Lead Pastel Leaching and Sulfate Removal for Lead Recovery
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Solution Overview
Problem
Current lead recovery processes from lead-acid accumulators involve high energy consumption, costly desulfurization steps, and formation of encrusting deposits due to sulfate ions, which complicate the electrochemical recovery of high-purity lead.
Innovation Solution
A process that leaches lead pastel with an ammonium chloride solution, precipitates sulfate ions with quicklime to form calcium sulfate, and then undergoes electroplating to recover high-purity lead, eliminating the need for preliminary desulfurization and reducing energy consumption by using sonication to detach lead from the cathode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If preliminary desulfurization is performed using alkaline compounds or ammonium salts, then sulfur is removed from the pastel to prevent sulfate encrustation, but high energy consumption is required for crystallization and purification steps
Solution Approach 1:
The patent extracts sulfate ions from the leachate solution using calcium carbonate precipitation, separating the harmful sulfate component before electrochemical processing. This prevents sulfate encrustation on heat exchangers and equipment while avoiding the energy-intensive crystallization steps required by traditional desulfurization methods.
Solution Approach 2:
The patent performs preliminary desulfurization by adding calcium carbonate to the leachate before electrochemical treatment, removing sulfate ions in advance. This preliminary action prevents subsequent encrustation problems during electrolysis and eliminates the need for post-processing crystallization steps that consume large amounts of energy.
2Productivity
If pyrometallurgical processes are used to recover lead from pastel and metallic fraction, then lead recovery is achieved, but high energy consumption and formation of gaseous effluents requiring expensive purification treatments occur
Solution Approach 1:
The patent replaces the pyrometallurgical melting system with a hydrometallurgical-le electrochemical system. Instead of high-temperature melting requiring fuel combustion, the process uses aqueous leaching followed by low-energy electrochemical reduction to deposit pure lead on cathodes, dramatically reducing fuel consumption and eliminating SO2 emissions.
Solution Approach 2:
The patent changes the operational parameters from high-temperature pyrometallurgical conditions to ambient or moderate temperature hydrometallurgical and electrochemical conditions. This parameter change transforms the energy-intensive melting process into a low-energy leaching and electro deposition process, reducing both fuel consumption and environmental impact.
3Loss of substance
If ammonium salts are used for desulfurization instead of alkaline compounds, then the residue has greater commercial value as fertilizer, but the energy consumption for crystallization remains high
Solution Approach 1:
The patent uses calcium carbonate (limestone), a cheap and abundant material, as the desulfurizing agent instead of expensive ammonium salts. The calcium carbonate precipitates sulfate as calcium sulfate, which has low commercial value but eliminates the need for energy-intensive crystallization processes required to produce marketable ammonium sulfate fertilizer.
4Productivity
If electrochemical treatment is performed on leachate containing sulfate ions, then lead can be recovered, but encrustations form on heat exchangers requiring difficult removal with high-pressure water jets
Solution Approach 1:
The patent performs preliminary desulfurization of the leachate by precipitating sulfate ions with calcium carbonate before the electrochemical treatment step. This preliminary removal of sulfate prevents encrustation on heat exchangers and equipment during electrolysis, eliminating the need for difficult maintenance operations involving high-pressure water jets.
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 high-purity lead recovery (>99.99%) with reduced energy consumption and minimizes encrustation issues, simplifying the process and reducing equipment complexity and costs.
Implementation Method 1
leaching lead pastel with an ammonium chloride solution
Implementation Method 2
precipitates sulfate ions with quicklime to form calcium sulfate
Implementation Method 3
undergoes electroplating to recover high-purity lead
Implementation Method 4
using sonication to detach lead from the cathode
Data Source
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AI summary
The present invention concerns a process for the recovery of lead from a lead pastel electrolytically, where the pastel contains lead sulfate. The process provides for the leaching of the non-desulfurised pastel and the subsequent removal of the sulfates by precipitation; the leachate containing the lead ions is then subjected to electrolysis for the recovery of metal lead. The present invention further relates to a process for the recovery of lead accumulator components, wherein the lead contained in the pastel of the accumulators is recovered according to the aforesaid process.