In the past 10 years, China refractory material industry has made great progress. The quality of some refractory materials has reached or approached the international advanced level. It has made an important contribution to prolonging the service life of glass furnaces. The age has doubled, reaching more than 10 years. The materials and types of regenerator walls and lattice bodies have changed a lot, especially the use of cylindrical and cross-shaped lattice bricks, which have played a great role in prolonging the service life of the regenerator, but during use , I also encountered some problems. The author makes some discussions based on years of experience in use and design.
1 Material and matching of grid body
The material and matching of the lattice body have a direct impact on its service life, heat storage capacity, energy saving effect and economic rationality. Introduce several more successful typical grid configuration schemes.
1.1 Mainly based on alkaline materials, high-purity magnesia bricks and direct-bonded magnesia-chrome bricks
In this scheme, low-porosity clay brick ZGN242 is generally used for the lower layer of the lattice body, direct-bonded magnesia-chrome brick DMC212 is used for the middle, 95 high-purity magnesia bricks are used for the upper high temperature zone, and 97 high-purity magnesia bricks or sintered AZS bricks are used for the top layer. After the author has nearly 10 years of experience in a 400 t/d float furnace, under normal use, the life of this preparation scheme can reach more than 8 to 10 years, but there are also some parts in the process of use. The problem of clogging and collapsing requires slag removal treatment, but the checker bricks have not been replaced. The primary manifestation of problems with this scheme is that high-purity magnesia bricks crack at high temperatures, which some people call "silicate explosions" or "walnut cakes"; and there are nodules and blockages in the central grid, which leads to the damage of the grid bricks. Regarding the damage mechanism of magnesia bricks, it is generally considered that it is attacked by SiO2, V2O5 and CaO in the high temperature zone. The specific reaction is
3C2S + 2MgO + SiO2 → 2C3MS2 volume increase 13%
C2S + 2 MgO + SiO2 → 2CMS volume increase by 30%
2MgO + SiO2 →M2S volume increase 96%
V2O5 + C2S → calcium vitriol + calcium vitriol
M2S + CaO → C3MS2 ,CMS
In the formula, C2S is dicalcium silicate (2CaO·SiO2), C3MS2 is magnesium rhodonite (3CaO·MgO·2 SiO2), melting point is 1 575 ℃, CMS is forsterite (CaO·MgO·SiO2), melting point At 1 495 ℃, M2S is forsterite (Mg2SiO4). In the middle of the lattice body, the condensation zone, the lattice bricks are mainly corroded by SO3 and Na2SO4. SO3 is generated by the reaction of SO2 and O2 in the flue gas, and Na2SO4 is generated by the reaction of SO3 and the volatilized NaOH in the glass composition. The specific response is
MgO + SO3 →MgSO4 CaO + SO3 →CaSO4 MgO + Na2SO4 → sodium magnesium sulfate
The shape of the checker bricks currently used in this preparation scheme is generally cylindrical. It is relatively safe to use in kilns with a design kiln age of 6 to 8 years, and the effect is good, and it is also more economical. However, when the design kiln age is more than 8 years, there are certain risks. .
1.2 Partial use of magnesia-zirconium bricks in the above scheme
The top layer of the lattice body is susceptible to the erosion of dust and V2O5 in the heavy oil, and the high-purity magnesia bricks are easily damaged. The corrosion of SiO2 and V2O5, the forsterite phase has been formed, the load softening temperature and high-temperature volume stability are better than high-purity magnesia bricks, and the price is lower than that of AZS products, so high-grade magnesia-zirconia bricks can be used in this part. Practice has proved that the effect is better good. Only using magnesia-zirconium bricks on the top layer can only be partially improved, but the overall life of the grid body does not have much impact. A more reasonable solution is to use ceramic-bonded high-temperature sintered high-purity magnesia bricks in the high-temperature zone except the top layer, and use high-quality magnesia-zirconium bricks in the central condensation zone instead of directly bonded magnesia-chrome bricks containing Cr2O3, which can not only improve the use effect, but also Reduce Cr2O3 pollution to water sources. The magnesia-zirconium brick is made by sintering MgO and ZrSiO4, and the reaction formula is
MgO + ZrSiO4 →Mg2SiO4 + ZrO2
The matrix is anti-corrosion phase, Mg2SiO4 and ZrO2 form a protective layer on the periclase surface to prevent it from being corroded. The magnesia-zirconium brick is not affected by sulfate infiltration during use, and sulfate does not stick in the condensation zone and does not block the grid holes. After 13 years of continuous use of a 500 t/d float kiln using this configuration plan, only the top checker bricks were corroded and damaged, and the lower checker bricks were intact and were still being used. This kiln checker brick is an imported strip brick.
1.3 Use cross-shaped fused checker bricks
Cross-shaped fused checker bricks are rarely used in domestic float kilns because of their high price, although their service life and heat storage effect are very good.
1.4 The use of new super low-porosity clay cross-shaped checker bricks
On a 250 t/d ultra-white calendering kiln, the author first adopted the configuration of super clay + sintered AZS cross checker bricks. From the perspective of the use of this scheme on kilns in other industries, the effect is very good, and the service life can be 8 years. Above, super clay replaces directly bonded magnesia-chrome bricks, which not only reduces environmental pollution, but is also cheaper than magnesia-zirconium bricks. It is worthy of reference for the float glass industry. The physical and chemical indicators are shown in Table 1. This material has good high temperature thermal stability, slightly expands at 1100 ℃, and slightly shrinks at about 1400 ℃.
.jpg)
Table 1. Some physical and chemical properties of super clay bricks
2 Material and matching of the wall of the regenerator
The material and matching of the regenerator wall include end walls and partition walls. The lower wall uses low-porosity clay bricks and low-creep high-alumina bricks. There is basically no problem in using one kiln period. Most of the upper and middle float kilns will When using directly combined magnesia-chrome bricks, two problems were found to be serious during use. One is the initial stage of the kiln, about 200 ℃, low temperature inflation, causing the wall to loose and crack, and near the tuyetoe at the initial stage of production, the lower part of the fake tuyere appeared. Fire penetration affects production and requires hot repair; second, the wall collapses during operation, causing blockage and damage to the grid, which has to be hot repaired and replaced, which seriously affects production and the age of the kiln. Extensive use of chromium-containing refractories will seriously pollute water resources and has been banned in some countries. For the target wall of the regenerator, you can choose ordinary cast 33 # fused zirconia corundum bricks, which are better in use than directly combined with magnesia chrome bricks, but after a long time, they will peel off and block the grid holes. For the middle and upper wall, the author believes that there are two feasible schemes based on experience. One is to use magnesia-zirconium bricks, but the quality of the bricks must pass. Due to price issues, domestic manufacturers seldom use them; the other solution is to use super clay bricks for the central wall, and super super clay bricks for the upper wall and chute or better. The composite corundum 2 mullite bricks expand very little during the baking process and have almost no effect on the wall. The effect is very good, and the price is acceptable. The author thinks that it is very valuable for promotion and use.
