The lattice body is an important part of the heat storage and heat transfer in the regenerator. The lattice brick is required to be able to withstand high temperature, corrosion resistance, more heat storage, fast heat transfer, and good resistance to rapid cold and heat.
The heat storage effect of the regenerator is usually measured by the size of the heated area of ??the grid, that is, the surface area of ??the grid that can exchange heat. The larger the heat storage area is, the more heat is stored and the more heat halo is released, which can fully increase the preheating temperature of air and gas, which is more beneficial to fuel combustion.
Different alkaline checker bricks are used according to the different temperatures of the top, upper, middle and bottom parts of the regenerator and the amount of flying material.
The top part (above 1400℃) is easy to form a liquid phase with the brick body due to high temperature and a lot of flying materials, which is easy to stick the flying materials and cause the brick body to stress. Therefore, the top part is made of zirconium with excellent creep resistance at high temperatures Bricks or 98% high-purity magnesia bricks (because the MgO in the high-purity magnesia brick reacts with the ultrafine powder SiO2 that is flying into the regenerator to form a low-temperature eutectic, it is easy to enter the 1#~3# top grid of the fly Zirconium bricks are mostly used for the body, and 98% high-purity magnesia bricks are mostly used for the lattice body of the end regenerator that is not affected by flying materials.
The upper part (1000~1400℃) has less fly material sinking, and high-purity magnesia bricks can be used.
There are very few flying materials in the middle part (800~1000℃), but it is a sulfate condensed area, which is easy to cause magnesium bricks to react with flying materials to form magnesium silicate (MgSiO3). At the same time, Glauber's salt in the batch is formed during the reaction process and the fuel combustion process. The SO2 and SO3 are also easy to react with magnesium oxide:
MgO+SO2→MgSO3 MgO+SO3→MgSO4
The generated magnesium sulfate or magnesium sulfite is repeatedly solidified and liquefied, and its volume expands to cause damage to the structure of the magnesia brick. Therefore, the direct bonding magnesia chrome brick (DMC-12) with good thermal stability and low porosity is selected for this part (in environmental protection requirements) Magnesia chrome bricks are not allowed in the area, periclase + forsterite bricks are often used).
The temperature at the bottom (below 800℃) alternates between hot and cold, with heavy load and less erosion by alkaline materials. Therefore, materials with good thermal stability and load-bearing strength are required. Low-porosity clay bricks (DN-12, DN-13 or DN-15) or
sillimanite brick. If the performance of various alkaline bricks is not considered and used in general, it will affect other grids when a certain part of the grid is damaged, thereby reducing the life of the overall grid. Since most basic refractory bricks, including magnesia chrome bricks, are easily damaged in an atmosphere containing cracked hydrocarbons (reducing atmosphere). Therefore, alkaline bricks can only be used in air regenerators and cannot be used in gas regenerators.
For the regenerator lattice body susceptible to fly material erosion, the commonly used lattice brick configuration from bottom to top is: low-porosity bonded brick or sillimanite brick → 12% chromium directly bonded magnesia-chrome brick or magnesia-zirconium brick Or forsterite bricks→96% high-purity fused magnesia bricks→98% high-purity fused magnesia bricks→2~4 layers of magnesia-zirconium bricks (VZ) or sintered zirconium corundum bricks; in order to save investment, there is less erosion of flying materials For the last 1~2 pairs of regenerator lattice bodies, the top can not use magnesia-zirconium bricks or sintered zirconium corundum bricks, but 98% high-purity fused magnesia bricks can be directly laid on the top.
With the development of refractory materials, checker bricks have evolved from strip bricks to cylindrical bricks and cross-shaped bricks, and the way of laying grids has also evolved from traditional strip brick basket-style and well-style laying-up to the current cylindrical bricks. Bricks and cross-shaped bricks are directly laid. The improved checker brick is not only convenient for construction, but also has a more reasonable brick structure and higher stability of the combination between the bricks, so that the stacking height can be greatly increased and the heat storage capacity is stronger.
