On State-of-the-Art and Alternative Energy-Efficient Lifting Technologies for Deep Sea Mining

The main aim of this article is to study and evaluate existing and potential lifting technologies used in deep sea mining. The lifting is an energy intensive operation and can be decisive if a mining operation is feasible or not. An additional goal for this study was to see if it can be rewarding to utilise the potential energy in the returned masses, because the excess material has to be returned to the ocean bottom so that no microorganisms would be released on the ocean surface. After a general study of possible solutions, regulations and existing projects, the technologies further explored in this study include an in-line pump system, a tubular-disc conveyor and a bucket conveyor, all with modifications to suit deep sea mining. To compare different lifting technologies an estimate for power consumption to lift the mined material from 1000 m depth at three different rates, namely 75, 150, 300 tons/hour, is considered. To calculate the power requirements realistic system parameters are considered and internal system resistance are also taken into account. The results show that the power consumption for the tubular and bucket conveyor are almost in the same range, while the pump system requires about two to three times more power than them. This indicates that there are feasible alternatives to hydraulic lifting by adapting existing onshore based technologies for deep sea mining.