Hot Briquette Iron Moldability via CO2 Ratio Control
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Solution Overview
Problem
Reduced iron produced by the rotary hearth furnace (RHF) has low metal iron content, high oxide impurities, and residual carbon, making it unsuitable for hot briquetting and inefficient for use in blast furnaces, leading to reoxidation issues and increased energy consumption.
Innovation Solution
A method involving the production of hot briquette iron (HBI) with a metal iron content of 50% or more and carbon content of 5% or less, using a specific carbon monoxide to carbon dioxide ratio in the rotary hearth furnace, followed by compression-molding at controlled temperatures and densities to create a dense, reoxidation-resistant product suitable for blast furnace use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If reduced iron is produced by rotary hearth furnace using conventional methods, then production cost is low and productivity is high, but metal iron content is low and oxide impurities are high
Solution Approach 1:
The patent applies parameter changes by optimizing the carbon to oxygen atomic ratio (0.7-1.5) and controlling the CO/CO2 ratio (0.3-1.2) in the reduction atmosphere, along with specific temperature ranges (1200-1420°C) and residence times, to transform the reduction process outcomes and achieve high metal iron content while controlling impurities
Solution Approach 2:
The patent implements preliminary action by conducting partial reduction in the rotary hearth furnace to produce partially-reduced iron with controlled metallization ratio (50-85%), which is then further reduced and melted in the blast furnace, allowing optimized distribution of reduction stages
2Use of energy by moving object
If reduced iron with high oxide impurities is used in blast furnace, then energy consumption increases, but using conventional production methods maintains low production cost
Solution Approach 1:
The patent controls the carbon to oxygen atomic ratio (0.7-1.5) and CO/CO2 ratio (0.3-1.2) parameters during reduction to minimize oxide impurities while maintaining efficient energy utilization, achieving both low energy consumption and high metallization ratio
3Reliability
If reduced iron is stored or transported without hot-molding, then handling is simple, but reoxidation occurs and storage stability decreases
Solution Approach 1:
The patent applies parameter changes by controlling the metallization ratio (50-85%) and carbon content (5% or less) through optimized reduction parameters, which inherently improves the material's reoxidation resistance and storage stability without requiring additional protective measures
4Ease of manufacture
If carbon content in reduced iron is high, then reduction reaction is sufficient, but moldability during hot briquetting deteriorates
Solution Approach 1:
The patent optimizes the carbon to oxygen atomic ratio (0.7-1.5) and controls the CO/CO2 ratio (0.3-1.2) to achieve complete reduction with minimal residual carbon (5% or less), ensuring excellent moldability while maintaining efficient carbon utilization during reduction
Solution Approach 2:
The patent implements self-service by allowing the reduction process itself to naturally consume carbon through the optimized carbon to oxygen ratio and CO/CO2 atmosphere, eliminating the need for separate carbon removal steps and directly producing material with optimal moldability
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
The method produces HBI with improved moldability and storage stability, reducing reoxidation and enabling efficient transportation, while optimizing energy consumption and increasing pig iron production when supplied to blast furnaces.
Implementation Method 1
producing, in an atmosphere at a maximum temperature of 1200°C to 1420°C at a ratio of carbon monoxide to carbon dioxide of 0.3 to 1.2, a reduced iron-containing material
Implementation Method 2
the cast is heated by radiation heat from gas of an upper portion in the furnace
Implementation Method 3
compression-molding the reduced iron-containing material at a temperature of 500°C to 800°C by a roller-type mold
Data Source
Figure 1~3
AI summary
In a method of producing a reduced iron cast, a cast of a powder which includes total iron of 40% or more and an atomic molar amount of fixed carbon of 0.7 to 1.5 times the atomic molar amount of oxygen compounded with metal oxide reduced in a carbon monoxide atmosphere at 1200°C is reduced in a rotary hearth furnace. The method includes: producing, in an atmosphere at a maximum temperature of 1200°C to 1420°C at a ratio of carbon monoxide to carbon dioxide of 0.3 to 1.2 in the reduced material, a reduced iron-containing material in which a ratio of metal iron is 50 mass% or more and a ratio of carbon is 5 mass% or less; and compression-molding the reduced iron-containing material at a temperature of 500°C to 800°C by a roller-type mold.