KR900001018B1 - Process for recovering silver from pb/ag cake - Google Patents

Abstract

A process for recovering silver from Pb/Ag cake uses H2SO4 or H2SO4 and sulfidizing agent as floating agent. The concentration of H2SO4 is 10-70g/litre and that of slury, 100-300g/l, and air is used to float.

Description

Recovery of silver from Pb / Ag cake generated during wet zinc smelting

1 is a process chart showing the recovery method of the present invention.

* Explanation of symbols for main parts of the drawings

1: Pb / Ag cake 2: sulfuric acid

3: water 4: sulfidizing agent

5: Repulper 6: Conditioner

7: Rougher Cell 8: Scavenger Cell

9: filter press 10: filtering tank

11: Frosted tank 12: Cleaner Cell

13: Settlr 14: centrifuge

15: frost 16: frost

17: frost 18: centrifuge filtrate

19: Centrifuge filtrate

20, 21: Filter Press Filtrate

22: barge tailing residue (tailing residue) 23: silver concentrate

The present invention relates to a method for recovering silver from a Pb / Ag cake generated in a wet zinc smelting process. A feature of the present invention is that at the time of recovering the silver contained in the Pb / Ag cake by the flotation method, the sulfuric acid concentration of 10 to 70 g / 1 (pH 0.9 to 0.1 equivalent) using sulfuric acid as the reagent for the flotation operation or A method of selectively recovering silver by adding a sulfiding agent.

Zinc concentrates currently traded internationally generally contain 48% to 53% zinc, 30% to 34% sulfur, 2% to 12% iron, 1% to 3% lead, and 50 to 500 g / ton silver. Silver is an important by-product of about 5% of zinc in zinc concentrates at the current price level and, if recovered in salable form, can contribute significantly to the economic inventory of zinc smelting.

The wet zinc smelting process involves the roasting process of oxidizing the concentrate, the leaching process of leaching the roasted oxide ore into the sulfuric acid solution to obtain a zinc sulfate solution, the semen process of removing impurities from the zinc sulfate solution, and the zinc sulfate solution from which the impurities are removed. It consists of an electrolytic process in which metal zinc is obtained through decomposition. Silver and lead in zinc concentrate do not dissolve in sulfuric acid solution in the leaching process and are generated as a residue, which is usually referred to as a Pb / Ag cake. The composition of the Pb / Ag cake may vary depending on the composition of the concentrate, the conditions of the leaching process, etc., but is generally composed of 300 to 1200 g / ton of silver and 15 to 25% of lead.

These Pb / Ag cakes are used as raw materials to the smelting furnace of soft smelting, or to the ISP (Imperial Smelting Process) of simultaneous smelting of zinc, but the low content of lead and low energy value of its own make it impossible to use it alone and make small amounts of branding. The amount of use has been extremely limited because it must be blended. In addition, a method of recovering lead and silver by smelting Pb / Ag cake alone in an electric furnace was attempted by Mitsubishi Metal Co., Ltd. of Japan, but it was stopped because of economic feasibility.

As a result, new methods for reprocessing Pb / Ag cakes to improve the quality of silver or lead have been sought. One example is Austrian De Zinc SA of Spain, in Finnish Patent Application No. 3435/70. This is the proposed method. In this patent application, the silver and lead components in the Pb / Ag cake are dissolved in the chloride double salt form in the presence of an oxidizing agent in a chloride solution, and then silver and lead are replaced by sulfides or insolubles in a metallic state.

This method requires a large amount of reagents and is difficult to commercialize due to the problem of disposal of waste liquid after recovering silver and lead.

Currently the only commercialization is a method of increasing the content of silver and lead by Pb / Ag cake by the flotation method.

In the enrichment method of silver and lead by the flotation method of Austrian or DeZinc company in Spain, published under Spanish Patent Application No. 411058 (January 27, 1973), Pb / Ag cakes containing no ferrite were first floundered. A silver concentrate of 14,000 g / ton and a second concentrate of 55% lead are recovered separately. In the first barge, the pH of the barge slurry is adjusted to 2 to 4.5, and the collectors such as xanthate or dithiophosphate are used. In the second barge, sodium sulfide and xanthate or dithiophosphate as a sulfiding agent are used. Used. The silver recovery rate is 60% in the primary barge and 91% in the secondary barge is shown.

