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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]

Unwanted build-up of carbonaceous deposits on RFCC equipment surface is a key process limitation to achieving the economic benefits of longer run length. This paper focuses on the carbonaceous deposition on the outer surface of vortex finder of secondary cyclone. Macroscopic features of industrial deposits are reported in detail. Extensive characterization studies such as elemental analysis, scanning electron microscopy, energy dispersive spectrometry, thermal behavior were conducted and size distribution of catalyst particles in deposits was measured. Computational fluid dynamics method was used to obtain the gas flow field around the vortex finder. The role of gas flow to the buildup of deposits was discussed. The results will provide comprehensive understanding of deposit formation and insight into the process and operation improvement. [ABSTRACT FROM AUTHOR]

• The dynamic characteristics are described by the tangential velocity fluctuations. • Low-frequency velocity fluctuation has transfer behavior on frequency domain. • PSD of the velocity fluctuation frequency has attenuation characteristics. • The hopper leads to a second dominant frequency emerged in the local region. • Dominant frequencies increase as Re increased. The dynamic characteristics of the gas flow field in a reverse cyclone were investigated experimentally in this study by measuring instantaneous tangential velocity with hot wire anemometry (HWA). The instantaneous tangential velocity was found to continuously fluctuate by both low and high frequencies with time. Further analyses of measured data regarding time and frequency domains by standard deviation and spectral analysis revealed that the fluctuation intensities were stronger in the center region than that near the wall, and stronger still near the dust outlet. One dominant frequency (f 1) prevailed in entire space of the cyclone and remained almost unchanged, while the power spectral density (PSD) of f 1 decreased significantly with increased radial position. To this effect, the low-frequency velocity fluctuation exhibited transfer behavior and attenuation characteristics. Besides, another dominant frequency (f 2) generated by the hopper (the hopper led to a new fluctuation) and emerged just in the local region of the dust outlet. Analyses suggested that both dominant frequencies originated from the sway of the gas swirling flow, f 1 was from the cyclone, and f 2 from the hopper. The dominant frequencies also increased as Re increased, and in the cyclone with a hopper, the region affected by f 2 grew in size as Re increased. [ABSTRACT FROM AUTHOR]

The particle velocity and solid concentration distribution in the near-wall region of a cyclone separator was experimentally studied. A series of measurement experiments were conducted based on the high-speed particle shadow velocimetry (HPSV) method. The experiment was conducted on a ϕ 160 mm cyclone at an inlet velocity of 12-20 m/s and inlet concentration of 30-300 g/m3 with glass beads whose median diameter was 136.7 μm. The measured results of the microscopic particle movement demonstrate the moving behavior of the spiral particle band near the cyclone wall. It was found that the particle velocity and solid concentration are greatly different from those in and outside the particle band. The particle velocity inside the particle band can drop to 1.9 m/s, while the dispersed particle velocity outside the particle band away from the wall can reach 15.2 m/s. Along the downward movement of particle band, the particle velocity decrease and velocity fluctuation become milder, the solid concentration increases four times and reaches the highest at the cone wall. On the cross-section plane, the solid concentration decreases along the radial direction away from the wall. In the near-wall region inside particle band, the solid concentration can reach 0.004 or even higher, which is 32 times higher than the inlet solid concentration. This study helps to understand the complex gas-solid two-phase flow phenomena in cyclones. [Display omitted] • A novel High-speed particle velocimetry (HPSV) measure method was employed. • Microscopic images of particles inside the spiral band were photographed for the first time. • Particle velocity and solid concentration are greatly different from those in and outside the spiral particle band. [ABSTRACT FROM AUTHOR]

• Dynamic characteristics are described by fluctuations of tangential velocity. • Gas leakage caused the vortex core to swing from geometric center to wall. • Vortex tail has been located by tangential velocity measurement at first time. • High frequency (~131 Hz) was produced by the rotation of the quasi-forced vortex. • Low frequency (~35 Hz) was related to the swing of the vortex core. Experimental investigation on the dynamic characteristics of vortex flow in a cyclone was performed, particularly focused on the effects of the gas leakage from the dipleg. The instantaneous tangential velocities were measured by hot wire/film anemometry (HWFA) under the conditions of different gas leakage velocities, and then analyzed in the time and frequency-domains. The results showed that, on one hand, gas leakage reduced the time-averaged tangential velocity, on the other hand, gas leakage made the instantaneous tangential velocity fluctuate more intensely, particularly in the lower region of the cyclone, while both could deteriorate separation efficiency. In addition, when the gas leakage velocity exceeded a certain value, the vortex tail swung heavily and re-entrained separated particles to escape through the exit tube, which might have further deteriorated the separation efficiency. Frequency-domain analysis revealed that there were two dominant frequencies in the cylindrical space. The high frequency (~131 Hz) was produced by the rotation of the quasi-forced vortex, while the low frequency (~35 Hz) was related to the swing of the vortex core. The amplitudes of the two dominant frequencies were clearly attenuated along the radial direction. With gas leakage velocity increasing to higher values, high frequency amplitudes were weakened, while the low frequency amplitudes were enhanced. This study revealed some mechanisms of the effects of gas leakage on the time-averaged and dynamic flow field in the cyclone. [ABSTRACT FROM AUTHOR]