Abstract:

Seafloor mineral grain collection technology is the key technology of deep-sea mining, in which the mechanical collection method with high collection efficiency and high reliability has great potential for engineering application. A mechanical collection device by comb shovel is designed, and CFD-MMP numerical simulation and experimental methods are used to investigate the effects of different geometric parameters on the collection of mineral grains and the disturbed characteristics of sediments. The effects of depth of penetration to grain size ratioD/d, comb shovel gap to grain size ratioB/d, comb shovel extension distance to grain size ratioC/d, comb shovel angleα on the collection rateη, and the effects ofD/d and other parameters on sediment volume fractionγi and turbidityTui at the monitoring point are investigated. It is found that: sediment adhesion of comb shovel head is the main factor leading to the decrease ofη and the appearance of local minima; whenα is small, the angle of entering the soil is insufficient, and whenα is large, the grains of ore are staggered with the soil levelling and the collecting position, theη is lower; whenD/d =0.5,B/d=0.86,C/d=1.68, andα=π/2,η reaches the maximum value of 92%.γi-D/d curve is linear; when 0<D/d ≤ 1, it can simultaneously obtain the improvement ofη and the ratio of suspended sediment quality to the collected mass of ore particlesms/mn decreases to achieve high-efficiency and low-turbulence ore collection; whenD/d=0.5,ms/mn reaches a minimum value of 5.95%. This study provides theoretical support for revealing the mechanism of ore collection and designing and developing high-efficiency, low-disturbance mechanical ore collection technology.

Key words:  , polymetallic nodule, mechanical collection by comb shovels, mineral particle collection characteristics, sediment disturbance characteristics