The scope of work awarded to DRA involves the detailed design of the vessel-mounted material processing facilities. With a design capacity of 400t/h, the plant will include screening the seafloor massive sulphides into a number of size fractions, followed by dewatering using centrifuges and filter presses, eventually filtering to 8 microns. The combined dewatered product will then be temporarily stored in the vessel’s hold, prior to transshipment via Handimax vessels to Nautilus’ processing partner in China. The remaining filtered water is then returned via the enclosed riser system to drive the subsea lift pump and discharged within 50m of the seafloor from where it originally came.

The detailed design phase is expected to be completed in the December 2015 quarter, following which the vessel-mounted modules will be fabricated and pre-commissioned onshore prior to integration onto the completed vessel. Fabrication of the process plant is expected to commence in early 2016; with first production from the Solwara 1 project being scheduled for 2018.

Mike Johnston, CEO of Nautilus, commented: “The project team has been working closely with DRA for several years on studies and early engineering. DRA has extensive experience with similar floating dewatering/mineral processing facilities in related offshore industries. We are pleased to have them utilise this experience when they carry out the detailed design for our on-board processing facilities.”

Donald Holley, reguional director at DRA, said: “It is pleasing for us to be able to apply DRA’s previous experience in designing vessel-mounted process plants to the Solwara 1 project. This special experience has been gained from our off-shore diamond recovery projects off the coast of southwest Africa. It includes overcoming the challenges in designing and operating process plants mounted on ships resulting particularly from the impact of the dynamic environment from wave movement, and the need for modular construction.”