Turning Waste into Profit: A Case Study in Cost-Effective Sulfur Recovery from Lead-Zinc Tailings

Pyrite separation from tailings is abbreviated as sulfur recovery. Flotation is generally used for the beneficiation of lead-zinc ores. The particle size of flotation tailings is generally fine. To ensure that certain economic benefits can be obtained without polluting the environment, efficient, energy-saving and environmentally friendly methods and equipment must be used to extract pyrite from flotation tailings.

Now， we will analyze the recovery of lead-zinc ore sulfur according to our actual case.

After the lead-zinc ore beneficiation process was put into operation, the ore produced two products: lead-zinc mixed concentrate and zinc concentrate. For some reasons, sulfur has not been recycled, and mineral resources are seriously wasted, affecting the economic benefits of beneficiation.

With the increase in the price of sulphur concentrate, the potential value of sulphur in the ore has increased, and the recovery of sulphur has been emphasized.

A detailed study has been conducted on the recovery of sulfur by flotation of lead-zinc ore. Aiming at the main influencing factors and laws of sulfur flotation, a reasonable technological process was adopted and the best conditions were selected to obtain a sulfur concentrate with a sulfur grade of 35.12% and a sulfur recovery rate of 35.40%.

1. Properties of raw ore

Relative mineral content in lead-zinc ore

Mineral name	Content (%)	Mineral name	Content (%)
galena	3.3	Lead alum	0.4
sphalerite	20.9	Cerussite	0.2
Pyrite	13.9	Arsenopyrite	0.1
Smithsonite	1.9	Pyrrhotite	0.1
Chalcopyrite	0.1	gangue	59.1

The lead grade of the raw ore is 3.29%, the zinc grade is 14.43%, and the sulfur grade is 15.09%, of which the pyrite and pyrrhotite contain 7.42% and 0.056% of the raw ore respectively. This shows that the object of sulfur recovery is mainly the sulfur in pyrite.

 

2. Experimental study on Flotation of lead-zinc ore

Usually, for pyrite-type lead-zinc sulfide ores, the priority flotation process of lead, zinc and sulfur is mostly used.
(Process characteristics: adding lime to inhibit pyrite, adding an inhibitor of sphalerite in a highly alkaline medium to separate lead and zinc; then adding copper sulfate for zinc separation; when zinc tailings are selected for sulfur, first use sulfuric acid to activate, and then Add a lot of xanthate to flotate iron sulfide minerals.)

After mining improvement: use priority to select lead, lead rough beneficiation concentrate is selected to obtain lead concentrate; lead tailings are subjected to partial mixed flotation of lead and zinc, and the lead and zinc rough concentrate is reground to select lead-zinc mixed concentrate. The mixed flotation tailings are subjected to zinc-sulfur mixed flotation, and the mixed concentrate zinc-sulfur is separated to obtain zinc concentrate and sulfur concentrate.

3. Economic benefit calculation

This process is used in production, no need to add equipment for sulfur selection, only 50 grams of xanthate per ton of raw ore needs to be added.
The annual processing capacity of lead-zinc ore is 300,000 tons, the raw ore contains about 15% sulfur, the grade of sulfur concentrate reaches 35%, and the recovery rate of sulfur in the sulfur concentrate reaches 35%. The annual output of sulfur concentrate is 45,000 tons. Calculated at the latest price of RMB 130/ton of sulfur concentrate, the annual increase in revenue is $912,340. After deducting the sales and transportation costs of $9/ton, the increased cost of sulfur concentrate and xanthate is $47,190, and the annual growth benefit of sulfur recovery is about $440,440.

4. Summary

The raw lead-zinc ore contains sulfide ore. In addition to lead-zinc minerals, it also contains about 14% iron sulfide minerals, including about 7.4% sulfur, which has considerable recycling value.