Circulating Fluidized Bed Roaster for Low Sulfur Calcine
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
PGM sulfide concentrates with sulfur content between 2 to 7 wt-% are difficult to process directly in electric furnaces due to high sulfur content, and conventional roasting methods fail to achieve low enough sulfur levels for autothermal sulfuric acid production.
Innovation Solution
A process involving dead roasting of metal sulfide concentrates in a circulating fluidized bed at 950 to 1100° C, with waste gas preheating using a recuperator or drying using a Venturi drier to reduce sulfur content to less than 1 wt-%, allowing for autothermal sulfuric acid plant operation with reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional roasting methods are used to treat PGM sulfide concentrates, then the sulfur content in the roasted product is reduced, but the sulfur content remains too high (above 1 wt-%) for autothermal sulfuric acid production
Solution Approach 1:
The patent applies parameter changes by operating the fluidized bed roaster at elevated temperatures (950-1100°C) and controlling the oxygen excess coefficient (λ) within specific ranges (1.05-1.20). These parameter adjustments optimize the roasting reaction to achieve sulfur content in the calcine product below 1 wt-%, making it suitable for autothermal sulfuric acid production. The controlled oxidation conditions and temperature parameters enable precise control over sulfur removal efficiency.
2Ease of manufacture
If PGM sulfide concentrates with high sulfur content (2-7 wt-%) are treated directly in electric furnaces, then metal recovery is possible, but the high sulfur content prevents efficient SO2 separation and autothermal operation
Solution Approach 1:
The patent applies preliminary action by performing a roasting treatment before metal recovery. The sulfide concentrate is first roasted in a fluidized bed to convert sulfur to SO2 gas and produce calcine with low sulfur content (<1 wt-%). This preliminary sulfur removal step enables subsequent efficient SO2 separation and autothermal operation in the electric furnace, avoiding the energy-intensive processes required when treating high sulfur concentrates directly.
3Quantity of substance
If conventional overall plants with roaster, gas cleaning and sulfuric acid plant are used, then complete sulfur recovery is possible, but the low sulfur content in the concentrate (2-7 wt-%) results in too low SO2 concentration for autothermal operation
Solution Approach 1:
The patent applies the extraction principle by removing sulfur from the solid concentrate phase and transferring it to the gas phase as SO2 during the roasting process. The fluidized bed roaster efficiently extracts sulfur from the PGM sulfide concentrate, producing calcine with <1 wt% sulfur and concentrated SO2 waste gas. This extraction enables subsequent autothermal sulfuric acid production despite the low initial sulfur content in the concentrate.
4Loss of energy
If heat recovery is implemented using a recuperator or Venturi drier, then fuel consumption is reduced, but additional equipment complexity is introduced
Solution Approach 1:
The patent applies the blessing in disguise principle by converting the hot waste gas from the roasting process, which would normally be wasted heat, into a useful resource. The waste gas is directed through a recuperator or Venturi drier to preheat the incoming sulfide concentrate and/or air, thereby reducing fuel consumption. This transforms the harmful waste heat into a beneficial energy source, improving overall process efficiency despite the added equipment complexity.
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 effectively decreases sulfur content in calcine products to less than 1 wt-%, enabling autothermal operation of sulfuric acid plants with reduced energy input and increased flexibility, while utilizing heat recovery to minimize fuel consumption and enhance SO2 concentration for efficient acid production.
Implementation Method 1
dead roasting a metal sulfide concentrate in a circulating fluidized bed at a temperature of about 950 to 1050° C.
Implementation Method 2
The concentrate is roasted in a circulating fluidized bed... the sulfur is withdrawn from the roasting reactor
Implementation Method 3
A waste gas of the fluidized bed is passed through at least one of: a recuperator so as to preheat at least a portion of fluidizing air of the fluidized bed
Implementation Method 4
a Venturi drier so as to dry at least a portion of the concentrate to be roasted
Implementation Method 5
The concentrate is roasted in a circulating fluidized bed
Data Source
AI summary
A process for producing calcine products includes dead roasting a metal sulfide concentrate having a low sulfur content. The concentrate is roasted in a circulating fluidized bed at a temperature of about 950 to 1050° C. A waste gas of the fluidized bed is passed through at least one of a recuperator and a Venturi drier so as to respectively provide at least one of a preheating of at least a portion of air fluidizing the fluidized bed and a drying of at least a portion of the concentrate to be roasted. The calcine product obtained in the fluidized bed with a sulfur content of less than 1 wt-% is provided for further processing.