From the high energy consumption, high pollution and low benefit development model of the high temperature industry, with the enhancement of resources, energy and environmental protection constraints, green manufacturing and environmentally friendly manufacturing will definitely become one of the main directions of its brick-type upgrade. Therefore, the development of energy-saving technology, energy-saving equipment and energy-saving materials has received much attention. In order to improve the energy-saving effect of thermal kilns, the number and scope of lightweight castable refractory applications are gradually expanding, from permanent layers, thermal insulation layers to working layers, Expand from medium and low temperature parts to medium and high temperature parts, and transition from a low load environment to a high load environment.
At present, the technology of lightweight castable refractory used in the working layer at medium and low temperature <1200℃ has basically matured, but the performance used in the high temperature range (1200~1500℃) needs to be improved to meet the requirements.
The raw material preparation of traditional lightweight castable refractory mainly uses lightweight aggregates and heavy fine powders. The lightweight aggregates used have larger pore diameters and lower strengths, so the thermal conductivity is higher. The low strength affects the overall strength of the lightweight castable refractory, limiting its use at higher temperatures.
Therefore, the traditional production process will be abandoned and the microporous aggregate and high-strength aggregate will be used this time. The raw materials used are mainly microporous light mullite, hollow spheres, high alumina bauxite, drift beads, kyanite, silica micropowder, alumina micropowder, pure calcium aluminate cement, raw bauxite powder, andalusite, etc. , all kinds of raw materials are weighed according to the proportion, put into the mixer, dry mixed for 2 minutes, then add water and stir evenly, vibrate and cast into a strip sample of 40mmX40mmX160mm, cure for 24h and demould, dry at 110℃X24h, and press after burning at 1350℃X3h. Relevant standards test its bulk density, normal temperature compressive strength, high temperature flexural strength, heating permanent line change, thermal conductivity and other indicators.
The configuration of traditional lightweight castable refractory mainly uses lightweight aggregates and heavy fine powders. Both the lightweight aggregates used and the pores in the matrix have large diameters, resulting in low strength and high thermal conductivity, and can only be used in medium and low temperature parts. 1200℃. It can be known from the principle of heat transfer that the smaller the pore size of the pores in the material, the lower the thermal conductivity at high temperature, and the material with the microporous structure has better thermal insulation effect.
When the void size inside the material is close to the mean free path of the gaseous molecules, the activity of the gaseous molecules will be restricted, and it is difficult for the gaseous molecules to collide with each other, so that the convective heat transfer path of the gas is blocked. Therefore, in order to obtain a lightweight amorphous refractory material with better thermal insulation effect, the method of realizing micropores is the key, and it is hoped that the micropores are uniformly distributed in the material.
It has many years of practical experience in using general light-weight castables as thermal insulation layers for industrial furnace linings. However, it is difficult to withstand the flame erosion in the furnace, especially the mechanical collision of the billet, because of its low strength and high temperature shrinkage for the working layer of the lining of the steel rolling heating furnace. The use of newly developed lightweight castable refractory to replace the previous refractory materials has improved the efficiency and quality of the kiln and promoted the long-term stable use of the kiln.
