曝气条件对等温层曝气器充氧性能的影响

分析了等温层曝气器曝气室内气泡—水接触界面的氧传质过程,确定了表征氧传质效果的各项参数,在双膜理论基础上建立了等温层曝气充氧动力学模型及其解析方法.应用本模型预测了美国Prince湖等温层曝气器的充氧效果.根据等温层曝气充氧动力学模型的预测结果,随曝气量的增加和气泡直径的减小,氧总传质系数和氧传质速率均增大;随曝气量和气泡直径的增大,曝气效率下降.在等温层曝气器结构固定的情况下,减小气泡直径和增加水深均有利于改善曝气室的充氧效果,尤其是当气泡直径达到μm级别时;当曝气量超过一定临界值0.06m3/s时,曝气室的充氧效果略有削弱.根据曝气量对氧传质速率、曝气效率和单位时间内曝气室的充氧量的影响特性曲线,可确定等温层曝气器的优化运行条件.

Effects of aeration conditions on the oxygenation performance of a hypolimnetic aerator

Oxygen transfer process from the air bubbles to the water was mainly analyzed in the aeration chamber of a hypolimnetic aerator, parameters characterizing the effectiveness of oxygen transfer were properly determined,a dynamical model of oxygen transfer for hypolimnetic aeration was developed based on the double-layer theory. The effectiveness of oxygenation was well predicted using the developed dynamical model of oxygen transfer for hypolimnetic aeration. Based on the predicted results using the dynamical model of oxygen transfer, when the air flowrate increased or the bubble diameter decreased, the oxygen transfer coefficient and the oxygen transfer rate increased. When the air flowrate and bubble diameter increased, the aeration efficiency decreased. Under fixed configuration conditions of a hypolimnetic aerator, decreasing the bubble diameter and increasing the water depth above the air diffusors would be helpful to improve the effectiveness of oxygenation in the aeration chamber of a hypolimnetic aerator, especially when the bubble diameter was of micrometer level. When the air flowrate increased to a critical value of 0.06m3/s, the effectiveness of oxygenation in the aeration chamber would become weaker. Judged from the influencing characteristic curves of air flowrate on the oxygen transfer rate, aeration efficiency and oxygen input of the aeration chamber per unit time, the optimized operational conditions of a hypolimnetic aerator can be determined.