Low-Carbon Ferromanganese Decarburization with Slag Ratio Control
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Solution Overview
Problem
Existing methods for producing low-carbon ferromanganese face challenges such as low Mn yield, high production costs, and decreased tuyere service life due to manganese oxidation and vaporization, as well as inefficiencies in decarburization processes.
Innovation Solution
A method involving top-blowing an oxidizing gas into a converter-type reaction vessel, adjusting slag composition to (CaO+MgO)/(Al2O3+SiO2) between 0.4 and 5.0, and maintaining an agitation power density of at least 500 W/t, with optional auxiliary materials like MgO, to enhance Mn recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-carbon ferromanganese is decarburized by blowing oxygen gas from bottom tuyere at high temperature, then carbon removal efficiency is improved, but manganese oxidation and vaporization increase causing decreased Mn yield
Solution Approach 1:
Instead of blowing oxygen from the bottom tuyere (conventional method), the patent inverts the approach by blowing oxygen from the top of the furnace. This top-blowing method allows oxygen to react with carbon at the molten metal surface, reducing carbon content while minimizing penetration into the bulk metal that would cause manganese oxidation and vaporization.
Solution Approach 2:
The patent applies local quality by controlling the oxidation reaction to occur primarily at the surface layer of the molten metal where oxygen contacts the bath, rather than throughout the entire metal volume. This localized decarburization at the surface reduces overall manganese loss while effectively removing carbon.
2Manufacturing precision
If silicon-manganese molten metal is used as starting material for desiliconization method, then medium- and low-carbon ferromanganese can be produced, but power costs increase due to electric furnace usage
Solution Approach 1:
The patent changes the key parameter of starting material from silicon-manganese alloy to high-carbon ferromanganese, and changes the decarburization method from electric furnace oxidation to top-blowing oxidation in a conventional furnace. This parameter change maintains carbon content control capability while dramatically reducing power consumption by eliminating the need for electric furnace operation.
Solution Approach 2:
The patent replaces the expensive silicon-manganese alloy (SiMn) starting material with cheaper high-carbon ferromanganese (HCFeMn). The subsequent top-blowing decarburization process efficiently removes excess carbon, producing the desired low-carbon ferromanganese product at lower material and energy costs.
3Productivity
If oxygen gas is blown into ferromanganese molten metal to remove carbon, then decarburization is achieved, but manganese oxide formation and manganese vapor generation occur causing yield decrease
Solution Approach 1:
The patent inverts the conventional bottom-blowing method by implementing top-blowing of oxygen. This reversal changes the reaction dynamics: oxygen reacts with carbon at the surface rather than penetrating from the bottom, achieving decarburization while suppressing manganese oxidation and vaporization that occur with bottom-blowing high-temperature oxidation.
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 achieves a high Mn yield by optimizing slag composition and agitation, reducing MnO in the slag efficiently and extending tuyere life, thus improving economic viability.
Implementation Method 1
a method of removing carbon in molten metal by oxidation by blowing an oxygen gas into high-carbon ferromanganese molten metal
Implementation Method 2
The equations (1) to (4) show that, since the equation (1) is an endothermic reaction, an increase in the temperature of the molten metal
Implementation Method 3
The decarburization reaction of ferromanganese molten metal is usually represented by following equation (1), and an equilibrium constant K thereof can be represented by the following equation (2). (MnO)+[C]=[Mn]+CO
Data Source
AI summary
A method for producing low-carbon ferromanganese capable of achieving a high Mn yield. In producing low-carbon ferromanganese by blowing an oxidizing gas from a top-blowing lance onto a bath face of high-carbon ferromanganese molten metal accommodated in a reaction vessel provided with a top-blowing lance and bottom-blowing tuyere to perform decarburization, the slag composition during the blowing is adjusted so that a value of (CaO+MgO)/(Al2O3+SiO2) on a mass basis in the slag composition is not less than 0.4 but not more than 5.0. Also, agitation is performed under a condition that an agitation power density ε of an agitation gas blown through the bottom-blowing tuyere is not less than 500 W/t.