Analyse par utilisation de l'oxygène de différentes configurations d'un pilote ciblant la diffusion d'un gaz dans l'eau

Abstract

There is a plurality of system for dissolving a gas in a goal of water treatment. The purpose of this work is to develop a reference technology. The main objective is to empirically validate the technical interest to work on the area of diffusion of the gas in water. To do this, a pilot is built and calibrated. A basic configuration of the pilot is set, the free jet mode. Then different configurations (nozzle mode, static mixers mode, Rachig rings mode, LTCP mode) changing a diffusion aspect of the free jet mode are tested. The oxygen gas is used for testing the water reoxygenation at different G/L (v/v) ratio. The sodium sulfite is used for deoxygenation and the monitoring of a tracer. A fast capture camera served the measurement of parameters on the gas bubbles. It should be noted that the increase of the G/L ratio in the free jet mode increases the ability to oxygenate. In return, the transfer efficiency of the oxygen mass added per liter of treated water decreases. The average size of bubbles observed as well as their shape irregularity step up as the G/L ratio increase. At a first step of reoxygenation of the test water at G/L = 0.08, the ability to dissolve compared to the background noise indicates that the free jet mode is (19.0 ± 0 5) % more effective followed at (22 ± 2) % by the free jet mode with a restriction on water flow. Adding a nozzle makes that percentage passed to (26 ± 1) % and the addition of static mixers to (31 ± 2) %. Mode with Rachig rings has the opposite effect and lowers the percentage to (15 ± 2) % while shortening the primary contact area (LTCP mode) maintains a performance around (18 ± 3) %. Another observation at that step, the transfer efficiency of oxygen added per liter of treated water is of (7 ± 3) % for the free jet mode, of (16 ± 2) % in the free jet mode with restriction, of (19 ± 1) % for the nozzle mode, (23 ± 1) % for the mode with static mixers, (11 ± 2) % for Rachig rings mode and (13 ± 2) % for LTCP mode. The tracer monitoring indicates that the nozzle and the static mixers promote mixing and the ability to interact. These two modes also point the interest to evenly distribute the water pressure along the circuit and increase the gas pressure. Then we must continue to work on the diffusion area of the gas while performance must be evaluated according to an optimal combination of multiple criteria. It is suggested to test extend of the primary contact zone of the pilot, to measure the combined effect of the nozzle and the static mixers and to verify the usefulness of the venturi injector as the gas is injected under pressure. The case of the Rachig rings should be further on the assumption of oxygen retention in the surface of the plates as well as the work started using the fast capture camera as a tool for measuring the distribution and the bubble size.

Date	17 Mar 2014
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Robert Hausler (Supervisor)