Study And Optimize On Gas-Solid Two-Phase Flow In Cyclone Separator With Downward Exhaust Outlet

Cyclone separator with downward exhaust outlet has the flow structure of single swirl flow, and it has lower pressure loss. Cyclone separator with downward exhaust outlet is suitable for the theπtype arrangement of CFB boilers, but cyclone separator with upward exhaust gas has a severe entrainment of the fine particles, leading to a low separating efficiency of the fine particles. To increase the separating efficiency of the fine particles and keep pressure drop low, it needs to further study for the separating mechanism and improve its performance by optimization design of the structure.The research adopts numerical simulation and theory analysis methods to sudy the gas-solid two-phase flow, separating mechanism, pressure distribution and pressure loss in details. Based on these study results, an optimization scheme to increase the separating efficiency and decrease the pressure loss of the Cyclone separator with downward exhaust outlet is presented in the project. According to the results and analysis, the main conclusions are as follows:①When the Cyclone separator with downward exhaust outlet has the taper import, the gas-particle mixture is accelerated in the tapered duct, and the particles get a higher penetration ability in the flow. Then, more particles can penetrate the vortex to reach the Cyclone separator wall, and the separating efficiency increases. However, with gas accelerated, vortex gets more intensive, and the pressure loss also increases.②When the diameter of diversion object increases, the swirl intensity of cyclone separator gets more acute, the function of centrifugal force is strengthed, but spin kinetic energy loss increases, so separating efficiency may be inhanced and pressure loss increases.③When exhaust pipe uses the cone structure entrance, optimal design of the obliquity and bottom diameter can effectively prevent solid particles in ash bucket turning back into the exhaust pipe along the outside wall of exhaust pipe, consequently, separating efficiency increases.④When the exhaust pipe moves dowmward, separating efficiency increases initially and then decreases. It proves that the distance between the diversion object and the exhaust duct has an optimal value.⑤When the diameter of exhaust duct minishes, separating efficiency is enhanced, but pressure loss increases when gas flows into the exhaust duct. Moreover, centrifugal force field of rotary gas reinforces, local pressure also loss increases.⑥When insertion height of exhaust duct increases, pressure loss increases. At the same time, the exhaust gas entrance is far away from high turbulence intensity area, so separating efficiency increases;⑦The center of vertex in cyclone separator with downward exhaust gas is not at the center of its geometric center. When exhaust gas duct offsets in right angle with right distance, separating efficiency increases.⑧The cyclone separator with downward exhaust gas is improved by adopting tapered entrance and cone shaped exhaust pipe entrance, moveing the exhaust pipe dowmward.The separating efficiency for fine particles increases evidencely , especially when the particle size less than 20μm, the separating efficiency for the same particle size increasing 37.75% at most.The total separating efficiency also increases as well as the pressure drop.