How to Construct Refractory Plastics to Achieve Zero Expansion

The fire-resistant plastic can be constructed conveniently and quickly, and the state of use is stable. If you want the plastic to achieve zero expansion, you need to adopt a zero-expansion design to offset the expansion and contraction of the plastic at high temperatures.

The plastic has a certain degree of plasticity when the temperature is high, and the zero expansion of the plastic is that it can withstand the drastic changes of the furnace temperature and resist frequent shutdown and heating. The mold can be dismantled immediately after plastic construction. If it is maintenance, no oven is needed, and it can be put into use directly as the furnace temperature rises.

The Construction of Plastic Refractory

However, during construction, attention should be paid to drawing-form construction to ensure that the deformation of the steel structure and the lining furnace are synchronized. In addition, the anchoring brick must be evenly stressed, so as to avoid breakage and roof collapse during use.

The zero-expansion design is to support the mold first during construction to ensure that the construction site is clean. Then lay refractory plastic blanks on the rammed part. Only a single layer of material can be laid each time with the hammerhead down, moving and overlapping back and forth to make the plastic smooth and compact. If the anchor brick is constructed, the refractory plastic ramming surface must be 16-20mm higher than the bottom surface of the anchor brick. Put a wooden mold on the anchor brick, straighten it and hammer out tooth marks. The plastic around the anchor bricks should be rammed and compacted.

Refractory plastic construction should be laid out and rammed layer by layer, and each layer should be shaved and kept at the same height as the construction surface. In case of intermittent plastic ramming, use a plastic sheet to cover the rammed surface. If it is snowing, shave the material surface. When the construction is interrupted for a long time, the joint should be left between the two rows of anchor bricks.

If the plastic is used on the top of the furnace, the force direction of the hammerhead should be level when ramming. The seam of the material surface and the working surface of the furnace top should be vertical, and the peeling layer must not overlap with the seam of the material surface during the production process. The plastic material should be rammed from the seam of the blank on the top of the furnace. When the construction is intermittent, cut the material vertical furnace shell into right angles and cover it with a plastic sheet to prevent water loss. Before using anchoring bricks or hanging bricks, the wooden mold bricks with the same tooth shape should be used to tighten and drive into plastics to form a tooth mark, and then the anchor bricks are embedded and fixed tightly.

Dismantle the mold as soon as possible after the plastic construction to disperse the water. When trimming, lightly beat the plastic around the end face of the anchor brick with a wooden hammer or a ramming hammer to make it tightly bite. Trimming includes shaving, piercing vents, or cutting expansion joints.

During construction, the refractory plastic can not be in contact with water. When constructing the castable in contact with the plastic, it is also necessary to make the plastic waterproof. The mold should be dismantled as soon as possible before drying to make the masonry dry naturally.

Due to the "zero expansion" design of refractory plastics, the masonry is filled with refractory fibers at the cracks and expansions after drying and baking to prevent the lining from venting and smoking at low temperatures. The cracks and expansion joints will close at about 1350℃.

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Selection of Checker Brick Material for Regenerator of Glass Kiln

The lattice body is an important part of the heat storage and heat transfer in the regenerator. The checker bricks used are required to be able to withstand high temperature, corrosion resistance, high heat storage, fast heat transfer, and good resistance to rapid cold and heat.

Measure the heat storage effect of the regenerator is usually determined 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. Thereby, the preheating temperature of air and gas can be fully increased, which is more beneficial to the combustion of fuel.

Checker Brick for Regenerator of Glass Kiln

Different alkaline checker bricks are used according to the different temperatures and the amount of flying material at the top, upper, middle, and bottom parts of the regenerator.

The temperature at the top is above 1400°C. Due to the high temperature and a lot of flying materials, it is easy to form a liquid phase with the brick body, which is easy to stick the flying materials and cause the brick body to stress. Therefore, the top is made of zirconium bricks with excellent creep resistance at high temperatures 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, it will form a low-temperature eutectic. Therefore, the top lattice body of 1# 3# that is easy to enter the fly material mostly uses zirconium brick, and the lattice body of the end regenerator that is not affected by the fly material mostly uses 98% high-purity magnesia brick.

RS High-Quality Checker Bricks for Sale

The temperature of the upper part is 1000~1400℃, the flying material is less settled, and high purity magnesia bricks can be used.

The temperature in the middle part is 800~1000℃, and there are very few flying materials, but it is a sulfate agglomeration area, which is easy to cause magnesium bricks to react with flying materials to form magnesium silicate (MgSiO3). At the same time, SO2 and SO3 formed during the reaction process of Glauber's salt in the batch and the process of fuel combustion 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 the volume expands to cause damage to the magnesia brick structure. Therefore, the direct bonding magnesia chrome brick (DMC-12) with good thermal stability and low porosity is selected for this part. Magnesia chrome bricks are not allowed in areas with high environmental protection requirements, and periclase + forsterite bricks are often used.

The bottom temperature is below 800℃, the temperature is alternately hot and cold, the load is heavy, and it is less corroded by alkaline materials. Therefore, as long as the materials have good thermal stability and load-bearing strength, low-porosity clay bricks (DN-12, DN-13, or DN-15) or sillimanite bricks are usually used. If the performance of various alkaline bricks is not considered and used in general, it will affect other grids when one part of the grid is damaged. Thereby reducing the life of the overall grid body. 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 regenerator grids that are susceptible to fly material erosion, the commonly used checker bricks are arranged in order from bottom to top. Low-porosity bonded bricks or sillimanite bricks → 12% chromium directly bonded magnesia-chrome bricks or magnesia-zirconia bricks or forsterite bricks → 96% high-purity fused magnesia bricks → 98% high-purity fused magnesia bricks → 24 layered magnesia zirconium brick (VZ) or sintered zirconium corundum brick. In order to save investment, the last 12 pairs of regenerator grids that have less erosion of flying materials can not use magnesia-zirconium bricks or sintered zirconium corundum bricks on the top, but directly stack 98% high-purity fused magnesia bricks on the top.

Development of Checker Bricks

With the development of refractory materials, checker bricks have developed from strip bricks to cylindrical bricks and cross bricks. The yard-laying method of the lattice body has also evolved from the traditional bar-shaped brick basket-type and well-shaped yard-laying to the current cylindrical brick and cross-shaped brick direct lay-up. The improved checker brick is not only convenient for construction but also has a more reasonable brick structure. The stability of the combination between the bricks is higher so that the height of the stack can be greatly increased, and the heat storage capacity is stronger.

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