Analysis of Drying Process of Wet Materials

In modern society, drying materials has been an important part in many fields of production, and the selection of the drying equipments directly impact the drying effect. There is a suitable way, a high quality drying equipment can achieve the result in the condition of enterprises pursuing production efficiency and cost, and saving energy consumption. Here is the introduction of the drying process of wet materials:

1. Drying process of wet materials

Drying condition: flow rate, humidity and temperature of the drying medium (hot air).

Due to the high temperature air and low temperature materials, there is the heat transfer impetus between hot air and materials when the hot air flows past the surface of the wet materials steadily. Hot air transfers the heat to materials by cross-ventilation, materials use the heat to gasify the water in it, then taken away by the airflow continuously, and the humidity ratio of the materials continuously falling. It finishes the drying process, when it falls to the equilibrium water content.

There are two mutual processes of heat transfer and mass transfer in the drying process. Heat transfer is that hot air transfers the heat to materials to used for gasifying the moisture and heat materials; mass transfer is evaporating the moisture in the materials and mixing into the hot air, dried by reducing the water content.

2. Features of the drying process

In the drying process, due to the material has a certain size, it can be regarded as granule with certain size from microcosmic view, even it is the very fine powder. In fact, the mechanism of the heat and mass transfer process above mentioned is different between hot air and materials granule, and the internal of the materials granule as well. Theoretically, it divides heat and mass transfer into the heat and mass transfer process of hot air flow and the surface of materials, and the heat and mass transfer process of materials internal. These two different processes affect the materials drying process, and they play the different roles in different drying process, which results in drying the wet materials in fast and stable speed in the previous phase, but in slower and slower speed in posterior phase, so the drying process is divided into constant speed drying and reduction speed drying.