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A Mass Transfer Experiment Using Deoxygenation and Aeration of Water

Ramesh C. Chawla1 and Ali Pourhashemi2 1 Department of Chemical Engineering, Howard University, Washington, DC 20059 2 Dept. of Chemical & Biochemical Engineering, Christian Brothers University, Memphis, TN 38104

Abstract To demonstrate the phenomenon of mass transfer, an experiment was developed to measure the overall and individual mass transfer coefficients in the opposite processes of deoxygenation and aeration. Both these processes have practical applications in chemical, environmental and mechanical systems.

Streams of N2 (deaeration/deoxygenation process) or Air (aeration/oxygenation process) were bubbled through a semi batch reactor containing water. The contents of the reactor were mixed using an external recirculating pump to provide uniform conditions of concentration in the reactor. The dissolved oxygen concentration in water can be reduced from the saturation limit of 8-9 mg/L at room temperature to 1-2 mg/L at the end of deoxygenation cycle. In the reverse process of aeration, dissolved oxygen concentration was raised from 1-2 mg/L to the saturation limit.

Dissolved oxygen concentration, volume of aqueous phase, and flow rate and composition of incoming gas stream were continuously measured. Using appropriate mass transfer relationships, experimental data are analyzed for the determination of individual (kL and kg) and overall (KL and Kg) mass transfer coefficients based on liquid (L) and gas (g) phase resistances. Two sets of four mass transfer coefficients (kL, kg, KL and Kg), determined for each process; aeration and deoxygenation, provide a basis for comparison and discussion of results.

The experiment, developed from the Masters’ thesis of one of the authors, offers the chemical and other engineering students an opportunity to understand the theory and application of mass transfer phenomenon and can be performed in one laboratory session of three hours. Only air, nitrogen and water are used in the experiment. Use of potentially harmful chemicals is avoided, resulting in increased safety and cost savings in the purchasing and disposal of chemicals. The experimental setup is simple and inexpensive, and can be developed in-house. In addition to determination of mass transfer parameters, the experiment can also be used for open-ended design problems based on the results from the experiment.

Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition Copyright  2004, American Society for Engineering Education

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Chawla, R., & Pourhashemi, A. (2004, June), A Mass Transfer Experiment Using Deoxygenation And Aeration Of Water Paper presented at 2004 Annual Conference, Salt Lake City, Utah. 10.18260/1-2--13606