The commonly used flotation principle processes for processing lead-zinc sulfide ores include priority flotation, mixed flotation and equal flotation.
No matter which process is used, you will encounter the problems of lead-zinc separation and zinc-sulfur separation. The key to separation is a reasonable and low selection of regulators.
Since the floatability of most galena is better than that of sphalerite, all methods of suppressing zinc and lead floating are commonly used. The pharmaceutical solutions for inhibiting zinc include cyanide method and cyanide-free method. In the cyanide method, zinc sulfate is often used in combination with cyanide to enhance the inhibitory effect. For example, a certain processing plant uses sodium cyanide and zinc sulfate in combination to reduce the cyanide dosage to 20~30g/t, and some even reduce it to 3 ~5g/t. Practice has proven that it not only reduces the dosage, but also increases the recovery rate of lead.
In order to avoid cyanide pollution to the environment, cyanide-free or cyanide-less methods are currently being promoted at home and abroad. The following cyanide-free methods are commonly used in the lead and zinc separation industry:
1. Floating lead inhibits zinc
(1) Zinc sulfate + sodium carbonate (or sodium sulfide or lime);
A certain lead-zinc-sulfur mine adopts a preferential flotation process. ZnSo4+Na2CO3 (1.4:1) was used to suppress sphalerite when floating lead. Compared with the cyanide method, the lead concentrate grade increased from 39.12% to 41.80%, and the recovery rate was from The zinc concentrate grade increased from 74.59% to 75.60%, the zinc concentrate grade increased from 43.59% to 48.43%, and the recovery rate increased from 88.54% to 90.03%.
(2) Zinc sulfate + sulfite;
(3) Zinc sulfate + thiosulfate;
(4) Sodium hydroxide (PH=9.5, collected with black powder);
(5) Use zinc sulfate alone to inhibit zinc;
(6) Use SO2 gas to suppress zinc.
2. Floating zinc suppresses lead
(1) Lime;
(2) Water glass;
(3) Water glass + sodium sulfide.
The above three methods are used when galena is severely oxidized and its floatability becomes poor.
For floating lead, black medicine and xanthate are often used as collectors, or ethyl sulfide alone with good selectivity is used as a collector. Some foreign processing plants also mix sulfosuccinic acid (A-22) with xanthate.
Since lime has an inhibitory effect on galena, when there is little pyrite in the ore, it is more advantageous to use sodium carbonate as a pH adjuster for floating lead. When the pyrite content in the raw ore is high, it is better to use lime as a pH adjuster. Because lime can inhibit the associated pyrite, it is beneficial to floating lead.
Resurrecting suppressed sphalerite using copper sulfate. In order to avoid copper sulfate and xanthate directly forming copper xanthate during the slurry mixing process and reducing the effectiveness of the agent, copper sulfate is generally added first, and then the xanthate is added after stirring for 3 to 5 minutes.
When there are two parts that are easy to float and those that are difficult to float in the sphalerite, in order to save chemicals and improve the separation index of lead and zinc, a floatable process can be adopted, which mainly uses lead and floats lead and zinc.
3.Method for zinc and sulfur separation
(1) Floating zinc suppresses sulfur
1. Lime method
This is the most commonly used sulfur suppression method. This method can be used to process raw ore and separate zinc-sulfur mixed concentrate. When using this method, use lime to adjust the pH, usually above 11, so that the pyrite is suppressed. This method is simple, and the chemical used is lime, which is cheap and easy to obtain. However, the use of lime can easily cause scaling of flotation equipment, especially pipelines, and the sulfur concentrate is not easy to filter, resulting in a high moisture content of the concentrate.
2.Heating method
For some pyrites with high planktonic activity, suppression by lime method is often ineffective. When the slurry is heated, the surface oxidation degrees of sphalerite and pyrite are different. After the zinc-sulfur mixed concentrate is heated, aerated and stirred, the floatability of pyrite decreases, while the floatability of sphalerite remains.
Research shows that zinc and sulfur can be separated by steam heating for the separation of zinc-sulfur mixed concentrates. The coarse separation temperature is 42~43°C, and the fine separation without heating or adding any chemicals can separate zinc and sulfur. The obtained index is 6.2% higher than the zinc concentrate produced by lime method, and the recovery rate is 4.8% higher.
3. Lime plus a small amount of cyanide
When lime alone cannot effectively suppress iron sulfide, add a small amount of cyanide (for example: NaCN5g/t in Hesan Processing Plant, NaCN20g/t in Siding Processing Plant) to improve zinc-sulfur separation.
(2) Floating sulfur suppresses zinc
Sulfur dioxide + steam heating method This method has been applied in the Brunswick mineral processing plant in Canada. The zinc concentrate obtained by the plant contains a lot of pyrite. In order to improve the quality, the slurry is treated with sulfur dioxide gas and then heated with steam to suppress zinc and float sulfur.
The specific method is to introduce sulfur dioxide gas from the bottom of the first stirring tank and control the pH = 4.5 to 4.8. Inject steam into the second and third stirring tanks and heat it to 77 to 82°C. When roughing pyrite, the pH is 5.0~5.3, and xanthate is used as collector. The flotation tailings are the final zinc concentrate. In addition to pyrite, the foam product also contains zinc. After being selected, it is used as medium ore and returned to the medium ore at the front of the process for regrinding. Accurate control of pH and temperature is the key to this process. After treatment, the zinc concentrate product increased from 50% to 51% zinc to 57% to 58%.
Post time: Jun-24-2024
