Fire refining method for complex lead bullion

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 pyrorefining method Technical Field

[0001] The invention relates to a complex crude lead pyrorefining method, belonging to the technical field of nonferrous metal metallurgy. Background Art

[0002] Lead is inexpensive, readily available, and possesses excellent corrosion and radiation resistance, making it widely used in industries such as chemicals, cables, batteries, and radiation protection. In 2021, my country ranked first in the world in both refined lead production and consumption. However, my country's lead ore resources face challenges, including a preponderance of poor-quality ores, a scarcity of rich-quality ores, and high impurity content, particularly high concentrations of copper, tin, arsenic, antimony, and bismuth, posing significant challenges to the lead refining process.

[0003] In modern lead smelting, lead concentrate undergoes direct lead smelting to produce crude lead, which is then refined into refined lead. Crude lead refining typically involves pyrometallurgy and electrolytic refining. Currently, pyrometallurgy is the most common method used by companies worldwide, accounting for approximately 70% of refined lead output. Foreign lead ores, which contain fewer impurities, primarily undergo pyrometallurgy for crude lead obtained through reduction smelting. Domestic lead ores, which contain a wide variety of impurities, primarily undergo electrolytic refining for crude lead obtained through reduction smelting. Pyrometallurgy involves six steps: first, smelting to remove copper; then, adding sulfur for deep copper removal; then, adding alkali to remove tin, arsenic, and antimony; finally, adding zinc to remove silver; finally, removing zinc and bismuth. The smelting method initially removes copper, theoretically down to 0.06%. Sulfur is then added to further remove the copper to 0.001-0.005%. Arsenic, antimony, and tin are typically removed by oxidation with sodium hydroxide and sodium nitrate. Silver is removed by adding zinc, concentrating it in a silver-zinc shell. Residual zinc after silver removal can be removed using oxidation, chlorination, alkaline, and vacuum methods. Bismuth is removed by adding calcium and magnesium. Traditional crude lead fire refining removes each impurity by adding reagents to create slag. This requires the addition of large amounts of reagents, resulting in large slag volumes and high energy consumption. The process is long and time-consuming, causing significant environmental pollution and introducing numerous new impurities.

[0004] During electrolytic refining, crude lead undergoes initial copper and tin removal, anode plates are cast, and electrolysis in an electrolyte produces cathode lead and anode mud. The cathode lead is then cast into lead ingots. Precious metals are concentrated in the anode mud, requiring the entire lead refining process to produce the lead anode mud, which is then recovered from the lead anode mud. Electrolytic refining produces high-quality products and is particularly suitable for processing crude lead with high silver and bismuth content. However, it requires a long production process, high investment, and significant wastewater, leading to a long precious metal recovery cycle. Lead smelters in my country generally utilize a preliminary fire refining followed by electrolytic refining. The preliminary fire refining primarily removes copper and tin. After the copper is removed, it is cast into anode plates for electrolysis to produce electrolytic lead. The need for preliminary fire refining during the lead refining process results in a lengthy refining process, high construction investment, and the generation of significant wastewater.

[0005] Patent publication number CN201210031769.0 discloses a method for direct electrolytic refining of crude lead. Crude lead is cast into crude lead anodes, which are then enclosed in anode bags. Electrolysis is then carried out in an electrolyte solution containing additives and perchloric acid-lead perchlorate. The lead in the anodes is electrodeposited onto cathodes, producing electrolead at the cathodes and anode mud at the anodes. This method, in which the crude lead is directly electrorefined without pre-refining, results in high levels of impurities such as tin and copper, which affect electrolysis efficiency. Tin can also enter the cathode lead, reducing its quality and potentially rendering the lead ingots substandard due to high impurity levels. New processes are needed to remove some of these impurities. Patent publication number CN201810619887.0 discloses a method for pyro-refining complex crude lead. The crude lead melt is oxidized at 800-850°C to produce lead liquid, which is then reoxidized at 850-900°C to produce fumed lead oxide. The fumed lead oxide is then reduced to a reduced product, which is then repeatedly processed to produce refined lead. This method requires repeated oxidation and reduction, consumes a lot of energy, produces large amounts of slag, and does not specifically recover precious metals. Patent publication number CN87104574 discloses a new pyro-refining technology for crude lead. The crude lead undergoes smelting and sulfur addition to remove copper, followed by alkaline compressed air and oxygen to remove arsenic, antimony, and tin. Then, silver and bismuth are removed by crystallization to produce refined lead and silver-rich lead. The silver-rich lead is vacuum distilled to produce crude silver and refined lead or a lead alloy. The crude silver is electrolyzed to produce electrosilver and anode mud, from which gold is recovered. This method requires that the impurity silver content in the crude lead be less than 1%, and the bismuth content be between 0.02-0.2%. The impurity content requirements are high and it is difficult to meet the refining needs of modern high-bismuth crude lead. A large amount of sulfur, sodium hydroxide and other reagents need to be added 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%, and silver 0.18444%. In the middle of the last century, the impurity content of crude lead was generally low, and the method described 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 and high contents of impurities. The copper, tin, arsenic, antimony, bismuth, and silver contents in the crude lead obtained from the melt far exceed 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 this patent application was ultimately not 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.

