Sponge Iron Carbon Content via CO-Rich Gas Injection
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Solution Overview
Problem
Commercial direct reduction processes struggle to achieve high carbon content in sponge iron due to equilibrium-limited reactions and limitations in increasing CO and CH4 in the reducing gas stream, leading to suboptimal energy utilization and carbon deposition issues.
Innovation Solution
The use of membrane modules to separate hydrogen and CO2 from a reformed gas stream, producing a CO-rich gas stream that is injected into the transition or cooling zone of the reduction furnace, enhancing carbon content through exothermic reactions while maintaining high temperatures, optionally blended with a hydrocarbon-rich stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the degree of reduction is increased to remove remaining oxygen from partially reacted material, then the carbon content of sponge iron increases, but an excessively long residence time is required which reduces productivity
Solution Approach 1:
The patent changes the chemical composition parameters of the reducing gas stream by introducing a hydrocarbon-rich stream (containing CH4, C2H6, C3H8) blended with the conventional CO-H2 reducing gas. This parameter change enables carbon deposition through hydrocarbon cracking and carbonization reactions on the sponge iron surface, increasing carbon content without requiring extended residence time for oxygen removal
Solution Approach 2:
The patent implements continuous carbon deposition by maintaining a steady flow of hydrocarbon-rich gas stream through the reduction zone. The continuous presence of hydrocarbons ensures ongoing carbon supply to the sponge iron surface, allowing carbon content increase to occur continuously throughout the reduction process rather than requiring prolonged exposure
2Quantity of substance
If the amount of CO and CH4 in the reducing gas stream is increased to enhance carbon deposition, then the carbon content of sponge iron increases, but cooling effects from endothermic reactions and direct heat removal reduce the temperature necessary for efficient reduction
Solution Approach 1:
The patent applies local quality by injecting the hydrocarbon-rich stream specifically in the transition zone or lower reduction zone where carbon deposition is desired, rather than uniformly throughout the entire reduction furnace. This localized application allows carbon enrichment in specific regions without causing excessive cooling in the high-temperature reduction zones where Fe2O3 to Fe conversion occurs
Solution Approach 2:
The patent converts the potentially harmful cooling effect of hydrocarbon injection into a beneficial dual-function process. The hydrocarbon stream serves both as a carbon source for deposition and as a temperature regulator, preventing overheating in the transition zone while still enabling carbon enrichment. The endothermic cracking reactions provide controlled cooling that prevents sintering while maintaining sufficient temperature for carbonization
3Productivity
If temperature is increased to accelerate reduction reactions, then the reduction rate increases, but the temperature must be kept below the sintering temperature to prevent cluster formation inside the reduction reactor
Solution Approach 1:
The patent introduces dynamic temperature control by utilizing the endothermic cracking of hydrocarbons in the transition zone to locally reduce temperature. This creates a dynamic thermal environment where the temperature is automatically regulated by the hydrocarbon injection rate, allowing the system to adapt temperature conditions to prevent sintering while maintaining reduction efficiency
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 method effectively increases the carbon content of sponge iron, improves thermal efficiency, and maintains high temperatures within the reduction zone, enhancing productivity and reducing operational costs without affecting existing plant operations.
Implementation Method 1
The use of membrane modules to separate hydrogen and CO2 from a reformed gas stream
Implementation Method 2
enhancing carbon content through exothermic reactions while maintaining high temperatures
Implementation Method 3
the reaction of iron ore in a reactive gas stream containing reducing agents, such as H2 and CO
Data Source
AI summary
Methods and systems for producing direct reduced iron having increased carbon content, comprising: providing a reformed gas stream from a reformer; delivering the reformed gas stream to a carbon monoxide recovery unit to form a carbon monoxide-rich gas stream and a hydrogen-rich gas stream; and delivering the carbon-monoxide-rich gas stream to a direct reduction furnace and exposing partially or completely reduced iron oxide to the carbon monoxide-rich gas stream to increase the carbon content of resulting direct reduced iron. The carbon monoxide-rich gas stream is delivered to one of a transition zone and a cooling zone of the direct reduction furnace. Optionally, the method further comprises mixing the carbon monoxide-rich gas stream with a hydrocarbon-rich gas stream.