Porosity of spacer-filled channels in spiral-wound membrane systems: Quantification methods and impact on hydraulic characterization.
Porosity of spacer-filled channels in spiral-wound membrane systems: Quantification methods and impact on hydraulic characterization.
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DOI：
10.1016/j.watres.2017.04.034
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发表时间：
2017-08
期刊：
影响因子：
12.8
通讯作者：
A. Siddiqui;S. Lehmann;V. Haaksman;J. Ogier;C. Schellenberg;M. Loosdrecht;J. Kruithof;J. Vrouwenvelder;J. Vrouwenvelder
中科院分区：
文献类型：
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作者：
A. Siddiqui;S. Lehmann;V. Haaksman;J. Ogier;C. Schellenberg;M. Loosdrecht;J. Kruithof;J. Vrouwenvelder;J. Vrouwenvelder
填充间隔器的进料通道的孔隙率影响螺旋缠绕膜系统的流体力学性能，并影响系统的整体性能。因此，为了了解和改善用于海水淡化和废水回用的螺旋缠绕膜系统的流体力学，需要对进料通道孔隙率的影响进行准确的测量和详细的了解。这项研究的目的是评估不同几何形状和厚度的进料隔板的孔隙度测量技术的准确性，以及使用不准确的方法进行流体动力学预测的后果，这可能会影响渗透液的生产。应用了6种技术测量孔隙率，即基于间隔链计数的3种体积技术与立方体(SC)、圆柱体(VCC)和椭球体积计算(VCE)相结合，以及基于体积位移(VD)、重量和密度(WD)和CT扫描的3种独立技术。介绍了CT法作为其他5种已有和实际应用的方法的替代方法，用于测量孔隙率的6个馈送间隔装置在灯丝厚度、灯丝之间的夹角和网目尺寸上都不同。研究结果显示，用这六种方法测量的孔隙率存在差异。显微技术SC、VCC和VCE的结果与VD、WD和CT的测量结果有显著偏差，显示出所有间隔器类型的孔隙度值相似。根据孔隙度测量技术的最大偏差从−6%到−+6%，(I)线速度偏差分别为−5.6%和+6.4%，(Ii)压降偏差分别为31%和+43%，说明准确测量孔隙度的重要性。由于精度和标准差的原因，在确定充填间隔槽孔隙度时，应采用VD和WD方法，而对于数值模拟，推荐使用CT方法。孔隙度与流速呈线性关系，对压降的影响呈超线性关系。准确的孔隙率数据是评估螺旋缠绕膜系统中进料间隔器性能的关键。填充间隔物的进料通道的孔隙率对膜的性能和生物污染影响很大。
The porosity of spacer-filled feed channels influences the hydrodynamics of spiral-wound membrane systems and impacts the overall performance of the system. Therefore, an exact measurement and a detailed understanding of the impact of the feed channel porosity is required to understand and improve the hydrodynamics of spiral-wound membrane systems applied for desalination and wastewater reuse. The objectives of this study were to assess the accuracy of porosity measurement techniques for feed spacers differing in geometry and thickness and the consequences of using an inaccurate method on hydrodynamic predictions, which may affect permeate production. Six techniques were applied to measure the porosity namely, three volumetric techniques based on spacer strand count together with a cuboidal (SC), cylindrical (VCC) and ellipsoidal volume calculation (VCE) and three independent techniques based on volume displacement (VD), weight and density (WD) and computed tomography (CT) scanning. The CT method was introduced as an alternative for the other five already existing and applied methods in practice.Six feed spacers used for the porosity measurement differed in filament thickness, angle between the filaments and mesh-size. The results of the studies showed differences between the porosities, measured by the six methods. The results of the microscopic techniques SC, VCC and VCE deviated significantly from measurements by VD, WD and CT, which showed similar porosity values for all spacer types.Depending on the maximum deviation of the porosity measurement techniques from −6% to +6%, (i) the linear velocity deviations were −5.6% and +6.4% respectively and (ii) the pressure drop deviations were −31% and +43% respectively, illustrating the importance of an accurate porosity measurement. Because of the accuracy and standard deviation, the VD and WD method should be applied for the porosity determination of spacer-filled channels, while the CT method is recommended for numerical modelling purposes. The porosity has a linear relationship with the flow velocity and a superlinear effect on the pressure drop. Accurate porosity data are essential to evaluate feed spacer performance in spiral-wound membrane systems. Porosity of spacer-filled feed channels has a strong impact on membrane performance and biofouling impact.