Polyamine Desulphurization of Lead-Acid Battery Paste
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Solution Overview
Problem
The pyrometallurgical process for recycling lead-acid batteries is hindered by sulfur contamination in the battery paste, leading to sulfur dioxide emissions, energy consumption, and hazardous slag formation, which requires additional processing steps and results in lead loss and environmental concerns.
Innovation Solution
A method using a circulating aqueous solution of polyamines, such as triethylenetetramine, to extract lead(II) sulfate from the battery paste, where the solution is saturated with carbon dioxide to form lead(II) carbonate, which is then filtered and recycled, allowing for regeneration and reduction of sulfur content, thereby minimizing slag formation and enabling environmentally safer lead production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If pyrometallurgical processing is used to recycle lead-acid batteries, then lead can be recovered, but sulfur contamination causes sulfur dioxide emissions, energy consumption, and hazardous slag formation
Solution Approach 1:
The patent extracts sulfur from battery paste before pyrometallurgical processing using aqueous ammonia solution. The ammonia selectively binds with sulfur to form soluble ammonium sulfide, which is then separated from the paste. This pre-extraction removes the harmful sulfur contaminant that would otherwise cause SO2 emissions and hazardous slag during lead recovery processing.
Solution Approach 2:
Aqueous ammonia serves as an intermediary substance that mediates between the battery paste and the sulfur removal process. The ammonia solution selectively interacts with sulfur compounds in the paste, forming intermediate ammonium sulfide complexes that can be easily separated, thereby enabling clean sulfur removal without directly affecting the lead recovery process.
2Quantity of substance
If conventional desulphurization with sodium carbonate or sodium hydroxide is used, then sulfur content is reduced, but a technologically complex process of heavy metals removal is required
Solution Approach 1:
Aqueous ammonia acts as a selective intermediary reagent that specifically targets sulfur compounds while leaving heavy metals in the paste unaffected. This selective interaction simplifies the overall process by eliminating the need for subsequent heavy metals removal steps that would be required when using conventional desulphurization methods like sodium carbonate or hydroxide.
Solution Approach 2:
The patent changes the chemical parameter of the leaching solution from conventional alkaline agents (sodium carbonate/hydroxide) to aqueous ammonia. This parameter change fundamentally alters the chemistry of the desulphurization process, enabling selective sulfur removal through ammonium sulfide formation while maintaining heavy metals in their original state, thus simplifying downstream processing.
3Quantity of substance
If processing additives such as iron scrap and soda ash are used during lead smelting, then sulfur can be transferred to slag, but additional energy is consumed and hazardous waste is generated
Solution Approach 1:
The patent performs preliminary desulphurization of battery paste using aqueous ammonia before the lead smelting process. By removing sulfur in advance through ammonium sulfide formation and separation, the need for subsequent sulfur transfer to slag during smelting is eliminated, thereby avoiding the energy consumption and hazardous waste generation associated with using iron scrap and soda ash additives.
Solution Approach 2:
The patent converts the harmful sulfur contaminant into a beneficial separated stream by forming soluble ammonium sulfide that can be easily removed. This transforms the sulfur problem from a source of emissions and hazardous slag into a separable component, eliminating the need for energy-intensive sulfur transfer processes and hazardous waste disposal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves a significant reduction in slag formation, allowing for a virtually waste-free process with low sulfur content paste, resulting in a more efficient and environmentally friendly lead production process, and produces gypsum suitable for building materials.
Implementation Method 1
extracting lead(II) sulphate contained in the battery paste with a circulating aqueous solution of a polyamine
Implementation Method 2
the process of battery paste leaching with a circulating aqueous solution of a polyamine... is carried out simultaneously with saturation of the solution with carbon dioxide, after which lead(II) carbonate and other non-leachable constituents of the battery paste are removed by filtration
Implementation Method 3
The solution obtained is regenerated, preferably in a continuous crystallizer, with a suspension of calcium hydroxide produced from the circulating aqueous solution and hydrated or burnt lime, whereas the regeneration process yields gypsum and regenerated circulating solution
Implementation Method 4
lead(II) carbonate and other non-leachable constituents of the battery paste are removed by filtration from the suspension obtained, preferably on a pressure filter enabling washing of the filter cake with water
Data Source
AI summary
The invention relates to a method of desulphurizing battery paste in the process of recycling lead-acid batteries. The paste desulphurizing stage of the method according to the invention is carried out in an aqueous solution of a defined amine or of a mixture of polyamines, wherein the said solution is saturated with carbon dioxide to remove the remainder of calcium from the solution and then filtered to isolate precipitated calcium carbonate, preferably by using pressure filtration, thereafter the battery paste is leached with the thus obtained circulating aqueous solution of the polyamine or of a mixture of polyamines, followed by filtration of the suspension obtained, preferably by using pressure filtration and washing on the filter, to obtain a desulphurized paste of low sulphur content and the circulating solution. The solution is regenerated by removing therefrom the remainder of lead and carbon dioxide by acting upon it with sulphuric acid and then filtered to separate lead sulphate and recycled to the basic process. The circulating amine solution is regenerated with calcium hydroxide in a crystallizer to obtain a gypsum suspension, which is separated by pressure filtration and washed on the filter to produce gypsum and the circulating solution, wherein the concentration of the polyamine or of the mixture of polyamines in the solution is adjusted by admixing a new portion of the polyamine or of the mixture of polyamines, and the adjusted solution is returned to the start of the process.