A certain refractory gold ore belongs to the fine-grained leaching type. During the beneficiation test, the gold leaching rate of the original ore by cyanide leaching was about 30%. The conventional one-stage grinding and flotation process, one-stage grinding+gravity separation+flotation process, cannot effectively improve the gold recovery rate. The comprehensive indicators of the stage grinding and flotation process are good. Therefore, it is determined to use the stage grinding and flotation process for research.
The valuable elements in this fine-grained disseminated gold ore are mainly gold, while the harmful elements are arsenic, carbon, and antimony; The main gangue minerals include quartz, mica, calcite, monazite, pyrite, arsenopyrite, etc., and also contain small amounts of metallic minerals such as antimonite, galena, and sphalerite.
(1) Determination of Grinding Fineness for a Section
The symbiotic relationship between gold bearing minerals and vein minerals is complex, with uneven distribution of coarse and fine particles. In order to obtain better gold recovery indicators, it is necessary to select a suitable grinding fineness, so that relatively coarse particles of gold minerals are preferentially dissociated and recovered in a timely manner.
A grinding fineness test is conducted using a single coarse selection process, with a dosage of 100g/t for the collector butyl xanthate and 40g/t for the foaming agent 2 # oil. Taking into account flotation indicators and grinding cost factors, it is determined that a grinding fineness of -0.074mm accounts for 52%.
(2) PH value test
The pH value of the slurry affects the electrical properties of the mineral surface and the effectiveness of the reagent. The pH adjuster calcium oxide dosage test adopts a one-time coarse selection process, with a first stage grinding fineness of -0.074mm accounting for 52%, butyl xanthate dosage of 100g/t, and 2 # oil dosage of 40g/t
The pH value of the slurry increases, and the gold grade of the coarse concentrate significantly decreases. The recovery rate first increases slightly and then decreases significantly. Taking into account all factors, the pH value of a rough selected slurry is determined to be 8, and the corresponding amount of calcium oxide is 750g/t.
(3) Type and dosage test of collector
By comparing four collectors, namely butyl xanthate, isoamyl sodium xanthate, Y98, and Y89, it was found that butyl xanthate not only had the highest gold grade in the crude concentrate, but also had the highest gold recovery rate. Therefore, butyl xanthate was chosen as the collector, with a dosage of 60g/t.
(4) Two stage grinding fineness test
The two-stage grinding process should not only fully dissociate fine gold particles, but also prevent the influence of mud on flotation. The second stage grinding fineness test uses coarse tailings for primary grinding, and the second stage grinding fineness test adopts a one-time flotation process. The dosage of calcium oxide is 500g/t, the dosage of butyl xanthate is 50g/t, and the dosage of 2 # oil is 30g/t. Taking into account flotation indicators and grinding cost factors, the second stage grinding fineness of -0.074mm is determined to account for 87%.
Based on the condition test and open circuit test, a flotation closed-circuit test was conducted. The test process and conditions are shown in the following figure. The closed-circuit process shown in the figure processed the ore and obtained a comprehensive concentrate gold grade of 41.77g/t with a recovery rate of 86.51%. The test indicators are good.
Under the conditions of a first stage grinding fineness of -0.074mm52%, a second stage grinding fineness of -0.074mm87%, a slurry pH value of 8.0 adjusted with calcium oxide, a butyl xanthate dosage of 150 g/t, and a 2 # oil dosage of 95 g/t, the comprehensive concentrate gold grade obtained from the closed-circuit test is 41.77 g/t, and the recovery rate is 86.51%.
For this fine-grained leaching type refractory gold ore, the stage grinding stage separation process has a better recovery effect, with a gold recovery rate increased by about 8 percentage points, which can significantly improve the economic benefits of the enterprise.
