Removal Of Dissolved Oxygen From Water Using Hollow Fiber Membrane Contactor

Dissolved oxygen refers to the oxygen that is dissolved in water. The concentration of dissolved oxygen in water is required to maintain at a very low level for use in various industrial fields. Current methods of removing oxygen include thermal method, vacuum method, stripping method, chemical method, and so on. However, they all more or less suffer some drawbacks.Recently, a new method of dissolved oxygen removal has been developed, which is called the hollow fiber membrane contactor. This method is a combination of conventional degassing method and the membrane technology. The use of a membrane contactor in comparison to more traditional physical methods has many advantages: a large surface area per unit volume; fast mass transfer rates; independent control of phase flow rates; no dispersion between phases and the possibility of a modular construction. These advantages make the membrane contactor an attractive choice over other available methods. At present, there are only a few domestic researchers doing some work in this area, and this method needs to be further investigated to be used widely in the industry.In this paper, home-made polypropylene hollow fiber membrane contactors are used to remove dissolved oxygen from water. The influence of vacuum level, water velocity, temperature, and effective length of hollow fiber membrane on the oxygen removal ratio is investigated for the lumen side flow and shell side flow, respectively. The results show that (1) the dissolved oxygen removal increases with the increase of vacuum level for both lumen side flow and shell side flow; (2) water flow rate has a different influence on oxygen removal at different flow rate range; (3) temperature nearly has no effect on dissolved oxygen removal, but when the temperature is increased, both the concentrations of oxygen in inlet and outlet water will decrease, which is beneficial to meet the oxygen concentration requirement given the same removal; (4) the effective length of the hollow fiber membrane does have some effect on the dissolved oxygen removal, and the removal increases with the length of the membrane.In this paper, the influencing factors for the mass transfer coefficient are also investigated, and the result shows that the mass transfer coefficient obeys the same rule as that for the removal ratio, and the theoretically calculated mass transfer flux is larger than the measured mass transfer flux. The reasons for these phenomena are explored. In addition, the Sherwood numbers are obtained for both the lumen side flow and shell side flow.