Method for removing copper and improving gold and silver recovery rate by fire refining of crude silver

Abstract

This invention relates to a method for improving gold and silver recovery by pyrometallurgical refining of crude silver to remove copper. The process steps are as follows: copper-containing precious metal materials are treated by reduction smelting-vacuum distillation to produce a crude silver alloy; the crude silver alloy is then pyrometallurgically refined in a silver separation furnace by blowing compressed air to remove impurities; a slagging agent is then added to the crude silver melt while simultaneously blowing air; finally, a copper-removing agent is added in batches for oxidation to remove copper; the copper-removed slag is then subjected to pressurized acid leaching to recover gold, silver, and copper. The production process proposed in this invention can efficiently remove impurities such as copper from the crude silver alloy, while simultaneously reducing the gold and silver content in the copper-removed slag. After the copper-removed slag is treated by a hydrometallurgical process, gold, silver, and copper are comprehensively recovered, thus improving the gold and silver recovery rate. Furthermore, this method does not generate polluting gases, reducing environmental pollution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pyrometallurgical process, and relates to a method for removing copper in crude silver pyrometallurgical refining to improve gold and silver recovery rate. BACKGROUND

[0002] In the process of extracting precious metals by fire refining, for high-copper lead anode slime and copper-containing precious metal materials, a strong oxidizing agent needs to be added in the silver separation furnace to oxidize copper in the lead anode slime to form slag and achieve the purpose of separating from precious metals. The higher the content of copper oxide in the silver separation furnace slag, the greater the viscosity of the slag, and the more the physical entrainment of precious metals when the slag is discharged, which greatly affects the recovery rate of precious metals. At the same time, the copper oxide slag needs to be reprocessed in the furnace due to the high grade of precious metals contained, thereby increasing the smelting cost.

[0003] The process of copper removal by pyrometallurgical refining of precious metal materials is mainly divided into two categories according to the classification of raw materials. One is for low-melting non-ferrous metals, mainly for the removal of copper in the smelting process of lead and antimony. The process is basically biased towards sulfur copper removal. For example, Wang Weiguo of Guangxi Wanshi Zhi Rare and Precious Metal Technology Co., Ltd. proposed a copper removal agent for antimony smelting production and its application (CN111041231A). A copper removal agent for antimony smelting production was developed, which includes elemental sulfur or sulfur-containing compounds, including elemental phosphorus or phosphorus-containing compounds; the elemental sulfur or sulfur-containing compounds, elemental phosphorus or phosphorus-containing compounds are used alone or mixed in a certain proportion to prepare a copper removal agent for antimony refining. Xu Peilun et al. of Mengzi Mining and Metallurgy Co., Ltd. proposed a treatment method for high-tin and high-copper alloys containing antimony (CN109306409A), which utilizes temperature from high to low to sequentially separate tin, antimony and copper. The above two processes both use the method of fractional crystallization-sulfur copper removal to separate copper from antimony, but in order to reduce the copper content to a certain range, the temperature difference needs to be repeatedly adjusted for fractional crystallization and copper removal, which seriously affects the production efficiency of antimony; secondly, in the process of adding sulfur, sulfur first reacts with antimony before reacting with copper, which requires excessive sulfide. Excessive sulfide will form a large amount of solid slag in the subsequent production process, increasing the subsequent environmental protection cost. The other category is high-melting non-ferrous metals, mainly for the smelting production of gold and silver. Since the pyrometallurgical refining temperature of gold and silver needs to be above 1000℃, sulfur does not play a role in copper removal under this process condition. For high-melting non-ferrous metals, the conventional copper removal process mainly adds saltpeter and sodium carbonate to the silver separation furnace to assist in copper removal. Currently, there is no similar patent disclosed in China. In the journal "Copper Industry Engineering", Li Zhi et al. published "Production Practice of Impurity Control of Gold and Silver Alloy Plates", which introduces the copper removal process in the silver separation furnace. The traditional saltpeter copper removal process adds saltpeter to the silver separation furnace, and manually stirs the saltpeter and gold and silver melt to ensure full contact. However, the disadvantage is that saltpeter is easy to decompose at high temperatures due to its low density, and the utilization rate of saltpeter is extremely low. Through the exploration of production process control, it is found that the effect of saltpeter alloying is not satisfactory, and most importantly, saltpeter produces copper slag, the gold and silver grade is high, and must be treated again, but the copper element has not been opened up and continues to enrich in the process.

[0004] Therefore, to do a good job in copper removal refining of high-melting point metals aims to improve the recovery rate of gold and silver, reduce production costs, reduce environmental pressure, realize the comprehensive recovery of valuable elements, and create better economic and social benefits. SUMMARY

[0005] In order to overcome the problems in the above-mentioned technology, the purpose of the present application is to provide a method for improving the recovery rate of gold and silver by pyrometallurgical refining of crude silver.

