Magnesium Extraction via HCl Recovery Loop and Sulfuric Acid Regeneration
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Solution Overview
Problem
Current processes for extracting magnesium from magnesium-bearing ores, such as asbestos tailings, are energy-intensive and inefficient, as they require high temperatures and significant water evaporation, leading to high energy costs and limited profitability due to the recovery of only magnesium, with nickel and other metals being considered impurities.
Innovation Solution
A process involving leaching with HCl, followed by filtration and pH adjustment to extract magnesium chloride, which is then converted into magnesium sulfate and hydrochloric acid, allowing for the recovery of nickel and silica, with the use of sulfuric acid for hydrochloric acid regeneration and thermal decomposition to produce magnesium oxide, reducing energy consumption and enhancing product diversity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional electrolysis of magnesium chloride is used to regenerate hydrochloric acid, then magnesium is recovered, but hydrochloric acid regeneration requires direct synthesis between chlorine gas and external hydrogen source which is complex and energy-intensive
Solution Approach 1:
The patent uses sulfuric acid as an intermediary substance to transfer chlorine from magnesium chloride to produce hydrochloric acid. Instead of directly synthesizing HCl from chlorine gas and hydrogen, the process mediates through sulfuric acid which reacts with magnesium chloride to release HCl gas that is then absorbed in water to form hydrochloric acid solution, simplifying the equipment requirements
Solution Approach 2:
The patent replaces the mechanical/equipment-intensive direct synthesis method with a chemical reaction-based approach using sulfuric acid. The system substitutes complex synthesis equipment with simpler reaction vessels and absorption towers, replacing direct gas-phase synthesis with solution-phase chemistry followed by gas absorption
2Productivity
If heating and water evaporation are used to recuperate magnesium salt, then magnesium chloride is obtained, but large amounts of energy are consumed
Solution Approach 1:
The patent changes the physical state parameters by conducting the reaction in aqueous solution rather than requiring complete evaporation to dryness. The process maintains the system in liquid phase where possible, using solution chemistry to transfer magnesium between compounds, thereby avoiding the high energy cost of evaporating large volumes of water
Solution Approach 2:
The patent extracts magnesium from the ore in chloride form, then transfers it to sulfate form in solution, and finally recovers it as oxide through thermal decomposition of the sulfate. This multi-step extraction approach allows magnesium to be recovered in solid oxide form without requiring evaporation of the bulk water used in the leaching and reaction processes
3Device complexity
If only magnesium is recovered from serpentine tailings, then the process is simple, but nickel and other valuable metals are lost as impurities
Solution Approach 1:
The patent makes the process multi-functional by designing it to simultaneously recover multiple valuable metals from the ore. The leaching and reaction steps are configured to extract not only magnesium but also nickel and other base metals, which are then separated through controlled precipitation at different pH stages, allowing one process system to serve multiple recovery functions
Solution Approach 2:
The patent segments the metal recovery process into distinct stages: initial leaching to dissolve all metals, then sequential precipitation steps at different pH levels to separate and recover different metal groups. This segmentation allows nickel and other metals to be recovered in separate streams from magnesium, preventing loss while maintaining overall process efficiency
4Quantity of substance
If dilute hydrochloric acid is used for leaching, then magnesium and nickel can be extracted, but the process requires large volumes of acid and water
Solution Approach 1:
The patent recovers and reuses the hydrochloric acid and water from the leaching process. The acid is regenerated through the sulfuric acid reaction with magnesium chloride, and the water is recovered from the solution after magnesium sulfate formation. This recovery system reduces the net consumption of both acid and water, addressing the concern about large volumes being required and lost
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 process effectively extracts magnesium metal while recovering nickel and silica, reducing energy costs and enhancing the economic viability of magnesium production by utilizing sulfuric acid for hydrochloric acid regeneration and thermal decomposition to produce magnesium oxide, thereby improving the overall efficiency and profitability of magnesium extraction.
Implementation Method 1
adding the magnesium chloride brine into sulfuric acid forming magnesium sulfate and hydrochloric acid
Implementation Method 2
thermally decomposing the magnesium sulfate in sulphur dioxide gas and magnesium oxide
Implementation Method 3
the hydrochloric acid produced being absorbed in water to form a hydrochloric acid solution
Data Source
AI summary
The present description relates to a process for extracting magnesium compounds from magnesium-bearing ores comprising leaching serpentine tailing with dilute HCl to dissolve the magnesium and other elements like iron and nickel. The residual silica is removed and the rich solution is further neutralized to eliminate impurities and recover nickel. Magnesium chloride is transformed in magnesium sulfate and hydrochloric acid by reaction with sulfuric acid. The magnesium sulfate can be further decomposed in magnesium oxyde and sulphur dioxyde by calcination. The sulphur gas can further be converted into sulfuric acid.