A method for removing cadmium from lead-antimony smelting

Abstract

The application discloses a method for removing cadmium in lead-antimony smelting, which comprises the following steps: S1, after the slag in the furnace is cleaned, the temperature of the alloy liquid in the furnace is increased to 800 DEG C; S2, prepared lead-removing slag is put into the furnace through a discharging opening for smelting; S3, after the smelting is completed and the molten liquid is in a water-like state, compressed air is blown into the antimony liquid through a small air pipe which is added from the furnace door, the blowing is continuously carried out for 60-90 minutes under the furnace temperature of 700 DEG C-850 DEG C, during the period of the small air pipe, the operator should swing the air pipe once every 20-30 minutes, the position of the small air pipe is changed, and the smelting pool is uniformly stirred; when the surface of the slag is gray-black, the small air pipe is drawn out for slag cleaning, then the operation is repeated, sampling and testing are carried out until the cadmium content of the product reaches the requirement, and the cadmium-removed crude lead-antimony alloy is obtained. The method has the advantages that no lead-removing agent is needed, no solid waste is newly generated, the processing cost of intermediate materials is reduced, and the method has wide market promotion value.

Description

[Technical Field]

[0001] This invention belongs to the field of lead smelting and production, and specifically relates to a method for removing cadmium in lead and antimony smelting. [Background Technology]

[0002] Currently, in many cases, antimony oxide powder contains an average of 1500 ppm of cadmium, which fails to meet the inherent quality requirements when producing high-lead antimony products, while market demand requires cadmium levels to be less than 500 ppm. Therefore, refining is necessary to remove cadmium in order to meet the inherent quality requirements of the products.

[0003] Currently, most methods for removing cadmium in lead and antimony smelting involve using lead-removing agents.

[0004] Example 1: Existing technology CN105970005B discloses a pyrometallurgical method for separating antimony and lead in high-lead antimony, which involves adding a covering binder to high-lead antimony, heating and melting it, adding a lead-removing agent in stages, controlling the temperature during the reaction, stirring occasionally, and pouring the antimony liquid out to cast ingots. The lead content in the high-lead antimony is 0.3-15.0% by mass. The covering binder is a mixture of two or more of sodium carbonate, sodium hydroxide, sodium sulfate, sodium chloride, calcium chloride, or potassium chloride. The amount of the covering binder added is 10-20% of the mass of the high-lead antimony raw material. The lead-removing agent is ferric disulfide. When the lead content in the high-lead antimony is ≥3.0% by mass, the amount of the lead-removing agent added is 1.5-5.0 times the theoretical lead removal mass. When the lead content in the high-lead antimony is <3.0% by mass, the amount of the lead-removing agent added is 5.0-10.0 times the theoretical lead removal mass.

[0005] Example 2: CN1047407C Antimony Pyrometallurgical Refining Lead Removal Method and its Liquid Lead Removal Agent. Specifically, an antimony pyrometallurgical refining lead removal method is disclosed, with a reaction temperature of 700-1900℃. The characteristic is that a liquid lead removal agent mainly composed of phosphorus-containing oxyacid and sulfuric acid is atomized with nitrogen and directly sprayed into the high-temperature antimony melt. The weight percentage of each component of the liquid lead removal agent is 85% phosphorus-containing oxyacid + sulfuric acid and 15% stabilizer. The stabilizer is any one of ammonium chloride, ammonium bicarbonate, phosphorus pentoxide, and ammonium phosphate.

[0006] Example 3: CN101928842A describes a lead removal agent and method for antimony pyrometallurgical refining. The lead removal agent is a liquid, phosphorus-containing oxyacid liquid. The method involves controlling the reaction temperature to >800 degrees Celsius during antimony refining, directly injecting the liquid lead removal agent onto the molten antimony in the high-temperature antimony smelting furnace, then agitating the molten antimony with forced draft for 30-50 minutes to allow for full reaction, and finally removing the slag. This invention's lead removal agent produces only trace amounts of water vapor when added to the metallurgical furnace, achieving complete environmental friendliness and reducing pollution. Furthermore, it achieves faster and better lead removal than traditional lead removal agents, increasing metal recovery rates and reducing resource waste.

[0007] However, the existing technologies mentioned above all have technical problems. When removing cadmium in lead-antimony smelting, additional lead removal agents need to be added. In the actual production process, there is no additional new solid waste generated. In addition, there is a possibility that the lead metal in the furnace may also be carried away.

