Zero-Oxygen Ironmaking with Shaft Pre-Reduction and Hot Gas Injection
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Solution Overview
Problem
Existing gas-based shaft furnace processes for ironmaking face challenges such as high raw material and energy costs, safety risks, low operation efficiency, and difficulty in scaling up due to stringent ore quality requirements, leading to high operating costs and carbon emissions.
Innovation Solution
A method involving hot-charging self-fluxing oxidized pellets into a gas-based shaft furnace, using a combination of cold and hot reducing gases for pre-reduction, followed by superheated reducing gas injection in an oxygen-free injection furnace to produce molten iron and slag, with heat recovery and recycling of gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If gas-based shaft furnace process is used for ironmaking, then carbon emissions are reduced compared to blast furnace, but raw material cost and operating cost increase significantly
Solution Approach 1:
The patent performs pre-reduction of iron ore pellets in the shaft furnace before melting, achieving metallization rates of 85-95%. This preliminary action converts most iron ore to metallic iron in the solid state, reducing the burden on the subsequent melting stage and allowing the use of lower quality ores that would otherwise be too expensive for direct melting
Solution Approach 2:
The patent changes the metallization rate parameter to operate at 85-95% rather than 100%, and controls the H2:CO ratio in the reducing gas to optimize both cost and efficiency. This parameter optimization allows cost-effective operation with lower quality iron ore pellets while maintaining low carbon emissions
2Manufacturing precision
If existing gas-based shaft furnace process is used, then deep melting-separation requires electric furnace, but this increases operating cost by 600-1000 yuan/tonne
Solution Approach 1:
The patent merges the reduction and melting operations into a single integrated oxygen-free injection furnace. The pre-reduced iron (DRI) with 85-95% metallization rate from the shaft furnace is directly charged into the injection furnace where carbon injection provides both heat and reducing atmosphere, eliminating the need for separate electric furnace melting and achieving cost-effective operation
3Use of energy by moving object
If hot-charging self-fluxing pellets is implemented, then energy consumption is reduced, but system complexity increases
Solution Approach 1:
The pellets are pre-heated to 200-400°C before charging into the shaft furnace, and the shaft furnace itself is pre-heated to 800-1000°C. This preliminary heating action reduces the energy required during the actual reduction and melting process, lowering overall energy consumption while the integrated design keeps system complexity manageable
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
Reduces energy consumption, lowers costs, enhances metallization rates, and improves system availability, enabling efficient production of high-temperature molten iron and slag with reduced carbon emissions, suitable for various ore grades and promoting large-scale capacity.
Implementation Method 1
superheated reducing gas is injected into the furnace hearth of the oxygen-free injection furnace. The DRI is further reduced and heated within the oxygen-free injection furnace to produce high-temperature molten iron and slag
Implementation Method 2
The gaseous products generated in the gas-based shaft furnace and the oxygen-free injection furnace are subjected to heat recovery via a heat exchanger
Implementation Method 3
The gaseous products generated in the gas-based shaft furnace and the oxygen-free injection furnace are subjected to heat recovery via a heat exchanger
Data Source
Figure 1
AI summary
The present invention relates to the technical field of non-blast furnace low-carbon metallurgy, and relates to a zero-oxygen injection low-carbon ironmaking method. The method comprises: loading hot-state self-fluxing oxidized pellets into a gas-based shaft furnace from the top of the furnace, injecting cold reducing gas into the gas-based shaft furnace from the bottom of the gas-based shaft furnace, and meanwhile, injecting hot reducing gas into the gas-based shaft furnace from the junction of a reducing section and a cooling section of the gas-based shaft furnace, wherein the cold reducing gas is heated in the rising process and mixed with the hot reducing gas, then the mixed gas undergoes a pre-reduction reaction with the self-fluxing oxidized pellets to obtain hot-state direct reduced iron, and the hot-state direct reduced iron is cooled by the cold reducing gas in the cooling section to obtain direct reduced iron; and loading a solid carbon material and the direct reduced iron into a zero-oxygen injection furnace from the top of the furnace, injecting superhot reducing gas into the zero-oxygen injection furnace, and the direct reduced iron undergoing reduction melting to obtain liquid slag and molten iron. The present invention reduces gas heating energy consumption, and significantly reduces carbon emission compared with a blast furnace.