[0006] The technical scheme of the present application is implemented as follows: a method for removing copper and improving gold and silver recovery rate in rough silver fire refining, comprising the following process steps:

[0007] a. A copper-containing precious metal material is mixed with coke and soda ash at a ratio of 100:5-8:5-12, and then reduced and smelted at 1200-1250 DEG C to obtain a rough antimony alloy; the rough antimony alloy is treated by oxidation and blowing-refining-vacuum rectification to obtain a rough silver alloy;

[0008] b. The rough silver alloy is added into a silver refining furnace, compressed air is blown in at a temperature of 1000-1100 DEG C to remove impurities by inserting blowing, and the blowing operation is stopped after observing that there is no obvious smoke on the surface of the rough silver melt and the surface is bright;

[0009] c. A slagging agent is added into the rough silver melt, and inserting blowing is simultaneously performed, the blowing is stopped after observing that the surface of the melt is completely covered with floating slag, and the solid oxide slag formed by slagging on the surface of the alloy melt is removed;

[0010] d. A copper removal agent is added into the alloy melt in step c to remove copper by oxidation;

[0011] e. Copper removal slag is obtained after the oxidation and copper removal in step d, the copper in the copper removal slag is in the form of copper sulfate and enters the liquid phase, and then the copper removal slag is treated by pressure acid leaching, the copper in the copper removal slag is converted into copper sulfate, and then the copper sulfate is neutralized by acid and base to obtain a rough copper slag which is transferred to a copper smelting system, and the precious metals gold and silver are left in the slag and returned to the silver refining furnace for smelting treatment;

[0012] Preferably, the rough silver alloy in step a contains 0.4%-0.6% gold, 42%-50% silver, 12%-16% copper and 15%-20% antimony;

[0013] Preferably, compressed air is used for inserting blowing in step b, and the air pipe is inserted into the liquid surface by 20 cm, which can remove As, Sb, Pb and part of Cu in the rough silver alloy;

[0014] Preferably, the slagging agent in step c is soda ash and saltpeter, and the adding ratio is 100:3-5:1-2, the purpose of adding soda ash is to remove Se and Te and form solid slag, and the purpose of adding saltpeter is to release oxygen under the action of high temperature, strengthen the oxidation atmosphere and ensure that the generated solid slag is all oxide slag;

[0015] Preferably, the copper removal agent in step d is iron red, the adding amount is 2:5 of iron copper molar ratio, the adding mode is to add in three batches according to the mass ratio of 4:3:3, and the interval time of each adding is 1-2 h, which can ensure that the reaction can be fully carried out;

[0016] Preferably, the pressure acid leaching pressure in step e is 0.6 Mpa, the sulfuric acid concentration is 3 mol / L, the liquid-solid ratio is 5:1, and the leaching temperature is 60 DEG C.

[0017] The beneficial effects of the present application are that the method for removing copper and improving gold and silver recovery rate of crude silver fire refining utilizes iron red to replace fire nitre to remove copper, and decomposition does not occur at a high temperature of >1300℃, the density of iron red is greater than that of nitre, the penetration of iron red is strong in a molten state, and copper below the liquid surface of the crude silver melt is reacted to achieve the purpose of effective copper removal; the flowability of iron red in a molten state is very good, and agglomeration of gold and silver does not occur during the copper removal process, the gold and silver grade in the copper removal slag is reduced, and the gold and silver recovery rate is improved. The advantage of using iron red is that no polluting gas is generated during the reaction process, and it is green and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The process flowchart of the present application is shown in the figure. DETAILED DESCRIPTION

[0019] In order to better understand and implement, the content of the present application will be described in detail below in combination with examples, and the content of the present application is not limited to the following examples.

[0020] A method for removing copper and improving gold and silver recovery rate of crude silver fire refining is described in detail as follows:

[0021] Example 1: The following steps are used:

[0022] Copper-containing precious metal materials are mixed with coke and soda ash at a ratio of 100:5:8 under the condition of reduction smelting at 1230℃, and crude antimony alloy is produced, the crude antimony alloy is refined and then transferred into an oxidation pot for blowing smelting of antimony white, and antimony white products are produced, and the remaining alloy after the blowing smelting of antimony white is used as raw material for producing gold and silver and is separated by a vacuum distillation process to obtain crude silver alloy containing 0.48% of gold, 45.32% of silver, 14.45% of copper and 18.66% of antimony (see Table 1);

[0023] Table 1: Element content of crude silver alloy

[0024]

