scenarios for the marine mining of heavy minerals
DESCRIPTION
With the increased understanding of the occurrence of heavy minerals offshore, the need for efficient marine mining systems is emerging. This marine environment demands a dredge mining solution as dry truck & shovel operations are no longer possible. For the marine mining of heavy minerals, multiple scenarios can be developed. They can differ both in the mining systems used and in the sequence and location of process steps required. The selection of the dredge mining equipment is generally a function of the required depth of excavation, the soil conditions and the target production. In a marine environment, the climate and sea conditions also need to be accounted for. Examples of dredge mining equipment include wheel suction dredgers, applicable in shallow depths for medium to loose sandy deposits and high productions. Wheel dredgers however have limited tolerance for wave conditions, so will likely find applications in sheltered bay or harbour locations. Trailing suction hopper dredgers are applicable in deeper waters for loose sand deposits and high productions. They have a higher tolerance for wave conditions and can therefore be successfully applied offshore. Given the relatively low grades of heavy minerals found in the deposits, it is preferable to perform a first concentration step as quickly as possible after the mining to create a concentrate. In conventional, inland dredge mining operations this is done at the floating primary concentrating plant. Spiral concentrators are the equipment generally used for this process. In a marine environment, application of spirals on a floating platform will be strongly dependent on the sea state conditions. Wave induced motions of the floating platform will disrupt the concentration process of the spirals. This limits the application of the spirals to steady platform. Combining the optimal dredge mining equipment with the optimal processing solution is a complex process. Both aspects cannot be regarded individually and have to be seen as an integrated process where capacities and process characteristics have to matched to find the optimal integrated marine mining solution. As example a case will be presented for the mining of heavy minerals approx. 30 km off the coast of Western Australia. Multiple scenarios for this case were produced. These include the use of a stationary suction dredger that fills barges that were tugged to a port facility where a process facility was located. An alternative scenario would use a trailing suction hopper dredger to mine the ore, sail to port and dump the material in water near the quay, where a small second dredger would re-handle to ore and directly feed a process installation onshore. Selection of the optimal scenario requires careful and detailed evaluation of all applicable variables.TRANSCRIPT
Scenarios for the Marine Mining of Heavy Minerals
Bart HogewegAndrina DrostRogier Kalis
Heavy Mineral Conference 2013Visakhapatnam, India27-29 November 2013
IHC Mining B.V.The Netherlands
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IHC Merwede Overview
IHC Merwede facts & figures:• Financial turnover in 2012: EUR 0.9 billion
• Staff in 2012: 3,200
• 5 Shipyards in The Netherlands, 1 in China; Singapore & Batam with Jaya Shipbuilding & Engineering
• World wide services and manufacturing locations
Outline
• Introduction• Marine mining technology• Mineral processing in marine environments• Marine mining scenarios• Conclusions
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Mining of the seafloor has been ongoing for a long time
• Offshore gold and tin mining started in early 1900s
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Introduction / Mining / Processing / Scenarios
Current marine mining activities are still based around historic areas…
• PT Timah operates offshore Indonesia with large integrated bucket ladder dredgers• In water depths to 50 m• Recently, IHC and PT Timah converted one of the dredgers to a hydraulic wheel
dredger, extending water depth to 70 m
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Source: PT Timah
Introduction / Mining / Processing / Scenarios
…but also moved into new areas
• De Beers Marine operates a mining vessel with a crawler offshore Namibia• Diamonds are mined from water depths to 150 m
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Source: De Beers Marine
Introduction / Mining / Processing / Scenarios
Heavy minerals are found offshore in relatively shallow water depths
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Offshore placers: Diamonds, gold, tin, heavy minerals (Ti-Zr)
PhosphatesCrust (Mn, Co)
Seafloor Massive Sulphides (Cu, Au, Zn)Nodules (Mn, Ni, Cu)
Source: GRID-UNEP
Introduction / Mining / Processing / Scenarios
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Heavy minerals are very suitable for dredge mining
• Richards Bay Minerals is world largest heavy minerals mining operation, using mining dredgers in multiple ponds
Introduction / Mining / Processing / Scenarios
How can we build a pond on the other side of the shore line?10
Introduction / Mining / Processing / Scenarios
Different concepts can be used for marine mining
• Stationary• Cutter/wheel suction dredger• Bucket ladder dredger
• Trailing• Trailing suction hopper dredger
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Introduction / Mining / Processing / Scenarios
Moving offshore brings in factors like wind, waves, currents etc.
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• Cutter suction dredgers are fixed to ground by spud wave action limits operation• Trailing suction hopper dredgers don’t have this limitation
Introduction / Mining / Processing / Scenarios
Wind and waves also have a large impact on the separation of heavy minerals
• Sea state and resulting vessel motions have impact on performance of separation equipment
• Vessel movements inhibit proper operation of spiral concentrators
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Introduction / Mining / Processing / Scenarios
Technology can provide solutions, but they come at a price
• Increase size of the platform to create more stability
• Motion compensation
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Source: Husky Energy
Source: Barge Master
Introduction / Mining / Processing / Scenarios
Combining mining and mineral processing results in different mining scenarios
• Integrated platform combining mining and mineral processing functions
• De-coupled functions
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Introduction / Mining / Processing / Scenarios
An integrated solution provides distinct benefits, but has limited application in sea state
• Single unit• Direct tailing repositioning, no tailing transportation required• Well suited for mining of thicker layers of material
• Limited sea state, as processing is integrated onboard the dredge
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Introduction / Mining / Processing / Scenarios
Separated functions provide more flexibility
• Opportunity to use trailing suction hopper dredgers
• Operating cycle: process is discontinuous
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Dredging
Transport
Transport
DumpingPumping ashore Rain-bowing
Introduction / Mining / Processing / Scenarios
Choices in mining cycle can create a variation of scenarios
• Similar to the operating cycle of the TSHD, a mining cycle can be setup• For each step in cycle, different options exist
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Mining
Transporttailings
Transport ore
Process plant Concentrate
Source: Van Oord
• TSHD• CSD• WSD
• Floating• Onshore
• TSHD• Barge
Introduction / Mining / Processing / Scenarios
Various scenarios are usually possible. Logistics determine the optimal scenario
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Example 1
Example 2
Example 3
Introduction / Mining / Processing / Scenarios
Finding the optimal requires thorough analysis
• Multiple technology solutions for marine mining are available
• Factors as proximity to shore, wind and wave conditions have a large impact on both the mining and mineral processing options for a mining scenario
• Mining scenarios are a combination of mining, processing and transportation methods selected on a project-to-project basis
• The optimal mining scenario is driven by logistics
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Introduction / Mining / Processing / Scenarios