Abstract: Systems and methods are provided for vacuum spray drying. In one example, a method for spray drying includes estimating an outlet temperature to achieve a minimum drying rate at atmospheric pressure based on a selected liquid feed and a selected liquid to gas ratio, calculating a predicted dryer pressure at which the minimum drying rate can be reached at a reduced outlet temperature, and spray drying the selected liquid feed at the selected liquid to gas ratio, the predicted dryer pressure and the reduced outlet temperature. The reduced outlet temperature is less than a maximum temperature and the predicted dryer pressure includes an approximation for droplet solidification.