A lead removing agent and its use

Abstract

The application discloses a kind of lead removal agent, including the following mass percentage of components: 30-50% boron calcium alloy, 10-20% sodium fluorosilicate, 10-20% sodium fluoroaluminate, 15-25% calcium fluoride and 5-10% silicon dioxide.The application also discloses the application of the lead removal agent in waste brass lead removal and the method for producing lead-free brass by using waste brass.The lead removal agent of the application contains boron calcium alloy, which can react with Pb and Pb compound in copper water to generate CaPb and CaPb2.CaPb and CaPb2 have low density and can float to be fished out.B element can react with Al and Fe in copper to produce heterogeneous nucleation points, which can provide crystallization nucleation during melting and crystallization process, and can greatly refine ingot grain structure.The lead removal agent of the application can reduce the Pb content in waste brass to 0.01wt%, and has excellent lead removal effect, and has wide application prospect in waste brass recovery and recycling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of copper melt purification and waste copper recycling and reuse, and particularly relates to a lead removal agent and application thereof. BACKGROUND

[0002] China, as the largest copper processing material producing and consuming country, has an increasing demand for recycled copper. The sorted recycled copper can be used as a copper raw material in the smelting process, and has the advantages of energy saving, environmental protection and economy compared with primary copper.

[0003] Recycled copper is generally derived from scrap copper-containing waste, processing waste, copper slag and the like, and has a wide source and complex composition. It needs to be strictly sorted before use, otherwise it may lead to abnormal composition and performance of copper products. Waste and old yellow scrap copper is one of the more common types of scrap copper, and in addition to main elements such as copper and zinc, it may also contain elements such as lead, tin, silicon, nickel and iron. It is generally downgraded for the production of lead brass products and cannot be upgraded for the production of common brass or lead-free brass. This undoubtedly reduces the application range of scrap yellow scrap copper and increases the production cost of lead-free brass.

[0004] Patent document CN103146939B discloses a method for reducing the lead content in lead brass, and the main components of the additive are calcium-magnesium alloy, boric acid, and rare earth cerium, yttrium and lanthanum oxides. The main mechanism is to form a metal compound with lead and remove it as an impurity from the melt by high-temperature metallurgical methods. However, the increase in the residual amount of Mg in the additive reduces the processing performance of the brass. In addition, the cost of rare earth cerium, yttrium and lanthanum oxides is relatively high.

[0005] Patent document CN102251136A discloses a lead removal composite agent for waste red copper and a manufacturing method thereof. Quartz sand, sodium borate, calcium salt, sodium chloride and fly ash are used. Lead is first oxidized when used, but the binding ability of the matrix element Zn to oxygen in brass is stronger than that of Pb. This method is difficult to remove Pb in brass.

[0006] Therefore, in view of the deficiencies of the prior art, it is of great significance to find a new lead removal agent to remove lead from scrap copper for the recycling and reuse of scrap copper, and to protect the environment and regenerate copper resources in China. SUMMARY

[0007] To solve the above technical problems, the present application provides a lead removal agent which has excellent lead removal performance and can refine the grain structure of the ingot.

[0008] A lead removal agent comprises the following components in mass percentage: 30-50% of calcium-boron alloy, 10-20% of sodium fluorosilicate, 10-20% of sodium fluoroaluminate, 15-25% of calcium fluoride and 5-10% of silicon dioxide.

[0009] The lead removal agent of the present application contains a boron-calcium alloy, which can react with Pb and Pb compounds in copper water to form CaPb and CaPb2, and the CaPb and CaPb2 can be floated to be removed by skimming due to their low density; the element B can react with Al and Fe in the copper dross to form heterogeneous nucleation points, which can provide nucleation during melting and casting, and greatly refine the grain structure of the ingot.

[0010] The sodium fluorosilicate can reduce the melting point of the copper dross, separate the copper dross or copper dross scraps coated with oxides, and re-melt into the copper liquid; the NaF generated by the decomposition reaction can reduce the viscosity of the copper dross and cover and protect the copper water.

[0011] The sodium fluoroaluminate can reduce the viscosity of the copper dross and improve its fluidity, thereby providing conditions for the floating of CaPb and CaPb2.

[0012] The calcium fluoride can improve the fluidity of the copper dross and reduce its viscosity, and the surface coverage can isolate oxygen from entering.

[0013] The silicon dioxide can form silicates with other metals and cover the surface to form slag.

[0014] Preferably, the content of boron in the boron-calcium alloy is 10-20wt%. Although the element B can provide nucleation during melting and casting and refine the grain structure of the ingot, too much B will cause difficulties in subsequent processing. Therefore, the content of B in the boron-calcium alloy is selected to be 10-20wt% in the present application.

[0015] The present application also provides the application of the lead removal agent in the removal of Pb from waste brass. The lead removal agent of the present application can reduce the content of Pb in the waste brass to below 0.06wt%, and has excellent lead removal effect.

