Molten Salt Electrolysis of Coal Ash for Silicon-Aluminum Recovery
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Solution Overview
Problem
Coal ash, a byproduct of coal-fired power plants, occupies land and pollutes soil and water bodies, and contains harmful heavy metals, necessitating an effective method for resource recovery.
Innovation Solution
A method involving calcination, ball milling, and molten salt electrolysis is used to recover metal resources from coal ash, utilizing calcium chloride or other chlorides as electrolytes, with controlled temperature and inert atmosphere to produce a silicon-aluminum alloy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If molten salt electrolysis is used to recover metals from coal ash, then metal recovery efficiency and purity are improved, but energy consumption increases due to high temperature requirements (550-900°C)
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte system by using molten salt (such as CaCl2, NaCl, KCl mixtures) instead of traditional aqueous electrolytes, enabling metal extraction at lower temperatures (550-900°C) while maintaining high metal purity through controlled electrolysis potential and pH conditions
Solution Approach 2:
The patent employs composite approaches by combining molten salt electrolysis with pre-treatment processes (calcination, ball milling) and post-treatment steps (filtration, washing), creating an integrated multi-stage system that optimizes both energy efficiency and metal recovery purity
2Ease of operation
If traditional methods are used to dispose of coal ash, then handling simplicity is maintained, but land occupation and environmental pollution increase
Solution Approach 1:
The patent converts the harmful waste product (coal ash containing heavy metals and silicates) into valuable metal resources (Al, Si, Fe, Ca, Mg) through electrolytic extraction, transforming an environmental liability into an economic asset while eliminating pollution concerns
Solution Approach 2:
The patent implements a recovery system that extracts valuable metals from coal ash that would otherwise be discarded as waste, using calcination to prepare the ash, followed by ball milling and molten salt electrolysis to recover aluminum, silicon, and other metals in usable forms
3Productivity
If calcination and ball milling are performed before electrolysis, then metal extraction efficiency is improved, but process complexity and time consumption increase
Solution Approach 1:
The patent applies preliminary treatments (calcination at high temperature to remove organics and volatile components, followed by ball milling to reduce particle size and increase surface area) before the main electrolysis process, preparing the coal ash in advance to enhance metal extraction efficiency during electrolysis
Solution Approach 2:
The patent divides the overall metal recovery process into distinct sequential stages: calcination stage, ball milling stage, and electrolysis stage, allowing each process to be optimized independently and facilitating better control over the transformation of coal ash into recoverable metals
4Manufacturing precision
If inert atmosphere and oxygen-free conditions are maintained during electrolysis, then metal purity is improved, but equipment requirements and operational complexity increase
Solution Approach 1:
The patent uses an inert atmosphere (such as nitrogen or argon gas environment) during the molten salt electrolysis process to prevent oxidation of the extracted metals and to maintain oxygen-free conditions, ensuring high metal purity without requiring overly complex equipment
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
The method efficiently recovers metals with low energy consumption, reduces carbon content, and improves metal purity, while minimizing toxicity and corrosivity compared to cryolite systems.
Implementation Method 1
performing electrolytic reaction under an oxygen-free condition at an electrolytic reaction temperature of 550° C. to 900° C. in the reactor to obtain a reaction product
Implementation Method 2
calcinating the coal ash for decarburization to obtain the decarburized coal ash
Data Source
AI summary
A method for recovering metal resources in coal ash by molten salt electrolysis includes: calcinating the coal ash for decarburization to obtain the decarburized coal ash; subjecting the decarburized coal ash to ball milling to obtain coal ash powders; pressing the coal ash powders to form a plate; placing the plate as a cathode into an electrolyte in a reactor, and performing electrolytic reaction under an oxygen-free condition at an electrolytic reaction temperature of 550° C. to 900° C. in the reactor to obtain a reaction product; and removing the reaction product from the reactor, cooling the reaction product to room temperature in an inert atmosphere, and cleaning the cooled reaction product to obtain a silicon-aluminum based alloy.