Studies on Removal of Calcium Ion from Aqueous Solutions by Carbon Dioxide Gas Injection Method
| Autor: | Chen, Bing-Shing, 陳秉訓 |
|---|---|
| Rok vydání: | 1999 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 87 The most profound global threat to humankind today is the release of greenhouse gases into the atmosphere that results in global warming due to our economic activities. The main greenhouse gases are carbon dioxide, ozone, methane, nitrous oxide, and the chlorofluorocarbons (CFCs). These gases in the atmosphere block infrared radiation from escaping directly from the surface to space. Then energy of infrared radiation converts to heat so that our earth becomes warmer. Moreover, carbon dioxide is currently responsible for over 60% of the "enhanced" greenhouse effect, which isthe cause of climate change. In this study we present a new method to reduce CO2 emissions. CO2 is absorbed into an aqueous solution and fixed into carbonate salts. Besides, we can also remove Ca2＋ ion from aqueous solutions and solve the hard water problem. This method is a combination of the fluidized bed crystalliation technology and the double-tube gas injector invented by Kubota et al. in 1990. For our laborary a fluidized bed crystallizer has been used to grow CaCO3 crystals and this process is well-developed in our laborary. The main difference between the present method and that in the past is that CO2 is injected into aqueous solutions with a double-tube gas injector to supply CO32－ instead of using aqueous Na2CO3 solution. Some operational variables such as CO2 gas injection rate, temperature, superficial velocity in the fluidized bed, pH, and initial Ca2＋ concentration, were investigated. This method is workable and the main operational variable is CO2 gas injection rate. Moreover, by adding Monoethanolamine（MEA）into aqueous solution the Ca2＋ removal efficiency is improved a lot, but nucleation will occur if CO2 is continously injected into the system. In addition, it is shown that temperature and superficial velocity do not influence Ca2＋ removal efficiency and that the choice of pH is better for 9.5. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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