Structure And Properties Of Periclase-forsterite Refractories For Regenerator Of Glass Furnace

The regenerator is an important heat exchange equipment for glass furnace.And middle checker is the key part for the regenerator.However,the traditional refractories for the checker,such as magnesia bricks,have problems of low thermal shock stability and resistence to sodium sulfate and gaseous SO₃ during the glass manufacturing process,causing damages of bricks for the formation of MgSO₄ from MgO.Although the substitution of magnesium-zirconium bricks for magnesium-chromium bricks can protect Mg²⁺and avoid the Cr⁶⁺pollution,but the high cost of magnesium-zirconium bricks limited its industrial application.Recently,glass companies introduced forsterite-magnesia bricks in the middle regenerator grid,but the mentioned refractories still present problems of high impurity content and porosity.Therefore,the present research carried out the materials design.The effects of composition,particle size,calcining process,and additives on the formation and sintering densification mechanisms of forsterite were analyzed systematically.Based on the researches of sintering densification behavior,strength,resistance to thermal shock,high temperature creep behavior and microstructure of the prepared materials,relationships among composition,structure and properties were constructed.The research conclusions have been summerized as follows:?1?As for samples with the ratio of MgO to Si O₂ as 2,forsterite could be detected form 1200?,and enstatite formed from 1400?and transformed into forsterite at1600?.The increasing temperature promotes the formation of forsterite.The excessive MgO in materials could inhibit the growth of enstatite and promote the development of forsterite.The excessive SiO₂ in materials promoted the growth of enstatite,which disappears at 1500?,and the high-temperature liquid phase occurs at 1600?,promoting the development of forsterite and densification of samples.?2?The ball-milling destroyed the internal porosity,shortened the diffusion path of ions under high temperatures,promoting the reaction and sintering process.Then the mentioned samples presented high bulk density of 2.97 g/cm³ and the relative density of92.2%.The high-energy ball milling destroyed the surface state of particles,resulting in crystal defects and lattice distortion.Thus,the bulk density was increased to 3.07 g/cm³and the relative density of about 95.3%.Determined by the integrated sintering theory,the sintering densification mechanism of the prepared forsterite is bulk diffusion.And the calculated apparent activation energy of the sintered forsterite processed by high-energy ball milling is about 606.7 kJ/mol.?3?The studied additives present different mechanisms.Lanthanum-containing silicate phases could be detected between grains of periclase and forsterite with the introduction of La₂O₃;The sintering procedure could be promoted with the replacement of Y³⁺for Mg²⁺;Silicate liquid phases formed on the surface of forsterite grain and intergranular region under high temperatures with the addition of BaSO₄;And silicate phases could also be detected in the intergranular region,promoting the sintering procedure for sampled added with SrCO₃.?4?La₂O₃ and BaSO₄ present different affecting mechanisms for the structure and properties of the prepared periclase-forsterite refractories.The formation of rod-like silicate crystals increased the high-temperature strength and resistance to thermal shock with the addition of La₂O₃.As for samples with BaSO₄,the formation of silicate liquid phases promoted the sintering procedure,increasing the bulk density and cold crushing strength,however,the formation of silicate liquid phases also depressed the high-temperature strength and the penetration area by molten glass batch.?5?The main performances of the prepared periclase-forsterite refractories are presented as follows:the bulk density was about 2.90³.13 g/cm³,the apparent porosity12.1¹7.5%,linear change rate after fired-1.24%^-2.65%,cold flexural strength4.0¹0.0MPa,crushing strength 64.7⁸1.6MPa;HMOR?1200??6.6¹5.3MPa,thermal shock resistance?air cooling at 1100??more than 25 times.