[0025] The produced 5 tons of crude silver alloy are subjected to melting treatment by a silver separation furnace, and after melting, compressed air is blown at 1100℃ to insert and remove impurities. Pure soda 175kg and nitre 50kg are added, and iron red is added in three times of 101kg, 76kg and 76kg, and the blowing smelting is continued, and copper slag 2125kg is produced, and the alloy after copper removal is 2349kg. The copper slag is subjected to ball milling-pressurized acid leaching process, the pressure is 0.6Mpa, the sulfuric acid concentration is 3mol / L, the liquid-solid ratio is 5:1, and the leaching temperature is 60℃, and the precious metals gold and silver in the leaching slag are returned to the silver separation furnace for smelting treatment.

[0026] Comparative Example 1: 5 tons of crude silver alloy was subjected to melting treatment using a silver separation furnace. After melting, compressed air was blown in at 1100°C to remove impurities by insertion. Pure soda 175 kg and nitre 250 kg were added and insertion was carried out simultaneously, resulting in copper slag 2050 kg. After copper removal, alloy 2311 kg was obtained. The copper slag was processed in a copper smelting system.

[0027] Table II Comparison of the content of each element in the copper slag produced in the examples and comparative examples

[0028]

[0029] Note: The unit of the elements is g / t.

[0030] Table III Comparison of the content of each element in the alloy after copper removal in the examples and comparative examples

[0031]

[0032] Table IV Comparison of gold and silver recovery rates in the examples and comparative examples

[0033]

[0034] Conclusion: Compared with Comparative Example 1 using nitre as the oxidizing agent for copper removal, the mass of the copper slag and the alloy after copper removal both increased in Example 1 using iron red as the oxidizing agent, but the increase was not significant. In Example 1 using iron red as the oxidizing agent, the gold and silver grades in the copper slag were significantly reduced, and the copper grade was significantly increased, indicating a significant effect of copper removal. The copper slag was treated by two methods, and in Example 1, the gold recovery rate increased by 2.54%, and the silver recovery rate increased by 3%.

Claims

1. A method for copper removal in the fire refining of crude silver to improve the recovery of gold and silver, characterized in that The process comprises the following steps: a. A copper-containing precious metal material is mixed with coke and soda ash at a ratio of 100:5-8:5-12, and then reduced and smelted at 1200-1250 DEG C to produce a crude antimony alloy, which is treated by oxidation and blowing-vacuum distillation to produce a crude silver alloy; b. The crude silver alloy is added to a silver separation furnace, and compressed air is blown into the furnace at a temperature of 1000-1100 DEG C to remove impurities, and the blowing is stopped when no obvious smoke is observed on the surface of the crude silver melt and the surface is bright; c. A slagging agent is added to the crude silver melt, and blowing is performed simultaneously, and the blowing is stopped when the surface of the melt is completely covered with slag, and the solid oxide slag formed on the surface of the alloy melt is removed; d. A copper removal agent is added to the alloy melt in step c to remove copper, and the copper removal agent is iron red, and the addition amount is an iron-copper molar ratio of 2:5, and the addition method is to add in three batches according to a mass ratio of 4:3:3, and the interval time between each addition is 1-2 h to ensure that the reaction can proceed fully; e. After the oxidation and copper removal in step d, a copper removal slag is produced, and the copper removal slag is treated by a pressurized acid leaching process, and the copper in the copper removal slag is in the form of copper sulfate in the liquid phase, and is treated by acid-base neutralization to produce a crude copper slag which is transferred to a copper smelting system, and the precious metals gold and silver are left in the slag and returned to the silver separation furnace for smelting treatment.

2. A process for copper removal and improved gold and silver recovery from crude silver by fire refining as claimed in claim 1 wherein The crude silver alloy in step a contains 0.4-0.6% gold, 42-50% silver, 12-16% copper, and 15-20% antimony.

3. A process for copper removal and improved gold and silver recovery from crude silver by fire refining according to claim 1 or 2, characterized in that In step b, compressed air is used for blowing, and the air pipe is inserted into the liquid surface 20 cm below.

4. The method for removing copper and improving the recovery of gold and silver in the fire refining of crude silver according to claim 1 or 2, characterized in that In step c, the slagging agent is soda ash and saltpeter, and the addition ratio is 100:3-5:1-2 of alloy:soda ash:saltpeter.

5. The method for removing copper and improving the recovery of gold and silver in the fire refining of crude silver according to claim 1 or 2, characterized in that In step e, the pressure of the pressurized acid leaching is 0.6 MPa, the sulfuric acid concentration is 3 mol / L, the liquid-solid ratio is 5:1, and the leaching temperature is 60 DEG C.

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