Deep Ocean Resources

The deep oceans have abundant mineral resources like Polymetallic nodules; cobalt rich manganese crust and hydrothermal deposits.Utilising this mineral wealth for the benefit of mankind will be the focus of ocean mining activities in future.Polymetallic nodules have economically valuable metals such as Copper, Cobalt, Nickel and Manganese and are viewed as potential resources for the depleting land resources and increasing demand.

Area Allocated:

The deep oceans have abundant mineral resources like Polymetallic nodules; cobalt rich manganese crust and hydrothermal deposits.Utilising this mineral wealth for the benefit of mankind will be the focus of ocean mining activities in future.Polymetallic nodules have economically valuable metals such as Copper, Cobalt, Nickel and Manganese and are viewed as potential resources for the depleting land resources and increasing demand.

Background of the Project

There are 380 million tons of nodules in the retained Indian Pioneer area. Development of deep sub-sea technology for mining these resources is a major challenge, considering the high pressure environment and very soft soils. NIOT has been working on a mining concept where a crawler based mining machine collects, crushes and pumps nodules to the mother ship using a positive displacement pump through a flexible riser system.

NIOT, Deep Sea Technologies group has been given a mandate to develop an Integrated Mining System for mining Polymetallic nodules from a depth of 5000-5500 m by Ministry of Earth Sciences (MoES), Govt of India under Deep Ocean Mission (DOM) programme. The work has been taken up in phases.

Mandate

Deep sea Mining -Progressive developments:

Deep sea mining of manganese nodules from soft ocean floor at 5000 to 6000 metres depth is a major technological challenge. India has been working on developing this complex technology in a phased manner. To minimize development costs and associated risks, initial efforts are focused on realization and qualification of machinery for shallow waters, followed by further development of machinery in deep waters.

As a first step, an Underwater Mining system operable at 500 meters water depth was developed. An initial study was done on the various deep sea mining and flexible riser concepts. The mining machinewas designed to operate on soft seabed and has special track belts with involute track belts to compact the seabed during locomotion.Underwater mining system with a flexible riser concept was validated in the Indian seas at 410m water depth. Further the mining machine was upgraded with crusher, nodule pickup and collection unit and was demonstrated at 510m water depth off the coast of Malvan

Optimisation and design of an integrated mining system for Polymetallic nodules from depths of 5000-6000m depends on the in-situ measurements of the sea floor soil properties. An in-situ soil tester capable of operation at 6000m water depth was developed by NIOT and demonstrated at 5462m water depth at the Test mine site (TMS), CIOB and used for further survey activities.

Pumping studies

Locomotion demonstration at 5270m water depth

The mining machine was tested for locomotion and maneuverability at the central Indian Ocean Basin (CIOB) at the depths of 5270m. The primary objective of the trials was to test seabed locomotion/ traction capability on soft soil and the functionality of the various systems, viz. mechanical moving parts, hydraulic power unit, electrical systems and the instrumentation, at the extreme ambient hydrostatic pressures and very low temperatures of 1 - 4 deg C.The machine was operated extensively, covering a cumulative distance of over 120 m with 2.5 hours of operation on the sea bed at depths of 5270m. This achievement records the first tethered sea bed moving machine to operate at this depth.

Proposed work:

On completion of locomotion sea trials of the mining machine at CIOB, The machine is being augmented with an indigenously designed mechanical pickup and collector system for collection and conveying of collected nodules from the sea floor to the pumping system. A crusher and pumping system is being installed on the machine to convey the crushed nodules to the pump frame which is suspended from ship by the umbilical cable. The planned mining machine, apart from the locomotion system, would have a rake type nodule collection system at the advancing end of the machine and a nodule crusher, feeder and slurry pumping system.

Initially it is proposed to conduct the sea trial without the pumping station, where the collected nodules shall be discharged locally at a height of 50-80m above sea bed. The trials will be conducted in coordination with the National Institute of Oceanography (NIO), Goa, who would be assessing and monitoring the environmental impact due to the seabed nodule collection through dedicated moored and instrumented sub-sea data buoys. Pumping will be attempted through a 150 - 200 m long flexible hose, the slurry being discharged about 50 - 80 m above the seabed.