ABSTRACT

During the late 1970s pilot mining tests carried out on manganese nodules in the Pacific and metalliferous mud in the Red Sea demonstrated the technical feasibility of deep sea mining operations. However, the production of manganese nodules on a commercial scale is subject to numerous technical problems. As a result a German/French joint development project has been underway since 1985 into the following key points; nodule pick-up device, locomotion of self propelled collectors, hydraulic lifting of nodules. This paper presents the scope of this R+D program, its main results to date and future prospects.

INTRODUCTION

Ten years ago deep sea mining, i.e. the production of ore-bearing minerals from the deep sea was at a zenith and enjoyed a large amount of interest worldwide. Spring 1978 saw the first continuous pilot scale production of manganese nodules from the floor of the Pacific ocean (OMI Pilot Mining Test) and May 1979 saw the first production of metalliferous sediments from the floor of the Red Sea (Saudi Sudanese Red Sea Commission, Preussag, Pre Pilot Mining Test)..

We now know that these forecasts were incorrect. The start of commercial deep sea mining has moved further away for a number of reasons of which price development in the metal market was undoubtedly one of the more important. This does not mean that development of deep sea mining technologies has ground to a complete standstill. On the contrary; the number of countries in which corresponding research is underway has increased. The USA, Japan, France and Germany have been joined by the USSR, India and Finland. For some years now development work in Germany has concentrated on the development and optimization of critical components and subsystems of deep sea mining techniques, whereby the demand for environmentally non-disruptive production methods has increasingly been taken into account. The following report concentrates on this work where by manganese nodule production technologies represent the major focus.

There follows a brief review of the pilot mining tests executed in the late seventies as an outline of the scope of work.

BRIEF REVIEW OF PILOT OPERATIONS

The first successful pilot mining test on manganese nodules was carried out in 1978 by OMI (Ocean Management Inc.) in which 800 tonnes of nodules were recovered from the floor of the Pacific ocean.

This was a joint venture involving American, Japanese, Canadian and German companies (Fig. 1).

The mining system comprised:

  • the converted drill ship. SEDCO 445

  • a 5500 m long pipe string

  • a towed collector

Two types of hydraulic lifting systems were tested successfully:

  • an air lift system

  • a pump lift system (multistage mixed flow pumps)

Two different nodule collector concepts were tested (Fig. 2):

  • hydraulic

  • mechanical

The overall system design had a mining rate of around 30 t/h.

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