc. Its drying principle is to physically adsorb water molecules in its internal pore structure. There are two types of adsorption methods: static adsorption and dynamic adsorption. The difference between the two adsorption methods is that static adsorption is equivalent to passive absorption and is adsorbed by the adsorption characteristics of the desiccant itself. Dynamic adsorption is equivalent to active absorption, and requires specific equipment to assist adsorption, such as pressurization, decompression, and ultrasonic waves.