Alternative Collector Solutions

Learn about the ways the Quadra mining team is helping our clients solve challenges and improve business processes.

Summary

An open-pit copper-molybdenum mine located in British Columbia, Canada announced the opening of a new mineral processing plant.The flotation process used a blend of sodium isopropyl xanthate (SIPX) and diesel oil emulsion (DOE) as bulk collectors. The molybdenum facility was idled due to low market prices and high operational costs. Quadra Chemicals partnered with Chevron Phillips Chemical (CP Chem) for lab tests and plant trials. A new collector blend was developed. SIPX and diesel oil emulsion were substituted. The molybdenum facility restarted in autumn of that year. Copper and molybdenum recoveries improved by 0.9% and 4% respectively.

Situation

 

An open-pit copper-molybdenum (Cu-Mo) mine located in British Columbia, Canada announced the opening of a new standalone mineral processing plant (commonly known as a concentrator), the acquisition of new mining equipment, and improved economics featuring a 50% decrease in strip ratio, a new National Instrument (NI) 43-101 compliant reserve, and lower comminution costs. The new target recoveries for both concentrators were 86% Cu and 50% Mo.

Figure 1: Simplified grinding and bulk flotation flowsheet for both concentrators.

For bulk flotation, chalcopyrite (CuFeS2) and molybdenite (MoS2) were the primary minerals. Feed mineralogy varied as mining advanced to new ore zones. The bulk flotation circuit used a blend of sodium isopropyl xanthate (SIPX) and diesel oil emulsion (DOE) as bulk Cu-Mo collectors. pH over 10.5 was required to reach target Cu-Mo recoveries. Lime consumption was high.

The Mo facility was idled due to low market prices and high operational costs. The metallurgical group worked exceptionally hard to find solutions to improve recoveries, hoping to restart Mo production as soon as possible. Testing alternative collectors was a top priority.

 

Solution

First Round – Cu Recovery

A blend of dithiophosphate (DTP), thionocarbamate (TNC) and mercaptobenzothiazole (MBT) were added to SIPX as secondary Cu collectors, which increased Cu recovery by 3%.

 

Second Round – Mo Recovery

Quadra Chemicals partnered with Chevron Phillips Chemical (CP Chem) to participate in the second, third and fourth rounds of tests/trials.

CP Chem tested 4 specialty collectors (red, black, blue and green curves) at a low dosage and high dosage against DOE (turquoise curve) at actual dosage:

 

The collectors represented by the red and black curves outperformed the rest and thus were selected for plant trials. The red was trialed first during Q3 of that year due to lower cost and slightly better performance. Mo recovery increased by 8% on average; however, the operators were concerned about the odor and requested to try the other (black curve), which was odorless. Mo recovery was significantly more sensitive to grind size and feed mineralogy, resulting in a 2% increase for the first trial and 11% for the second. The odorless collector was selected by the operators to move forward as the substitute to DOE.

 

 

Third Round – Overall Cu-Mo Recovery

During Q4 fo that year, after the second round of tests/trials, CP Chem tested the current blend with alternative sulfide collectors. Lab results showed Cu-Mo recovery improvement with the addition of the new collector (green curve) to the current blend (blue curve):

 

The new blend, branded MC17A, was trialed during Q1 of the following year. Each collector’s dosage and dosing point were adjusted progressively. The SIPX/DTP/TNC/MTB blend served as the baseline for comparison. Using MC17A as the primary blend and SIPX/DTP/TNC/MTB as the secondary blend improved Cu recovery by 1% and Mo recovery by 8%.

 

Fourth Round – Tailings Recovery and pH

Rougher tailings samples were tested to determine whether additional recovery was possible. Lab results showed that by replacing SIPX with MC17A in the secondary blend, Cu-Mo recoveries improved by 4% and 2% respectively:

Plant trials were performed during Q3, showing Cu-Mo recovery improvements of 0.4% and 3%. Discrepancies between lab and trial results were due to fluctuations in grind size and feed mineralogy. pH was decreased from 10.5 to 9.8 in September, with no significant recovery losses thanks to the removal of SIPX.

 

Results

As of Q4 that year, CP Chem’s specialty blend MC17A and DTP/TNC/MTB officially replaced SIPX/DOE in production at both concentrators.

 

Figure 6: Tailings box before
Figure 7: Tailings box after.

In September, the Mo facility downstream restarted and produced 185,000 lbs of Mo for the month.

 

The new concentrator’s average grind size decreased during Q3-Q4 that calendar year and its effect on Cu recovery was analyzed:

The scatter plot shows Cu recovery improvement at the end of July when SIPX was substituted by CP Chem’s collectors in the secondary blend, and no significant loss mid-September when pH was lowered from 10.5 to 9.8. As expected, the new collectors were sensitive to grind size, with a 0.5% increase in Cu recovery per 1% decrease in +65 mesh fraction (212 µm). Comminution presented the next opportunity for improvement.

 

Benefits

  • Improved Cu recovery by 0.9%
  • Improved Mo recovery by 4%
  • Eliminated SIPX (CS2 vapour)
  • Reduced lime consumption (pH 10.5 to 9.8)