WO2024255008A1 - Fire refining method for complex lead bullion - Google Patents

Abstract

A fire refining method for complex lead bullion, belonging to the technical field of nonferrous metallurgy. The method comprises: condensing complex lead bullion, so as to obtain low-copper lead and copper dross I; crystallizing the obtained low-copper lead to remove silver and bismuth, so as to obtain low-silver lead and high-silver lead; adding sulfur to the obtained low-silver lead to deeply remove copper, so as to obtain copper-removed lead and copper dross II; and removing arsenic, antimony and tin from the obtained copper-removed lead via an alkaline method, so as to obtain refined lead and arsenic-antimony-tin slag. By using the ''condensation-crystallization-slagging'' method for refining lead, the present invention changes traditional six refining steps into four refining steps, where the lead refining period is shortened by 10%-30%, the silver recovery period is 20%-30% shorter than those in traditional methods, the energy consumption is reduced by 10-20% and the quantity of reagents is reduced by 30%-60%, thereby allowing for significant economic benefits and industrial application.

Description

A complex crude lead pyrometallurgical refining method Technical Field

The invention relates to a complex crude lead pyrometallurgical refining method, belonging to the technical field of nonferrous metal metallurgy.

Background Art

Lead is cheap, has high production volume, and has excellent corrosion and radiation resistance. It is widely used in chemical, cable, battery, and radioactive protection industries. In 2021, my country's refined lead production and consumption ranked first in the world. my country's lead ore resources face problems such as more poor ores, fewer rich ores, and high impurity content. Among them, the content of copper, tin, arsenic, antimony, and bismuth is high, which brings severe challenges to the lead refining process.

In modern lead smelting, lead concentrate is directly smelted to obtain crude lead, and crude lead is refined to obtain refined lead. Crude lead refining usually includes pyrometallurgy and electrolytic refining. At present, there are many companies in the world that use pyrometallurgy to refine crude lead, accounting for about 70% of the refined output. Foreign lead ore has few impurities, and crude lead obtained by reduction smelting is mainly refined by pyrometallurgy; domestic lead ore has many types of impurities, and crude lead obtained by reduction smelting is mainly refined by electrolytic refining. In pyrometallurgy, crude lead is first smelted to remove copper, then sulfur is added to deeply remove copper, alkali is added to remove tin, arsenic and antimony, zinc is added to remove silver, zinc is removed, and bismuth is removed to finally obtain refined lead. The smelting method is used for preliminary copper removal, which can theoretically remove copper to 0.06%, and then sulfur is added to deeply remove copper to 0.001-0.005%; sodium hydroxide and sodium nitrate are generally used to remove arsenic, antimony and tin impurities by oxidation and removal; silver is removed by adding zinc to enrich the silver in the silver-zinc shell; some residual zinc after silver removal can be removed by oxidation, chlorination, alkali and vacuum methods; bismuth is removed by adding calcium and magnesium. In the traditional crude lead pyrometallurgical refining method, each impurity is removed by adding agents to form slag, which requires the addition of a large amount of reagents, a large amount of slag, high energy consumption, a long and time-consuming process, serious environmental pollution, and the introduction of a large number of new impurities.

In electrolytic refining, copper and tin are initially removed from crude lead, anode plates are cast, and cathode lead and anode mud are obtained by electrolysis in electrolyte. The cathode lead is cast into lead ingots. Precious metals are enriched in anode mud, and the lead anode mud must be obtained during the entire lead refining process, and finally recovered from the lead anode mud. The electrolytic refining product is of high quality and is particularly suitable for processing crude lead with high silver and bismuth content. At the same time, it takes a long time to exist, requires large investment, produces a lot of waste liquid, and has a long precious metal recovery cycle. Lead smelters in my country generally adopt preliminary fire refining-electrolytic refining. Preliminary fire refining mainly removes copper and tin. After removing the tin copper, it is cast into anode plates for electrolysis to produce electrolytic lead. Preliminary fire refining is required in the lead refining process, which will result in a long refining process, large construction investment, and the generation of a large amount of waste liquid.

