Study for the Granulation of Calcium Fluoride Powders

• Main Authors: Jhih-Jing Chang, 張智景
• Other Authors: Cheng-Hsien Tsai
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/28535438981762791278

碩士 === 國立高雄應用科技大學 === 化學工程與材料工程系博碩士班 === 103 === The quantity of calcium fluoride (CaF2) sludge from wastewater treatment in high technical industry is enormous. However, due to limited territory in Taiwan, landfilling large amount of CaF2 is an issue. More importantly, inappropriate treatment of CaF2 sludge can cause serious environmental damage. In this study, dry CaF2 powders are added with emulsified asphalt and water to make fluorite block for steelmaking. Added emulsified asphalt was in the range of 0 to 13%. The particle size of calcium fluoride powders was as follows: < 0.075 , 0.075-0.15, and 0.15-0.325 mm. And, the percentage of moisture was 35-55%. The results showed that there was without chemical bonding after mixing and granulating CaF2 powders with emulsified asphalt. So, physical bonding must be the reason that causes attraction between the surfaces of CaF2 powders and emulsified asphalt. The physical force on the interfaces includes van der Waals force, which is intermolecular attraction, emulsified asphalt bridge attached on the surface of particles and mechanical interlocking bonds between particles. At room temperature, CaF2 powders and emulsified asphalt are mixing for half an hour. The particle size of CaF2 is 0.15-0.325 mm, the amount of moisture is 35wt%. And the quantity of emulsified asphalt is 7 wt%. For granulation, fluorite block is extruded by using a mold. Through the uniaxial compressive strength test and the three point bending strength test, the strength of fluorite block were 17.7 kgf/cm2 and 5.44 kgf/cm2, respectively. By the drum strength test, the weight ratio of sieve is above 88% (88.2%) for without passing 6.3 mm sieve. Therefore, with these conditions, the strength of granulated fluorite block that meets the standard of steelmaking is produced.