Abstract:

In order to analyze the physical field distribution and droplet movement pattern inside centrifugal spray dryer, a three-dimensional steady-state mathematical model of the spray drying process was established by using the Euler-Lagrange method coupling the single-droplet drying model. Experiments were conducted on a pilot-scale centrifugal spray drying system using 70% (wet basis) maltodextrin solution as the feedstock, and the temperature distribution inside the dryer was measured. The results showed that the simulated temperatures at characteristic points agreed well with the experimental values with 1.84% of average relative error, demonstrating the accuracy and reliability of the simulation results. Examination of continuous phase transfer process revealed that the three-dimensional physical field showed a cylindrically asymmetric distribution, having higher temperatures, lower water vapor contents, and greater airflow velocities at the center area of the tower. Analysis of droplet movement trajectory and drying process found that larger droplets had longer drying times, while smaller droplets had shorter drying times but longer residual time due to the occurrence of swirling and backflow. The effects of inlet air temperature, atomization disc rotation speed, and inlet air angle on the physical field distribution and droplet drying behavior inside the tower were studied by simulation, and the mass and heat transfer mechanism of spray drying process were analyzed.

Key words: spray drying, numerical simulation, single-droplet drying kinetics, motion trajectory, mass and heat transfer

摘要：

为了分析离心式喷雾干燥塔内物理场分布和液滴运动规律，采用欧拉-拉格朗日法，耦合单液滴干燥模型，建立了喷雾干燥过程的三维稳态数学模型。以70%（湿基）麦芽糊精溶液为原料液，在中试喷雾干燥系统上进行实验，测定了塔内温度分布。结果表明，模拟的塔内特征点温度与实验结果吻合良好，平均相对误差为1.84%，验证了模拟结果的准确性和可靠性。考察塔内连续相传递过程发现，三维物理场分布不是轴对称的，塔中心区域具有较高的温度、较低的水蒸气含量和较大的气流速度。分析液滴运动轨迹和干燥过程发现，较大的液滴干燥时间较长，较小的液滴干燥时间短但由于发生回旋返混停留时间较长。模拟研究了进风温度、雾化盘转速和进风角度对塔内物理场分布和液滴干燥行为的影响，分析了喷雾干燥过程的传质传热机理。

关键词: 喷雾干燥, 数值模拟, 单液滴干燥动力学, 运动轨迹, 传质传热