直接接触式膜蒸馏工艺浓缩尿素溶液的研究

Study of direct contact membrane distillation for the concentration of urea solution

采用直接接触式膜蒸馏工艺浓缩尿素溶液,考察了尿素浓度和原料液温度对膜蒸馏过水通量以及尿素截留率的影响。结果表明,原料液温度的提高可以大幅提升膜通量,但当尿素溶液温度达到60℃时,尿素的水解程度提高,不利于膜对尿素的截留;溶液中尿素浓度的提高使溶液的蒸汽压有所降低,从而降低了膜蒸馏的过水通量,但总氮截留率进一步提高;膜表面液体流速对膜通量的促进作用有限,对尿素的截留效果几乎没有影响。在实验条件下,尿素的截留率保持在99.82%～100%,说明膜蒸馏工艺在尿素溶液的浓缩和含尿素废水的处理中具有很好的应用前景。

A direct contact membrane distillation process was used for concentrating urea solution.Water flux and retention rate of urea were studied as functions of the urea content and feed temperature.The results showed that the water flux increased significantly with the feed temperature.When temperature of the urea solution reached 60 ℃,the hydrolysis of urea was enhanced;thus its retention rate revealed decline.Increase of the urea content reduced the vapor pressure of the feed solution,which led to decrease of the water flux while increase of the nitrogen retention rate.The feed flow velocity had limit enhancement on the membrane flux and had a negligible effect on the urea rejection.In this study,the urea retention rates of 99.82% ～ 100% were obtained.It demonstrated that the membrane distillation had good prospects on concentrating urea solution and treatment of urea wastewater.