[0006] The present invention adopts the method of condensation-crystallization-slagging to refine lead and remove impurities from complex crude lead, thereby solving the problems of crude lead having many types of impurities, high content, complex process and high smelting cost.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] To address the aforementioned problems and shortcomings of the prior art, the present invention provides a complex crude lead pyrorefining method. This method features simple processing, convenient operation, minimal equipment requirements, low cost, high-quality raw materials, and a safe and controllable process. The present invention is achieved through the following technical solutions.

[0009] A fire refining method for complex crude lead comprises the following steps: condensing the complex crude lead to mainly remove copper, and also removing a large amount of tin, arsenic, antimony and other impurities, to obtain low-copper lead and copper scum I; continuously crystallizing the low-copper lead to mainly remove silver and bismuth, and also partially remove other impurities such as antimony, arsenic, tin, and copper, to obtain low-silver lead and high-silver lead; deeply decoppering the low-silver lead by adding sulfur to obtain decoppered lead and copper scum II; and adding alkali to the decoppered lead to remove arsenic, antimony, and tin, to obtain refined lead and arsenic, antimony, and tin slag. The specific steps comprise:

[0010] (1) The complex crude lead is condensed to obtain low-copper lead and copper slag I. During this process, copper will condense and precipitate, and some copper will form high-melting-point compounds with arsenic, antimony and tin, floating on the lead liquid. These high-melting-point compounds are copper slag, which is removed by slag shavings, and low-copper lead is obtained under the slag.

[0011] (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;

[0012] (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;

[0013] (4) Add alkali to the copper-removed lead obtained in step (3) to obtain refined lead and arsenic, antimony and tin slag.

[0014] 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%.

[0015] The condensation process in step (1) is to first heat the temperature to 480-960°C, then cool it 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 slag is separated by centrifugation to obtain low-copper lead, which can reduce the slag production rate and improve the metal recovery rate.

[0016] 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 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).

[0017] In the step (3), the sulfur-adding deep decoppering reagent is sulfur, the temperature is 328-360° C., and the stirring rate is 2-20 r / min.

[0018] In the step (4), the reagents for removing arsenic, antimony and tin by alkaline method are sodium nitrate (NaNO3) and sodium hydroxide (NaOH), and the operating temperature is 380-480°C.

[0019] The copper scum I obtained in step (1) and the copper scum II obtained in step (3) are recovered and processed.

[0020] The arsenic, antimony and tin slag obtained in step (4) is recovered and processed.

[0021] The high-silver lead silver obtained in step (2) is enriched more than 3 times.

[0022] The high-silver lead obtained in step (2) is sent to a silver refining step.

[0023] The direct recovery rate of silver in the high-silver lead in step (2) is greater than 92%.

[0024] 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.

[0025] The step (1) condensation refers to the process of liquid phase transformation into solid phase in nonferrous metal metallurgy.

[0026] The refined lead in the above step (4) has a purity of 99.94 wt% or more, contains less than 0.005 wt% of copper, less than 0.001 wt% of tin, less than 0.001 wt% of arsenic, less than 0.001 wt% of antimony, less than 0.008 wt% of silver, less than 0.06 wt% of bismuth, less than 0.0005 wt% of zinc, less than 0.002 wt% of iron, less than 0.002 wt% of chromium, and less than 0.002 wt% of nickel.