[0016] The present application also provides a method for producing lead-free brass from waste brass, which comprises the following steps:

[0017] (1) After sorting the waste brass to remove impurities, the waste brass is added into a smelting furnace and smelted until completely melted;

[0018] (2) The temperature of the melt is adjusted to 920-980℃, the lead removal agent is added into the melt, stirred, and heat-insulated, and then the temperature of the melt is increased to 990-1050℃ for refining, skimming, tapping, and pouring.

[0019] Preferably, the sorting is sequentially performed by using a magnetic screen, a mechanical screen, and gravity sorting.

[0020] Preferably, the content of Pb in the waste brass is 1-3.5wt%, and the mass ratio of the waste brass to the lead removal agent is 50-150:1.

[0021] Preferably, the lead content in the scrap brass is 1.5-3wt%, and the mass ratio of the scrap brass to the calcium element in the lead removal agent is 200-400:1. Controlling the mass ratio of the lead removal agent to the calcium element in the present application within this range can make the calcium combine with the lead to form the floatable metal compound CaPb and CaPb2, thereby being removed by slagging.

[0022] Preferably, the lead content in the scrap brass is 1.5-3wt%, and the mass ratio of the scrap brass to the boron element in the lead removal agent is 800-1200:1. Controlling the mass ratio of the scrap brass to the boron element in the lead removal agent within this range in the present application can avoid the material becoming brittle due to excessive boron, causing processing cracking, and greatly refining the ingot grain structure.

[0023] Preferably, the lead removal agent is added into the melt after being coated with copper and platinum.

[0024] Preferably, the stirring time is 3-5min, and the holding time is 10-15min.

[0025] The present application first sorts the scrap brass, removes the impurities, and then melts until completely melted. The melt temperature is adjusted to 920-980℃, the lead removal agent is added and stirred, and then held to form the metal compound CaPb and CaPb2 of lead. CaPb and CaPb2 have low density and float up. Then the melt is heated to 990-1050℃ for refining, slagging, tapping and pouring. The lead removal agent of the present application can reduce the Pb content in the scrap brass to below 0.06wt%, even as low as 0.01wt%, and has excellent lead removal effect. Moreover, the lead removal agent of the present application can provide crystal nucleation during the melting and crystallization process, greatly refining the ingot grain structure, and the grain size can reach 0.01-0.05mm.

[0026] Compared with the prior art, the present application has at least the following beneficial effects:

[0027] (1) The lead removal agent of the present application contains boron-calcium alloy, which can react with Pb and Pb compounds in copper water to form CaPb and CaPb2, and CaPb and CaPb2 have low density and can float up to be removed by slagging. The B element can react with Al and Fe in the scrap brass to produce heterogeneous nucleation points, which can provide crystal nucleation during the melting and crystallization process, greatly refining the ingot grain structure.

[0028] (2) The lead removal agent of the present application can reduce the Pb content in the scrap brass to below 0.06wt%, even as low as 0.01wt%, and has extremely excellent lead removal effect, and has broad application prospects in the recycling and reuse of scrap brass. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1is a macroscopic metallographic photo of the crystalline structure of the brass cast by Example 4;

[0030] Figure 2 is a macroscopic metallographic photo of the crystalline structure of the brass cast by the comparative example. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application.

[0032] The compositions of the lead removal agents in the embodiments and the comparative example of the present application are shown in Table 1.

[0033] Table 1 Composition of the lead removal agent in the embodiments and the comparative example (wt%)

[0034]

[0035] Example 1:

[0036] (1) Pretreatment of the waste brass: The yellow brass is sorted to remove impurities by magnetic screening, mechanical screening and gravity separation;

[0037] (2) According to the composition requirements, 200 kg of waste yellow brass is taken and added into a smelting furnace to be smelted until completely melted;

[0038] (3) The temperature of the melt is adjusted to 920℃, the Pb content is measured to be 2.9wt% by a direct-reading spectrometer, and 0.7% of the copper water mass of the copper foil coated lead removal agent is added into the melt, the composition is shown in Table 1. After the lead removal agent is added, the mechanical stirring is carried out for 3 min, and then the melt is kept for 10 min, after that the melt is heated to 990℃, the Pb content is measured to be 0.05wt% by a direct-reading spectrometer after sampling, and after refining, slagging, tapping and pouring, the average grain size of the ingot is 0.05mm.

[0039] Example 2:

[0040] (1) Pretreatment of the waste brass: The yellow brass is sorted to remove impurities by magnetic screening, mechanical screening and gravity separation;

[0041] (2) According to the composition requirements, 200 kg of waste yellow brass is taken and added into a smelting furnace to be smelted until completely melted;

[0042] (3) Adjust the melt temperature to 940℃, the Pb content is 3.0wt% by direct reading spectrometer, add 0.9% copper water mass copper foil coated de-lead agent in the melt, the composition is shown in Table 1. After adding the de-lead agent, mechanically stir for 3.5min, then keep for 12min, then heat the melt to 1000℃, the Pb content is 0.06wt% by direct reading spectrometer after sampling, after refining, slagging, tapping and pouring, the average grain size of the ingot is 0.04mm.

