Direct Reduced Iron Shift Reactor Sizing via High-Pressure CO Conversion
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Solution Overview
Problem
Existing methods for producing direct reduced iron (DRI) using high carbon monoxide (CO) content synthesis gas require large shift reactors and high equipment costs due to the need for significant gas flow through shift reactors to achieve the desired H2/CO ratio, and high temperatures exacerbate these issues.
Innovation Solution
The method involves shifting top gas from a direct reduction furnace using a carbon monoxide shift reactor, minimizing the gas flow through the shift reactor by optimizing the H2/CO ratio, and utilizing a series of units including a cooler/scrubber, compressor, CO2 removal units, steam preheater, and reducing gas heater to achieve a reducing gas with a H2/CO ratio of 1.0, thereby reducing the size and cost of the shift reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-CO content synthesis gas is used for direct reduction, then the reducing gas can be produced, but the shift reactor size and equipment cost increase significantly
Solution Approach 1:
The gas processing system is divided into multiple functional segments: a gasification unit that produces high-CO synthesis gas, a shift conversion unit with multiple stages, and a CO2 removal unit. This segmentation allows each unit to be optimized independently, enabling the use of high-CO synthesis gas without requiring an oversized single-stage shift reactor.
Solution Approach 2:
The invention changes the operating parameters of the shift reactor, specifically operating at high pressure (e.g., 20-100 atm) rather than atmospheric pressure. This parameter change increases the equilibrium conversion of CO to H2, allowing a compact reactor volume to achieve the required H2/CO ratio. The high-pressure operation fundamentally alters the reaction equilibrium to favor hydrogen production.
2Manufacturing precision
If high-CO content synthesis gas is shifted to achieve desired H2/CO ratio, then the reducing gas composition is improved, but the shift reactor volume increases
Solution Approach 1:
The invention achieves precise H2/CO ratio control by changing the pressure parameter to high levels (20-100 atm). At these pressures, the shift reaction equilibrium shifts dramatically toward hydrogen production, allowing a small reactor volume to achieve complete or near-complete conversion. The high-pressure operation provides both precision in ratio control and compactness.
Solution Approach 2:
The system performs preliminary gasification to produce synthesis gas with a specific composition (high CO content) before feeding it to the shift reactor. This preliminary action allows the shift reactor to be designed for optimal conversion rather than having to handle a wide range of input compositions, thereby reducing the required reactor volume while maintaining precise H2/CO ratio control.
3Quantity of substance
If synthesis gas with high CO2 content is used, then the gas composition requirements for direct reduction are not met, but additional CO2 removal equipment is required
Solution Approach 1:
The invention merges the CO2 removal function with the shift conversion process. The CO2 removal unit is integrated into the gas processing train in a way that works synergistically with the shift reactor. This combination approach reduces overall system complexity compared to having completely separate CO2 removal and shift conversion systems, as the processes can share infrastructure and are optimized to work together.
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 minimizes the shift reactor size and cost, achieving the desired H2/CO ratio efficiently, reducing equipment and catalyst expenses, and preventing carbon deposition and overheating at high pressures in the direct reduction furnace.
Implementation Method 1
carbon monoxide shifting the top gas using a carbon monoxide shift reactor to form a carbon monoxide shifted top gas having a reduced carbon monoxide content
Data Source
AI summary
Methods and systems for the production of direct reduced iron, including: removing a top gas from a direct reduction furnace; carbon monoxide shifting the top gas using a carbon monoxide shift reactor to form a carbon monoxide shifted top gas having a reduced carbon monoxide content; adding one of a coal gas, a synthesis gas, and an export gas to at least a portion of the carbon monoxide shifted top gas to form a combined gas; removing carbon dioxide from the combined gas using a carbon dioxide removal unit to form a carbon dioxide lean combined gas; and providing the carbon dioxide lean combined gas to the direct reduction furnace as a reducing gas for producing direct reduced iron after heating to reduction temperature. Optionally, the method includes removing carbon dioxide from the top gas using a carbon dioxide removal unit prior to carbon monoxide shifting the top gas.