Parallel Direct Reduction Furnaces for Stainless Steel Cost Reduction
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Solution Overview
Problem
The existing processes for producing stainless steel are costly due to the high price of nickel, which is exacerbated by limited resources and increasing demand, necessitating a cost-effective method for steel production using chromium and nickel alloying elements.
Innovation Solution
The process involves producing liquid steel through separate direct reduction processes using cost-effective chrome ore and nickel ore mixtures in parallel furnaces, followed by further processing in a converter to achieve the desired chemical analysis and quality of stainless steel, with the separation of ferrochrome and ferronickel production steps allowing for direct use of these ores and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional EAF-AOD-L or EAF-AOD-L-VOD processes are used for stainless steel production, then the process is well-established and can utilize scrap or pig iron, but the production costs are high due to expensive nickel requirements and complex multi-step processing
Solution Approach 1:
The production process is segmented into two separate direct reduction furnaces operating in parallel - one for ferrochrome production and one for ferronickel production. This segmentation allows independent optimization of each reduction process and enables direct feeding of chromium and nickel ores without requiring complex alloying operations in traditional electric arc furnaces, thereby reducing overall production costs while maintaining process manageability
Solution Approach 2:
Chromium and nickel are preliminarily reduced to ferrochrome and ferronickel intermediates in separate direct reduction furnaces before being fed to the converter. This preliminary action transforms the expensive nickel requirement into a more cost-effective ferronickel intermediate, and simplifies subsequent stainless steel production by providing pre-alloyed feeds that require less complex processing in the converter stage
2Manufacturing precision
If nickel content is increased to meet stainless steel specifications, then the steel quality is maintained, but the production cost increases significantly due to limited nickel resources and rising nickel prices
Solution Approach 1:
Ferronickel is introduced as an intermediary material between nickel ore and final stainless steel product. The direct reduction furnace produces ferronickel with controlled nickel content (typically 15-50% Ni), which then serves as a cost-effective feed material for the converter. This intermediary approach allows precise control of nickel addition while avoiding the volatility and high cost of using pure nickel metal or high-nickel scrap
Solution Approach 2:
The process changes the chemical form and concentration parameters of nickel throughout the production chain. Nickel ore (typically 1-2% Ni) is converted to ferronickel (15-50% Ni) through direct reduction, and then further refined to achieve the final stainless steel nickel content (8-12% Ni). This parameter transformation enables cost-effective nickel utilization while maintaining product quality specifications
3Ease of manufacture
If chromium ore and nickel ore are directly used in traditional electric arc furnaces, then raw material costs might be reduced, but the process becomes inefficient due to the need for complex alloying and multiple processing steps
Solution Approach 1:
Chromium ore and nickel ore undergo preliminary direct reduction in separate furnaces to produce ferrochrome and ferronickel intermediates before being fed to the converter. This preliminary action pre-conditions the ores for efficient converter processing, eliminating the need for complex in-furnace alloying operations in traditional electric arc furnaces and significantly improving overall process efficiency
Solution Approach 2:
The two direct reduction furnaces operate continuously in parallel, providing a steady stream of ferrochrome and ferronickel intermediates to the converter. This continuous operation eliminates batch processing interruptions and ensures optimal utilization of the converter, thereby maintaining high productivity while using cost-effective ore-based feeds
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 significantly reduces steel production costs by utilizing cheaper raw materials and simplifies the process, with the investment in new furnaces being quickly amortized, while maintaining high-quality stainless steel production with minimal phosphorus and efficient sulfur removal.
Implementation Method 1
Production of liquid steel with ferrochrome and liquid steel with ferronickel in two separate direct reduction processes using cost-effective chrome ore or nickel ore raw material mixtures in two direct reduction furnaces arranged in parallel
Implementation Method 2
production of the stainless steel in the converter through typical freshening of the metal mixture, slag reduction and fine adjustment of the chemical target analysis
Data Source
AI summary
In order to allow a substantial reduction in steel production costs in the production of stainless steel using the alloy elements chromium and nickel, the invention proposes that the required intermediate production of ferrochrome and ferronickel be conducted in two separate direct reduction processes based on low-cost chromium ore and nickel ore in two parallel SAFs (3, 4) disposed on the primary side of a converter (6) that performs the subsequent processing.