| With the utilization of fossil fuel during the progress of social development, the global climate change caused by CO2emission is attracting more and more attention. CO2capture and sequestration is an important way to slow down the greenhouse effect. However, a variety of methods and technologies should be studied to solve the problem, for the reason that no single one can settle it alone.This paper reports a new method to realize the permanent fixation and resource utilization of CO2. CO2is fixed by Ca2+/Mg2+-rich solutions such as desalinated seawater, subsurface brine and industrial waste water through carbonation reaction using insoluble organic amine to raise pH value. This method can realize the fixation of CO2and the production of pure by-product. Besides, the insoluble organic amine is easy to be regenerated and recycled.Firstly, the feasibility of CO2fixation using Ca2+/Mg2+-rich solutions is verified. The integrated carbonate system of desalinated seawater is analyzed and it shows that the carbonation reaction between CO2and Ca+/Mg2+-rich solutions can be realized by raising the concentration of CO32-, which is effected by the CO2partial pressure and alkalinity of the solution. This paper put emphases on the selection of additive that can both raise the pH value of the solution and be recycled. Inorganic alkali and soluble organic amine are explored in the first place and the results show that they can enhance the carbonation reaction. However, no appropriate way is found to realize the regeneration. Considering the fact that the insoluble organic amine can not only raise the pH value of the solution but also easily to be regenerated, the idea that to enhance the carbonation reaction with insoluble organic amine is put forward and the feasibility is analyzed theoretically.Secondly, elementary experiments on the feasibility of using insoluble organic amine to enhance the carbonation reaction between CO2and Ca2+/Mg2+-rich solutions are carried out. It shows that the calcium ions can precipitate in the form of calcium carbonate while the magnesium ions don’t precipitate. Meanwhile, about95%of the insoluble organic amine can be regenerated by stronger ammonia water. The results of the elementary experiments indicate that this idea is feasible and the regeneration rate of insoluble organic amine is considerable.In the end, detailed experiments are carried out using additive composed of tributylamine and n-butylalcohol to raise the pH value of the desalinated seawater in the process of CO2fixation. The effects of the parameters during the experiments on the carbonation reaction are studied, such as dilution ratio, phase ratio, stirring time, stirring rate and temperature. It shows that the precipitation rate of Ca2+amounts to90%under the condition that the dilution ratio, phase ratio, stirring rate and temperature are respectively2:1,3.5:1,500r/min and20℃Besides, another experiment using trioctylamine and n-butylalcohol to enhance the carbonation reaction is tried simply. The experiments of insoluble organic amine regeneration by stronger ammonia water and calcium hydroxide are carried out respectively. The results indicate that the regeneration rate amouts to95%when stronger ammonia water is used and100%when calcium hydroxide is used. The activity of the regenerated organic amine and the fresh organic amine is compared and it shows that the regennerated organic amine still maintain high activitiy after thrice regeneration by calcium hydroxide. Thus, it is feasible to realize the regeneration and recycle of the insoluble organic amine.A craft is put forward to realize CO2fixiation through the carbonation reaction between CO2and desalinated seawater, which is enhanced by insoluble organic amine. In this craft, the magnesium ions are firstly replaced by calcium ions that are easily to precipitate in the form of magnesium hydroxide which can also fix CO2. Besides, the insoluble organic amine can be regenerated and recycled. |
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