Crystal Morphology and Growth Kinetics of Calcium Carbonate in A Semi-batch Reactor with Double-tube Gas Injection Nozzle

• Main Authors: Lee,Kun-Chung, 李坤忠
• Other Authors: Tai,Yi-Der
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/42013607132017778138

碩士 === 國立臺灣大學 === 化學工程研究所 === 81 === For sparingly solube crystals the solution method was usually employed to study the kinetics of primary nucleation and crystal growth. However, the gas bubbling method was mainly used in the industrial production of Calcium Carbonate and in the treatment of softening water. Few reports have been found in the literature to study the kinetics of primary nucleation and growth by the gas-injection method. Control of crystal morphology was investigated in this study. It is found that the pH value and the initial Calciumion concentr -ation,but not the supersaturation, are the factors which dete -rmine whether calcite, aragonite, or vaterite would be nucleated from a supersatration Calcium Carbonate solution. The Calcium ion concentration for themaximum yield of calcite is found to be 0.015 M. Aragonite isonly found when the pH value is less than 8.0. Low yield ofcalcite of can be obtained by the gas- injection method. Additionally, the growth of small calcite (20－163 micro meter) and large calcite crystal (163－327.5 micro meter) were conducted in the supersaturation range of 0.1－1.49 nad 0.51－ 2.03, respectively. The results show that surface integration was the rate- determining step for the growth of small and large calcite crystals. The growth rate of large calcite crystal was size independent, but that of small calcite was size dependent.