Pneumatic Spray Dryer

 Overview

  The pneumatic spray dryer is a type of spray drying equipment that uses high-speed airflow to exert a frictional splitting effect on the liquid film of the feed, thereby atomizing the liquid, drying it, and collecting the product. The high-speed gas can be steam or compressed air. The process of the solution being broken into fine mist occurs when the high-speed gas is ejected from the nozzle at a very high velocity (generally 200–300 m/s, sometimes even supersonic), while the outflow velocity of the solution is relatively low. Therefore, there is a fairly high relative velocity between the gas flow and the liquid flow. Friction is thus generated, causing the liquid to be drawn into long, slender filaments. These filaments quickly break at their thinner points, forming small spherical droplets. The lifetime of the filaments depends on the relative gas velocity and the viscosity of the solution. The higher the relative velocity, the finer the filaments, the shorter their lifetime, and the finer the resulting droplets. The higher the viscosity of the solution, the longer the filaments persist, and they often dry before breaking.

Working Principle

  Its core lies in the pneumatic atomizer (or nozzle). During operation, the feed liquid is pumped to the nozzle, while compressed air or steam is ejected from the nozzle at an extremely high velocity (typically up to 200 m/s, or even over 300 m/s). Due to the huge velocity difference between the two fluids, powerful friction and shear forces are generated, instantly tearing, stretching, and breaking the feed liquid into fine droplets. After entering the drying tower, these droplets undergo rapid heat exchange with heated hot air, usually evaporating moisture or solvent within a very short time (such as 10–30 seconds). The dried solid product then enters collection devices such as a cyclone separator along with the airflow, achieving gas-solid separation.

Features

  1、The pneumatic atomizer has a simple structure and low wear;
  2、Atomization of high-viscosity feed liquids;
  3、 Pneumatic atomization produces finer droplets;
  4、 The pneumatic atomizer offers high operational flexibility, meaning the processing capacity can be adjusted within a certain range, and adjusting the gas-liquid ratio can control the droplet size, thereby controlling the particle size of the finished product.

Applications

  It is mainly used for spray drying of ultrafine powders and high-viscosity materials, and is widely applied in industries such as pharmaceuticals, battery materials, and nanomaterials.

Flow Diagram