[0027] The lead recovery rate in the method of the present invention is above 99.96%.

[0028] The beneficial effects of the present invention are:

[0029] 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.

[0030] 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.

[0031] 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, greatly reducing the use of lead refining additives.

[0032] 4. The "condensation-crystallization-slagging" fire-refining lead process of the present invention is a physical method with a short smelting cycle, low energy consumption, low investment and simple equipment.

[0033] 5. The raw materials of the present invention have high adaptability and can be used for various complex crude lead with high metal recovery rate.

[0034] 6. The cycle of the lead refining process of the present invention, which involves condensation-crystallization-slagging, is one day, with an energy consumption of 250-300 kW·h / t.

[0035] 7. This invention utilizes a "condensation-crystallization-slag-forming" method for lead refining, reducing the traditional six-step refining process to four. This reduces the silver recovery cycle by 20%-30%, the lead refining cycle by 10%-30%, and energy consumption by 10%-20%. This invention offers significant economic benefits and is ready for full industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Fig. 1 is a process flow chart of the present invention;

[0037] Figure 2 is a physical picture of the raw materials and some refined lead products of Example 1 of the present invention; (a) is the complex crude lead raw material, and (b) is some refined lead products. Implementation Method

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0039] As shown in FIG1 , the complex crude lead fire refining method adopts condensation-crystallization-slagging to refine lead, and the specific steps include:

[0040] (1) 10 tons of complex crude lead (composition shown in 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 shown in Table 1) and copper scum I (scum above the lead melt).

[0041] (2) The low-copper lead obtained in step (1) is crystallized to remove silver and bismuth. 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℃, and 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. 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 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.

[0042] (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.

[0043] (4) The copper-removed lead obtained in step (3) was subjected to an alkali-addition operation to remove arsenic, antimony and tin. At a temperature of 400°C, 7.16 kg of sodium nitrate (NaNO3) 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 is shown in Table 1). The operation lasted for 3 hours.

[0044] The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 2, and the pictures of crude lead raw material samples and some actual pictures of refined lead products are shown in Figure 2.

[0045] Table 1 Chemical composition of complex crude lead raw materials and products

[0046]

[0047] Table 2 Economic indicators of crude lead refining

[0048]

[0049] As can be seen from Table 1, after condensation, the copper content of the complex crude lead is reduced to 0.112%, and the impurities 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 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-removing lead and alkali refining, the arsenic content is 0.0005%, and the antimony content is 0.0008%. All impurities reach Pb99.970 grade.

[0050] Table 2 shows that compared with the traditional six-step process, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, and the direct recovery rate of silver reaches 96.59%, while the lead recovery rate reaches 99.97%. This method has significant economic benefits and is now ready for full industrial application. Example 2

[0051] As shown in FIG1 , the complex crude lead fire refining method adopts condensation-crystallization-slagging to refine lead, and the specific steps include:

[0052] (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 with sufficient stirring. 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).

[0053] (2) The low-copper lead obtained in step (1) is crystallized to remove silver and bismuth. 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℃, and 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 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 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 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.

[0054] (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 2.5 hours.

[0055] (4) The copper-removed lead obtained in step (3) was subjected to an alkali-addition operation to remove arsenic, antimony, and tin. At a temperature of 480°C, 2.48 kg of sodium nitrate (NaNO3) and 6.81 kg of sodium hydroxide (NaOH) were added to remove the arsenic, antimony, and tin slag on the surface to obtain refined lead (see Table 3 for mass and composition). The operation lasted for 3 hours.

[0056] The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 4.

[0057] Table 3 Chemical composition of complex crude lead raw materials and products

[0058]

[0059] Table 4 Economic indicators of crude lead refining

[0060]

[0061] As can be seen from Table 3, after condensation, the copper content of the complex crude lead is reduced to 0.051%, and the impurities 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 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-removing lead and alkali refining, the arsenic content is 0.0005%, and the antimony content is 0.0005%. All impurities reach Pb99.970 grade.