The patent with publication number CN201210031769.0 discloses a method for direct electrolytic refining of crude lead, wherein crude lead is cast into a crude lead anode which is placed in an anode bag, and electrolysis is performed in an additive and perchloric acid-lead perchlorate electrolyte, and the lead in the anode is electrodeposited on the cathode to obtain electrolytic lead at the cathode and anode mud at the anode. In this method, the crude lead is directly electrolytically refined without pre-refining, and the high content of impurity elements such as tin and copper in the crude lead affects the electrolysis efficiency. Tin will enter the cathode lead, which will reduce the quality of the cathode lead, and even the impurity content is high, and the lead ingot is unqualified, and a new process is needed to remove some impurities. The patent with publication number CN201810619887.0 discloses a method for fire refining of complex crude lead, wherein the crude lead melt is oxidized at 800-850°C to obtain lead liquid, the obtained lead liquid is reoxidized at 850-900°C to obtain smoke-like lead oxide, the obtained smoke-like lead oxide is reduced to obtain a reduced product, and the obtained reduced product is repeatedly treated to obtain refined lead. This method requires repeated oxidation and reduction, has high energy consumption, large slag volume, and does not specifically recover precious metals. The patent with publication number CN87104574 discloses a new technology for fire refining of crude lead, wherein the crude lead is subjected to smelting-addition of sulfur to remove copper, alkaline compressed air and oxygen to remove arsenic, antimony and tin, and then crystallization to remove silver and bismuth to obtain refined lead and silver-rich lead, the silver-rich lead is vacuum distilled to obtain crude silver and refined lead or lead alloy, the crude silver is electrolyzed to obtain electrosilver and anode mud, and gold is recovered from the anode mud. This method requires that the impurity silver content in the crude lead be less than 1%, and the bismuth content be 0.02-0.2%. It has high requirements for impurity content and is difficult to meet the refining needs of modern high-bismuth crude lead. It is necessary to add a large amount of sulfur, sodium hydroxide and other reagents to remove copper, tin, arsenic and antimony, which increases the smelting cost. According to the book "Lead Metallurgy" edited by the Nonferrous Heavy Metal Smelting Teaching and Research Section of Northeast Polytechnic University in 1960, the highest impurities in crude lead are: copper 2.028%, tin 0.019%, arsenic 0.957%, antimony 0.66%, bismuth 0.11%, silver 0.18444%, and the impurity content of crude lead in the middle of the last century was generally low. The method in the patent with publication number CN87104574 can be well achieved. However, in recent years, my country's lead ore products have been faced with the characteristics of many types of impurities and high content. The content of copper, tin, arsenic, antimony, bismuth and silver in the crude lead obtained from the smelting material far exceeds the impurity content of crude lead in the last century. Refining using this method will add more reagents and produce more slag. Therefore, the technical solution recorded in the patent application was not finally industrialized. At present, my country generally adopts the method of electrolytic refining of crude lead to avoid adding a large amount of reagents for impurity removal.

The present invention adopts the method of condensation-crystallization-slag making to refine lead and remove impurities from complex crude lead, so as to solve the problems of multiple impurity types and high content in crude lead, complex process and high smelting cost.

In view of this, the present invention is proposed.

Summary of the invention

In view of the problems and shortcomings of the above-mentioned prior art, the present invention provides a complex crude lead pyrometallurgical refining method. The method has simple process, convenient operation, simple required equipment, low cost, high suitability of raw materials, and safe and controllable process. The present invention is implemented by the following technical solutions.

A complex crude lead pyrometallurgical refining method adopts condensation-crystallization-slag making to refine lead, wherein the complex crude lead is condensed, mainly for removing copper, and other impurities such as tin, arsenic, antimony, etc. are also removed in large quantities to obtain low-copper lead and copper scum I; the low-copper lead is continuously crystallized, mainly for removing silver and bismuth, and other impurities such as antimony, arsenic, tin, copper, etc. are also partially removed to obtain low-silver lead and high-silver lead; the low-silver lead is deeply decoppered by adding sulfur to obtain copper-removed lead and copper scum II; the copper-removed lead is added with alkali to remove arsenic, antimony, and tin to obtain refined lead and arsenic, antimony, and tin slag, and the specific steps include:

(1) The complex crude lead is condensed to obtain low-copper lead and copper scum I. During this process, copper will condense and precipitate, and part of the copper will form high-melting point compounds with arsenic, antimony and tin, floating on the lead liquid. These high-melting point compounds are copper scum, which are removed by scooping out the scum, and low-copper lead is obtained under the scum.

