Method for extracting lead from lead-containing waste through pyrogenic enrichment and reduction

Abstract

The invention discloses a method for extracting lead from lead-containing waste through pyrogenic enrichment and reduction, which comprises the following steps of: 1, enriching the lead-containing waste in an enrichment kiln at low temperature of 600-750 DEG C in a weak oxidizing atmosphere for 3-5 hours to generate porous lead-rich slag; 2, in a reduction furnace, the porous lead-rich slag and biomass charcoal are mixed firstly, then CO / COmixed gas is introduced, and controllable reduction is carried out at the temperature of 900-950 DEG C in two stages; 3, in a condenser, the reduced lead steam is subjected to three-stage gradient condensation separation at the temperature of 600-650 DEG C, 450-500 DEG C and 200-250 DEG C, and then flue gas electrostatic dust collection is conducted. The method has the technical advantages of low energy consumption, less lead smoke dust and high lead recovery rate.

Description

Technical Field

[0001] This invention relates to the field of lead recycling technology, specifically to a method for pyrometallurgical enrichment and reduction of lead from lead-containing waste materials (such as lead-acid battery waste, lead paste, lead slag, etc.). Background Technology

[0002] The invention patent with patent number CN202211615237.1 provides a method for improving the smelting and recycling of complex lead-containing hazardous waste based on precise batching. The steps are: (1) sorting and stacking; (2) linkage of multiple electronic belt scales; (3) setting the batching ratio; (4) batching efficiency inspection; (5) granulation; (6) bottom-blown furnace smelting. This method achieves precise feeding by combining precise batching and verification of multiple belt scales according to the sulfur content, achieving an error of less than 3%. Compared with the traditional batching method, it can significantly reduce the furnace condition problems of bottom-blown furnace smelting, and has the characteristics of large production capacity and high operating rate. It can realize the comprehensive recovery of valuable metals such as lead, antimony, copper, silver, and tin from complex lead-containing hazardous waste.

[0003] Patent CN202010567296.0 discloses a chemical treatment method for lead-containing waste, comprising the following steps: Step 1: Solvent preparation, adding ammonium salts that do not form precipitates with lead ions to water to prepare a solvent, and adding acid to adjust the pH of the solvent to 3-6.5; Step 2: Oxidation, placing lead-containing dust into the solvent, and separating the supernatant when the lead-containing dust no longer decreases; Step 3: Carbonation treatment, adding carbonates to the supernatant, adjusting the pH of the supernatant to 7-9, continuing the reaction for 1-3 hours, and then filtering to obtain lead white. This chemical treatment method can avoid the diffusion of large amounts of lead-containing waste, thereby improving the lead recovery rate.

[0004] Traditional pyrometallurgical lead extraction is energy-intensive, with significant lead volatilization losses (>5%) and low metal recovery rates (typically <95%). The flue gas contains sulfur, lead dust, and dioxins, causing severe pollution, and tail gas treatment costs account for more than 30% of the total investment. The smelting process requires the addition of large amounts of flux (such as iron filings and sodium carbonate), resulting in high lead content in the slag (>3%), necessitating secondary treatment. Summary of the Invention

[0005] The purpose of this invention is to provide a pyrometallurgical enrichment and reduction method for lead extraction from lead-rich waste. This invention has the technical advantages of strong adaptability to lead-containing waste, low overall energy consumption, minimal environmental pollution, and high recovery rate.

[0006] The technical solution of the present invention,

[0007] A method for pyrometallurgical enrichment and reduction of lead from lead-containing waste includes the following steps:

[0008] Step 1. In an enrichment kiln, lead-containing waste is enriched at a low temperature of 600-750℃ in a weak oxidizing atmosphere for 3-5 hours to generate porous lead-rich slag.

[0009] Step 2. In the reduction furnace, the porous lead-rich slag is first mixed with biochar, and then a CO / CO2 mixed gas is introduced for two-stage controlled reduction at 900-950℃.

[0010] Step 3. In the condenser, the reduced lead vapor is separated by three-stage gradient condensation at 600-650℃, 450-500℃ and 200-250℃, and then subjected to electrostatic dust collection of flue gas.

[0011] Furthermore, in step 1, the O2 content in the weakly oxidizing atmosphere is 5-8%.

[0012] Furthermore, in step 2, the biochar is palm shell char, with a fixed carbon content of ≥75%, and the amount added is 6-15% of the mass of lead-rich slag.

[0013] Furthermore, in step 2, the first stage of the two-stage reduction involves introducing a CO / CO2 mixed gas with a volume ratio of 3:1, a reduction rate of 70-80%, and a reduction time of 4-6 hours.

[0014] Furthermore, in step 2, the second stage of the two-stage reduction is a closed-loop deep reduction in a CO / CO2 mixed atmosphere for 5-7 hours, with a final slag lead content ≤1.5%.

[0015] Furthermore, in step 3, the three-stage gradient condensation specifically involves: first-stage condensation at 600-650℃ to condense high-melting-point metals; second-stage condensation at 450-500℃ to collect crude lead; and third-stage condensation at 200-250℃ for electrostatic dust collection to capture micron-sized lead powder.

[0016] Furthermore, after the three-stage gradient condensation, it is connected to an electrostatic precipitator.

[0017] Furthermore, the total lead recovery rate during the recycling process is ≥99%.

