Novel recycling process for lead-acid battery paste without SO2 generation - Reaction mechanism and industrial pilot campaign

Lin

et al. 2019

Minerals

Self Cite

A novel and cleaner process for lead and silver recycling from multiple lead-containing wastes, e.g., lead ash, lead sludge, lead slag, and ferric sludge, by reductive sulfur-fixing smelting was proposed. In this process, coke and iron-containing wastes were employed as reductive agent and sulfur-fixing agent, respectively. A Na2CO3-Na2SO4 mixture was added as flux. The feasibility of this process was detected from thermodynamic and experimental perspectives. The influence of Fe/SiO2 and CaO/SiO2, composition of the molten salt, coke addition, smelting temperature, and smelting time on direct Pb recovery and sulfur-fixation efficiency were investigated. The optimal process conditions were determined as follows: WCoke = 15% WPb wastes, W Na 2 CO 3 / W Na 2 SO 4 = 0.7/0.3, Fe/SiO2 = 1.10, CaO/SiO2 = 0.30, smelting temperature 1200 °C, and smelting time 2 h, where W represents weight. Under these optimum conditions, 92.4% Pb and 98.8% Ag were directly recovered in crude lead bullion in one step treatment, and total 98.6% sulfur was fixed. The generation and emissions of SO2 can be avoided. The main phases in ferrous matte obtained were FeS, NaFeS2, Fe2Zn3S5, and a little entrained Pb. The slag was a FeO-SiO2-CaO-Na2O quaternary melt.

Section: (A)mentioning

confidence: 99%

Cleaner Extraction of Lead from Complex Lead-Containing Wastes by Reductive Sulfur-Fixing Smelting with Low SO2 Emission

Lin

et al. 2019

Minerals

Self Cite

“…PbSO 4 can be reduced to PbS at relative high temperature 22,23 . PbS will probably continually react with sulfur fixing agent to transform sulfur.…”

Section: Thermodynamic Calculationsmentioning

confidence: 99%

“…The technical difficulty of the process associated with implementation mainly lie in the controlling of reducing atmosphere. As / 2 was increased, Pb extraction reactions took place between PbS and Fe 3 O 422 . Metallic Pb and FeS generated.…”

mentioning

confidence: 99%

Recycling of Spent Lead-Acid Battery for Lead Extraction with Sulfur Conservation

Taskinen

et al. 2019

JOM

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This study proposed a cleaner pyrometallurgical lead-acid battery (LAB) recycling method for lead extraction and sulfur conservation without excessive amount of SO 2 generation. Reducing atmosphere was introduced to the lead paste recycling system to selectively reduce PbSO 4 to PbS. At the same time, PbO and PbO 2 components contained in the lead paste was also reduced to metallic Pb. Then the intermediate PbS further reacted with sulfur-fixing agent, typically Fe 3 O 4 , to generate PbO and FeS. Sulfur was transformed from PbSO 4 to PbS and conserved as FeS finally. Thus SO 2 emissions and pollution were significantly eliminated. This work investigated the thermodynamic and experimental feasibility and phase conversion mechanism of this method proposed, the detailed lead extraction and sulfur fixing mechanisms were clarified, and the phase transformation and microstructural evolution processes were characterized. Additionally, bench experimental of industrial, end-of-life LAB paste was conducted to detect the lead recovery and sulfur fixation efficiency.

“…18 As a result, the stringent environmental requirements are increasingly difficult to meet with current pyro-and hydrometallurgical recycling technologies. Therefore, the lead industry is keen to seek advanced technologies 19 which are more economical, minimize environmental pollution, 20 and reduce energy usage and production costs.…”

Section: Introductionmentioning

confidence: 99%

Spent Lead-Acid Battery Recycling via Reductive Sulfur-Fixing Smelting and Its Reaction Mechanism in the PbSO4-Fe3O4-Na2CO3-C System

Taskinen

et al. 2019

JOM

Self Cite

An innovative and environmentally friendly lead-acid battery paste recycling method is proposed. The reductive sulfur-fixing recycling technique was used to simultaneously extract lead and immobilize sulfur. SO 2 emissions and pollution were significantly eliminated. In this work, the detailed lead extraction and sulfur-fixing mechanisms in the PbSO 4-Fe 3 O 4-Na 2 CO 3-C system were investigated thermodynamically and experimentally, and the phase transformation and microstructural evolution processes characterized. In addition, a series of bench-scale pilot experiments were carried out to confirm the feasibility of the technique. The results show that the lead extraction and sulfur-fixing reactions followed the shrinking unreacted-core model. The recycling products were separated into three distinct layers: slag, matte, and crude lead bullion. Primary recoveries of 96.2% for lead and 98.9% for sulfur were obtained. The purity of the crude lead bullion was 98.6 wt.%. Sulfur was fixed in the solidified matte as FeS and NaFeS 2 .