(2) removing silver and bismuth from the low-copper lead obtained in step (1) by crystallization to obtain low-silver lead and high-silver lead;

(3) adding sulfur to the low-silver lead obtained in step (2) to perform deep copper removal to obtain copper-removed lead and copper slag II;

(4) Add alkali to the copper-free lead obtained in step (3) to obtain refined lead and arsenic, antimony and tin slag.

The complex crude lead of step (1) comprises lead, copper, tin, arsenic, antimony, silver, bismuth, zinc, iron, chromium and nickel, wherein the lead content is 78.5-99.5wt%, the copper content is 0.01-5.5wt%, the tin content is 0.01-3.2wt%, the arsenic content is 0.02-5.6wt%, the antimony content is 0.02-5.2wt%, the silver content is 0.02-1.5wt%, the bismuth content is 0.01-0.5wt%, and the nickel, iron, zinc and chromium content are all less than 0.1wt%. The sum of the above metal contents is 100%.

The condensation process of step (1) is to first heat up to 480-960°C, then cool down to 320-446°C for condensation, with a cooling rate of 2-8°C/min and a condensation time of 1-5h. The condensed copper scum is separated by centrifugation to obtain low-copper lead, which can reduce the slag production rate and improve the metal recovery rate.

The crystallization enrichment equipment in the step (2) of crystallizing and enriching silver has an inclination angle of 4-12°, a rotation speed of 3-11 r/min, a temperature gradient of 304-335°C, a temperature gradient increment greater than 0.1°C, a high silver lead discharge time interval of 8-52 min/time, a discharge time of 20-80 s, and a processing capacity of 1-30 tons/(unit·day).

The sulfur-adding deep decopperizing reagent in step (3) is sulfur, the temperature is 328-360° C., and the stirring speed is 2-20 r/min.

In the step (4), the reagents for removing arsenic, antimony and tin by alkaline method are sodium nitrate (NaNO ₃ ) and sodium hydroxide (NaOH), and the operating temperature is 380-480° C.

The copper scum I obtained in step (1) and the copper scum II obtained in step (3) are recovered and processed.

The arsenic, antimony and tin slag obtained in step (4) is recovered and processed.

The high-silver lead obtained in step (2) is more than 3 times rich in silver.

The high-silver lead obtained in step (2) is sent to a silver refining step.

The direct recovery rate of silver in the high-silver lead in the above step (2) is greater than 92%.

The crystallization enrichment equipment in the above step (2) is an existing crystallization enrichment equipment, which is the equipment disclosed in the application publication number CN113999992A.

The step (1) condensation refers to the process of liquid phase transformation into solid phase in non-ferrous metal metallurgy.

In the above step (4), the purity of the refined lead is above 99.94wt%, the copper content is less than 0.005wt%, the tin content is less than 0.001wt%, the arsenic content is less than 0.001wt%, the antimony content is less than 0.001wt%, the silver content is less than 0.008wt%, the bismuth content is less than 0.06wt%, the zinc content is less than 0.0005wt%, the iron content is less than 0.002wt%, the chromium content is less than 0.002wt%, and the nickel content is less than 0.002wt%.

The lead recovery rate in the above method of the present invention is above 99.96%.

The beneficial effects of the present invention are:

1. The present invention adopts the condensation method to remove a large amount of copper, tin, arsenic and antimony, with a short process and low smelting cost.

2. The low-copper lead of the present invention removes silver and bismuth by crystallization (physical method), and the silver and bismuth are enriched in the high-silver lead without introducing new impurities, and the direct recovery rate of silver is high.

3. The present invention enriches a large amount of arsenic, antimony, tin and copper in high-silver lead through crystallization, and only a small amount of tin, arsenic, antimony and copper remains in low-silver lead, thereby greatly reducing the use of lead refining additives.

4. The "condensation-crystallization-slag-making" fire-refining lead process of the present invention belongs to a physical method, with a short smelting cycle, low energy consumption, low investment and simple equipment.

5. The raw material of the present invention has high adaptability and can be used for various complex crude lead with high metal recovery rate.

6. The cycle of lead refining by the "condensation-crystallization-slag making" method of the present invention is 1 day, and the energy consumption is 250-300 (kW·h/t).

