| dc.description.abstract | As the industry fastly developed, it made shortage of fossile energy and serious air pollution. It is important to find out the renewable energy and reduce the emission of gas pollutant. Hydrogen energy is one kind of non-polluting and renewable fuel. As the people demend for more hydrogen energy and discoved new hydrogen production technology, it increased the utilization of hydrogen energy. The first part of study is to simulate hydrogen purification by applying composite palladium membrane reactor combined with pressure swing adsorption (PSA) hybrid process. This membrane reactor is adapted to produce hydrogen from methanol steam-reforming, where the permeated membrane hydrogen is mixed with sweep gas. The gas mixture from the membrane reactor is then fed into a dual-bed six-step pressure swing adsorption process, filled with zeolite 5A for hydrogen purification.
The new-shape-structured materials, carbon monoliths, are characterized by straight parallel channels separated by thin wall, high void fraction and large geometric surface area, resulting in a low pressure drop under high flow rate and large contact area. These properties make carbon monoliths have the advantage on adsorption application.
The second part of this study simulates the dynamic adsorption of butane on carbon-coated ceramic monoliths under isothermal condition. The parameters considered in the mathematical model include the mass transfer coefficient to the channel wall, effective diffusion within the pore structure and the axial dispersion model. The adsorption is expressed by the Dubinin-Radushkevich isotherm. The effect on increasing thickness of carbon-coated layer could raise the amount of adsorbate, although the thicker carbon layer would take longer time for stream diffusion to reach the saturated adsorption and breakthrough.
Then the third part of this study develops mathematic model and simulates the adsorption separation of butane/air and CO2/N2 on carbon-coated ceramic monoliths for pressure swing adsorption processes under isothermal condition. In the three-step butane/air PSA process simulation study, increasing the thickness of carbon coated layer can increase the butane purity and recovery at the same valve value operation, but increasing the feed pressure will decrease the butane purity and recovery. For the other five-step pressure swing adsorption process for CO2/N2 on carbon-coated monoliths, when the mass transfer resistance between the gas and solid phase is small than that in the carbon coated layer, using an idle step is useful to improve the CO2 purity with an appropriate idle step time.
The fourth part of study simulates the adsorption separation of CO2 from flue gas with 17% CO2 and 83% N2 on a carbon monolithic adsorber for a three-step rapid pressure swing adsorption process, which operates in the sequence of adsorption, rinse and desorption, under isothermal condition. The simulation results exhibit that the rinse step with a CO2 rich stream should be employed to enhance product purity. As to the effect of step time, increasing the rinse step time shows the greatest effect on increasing purity and decreasing recovery of CO2. Additinally, decreasing adsorber length and increasing rinse pressure are beneficial to improving the CO2 purity in production, but the CO2 recovery decreases at the same time.
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