In the actual production process, there are still some problems in the production of forsterite semi-lightweight bricks. The specific solutions are as follows:
1) Extrusion molding was used to prepare forsterite semi-lightweight bricks, and the amount of added water was too large. As a result, when the sample came out of the extruder, the force exerted by the extruder on the adobe was suddenly released, causing a certain deformation of the adobe, and the drying time of the green body was too long, which affected the industrial production cycle. The solution to this problem is to change the molding method from extrusion molding to vibration molding, which can reduce the amount of added water. Since the vibration molding bricks are made of standard abrasive tools, the products can be used directly without shaping after firing.
2) During the drying and firing process of the bricks in the tunnel kiln, the temperature in the firing zone of the general tunnel kiln is not stable, and the temperature difference between the middle and both sides of the kiln is too large, resulting in insufficient firing temperature of some products, which affects the growth of forsterite grains and leads to a decrease in product strength. The solution is to properly increase the gap between adobes and prolong the heat preservation time of the green body in the firing zone when the adobes are stacked.
3) As shown in Figures 1 and 2, there are many cracks in the product after firing, and the yield is not high. On the one hand, the reason may be that the adobe is fired before it is completely dry, which causes the moisture to drain out too quickly during the firing process, resulting in cracks. The solution is to prolong the natural drying time or prolong the residence time of the kiln car in the low temperature zone (100~200°C). On the other hand, the reason may be that the main raw materials used are light-burned magnesia and forsterite raw meal fine powder. Light-burned magnesia can quickly and completely hydrate at room temperature to form Mg(OH)2. During the firing process, at about 0~600°C, the pore-forming agent and binder in the adobe burn out, Mg(OH)2 decomposes, and the serpentine in the forsterite fine powder is dehydrated to form forsterite and amorphous MgSiO3; when it rises to about 1000°C, amorphous Mg SiO3 turns into enstatite; when the temperature continues to rise to 1400~1500°C, the material is completely sintered. In the magnesium-rich system, the final products are forsterite, magnesium ferrite and periclase. During the whole process, the material undergoes a relatively intense chemical reaction, accompanied by different degrees of shrinkage, resulting in cracks in the adobe. The solution is to keep warm at the place where the phase reaction is intense during the firing process, or increase the residence time of the kiln car at this temperature point in the firing zone, especially around 600°C and 1100°C.
4) Forsterite semi-lightweight bricks prepared by the burn-off method, rice husk powder is used as a pore-forming agent and a silicon source, and dextrin is used as a binder and a pore-forming agent at the same time. Its microstructure shows that the size and shape of the internal pores of the product are different, which affects the use of the product. Intensity and thermal conductivity reduce the heat insulation effect. Aiming at this problem, the solution is to study the particle size and shape of the pore-forming agent on the performance of the sample, and this problem is being solved.