7. The present invention adopts the method of "condensation-crystallization-slag making" to refine lead, changing the traditional six-step refining into four-step refining. The silver recovery cycle is shortened by 20%-30% compared with the traditional method, the lead refining cycle is shortened by 10%-30%, and the energy consumption is reduced by 10-20%. The present invention has obvious economic benefits and can be fully industrialized.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a process flow chart of the present invention;

Figure 2 is a physical picture of the raw materials and some refined lead products of Example 1 of the present invention; (a) is a complex crude lead raw material, and (b) is a part of the refined lead product.

Implementation

The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

Example 1

As shown in FIG1 , the complex crude lead pyrometallurgical refining method adopts condensation-crystallization-slag making to refine lead, and the specific steps include:

(1) 10 t of complex crude lead (composition see Table 1) was condensed in a condensation pot with a diameter of 1.6 m and a depth of 0.7 m. The temperature was first raised to 650 °C, then cooled to 333 °C at a rate of 5 °C/min and stirred thoroughly. The condensation was continued for 2 h to obtain low-copper lead below the scum (mass and composition see Table 1) and copper scum I (scum above the lead melt);

(2) Remove silver and bismuth from the low copper lead obtained in step (1) by crystallization. The crystallization enrichment equipment is 3m long, 0.52m wide and 0.31m deep. The equipment slope is adjusted to 8°, the rotation speed is 3r/min, the temperature gradient is 305℃-335℃, and the temperature gradient of the equipment increases from low to high as follows: 305℃, 314℃, 320℃, 325℃, 330℃, 335℃, to obtain low silver lead and high silver lead; put the low copper lead melt into the crystallization enrichment silver equipment, when the melt covers the screw shaft, slow down the liquid inlet flow rate, precipitate crystals by natural cooling, and transport the crystals by spiral to high temperature melting and purification to obtain low silver lead, and the molten liquid is refluxed to the low temperature section for further crystallization. After a period of time, the lead content in the low temperature section decreases, and the silver, bismuth, arsenic, antimony and tin content increases to obtain high silver lead. The high silver lead is discharged at a time interval of 30min and the discharge time is 20s. The quality and composition of low silver lead and high silver lead are shown in Table 1. The operation lasts for 9 hours;

(3) The low-silver lead obtained in step (2) was subjected to a deep decoppering operation by adding sulfur (sulfur, the amount of sulfur added was 3.01 kg), the operating temperature was 350°C, the stirring rate was 8 r/min, and copper-free lead (mass and composition table are shown in Table 1) and copper slag II were obtained. The operation lasted for 2 hours.

(4) The copper-free lead obtained in step (3) was subjected to an alkali-adding operation to remove arsenic, antimony and tin. At a temperature of 400°C, 7.16 kg of sodium nitrate (NaNO ₃ ) and 18.51 kg of sodium hydroxide (NaOH) were added, and the arsenic, antimony and tin slag on the surface was removed to obtain refined lead (the mass and composition table are shown in Table 1). The operation lasted for 3 hours.

The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 2, and the crude lead raw material sample pictures and some actual pictures of refined lead products are shown in Figure 2.

Table 1 Chemical composition of complex crude lead raw materials and products

Table 2 Economic indicators of crude lead refining

From Table 1, it can be seen that after condensation, the copper content of the complex crude lead is reduced to 0.112%, and the impurities of arsenic, antimony and tin are significantly reduced. The zinc, iron, cadmium and nickel in the impurities can meet the national standard requirements of "Lead Ingots". The low-silver lead obtained by crystallization contains 0.0024% silver, which is lower than the silver content in Pb99.985 grade. The silver direct recovery rate is 96.59%. The high-silver lead contains 0.39% silver, and the silver is enriched by 3.28 times. After deep decoppering with sulfur, the low-silver lead contains 0.001% copper. After copper-free lead and alkali refining, the arsenic content is 0.0005%, and the antimony content is 0.0008%. All impurities reach Pb99.970 grade.

From Table 2, we can see that compared with the traditional six-step method, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, the direct recovery rate of silver reaches 96.59%, and the lead recovery rate reaches 99.97%. It has obvious economic benefits and can be fully industrialized.

