What is the principle and function of a heat-free regenerative adsorption dryer?

Physical adsorption is commonly used to dry compressed air. Adsorption is a phenomenon in which there is a transfer of adsorbate molecules between phases due to the interactions between the adsorbate molecules and the adsorbent molecules. When the compressed air to be dried is in full contact with the adsorbent for an unlimited period of time, the water molecules in the air diffuse onto the adsorbent and are adsorbed due to van der Waals forces. Meanwhile, due to their own thermal motion and collisions with external gaseous molecules, some of the adsorbed water molecules leave the surface of the adsorbent and return to the gas phase, a process known as desorption. When the amount of water molecules adsorbed and the amount desorbed are equal at the same time, a dynamic adsorption equilibrium is reached. At this point, both adsorption and desorption processes are taking place, but at equal rates. This dynamic adsorption equilibrium is established under certain temperature and pressure conditions. When temperature and pressure change, the original equilibrium in the system is disrupted, and a new equilibrium is established. 　　Adsorption dryers are generally of the double-tower type, with one tower used for adsorption and the other for desorption. Depending on the regeneration method, they can be divided into heatless regeneration dryers, heat-regeneration dryers, and micro-heat regeneration dryers. The actual operation of a heat-free regeneration dryer consists of three stages: adsorption, regeneration, and pressure equalization. In contrast, a microheat and heat-based regeneration dryer go through a cycle of four stages: adsorption, regeneration, cooling, and pressure equalization. During operation, compressed air alternately flows through two tower-shaped containers filled with adsorbent: while one tower is adsorbing at operating pressure (high water vapor partial pressure), the other tower is desorbing at a pressure close to atmospheric pressure (low water vapor partial pressure) using the PSA method, or under heat using the TSA method. Then, the two towers switch roles in accordance with a predetermined sequence.

Slightly warm regeneration is better....

Thermoregenerative methods are more convenient; most of our offshore platforms use thermoregenerative ones

For pneumatic butterfly valves, is it better to use a heat-free dryer or a slightly heated dryer as the air source?

Good equipment! Could you explain the working principle in detail?