Analysis of the fiber-forming process for refractory ceramic fibers

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Since the 1980s, Shanxian Electrical Appliance Factory introduced from the United States the technology and equipment for producing ceramic fiber needle-punched mats via continuous melting and secondary spraying, with an annual production capacity of 500 tons, as well as equipment for manufacturing vacuum-formed shaped products with an annual capacity of 300 tons. Beijing Shougang and Guizhou Guinai subsequently adopted from the American company CE the technology and equipment for producing double-sided needle-punched ceramic fiber mats through continuous melting and spinning, with an annual production capacity of 1,000 tons. In the mid-1980s, Shanxian Electrical Appliance Factory acquired from the French company FRRER the technology and equipment for producing double-sided needle-punched mats via vertical spraying, with an annual capacity of 800 tons, as well as equipment for vacuum forming, with an annual capacity of 400 tons. Later on, with the development of domestic fiber companies and the entry of foreign firms into the field of ceramic fiber production in China, ceramic fiber production in the country became more scaled up, featuring a wider range of products and varieties as well as broader applications. As a result, ceramic fiber products in China have played a very important role in helping various industries save energy and reduce consumption. At present, ceramic fiber products in our country are classified by shape into cotton, felt, boards, blankets, paper, cloth, ropes, woven products, various folded blocks and modules, various vacuum-formed shaped products, various compressed shaped products, various fiber spray coatings, various fiber castables, various fiber ramming materials, and various fiber surface coatings ； By product density: It can meet the various requirements for both low and high densities, with production densities ranging from 80 Kg/M3 to 1200 Kg/M3. Depending on the usage environment of fiber products, there are hydrophilic absorbent fibers available; in addition, water-retaining fibers that offer moisture resistance and waterproofing properties can also be produced. The operating temperatures have also been categorized: fibers with an operating temperature of 800°C and an Ai2O3 content of less than 40% are considered ordinary fibers; those with a operating temperature of 1000°C and an Ai2O3 content of over 45% are standard fibers; fibers with a operating temperature of 1100°C–1260°C and an Ai2O3 content of 45%–47% are high-purity fibers; and those with a operating temperature of 1300–1400°C and an Ai2O3 content of 47%–55% are high-alumina fibers. The operating temperature of fibers is generally related to the aluminum content and other additives in the fiber product. When Ai2O3 accounts for 72%-75%, it results in polycrystalline mullite fibers, and such fiber products can typically be used at temperatures of 1450-1500°C. When Ai2O3 accounts for 85%-95%, it yields alumina fibers, which can generally operate at temperatures up to 1600°C. The latter two types are not produced by melting methods; they are manufactured through chemical processes and do not fall under the category of aluminum silicate fibers. Nevertheless, their usage is increasing year by year both domestically and internationally, so they are discussed here. Additionally, in the aluminum silicate series, fibers produced by adding other substances during the manufacturing process are called chromium-containing fibers when chromium is added, and zirconium-containing fibers when zirconium is added. The operating temperatures for these two types of fiber products are generally the same as those for zirconium-containing fibers, typically around 1300–1450°C. Calcium addition results in fibers that are biodegradable; these are known as eco-friendly fibers. Vacuum-formed products can be further divided into organic and inorganic types based on the additives used in their production process. In the future, with the discovery of new raw materials for producing refractory ceramic fibers, new types of fibers will continue to emerge. In China, corundum fibers have already been produced using corundum as a raw material, and corresponding **patents have been obtained. In some areas, experiments are being conducted to produce fibers using spinel as a raw material, and initial progress has been made in this regard. In this section, we will mainly discuss the blowing process and fiber-spinning process during the initial stage of producing refractory ceramic fibers. These two production processes are quite critical in the manufacture of refractory ceramic fibers, and many manufacturers are constantly exploring and researching them, as they directly affect the quality and output of the fiber products. Due to the limited theoretical information available on these processes both domestically and internationally, as well as my own limited experience, I will share what I know, along with the problems encountered and the solutions tried in production practice and equipment adjustment, for everyone’s discussion. If there are any mistakes, I kindly ask experts and industry professionals to point them out. This time, we will discuss this production process and equipment in two sections. The first section will focus on the spraying processes and methods currently used by manufacturers to produce ceramic fibers, while the second section will cover the spinning processes and methods employed by manufacturers today for producing ceramic fibers.