What is the actual difference between Evaporation and Drying?
Because these both are unit operations and mainly incorporated in Pharmaceutical Production and Manufacturing.
As per chemistry the definition of Evaporation is the process which do not require temperature(Heat) more than room temperature. While "Drying "do not necessarily happens at room temperature.It may be or may not be require some quantity of external heat .
Dear Gaurav,
Generally, the term drying refers to the moisture separation solids, gases or liquids. For drying gases and liquids, adsorption is often used. The drying of solid products is particularly applicable to the food industry. During the heat drying of solids, moisture is removed from the product by evaporation. The drying process depends on the manner in which moisture is present in the product. Initially, there is first evaporation of the liquid to the surface of the product to be dried. Once this liquid has been removed, the drying affects the moisture present in the capillaries and pores. Since the forces capillaries and resistance to diffusion must be overcome, the drying rate decreases. For the crystal structures, the bound water may be removed by a strong warming and low drying rates.
In the field of engineering thermal processes, evaporation is the separation of the solvent solution. For example salt water contains a salt (solid dissolved) and a solvent (water). The addition of heat causes the evaporation and evacuation of the pure solvent present in the solution (in this example water). The concentration of dissolved solids (salt) in the residual solution is thus higher than before the heat input.
With my best regards
Prof. Bachir ACHOUR
Evaporation and drying as Chemical Engineering unit operations differs in the way of a vapor phase is separated of a solid or liquid phase.
Evaporation is a liquid-vapor separation process in which a generally homogeneous liquid phase is thermally saturated by heat and then the vapor is separated by ebullition. The term thermally saturated means that heat is transferred to the liquid phase until its vapor pressure (temperature function) reaches the same value of surrounding pressure. In this state the liquid phase reaches its boiling point (or saturated liquid).Heat must be added in order to supply the evaporation latent heat at ebullition. As example the clarified sugar (sucrose) solution obtained from squeezing of sugarcane (Saccharum officinarum) is concentrated by evaporation previous its crystallization.
Drying is a solid-gas or liquid-gas separation process in which a liquid component is separated from a generally heterogeneous solid or liquid phase as vapor in a gas flow. Heat may be added in order to supply the evaporation latent heat. In this case the separation occurs by vapor pressure gradient instead of ebullition, and the evaporation latent heat can be taken from the gas phase. As example, fruits (heterogeneous solid phase) can be drying (the water is separated) in a tunnel dryer with air flow at different temperatures below to water boiling point. The separation is due to water vapor pressure gradient between fruit surface and the air, and the evaporation latent heat is supplied by the same air producing a temperature failing between inlet and outlet. Other example, milk (heterogeneous liquid phase) can be converted in powder milk in a spray dryer in which the milk is sprayed in an air flow. As the same of the first drying example the separation is due to water vapor pressure gradient between milk drops surface and the air, and the evaporation latent heat is supplied by the same air producing a temperature failing between inlet and outlet.
The final objective and procedure..
You can dry a solution using a bloting paper etc.
In evaporation liquid is separated from a solution either by raising the temperature or lowering the pressure ...
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