[0043] Example 3:

[0044] (1) Pretreatment of waste brass: sort the brass scrap, remove impurities by magnetic screening, mechanical screening and gravity separation;

[0045] (2) According to the composition requirements, take 150kg of waste brass scrap, add it to the smelting furnace and melt until completely melted;

[0046] (3) Adjust the melt temperature to 960℃, the Pb content is 2.9wt% by direct reading spectrometer, add 1.2% copper water mass copper foil coated de-lead agent in the melt, the composition is shown in Table 1. After adding the de-lead agent, mechanically stir for 4min, then keep for 13min, then heat the melt to 1010℃, the Pb content is 0.02wt% by direct reading spectrometer after sampling, after refining, slagging, tapping and pouring, the average grain size of the ingot is 0.03mm.

[0047] Example 4:

[0048] (1) Pretreatment of waste brass: sort the brass scrap, remove impurities by magnetic screening, mechanical screening and gravity separation;

[0049] (2) According to the composition requirements, take 250kg of waste brass scrap, add it to the smelting furnace and melt until completely melted;

[0050] (3) Adjust the melt temperature to 980℃, the Pb content is 2.75wt% by direct reading spectrometer, add 1.8% copper water mass copper foil coated de-lead agent in the melt, the composition is shown in Table 1. After adding the de-lead agent, mechanically stir for 5min, then keep for 15min, then heat the melt to 1050℃, the Pb content is 0.01wt% by direct reading spectrometer after sampling, after refining, slagging, tapping and pouring, the average grain size of the ingot is 0.01mm, the macroscopic metallographic photograph of the brass crystalline structure of this example is shown in Figure 1 .

[0051] Comparative Example:

[0052] (1) Pretreatment of waste brass: sort the brass scrap, remove impurities by magnetic screening, mechanical screening and gravity separation;

[0053] (2) According to the composition requirement, 250 kg of waste and old yellow copper alloy was taken and added into a smelting furnace to be smelted until completely melted;

[0054] (3) The temperature of the melt was adjusted to 980°C, the content of Pb was 3.51wt% measured by direct-reading spectrometer, mechanical stirring was carried out for 5 min, and then the melt was kept for 15 min, after that the temperature of the melt was increased to 1050°C, the content of Pb was 2.7wt% measured by direct-reading spectrometer after sampling, after refining, slagging, tapping and pouring, the average grain size of the ingot was 0.15 mm, and the macroscopic metallographic photo of the crystalline structure of the brass of the present comparative example was shown in Figure 2 The comparison Figure 1 and Figure 2 indicated that the lead removal agent of the present example could greatly refine the crystalline structure of the ingot.

Claims

1. A lead removal agent, characterized in that, The lead removal agent comprises the following components in mass percentage: 30-50% of boron-calcium alloy, 10-20% of sodium fluorosilicate, 10-20% of sodium fluoroaluminate, 15-25% of calcium fluoride and 5-10% of silicon dioxide; the boron content in the boron-calcium alloy is 10-20 wt%.

2. The application of the lead removal agent of claim 1 in lead removal of scrap brass.

3. A method for producing a lead-free brass using scrap brass, characterized by, The method comprises the following steps: (1) adding the sorted scrap brass into a smelting furnace and smelting until completely melted; (2) adjusting the temperature of the melt to 920-980℃, adding the lead removal agent of claim 1 into the melt, stirring, keeping warm, then increasing the temperature of the melt to 990-1050℃ for refining, slagging, tapping and pouring.

4. The method of producing lead-free brass from scrap brass as claimed in claim 3, wherein, The sorting is sequentially carried out by magnetic screening, mechanical screening and gravity sorting.

5. The method of producing lead-free brass from scrap brass as claimed in claim 3, wherein, The lead content in the scrap brass is 1-3.5 wt%, and the mass ratio of the scrap brass to the lead removal agent is 50-150:

1.

6. The method of producing lead-free brass from scrap brass as claimed in claim 3, wherein, The lead content in the scrap brass is 1.5-3 wt%, and the mass ratio of the scrap brass to the calcium element in the lead removal agent is 200-400:

1.

7. The method for producing lead-free brass by using scrap brass according to claim 3, wherein the lead content in the scrap brass is 1.5-3 wt%, and the mass ratio of the scrap brass to the boron element in the lead removal agent is 800-1200:

1.

8. The method of producing lead-free brass from scrap brass as claimed in claim 3, wherein, The stirring time is 3-5 min, and the keeping warm time is 10-15 min.

9. The method of producing unleaded brass from scrap brass alloy according to any one of claims 3 to 8, wherein The grain size of the lead-free brass ingot is 0.01-0.05 mm.

Images