Pb / Ag cakes can also be used to treat zinc leaching residues of the Sociate des Mines et Faunderies de Zinc de la Vielle Montagne of Belgium published in Japanese Patent Application Laid-Open No. 52-35197 (March 17, 1977). After completely dissolving and removing ferrite in a high temperature high acid, a method of separating and recovering a silver concentrate having a silver content of 5,700 to 10,500 g / ton and a lead concentrate of 56 to 59% of lead secondly has been proposed. Here too, in the primary barge, the pH of the barge slurry is adjusted to 1 to 5 and the mixture of xanthate, alkyl or allyldithiophosphate or alkyl and aryldithiophosphate, or isopropylethylthiocarbatate (about 10% of sulfo And a collector of alkyl or aryl biacid salts (particularly inorganic salts) were used in the secondary flotation. In this method, the recovery rate of silver is 80 to 91% in the primary barge, the lead recovery is 94% in the secondary barge is shown.

This flotation method is high enough to sell silver and lead concentrate, which is the final product to be recovered, and the recovery rate is high enough to satisfy, but has the following disadvantages. In other words, to be a ferrite-free Pb / Ag cake, the zinc leach residue must be leached to very high sulfuric acid concentrations. In order to maintain such Pb / Ag cakes in the range of pH 1 to 5 (or 2 to 4.5) in the flotation process, there is a disadvantage of having to dilute them with a large amount of water inevitably flowing into the Pb / Ag cake. In addition, since many types of reagents such as bubbles, collectors, and activators are used in the first and second barges, the amount of water used to control the pH as well as the cost of the reagents is largely used for wastewater. Will occur.

The present invention proposes a floatation method for recovering silver from a Pb / Ag cake in a new way which improves the disadvantages of the above-mentioned Spanish Patent Application No. 411058 and Japanese Patent Laid-Open No. 52-35197.

According to the present invention, a Pb / Ag cake generated in a wet zinc smelting process using sulfuric acid as a reagent is subjected to a flotation operation at a strong acidity of sulfuric acid concentration of 10 to 70 g / 1 (pH 0.9 to 0.1 equivalent) or a slight sulfidizing agent It is a new method to recover the concentrated silver concentrate by adding a barge operation.

In the recovery method of the present invention, a recycle concentration (filter press filtrate, centrifuge filtrate), water, and sulfuric acid are added to a Pb / Ag cake to obtain a slurry concentration of 100 to 300 g / 1, and an acidity of 10 to 70 g / 1 ( pH 0.9 to 0.1 equivalent) and then the slurry is subjected to the flotation process, in which the air is used to float the silver, or H ₂ S, Na ₂ S and / or sulfidizing agent to the slurry under acidic conditions. Alternatively, NaSH or the like is added to the flotation process to air the silver using air. Silver (and some lead) is recovered and collected as Frosted, washed and filtered to recover silver concentrate. The silver content of the silver concentrate is between 8,000 and 12,000 g / ton and the silver recovery is between 80% and 90%.

Although the acidity of the Pb / Ag cake in the present invention is in a certain range but varies from cake to cake, the recycled solution and concentrated sulfuric acid are added accordingly to adjust the sulfuric acid concentration of the flotation slurry to 10 to 70 g / 1.

The sulfuric acid actually added as a reagent consists of the sum of the Pb / Ag cake itself content and the amount of sulfuric acid introduced into the repulper and conditioner. In the present invention, the Pb / Ag cake itself contains a large amount of sulfuric acid and is recycled. Since the liquid itself has a high acidity, a small amount is actually used.

In the present invention, there is provided a method of performing a barge using sulfuric acid as a reagent, and a method of adding a sulfidizing agent to a barge slurry without adding any other flocculant or foaming agent. As sulfiding agent, 0.2 to 4 g of H ₂ S, Na ₂ S and / or NaSH is used per 1 l of the sludge slurries, and the recovery rate of the sludge is increased by about 5% or more than when the sulfidizing agent is not added.

The amount of air supplied during barge operation is adjusted to allow all silver components to be buoyed as much as possible, and it is generally preferred to carry out 700 Nm3 per ton of Pb / Ag cake.

A feature of the present invention lies in the simple process operation of carrying out barges using only sulfuric acid or some sulfidizing agent in barge operation and also the recycling of the barge process filtrate.

If necessary, the floating process of the present invention may be carried out in several multi-stage processes, and a washing process, a solid-liquid separation process, and the like may be provided where necessary in process design.

Another advantage of the present invention is the wide range of acidity of the barge operation is very convenient in practical operation, and since the starting material Pb / Ag cake can be directly added to the raw material of the barge operation without washing or neutralizing process, a separate neutralizer or dilution water There is no need to reduce the need for water as a whole.

Detailed description of the invention will be described in more detail with reference to FIG.

The raw material Pb / Ag cake 1 is made into a mixed liquid state in the repulper 5 with filter press filtrate 20, centrifuge filtrate 19, water and sulfuric acid circulated several times. Here, the slurry concentration is 300 to 600 g / 1, and the sulfuric acid concentration is 50 to 120 g / 1. This slurry is supplied with additional supply of water and tailing of the cleaner cell 12 in the conditioner 6 to a sulfuric acid concentration in the range of 10 g to 70 g / 1 and, upon addition of the sulfiding agent, to Na ₂ S, NaSH and H. At least one selected from the group consisting of ₂ S is added in the range of 0.2 g to 4 g per 1 l of slurry, and the slurry concentration is finally adjusted to 100 g to 300 g / l.

