Carburized Sponge Iron via Hydrogen Reduction and CO2 Seal Gas
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Solution Overview
Problem
Existing steel production processes emit high levels of CO2 due to the use of carbonaceous reductants, and there is a need for a more environmentally friendly method to produce carbon-containing crude iron that can be used as a drop-in replacement for current methods.
Innovation Solution
A process using hydrogen direct reduction (H-DR) with carbon dioxide as a seal gas to carburize sponge iron, where CO2 is converted to CO and subsequently reacts to carburize the sponge iron, reducing net CO2 emissions and eliminating the need for additional carburizing gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbonaceous reductants are used to reduce iron oxide, then the reduction process is effective, but high levels of CO2 are emitted
Solution Approach 1:
The invention changes the chemical composition parameters of the reducing gas from carbonaceous (CO, H2 with CO2) to hydrogen-based (H2 with minimal CO2), fundamentally altering the reduction chemistry to eliminate CO2-generating reactions while maintaining effective iron oxide reduction through hydrogen chemistry
Solution Approach 2:
The invention converts the previously harmful CO2 emissions into a beneficial by-product of the reduction process. The CO2 generated during hydrogen reduction is not discarded but captured and reused as a carburizing agent, transforming an environmental liability into a valuable process input that provides both carbon for the steel and acts as a sealing gas
2Object-generated harmful factors
If hydrogen gas is used as reductant, then CO2 emissions are reduced, but the sponge iron lacks carbon content
Solution Approach 1:
The invention merges two previously separate process stages into one integrated operation: the hydrogen reduction process and the carburization process. By capturing CO2 from the reduction off-gas and recycling it back into the reduction shaft, the system simultaneously performs reduction and carbon incorporation, eliminating the need for separate carburizing operations and external carbon sources
Solution Approach 2:
The system makes the reduction process self-sufficient by using its own by-product (CO2 from hydrogen reduction) to fulfill the carbon requirement. The CO2 that would normally be emitted is instead recycled to provide carbon for the sponge iron and to serve as sealing gas, making the process internally sustainable without external carbon inputs
3Reliability
If seal gas is introduced during charging and discharging, then the process is sealed properly, but inert gases accumulate in the system
Solution Approach 1:
The invention changes the chemical nature of the seal gas from inert (nitrogen, air) to reactive (CO2). This parameter change transforms the seal gas from a substance that accumulates uselessly in the system to one that actively participates in the chemical reactions, providing carbon for carburization while maintaining the sealing function during charging and discharging operations
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
Produces carburized sponge iron with low concomitant CO2 emissions, utilizing renewable sources for carbon and hydrogen, and avoiding the accumulation of inert gases, thus simplifying the process and reducing costs.
Implementation Method 1
reducing gas, which comprises make-up gas and recycled top gas, is introduced into the direct reduction shaft in countercurrent flow to the iron ore in order to reduce the iron ore and produce carburized sponge iron
Implementation Method 2
CO2 is converted to CO and subsequently reacts to carburize the sponge iron
Implementation Method 3
carburized sponge iron with low concomitant CO2 emissions
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
The present disclosure relates to a process for the production of carburized sponge iron (208), comprising the steps of charging (s303a) iron ore (207) into a direct reduction shaft (211), and/or discharging (s303b) carburized sponge iron (208) from the direct reduction shaft, whereby a seal gas (223) is introduced into the direct reduction shaft; removing (s305) a top gas (216) from the direct reduction shaft; recycling (s307) a proportion of the top gas and mixing with a make-up gas (215) to form a reducing gas (217); and introducing (s309) the reducing gas into the direct reduction shaft in countercurrent flow to the iron ore in order to reduce the iron ore and produce carburized sponge iron. The seal gas consists essentially of carbon dioxide, and the make-up gas comprises greater than 80 vol% hydrogen gas. The disclosure further relates to a system for the production of carburized sponge iron, as well as a carburized sponge iron produced by the aforementioned process.