Continuous Oxidative Nickel Leaching With Controlled Acid Depletion
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Solution Overview
Problem
Existing processes for oxidative leaching of nickel in sulphuric acid with hydrogen peroxide are inefficient, leading to entrainment of non-reacted metal fines and suboptimal use of reactants, requiring improved processes for high throughput and ease of operation.
Innovation Solution
A continuous process in a column reactor with controlled acid depletion, maintaining a specific acid ratio and flow rate to maximize nickel conversion to nickel sulphate, ensuring the temperature remains below the boiling point, and utilizing a 1D flow profile to minimize entrainment of unreacted particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If progressive introduction of hydrogen peroxide solution is used, then conversion rate of nickel to nickel sulphate is improved, but temperature control becomes difficult due to highly exothermic reaction
Solution Approach 1:
The continuous leaching process is divided into multiple stages along the column height, with hydrogen peroxide introduced progressively at different levels. This segmentation allows the exothermic reaction to occur in controlled stages rather than all at once, managing the heat generation while maintaining high conversion rates.
Solution Approach 2:
The column is pre-filled with nickel metal particles before introducing the leaching solution. This preliminary preparation ensures that when the hydrogen peroxide-containing solution is introduced, the reaction occurs efficiently from the start, maximizing conversion rate while the continuous flow regime prevents excessive temperature buildup.
2Productivity
If high flow rate is used to increase throughput, then productivity is improved, but entrainment of non-reacted metal fines increases
Solution Approach 1:
The process operates in a continuous dynamic flow regime where liquid moves upward through the packed bed of nickel particles. The flow rate is optimized to be high enough for productivity but controlled to maintain laminar or transitional flow characteristics that prevent excessive turbulence and entrainment of metal fines, unlike batch or static processes.
Solution Approach 2:
The continuous flow process maintains constant movement of the leaching solution through the nickel bed, ensuring uninterrupted reaction and product removal. This continuous action allows for sustained high throughput while the steady flow conditions prevent the intermittent turbulence that causes fine particle entrainment in batch processes.
3Productivity
If acid concentration is substantially depleted in the leaching solution, then conversion rate is maximized, but reactant consumption increases
Solution Approach 1:
The continuous flow process allows the leaching solution to percolate through the entire nickel bed, maximizing contact time and acid utilization. The solution is continuously replenished and circulated, ensuring that acid is consumed efficiently throughout the column rather than being wasted in batch processes where excess acid is typically used to drive the reaction.
Solution Approach 2:
The process operates with varying acid concentration along the column height, with fresh acid entering at the bottom and progressively depleted acid exiting at the top. This gradient in acid concentration optimizes the reaction driving force throughout the bed while minimizing total acid consumption compared to using uniformly high acid concentrations throughout the system.
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 process achieves high conversion rates of nickel to nickel sulphate while maintaining process control, reducing entrainment of non-reacted metal fines, and optimizing the use of reactants, thereby enhancing operational efficiency and capacity.
Implementation Method 1
oxidative leaching of Ni metal in an aqueous sulphuric acid solution in presence of hydrogen peroxide
Implementation Method 2
This process is also known as oxidative leaching of Ni metal, a process which is highly exothermic (−423 KJ/mol)
Data Source
AI summary
The present invention provides a process for the preparation of a nickel sulphate solution in a column reactor, whereby metal particles containing nickel are reacted with an oxidative leach solution comprising sulphuric acid and hydrogen peroxide in water and whereby the acid in the oxidative leaching solution is substantially depleted.