污染膜清洗条件优化及清洗动力学模型的建立

发布时间：2018-08-24 15:14

【摘要】：膜技术由于具有操作简单、效率高、节能环保、占地面积小等技术优点而在各工业领域得到广泛应用。然而,膜污染在膜分离过程中不可避免,膜清洗是解决这一难题的直接方法。本文针对膜生物反应器(MBR)中污染的微滤膜采取了水力预清洗与化学清洗相结合方法,建立了相应的动力学模型,并计算了不同操作条件(温度,操作压力,搅拌转速)对模型参数的影响贡献率。此外,还针对特种设备中灰尘沉积的聚砜膜,采用超声波清洗与化学清洗相结合的方法对其进行了清洗。得出如下结论:(1)对于MBR中污染膜的清洗过程而言:①次氯酸钠的清洗效果最好,其次是十二烷基磺酸钠和氢氧化钠;②膜的通量恢复率都随清洗剂浓度的增大先增大后趋于稳定;③膜的通量恢复率随清洗时间的增大先增大后趋于稳定;④膜的通量恢复率随温度的提高而增大;⑤膜的通量恢复率随操作压力的增大而减小;⑥膜的通量恢复率随搅拌速度的增大而略微增大。最终确定的最佳清洗方案为:在不施加压力的情况下,以0.5 wt%的次氯酸钠在400 rpm的搅拌下清洗15 min,清洗温度可据实际情况来选择。(2)对于被灰尘和油性物质污染的聚砜膜的清洗过程而言:①膜的通量恢复率随着超声电流的增大而增大;②膜的通量恢复率随着超声时间的增大而增大;③在先碱后酸清洗过程中,当柠檬酸清洗条件一定时,随着次氯酸钠浓度的增加,通量恢复率基本上呈先增大后减小的趋势,次氯酸钠质量浓度为0.3%时的清洗效果最佳;当次氯酸钠清洗条件一定时,随柠檬酸浓度的增加,通量恢复率的变化却没有规律性,0.3 wt%次氯酸钠与15 wt%柠檬酸对该污染膜的清洗效果最好;④先碱后酸的清洗效果优于先酸后碱;⑤超声清洗和化学清洗结合的清洗效果优于超声清洗和化学清洗;⑥膜的通量恢复率随着温度的增大先增大后减小。(3)基于Hom-Haas模型,本文提出了化学清洗动力学模型。该模型描述了化学清洗过程中通量恢复率随清洗时间和清洗剂浓度的变化关系。理论分析表明模型可行。将该模型用于MBR污染膜的化学清洗过程时可得到如下结论:模型能够准确描述次氯酸钠清洗过程中通量恢复率随清洗时间和清洗剂浓度的变化情况。模型预测值与新的实验数据的直观比较进一步证明了该模型的有效性。此外,还通过线性回归分析了各操作条件对模型预测值的贡献率。结果表明:模型参数m、n只与操作压力和温度的有关,而速率常数k则决定于操作压力、温度和搅拌转速。该模型能够准确描述氢氧化钠和十二烷基磺酸钠这两种清洗剂的清洗过程。此外,还通过线性回归分析了各操作条件对模型预测值的贡献率。
[Abstract]:Membrane technology has been widely used in various industrial fields because of its advantages such as simple operation, high efficiency, energy saving and environmental protection, small occupation area and so on. However, membrane fouling is inevitable in the process of membrane separation, and membrane cleaning is a direct method to solve this problem. In this paper, the method of combination of hydraulic precleaning and chemical cleaning is adopted for the microfiltration membrane fouled in membrane bioreactor (MBR), the corresponding kinetic model is established, and the different operating conditions (temperature, operating pressure) are calculated. The effect of stirring speed on the model parameters. In addition, the polysulfone membrane deposited in the special equipment was cleaned by the method of ultrasonic cleaning and chemical cleaning. The conclusions are as follows: (1) for the cleaning process of contaminated membrane in MBR, the cleaning effect of sodium 1 chlorite is the best, followed by sodium dodecyl sulfonate and sodium hydroxide; (2) the flux recovery rate of the membrane increased firstly with the increase of the concentration of cleaning agent, and then tended to stabilize with the increase of cleaning time. The flux recovery rate of the membrane increased with the increase of the cleaning time, and then the flux recovery rate of the membrane tended to increase with the increase of the temperature. (5) the flux recovery rate of the membrane decreases with the increase of the operating pressure, and the flux recovery rate of the membrane increases slightly with the increase of the stirring speed. The best way to clean it is to do it without pressure, The cleaning temperature of 0.5 wt% sodium hypochlorite for 15 min, can be selected according to the actual situation. (2) for the cleaning process of polysulfone membrane contaminated by dust and oily substances, the flux recovery rate of the 1 / 1 membrane is with ultrasonic electrolysis. The increase of flow; 2 the flux recovery rate of the membrane increases with the increase of ultrasonic time. When the cleaning conditions of citric acid are constant, the flux recovery rate increases firstly and then decreases with the increase of sodium hypochlorite concentration. The cleaning effect of sodium hypochlorite was the best when the mass concentration of sodium hypochlorite was 0.3.When the cleaning conditions of sodium hypochlorite were constant, with the increase of citric acid concentration, The change of flux recovery rate was not regular. The cleaning effect of sodium hypochlorite (0.3 wt%) and citric acid (15 wt%) on the fouled membrane was better than that on the first alkali and then the acid. (5) the cleaning effect of ultrasonic cleaning and chemical cleaning is better than that of ultrasonic cleaning and chemical cleaning. (3) based on the Hom-Haas model, the kinetic model of chemical cleaning is proposed. The model describes the relationship between flux recovery rate and cleaning time and concentration during chemical cleaning. Theoretical analysis shows that the model is feasible. When the model is applied to the chemical cleaning process of MBR contaminated membrane, the conclusion can be drawn as follows: the model can accurately describe the flux recovery rate of sodium hypochlorite cleaning process with the cleaning time and the concentration of cleaning agent. The validity of the model is further proved by comparing the predicted values with the new experimental data. In addition, the contribution rate of each operating condition to the predicted value of the model is analyzed by linear regression analysis. The results show that the model parameter MN is only related to the operating pressure and temperature, while the rate constant k is determined by the operating pressure, temperature and stirring speed. The model can accurately describe the cleaning process of sodium hydroxide and sodium dodecyl sulfonate. In addition, the contribution rate of each operating condition to the predicted value of the model is analyzed by linear regression analysis.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

【共引文献】