Metal Sulfide Roasting via Particle Segmentation and Pelletizing
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Solution Overview
Problem
Current roasting processes face issues with temperature differences within the roaster, leading to incomplete roasting, ferrite formation, and increased sulfide and sulfate sulfur content in calcine particles, which affect downstream leaching steps and metal recovery.
Innovation Solution
Separating concentrate particles into larger pellets before roasting, ensuring at least 80% of the pellets have a diameter of 80% of the average particle size, and pelletizing small calcine particles to achieve homogeneous residence times, reduce sulfation, and minimize sulfide and sulfate sulfur content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If concentrate particles are roasted in a fluidized bed at high temperatures, then roasting efficiency is improved, but temperature differences between roaster top and bottom increase causing incomplete roasting and ferrite formation
Solution Approach 1:
The concentrate particles are separated into different size fractions (fine particles <15 μm and coarse particles ≥15 μm) before roasting. This segmentation allows each fraction to be roasted under optimized conditions, preventing the temperature differences that cause incomplete roasting and ferrite formation while maintaining high roasting efficiency.
2Quantity of substance
If small concentrate particles are roasted, then metal yield is improved, but sulfide and sulfate sulfur content in calcine increases affecting downstream leaching
Solution Approach 1:
Fine concentrate particles (<15 μm) are separated and pre-roasted in a separate stream before being combined with coarse particles. This preliminary action ensures complete oxidation of sulfur in fine particles, reducing sulfide and sulfate sulfur content in the final calcine while maintaining high metal yield from the fine particles.
3Reliability
If roasting temperature is increased to improve roasting completeness, then sulfur oxidation is enhanced, but refractory life is reduced and energy consumption increases
Solution Approach 1:
Different temperature regimes are applied to different particle size fractions. Fine particles are roasted at higher temperatures to ensure complete sulfur oxidation, while coarse particles are roasted at moderate temperatures. This local quality approach achieves complete roasting without subjecting the entire system to high temperatures that would reduce refractory life and increase energy consumption.
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 approach reduces temperature differences, enhances roaster capacity, prolongs refractory life, minimizes ferrite formation, and ensures complete oxidation of sulfur and carbon, leading to improved metal recovery and leaching efficiency.
Implementation Method 1
oxidation of small concentrate particles at the top of the roaster occurs
Implementation Method 2
thermally treated at temperatures between 500 and 1200 °C in a fluidized bed
Implementation Method 3
gases and at least small particles of the roasted concentrate (calcine) are withdrawn over the top of the roaster and fed into at least one separating device for separating solid particles
Implementation Method 4
a cooling of the gas-solid-mixture is particularly important
Implementation Method 5
cyclone(s) connected in parallel or in series
Implementation Method 6
an electrostatic precipitator (ESP) is foreseen downstream of the separating device
Data Source
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AI summary
The invention describes a process for roasting of metal concentrate. Concentrate particles are fed into a roaster where they are thermally treated at a temperature in the range of 500 and 1200°C in a fluidized bed to form a calcine. At least parts of the calcine are withdrawn from the roaster together with a gas stream as a solid fraction. Concentrate particles with a diameter at least 50% smaller than the average diameter of the concentrate particles are separated as small particles and/or that particles from the gas-solid-fraction are separated in at least one step as small calcine particles and/or that particles are gained in another hydrometallurgical step as other particles. The small particles and/or at least part of the small calcine particles and/or at least parts of the other particles are pelletized, whereby at least 80 % of the pellets feature a diameter of at least 80% of the concentrate particles average diameter. The pellets are fed into the roaster.