Compare rotary gypsum dryers vs. flash gypsum dryers

In industrial production, rotary dryer and flash dryer are two common gypsum drying equipment. The newly mined gypsum has a high moisture content, which can affect its compressive strength and easily crack during processing, affecting the quality of the final product. Therefore, gypsum must be dried first. There are big differences between rotary dryer and flash dryer in terms of working principle, energy consumption, applicability, and footprint. I will explain them in detail below.

Working principle

The gypsum rotary dryer consists of a slightly inclined horizontal rotating drum. Wet gypsum enters from one end and gradually moves to the other end with the assistance of gravity and drum movement. The blades (or elevators) inside the drum lift the material and drop it into the high-temperature airflow. This forms a layered material curtain, optimizing the heat transfer between the process gas and the product.

For flash dryer, wet materials (such as desulfurization gypsum filter cake) enter the bottom of the drying chamber through a screw conveyor. Due to the special inverted conical structure of the feed inlet design, the material is sheared and dispersed into extremely fine particles by high-speed rotating hot air. The material is in a boiling state in the drying chamber and undergoes high-intensity heat and mass transfer with high-temperature hot air flow (usually>200 ℃). Water evaporates rapidly, and the entire process only takes a few seconds. The coarse particles that are not completely dried continue to dry due to gravity, while the fine powder rises with the airflow and is captured and discharged by the cyclone separator.

Energy consumption

The rotary dryer rotates the drum body to directly or indirectly contact gypsum with the heat medium, ensuring stable heat transfer. It is suitable for gypsum with high moisture content and wide particle size distribution, and has good tolerance to feed fluctuations. It can still maintain a certain thermal efficiency at low loads. But with a large heat dissipation area, if insulation or control is poor, heat loss will increase and energy consumption will rise; Fine powder or high moisture materials are prone to sticking to walls and clumping, which can reduce efficiency.

The flash dryer uses high-speed hot air flow to instantly dry gypsum suspension, with fast heat transfer, short residence time, and low heat loss. The gas-solid co current fully utilizes thermal energy, and the unit energy consumption is often lower than that of the drum, especially suitable for fine powder high humidity gypsum. But its energy saving depends on the feeding conditions: it requires fine and uniform particle size, moderate moisture content, and high power for fans and heating at low loads, which weakens the energy consumption advantage; Coarse particles or clumps can easily cause blockage and wear, affecting operation and energy efficiency.

Capacity and space

Rotary dryers can process hundreds to thousands of tons of gypsum material per day, it is an ideal choice for large-scale gypsum production. However, rotary dryers take up more space, the largest rotary dryers can reach a length of 100m. And the flash dryer has a compact volume, which is very suitable for small factories with moderate processing capacity and limited space.

When choosing a gypsum dryer, it is necessary to consider multiple factors such as gypsum form, purpose, processing capacity, and site, and select the most suitable equipment.