| The total amount of carbon dioxide emission is in a first place from China which regards fossil fuel as major energy throughout the world, and the main source of emissions is from coal-fired power plant, which is main factor to cause the greenhouse effect. Therefore, how to separate carbon dioxide from flue gas is an urgent problem to be solved.There are so many methods to separate carbon dioxide from mixed gas, such as absorption, adsorption, membrane separation. Thereinto the adsorption method is simple, no corrosion issues and low energy consumption, which has become a focus of attention in the research and application in engineering practice. However, since the carbon dioxide from flue gas possesses the characteristics of high flow velocity, high tmperature and low carbon dioxide concentration as well as the research of capture carbon dioxide from fuel gas by adsorption has many technical difficulties the adsorption, so it is not yet obtain the engineering application.First the research analysed the characteristics of carbon dioxide from flue gas, and then building the experimental system, using nitrogen and carbon dioxide mixed gas simulated flue gas and selecting four common adsorbents (activated carbon, zeolite, pan-based activated carbon fiber and viscose-based activated carbon fiber), contrary to the different different temperature and flow, respectively tested the concentration of the nitrogen and carbon dioxide in the outlet of the adsorber. By drawing the breakthrough curve, calculating carbon dioxide adsorption capacity, the result show that the four adsorbent adsorption breakthrough time of nitrogen are all very short, but the breakthrough time of carbon dioxide by viscose-based activated carbon fiber is longest,360s, which is explain that viscose-based activated carbon fiber has the better optional to adsorb the carbon dioxide of the flue gas. And the regenerative thermal stability of the viscose-based activated carbon fiber is best, the adsorbance is stable at2.33mol/kg.Tested the dynamic performance of the viscose-based activated carbon fiber including the desorption performance to carbon dioxide, electrical conductivity, electricity desorption performance, fitting the adsorption and desorption of activated carbon fibers isotherm equation. The experimental results showed that under the same loading quality, the current and voltage of the activated carbon fibers is a basically a linear relationship, and resistance is constant.Based on thermodynamics and kinetics of adsorption establish a mathematical model of the capture carbon dioxide adsorption, First treated dimensionless on the equations, then used the finite difference method to solve equations, comparison of experimental data using the authentication explain that the model is reliability. Further analysis on the effects of adsorption process by the heat transfer coefficient and the mass transfer coefficient, the results show that the heat transfer coefficient is higher impact the concentration on export. But with the increase of mass transfer coefficient, the carbon dioxide concentration on export is decrease and then increase, reducing the ambient temperature of the adsorber can improve the adsorption rate and adsorption capacity.On the basis of analyzing desorption mass and heat transfer characteristics of the viscose-based activated carbon fiber, the research established desorption process mathematical model, simulated desorption and desorption rate changes in pressure swing desorption, it drew that desorption conditions in the step-down, the desorption rate merely78%and the desorption process affected by the thermal effect is larger. Simulating the completion differences of the desorption process in different temperatures, found that taken improvement measures to the desorption process at high ambient temperatures can improve the desorption speed and desorption rate in the end.In order to improve the adsorption desorption rate of adsorbed capture carbon dioxide, we proposed the technology improvement program, including adsorber with outside casing and ohmic heating adsorbent. According improvements designed casing adsorber and energized type adsorber, established their calculation model and calculated typical operating condition, we can found that through in the adsorption process of the casing adsorber into cold water can reduce40s absorption time and increase0.08mol/kg adsorption quantity, through in the adsorption process of the casing adsorber into hot wate can reduce90s absorption time and increase desorption rate from0.78to0.81. Although energized type adsorber with low-voltage extended the desorption time180s, increased the desorption rate from78%to84%. The desorption time of the substation temperature and pressure swing process is merely310s, but the desorption rate reach up to92.4%.Finally on the basis of the comprehensive research, designed twin towers combined transformer substation variable temperature on capture carbon dioxide system, established a continuous dynamic mathematical model for the capture process, simulated the changes of amount of carbon dioxide on the adsorbent over time. Studyed the dynamic performance of carbon dioxide capture adsorptive separation process by the capture time, capture rate, energy consumption and other performance indicators, we can found that on the basis with a small increase in pump energy consumption and electricity consumption, the new system can improve catches of20.62%, reduce35.63%of the capture time and rose the capture rate from0.88to0.65.Through the study of this paper, it proved that pressure swing adsorption substation desorption is feasibility in the capture carbon dioxide from flue gas. The result of this research will provide a theoretical basis and technical support on the application of the capture carbon dioxide from flue gas system. |
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