Direct Reduction Gas Recirculation Using Furnace and Converter Off-Gases
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Solution Overview
Problem
Existing integrated steelworks processes fail to optimally utilize energetically and materially valuable process gases, leading to inefficiencies and unnecessary external gas additions.
Innovation Solution
Recirculate and process electric furnace and converter gases within a closed-loop system, integrating dehumidification and CO₂ separation to enhance the quality and reduce reliance on external fresh gases like methane and hydrogen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If converter gas and electric furnace gas are recirculated and integrated into the reduction gas system, then the utilization efficiency of process gases is improved, but the complexity of gas processing and system integration increases
Solution Approach 1:
The patent merges converter gas and electric furnace gas streams into a unified recirculation system, combining multiple gas sources to create a comprehensive process gas utilization network that maximizes energy recovery while sharing common infrastructure
Solution Approach 2:
The recirculated process gases serve multiple functions: they provide reducing agents for iron ore reduction, serve as fuel for heating systems, and maintain atmospheric control in various process zones, thereby maximizing the utility of recovered gases
2Manufacturing precision
If dehumidification and CO₂ separation are implemented in the gas recirculation system, then the purity of reduction gas is improved, but the manufacturing complexity and operational difficulty increase
Solution Approach 1:
Dehumidification and CO₂ separation are performed in advance before gases enter the reduction reactor, ensuring that high-purity reduction gas is prepared beforehand and preventing impurities from affecting the reduction process
Solution Approach 2:
The patent introduces intermediate processing stages with separation units and purification systems that act as mediators between the raw process gases and the reduction reactor, enabling gradual purification while maintaining system controllability
3Quantity of substance
If external fresh gases like methane and hydrogen are reduced or eliminated, then operating costs are reduced, but the reliability of maintaining adequate reducing gas composition may worsen
Solution Approach 1:
The system implements feedback control by continuously monitoring the composition of recirculated gases and adjusting process parameters such as recirculation rates, heating temperatures, and injection points to maintain optimal reducing gas composition without external supplements
Solution Approach 2:
The process gases from converter and electric furnace self-sustain the reduction process by providing sufficient reducing agents (CO and H2) through recirculation, making the system self sufficient and eliminating dependency on external gas supplies
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
Enhances the efficiency and reduces the need for external gas inputs, optimizing the use of existing gases and minimizing impurities, thereby improving the overall process economics and environmental footprint.
Implementation Method 1
heated in at least one reduction gas heater
Implementation Method 2
in at least one reformer
Implementation Method 3
at least one electric furnace for melting the sponge iron to pig iron
Implementation Method 4
at least one converter for refining pig iron to crude steel or steel
Data Source
Figure 1
AI summary
The invention relates to a method for operating a direct reduction reactor (2) in an integrated steelworks (1), comprising at least one direct reduction reactor (2) for directly reducing iron oxide carriers (io) to directly reduced iron carriers (ri) and generating reactor gas (TG), at least one electric furnace (3) for melting the sponge iron to pig iron and generating electric furnace gas (EG), and at least one converter (4) for refining pig iron to crude steel or steel and generating converter gas (KG), wherein at least a portion of the reactor gas (TG) discharged from the direct reduction reactor (1) is circulated (I), heated in at least one reduction gas heater (5) or in at least one reformer, and returned to the direct reduction reactor (2) as reduction gas (RG).wherein the electric furnace gas (EG) discharged from the electric furnace (3) or a mixture of the converter gas (KG) discharged from the converter (4) and the electric furnace gas (EG) discharged from the electric furnace (3) is at least partially added to the reduction gas (RG) before being introduced into the at least one reduction gas heater (5) or into the at least one reformer.