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The natural vortex length is a complex turbulent dynamic phenomenon of cyclone separator, which can provide reference for the height design. It is calculated by the axial distance between the vortex end and the bottom of vortex finder. At present, scholars mainly attribute the influencing factors of natural vortex length to cylinder diameter, inlet area and vortex finder diameter, ignoring the influence of other structural parameters and operating parameters, so the accuracy and applicability of empirical formula are poor. This study described the mechanism of the vortex end and analyzed the PVC phenomenon. Then, an example was provided to illustrate the limitations and shortcomings of empirical formula. In addition, the influences of some geometric parameters and operating parameters on natural vortex length were summarized. Therefore, this work could provide an important reference for design optimization of cyclone separator height. [ABSTRACT FROM AUTHOR]

Current studies on improving the separation performance of cyclone separators focus on five aspects: i] geometry-structure optimization, ii] geometry-parameter optimization, iii] operation-parameter optimization, iv] operating-condition optimization, and v] internal component optimization. Many scholars work on the design and use of internal components in a cyclone separator to solve various industrial problems, but they seldom systematically classify these internal components. In the last 1999–2019 years, reports on such classification were relatively rare. Compared to the other four aspects, the internal components optimization has a unique advantage: when the equipment operation fails, there is no need to replace the original equipment, just the defective component, which greatly saves both maintenance and engineering expenses. In this review, several kinds of internal cyclone components are systematically summarized and classified, including their mechanism and usage effect. Furthermore, the trends in internal component development have also been prospected. Combined applications, development of new components and applications of new materials are the three main trends. In the future, internal components will be more diversified, detailed, precise and simplified. Finally, we expect that these developments will not only improve the separation efficiency and reduce the pressure drop but also satisfy requirements in environmental protection and process security. [ABSTRACT FROM AUTHOR]

Gas leakage from the dipleg of a cyclone separator usually exists due to the the inlet and dipleg output being in a common space. To gain further insight into the pressure characteristics produced by such gas leakage, the pressure drops and instantaneous pressures in a cyclone separator were measured by a U‐tube and dynamic pressure sensors, respectively, under the conditions of different inlet velocities and gas leakage rates. The results showed that the pressure drop linearly decreased with increased gas leakage rate. And the instantaneous pressure fluctuation amplitudes of some regions were greatly affected by gas leakage variations. Instantaneous pressure data were processed in terms of SD, which revealed that the oscillation of the vortex core caused the pressure fluctuations. When the pressure of the upward gas leakage was equal to that of the axial wall surface, the end of the vortex core attached to the lateral wall and formed the larger pressure fluctuation. A power spectral density analysis was carried out for pressure time‐series data, and then the swing frequency (180 Hz) of the vortex core end was detected on the cyclone separator wall surface in the cone lower region (tapping 4). As a consequence, gas leakage could lead to separated particles being re‐entrained, which might heavily deteriorate separation performance of the cyclone separator. [ABSTRACT FROM AUTHOR]

Systematic experimental work was conducted to study the solids acceleration length in a 15-m high riser. A more feasible method is proposed in this study to determine the solids acceleration length from the standard deviations of the measured pressure fluctuations. With this method and the experimental results, the clear relationship of the solids acceleration length versus solid circulating rate is obtained. Generally, the solids acceleration length (expressed inLacc) increases with theGsrising and decreases with theGsreducing gradually. Reasonable explanations are also provided for the observed variation trends of the solids acceleration length. In addition, it is found that the pressure fluctuations in the riser have two sources. One is the feeding flow oscillation at the inlet of the riser and the other is the fluctuations by solids back-mixing, solids dispersion and solids reunion in the process of the solids movement in the riser. The method can be used to distinguish the boundary of solids movement between the solids acceleration region and the fully developed region. It is very important to take the solids acceleration into account both for the modelling of gas-solid flow in the riser and for the design and operation of circulating fluidised bed (CFB) reactors. [ABSTRACT FROM AUTHOR]

The instability characteristics of gas swirling flow in a cyclone were investigated experimentally by measuring the instantaneous tangential velocity with the hot‐wire anemometry. The results showed that the instantaneous tangential velocity fluctuated continuously with time at both low and high frequencies. Further analysis of measured data regarding time and frequency domain by probability density and spectral methods revealed that the velocity fluctuation was affected not only by the turbulence flow itself but also by gas swirling flow instability. Also, the distributions of dominant frequency and amplitude indicated that low‐frequency velocity fluctuation caused by the instability had the transfer behavior and attenuation character, which could be characterized by the dominant frequency that varied little along the radial position and decreased gradually along the axial direction, while the amplitude increased significantly with decreased radial position. Due to the gas swirling instability, the turbulence intensity and the fine particle diffusion were enhanced, which would degrade the separation efficiency of cyclone. [ABSTRACT FROM AUTHOR]