Example 2

As shown in FIG1 , the complex crude lead pyrometallurgical refining method adopts condensation-crystallization-slag making to refine lead, and the specific steps include:

(1) 10 t of complex crude lead (composition see Table 3) was condensed in a condensation pot with a diameter of 1.6 m and a depth of 0.7 m. The temperature was first raised to 500 °C, then cooled to 340 °C at a rate of 2 °C/min and stirred thoroughly. The condensation was continued for 2 h to obtain low-copper lead below the scum (mass and composition see Table 3) and copper scum I (scum above the lead melt);

(2) Remove silver and bismuth from the low copper lead obtained in step (1) by crystallization. The crystallization enrichment equipment is 3m long, 0.52m wide and 0.31m deep. The equipment slope is adjusted to 12°, the rotation speed is 3r/min, the temperature gradient is 305℃-335℃, and the temperature gradient of the equipment increases from low to high as follows: 305℃, 315℃, 320℃, 325℃, 330℃, 335℃, to obtain low silver lead and high silver lead; put the low copper lead melt into the crystallization enrichment silver equipment, when the melt covers the screw shaft, slow down the liquid inlet flow rate, precipitate crystals by natural cooling, and transport the crystals by spiral to high temperature melting and purification to obtain low silver lead, and the molten liquid is refluxed to the low temperature section for further crystallization. After a period of time, the lead content in the low temperature section decreases, and the silver, bismuth, arsenic, antimony and tin content increases to obtain high silver lead. The high silver lead discharge time interval is 50min, and the discharge time is 60s. The quality and composition of low silver lead and high silver lead are shown in Table 3. The operation lasts 11 hours;

(3) The low-silver lead obtained in step (2) was subjected to a deep decoppering operation by adding sulfur (sulfur, the amount of sulfur added was 2.61 kg), the operating temperature was 360°C, the stirring rate was 15 r/min, and copper-free lead (mass and composition table are shown in Table 3) and copper slag II were obtained. The operation lasted for 2.5 hours.

(4) The copper-free lead obtained in step (3) was subjected to an alkali-adding operation to remove arsenic, antimony and tin. At a temperature of 480°C, 2.48 kg of sodium nitrate (NaNO ₃ ) and 6.81 kg of sodium hydroxide (NaOH) were added, and the arsenic, antimony and tin slag on the surface was removed to obtain refined lead (the mass and composition table are shown in Table 3). The operation lasted for 3 hours.

The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 4.

Table 3 Chemical composition of complex crude lead raw materials and products

Table 4 Economic indicators of crude lead refining

From Table 3, it can be seen that after condensation, the copper content of the complex crude lead is reduced to 0.051%, and the impurities of arsenic, antimony and tin are significantly reduced. The zinc, iron, cadmium and nickel in the impurities can meet the national standard requirements of "Lead Ingots". The low-silver lead obtained by crystallization contains 0.0051% silver, which is lower than the silver content in Pb99.940 grade. The silver direct recovery rate is 92.77%. The high-silver lead contains 1.59% silver, and the silver is enriched by 4.72 times. After deep decoppering with sulfur, the low-silver lead contains 0.001% copper. After copper-free lead is refined with alkali, the arsenic content is 0.0005%, and the antimony content is 0.0005%. All impurities reach Pb99.970 grade.

From Table 4, we can see that compared with the traditional six-step method, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, the direct recovery rate of silver reaches 92.77%, and the recovery rate of lead reaches 99.976%. It has obvious economic benefits and can be fully industrialized.

Example 3

As shown in FIG1 , the complex crude lead pyrometallurgical refining method adopts condensation-crystallization-slag making to refine lead, and the specific steps include:

(1) 50 t of complex crude lead (composition see Table 5) was condensed in a condensation pot with a diameter of 2.8 m and a depth of 1 m. The temperature was first raised to 900 °C, then cooled to 340 °C at a rate of 8 °C/min and stirred thoroughly. The condensation was continued for 3 h to obtain low-copper lead below the scum (mass and composition see Table 5) and copper scum I (scum above the lead melt);

