Abstract: The present invention relates to a spray drying apparatus (1) comprising; a spray dryer chamber (10) with a feed inlet device (11), a process air inlet (12) and a process air discharge (13), a process air temperature measuring means (16), and a process air heater (17) for heating a process air volume, an adsorption dehumidification device for dehumidification of the process air comprising an adsorption source (41), a process air section (43) and a regeneration air section (44) and having means (22, 23) for heating a regeneration air volume to a regeneration air temperature and means (25) for measuring the regeneration air temperature, and a regeneration air fan (30) configured for transporting the regeneration air volume, and moisture content measuring means (18, 19) for determining a moisture content in the process air.