Controlling adsorption dryers with heatless regeneration presents no problems. One or two main and exhaust valves, depending on the design, are actuated either directly or indirectly by means of a time controlled cycle timer. The main valves are required for switching over from adsorption to desorption and back, the exhaust valves for the functions of desorption and pressure build-up. The installed electrical capacity is thus low. Two valves, simultaneously actuated, and the time control need an electrical power of about 30-40 Watt. Using this control system, an effective running time harmonisation between the adsorption dryer with heatless regeneration and a discontinuously operating compressor can be achieved fairly simply. The on/off contact of the main switch of the dryer is linked to the signal emitter (pressure switch) of the compressor control.
The synchronisation between compressor and adsorption dryer, therefore, brings about adaptation of the regenerative output of the dryer to the running time of the compressor. This switching system cannot, however, achieve adaptation to differences in pressure or moisture load. Fully pneumatic control systems, as an alternative to standard electrical controls, are utilised when there is a risk of explosion or where mobile application means no availability of an electrical supply.
Fully pneumatic control systems are expedient only under conditions of continuous running. With discontinuous operation, harmonisation between the dryer output and the desorption performance via synchronisation of dryer and compressor can only be achieved with difficulty.
