Polylactic Acid (PLA)
1. Material Overview
Polylactic acid (PLA) is a biodegradable thermoplastic polyester produced from renewable biomass resources such as corn and sugarcane through fermentation. It possesses excellent biocompatibility, mechanical properties, and processing performance, and has broad application prospects in packaging, medical, textile, and many other fields.
PLA is highly hygroscopic, readily absorbing moisture from the air. This characteristic makes thorough drying during processing crucial; otherwise, product quality and processing performance will be affected.
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2. Process Introduction
The entire system consists of four sections such as conveying system, crystallization system, drying system, and cooling system. Polylactic acid granules are conveyed under positive pressure by blower to buffer silo at the top. After crystallization and drying, the material changes from transparent to opaque state (determined as crystallization). After drying, the moisture content is less than 500 ppm, and the material is then cooled. All rotary valves in the system have airlock and uniform feeding functions. The crystallization, drying, and cooling systems all use closed-loop circulation to ensure the cleanliness of the gases in contact with the material.
3. Technical Advantages
(1) Crystallization, Drying, and Cooling Fluid Bed Dryer
One of the key components of the crystallizer, dryer, and cooling fluid bed dryer is the crystallization chamber, drying chamber, and fluidization chamber. Inside the chamber, materials move from the inlet to the outlet with the help of airflow and become fluidized. The air distribution plate is crucial for ensuring the normal operation of the air chamber; it needs sufficient pressure drop to ensure uniform airflow. Air distribution plate designed by Tianli has a reasonable opening ratio, ensuring uniform airflow while preventing material leakage. The crystallizer and dryer have an increased height and width, increasing the cross-sectional area of the upper part and reducing the airflow velocity, thus reducing the entrained dust. The dryer is equipped with sight glasses for process monitoring. Inspection ports are evenly distributed at the top, middle, and bottom of the dryer for easy inspection, cleaning, and maintenance.
4. Technical Benefit
(1) Significantly reduced energy consumption cost
The uniform hot air distribution combined with closed-loop circulation for waste heat recovery can reduce heat loss due to heat source venting.
(2) Reduced raw material loss rate
The suspension drying method reduces particle breakage; fully enclosed conveying prevents dust leakage; online temperature control and moisture monitoring ensure process stability, reducing the probability of defective products.
(3) Optimized labor and maintenance costs
The conventional fluid bed dryer has a simple structure with no complex components, few vulnerable parts, and low maintenance frequency.
(4) Environmental friendly protection
Fully enclosed operation eliminates waste gas and dust emissions, requiring no additional exhaust gas treatment equipment;
Continuous and stable operation can ensure large-scale production, reaching environmental standard without additional rectification risks.