A summary of several disadvantages of phosphate-bound zirconia zirconia tamping materials
Zircon has been used as a high-grade refractory material because of its high refractoriness, low coefficient of thermal expansion, good thermal shock stability and excellent resistance to steel and alkaline slag erosion. With the popularization and application of oxy-rich combustion technology, the increase of melting temperature of glass melting kiln, and the development of overall sealing and insulation technology of glass kiln, it makes the environment of using pool-bottom tamping material become more demanding.
Coupled with the glass enterprises to use recycled broken as a component of the material, recycled glass in the metal impurities will be deposited in the bottom of the pool, and gradually penetrate into the pounding layer to form a kind of "down hole" erosion, so that the bottom of the pool pounding material erosion damage aggravated.
Zircon tamping material belongs to unshaped refractory material, the amount of binding agent added in the construction process, the amount of water added, maintenance conditions have a great impact on its use. At present, most of the zircon tamping materials use phosphoric acid or phosphate as binding agent, phosphate is easy to absorb moisture, phosphoric acid or phosphate binding agent will react with some components in the tamping material, which is easy to produce large air holes. Harmful P2O5 transfer volatilization at high temperature and formation of low-melting material also reduces the high-temperature performance of the tamping material. In order to reduce the cost of zircon tamping material, improve the construction efficiency at the construction site, improve the quality of zircon tamping material, and prolong the service life of zircon tamping material, several drawbacks of phosphate bonded zircon tamping material are summarized.
The main raw materials used in the test were: zircon brick aggregate (0~3mm), zircon sand (80~150 mesh), zircon powder (≤0.045mm), zircon micropowder (≤0.002mm), regenerated electrofused zircon corundum powder (≤0.045mm), and industrial phosphoric acid (85%). The proportioning method is shown in Table 1 below:
Industrial phosphoric acid combined with the test process, will be in accordance with the table of ingredients, into the mixing pot stirring for 2min, add phosphoric acid mixing 3min, pounding molding for 40mmX40mm160mm specimens, maintenance at room temperature, final condensation after demolding, record the demolding time, and then dry in the drying oven at 130 ℃ for 24h at 1200 ℃ respectively, insulation 3h heat treatment. Table 2 below shows the demolding time of the specimens:
From the table, it can be seen that the hardening time of phosphoric acid bonded specimens B1~B7 is 32~34 h. After heat treatment at 1200 ℃ for 3 h, the specimens of various indexes are listed in Table 3, which can be seen in Table 3, with the increase in the percentage of regenerated zirconium corundum powder, the specimen's compressive strength does not have regular changes, and the flexural strength fluctuates with the trend to increase; the rate of change of the line with the increase in the regenerated zirconium corundum powder, shrinkage increase The bulk density decreases with the increase of regenerated zirconium corundum powder, and the water absorption and apparent porosity increase with the increase of regenerated zirconium corundum powder.
At present, the more commonly used zirconia pounding material using phosphoric acid bonding. However, phosphoric acid bonding and the following shortcomings:
① phosphoric acid will react with the impurities in the regenerated zirconia corundum powder, resulting in porosity, reducing the erosion resistance of zirconia tamping material;
② phosphoric acid bonding zirconia tamping material at room temperature can not be hardened to provide strength, the need to add coagulant promoter, and the addition of hardening agent will be added into the more impurities, is not conducive to long-term use of zirconia tamping material;
③ in the long term high temperature effect of P2O5 will be transferred and volatilized, which will reduce the strength of zircon pounding material and affect the service life.
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