Laterite Ore Component Recovery via Iron Reduction
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Solution Overview
Problem
The separation of components from laterite ores is challenging due to iron contamination, which complicates alumina recovery, and existing processes often focus on pure alumina feeds with minimal iron contamination, neglecting the value in all laterite constituents.
Innovation Solution
The process involves acid digestion of laterite ore with sulfuric acid to dissolve constituents except silica, followed by filtration and chemical treatments to convert ferric iron to ferrous form, allowing for separation and purification of aluminum, iron, and magnesium compounds through precipitation and crystallization, producing ultra-pure products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If iron is present in ferric form during alumina recovery, then iron contamination occurs and iron inclusions are formed, but converting iron to ferrous form and separating it allows for complete iron removal and pure alumina production
Solution Approach 1:
The patent changes the oxidation state parameter of iron from ferric (Fe³⁺) to ferrous (Fe²⁺) form through reduction. This parameter change enables selective precipitation of ferrous iron as oxalate or carbonate, separating it from alumina and eliminating iron inclusions in the final product.
Solution Approach 2:
The patent extracts iron from the alumina processing stream by converting it to ferrous form and precipitating it as ferrous oxalate or ferrous carbonate. This extraction removes the harmful iron contamination before alumina crystallization, ensuring high purity alumina product.
2Manufacturing precision
If multiple crystallization steps are performed, then product purity increases to extremely pure levels, but process complexity and time increase
Solution Approach 1:
The patent performs preliminary removal of iron contaminants by converting ferric iron to ferrous form and precipitating it before the alumina crystallization process. This preliminary action prevents iron inclusions from forming during crystallization, allowing fewer crystallization steps to achieve the desired purity level.
Solution Approach 2:
The patent converts the harmful ferric iron into ferrous iron, which can be selectively precipitated as a benefit. This conversion transforms the contamination problem into a separable intermediate that can be removed, turning the harmful iron into a manageable byproduct stream.
3Quantity of substance
If all constituents of laterite are processed for value recovery, then commercial value is maximized, but process complexity increases compared to processing only pure alumina feeds
Solution Approach 1:
The patent creates a multi-functional process that recovers multiple valuable constituents from laterite: alumina as the primary product, iron as ferrous oxalate or ferrous carbonate, and other metal ions. This universal approach extracts value from all major components rather than treating iron solely as a contaminant to be discarded.
Solution Approach 2:
The patent recovers iron and other metal ions that would traditionally be discarded as waste or red mud in alumina processing. By converting ferric iron to ferrous form and selectively precipitating it, the process recovers iron as a valuable byproduct while still producing high-purity alumina.
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 effectively separates and purifies alumina and other valuable components from laterite ores, maximizing the extraction of commercially valuable materials by minimizing iron inclusions and utilizing multiple crystallizations to achieve extremely pure products.
Implementation Method 1
The acid digestion of a laterite ore with sulfuric acid is used to dissolve all constituents except silica
Implementation Method 2
Solution flow over metallic iron reduces ferric sulfate to ferrous sulfate
Implementation Method 3
Controlled ammonia addition promotes hydrolysis and precipitation of hydrated titania from titanyl sulfate
Implementation Method 4
The steep solubility curve of ammonium alum allows preferential separation by crystallization
Implementation Method 5
Ammonia addition to ammonium alum solution precipitates aluminum hydroxide as a primary product
Implementation Method 6
The addition of oxalic acid generates insoluble ferrous oxalate as the second major product
Data Source
AI summary
Digestion of a laterite with sulfuric acid dissolves all constituents except silica. The resulting sulfates—aluminum sulfate, ferric sulfate, titanyl sulfate, and magnesium sulfate—remain in solution at approximately 90° C. Hot filtration separates silica. Solution flow over iron reduces ferric sulfate to ferrous sulfate. Controlled ammonia addition promotes hydrolysis and precipitation of hydrated titania from titanyl sulfate that is removed by filtration. Addition of ammonium sulfate forms ferrous ammonium sulfate and ammonium aluminum sulfate solutions. Alum is preferentially separated by crystallization. Addition of ammonium bicarbonate to an ammonium alum solution precipitates ammonium aluminum carbonate which may be heated to produce alumina, ammonia, and carbon dioxide. The addition of oxalic acid generates insoluble ferrous oxalate which thermally decomposes to ferrous oxide and carbon monoxide which is used to reduce the ferrous oxide to metallic iron. Further oxalic acid addition precipitates magnesium oxalate which is thermally decomposed to magnesium oxide.