Extracting pyrite (pyrite) from coal gangue and processing it into sulfur concentrate, the current mainstream process routes mainly include re-election and flotation, each with its own applicable scenarios. Modern production often uses a combination of raw material characteristics.
The following is a detailed comparison and process description of two core processes:
Process type, core principles, core equipment, adaptability to raw material product indicators, reference advantages and disadvantages
The reselection process utilizes the density difference between pyrite and gangue for physical separation of coarse particles and gangue with significant density differences using jigs, shakers, and heavy medium cyclones; Suitable for low-cost, large-scale processing of sulfur grades ≥ 30%, with a recovery rate of around 60%. Low cost and no chemical pollution; But the fine-grained recovery rate is relatively low
The flotation process utilizes the differences in chemical properties of mineral surfaces to separate fine particles and tightly embedded gangue through bubble attachment in flotation machines, agitation tanks, and chemical addition systems; For high-value and high-precision recovery scenarios with sulfur grades ranging from 35% to 40% and a recovery rate of over 80%, the sorting accuracy is high and the recovery rate is good; But it requires the use of medication, resulting in higher operating costs
1. Re selection process (low-cost, high-capacity route)
Re selection is a traditional mineral processing method that achieves mineral separation through gravity. The core process flow is as follows:
Crushing and grading: The raw materials are first subjected to coarse crushing, medium crushing, and fine crushing to a particle size suitable for reselection (usually less than 8mm or even finer), so that pyrite and gangue can be fully decomposed and separated.
Classification screening: Materials are classified by particle size through a vibrating screen, and materials of different particle sizes will be processed by different re-election equipment to improve sorting efficiency.
Gravity sorting (core process)
Coarse particle size: Sorting is carried out using a jigs, and the alternating water flow from top to bottom is used to separate light and heavy minerals.
Fine grained: precise sorting is carried out using a shaker. Under the repeated movement of the bed surface and lateral water flow, pyrite (high specific gravity) and gangue (low specific gravity) are discharged in different directions. Research has shown that the lower limit of effective particle size for shaker separation can reach 0.038mm, and the concentrate grade is higher when the dissociation degree is good.
Heavy medium cyclone: Magnetite powder can also be mixed into a heavy suspension to achieve efficient separation in a centrifugal field, which can directly produce sulfur concentrate with a sulfur content greater than 30%.
Dehydration: The sorted sulfur concentrate sand enters the dehydration screen or sedimentation tank to obtain the final product.
Jig Machine
Spiral Chute
After jig machine separation get concentrate
REPORT Sulfur from 10% grade improve to 45% grade
2. Flotation process (high-precision, high recovery route)
When the particle size of pyrite is extremely fine and requires fine grinding to dissociate, flotation is a better choice. It can be precisely controlled by chemicals to obtain higher grade sulfur concentrate sand.
Fine grinding: Grind coal gangue to a very fine particle size (such as -0.074mm, accounting for more than 60%) to ensure the dissociation of pyrite monomers.
Slurry mixing and dosing (core process): The slurry enters the mixing tank and chemical agents are added in sequence, usually including:
Adjusting agent: Adjust the pH value to an acidic environment with sulfuric acid; Use lime to suppress minerals other than pyrite.
Activating agent: Add copper sulfate to promote the interaction between the surface of pyrite and the collector.
Collector: Add butyl xanthate to selectively attach to the surface of pyrite, enhancing its hydrophobicity.
Foaming agent: add 2 # oil to produce stable foam.
Flotation separation: after aeration and agitation, hydrophobic pyrite particles attach to bubbles to form a mineralized foam layer, which is scraped out as "concentrate"; The useless gangue remains in the slurry and becomes "tailings". To obtain high-quality products, a process of "one rough selection, multiple selections" is usually adopted.
Product treatment: foam products are filtered and dehydrated to obtain high-grade sulfur concentrate.
3. Typical industrial practice cases
Xinghe Company in Jinsha County, Guizhou Province is currently the benchmark project for sulfur extraction from coal gangue in China. The process adopts a combined process, combining reselection with flotation to achieve a "dry and refined":
Crushing and Grinding: Crushing and grinding coal gangue to fully "liberate" pyrite.
Re selection pre enrichment: Using cyclone and other re selection equipment, based on density differences, most of the pyrite is initially separated to quickly obtain coarse-grained sulfur concentrate sand.
Fine flotation extraction: The fine tailings after reselection are subjected to flotation, and residual fine pyrite is further extracted using reagents to ensure maximum recovery rate.
Final product: The final output of sulfur concentrate sand has a high sulfur content and becomes a high-quality raw material for manufacturing sulfuric acid.
Summary: How to choose the process?
Pursuing low cost, large processing capacity, and coarse raw material particle size: Prioritize reselection, especially the shaking table sorting process.
Pursuing high grade, high recovery rate, and fine particle size of raw material embedding: flotation technology is given priority consideration.
Industrial production and pursuit of maximum resource utilization: It is recommended to adopt a combined process of re-election and flotation, taking into account both production capacity and recovery rate
