CO2 Steam Reformer for Direct Reduced Iron Fuel Flexibility
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Solution Overview
Problem
Existing direct reduction (DR) processes for iron ore are limited by the need for abundant natural gas and are inefficient when using liquid or solid fuels, as they require costly gasification processes that produce unsuitable reducing gases with unfavorable reductant ratios, leading to excessive fuel consumption and operational challenges.
Innovation Solution
Replacing the traditional gasifier with a CO2 and steam reformer fed by recovered CO2 and natural gas, which generates syngas through catalytic reforming, and combines it with recycled off-gas to form a reducing gas stream for the DR shaft furnace, optimizing the reductant ratio and reducing fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional gasifier is used to convert liquid or solid fuels to reducing gas, then the process can operate with diverse fuel sources, but the reductant ratio becomes unfavorable and fuel consumption increases
Solution Approach 1:
The patent changes the chemical parameters of the reforming process by using CO2 and steam instead of traditional gasification methods. This allows optimization of the reductant ratio (H2/CO) in the reducing gas while maintaining flexibility in fuel sources. The reformer operates under controlled conditions to produce syngas with favorable composition for direct reduction.
Solution Approach 2:
The system incorporates feedback by recycling the off-gas from the shaft furnace back to the reformer. The off-gas containing unreacted components is fed into the reformer to be converted into additional reducing agents, creating a closed-loop system that improves fuel efficiency and reduces waste.
2Adaptability or versatility
If a gasifier is used to produce reducing gas from liquid or solid fuels, then external fuel sources can be utilized, but the resulting reducing gas has unfavorable reductant ratios
Solution Approach 1:
The patent employs parameter changes by controlling the reforming conditions (temperature, pressure, CO2/steam ratios) to precisely control the composition of the reducing gas. The reformer is designed to produce syngas with optimized H2/CO ratios suitable for direct reduction, regardless of the external fuel source used.
Solution Approach 2:
The reformer acts as an intermediary device that converts diverse external fuel sources into a standardized reducing gas with controlled composition. It mediates between the variable fuel input and the requirements for precise reductant ratio in the shaft furnace, ensuring consistent process conditions.
3Productivity
If water-gas shift reactions occur within the shaft furnace, then additional reducing agents can be generated, but operational stability decreases and process control becomes difficult
Solution Approach 1:
The patent applies preliminary action by performing the water-gas shift reaction externally in the reformer before the gas enters the shaft furnace. The off-gas is pre-treated and reformed in a controlled environment, stabilizing the reducing gas composition before it enters the reduction zone, thereby preventing unwanted reactions within the furnace.
Solution Approach 2:
The system extracts the water-gas shift reaction from the shaft furnace process and relocates it to the reformer. This separation allows the shift reaction to occur under controlled conditions externally, removing the source of operational instability from the critical reduction zone while still generating additional reducing agents.
4Device complexity
If CO2 is not removed from the off-gas before recycling, then the process simplicity is maintained, but the reducing gas quality deteriorates
Solution Approach 1:
The patent merges the CO2 removal function with the reforming process. Instead of a separate CO2 removal step, the CO2 is directly fed into the reformer where it serves as a reactant for syngas production. This integration eliminates the need for complex CO2 separation equipment while improving reducing gas quality.
Solution Approach 2:
The system converts the potentially harmful effect of CO2 accumulation (which would degrade reducing gas quality) into a beneficial reactant for the reforming process. CO2 removed from the off-gas is fed back to the reformer to produce additional H2 and CO, transforming a quality problem into a productivity advantage.
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 enhances the efficiency of the DR process by minimizing external fuel use, stabilizing the operation, and preventing water-gas shift reactions within the furnace, resulting in a high-quality reducing gas with improved reductant and oxidant ratios, thus reducing fuel costs and operational inefficiencies.
Implementation Method 1
the feed gas is converted to syngas through a catalytically-driven reforming of natural gas with CO2 and steam
Implementation Method 2
water-gas shift reacting the recycled off-gas stream from the DR shaft furnace
Data Source
AI summary
Methods and systems for producing direct reduced iron (DRI), comprising: generating a syngas stream in a carbon dioxide (CO2) and steam reformer; and providing the syngas stream to a direct reduction (DR) shaft furnace as a reducing gas stream. The methods and systems also comprise combining the syngas stream with a recycled off-gas stream from the DR shaft furnace to form the reducing gas stream. The methods and systems further comprise removing carbon dioxide (CO2) from the recycled off-gas stream from the DR shaft furnace prior to combining it with the syngas stream to form the reducing gas stream. The methods and systems still further comprise feeding CO2 removed from the recycled off-gas stream from the DR shaft furnace to the CO2 and steam reformer. The methods and systems still further comprise feeding recycled off-gas from the recycled off-gas stream from the DR shaft furnace to the CO2 and steam reformer.