Hydrometallurgical Nickel Leaching ORP Control
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Solution Overview
Problem
Conventional hydrometallurgical processes for nickel oxide ore face challenges in controlling oxidation-reduction potential, leading to inefficient leaching of nickel and cobalt, excessive energy consumption, and increased costs due to variations in ore composition and organic content, which result in impurity issues and reduced leaching rates.
Innovation Solution
A hydrometallurgical process that adjusts the oxygen purity of blown gas to 21-60% and oxygen blowing amount to 200-600 Nm3-O2/t-C, while maintaining a carbon grade of 0.1-0.5% in the ore slurry, to control the oxidation-reduction potential between 400-650 mV, thereby optimizing iron oxidation and reducing sulfuric acid usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional pyrometallurgical processes are used for nickel oxide ore, then nickel and cobalt can be recovered, but energy consumption increases and cost rises due to drying and roasting steps
Solution Approach 1:
The patent changes the fundamental parameters of the processing method from pyrometallurgical (high temperature roasting) to hydrometallurgical (acid leaching at lower temperatures). By using sulfuric acid leaching under controlled conditions, the process eliminates energy-intensive drying and roasting steps while maintaining effective nickel and cobalt recovery, directly resolving the contradiction between energy consumption and recovery efficiency
Solution Approach 2:
The patent replaces the mechanical/thermal pyrometallurgical system with a chemical hydrometallurgical system. Instead of using high temperature and mechanical roasting, the process uses chemical reactions with sulfuric acid to dissolve and separate nickel and cobalt, substituting a chemical mechanism for a thermal-mechanical one to reduce energy loss
2Loss of energy
If conventional smelting processes are used, then nickel and cobalt can be separated from iron, but selective reduction is impossible leading to waste in energy and cost
Solution Approach 1:
The patent changes the chemical parameters by introducing sulfuric acid leaching with controlled oxidation-reduction potential and pH levels. This allows selective dissolution of nickel and cobalt while leaving iron in the residue, achieving manufacturing precision in separation without the energy waste of conventional smelting processes that cannot selectively reduce metals
Solution Approach 2:
The patent uses sulfuric acid as an intermediary chemical agent that facilitates selective separation. The acid acts as a mediator that selectively reacts with nickel and cobalt oxides to form soluble salts, while iron remains insoluble under the controlled conditions, enabling precise separation without direct thermal processing
3Loss of energy
If high pressure acid leach is used without roasting step, then energy and cost are reduced, but oxidation-reduction potential varies widely depending on organic component content
Solution Approach 1:
The patent implements feedback control by monitoring and adjusting the oxidation-reduction potential during the leaching process. Based on the measured ORP and organic content of the ore, the process dynamically adjusts parameters such as acid concentration, temperature, and aeration to maintain optimal leaching conditions, ensuring reliable nickel and cobalt recovery despite variations in ore composition
Solution Approach 2:
The patent introduces dynamic adjustment of process parameters based on real-time conditions. The oxidation-reduction potential, temperature, and acid concentration are not fixed but are dynamically optimized during leaching to account for variations in organic content and ore composition, maintaining process reliability while eliminating the energy-intensive roasting step
4Manufacturing precision
If oxidation-reduction potential is too high during leaching, then chromium is leached out as hexavalent chromium, but removing it requires additional reducing agents increasing smelting cost
Solution Approach 1:
The patent precisely controls the oxidation-reduction potential within a specific range (400-650 mV) to achieve selective leaching. By maintaining ORP in this optimized window, chromium is kept in the trivalent state and remains in the residue while nickel and cobalt are leached, achieving manufacturing precision in metal separation without the need for additional reducing agents to remove hexavalent chromium
Solution Approach 2:
The patent applies partial oxidation by controlling the ORP to be sufficiently high to leach nickel and cobalt but not excessively high to oxidize chromium to hexavalent state. This partial action approach achieves the desired separation precision while avoiding the harmful over-oxidation that would increase processing costs
5Reliability
If oxidation-reduction potential is too low during leaching, then titanium autoclave material is deteriorated and iron hydrolysis is inhibited, but controlling ORP requires precise oxygen management
Solution Approach 1:
The patent establishes a specific ORP range (400-650 mV) that ensures sufficient oxidation to protect titanium autoclave material from deterioration while maintaining effective iron hydrolysis and nickel-cobalt leaching. This parameter optimization achieves material durability without requiring overly complex oxygen management systems
Solution Approach 2:
The patent maintains continuous controlled aeration during the leaching process to sustain the optimal oxidation-reduction potential. This continuous action ensures consistent protection of the autoclave material and stable leaching performance throughout the process, achieving reliability through sustained controlled oxidation rather than intermittent complex interventions
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 achieves a high iron oxidation ratio, fixing iron as hematite, reducing sulfuric acid consumption, and enhancing the leaching rate of nickel and cobalt, while minimizing impurity levels and energy costs.
Implementation Method 1
a leaching step (which corresponds to a 'second step' mentioned below) of adding sulfuric acid to the ore slurry and performing a leaching treatment under high temperature of not less than 200 degrees C. and high pressure
Implementation Method 2
a major impurity, iron, is fixed as a leach residue in the form of hematite (Fe2O3)
Implementation Method 3
performing a leaching treatment under high temperature of not less than 200 degrees C. and high pressure by an autoclave or the like
Implementation Method 4
the oxidation-reduction potential and the temperature of a leachate in a pressure leaching reaction vessel are controlled, whereby a major impurity, iron, is fixed as a leach residue
Data Source
AI summary
Provided is a hydrometallurgical process for nickel oxide ore by high pressure acid leach that achieves a high iron oxidation ratio. The carbon grade in ore slurry and the flow rate are measured to determine the amount of carbon to be fed, and then, sulfuric acid is added. The blowing ratio of high pressure air and high pressure oxygen is adjusted so as to attain an oxygen purity of 21% to 60%. While the oxygen purity is maintained, an oxygen blowing amount per weight of carbon contained in the ore slurry and fed in the second step is adjusted to 200 to 600 Nm3, whereby ORP (Ag/AgCl basis) in the leaching treatment is controlled to 400 to 650 mV.