Geology topics
Michael Timmons
Publications and source records attributed to Michael Timmons.
Modeling gas transfer in a spray tower oxygen absorber
A computer model characterizing the performance of a spray tower oxygen absorption system was developed based on finite difference mass transfer calculations. Performance was assessed in terms of oxygen utilization, transfer efficiency, and economy. Pilot scale tests verified model assumptions and performance predictions. Simulation runs indicated spray tower head and oxygen feed requirements for desired changes in dissolved oxygen (DO) exceeded those required for packed column equipment. Spray tower performance was improved by increasing hydraulic loading from 35 to 85 kg m −2 s −1 and by increasing tower height from 1·25 to 2·50 m. The effluent DO concentration that minimized variable costs of oxygen transfer was lower in the spray tower than in the packed tower, indicating clean water use of the spray tower will be limited to moderate effluent DO requirement applications (DO <20 mg l −1 ).
Gas-phase axial dispersion in a spray tower
Gas-phase axial dispersion (mixing of the composition of the gas phase along the longitudinal axis) was characterized in an enclosed spray tower for purposes of establishing reactor type for the solute-solvent pair oxygen and water. Test condition variables were spray tower height (TH), 1·52, 2·03 and 2·54 m; hydraulic loading (HL), 44·2, 66·3 and 88·4 kg/m 2 s; the ratio of volumetric oxygen injection to water flow rate (G/L), 1·0, 2·5 and 5·0%; the ratio of volumetric bulk tower gas recirculation flow rate to water flow rate (BG/L), 0, 500 and 700%; and bulk tower gas recirculation direction, counter-current to and co-current to the water flow. Gas composition measurements (% O 2 ) made across the long axis of the tower under steady-state conditions provided 1020 independent observations and 240 gas composition profiles. Factors showing a significant effect ( P < 0·05) on gas composition were TH, HL, G/L and BG/L. Sample location as a percentage of TH did not have a significant effect on gas composition and accordingly profile slopes were not different from zero ( P > 0·05). Profile data indicate a completely mixed gas phase within the tower. The dispersion observed was attributed to the lack of a significant pressure drop along the axis of the reaction vessel, forces due to nozzle operation, and to bulk tower gas recirculation.