Date of Award

Spring 5-2023

Degree Type

Thesis

Degree Name

Master of Science in Materials Science and Engineering (MSMSE)

Department

Materials Science

Committee Chair

Courtney Young

First Advisor

Richard LaDouceur

Second Advisor

Robin Bullock

Third Advisor

Mar LeVier

Abstract

Disa Technologies’ High-Pressure Slurry Ablation (HPSA) is a patented particle attrition technology for the comminution and selective liberation of minerals. Two slurry streams are pumped at high pressure through opposing nozzles and collisions between solid particles suspended in the slurry streams cause breakage of the feed material. HPSA was evaluated for improving the rougher flotation of molybdenite from Cu-Mo bulk concentrate and gold-bearing pyrite from gold tailings.

Copper/molybdenum samples were provided by Montana Resources in Butte, Montana. A two-factor factorial design of experiments was used to identify HPSA operating conditions which gave the highest increase in flotation performance. Variables were solids concentration (10 and 20 wt%) and pump speed (40 and 60 Hz). Samples were collected after HPSA times of 0, 7.5, 15, 22.5, and 30 minutes. Each of these timed samples were then tested for flotation performance using Aminpro’s Simple Kinetic Test Procedure to evaluate the impact of HPSA on molybdenum and copper recovery and grade, and sieve analyses were done to measure changes in particle size distributions. After reviewing the results of these four tests, it was decided to do an additional test at 60 Hz and 30 wt% solids. The tests with a pump speed of 60 Hz and solids concentrations of 20 and 30 wt% showed positive trends where the flotation performance of post-HPSA samples improved with increased processing times; however, the analysis was hindered by sampling problems caused by flotation of sulfides in the sump of the HPSA unit.

Gold tailings samples were collected from Barrick’s Golden Sunlight mine in Jefferson County, Montana where aged gold tailings are being reprocessed by flotation to recover gold‑bearing pyrite for use as fuel in autoclaves. As part of the work with gold tailings, different flotation reagents from Quadra Chemicals were tested on as-received tailings to identify a chemistry which gave high pyrite recoveries compared to potassium amyl xanthate (PAX) and methyl isobutyl carbinol (MIBC), the flotation chemistry used by Golden Sunlight at the time of this study. Quadra Chemical’s Polyfloat 7040 collector with MIBC as a frother gave the highest recoveries of the reagents tested, so 7040/MIBC and PAX/MIBC were used in the HPSA flotation tests. Based on the results of the copper/molybdenum tests, a single HPSA test with gold tailings was done at a pump speed of 60 Hz solids concentration of 20 wt%. Samples for flotation and size analysis were taken after 0, 3, 6, and 9 minutes of HPSA. Results showed an initial increase in particle size and decrease in flotation performance compared to the as-received gold tailings upon addition to the sump which was attributed to size segregation of material in the sump of the HPSA unit and removal of water-soluble sulfates and organics present in the tailings. Despite the initial decrease in flotation performance, the post-HPSA samples showed substantial improvements in recovery of iron and sulfur.

Overall, results indicate that HPSA does improve flotation of molybdenite from Cu-Mo bulk concentrate and gold-bearing pyrite from gold tailings, however sampling problems caused by flotation and size segregation in the HPSA sump preclude a definitive conclusion. Additional testing and changes to the design of the HPSA unit used for laboratory testing are recommended.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of

Master of Science in Metallurgical and Mineral Processing Engineering

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