Compressed air dryer

The invention relates to a compressed air dryer in the field of air dehumidifying technological equipment. The compressed air dryer comprises an adsorption tank A and an adsorption tank B which are arranged in parallel and are filled with adsorbents; the lower parts of the adsorption tank A and the adsorption tank B are connected in parallel via two air inlet valves and two humidity discharging valves; an air inlet is formed between the two air inlet valves; a silencer is arranged between the two humidity discharging valves; the upper parts of the adsorption tank A and the adsorption tank B are connected via a throttle valve, a pilot valve and two check valves; the output ends of the two check valves are opposite to each other; a moisture detection instrument and an air outlet valve are connected between the check valves. The compressed air dryer realizes two functions of drying and dehydration regeneration, realizes water closed ring automatic control, and is simple and reliable in structure; a control syste