Reduction of energy consumption when using a grab for deep-sea mining operations

RJ Kuiper, Xiuhan Chen, JCL Frumau, Sape Miedema

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review


Recent developments for deep-sea mining have shown multiple scenarios of gaining mineral deposits of Seafloor Massive Sulfides (SMS). One of the problems for these scenarios is the overall large energy consumption of processing rock material which are a technological challenge and are increasing production costs. This paper compares two methods for deep-sea rock excavation on their energy consumption, based on rudimentary calculations.

The best known scenario for gaining mineral deposits from the seabed is to excavate rock materials with a crown or drum cutter and pump the fluidized crushed materials to the vessel at the surface. This process requires high cutting forces deep-sea due to the hyperbaric effect at large water depths, when cutting with full cavitation. This high energy consuming process therefore requires a considerable amount of subsea installed power.

An alternative scenario is to use a hydraulic grab for excavating mineral deposits and not crush all the materials entirely subsea. Using a grab would be very beneficial in rough terrains and unstable seafloor conditions, compared to track-driven vehicles typically used for crown or drum cutters. Also specific cutting forces are much lower when using a grab, because it is not cutting at full cavitation in hyperbaric conditions. However the main advantage is to keep most of the rock intact which allows the material to be crushed at the surface. Mechanically uplifting large pieces of rock therefore could have the advantage that most of the required power can be installed at the surface, rather than subsea for the traditionally proposed hydraulic pumping systems. The rock can then be further crushed under atmospheric pressure at the surface, avoiding the hyperbaric effect. The combination of using a grab and further crushing at atmospheric conditions is more energy efficient and therefore requires substantially less installed subsea power.

Using rudimentary calculations, a great reduction of energy consumption is found for using a grab compared to typically used crown or drum cutters. Substantially less subsea installed power is required for excavating the mineral deposits with a grab. Although additional crushing needs to be done at the surface, the overall required installed power for using a grab still can be much less than fully subsea excavating and crushing.
Original languageEnglish
Title of host publicationProceedings Offshore Technology Conference 2016
Place of PublicationHouston, TX, USA
Pages1 -13
ISBN (Print)978-1-61399-437-5
Publication statusPublished - 2016
EventOffshore Technology Conference 2016 - Houston, United States
Duration: 2 May 20165 May 2016


ConferenceOffshore Technology Conference 2016
Abbreviated titleOTC 2016
CountryUnited States


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