Hydrogen Gas Recycling in Direct Reduction Shaft
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Solution Overview
Problem
The steel industry's carbonaceous reduction processes emit significant CO2, and using hydrogen as a reductant in direct reduction of iron ore poses challenges in energy efficiency and NOx emissions due to the need for flaring unreacted hydrogen gas.
Innovation Solution
A process and system for recycling unreacted hydrogen gas from the direct reduction shaft by utilizing a secondary circuit to control pressure and reduce hydrogen loss, allowing for efficient reuse of hydrogen as a reduction gas, thereby minimizing NOx emissions and energy wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If unreacted hydrogen gas is flared in conventional direct reduction processes, then CO2 emissions are reduced, but energy efficiency deteriorates and NOx emissions increase
Solution Approach 1:
The patent recovers unreacted hydrogen gas from the top gas stream that would otherwise be flared, and reinjects it into the reduction shaft. This prevents energy waste from flaring while avoiding CO2 emissions, directly resolving the contradiction between harmful emissions and energy efficiency
Solution Approach 2:
The patent creates a continuous circulation system where hydrogen gas is constantly recovered, compressed, and reinjected into the reduction process. This continuous recycling eliminates the need for flaring while maintaining energy efficiency and preventing NOx emissions
2Object-generated harmful factors
If hydrogen gas is used as reductant instead of carbonaceous reductants, then CO2 emissions are reduced, but the complexity of handling unreacted hydrogen increases
Solution Approach 1:
The system uses its own unreacted hydrogen gas as the recycling medium, eliminating the need for external hydrogen sources or complex purification systems. The top gas is directly compressed and reinjected, simplifying the overall system while achieving CO2 emission reduction
Solution Approach 2:
The top gas stream serves multiple functions: it carries unreacted hydrogen for recycling, provides process information about reduction efficiency, and acts as the recycling medium itself. This multi-functionality reduces system complexity while achieving the desired environmental benefits
3Loss of substance
If top gas is flared to remove unreacted hydrogen, then hydrogen loss is minimized, but NOx emissions increase
Solution Approach 1:
Instead of discarding unreacted hydrogen through flaring, the patent recovers it via compression and reinjection. This eliminates both hydrogen loss and the harmful NOx emissions that would result from combustion, simultaneously addressing both parameters
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 reduces operating costs and minimizes NOx emissions by recycling hydrogen, enhancing energy efficiency and reducing CO2 emissions in the steel production process.
Implementation Method 1
a first compressor provided in a gas line leading from the reduction gas source to the direct reduction shaft
Implementation Method 2
conducting said portion of gas through a secondary circuit while reducing the pressure of said portion of gas
Implementation Method 3
mixing said part with reduction gas from the reduction gas source at a point downstream a first compressor provided in a gas line leading from the reduction gas source to the direct reduction shaft
Data Source
AI summary
A system for the production of sponge iron, the system including a direct reduction shaft including a first inlet for introduction of iron ore into the shaft, a first outlet for removing sponge iron from the shaft, a reduction gas source, connected through a gas line with the shaft, a first compressor in said gas line, and a primary circuit for conducting at least a part of the top gas therethrough. The primary circuit is connected in one end with shaft and in another end with said gas line downstream said first compressor. The system also includes a secondary circuit for conducting at least a portion of gas removed from gas conducted through the primary circuit, said secondary circuit being connected in one end to the primary circuit and in another end to said gas line upstream said first compressor. The system further includes means therein for reducing the pressure of said portion of gas conducted through the secondary circuit, and a first valve for controlling a flow of said portion of gas into the secondary circuit.