Comprehensive recovery of gold and silver in pyrite cinder
After pyrite roasting acid residues and the rest of the dust, collectively referred to as pyrite cinder or sulfuric acid residue, referred to as slag. Cinder main component is Fe, the content thereof is generally 40% to 55%, cinder portion further containing a certain amount of non-ferrous metals silver and gold. Therefore, pyrite cinder is a valuable comprehensive utilization of raw materials. At present, the main methods for comprehensively recovering gold and silver in pyrite cinder are: flotation method, re-election method, combined metallurgy method, cyanidation method, and chlorination method.
1. Using flotation to recover silver from pyrite cinder
Bajiazi lead zinc mineral concentrate the sulfur-containing silver average grade of 140 to 200 g / t, the mine 45,000 tons annual sulfur concentrate, containing a total of 675 tons of silver.
The slag sample of recovered silver is taken from the slag plant of the plant. After the sulfur concentrate is removed from most of the sulphur in the boiling furnace, the silver is enriched, and the silver grade in the slag is 190-200 g/ton. According to the nature of the slag, the slag is directly subjected to flotation without grinding. After one rough selection, four sweeps, one sweep, the silver concentrate is selected, the tailings are discarded, and the silver concentrate grade is selected as 1027. ~1175.55 g / ton. The silver recovery rate is 50.35%~54.12%.
The main technical operating conditions are: pulp pH 4.5, with thiobenzothiazole and isoamyl sodium black drug mixed collector added in multiple stages, the foaming agent is 2 # oil. The selected silver concentrate grade is 1027~1175g/ton. The silver recovery rate is 50.35%. The process flow is shown in Figure 1.
The Shuikoushan lead-zinc mine produces about 100,000 tons of sulfur concentrate per year. The sulfur concentrate contains a small amount of gold and silver, and the gold grade is 1.5~2.0 g/ton. The silver grade is 15~30g/ton. After the sulfur concentrate is calcined in a boiling furnace to remove most of the sulfur, the remaining pyrite residue has a relatively rich gold and silver grade, the gold grade is 2~3 g/ton, and the silver grade is 20-50 g/ton. The iron grade is 45% to 50%. [next]
According to the nature of the slag, a shaker-flotation and a single flotation test were carried out. The shaker-flotation combined process, the middle ore and tailings after the shaker sorting, is subjected to flotation after grinding. The process flow is shown in Figure 2, and the test results are shown in Table 1. Table 1 Shaker Re-election - Flotation Test Indicators
product name | Yield (%) | Grade (g / ton) | Recovery rate(%) | ||
Au | Ag | Au | Ag | ||
Shaker concentrate | 8.25 | 6.70 | 38 | 17.11 | 5.72 |
Flotation concentrate | 8.78 | 15.00 | 161 | 40.77 | 25.79 |
Total concentrate | 17.03 | 11.00 | 101 | 57.88 | 31.51 |
Flotation mine | 1.97 | 3.30 | 96 | 2.01 | 3.45 |
Tailings | 81.00 | 1.60 | 44 | 40.11 | 65.04 |
Raw slag | 100.0 | 3.23 | 55 | 100.0 | 100.00 |
From the test results, the total recovery rate of gold is 57.88%, the average grade is 11 g/ton, the average grade of silver is 101 g/ton, and the recovery rate is 31.51%. However, it can be seen from the table that the re-election of the shaker has no enrichment effect on silver, and the silver grade of the shaker concentrate is only 38 g/ton, and there is no high original slag. [next]
The slag is finally subjected to a stage grinding stage selection process. The process flow of the flotation test is shown in Figure 2, and the test results are shown in Table 2.
Table 2 Flotation closed circuit test results
product name | Yield (%) | Grade (g / ton) | Recovery rate(%) | ||
Au | Ag | Au | Ag | ||
Concentrate 1 | 6.44 | 24.0 | 106.0 | 51.11 | 32.03 |
Concentrate 2 | 4.72 | 12.5 | 81.0 | 19.51 | 17.94 |
Total concentrate | 11.16 | 19.14 | 95.40 | 70.62 | 49.97 |
Tailings | 88.84 | 1.00 | 12.00 | 29.36 | 50.03 |
Raw slag | 100.00 | 3.02 | 21.31 | 100.00 | 100.00 |
2. The combined process of metallurgy and metallurgy recovers gold and silver from the slag
Muping phosphorus fertilizer plant fluidized bed furnace using pyrite roasting acid, sulfur concentrate mainly pyrite and pyrrhotite. The natural gold particle size is very fine, and the 0.057-0.074mm particle size accounts for 11.3%. 52.5% of the gold is less than 0.01mm. Natural presence of cracks forming the main gold pyrite and pyrrhotite, the arsenic-containing pyrite less. During the calcination process, acid is removed due to the sulfur in the pyrite. The original metal sulfide turned into an oxide. Therefore, the gold in the slag is relatively enriched, and the slag is loose after being quenched by water quenching, and cracks and secondary cleavage occur many times. This is very beneficial for grinding and leaching operations. Therefore, it can be done without grinding or rough grinding. The slime shaker is used for re-election and the concentrate is re-selected for cyanidation. The process flow is shown in Figure 3.
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3. Direct cyanidation leaching gold extraction process of pyrite cinder
The direct cyanidation method is suitable for treating pyrite cinder containing more than 3 g/ton of gold. The gold-containing iron ore slag is different from the cyanide of gold ore or gold concentrate in cyanidation. The characteristics and composition of pyrite cinders, the state in which gold is present and its process flow have their own characteristics. After the pyrite slag is discharged from the roaster, it usually needs to be cooled with water, so the slag must be dehydrated; after the insoluble gold-containing sulphur concentrate is calcined, in addition to cold quenching the slag, it needs to be strongly Rinsing and chemical treatment to carry out the necessary grinding operations.
Rinse pyrite cinder object is to remove copper sulfuric acid, metal oxides, iron salts, and other impurities. The incorporation of these impurities or compounds into the cyanidation operation will increase the consumption of cyanide and lime, the dissolution of the purified gold, and the process of precipitating gold. The characteristics of cyanide-consuming substances and other active ingredients in pyrite cinder are different. Therefore, the intensity of the rinsing is also different. The rinsing operation includes the steps of grading, concentrating and filtering the hydrocyclone. Although the process of processing the pyrite slag is complicated, it can be used in the subsequent leaching of gold. The consumption of cyanide is greatly reduced and the leaching rate of gold can be increased.
For example, the Rushan Chemical Plant discharges about 17,000 tons of golden iron ore slag per year, with an average silver content of 6.7 g/ton. The slag is stored for a long time, polluting the environment and causing large losses. In order to comprehensively recover the gold in the slag, in January 1985, China's first large-scale sulfuric acid slag gold extraction workshop was built in the plant with a treatment capacity of 100 tons/day.
Cyanide leaching conditions: alkali pretreatment for 1 hour, lime for 5kg/t, leaching time for 24 hours, NaCN dosage 1.5kg/t, leaching concentration 33%, grinding fineness less than 0.045mm for 70%, zinc powder for 0.5kg /t, the amount of lead acetate is 200g/t.
Cyanide leaching technical indicators: gold leaching rate of 67.97%, washing rate of 97.30%, replacement rate of 97.87%, smelting recovery rate of 97.60%, total recovery rate of 63.82%, the plant with an annual output of 62.5kg of gold, silver 134kg. The direct cyanidation process of the slag is shown in Figure 4.
references
1. "Comprehensive recovery of associated gold and silver" Cai Ling, Sun Changquan, etc.
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