Direct Reduction Gas Flexibility With CO2 Removal and Heat Recovery
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Solution Overview
Problem
Current direct reduction systems for producing metallic iron emit high levels of carbon dioxide and require significant modifications to switch to hydrogen-based reducing gases, leading to inefficiencies and increased greenhouse gas emissions.
Innovation Solution
A flexible direct reduction system that utilizes a combination of hydrogen and hydrocarbon-containing gases, with a recovery and treatment line that includes heat-exchange devices and carbon dioxide removal, allowing seamless adaptation to different gas sources without equipment modifications, and optimizing system pressure and nitrogen injection for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If make-up gas containing carbon (such as natural gas, coke oven gas, corex gas, syn gas) is used to promote methane reforming reactions inside the reduction reactor, then the reduction process can proceed, but greenhouse gas emissions (CO2) increase and carbon monoxide content in the reducing gas increases leading to fines production and cluster formation
Solution Approach 1:
The invention changes the chemical composition parameters of the make-up gas by introducing gases with different hydrogen-to-carbon ratios (such as natural gas, coke oven gas, corex gas, or syn gas in various combinations), allowing optimization of the reduction process while controlling CO2 emissions and minimizing fines production through parameter adjustment
Solution Approach 2:
The invention uses composite gas mixtures combining different types of make-up gases (hydrocarbon-containing gases with different H2/CO ratios) to achieve a balanced reducing atmosphere that maintains productivity while reducing harmful emissions and minimizing carbon monoxide-related problems
2Productivity
If the reducing gas flow is increased to improve reduction efficiency, then productivity increases, but the system requires significant modifications to switch to hydrogen-based reducing gases
Solution Approach 1:
The invention designs the reduction reactor system to be universally compatible with multiple types of make-up gases (natural gas, coke oven gas, corex gas, syn gas, and their mixtures) without requiring significant structural modifications, allowing the same equipment to handle different gas compositions and maintain high reduction efficiency
3Productivity
If carbon monoxide content in the reducing gas is increased to maintain reduction reactions, then the reduction process continues, but fines production increases and cluster formation risk increases hindering solid mass movement
Solution Approach 1:
The invention carefully controls the CO content parameter in the reducing gas by selecting and mixing appropriate make-up gases, maintaining enough carbon monoxide to sustain reduction reactions while keeping the concentration below thresholds that would cause excessive fines production and cluster formation, thus preserving solid mass flowability
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
Reduces carbon dioxide emissions below 40 Nm3/tDRI, enhances system flexibility, maintains high process availability, and minimizes operational disruptions, while increasing the efficiency and reliability of the reduction process.
Implementation Method 1
The recovery and treatment line comprises at least one first heat-exchange device where heat is transferred from the exhaust gas to a heat-transfer fluid; the treatment and feeding line comprises at least one second heat-exchange device where heat of the heat-transfer fluid is transferred to the process gas
Implementation Method 2
The recovery and treatment line also comprises at least one carbon dioxide removal device, for removing carbon dioxide from the exhaust gas
Implementation Method 3
Fe2O3+3H2→2Fe+3H2O; Fe2O3+3CO→2Fe+3CO2; The hydrogen and carbon monoxide react with the oxygen of the iron oxide and are transformed into water and carbon dioxide
Implementation Method 4
supplied with natural gas to promote methane reforming reactions inside the reduction reactor
Implementation Method 5
because of the increase in temperature due to the reduction with carbon monoxide, which is exothermic
Data Source
AI summary
The present invention provides a reduction system and method that can be operated with any proportion of gaseous hydrogen-containing gases and gaseous hydrocarbon-containing gases having the possibility of continuing its operation, ensuring an high process availability and negligible loss of production, when the gaseous hydrogen-containing gas for any reason is not available and allow the substitution of the gaseous hydrogen-containing gas with a gaseous hydrocarbon-containing gas with minor adjustments in the plant operation. The reduction system of the invention is designed to be implemented in new and already built direct reduction plants to operate efficiently and has lower capital and operation costs.