In manganese nodule mining hydraulic lifting is one of the methods of conveying the nodules from the ocean floor to the surface. The hydraulic behaviour of such large solids in a tube is different from what we know about small grains and suspensions. This paper deals with the hydraulic behaviour of uncrushed nodules in a tube. Hydraulic behaviour means chiefly: Velocity of the solids, spatial concentration and pressure drop, their interrelation with the water velocity and the diameter of the solids. Tests have been made. In the first series these parameters were investigated with solids of uniform diameter (homogeneous mixtures). The second series dealt with solids of different sizes (inhomogeneous mixtures). Empirical equations based on dimensionless numbers have been established in order to render the test results applicable to larger systems. With the solid velocity and the frictional factors known, the set of equations can be used to compute and design a conveyer system to a high degree of reliability.
Vertical hydraulic lifting has been used in the mining industry to convey coal iron ore from the pits to the surface.1–5 In marine mining of manganese nodules special conditions area given. International efforts are being made to solve both technical and jurisdictional problems related to this new industry.6–7
The complicated designing procedure for a mining system can be reduced to some simplifying relatives, which are displayed in the "interdependence triangle" of Fig. 1. A production goal for the nodules has been fixed. The reservoir and environmental parameters of the mining site are the main input data. The technical response is given by the installed mining equipment and the mode of operation. This has to be chosen such that the performance and optimization parameters can be computed. The loop is now closed. If one of these corner marks is changed it will affect the others.
Two general considerations apply to a mining and conveyer system:
The nodules should not be crushed to a greater extent than inevitable in the collector on the ocean floor in order to reduce the dewatering costs on the mining ship.
The diameter of the conveyer tube should be kept small in order to reduce the drag of the string in the ocean current.
For the designer of a mining system a set of equations is necessary for doing the computer work. Therefore, the hydraulic behaviour of the nodules in the conveyer tube must be known.
It was found in previous studies that the known relations of slurry conveyance cannot simply be transferred to the large solids in question. Therefore, a research program was started in which special attention was payed to
the study of the physical and technical phenomena during the process of conveyance of large solids,
establishing empirical equations for the calculation of both the performance and the optimization of a hydraulic conveyer system.