(2) Remove silver and bismuth from the low copper lead obtained in step (1) by crystallization. The crystallization enrichment equipment is 4m long, 0.61m wide and 0.42m deep. The equipment slope is adjusted to 10°, the rotation speed is 10r/min, the temperature gradient is 305℃-335℃, and the temperature gradient of the equipment increases from low to high as follows: 305℃, 313℃, 320℃, 325℃, 331℃, 335℃, to obtain low silver lead and high silver lead; put the low copper lead melt into the crystallization enrichment silver equipment, when the melt covers the screw shaft, slow down the liquid inlet flow rate, precipitate crystals by natural cooling, and transport the crystals by spiral to high temperature melting and purification to obtain low silver lead, and the molten liquid is refluxed to the low temperature section for further crystallization. After a period of time, the lead content in the low temperature section decreases, and the silver, bismuth, arsenic, antimony and tin content increases to obtain high silver lead. The high silver lead discharge time interval is 10min, and the discharge time is 20s. The quality and composition of low silver lead and high silver lead are shown in Table 5. The operation lasts for 12 hours;

(3) The low-silver lead obtained in step (2) was subjected to a deep decoppering operation by adding sulfur (sulfur, the amount of sulfur added was 115 kg), the operating temperature was 360°C, the stirring rate was 10 r/min, and copper-free lead (the mass and composition table are shown in Table 5) and copper slag II were obtained. The operation lasted for 2 hours.

(4) The copper-free lead obtained in step (3) was subjected to an alkali-adding operation to remove arsenic, antimony and tin. At a temperature of 450°C, 155.12 kg of sodium nitrate (NaNO ₃ ) and 427.56 kg of sodium hydroxide (NaOH) were added, and the arsenic, antimony and tin slag on the surface was removed to obtain refined lead (the mass and composition table are shown in Table 5). The operation lasted for 3 hours.

The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 6.

Table 5 Chemical composition of complex crude lead raw materials and products

Table 6 Economic indicators of crude lead refining

From Table 5, it can be seen that after condensation, the copper content of the complex crude lead is reduced to 0.336%, and the impurities of arsenic, antimony and tin are significantly reduced. The zinc, iron, cadmium and nickel in the impurities can all meet the national standard requirements of "Lead Ingot". The low-silver lead obtained by crystallization contains 0.0056% silver, which is lower than the silver content in Pb99.940 grade. The high-silver lead contains 1.166% silver, and the silver is enriched by 5.61 times. The low-silver lead contains 0.004% copper after deep decoppering with sulfur. After copper-free lead is refined with alkali, the arsenic content is 0.001%, and the antimony content is 0.0008%. All impurities reach Pb99.940 grade.

From Table 6, we can see that compared with the traditional six-step method, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, the direct recovery rate of silver reaches 93.47%, and the recovery rate of lead reaches 99.98%. It has obvious economic benefits and can be fully industrialized.

Example 4

As shown in FIG1 , the complex crude lead pyrometallurgical refining method adopts condensation-crystallization-slag making to refine lead, and the specific steps include:

(1) 50 tons of complex crude lead (composition see Table 7) was condensed in a condensation pot with a diameter of 2.8 m and a depth of 1 m. The temperature was first raised to 900 °C, then cooled to 340 °C at a rate of 8 °C/min and stirred thoroughly. The condensation was continued for 3 h to obtain low-copper lead below the scum (mass and composition see Table 7) and copper scum I (scum above the lead melt);

(2) The low copper lead obtained in step (1) is crystallized to remove silver and bismuth. The crystallization enrichment equipment is 4m long, 0.61m wide and 0.42m deep. The equipment slope is adjusted to 10°, the rotation speed is 6r/min, the temperature gradient is 305℃-335℃, and the temperature gradient of the equipment increases from low to high as follows: 305℃, 312℃, 318℃, 325℃, 329℃, 335℃, to obtain low silver lead and high silver lead; the low copper lead melt is placed in the crystallization enrichment silver equipment. When the melt covers the screw shaft, the liquid inlet flow rate is slowed down, and the crystals are precipitated by natural cooling. The crystals are transported to high temperature melting and purification by the spiral to obtain low silver lead. The molten liquid is refluxed to the low temperature section for further crystallization. After a period of time, the lead content in the low temperature section is reduced, and the silver, bismuth, arsenic, antimony and tin content is increased to obtain high silver lead. The high silver lead is discharged at a time interval of 45min and the discharge time is 50s. The quality and composition of low silver lead and high silver lead are shown in Table 7. The operation lasts for 16 hours.

(3) The low-silver lead obtained in step (2) was subjected to a deep decoppering operation by adding sulfur (sulfur, the amount of sulfur added was 6.86 kg), the operating temperature was 338°C, the stirring rate was 6 r/min, and copper-free lead (the mass and composition table are shown in Table 7) and copper slag II were obtained. The operation lasted for 2 hours.

