Zirconia Refractory Composition for Glass Furnace Integrity
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Solution Overview
Problem
Conventional fused and cast refractory products with high zirconia content face challenges in maintaining mechanical integrity and corrosion resistance, particularly due to volume changes during thermal expansion, leading to potential cracking and reduced longevity in glassmaking furnaces.
Innovation Solution
A refractory product with a specific composition of ZrO2, HfO2, SiO2, Y2O3, CaO, B2O3, Na2O, and Al2O3, optimized to reduce maximum expansion temperature and ensure joint closure, manufactured through a controlled melting and casting process, which includes careful selection of raw materials and controlled cooling to minimize porosity and mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fused and cast refractory products with high zirconia content are used, then corrosion resistance is improved, but volume changes during thermal expansion cause mechanical stresses leading to cracking and reduced longevity
Solution Approach 1:
The invention changes the chemical composition parameters by strictly limiting SiO2 to 2-10% and controlling Al2O3, B2O3, Na2O, K2O, Y2O3, CaO, and other oxides within specific ranges. This parameter optimization modifies the thermal expansion behavior and phase transformation characteristics of the refractory product, reducing volume changes during heating and preventing mechanical cracking while maintaining high corrosion resistance
Solution Approach 2:
The invention creates a composite refractory material system where zirconia (80-98%) forms the primary matrix, stabilized by carefully controlled amounts of silica, alumina, boron oxide, and other oxides. This composite structure leverages the complementary properties of each component: zirconia provides corrosion resistance, while the controlled additives modify thermal expansion and prevent harmful phase transformations, achieving both reliability and mechanical integrity
2Reliability
If zirconia and silica are present in the product, then corrosion resistance is improved, but zircon formation occurs accompanied by a decrease in volume of about 20%, creating mechanical stresses that cause cracks
Solution Approach 1:
The invention applies preliminary anti-action by pre-configuring the chemical composition to prevent harmful zircon formation. By strictly limiting SiO2 to 2-10% and controlling the ratios of other oxides, the product is designed beforehand to avoid the thermodynamic conditions that would trigger zircon precipitation and associated 20% volume decrease, thereby preventing mechanical stresses and cracks before they can occur during service
Solution Approach 2:
The invention changes the chemical composition parameters to shift the phase equilibrium conditions. By optimizing the SiO2 content to 2-10% and controlling Al2O3, B2O3, and other oxides within specific ranges, the product's thermal and chemical behavior is modified to prevent zircon formation during heating, eliminating the harmful volume decrease and associated mechanical stresses
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 product exhibits improved dilatometric behavior, ensuring total closure of joints and maintaining high industrial feasibility, thereby enhancing corrosion resistance and longevity in glassmaking furnaces by shifting the critical contact region to a less corrosive area.
Implementation Method 1
Zirconia exists in three crystallographic forms. In the absence of dopant, zirconia is in the monoclinic form up to 1150° C., in the stable tetragonal form between 1150° C. and 2370° C.
Implementation Method 2
the transformation from the monoclinic phase to the tetragonal phase is accompanied by a decrease in volume of the joints by reversible thermal expansion of about 4.5%
Implementation Method 3
electrocast products with a high content of zirconia are reputed for their very high corrosion resistance without coloring the glass produced and without generating defects
Implementation Method 4
The molten material is then cast in a mold and the product obtained then undergoes a cycle of controlled cooling in order to be brought to room temperature without fracturing
Data Source
AI summary
Fused cast refractory product comprising in percentages by weight on the basis of the oxides and for a total of 100%, —ZrO2; balance to 100%, —HfO2: <5% SiO2: 2% to 10%; —Y2O3: 0.4% to 2.0%; —CaO: 4.0% to 8.0%; —B2O3+Na2O+K2O: 0.4% to 3.0% —Al2O3: 0.3% to 2.0%; —P2O5: <0.05%; —Fe2O3+TiO2: <0.55%; —other species: <1.5%. Application in glass melting furnaces.