Trend 1: Combined Drying

In drying equipment, each type of equipment has its own advantages and disadvantages. Due to the characteristics of drying equipment, when using a single drying equipment, the following problems may be encountered in its application: (1) the moisture content cannot be met; (2) the forming requirements cannot be met when using a single drying equipment; (3) the energy consumption of a single dryer is relatively high.

For example, the following conclusions can be drawn when using infrared, hot air, and microwave drying: (1) during the drying process, the drying particles are fluidized or dynamic, making it easy for the material to be evenly and fully mixed with the hot air; (2) conventional drying consumes relatively less electricity than microwave drying; (3) due to the different drying mechanisms, the drying rate of materials in conventional drying is lower than that in microwave drying, especially when drying some materials that are difficult to dehydrate in the later stages, not only is the speed slow, but it will also have a certain impact on the quality of the material. Therefore, some people have studied the drying curves of different drying methods and believe that: the moisture content of microwave drying decreases continuously, and the drying process is mostly in the rapid dehydration stage, with the curvature of the drying curve changing rapidly in the early and late stages. In the early stages of drying, the drying rates of airflow drying and microwave drying are very similar. Therefore, airflow drying can be considered, which reduces costs while achieving the desired drying effect.

Trend Two: Closed-Loop Circulation
In pharmaceutical and chemical production, the liquid used to dry materials often contains organic solvents, or is easily oxidized, flammable, or explosive; some may even be toxic. Using these materials in conventional drying equipment presents two problems: (1) environmental problems due to toxic material leakage; (2) some highly volatile or easily oxidizable materials are prone to explosion during drying, causing damage to the equipment or injury to operators. The problems exposed by conventional drying necessitate a closed-loop circulation system for the entire drying process. For current large-scale industrial production, closed-loop circulation is also a direction for the development of drying production for some materials.

Trend Three: Enhanced Drying

The first method mentioned above can be applied to airflow drying, changing straight-pipe airflow drying to pulsed airflow, causing the dried particles to accelerate multiple times under the action of the pulsed airflow, thus enhancing the heat and mass transfer process; it can also be applied to the air inlet device of spray drying to control the movement of atomization.

The second method mentioned above can be applied to: (1) In spray drying, atomizers for high-viscosity materials can be developed, and air inlet distribution devices can be studied to ensure that the air velocity at the center of the drying tower and the tower wall are basically the same, reducing wall adhesion during spray drying;

(2) In fluidized bed drying, a rotating partition plate is added, which rotates from the middle of the fluidized bed to the outlet. Wet material is added from the middle of the fluidized bed, and under the control of the rotating partition plate, the material moves while fluidizing from the inlet to the outlet without interruption, thus ensuring a uniform residence time of the material in the fluidized bed.