ABSTRACT

The paper describes a novel method for lifting manganese nodules from the ocean floor to the water surface by means of capsules in a vertical conduit.

A mathematical model for vertical capsule transport is given, which is checked by experiments in vertical pipes having a diameter of 0.07 m. and 0.3 m. Based on these test results a deep ocean mining system is designed with emphasis on low energy requirements and high reliability.

Test results in the paper show that the vertical transport of the proposed system can be achieved with a much higher efficiency than the reported data for airlifts, jetpumps and underwaterpumps, which makes the system attractive in view of energy requirements. The dual pipe system consists of a vertical 1 m diameter falling pipe ill which the empty capsules are transported downward and a 1 m diameter raising pipe in which the filled capsules are lifted. The underwater filing station is executed as a very simple filling point with elimination of complicated locks, thus achieving a high degree of reliability.

INTRODUCTION

Vertical transport of ore from the sea-bottom to the sea surface can be accomplished by means of a pipeline. This is also the case for lifting manganese nodules. A great number of 1,2,3 the proposed vertical lifting systems for manganese nodules deals with pipeline transport especially because of the reliability and the simplicity of this method. A drawback of slurry transport for this purpose is the high velocity that has to be maintained in the conduit to keep the nodules moving. Especially large nodules have a considerable settling velocity thus requiring a high water velocity in the pipe.

These high transport velocities can cause large pressure drops and high, energy consumption, depending on the pumping method applied. That is the reason that in the Mechanical Engineering Department laboratory of the Twente University of Technology a project was started for the development of a manganese nodule mining system with emphasis on high reliability and low energy requirements. This was achieved by selecting a pipeline system in which the transport velocity could be kept moderate. Such a low velocity vertical transport system is possible by using a capsule pipeline. Capsules can be pumped in a pipeline at a considerable lower velocity than the required velocities in slurry pipelines. For this purpose the capsules can be cylinders without covers. The diameter of the capsule is about 95 to 98 %of the diameter of the pipeline. These cylinders can easily be moved in the pipeline by a waterflow. The difference between vertical slurry transport and capsule transport is depicted in figure 1.

For designing capsule pipeline systems the designer needs mathematical models to predict especially capsule velocities, pressure drops and energy requirements. For this reason a simplified mathematical model for vertical capsule transport is introduced.

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