Selection of Refractories for Glass Furnace Regenerator
Modern large-scale glass furnace, such as float glass furnace, currently use regenerator to recover heat. It use refractories as regenerators (called checker) to store part of the heat of the flue gases discharged from the furnace. Used to heat the combustion air entering the furnace. The three major advantages of the regenerator are: no airtightness separation required between exhaust gas and air; the preheating temperature of the air is high (1100~1300℃); the heat recovered from the exhaust gas is quite high, and the heat recovery can be as high as 60% ~70%. The performance of the regenerator largely depends on the selection of refractories and whether the masonry is reasonable and properly matched. It plays an important role in glass quality, energy consumption, furnace life and product cost, so it must pay attention to the selection and configuration of refractories in the regenerator.
◾ The structure and materials of the regenerator
The regenerator is composed of crown, front wall, back wall, checker bricks,rider arch,etc. The operating temperature is divided into the upper part for 1200~1500℃, the middle part for 800~1200℃, and the lower part for <800℃:
1. The crown of regenerator (brick thickness 350mm, with 3*64mm insulation bricks outside) be used under the conditions of batch carry-over erosion, high temperature changes, and oxidation-reduction reactions. The suitable refractory is high-quality silica bricks;
2.The target wall of the regenerator (brick thickness 350mm) can directly use AZS33# zirconium corundum bricks or high-purity fused magnesia bricks;
3. Main wall and back wall: the upper part (brick thickness 350mm), the use conditions are the same as the regenerator crown, so the suitable refractory is high-quality silica bricks; the middle part (brick thickness 230mm), the use condition is medium temperature change, the refractory can choose the high alumina bricks or magnesium bricks Brick; the lower part (brick thickness 350mm), the use conditions are low temperature change, and low porosity clay bricks can be used;
4. The usage conditions of the rider arch are the same as the lower checker bricks, so the low porosity clay bricks can be used.
◾ About the choice of checker work
1 The upper part of checker work
The temperature drop per meter in the regenerator is generally 80 to 100°C, and the temperature at the upper part of the checker work reaches a maximum of 1200°C to 1500°C. For the upper part of the checker work with a temperature above 1300°C, it is advisable to use the high-purity magnesia bricks. The bricks are fired with high-purity sintered magnesia as raw material. The content of CaO, SiO2 and Fe2O3 is low, and has a very high density and excellent creep resistance, and it can effectively resist the erosion of alkaline gas and batch carry-over.
The specifications of checker bricks currently used in the upper part of the regenerator are as follows:
2 The middle part of checker work
The temperature of the middle part of the checker work is about 800°C-1200°C, and magnesia-chromium, forsterite and magnesium-aluminum refractories can be used. Magnesium-aluminum materials are highly resistant to sulfate erosion, but are expensive. This type of refractory material has not yet been widely used in China. The use temperature of forsterite bricks should not exceed 1050°C and should be used in the low temperature zone of the middle part.
There is a phenomenon of repeated liquefaction and solidification of sulfate in the middle part of the checker work. In order to improve the corrosion resistance of magnesia-chromium bricks, its Cr2O3 content should be increased as much as possible and the degree of direct bonding of the mineral phase should be increased so that the chromium spinel wraps the periclase particles. It will be extend the service life.
3 The lower part of checker work
The temperature of the lower part of the checker work is below 800°C, and the chemical corrosion is weak. However, the total weight of a regenerator checker work is at least 40 to 50t, and the unit load of the lower part of the checker work is as high as 8 to 10t/m2. In addition, there is a need to use flame method to melt and clean the lower checker work. Therefore, high-quality low-porosity clay bricks with strong creep resistance and good thermal shock resistance should be used. In order to prevent the contact reaction between alkaline bricks and clay bricks, high alumina bricks can be used as a transition layer between the middle and lower part of the checker work.
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