(4) The copper-free lead obtained in step (3) was subjected to an alkali-adding operation to remove arsenic, antimony and tin. At a temperature of 380°C, 8.16 kg of sodium nitrate (NaNO ₃ ) and 23.98 kg of sodium hydroxide (NaOH) were added, and the arsenic, antimony and tin slag on the surface was removed to obtain refined lead (the mass and composition table are shown in Table 7). The operation lasted for 4 hours.

The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 8.

Table 7 Chemical composition of complex crude lead raw materials and products

Table 8 Economic indicators of crude lead refining

From Table 7, it can be seen that after condensation, the copper content of the complex crude lead is reduced to 0.0126%, and the impurities of arsenic, antimony and tin are significantly reduced. The zinc, iron, cadmium and nickel in the impurities can meet the national standard requirements of "Lead Ingots". The low-silver lead obtained by crystallization contains 0.0019% silver, which is lower than the silver content in Pb99.985 grade. The high-silver lead contains 0.39% silver, and the silver is enriched by 3.25 times. After deep decoppering with sulfur, the low-silver lead contains 0.001% copper. After copper-free lead is refined with alkali, the arsenic content is 0.001%, and the antimony content is 0.001%. All impurities reach Pb99.970 grade.

From Table 8, we can see that compared with the traditional six-step method, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, the direct recovery rate of silver reaches 97.15%, and the recovery rate of lead reaches 99.99%. It has obvious economic benefits and can be fully industrialized.

The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims (8)

A complex crude lead pyro-refining method, characterized by adopting condensation-crystallization-slag making, and the specific steps include: (1) condensing complex crude lead to obtain low-copper lead and copper slag I; (2) removing silver and bismuth from the low-copper lead obtained in step (1) by crystallization to obtain low-silver lead and high-silver lead; (3) adding sulfur to the low-silver lead obtained in step (2) to perform deep copper removal to obtain copper-removed lead and copper slag II; (4) removing the copper, lead, tin, arsenic and antimony obtained in step (3) by alkaline method to obtain refined lead and arsenic, antimony and tin slag. The complex crude lead fire refining method according to claim 1 is characterized in that the complex crude lead in step (1) comprises lead, copper, tin, arsenic, antimony, silver, bismuth, zinc, iron, chromium and nickel, wherein the lead content is 78.5-99.5wt%, the copper content is 0.01-5.5wt%, the tin content is 0.01-3.2wt%, the arsenic content is 0.02-5.6wt%, the antimony content is 0.02-5.2wt%, the silver content is 0.02-1.5wt%, the bismuth content is 0.01-0.5wt%, and the nickel, iron, zinc and chromium content are all less than 0.1wt%. The complex crude lead fire refining method according to claim 1 is characterized in that: the condensation process in step (1) is to first heat up to 480-960°C and then cool down to 320-446°C for condensation, with a cooling rate of 2-8°C/min and a condensation time of 1-5h. The complex crude lead pyro-refining method according to claim 1 is characterized in that: the crystallization enrichment equipment in the step (2) of crystallizing and enriching silver has an inclination angle of 4-12°, a rotation speed of 3-11 r/min, a temperature gradient of 304-335°C, a temperature gradient increasing by more than 0.1°C, a high silver lead tapping time interval of 8-52 min/time, a tapping time of 20-80 s, and a processing capacity of 1-30 tons/unit/day. The complex crude lead pyrorefining method according to claim 1 is characterized in that: the sulfur-adding deep decopperizing reagent in step (3) is sulfur, the temperature is 328-360°C, and the stirring rate is 2-20r/min. The complex crude lead pyro-refining method according to claim 1 is characterized in that: the reagents for removing arsenic, antimony and tin by alkaline method in step (4) are sodium nitrate and sodium hydroxide, and the operating temperature is 380-480°C. The complex crude lead pyrometallurgical refining method according to claim 1 is characterized in that the copper slag I obtained in step (1), the copper slag II obtained in step (3), and the arsenic, antimony and tin slag obtained in step (4) are classified and recovered. The complex crude lead fire refining method according to claim 1 is characterized in that the high-silver lead obtained in step (2) is sent to a silver refining step.