Task 3 – Tailings Dust Emissions

 

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updates: 8/31/16

afternoon of 8/31/16

Background

Tailings are a byproduct of mill operations and are comprised of residual solids suspended in process water. Tailings are discharged from mill thickeners (~45% solids content by weight) and sent to tailings storage facilities (TSFs), which are typically constructed in stages or on a continuous basis over a period of time. As deposited tailings begin to dry, the surface area of the TSFs becomes subject to erosion and has the potential to release dust emissions during high wind events. In order to minimize or eliminate the potential for fugitive dust events, facilities rely on conventional dust control solutions, which are generally costly and short lived. These solutions are reliant on a combination of the following controls:

  • Application of water
  • Application of wetting agents (i.e. surfactants)
  • Limit vehicle access and travel speeds
  • Encrustation
  • Chemical stabilization
  • Mulching and landscaping
  • Hay crimping
  • Wind fencing/wind break
  • Compaction
  • Agglomeration

Innovative approaches to controlling tailings dust emissions are regularly evaluated by environmental technology teams for purposes of developing solutions at facilities that want to (1) reduce liabilities, (2) reduce costs, and (3) reduce and reallocate the use of water. One such innovative approach examines the possibility of making a gravel-like material from the mill tailings, which can then be reapplied to the TSFs as a cover material.


Problem Statement

Your team will evaluate cost-effective options for reducing tailings dust emissions. Such options should include a review of existing control measures in order to understand the limitations associated with certain physical and environmental aspects (dam stability, accessibility, material composition, etc.) of the tailings storage areas. Your team must propose ways of utilizing existing tailing material to reduce the dust and reduce the expense of currently used methods. You must quantify the advantages of your options against the existing control measures while addressing the re-use of materials (tailings, water, binding agents, paper, and other products that are readily available at a remote and rural location of a mining operation).


Design Considerations

The primary objective is to find a method of mixing and shaping the mineral tailings as such that when a readily available material/substance is introduced into the mix it forms a secondary mineral matrix that can bind mine tailing particles together. The proposed material/substance would have to be mixed with the top layer of TSF so it can form small nuggets, perhaps ½“ to 1” in diameter, simulating the natural clods or ‘peds’ found in some soil types. The secondary objective is to find a method of application as such that freshly formed, synthetic peds can be immediately laid back down in a layer that is several inches thick across the TSF’s surface. The resulting gravel-like layer should significantly reduce or eliminate blowing dust and should allow rainwater to easily permeate the layer and soak into individual peds where it would be more effectively retained.

Your proposed design should examine:

  1. Effectiveness of the cover material in reducing water erosion and wind friction velocity.
  2. Cost-effective methods for agglomerating and/or compacting tailings material into a gravel product.
  3. Conceptual or off-the-shelf technology that can make this design a portable, batch operation.
  4. Application of the reconstituted material on the TSFs, either as a standalone approach or as a component of the above (see #3).
  5. Longevity of the reconstituted material before it is reabsorbed into the TSFs.
  6. Duration of binding reaction and/or process in order to achieve maximum aggregation and/or compaction.
  7. Longevity of the reconstituted material before it is reabsorbed into the TSFs.

Bench-Scale Demonstration

Bench scale demonstrations should be limited to at least three aspects of the design considerations listed above.


Written Report Requirements

The written report should demonstrate your team’s insight into the full scope of the issue and include all aspects of the problem and your proposed solution. The report will be evaluated for quality of writing, organization, clarity, reason, and coherence. Standards for publications in technical journals apply.  In addition to the listed requirements, your report must address in detail the items highlighted in the Problem Statement, Design Considerations, and Evaluation Criteria.


Evaluation Criteria

Each team is advised to read the Participation Guide for a comprehensive understanding of the contest evaluation criteria. Upon registration, WERC will provide you with a copy of the Public Involvement Plan and Participation Guide.

Additionally, your proposed solution will be evaluated on the following:

    • Technical fundamentals, performance, safety and other issues stated in the problem statement
    • Potential for real-life implementation
    • Thoroughness and quality of the economic analysis
    • Originality, innovativeness, functionality, ease of use, maintainability, reliability, and affordability of the proposed technology
    • How well the bench-scale represents your full scale design concept
    • Other specific evaluation criteria may be provided at a later date