When producing silicon bricks, why should waste silicon bricks be added to the ingredients?
When preparing silica brick mortar, a certain amount of waste silica brick is usually added to the ingredients, the purpose of which is to reduce the expansion and stress generated during the firing of the product, reduce the generation of cracks, and increase the yield. The amount added is related to the shape and weight of the brick. For special-shaped bricks weighing less than 25kg, 20%+25kg or more special-shaped bricks can be added 30%; for special-shaped silica bricks, 30% can be added. Pay attention to this problem when adding waste silica bricks. Excessive addition will reduce the refractoriness and mechanical strength of the product and increase the porosity. Therefore, the amount of waste bricks should not be too much.
What is the commonly used bonding agent?
The binders used in the manufacture of silica bricks are sulfite pulp waste liquid and lime milk. When lime milk is used as a binder, it acts as a plasticizer. The lime milk increases the strength of the bricks during the drying process, and becomes a mineralizer during firing, which promotes the conversion of quartz.
Lime should contain a large amount of active CaO, undecomposed CaCO, and MgCO, no more than 5%, and ALO, +Fe:OJ+SiO no more than 5%. When it contains large particles of under-burned Ca-CO and over-burned lime, the product will produce molten holes, which will affect the quality of the product.
The amount of lime added should be converted into CaO during the batching. The amount of lime added depends on the product, and usually fluctuates between 1.5% and 2.5%. For example, in the production of coke oven silica bricks, the amount of CaO added is 2.0~3.0%i, and the amount of Ca0 added is 1.4~1.75% for the production of electric furnace silica bricks.
What are the ingredients of silica bricks?
Use high-quality silica with an impurity ontent of less than 0.5%, rinse with tap water before batching to ensure the quality of the early stage. Mixing fast-conversion quartz and slow-conversion quartz during batching can reduce the sintering temperature by 20°C. In the batching process, the critical particle size is reduced from 3mm to 2mm, which can increase the interface energy of the material and promote the conversion of quartz.
In addition, the selection of new mineralizers is also very important to improve product quality. At present, the mineralizer that most producers add to the ingredients is still lime milk and iron scales. In order to increase the load softening temperature of the product, the amount of FeO added has been reduced from 2.5% to less than 1%. If feldspar minerals or composite mineralizers containing alkali metals are used, better results can be achieved.
