| The technology of oxygen and nitrogen separation is widely used in fuel combustion,fermentation oxidation, medical treatment and so on. Compared with the traditional separation technology, the idea of “magnetic membranes” was recently introduced, based on the observation that oxygen and nitrogen have quite different magnetic properties, oxygen is paramagnetic, whereas nitrogen is diamagnetic. The technology brings us higher efficiency,simpler equipment, easier operation and lower energy consumption than traditional separation technology.In this paper, polyether block amide(PEBA) was selected as the polymer, in which PEBA2533 was chosen as the basic membrane whose hard segment(PA) contents is 20%while the soft segment(PTMO) is 80%. A series of magnetic membranes were prepared by adding different magnetic particles. Oxygen and nitrogen gas permeation and air separation properties of different magnetic membranes were also studied. The main conclusions are listed below:(1) The magnetic particles including reduced iron,magnetite and ferrocene were respectively mixed in PEBA2533, preparing a series of different contents blend membranes.The characterizations of the as-synthesized membranes were studied by FTIR, SEM, DSC and the mechanical properties. The effects of kinds of doping agents and doping amount, on the pure gas permeation of the magnetic membranes were mainly investigated by gas permeation technique. The gas permeation and mechanical properties test results showed that it was better when the doping amount of the three blend membranes were all about 10 wt.%~20wt.%. One of the highest gas permeability for O2 and the selectivity for O2/N2 was the magnetic membranes mixed by the reduced iron, secondly is the magnetite and the worst is the ferrocene.(2) The direct current and coil around the membrane cell were used to produce external magnetic field. We focus our attention on the study of the three magnetic membranes as PEBA/Fe-10%, PEBA/Fe3O4-10% and PEBA/ferrocene-20%, showing excellent permeation properties. The influence of external magnetic field on performance of the three magnetic membranes and pure membrane for O2/N2 permeation was evaluated respectively, and then the theoretical analysis was given by “magnetic channel”. In addition, the magnetic membranes with different kinds of doping agents and doping amount under the same magnetic field were also researched. Gas permeation test results showed that the gas permeation of the three magnetic membranes and pure membrane had improved a lot in the presence of external magnetic field, in which O2 permeability of the pure membrane had improved 5.63 Barrer and the magnetic membrane PEBA/Fe-10% had higher O2 permeability and selectivity as 35.66 Barrer and 4.21, improving 13.87 Barrer and 1.53 times, compared to no external magnetic field. Besides, O2 permeability of the magnetic membranes were increased by increasing magnetic particle content under the same magnetic field intensity, in which PEBA/Fe had outstanding O2 permeability as 36.30 Barrer while the reduced iron content was up to 20%.(3) The impact of different blend membranes with different doping amount on air separation were researched. The results showed that the mixed gas permeability was lower than pure gas permeability of the membranes, while the selectivity increased. More over, the influence of different magnetic field intensity on air separation of the three magnetic membranes were studied; The apparatus of magnetic-membrane for air separation were also made and the magnetic membrane PEBA/Fe-10% were investigated in the presence of the magnetic field, used for oxygen enrichment in the air. Reaearch had been performed on the influence of the enrichment level in the external magnetic field, the gas pressure,the gas temperature and the gas flow. And the corresponding theoretical was also analysised,summarizing the beneficial parameters both for oxygen permeability and enrichment concentration. Our results presented as follows: The oxygen permeability and selectivity and the enrichment concentration of the three magnetic membranes all increased while increasing the magnetic field intensity on air separation. O2 permeability was improved by nearly 1.73 times at most and the selectivity was 1.72 times of the magnetic membrane PEBA/Fe-10%while the magnetic field increased to 0.52 T, in addition, the rich oxygen concentration increased as the magnetic field strength increased, which could come up to 37%, compared to the feed side 21% in fresh air, increasing 16 percentage point; Instead, the oxygen concentration decreased while increasing the gas pressure even though it was in favour of O2 permeability, we selected 0.1MPa as usual. Meanwhile, O2 permeability could be improved a lot while increasing gas temperature but the oxygen concentration decreased, so we selected15?C as usual. In addition, there was an optimal ratio between the inlet and outlet airflow and should be about 2:1, which could make oxygen enrichment concentration reach above 36%. |
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