An Air-Lift Pump has attracted special interest as one of the lifting techniques for marine mineral resources, because of its simplicity and no underwater moving parts for the pump. The experimental and theoretical studies on this pump-have been also actively done in recent years.
The authors carried out the fundamental experiments in indoor apparatus and larger scale of field test in the sea, in order to grasp its lifting characteristics of solids, and more over tried to compare the measured values of lifted solids weight with its calculated ones which were the theoretically derived by applying the momentum equation to the pump model. Concerning the indoor experiments (pipe length: l3.5m), the lifted volume of water and solids and friction head loss were measured by the change of pipe dia. (D=46.7 mm, 75.7 mm, 129.5 mm), pipe inclination (8=90°, 70°, 50°), physical properties of solids and conveying fluids.
Concerning the field test in the sea, the lifted volume of water and solids and friction head loss were also measured in the pump with 155.4 mm pipe dia. and about 40 m pipe length, for the comparison with the indoor experimental results. The solids used in the sea water test were simulated manganese nodules with 36.3 mm particle dia. and 1.96 specific gravity.
In this paper, the fundamental design criteria for the lifting of solids by air-lift pump are clarified on the basis of these experimental and theoretical results.
The air-lift pump has been remarked as one of the effective lifting techniques for marine mineral resources, as it has advantages comparing with other pumps, such as its simplicity and no moving parts except the air compressor. But the systematic research on the air-lift pump has been scarely done, so that studies of Kawashima &Noda, 1)2), Okayama & Yagi3) and Weber4) are only available.
The authors grasped the influence of following factors on the lifting characteristics of air-lift pump, through the indoor and seawater test.
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pipe diameter, pipe inclination and pipe length
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physical properties of solids
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specific weight of conveying fluid
In addition, the theoretical equations 5) 6) for lifted solids weight was induced by the momentum theory, and with this result, the comparison between calculated and measured values was made, and furthermore, the examples of numerical calculation on its lifting characteristics were also indicated.
Fig. 1 shows the schematic experimental apparatus. The unforced suction device was adopted for the solids feeder, and with the rotating drum containing solids rotated by hydraulic motor, the solids surface smoothed by the scraper ® were sucked into the suction pipe (6). As supplying the air into the pipe by the air injector, the solids began to ascend in the pipe to be blown off into the connecting pipe and then proceeded through the flow split pipe (16) and the return pipe (11) to be deposited into the rotating drum, and then circulated to the suction again.
