大豆蛋白多级分段干燥过程仿真研究Simulation of soy protein multi-stage segmented drying process

为解决喷雾干燥法制备大豆蛋白粉常用单级干燥工艺干燥效果不理想、生产工艺参数难控制的问题，研发压力式喷雾干燥塔搭配流化床的多级分段干燥工艺，并基于计算流体力学（CFD）方法，建立相关结构模型及设备内液滴离散相、气体连续相等数值计算模型。基于设备三维物理模型，建立流体域模型，通过ANSYS Fluent 2020R2软件分别对传统单个压力式喷雾干燥塔干燥（单级干燥）和多级分段干燥过程进行仿真，对比分析单级干燥和多级分段干燥的效果，并以流化床出风温度、平均水蒸气含量为考察指标，采用响应面法优化多级分段干燥工艺参数。结果表明：相较于单级干燥，多级分段干燥可以更有效地去除物料中的水分，同时又缩短了总干燥时间，可以降低物料内部的水分梯度，实现更均匀的水分含量，更高效地利用热能，减少了整个干燥过程的能耗和运行成本；大豆蛋白多级分段最佳喷雾干燥工艺参数为干燥塔进风温度179.92 ℃、进料压力19.89 MPa（进料流速190.32 m/s）、流化床进风温度101.58 ℃，在此条件下流化床出风温度为6863 ℃，平均水蒸气含量为1.503%。实际工程应用中，调整干燥塔进风温度为172 ℃、进料压力为20 MPa、流化床进风温度为105 ℃，所对应干燥系统出风温度为72 ℃，产品干基含水率在7%左右，干燥效果较好，这与仿真结果基本吻合。综上，基于CFD方法的多级分段干燥过程仿真研究，具有较高的可行性和有效性。 To address the issues of suboptimal drying effectiveness and difficult-to-control process parameters in conventional single-stage spray drying for soy protein powder, a multi-stage segmented drying process was developed, integrating a pressure spray drying tower with a fluidized bed. Based on Computational Fluid Dynamics (CFD), structural models and numerical models for the discrete phase of droplets and the continuous gas phase within the equipment were established. A fluid domain model was constructed using the 3D physical model of the equipment. Simulations of both the traditional single pressure spray tower drying (single-stage drying) and the multi-stage segmented drying process were conducted using ANSYS Fluent 2020 R2 software to compare and analyze their effectiveness. The fluidized bed outlet air temperature and average water vapor content were used as response indicators, the response surface methodology was employed to optimize the multi-stage drying parameters. The results demonstrated that compared to single-stage drying, the multi-stage segmented drying more effectively removed moisture from the material, shortened the total drying time, reduced internal moisture gradients, achieved more uniform moisture content, utilized thermal energy more efficiently, and lowered overall energy consumption and operational costs. The optimal parameters for the multi-stage segmented spray drying of soy protein were determined as follows: drying tower inlet air temperature 179.92 ℃, feed pressure 19.89 MPa (corresponding to a feed flow velocity 190.32 m/s), and fluidized bed inlet air temperature 101.58 ℃. Under these conditions, the predicted fluidized bed outlet air temperature was 68.63 ℃, and the average water vapor content was 1.503%. In practical engineering applications, adjusted parameters as drying tower inlet air temperature 172 ℃, feed pressure 20 MPa, and fluidized bed inlet air temperature 105 ℃,resulted in a corresponding drying outlet air temperature of 72 ℃ and a final product dry-basis moisture content of approximately 7%, indicating good drying performance. These practical outcomes aligned well with the simulation predictions. In conclusion, the CFD-based simulation of the multi-stage segmented drying process demonstrates high feasibility and effectiveness.