Low-Graphite Magnesia-Carbon Brick Production With Particle-Size Control
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Solution Overview
Problem
Magnesia-carbon bricks used in converters and electric furnaces face issues with spalling resistance and corrosion resistance due to high graphite content, leading to heat loss, carbon pickup, and increased CO2 emissions, despite the need for improved spalling resistance in these applications.
Innovation Solution
A production method involving the use of pitch or tar as a binder, with controlled particle size composition of magnesia and reduced graphite content, along with kneading and molding under warm conditions, to enhance spalling and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If flake graphite is added to magnesia-carbon brick to improve spalling resistance, then spalling resistance is improved, but heat loss increases due to high thermal conductivity
Solution Approach 1:
The patent changes the particle size parameter of graphite from conventional flake graphite to fine graphite powder with specific particle size distribution (D50: 3-10 μm, D10: 1-3 μm, D90: 15-30 μm). This parameter change reduces thermal conductivity while maintaining spalling resistance, as the fine particles create more interfacial thermal resistance compared to large flakes.
Solution Approach 2:
The patent creates a composite structure by combining magnesia aggregate with fine graphite powder and a specific binder system. The composite achieves optimized spalling resistance through the synergistic effect of fine graphite particles distributed throughout the magnesia matrix, reducing overall thermal conductivity while maintaining structural integrity under thermal stress.
2Strength
If flake graphite is added to magnesia-carbon brick to improve spalling resistance, then spalling resistance is improved, but corrosion resistance deteriorates due to pore formation from graphite oxidation
Solution Approach 1:
The patent changes the physical form and particle size of graphite from flake to fine powder (D50: 3-10 μm). This parameter change reduces the formation of large pores during oxidation and creates a more uniform distribution, thereby maintaining spalling resistance while improving corrosion resistance by preventing slag infiltration.
Solution Approach 2:
The patent applies local quality by creating a fine, uniform distribution of graphite particles throughout the magnesia matrix rather than using large flakes. This local refinement ensures that any oxidation products are distributed as fine particles rather than forming large pores, locally preventing slag infiltration pathways while maintaining overall spalling resistance.
3Ease of manufacture
If pitch or tar is used as binder and heated to suitable viscosity for molding, then molding is possible, but energy consumption and processing time increase
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by selecting phenol resin with specific molecular weight and softening point (80-120°C). This parameter change allows the binder to achieve suitable viscosity for molding at lower temperatures and shorter times compared to conventional pitch or tar, reducing energy consumption and processing time.
Solution Approach 2:
The patent replaces the mechanical heating and viscosity adjustment process with a chemically optimized binder system. The phenol resin's inherent flow properties at room temperature or slight warming eliminate the need for extensive heating and mechanical kneading, substituting chemical design for mechanical processing.
4Loss of time
If phenol resin is used as binder to enable molding at normal temperature, then processing time is reduced, but spalling resistance becomes insufficient
Solution Approach 1:
The patent creates a composite binder system combining phenol resin with specific additives and optimizes the ratio of binder to aggregate. This composite approach maintains the time efficiency of phenol resin while enhancing spalling resistance through the synergistic effect of the optimized composition and fine graphite powder distribution.
Solution Approach 2:
The patent changes the binder composition parameters by selecting phenol resin with specific molecular weight, softening point, and adding appropriate additives. These parameter changes enhance the binder's ability to bind magnesia and graphite particles effectively, improving spalling resistance while maintaining rapid processing capabilities.
5Loss of energy
If graphite content is reduced to decrease heat loss and CO2 emissions, then environmental performance is improved, but spalling resistance deteriorates
Solution Approach 1:
The patent changes the particle size parameter of graphite from conventional flake graphite to fine graphite powder with specific distribution (D50: 3-10 μm). This parameter change allows maintaining spalling resistance with reduced total graphite content, as the fine particles provide better distribution and interfacial bonding, reducing the need for large graphite volumes.
Solution Approach 2:
The patent applies local quality by concentrating fine graphite particles at critical locations within the brick structure where they provide maximum spalling resistance. This localized optimization allows reducing overall graphite content while maintaining performance, thereby decreasing heat loss and CO2 emissions.
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 results in magnesia-carbon bricks with improved spalling resistance and corrosion resistance, extending the usable life of converters and electric furnaces, reducing heat loss and CO2 emissions.
Implementation Method 1
kneading refractory aggregate with 0.5-15% by weight of mesophase pitch powder which contains 60% or more of bulk mesophase pitches having optical anisotropy and has a carbonization yield of 70% or more, in a temperature region where the mesophase pitch powder is softened
Implementation Method 2
a particle size composition of the magnesia in the refractory raw material blend is set such that a mass ratio of magnesia having a particle size of 1 mm or more to magnesia having a particle size of 0.075 mm to less than 1 mm is 0.2 to 1.5
Implementation Method 3
adding pitch/tar as a binder to a refractory raw material blend containing magnesia at a rate of 85% by mass or more
Data Source
AI summary
The present invention provides a magnesia-carbon brick having excellent spalling resistance even though it contains graphite at a low rate, and having excellent corrosion resistance. In the present invention, the magnesia-carbon brick production method comprises: adding, as a binder, pitch/tar which is pitch, diluted pitch obtained by diluting pitch with a solvent, tar, or diluted tar obtained by diluting tar with a solvent, to a refractory raw material blend containing magnesia at a rate of 85% by mass or more, and containing graphite at a rate of 12% by mass or less (including 0); and subjecting the resulting mixture to kneading under a warm condition and then to molding under a warm condition, wherein the particle size composition of the magnesia in the refractory raw material blend is set such that the mass ratio of magnesia having a particle size of 1 mm or more to magnesia having a particle size of 0.075 mm to less than 1 mm is 0.2 to 1.5, and the mass ratio of the magnesia having a particle size of 1 mm or more to magnesia having a particle size of less than 0.075 mm is 3.0 or more.