[0008] Therefore, researching a method for sealing the tuyere in a side-blown furnace of a molten pool that can accelerate the tuyere opening speed while reducing the labor intensity of tuyere opening is of great practical significance. [Summary of the Invention]

[0009] The purpose of this invention is to address the above-mentioned problems by providing a method for removing cadmium in lead-antimony smelting that eliminates the need for lead-removing agents, avoids generating new solid waste, reduces the cost of processing intermediate materials, and has broad market potential.

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A method for removing cadmium in lead-antimony smelting includes the following steps:

[0012] S1. After removing the slag from the furnace, raise the temperature of the molten alloy in the furnace to 800℃;

[0013] S2. The prepared lead-removing slag is fed into the feed port for smelting;

[0014] S3. After the antimony melt is melted into a liquid state, compressed air is blown into the molten antimony through a small air duct added through the furnace door. The air is blown continuously for 60-90 minutes at a furnace temperature of 700℃-850℃. When blowing compressed air into the molten antimony, the small air duct opening is inserted to the bottom of the molten antimony in the molten pool. During the setup of the small air duct, the operator should swing the air duct every 20-30 minutes to change its position, striving to ensure that every part of the molten pool is evenly stirred. When the slag surface turns grayish-black, the small air duct can be removed for slag removal. The process is then repeated, and samples are taken for testing until the cadmium content of the product meets the requirements, thus obtaining a cadmium-free crude lead-antimony alloy.

[0015] To further explain, in step S2, the lead content in the lead-removing slag is 20% to 45% by mass.

[0016] To further explain, in step S1, the foamy slag is the foamy slag obtained by the reduction smelting method in a reverberatory furnace for lead and antimony smelting.

[0017] To further explain, before the reverberatory furnace reduction smelting, it is necessary to prepare the materials, then fill the furnace with the materials, and after filling the furnace, take an alloy sample from the furnace to test the cadmium element, determine the cadmium content, and then determine the number of cadmium removal cycles.

[0018] To further explain, the ingredients are a mixture of soda ash, antimony oxide, and reducing coal, in a mass ratio of soda ash: antimony oxide: reducing coal = 2-4: 100: 8-12.

[0019] To further explain, the dust-laden flue gas generated by the reverberatory furnace reduction smelting method needs to be cooled and then collected by bag filters in the bag filter chamber. The obtained antimony oxide will be returned for batching, and the flue gas will be discharged into the atmosphere.

[0020] Lead slag is produced during the lead removal process in the production of refined antimony. The chemical reaction equations are: 2Pb + O2 = 2PbO, PbO + 2HPO3 = Pb(PO3)2 + H2O. In this way, lead metaphosphate slag floats on the surface of the antimony liquid and can be skimmed off from the slag channel, thus achieving the separation of lead and antimony.

[0021] The principle of cadmium removal:

[0022] The cadmium contained in the antimony liquid is oxidized by oxygen in the air and reacts with molten metaphosphoric acid to form cadmium metaphosphate. The chemical reaction equations are: 2Cd + O2 = 2CdO, CdO + 2HPO3 = Cd(PO3)2 + H2O. In this way, the cadmium metaphosphate slag floats on the surface of the antimony liquid and can be skimmed off from the slag channel, thus achieving the separation of cadmium and antimony.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] By employing lead-removing slag for cadmium removal, cadmium is effectively removed while lead inside the furnace is not, thus achieving the goal of cadmium removal. This approach saves on the input of lead-removing agents and fully utilizes the lead-removing slag for recycling, preventing the generation of new solid waste and benefiting safety and environmental protection. Simultaneously, it reduces the amount of lead to be prepared, saving production costs. It is estimated that annual production cost savings will be at least 600,000 yuan, demonstrating significant market potential. [Attached Image Description]

[0025] Figure 1 This is a schematic diagram of the process of this invention.

Detailed Implementation Methods

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1:

[0028] A method for removing cadmium in lead-antimony smelting includes the following steps:

[0029] S1. Mix soda ash, antimony oxide, and reducing coal in a mass ratio of soda ash: antimony oxide: reducing coal = 2:100:8. Then, fill the furnace with the mixture. After filling the furnace, take an alloy sample from the furnace to test for cadmium content and determine the number of cadmium removal cycles. Next, reduce the slag obtained from the reverberatory furnace reduction smelting. After removing the slag from the furnace, raise the temperature of the alloy liquid in the furnace to 800℃. The dusty flue gas generated by the reverberatory furnace reduction smelting method needs to be cooled and then collected by bag filter in the bag filter chamber. The obtained antimony oxide will be returned for batching, and the flue gas will be discharged into the atmosphere.

[0030] S2. The prepared lead-removing slag is fed into the feed port for smelting. The lead content in the lead-removing slag is 20%.

