Multi-scale analysis and non-linear analysis were combined to investigate the hydrodynamics of fluidized beds with and without horizontal tubes. Pressure fluctuations were measured and analyzed employing discrete wave...Multi-scale analysis and non-linear analysis were combined to investigate the hydrodynamics of fluidized beds with and without horizontal tubes. Pressure fluctuations were measured and analyzed employing discrete wavelet analysis, recurrence plot analysis, and recurrence quantification analysis. A systematic procedure was followed to determine wavelet parameters. At low gas velocities, the energy of macro-structures reduces with the addition of the first tube and then increases with the addition of a second tube. However, there is no notable difference at high gas velocities. Determinism is high for the bed without tubes, which can be attributed to the periodic behavior of bubbles. Determinism decreases with the addition of tubes because the breakage of bubbles results in less periodic behavior. The three methods of analysis used in this study captured the effects of immersed tubes on the hydrodynamics of fluidized beds. Recurrence quantitative analysis was found to be a powerful and easy-to-use method that can capture the nonlinear characteristics of fluidized beds much more quickly than conventional methods of nonlinear analysis. This method can thus be effectively used for the online monitoring of hydrodynamic changes in fluidized beds.展开更多
The dynamic features of an agglomerate bubbling fluidization of nanoparticles were investigated through the analysis of pressure fluctuations. Experiments were carried out in a lab-scale fluidized bed at ambient condi...The dynamic features of an agglomerate bubbling fluidization of nanoparticles were investigated through the analysis of pressure fluctuations. Experiments were carried out in a lab-scale fluidized bed at ambient conditions using 10-15 nm silica nanoparticles without any surface modification. Pressure fluctuation signals were processed in both frequency and time-frequency domains to characterize the behavior of various scales of phenomena (i.e.. macro-, meso-, and micro-structures) during fluidization. Due to the aggregation of nanoparticles, three separate broad peaks were observed in the frequency spectra of the pressure signals measured in the bubbling fluidized bed of nanoparticles. A non-intrusive method based on the decoupling of pressure fluctuations recorded simultaneously in the plenum and in the bed was used to determine the approximate size of the bubbles in the bed.展开更多
Carbon nanotubes-based materials have been identified as promising sorbents for efficient CO_(2)capture in fluidized beds,suffering from insufficient contact with CO_(2)for the high-level CO_(2)capture capacity.This s...Carbon nanotubes-based materials have been identified as promising sorbents for efficient CO_(2)capture in fluidized beds,suffering from insufficient contact with CO_(2)for the high-level CO_(2)capture capacity.This study focuses on promoting the fluidizability of hard-to-fluidize pure and synthesized silica-coated amine-functionalized carbon nanotubes.The novel synthesized sorbent presents a superior sorption capacity of about 25 times higher than pure carbon nanotubes during 5 consecutive adsorption/regeneration cycles.The low-cost fluidizable-SiO_(2)nanoparticles are used as assistant material to improve the fluidity of carbon nanotubes-based sorbents.Results reveal that a minimum amount of 7.5 and 5 wt%SiO_(2)nanoparticles are required to achieve an agglomerate particulate fluidization behavior for pure and synthesized carbon nanotubes,respectively.Pure carbon nanotubes+7.5 wt%SiO_(2)and synthesized carbon nanotubes+5 wt%SiO_(2)indicates an agglomerate particulate fluidization characteristic,including the high-level bed expansion ratio,low minimum fluidization velocity(1.5 and 1.6 cm·s^(–1)),high Richardson−Zaki n index(5.2 and 5.3>5),and lowΠvalue(83.2 and 84.8<100,respectively).Chemical modification of carbon nanotubes causes not only enhanced CO_(2)uptake capacity but also decreases the required amount of silica additive to reach a homogeneous fluidization behavior for synthesized carbon nanotubes sorbent.展开更多
基金supported by the Iranian National Science Foundation(Grant No.93/36348)
文摘Multi-scale analysis and non-linear analysis were combined to investigate the hydrodynamics of fluidized beds with and without horizontal tubes. Pressure fluctuations were measured and analyzed employing discrete wavelet analysis, recurrence plot analysis, and recurrence quantification analysis. A systematic procedure was followed to determine wavelet parameters. At low gas velocities, the energy of macro-structures reduces with the addition of the first tube and then increases with the addition of a second tube. However, there is no notable difference at high gas velocities. Determinism is high for the bed without tubes, which can be attributed to the periodic behavior of bubbles. Determinism decreases with the addition of tubes because the breakage of bubbles results in less periodic behavior. The three methods of analysis used in this study captured the effects of immersed tubes on the hydrodynamics of fluidized beds. Recurrence quantitative analysis was found to be a powerful and easy-to-use method that can capture the nonlinear characteristics of fluidized beds much more quickly than conventional methods of nonlinear analysis. This method can thus be effectively used for the online monitoring of hydrodynamic changes in fluidized beds.
文摘The dynamic features of an agglomerate bubbling fluidization of nanoparticles were investigated through the analysis of pressure fluctuations. Experiments were carried out in a lab-scale fluidized bed at ambient conditions using 10-15 nm silica nanoparticles without any surface modification. Pressure fluctuation signals were processed in both frequency and time-frequency domains to characterize the behavior of various scales of phenomena (i.e.. macro-, meso-, and micro-structures) during fluidization. Due to the aggregation of nanoparticles, three separate broad peaks were observed in the frequency spectra of the pressure signals measured in the bubbling fluidized bed of nanoparticles. A non-intrusive method based on the decoupling of pressure fluctuations recorded simultaneously in the plenum and in the bed was used to determine the approximate size of the bubbles in the bed.
文摘Carbon nanotubes-based materials have been identified as promising sorbents for efficient CO_(2)capture in fluidized beds,suffering from insufficient contact with CO_(2)for the high-level CO_(2)capture capacity.This study focuses on promoting the fluidizability of hard-to-fluidize pure and synthesized silica-coated amine-functionalized carbon nanotubes.The novel synthesized sorbent presents a superior sorption capacity of about 25 times higher than pure carbon nanotubes during 5 consecutive adsorption/regeneration cycles.The low-cost fluidizable-SiO_(2)nanoparticles are used as assistant material to improve the fluidity of carbon nanotubes-based sorbents.Results reveal that a minimum amount of 7.5 and 5 wt%SiO_(2)nanoparticles are required to achieve an agglomerate particulate fluidization behavior for pure and synthesized carbon nanotubes,respectively.Pure carbon nanotubes+7.5 wt%SiO_(2)and synthesized carbon nanotubes+5 wt%SiO_(2)indicates an agglomerate particulate fluidization characteristic,including the high-level bed expansion ratio,low minimum fluidization velocity(1.5 and 1.6 cm·s^(–1)),high Richardson−Zaki n index(5.2 and 5.3>5),and lowΠvalue(83.2 and 84.8<100,respectively).Chemical modification of carbon nanotubes causes not only enhanced CO_(2)uptake capacity but also decreases the required amount of silica additive to reach a homogeneous fluidization behavior for synthesized carbon nanotubes sorbent.