Numerical Simulation And Experimental Study Of Conveying Vessel For Plug-flow Pneumatic Conveying

The conveying vessel is one of the key equipments in pneumatic systems, whichhave been widely used in industries. The gas-solid flow in the conveying vessel isfeatured with intensive inter-phase interactions and complex flow patterns. In thisresearch, a numerical simulation and an experimental approaching were used to studythe gas-solid flow behavior and the conveying performance of a novel pilot-conveyingvessel. A simplified2D facility was used in the experiment. As to the numericalsimulation, the Euler two-fluid model, the k-ε turbulent model and the kinetic theoryof granular were adopted.It was found that the total spent time decreases when the velocity of the gas inlet isincreased. There is no obvious similar trend as the pressure is increased. Based on themass flow rate at the outlet the process is predicted to be divided into three stages:rising, static and declining. When the gas velocity is increased, the time consumptionof the rising stage changes little, the static stage decreases and the declining stageincreases. There is little effect on the time consumptions of the three stages when thepressure is increased. The turning point between the static and declining stage willappear due to the dilution of the whole bed as well as the particles near the bottom.The gas-solid flow region above the nozzles is distinguished into two general parts.One part is near the wall. The organization of this part is similar to that of the spoutedbed caused by the upper nozzles, from which the gas penetrates the bed. The otherpart is structured similar to the bubble bed near the center formed by the lowernozzles, from which the gas is divided into bubbles.The particle concentration within the bed decreases as the height increases and, onaverage, decreases over time. The secondary flow of gas tends to be uniform as theheight and time increase. The pressure decreases as the height of the bed increases.However, an exception is made when the bed surface is below the upper nozzles. Atthe bottom, a dead zone is indicated, which makes part of particles remain. Optimaldesigns were examined to eliminate the blind spots and particles remaining.The mass flow rate based on the outlet increases as the gas velocity is increased. Afitted curve of the output and input was obtained. It is indicated that the conveying performance is hardly improved when the flow rate of the gas is increased. On thecontrary, the increasing gas will increase the energy consumption and reduce theefficiency. The solid/gas ratio based on the outflow increases as the pipe diameterincreases with a constant gas flow rate.