[0062] Table 4 shows that compared with the traditional six-step process, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, and the direct silver recovery rate reaches 92.77%, while the lead recovery rate reaches 99.976%. This method has significant economic benefits and is now ready for full industrial application. Example 3

[0063] As shown in FIG1 , the complex crude lead fire refining method adopts condensation-crystallization-slagging to refine lead, and the specific steps include:

[0064] (1) 50 tons of complex crude lead (composition shown in 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 with sufficient stirring. The condensation was continued for 3 h to obtain low-copper lead below the scum (mass and composition shown in Table 5) and copper scum I (scum above the lead melt).

[0065] (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 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℃, and 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 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 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 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 12 hours.

[0066] (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 (mass and composition table are shown in Table 5) and copper slag II were obtained. The operation lasted for 2 hours.

[0067] (4) The copper-removed lead obtained in step (3) was subjected to an alkali-addition operation to remove arsenic, antimony and tin. At a temperature of 450°C, 155.12 kg of sodium nitrate (NaNO3) 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 is shown in Table 5). The operation lasted for 3 hours.

[0068] The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 6.

[0069] Table 5 Chemical composition of complex crude lead raw materials and products

[0070]

[0071] Table 6 Economic indicators of crude lead refining

[0072]

[0073] From Table 5, it can be seen that after coagulation, 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 Ingots". 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. After deep decoppering with sulfur, the low-silver lead contains 0.004% copper. After alkali refining of copper-free lead, the arsenic content is 0.001% and the antimony content is 0.0008%. All impurities reach the Pb99.940 grade.

[0074] Table 6 shows that compared with the traditional six-step process, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, and the direct silver recovery rate reaches 93.47% and the lead recovery rate reaches 99.98%. This method has significant economic benefits and is now ready for full industrial application. Example 4

[0075] As shown in FIG1 , the complex crude lead fire refining method adopts condensation-crystallization-slagging to refine lead, and the specific steps include:

[0076] (1) 50 tons of complex crude lead (composition shown in 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 with sufficient stirring. The condensation was continued for 3 h to obtain low-copper lead below the scum (mass and composition shown in Table 7) and copper scum I (scum above the lead melt).

[0077] (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℃, and 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 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 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 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 16 hours.

[0078] (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 (mass and composition table are shown in Table 7) and copper slag II were obtained. The operation lasted for 2 hours.

[0079] (4) The copper-removed lead obtained in step (3) was subjected to an alkali-addition operation to remove arsenic, antimony and tin. At a temperature of 380°C, 8.16 kg of sodium nitrate (NaNO3) 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 is shown in Table 7). The operation lasted for 4 hours.

[0080] The comprehensive energy consumption and economic and technical indicators of this operation are shown in Table 8.

[0081] Table 7 Chemical composition of complex crude lead raw materials and products

[0082]

[0083] Table 8 Economic indicators of crude lead refining

[0084]

[0085] It can be seen from Table 7 that after condensation, the copper content of the complex crude lead is reduced to 0.0126%, and the impurities 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 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-removing lead and alkali refining, the arsenic content is 0.001%, and the antimony content is 0.001%. All impurities reach Pb99.970 grade.

[0086] Table 8 shows that compared with the traditional six-step process, the lead refining cycle is shortened by 10%-30%, energy consumption is reduced by 10%-20%, and the direct silver recovery rate reaches 97.15%, while the lead recovery rate reaches 99.99%. This method has significant economic benefits and is now ready for full industrial application.

[0087] The above describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A complex crude lead pyro-refining method, characterized in that: The condensation-crystallization-slagging method is adopted, 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.

2. The complex crude lead fire refining method according to claim 1, characterized in that: 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%.

3. The complex crude lead fire refining method according to claim 1, characterized in that: 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.

4. The complex crude lead fire refining method according to claim 1, 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 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.

5. The complex crude lead fire refining method according to claim 1, characterized in that: 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.

6. The complex crude lead fire refining method according to claim 1, characterized in that: In the step (4), the reagents for removing arsenic, antimony and tin by alkaline method are sodium nitrate and sodium hydroxide, and the operating temperature is 380-480°C.

7. The complex crude lead fire refining method according to claim 1, characterized in that: The copper scum I obtained in step (1), the copper scum II obtained in step (3), and the arsenic, antimony, and tin slag obtained in step (4) are classified and recovered.

8. The complex crude lead fire refining method according to claim 1, characterized in that: The high-silver lead obtained in step (2) is sent to a silver refining step.

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