Dredging Technology for Deep Sea Mining Operations

Abstract

Abstract There is little doubt that the tremendous increase in capacities of equipment is the most eye-catching development within the dredging industry. A general misperception however is that the reduced dredging costs over the last decades are simply a result of an increase in capacity only. Other equally important factors are the increase in efficiency as well as a reduction of down time resulting from a sound design philosophy in combination with the continuous improvement of key subsystems and individual components like excavation tools, high efficiency dredge pumps, robust submersible drives and integrated automation systems. Deep sea mining operations by nature are performed (or planned) in challenging environments. Another typifying characteristic of deep sea mining operations is the relatively high investment cost. This combination challenges engineers to design configurations able to mine the desired production rate in an efficient way. As design choices made for individual systems impact other parts of the system, it is vital to follow an integral approach to establish the one optimal overall system. Based on what is considered to be a ‘proven technology’ in the dredging industry and more particularly in dredge mining it will be illustrated how design choices made regarding the excavation and hydraulic transport system impact on other parts of the overall system. Ultimate goal hereby is to establish the desired output at minimum Capex and Opex. Introduction Dredging and especially dredge mining learns that the excavation system, the slurry transportation system and the processing plant cannot be considered as individual sub-systems. These systems in any ‘traditional dredge mining’ operation interrelate to such an extend that they must be developed towards an integral solution. The nominal production, peak production and variability of these figures must match for all sub-systems in the overall mining system to optimize the mining efficiency. We call this the ‘game of capacities’. Section 1 of this paper describes two ‘traditional dredge mining’ operations. This to illustrate that dredge mining indeed shows many similarities with a deep sea mining operation. Given the lessons from dredge mining, section 2 will discuss design considerations regarding a deep sea mining configuration comprising a Seafloor Mining Tool, Hydraulic Transport System and Surface Support Vessel equipped with a (pre-) processing plant. Revealed will be how the design choices made for individual systems impact other parts of the system. This to substantiate our statement: an integral approach is vital to establish the one optimal overall system.