The drying process of sand rotary dryer mainly includes three stages: ‌ preheating stage, main drying stage (some equipment may be called drying stage) and slow cooling stage (or cooling stage) ‌. Here's a breakdown of the stages:
‌1. Warm-up stage:
Objective: To fully preheat sand and increase its temperature to prepare for the subsequent drying process.
Temperature control: Generally controlled at about 100 ° C (three cylinder sand dryer may be controlled between 200-300 ° C).
Time: Approximately 30 minutes (a three-cylinder sand dryer may take 10-15 minutes).
Function: Make the water inside the sand gradually spread outward, improve the drying efficiency.
‌2. Main drying stage (drying stage):
Objective: To make the sand lose water quickly under the action of high temperature to achieve the ideal drying effect.
Temperature control: The general control is about 200 ° C (the three-cylinder sand dryer may be controlled between 300-400 ° C).
Time: Depending on the initial moisture and target moisture content of the sand, it can usually take 2-3 hours (depending on the type of equipment and the sand condition).
Process: Under the action of high temperature and hot air, the water of sand is quickly evaporated and discharged from the dryer. At the same time, the sand continues to roll in the body of the cylinder, in full contact with the hot air, speeding up the drying speed.
‌3. Slow cooling stage (cooling stage):
Objective: To avoid cracking of sand due to rapid cooling.
Temperature control: Generally controlled at about 100 ° C (three cylinder sand dryer may be controlled between 100-200 ° C).
Time: Approximately 30 minutes (a three-cylinder sand dryer may take 1-2 hours).
Function: Make the sand gradually cool down from the high temperature state, ensure the quality of the sand.
In summary, the drying process of the sand rotary dryer is a fine and systematic project, and the precise control of the three stages of preheating, main drying and slow cooling can ensure that the sand gets an efficient and uniform drying effect.