[0018] The beneficial effects of this invention are:

[0019] ① Low-temperature enrichment is highly innovative in design. Under a weak oxidizing atmosphere (oxygen content 5-8%) at 600-750℃, lead in waste is converted into PbO, generating porous lead-rich slag (lead content >65%). The temperature is 200℃ lower than that of traditional processes, resulting in lower energy consumption and effective suppression of lead volatilization.

[0020] ② Segmented reduction: Lead-rich slag and biochar (fixed carbon ≥75%) are mixed at a mass ratio of 10:1-15:1 and reduced in two stages at 900-950℃. Stage 1: Biochar is added, and the reduction rate is controlled to 70-80%. Stage 2: Deep reduction is carried out under closed conditions, and the lead content of the final slag is ≤1.5%. Biochar replaces coke to reduce sulfur input, and segmented reduction reduces lead dust generation.

[0021] ③ Gradient condensation of lead vapor: Reduced lead vapor undergoes three-stage condensation. Stage 1: 600-650℃ condensation of high-melting-point metals (such as antimony and copper alloys); Stage 2: 450-500℃ collection of crude lead (purity >98%); Stage 3: 200-250℃ electrostatic dust collection of micron-sized lead powder, resulting in a high recovery rate. Detailed Implementation

[0022] Example 1

[0023] 500 kg of lead-acid battery waste was enriched and weakly oxidized and roasted at 650℃ for 2 h to obtain lead-rich slag (PbO content 68.3%). The lead-rich slag was reduced by adding 10% palm shell char for 1 h in the first stage, and then reduced in a closed system at 950℃ for 0.5 h at 900℃ / CO:CO2=3:1. The slag was condensed at 650℃ in the first stage, 450℃ in the second stage, and 250℃ in the third stage to condense crude lead. The total recovery rate of the three-stage condensation was 99.5%.

[0024] Example 2

[0025] 500 kg of copper smelting dust / slag was enriched and weakly oxidized and roasted at 700℃ for 3 h to obtain lead-rich slag (PbO content 75.7%). The lead-rich slag was reduced by adding 12% palm shell char for 1.5 h in the first stage, and then reduced at 900℃ for 1.5 h at 950℃ / CO:CO2=8:1. The second stage was closed reduction at 900℃ for 2 h. The first stage condensation was carried out at 600℃, the second stage at 500℃, and the third stage at 200℃ to condense crude lead. The total recovery rate of the three-stage condensation was 99.7%.

[0026] Example 3

[0027] 500 kg of tin refining slag was enriched and weakly oxidized and roasted at 750℃ for 2 h to obtain lead-rich slag (PbO content 65.3%). The lead-rich slag was reduced by adding 15% palm shell char for 1 h in the first stage, and then reduced in a closed system at 950℃ for 3 h at a ratio of CO:CO2=10:1. The slag was condensed at 650℃ in the first stage, 450℃ in the second stage, and 250℃ in the third stage to condense crude lead. The total recovery rate of the three-stage condensation was 99.8%.

Claims

1. A method for pyrometallurgical enrichment and reduction of lead from lead-containing waste, characterized in that, Includes the following steps: Step 1. In an enrichment kiln, lead-containing waste is enriched at a low temperature of 600-750℃ in a weak oxidizing atmosphere for 3-5 hours to generate porous lead-rich slag. Step 2. In the reduction furnace, the porous lead-rich slag is first mixed with biochar, and then a CO / CO2 mixed gas is introduced for two-stage controlled reduction at 900-950℃. Step 3. In the condenser, the reduced lead vapor is separated by three-stage gradient condensation at 600-650℃, 450-500℃ and 200-250℃, and then subjected to electrostatic dust collection of flue gas.

2. The method for pyrometallurgical enrichment and reduction of lead from lead-containing waste as described in claim 1, characterized in that, In step 1, the O2 content in the weakly oxidizing atmosphere is 5-8%.

3. The method for pyrometallurgical enrichment and reduction of lead from lead-containing waste as described in claim 1, characterized in that, In step 2, the biochar is palm shell char, with a fixed carbon content of ≥75%, and the amount added is 6-15% of the mass of lead-rich slag.

4. The method for pyrometallurgical enrichment and reduction of lead from lead-containing waste as described in claim 1, characterized in that, In step 2, the first stage of the two-stage reduction involves introducing a CO / CO2 mixture with a volume ratio of 3:1, a reduction rate of 70-80%, and a reduction time of 4-6 hours.

5. The method for pyrometallurgical enrichment and reduction of lead from lead-containing waste as described in claim 1, characterized in that, In step 2, the second stage of the two-stage reduction is a closed-loop deep reduction in a CO / CO2 mixed atmosphere for 5-7 hours, with a final slag lead content ≤1.5%.

6. The method for pyrometallurgical enrichment and reduction of lead from lead-containing waste as described in claim 1, characterized in that, In step 3, the three-stage gradient condensation is as follows: the first stage condensation is at 600-650℃ to condense high-melting-point metals; the second stage condensation is at 450-500℃ to collect crude lead; and the third stage condensation is at 200-250℃ to collect micron-sized lead powder using electrostatic dust collection.

7. The method for pyrometallurgical enrichment and reduction of lead from lead-containing waste as described in claim 1, characterized in that, After three-stage gradient condensation, it is connected to an electrostatic precipitator.

8. The method for pyrometallurgical enrichment and reduction of lead from lead-containing waste as described in claim 1, characterized in that, The total lead recovery rate during the recycling process is ≥99%.