DEL049 1221377 Assessing tailing behaviour and use of flocculants in deep sea mining projects
Aanleiding van het project
Chatham Rock Phosphate (CRP) aims to be the premier supplier of direct application phosphate to the New Zealand and global agricultural sector, supporting sustainable farming and agricultural processes. To
realize this objective phosphate will be mined at the 400 meter deep Chatham Rise, located in the SW South Pacific Ocean. Chatham Rock Phosphate’s failure to get an environmental consent for marine mining
in New Zealand is one example of the increasing global need to develop validated tools and methodologies to predict, adaptively manage and reduce the environmental effects of marine mining.
Doel van het project
A final goal is to improve our knowledge and predictive capabilities of both the plume dispersion and the continuous process of settling, deposition, consolidation and associated shear strength development of
tailings, and what effect the use of flocculants might have on this.
Omschrijving van de activiteiten
The study comprises 3 phases, each comprising a number of analyses.
Phase 1: laboratory analyses of mine tailing behaviour
1. Collation of typical tailing samples for further laboratory analyses (2016/2017)
2. Accurate determination of sediment settling velocities
3. Settling and consolidation columns
Phase 2: laboratory analyses to assess the effect flocculants on tailing behaviour
4. Selection of flocculants legal for use in New Zealand
5. Determination of optimal flocculants dosage
6. Assess operational parameters affecting flocculants performance
7. Accurate determination of settling velocities
8. Settling and consolidation columns.
Phase 3: modelling
9. 1DV modelling (with and without flocculants)
10. Reporting; elaboration of results in a set of guidelines.
The majority of the work will be executed in 2017. Pending approval it is aimed for to start the first activity before the end of 2016. Decisions on the details of the implementation of phase 2 and 3 will be
based on the results of phase 1.
The main project results are:
1. A set of prototype guidelines and lessons learned on:
a. Validating the critical sediment parameters required to predict mine tailing (sediment) plume dispersion without a need for trial mining.
b. Assessing the feasibility and effectiveness of the use of flocculants as a measure in an adaptive mining strategy.
2. Results of how the guideline works for the Chatham Rise project.
Although these guidelines will be developed in the context of the Chatham deep sea mining project, they will be useful in the much broader context of marine mining and dredging for marine infrastructure development.
This implies that, besides relevant for the TKI Delta Technology, the envisaged results of this project are also relevant for the TKI ‘Maritiem – Winnen op zee’.
In case of positive results, it is likely that the PPS will be continued (see also \\\”valorisation\\\”)
Validation of (modelling) tools to predict and manage plume dispersion for deep sea mining (or dredging) operations is hampered by a general lack of field observations on the behaviour of mine tailing plumes in
deep to very deep water. Validation of hydrodynamic models, underlying sediment models, is feasible by executing long-term (months-year) field observations. Field validation of the predicted sediment plume dispersion is much more difficult, as it requires trial mining. Apart from being extremely expensive, trial mining usually also requires an environmental permit, i.e. a catch 22.
As an alternative approach, this study investigates the behaviour of mine tailings using an innovative combination of state of the art laboratory analyses and 1DV modelling to assess both the plume
dispersion and the continuous process of settling, deposition and bed formation of mine tailings. The analyses results enable us to narrow down the uncertainties in the critical sediment parameters required for prediction of (re)suspension and dispersion of mine tailings.
Additionally, this project investigates the use of, economically feasible and environmentally acceptable and effective, flocculants as an innovative measure to control (mitigate) the behaviour of the mine tailing plume in deep water, as part of an adaptive management strategy. Mitigation and adaptive management of (deep sea) mining operations is new; as far as we know flocculants have never been used in this type of projects.
The results of the study will be of general interest because prediction and management of sediment plumes will be an issue for most marine mining and dredging projects. As such this project proposal meets the valorisation objectives of the Knowledge Innovation Cluster ‘Sustainable use of estuaries, seas and oceans’ of the TKI Delta Technology and Maritime in an international context.
The results will be reported in an accessible set of prototype guidelines and lessons learned. Prototype, because currently these guidelines do not exist. Application in other future mining and dredging projects may
result in further improvements/refinement and validation of the methodology.
Furthermore, the PPS aims for a presentation and publication of the results at a (mining) conference or publication in a journal. The results of this study will be implemented in CRP’s updated application for an environmental consent for phosphate mining on the Chatham Rise, currently envisaged for end 2017.
Another implementation of results is envisaged for a similar mining project of CRP off the coast of Namibia, Africa.
Besides mining projects, the collaboration partners are involved in various dredging projects around the world where there is a potential need and opportunity for implementation of the results of this project.