操作压力对过热蒸汽流化床干燥的影响

Effect of operation pressure on superheated steam fluidized bed drying

针对操作压力对过热蒸汽流化床干燥过程中蒸汽-颗粒物料两相流动特性、传热传质特性的影响具有非线性特征问题,基于油菜籽过热蒸汽流化床干燥过程的轴对称二维非稳态数学模型,仿真研究了操作压力对颗粒物料干燥动力学的影响规律,对负压、常压附近和高压环境下操作压力与最大干燥速率之间的关系进行了定量分析,并得到了进口过热蒸汽温度和流速设定条件下颗粒物料过热蒸汽流化床干燥的最佳操作压力参数值。数值模拟结果表明:进口过热蒸汽温度358K、流速2.5m/s、颗粒物料直径1.0mm时,过热蒸汽流化床干燥最佳操作压力为0.02MPa;进口过热蒸汽温度403K、流速2.5m/s、颗粒物料直径1.0mm时,最佳干燥操作压力为0.10MPa;进口过热蒸汽温度443K、流速2.0m/s、颗粒物料直径2.0mm时,最佳干燥操作压力为0.2 MPa。

In superheated steam fluidized bed drying, the operation pressure significantly influences the heat and mass transfer and the steam-particle two-phase flow with nonlinear characteristics. Base on the two-dimensional unsteady model of drying process of rapeseeds, numerical simulation was carried out to investigate the influence of operation pressure on the kinetics of superheated steam fluidized bed drying. Under negative pressure, near atmospheric pressure and high pressure, the relationship between the operation pressure and maximum drying rate was quantitatively analyzed respectively. For superheated steam fluidized bed drying of granular products with the inlet steam temperature and flow rate, the values of the optimal operation pressure were obtained. Simulation results show that, with inlet steam temperature of 358 K, flow velocity of 2.5 m/s and particle diameter of 1.0 mm, the optimal pressure is 0.02 MPa; with inlet steam temperature of 403 K, flow velocity of 2.5 m/s and particle diameter of 1.0 mm, the optimal pressure is 0.1 MPa; with inlet steam temperature of 443 K, flow velocity of 2.0 m/s and particle diameter of 2.0 mm, the optimal pressure is 0.2 MPa.