Development of an appropriate air nozzle and air saturator for the dissolved air flotation as a solid-liquid separation process in potable water treatment
| dc.contributor.author | Elvin Wei Jin, Tan | |
| dc.date.accessioned | 2014-11-14T07:50:13Z | |
| dc.date.available | 2014-11-14T07:50:13Z | |
| dc.date.issued | 2004 | |
| dc.description | Master | en_US |
| dc.description.abstract | The aim of this research is to develop and evaluate air injection nozzles and air saturators for the DAF process in solid- liquid separation in potable water treatment. These two components are the most critical in ensuring the feasibility and success of the DAF process. The efficiency of the air saturators as well as the performance of the air injection nozzle were evaluated. Two types of unpacked saturators were designed (the unpacked plate distributor (PD) saturator and the unpacked spray nozzle (SN) saturator) and the efficiency of these unpacked saturators were evaluated at different flow conditions. The parameters observed for the unpacked PD saturator were the saturator pressure and flow rate. It was found that the increase of flow rate would lead to the increase of saturator efficiency for the unpacked PD saturator. Saturator pressure however does not have a significant effect towards the unpacked PD saturator efficiency. The unpacked SN saturator showed reasonable efficiency when it was tested at a flow rate of 6 LPM for 500 and 600 kPa saturator pressure. An unexpected trend was observed for the effect of saturator pressure towards the saturator efficiency of the unpacked SN saturator. At lower operating pressure, the efficiency was observed to be higher when compared to higher operating pressure giving the mean saturator efficiency of 81% and 73% respectively. Comparison of the performance for the two saturators showed that the unpacked SN saturator outperformed the PD saturator for the two saturator pressures (500 kPa and 600 kPa) tested at a flow rate of 6 LPM. The optimum operating conditions for the unpacked SN saturator were found to be at 500 kPa saturator pressure and flow rate of 6 LPM giving 81% of mean saturator efficiency. Three designs of experimental air injection nozzles were evaluated in terms of air precipitation efficiency and mean bubble size produced through injection of supersaturated stream. The first air injection nozzle was a nozzle with one orifice and six distribution channels (equal diameter). The distributing channels are placed at the base of an impinging surface giving a 90° directional change. The distributing channels are located evenly at each mid-section of the hexagonal plane of the nozzle. The orifice was also threaded to increase friction of the traveling stream. The second design employed a conical divergence angle of 90° from the inner distribution channel to the outer distribution channel. The shorter passageway through the distributing channel would give an abrupt release and a quicker expansion of the supersaturated pressurized stream. The third design had 2 directional changes from the orifice to the six distribution channel located evenly at the mid-section of the hexagonal plane of the nozzle. The nozzles were tested on various flow conditions. Several parameters of test were observed to study the effect on the size of bubbles produced. Smaller size ratio of the orifice to distribution outlet were found to produce smaller bubbles for all three nozzle designs for two flow rates tested (2 and 4 LPM). Higher injection flow rate (4 LPM) were found to produce smaller bubbles for all three nozzle designs when compared to a low flow rate injection (2 LPM). The results indicated that the best nozzle design is nozzle type 2 (conical divergence feature) with an orifice to distribution outlet size ratio of 1:1 at a flow rate of 4 LPM produced the smallest mean bubble size (55 μm) when compared to other nozzles. The air precipitation efficiencies for all three nozzles were found to be reasonable (84%- 87%). Nozzle type 2 was later compared to a commercial air injection nozzle at a pressure of 600 kPa and flow rate of 4 LPM. The results indicated that the experimental nozzle produced smaller bubbles compared to the commercial injection nozzle. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/495 | |
| dc.language.iso | en | en_US |
| dc.subject | Industrial technology | en_US |
| dc.subject | Air nozzle | en_US |
| dc.subject | Water Treatment | en_US |
| dc.title | Development of an appropriate air nozzle and air saturator for the dissolved air flotation as a solid-liquid separation process in potable water treatment | en_US |
| dc.type | Thesis | en_US |
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