The present invention relates to a method for mineral separation, and in particular to a method for mercury-antimony flotation separation of mercury-antimony paragenetic sulfide ore.

In the background art, current domestic and international industrial separation of mercury and antimony from mercury-antimony paragenetic sulfide ores employs pyrometallurgical methods and combined beneficiation-metallurgy processes. Among them, the process flowsheet of “bulk flotation → bulk concentrate → mercury-antimony separation (with addition of potassium dichromate) → mercury and antimony products” is complex and yields unsatisfactory indices. The “bulk flotation – bulk concentrate distillation separation” method, although giving better indices, involves complicated process and operating conditions and high production costs. The “bulk concentrate – low-temperature roasting (400°C–450°C)” separation method, though with a narrow temperature control range, still causes desulfurization of stibnite, producing antimony oxides, especially high-valent antimony oxides, which complicates the antimony extraction process and increases production costs; moreover, mercury recovery is only 75.7% and antimony recovery only 85.5%. The above several mercury-antimony separation methods generally suffer from drawbacks such as high cost, high energy consumption, environmental pollution, and complex processes.

The object of the present invention is to overcome the above deficiencies in the background art and to provide a method for mercury-antimony flotation separation of mercury-antimony paragenetic sulfide ore. By using this method, the recoveries of mercury and antimony can be effectively improved, the process is simple, and production costs are reduced.

To achieve the above object, the present invention adopts the following technical solution:

A method for mercury-antimony flotation separation of mercury-antimony paragenetic sulfide ore, characterized in that the method sequentially comprises the following steps: raw ore → crushing → grinding and classification → bulk flotation → bulk concentrate de‑reagenting → selective depression → separation flotation → concentrate dewatering.

The bulk flotation operation may include one stage of roughing, two stages of cleaning, and two stages of scavenging.

The separation flotation operation may include one stage of roughing, three stages of cleaning, and one stage of scavenging.

The reagents used in bulk flotation may include activator, collector, and frother.

The activator used in bulk flotation may be lead nitrate, the collector may be butyl xanthate, and the frother may be pine oil.

In the bulk concentrate de‑reagenting, a de‑reagent agent may be added, the pulp density may be 10%, the dosage of de‑reagent agent may be 250 g/t, and the de‑reagenting time may be 2.5 hours.

In the selective depression, the pulp density may be 10%, the dosage of potassium dichromate may be 1000 g/t, and the depression time may be 1.25 hours.

The raw ore particle size may be 0–50 mm, the crushed ore size may be 1–10 mm, the overflow concentration of grinding and classification may be 30%, and the overflow fineness may be 75% passing -0.074 mm.

The accompanying drawing is a process flowsheet of the present invention.

The present invention will be described in further detail below with reference to the accompanying drawing. Referring to the drawing, the process flowsheet of the mercury-antimony flotation separation method for mercury-antimony paragenetic sulfide ore according to the present invention is: raw ore → crushing → grinding and classification → bulk flotation → bulk concentrate de‑reagenting → selective depression → separation flotation → concentrate dewatering. The individual steps in the process flowsheet are described in further detail below:

1. Crushing: Large ore blocks with a diameter greater than 50 mm are hand-broken to less than 50 mm, and then crushed by a hammer crusher to powder ore of less than 10 mm.
2. Grinding and classification: The powder ore of less than 10 mm is fed by a trough feeder into a ball mill in closed circuit with a spiral classifier for one-stage closed-circuit grinding. After classification of the grinding product, the sands are returned to the ball mill, and the classifier overflow is fed to the bulk flotation operation. The classifier overflow concentration is 30%, and the overflow fineness is 75% passing -0.074 mm.
3. Bulk flotation: The classifier overflow is conditioned in a conditioning tank with the addition of activator lead nitrate, collector butyl xanthate, and frother pine oil for full interaction between flotation reagents and mineral surfaces. The pulp then enters flotation cells for bulk flotation. After one stage of roughing, three stages of cleaning, and two stages of scavenging, the tailings are discharged, and the bulk concentrate proceeds to the de‑reagenting operation. Table 1 shows the reagent scheme in bulk flotation, and Table 2 shows the operating parameters of the beneficiation equipment in bulk flotation.
4. De‑reagenting: After bulk flotation, the bulk concentrate enters a conditioning tank. To remove flotation reagents from the bulk concentrate, a de‑reagent agent is added to the bulk concentrate under stirring for de‑reagenting. The pulp density is 10%, the dosage of de‑reagent agent is 250 g/t, and the de‑reagenting time is 2.5 hours.
5. Selective depression: To achieve mercury-antimony flotation separation, potassium dichromate is added to the de‑reagentized bulk concentrate in a conditioning tank to selectively depress stibnite. In the selective depression, the pulp density is 10%, the potassium dichromate dosage is 1000 g/t, and the depression time is 1.25 hours.
6. Separation flotation: The bulk concentrate after de‑reagenting and depression of stibnite is conditioned in a conditioning tank with butyl xanthate and pine oil, and then enters flotation cells for separation flotation. After one stage of roughing, three stages of cleaning, and one stage of scavenging, high‑grade mercury concentrate and antimony concentrate are obtained. Potassium dichromate is added in the first and second cleaning stages. Table 3 shows the reagent scheme in separation flotation, and Table 4 shows the operating parameters of the beneficiation equipment in the separation flotation cycle.
7. Concentrate dewatering: Mercury concentrate is settled in a settling pond, the clear water is discharged into a sewage ditch, and the settled mercury concentrate is periodically bagged. Antimony concentrate is dewatered and thickened in a center‑drive thickener and then filtered in a rotary drum filter.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. It is the first time that a beneficiation method is used for industrial separation of mercury and antimony from mercury-antimony paragenetic sulfide ores. The process is simple, reduces plant investment and production costs, significantly reduces environmental pollution, and brings remarkable economic and social benefits.
2. By adopting a reasonable de‑reagenting formulation and de‑reagenting process, effective separation of mercury and antimony in the bulk concentrate is achieved. The obtained mercury concentrate contains 65% Hg, the antimony concentrate contains 55% Sb, the mercury recovery reaches 82.17%, and the antimony recovery reaches 90.11%, with very obvious effects.
3. After separation by the process technology of the present invention, the mercury-antimony paragenetic sulfide ore is smelted, which reduces smelting costs and greatly improves the overall recoveries of products: the recovery of finished mercury is increased by 20.85% and that of antimony by 7.43%.

Table 1 Reagent scheme in bulk flotation

Table 2 Characteristics of beneficiation equipment in bulk flotation cycle

Table 3 Reagent scheme in separation flotation

Table 4 Characteristics of beneficiation equipment in separation flotation cycle