Effect of modifications on Stairmand high efficiency type cyclone geometry on collection efficiency and pressure drop

Being generated as a result of especially powder production processes, particulate-rich flue gases need to be treated prior to emission in order to reduce particle emissions in to the atmosphere. Cyclone separators are one of the most commonly used control devices for this purpose. High concentrations of particulate matter in the flue gases may upset the control devices unless the concentration is reduced by a preliminary control system. Cyclone separators can be used both as a preliminary treatment system and as a main particulate control system. In the design and operation of cyclone separators, it is of great importance to obtain highest removal efficiencies along with operational costs as low as possible. That is, two most important design criteria for cyclone separators are particle removal efficiency and pressure drop. The aim of this study is investigate the effects of inlet dimensions, body height, conical height, and outlet dimensions of the cyclone on pressure drop and particle collection efficiency. For this purpose, a number of cyclone designs were studied. All of the cyclone designs were based on Stairmand-high efficiency type cyclone. Besides, all of the cyclones were operated at six different inlet flowrates. A lab-scale experiment setup was installed. The experimental setup comprised of an air blower, an approach channel, a particle generator, and cyclone separator. The highest clean pressure drop was measured as 2050 Pa for the cyclone with the smallest inlet (a=0.4D ve b=0.2D) dimensions, the shortest body (hb=D) and conical height (hc=2D), the smallest outlet pipe diameter (De=0.4D), and the longest outlet pipe length (S=0.7D). On the other hand, the lowest pressure drop was 310 Pa for the cyclone witha=0.5D, b=0.2D, hb=2D, hc=3D, De=0.6D, and S=0.5D. At the highest inlet velocity, the pressure drop in the cyclone of Stairmand-high efficiency type was measured as 765 Pa. For Stairmand-high efficiency type cyclone, the pressure drop was measured as 1500 Pa, 765 Pa, and 370 Pa, respectively for outlet pipe diameters of 0.4D, 0.5D ve 0.6D. Among cyclone geometry parameters, outlet pipe diameter was the most effective on pressure drop while the outlet pipe length was the least effective. In the second part of the study, particulate collection efficiencies were also determined for cyclone dimensions based on Stairmand-high efficiency type. For this purpose, wheat flour of 0.6 kg/L density was mixed with the gaseous flow in the approach channel. The increase in outlet pipe length lead to increase in particle collection efficiency while it was negatively affected by the increase in outlet diameter. The particle collection efficiency increased up to a certain level as the outlet pipe dimensions changed. After an optimum point, the collection efficiency started to decrease. Therefore, an optimum point could be reached for diameter/length ratio of the outlet pipe for the highest particle collection efficiency and the lowest pressure drop. Finally, the effects of body and conical heights of the cyclone on clean pressure drop was investigated by CFD (computational fluid dynamics) model. The results suggested that CFD model was satisfactory to explain complex phenomena in the fluid flow within cyclone separators. Key Words: Particulate matter, cyclone, pressure drop, collection efficiency, CFD