[0031] S3. After the antimony melt is melted into a liquid state, compressed air is blown into the molten antimony through a small air duct added through the furnace door. The air is blown continuously for 60 minutes at a furnace temperature of 700℃. When blowing compressed air into the antimony melt, the small air duct is inserted to the bottom of the molten antimony in the molten pool. During the installation of the small air duct, the operator swings the air duct every 20 minutes to change its position, striving to ensure that every part of the molten pool is stirred evenly. When the slag surface turns grayish-black, the small air duct can be pulled out to remove the slag. Then the operation is repeated, and samples are taken for testing until the cadmium content of the product meets the requirements. This will yield a cadmium-free crude lead-antimony alloy. The operation is repeated until it is qualified, and a cadmium-free crude lead-antimony alloy is obtained.

[0032] Example 2:

[0033] A method for removing cadmium in lead-antimony smelting includes the following steps:

[0034] S1. Mix soda ash, antimony oxide, and reducing coal in a mass ratio of soda ash: antimony oxide: reducing coal = 4:100:12. Then fill the furnace with the mixture. After filling the furnace, take an alloy sample from the furnace to test for cadmium content and determine the number of cadmium removal cycles. Next, reduce the slag obtained from the reverberatory furnace reduction smelting. After removing the slag from the furnace, raise the temperature of the alloy liquid in the furnace to 800℃. The dusty flue gas generated by the reverberatory furnace reduction smelting method needs to be cooled and then collected by bag filter in the bag filter chamber. The obtained antimony oxide will be returned for batching, and the flue gas will be discharged into the atmosphere.

[0035] S2. The prepared lead-removing slag is fed into the feed port for smelting. The lead content in the lead-removing slag is 45%.

[0036] S3. After the antimony melt is melted into a liquid state, compressed air is blown into the molten antimony through a small air duct added through the furnace door. The air is blown continuously for 90 minutes at a furnace temperature of 850℃. When blowing compressed air into the antimony melt, the small air duct is inserted into the bottom of the molten antimony in the molten pool. During the installation of the small air duct, the operator swings the air duct every 30 minutes to change the position of the small air duct, striving to ensure that every part of the molten pool is stirred evenly. When the slag surface turns grayish-black, the small air duct can be pulled out to remove the slag. Then the operation is repeated, and samples are taken for testing until the cadmium content of the product meets the requirements. This yields a crude lead-antimony alloy with cadmium removed.

[0037] Example 3:

[0038] A method for removing cadmium in lead-antimony smelting includes the following steps:

[0039] S1. Mix soda ash, antimony oxide, and reducing coal in a mass ratio of soda ash: antimony oxide: reducing coal = 3:100:9. Then, fill the furnace with the mixture. After filling the furnace, take an alloy sample from the furnace to test for cadmium content and determine the number of cadmium removal cycles. Next, reduce the slag obtained from the reverberatory furnace reduction smelting. After removing the slag from the furnace, raise the temperature of the alloy liquid in the furnace to 800℃. The dusty flue gas generated by the reverberatory furnace reduction smelting method needs to be cooled and then collected by bag filter in the bag filter chamber. The obtained antimony oxide will be returned for batching, and the flue gas will be discharged into the atmosphere.

[0040] S2. The prepared lead-removing slag is fed into the feed port for smelting. The lead content in the lead-removing slag is 25%.

[0041] S3. After the antimony melt is melted into a liquid state, compressed air is blown into the molten antimony through a small air duct added through the furnace door. The air is blown continuously for 70 minutes at a furnace temperature of 750℃. When blowing compressed air into the antimony melt, the small air duct is inserted to the bottom of the molten antimony in the molten pool. During the installation of the small air duct, the operator swings the air duct every 25 minutes to change the position of the small air duct, striving to ensure that every part of the molten pool is stirred evenly. When the slag surface turns grayish-black, the small air duct can be pulled out to remove the slag. Then the operation is repeated, and samples are taken for testing until the cadmium content of the product meets the requirements. This will yield a cadmium-free crude lead-antimony alloy. The operation is repeated until it is qualified, and a cadmium-free crude lead-antimony alloy is obtained.

[0042] Example 4:

[0043] A method for removing cadmium in lead-antimony smelting includes the following steps:

[0044] S1. Mix soda ash, antimony oxide, and reducing coal in a mass ratio of soda ash: antimony oxide: reducing coal = 2:100:10. Then, fill the furnace with the mixture. After filling the furnace, take an alloy sample from the furnace to test for cadmium content and determine the number of cadmium removal cycles. Next, reduce the slag obtained from the reverberatory furnace reduction smelting. After removing the slag from the furnace, raise the temperature of the alloy liquid in the furnace to 800℃. The dusty flue gas generated by the reverberatory furnace reduction smelting method needs to be cooled and then collected by bag filter in the bag filter chamber. The obtained antimony oxide will be returned for batching, and the flue gas will be discharged into the atmosphere.

