Difference between drying evaporation and dehydration
"Dehydrating agents remove water which is chemically bound to a substance for e.g water of crystallization. While on the other hand a drying agent simply removes excess water present in a substance which is not chemically bound to it. #pmgengineering #foodprocessing #foodindustry #foodtechnology #foodscience #engineering #science"
Drying, dehydration and evaporation are used almost interchangeably in day-to-day plant conversation, yet they describe different unit operations with different equipment, control requirements and end results. Drying is the process of removing water or other solvent from a solid, liquid or gas — a physical change that occurs when moisture is lost from a substance. Dehydration is the reduction of moisture in food to low levels for improved shelf life, and is one of the oldest methods of food preservation. Evaporation is a form of vaporisation that usually happens on the surface of liquids and involves the transition of liquid particles into the gaseous phase.
The distinction matters when a feed material and a target specification are being matched to a machine. Drying is applied to a solid, semi solid or a liquid, and evaporation is likewise listed against a solid, semi solid or a liquid, while dehydration is applied to a water-containing compound such as aqueous solutions. On the by-product side, drying removes water or any other solvent, whereas both dehydration and evaporation yield water as an essential by-product — which is why the removed stream itself often becomes a design consideration in evaporation and dehydration systems.
Process severity is the third dividing line, and it drives capital cost. Drying can use mild conditions such as the application of hot air or sun drying. Evaporation can also use mild conditions, such as the application of direct heat and basic equipment. Dehydration needs more controlled temperature and humidity conditions with sophisticated equipment, because the objective is a defined low residual moisture that will hold shelf life rather than simply the removal of surface liquid. Specifying the wrong one of the three leads either to over-engineered plant or to product that does not meet its keeping-quality target.