The slurry of the Pb / Ag cake having the sulfuric acid concentration and the slurry concentration adjusted is supplied to the floating cells 7, 8, and 12 to perform floating operation. Floating operation is usually carried out by bubbling with air and the amount of air is in the range of 600Nm3 to 800Nm3 / ton based on the Pb / Ag cake.

The barge cell is not specially designed, and as a conventional barge device, in order to increase the recovery rate of silver to the product, the primary barge is performed in the rapper cell 7 and the tailing of the rapper cell is again performed in the scavenger cell 8. Frost in the rapper cell 7 and the scavenger cell 8 is collected in the frost tank 11 and then the final barge is made in the cleaner cell 12.

The frost 17 in the cleaner cell 12 is solid-liquid separated in the settler 13 and the centrifuge 14 to become the final silver concentrate 23, and the tailing is conditioner to recover the double silver content again. Is sent. The tailing of the scavenger cell 8 is collected in the tailing tank 9 and solid-liquid separated in the filter press 10 so that the tailing residue 22 is disposed of in a stockyard and the filtrate is partially recycled.

Typical grades of Pb / Ag cake used as raw materials in this process are 3 to 15% zinc, 3 to 13% iron, 15 to 35% lead, 12 to 18% sulfur, and the silver content is about 200 to 1500 g / ton. After flotation, the silver content in the silver concentrate is 6,000 to 12,000 g / ton and the recovery of silver is 80 to 90%.

The following examples further illustrate the present invention, and the present invention is not limited to any form.

Example 1

Take 2 kg of dried Pb / Ag cake of composition 6.2% zinc, 6% iron, 20.5% lead, 15.5% sulfur and 802g / ton silver, turbid with 9l of water and 350g of sulfuric acid for 5 minutes with a stirrer to make slurry concentration 200g / l And acidity to about 50 g / lH ₂ SO ₄ .

The resulting slurry was placed in a laboratory barge cell and buoyed by bubbling over about 10 minutes to collect the subsidiary material, and then washed and solid-liquid separated to obtain 140 g of silver concentrate. Buoy tailing residue was generated 1820g.

The silver concentrate and barge tailing residue composition was as follows, and silver recovery was 82.5%.

Example 2

Take the same Pb / Ag cake as in the sample of Example 1, 2 kg and turbid with 9.5 l of water and 50 g of sulfuric acid for 3 minutes with a stirrer to make a slurry concentration of about 200 g / l and acidity of about 17 g / lH ₂ SO ₄ , followed by sulfiding Add 200 ml of zero 3% NaSH and turbid again for 3 minutes. The resulting slurry was placed in a laboratory buoy cell to be buoyed by bubbling over about 10 minutes to collect the subsidiary material, which was washed and solid-liquid separated to obtain 148 g of silver concentrate. 1859 g of the barge tailing residue occurred. The silver concentrate and flotation tailing residue composition was as follows and silver recovery was 87%.

Example 3

3 kg of dried Pb / Ag cake with a composition of 9.5% zinc, 8.8% iron, 19.5% lead, 14.2% sulfur, and 704 g / ton silver, was turbid with 20 liters of water and 250 g of sulfuric acid for 5 minutes with a stirrer. And acidity to about 30 g / l.

The resulting slurry was placed in a laboratory buoy cell and buoyed for 10 minutes by bubbling to collect the secondary product, followed by washing and solid-liquid separation to obtain 195 g of silver concentrate. First, 2765 g of tailing residue was generated. The silver recovery and flotation tailing residue composition was 81.3%.

Claims (3)

In recovering silver from Pb / Ag cake by flotation operation, sulfuric acid concentration during flotation operation using sulfuric acid as the reagent for flotation operation or using sulfuric acid and sulfidizing agent at a strong acidity of 10 to 70 g / l, and slurry A method for recovering silver from a Pb / Ag cake, characterized in that the concentration is performed by air at a concentration of 100 g / l to 300 g / l. The method of claim 1, wherein the sulfiding agent is subjected to the barge by adding 0.2g to 4g per 1l of the flotation slurry at least one selected from the group consisting of H ₂ S, Na ₂ S and NaSH from the Pb / Ag cake How to recover silver. 2. The Pb according to claim 1, wherein the sulfuric acid consists of the sum of sulfuric acid originally contained in the Pb / Ag cake and sulfuric acid added to the repulper and sulfuric acid contained in the recirculating fluid (filter press filtrate and centrifugal filtrate). To recover silver from ag / Ag cake

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