[0045] S2. The prepared lead-removing slag is fed into the feed port for smelting. The lead content in the lead-removing slag is 35%.

[0046] S3. After the antimony melt is melted into a liquid state, compressed air is blown into the molten antimony through a small air duct added through the furnace door. The air is blown continuously for 90 minutes at a furnace temperature of 800℃. When blowing compressed air into the antimony melt, the small air duct is inserted to the bottom of the molten antimony in the molten pool. During the installation of the small air duct, the operator swings the air duct every 28 minutes to change its position, striving to ensure that every part of the molten pool is evenly stirred. When the slag surface turns grayish-black, the small air duct can be pulled out to remove the slag. Then the operation is repeated, and samples are taken for testing until the cadmium content of the product meets the requirements. This yields a cadmium-free crude lead-antimony alloy. The operation is repeated until it is qualified, and a cadmium-free crude lead-antimony alloy is obtained.

[0047] Cost comparison:

[0048] (1) Using lead-removing slag for cadmium removal, a normal monthly production of 3 furnaces (180 tons of high-lead antimony) is achieved, with each furnace producing 60 tons. The average cadmium content needs to be reduced from 1500 ppm to below 500 ppm, requiring two repeated cadmium removal operations to achieve the product's intrinsic quality requirements. If lead-removing agents are used, 1 ton is needed each time, resulting in 2 tons consumed per furnace. The monthly savings from 3 furnaces would be 3 × 2 = 6 tons of lead-removing agents. The current market price for each ton of lead-removing agent is 7450 × 3 × 2 = 44,700 yuan. The annual cost savings would be 44,700 × 12 = 536,400 yuan.

[0049] (2) If chemicals are used for cadmium removal instead of lead slag, an additional 1.1 × 6 = 6.6 tons of cadmium slag will be generated, resulting in additional solid waste. Although the additional solid waste can be recycled back into the smelting furnace for use in batching, it still increases production costs. Assuming a recycling cost of 1200 yuan per ton, this would result in an additional 6.6 × 1200 × 12 = 95,040 yuan per year, further straining intermediate material storage areas.

[0050] The total cost savings from the above two items for the year is: 536,400 + 95,040 = 631,440 yuan.

[0051] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for removing cadmium in lead-antimony smelting, characterized in that, Includes the following steps: S1. After removing the slag from the furnace, raise the temperature of the alloy liquid in the furnace to 800℃; the slag is the slag obtained by the reduction smelting method in a reverberatory furnace for lead and antimony smelting. S2. The prepared lead-removing slag is fed into the feed port for smelting; the lead content in the lead-removing slag is 20% to 45% by mass; the lead-removing slag is the slag from which lead metaphosphate floats on the surface of the antimony liquid during the production of refined antimony and is skimmed off from the slag channel. S3. After the antimony melt is melted into a liquid state, compressed air is blown into the molten antimony through a small air duct added through the furnace door. The air is blown continuously for 60 to 90 minutes at a furnace temperature of 700℃~850℃. When blowing compressed air into the antimony melt, the small air duct outlet is inserted to the bottom of the molten antimony in the molten pool. During the setup of the small air duct, the operator should swing the air duct every 20 to 30 minutes to change the position of the small air duct, striving to ensure that every part of the molten pool is stirred evenly. When the slag surface turns grayish-black, the small air duct can be pulled out to remove the slag. Then the operation is repeated, and samples are taken for testing until the cadmium content of the product meets the requirements. This yields a crude lead-antimony alloy with cadmium removed.

2. The method for removing cadmium in lead-antimony smelting according to claim 1, characterized in that, Before performing reverberatory furnace reduction smelting, it is necessary to prepare the materials, then fill the furnace with the materials. After the furnace is filled, take an alloy sample from the furnace to test for cadmium content, determine the cadmium content, and then determine the number of cadmium removal cycles.

3. The method for removing cadmium in lead-antimony smelting according to claim 2, characterized in that, The ingredients are a mixture of soda ash, antimony oxide, and reducing coal, in a mass ratio of soda ash: antimony oxide: reducing coal = 2-4: 100: 8-12.

4. The method for removing cadmium from lead-antimony smelting according to claim 1, characterized in that, The dust-laden flue gas generated by the reverberatory furnace reduction smelting method needs to be cooled and then collected by bag filters in the bag filter chamber. The obtained antimony oxide will be returned for batching, and the flue gas will be discharged into the atmosphere.

Images