Steel Mill CO2 Capture With Alkaline Recycling for DRI Reduction
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Solution Overview
Problem
The steel industry faces challenges in efficiently capturing and recycling carbon dioxide due to the high emissions from the iron manufacturing process, particularly in the FINEX process, which requires specific adsorption conditions and lacks effective methods for utilizing captured carbon dioxide.
Innovation Solution
A system utilizing a basic alkaline mixture solution to capture and convert carbon dioxide into sodium carbonate or sodium bicarbonate, which is then stored and transported to offshore structures, reducing the oxidation level of the reducing gas to increase the Direct Reduced Iron (DRI) reduction rate and recycling the carbon dioxide into useful resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If CO2 PSA technology is used to reduce carbon dioxide in exhaust gas, then carbon dioxide removal is achieved, but specific adsorption conditions (temperature 15-40°C, pressure 4-6 bar) and high-performance adsorption agents are required
Solution Approach 1:
The patent changes the fundamental parameter of CO2 removal from adsorption-based (PSA) to chemical reaction-based (alkaline solution absorption). This allows the process to operate under different conditions - using liquid alkaline solutions that can absorb CO2 through chemical reaction rather than requiring specific temperature and pressure ranges for adsorption. The reaction NaOH + CO2 → NaHCO3 occurs readily without needing precise parameter control.
Solution Approach 2:
The patent replaces the mechanical/physical adsorption system (PSA requiring pressure swing, temperature control, and specialized adsorption agents) with a chemical reaction system using alkaline solutions. This substitution eliminates the need for complex adsorption equipment and agent selection, as the chemical reaction between NaOH and CO2 is straightforward and does not require specialized materials or precise operational parameters.
2Productivity
If captured carbon dioxide is not utilized or stored, then capture process is simple, but carbon dioxide capture products cannot be effectively used or stored
Solution Approach 1:
The patent converts the previously harmful CO2 emission into a useful chemical product (sodium bicarbonate or sodium carbonate). Instead of simply capturing and storing CO2, the system chemically transforms it through reaction with alkaline solutions, producing valuable commodities that can be utilized in various industries such as food processing, pharmaceuticals, and chemical manufacturing. This eliminates the need for complex storage infrastructure while creating economic value.
Solution Approach 2:
The patent recovers carbon dioxide from exhaust gas and transforms it into useful sodium bicarbonate or carbonate products. Rather than discarding captured CO2 or investing in long-term storage solutions, the system recovers the carbon in the form of valuable chemical products that can be immediately utilized, turning a waste stream into a resource.
3Productivity
If conventional blast furnace method is used for iron manufacturing, then molten iron production is achieved, but auxiliary facilities (coke manufacturing, sintering) and complex purification facilities are required
Solution Approach 1:
The patent extracts and removes CO2 from the exhaust gas stream using alkaline solution absorption towers. By taking out the harmful CO2 component through chemical reaction with NaOH or KOH solutions, the system simplifies the overall process compared to conventional blast furnaces that require multiple auxiliary facilities for pollutant management. The CO2 removal function is separated into a dedicated absorption system rather than requiring integrated complex purification infrastructure.
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 system effectively captures and recycles carbon dioxide, producing valuable resources like sodium carbonate or sodium bicarbonate, reduces storage and transportation costs, and increases the DRI reduction rate, while addressing the limitations of conventional CO2 PSA technology.
Implementation Method 1
a basic alkaline mixture solution to capture and convert carbon dioxide into sodium carbonate or sodium bicarbonate
Implementation Method 2
at least one fluidized bed reduction furnace configured to reduce fine iron ore to reduced iron by reacting the fine iron ore with a reducing gas
Data Source
AI summary
Proposed is a system for carbon dioxide capture and carbon recycling for a steel mill. The system includes a fluidized bed reduction furnace configured to reduce fine iron ore to reduced iron by using a reducing gas, a first discharge means configured to discharge an exhaust gas generated from the fluidized bed reduction furnace, a melting furnace configured to manufacture molten iron, a second discharge means configured to discharge an exhaust gas generated from the melting furnace, and a reactor configured such that when the reactor receives the exhaust gas discharged from the fluidized bed reduction furnace and the melting furnace as the reducing gas, the reactor captures carbon dioxide in the reducing gas by reacting the reducing gas with a basic alkaline mixture solution, and then collects a reactant and injects, into the fluidized bed reduction furnace, the reducing gas from which carbon dioxide is removed.