卷烟厂废水反渗透分离过程的数值模拟研究

Numerical Study on the Reverse Osmosis Separation Process of Cigarette Factory Wastewater

摘要: 基于反渗透分离的高品质再生水回用是提高卷烟厂水资源利用效率的重要途径。以某卷烟厂废水处理产生的回用水作为进水水质条件，通过计算流体力学软件建立反渗透分离用户自定义函数模型，考察了进水温度和压力对反渗透分离过程产水与脱盐效果的影响。模拟结果表明：进水压力对膜面温度和流道内压力分布的影响明显弱于温度；浓水流道内沿程压力损失沿着膜片长度方向逐渐累积增大，进水压力升高使更多水透过膜、浓水流量减小，故总压力损失随进水压力升高而降低。膜元件边界层内无机盐浓度沿轴向增高，产生浓差极化现象，致使膜元件尾端容易受到结垢影响。随着进水温度或压力升高，边界层内无机盐浓度升高。膜元件边界层内存在明显的通量梯度；进水压力提高导致边界层内通量梯度和最大通量均增加。反渗透膜的过膜水通量沿轴向逐渐递减，且随着进水压力升高，过膜水通量增加，同时其衰减程度提高。进水压力对浓差极化现象和过膜水通量的影响强于温度。研究结果可为实际进水条件下混合盐溶液反渗透分离过程流道内的流动特征和无机盐分布及运行优化提供参考。

Abstract: High-quality reclaimed water reuse based on reverse osmosis (RO) separation is an important route to improving water resource utilization efficiency in cigarette factories. Taking the reclaimed water produced by the wastewater treatment of a cigarette factory as the influent water, a user-defined function (UDF) model for RO separation was established using computational fluid dynamics (CFD) software, and the effects of influent temperature and pressure on the water production and desalination performance of the RO separation process were investigated. The simulation results show that the influence of influent pressure on the membrane surface temperature and the pressure distribution in the flow channel is significantly weaker than that of temperature. The head loss in the concentrate channel gradually increases along the axial direction of the membrane element. As the influent pressure rises, the head loss gradually declines. The concentration of inorganic salts in the boundary layer of the membrane element increases elevates along the axial direction, resulting in concentration polarization, making the end of the membrane element susceptible to scaling. With the increment of influent temperature or pressure, the concentration of inorganic salts in the boundary layer rises. An obvious flux gradient in the boundary layer of the membrane element exists. As the influent pressure increases, both the flux gradient and the maximum flux in the boundary layer rise. The permeate flux of the RO membrane gradually drops along the axial direction, and with the increment of influent pressure, the permeate flux increases along with the increase of its attenuation degree. The influence of influent pressure on concentration polarization and permeate flux is stronger than that of temperature. The work provides a reference for the flow characteristics and inorganic salts distribution in the flow channel as well as for operational optimization.