Fine particle separation is a grand challenge in the mining and mineral processing industry. The industry standard process, froth flotation, is extremely robust and adaptable; however, it is inefficient for particles less than 20 microns. Owing to this limitation, some mining sectors, such as coal, opt to discard the ultrafine particles to waste impoundments as the costs to recover and dewater these materials are prohibitive. The Hydrophilic Hydrophobic Process (HHS) is one alternative to flotation that uses a recyclable solvent, rather than air bubbles, to selectively recover fine hydrophobic particles. Prior laboratory, proof-of-concept, and demonstration-scale testing has shown that the HHS process is extremely efficient, having no effective size limitation. The purpose of this research was to continue the development and improvement of the HHS process, through the design, construction, and testing of a mobile pilot plant. The pilot plant would in turn be used to demonstrate the robustness of the HHS process through a systemic study of multiple coal sources and ranks. In addition, the pilot plant would serve as a testbed for inquiry-based process intensification, the development and evaluation of design criteria for the various unit operation.
Through the course of this research, a 50 lb./hr. (product rate) pilot plant was constructed and commissioned. Initial investigations focused on the shakedown and design of key unit operations, including the agglomeration and de-emulsification (i.e. Morganizing) steps. Studies showed that the initial design of these units, namely pump induced mixing in agglomeration and packed bed emulsification in the Morganizer, were not adequate to meet production demands, and as such, these stages were redesigned after appropriate fundamental evaluations. After implementing the design changes, the pilot plant was successfully operated over a 7-month period, routinely producing bituminous products with less than6% ash and less than 10% moisture as well as anthracite products with less than 3% ash and less than 4% moisture.
This study also evaluated a new approach to de-emulsification using a jig based Morganizer in place of the standard oscillating column Morganizer. The jig utilizes a pulsing mechanism to move liquid to break up agglomerates versus the mechanical disk stack. Preliminary results showed that the jig Morganizer was comparable to the oscillating unit at more than half the size. This new design provides a pathway for reduced cost, footprint, and improved scalability.
Lastly, this study evaluated both the HHS process and dual-scan X-ray based particle sorting as means of increasing the REE content of coal-based materials. Data from a pilot-scale x-ray sorter showed the unit was capable of preconcentrating REEs to over 300 ppm, while data from the HHS similarly showed the process was capable of REE recoveries of 85-90% and of preconcentrating REEs above 300 ppm. Altogether, these results indicate That both of these technologies are capable of efficiently and cost effectively preconcentrate REEs from wastes streams at operating coal preparation plants. / Doctor of Philosophy / The mining sector has traditionally been a large producer of waste, with the vast majority of this waste being ultrafine particles that are unable to be recovered using conventional technologies. These particles are often disposed of in large surface impoundments, which are an environmental and social liability in many mining districts. This study has evaluated a novel method of fine particle separation, the hydrophobic-hydrophilic separation (HHS) process. The HHS process uses a recyclable oil to selectively agglomerate fine particles, which are subsequently dispersed and recovered. The oil is then filtered and recycled within the process creating an approach that is both efficient and environmentally friendly. In this study, a mobile pilot HHS plant was constructed and tested, with the results showing that the HHS can effectively recover fine carbon from waste coals, thus turning an environmental liability into a potential value stream for high-end applications. In addition, the study showed that the process can be further improved to reduce costs while improving overall efficiency. Overall, this study has provided the data needed to further commercialize the HHS process. If widely deployed, the HHS process has the potential to both reduce the current amount of waste fines being generated and reclaim the existing impoundments.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119229 |
| Date | 03 June 2024 |
| Creators | Sechrist, Chad Michael |
| Contributors | Mining Engineering, Noble, Christopher Aaron, Yoon, Roe H., Huang, Kaiwu, Honaker, Ricky Quay |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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