Phosphogypsum Decomposition via Carbon Reduction
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Solution Overview
Problem
The decomposition of phosphogypsum (PG) into calcium oxide (CaO) and sulfur dioxide (SO2) is energy-intensive and economically infeasible due to high energy consumption and the production of unwanted calcium sulfide (CaS) byproducts, making existing methods costly and environmentally impactful.
Innovation Solution
A process involving a reactor with phosphogypsum and a solid carbon source, where dioxygen is reacted to generate carbon oxide, which then decomposes calcium sulfate into calcium oxide and sulfur dioxide at 1100°C, optimizing the carbon to phosphogypsum and oxygen to carbon ratios to achieve high conversion and low CaS yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If phosphogypsum is decomposed at high temperature (1400°C) in air, then decomposition to CaO and SO2 is achieved, but energy consumption becomes excessively high
Solution Approach 1:
The patent changes the chemical composition parameters by introducing carbon source and controlling oxygen concentration. This allows decomposition to proceed at lower temperatures (1100-1300°C) through chemical reduction mechanisms, thereby reducing energy consumption while maintaining effective decomposition
Solution Approach 2:
The patent introduces carbon source as an intermediary substance that facilitates the decomposition reaction. The carbon acts as a reducing agent, enabling CaSO4 decomposition at lower temperatures by providing an alternative reaction pathway that does not require high thermal energy input
2Temperature
If decomposition is performed in reductive atmosphere with CO, then decomposition temperature is reduced to 1100°C, but calcium sulfide (CaS) byproduct is produced
Solution Approach 1:
The patent creates different local chemical environments within the reaction system by controlling oxygen distribution. In regions with sufficient oxygen, CaS is oxidized to CaSO4 which then decomposes to desired products, while in other regions carbon provides reducing conditions to maintain lower overall temperature
Solution Approach 2:
The patent converts the harmful CaS byproduct into a beneficial intermediate. CaS formed in reductive zones is subsequently oxidized by introduced oxygen to form CaSO4, which then decomposes to produce the desired CaO and SO2, thereby transforming a harmful byproduct into a useful reaction intermediate
3Temperature
If pure CO or C-PG solid-solid reaction is used, then decomposition occurs at lower temperature, but considerable energy is still required making the method economically infeasible
Solution Approach 1:
The patent makes the carbon source multi-functional: it serves as both the reducing agent for temperature reduction and as the energy source through combustion. The carbon performs multiple roles (reductant, fuel, and temperature controller), eliminating the need for separate energy input systems and making the process economically viable
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 reduces energy consumption and CaS production, achieving 80% or more calcium sulfate conversion to CaO and SO2 with minimal CaS yield, making the method more eco-efficient and economically viable.
Implementation Method 1
reacting a flow of dioxygen (O2) with the source of carbon (C) so as to generate carbon oxide (CO)
Implementation Method 2
reacting carbon oxide (CO) obtained in step b) with calcium sulfate (CaSO4) of the phosphogypsum to produce calcium oxide (CaO) and sulfur dioxide (SO2)
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3~4
AI summary
The present invention relates to a process for decomposing calcium sulfate (CaSO4) present in phosphogypsum (PG), comprising the following steps : a) providing a reactor containing phosphogypsum (PG) and a solid source of carbon (C), b) reacting a flow of dioxygen (Oz) with the source of carbon (C) so as to generate carbon oxide (CO), c) reacting carbon oxide (CO) obtained in step a) with calcium sulfate (CaS04) of the phosphoqypsurn to produce calcium oxide (CaO) and sulfoxide (SO2) according to the following reaction : CaS04 + CO → CaO +SO2 + CO2 wherein the mass ratio C/PG is between 0.2 and DA, and the mass ratio 15 O2/PG is between 0.5 and 1.5.