Research On Energy Saving Method Of Pneumatic Conveying Technology Based On Oscillating Flow

Pneumatic conveying is an important technique used in a significant number of chemical and industrial processes, such as the coal energy conversion systems, pharmaceutical, cement, and drying and transport of solid materials. Although it has many advantages, for example safety, low cost, automation, layout flexibility and environmental friend, the conventional pneumatic conveying is frequently operated in the dilute phase regime in the high air velocity region and causes power consumption, pipe erosion and particle degradation. Then it becomes an important design criterion to keep the pressure drop and conveying velocity as low as possible under the condition of the steady pneumatic conveying system. The purpose of this study was to develop an energy-saving technique in the horizontal pneumatic conveying system through experimental study and theoretical analysis.(1)We aimed at a new pneumatic conveying system where soft fins were mounted in a horizontal or vertical plane through the pipe axis in the front of inlet was proposed in order to reduce power consumption and conveying velocity. This experimental study focused on the effect of the different fin's lengths on the horizontal pneumatic conveying system in terms of frequency characteristics of fin's oscillation, pressure drop, conveying velocity, particle flow pattern, power consumption and additional pressure drop. It was found that power consumption and conveying velocity were reduced by using soft fins comparing with the conventional pneumatic conveying.(2)The distributions of the particle velocity were respectively measured by the high-speed PIV and image processing techniques for the cases of horizontally and vertically mounted soft fins, and analyzed the experimental data through the fast Fourier transform. For the particle velocity, it was found that although the air velocities of the fins were lower than that of non-fin, the particle concentration of the fins was slightly lower than that of non-fin near the bottom and was higher than of non-fin near the top of pipeline, especially in the case of the long fin. And the particle velocities of the long fins was higher than that of non-fin, indicating that the long fins accelerate easily the particles and resulted in low pressure drop and low air velocity. Compared with the experimental data of two kinds of working conditions, proved that the vertical installation soft fin owns better energy saving effect of pneumatic conveying.(3)We also researched the effect of the soft fin to the the power spectrum of particle fluctuation velocity. It was found that the power spectra peaks of fins, especially the longer fins, were larger than that of non-fin even at lower air velocity, suggesting the accelerating efficiency of fins' vibration. Meanwhile, enhancing the fins' oscillation generated large particle energy, even at lower air velocity, so that the particles were more easily accelerated and suspended.